JPH04222889A - Electrically conductive resin paste - Google Patents

Abstract

PURPOSE:To obtain the subject paste excellent in close-contacting property, adhesivity and stress characteristics and suitable for the mounting of a large- sized semiconductor chip by compounding an electrically conductive filler, an insulating filler, a silicone-modified polyimide resin and an organic solvent at specific ratios. CONSTITUTION:The objective paste can be produced by compounding (A) an electrically conductive filler, (B) an insulating filler, (C) a silicone-modified polyimide resin composed of an aromatic acid dianhydride, an aromatic diamine compound and a compound of formula (R1 is 1-5C bivalent aliphatic group, etc.; R2 and R3 are univalent aliphatic group, etc.; l is 1-100), etc., containing >=5wt.% of the silicone component and having an imidation degree of the imidatable silicone-modified polyamic acid of >=80wt.% and (D) an organic solvent at weight ratios A/(B+C) of 50/50 to 90/10, B/(A+C) of 0.1/99.9 to 49/51 and D/(A+B+C) of 0.01/100 to 50/100.

Description

[Detailed description of the invention]

0001

[Industrial Application Field] The present invention is a conductive resin paste that is composed of a conductive filler, an insulating filler, a silicone-modified polyimide resin, and an organic solvent, and is used to bond semiconductor elements such as ICs and LSIs to metal frames, ceramic substrates, etc. It is related to. More specifically, after mounting a chip in a package such as a ceramic package using the paste, the adhesion strength between the chip and the inside of the package is maintained sufficiently even when exposed to high temperatures of 300°C or more like a hermetic seal. The present invention relates to a conductive resin paste obtained.

0002

[Prior Art] Conventionally, regarding ceramic packages,
When mounting a semiconductor element in a package, Au-Si
It was common to join by eutectic method and then seal by hermetic seal. However, as the chip size increases due to the high integration of semiconductor devices, the stress generated in the chip when subjected to thermal history leads to a decrease in reliability, so the mounting material itself is required to have stress relaxation properties. There is. In recent years, conductive resin paste, which is a mixture of epoxy resin and conductive filler such as silver powder, has come into use because it is superior to the conventional Au-Si eutectic method in terms of workability, mass production, and stress relaxation. However, in the case of ceramic packages, there is a process of sealing the glass at a high temperature of 300°C or higher, and epoxy resin systems are insufficient in terms of heat resistance, and a large amount of decomposition gas is generated during sealing, increasing internal stress. There was a problem in that the seal portion would swell. On the other hand, attempts have been made to make conductive resin paste by mixing conductive filler with polyimide resin, which has excellent heat resistance, but polyimide resin, which has excellent heat resistance, has a high glass transition temperature and cannot be dissolved. It is necessary to dissolve it in an organic solvent, and to do so, it was necessary to make it into a varnish in the form of polyamic acid, which is a polyimide precursor. However, since polyamic acid has an amide group and a carboxyl group in its molecule, the interaction between molecules is extremely strong, and in order to obtain a solution with a viscosity of several tens to 100 poise, the concentration must be lower than 30% by weight. It was necessary to suppress it. When a conductive filler is mixed with polyamic acid containing 70% or more of an organic solvent and made into a paste, the amount of solvent becomes 30% or more by weight in the mounting resin, and when the chip is mounted, the solvent during curing heating is Voids were formed in the cured product as traces of removal, causing a decrease in adhesive strength and poor electrical conductivity and heat conduction, which was unfavorable from a reliability standpoint. For these reasons, there has been a strong demand for a highly reliable conductive resin paste as a mounting material for semiconductor devices, which has excellent adhesion, heat resistance, stress relaxation properties, and has no voids in the cured product.

0003

[Object of the Invention] The present inventors have discovered that after mounting a large chip such as an IC in a ceramic package, there is little gas generated during hermetic sealing, and there is no decrease in adhesive strength.
As a result of extensive research in an attempt to obtain a conductive resin paste with extremely few voids in the cured product, which can cause poor reliability, we dissolved silicone-modified polyimide resin in a small amount of organic solvent and created a conductive filler and an insulating paste. The conductive resin paste obtained by adding filler has excellent stress relaxation properties, and generates little decomposition gas even after the glass sealing process.
It was found that there was little decrease in adhesive strength, and there were very few voids in the cured product, which led to the completion of the present invention.

[0004] The purpose is to create a conductive resin paste that satisfies various properties such as electrical properties, mechanical properties, and impurity concentration as a mounting resin, has excellent reliability, and has excellent stress relaxation properties. It is on offer.

[0005]

Structure of the Invention The present invention comprises a conductive filler (A), an insulating filler (B), a silicone-modified polyimide resin (C
) and an organic solvent (D), wherein the weight ratio of (A), (B), and (C) is (A)/{
(B)+(C)}=50/50~90/10, (B)/
{(A)+(C)}=0.1/99.9 to 49/51, and the weight ratio of (D) is (D)/{(A)+(B
)+(C)}=0.01/100 to 50/100, and the silicone-modified polyimide resin (C) is an aromatic acid dianhydride and an aromatic diamine compound. and formula [I] and/or [II]

[0006]

[Case 2]

It consists of a silicone compound represented by the following formula, the silicone component accounts for at least 5% by weight of the total resin content, and at least 80% or more of the silicone-modified polyamic acid that can be imidized is imidized. This is a conductive resin paste characterized by:

[0008] Examples of the conductive filler used in the present invention include powders of metals such as nickel, copper, silver, gold, and AI, and carbon black, but are not particularly limited. However, in the conductive filler used in the present invention, the content of ionic impurities such as halogen ions and alkali metal ions is preferably 10 ppm or less. Further, the shape of the particles used may be flaky, dendritic, spherical, or the like. A mixture of different conductive fillers can also be used. Regarding the particle size, relatively coarse particles and fine particles may be appropriately mixed. The particle size to obtain the necessary properties is 0.01~
50 μm is desirable.

Examples of the insulating filler used in the present invention include calcium carbonate, silica, silicon carbide, silicon nitride, alumina borate, aluminum oxide, zinc oxide, magnesium oxide, titanium oxide, boron nitride, and aluminum nitride. However, it is not particularly limited to these, and two or more different insulating fillers may be used in combination. As for the shape, flaky, dendritic, spherical, etc. are used. There is no problem even if particles of different particle sizes are mixed and used. In the insulating filler used in the present invention, the content of ionic impurities such as halogen ions and alkali metal ions is preferably 10p.
It is desirable that it is below pm.

The conductive filler (A) used in the present invention is necessary for imparting conductivity after the paste is cured, and the insulating filler (B) controls the fluidity of the paste when it is cured, and the voids are prevented from being cured. This is necessary to prevent it from remaining in things. The proportion of these pastes is based on the binder, silicone-modified polyimide resin (
Combined with C), (A)/{(B)+(C)}=50/5
0 to 90/10, (B) {(A) + (C)} = 0.1/
It is desirable that it is 99.9 to 49/51. When the conductive filler (A) is less than 50% by weight based on (B) and (C), conductivity cannot be obtained, which is not preferable, and when it exceeds 90% by weight, the viscosity of the paste increases significantly, Unfavorable in terms of workability. In addition, insulating filler (
If B) is less than 5% by weight based on (A) and (C), the fluidity during hardening of the paste cannot be sufficiently controlled, which is undesirable. If it exceeds 50% by weight, the viscosity increases and workability is This is undesirable from the point of view, and it is undesirable because sufficient conductivity cannot be obtained.

The silicone-modified polyimide resin used in the present invention is an imide of a silicone polyamic acid obtained by reacting an aromatic acid dianhydride with an aromatic diamine compound and a terminal diamino silicone compound and/or an acid anhydride-terminated silicone compound. It can be obtained by converting Further, it is necessary that the silicone component is contained in an amount of at least 5% by weight in the total resin content, and it is desirable that the imidization rate is at least 80% or more. If the silicone modification rate is less than 5%, the adhesion between the chip and the substrate will be significantly reduced, and the adhesion strength after glass seal heat treatment at 300° C. or higher will also be extremely low, which is not preferable. In addition, if the imidization rate is less than 80%, the amide group and carboxyl group in the molecule interact with each other through intermolecular hydrogen bonds, and in order to obtain a solution with a viscosity of 100 poise or less with good workability, it is necessary to The concentration needs to be 30% or less, which inevitably increases the amount of organic solvent contained in the paste, which is not preferable because it causes noticeable voids during heat curing.

Examples of acid anhydride components constituting the silicone-modified polyimide resin used in the present invention include pyromellitic dianhydride, 3,3',4,4'-benzophenonetetracarboxylic dianhydride ,2,2',3,
3'-benzophenone tetracarboxylic dianhydride, 2,
3,3',4'-benzophenonetetracarboxylic dianhydride, naphthalene-2,3,6,7-tetracarboxylic dianhydride, naphthalene-1,2,5,6-tetocarboxylic dianhydride, naphthalene -1,2,4,5-tetracarboxylic dianhydride, naphthalene-1,4,5,8-tetracarboxylic dianhydride, naphthalene-1,2,6,7-tetracarboxylic dianhydride, 4,8-dimethyl-1,2,
3,5,6,7-hexahydronaphthalene-1,2,5
, 6-tetracarboxylic dianhydride, 4,8-dimethyl-
1,2,3,5,6,7-hexahydronaphthalene-2
, 3,6,7-tetracarboxylic dianhydride, 2,6-dichloronaphthalene-1,4,5,8-tetracarboxylic dianhydride, 2,7-dichloronaphthalene-1,4,5,
8-Tetracarboxylic dianhydride, 2,3,6,7-tetrachloronaphthalene-1,4,5,8-tetracarboxylic dianhydride, 1,4,5,8-tetrachloronaphthalene-2, 3,6,7-tetracarboxylic dianhydride, 3,3
',4,4'-diphenyltetracarboxylic dianhydride,
2,2',3,3'-diphenyltetracarboxylic dianhydride, 2,3,3',4'-diphenyltetracarboxylic dianhydride, 3,3'',4,4''-p- Terphenyltetracarboxylic dianhydride, 2,2'',3,3''
-p-terphenyltetracarboxylic dianhydride, 2,3
, 3'',4''-p-terphenyltetracarboxylic dianhydride, 2,2-bis(2,3-dicarboxyphenyl)-propane dianhydride, 2,2-bis(3,4- dicarboxyphenyl)-propane dianhydride, bis(2,3
-dicarboxyphenyl)ether dianhydride, bis(3
, 4-dicarboxyphenyl)ether dianhydride, bis(2,3-dicarboxyphenyl)methane dianhydride, bis(3,4-dicarboxyphenyl)methane dianhydride,
Bis(2,3-dicarboxyphenyl)sulfone dianhydride, bis(3,4-dicarboxyphenyl)sulfone dianhydride, 1,1-bis(2,3-dicarboxyphenyl)ethane dianhydride, 1 , 1-bis(3,4-dicarboxyphenyl)ethane dianhydride, perylene-2,3,8,
9-tetracarboxylic dianhydride, perylene-3,4,9
, 10-tetracarboxylic dianhydride, perylene-4,5
, 10,11-tetracarboxylic dianhydride, perylene-
5,6,11,12-tetracarboxylic dianhydride, phenanthrene-1,2,7,8-tetracarboxylic dianhydride, phenanthrene-1,2,6,7-tetracarboxylic dianhydride, phenanthrene -1,2,9,10-tetracarboxylic dianhydride, cyclopentane-1,2,3,
4-tetracarboxylic dianhydride, pyrazine-2,3,5
, 6-tetracarboxylic dianhydride, pyrrolidine-2,3
, 4,5-tetracarboxylic dianhydride, thiophene-2
, 3,4,5-tetracarboxylic dianhydride and the like, but are not limited thereto.

[0013] Examples of acid anhydride-terminated silicone compounds include

[0014]

[Chemical formula 3]

[0015] etc., but there are no particular limitations.

Specific examples of the aromatic diamine used in the present invention include 3,3'-dimethyl-4,4
'-Diaminobiphenyl, 4,6-dimethyl-m-phenylenediamine, 2,5-dimethyl-p-phenylenediamine, 2,4-diaminomesitylene, 4,4'-methylenedi-o-toluidine, 4,4'- Methylene di-2,
6-xylidine, 4,4'-methylene-2,6-diethylaniline, 2,4-toluenediamine, m-phenylene-diamine, p-phenylene-diamine, 4,4'-
Diamino-diphenylpropane, 3,3'-diamino-
diphenylpropane, 4,4'-diphenylethane, 3
, 3'-diamino-diphenyl ethane, 4,4'-diamino-diphenylmethane, 3,3'-diamino-diphenylmethane, 4,4'-diamino-diphenyl sulfide, 3,3'-diamino-diphenyl sulfide, 4,
4'-diamino-diphenyl sulfone, 3,3'-diamino-diphenyl sulfone, 4,4'-diamino-diphenyl ether, 3,3'-diamino-diphenyl ether, benzidine, 3,3'-diamino-biphenyl,
3,3'-dimethyl-4,4'-diamino-biphenyl, 3,3'-dimethoxy-benzidine, 4,4''-diamino-p-terphenyl, 3,3''-diamino-p
-terphenyl, bis(p-amino-cyclohexyl)
Methane, bis(p-β-amino-t-butylphenyl)
Ether, bis(p-β-methyl-δ-aminopentyl)benzene, p-bis(2-methyl-4-amino-pentyl)benzene, p-bis(1,1-dimethyl-5-amino-pentyl)benzene , 1,5-diamino-naphthalene, 2,6-diamino-naphthalene, 2,4-bis(
β-amino-t-butyl)toluene, 2,4-diamino-toluene, m-xylene-2,5-diamine, p-xylene-2,5-diamine, m-xylylene-diamine, p-xylylene-diamine, 2,6-diamino-pyridine, 2,5-diamino-pyridine, 2,5-diamino-1,3,4-oxadiazole, 1,4-diamino-
Cyclohexane, piperazine, methylene-diamine, ethylene-diamine, propylene-diamine, 2,2-dimethyl-propylene-diamine, tetramethylene-diamine, pentamethylene-diamine, hexamethylene-diamine, 2,5-dimethyl-hexamethylene-diamine Diamine, 3-methoxy-hexamethylene-diamine, heptamethylene-diamine, 2,5-dimethyl-heptamethylene-diamine, 3-methyl-heptamethylene-diamine,
4,4-dimethyl-heptamethylene-diamine, octamethylene-diamine, 4,4-dimethyl-heptamethylene-diamine, octamethylene-diamine, nonamethylene-diamine, 5-methyl-nonamethylene-diamine,
2,5-dimethyl-nonamethylene-diamine, decamethylene-diamine, 1,10-diamino-1,10-dimethyl-decane, 2,11-diamino-dodecane, 1,12-
Examples include, but are not limited to, diamino-octadecane, 2,12-diamino-octadecane, and 2,17-diamino-icosane.

An example of a diamine-terminated silicone compound is:

[0018]

[C4]

[0019] However, it is not particularly limited to this.

[0020] The organic solvent for dissolving the silicone-modified polyimide used in the present invention is not particularly limited, but it may be one type or a mixed solvent of two or more types as long as it can be uniformly dissolved. do not have. Typical solvents of this type are N,N-dimethylformamide, N,N-dimethylacetamide, and N,N-dimethylformamide.
-diethylformamide, N,N-diethylacetamide, N,N-dimethylmethoxyacetamide, dimethylsulfoxide, hexamethylphosphoamide, N-methyl-2-pyrrolidone, pyridine, dimethylsulfone, tetramethylsulfone, dimethyltetramethylesulfone,
Examples include γ-butyrolactone, diglyme, tetrahydrofuran, methylene chloride, dioxane, cyclohexanone, etc., and a poor solvent can be used as a volatility regulator, a film smoothing agent, etc. as long as it can be uniformly dissolved.

Organic solvent (D) used in the present invention
The weight ratio of (D)/{(A)+(B)+(C)}=
It is desirable that it is 0.01/100 to 50/100. If it is less than 0.01/100, the viscosity of the paste becomes extremely high, which is undesirable from the viewpoint of workability, and if it exceeds 50/100, voids are likely to occur when the paste hardens, which is undesirable.

Furthermore, in the present invention, an antifoaming agent may be added if necessary.

The manufacturing process of the conductive resin paste is as follows. Conductive filler (A), insulating filler (B)
), silicone-modified polyimide resin (C), organic solvent (
Weigh D), add antifoaming agent, etc. as necessary, and mix it with a stirrer.
Make a uniform paste using a pickler, mortar, triple roll, kneader, etc. alone or in appropriate combination. The conductive resin paste of the present invention can be applied to a metal frame or ceramic package using a regular dispenser, and after mounting a chip such as an IC, it can be heated and cured in an oven or on a hot plate for bonding. I can do it. The present invention will be specifically explained below using Examples.

[0024]

[Example] (Silicone-modified polyimide resin Synthesis Example 1) A four-necked separable flask equipped with a thermometer, stirrer, raw material inlet, and dry nitrogen gas inlet tube contained 3, 3', 4,
4'-benzophenone tetracarboxylic dianhydride 32.
22g (0.1 mol) N-methyl-2-pyrrolidone 24
0g of silicone diamine of the following formula.

002
5]

[C5]

16.84 g (0.02 mol) was added dropwise over 1 hour using a dropping funnel, and the mixture was gradually reacted.
Continue stirring for an hour. During this period, dry nitrogen gas was kept flowing, and the system was further cooled in an ice bath to maintain the system at 20°C. Next, 10.63 g (0.06 mol) of 2,6-diamino-4-trifluoromethylpyridine and 2.44 g (0.02 mol) of 2,4-diaminotoluene were added to this system, and the system was further heated at 20°C. Stirring was continued for 5 hours while maintaining the temperature to complete the reaction. Subsequently, 72 g of toluene is added to this system, the dry nitrogen gas inlet tube is removed, a Dean starch reflux condenser tube is installed in its place, the ice bath is removed, and the system is heated in an oil bath to raise the temperature of the system. Heating is continued while water generated during imidization is removed from the system by azeotropy with toluene.
Imidization was carried out at 140-150°C, and the reaction was terminated after 5 hours when no water was produced. This polyimide siloxane varnish was added dropwise to 30 liters of pure water over 1 hour with stirring to precipitate the resin, and after filtering to collect only the solid content, it was dried in a dryer at 120°C for 3 hours. . The FT-IR spectrum of the polyimide resin thus obtained was measured, and the imidization rate was determined from the absorption based on the amide bond before imidization appearing at 1650 cm-1 and the absorption based on the imide ring appearing at 1780 cm-1. It was found that 100% of the material was imidized.

(Silicone-modified polyimide resin Synthesis Example 2) Following the same method as Synthesis Example 1, 3,3',4,4
3,3',4,4'-oxydiphthalic dianhydride instead of '-benzophenonetetracarboxylic dianhydride31.
2,6-diamino-4-
9.76 g of 2,4-diaminotoluene instead of the trifluoromethylpyridine/2,4-diaminotoluene mixture (
0.08 mol) is used. The imidization rate of the obtained silicone-modified polyimide resin was 100%.

(Silicone-modified polyimide resin Synthesis Example 3) After a silicone-modified polyamic acid was synthesized using the same method and composition as in Synthesis Example 1, the imidization reaction was completed in one hour. The imidization rate of the obtained silicone-modified polyimide resin was 65%.

(Silicone-modified polyimide resin Synthesis Example 4) By removing silicone diamine from the composition of Synthesis Example 2,
The amount of 2,4-diaminotoluene was 12.22 g (0.1
After synthesizing polyamic acid (mol), the imidization reaction was completed in 30 minutes. The imidization rate of the obtained polyimide resin was 30%.

(Example 1) 100 parts by weight of the silicone-modified polyimide resin obtained in Synthesis Example 1, 400 parts by weight of silver powder with an average particle size of 5 μm, 10 parts by weight of aluminum oxide with an average particle size of 0.02 μm, N-methyl -2-pyrrolidone 100
parts by weight and 20 parts by weight of dioxane were stirred to form a uniform dispersion, and the mixture was kneaded with three rolls to obtain a uniform resin paste for mounting. Adhesive strength immediately after applying the obtained paste to a ceramic package, mounting a 10 x 7 mm square silicon chip, and curing at 1 hour/150°C + 1 hour/280°C and further processing at 420°C for 30 minutes. When measured with a Tensilon universal testing machine, all of them were over the measurement limit of 20 kgf. Further, when the void area inside the cured paste was examined using a soft X-ray image measuring device, it was found to be less than 5% of the total area. Further, when the volume resistivity was measured, it was found to be 1×10 −4 Ω-cm.

(Example 2) A mounting resin paste was obtained in the same manner as in Example 1 except that 5 parts by weight of anhydrous silica with an average particle size of 0.02 μm was used instead of aluminum oxide in the paste composition. Ta. As a result of measuring the adhesive strength in the same manner as in Example 1, the strength both before and after the heat treatment at 420° C. for 30 minutes was 20 kgf or more. Further, the void area in the cured product was less than 5%. The volume resistivity is 1
×10 −4 Ω-cm.

(Examples 3 to 6 and Comparative Examples 1 to 5) Mounting resin pastes were obtained in the same manner as in Example 1 with the paste compositions shown in Table 1, and the results shown in Table 1 were obtained.

[0033]

[Table 1]

As in Examples 1 and 2 and Examples 3 to 6 in Table 1, chips were prepared using a mounting resin paste consisting of a specific proportion of a conductive filler, an insulating filler, a silicone-modified polyimide resin, and an organic solvent. When you glue the
The adhesive strength was 20% after curing by heat treatment at 420℃ for 30 minutes.
A value of kgf/(10×7 mm square) or more was obtained, and it can be seen that the adhesive force after high-temperature sealing of the hermetic seal is also excellent. In addition, the void area is all less than 5%, which is excellent.
The volume resistivity was 1×10 −4 Ω-cm, and it had sufficient electrical conductivity.

When using silicone-modified polyimide that has not been sufficiently imidized as in Comparative Example 1, the viscosity of the paste becomes high, and the amount of organic solvent has to be increased in terms of workability, which causes voids. Thus, voids were generated in 40% of the area of the cured product, and the adhesion strength also significantly decreased, especially after heat treatment. When a normal polyimide resin containing no silicone component was used as a binder as in Comparative Example 2, the adhesion strength was extremely reduced, and the amount of organic solvent increased from the viewpoint of workability, which was undesirable as it led to the generation of voids. If the conductive filler component was small as in Comparative Example 3, sufficient conductivity could not be obtained, which was not preferable. On the other hand, if there was too much conductive filler as in Comparative Example 4, the amount of silicone-modified polyimide resin as a binder would be relatively small, resulting in a decrease in adhesion strength, which was not preferable. If no insulating filler was used at all as in Comparative Example 5, although the adhesion strength was sufficient, the fluidity during curing could not be controlled and voids remained as a way for the solvent to escape, which was undesirable.

[0036]

[Effects of the invention] The conductive resin paste of the present invention contains copper, 4
It can be used to bond semiconductor elements such as ICs to metal frames such as 2-alloy, ceramic substrates, and organic substrates such as glass epoxy.It is especially suitable for bonding large chips of 10 mm square or more, and produces extremely few voids. Because it uses a silicone-modified polyimide resin with a low elastic modulus as a binder, it has excellent stress relaxation properties. In addition, the silicone component has good adhesion to the substrate, and it maintains strong adhesion even when subjected to heat history of over 300 degrees Celsius, such as in the glass sealing process of ceramic packages, and is a highly reliable mounting resin. It is a paste.

Claims (2)

[Claims] 1. A conductive resin paste comprising a conductive filler (A), an insulating filler (B), a silicone-modified polyimide resin (C), and an organic solvent (D), the paste comprising (A), (B), The weight ratio of (C) is (A)/{(B
)+(C)}=50/50~90/10,(B)/{(
A) + (C)} = 0.1/99.9 to 49/51, and the weight ratio of (D) is (D)/{(A) + (B) +
(C)}=0.01/100 to 50/100. Claim 2: Silicone-modified polyimide resin (
C) consists of an aromatic acid dianhydride, an aromatic diamine compound, and a silicone compound represented by formula [I] and/or [II] [Chemical formula 1], and the silicone component is at least 5% by weight or more in the total resin content. The conductive resin paste according to claim 1, wherein at least 80% or more of the silicone-modified polyamic acid that can be imidized is imidized.