JPS63102103A - Conducting paste - Google Patents

Abstract

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

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a paste for cerdip substrates and a paste for hybrid integrated circuits.

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 hybrid ICs
In the field of C, there is a strong trend toward large-scale hybrid ICs with excellent heat resistance and thermal shock resistance, especially in industrial equipment such as automotive control circuits and power supply devices.Recent hybrid ICs include diodes and diodes on ceramic substrates. In addition to active components such as transistors and semiconductor ICs, it is equipped with 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 mounting individual components or IC elements on a ceramic substrate, or by making full use of thick film technology. A cerdip IC usually has a silicon IC chip fixed on an alumina substrate with an A pattern of about 20,392 to 86% using a bonding paste.

Recently, aluminum nitride (AIN) has come into use because of its properties such as heat resistance and good thermal conductivity.

Usually, Au-based paste, solder, glass, etc. are used as a bonding method for the cerdip. A
U-based paste has excellent conductivity, is completely chemically stable, and has the best bondability with Au wire.
It easily alloys with St, has very good adhesion to the substrate, and has particularly excellent reliability, but it has the disadvantage of being expensive. To solve this problem, an Ag-Pd paste has been developed in place of AulAg, to which Pd is added to prevent migration, which is a disadvantage of Ag.

These conventional pastes are made by mixing metal powder with a glass metal oxide and kneading the mixture using a vehicle, and the adhesion to the ceramic substrate relies mostly on sintered bonding of the glass lift.

However, glass frit is susceptible to thermal shock, and has the disadvantage that its adhesive strength deteriorates due to heat during the process of baking and packaging the substrate, or due to changes in environmental temperature during use. In order to improve the adhesive strength with the ceramic substrate, attempts have been made to chemically bond with the ceramic substrate by adding a small amount of Cu, but as long as glass frit is used, it is difficult to dramatically improve the thermal deterioration characteristics. Met.

In addition, especially for aluminum nitride substrates, frit-type pastes have poor dispersion during dotting or printing, and not only do they not form a uniform metallized film, but also do not sufficiently diffuse onto the ceramic substrate, resulting in insufficient adhesion strength of the film. It also has the disadvantage of insufficient solder wettability and wire bonding properties.

Problems to be Solved by the Invention In order to solve the above-mentioned drawbacks of aluminum nitride substrates, an attempt was made to provide a paste using a composite powder of silver and copper without using a frit.

Means and Effects for Solving the Problem The present inventors previously used a composite fine powder of silver (Ag) and @(Cu), and added yttrium oxide and organic copper or vanadium pentoxide. proposed a conductive paste to
908), the present invention further improves the previous proposal and is aimed at stably increasing the adhesive strength particularly to aluminum nitride substrates.

The present 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 or vanadium pentoxide, and further contains a copper organic substance in a pure copper paste. A.
This is a conductive paste especially for aluminum nitride substrates, which has the effect of preventing g migration and improving wire adhesion and solder properties.

Next, the present invention will be explained in detail.

The conductive paste of the present invention consists of solid components consisting of metal powder, yttrium oxide or vanadium pentoxide in terms of wood, and organic copper, with the remainder being a vehicle.

Metal powders include ^g powder, composite powder of Ag and Cu, p
As the T-grain powder, a composite powder of Ag and PT is used.

In the present invention, the silver fine powder used has a particle size of 10 μm or less, preferably a layer having an average particle size (D5o) of 0.5 to 5 μm. If it is larger than 10 gm, the dispersibility in the vehicle will be poor and the needle may become clogged during dotting. Furthermore, line resolution deteriorates during printing, making it difficult to obtain a smooth finished surface after firing. #! The powder does not need to be special, and silver powder obtained by a normal reduction method or electrolysis 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 alloy powder, etc. can be used. In particular, mechanical alloy powder is the result of 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 copper particles without causing any damage. When mechanical alloy powder is used, it has the advantage that composite powders having a wide range of Cu contents can be arbitrarily selected and used. ! The particle size of the composite powder of I and copper is 10 or less,
Preferably, the average particle size (D5o) is 0.5 to 5 JLm, and the copper content in the silver and copper composite powder is 20
~95% is appropriate. If the copper content is less than 20%, the film strength will not be sufficient when used as a paste, resulting in
%, the effect of composite powdering 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 aluminum nitride 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.

In the present invention, platinum is added.

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, plating 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 10 gm or less, average particle size (D5o)
The platinum content is preferably about 5 pm or less, and the platinum content is preferably 10 to 30% based on the metal powder in the paste.
It is 20%. If the platinum content is 10% or less, no effect of addition is observed, and if the platinum content is 30% or more, the effect of platinum addition is saturated.

By adding a large amount of platinum within the above range, it is possible to improve solderability while keeping the sheet resistance low, prevent migration, and raise the melting point of the paste to 1000~
It becomes possible to form a strong film that can withstand firing at 1200°C.

The metal powder content in the conductive paste must be 60 to 80%; otherwise, a paste viscosity that is easy to handle cannot be obtained.

The present invention contains yttrium oxide or vanadium pentoxide to improve compatibility with ceramics.

Yttrium oxide (Y2O3) is preferably produced by a chemical method and has a purity of 89.6% or more.

The average particle size is preferably 5 or less, and the finer the particle size is, the better to improve strength or improve dispersibility.If the average particle size is 10g, m or more, uniform dispersibility This is not desirable in terms of surface smoothness.

It has been found that adding yttrium oxide in an amount of 20 ppm to 2%, preferably 0.05 to 1%, in the solid component of the paste has a remarkable effect on improving adhesive strength. If the amount added is less than 20 ppm, no effect will be observed, and if it exceeds 2%, Y2O3 will precipitate. 1) It will have an adverse effect on surface smoothness and inhibit die attachability. 0) How to maintain surface smoothness and improve adhesive strength It is preferable to add 0.05 to 1% to the solid component of the paste.

The Y2O5 added in the present invention is chemically produced, and preferably has a purity of 98.9% or more.0 particle size is an average particle size of 5 or less, preferably 2JL or less, and the finer the better the dispersibility. The effect on strength is also favorable; conversely, if the average particle size is 5 JL or more, it is unfavorable in terms of strength, surface smoothness, and uniform dispersibility.* The addition rate of V 205 is 20 pps.
+2% is optimal. If the amount is less than 20 ppm, no significant effect on strength is observed; if it is added more than 2%, the color tone changes, the number of pores increases, the surface roughness becomes rough, and die attachability (Si (difficult to attach) deteriorates. The effect of Y2O3 is recognized at a firing temperature of 900°C or higher, but the effect is not significant at a firing temperature of 800°C or lower.Addition of both is preferred in order to maintain strength more stably over a wider temperature range.

The copper organic substance used in the present invention is represented by the general formula (R is a saturated hydrocarbon), and is a cyclic terpene derivative or R-9-Cu or R-9-C
The content of tji, which may be represented by the general formula u-9-R, is generally from 3 to 10% by weight. Specifically, there are resinate copper, copper aryl mercaptide, copper terpene methide, and the like. These organic coppers exist in a state dissolved in a solvent in the paste. Organic copper can be produced using the IR method (Infra-
Red Absorption Spectrum, infrared absorption spectrum), NMR method (Nuclear M
Its presence can be determined by distinguishing it from metallic copper using methods such as agnetic resonance (nuclear magnetic resonance method).

The effects of using a copper organic substance are as follows: i) Since it is a liquid, it mixes well with the vehicle, making it possible to form a paste with excellent dispersibility.

il) There is almost no segregation even when dotted on a substrate.

1ii) In the firing process, A g / Cu composite powder, y
The 2o3 powder mainly contributes to the adhesive strength with the substrate, and since the copper organic substance is uniformly dispersed, it has the effect of promoting sintering between the metallized layers.

Therefore, variations in adhesive strength are reduced, and a product with stable strength can be obtained.

The vehicle has the function of uniformly dispersing the fine metal powder, has appropriate viscosity and surface tension when used, and has the function of smoothly dispersing it on the applied surface.The vehicle used in the present invention is made of commonly used ethyl cellulose as a binder. As,
Organic solvents such as terpineol, butylcarpitol, butylcarpitol acetate, and texanol can be used as the solvent. 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.
In the paste state, the viscosity should be adjusted high to avoid separation and segregation of fine metal powder particles, but in the case of dotting, it should be diluted with a solvent and the viscosity should be adjusted to 40-450
Adjust the viscosity to cps. For printing, use high viscosity.

In the present invention, palladium may be added if necessary.

It is a widely known fact that palladium-added paste has the effect of preventing silver migration. Taheest with palladium added alone has the disadvantage that the palladium is converted into metal during the firing process, resulting in an increase in conductor resistance. Therefore, when adding palladium alone, it is preferable to use a fine powder with a particle size (D5o) of 27A11 or less.Also, by using a powder that combines palladium with silver, it is possible to prevent palladium from oxidizing. A film with an extremely good flatness can be obtained.

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#L11 or less, the average particle size (D
5o) is preferably about 5 final layers or less.

The palladium content is 0 relative to the metal powder 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. Palladium is particularly effective when less platinum is used.

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

A paste was prepared by kneading in a three-roll mill using the metal powder shown in Table 1, yttrium oxide, and vanadium pentoxide, and using terpineol containing P1 copper as a vehicle, ethyl cellulose, and a surfactant.

(The following is a blank space) As the silver powder, a commercially available reduced powder was used, and the purity was 99.8% and the particle size was 1 to 4 pots m.

A mechanical alloy powder obtained by mixing and pulverizing 10% silver powder and 80% 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 1 OIL or less.

As platinum, commercially available fine powder of 0.5 to G, 8 p, m, and coprecipitated powder with a ratio of silver to platinum of 85:15 were dispersed in 5 pots or less.

Palladium is a commercially available fine powder with a particle size of 0.8 to 1.8μ,
A coprecipitated powder having a weight ratio of silver and palladium of 7:3 was dispersed in less than 5 μL.

Yttrium oxide has an average particle size of 1.2 tiles and a purity of 98.9.
% of commercially available products were used.

V2o5 was a commercially available product with a purity of 98.8% and a particle size of 3 #L or less.

The vehicle components used were 12% ethyl cellulose based on terpineol, 2.5% nonionic surfactant, and resinate copper added in advance as a copper organic substance.

The proportions of the vehicle component and resinate copper were such that the vehicle component was 11 parts by weight and the resinate copper was 4 parts by weight based on the entire paste.

Since the Cu content in the resinate steel is 6.4%, the pure Cu content from the resinate copper is 0.258 parts by weight.

These metal powders, yttrium oxide, vanadium pentoxide, vehicle, and copper resinate were thoroughly kneaded using a three-roll mill under the compounding conditions shown in Table 1 to obtain a paste. The viscosity at that time is Brookfield viscometer HB
When measured using spindle No. 14 at T, 2
It was 00±50 Kcps.

The substrate is aluminum nitride (dimensions 24.5X 24.5X O,
835 idiom) was used.

The aluminum nitride substrate was used after cleaning with Triclean. A conductive circuit was formed in a predetermined pattern on an aluminum nitride substrate by screen printing using the paste. Printing conditions are 200M
e s h Stainless steel bias tension, emulsion thickness 45.

After printing, the conductive paste was leveled for 10 minutes, dried at 120° C. for 30 minutes, and fired in an AMC type thick film firing furnace manufactured by Watkins & Johnson in an atmospheric atmosphere. The firing conditions were a 60 minute profile with peak temperatures of 1310°C and 820°C for 8 minutes.

The surface of the paste film thus obtained was observed, and the sheet resistance of the film was measured.

Further 2. An L-shaped copper wire (tin-plated) with a diameter of 0.6 mm was fixed onto the pad of the OX 2.0 layer opening using 6/4 solder, and the adhesive strength was measured using a vertical pound tester. These results are shown in Table 2.

(Left below) Next, using an ultrasonic wire bonder made by West Bond, we bonded a thin wire (humanities - 1% Si) with a diameter of 30 l, and measured the bonding strength using a wire pull tester. did. This result is also listed in Table 2. The values in Table 0 indicate the average value of the cutting force for 10 times, and
The mark indicates peeling at the wire joint.

Furthermore, solder wettability was investigated by using solder with a 6:4 composition and immersing the solder pot at 260° C. while controlling the temperature. These results are also listed in Table 2. In the 0 table, 0 indicates the case where the solder was applied according to the pattern, and the x mark indicates the case where the solder was applied only partially.

As is clear from the results in Table 2, the conductive paste according to the present invention has low sheet resistance after firing, high adhesive strength with the ceramic substrate, and excellent solder wettability.

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.

It is clear that the present invention exhibits excellent adhesion even to aluminum nitride substrates.

Claims (1)

[Claims] 1) 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 content of copper in the powder is 0.1-10% and the content of platinum is 10-3
0%, further contains 20 ppm to 2% of yttrium oxide or vanadium pentoxide in the solid component, further contains copper organic matter in a range where the total copper purity in the paste is 0.1 to 10%, and the remainder is A conductive paste characterized by comprising a vehicle component.