JP2005159038A - Low temperature fired ceramic substrate manufacturing method - Google Patents

Abstract

In a method for manufacturing a multilayer ceramic substrate, a constraining sheet made of an inorganic composition that does not sinter at the firing temperature of the ceramic substrate is laminated on at least one surface of a green sheet laminate and fired in a continuous furnace. In particular, a method of manufacturing a ceramic substrate for obtaining a ceramic substrate having high dimensional accuracy by suppressing dimensional variations in the substrate is provided.
The restraining sheet 5 provided on the surface of a laminate 4 has a filling rate of the inorganic composition gradually reduced from the rear end side to the front end side with respect to the moving direction of the movable belt.
[Selection] Figure 2

Description

  The present invention relates to a method for producing a low-temperature fired ceramic substrate, and more particularly to a method for producing a low-temperature fired ceramic substrate for forming a multilayer wiring board, a semiconductor element housing package, and the like with high dimensional accuracy.

  In recent years, in a wiring board applied to a package for housing a semiconductor element in which semiconductor elements such as IC and LSI, which have been highly integrated, are mounted, and a hybrid integrated circuit device in which various electronic components are mounted, the density and There is a demand for resistance and reduction in size and weight, and a low dielectric constant is obtained compared to alumina-based ceramic materials, and a low-resistance metal such as Cu can be used as a wiring circuit layer. The so-called low-temperature fired ceramic wiring board has attracted more attention.

  In addition, as the density of wiring boards increases, the demand for higher dimensional accuracy is also increasing. Since low-temperature fired ceramics can be fired at a lower temperature than alumina-based ceramic materials and the like, for example, a firing method as described in Patent Document 1 below has been proposed.

In the firing method disclosed in Patent Document 1, when firing a laminate formed by laminating a plurality of green sheets containing inorganic components such as glass powder and ceramic filler together with an electrode pattern, the firing temperature of this laminate is A sheet made of an inorganic composition that is not sintered is laminated on both sides of the laminate and subjected to a firing treatment. With such a sheet, the laminate can be sintered with almost no shrinkage in the plane direction. Higher dimensional accuracy can be obtained.
Japanese Patent No. 2554415

  However, when the above-described method is applied to a continuous furnace, the firing shrinkage rate of the laminated body placed on the movable belt is changed from the entrance side to the exit side of the movable belt into the furnace, that is, the traveling direction of the movable belt. On the other hand, there is a problem that the shrinkage gradually decreases from the rear end side to the front end side, and as a result, the variation in the shrinkage rate in the substrate increases.

  Accordingly, the present invention provides a method for producing a multilayer ceramic substrate in which a restraining sheet made of an inorganic composition that does not sinter at the firing temperature of the ceramic substrate is laminated on at least one surface of the green sheet laminate and fired. It is an object of the present invention to provide a method for manufacturing a ceramic wiring board for obtaining a ceramic substrate having high dimensional accuracy by suppressing dimensional variations in the substrate even when firing in a furnace.

  In the method for producing a low-temperature fired ceramic substrate of the present invention, an electrode pattern and a via-hole conductor are formed on a green sheet containing at least an inorganic component, and a laminate of a desired number of green sheets produced in the same manner is laminated. After laminating sheets made of an inorganic composition that does not sinter at the firing temperature on the front and back surfaces of the laminate, the laminate is placed on a movable belt and fired by passing through a region heated to a desired temperature. In the method of manufacturing a low-temperature fired ceramic substrate, the sheet is then removed, and the sheet provided on the surface has a filling rate of the inorganic composition with respect to a traveling direction of the movable belt. It is characterized by being gradually reduced from the side to the tip side.

  According to the present invention, in the continuous firing by the movable belt, by using the restraining sheet as described above, the firing shrinkage rate of the laminated body is gradually increased from the rear end side to the front end side with respect to the moving direction of the movable belt. As a result, it is possible to reduce the variation in the shrinkage rate in the substrate.

  In the present invention, when the restraining sheet is equally divided into two equal parts from the rear end side to the front end side in the moving direction of the movable belt, the ratio of the low filling portion to the high filling portion of the inorganic composition By setting the ratio to 70 to 95%, it is possible to match the change in the firing shrinkage rate of the laminate that changes from the rear end side to the front end side of the movable belt, thereby further reducing the variation in the shrinkage rate in the substrate. .

  Further, according to the present invention, by laminating one or more restraining sheets on the upper and lower surfaces of the laminate, the laminate can be evenly restrained from both the upper and lower surfaces, thereby reducing the firing shrinkage ratio of the upper and lower surfaces of the laminate. Can be even.

  In the present invention, when the thickness of the sheet is t1 and the thickness of the laminate is t2, the laminate is thickly laminated on one side so as to satisfy the relationship of t1 / t2 ≧ 0.1. The restraint property of the sheet can be improved.

  In addition, by including glass powder as the inorganic composition in the sheet and setting the content to 1 to 15% by volume of the inorganic component in the green sheet, the adhesion of the sheet to the laminate during firing can be optimized. The restraint property can be enhanced, and at the same time, the sheet after firing can be easily removed.

The inorganic composition for enhancing the non-shrinkage of the sheet is preferably a ceramic having a high melting point. Al ₂ O ₃ , SiO ₂ , MgO, ZrO ₂ , TiO ₂ , MgAl ₂ O ₃ , ZnAl ₂ O ₄ , Mg ₂ SiO ₄ as a main component.

  In addition, the manufacturing method of the present invention is a glass ceramic substrate that can be fired in a temperature range in which the electrode pattern can be a metal sintered body or metal foil containing at least one of Au, Ag, Cu, Pd, and Pt. It is suitable for manufacturing.

  Hereinafter, the manufacturing method of the low-temperature baking ceramic substrate of this invention is demonstrated based on FIG.

  According to FIG. 1, the low-temperature fired ceramic substrate as described above includes (a) a step of obtaining a green sheet made of a low-temperature fired ceramic composition such as an inorganic component, and (b) drilling the green sheet to form via holes. Forming and filling a via hole with a conductive paste; (c) forming a wiring circuit layer on the surface of the green sheet by a screen printing method; and green sheets produced through steps (a) to (c). And (e) laminating sheets of an inorganic composition that does not sinter at the firing temperature of the low-temperature fired ceramics on both sides of the laminate. Steps (f) and (g) firing the composite laminate produced through steps (a) to (e) at a temperature not higher than the melting point of the metal conductor constituting the wiring circuit layer. It is manufactured through a step of removing the sheet from engagement laminate. Hereinafter, each process will be described in detail.

(A) In the step of obtaining a green sheet comprising a low-temperature fired ceramic composition, a predetermined amount of glass powder and ceramic filler powder are weighed as raw material powders, and further an organic binder, plasticizer, organic solvent, etc. are added to prepare a slurry. Then, a green sheet 1 forming a ceramic wiring board having a thickness of 50 to 500 μm is formed by forming into a sheet shape by a known forming method such as a doctor blade method, a rolling method, or a pressing method. As a glass component to be used, it contains at least SiO ₂ and contains at least one of Al ₂ O ₃ , B ₂ O ₃ , ZnO, PbO, alkaline earth metal oxide, and alkali metal oxide. For example, borosilicate such as SiO ₂ —B ₂ O ₃ system, SiO ₂ —B ₂ O ₃ —Al ₂ O ₃ system—MO system (wherein M represents Ca, Sr, Mg, Ba or Zn). Acid glass, alkali silicate glass, Ba glass, Pb glass, Bi glass, and the like can be given. These glasses are also amorphous glass by firing, and by firing, lithium silicate, quartz, cristobalite, cordierite, mullite, ananosite, serdian, spinel, garnite, willemite, What precipitates at least one kind of crystals of dolomite, petalite, diopside and substituted derivatives thereof is used.

As the ceramic filler, SiO ₂ such as quartz and cristobalite, Al ₂ O ₃ , ZrO ₂ , cordierite, mullite, forsterite, enstatite, spinel, magnesia and the like are preferably used.

  (B) In the process of drilling a green sheet, forming a via hole, and filling the via hole with a conductive paste, the diameter of the green sheet 1 obtained in (a) is increased by laser, micro drill, punching, or the like. A through hole of 30 to 300 μm is formed, and a via conductor paste is filled therein to form the via hole conductor 2. The conductive paste for vias is obtained by uniformly mixing an organic binder such as acrylic resin and an organic solvent such as terpineol or dibutyl phthalate into a metal powder mainly composed of at least one of Au, Cu, Ag, Pd, and Pt. Formed. The organic binder is mixed in an amount of 0.5 to 15.0% by mass with respect to 100% by mass of the metal component, and the organic solvent is mixed in a proportion of 5 to 100% by mass with respect to 100% by mass of the solid component and the organic binder. It is desirable. Note that a slight amount of ceramic filler or glass component may be added to the via conductor paste.

  (C) In the step of forming a wiring circuit layer on the surface of the green sheet by screen printing or the like, a wiring pattern 3 is formed on the surface of the green sheet 1 on which the via-hole conductor 2 is formed by screen printing. Alternatively, the electrode pattern 3 is formed by transferring a metal foil. The conductor paste for the electrode pattern 3 is produced by the same method as that for the via conductor paste, and is produced by changing components and blending ratios as necessary. On the other hand, as a method for forming the electrode pattern 3 by a transfer method using a metal foil, first, a metal foil is bonded onto a transfer film made of a polymer material or the like, and then a mirror image resist is applied to the surface of the metal foil on the circuit pattern. After coating, the etching process and the resist removal are performed to form a mirror image wiring circuit, and the transfer film on which the mirror image wiring circuit is formed is aligned with the surface of the green sheet 1 on which the via-hole conductor 2 is formed and laminated. After the pressure bonding, the green film 1 including the electrode pattern 3 connected to the via-hole conductor 2 is formed by peeling off the transfer film. It should be noted that the electrode pattern 3 formed by the printing method and the transfer method may be either one or both.

  (D) In the step of laminating the green sheets 1 on which the electrode patterns 3 are formed to produce a laminate, the laminate 4 is formed by laminating and pressing a plurality of green sheets 1 obtained in the same manner. For the lamination of the green sheets 1, a method of applying heat and pressure to the stacked green sheets 1 and thermocompression bonding, a method of applying an adhesive composed of an organic binder, a plasticizer, a solvent, etc. between the sheets, and thermocompression bonding, etc. Can be adopted.

  (E) In the step of laminating sheets made of an inorganic composition that does not sinter at the firing temperature of the low-temperature fired ceramics on both sides of the laminate, the sheets are pressed on both sides of the laminate 4 to form the composite laminate 6. Make it.

  The present invention produces a composite laminate 6 in which a constraining sheet 5 is laminated on a laminate 4 in which at least green sheets are laminated, and the composite laminate 6 is placed on a movable belt and heated to a desired temperature. The sheet 5 is removed after that by performing a baking treatment by passing the sheet. According to such a manufacturing method, when firing in a continuous furnace, there is a problem that the shrinkage start timing is shifted due to the temperature distribution in the traveling direction of the movable belt, and the shrinkage rate gradually decreases. By using the sheet 5 of the present invention, the restraining force can be adjusted, and in-plane firing shrinkage variation can be suppressed to ± 0.05% or less even when a continuous furnace is used.

The sheet is mainly composed of at least one of Al ₂ O ₃ , SiO ₂ , MgO, ZrO ₂ , TiO ₂ , MgAl ₂ O ₄ , ZnAl ₂ O ₄ and Mg ₂ SiO ₄ , and has an average particle size of 0.5 to 5 μm. The raw material powder comprises 80 to 99.5% by mass, particularly 90 to 97% by mass, 1 to 15% by mass, particularly 3 to 10% by mass of glass powder having a softening point at 450 to 950 ° C., particularly 650 to 900 ° C. . Here, it is preferable that the restraint sheet 5 contains a glass component, in other words, an amorphous component in an amount of 1 to 15% by mass, particularly 3 to 10% by mass. This is because if the glass content is less than 1% by mass, the restraint force of firing shrinkage of the laminate 4 by the restraining sheet 5 is reduced and the dimensional accuracy is deteriorated, and the diffusion of glass components from the laminate 4 in the firing process. This is because a large number of voids are generated on the surface of the low-temperature fired ceramic substrate 7 after sintering. On the other hand, if the amount of glass is more than 15% by mass, the restraint sheet 5 shrinks due to firing, so that it is difficult to restrain the shrinkage of the laminate 4 and the sintered restraint sheet 5 is lowered at a low temperature. This is because it becomes difficult to remove from the fired ceramic wiring substrate 7.

  Moreover, as a glass component contained in the sheet | seat 5 for restraint, it is desirable that a softening point is below the firing temperature of the laminated body 4, and is higher than the decomposition volatilization temperature of the organic component of the sheet | seat 5 for restraint. Specifically, the softening point of the constraining sheet 5 is preferably 450 to 950 ° C, particularly preferably 650 to 900 ° C. When the softening point of the glass is lower than 450 ° C., the glass softened during the removal of the organic component from the laminate 4 may block the organic component removal path, and the organic component may not be completely removed.

  On the other hand, when the glass softening point exceeds 950 ° C., it does not act as a binder to the green sheet 1 under the normal firing conditions of the green sheet laminate 4. The glass may be different from the glass component contained in the green sheet 1 described above, but it is desirable to use the same glass in order to prevent the diffusion of the glass of the laminate 4.

  After preparing the raw materials that satisfy the above conditions and preparing the slurry, it is formed into a sheet by the doctor blade method, but when drying the slurry, on the left side or the right side with respect to the direction of travel of the drying line By performing drying and not performing drying on the opposite side, it is possible to obtain a restraining sheet 5 in which the filling rate of the inorganic composition 10 gradually changes. Specifically, the ratio of the low filling portion L to the high filling portion H of the restraining sheet 5 is desirably 70 to 95%. A schematic plan view of the restraining sheet of the present invention is shown in FIG. Arrows indicate how to proceed.

  Here, the thickness t1 of the restraining sheet 5 laminated on the laminate 4 is t1 / t2 ≧ 0.1 or more, optimally 0.25 or more with respect to the thickness t2 of the laminate 4 only on one side. Desirably, if it is thinner than 0.1, the binding force may be reduced. In addition, if the volatilization of the organic component is facilitated and the removability of the restraining sheet 5 from the glass ceramic substrate 7 is taken into consideration, the thickness of the restraining sheet 5 is desirably 800 μm or less, and optimally 600 μm or less. .

  (F) In the step of firing the prepared composite laminate 6 at a temperature not higher than the melting point of the metal conductor, the composite laminate 6 is heated at 100 to 800 ° C., particularly 400 to 750 ° C. The organic components are decomposed and removed, and then co-fired at 800 to 1000 ° C. At this time, when the wiring pattern 3 and the via-hole conductor 2 are mainly composed of Cu, the wiring pattern 3 and the via-hole conductor 2 must be fired in a nitrogen atmosphere, and when Au, Ag, Pd, and Pt are mainly composed, the firing atmosphere is Can be done in the atmosphere. Further, if the cooling rate after firing is too fast, cracks due to the difference in thermal expansion between the low-temperature fired ceramic substrate 7, the wiring pattern 3, and the restraining sheet 5 occur, so the cooling rate is 400 ° C./hr or less. Is desirable. Moreover, a load may be applied by placing a weight on the upper surface of the composite laminate 6 in order to prevent warping during firing. The load is suitably 25 Pa to 1 MPa, particularly 50 to 500 Pa.

  Here, firing is preferably performed in a continuous furnace in consideration of mass productivity. However, when firing is performed in a continuous furnace, there arises a problem that the shrinkage rate gradually decreases with respect to the traveling direction of the movable belt. However, by using the restraint sheet 5 of the present invention, the composite laminate 6 is placed on the movable belt so that the low filling portion of the restraint sheet is in front of the moving direction of the movable belt. Even in the case of firing in a continuous furnace, in-plane firing shrinkage variation can be suppressed to ± 0.05% or less.

  (G) In the step of removing the restraining sheet 5 from the composite laminate 6, restraining from the low-temperature fired ceramic substrate 7 using methods such as ultrasonic cleaning, polishing, water jet, chemical blasting, sand blasting, and wet blasting. The sheet 5 is removed.

  The low-temperature fired ceramic wiring board 7 obtained in this way has shrinkage during firing suppressed only in the thickness direction by the restraining sheet 5, so that the in-plane shrinkage of the laminate 4 is suppressed to 0.05% or less. Moreover, since the laminated body 4 is uniformly and reliably bonded to the entire surface by the restraining sheet 5, it is possible to prevent warping or deformation from occurring due to partial peeling of the sheet 5 or the like. In addition, the restraining force can be adjusted. As a result, the phenomenon that the shrinkage rate gradually decreases from the rear end side to the front end side with respect to the traveling direction of the movable belt, which occurs when firing in a continuous furnace, can be prevented, and in-plane firing is performed. Shrinkage variation can be suppressed to ± 0.05% or less. Thus, a low-temperature fired ceramic substrate 7 having high dimensional accuracy can be obtained.

The low-temperature fired ceramic substrate of the present invention was evaluated based on the following examples. First, 60% by mass of a crystallized glass powder having a composition of SiO ₂ : 50% by mass, MgO: 18.5% by mass, CaO: 26% by mass, and Al ₂ O ₃ : 5.5% by mass, and a ceramic filler component As a result, 40% by mass of Al ₂ O ₃ was weighed to prepare a glass ceramic composition. Using a slurry prepared by adding an acrylic resin as an organic binder, DBP (dibutyl phthalate) as a plasticizer, and toluene and isopropyl alcohol as a solvent, a 200 μm thick grease is formed by a doctor blade method. A sheet was prepared.

  Next, 12% by mass of glass powder was weighed with respect to 100% by mass of Cu powder, and acrylic resin as an organic binder and DBP as a solvent were added and kneaded to prepare a via hole conductor paste sample. The amount of the organic binder in the via hole paste sample was 12% by mass with respect to the Cu powder, and the solvent was added at a ratio of 36% by mass with respect to the solid component and the organic binder. This Cu paste was filled in via holes formed at predetermined locations on the green sheet.

  Further, 0.2% by mass of alumina powder and 1% by mass of glass powder are weighed with respect to 100% by mass of Cu powder, and acrylic resin as an organic binder and DBP as a solvent are added and kneaded, and a Cu paste sample for pattern Was made. The amount of the organic binder was 15% by mass with respect to the main component, and the solvent was added at a rate of 13% by mass with respect to the solid component and the organic binder. A predetermined electrode pattern was formed by screen printing on a green sheet in which the obtained Cu paste was filled with the previous via-hole conductor paste. The printed thickness of the electrode pattern at this time was 10 to 30 μm. Thereafter, five green sheets each having a desired electrode pattern were laminated and pressure laminated under the conditions of 45 ° C. and 4 MPa to produce a laminate.

Next, as a restraining sheet for laminating on the front and back surfaces of this laminate, Al ₂ O ₃ having an average particle size of 3 μm is shown in Table 1 using the same glass as the glass component in the green sheet. A restraining sheet having a thickness of 250 μm made of the composition was prepared. The organic binder, plasticizer, solvent, and the like at the time of sheet preparation were the same as those for the green sheet. The obtained restraining sheet was provided with the difference in filling rate shown in Table 2. Next, the sheet was pressed and laminated at 45 ° C. and 5 MPa on both surfaces of the laminate to obtain a composite laminate.

Subsequently, the composite laminate was fired using a continuous furnace. First, the composite laminate is placed on a base plate made of Al ₂ O ₃ , fired at 750 ° C. in a nitrogen atmosphere in order to decompose and remove organic components such as an organic binder, and then 900 in a nitrogen atmosphere. Firing was carried out at 1 ° C. for 1 hour. Thereafter, the fired sheet was removed by blasting to produce a low-temperature fired ceramic wiring board made of glass ceramics.

For evaluation, ten samples were prepared under the conditions shown in Table 2, and dimensional tolerances were evaluated using a three-dimensional measuring machine. That is, as shown in FIG. 3, dimensional variation after firing (6σ (σ: σ: 3) in three measurement points x1 to x3 in the direction perpendicular to the moving direction (in the direction of the arrow) of the movable belt of the continuous firing furnace. Standard deviation)). As a comparative example, a sample fired using a sheet having no change in filling rate was prepared and evaluated in the same manner as in the present invention.

  As is apparent from Table 2, the sample No. using the sheet of the present invention. In 2-10, a wiring board with high dimensional accuracy with a dimensional tolerance of ± 0.075% or less could be manufactured. In particular, Sample No. with a ratio of the low filling portion to the high filling portion of 70 to 95%. In 3-6 and 8-10, the dimensional tolerance could be ± 0.072% or less. Furthermore, sample No. obtained using the sheet | seat which made the glass amount in a sheet | seat 5 mass%, and made the ratio of the filling rate of an inorganic composition 70-95%. In 3 to 6, the dimensional tolerance could be ± 0.05% or less.

  On the other hand, Sample No. using a sheet that did not change the filling rate of the inorganic composition. 1, the dimensional tolerance was as large as ± 0.085.

It is the schematic for demonstrating the low-temperature baking ceramic wiring board of this invention. It is a schematic diagram for demonstrating a sheet | seat. It is the schematic for demonstrating the measurement location of a sample.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Green sheet 2 Via-hole conductor 3 Wiring pattern 4 Laminated body 5 Sheet 6 Composite laminated body 7 Low-temperature firing ceramic wiring board

Claims (7)

A sheet made of an inorganic composition that does not sinter at the firing temperature of the low-temperature fired ceramic on a laminate in which an electrode pattern and a via-hole conductor are formed on a green sheet containing at least an inorganic component, and a desired number of green sheets are similarly laminated. Is laminated on the front and back surfaces of the laminate, and then the laminate is placed on a movable belt, subjected to a firing treatment by passing through a region heated to a desired temperature, and then the sheet is removed. In the method for producing a fired ceramic substrate, the sheet provided on the surface is characterized in that the filling rate of the inorganic composition is gradually reduced from the rear end side to the front end side with respect to the traveling direction of the movable belt. A method for producing a low-temperature fired ceramic substrate. The ratio of the low filling portion to the high filling portion of the inorganic composition is 70 to 95% when the sheet is equally divided into two equal parts from the rear end side to the front end side in the moving belt moving direction. The method for producing a low-temperature fired ceramic substrate according to claim 1 The method for producing a low-temperature fired ceramic substrate according to claim 1 or 2, wherein one or more sheets are laminated on both upper and lower surfaces of the laminate. The low-temperature fired ceramic according to any one of claims 1 to 3, wherein the inorganic composition in the sheet contains glass powder, and the content thereof is 1 to 15% by volume of the inorganic component in the green sheet. A method for manufacturing a substrate. 5. The low temperature according to claim 1, wherein the relationship of t1 / t2 ≧ 0.1 is satisfied on one side when the thickness of the sheet is t1 and the thickness of the laminate is t2. A method for producing a fired ceramic substrate. The inorganic composition mainly contains at least one of Al ₂ O ₃ , SiO ₂ , MgO, ZrO ₂ , TiO ₂ , MgAl ₂ O ₃ , ZnAl ₂ O ₄ , and Mg ₂ SiO _4. Item 6. The method for producing a low-temperature fired ceramic substrate according to any one of Items 1 to 5. The low-temperature fired ceramic substrate according to any one of claims 1 to 6, wherein the electrode pattern is made of a metal sintered body or metal foil containing at least one of Au, Ag, Cu, Pd, and Pt. Production method.

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