JPS59132503A - Composition for forming conductive film - 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] The present invention relates to a paste composition for forming a conductive film.

In order to bond a semiconductor element to a ceramic substrate through a low-melting solder such as a unified silicon eutectic alloy, it is necessary that a metal coating be formed on the ceramic substrate. Conventionally, gold paste, which is a mixture of gold powder and glass powder with an organic vehicle, has been generally used to form a metal film on a ceramic substrate.

When the gold paste is applied to a ceramic substrate and fired, the gold powder becomes a ceramic substrate by melting the glass!
i! If @ is applied, the gold powder is sintered to form a gold coating with a substantially uniform thickness, which exhibits electrical conductivity.

The S1 chip can also be bonded directly to this gold coating. However, when a semiconductor element such as Si 2 , GaP, XGaAs, etc. is bonded to a substrate via an alloy brazing material, the metal covering 11ψ does not need to be made of gold. For this reason, in recent years, a paste for forming a conductive film has appeared that contains inexpensive silver powder instead of gold powder and palladium powder as a palladium source.

The addition of a palladium source causes a decrease in the conductivity of the film, or is effective in preventing discoloration due to oxidation and sulfurization, so 0. It is added in an amount of 1 to 5% by weight.

Such silver thread paste is constructed with reference to the composition of the gold paste described above, and has an average particle size of silver powder of ~3 μm.
m granular silver powder is used, glass powder is contained per 10 θ weight parts of the conductive component, and depending on the case, n oxide, dX bismuth oxide, etc. may be added within the range of up to 7 pawls.

By the way, one of the 11 package ships for semiconductor integrated circuit (IC) equipment lights was CerDIP (CerDIP).
XOθ-ramic Dual In1ine, Pa
There is a type (abbreviation for ckage), and this '! The single type uses a ceramic plate as a substrate, which has a flat-bottomed depression (called a cavity) in the center of the upper surface.

A conductive coating is formed on the bottom of this cavity. Therefore, the gold paste and silver thread paste must first be applied to the bottom of the cavity. Screen printing can be applied to normal paste application, but if the cavity is deep, screen printing cannot be applied, so the paste is diluted with an organic solvent to increase fluidity and applied by dropping it into the cavity. That's what I do. The board on which the paste was dropped is 7
A conductive film is formed at the bottom of the cavity by heating the paste to 00 to /30'C to evaporate the organic solvent in the paste to form a dry film, and then firing it in a firing oven. When using such a paste application method, the diluted paste is
I use it within 3 days, but sometimes I use it after leaving it for a week or more. However, when used after being left for such a long period of time, black spots can be seen scattered on the dried film, and these black spots do not disappear even after firing. Since the solid content of diluted paste tends to settle, it is always stirred before use, but the ink dots do not disappear even if the paste is thoroughly stirred. A detailed examination of these black spots revealed that they were agglomerations of palladium powder. If palladium forms sunspots, the conductive film will not become a silver-palladium alloy, and will not only be useless in preventing discoloration, but also have the drawback that soldering at the sunspots will be poor.

The present invention was made in order to provide a silver thread paste that does not cause agglomeration of palladium even if it is left for a long period of time after being diluted.

In order to achieve this object, the composition for forming a conductive film of the present invention uses at least one type selected from the group consisting of palladium powder, palladium oxide powder, and silver-palladium alloy powder having an average particle size of 0.7 to 3 μm as a palladium source. It is distinctive in that it uses

Conventionally, palladium powder with a particle size of O0θ/~0.06 μm has been used as a palladium source. This palladium powder is usually made by adding a weak reducing agent to the palladium chloride solution? ! J-
It is something that was given. Palladium oxide powder is obtained by roasting this palladium powder in air.

As a result of using this palladium oxide powder as a palladium source, it was surprisingly discovered that palladium did not aggregate even if the diluted paste was left for about Ω weeks. Roasting palladium powder causes some sintering, which increases the average particle size. Based on this discovery, the inventors manually experimented with various palladium particles with different particle sizes, and found that the average particle size was 0. It was found that the palladium source did not agglomerate even if it was left for about Ω weeks if it was above /lrm. The larger the average particle size of the palladium source, the greater the effect of preventing agglomeration II-, or the adhesive strength of the conductive film obtained by firing with the substrate will be modified, so it cannot be made too large.

For this reason, the average particle size of the palladium source was set to 3 μm or less.

As a palladium source, silver-palladium alloy powder can also be used in addition to palladium powder and oxidized Baladywe powder.

This alloy powder is obtained by adding sodium carbonate to a mixed solution of silver nitrate and palladium nitrate and reducing the resulting silver-palladium carbonate.

According to the composition of the present invention, the diluted paste is left open for a long time.
Since the palladium source does not agglomerate, it is now possible to reuse the unused paste, making it possible to effectively utilize expensive IJ materials.

An experimental example is shown below.

Silver powder with an average particle size of 9 μm (Ag − as a Pd source)
When using Pd alloy powder, reduce its silver content) Heavy J, Bi part, PbO:BO: 5iO-Otsu θ:
10: 302 3 2 ('111m ratio) lead borax acid crow powder 2 parts by weight, Pd powder with a particle size of Yuzu, PdO powder, Ag: Pd = 70
A paste was prepared by kneading 30 parts by weight of a terpineol solution (vehicle) containing 20% by weight of ethyl cellulose and 1 part by weight in terms of Ag-Pd alloy powder E Pd. Next, 700 parts by weight of terpineol was added to 100 parts by weight of this paste to dilute it, and 3.5.
7.10, /λ, 15. After 7 and 20 days, the solution was dropped into the cavity of an alumina substrate, and the resulting film was observed after drying and processing at 7.30'C and after firing at QOOC to determine whether there was agglomeration of palladium. The results are shown in Table 1.

In Table 1, those that were not agglomerated are marked with a circle; those that were found to be collected are marked with an x.

/ k Comparative Example // /, A, 2('I)rm), 2
30 10000000000 / Co. The adhesive strength was measured by applying Ω, -m'9y to the conductive film through a gold-silicon alloy brazing material containing 2% silicon orthogonally irradiated with -mm square, thickness, and 20 μm.
, S1 chips with thickness Q and 11 mm are bonded using a die bonder, and a load is applied to the side surface of the bonded Si chips at Ji1'=
), this was done by reading the force at the time of peeling.

From Table 1, palladium sources are Pd powder, PdO powder, Ag-P
dThe average particle size is 0. regardless of the type of alloy powder. /μm
It can be seen that the number of days of exposure for 0.0 g μm 1 Samurai was dramatically improved from 5 days to 72 days, and that for 0.2 μm or more, all cases could withstand exposure to 1 rC for 20 days or more. However, the adhesive strength is ＼1
It decreases as the average particle size increases, and in terms of μm it becomes 7.2 to 9. For practical purposes, /Jkg or more is required.
Therefore, from this result, the average particle size of the Pd source is -f-
Limited.

Applicant: Sumitomo Metal Mining Co., Ltd. Decoy L Super Earth #F Shozo-0-

Claims (1)

[Claims] (1) Contains silver powder and a radium source as a conductive component I
However, the palladium source contains 0.0% in the total conductive component. Contains Ω~5 weight% of glass powder per 700 parts by weight of the conductive component.
In the paste-like conductive film forming composition containing ~5 parts by weight, the palladium has an average particle size of 0.7 to 3 μm.
A composition for forming a conductive film, characterized in that it is at least one selected from the group consisting of palladium powder, palladium oxide powder, and silver-palladium alloy powder.