JPH0431336A - Thick film conductor composition - Google Patents

Abstract

PURPOSE:To obtain a thick film conductor composition having high adhering strength to aluminum nitride and high reliability by adding a vehicle component to glass powder having a specific composition, copper oxide, Cu-Ag alloy powder and Cu powder and making to pasty state. CONSTITUTION:40-5wt.% vehicle component is added to 60-95wt.% inorganic solid component composed of 1-10wt.% glass powder comprising 40-60wt.% ZnO, 10-45wt,% B2O3 and 4-30wt.% SiO2, 0,5-13wt.% copper oxide, 1-10wt.% Cu-Ag alloy powder and Cu powder of residual part and kneaded to pasty state to afford the aimed thick film conductor composition for porcelain plate. Other said components, at least a species of Al2O3, BaO and ZrO is able to be suitably added to stabilize glass. Furthermore, PbO is also able to be suitably added and Al2O3 and BaO are able to be added within a range not generating steep raising of softening point. Said Al2O3 is able to be added in a range of <=10wt.% and BaO is also able to be added in a range of <=10wt.%.

Description

[Detailed description of the invention]

(Industrial Application Field) The present invention relates to a copper-based conductor composition for ceramic substrates, which has particularly high aluminum nitride adhesive strength and high reliability, and is suitable for forming conductors on ceramic substrates. be. (Prior art and problems to be solved) Conventionally, in the manufacturing method of circuit boards, methods for forming a metallized layer on the surface of the substrate include Au, Ag, Ag/Pd, Ag/P
Noble metal pastes such as T, Ag/Pd/Pt, etc. are mainly used. but. These noble metal pastes are expensive, and in particular, pastes containing Ag as a main component have problems such as poor fuguration and solder leaching resistance. To solve these problems, attempts have been made to improve the characteristics by adding Pd or PT to Ag. However, addition of Pd, Pt, etc. becomes more expensive, and improvement in characteristics is not sufficient. For this reason, attempts have been made to develop inexpensive copper pastes that are solder-eating and free from migration, and various types have been proposed. For example, JP-A-53-49296, JP-A-56-93396
There are numbers, etc. In addition, the applicant had previously applied for a patent application filed in 1986-2.
As proposed in No. 76742, we have developed a copper paste that contains Bi2O, CuO, and Pd powders and does not contain glass frit. However, even when these pastes are baked on aluminum nitride, it is difficult to obtain high adhesive strength.
This is because AQN is stable in the N2 atmosphere in which the Cu paste is fired, so it has poor wettability with glass frit and is less likely to react with glass or metal oxides. An object of the present invention is to eliminate the drawbacks of the prior art described above and to provide an inexpensive and highly reliable copper paste that has excellent adhesion even to AQN. (Means for Solving the Problems) In order to achieve the above object, the present inventor investigated the composition and additives of glass frit in order to obtain a copper-based conductor composition that has excellent adhesive strength to AQN. As a result, we discovered that it is possible to make the copper-based conductor composition according to the above proposal by adding a glass frit of a specific composition and various additives, and hereby the present invention has been made. That is, in the present invention, ZnO: 40 to 60%, B, 03
= 10-45% and SiO, 1-10% of a specific composition of glass powder consisting of 4-30%, and 0.5-13% copper oxide
and 60 to 95% of the inorganic solid component with a composition including 1 to 10% of Cu-Ag alloy powder and the balance consisting of Cu powder,
The gist of the present invention is to provide a thick film conductor composition excellent for use in ceramic substrates, particularly aluminum nitride substrates, which is characterized by being kneaded with 40 to 5% of a vehicle component and made into a paste. (Function) First, the reason for limiting the solid component in the present invention will be explained. The 1-radius glass powder softens and becomes fluid during the firing process, diffuses onto and into the substrate, and plays the role of bonding the conductor composition and the substrate. In addition, a portion of the softened glass also has the role of promoting sintering of the copper powder. For this purpose, glass powder is added in an amount of 1 to 10% based on the total solid component. 1
If the amount is less than 10%, the adhesive strength with the substrate cannot be obtained, and if it exceeds 10%, the solder wettability deteriorates, which is not preferable. However, the composition of the glass powder must be as shown below. ZnO: ZnO is the main component of glass powder, and has the effect of lowering the softening point of glass and improving wettability with the AQN substrate. If the ZnO content in the glass component is less than 40%, the softening point of the glass will be higher than the firing temperature range (850 to 900°C), and the above effects cannot be obtained. On the other hand, if it exceeds 6o% and difficult to vitrify. Therefore, the amount of ZnO based on the entire glass powder is 40 to 60%.
The range shall be . B20. : B20. If the content is small, it is difficult to vitrify and it is difficult to lower the softening point, so 10% of
The above is necessary. However, if it exceeds 45%, it tends to adsorb moisture, resulting in poor stability, a large coefficient of thermal expansion, and difficulty in matching with the substrate. Therefore, the amount of B and O relative to the entire glass powder is 10 to 45
% range. 5in2: If the content of Sin is low, stability such as water resistance will be poor, so it should be 4% or more in the glass component, but if it exceeds 30%, the softening point will rise, which is not preferable. Therefore, the amount of Sin based on the entire glass powder is in the range of 4 to 30%. In addition to the above essential components, AΩ, 0. , BaO and ZrO2
One or more of these can be added as appropriate to stabilize the glass, and PbO can also be added as appropriate. AQ, 0. , BaO: AQzo3 and BaO can be added in an amount of 10% or less for AQ203 and 10% or less for BaO as long as the softening point does not rise sharply. ZrO2: If the content of ZrO2 is large, it becomes easier to deliver the product, so it is desirable to limit the content to within 5% of the total glass component. PbO: PbO has the effect of lowering the softening point, and can be added as necessary to adjust the softening point. However, P
If bO exceeds 15%, the thermal expansion coefficient increases and the glass tends to deteriorate due to the influence of the binder during firing (in an N2 atmosphere), so the amount added should be within 15% of the total glass component. It is desirable to stay. In addition to this, T of 3% or less is added to stabilize the glass.
iO2, Sr01Mg0. It is possible to add Fe2O, CaO, etc. Furthermore, as solid components, in addition to the above-mentioned glass powder, it is essential to add appropriate amounts of oxidized steel, Cu-A&: alloy, and copper powder, as described below, and if necessary, bismuth oxide. (Bi, O, etc.) can also be added as appropriate. Quantification 1 - Oxidized steel may be added in the form of either CuO or Cu2O. These have the effect of promoting sintering of copper particles in the copper paste and forming a conductor. This is considered to be because the vehicle decomposes during firing to form a reducing atmosphere, and a portion of the oxidized steel becomes active Cu, which acts as a sintering aid. Further, a part of it reacts with AQN to produce a CuAQO phase, which also plays a role in improving adhesion. To do this, it is necessary to add 0.5 of copper oxide powder to the entire solid component.
Add in a range of ~13%. If it is less than 0.5%, the effect cannot be obtained, and if it exceeds 13%, solder wettability will deteriorate and sheet resistance will increase. The Cu-Ag alloy powder is added to form a conductor and to improve the solder wettability of the conductor composition. The amount added is in the range of 1 to 10%. If it is less than 1%, the effect cannot be obtained, and if it exceeds 10%, the adhesive strength begins to deteriorate, which is not preferable. The Cu-Ag alloy powder can be used either as a pulverized powder obtained by mechanical alloying or as a powder whose surface is chemically coated with silver on the surface of the copper powder. In the case of mechanical alloying, the powders of each component are first mixed and agitated for the required time under high speed and high energy using a crusher, ball mill, attritor, etc. A mechanically interlocking composite powder in the form of a so-called mechanical alloy is obtained. In addition, the content of Ag is 0 with respect to the whole Cu-Ag alloy powder.
．． It is preferably 5 to 25%. This is because if it is less than 0.5%, the above effects cannot be obtained, and if it exceeds 25%, the effect itself remains the same, but the cost simply increases, and no economic advantage can be obtained. Placement part J3 (Bismuth oxide powder brought in can be added as appropriate because it improves the adhesion effect with AQN and also has the effect of improving solder wettability by converting a part of bismuth oxide into Bi during firing.) In this case, the amount of bismuth oxide should be in the range of 1 to 10. If it is less than 1%, the effect will not be obtained, and if it exceeds 10%, the effect on solder wetting will be adversely affected. !■ The remainder of the powder solid component is It consists essentially of copper powder. Copper powder forms a conductor and has the effect of reducing sheet resistance and improving solder wettability. In particular, fine copper powder has the effect of improving the strength within the metallized layer. Yes, solder wettability,
Effective for surface smoothness. Since the copper fine powder has a large specific surface area, it has a large surface energy, and is therefore considered to improve the strength within the metallized layer in order to promote sintering of the Cu powder. Moreover, the surface smoothness can be improved due to the good sinterability. In addition, with regard to solder wettability, the large specific surface area of the fine copper powder has the effect of preventing softened glass within the system from floating to the metallized surface, which is thought to improve solder wettability. The particle size of the copper powder has a great effect on the metallized state after firing, so the particle size of the copper powder is preferably in the range of 0.4 to 10 μ-.
．． It is desirable to keep it within the range of 4 to 5 μ-. In addition, the oxygen concentration of the copper powder affects the solder wettability and sheet resistance, and has a particularly large effect on the solder wettability after metallization, so it is desirable to control it appropriately.According to the experimental research of the present inventor. , 065% or less. The concentration of the above-mentioned solid components has a great effect on the density of the metallized surface, so it is necessary to set it to 60 to 95%. If it is less than 60%, many pores will occur on the metallized surface, resulting in poor solder wettability, high sheet resistance, and particularly strong adhesion cannot be obtained.On the other hand, if it exceeds 95%, crosstalk will be difficult and printability will be poor. This is not preferable as it will make it extremely bad. In addition, since the particle size of the solid component affects various properties of the copper paste, it is desirable to control it appropriately. Such a solid component is dispersed in 40 to 5% of a vehicle component such as an organic binder and an organic solvent and kneaded to form a paste. As the organic solvent, terpineol, butylcarpitol, texanol, butylcarpitol acetate, etc. can be used, and as the organic binder, for example, ethyl cellulose can be used. The above thick film conductor composition may be produced by adding the vehicle component to a mixed powder of solid component raw materials and kneading the mixture to form a paste. The thick film conductor composition of the present invention can obtain an adhesive strength of 3 kg or more even when fired at a low temperature of 900° C. or less. Of course, such conductor compositions are not limited to AQH, but also include Al, O
It is also applicable to ceramic substrates such as , mullite, etc. The present invention promotes adhesion between the conductor and the substrate and also promotes sintering of the metal particles by using glass with a specific composition when forming the conductor using copper powder and copper-silver mixed powder. , thereby obtaining a strong and low-resistance conductor. (Example) Next, an example of the present invention will be shown. Prepare each powder shown in Table 1, use Texanol as a vehicle, and use ethyl cellulose as a binder to obtain a predetermined solid (wi-forming component) concentration (85%).
They were mixed and kneaded to obtain a paste. The copper powder used was a reduced copper powder having an average particle size of 2 .mu.m that had been subjected to a reduction treatment at 2.degree. C. in a hydrogen stream. A three-roll mill was used to mix the vehicle and powder. The viscosity of the paste is printable viscosity 200-250
kcps was specifically adjusted with ethylcellulose in the vehicle. Using the obtained paste, a standard pattern was printed on one side of an AMN substrate with a purity of 94% or higher. Leveling after printing was carried out for 15 minutes, and drying was carried out for 12°CX1S minutes. A thick film firing furnace was used for firing in a nitrogen atmosphere. Firing conditions are 60 minutes profile, peak temperature 850℃
XIO minutes. The fired film thickness was 14 to 18 microns. Table 1 also shows evaluation results of characteristic values (adhesive strength, solder wettability, and sheet resistance). In addition, to measure the adhesive strength, as shown in FIG. A wire was attached and the peel strength was measured using the 906 Beer method. A case where the adhesive strength was 3 kg or more was evaluated as good. Further, the sheet resistance was measured using a digital volt meter, and a case of 5 Ω/mouth or less was evaluated as good. Solder wettability was evaluated by melting 6/4 solder using a 2■■ pad, dipping it in a solder bath whose temperature was controlled at 230° C., and measuring the wetted area of each pad. Mark O if the wetted area is 95% or more, Q if it is 90-95%.
Each test was evaluated as good with a mark, and if it was 90% or less, a Δ mark and an X mark were added depending on the degree of failure, and it was evaluated as failing. As shown in Table 1, high adhesive strength was obtained even at low firing temperatures, and the solder wettability was good. The sheet resistance is also a satisfactory value.

[Left below]

Each powder shown in Table 2 was prepared in the same manner as in Example 1, using Texanol as a vehicle and ethyl cellulose as a binder, and a predetermined solids concentration (85%). ) and kneaded to obtain a paste. Using the obtained paste, a standard pattern was printed on one side of an AQN substrate with a purity of 94% or higher. Leveling after printing was carried out for 15 minutes, and drying was carried out at 120'C for 15 minutes. A thick film firing furnace was used for firing in a nitrogen atmosphere. Firing conditions are 60 minutes profile, peak temperature 850℃
x10 minutes. The fired film thickness was 14 to 18 microns. Table 2 shows the evaluation results of the characteristic values (adhesive strength, solder wettability, and sheet resistance). Note that the measurement and evaluation of adhesive strength, sheet resistance, and evaluation of solder wettability were the same as in Example 1. As shown in Table 2, high adhesive strength was obtained even at low firing temperatures, the solder wettability was good, and the sheet resistance was also a satisfactory value.

[Left below]

Prepare each powder shown in Table 3, and use Texanol as a vehicle and ethyl cellulose as a binder to obtain a predetermined solid concentration (solid component) in the same manner as in Example. 86%) and mixed to obtain a paste. Using the obtained paste, a standard pattern was printed on one side of an AQN substrate with a purity of 94% or higher. Leveling after printing was carried out for 15 minutes, and drying was carried out at 120° C. for 15 minutes. A thick film firing furnace was used for firing in a nitrogen atmosphere. Firing conditions are 60 minute profile, peak temperature 850℃
The duration was 10 minutes. The fired film thickness was 14 to 18μ6.
Table 3 also shows evaluation results of characteristic values (adhesive strength, solder wettability, and sheet resistance). Note that the measurement and evaluation of adhesive strength, sheet resistance, and evaluation of solder wettability were the same as in Example 1. As shown in Table 3, high adhesive strength is obtained even at low firing temperatures, the solder wettability is good, and the sheet resistance is also a satisfactory value.

[Left below]

Each powder shown in Table 4 was prepared, and in the same manner as in Example 1, using Texanol as the vehicle and ethyl cellulose as the binder, a predetermined solid concentration (86%) was prepared. ) and kneaded to obtain a paste. Using the obtained paste, a standard pattern was printed on one side of an AQN substrate with a purity of 94% or higher. Leveling after printing was carried out for 15 minutes, and drying was carried out at 120'C for 15 minutes. A thick film firing furnace was used for firing in a nitrogen atmosphere. Firing conditions are 60 minutes profile, peak temperature 850℃
x10 minutes. The fired film thickness was 14 to 18 microns. Table 4 also shows evaluation results of characteristic values (adhesive strength, solder wettability, and sheet resistance). Note that the measurement and evaluation of adhesive strength, sheet resistance, and evaluation of solder wettability were the same as in Example 1. Table 4 shows that high adhesive strength was obtained even at low firing temperatures, and the solder wettability was good. The sheet resistance is also a satisfactory value.

[Left below]

(Effects of the Invention) As detailed above, in the present invention, a glass frit of a specific composition characterized by ZnO is added to copper powder as a solid component, and copper oxide, Cυ-Ag alloy powder, and copper powder are further added. The conductor composition contains high adhesive strength, excellent solder wettability, no solder erosion, no migration, and there are no restrictions on the material of the board, making it suitable for various grades of AQN boards. It is possible to provide a highly reliable and inexpensive product that can be applied to other applications.

[Brief explanation of the drawing]

FIG. 1 is a diagram illustrating the procedure for measuring adhesive strength. Patent applicant: Showa Denko Co., Ltd.

Claims (4)

[Claims] (1) In weight% (the same applies hereinafter), ZnO: 40 to 60%
, B_2O_3: 10-45% and SiO_2: 4-3
1-10% of glass powder consisting of 0% and 0.5-10% of copper oxide
A vehicle component of 40 to 5% was added to an inorganic solid component of 60 to 95% with a composition of 13% and 1 to 10% of Cu-Ag alloy powder, and the remainder was Cu powder, and kneaded to form a paste. A thick film conductor composition for a ceramic substrate characterized by: (2) The glass powder further includes AlO_3: 10% or less,
The thick film conductor composition for a ceramic substrate according to claim 1, which contains one or more of BaO: 10% or less and ZrO_2: 5% or less. (3) The thick film conductor composition for a ceramic substrate according to claim 1 or 2, wherein the glass powder further contains PbO: 15% or less. (4) The inorganic solid component further contains 1 to 10 bismuth oxides.
%. The thick film conductor composition for a ceramic substrate according to claim 1, 2 or 3.