CN1757272A - Multilayer ceramic substrate, manufacturing method thereof, and electronic device using same - Google Patents

Abstract

The invention relates to the manufacture method of a multi-layer ceramic base plate. The method adopts the following steps: step one, powder carrying ceramic material and slime carrying organic binder are used for manufacturing raw film used for a base plate which can be sintered at a low temperature; step two, after an electrode is formed on the raw film used for the base plate, a non-sintered multi-layer ceramic base plate is cascaded and manufactured; step three, a restraint layer including inorganic particles (which is provided with the particle diameter of larger than 0.3 micrometers and 0.3 to 0.4 times of the average diameter of the powder of the ceramic material) not sintered at the sintering temperature of the non-sintered multi-layer ceramic base plate and the organic binder is closely connected with the upper surface and/or the lower surface of the non-sintered multi-layer ceramic base plate including outer electrodes to produce an integrated laminated body; step four, the laminated body is sintered; step five, through removing the restraint layer from the surface of the sintered laminated body, the contraction percentage in the manufacturing face is within 1 percent (the deviation is within 0.1 percent), for the inorganic particles residual on the outer electrode, and relative to the metal forming the outer electrode and the metal forming the inorganic particle, the proportion of the total amount of the metal forming the inorganic particles is below 20 percent of the mass of the multi-layer ceramic base plate.

Description

Multilayer ceramic substrate, manufacturing method thereof, and electronic device using same

technical field

The present invention relates to a multilayer ceramic substrate produced by a non-shrinkage process capable of low-temperature sintering, a method for producing the same, and electronic equipment for mobile phones and information terminal devices equipped with the multilayer ceramic substrate.

Background technique

Currently, multilayer ceramic substrates are widely used in the field of mobile communication terminals such as mobile phones to constitute various electronic components such as antenna switch modules, PA module substrates, filters, chip antennas, and various assembly components.

A multilayer ceramic substrate is formed by laminating a plurality of ceramic layers, and has internal electrodes formed on each ceramic layer, via hole electrodes penetrating through the ceramic layers to connect the internal electrodes, and formed on the outside. There are external electrodes. A multilayer ceramic substrate is usually mounted on the surface of a mother substrate after mounting a semiconductor chip or other chip components. In order to achieve multifunctionality, high density, and high performance, wiring electrodes and external electrodes are arranged at high density.

However, in the sintering process for obtaining a multilayer ceramic substrate, the ceramic shrinks by about 10 to 25%. Since such large sintering shrinkage does not occur uniformly on the entire multilayer ceramic substrate, warpage or deformation occurs. Such warpage or deformation not only degrades the characteristics of the multilayer ceramic substrate, but also hinders its mounting operation, and hinders the increase in the density of electrodes. Therefore, it is desirable to reduce the shrinkage due to sintering to 1% or less and to reduce the variation in shrinkage, thereby suppressing warpage to 30 μm or less per 50 mm length.

In addition, since low-resistance Ag-based electrode paste materials have recently been used, sintering of multilayer ceramic substrates is performed at a low temperature of about 800 to 1000°C. As a result, green sheets of LTCC (Low Temperature Co-fired Ceramics) that can be sintered at temperatures below 1000°C have gradually begun to be used, especially ceramic powders such as glass powder, alumina, mullite, and cordierite. The glass-ceramic green sheets made of organic binder and plasticizer are integrally sintered without shrinkage on the X-Y plane of the multilayer ceramic substrate, so-called "non-shrinkage process".

For example, Patent No. 2554415 (Patent Document 1) and Patent No. 2617643 (US Patent No. 5,254,191 and US Patent No. 5,085,720) (Patent Document 2) disclose the following method, that is, prepare A substrate green sheet composed of a mixture of ceramic powder and a sinterable inorganic binder (glass component), and inorganic particles (alumina, etc.) that cannot be sintered at the sintering temperature of the substrate green sheet dispersed in an organic bond. A constraining green sheet formed from the mixture obtained in the substrate is laminated to form an unsintered multilayer ceramic substrate, and the constraining green sheets are adhered to the upper and lower surfaces of the unsintered ceramic substrate, followed by sintering. According to this method, the sinterable inorganic binder contained in the substrate green sheet penetrates into the constraining green sheet layer to a thickness of 50 μm or less to bond the two green sheets, but the constraining green sheet composed of inorganic particles is not substantially sintered. , so it does not shrink, thereby suppressing the shrinkage of the X-Y plane of the substrate green sheet that is in close contact with it.

Patent No. 3335970 (Patent Document 3) proposes that a glass component is also contained in the constraining green sheet in order to increase the bonding strength between the substrate green sheet and the constraining green sheet as compared with Patent No. 2554415 (Patent Document 1).

Japanese Patent Application Laid-Open No. 9-266363 (Patent Document 4) proposes that the constraining green sheet part fixed to the surface of the substrate by the action of the impregnated glass component is not peeled off from the substrate green sheet, and that it is directly used as the surface of the substrate. use.

Japanese Patent Application Laid-Open No. 11-354924 (Patent Document 5) proposes that by setting the difference in thermal expansion coefficient between the sintered multilayer ceramic substrate and the constraining green sheet within a given range, thermal stress is used to separate the constraining green sheet from the multilayer Peel off the ceramic substrate.

According to the non-shrinkage step, by constraining the substrate green sheet by the constraining green sheet, the substrate green sheet shrinks in the thickness direction, but the shrinkage in the X-Y plane is suppressed. However, as described in Patent No. 3335970 (Patent Document 3), until now, attention has been mainly focused on how to improve the bonding force between the substrate green sheet and the constraining green sheet. In the prior art described above, since the constraining green sheet after sintering is a porous powdery sheet in which the organic binder has evaporated, it can be removed relatively easily, but it is often impossible to remove it completely in practice. Therefore, it is necessary to stabilize the properties of the surface of the multilayer ceramic substrate. For example, it is necessary to consider the influence on the external electrodes on the upper and lower surfaces of the multilayer ceramic substrate, and the influence on the Ni or Au metallization film formed on the external electrodes after sintering.

Here, the behavior of the glass component contained in the substrate green sheet is examined. The glass component softens as the sintering proceeds, and is eluted to the surface of the green substrate sheet. On the other hand, in the constraining green sheet, voids may be generated in traces of the volatilized organic binder. Therefore, the liquefied glass permeates into the pores of the constraining green sheet due to capillary action or the like. Although the penetration depth varies depending on various conditions, it is typically about 50 μm. Utilizing the impregnation of the glass, the two green sheets are firmly bonded. However, at the same time, since the external electrodes on the surface of the substrate green sheet float on the molten glass eluted to the surface of the substrate green sheet, it is difficult to maintain the accuracy and quality thereof. In addition, glass components may adhere to the surface of the external electrodes during the impregnation process, which may cause poor contact and poor coating.

In addition, during sintering, it was also observed that alumina particles, which are the main raw material of the constraining green sheet, intruded into the substrate green sheet. Sandblasting or grinding is sufficient to remove deeply buried alumina particles from the multilayer ceramic substrate. However, since the external electrodes on the surface are also removed in this way, an additional process of forming external electrodes is required. .

As described above, the conventional non-shrinkage process is not suitable when applied to a green multilayer ceramic substrate on which external electrodes are formed. Therefore, conventionally, after the constraining layer is removed after firing the multilayer ceramic substrate, external electrodes are printed and fired.

Patent Document 1: Patent No. 2554415

Patent Document 2: Patent No. 2617643

Patent Document 3: Patent No. 3335970

Patent Document 4: Japanese Unexamined Patent Publication No. 9-266363

Patent Document 5: Japanese Unexamined Patent Publication No. 11-354924

Contents of the invention

Therefore, an object of the present invention is to provide a multilayer ceramic substrate obtained by sintering an unsintered multilayer ceramic substrate with external electrodes formed on its surface without shrinkage. In-plane shrinkage is suppressed, there is little warping or deformation, there is no solder erosion of external electrodes, and the coating property is good.

Another object of the present invention is to provide a method for producing a multilayer ceramic substrate by providing a constraining layer on the upper surface and/or lower surface of the unsintered multilayer ceramic substrate including external electrodes and sintering to produce a sufficient constraining force and suppress method to avoid adverse effects on the external electrode surface. Wherein, external electrodes are formed on the surface of the unsintered multilayer ceramic substrate.

Another object of the present invention is to provide an electronic device using such a multilayer ceramic substrate.

The multilayer ceramic substrate according to aspect 1 of the present invention is characterized in that an external electrode is formed on at least the upper surface of an unsintered multilayer ceramic substrate obtained by laminating substrate green sheets including ceramic materials and capable of low-temperature sintering. The constrained layer mainly composed of inorganic particles that are not sintered at the sintering temperature of the green multilayer ceramic substrate is formed in such a manner that it is in close contact with the upper surface and/or lower surface of the green multilayer ceramic substrate including the external electrodes An integrated laminate obtained by removing the constrained layer after sintering the laminate, wherein the in-plane shrinkage of the multilayer ceramic substrate is within 1% (the deviation is within 0.1%), and the In the inorganic particles remaining on the external electrodes, the ratio of the metal constituting the inorganic particles to the total amount of the metal constituting the external electrodes and the metal constituting the inorganic particles is 20% by mass or less. .

The ceramic material preferably contains 10 to 60 mass % of Al in terms of Al ₂ O ₃ , 25 to 60 mass % of Si in terms of SiO ₂ , and 7.5 to 50 mass % in terms of SrO in the state of oxides as main components. Mass % of Sr and 0 to 20 mass % of Ti in terms of TiO ₂ (the total amount of Al ₂ O ₃ , SiO ₂ , SrO and TiO ₂ is 100 mass %), at 700°C to 850°C A powdery substance that is crushed after calcination. The ceramic material preferably contains 0.1 to 10 parts by mass of Bi in terms of Bi ₂ O ₃ as an auxiliary component per 100 parts by mass of the main component. The ceramic material more preferably contains a plasticizer and a solvent.

The auxiliary components preferably contain 0.1 to 10 parts by mass of Bi in terms of Bi ₂ O ₃ , 0.1 to 5 parts by mass of Na in terms of Na ₂ O , and Na in terms of K ₂ per 100 parts by mass of the main component. At least one selected from the group consisting of 0.1 to 5 parts by mass of K in terms of O and 0.1 to 5 parts by mass of Co in terms of CoO, Cu of 0.01 to 5 parts by mass in terms of CuO, and MnO ₂ In conversion, it is at least one selected from the group consisting of 0.01 to 5 parts by mass of Mn and 0.01 to 5 parts by mass of Ag. The auxiliary component may further contain 0.01 to 2 parts by mass of Zr in terms of ZrO ₂ .

The multilayer ceramic substrate according to the second aspect of the present invention is characterized in that an external electrode is formed on at least the upper surface of an unsintered multilayer ceramic substrate obtained by laminating low-temperature sinterable substrate green sheets including ceramic materials, and the external electrodes are formed according to The constrained layer mainly composed of inorganic particles that are not sintered at the sintering temperature of the green multilayer ceramic substrate is formed in such a manner that it is in close contact with the upper surface and/or lower surface of the green multilayer ceramic substrate including the external electrodes An integrated laminate is obtained by removing the constrained layer after sintering the laminate, wherein the substrate has a structure including feldspar group crystals mainly composed of strontium feldspar and alumina crystals.

Strontium feldspar generally has a composition of SrAl ₂ Si ₂ O ₈ . At least a part of strontium feldspar crystals is preferably hexagonal.

In this multilayer ceramic substrate, it is preferable that the in-plane shrinkage rate is also within 1% (within a deviation of 0.1%). For the inorganic particles remaining on the external electrodes, the metal constituting the inorganic particles The ratio to the total amount of the metal constituting the external electrode and the metal constituting the inorganic particles is also 20% by mass or less.

The first method of manufacturing a multilayer ceramic substrate according to the present invention is characterized by (a) manufacturing a substrate green sheet capable of low-temperature sintering by using a slurry containing ceramic material powder and an organic binder, (b) After forming electrodes on the green sheets for the substrate, stack them to make an unsintered multilayer ceramic substrate, (c) make a constrained layer containing inorganic particles and an organic binder that are not sintered at the sintering temperature of the unsintered multilayer ceramic substrate, and The upper and/or lower surfaces of the unsintered multilayer ceramic substrate including the external electrodes are closely arranged to form an integrated laminated body, (d) sintering the laminated body, (e) removing the constrained layer from the In the step of removing the surface of the sintered laminate, the average particle size of the inorganic particles is 0.3 μm or more, which is 0.3 to 4 times the average particle size of the ceramic material powder.

The second manufacturing method of the multilayer ceramic substrate of the present invention is characterized in that (a) Al is 10 to 60 mass % in terms of Al ₂ O ₃ , Si is 25 to 60 mass % in terms of SiO ₂ , and SrO is A ceramic whose main components are 7.5 to 50 mass % of Sr in terms of TiO ₂ and 0 to 20 mass % in terms of TiO 2 (the total of Al ₂ O ₃ , SiO ₂ , SrO, and TiO ₂ is 100 mass %) The material is calcined at 700°C to 850°C and crushed, (b) using a slurry containing the obtained calcined body fine powder and an organic binder, a green sheet for a substrate capable of low-temperature sintering is produced, and (c) the substrate is After electrodes are formed on the green sheet, laminated to produce a green multilayer ceramic substrate, (d) a constraining layer containing inorganic particles that are not sintered at the sintering temperature of the green multilayer ceramic substrate and an organic binder, and The upper and/or lower surfaces of the unsintered multilayer ceramic substrate including the external electrodes are closely arranged to form an integrated laminate, (e) sintering the laminate at 800°C to 1000C, (f) The constraining layer is removed from the laminate.

The green sheet for a substrate preferably contains an auxiliary component of 0.1 to 10 parts by mass of Bi in terms of Bi ₂ O ₃ and 0.1 to 10 parts by mass in terms of Na ₂ O , per 100 parts by mass of the main component. At least one selected from the group consisting of 0.1 to 5 parts by mass of Na, 0.1 to 5 parts by mass of K in terms of _K2O , and 0.1 to 5 parts by mass of Co in terms of CoO, and At least one selected from the group consisting of 0.01 to 5 parts by mass of Cu, 0.01 to 5 parts by mass of Mn in terms of MnO ₂ , and 0.01 to 5 parts by mass of Ag. The green sheet for a substrate may further contain 0.01 to 2 parts by mass of Zr in terms of ZrO ₂ .

In the second method, it is preferable that the average particle diameter of the inorganic particles is also 0.3 μm or more, which is 0.3 to 4 times the average particle diameter of the fine powder of the calcined body of the ceramic material.

In either method, as the constraining layer, it is preferable to form a constraining green sheet containing inorganic particles and an organic binder on a carrier film, so that the carrier film contact surface of the constraining green sheet and the unsintered The upper and/or lower surfaces of the multilayer ceramic substrate including the external electrodes are in close contact.

The constrained layer is preferably made to have a thickness of 50 μm or more. In addition, it is preferable to form a first constrained layer having a thickness of 10 μm or more by coating, and to overlay the green sheet for constraining thereon as a second constrained layer to form a constrained layer of 50 μm or more in total.

Preferably, the unsintered multilayer ceramic substrate is produced in the state of an aggregate substrate capable of being divided into a plurality of substrate pieces by dividing grooves, and the constraining layer is provided on the upper surface and/or lower surface of the aggregate substrate including the external electrodes. .

The electronic device of the present invention can be obtained by surface-mounting the multilayer ceramic substrate on a circuit board.

According to the present invention, the inorganic particles in the constraining layer can exert moderate constraining force on the green multilayer ceramic substrate having external electrodes, and the in-plane shrinkage can be suppressed within 1% (within ±0.1%). Since the inorganic particles remain on the external electrodes to such an extent that they do not substantially adversely affect the plating properties, the solder erosion resistance and strength of the electrodes are improved.

Description of drawings

FIG. 1 is a cross-sectional view showing an aggregated substrate-like green multilayer ceramic substrate before forming a constrained layer.

Fig. 2 is a perspective view showing the upper surface of the green multilayer ceramic substrate of Fig. 1 .

Fig. 3 is a cross-sectional view showing a green multilayer ceramic substrate after forming a constrained layer.

4 is a cross-sectional view showing a module in which chip components such as semiconductor elements are mounted on the multilayer ceramic substrate of the present invention.

Fig. 5 is a cross-sectional view showing an example of a multilayer ceramic substrate with cavities.

Fig. 6(a) is a flow chart showing an example of the manufacturing process of the multilayer ceramic substrate of the present invention.

Fig. 6(b) is a flow chart showing another example of the manufacturing process of the multilayer ceramic substrate of the present invention.

Fig. 6(c) is a flow chart showing another example of the manufacturing process of the multilayer ceramic substrate of the present invention.

7 is a graph showing powder X-ray diffraction patterns in the state of mixed powder, calcined powder, and sintered body of a low-temperature sintered ceramic material.

Fig. 8(a) is a scanning electron micrograph of a calcined body of a low-temperature sintered ceramic material.

Fig. 8(b) is a scanning electron micrograph of a powder obtained by pulverizing a calcined body of a low-temperature sintered ceramic material.

Fig. 9(a) is a graph showing an X-ray diffraction pattern of a multilayer ceramic substrate sintered at 850°C.

Fig. 9(b) is a graph showing an X-ray diffraction pattern of a multilayer ceramic substrate sintered at 860°C.

Fig. 9(c) is a graph showing an X-ray diffraction pattern of a multilayer ceramic substrate sintered at 875°C.

Fig. 10 is a block diagram showing one particle used in a high-frequency component using the multilayer ceramic substrate of the present invention.

11 is a schematic perspective view showing a main printed circuit board of a mobile phone on which a high-frequency component using the multilayer ceramic substrate of the present invention is mounted.

Detailed ways

[1] Multilayer ceramic substrate

The multilayer ceramic substrate of the present invention is obtained by forming external electrodes on at least the upper surface of a green multilayer ceramic substrate in which low-temperature sinterable substrate green sheets containing ceramic materials are laminated, and the green A constrained layer mainly composed of inorganic particles that are not sintered at the sintering temperature of the multilayer ceramic substrate is closely arranged on the upper surface and/or lower surface of the unsintered multilayer ceramic substrate including external electrodes to form an integrated laminate , after the laminate is sintered, the constraining layer is removed. Thus, the in-plane shrinkage of the multilayer ceramic substrate of the present invention is within 1% (deviation within 0.1%). For the inorganic particles remaining on the external electrodes, the metal constituting the inorganic particles is relatively The ratio of the metal of the external electrode to the total amount of the metal constituting the inorganic particles is 20% by mass or less.

Components other than Al ₂ O ₃ and TiO ₂ are vitrified by firing a ceramic material capable of low-temperature sintering (hereinafter referred to as “low-temperature sintering ceramic material”). Some Al ₂ O ₃ and TiO ₂ can enter the glass. In order to achieve uniform vitrification with _SiO2 as the main component, the composition needs to be melted at a firing temperature above 1300 °C. In the calcined body obtained at 700°C to 850°C, the SiO ₂ phase remained, and the glass phase was uniformly deviated. A finely pulverized calcined body composed of ceramic particles and a glass phase has a structure in which the ceramic particles are partially or entirely covered with glass. Compared with a conventional low-temperature sintered ceramic material composed of a mixture of glass particles and ceramic particles produced by a melting method, the glass in the calcined body powder used in the present invention is not sufficiently vitrified and is in a state where it is difficult to flow . When such calcined powder is used, the reactivity of the glass component is low at the time of main sintering, and the glass component is in an inert and highly viscous state at the interface between the unsintered multilayer ceramic substrate and the constrained layer. That is, when compared with the sintering behavior of a green multilayer ceramic substrate composed of a mixture of glass particles and ceramic particles, the fluidity of the glass component is suppressed in the green multilayer ceramic substrate composed of finely pulverized powder of the calcined body , in a state where it is difficult to seep out to the surface. Therefore, the glass component does not adhere to the external electrodes of the multilayer ceramic substrate. In addition, the lowering of the fluidity of the glass component can also prevent inorganic particles such as alumina from being buried in the green multilayer ceramic substrate.

In a glass-ceramic green sheet composed of a mixture of glass powder and ceramic powder, densification tends to be difficult if the glass powder is separated, but in the finely pulverized powder of the calcined body, the ceramic particles are partly or entirely bound by the glass. Therefore, the contact between the glasses is tight, and densification can be achieved even at the sintering temperature that slightly imparts softening and fluidity.

Although the low-temperature sintered ceramic material used in the second production method of the present invention does not contain Pb and B, it can also be densified by low-temperature sintering. Among the auxiliary components, Bi, Na, K, and Co function as sintering aids, so that sintering at a lower temperature and dielectric properties with a high Q value can be obtained. Cu, Mn, and Ag have a crystallization promoting effect and can realize low-temperature sintering. With sintering at a lower temperature, melting of the glass component is suppressed.

The structure of the sintered multilayer ceramic substrate includes strontium feldspar (SrAl ₂ Si ₂ O ₈ ) in which Ca of the anorthite crystal is replaced by Sr. A ceramic substrate having a structure mainly composed of strontium feldspar and in which Al ₂ O ₃ crystals exist in an island shape has excellent mechanical strength. In addition, when the strontium feldspar is a hexagonal crystal, the strength of the substrate is further improved. This is considered to be due to the use of the low-temperature sintered ceramic material for this structure. Even in the non-shrinking process, strontium feldspar crystals are precipitated from the glass phase of the calcined body constituting the green sheet by sintering at about 850° C. or higher. In this way, the apparent viscosity of the glass phase increases, and the flow of the glass component is suppressed.

Preferably, the average particle size of the inorganic particles constituting the constrained layer is 0.3 μm or more, and is 0.3 to 4 times the average particle size of the low-temperature sintered ceramic material powder. For example, when the average particle diameter of the substrate green sheet powder is about 1 to 3 μm, the average particle diameter of the inorganic particles is 0.3 to 4 μm. This makes it easy to remove inorganic particles such as alumina remaining on the surface of the external electrodes. A small amount of remaining inorganic particles does not substantially affect the coating properties, but shows effects on solder erosion and improvement of electrode strength.

When the average particle size of the powder of the ceramic material is less than 1 μm, especially less than 0.6 μm, it is difficult to form a substrate green sheet, and when it exceeds 3 μm, it is difficult to produce a substrate green sheet as thin as 20 μm or less. In addition, the above-mentioned relationship is also established in the case of using a finely pulverized powder after calcining a low-temperature sintered ceramic material. The average particle size of the calcined body pulverized powder is more preferably 1 to 3 μm, most preferably 1 to 1.5 μm.

When the average particle diameter of the inorganic particles for the constrained layer is less than 0.3 μm, in order to obtain the viscosity necessary for printing, the amount of binder becomes too much (the filling rate of the inorganic particles becomes too small), and it is impossible to Equal binding force is exerted on both the flat part and the dividing groove of the substrate green sheet. On the other hand, when the average particle diameter of the inorganic particles exceeds 4 μm, the binding force particularly in the dividing groove becomes weak. The more preferable average particle diameter of an inorganic particle is 0.5-2 micrometers.

When the constrained layer has a thickness of 50 μm or more, it is preferable because the sintering shrinkage of the X-Y plane of the substrate green sheet can be suppressed to 1% or less. When the thickness of the constrained layer is less than 50 μm, the constraining force is insufficient, and it is difficult to suppress the sintering shrinkage of the X-Y plane of the substrate green sheet. In the case of printing, when the thickness of the constrained layer exceeds 500 μm, cracks occur. Therefore, when the constrained layer is formed by printing, the preferable thickness of the constrained layer is 50 μm to 500 μm. On the other hand, when using a constrained layer in the form of a green sheet, the upper limit of the thickness of the constrained layer is not particularly limited.

When using an inorganic composition containing an organic binder in inorganic particles such as aluminum oxide, and adding a plasticizer, a dispersant, and a solvent to make the constraining layer, it is best to form a constrained layer with a given thickness on the carrying film. The green sheet is used so that the carrier film contact surface of the constraining green sheet closely overlaps with the upper and/or lower surfaces of the unsintered multilayer ceramic substrate including the external electrodes. At this time, since the degree of fixation between the inorganic particles and the substrate green sheet is appropriate, the constrained layer is sufficiently removed after sintering.

The force with which the constrained layer constrains the substrate green sheet can be controlled by the thickness of the constrained layer, the material, particle size, particle size distribution and content of the inorganic particles constituting the constrained layer, and the surface state of the constrained layer.

In the low-temperature sintered ceramic material used in the present invention, SiO ₂ , SrO, and auxiliary components are vitrified. A certain amount of Al ₂ O ₃ and TiO ₂ can enter the glass. However, at a calcination temperature of 700 to 850° C., since the glass component is not completely melted, the calcined body is in a state where an incomplete glass phase and a ceramic component are mixed. Furthermore, when the firing temperature is less than 700°C, vitrification is insufficient, and when it exceeds 850°C, fine pulverization of the calcined body becomes difficult. When the finely pulverized powder of such a calcined body is sintered at 800 to 1000°C, the glass component acts as a sintering accelerator, densifies the substrate green sheet, and reacts with Al ₂ O ₃ to precipitate SrAl ₂ Si ₂ O ₈ crystals, giving a high dielectric characteristic of Q(1/tanδ) to the substrate green sheet. That is, the sintered substrate has a structure composed of SrAl ₂ Si ₂ O ₈ crystals precipitated from the glass component, the remainder of the alumina crystals charged as the raw material, and the remainder of the glass component, and the glass component hardly permeates the constrained layer.

In FIG. 1 , a green multilayer ceramic substrate 10 is formed by laminating a plurality of substrate green sheets 8 on which internal electrodes 2 are printed using a paste mainly composed of Ag. Internal electrodes 2 of the respective layers are connected by through-hole electrodes 3 filled with conductors in through-holes provided in green sheet 8 . External electrodes 4 are formed on the upper and lower surfaces (and side surfaces as necessary) of the substrate 10 . There are cases where side electrodes are provided for connecting mounted components and circuit boards, but recently, the through-hole electrodes 3 are guided to the bottom surface of the substrate 10 to perform BGA or LGA connection using ball solder. In any case, it is necessary to form the external electrode 4 as an input/output terminal for connection to a ground electrode or a circuit board under the substrate 10 . On the upper surface of the substrate 10, as shown in FIG. The external electrode 4 is used for wiring connected to other elements.

The external electrodes 4 are formed by printing using Ag conductor paste at the stage of the green ceramic substrate 10 . After sintering, Ni and Au films are plated on the Ag electrodes as island electrodes. As the density of electrodes in multilayer ceramic substrates increases, the external electrodes 4 need to be mounted and arranged. Therefore, even if the positions of the external electrodes 4 are slightly misaligned, it may not be possible to connect mounted components. In addition, when impurities and the like adhere to the external electrodes 4, it becomes difficult to form a Ni film and an Au film, which causes poor connection. The presence of such external electrodes 4 also affects the flatness of the substrate 10 .

Since one multilayer ceramic substrate is at most a few microns square in size, generally, a large aggregate substrate of about 100 to 200 mm square is formed by forming a plurality of multilayer ceramic substrates as small pieces, and divided into individual substrates in the final process. small pieces. Therefore, the term "multilayer ceramic substrate" in this specification includes not only individual multilayer ceramic substrates but also aggregated substrates before division.

As shown in FIG. 3 , the unsintered multilayer ceramic substrate 10 has constrained layers 6 and 6 formed on the upper and/or lower surfaces, and then sintered to remove the constrained layers. After mounting chip components such as PIN diodes 7 b and chip capacitors 7 a on the upper surface of the multilayer ceramic substrate to form the module substrate 1 , it is divided into individual multilayer ceramic substrates along dividing grooves 5 . The module board 1 is mounted on a circuit board together with other electronic components, and an electronic device such as a mobile phone is configured using the circuit board.

FIG. 5 shows a multilayer ceramic substrate 21 with cavities 20 . The substrate 21 is also formed by laminating a plurality of green sheets 28 , but a cavity 20 for mounting the semiconductor element 7 c is formed in the upper part. Internal electrodes 22 are printed on each green sheet 28 and connected by through-hole electrodes 23 . External electrodes 24 for mounting chip components or external electrodes 25 serving as input/output terminals are formed on the upper surface and the lower surface of the substrate 21 . A covering layer 31 is appropriately formed around the external electrodes 24 and 25 to prevent the flow of solder. An electrode 26 for mounting a semiconductor element is formed in the cavity 20, and the semiconductor element 7c is mounted thereon using a solder paste 32 or the like. The input/output electrodes of the semiconductor element 7 c are connected to the terminal electrodes 25 by bonding wires 27 . Thermal vias 35 extending toward the rear side of the substrate are formed on the bottom surface of the cavity 20 and are connected to rear terminals 36 of the substrate. The backside terminals 36 are connection terminals for mounting and electrically connecting the substrate 21 itself to another larger-scale mounting substrate such as a PCB substrate mainly composed of a portable terminal or the like, and are arranged in a substantially grid pattern. Furthermore, Ni plating, Au plating, or the like is finally applied to the external electrodes formed on the front and back surfaces of the multilayer substrate 21 .

[2] Manufacturing method of multilayer ceramic substrate

(A) Material of substrate green sheet

The composition of the low-temperature sintered ceramic material constituting the substrate green sheet contains, for example, 10 to 60 mass % of Al in terms of Al ₂ O ₃ and 25 to 60 mass % in terms of SiO ₂ in the state of oxides as main components. % Si, 7.5 to 50 mass % of Sr in terms of SrO, and 0 to 20 mass % of Ti in terms of TiO ₂ (wherein the total amount of Al ₂ O ₃ , SiO ₂ , SrO and TiO ₂ is 100 quality%). The low-temperature sintered ceramic material may contain 0.1 to 10 parts by mass of Bi in terms of Bi ₂ O ₃ as an auxiliary component per 100 parts by mass of the main component. In the case of a composition consisting only of main components, the green sheet for a substrate is sintered at a temperature of 1000° C. or lower. In addition, in the case of a composition further containing auxiliary components, the green sheet for a substrate can be sintered even at a temperature of 900° C. or lower. In this way, high-conductivity metals such as silver, copper, and gold can be used as conductors for electrodes, and the green sheets for substrates and electrodes can be integrally sintered.

The auxiliary components preferably contain 0.1 to 10 parts by mass of Bi in terms of _Bi2O3 , _0.1 to 5 parts by mass of Na in terms of _Na2O , _and At least one selected from the group consisting of 0.1 to 5 parts by mass of K and 0.1 to 5 parts by mass of Co in terms of CoO. These auxiliary components have the effect of lowering the softening point of the glass obtained by sintering, so that a ceramic material sintered at a lower temperature can be obtained. In addition, dielectric properties with a high Q can be obtained at a sintering temperature of 1000° C. or lower.

In addition, the auxiliary component contains 0.01 to 5 parts by mass of Cu in terms of CuO, 0.01 to 5 parts by mass of Mn in terms of MnO ₂ , and 0.01 to 5 parts by mass of Ag with respect to 100 parts by mass of the main component. At least one selected from the group. These auxiliary components are added in order to achieve low-temperature sintering because they have an effect of promoting crystallization mainly in the sintering process.

(1) Al: 10 to 60 parts by mass (in terms of Al ₂ O ₃ )

When Al is more than 60% by mass in terms of Al ₂ O ₃ , the sintered density does not sufficiently increase in sintering at a low temperature of 1000° C. or lower, so the substrate becomes porous, and good properties cannot be obtained due to moisture absorption or the like. In addition, when Al is less than 10% by mass in terms of Al ₂ O ₃ , the substrate does not have good high strength. A more preferable content of Al is 40 to 55% by mass (in terms of Al ₂ O ₃ ).

(2) Si: 25 to 60% by mass (in terms of SiO ₂ )

When Si is less than 25% by mass or exceeds 60% by mass in terms of SiO ₂ , the ceramic substrate becomes porous because the sintered density does not sufficiently increase during sintering at a low temperature of 1000° C. or lower. A more preferable content of Si is 31 to 45% by mass (in terms of SiO ₂ ).

(3) Sr: 7.5 to 50% by mass (in terms of SrO)

When Sr is less than 7.5% by mass or exceeds 50% by mass in terms of SrO, the sintered density does not sufficiently increase during sintering at a low temperature of 1000° C. or lower, and thus the ceramic substrate becomes porous. A more preferable content of Sr is 7.5-17.5 mass % (SrO conversion).

(4) Ti: 0 to 20% by mass (in terms of TiO ₂ )

When Ti is more than 20% by mass in terms of TiO ₂ , the sintered density does not sufficiently increase in low-temperature sintering at 1000° C. or lower, and the substrate becomes porous. In addition, the temperature coefficient of the resonant frequency of ceramics also increases as the content of Ti increases, and good characteristics cannot be obtained. The temperature coefficient τf of the resonant frequency of ceramics not containing Ti is -20 to -40 ppm/°C, but τf increases as the compounding amount of Ti increases. Therefore, it is very easy to adjust τf to 0 ppm/°C by using the compounding amount of Ti. A more preferable content of Ti is 0 to 10% by mass (in terms of TiO ₂ ).

(5) Bi: 0.1 to 10 parts by mass

Bi has the effect of lowering the softening point of the glass produced in the calcination step and lowering the sintering temperature. Bi can also enable high-Q dielectric properties to be obtained at sintering temperatures below 1000°C. However, when Bi is more than 10 parts by mass relative to 100 parts by mass of the main component in terms of Bi ₂ O ₃ , the Q value becomes small. Therefore, Bi is preferably 10 parts by mass or less, more preferably 5 parts by mass or less. On the other hand, when Bi is less than 0.1 parts by mass, there is substantially no effect of low-temperature sintering. Therefore, Bi is preferably 0.1 parts by mass or more, and more preferably 0.2 parts by mass or more.

(6) Na, K and Co: 0.1 to 5 parts by mass

When Na, K, and Co are respectively less than 0.1 parts by mass in terms of Na ₂ O, K ₂ O, and CoO with respect to 100 parts by mass of the main components, the effect of lowering the softening point of glass is insufficient. On the other hand, when each exceeds 5 parts by mass, the dielectric loss becomes too large. Therefore, all of Na, K, and Co are preferably 0.1 to 5 parts by mass.

(7) Cu and Mn: 0.01 to 5 parts by mass

Cu and Mn have the effect of promoting the crystallization of the ceramic dielectric and realizing low-temperature sintering in the sintering process. When both Cu and Mn are less than 0.01 parts by mass (in terms of CuO or MnO ₂ ), the addition effect is insufficient, and therefore a substrate with a high Q value cannot be obtained during sintering at 900° C. or lower. Moreover, when exceeding 5 mass parts, low-temperature sinterability will be impaired. Therefore, Cu and Mn are preferably 0.01 to 5 parts by mass.

(8) Ag: 0.01 to 5 parts by mass

Ag has the effect of lowering the softening point of glass and promoting crystallization, and can realize low-temperature sintering. However, when Ag is 0.01 parts by mass, the effect of addition is insufficient. On the other hand, when it exceeds 5 parts by mass, the dielectric loss becomes too large. Therefore, Ag is preferably 0.01 to 5 parts by mass. Ag is more preferably 2 parts by mass or less.

(9) Zr: 0.01 to 2 parts by mass

Moreover, when 0.01-2 mass parts of Zr is contained in conversion of _ZrO2 , the mechanical strength of a board|substrate will improve.

(10) Pb and B

The low-temperature sintered ceramic material used in the present invention does not contain Pb and B contained in conventional materials. Since PbO is a hazardous substance, it costs a lot of money to dispose of PbO-containing waste, and care must also be taken in the handling of PbO in the production process. In addition, _B2O3 has problems such as dissolving in water and alcohol during the manufacturing process, _segregating during drying, or reacting with electrode materials during sintering, or reacting with organic binders to deteriorate the performance of the binder. . The low-temperature sintered ceramic material used in the present invention is environmentally friendly because it does not contain such harmful elements.

(B) Fabrication of substrate green sheets

The powders of the main components and auxiliary components were wet mixed in a ball mill. After heating and drying the obtained slurry to evaporate water, it is crushed and calcined at 700 to 850°C. The calcination time is preferably 1 to 3 hours. The calcined body is put into a ball mill and wet pulverized for 10 to 40 hours to form a fine powder with an average particle diameter of 0.6 to 2 μm. The calcined body finely pulverized powder is a particle in which ceramic particles are partially or entirely covered with glass.

The organic binder is appropriately selected in order to adjust the strength, porosity, pressure-bonding property, dimensional stability, etc. of the green sheet. Preferred organic binders are, for example, polyvinyl butyral resins and polymethacrylic resins. The added amount of the organic binder is 5 mass % or more of the whole green sheet, Preferably it is 10-20 mass %.

It is preferable to add butyl phthaloyl glycolate butyl (BPBG), n-butyl di-phthalate, etc. as a plasticizer, and it is preferable to add ethanol, butanol, toluene, isopropanol, etc. as a solvent. By mixing these raw materials with a ball mill, a slurry of calcined body finely pulverized powder was prepared. In order to improve the uniformity of the slurry, it is also effective to add a dispersant as needed.

After defoaming the slurry under reduced pressure and adjusting the viscosity by partially evaporating the solvent, the slurry was formed into a sheet on a carrier film by the doctor blade method. As the carrier film, a polyethylene terephthalate (PET) film is preferable in view of mechanical strength, surface smoothness, and the like. The obtained substrate green sheet is cut into a predetermined size according to the carrier film.

(C) Fabrication of unsintered multilayer ceramic substrate

After the substrate green sheet is sufficiently dried, through-holes 3 are provided, the through-holes 3 are filled with Ag-based conductor paste, and then internal electrode patterns 2 are printed using the Ag-based conductor paste. Patterns of the external electrodes 4 are formed on the upper and lower substrate green sheets, respectively. After laminating these substrates with green sheets, thermocompression bonding is performed. The thickness of the green sheet laminate is determined by the target module, but generally, it is preferably set to 1.0 to 2.0 mm.

The thermocompression bonding conditions are preferably a temperature of 50 to 95° C. and a pressure of 50 to 200 kg/cm ² (4.9 to 19.6 MPa). The pattern of the external electrodes 4 may also be formed after thermocompression bonding. Thereafter, as shown in FIG. 2 , dividing grooves 5 are formed in accordance with the dimensions of the substrate pieces 1A to 4A, 1B to 4B, and 1C to 4C (all symbols are not shown). When the dividing groove 5 is formed, the inorganic paste of the constraining layer also enters the groove, and the constraining force becomes larger.

(D) Preparation of paste for restraint

The constrained layer 6 is composed of inorganic particles that are not sintered at the sintering temperature of the unsintered multilayer ceramic substrate made of low-temperature sintered ceramic material. As the inorganic particles, alumina powder, zirconia powder, or the like is preferably used. In order to control the binding force, the average particle diameter of the inorganic particles is preferably 0.3 to 4 μm. When the average particle size of the inorganic particles is less than 0.3 μm, the amount of binder required to obtain the viscosity required for printing increases (the filling rate of the inorganic particles decreases), and sufficient binding force cannot be exerted. When the average particle diameter of the inorganic particles exceeds 4 μm, the binding force in the dividing groove 5 becomes weak. The average particle diameter of the inorganic particles is preferably 1 to 4 μm.

The average particle diameter Dc of the inorganic particles is preferably adjusted to be 0.3 to 4 times the average particle diameter Ds of the ceramic material powder or calcined body fine powder constituting the substrate green sheet. In particular, in order to prevent the inorganic particles from remaining on the external electrodes of the unsintered multilayer ceramic substrate, the average particle diameter Dc of the inorganic particles is preferably equal to or greater than the average particle diameter Ds of the ceramic powder or calcined body fine powder. Specifically, Dc/Ds is preferably 1-4, more preferably 1.5-4.

The selection conditions of the organic binder in the constraining layer are not stricter than those in the case of the substrate green sheet, and the addition amount may be small. As the organic binder, fiber-based resins or polymethacrylic resins with good thermal decomposability are preferable. In addition, as the plasticizer, butylphthalyl butyl glycolate (BPBG), n-butyl di-phthalate, and the like are preferable. As the solvent, alcohols such as ethanol, butanol, isopropanol and terpineol are preferable. When the constraining layer is formed by printing, the amount of the organic binder added is preferably 1.5 to 4% by mass in order to ensure the viscosity required for printing and the adhesion between the powders in the paste and the substrate.

(E) Preparation of green sheets for restraint

When a green sheet is used as the constraining layer 6, a sheet of an inorganic composition to which 8 to 15 parts by weight of an organic binder and a solvent are added to 100 parts by weight of inorganic particles is formed on a carrier film by a doctor blade method. It is also possible to add 4 to 8 parts by weight of plasticizer and a small amount of dispersant. Inorganic particles, organic binders, plasticizers and solvents are mixed with a ball mill to make a slurry for restraint.

After defoaming the slurry under reduced pressure and adjusting the viscosity by partially evaporating the solvent, the slurry was formed into a thin sheet on the carrier film by the doctor blade method. The obtained constraining green sheet is cut into a predetermined size according to the carrier film.

(F) Formation of constrained layer on unsintered multilayer ceramic substrate

When forming the constraining layer 6 on the upper and/or lower surfaces of the green multilayer ceramic substrate 10, (a) the paste of the inorganic composition is printed on the green multilayer ceramic substrate to a required thickness (repeatedly as required) printing and drying), or (b) prefabricating a constraining green sheet of required thickness from the inorganic composition so that it overlaps with the unsintered multilayer ceramic substrate, or (c) superimposing the constraining green sheet on the printed constraining layer raw slices, or (d) combining them.

The thickness of the constrained layer is 50 μm or more on one side of the green multilayer ceramic substrate. When the thickness of the constrained layer is less than 50 μm, the constraining force is insufficient, and the sintering shrinkage in the X-Y plane of the unsintered multilayer ceramic substrate cannot be sufficiently suppressed. When the constrained layer is more than 50 μm, the sintering shrinkage of the X-Y plane of the unsintered multilayer ceramic substrate can be suppressed below 1%. When a green sheet is used as the constraining layer, although there is no particular limitation on the upper limit of the thickness, when the constraining layer is printed, cracks may be generated in the printed layer with a thickness exceeding 500 μm. Therefore, when the constraining layer is formed by printing, the appropriate thickness is 50 μm to 500 μm.

When using green sheets for constraining, they are stacked and crimped on the upper and/or lower surfaces of the green multilayer ceramic substrate including the external electrodes so that the contact surface with the carrier film is in close contact with the surface of the green multilayer ceramic substrate. . When the contact surface with the carrier film is brought into close contact with the unsintered multilayer ceramic substrate, it is extremely easy to remove the constrained layer after sintering. The reason for this is presumed as follows. That is, the binder in the constraining green sheet is concentrated on the contact surface with the carrier film. As a result, the binding force to the green multilayer ceramic substrate at the interface with the carrier film is large, and the fixation of inorganic particles to the green multilayer ceramic substrate is relieved (buffer effect). Therefore, when the contact surface of the constraining green sheet and the carrier film is brought into close contact with the surface of the unsintered multilayer ceramic substrate, it is possible to easily remove the inorganic particles after sintering while maintaining sufficient constraining force.

There is no theoretical limit to the thickness of the constraining green sheet, but practically many printing and drying steps are required to produce a thick constraining layer by printing. However, the highly fluid paste used in the printing method enters recesses such as dividing grooves of the green multilayer ceramic substrate, and a high confining effect is obtained. Therefore, it is preferable to form a first constraining layer of a certain thickness by a printing method, and to overlay a green sheet of a desired thickness as a second constraining layer thereon. At this time, it is preferable to form the first constrained layer with a thickness of 10 μm or more by printing, and to form the second constrained layer by laminating the green sheet for constraining thereon, to form a constrained layer with a thickness of 50 μm or more in total.

The constraining green sheet was bonded to the unsintered multilayer ceramic substrate by thermocompression. The conditions for thermocompression bonding of the substrate green sheet to the green multilayer ceramic substrate are a temperature of 50-90°C and a pressure of 50-200kg/cm ² (4.9-19.6MPa).

(G) Sintering of unsintered multilayer ceramic substrate with constrained layer

After holding at 400 to 650° C. for 2 to 10 hours to remove the binder, sintering is carried out by holding at 800 to 1000° C. for 1 to 4 hours. When the sintering temperature is less than 800°C, even if the sintering time is prolonged, it is difficult to achieve densification of the substrate. In addition, when the sintering temperature exceeds 1000°C, the formation of Ag-based electrode materials becomes difficult, and it is impossible to obtain a material with ideal dielectric properties. multilayer ceramic substrate.

(H) Removal of Constrained Layer

After sintering, alumina particles adhering to the surface of the multilayer ceramic substrate (especially the external electrodes) are removed. This is performed by placing the sintered multilayer ceramic substrate in water in an ultrasonic cleaning tank and applying ultrasonic waves. Although most of the alumina particles can be removed by ultrasonic cleaning, the alumina particles on the external electrodes (such as Ag pads) cannot be completely removed by ultrasonic cleaning. Thereby, the alumina particles are removed by sandblasting with controlled impact to such an extent that the external electrodes are not damaged as needed. As the sand material, alumina, glass, zircon, resin particles and the like can be used. Furthermore, even if some alumina particles remained after ultrasonic cleaning, the coating property was relatively good. In particular, when aluminum oxide particles remain moderately, the corrosion resistance of the external electrode made of Ag improves.

(I) Mounting of components and division of assembly substrates

On the Ag pad from which the aluminum oxide particles were removed, a Ni plating film, an Au plating film, etc. were formed by an electroless plating method. After screen-printing solder patterns on external electrodes metallized with Ni and Au, components such as semiconductor elements are mounted and connected by reflow. In the case of a semiconductor element for wire bonding, wire bonding connection is performed after reflow processing. Finally, individual multilayer ceramic substrates are obtained by cutting the collective substrate along the dividing grooves.

Figure 6(a) shows the manufacturing process of the multilayer ceramic substrate when the constraining layer is formed by printing the inorganic particle paste on the unsintered multilayer ceramic substrate, and Figure 6(b) shows the process of laminating the constraining green sheet on the The manufacturing process of the multilayer ceramic substrate when the constrained layer is formed on the unsintered multilayer ceramic substrate. Figure 6(c) shows that the first constrained layer is formed by printing the inorganic particle paste on the unsintered multilayer ceramic substrate. Then, the manufacturing process of the multilayer ceramic substrate when the second constraining layer is formed by laminating the constraining green sheet on the unsintered multilayer ceramic substrate.

Although the present invention will be described in more detail using the following examples, the present invention is not limited to these examples.

Example 1

Al ₂ O ₃ powder with a purity of 99.9% and an average particle size of 0.5 μm, SiO ₂ powder with a purity of 99.9% or more and an average particle size of 0.5 μm or less, and SrCO ₃ powder with a purity of 99.9% and an average particle size of 0.5 μm and a purity of 99.9% And TiO ₂ powder with an average particle size of 0.5 μm and Bi ₂ O ₃ powder, Na ₂ CO ₃ powder, K ₂ CO ₃ powder, CuO powder, Ag powder, MnO with a purity of 99.9% and an average particle size of 0.5-5 μm, respectively ₂ powder and Co ₃ O ₄ powder, and produced low-temperature sintered ceramic materials with the composition shown in Table 1. In the sample No., those without ^* are samples within the scope of the present invention, and those with ^* are outside the scope of the present invention (the same applies hereinafter).

(B) Fabrication of substrate green sheets

The mixed powder having the composition shown in Table 1 was charged into a ball mill made of polyethylene, further, media balls made of zirconia and pure water were charged, and wet mixing was performed for 20 hours. The obtained slurry was heat-dried, crushed with an automatic mortar, placed in an alumina crucible, and calcined at 800° C. for 2 hours. The obtained calcined body was put into the ball mill, wet pulverized for 17 hours, and then dried to obtain a fine powder having an average particle diameter of 1 μm.

In 100 parts by weight of the calcined body micropowder, add 15 parts by weight of polyvinyl butyral resin as an organic binder, add 7.5 parts by weight of butyl phthaloyl glycolate (BPBG) as a plasticizer, And ethanol was added as a solvent, and it mixed with the ball mill, and the slurry was produced. Also, a dispersant was not added.

The slurry was defoamed under reduced pressure, and ethanol was partially evaporated to adjust the viscosity to about 7 Pa·s. The slurry was formed into a thin sheet on a carrier film made of PET by the doctor blade method, and dried to obtain a green sheet for a substrate with a thickness of 0.15 mm. The substrate green sheet was cut into 180 mm squares according to the carrier sheet.

After the substrate green sheet was sufficiently dried, internal electrode patterns and external electrode patterns were formed using a conductive paste mainly composed of Ag. The substrate green sheets on which the electrodes were formed were temporarily crimped one by one at a temperature of 60°C and a pressure of 30kg/cm ² (2.8MPa), and then pressed at a temperature of 85°C and a pressure of 110kg/cm ² (10.8MPa). thermocompression. The obtained green multilayer ceramic substrate (assembled substrate) had a thickness of 1.3 mm.

The cutting edge was pressed against the green multilayer ceramic substrate (assembled substrate), and division grooves 5 having an isosceles triangular cross-sectional shape with a width of 0.15 mm and a depth of 0.1 mm were formed at intervals of 10 mm×15 mm.

With respect to 100 parts by weight of alumina powder with an average particle diameter of 0.5 μm, 10.2 parts by weight of polyvinyl butyral resin as an organic binder, 6.2 parts by weight of BPBG and ethanol as a plasticizer were mixed with a ball mill to produce Slurry with no dispersant added. The slurry was defoamed under reduced pressure to partially evaporate the solvent, and then adjusted to a viscosity of about 5 Pa·s. Then, this slurry was formed into a sheet form on a carrier film made of PET by the doctor blade method, and it was dried to obtain a green sheet for restraint with a thickness of 0.15 mm. The green sheet for restraint was cut into 180 mm squares according to the carrier sheet.

In such a way that the contact surface of the carrier film is in close contact with the surface of the assembly substrate, the constraining green sheets are superimposed on the upper and lower surfaces of the assembly substrate, and thermocompression bonded at a temperature of 85°C and a pressure of 110kg/cm ² (10.8MPa) to form an integrated laminate.

In the batch furnace of the atmospheric atmosphere, the laminate was kept at 500°C for 4 hours to remove the binder, then the temperature was raised to 900°C at a rate of 3°C/min, and it was sintered by holding at this temperature for 2 hours. Cool naturally in the furnace.

Alumina particles were removed from the sintered laminate by ultrasonic cleaning. With respect to the obtained assembly substrate, the shrinkage rate and its variation in the X-Y plane, compactness, high-frequency characteristics, and the state of the external electrodes were evaluated by the following methods. The evaluation results are shown in Table 1.

(1) Shrinkage in the X-Y plane

Select a total of 8 chip parts located in the four corners and the center of the four sides of the collective substrate before forming the constraining layer, and measure the X-axis direction and the Y-axis direction of the two diagonal lines of each chip part with a three-dimensional coordinate measuring device. The distance of XY coordinates X ₀ , Y ₀ is obtained. Similarly, the distances in the X-axis direction and the Y-axis direction of the two diagonal lines of each small piece were measured for the sintered aggregate substrate, and XY coordinate values X _n and Y _n were obtained. The average ratio of X _n /X ₀ and Y _n /Y ₀ for eight small pieces (n=1 to 8) was used as the sintering shrinkage of the aggregated substrate sintered after forming the constrained layer. In addition, the deviation of these ratios was regarded as the deviation of shrinkage rate.

(2) Density

Based on the thickness D ₁ of the aggregated substrate after sintering relative to the thickness (Z-axis direction) D ₀ of the aggregated substrate before forming the constraining layer, the sintering shrinkage ratio (D ₁ /D ₀ ) in the Z-axis direction was obtained by using the following The benchmark evaluates compactness.

D ₁ /D ₀ below 60%: good

D ₁ /D ₀ more than 60%: bad

(3) High frequency characteristics

The dielectric loss tangent tan δ of the sintered aggregate substrate was measured at 2 GHz, and the high-frequency characteristics were evaluated using the following criteria.

tanδ below 0.01: good

tan δ exceeding 0.01: poor

(4) State of external electrodes (coating properties)

After sintering, each sample from which the constrained layer was removed by ultrasonic cleaning was subjected to Ni plating with an average film thickness of 5 μm and Au plating with an average film thickness of 0.4 μm using commercially available electroless Ni plating solution and Au plating solution. The plated external electrodes were observed with a SEM, and the state of the external electrodes was evaluated based on the area ratio of the plated film adhering to the external electrodes according to the following criteria.

Coating area ratio is 100%: excellent

The area ratio of the coating is less than 100% and more than 90%: Good

The area ratio of the coating film is less than 90%: bad

Table 1 Sample No. Al ₂ O ₃ SiO ₂ SrO TiO ₂ Bi ₂ O ₃ Na ₂ O K ₂ O CoO CuO _MnO2 Ag ^* 1 10 50 40 - - - - - - - - 2 15 50 35 - 2 1 0.5 - 0.3 - 0.5 3 20 50 30 - 2 1 0.5 - 0.3 - 0.5 4 25 35 40 - 3 0.1 - - - - - 5 25 35 40 - 1 - - 0.5 - - - ^* 6 25 35 40 - 0.2 - - 6 - - - 7 51.5 31 17.5 - 2 1 0.5 - 0.3 - 0.5 ^* 8 51.5 31 17.5 - 12 1 0.5 - 0.3 - 0.5 9 51.5 31 17.5 - 3 1 0.5 - 0.3 - - 10 51.5 31 17.5 - 3 1.5 0.5 - 0.3 - - ^* 11 51.5 31 17.5 - 3 7 0.5 - 0.3 - 0.5 12 51.5 31 17.5 - 3 1 1 - 0.3 - 0.5 ^* 13 51.5 31 17.5 - 3 1 7 - 0.3 - 0.5 14 51.5 31 17.5 - 3 1 0.5 - 0.5 - 0.5 ^* 15 51.5 31 17.5 - 3 1 0.5 - 7 - 0.5 16 55 32.5 12.5 - 2 1 0.5 - 0.3 - 0.5 17 30 45 15 10 3 1.5 0.5 - 0.5 - 0.5 18 30 45 15 10 2 1 0.5 - 0.3 - 0.5 19 30 45 15 10 3 1 0.5 - 0.5 - - ^* 20 35 50 5 10 3 1.5 0.5 - 0.5 - - twenty one 40 35 15 10 2 1 0.5 - 0.3 - 0.5 twenty two 43.27 38.46 14.42 3.85 2 2 0.5 - 0.3 - - twenty three 43.27 38.46 14.42 3.85 2 2 0.5 0.2 0.3 - - twenty four 43.27 38.46 14.42 3.85 2 2 0.5 0.4 0.3 - - 25 43.27 38.46 14.42 3.85 2 2 0.5 - 0.3 0.2 - 26 43.27 38.46 14.42 3.85 2 2 0.5 - 0.3 0.4 - 27 48.08 36.06 12.02 3.84 2 2 0.5 - 0.3 - - 28 46 38 12 4 2.5 2 0.5 - 0.3 - - 29 48 38 10 4 2.5 2 0.5 - 0.3 0.5 - 30 50 36 10 4 2.5 2 0.5 - 0.3 0.5 - 31 50.5 38 7.5 4 2.5 2 0.5 - 0.3 0.5 - 32 48 36 12 4 2.5 2 0.5 - 0.3 - 0.5 33 48 36 12 4 2.5 2 0.5 - 0.3 0.5 - 34 50 32.5 12.5 5 2 1 0.5 - 0.3 - 0.5

Table 1 (continued) Sample No. Firing temperature (°C) XY plane Density High frequency characteristics Status of external electrodes Shrinkage(%) Deviation (±%) ^{(1) *} 1 1000 - - bad bad - 2 950 0.8 0.07 good good excellent 3 875 0.7 0.06 good good excellent 4 875 0.7 0.06 good good excellent 5 875 0.8 0.07 good good excellent ^* 6 950 - - bad bad - 7 900 0.6 0.05 good good excellent ^* 8 900 - - bad bad - 9 900 0.6 0.05 good good excellent 10 900 0.6 0.05 good good excellent ^* 11 950 - - bad bad - 12 900 0.6 0.05 good good excellent ^* 13 950 - - bad bad - 14 900 0.6 0.05 good good excellent ^* 15 950 - - bad bad - 16 900 0.7 0.06 good good excellent 17 925 0.7 0.06 good good excellent 18 950 0.7 0.06 good good excellent 19 950 0.7 0.06 good good excellent ^* 20 950 - - bad bad - twenty one 950 0.5 0.05 good good excellent twenty two 925 0.5 0.05 good good excellent twenty three 925 0.5 0.05 good good excellent twenty four 925 0.5 0.05 good good excellent 25 925 0.5 0.05 good good excellent 26 925 0.5 0.05 good good excellent 27 900 0.5 0.05 good good excellent 28 900 0.5 0.05 good good excellent 29 900 0.4 0.05 good good excellent 30 900 0.4 0.05 good good excellent 31 900 0.5 0.05 good good excellent 32 900 0.5 0.05 good good excellent 33 900 0.5 0.05 good good excellent 34 950 0.4 0.05 good good excellent

Note: (1) Expressed in absolute value.

It can be seen from Table 1 that the sintering shrinkage rate in the X-Y plane of the multilayer ceramic substrate of the present invention is less than 1%, and the deviation of the sintering shrinkage rate is within ±0.07%. In addition, the multilayer ceramic substrate of the present invention is good in any of denseness, high-frequency characteristics, and the state of external electrodes.

Example 2

Use Al ₂ O ₃ powder with a purity of 99.9% and an average particle size of 0.5 μm, SiO ₂ powder with a purity of 99.9% or more and an average particle size of 0.5 μm or less, and SrCO ₃ powder with a purity of 99.9% and an average particle size of 0.5 μm, respectively. 99.9% _Bi2O3 powder, _Na2CO3 powder, _K2CO3 powder, CuO powder and _MnO2 powder with an _average particle size of 0.5 to 5 μm were prepared as _shown below containing Al, Si, _Sr and A low-temperature sintered ceramic material (corresponding to sample No. 29 in Table 1) having a main component of Ti and auxiliary components of Bi, Na, K, Cu, and Mn.

main ingredient

Al: 48% by mass (in terms of Al ₂ O ₃ )

Si: 38% by mass (in terms of SiO ₂ )

Sr: 10% by mass (in terms of SrO)

Ti: 4% by mass (in terms of TiO ₂ )

Auxiliary components (relative to 100 parts by mass of main components)

Bi: 2.5 parts by mass (converted to Bi ₂ O ₃ )

Na: 2 parts by mass (converted to Na ₂ O)

K: 0.5 parts by mass (converted to K ₂ O)

Cu: 0.3 parts by mass (calculated as CuO)

Mn: 0.5 parts by mass (converted to MnO ₂ )

In the same manner as in Example 1, the low-temperature sintered ceramic material was calcined, and the obtained calcined bodies were finely pulverized into average particle diameters of about 1 μm and about 3 μm, respectively, to produce green sheets for substrates.

A constrained layer having a total thickness of 30 to 550 μm is formed by using alumina particles having an average particle diameter of 0.2 to 5 μm by a printing method and/or a green sheet method. Separation grooves were formed in samples other than No. 44. Laminates made of unsintered multilayer ceramic substrates provided with constrained layers were all sintered under the same conditions as in Example 1. From the sintered laminate, the alumina particles in the constrained layer were removed by ultrasonic cleaning to obtain a composite substrate. For each assembly substrate, the shrinkage rate and its variation in the X-Y plane and the coating property were evaluated in the same manner as in Example 1. In addition, the residual amount and particle diameter of alumina particles on the external electrodes, and warpage of the substrate were evaluated by the following methods. Solder erosion state of bending and external electrodes. The evaluation results are shown in Table 2.

(1) Amount of residual alumina on the external electrodes

Using FE-SEM (Hitachi S-4500, acceleration voltage 15kV), conduct EDX analysis of Ag-Kα and Al-Kα on the surface of the external electrode (excluding impurities such as oxygen), and obtain Ag from the peak intensity of Ag and Ag by the standardless method and the mass % of Al. Since the mass % of Al is proportional to the remaining amount of aluminum oxide on the electrode surface, the remaining amount of aluminum oxide is represented by the mass % of Al [Al/(Al+Ag)×100(%)].

(2) Number of alumina particles

In the FE-SEM photo (3000-5000 times) of the surface of the external electrode, in the area where alumina particles exist, a straight line with a length equivalent to 20 μm is drawn arbitrarily, and the crossed alumina particles (limited to those used in the constrained layer) are selected. The average of the number of alumina particles intersecting two straight lines with a large number of particles having a particle diameter corresponding to the particle diameter of the alumina particles was obtained. Furthermore, carbon was vapor-deposited on each sample, and EDX analysis was performed at an acceleration voltage of 15 kV.

(3) warping

When measuring the shrinkage rate, the height difference (Z-axis direction) between the diagonal lines of any one of the measured small piece parts was obtained using a three-dimensional coordinate measuring device, and it was regarded as warpage. The allowable value of warpage is about 40 μm.

(4) Solder erosion state

After immersing each sample from which the constrained layer was removed by ultrasonic waves in a Sn _3.5 -Ag solder bath kept at 245° C. for 1 minute, the external electrodes were observed with an optical microscope. Based on the area ratio of metal (Ag+attached solder) on the external electrodes, the state of solder erosion of each sample was evaluated according to the following criteria.

The area ratio of the metal of the external electrode is more than 95%: excellent

The area ratio of the metal of the external electrode is less than 95% and more than 85%: Good

The area ratio of the metal of the external electrodes is less than 85%: Defective

Table 2 Sample No. Average particle size (μm) of ceramic particles ⁽¹⁾ binding layer Separation groove Average particle size of alumina (μm) Printing film thickness (μm) Film thickness of green sheet (μm) Adhesive surface ⁽²⁾ Total thickness of constrained layer (μm) 35 1 0.3 30 300 PET surface ⁽³⁾ 330 have 36 1 0.4 30 300 PET surface 330 have 37 1 0.5 10 40 PET surface 50 have 38 1 0.5 10 100 PET surface 110 have 39 1 0.5 0 300 PET surface 300 have 40 1 0.5 10 300 PET surface 310 have 41 1 0.5 10 500 PET surface 510 have 42 1 0.5 30 100 PET surface 130 have 43 1 0.5 30 300 PET surface 330 have 44 1 0.5 30 300 PET surface 330 none 45 1 0.5 50 0 - 50 have 46 1 0.5 50 40 PET surface 90 have 47 1 0.5 50 100 PET surface 150 have 48 1 0.5 50 300 PET surface 350 have 49 1 0.5 50 500 PET surface 550 have 50 1 1 30 300 PET surface 330 have 51 1 1.5 30 300 PET surface 330 have 52 1 2 30 300 PET surface 330 have 53 1 3 30 300 PET surface 330 have 54 1 4 30 300 PET surface 330 have 55 1 0.5 0 300 free surface 300 have 56 1 0.5 30 300 free surface 330 have 57 3 0.9 0 300 PET surface 300 have 58 3 0.9 30 300 PET surface 330 have 59 3 0.9 0 300 free surface 300 have 60 3 0.9 30 300 free surface 330 have ^* 61 1 0.2 30 300 PET surface 330 have ^* 62 1 0.2 30 0 - 30 have ^* 63 1 5 30 300 PET surface 330 have ^* 64 1 0.5 500 0 - 500 have

Note: (1) Ceramic particles in substrate green sheets

(2) The surface of the constrained layer that is in close contact with the surface of the unsintered multilayer ceramic substrate

(3) The contact surface of the constraining green sheet and the PET film is in close contact with the unsintered multilayer ceramic substrate.

Table 2 (continued) Sample No. Alumina particles on external electrodes Shrinkage in XY plane (%) Deviation (±%) ⁽¹⁾ Warpage (μm) Solder Erosion Coating Al (mass%) Particle size (μm) Number per 20μm 35 10 0.3 4.5 0.7 0.05 20 excellent good 36 8 0.4 3.5 0.7 0.05 19 excellent good 37 6 0.5 2.5 1 0.07 25 excellent excellent 38 6 0.5 2.5 0.7 0.05 19 excellent excellent 39 6 0.5 2.5 0.5 0.05 16 excellent excellent 40 6 0.5 2.5 0.4 0.04 15 excellent excellent 41 6 0.5 2.5 0.3 0.03 13 excellent excellent 42 6 0.5 2.5 0.6 0.05 17 excellent excellent 43 6 0.5 2.5 0.4 0.03 13 excellent excellent 44 6 0.5 2.5 0.3 0.02 10 excellent excellent 45 6 0.5 2.5 1 0.07 25 excellent excellent 46 6 0.5 2.5 0.8 0.06 twenty three excellent excellent 47 6 0.5 2.5 0.7 0.05 17 excellent excellent 48 6 0.5 2.5 0.4 0.03 12 excellent excellent 49 6 0.5 2.5 0.3 0.02 11 excellent excellent 50 5 1 2 0.5 0.04 16 excellent excellent 51 3 1.5 1 0.5 0.04 12 excellent excellent 52 3 2 1 0.5 0.04 15 excellent excellent 53 2 3 0.5 0.7 0.05 18 excellent excellent 54 2 4 0.2 1 0.07 25 excellent excellent 55 12 0.5 5 0.5 0.04 15 excellent good 56 6 0.5 2.5 0.4 0.03 13 excellent excellent 57 5 0.9 2 0.5 0.05 16 excellent excellent 58 5 0.9 2 0.4 0.03 13 excellent excellent 59 10 0.9 4 0.5 0.04 15 excellent good 60 6 0.9 2.5 0.4 0.03 13 excellent excellent ^* 61 twenty three 0.2 16 1 0.11 26 - - ^* 62 ⁽²⁾ - - - - - - - - ^* 63 ⁽³⁾ 2 5 0 1.2 0.13 45 excellent excellent ^* 64 ⁽²⁾ - - - - - - - -

Note: (1) expressed in absolute value

(2) The constrained layer produces cracks after printing and drying

(3) The binding force is weak.

Example 3

A mixed powder of glass powder and ceramic powder is used for the substrate green sheet. That is, a mixture of ceramic powders (oxides or carbonates) other than Al ₂ O ₃ powders among the raw material powders for low-temperature sintered ceramic materials of the same composition as in Example 2 was put into an alumina crucible, and heated in an electric furnace. Heat treatment was performed at 1400° C. for 2 hours to obtain a transparent glass block. After the glass block was cut out with a microtome, it was pulverized into average particle diameters of approximately 1 μm and 3 μm by a crusher and a ball mill, respectively. 48% by mass of alumina powder with an average particle size of about 1 μm, an organic binder, a plasticizer, and a solvent were mixed in a ball mill with 52% by mass of glass powder with an average particle size of about 1 μm, and the obtained slurry was prepared. Green sheets for substrates. Similarly, a green sheet for substrates was produced from a slurry obtained by mixing alumina powder with an average particle size of about 3 μm, an organic binder, a plasticizer, and a solvent with glass powder with an average particle size of about 3 μm. . In the same manner as in Example 1, substrate green sheets were stacked and bonded by thermocompression, and dividing grooves were formed as necessary.

Using alumina particles with an average particle diameter of 0.2 to 5 μm, constrained layers having a total thickness of 30 to 550 μm were formed by printing and/or green sheet method. After sintering each of the obtained laminates, the alumina particles in the constrained layer were removed by ultrasonic cleaning. Also, the conditions other than the above are the same as in Example 1.

For each of the obtained multilayer ceramic substrates, the shrinkage rate and deviation in the X-Y plane, the warpage of the substrate, the state of solder erosion of the external electrodes, the coating property, and the oxidation on the external electrodes were evaluated under the same conditions as in Examples 1 and 2. Residual form of aluminum. The evaluation results are shown in Table 3.

table 3 Sample No. Constraint layer Average particle size of alumina (μm) Printing film thickness (μm) Film thickness of green sheet (μm) Adhesive surface ⁽¹⁾ Total thickness of constrained layer (μm) 65 0.5 0 300 PET surface ⁽²⁾ 300 66 0.5 30 300 PET surface 330 67 0.5 30 300 PET surface 330 68 1 0 300 PET surface 300 69 2 0 300 PET surface 300 70 3 0 300 PET surface 300 71 4 0 300 PET surface 300 72 0.5 0 300 free surface 300 73 0.5 30 300 free surface 330 74 1 0 300 free surface 300 75 2 0 300 free surface 300 76 3 0 300 free surface 300 77 4 0 300 free surface 300 78 0.9 0 300 PET surface 300 79 0.9 30 300 PET surface 330 80 2 0 300 PET surface 300 81 3 0 300 PET surface 300 82 4 0 300 PET surface 300 83 0.9 0 300 free surface 300 84 0.9 30 300 free surface 330 85 2 0 300 free surface 300 86 3 0 300 free surface 300 87 4 0 300 free surface 300 ^* 88 0.2 30 0 - 30 ^* 89 5 30 300 PET surface 330 ^* 90 0.5 500 0 - 500 ^* 91 3 0 30 free surface 30 92 3 0 50 free surface 50 93 3 0 90 free surface 90

Note: (1) The surface of the constrained layer that is in close contact with the surface of the unsintered multilayer ceramic substrate

(2) The contact surface of the constraining green sheet and the PET film is in close contact with the unsintered multilayer ceramic substrate.

Table 3 (continued) Sample No. Average particle size (μm) of ceramic particles ⁽¹⁾ Separation groove Alumina particles on external electrodes Al (mass%) Particle size (μm) Number per 20μm 65 1 have 13 0.5 5.5 66 1 have 10 0.5 4.5 67 1 none 10 0.5 5 68 1 have 10 1 4 69 1 have 7 2 2 70 1 have 6 3 1 71 1 have 6 4 0.5 72 1 have 20 0.5 8.5 73 1 have 10 0.5 4.5 74 1 have 18 1 7 75 1 have 16 2 4.5 76 1 have 14 3 2.5 77 1 have 10 4 1 78 3 have 12 0.9 4.5 79 3 have 9 0.9 3.5 80 3 have 9 2 2.5 81 3 have 6 3 1 82 3 have 5 4 0.5 83 3 have 18 0.9 7 84 3 have 10 0.9 4 85 3 have 14 2 4 86 3 have 8 3 1.5 87 3 have 7 4 1 ^* 88 1 have - - - ^* 89 1 have 3 5 0 ^* 90 1 have - - - ^* 91 3 have 8 3 1.5 92 3 have 9 3 2 93 3 have 8 3 1.5

Note: (1) Ceramic particles in substrate green sheets

Table 3 (continued) Sample No. Shrinkage in XY plane (%) Deviation ⁽¹⁾ (±%) Warpage (μm) Solder Erosion Coating 65 0.6 0.05 17 excellent good 66 0.5 0.05 16 excellent good 67 0.6 0.05 20 excellent good 68 0.5 0.05 16 excellent good 69 0.5 0.05 16 excellent excellent 70 0.7 0.05 18 excellent excellent 71 1 0.07 twenty three excellent excellent 72 0.6 0.04 17 excellent good 73 0.5 0.05 16 excellent good 74 0.5 0.04 16 excellent good 75 0.5 0.05 16 excellent good 76 0.6 0.05 16 excellent good 77 0.8 0.06 19 excellent good 78 0.6 0.05 17 excellent good 79 0.5 0.05 16 excellent good 80 0.5 0.04 14 excellent good 81 0.5 0.05 16 excellent excellent 82 0.5 0.05 16 excellent excellent 83 0.6 0.04 14 excellent good 84 0.5 0.05 16 excellent good 85 0.5 0.03 13 excellent good 86 0.5 0.04 15 excellent excellent 87 0.5 0.04 15 excellent excellent ^* 88 ⁽²⁾ - - - - - ^* 89 ⁽³⁾ 16 0.34 30 excellent excellent ^* 90 ⁽²⁾ - - - - - ^* 91 ⁽³⁾ 14 0.29 35 excellent excellent 92 1 0.09 twenty two excellent excellent 93 0.6 0.08 20 excellent excellent

Note: (1) Expressed in absolute value.

(2) The constraining layer cracks after printing and drying.

(3) The binding force is weak.

From Table 2 and Table 3, it can be seen that the average particle size of the alumina particles constituting the constrained layer is 0.3 μm or more and in the range of 0.3 to 4 times the average particle size of the ceramic particles of the substrate green sheet. The shrinkage rate in the X-Y plane of the sintered multilayer ceramic substrate was within 1% (within ±0.1%), which was within the allowable range. On the contrary, when alumina particles having an average particle diameter outside the above-mentioned range were used, sufficient binding force could not be obtained, sintering shrinkage could not be suppressed, and cracks were observed on the multilayer ceramic substrate.

In addition, in the samples within the scope of the present invention, the amount of alumina particles remaining on the surface of the external electrodes was 20 mass % (Al basis) or less, especially 12 mass % or less, solder erosion was not caused, and the coating property was also good. The number of remaining alumina particles was within 10 in all the samples within the scope of the present invention. When comparing the substrate green sheet made of calcined body pulverized powder and the substrate green sheet made of a mixture of calcined body pulverized powder + glass pulverized powder, the former had less alumina residue in general.

In the case of the printed constraining layer, cracks were found to occur when the thickness was less than 50 μm or more than 500 μm. On the other hand, the constrained layer formed from a green sheet is excellent in reducing shrinkage and warpage because it can secure a sufficient thickness. At this time, when the PET surface side of the constraining green sheet was used as the constraining surface, it was found that the remaining amount of alumina on the electrodes was further reduced. If there is no dividing groove, both the shrinkage rate and the warpage are very good, but in the method of the present invention, even when the dividing groove is present, both the shrinkage rate variation and the warpage are very good. In addition, no solder erosion was observed in any of the samples.

In terms of coating properties, although samples No. 35, 36, 55, and 59 are not good enough (there are some poor coating parts at the corners of the electrodes), but there is no problem because the coating is formed on more than 90% of the electrode surface. .

The same effect can be obtained even if at least one of magnesia particles, zirconia particles, titania particles, and mullite particles is used as the constrained layer ceramic particles instead of alumina particles. In addition, the same result can be obtained even if the external electrodes are blasted with a sufficiently low impact force (for example, a projection pressure of 0.4 MPa) so as not to damage the external electrodes.

Example 4

The crystal phase of the low-temperature calcined ceramic material used in Example 2 was analyzed by X-ray diffraction method. Cu is used as the target, and its Kα rays are used in the diffracted X-ray source. The powder X-ray diffraction patterns of the mixed powder, calcined powder and sintered body are shown in FIG. 7 . The crystalline phase of the raw material was seen in the mixed powder. The existence of crystal phases of Al ₂ O ₃ , TiO ₂ , and SiO ₂ was confirmed in the calcined powder, and the existence of a glass phase was confirmed in a halo pattern from 20° to 30°. In addition, in the sintered body, new SrAl ₂ Si ₂ O ₈ (strontium feldspar) was confirmed to be precipitated. It is considered that due to the effect of such a structure, the influence on the electrode is reduced, and it is suitable for a non-shrinkage process.

A scanning electron micrograph of the calcined body and its pulverized product is shown in FIG. 8 . In the calcined body shown in Fig. 8(a), the white particles are Al ₂ O ₃ , the black parts are pores, and the continuous phase is a glass phase. In this way, in the calcined body, the Al ₂ O ₃ particles are partially or entirely covered with a glass phase. In the pulverized powder of the calcined body shown in FIG. 8( b ), the Al ₂ O ₃ particles are partially or entirely covered with a glass phase.

In addition, in order to test sintering at low temperature, Al was 49% by mass in terms of Al ₂ O ₃ , Si was 34% by mass in terms of SiO ₂ , Sr was 8.2% by mass in terms of SrO, and TiO ₂ was 8.2% by mass. 100 parts by mass of the main _component composed of 3% by mass of Ti, as auxiliary components, 2.5 parts by mass of Bi in terms of _Bi2O3 , ₂ parts by mass of Na in terms of Na2O, and 2.5 parts by mass in terms of _K2O A composition of 0.5 parts by mass of K, 0.3 parts by mass of Cu in terms of CuO, and 0.5 parts by mass of Mn in terms of Mn ₃ O ₄ was calcined at 800° C., and a sample was produced by the same method as described above. In this example, sintering was performed at 850°C, 860°C, and 875°C for 2 hours, respectively. These samples were subjected to X-ray diffraction measurement using Cu-Kα rays. 9( a ) to ( c ) show X-ray diffraction intensity patterns of samples sintered at 850°C, 860°C, and 875°C, respectively. In the figure, white circles represent Al ₂ O ₃ crystals, black triangles represent hexagonal SrAl ₂ Si ₂ O ₈ crystals, and white triangles represent monoclinic SrAl ₂ Si ₂ O ₈ crystals.

In FIGS. 9( a ) and ( b ), precipitation of hexagonal SrAl ₂ Si ₂ O ₈ crystals was confirmed in Al ₂ O ₃ crystals, TiO ₂ crystals, and SiO ₂ crystals. With the increase of sintering temperature, monoclinic SrAl ₂ Si ₂ O ₈ crystals are precipitated, and the intensity of diffraction peaks also increases. As a result of three-point bending tests performed on these samples, the flexural strength increased in the order of (b), (a), and (c) in which precipitation of hexagonal SrAl ₂ Si ₂ O ₈ crystals increased. From the viewpoint of strength, although precipitation of hexagonal SrAl ₂ Si ₂ O ₈ crystals is ideal, it is preferable to suppress precipitation of monoclinic SrAl ₂ Si ₂ O ₈ crystals.

Example 5

Al ₂ O ₃ powder with a purity of 99.9% and an average particle size of 0.5 μm, SiO ₂ powder with a purity of 99.9% or more and an average particle size of 0.5 μm or less, and SrCO ₃ powder with a purity of 99.9% and an average particle size of 0.5 μm and a purity of 99.9% and TiO ₂ powder with an average particle size of 0.5 μm, and Bi ₂ O ₃ powder, Na ₂ CO ₃ powder, K ₂ CO ₃ powder, CuO powder and MnO ₂ powder with a purity of 99.9% and an average particle size of 0.5 to 5 μm, respectively, According to the composition of 48% by mass of Al in terms _{of Al2O3} , 38% by mass of Si in terms of _SiO2 , 10% by mass of Sr in terms of SrO, and ₄ % by mass of Ti in terms of TiO2 The main component is 100 parts by mass, so that as _{auxiliary components, 2.5 parts by mass of Bi in terms of Bi2O3 , 2} parts by mass of Na in terms of Na2O, _0.5 parts by mass of K in terms of K2O, and They were mixed so as to have a composition of 0.3 parts by mass of Cu in terms of CuO and 0.5 parts by mass of Mn in terms of MnO ₂ (corresponding to sample No. 29 in Table 1). Using the obtained ceramic mixture, substrate green sheets having thicknesses of 15 μm, 50 μm, 100 μm, and 200 μm were prepared in the same manner as in Example 1. The calcining condition was 800° C.×2 hours, and the average particle diameter of the calcined body pulverized powder was about 1 μm.

Each substrate green sheet was cut into approximately squares of 180 mm, and perforations were formed on each green sheet with a predetermined thickness, and high-frequency circuit patterns for filters, antenna switches, and duplexers were printed. Electrode materials mainly composed of Ag are used for printing high-frequency circuit patterns. A circuit block diagram is shown in FIG. 10 . Nine sheets of predetermined thickness printed with a circuit pattern were stacked and crimped, external electrodes were printed, and dividing grooves were formed on the upper and lower sides to produce an integrated assembly substrate capable of being divided into a plurality of multilayer ceramic substrate pieces. Each multilayer ceramic substrate piece is approximately a quadrangular shape of 8mm×8mm, and the thickness before sintering is about 1.3mm. On the collective substrate of about 180mm×180mm, 400 multilayer ceramic substrate pieces are arranged in a grid form with dividing grooves.

Sample No. 51 was selected from Example 2, and the aluminum oxide constrained layer was printed on the upper and lower sides, calcined in the same manner as in Example 2, the constrained layer was removed, coating was performed, and then dried after cleaning.

Then, using a metal mask, a Pb-free solder paste was printed on a predetermined portion of the upper surface of the assembly substrate, and chip components were mounted, and a solder dip process was performed in a reflow furnace. In addition, semiconductor components are mounted, connected and sealed. Finally, the aggregated substrate is divided into multilayer ceramic substrates along the dividing grooves. The in-plane shrinkage of each 180 mm approximately square aggregate substrate is within 0.5% (within ±0.05%), and the height difference in the thickness direction (Z-axis direction) is as small as 50 μm. As a result, no problem occurred in any of the processes of solder paste printing and component mounting on a 400 g multilayer ceramic substrate chip. On the contrary, in the conventional method, the dimensional accuracy of the substrate is lowered due to shrinkage during sintering, so the number of multilayer ceramic substrate chips selected as products with no problems in soldering or component mounting is as small as about 250.

As shown in Fig. 11, the obtained multilayer ceramic substrates 11, 11' having functions of a high-frequency filter or an antenna switch are mounted on a printed circuit board 13 of a mobile phone. In addition, sub-boards, modules or components having other signal processing functions or circuit functions, semiconductor components 12, and the like are also mounted on the printed circuit board 13, and necessary connections are made. Since the multilayer ceramic substrate of the present invention has high dimensional accuracy and stable quality, main printed circuit boards of mobile phones using it can be manufactured with high quality and excellent productivity.

Claims (21)

1. A multilayer ceramic substrate, characterized in that, the multilayer ceramic substrate is manufactured according to the following method, that is, an unsintered multilayer ceramic substrate laminated with green sheets for substrates capable of low-temperature sintering comprising a ceramic material External electrodes are formed on at least the upper surface of the substrate, and the constraining layer mainly composed of inorganic particles that are not sintered at the sintering temperature of the green multilayer ceramic substrate, and the upper surface of the green multilayer ceramic substrate including the external electrodes and /or arranged in a close contact manner below to make an integrated laminate, which is obtained by removing the constrained layer after sintering the laminate; Wherein, the in-plane shrinkage of the multilayer ceramic substrate is within 1% (deviation within 0.1%), and for the inorganic particles remaining on the external electrodes, the metal constituting the inorganic particles is relatively A ratio of the metal of the external electrode to the total amount of the metal constituting the inorganic particles is 20% by mass or less. 2. The multilayer ceramic substrate according to claim 1, wherein the ceramic material contains, as main components, 10 to 60% by mass of Al in terms of Al ₂ O ₃ , and in the form of an oxide. 25 to 60 mass % of Si in terms of SiO ₂ , 7.5 to 50 mass % of Sr in terms of SrO, and 0 to 20 mass % of Ti in terms of TiO ₂ (among them, Al ₂ O ₃ , SiO ₂ , SrO and The total amount of TiO ₂ is set to 100% by mass), and it is calcined at 700°C to 850°C and then pulverized into powder. 3. The multilayer ceramic substrate according to claim 2, wherein the ceramic material contains 0.1 to 10 parts by mass in terms of _Bi2O3 as an auxiliary component per 100 parts by mass of _the main component. Servings of Bi. 4. The multilayer ceramic substrate according to claim 3, wherein the auxiliary component contains 0.1 to ₁₀ parts by mass of _Bi , At least one selected from the group consisting of 0.1 to 5 parts by mass of Na in terms of _Na2O , 0.1 to 5 parts by mass of K in terms of K2O, and 0.1 to 5 parts by _mass of Co in terms of CoO, and at least one selected from the group consisting of 0.01 to 5 parts by mass of Cu in conversion of CuO, 0.01 to 5 parts by mass of Mn in conversion of MnO ₂ , and 0.01 to 5 parts by mass of Ag. 5. A multi-layer ceramic substrate, characterized in that the multi-layer ceramic substrate is produced according to the following method, that is, an unsintered multi-layer substrate formed by laminating green sheets for substrates capable of low-temperature sintering including ceramic materials External electrodes are formed on at least the upper surface of the ceramic substrate, according to the constraining layer mainly composed of inorganic particles that are not sintered at the sintering temperature of the unsintered multilayer ceramic substrate, and the upper surface of the unsintered multilayer ceramic substrate including the external electrodes. And/or arranged in a close-contact manner below to make an integrated laminate, which is obtained by removing the constrained layer after sintering the laminate; Wherein, the multilayer ceramic substrate has a structure including feldspar group crystals mainly composed of strontium feldspar and alumina crystals. 6. The multilayer ceramic substrate according to claim 5, wherein at least a part of the strontium feldspar is hexagonal. 7. The multilayer ceramic substrate according to claim 5 or 6, wherein the in-plane shrinkage rate is within 1% (deviation within 0.1%), and the inorganic particles remaining on the external electrodes are Specifically, the ratio of the metal constituting the inorganic particles to the total amount of the metal constituting the external electrodes and the metal constituting the inorganic particles is 20% by mass or less. 8. A method for manufacturing a multilayer ceramic substrate, comprising: (a) manufacturing a substrate green sheet capable of low-temperature sintering by using a slurry containing ceramic material powder and an organic binder; After the electrodes are formed on the green sheets for the substrate, they are stacked to produce an unsintered multilayer ceramic substrate, (c) a constrained layer containing inorganic particles and an organic binder that are not sintered at the sintering temperature of the unsintered multilayer ceramic substrate , and the upper and/or lower surfaces of the unsintered multilayer ceramic substrate including the external electrodes are closely arranged to form an integrated laminated body, (d) sintering the laminated body, (e) constraining the laminated body In the step of removing a layer from the surface of the sintered laminate, the average particle size of the inorganic particles is 0.3 μm or more, which is 0.3 to 4 times the average particle size of the ceramic material powder. 9. The method for manufacturing a multilayer ceramic substrate according to claim 8, wherein, as the constraining layer, a constraining green sheet containing inorganic particles and an organic binder is formed on a carrier film so that the constraining layer The carrier film contact surface of the green sheet is in close contact with the upper and/or lower surfaces of the unsintered multilayer ceramic substrate including the external electrodes. 10. The method for manufacturing a multilayer ceramic substrate according to claim 8 or 9, wherein the constrained layer is made to have a thickness of 50 μm or more. 11. The method for manufacturing a multilayer ceramic substrate according to claim 8 or 9, wherein the first constraining layer having a thickness of 10 μm or more is formed by coating, and the constraining green sheet is stacked thereon as the second constraining layer. Two constrained layers, forming a constrained layer of more than 50 μm in total. 12. The method for manufacturing a multilayer ceramic substrate according to any one of claims 8 to 11, wherein the green multilayer substrate is manufactured in a state where it can be divided into a plurality of substrate pieces by a dividing groove. A ceramic substrate, wherein the constraining layer is provided on the upper surface and/or lower surface of the collective substrate including the external electrodes. 13. A method for producing a multilayer ceramic substrate, characterized in that (a) 10 to 60 mass % of Al in terms of Al ₂ O ₃ , 25 to 60 mass % of Si in terms of SiO ₂ , and SrO A ceramic whose main components are 7.5 to 50 mass % of Sr in terms of TiO ₂ and 0 to 20 mass % in terms of TiO 2 (the total amount of Al ₂ O ₃ , SiO ₂ , SrO, and TiO ₂ is 100 mass %) The material is calcined at 700°C to 850°C and then finely pulverized, (b) using a slurry containing the obtained calcined body fine powder and an organic binder, to produce a green sheet for a substrate that can be sintered at a low temperature, (c) on the substrate After forming the electrodes on the green sheets, lamination is performed to produce a green multilayer ceramic substrate, (d) a constrained layer containing inorganic particles and an organic binder that are not sintered at the sintering temperature of the green multilayer ceramic substrate, and the The upper and/or lower surfaces of the unsintered multilayer ceramic substrate including the external electrodes are closely arranged to make an integrated laminate, (e) sintering the laminate at 800°C to 1000°C, (f) The constraining layer is removed from the laminate. 14. The method for manufacturing a multilayer ceramic substrate according to claim 13, wherein the substrate green sheet contains an auxiliary component consisting of: 0.1 to ₁₀ parts by mass of Bi in terms of _Bi2O3 , 0.1 to 5 parts by mass of Na in terms of _Na2O , 0.1 to 5 parts by _mass of K in terms of K2O, and 0.1 to 5 parts by mass in terms of CoO At least one selected from the group consisting of 0.01 to 5 parts by mass of Co, and 0.01 to 5 parts by mass of Cu in terms of CuO, 0.01 to 5 parts by mass of Mn in terms of _MnO2 , and 0.01 to 5 parts by mass of Ag. At least one selected from the set of . 15. The method for producing a multilayer ceramic substrate according to claim 13 or 14, wherein the average particle diameter of the inorganic particles is more than 0.3 μm, which is the average particle diameter of the fine powder of the calcined body of the ceramic material 0.3 to 4 times of that. 16. The method for manufacturing a multilayer ceramic substrate according to any one of claims 13 to 15, wherein, as the constraining layer, a constraining raw material containing inorganic particles and an organic binder is formed on the carrier film. sheet, so that the contact surface of the carrier film of the constraining green sheet is in close contact with the upper surface and/or lower surface of the green multilayer ceramic substrate including the external electrodes. 17. The method for manufacturing a multilayer ceramic substrate according to any one of claims 13 to 16, wherein the constrained layer is made to have a thickness of 50 μm or more. 18. The method for manufacturing a multilayer ceramic substrate according to any one of claims 13 to 16, characterized in that the first constraining layer with a thickness of 10 μm or more is formed by coating, and the constraining material is superimposed on it. sheet as the second constrained layer, and a constrained layer of 50 μm or more in total was formed. 19. The method for manufacturing a multilayer ceramic substrate according to any one of claims 13 to 18, wherein the unsintered multilayer substrate is produced in a state that can be divided into a plurality of substrate pieces by a dividing groove. A ceramic substrate, wherein the constraining layer is provided on the upper surface and/or lower surface of the collective substrate including the external electrodes. 20. An electronic device in which the multilayer ceramic substrate according to any one of claims 1 to 7 is mounted on a surface of a circuit board. 21. An electronic device in which the multilayer ceramic substrate obtained by the method according to any one of claims 8 to 19 is mounted on the surface of a circuit board.

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