JPS6185705A - Conductive paste - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION FIELD OF INDUSTRIAL APPLICATION The present invention relates to pastes for cerdip substrates, in particular to drading pastes.

BACKGROUND OF THE INVENTION In recent years, electronic devices have become significantly thinner and more compact, and as the degree of integration has increased, reliability has further improved, and applications have continued to expand. Monolithic ICs are rapidly increasing in density and becoming smaller, while in the field of hybrid ICs, large ICs with excellent heat resistance and thermal shock resistance are being used, especially in industrial equipment such as automotive control circuits and M source devices. In recent years, there has been a strong trend toward integrated circuits (hybrid scale), and the latest Vibrift ICs have active components such as diodes, transistors, and semiconductor ICs mounted on ceramic substrates, as well as most electrical components such as coils, transformers, and capacitors. 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 filling individual parts or IC elements on a ceramic substrate or by making full use of thick film technology. Surdip IC is usually A
A silicon IC chip is fixed on a 20392-96% alumina substrate using a bonding paste.

Even more durable adhesion is required.

Usually, Au-based paste, solder, glass, etc. are used as a bonding method for the cerdip. A
U-based paste has excellent conductivity.

It is completely chemically stable, has the best bondability with Au wire, is easily alloyed with SI, has extremely good adhesion to substrates, and has particularly excellent reliability, but it has the drawback of being expensive. To solve this problem, an Ag-Pd paste has been developed in which Au is replaced with Ag and Pd is added to prevent migration, which is a disadvantage of Ag.

Problems to be Solved by the Invention These conventional pastes are made by mixing metal powder with glass-based metal oxide and kneading the mixture using a vehicle, and the adhesion to the alumina substrate is mainly due to the sintered bonding of the glass frit. It was something I could rely on.

However, glass frit is vulnerable to thermal shock.

It has the disadvantage that the adhesive strength deteriorates due to thermal deterioration due to the process of baking the substrate and packaging it, or due to changes in the environmental temperature during use. In order to improve the adhesive strength with aluminum substrates, attempts have been made to add a small amount of Cu or the like to chemically bond with the alumina substrate, but as long as glass frit is used, the thermal deterioration characteristics will not be dramatically improved. was difficult.

In other words, if Cu fine powder is simply added, it will separate from other metal fine powders due to the difference in specific gravity in the vehicle, resulting in poor dispersion during drudging and not only will not form a uniform metallized film, but will also result in alumina Since it is not sufficiently diffused into the substrate, the adhesive strength of the film becomes insufficient. In addition, there is a drawback that areas where Cu is segregated during the firing process are locally oxidized and colored, making it impossible to obtain a film with a uniform and smooth surface.

The present invention has been made in order to eliminate the above-mentioned drawbacks, and is a dredging paste for cerdip ICs that has excellent adhesive strength between an alumina substrate and a silicon chip, and also has excellent heat resistance and thermal shock resistance. , easy to use,
It is an object of the present invention to provide an inexpensive fritless type dressing paste.

Means and action for solving the problem The present inventors have previously proposed a conductive paste characterized by using a composite fine powder of silver (CAg) and copper (Cu) (
Japanese Patent Application No. 58-18914) 0 The purpose of the present invention is to further strengthen the adhesive strength by adding yttrium oxide to the above proposal. The gist of the first invention is to contain fine silver powder, fine composite powder of silver and copper, and yttrium oxide, with the remainder being a vehicle. The second invention contains a fine silver powder, a fine composite powder of silver and copper, a fine composite powder of silver and platinum, or a fine platinum powder and yttrium oxide, and the remainder is a vehicle. This has the effect of preventing migration and improving wire adhesion and solder properties.

The gist of the third invention is to contain a fine silver powder, a fine composite powder of silver and copper, a fine composite powder of silver and palladium, or a fine palladium powder and yttrium oxide, with the remainder being a vehicle. It is particularly effective in preventing Ag migration and has the effect of improving wire adhesion and solder properties.

Next, the present invention will be explained in detail. In the present invention, the fine silver powder used is one having a particle size of 1107z or less, preferably one having an average particle size (D blade) of 0.5 to 5.

If it is larger than 1107L, the dispersibility in the vehicle will be poor, and there is a risk that the needle will become clogged during drudging. Furthermore, it becomes difficult to obtain a smooth finished fired surface. The silver powder does not need to be special, and silver powder obtained by a normal reduction method or electrolytic method can be used.

The composite fine powder of silver and copper only needs to maintain a bond between the silver particles and the copper particles in the vehicle, and plating powder, co-precipitated powder, mechanical 70 powder, etc. can be used. In particular, mechanical alloy powder is obtained by mixing and pulverizing silver and copper powders by rotating them at high speed in a ball mill, and the silver particles and copper particles are mechanically interlocked and bonded, and no binder is used. It is possible to maintain a strong bond between silver particles and steel particles without causing any damage. The use of Mechanical 70I powder has the advantage that composite powders having a wide range of Cu contents can be selected and used. The particle size of the silver and copper composite powder is 10 gm or less, preferably the average particle size (Di) is 0.5 to 5 ligatures, and the copper content in the silver and copper composite powder is 2G. -!
35% is appropriate. If the copper content is less than 20%, the film strength will not be sufficient, and if it exceeds 95%, the effect of forming a composite powder will be lost. Further, it is desirable that the specific gravity value be as close as possible to an intermediate value between that of silver and copper in order to improve dispersibility in the vehicle.

The copper content in the metal powder in the conductive paste is 0.1
-10%, preferably 2-5%. Copper content is 0.
If the copper content is less than 1%, the diffusion into the alumina will be insufficient and the adhesive strength will not increase.If the copper content exceeds 10%, the oxidation of copper will become significant, which will even have an adverse effect.

The metal powder content in the conductive paste must be 90 to 90%; otherwise, a paste viscosity that is easy to handle cannot be obtained.

Yttrium oxide (Y203) is preferably produced by a chemical method and has a purity of 98.6% or more.

The average particle size is preferably less than 5 mm, and the finer the particle size is, the better to improve strength or improve dispersibility.When the average particle size is 1 mm or more, uniform dispersion This is not desirable in terms of surface smoothness.

It has been found that adding yttrium oxide in an amount of 0.02 to 2%, preferably 0.05 to 1%, in the solid component of the paste has a significant effect on improving adhesive strength. No effect is observed when the amount added is less than 0.05%, and when it exceeds 2%, Y2O3 precipitates, adversely affecting surface smoothness and inhibiting die attachability. 0 Maintains surface smoothness and improves adhesive strength. To achieve this, it is recommended to add 0.05 to 1% to the solid component of the paste.

The vehicle used in the present invention is made of ethyl cellulose, which is commonly used. As a binder,
As a solvent, btu such as terpineol, butylcarpitol, butylcarpitol acetate, texanol, etc.
Solvents can be used. Further, in order to improve the leakage with the metal powder, adding 0.5 to 10% of a surfactant improves the dispersibility. In addition, 0.1 to 2% of rosin resin is used as a dispersant.
% may be added. In the paste state, the viscosity is adjusted to be high to avoid separation and segregation of fine metal powder particles, but before use, dilute it with a solvent to a viscosity of 40 to 4500.
Adjust the viscosity to P3.

The first invention includes a fine silver powder and a composite fine powder of silver and copper, the total of these fine metal powder particles is 60 to 90%, and the content of copper in the fine metal powder is 0.1 to 90%. lθ%, and 0.02 ethyl oxide and thorium are added to the solid component.
It is a conductive paste containing ~2% and the remainder being vehicle. By configuring the paste as described above, it can withstand thermal shock and has strong bonding strength with significantly improved resistance to thermal deterioration. Further, the paste according to the present invention has good dispersibility during drudging, resulting in an excellent surface skin 119 having smooth and uniform baked clay characteristics.

The second invention is the first invention with platinum added,
Contains fine silver powder, fine composite powder of silver and copper, fine composite powder of silver and platinum or fine platinum powder, the total of these fine metal powder particles is 90 to 90%, and fine metal powder The content of copper in the solid component is 0.1 to 10%, and in the case of a composite powder with silver, the content of platinum is 0.2 to 30%, and furthermore, the content of yttrium oxide in the solid component is 0.02 to 10%. It is a conductive paste containing 2% and the remainder is vehicle. By configuring the paste as described above, it has strong bonding strength that can withstand thermal shock and has significantly improved thermal deterioration resistance.
It has the effect of preventing silver migration and improving wire bonding properties, fine line properties, solder properties, and conductivity. Furthermore, when connecting a wire to a part of the cavity, an AfL wire can be used, which has a great advantage.

Since platinum is chemically stable, it is effective to improve the above properties even when mixed alone, but using a composite powder with silver is even more effective because it is uniformly dispersed in the vehicle. As the composite powder of silver and platinum, non-dry powder, co-precipitated powder, mechanical alloy powder, etc. can be used. A suitable platinum content in the composite powder is 5 to 60%. Mechanical alloy powders with high platinum content can be easily obtained.

The powder particle size of the composite powder is 1 OIL- or less, the average particle size (
DMI) is preferably about 5 pm or less, and the platinum content is 0.2 to 10%, preferably 0.5 to 3.0%, based on the metal particles in the paste. Platinum content is 0.2%
Below, no effect of addition is observed, and above 10%, no cost reduction effect appears.

The third invention is the first invention with the addition of palladium, and includes a fine silver powder, a composite powder of silver and copper, a fine composite powder of silver and palladium, or a fine palladium powder. The total amount of fine metal powder particles is 60 to 90%, and the content of copper in the fine metal powder is 0.1 to 10%, the content of palladium is 0.2 to 30%, and further yttrium oxide. It is a conductive paste containing 0.02 to 2% of solid components, with the remainder being vehicle. By configuring the paste as described above, it not only has a strong bonding strength that can withstand thermal shock and has significantly improved thermal deterioration resistance, but also has a remarkable effect on preventing silver migration and improves wire bonding properties.

It has the effect of improving solder properties and producing a smooth, homogeneous film on the surface.

It is a widely known fact that pastes containing palladium have the effect of preventing silver migration, but in pastes containing only palladium, the palladium is easily oxidized during the firing process, resulting in extreme surface roughness. It has the disadvantage of becoming rough. Therefore, when palladium is added alone.

A fine powder with a particle size (050) of 21 Lm or less must be used.In the present invention, by using a powder in which palladium is composited with silver, a film with an extremely good planar state can be obtained while preventing palladium from oxidizing. I found out that it can be done.

Co-precipitation powder, mechanical alloy powder, and plating powder can be used as the composite powder of silver and palladium. The palladium content in the composite powder is 10-40%, preferably 2
0 to 30% is easy to use.

The particle size of the composite powder is 10 or less, the average particle size (DI
) should be about 5 or less.

The palladium content is 0 relative to the metal particles in the paste.
．． It is 2-30%, preferably 0.5-10%. This is because if the palladium content is less than 0.2%, the effect of addition is not recognized, and even if it is added in an amount of 30% or more, no significant improvement in properties can be expected.

Example Next, the present invention will be explained with reference to Examples.

A paste was prepared by kneading the metal powder and yttrium oxide shown in Table 1 in a three-roll mill using terpineol, ethyl cellulose, and a surfactant as vehicles.

A commercially available reduced silver powder was used, with a purity of 88.8% and a particle size of 1 to 4 L.

A mechanical alloy powder obtained by mixing and pulverizing 90% silver powder and 10% copper powder in a ball mill at high speed was used as a composite powder of silver and copper. The particle size of the composite powder was classified to 10 l or less.

As platinum, a commercially available fine powder of 0.5 to 0.8 gm and a co-precipitated powder with a ratio of silver to platinum of 85:15 were used by dispersing the platinum to a size of 5 gm or less.

The palladium used was a commercially available fine powder with a particle size of 0.8 to 1.8p, tx, and a co-precipitated powder with a weight ratio of silver to palladium of 723, which was dispersed in an amount of 5 ml or less.

Iatrium oxide has an average particle size of 1.2 and a purity of 999%.
A commercially available product was used.

The vehicle component used was one in which 12% ethyl cellulose and 2.5% nonionic surfactant were added to terpineol.

Table 1 shows these metal powders, yttrium oxide, and vehicle.
A paste was obtained by thoroughly kneading the mixture using a three-roll mill under the compounding conditions shown below. The viscosity at that time is Broakfield
d Viscometer HBT, 141! ! When measured using a spindle, it was 200±50 Kcps.

Next, the paste was adjusted to a final viscosity of about 100 cps using a 1:1 mixed solution of butyl calpitol and terpineol as a thinner, and used for drudging.

The substrate is black alumina (i) 2% Al2O3, size 3
The dimensions of the cavity were 8.25X B, 25X O, 18 mm.

The alumina substrate was used after cleaning with trichlorolene. A diluted paste whose viscosity was adjusted was applied dropwise onto this cavity by drudging.

The dorading device used was one manufactured by Shikashita Engineering. After the conductive paste was dredged and leveled for 1 hour, it was dried at 120° C. for 20 minutes, and then fired in an air atmosphere using a 4MC type thick film firing furnace manufactured by Watkins & Company. The firing conditions were a 60 minute profile with peak temperatures of 910°C and 920°C for 10 minutes.

The surface of the paste film thus obtained was observed, and the surface roughness was measured using a surface roughness meter manufactured by Tokyo Seimitsu. Fifty samples were used for each level.

Furthermore, a silicon chip was bonded at 450° C. using Die Attach 921 manufactured by West Bond Co., Ltd. using an Au preform of 2.5×2.5 Peng Roro×25 Peng. Characteristic tests were conducted on the thus obtained cerdip IC. These results are shown in Table 2.

Adhesive strength was determined by die attachability and Guibtsch test. The die attachability was determined by scribing in Japanese Patent Application Publication No. 2003-120002, and the mark Q in Table 2 indicates that the adhesive could be adhered in a short time. The Gui Push test was performed using a vertical pound tester manufactured by Engineered Fist Technical Protect Co., Ltd. on the test piece after the heat resistance test was completed.Table 2
The middle O mark indicates that all 20 test pieces have broken, the Δ mark indicates that even one of the 20 samples has peeled off the film, and the X mark indicates that all 20 test pieces have peeled off. This indicates that it has been peeled off.

For the above heat resistance test, a thermal cycle test and a thermal shock test were conducted. The test conditions are ILL-ST for thermal cycle test.
o 883B +010 C0NDITIO based on dispute 2
It was done in NC. Thermal shock test is the same < MIL
L-ST088381010 Fist 2, GOMDIT
This was done in IOIIIC.

The vertical tensile strength of the fired metallized film was measured using the following method. First, add 10g to the copper stud in the tip 2.85m1+
gold-silicon alloy teJ (
2.2wm x 2.2mm x 50μml) was used as a preform, and a silver plating stand was adhered while scribing at 450°C.Then, the silver plating stud was pulled at a constant speed of 16 l/min. The vertical pull strength was measured using a bush pull tester manufactured by Imada Seisakusho.

As is clear from the results in Table 2, the conductive paste using the composite fine powder of silver and copper according to the present invention has an extremely smooth surface after firing, and has a strong adhesive strength between the silicon chip and the fired metallized film. It is strong and exhibits an extremely excellent effect in that its adhesive strength does not deteriorate even after being subjected to thermal history.

It was found that conductive pastes using platinum powder or silver-platinum composite powder have a good baked-on film, further improve adhesive strength, and do not deteriorate due to thermal history.

The product of the present invention has a very low pounding resistance value, is stable over time, and has good bonding characteristics.
The ability to use aluminum wire is also a major advantage of the present invention.

A prepared paste made by simply mixing palladium powder has poor film quality after firing and poor die attachability unless the palladium particle size is made fine, but when using the mixed powder of silver and palladium according to the present invention, these drawbacks are overcome. This results in even better adhesive strength.

Claims (1)

[Scope of Claims] 1) The total amount of these metal fine powders is 60 to 90% (weight %, the same shall apply hereinafter), including fine silver powder and composite fine powder of silver and copper, and Copper content is 0.1-10%
Furthermore, 0.0 yttrium oxide is added to the solid component.
A conductive paste characterized by containing 2 to 2% and the remainder consisting of a vehicle component. 2) Contains a fine silver powder, a fine composite powder of silver and copper, a fine composite powder of silver and platinum, or a fine platinum powder, the total of these fine metal powders being 60 to 90%, and a fine metal powder. The copper content in the powder is 0.1-10% and the platinum content is 0.2-10%.
10% and further contains 0.02 to 2% of yttrium oxide in the solid component, with the remainder being a vehicle component. 3) Contains fine silver powder, fine composite powder of silver and copper, fine composite powder of silver and palladium, or fine palladium powder, the total of these fine metal powders is 60 to 90%, and fine metal powder The content of copper is 0.1 to 10%, the content of palladium is 0.2 to 30%, and the solid component contains yttrium oxide of 0.02 to 2%, with the remainder being from the vehicle component. A conductive paste characterized by: