JPS5844712B2 - adhesive composition - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an adhesive composition for bonding a semiconductor element and an external support electrode (lead frame) in a method of assembling a semiconductor device. An object of the present invention is to provide an adhesive composition that has sufficient heat resistance to withstand the hermetic sealing temperature and has the ability to firmly bond a semiconductor element and an external support electrode in a hermetically sealed semiconductor device. .

Conventionally, the bonding angle between the semiconductor element and the external support electrode was 500°.
The so-called Au-8i eutectic method, which uses a eutectic of Au and Si as a bonding material, which is controlled at a temperature similar to that of C, has been common.

However, in recent years, due to the sharp rise in the price of Au, the price ratio of bonding materials for semiconductor devices has increased, and attempts have been made to use Au-free bonding materials.

In the case of plastic packages, epoxy adhesives are mainly used in place of Au-8i eutectic adhesives.

However, when an epoxy adhesive is applied to a hermetically sealed semiconductor device, the epoxy adhesive usually has a
Since thermal decomposition starts at °C, the sealing temperature (350 °C in the case of Au-8n, 450 to 475 °C in the case of low melting point glass)
°C), it thermally decomposes and cannot function as an adhesive.

For this reason, polyimide adhesives have recently been used as adhesives for hermetically sealed semiconductor devices.
When using ordinary polyimide resin, there are the following problems.

That is, ordinary polyimide resins have a low adhesive strength with silicon wafers, and it is necessary to use an adhesion imparting agent in order to increase the adhesive strength.

Silane coupling agents are mainly used as adhesive properties, and it is known that aminosilane coupling agents are particularly useful for polyimide resins. 1
When added to polyimide acid, which is a precursor, the viscosity of the polyamic acid decreases significantly due to the grain size, which causes the problem that it must be added immediately before use.

To avoid this, there is a method of forming a coupling agent layer on the back surface of the wafer in advance and then applying an adhesive, but this method has the drawback of increasing the number of steps.

Therefore, the present inventors completed the present invention as a result of various studies aimed at improving these drawbacks of conventional polyimide adhesives.

The present invention relates to a repeating unit represented by the formula (1) of 0 to 1 to 50 moles φ obtained by reacting diaminosiloxane, a silicon-free organic diamine, and an organic tetrabasic acid dianhydride, and 50 to 99.9 moles. The present invention relates to an adhesive composition for bonding a semiconductor element and an external support electrode, which contains a polyimide-silicone precursor comprising a repeating unit represented by formula (2), a filler, and a solvent.

(However, R is a divalent hydrocarbon group, R' is a monovalent hydrocarbon group, R'' is a tetravalent organic group, A is a divalent organic group that is the residue of an organic diamine that does not contain silicon, n is an integer greater than or equal to 1).

Polyimide-silicone material consisting of a repeating unit represented by the above formula (1) and a repeating unit represented by the formula (2) 1
An example of the method for producing the precursor is described in Japanese Patent Publication No. 43-27439.

That is, a silicon-free organic diamine, diaminosiloxane, and an organic tetrabasic acid dianhydride are reacted in a solvent,
Polyamic acid, which is a polyimide-silicone precursor, is produced.

In the present invention, the repeating unit represented by the above formula (1) is in the range of 0.1 to 50 moles, and the repeating unit represented by formula (2) is in the range of 50 to 99,9 moles. is adjusted to this range by reacting diaminosiloxane in an amount of 0.1 to 50 mol and silicon-free organic diamine in an amount of 50 to 99.9 mol.

The diaminosiloxane used in the present invention has the general formula % Formula % One type or two or more types of these can be used.

Examples of silicon-free organic diamines include 4.4
'-Diaminodiphenyl ether, 4,4'-diaminodiphenylmethane, 4,4'-diaminodiphenyl sulfone, 4,4'-diaminodiphenyl sulfide, benzidine, mekphenylenediamine, paraphenylenediamine, 1,5-naphthalenediamine, One or more types of 2,6-naphthalenediamine and the like are used.

Examples of the organic tetrabasic acid dianhydride include pyromellitic dianhydride, 3,3',4,4'-diphenyltetracarboxylic dianhydride, 3.3',4.4'penzophenone 1-lacarboxylic dianhydride, Acid dianhydride, cyclopenkunetetracarboxylic dianhydride, 1,2゜5.6-Natsutalentitracarboxylic dianhydride, 2.3. ．． 6.7-
Naphthalenetetracarboxylic dianhydride, 2,3,5.6
-Pyridinetetracarboxylic dianhydride, 1,4,5.8
-Naphthalenetetracarboxylic dianhydride, 3,4,9.
10-perylenetetracarboxylic dianhydride, 4,4'-
There are sulfonyl cyphthalic dianhydrides, etc., and these are 1
A species or two or more species may be used.

An inert solvent is used when producing the polyamic acid precursor from the monomer compound, and particularly preferred is one that dissolves the polyamic acid produced.

For example, N-methyl-2-pyrrolidone, N,N-dimethylacetamide, N,N-dimethylformamide, N,
Eleven types or two or more types, such as N-diethylformamide, dimethyl sulfoxide, hexamethylphosphoramide, and tetramethylene sulfone, are used.

For synthesis of polyamic acids, silicon-free organic diamines, diaminosiloxanes, and organic tetrabasic acid dianhydrides are dissolved as much as possible in a purified inert solvent, and the system is heated to about 80°C or lower, especially around room temperature or lower. Stir while maintaining the temperature.

As a result, the reaction proceeds rapidly, the viscosity of the reaction system gradually increases, and a polyimide-silicone precursor is produced.

When producing a polyimide-silicone precursor from the above-mentioned monomer compounds, in order to obtain the best heat resistance, it is necessary to use an equimolar amount of organic tetrabasic acid dianhydride based on the total amount of silicon-free organic diamine and diaminosiloxane. It is preferable to use a material.

In the polyimide of the present invention, the proportion of repeating units represented by the formula (1) silicone precursor (R, R', square and n are the same as above) in the total copolymer is 0.
It is 1 to 50 moles φ.

This is because if the ratio of the above-mentioned repeating units is less than 0.1 molar ratio, the adhesion to the semiconductor element is poor, and it is necessary to use a coupling agent to ensure adhesion, which satisfies the purpose of the present invention. Because they don't.

In addition, as the content of the repeating unit increases, the heat resistance of the copolymer decreases, and when the content exceeds 50 molar units, the temperature at which weight loss starts becomes 350°C or lower, and the heat resistance applied during sealing of the sealing layer decreases. I can't stand it.

The adhesive composition of the present invention contains the solvent used in producing the polyimide-silicone precursor described above.

The solvent used in the above production includes aromatic solvents such as xylene and toluene, ketone solvents such as acetone, ether glycol solvents such as butyl cellosolve, etc. within a range where the polyimide-silicone precursor does not precipitate, usually 20% by weight. It can also be added in the downwind range.

The adhesive composition of the present invention contains a filler.

As the filler, either an inorganic filler or a conductive filler is used.

As the inorganic filler, silica, metal oxide, quartz glass powder, etc. can be used for the purpose of improving adhesive strength and imparting thixotropy.

In addition, if the electrode part of the element is on the external support electrode side of the element,
When heat dissipation is required, a conductive filler is used, and usually Ag powder is preferred, but a combination of carbon powder such as graphite or carbon black and Ag powder may also be used.

When using Ag powder as the conductive filler, the particle size thereof is preferably less than 5 μm in maximum particle size.

The thickness of the adhesive layer between the semiconductor element and the external supporting electrode is usually 10 to 30 μm, but in the case where Ag powder of 5 μm or more is aggregated, the thickness of the adhesive layer between the semiconductor element and the external supporting electrode is 10 to 30 μm.
This is because the semiconductor element and the external support electrode are not uniformly bonded to each other and sufficient adhesive strength cannot be obtained.

Although there is no particular restriction on the content of Ag powder, it is desirable to use it in a range of 50 to 90 weight parts based on the polyimide-silicone precursor from the viewpoint of adhesion and conductivity.

Bonding of a semiconductor element and an external support electrode using the adhesive composition of the present invention is carried out, for example, in the following manner.

The adhesive is applied by a dispenser or printing method onto the tab of the external support electrode which has been thoroughly cleaned in advance, and the semiconductor element is placed on it and light pressure is applied to make the semiconductor element and the external support electrode adhere well. Heat treatment is performed at a temperature of preferably 300 to 450°C for 30 seconds or more.

At this time, in order to slowly volatilize the solvent and eliminate the generation of bubbles, it is also possible to heat the mixture in advance at 80 to 120°C for 5 to 60 molecules.

At this time, the amount of adhesive applied on the tab is effective from the viewpoint of adhesion, such that when the semiconductor element and the external support electrode are brought into close contact, the adhesive slightly protrudes around the outer periphery of the semiconductor element.

The present invention will be specifically explained below using Examples.

Example 1 4,4 recrystallized using n-butanol as a solvent
'-Diaminodiphenyl ether 9.0.9° 1.2 g of 1,3-bis(aminopropyl)-tetramethyldisiloxane purified by distillation under reduced pressure and 10.9 g of pyromellitic anhydride recrystallized using acetic anhydride were distilled under reduced pressure. The reaction was carried out in 119.6 g of N-methyl 2-pyrrolidone purified by distillation to obtain a polyimide silicone precursor solution with a resin content of 14.5 weight φ and a viscosity of 1 i 125 poise (formula (1)
The repeating unit represented by formula (2) is 10 mol %, and the repeating unit represented by formula (2) is 90 mol %).

This solution was dropped onto the tab of the external support electrode, and after adhering the semiconductor element, heat treatment was performed at 100° C. for 30 minutes and at 350° C. for 30 minutes.

The adhesive strength between the semiconductor element and the external support electrode was measured using a push pull gauge and found to be 18 kg/ffl at 350°C, indicating that the adhesive strength was sufficient to withstand bonding pressure.

Furthermore, the weight loss start humidity i measured with a thermobalance was 450° C., and it was found that the material could sufficiently withstand the ceramic sealing temperature.

Comparative Example 1 4,4'-diaminodiphenyl ether 10.0.9 and pyromellitic anhydride 1 purified by the same method as Example 1
0.9 g of N-methyl-2-pyrrolidone purified by distillation was reacted in 118.4 g of N-methyl-2-pyrrolidone to obtain a polyamic acid solution having a resin concentration of 14.7 weight ratio and a viscosity of 35 poise.

Using this polyamic acid solution, the semiconductor element and the external support electrode were bonded together in the same manner as in Example 1, and the adhesive force at 350°C was measured to be 8 kg/crii, which is sufficient for the pressure during bonding. It was found that it had no adhesive strength.

Example 2 Polyimide-silicone precursor solution 1 used in Example 1
10.5 g of Ag powder with an average particle size of 1.2 μm was added to 0 (l) and mixed uniformly in a mortar.

Apply this on a glass plate and heat it for 30 minutes at 1000C for 35 minutes.
After heat treatment at 0° C. for 30 minutes, the volume resistivity was measured and found to be 10 Ω·.

Further, the semiconductor element and the external support electrode were bonded together in the same manner as in Example 1, and the bonding force was measured to be 20 kg/i.

The adhesive composition of the present invention makes it possible to firmly bond a semiconductor element and an external support electrode without using an adhesion aid such as a coupling agent, and also has sufficient heat resistance for heat treatment during ceramic sealing. It is something that has a nature.

Therefore, it is possible to replace the conventional Au-8i eutectic.
This has a significant effect on reducing the cost of semiconductor devices.

Claims (1)

[Claims] 1. 0 obtained by reacting diaminosiloxane, silicon-free organic diamine, and organic tetrabasic acid dianhydride.
, containing a polyimide-silicone precursor consisting of 1 to 50 mol% of repeating units represented by formula (1) and 50 to 99.9 mol φ of repeating units represented by formula (2), a filler, and a solvent. An adhesive composition for bonding a semiconductor element and an external support electrode. (However, R is a divalent hydrocarbon group, "is a monovalent hydrocarbon group, W is a tetravalent organic group, W is a divalent organic group that is the residue of an organic diamine that does not contain silicon, and n is a divalent organic group. 2. An adhesive composition for bonding a semiconductor element and an external support electrode according to claim 1, wherein the filler is a conductive filler. 3. The filler has a maximum particle size of 5 μm. The adhesive composition for bonding a semiconductor element and an external support electrode according to claim 1, which is an Ag powder of less than or equal to 10%.