JPH04112410A - Composition of thick film conductor - Google Patents

Abstract

PURPOSE:To improve solder corrosion resistance by adding specified quantities of glass powder and bismuth oxide in the paste of composition of thick film conductor. CONSTITUTION:This composition of thick films conductor is composed of a solid component, which is composed of 0.1 to 30% of palladium. 1 to 10 % of bismuth oxide. 0.5 to 10% of composite fine powder of silver and copper. 0.5 to 10 % of glass powder, and the vest of fine powder of silver and paste of a vehicle. The total of the fine powder of silver, the palladium powder, bismuth oxide, the composite fine powder of silver and copper and the glass powder is needed to be 60 to 90 % in the paste. The paste viscosity suitable for easy handling can not be obtained out of this range. This composition has the features of low value of sheet resistance, superior adhesion, and excellent solder reaching resistance property to a substrate made of aluminum nitride.

Description

[Detailed description of the invention]

(Industrial Application Field) The present invention relates to a thick film conductor composition, and more particularly to a paste for a deep dip board and a conductor composition for a hybrid integrated circuit. (Prior Art) In recent years, electronic devices have become significantly thinner and more compact, and as their degree of integration increases, their reliability has further improved, and their applications have continued to expand. Monolithic ICs are rapidly increasing in density and becoming smaller, while in the field of hybrid ICs, especially in industrial equipment such as automotive control circuits and power supplies, large-scale ICs with excellent heat resistance and thermal shock resistance are being used. There is a strong trend toward hybrid ICs. In recent Hybrid E-Cs, in addition to active components such as diodes, transistors, and semiconductor ICs, most electrical components such as coils, transformers, and capacitors are mounted on ceramic substrates. Hybrid integrated circuits have been developed that have further increased the degree of integration and have dramatically improved reliability. These hybrid ICs are constructed by mounting individual components or IC elements on a ceramic substrate or by making full use of thick film technology. Sardeep IC is 5 usually, A
A silicon IC chip is fixed onto an alumina substrate of about 92 to 96% l220 using bonding paste. Recently, aluminum nitride (AQN) has come into use due to its properties such as heat resistance and good thermal conductivity. Usually, Au-based paste has been used for the wiring of these hybrid ICs. However, although the Au-based paste has excellent conductivity and is completely chemically stable, it has the drawback of being expensive. To solve this problem, A4-Pt-based or Ag-Pd-based pastes have been developed in which Au is replaced with Ag and PT or Pd is added to prevent migration, which is a disadvantage of Ag. (Problems to be Solved by the Invention) The present inventors have also proposed Ag-Pd-based and Ag-Pt-based conductive pastes, as previously disclosed in JP-A-62-71110. However, although these pastes have excellent adhesion to AΩN substrates, there is a problem in that solder erosion sometimes occurs during soldering when components are mounted, making it difficult to obtain high reliability. The present invention further improves on the previous proposal and aims to provide a thick film conductor composition that can strengthen adhesive strength particularly to AQN substrates and improve solder corrosion resistance. (Means for Solving the Problems) In order to solve the above-mentioned problems, the present inventors reconsidered the component system of the thick film conductor composition according to the previous proposal, and conducted intensive research on a new component system. This is where the present invention is made. That is, in the present invention, the proportions in the solid components are palladium powder: 0.1 to 30%, bismuth oxide = 1 to 10%, silver and copper composite fine powder: 0.5 to 10%, and glass powder 20%. .5
~10%, the balance being a solid component consisting of fine silver powder, and a vehicle, in which the total amount of fine silver powder, palladium powder, bismuth oxide, fine composite powder of silver and copper, and glass powder is 60% in the paste. The gist of the present invention is a thick film conductor composition characterized in that the thickness of the conductor is 95%. In addition, in another aspect of the present invention, the proportions in the solid components are palladium powder 20.1 to 30%, bismuth oxide 1 to 10%, copper oxide 0.5 to 10%, and glass powder 0.5 to 30%. 10%, the balance being a solid component consisting of fine silver powder. A paste consisting of a vehicle, characterized in that the total content of fine silver powder, palladium powder, bismuth oxide, copper oxide, and glass powder is 60 to 95% in the paste. It is. (Function) In short, the present invention improves the solder corrosion resistance, which is a drawback of silver thread conductor compositions, by adding specific amounts of glass powder and bismuth oxide. Moreover, furthermore,
Addition of composite powder of silver and copper or copper oxide has the unique effect of increasing adhesive strength to the substrate. The composition of the present invention exhibits a remarkable effect particularly on /WIN substrates, but the substrates are not limited to AQN, and AQ20. It is applicable to all kinds of ceramic substrates such as , SiC, BeO, and mullite. Next, the effects of each component in the present invention will be explained. Fine silver powder is added to impart conductivity and has a particle size of 10
μI or less, preferably 0.5 to 5 μm in average particle size
Use the one. If it is larger than 10 μm, the dispersibility in the vehicle will be poor, and there is a risk that the needle will become cold during dotting. Furthermore, line resolution deteriorates during printing, making it difficult to obtain a smooth finished surface after firing. The fine silver powder does not need to be special, and silver powder obtained by a normal reduction method or electrolytic method can be used. In addition, the content of silver fine powder is the remainder of each component below in the entire solid component. Palladium powder Palladium has the effect of preventing silver migration. For this purpose, the content of palladium needs to be 0.1 to 30% based on the total solid components in the paste. The effect is not recognized at less than 0.1%, and 3%
Even if it is added in excess of 0%, no improvement in properties can be expected. Note that when palladium is added in the above range, it improves solder erosion while keeping the sheet resistance low, prevents migration, and increases the melting point of the paste.
It becomes possible to form a strong conductive film that can withstand firing at 200'C. Bismuth Oxide Bismuth oxide is effective in improving solder leaching resistance. However, if the amount added is less than 1%, this effect cannot be obtained. Moreover, when it exceeds 10%, the effect is saturated,
It tends to deteriorate other properties such as solder wettability. Therefore, the amount of bismuth oxide added is in the range of 1 to 10%. Composite powder of silver and copper The composite powder of silver and copper has the effect of improving the adhesion between the conductor composition and the AQN board, and can particularly improve the solder wettability. For this purpose, 0.5 to 10
% addition is necessary. If it is less than 0.5%, the effect cannot be obtained, and if it exceeds 10%, the adhesive strength begins to decrease, which is not preferable. This composite powder can be used as a coprecipitated powder, a mechanical alloy powder, a plating powder, or a powder in which the surface of the copper powder is chemically coated with silver, and the same effect can be obtained. In that case, the content of Ag is preferably 0.5 to 25% based on the entire composite powder. If it is less than 0.5%, the above-mentioned effects cannot be obtained, and if it exceeds 25%, the effect itself is saturated and the cost simply increases, so that no economic advantage can be obtained. Oxidized steel Copper oxide has the same effect as the silver and copper composite powder in improving adhesion to the AQN board, but its solder wettability is slightly inferior to the silver and copper composite powder. It can be added instead. This is due to the reaction between the AQN substrate and copper oxide during the firing process.
It is thought that this is to generate the AQ204 phase. For this purpose, 0.0% copper oxide powder is added to the entire solid component.
Add 5-10%. If it is less than 0.5%, the effect cannot be obtained, and if it exceeds 10%, solder wettability will deteriorate and sheet resistance will increase. Copper oxides include CuO and Cu2O
It may be added in any form. Glass Powder The glass powder preferably contains ZnO or PB○ as its main component, and either glass is added to improve the adhesion between the substrate and the conductor composition and to prevent solder erosion. The amount of glass powder added is in the range of 0.5 to 10% in all cases. If the amount added is less than 0.5%, the above effects cannot be obtained, and if it exceeds 10%, the sheet resistance increases and the solder wettability deteriorates significantly. The glass powder component will be explained in more detail below. ZnO-based glass powder ZnO-based glass powder has a coefficient of thermal expansion close to AQN, so it is suitable for the substrate and is effective against thermal cycle fatigue. In glass powder containing ZnO as a main component, ZnO has the effect of lowering the softening point of the glass and improving wettability with the AQN substrate. However, if the ZnO content is not more than 40%, the softening point of the glass will be lower than the firing temperature range (850-900℃).
), and the above effect cannot be obtained. On the other hand, if it exceeds 60%, it is difficult to vitrify it. Therefore, the amount of ZnO based on the entire glass powder is 4
A range of 0 to 60% is preferred. B20. If the content is small, it will be difficult to vitrify and it will be difficult to lower the softening point, so 10% or more is required. but,
If it exceeds 45%, it will tend to adsorb moisture, resulting in poor stability, a large coefficient of thermal expansion, and difficulty in matching with the substrate. Therefore, B20. The amount is preferably in the range of 10-45%. If the content of 5102 is small, stability such as water resistance will be poor, so 4% or more is required, but if it exceeds 30%, the softening point will increase, which is not preferable. Therefore, the amount of 8102 based on the entire glass powder is 4~
The range shall be 30%. AQ20. , BaO1Zr○2 can be added as appropriate to stabilize the glass. AQ201, BaO
are 10% each within the range that does not cause a sudden increase in the softening point.
The following are preferred. Since ZrO2 tends to crystallize if its content is high, it is preferable to keep it within 5%. PbO can be added as necessary to adjust the softening point. However, if PbO exceeds 15%, the coefficient of thermal expansion increases, so it is preferable to keep it within 15%. In addition, in order to stabilize the glass, Ti is added within 3%.
It is possible to add e2, SrO, MgO, Fe201, CaO, etc. PbO-based glass powder PbO-based glass powder has a thermal expansion coefficient of AQ. Since it is close to Ol, it is suitable for this substrate. In the case of glass containing PbO as a main component, PbO has the effect of lowering the softening point of the glass and improving wettability with the substrate. However, when the PbO content is less than 40%, the softening point of the glass becomes higher than the firing temperature range (850 to 900°C), and the above effects cannot be obtained. on the other hand,
If it exceeds 70%, the softening temperature will be too low, the solder wettability of the metallized phase will be poor, the thermal expansion coefficient will be too large, and the reliability after being in close contact with the substrate will be lacking. Therefore, the amount of PbO based on the entire glass powder is in the range of 40 to 70%. B20. If the content is small, it will be difficult to vitrify and it will be difficult to lower the softening point, so it is necessary to have a content of 10% or more. 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, B20. The amount should range from 10 to 45%. If the content of Sio2 is low, stability such as water resistance will be poor, so 4% or more is required, but if it exceeds 30%, the softening point will increase, which is not preferable. Therefore, the amount of 5102 based on the entire glass powder is in the range of 4 to 30%. ZnO can be added as appropriate in accordance with the proportions of PbO and Sio2 in order to adjust the softening point and the thermal expansion coefficient of the glass. The amount added is 40% or less. AQ20. , BaO, and CaO can be appropriately added in an amount of 10% or less in order to stabilize the glass. In addition, addition of Tie, SrO, MgO, Fe2O3, etc. within 3% is effective for stabilizing the glass, and therefore may be added as appropriate. Vehicle Vehicles are added to uniformly disperse the solid ingredients and form a paste that is easy to use. Examples include organic solvents such as terpineol, butylcarpitol, ethylcellulose, butylcarpitol acetate, and texanol. However, the total amount of the above solid components is 60 to 95% in the paste.
It needs to be %. Outside this range, a paste viscosity that is easy to handle cannot be obtained. (Example) Next, an example of the present invention will be shown. Using the solid components shown in Table 1 (silver powder, palladium powder, composite powder of silver and copper, bismuth oxide, copper oxide, etc.),
Terpineol, ethylcellulose, and a surfactant were used as vehicles and stirred in a three-roll mill to form 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 920'
CX was set for 10 minutes. The fired film thickness was 14 to 18 μm. Table 1 also shows evaluation results of characteristic values (adhesive strength, solder wettability, and sheet resistance). In addition, to measure the adhesive strength, a 2 mm opening pad was adhered to the pattern printed surface of the obtained AQN board, and a 0.8 m
A tin-plated copper wire of mφ was attached, and the peel strength was measured using the 90° peel 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 20IIIΩ/mouth or less was evaluated as good. Solder wettability was determined using a 2mm opening pad and 62Sn-
Evaluation was made by melting 36Pb-2Ag eutectic solder and dipping it in a solder bath whose temperature was controlled at 230°C, and measuring the wetted area of each bat. If the wet area is 95% or more, mark ◎, if it is 90-95%, mark O to evaluate it as good, and if it is 90% or less, mark △ and then mark X according to the degree. It was rated as failing. Furthermore, the solder corrosion resistance is 250 by using a 2mm mouth pad.
The operation of immersing the pad in a 625n-36Pb-2Ag eutectic solder bath at 625n-36Pb-2Ag for 10 seconds and taking it out was repeated, and the number of times when the area of the 2mm pad began to shrink was measured, and those that did so 5 times or more were considered to have passed. It can be seen from Table 1 that all of the invention examples exhibit excellent characteristic values. [Space 1 below] Example 2 Using the solid components shown in Table 2 (silver powder, palladium powder, composite powder of silver and copper, bismuth oxide, copper oxide, etc.),
Terpineol, ethylcellulose, and a surfactant were used as vehicles and stirred in a three-roll mill to form a paste. Using the obtained paste, a standard pattern was printed on one side of each of an AQN substrate or an AQ, 03 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 920℃
XIO minutes. The fired film thickness was 14 to 18 μm. Table 2 also shows evaluation results of characteristic values (adhesive strength, solder wettability, and sheet resistance). From Table 2, the products of the present invention are other than the AQN substrate. It can be seen that it can also be applied to AR20 and substrates.

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(Effects of the Invention) As detailed above, the present invention provides a conductor composition that has a low sheet resistance value, exhibits excellent adhesion, and has excellent solder leaching resistance, particularly to aluminum nitride substrates. It is possible to obtain Patent applicant Hisashi Nakamura, patent attorney representing Showa Denko K.K.

Claims (6)

[Claims] (1) In weight% (the same applies hereinafter), palladium powder: 0.
1-30%, Bismuth oxide: 1-10%, Silver and copper composite fine powder: 0.5-10%, Glass powder: 0.5-10%
, a paste consisting of a solid component with the remainder consisting of fine silver powder, and a vehicle, in which the total of fine silver powder, palladium powder, bismuth oxide, fine composite powder of silver and copper, and glass powder accounts for 60 to 95% of the paste. A thick film conductor composition characterized by: (2) Palladium powder: 0.1-30%, Bismuth oxide: 1-10%, Copper oxide: 0.5-10%, Glass powder:
A solid component consisting of 0.5 to 10% and the remainder consisting of fine silver powder,
1. A thick film conductor composition, which is a paste consisting of a vehicle, wherein the total amount of fine silver powder, palladium powder, bismuth oxide, copper oxide, and glass powder is 60 to 95% in the paste. (3) The glass powder contains ZnO: 40-60%, B_
The thick film conductor composition according to claim 1 or 2, which is a ternary composition consisting of 2O_3: 10 to 45% and SiO_2: 4 to 30%. (4) The glass powder further contains 10% Al_2O_3
The thick film conductor composition according to claim 3, which contains at least one of the following: BaO: 10% or less, ZrO_2: 5% or less, and PbO: 15% or less. (5) The glass powder contains PbO: 40 to 70%, B_
The thick film conductor composition according to claim 1 or 2, which is a ternary composition consisting of 2O_3: 10 to 45% and SiO_2: 4 to 30%. (6) The glass powder further contains 10% Al_2O_3
Below, BaO: 10% or less, CaO: 10% or less, and Z
The thick film conductor composition according to claim 5, which contains at least one type of nO: 40% or less.