JP2018006248A - Powder and conductive paste as well as production method of ceramic substrate - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a powder and a conductive paste, which are capable of suppressing occurrence of inconveniences such as defects or the like when a ceramic substrate with a conductive layer is produced and a production method of the ceramic substrate.SOLUTION: When a ceramic substrate 1 is produced, as a conductive paste that forms a conductive layer such as an internal wiring layer 5 and a surface wiring layer 7, a conductive paste added with a powder (that is coated gold powder) in which a surface of particles made of gold is covered with a coated layer made of zirconium is used. Thereby, in comparison with a case where a conductive paste containing gold powder without coat is used, a firing start temperature can be delayed. That is, since firing start temperatures of a ceramic green sheet 11 and a conductive pattern 17 made of the conductive paste can be approximated, that is, a firing shrinkage behavior can be suppressed, defect of the ceramic substrate 1 can be prevented from occurring.SELECTED DRAWING: Figure 3

Description

  The present invention relates to a powder and a conductive paste that can be used for manufacturing, for example, a ceramic package of an electronic component, a wireless communication module substrate, a control circuit substrate, a semiconductor inspection apparatus, and the like, and a method for manufacturing a ceramic substrate.

  Conventionally, for example, ceramic package substrates used for storing electronic components mainly contain 90 wt% or more of alumina and use tungsten (W) or molybdenum (Mn) as an electrode material.

  In recent years, ceramic materials that use silver (Ag) or copper (Cu) as an electrode material, which is called LTCC (Low Temperature Co-fired Ceramics), are used as ceramic package substrate materials (that is, low-temperature co-fired ceramics). It has been developed (see, for example, Patent Documents 1 to 4).

  In this type of technology, for example, when manufacturing a multilayer ceramic substrate, in the manufacturing process, a conductive paste (for example, Au paste) is printed on a green sheet made of insulating ceramic to form a conductive pattern, and then A plurality of these green sheets are laminated and fired to produce a multilayer ceramic substrate provided with a conductive layer.

JP 2008-192401 A JP 2008-103522 A JP 2005-133119 A JP 2001-189602 A

  However, in the above-described prior art, since there is a difference in the start timing of firing shrinkage between the green sheet serving as the insulating layer and the conductive pattern serving as the conductive layer, the substrate warpage after baking, the conductor peeling (peeling of the conductive layer), Defects in the ceramic substrate such as voids may occur.

  In addition, when the material of the electrode material is added to the conductive paste in the form of an organometallic resinate or the like, a solvent component is added, so that the viscosity of the conductive paste is lowered. As a result, there is another problem that variation in film thickness and film shape during printing of the conductive pattern occurs (that is, printability deteriorates).

  Accordingly, an object of the present invention is to provide a powder, a conductive paste, and a method for manufacturing a ceramic substrate that can suppress the occurrence of defects such as defects when a ceramic substrate is manufactured, for example.

(1) The first aspect of the present invention is a powder in which the surface of particles made of gold is coated with a coating layer made of zirconium.
In the first aspect, since the surface of the particles made of gold is coated with the coating layer made of zirconium, the powder has the following effects.

  When forming a conductive pattern on a ceramic green sheet using a conductive paste containing gold powder not coated with zirconium, and firing them simultaneously, as shown in FIG. 3, the ceramic green sheet (A) And the conductive paste (B) have greatly different firing start temperatures. Then, due to the difference in shrinkage start temperature (and hence the difference in shrinkage start timing), there is a risk that defects will occur in the ceramic substrate as described above.

  On the other hand, since the powder of the first aspect is coated with a coating layer made of zirconium on the surface of the particles made of gold, when the conductive paste containing this powder is fired, Compared with the case where the electrically conductive paste containing this powder is used, the firing start temperature can be delayed.

  As a result, as shown in FIG. 3, the firing start temperature of the ceramic green sheet (A) and the conductive paste (C) (using the gold powder whose gold particles are coated with zirconium) is compared with the conventional one. Since it can be made closer, that is, the behavior of firing shrinkage can be made uniform, it is possible to suppress the occurrence of defects such as substrate warpage, peeling of the conductive layer, voids, etc. due to differences in the timing of shrinkage initiation can do.

  Further, in order to suppress the occurrence of defects in the ceramic substrate described above, it is conceivable to add the material of the conductive layer (conductive material) to the conductive paste in the form of an organometallic resinate, etc. The solvent component is added, and the degree of freedom in designing the conductive paste is reduced. In addition, the decrease in the viscosity of the conductive paste may cause problems such as variations in film thickness and film shape when the conductive pattern is formed by the printing method (for example, deterioration of printability such as blurring occurring at the edge portion of the conductive pattern). There is.

  Apart from this, it is conceivable to add the material of the coating layer (coating material) to the conductive paste in powder form in addition to the gold powder. In this case, the dispersibility of the powder of the coating material in the conductive paste However, the effect of adding the powder of the coating material tends to appear locally. For example, localization of the added coating material occurs, and as a result, the warped shape of the conductive layer is not uniform, and the conductive layer is likely to be wavy, leading to peeling of the conductive layer (that is, conductor peeling). is there.

  On the other hand, in this first aspect, by using a powder in which the surface of particles made of gold is coated with zirconium, for example, as a conductive material of a conductive paste, a problem when a conductive material is added in the form of a resinate, Problems when the coating material is added in the form of a powder can be avoided.

  In other words, since it is not necessary to add a solvent component for forming a resinate, the degree of freedom in designing the conductive paste is high, and further, the occurrence of a decrease in the viscosity of the conductive paste can be prevented, thereby suppressing deterioration in printability and the like. be able to. Further, since a powder coating material is not added separately from the gold powder, the conductive layer is unlikely to swell, and therefore the conductor is unlikely to peel off.

  As described above, according to the first aspect, it is possible to suppress the deterioration of the printability and to suppress the occurrence of waviness in the conductive layer, and thus it is possible to suppress the occurrence of defects in the ceramic substrate. .

(2) In the second aspect of the present invention, the powder is a conductive material used for a conductive paste.
In the second aspect, since the powder having the above-described configuration is used as the conductive material used for the conductive paste, the printability is deteriorated when the ceramic substrate including the conductive layer is manufactured as in the first aspect. In addition, it is possible to suppress the occurrence of defects in the ceramic substrate due to the undulation of the conductive layer.

(3) A third aspect of the present invention is a conductive paste comprising the powder of the first or second aspect in a paste.
Since the third aspect is a conductive paste containing the above-described powder in the paste, the printability is deteriorated when a ceramic substrate provided with a conductive layer is manufactured as in the first aspect. In addition, it is possible to suppress the occurrence of defects in the ceramic substrate due to the undulation of the conductive layer.

(4) In the fourth aspect of the present invention, the conductive paste is a material for a conductive layer used for forming a conductive layer on a ceramic substrate.
In the fourth aspect, in order to form the conductive layer on the ceramic substrate, the conductive paste having the above-described configuration is used to print the ceramic substrate having the conductive layer as in the first aspect. It is possible to suppress the deterioration of the properties and to suppress the occurrence of defects in the ceramic substrate due to the undulation of the conductive layer.

  (5) According to a fifth aspect of the present invention, there is provided a ceramic provided with a conductive layer by forming a conductive pattern on a surface of a ceramic green sheet using a conductive paste and simultaneously firing the ceramic green sheet and the conductive pattern. In the method for manufacturing a ceramic substrate for manufacturing a substrate, as the conductive paste, a conductive paste containing a powder in which the surface of gold particles is coated with zirconium is used.

  In the fifth aspect, when a ceramic substrate is manufactured, a conductive paste containing a powder in which the surface of gold particles is coated with zirconium is used as the conductive paste. In addition, it is possible to suppress the occurrence of defects in the ceramic substrate due to the undulation of the conductive layer.

  (6) In a sixth aspect of the present invention, a plurality of the ceramic green sheets on which the conductive pattern is formed are stacked to form a stacked body, and the stacked body is simultaneously fired, so that at least one of the inside and the surface A multilayer ceramic substrate with a conductive layer is manufactured.

  In the sixth aspect, even when the ceramic substrate is a multilayer ceramic substrate, as described above, the printability is deteriorated, and it is possible to suppress the occurrence of defects in the ceramic substrate due to the waviness of the conductive layer. .

<Hereinafter, each configuration of the present invention will be described>
The conductive paste is a paste containing a conductive material (here, gold powder whose gold particles are coated with zirconium) in the paste.

A ceramic substrate is a substrate containing at least ceramic among ceramic and glass. Therefore, so-called glass ceramics are also within the scope of the present invention.
Examples of the ceramic include alumina and mullite. Examples of the glass include borosilicate glass.

The conductive layer is a conductive layer containing gold and zirconium (for example, containing gold as a main component).
The ceramic green sheet is an unfired layer in which the solid component in the material of the sheet contains at least the ceramic among the ceramic and glass.

  A conductive pattern is an unfired portion that becomes a conductive layer after firing formed of a conductive paste.

It is sectional drawing which fractured | ruptured the ceramic substrate of embodiment. It is explanatory drawing which shows the manufacturing method of the ceramic substrate of embodiment. It is a graph which shows the result (The relationship between a calcination temperature and shrinkage | contraction rate) of the thermomechanical analysis of Experimental example 2. FIG.

Hereinafter, embodiments of the method for producing a powder, a conductive paste, and a ceramic substrate of the present invention will be described with reference to the drawings.
In the embodiment described below, a multilayer ceramic substrate is taken as an example of the ceramic substrate.

[1. Embodiment]
[1-1. Configuration of ceramic substrate]
First, the structure of the ceramic substrate manufactured by the manufacturing method of the ceramic substrate of embodiment is demonstrated.

As shown in FIG. 1, the ceramic substrate 1 is a multilayer ceramic substrate in which a plurality of ceramic layers 3 are laminated in the thickness direction.
Inside the ceramic substrate 1, an internal wiring layer 5 is formed between adjacent ceramic layers 3 in the thickness direction. A surface wiring layer 7 is formed on the surface (for example, both or one of the upper surface and the lower surface) of the ceramic substrate 1.

  Further, the ceramic layer 3 is formed with internal wiring layers 5 (disposed in the thickness direction), vias 9 that electrically connect the internal wiring layers 5 and the surface wiring layer 7, and spaces (cavities) (not shown). Has been.

The ceramic layer 3 is a glass ceramic composed of, for example, borosilicate glass mainly containing SiO ₂ , Al ₂ O ₃ , and B ₂ O ₃ and alumina.
The internal wiring layer 5, the surface wiring layer 7, and the via 9 are conductive members made of gold and zirconium. Note that the main component of the conductive member is gold (that is, gold exceeds 50% by mass). Here, the ratio of gold is, for example, 85% by mass with respect to the whole of gold and zirconium.

[1-2. Manufacturing method of ceramic substrate]
Next, a method for manufacturing the ceramic substrate 1 will be described.
<Ceramic green sheet manufacturing process>
As ceramic raw material powder, borosilicate glass powder and alumina powder mainly composed of SiO ₂ , Al ₂ O ₃ , and B ₂ O ₃ were prepared.

As the alumina powder, one having an average particle diameter of 2 μm and a specific surface area of 3.0 m ² / g was used. As the borosilicate glass powder, one having an average particle diameter of 2.5 μm and a specific surface area of 5.0 m ² / g was used.

Furthermore, an allyl binder (acrylic resin) and DOP (dioctyl phthalate) were prepared as a binder component and a plasticizer component during sheet molding.
Next, the borosilicate glass powder and the alumina powder were weighed into an alumina pot so that the weight ratio was 50:50 and the total amount was 1 kg.

  Into this pot, 120 g of the acrylic resin and an amount of a solvent (IPA: toluene) and a plasticizer (DOP) necessary for giving an appropriate slurry viscosity and sheet strength are placed in the pot and mixed for 5 hours. Thus, a ceramic slurry was obtained.

Next, as shown in FIG. 2A, a ceramic green sheet 11 having a thickness of 0.25 mm was obtained by the doctor blade method using the obtained ceramic slurry.
<Process for producing coated gold powder>
As the gold powder, for example, a powder having an average particle diameter of 1 μm was prepared.

  Further, a metal component (zirconium) to be coated was dissolved (or dispersed) as an additive component in an organic solvent (toluene, xylene, other alcohols, etc.). In addition, 12 volume% (outside volume%) of the metal component was added to 100 volume% of the organic solvent.

  Next, gold powder was added to the solution (or dispersion) and dispersed and suspended in the solution. Thereby, the zirconium which is an additive component was made to adhere to the surface of gold powder. In addition, 50 g of gold powder was added to 500 ml of the solution.

Thereafter, the liquid component was evaporated to obtain a powder in which the surface of the gold powder was coated with zirconium (that is, coated gold powder).
In addition, you may add an additional component with respect to an electrically conductive paste by another method.

<Process for producing conductive paste>
As the conductive material constituting the conductive layers of the internal wiring layer 5 and the surface wiring layer 7, the above-described gold powder (coated gold powder) whose surface was coated with zirconium was used.

  As the varnish component of the conductive paste, an ethyl cellulose resin and a butyl carbitol solvent were used. Then, the varnish component and the coated gold powder were kneaded by a three-roll mill to obtain a conductive paste (coated gold conductive paste) containing the coated gold powder. The coated gold powder was added at a ratio of 85% by weight with respect to 15% by weight of the varnish component.

<Manufacturing process of ceramic substrate>
Next, as shown in FIG. 2B, openings (through holes) 13 serving as vias 9 and cavities were processed in the ceramic green sheet 11. Thereafter, the via conductor 15 was formed by filling the opening 13 serving as the via 9 with the coated gold conductive paste.

Next, as shown in FIG. 2 (c), a conductive pattern 17 to be the internal wiring layer 5 and the surface wiring layer 7 was formed on the ceramic green sheet 11 using the coated gold conductive paste.
Next, a plurality of the ceramic green sheets 11 (formed with the conductive pattern 17) were laminated to form a laminate 19, and the thickness of the laminate 19 was adjusted as appropriate to 0.65 mm.

  Next, the laminated body 19 was degreased by heating at 250 ° C. for 5 hours. In this heating, the temperature was raised and lowered at 2 ° C./min. Next, the laminated body 19 after degreasing was fired at 1000 ° C. for 1 hour to obtain a ceramic substrate 1.

[1-3. Experimental Example 1]
Next, Experimental Example 1 performed for confirming the effect of the present invention will be described.
In this experimental example 1, regarding the four types of ceramic substrate samples (Nos. 1 to 4) shown in Table 1 below, the paste used in manufacturing each sample was different, the paste viscosity, the printing state, the substrate warp. The conductor peeling (defect) was examined.

Sample Nos. 1 to 3 are comparative examples (outside the scope of the present invention), and sample No. 4 is an example of the present invention.
The contents of each sample will be described below.

  Sample No. 1 (no addition) of the comparative example uses a conductive paste (gold conductive paste) to which only gold powder is added. A sample ceramic substrate was produced by the same production method as in the above embodiment except that gold powder was used.

  Sample No. 2 (powder) of the comparative example uses a conductive paste obtained by adding zirconium (Zr) in a powder state to the gold conductive paste. Here, 2.5% by volume of zirconium powder was added to 100% by volume of the gold conductive paste. Other than that, a sample ceramic substrate was fabricated in the same manner as in the above embodiment.

  Sample No. 3 (resinate) of the comparative example uses a conductive paste in which an organometallic compound (resinate) obtained by dissolving a metal (Zr) in an organic solvent is added to the gold conductive paste. Here, 2.0% by weight of Zr resinate was added to 100% by weight of the gold conductive paste. In the other respects, a sample ceramic substrate was produced in the same manner as in the above embodiment.

  Sample No. 4 (coat) of the example of the present invention is a sample of a ceramic substrate as a sample, using the same conductive paste (coated gold conductive paste) as in the above embodiment, in the same manner as in the above embodiment. .

  And when manufacturing a ceramic substrate using the electrically conductive paste of each sample mentioned above, paste viscosity, a printing state, substrate curvature, and conductor peeling were measured by the following method. The results are shown in Table 1 below.

<Paste viscosity measurement>
Using the following rotor rotational viscometer, the viscosity (paste viscosity) of the conductive paste of each sample was measured at a temperature of 25 ° C. and a rotational speed of 10 rpm (of the rotor). The unit of paste viscosity is [Pa · s].

Rotor rotational viscometer: Brookfield LVDVE rotor symbol: S14
<Print status evaluation>
The printability (blurring, blurring, coating film shape, etc.) of the conductive pattern of each sample was examined. Specifically, the microscope pattern was observed for blurring and blurring at the edges of the conductive pattern, the film thickness was measured with the following surface roughness profile measuring instrument, and the wiring width was measured with a dimension measuring instrument.

Membrane shape measuring machine: manufactured by Tokyo Seimitsu, surface roughness contour shape measuring machine SURFCOM 1400D
Dimension measuring machine: NEXIV VMR-6555 manufactured by Nikon
<Board warpage>
Substrate warpage after firing was measured by the following laser warpage measuring machine. For the substrate warpage, four samples were measured for each of the sample Nos. 1 to 4, and the average value was obtained. Note that the unit of substrate warpage indicates the size [μm] of warpage in a plane size of 50 mm long × 50 mm wide (that is, 50 mm □).

Laser warpage measuring machine: Anritsu Laser warpage measuring machine <SEM observation>
The surface of the ceramic substrate after firing and the cross section (in the thickness direction) were observed with a scanning electron microscope (SEM), and defects such as the sintered state of the conductor (conductive layer) and peeling of the conductor were confirmed.

  SEM device: JEOL JSM-6330F

  In Table 1, the printing state “Δ” indicates that the film thickness of the conductive pattern is small (82% or less of the target value), and blurring has occurred. Further, the print state “◯” indicates that the conductive pattern has a large film thickness (90% or more of the target value) and no blurring has occurred.

  Moreover, the conductor peeling “x” indicates that peeling occurred as a whole in the conductive layer (after firing). The conductor peeling “Δ” indicates that peeling occurred in a part of the conductive layer. The conductor peeling “◯” indicates that no peeling occurred in the conductive layer.

As is apparent from Table 1, Sample No. 4 which is an example of the present invention has a high paste viscosity and a good printing state. Further, the substrate warp was small and the conductor was not peeled off.
On the other hand, Sample No. 1 of the comparative example is not preferable because the substrate warpage is large and the conductor is peeled off.

Further, Sample No. 2 of the comparative example is not preferable because the substrate warpage is slightly large and the conductor is partially peeled off.
Furthermore, Sample No. 3 of the comparative example is not preferable because the paste viscosity is low and the printing state is poor.

[1-4. Experimental Example 2]
Next, Experimental Example 2 in which the firing shrinkage rate was examined will be described.
In this Experimental Example 2, the following three types of samples (sample Nos. 5 to 7) were subjected to a dimensional variation rate (firing shrinkage rate) of 30 ° C. to 1000 ° C. by the following thermomechanical analyzer (TMA). Was measured.

Thermomechanical analyzer: Rigaku TMA8310
Sample No. 5: Pattern (A) using the ceramic slurry of the above embodiment
Sample No. 6: Pattern (B) using the gold conductive paste of Sample No. 1
Sample No. 7: Pattern (C) using the conductive paste (including Zr-coated gold powder) of the above embodiment of Sample No. 4
In the experiment, a rod-shaped pattern of 3 mm in length, 20 mm in width, and 3 mm in thickness was formed on the measurement base using the material of each sample and fired. Then, it was examined how much each pattern contracted in the longitudinal direction with the firing temperature. Specifically, the ratio of change in length with respect to the length of each initial pattern (firing shrinkage percentage%) was examined. The result is shown in FIG.

  As apparent from FIG. 3, the pattern C of sample No. 7 of the example of the present invention is close to the ceramic pattern A corresponding to the ceramic substrate and the firing shrinkage start timing (hence, the firing shrinkage behavior), and defects are caused during firing. It turns out that it is hard to produce etc.

  On the other hand, the pattern C of the sample No. 6 of the comparative example is greatly different from the ceramic pattern A in the firing shrinkage start timing, and hence the firing shrinkage behavior, and thus it is understood that defects and the like are likely to occur during firing. .

[1-5. effect]
In this embodiment, when the ceramic substrate 1 is manufactured, as a conductive paste for forming a conductive layer such as the internal wiring layer 5 and the surface wiring layer 7, the surface of the particles made of gold is coated with a coating layer made of zirconium. Since the conductive paste to which the powder (that is, coated gold powder) is added is used, the following effects are obtained.

  Specifically, in the present embodiment, since the surface of the gold particle is coated with a coating layer made of zirconium, the coated gold powder has no coating when the conductive paste containing the coated gold powder is fired. Compared with the case where a conductive paste containing gold powder is used, the firing start temperature can be delayed.

  As a result, the firing start temperature of the ceramic green sheet 11 and the conductive pattern 17 made of the conductive paste can be made closer than before, that is, the firing shrinkage behavior can be made uniform. Further, generation of defects such as substrate warpage, peeling of the conductive layer, and voids can be suppressed.

  Further, in this embodiment, by using the coated gold powder for the conductive paste, it is possible to avoid problems when the conductive material is added in the form of resinate and problems when the coating material is added in the form of powder. it can.

  In other words, since there is no need to add a solvent component to make a resinate, there is a high degree of freedom in designing the conductive paste, and it is possible to prevent a decrease in the viscosity of the conductive paste, thereby suppressing deterioration in printability and the like. can do. Further, since a powder coating material is not added separately from the gold powder, undulations are unlikely to occur in the conductive layer, and therefore conductor peeling is difficult to occur.

[1-6. Correspondence with Claims]
Here, the correspondence of the words in the claims and the embodiment will be described.
The ceramic substrate 1, the internal wiring layer 5 and the surface wiring layer 7, the ceramic green sheet 11, the conductive pattern 17, and the laminate 19 of the embodiment are respectively the ceramic substrate, the conductive layer, the ceramic green sheet, and the conductive pattern of the present invention. This corresponds to an example of the laminated body 19.

[2. Other Embodiments]
As mentioned above, although embodiment of this invention was described, this invention is not limited to the said embodiment, In the range which does not deviate from the summary of this invention, it is possible to implement in various aspects.

  (1) For example, in the above-described embodiment, the multilayer ceramic substrate provided with the internal wiring layer and the surface wiring layer is taken as an example, but the multilayer ceramic substrate provided with either the internal wiring layer or the surface wiring layer is used. May be.

(2) In the above-described embodiment, the multilayer ceramic substrate is taken as an example, but a ceramic substrate made of one ceramic layer may be used.
(3) About the composition of a ceramic substrate, it is not limited to the composition of the said embodiment, The ceramic substrate of various compositions is employable.

  (4) It should be noted that the constituent elements of the above-described embodiments can be appropriately combined.

DESCRIPTION OF SYMBOLS 1 ... Ceramic substrate 5 ... Internal wiring layer 7 ... Surface wiring layer 11 ... Ceramic green sheet 17 ... Conductive pattern 19 ... Laminate

Claims (6)

  A powder characterized in that the surface of particles composed of gold is coated with zirconium.   The powder according to claim 1, wherein the powder is a material for a conductive paste added to a conductive paste used to form a conductive layer on a ceramic substrate.   A conductive paste comprising the powder according to claim 1 or 2.   The conductive paste according to claim 3, wherein the conductive paste is a material for forming a conductive layer used for forming the conductive layer on the ceramic substrate. In the method of manufacturing a ceramic substrate, a conductive pattern is formed on the surface of the ceramic green sheet using a conductive paste, and the ceramic green sheet and the conductive pattern are simultaneously fired to manufacture a ceramic substrate having a conductive layer.
A method for producing a ceramic substrate, comprising using as the conductive paste a conductive paste containing a powder in which the surface of gold particles is coated with zirconium.   A multilayer ceramic substrate having the conductive layer therein is manufactured by laminating a plurality of the ceramic green sheets having the conductive pattern to form a multilayer body, and simultaneously firing the multilayer body. The method for manufacturing a ceramic substrate according to claim 5.