JP2012151159A - Conductive paste for ceramic multilayer circuit board - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a conductive paste for a ceramic multilayer circuit board capable of more effectively suppressing an occurrence of warpage when forming a conductor circuit by sintering simultaneously with a ceramic green sheet.SOLUTION: The conductive paste for a ceramic multilayer circuit board is manufactured by atomizing method. The average grain size is within a range of 2 to 9 μm and the maximum grain size is 40 μm or less. The conductive paste contains thin sliced atomization silver flake powder as conductive powder. The atomization silver flake powder is preferably 50 wt.% of the conductive powder or more.

Description

  The present invention relates to a conductive paste for a ceramic multilayer circuit board, and more particularly to a conductive paste capable of providing a multilayer circuit board capable of effectively suppressing the occurrence of warping even when fired simultaneously with a ceramic green sheet.

  Conventionally, alumina multilayer circuit boards have been mainly used as ceramic multilayer circuit boards. In order to manufacture an alumina multilayer circuit board, a high temperature of 1500 ° C. or higher is required for sintering alumina, and molybdenum-manganese (Mo—Mn) or tungsten (W) is used as a conductor material to withstand that temperature. ) Series high-temperature sintering materials were used.

  On the other hand, recently, low-temperature fired substrates that can be fired at a lower temperature than alumina are gradually being used. In this low-temperature fired substrate, sintering is possible at a firing temperature of 800 to 1000 ° C., so that the conductive material can be silver (Ag) or copper (Cu) having a lower resistance than Mo—Mn and W. Applications are being developed for CSP (chip size package) or MCM (multi-chip module) as high-density mounting substrates.

  The low-temperature fired substrate is generally a mixture of a glass frit component and a ceramic component, and is sintered at a low temperature using the low melting point of the glass frit to form a substrate.

  A method of manufacturing such a ceramic multilayer circuit board is such that a conductive paste is printed on a green sheet (ceramic green sheet) serving as a ceramic substrate, and in the via hole of the ceramic green sheet for electrical connection between the ceramic layers. This is a method in which a conductive paste is filled and a plurality of these ceramic green sheets are laminated and then fired at once. The ceramic green sheet becomes a ceramic substrate by firing, and the conductive paste becomes a wiring electrode layer (so-called wiring pattern) or via-hole electrode layer by firing.

  By the way, the ceramic multilayer circuit board manufactured in this way has a known problem that the substrate is warped after firing. The warpage of the substrate is a phenomenon that occurs because the ceramic green sheet and the conductive paste, which are materials having different shrinkage ratios at the time of firing, are fired at the same time. This warpage is mainly due to the shrinkage of the conductive paste occurring earlier than the shrinkage of the ceramic green sheet.

  Therefore, in order to solve the above problems, a technique for adjusting the particle size of the silver powder contained in the conductive paste has been proposed.

  For example, Patent Document 1 discloses a multilayer printed circuit board and a method for manufacturing the same, and the conductive paste used for the multilayer printed circuit board includes a substantially spherical silver powder having an average particle diameter of 5 to 25 μm, an organic vehicle, and the like. It consists of. Patent Document 2 discloses a conductive paste for a ceramic multilayer circuit board, which is a silver paste having an average particle diameter of 3 to 10 μm and a maximum particle diameter of 40 μm or less manufactured by an atomizing method. The powder is contained as a conductive powder.

JP-A-3-284896 JP-A-11-163487

  By the way, in recent years, since higher density is required in the multilayer ceramic electronic component, further reduction of the shrinkage rate is required in the ceramic multilayer circuit board in order to increase the density. If there is a large difference in the shrinkage rate during firing between the ceramic green sheet and the conductive paste, in addition to the occurrence of warping, the wiring pattern etc. may be peeled off from the ceramic substrate, or the wiring pattern etc. may be locally spheroidized. It is also known that disconnection may occur. Due to the increase in the density of the multilayer ceramic electronic component, there is a possibility that problems such as warping due to firing may occur even if the shrinkage rate is not a problem in the past.

  In general, the silver powder used for the conductive paste is manufactured by a chemical reduction method, and thus the average particle size is often in the range of 0.1 to 2 μm. When silver powder in this range is used for the conductive paste for a ceramic multilayer circuit board, the firing of the silver powder proceeds much faster than the firing of the ceramic green sheet, so that the occurrence of warpage cannot be suppressed.

  In the technique disclosed in Patent Document 1, the average particle size is increased within the range of 5 to 25 μm by calcining silver powder produced by a normal chemical reduction method. Such a silver powder (calcined silver powder) is in a form in which the original silver particles obtained by a chemical reduction method are gathered together, so that many cavities are generated inside the calcined silver powder. . Therefore, the calcined silver powder is fired faster than the silver powder having the same particle size and no voids. Therefore, the technique disclosed in Patent Document 1 cannot effectively solve problems such as warping due to high density.

  On the other hand, since the technique disclosed in Patent Document 2 produces silver powder by an atomizing method instead of a chemical reduction method, the average particle size is increased within a range of 3 to 10 μm, and the silver powder The maximum particle size is suppressed to 40 μm or less. Therefore, it is possible to form a conductor circuit with very little warp even when fired simultaneously with the ceramic green sheet. However, in order to cope with the recent increase in density, there is a tendency to further reduce the difference in shrinkage rate, and a conductive paste for a ceramic multilayer circuit board that can realize the demand has not been known. It was.

  The present invention has been made to solve such a problem, and when the conductor circuit is formed by firing simultaneously with the ceramic green sheet, it is possible to more effectively suppress the occurrence of warping of the circuit board. An object of the present invention is to provide a conductive paste for a ceramic multilayer circuit board.

  In order to solve the above-mentioned problem, the conductive paste for a ceramic multilayer circuit board according to the present invention is manufactured by laminating a plurality of ceramic green sheets and firing the ceramic multilayer circuit board. A conductive paste used for forming a layer, which contains at least silver powder as a conductive powder, the silver powder is produced by an atomizing method, and has an average particle size in a range of 2 to 9 μm and a maximum particle size Is 40 μm or less, and further thinned.

  In the said structure, it is preferable that the said silver powder is 50 weight% or more of the said electroconductive powder.

  Moreover, in the said structure, it is preferable that content of the said electroconductive powder is 95 weight% or less.

  Moreover, in the said structure, you may use together the powder of the at least 1 sort (s) of metal selected from the group of palladium, platinum, gold | metal | money, nickel, and copper as electroconductive powder other than the said silver powder.

  As described above, according to the present invention, when a conductive circuit is formed by firing the conductive paste for a ceramic multilayer circuit board according to the present invention at the same time as the ceramic green sheet, the occurrence of warping of the circuit board is further effectively achieved. There is an effect that it can be suppressed.

(A) is the electron micrograph which shows an example of the thinned silver powder used in the Example of this invention, (b) is the silver powder before thinning manufactured by the atomizing method. It is an electron micrograph which shows an example.

  Hereinafter, preferred embodiments of the present invention will be described. The conductive paste for a ceramic multilayer circuit board (hereinafter simply referred to as a conductive paste) according to the present invention forms a conductive layer when a ceramic multilayer circuit board is manufactured by laminating and firing a plurality of ceramic green sheets. The conductive powder contains a thinned piece of silver powder having an average particle diameter in a predetermined range.

[Composition of silver powder]
The silver powder contained in the conductive paste according to the present invention is an atomized silver flake powder obtained by flaking (flaking) one produced by an atomizing method (referred to as atomized silver powder). The atomizing method referred to in the present invention is a method of spherical pulverization by melting silver (Ag) at a high temperature and spraying the Ag liquid at a high speed from a nozzle. Specific examples of the method include a gas atomizing method using a gas as a medium for spraying Ag liquid at a high speed from a nozzle, or a water atomizing method using water as the medium, which is used in the present invention. Atomized silver powder can be produced by any method.

  The atomized silver powder may have an average particle diameter in the range of 2 to 9 μm. If the average particle size of the atomized silver powder is less than 2 μm, the warp cannot be sufficiently effectively reduced when the obtained conductive paste and the ceramic green sheet are fired simultaneously. Also, if the average particle size exceeds 9 μm, the size of the atomized silver flake powder obtained by slicing becomes too large, so that when the pattern is printed on the ceramic green sheet, the atomized silver flake powder clogs the screen. There is a risk of it happening.

  In addition, although the average particle diameter of the atomized silver powder disclosed in Patent Document 2 is in the range of 3 to 10 μm, in the present invention, the atomized silver powder is made into a thin piece. In consideration, the range of the average particle diameter in the present invention is shifted to a smaller side as a whole than the range disclosed in Patent Document 2.

  The atomized silver powder has an average particle size falling within the above range and a maximum particle size of 40 μm or less. When the maximum particle size of the atomized silver powder exceeds 40 μm, when the conductive paste is prepared, the atomized silver powder is crushed, resulting in a silver foil piece having a relatively large particle size. As described above, such a silver foil piece may cause clogging of the screen when pattern printing is performed on the ceramic green sheet.

  The atomized silver powder becomes atomized silver flake powder by being thinned, and is blended as the conductive powder of the conductive paste according to the present invention. The method of thinning is not particularly limited, and various known methods can be used. Specific examples include a method of crushing particles using a ball mill, a bead mill, an attritor mill, or the like, but is not particularly limited.

  The atomized silver flake powder used in the present invention has, for example, a plate-like shape as shown in FIG. 1 (a), whereas the atomized silver flake before thinning is, for example, FIG. As shown in b), both are substantially spherical. Thus, the “thinned silver powder” as used in the present invention is defined as a thickness average of 1 to 6 μm and a flat portion major axis average of 4 to 20 μm.

[Configuration of conductive paste]
The conductive paste according to the present invention contains the above-described atomized silver flake powder as the conductive powder, but may contain other known conductive powders. For example, at least one metal powder selected from the group consisting of palladium (Pd), platinum (Pt), gold (Au), nickel (Ni), and copper (Cu) can be used in combination. That is, the conductive paste according to the present invention may contain Pd powder, Pt powder, Au powder, Ni powder, or Cu powder as the conductive powder in addition to the atomized silver flake powder, or Pd powder, Pt You may contain 2 or more types of powder selected from powder, Au powder, Ni powder, and Cu powder. Furthermore, in the conductive paste according to the present invention, other metal powders may be included in addition to the metal powders of the group, depending on required characteristics and the like.

  The conductive paste according to the present invention contains an organic vehicle in addition to the conductive powder, and the conductive powder is dispersed in the organic vehicle.

  The specific structure of the organic vehicle used in the present invention is not particularly limited, and a resin known in the field of conductive paste can be suitably used. Specific examples include, but are not limited to, epoxy resins, polyester resins, urethane resins, (meth) acrylic resins, imide resins, amide resins, butyral resins, and modified cellulose. These resins include known copolymers or modified resins. Moreover, these resin may be used only by 1 type, and 2 or more types may be selected suitably and used.

  In the conductive paste according to the present invention, known additives and the like may be added in addition to the conductive powder and the organic vehicle. Specifically, for example, a dispersant that improves the dispersibility of the conductive powder, a thickener or solvent for adjusting the viscosity and fluidity of the conductive paste, and the thixotropy of the conductive paste are adjusted. Examples thereof include a thixotropic imparting agent, a glass frit that improves the adhesive strength after firing the conductive paste, and an organometallic compound. These additives can be added in a known amount within a range that does not deteriorate the properties of the conductive paste according to the present invention (particularly, suppression of warpage caused by firing).

  The content of the conductive powder contained in the conductive paste according to the present invention is preferably at least 95% by weight or less, more preferably in the range of 70 to 95% by weight, and in the range of 80 to 92% by weight. It is more preferable that it is within. Further, the content of the organic vehicle is preferably in the range of 5 to 30% by weight, and more preferably in the range of 8 to 20% by weight. If the conductive powder exceeds 95% by weight or the organic vehicle is less than 5% by weight, it may be difficult to obtain a paste-like composition. On the other hand, if the conductive powder is less than 70% by weight or the organic vehicle is more than 30% by weight, the drying property of the conductive paste at the time of firing tends to decrease and the shrinkage rate of the conductive paste at the time of firing tends to increase.

  The content is a composition when the total amount of the conductive powder and the organic vehicle is 100% by weight. However, when the additive other than these is included, the conductive powder, the organic vehicle and the additive are added. It goes without saying that the content of the agent can be appropriately adjusted within a known range depending on the type of the additive.

  Furthermore, in the conductive paste according to the present invention, the atomized silver flake powder preferably exceeds 50% by weight of the conductive powder. In other words, in the present invention, the atomized silver flake powder may be the main component of the conductive powder, and can be used together with Pd powder, Pt powder, Au powder, Ni powder, and Cu powder (or other conductive powder). In the case of containing one or more of these, the powder of these other metals should just be 50 weight% or less. If the atomized silver flake powder is less than 50% by weight of the conductive powder, it is not preferable because remarkable warpage tends to occur when fired together with the ceramic green sheet. However, it goes without saying that the content of the atomized silver flake powder in the conductive powder can be 50% by weight or less depending on the physical properties required of the conductive paste.

  In the present invention, as long as the atomized silver flake powder is the main component of the conductive powder, a silver powder that is not flakes can be used in combination. The silver powder that has not been sliced may be the above-described atomized silver powder or a silver powder produced by a chemical reduction method. The content is not particularly limited, and can be contained in a known range depending on the physical properties required for the conductive paste, use conditions, and the like.

  The manufacturing method of the electrically conductive paste which concerns on this invention is not specifically limited, A well-known method can be used suitably. Generally, it is produced by mixing and kneading the conductive powder containing atomized silver flake powder, an organic vehicle, and various additives as necessary with a known kneading apparatus having a plurality of rolls. Can do. Moreover, you may pre-knead with a well-known kneading apparatus before this kneading | mixing. Depending on conditions such as the composition of the conductive paste, the physical properties required for the conductive paste, or the type of additive, various manufacturing conditions such as mixing or kneading of each component, addition method, and the like are changed within a known range. Alternatively, known steps other than mixing or kneading can be added.

[Use of conductive paste]
The conductive paste according to the present invention is used for forming a conductive layer of a ceramic green sheet. A ceramic multilayer circuit board is manufactured by laminating and firing a plurality of the ceramic green sheets. The conductive layer of the ceramic green sheet includes a wiring electrode layer (so-called wiring pattern) patterned on the circuit board, and a via hole filled in the via hole formed in the ceramic green sheet in order to connect the upper and lower circuit boards. An electrode layer is mentioned. In the ceramic multilayer circuit board, most of the wiring electrode layers and the via-hole electrode layer are formed between the ceramic substrates, so that these electrode layers become “inner layers” of the ceramic multilayer circuit board. A “surface layer” wiring electrode layer and the like are also formed on the surface of the ceramic multilayer circuit board. The conductive paste according to the present invention can be suitably used for forming any one of the inner layer and the surface layer.

  In the present invention, the ceramic green sheet to which the conductive paste is applied may be a ceramic multilayer circuit board having a known configuration. As an example, a ceramic green sheet containing a ceramic component composed of a glass frit component, an aluminum oxide component, and the like and formed into a sheet shape by a known method, a glass ceramic green sheet for a fired substrate that is fired at 800 to 1000 ° C. Can be mentioned.

  Further, the method for applying the conductive paste to the ceramic green sheet is not particularly limited. Specific examples include known coating methods such as screen printing, gravure printing, offset printing, spin coating, dip coating, bar coating, and inkjet. Among these, screen printing is preferably used to form a wiring electrode layer (wiring pattern).

  The ceramic green sheets after applying the conductive paste are laminated by a known method and fired under known conditions to produce a ceramic multilayer circuit board. The ceramic green sheet becomes a ceramic substrate by firing, and the conductive paste becomes a conductive layer by fusing the conductive powder. Here, in the present invention, since the main component of the conductive paste of the conductive powder is atomized silver flake powder, it is possible to generally match the shrinkage ratio of the ceramic green sheet during firing and the shrinkage ratio of the conductive powder. Therefore, it is possible to manufacture a ceramic multilayer circuit board in which generation of warpage is suppressed.

  In particular, in the present invention, the atomized silver flake powder contained in the conductive powder is in the form of flakes (flakes) unlike conventional silver powder, so the difference in the shape of the silver powder is adjusted for the heat resistance of the conductive paste. Can be used. Therefore, the shrinkage rate of the conductive paste can be brought close to the shrinkage rate of the ceramic green sheet, and the range of shrinkage rate matching can be widened.

  Therefore, according to the present invention, the shrinkage rate can be widely changed by adjusting the content of the atomized silver flake powder in the conductive powder or by adjusting the composition of the conductive paste itself. A conductive paste corresponding to the shrinkage rate of the green sheet can be obtained. As a result, it is possible to form a conductor circuit with very little warp even when fired at the same time as the conductive paste and the ceramic green sheet, and it can be used particularly effectively in the production of a high-density ceramic multilayer circuit board. it can.

  The present invention will be described more specifically based on examples and comparative examples, but the present invention is not limited to this. Those skilled in the art can make various changes, modifications, and alterations without departing from the scope of the present invention. In the following examples and comparative examples, the warpage amount of the produced ceramic multilayer circuit board was measured by the following method.

(Measurement of warpage)
In each example or each comparative example, the total warpage amount of the obtained ceramic multilayer circuit board was measured using a warpage gauge (Digimatic Standard Outside Micrometer, manufactured by Mitutoyo Corporation) and measured from the total warpage amount. A value obtained by subtracting the thickness of the target substrate was used as a warp amount for evaluation.

(Manufacture of silver powder)
A spherical silver powder having various average particle diameters is produced by a known atomizing method or chemical reduction method, and a part of the atomized silver powder is exfoliated by the above-mentioned method of pulverizing with a ball mill to obtain a flaky shape. Atomized silver flake powder was produced. Thereby, as shown in Table 1, a total of 13 types of silver powder samples were obtained.

  An example of the atomized silver flake powder used in this example is shown in the electron micrograph of FIG. 1 (a), and an example of the atomized silver powder before flaking is shown in the electron micrograph of FIG. 1 (b). In addition, the atomized silver powder has a maximum particle size of 40 μm or less as it is (Ag1 to Ag3), before slicing (Ag4 to Ag8, Ag13), and a mixture thereof (Ag11, Ag12). ing.

Example 1
As the atomized silver flake powder, the silver powder Ag5 shown in Table 1 (average particle diameter before flaking) was used. The silver powder Ag5 and the organic vehicle (resin component: ethyl cellulose, solvent component: terpineol) were blended in the contents shown in Table 2, and after pre-kneading with a planetary mixer, a three-roll kneading apparatus (UFO manufactured by EME Co., Ltd.) The conductive paste of this example was prepared by kneading with a stirrer.

  Further, a ceramic green sheet having a thickness of 200 μm was prepared by forming a sheet of a mixture of 50 parts by weight of glass frit mainly composed of silicon oxide, aluminum oxide and boron oxide and 50 parts by weight of aluminum oxide.

  Then, on the ceramic green sheet, the conductive paste of the present example was screen-printed with a size of 10 mm □, five layers of them were hot-pressed, and then fired at a maximum temperature of 900 ° C. for 1 hour to thereby produce a ceramic multilayer. A circuit board was manufactured, and its warpage was measured by the method described above. The results are shown in Table 2.

(Example 2)
Example 1 except that the silver powder Ag6 shown in Table 1 (average particle diameter 5.0 μm before thinning) was used as the atomized silver flake powder, and the silver powder Ag6 and the organic vehicle were blended in the contents shown in Table 2. In the same manner as in Example 1, a conductive paste was prepared, a ceramic multilayer circuit board was manufactured, and the warpage was measured by the method described above. The results are shown in Table 2.

(Example 3)
A conductive paste was prepared in the same manner as in Example 2 except that silver powder Ag6 and an organic vehicle were blended in the contents shown in Table 2, and a ceramic multilayer circuit board was produced and the warpage was measured by the method described above. . The results are shown in Table 2.

Example 4
A conductive paste was prepared in the same manner as in Example 2 except that silver powder Ag6 and an organic vehicle were blended in the contents shown in Table 2, and a ceramic multilayer circuit board was produced and the warpage was measured by the method described above. . The results are shown in Table 2.

(Example 5)
A conductive paste was prepared in the same manner as in Example 1 except that the silver powder Ag7 shown in Table 1 (average particle size before thinning: 7.0 μm) shown in Table 1 was used as the atomized silver flake powder. The warpage was measured by the method described above. The results are shown in Table 2.

(Example 6)
The conductive paste was prepared in the same manner as in Example 1 except that the silver powder Ag8 shown in Table 1 (average particle diameter 9 μm before thinning) shown in Table 1 was used as the atomized silver flake powder, and a ceramic multilayer circuit board was manufactured. The warpage was measured by the method described above. The results are shown in Table 2.

(Example 7)
Except for using the mixed silver powder Ag11 shown in Table 1 as an atomized silver flake powder (25 wt% spherical atomized powder having an average particle size of 5.0 μm, 75 wt% flake powder having an average particle size of 5 μm before atomization) A conductive paste was prepared in the same manner as in Example 3, a ceramic multilayer circuit board was produced, and the warpage was measured by the method described above. The results are shown in Table 2.

(Comparative Example 1)
Instead of the atomized silver flake powder, a comparative conductive paste was prepared in the same manner as in Example 1 except that Ag1 (average particle size: 2.7 μm) of spherical atomized silver powder that was not flakes shown in Table 1 was used. As prepared, a ceramic multilayer circuit board was manufactured and the warpage was measured by the method described above. The results are shown in Table 3.

(Comparative Example 2)
A method for preparing a ceramic multilayer circuit board and preparing a ceramic multilayer circuit board in the same manner as in Comparative Example 1 except that Ag2 (average particle size: 5.0 μm) of the atomized silver powder shown in Table 1 was used. The warpage was measured with. The results are shown in Table 3.

(Comparative Example 3)
A comparative conductive paste was prepared in the same manner as in Comparative Example 1 except that Ag3 (average particle size: 7.6 μm) of atomized silver powder shown in Table 1 was used, and a ceramic multilayer circuit board was produced. The warpage was measured with. The results are shown in Table 3.

(Comparative Example 4)
A comparative conductive paste was prepared in the same manner as in Comparative Example 1 except that Ag4 shown in Table 1 (average particle diameter 1.0 μm before thinning) was used as the atomized silver flake powder, and a ceramic multilayer circuit board was manufactured. Then, the warpage was measured by the method described above. The results are shown in Table 3.

(Comparative Example 5)
Instead of atomized silver flake powder, Ag9 (average particle size 5.5 μm) of spherical silver powder by chemical reduction shown in Table 1 was used, and the silver powder Ag9 and organic vehicle were contained in the contents shown in Table 3. A comparative conductive paste was prepared in the same manner as in Example 1 except that it was blended, a ceramic multilayer circuit board was produced, and the warpage was measured by the method described above. The results are shown in Table 3.

(Comparative Example 6)
Except for using the mixed silver powder Ag12 shown in Table 1 (50% by weight of spherical atomized powder having an average particle size of 5.0 μm, 50% by weight of thin powder having an average particle size of 5 μm before atomization) as the atomized silver flake powder. A conductive paste was prepared in the same manner as in Example 3, a ceramic multilayer circuit board was produced, and the warpage was measured by the method described above. The results are shown in Table 3.

(Comparative Example 7)
In place of the atomized flake powder, the conductive paste was used in the same manner as in Example 3 except that Ag10, which is a flake powder obtained by slicing a spherical silver powder by a chemical reduction method by a ball mill, as shown in Table 1 was used. And a ceramic multilayer circuit board was manufactured, and the warpage was measured by the method described above. The results are shown in Table 3.

(Comparative Example 8)
A conductive paste was prepared in the same manner as in Example 1 except that the silver powder Ag13 shown in Table 1 (average particle diameter before thinning) of Table 1 was used as the atomized silver flake powder, and a ceramic multilayer circuit board was manufactured. The warpage was measured by the method described above. The results are shown in Table 2.

  From the results of Tables 2 and 3, it can be seen that if the ceramic multilayer circuit board is manufactured using the conductive paste according to the present invention, the occurrence of warping of the circuit board can be effectively suppressed.

  That is, (i) From the results of Examples 1 to 7 and Comparative Examples 1 to 3 and 6, if the conductive paste according to the present invention using atomized silver flake powder was used, comparison using atomized silver powder that was not flakes It has been found that the amount of warping of the circuit board can be reduced more effectively than when the conductive paste is used.

  In addition, (ii) from the results of Examples 1, 5 and 6 and Comparative Example 7, even if the silver powder was made into a thin piece, if the silver powder was produced by a chemical reduction method, the atomized silver thin piece It was found that the amount of warping of the circuit board was larger than that of the powder.

  Moreover, (iii) From the results of Examples 2 to 4, 7 and Comparative Example 6, the content of the atomized silver flake powder only needs to exceed 50% by weight, but if the content is too high, the amount of warpage increases. I understood. Although the warpage amount of Example 4 is larger than the warpage amounts of Comparative Examples 6 and 8, this warpage amount is a result for comparing the relative magnitudes based on the composition of the silver powder and the organic vehicle. Therefore, Example 4 does not show a result outside the scope of the present invention.

  Further, (iv) From the results of Comparative Examples 4 and 8, and Examples 1, 5 and 6, it was found that the average particle size before flaking is preferably in the range of 2 to 9 μm.

  Further, (v) From the results of Comparative Examples 5 and 7, when using silver powder produced by a chemical reduction method, even if it was sliced (Comparative Example 7) or not (Comparative Example 5), Not only when atomized silver flake powder is used (Examples 1-7, especially Examples 3 and 7), but also when compared with the case where atomized silver powder that has not been flaked (Comparative Examples 1-3) is warped. It turns out that the amount increases.

  It should be noted that the present invention is not limited to the description of the above-described embodiment, and various modifications are possible within the scope shown in the scope of the claims, and are disclosed in different embodiments and a plurality of modifications. Embodiments obtained by appropriately combining the technical means are also included in the technical scope of the present invention.

  The conductive paste according to the present invention can be suitably used for forming a conductive layer of a ceramic multilayer circuit board produced by laminating ceramic green sheets. Therefore, the present invention can be suitably used widely in the field of ceramic multilayer circuit boards.

Claims (4)

When manufacturing a ceramic multilayer circuit board by laminating and firing a plurality of ceramic green sheets, a conductive paste used to form a conductive layer of the ceramic green sheet,
Containing at least silver powder as conductive powder,
A ceramic multilayer, wherein the silver powder is produced by an atomizing method, has an average particle size in the range of 2 to 9 μm, a maximum particle size of 40 μm or less, and is further sliced Conductive paste for circuit boards.   The conductive paste for a ceramic multilayer circuit board according to claim 1, wherein the silver powder is 50 wt% or more of the conductive powder.   The conductive paste for a ceramic multilayer circuit board according to claim 1 or 2, wherein the content of the conductive powder is 95 wt% or less. 4. The powder according to claim 1, wherein at least one metal powder selected from the group consisting of palladium, platinum, gold, nickel and copper is used in combination as the conductive powder other than the silver powder. The conductive paste for a ceramic multilayer circuit board according to Item.