JPS63161015A - Electrically conductive resin paste - Google Patents

Abstract

PURPOSE:To obtain the titled paste outstanding in stress relaxation characteristics preventing ICs from failure, suitable for bonding of large-sized chips to copper frame, by blending silver powder, epoxy resin, curing agent and specific flexibilizer in specified proportions. CONSTITUTION:The objective paste can be obtained by blending (A) silver powder, (B) an epoxy resin, (C) a during agent, and (D) as the flexibilizer, an epoxy group-carrying polybutadiene compound in such weight ratios as A/(B+C+D)=60/40-90/10 and D/(B+C)=0.5/100-20/100.

Description

Detailed Description of the Invention [Field of Industrial Application] The present invention is a conductive resin paste consisting of silver powder, an epoxy resin, a hardening agent, and a polybutadiene compound as a flexibility imparting agent, and is used for semiconductor devices such as ICs and LSIs. This relates to a conductive resin paste for bonding materials to metal frames and the like. More specifically, when a large chip such as an IC is bonded to a copper frame and heat treated during the assembly process of the IC, it is possible to prevent chip cracks due to the difference in coefficient of thermal expansion between the large chip and the copper frame, and defective characteristics of the IC due to warping of the chip. The present invention relates to a conductive resin paste with excellent stress relaxation properties.

[Prior art]

Recent remarkable developments in the electronics industry have led to the integration of transistors, ICs, LSIs, and VLSIs, and the degree of circuit integration in these semiconductor devices has rapidly increased, making mass production possible. With the spread of semiconductor products, improving workability and reducing costs in their production have become important issues. Conventionally, the semiconductor element was attached to a conductor such as a metal frame using AU-3i.
It has been common practice to bond them using the eutectic method and then seal them with a barmetic seal to produce a semiconductor product. However, from the viewpoint of workability and cost during mass production, a resin encapsulation method was developed and is now common. Along with this, methods using solder materials and conductive resin pastes, that is, mounting resins, have been taken up as improvements to the Au-3i common product method in the mounting process.

However, the soldering method has drawbacks such as low reliability and easy contamination of element electrodes, and its use is limited to power transistors and power IC elements that require high thermal conductivity. On the other hand, mounting resins are superior in terms of workability and reliability compared to soldering methods, and the demand for them is rapidly increasing.

Furthermore, recently, chips have become larger due to the higher integration density of ICs, etc. On the other hand, since the conventionally used lead frame, 42 alloy frame, is expensive, copper frames are being used for cost reduction purposes. It's starting to feel like it's happening. When the size of a chip such as an IC becomes larger than approximately 4 to 5 m square, Au is used as the mounting method due to the difference in thermal expansion coefficient of the chip and that of the copper frame due to heating during the assembly process of the IC. When using the -3i eutectic method, poor characteristics due to chip cranking and warping have become a problem.

In other words, the coefficient of thermal expansion of silicon, which is the material of the chip, is 8 x 10-64-/"C, while for a 42 alloy frame it is 8X10-6 years/°C, but for a copper frame it is 2X10-5 = 1 = /℃.On the other hand, it is possible to use a mounting resin as a mounting method, but with conventional epoxy resin paste, the elastic modulus is This was too large to absorb the strain between the chip and the copper frame.On the other hand, linear polymer type polyimide resin systems have a lower elastic modulus than epoxy resins and can improve chip warpage.

However, in order to use polyimide resin as a mounting resin, N-methyl-2-pyrrolidone, N, N
- Must be dissolved in large amounts of polar solvents such as dimethylformamide to reduce viscosity. The amount of solvent at this time is more than 30% by weight in the mount resin, and when used to bond the chip and metal frame, voids are formed in the cured product as traces when the solvent is removed during curing heating. This is unfavorable from a reliability standpoint since it causes a decrease in strength and poor electrical conduction and thermal conduction. For this reason, there has been a strong demand for a highly reliable conductive resin paste that has excellent stress relaxation properties that can absorb the distortion of the chip and the copper frame, and has no voids or the like in the cured product.

[Purpose of the invention]

The present inventors have developed a conductive material that does not cause defective characteristics of the IC, etc. due to chip cracks or chip warping, even when a large chip such as an IC is combined with a copper frame, and does not generate voids in the cured product, which can cause poor reliability. As a result of intensive research into a resin paste, it was discovered that a conductive resin paste obtained by adding a specific polybutadiene compound as a flexibility imparting agent to epoxy resin had a small elastic modulus of the cured product, and a large chip and copper frame. It has been found that this material absorbs strain due to the difference in coefficient of thermal expansion and is excellent in stress relaxation, and does not generate voids in the cured product, leading to the completion of the present invention.

The aim is to create a conductive resin paste that satisfies the electrical properties, mechanical properties, impurity concentration, and other characteristics of a mounting resin, has excellent reliability, and has excellent stress relaxation properties. It is on offer.

[Structure of the invention]

The present invention provides a conductive resin paste comprising silver powder (A), an epoxy resin (B), a curing agent (C), and a flexibility imparting agent (D), in which the flexibility imparting agent is a polybutadiene compound having an epoxy group. and (A), (B), (C)
, the ratio of (D) is (A) / ((B) ±(C)
+(D)) =60/40~90/10, ((8
)+(C)/{D}=10010.5 to 100/15.

The silver powder used in the present invention preferably contains 10 pp of ionic impurities such as halogen ions and alkali metal ions.
It is desirable that it be less than m. In addition, the particle size used is flaky, dendritic, spherical, or the like.

Further, relatively coarse silver powder and fine silver powder may be mixed and used, and various shapes may be appropriately mixed.

The epoxy resin used in the present invention may be a normal one, but the content of hydrolyzable halogen groups is 50 (]).
I) Desirably less than m. The following types are used:

Phloroglycinol triglycidyl ether, trihydroxybiphenyl triglycidyl ether,
Tetraglycyl ether of tetrahydroxyphenyl, tetraglycyl ether of tetrahydroxybisphenol F, tetraglycyl ether of tetrahydroxybenzophenone, epoxidized novolak,
Epoxidized polyvinylphenol, triglycyl isocyanate, triglycyl cyanate, triglycyl s-triazine, triglycyl diaminophenol, tetraglycyl aminodiphenylmethane, tetraglycidyl biromellitic acid, triglycyl trimellitic acid, tetraglycyl seal resorcin, diglycidyl sphenol A1 diglycidyl bisphenol F1 diglycidyl bisphenol S1 dihydroxybenzophenone diglycidyl aniline, diglycidyloxybenzoic acid, diglycidyl aniline (0, m
1p) There are diglycidylanitoin, diglycidylaniline, diglycidylaniline, etc., and these can be used alone or in combination of two or more.

Furthermore, a low-viscosity epoxy resin generally called a reactive diluent may be used in combination with the above-mentioned epoxy resin. For example, alicyclic epoxy compounds such as vinyl cyclohexene dioxide, polyolefin epoxides such as diglycidyl phenyl glycidyl ether and dihinyl bezene diepoxy, glycidyl amines such as diglycidyl aniline and diglycidyl toluidine, butyl glycidyl ether, and phenyl glycidyl ether. , glycidyl ethers such as talesyl glycidyl ether.

The curing agent used in the present invention may be any conventional curing agent, such as polyhydric phenols, aromatic polybasic acids, aromatic polyamines, and the like.

The polyhydric phenols are preferably amorphous resinous substances that are initial condensates of phenols and aldehydes and contain as little free phenol as possible. For example, low-molecular liquid novolacs mainly composed of di- and tri-nuclear bodies obtained by reacting monohydric phenols such as phenol, cresol, and xylenol with bomaldehyde under strong acidity in a dilute aqueous solution, and 1 g IJ phenols. These include initial condensates under acidic conditions with polyfunctional aldehydes such as acrolein and glyoxal, and initial condensates under acidic conditions between formaldehyde and polyhydric phenols such as resorcinol, catechol, and hydroquinone.

Examples of aromatic polybasic acids include polybasic acids such as pyromellitic anhydride and trimellitic anhydride, and 2 and 3 thereof.
Polybasic acid derivatives whose molecules are linked by ester bonds with di- or tri-functional polyols, and di-functional acid anhydrides such as maleic anhydride, phthalic anhydride, endomethylene anhydride tetrahydrophthalic anhydride, and hexahydrophthalic anhydride. A eutectic mixture with the above-mentioned polybasic acid is used.

Two or more of these curing agents may be used in combination, if necessary.

The flexibility imparting agent used in the present invention is a polybutadiene compound having an epoxy group. It is well known that polybutadiene compounds generally have a small elastic modulus and excellent stress relaxation properties. However, it had poor adhesiveness and moisture resistance, and could not be used as a mounting resin. On the other hand, epoxy resin has excellent adhesiveness and moisture resistance, but is inferior in stress relaxation properties.

In the present invention, a polybutadiene compound with excellent stress relaxation properties is added to an epoxy resin with excellent adhesiveness and moisture resistance. At this time, it is necessary that the polybutadiene compound has an epoxy group. The functional groups of the epoxy resin react with the curing agent of the epoxy resin, resulting in a uniform cured product, resulting in a resin with a low elastic modulus, excellent stress relaxation properties, and excellent adhesiveness and moisture resistance.

An important point of the present invention is that the polybutadiene compound has an epoxy group and reacts with the hardening agent of the epoxy resin. Separation of the resin and polybutadiene compound occurs, resulting in unsuitable workability, and the cured product is not uniform, resulting in poor adhesion and poor moisture resistance.

The weight ratio of silver powder (A), epoxy resin (B), curing agent C), and flexibility imparting agent (D) of the conductive resin paste in the present invention is (A) / ((B) + ( C)
+(D)}=60/40 to 90/10 is preferable, and even if the ratio of silver powder (A) is higher than this, the electrical conductivity cannot be improved in proportion to the amount added, and the cost is also relatively high. . On the other hand, if the amount of silver powder (A) is less than this ratio range, the electrical conductivity, which is an important characteristic of the conductive resin paste, will decrease.

In addition, the weight ratio of the epoxy resin (B), curing agent (C), and flexibility imparting agent (D) in the resin component is ((B) + (C)
/{D}=10010.5 to 100/15 is preferable,
If the proportion of the flexibility-imparting agent (D) is higher than this, the adhesion and moisture resistance, which are disadvantages of polybutadiene compounds, will decrease.

On the other hand, if the amount of the flexibility imparting agent (0) decreases within this ratio range, the cured resin paste for mounting will not have the stress relaxation properties that are characteristic of polybutadiene compounds.

Furthermore, in the present invention, a curing accelerator, antifoaming agent, etc. may be added as necessary. Further, for viscosity adjustment, a solvent can be added to the cured product within a range that does not cause voids.

The manufacturing process of the conductive resin paste is as follows.

Weigh the silver powder (8), epoxy resin (B), hardening agent (C), and flexibility imparting agent (D), add a hardening accelerator, antifoaming agent, solvent, etc. as necessary, and mix with a stirrer. Use a container, mortar, triple roll, kneader, etc. alone or in appropriate combination to form a uniform paste.

The method of using the conductive resin paste of the present invention is that it can be applied to a metal frame with a regular dispenser, etc.
After mounting the chip, it can be cured and bonded by heating in an oven or on a hot plate.

〔Effect of the invention〕

The conductive resin paste of the present invention can be used for adhering semiconductor elements such as ICs to metal frames such as copper and 4270I, ceramic substrates, and organic substrates such as glass epoxy.In particular, the conductive resin paste can be used for bonding semiconductor elements such as ICs to metal frames such as copper and 4270I, and in particular to bonding semiconductor elements such as ICs to metal frames such as copper and 4270I. It is suitable for adhesion of copper frames and silicon chips, and can prevent chip cracks during heat treatment during the assembly process of ICs due to the difference in thermal expansion coefficient between the copper frame and silicon chip, as well as defective characteristics of ICs due to chip distortion. This is a mounting resin that has excellent stress relaxation properties, which were previously unavailable, and has no voids in the cured product, making it highly reliable.

〔Example〕

The present invention will be explained below with reference to Examples.

[Example 1] Halogen group content of 100 parts by weight of epoxy resin: 300
70 parts by weight of epoxidized phenol novolac (number average molecular weight: 540, epoxy equivalent: 170) of ppm and 30 parts by weight of glycysyl ester of C14 long chain fatty acids with halogen group content of 150 DI) were added in advance as a curing agent at 350 mesh pass. Micronized dicyandiamide 4
Parts by weight, polybutadiene compound having an epoxy group as a flexibility imparting agent (Product name Poly bd R-45E P
T; manufactured by Idemitsu Petrochemical ■) 8 parts by weight, 1,8 diaza-bicyclo(5,4,O)undecene-7 as a curing accelerator
0.5 parts by weight of resorcinol salt was stirred to make a uniform dispersion,
Furthermore, 400 parts of silver powder was added and kneaded using a three-roll mill to obtain a uniform resin paste for mounting.

The obtained paste was applied onto a copper frame, a 7 m square silicone chip was mounted, and the chip crank and chip distortion were examined after curing at 200° C. for 1 hour.

In addition, to prevent pellet distortion, tie both ends of the pellet 7! -Height measured vertically from the line to the top of the warp.

In addition, for the void test of the cured product, the paste was applied on a copper frame, a 5-angle glass piece was mounted, and 1 hour/200
After curing at ℃, the cured product was observed from above the glass piece.

These results are shown in Table 1 together with other properties. The obtained paste cured product has no chip cracks, has a small chip distortion of about 4 μm, has excellent stress relaxation properties, and has no voids in the cured product, and has other properties that are fully satisfactory as a mounting resin.

[Example 2] Epoxidized phenol novolac with a halogen group content of 300 ppm (number average molecular weight: 520
, epoxidized! : 175) 100 parts by weight, phenol novolac (number average molecular ti: 570) 65 as a curing agent
Heavy foot part, polybutadiene compound with epoxy group as a flexibility imparting agent (Product name Poly bd R-45EPT
: Idemitsu Petrochemical Co., Ltd.) 15 parts by weight, 0.5 parts by weight of the same hardening accelerator as in Example 1, and 60 parts by weight of n-butyl cellosolve acetate as a solvent were stirred to make a uniform dispersion, and silver powder was added. 700 parts by weight was added and kneaded with three rolls to obtain a uniform resin paste for mounting.

The properties of the 1q paste were investigated in the same manner as in Example 1, and the results are shown in Table 1.

There is no chip cracking, the chip distortion is as small as 3 μm, it has excellent stress relaxation properties, and there are no voids in the cured product, and the other properties are sufficient for use as a mounting resin.

[Comparative Example 1] In the same manner as in Example 2, only the flexibility imparting agent was replaced with a polybutadiene compound having no epoxy group (product name: Poly bd
R-45HT: Table 1 shows the characteristics of the mounting resin paste obtained as 20 parts by weight of Idemitsu Petrochemical (Idemitsu Wood).

In addition to severe chip distortion, chip adhesion was also weak.

[Comparative Example 2] Table 1 shows the characteristics of a mounting resin paste obtained in the same manner as in Example 2 except that only the flexibility imparting agent was removed.

Chip cracks occurred unless a flexibility imparting agent was added.

[Comparative Example 3] 113 parts by weight of polyimide resin of Pyromellit M/diaminodiphenyl ether condensation type (15% by weight N-methyl 2-pyrrolidone solution in polyamic acid type) and 8 parts by weight of silver powder
Table 1 shows the characteristics of the mounting resin paste obtained by kneading 0 parts by weight in the same manner as in Example 1.

Although the chip strain was small at 4μ, there were many voids in the cured product and the adhesive strength was weak.

(Comparative Example 4.5) In the same manner as in Example 2, in Comparative Example 4, no flexibility imparting agent was added.
．． 5 parts by weight, and in Comparative Example 5, 30 parts by weight to obtain a mounting resin paste.

The characteristic results are shown in Table 1. When the amount of flexibility imparting agent added was small, the chip strain was as large as 16 μm, and when the amount added was large, the adhesive strength was weak.

[Comparative Example 6] A resin paste for mounting was obtained in the same manner as in Example 2, using only 220 parts by weight of silver powder.

The characteristic results are shown in Table 1. Since the amount of silver powder was small, the volume resistivity was 1 x 10'' Ω-cm or more, making it unsuitable as a resin paste for mounting.

[Comparative Example 7] In the same manner as in Example 2, only the epoxy resin containing halogen group III! 2. A resin paste for mounting was obtained by using oooppm of epoxidized phenol novolak (number of molecules 530, epoxidation 1175).

The characteristic results are shown in Table 1, and the amount of hot water extracted impurities was as high as 54 DDm, and the PLT reliability was also poor.

Claims (1)

[Claims] 1. In a conductive resin paste consisting of silver powder (A), epoxy resin (B), curing agent (C) and flexibility imparting agent (D), the flexibility imparting agent is a polybutadiene compound having an epoxy group, The weight ratio of (A), (B), (C), and (D) is (A)/{(B)+(C)+(D)}=60/
40 to 90/10, and the weight ratio of (D) is (D
)/{(B)+(C)}=0.5/100~20/10
A conductive resin paste characterized by having a conductive resin paste of 0.