JPH04325515A - Resin composition for semiconductor sealing - Google Patents

Abstract

PURPOSE:To obtain the title composition excellent in soldering heat resistance and reliability of humidity resistance by mixing a specified epoxy resin with a curing agent, a specified amount of a filler and an unsaturated carboxylic acid-modified styrene block copolymer. CONSTITUTION:An epoxy resin essentially consisting of an epoxy resin of the formula (wherein two of R<1> to R<8> are each 2,3-epoxypropoxy and the others are H, halogen or 1-4C alkyl) [e.g. 1,5-di(2,3-epoxypropoxy)-naphthalene] is prepared. A modified styrene block copolymer is produced by copolymerizing or grafting a styrene block copolymer with an unsaturated carboxylic acid or its derivative (e.g. methyl acrylate). The title composition is produced by mixing the above epoxy resin with a curing agent (e.g. m-phenylenediamine) and 60-90wt.%, based on the total composition, filler (e.g. fused silica) as essential components.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an epoxy composition for encapsulating semiconductors which has excellent solder heat resistance, moisture resistance reliability and low stress properties.

0002

[Prior art] Epoxy resins have excellent heat resistance, moisture resistance, electrical properties, adhesive properties, etc., and can be given various properties depending on the formulation, so they are used as industrial materials such as paints, adhesives, and electrical insulation materials. has been done.

For example, as a sealing method for electronic circuit components such as semiconductor devices, hermetic seals using metals and ceramics, phenolic resins, silicone resins,
Resin sealing using epoxy resin or the like has been proposed. However, from the viewpoint of economy, productivity, and balance of physical properties, resin sealing using epoxy resin has become the main method.

On the other hand, recently, higher density and automation have been promoted in the mounting of components on printed circuit boards, and instead of the conventional "insertion mounting method" in which lead pins are inserted into holes in the board, components are soldered onto the surface of the board. The "surface mount method" for attaching devices has become popular. Along with this, the packaging has changed from the conventional DI.
From P (dual in-line package) to QFP (quad flat package) or SOP (small outline package) suitable for high-density mounting and surface mounting.
packaging), etc.

[0005] With the transition to the surface mounting method, the soldering process, which had not been a problem in the past, has become a big problem. In the conventional pin insertion mounting method, only the leads are partially heated during the soldering process, but in the surface mounting method, the entire package is immersed in a heating medium and heated. Soldering methods for surface mounting methods include immersion in a solder bath and heating with saturated vapor of inert gas (vapor phase method).
or an infrared reflow method, but in either method the entire package is heated to a high temperature of 210 to 270°C. For this reason, packages sealed with conventional sealing resin have problems such as cracks occurring in the resin part during soldering, and peeling at the interface between the chip and the resin, resulting in a decrease in reliability and making it unusable as a product.

[0006] The occurrence of cracks in the soldering process and the peeling of the interface between the chip and the resin are caused by the moisture absorbed between the post-curing and the mounting process becoming explosively vaporized and expanding during the soldering heating process. As a countermeasure to this problem, a method is used in which the post-cured package is completely dried and stored in a sealed container before being shipped.

Various improvements in sealing resins have also been studied. For example, by adding an epoxy resin having a naphthalene skeleton,
Method for achieving low stress in resin (Japanese Patent Application Laid-Open No. 2-88621
(Japanese Patent Application Laid-Open No. 2-110958).

On the other hand, when a semiconductor is encapsulated with an epoxy resin, the linear expansion coefficient of the epoxy resin is much larger than that of the semiconductor, so thermal stress is applied to the semiconductor element due to temperature changes, and this causes aluminum wiring to deteriorate. There were problems such as current leakage due to sliding and cracks occurring in the passivation film and the sealing resin itself, resulting in decreased reliability. In order to solve this problem and reduce the stress of the sealing resin, it is effective to lower the coefficient of linear expansion and the modulus of elasticity of the sealing resin.

[0009] In order to lower the linear expansion coefficient of the sealing resin, there are known methods of selecting the type of filler and filling the resin with a high filler.

[0010] Also, in order to lower the elastic modulus of the sealing resin, it is effective to add an elastomer component; for example, a method of adding a styrene block copolymer (Japanese Patent Laid-Open No. 63
-251419) and the like have been proposed.

[0011]

However, the method of enclosing a dry package in a container has the disadvantage that the manufacturing process and handling of the product are complicated, and the product price is high.

[0012] In addition, resins that have been improved by various methods are gradually producing effects, but they are still not sufficient. Adding an epoxy resin with a naphthalene skeleton,
Method for achieving low stress in resin (Japanese Patent Application Laid-Open No. 2-88621
(Japanese Patent Publication No. 2-110958) is effective in preventing cracks in the resin part during soldering, but when a large chip is used, the interface between the chip and the resin peels off, reducing moisture resistance reliability. was there.

On the other hand, in order to lower the elastic modulus of the sealing resin, there is a method of reducing the stress of the epoxy resin by adding a styrene block copolymer (Japanese Patent Laid-Open No. 63-2514).
19) is effective and effective in preventing cracks in the resin portion during soldering, but it did not solve the problem of peeling at the interface between the chip and the resin.

An object of the present invention is to solve the problem of peeling of the interface between the chip and the resin that occurs during the soldering process of a package using such a large chip, to prevent a decrease in reliability, and to prevent semiconductor elements from changing due to temperature changes. The thermal stress is small,
That is, the object of the present invention is to provide an epoxy composition for semiconductor encapsulation that has excellent soldering heat resistance, moisture resistance reliability, and low stress properties.

[0015]

[Means for Solving the Problems] The present inventors have achieved the above problems by adding a modified styrenic block copolymer to an epoxy resin with a specific structure, and have developed a method for semiconductor encapsulation that meets the purpose. It was discovered that an epoxy composition can be obtained, and the present invention was achieved.

That is, the present invention provides an epoxy resin (A),
A resin composition comprising a curing agent (B), a filler (C), and a modified styrenic block copolymer (D) as essential components, wherein the epoxy resin (A) has the following formula (I
)

[0017]

[Case 2]

(However, two of R1 to R8 are 2,
It represents a 3-epoxypropoxy group, and the others represent a hydrogen atom, a halogen atom, or an alkyl group having 1 to 4 carbon atoms. )
The modified styrenic block copolymer (D) contains the epoxy resin (a) represented by the following as an essential component, the proportion of the filler (C) is 60 to 90% by weight, and the modified styrenic block copolymer (D) is a styrenic block copolymer. The object of the present invention is to provide an epoxy composition for semiconductor encapsulation, which is made by copolymerizing or grafting a polymer with an unsaturated carboxylic acid or a derivative thereof.

The configuration of the present invention will be explained in detail below.

The epoxy resin (A) in the present invention has the following formula (I)

[0021]

[Chemical 3]

(However, two of R1 to R8 are 2,
It represents a 3-epoxypropoxy group, and the others represent a hydrogen atom, a halogen atom, or an alkyl group having 1 to 4 carbon atoms. )
It is important to contain the epoxy resin (a) having the skeleton represented by as an essential component in terms of soldering heat resistance and moisture resistance. In the above formula (I), two of R1 to R8 are 2,3-epoxypropoxy groups, but other six preferred examples include a hydrogen atom, a methyl group, an ethyl group, a propyl group, an i- propyl group, n-butyl group, se
Examples include c-butyl group, tert-butyl group, chlorine atom, and bromine atom.

Preferred specific examples of the epoxy resin (a) in the present invention include 1,5-di(2,3-epoxypropoxy)naphthalene, 1,5-di(2,3-epoxypropoxy)-7-methyl Naphthalene, 1,6-di(2
, 3-epoxypropoxy) naphthalene, 1,6-di(
2,3-Epoxypropoxy)-2-methylnaphthalene, 1,6-di(2,3-epoxypropoxy)-8-methylnaphthalene, 1,6-di(2,3-epoxypropoxy)-4,8- Dimethylnaphthalene, 2-bromo-1
, 6-di(2,3-epoxypropoxy)naphthalene,
Examples include 8-bromo-1,6-di(2,3-epoxypropoxy)naphthalene and 2,7-di(2,3-epoxypropoxy)naphthalene.

The epoxy resin (A) in the present invention may contain, in addition to the above-mentioned epoxy resin (a), other epoxy resins in addition to the epoxy resin (a). Other epoxy resins that can be used in combination include, for example, cresol novolak epoxy resins, phenol novolac epoxy resins, biphenyl epoxy resins, various novolac epoxy resins synthesized from bisphenol A and resorcinol, and bisphenol A. Examples include type epoxy resins, linear aliphatic epoxy resins, alicyclic epoxy resins, heterocyclic epoxy resins, and halogenated epoxy resins.

There is no particular restriction on the proportion of the epoxy resin (a) contained in the epoxy resin (A), and the effects of the present invention can be exhibited as long as the epoxy resin (a) is contained as an essential component. In order to exhibit a sufficient effect, epoxy resin (a) is usually mixed into epoxy resin (A) by 5%.
It is necessary to contain 0% by weight or more, preferably 70% by weight or more.

In the present invention, the blending amount of the epoxy resin (A) is usually 4 to 20% by weight, preferably 6 to 18% by weight.
It is.

The curing agent (B) in the present invention is not particularly limited as long as it can be cured by reacting with the epoxy resin (A), and specific examples thereof include phenol novolak resin, cresol novolak resin, bisphenol -Various novolac resins synthesized from Lure A and resorcinol, phenolic curing agents such as various polyhydric phenol compounds, acid anhydrides such as maleic anhydride, phthalic anhydride, and pyromellitic anhydride, metaphenylene diamine, diamino Examples include aromatic amines such as diphenylmethane and diaminodiphenylsulfone. For semiconductor encapsulation, phenolic curing agents are preferably used from the viewpoint of heat resistance, moisture resistance, and storage stability, and two or more types of curing agents may be used in combination depending on the application.

In the present invention, the amount of curing agent (B) is usually 2 to 15% by weight, preferably 3 to 10% by weight. Furthermore, the compounding ratio of the epoxy resin (A) and the curing agent (B) should be such that the chemical equivalent ratio of (B) to (A) is 0.7 to 1.3, especially 0. .8~1
．． It is preferable that it is in the range of 2.

[0029] Furthermore, in the present invention, epoxy resin (A)
A curing catalyst may be used to promote the curing reaction of and curing agent (B). The curing catalyst is not particularly limited as long as it promotes the curing reaction, and examples include 2-methylimidazole and 2-methylimidazole.
, 4-dimethylimidazole, 2-ethyl-4-methylimidazole, 2-phenylimidazole, 2-phenyl-4-methylimidazole, imidazole compounds such as 2-heptadecyl imidazole, triethylamine,
Benzyldimethylamine, α-methylbenzyldimethylamine, 2-(dimethylaminomethyl)phenol, 2
, 4,6-tris(dimethylaminomethyl)phenol, 1,8-diazabicyclo(5,4,0)undecene-
Tertiary amine compounds such as 7, zirconium tetramethoxide, zirconium tetrapropoxide, tetrakis (
Organometallic compounds such as acetylacetonato)zirconium, tri(acetylacetonato)aluminum, and organic compounds such as triphenylphosphine, trimethylphosphine, triethylphosphine, tributylphosphine, tri(p-methylphenyl)phosphine, tri(nonylphenyl)phosphine, etc. Examples include phosphine compounds. Among them, from the viewpoint of moisture resistance, organic phosphine compounds are preferred, and triphenylphosphine is particularly preferably used. Two or more of these curing catalysts may be used in combination depending on the application, and the amount added is preferably in the range of 0.5 to 5 parts by weight per 100 parts by weight of the epoxy resin (A).

Fillers (C) in the present invention include fused silica, crystalline silica, silicon nitride, silicon carbide, calcium carbonate, magnesium carbonate, alumina, magnesia, clay, talc, calcium silicate, titanium oxide,
Asbestos, glass fiber, etc. can be added. Among them, fused silica is preferably used because of its low stress properties.

[0031] Here, fused silica means amorphous silica having a true specific gravity of 2.3 or less. Its production does not necessarily have to go through a molten state, and any production method can be used. Examples include a method of melting crystalline silica and a method of synthesizing it from various raw materials.

In the present invention, the proportion of filler (C) is:
60 to 90% by weight of the total from the viewpoint of formability and low stress properties
It is.

In the present invention, it is preferable from the viewpoint of reliability that the filler (C) is previously surface-treated with a coupling agent such as a silane coupling agent or a titanate coupling agent. As the coupling agent, silane coupling agents such as epoxysilane, aminosilane, and mercaptosilane are preferably used.

The modified styrenic block copolymer (D) in the present invention is obtained by copolymerizing or grafting a styrenic block copolymer with an unsaturated carboxylic acid or a derivative thereof. The styrenic block copolymer consists of an aromatic vinyl hydrocarbon polymer block with a glass transition temperature of usually 25°C or higher, preferably 50°C or higher, and a conjugated diene polymer block with a glass transition temperature of 0°C or lower, preferably -25°C or lower. Includes linear, radial, and branched block copolymers consisting of combined blocks. Examples of the aromatic vinyl hydrocarbons include styrene, α-methylstyrene, o-methylstyrene, p-methylstyrene, 1,3-dimethylstyrene,
Examples include vinylnaphthalene, among which styrene is preferably used.

As the conjugated diene, butadiene (
1,3-butadiene), isoprene (2-methyl-1,
Among them, butadiene and isoprene are preferably used. The proportion of the aromatic vinyl hydrocarbon polymer block, which is the glass phase block, in the styrenic block copolymer is 10 to 50% by weight, and the proportion of the conjugated diene polymer block, which is the rubber phase block, is 90 to 50% by weight. preferable. There are many combinations of glass phase blocks and rubber phase blocks, and any of them may be used, but a triblock copolymer in which glass phase blocks are bonded to both ends of an intermediate rubber phase block is preferred. The number average molecular weight of the glass phase block in this case is preferably 3,000 to 150,000, particularly preferably 5,000 to 60,000. Further, the number average molecular weight of the rubber phase block is preferably 5,000 to 5,000.
300,000, particularly preferably 10,000 to 150
,000.

The styrenic block copolymer can be produced using a known living anionic polymerization method, but is not particularly limited thereto, and can also be produced using a cationic polymerization method or a radical polymerization method. Styrenic block copolymers also include hydrogenated block copolymers in which some of the unsaturated bonds of the block copolymers described above are reduced by hydrogenation. Here, it is preferable that 25% or less of the aromatic double bonds in the aromatic vinyl hydrocarbon polymer block and 80% or more of the aliphatic double bonds in the conjugated diene polymer block are hydrogenated. A preferred specific example of the styrenic block copolymer is polystyrene/polybutadiene/polystyrene triblock copolymer (SB
S), polystyrene/polyisoprene/polystyrene triblock copolymers (SIS), hydrogenated copolymers of SBS (SEBS), and hydrogenated copolymers of SIS. Among them, hydrogenated copolymer of SBS (SEB
Hydrogenated copolymers of S) and SIS are particularly preferably used.

The modified styrenic block copolymer (D) in the present invention is obtained by copolymerizing or grafting a styrenic block copolymer with an unsaturated carboxylic acid or a derivative thereof, but is usually produced by a grafting reaction. . Here, as the unsaturated carboxylic acid, acrylic acid, methacrylic acid, ethacrylic acid, crotonic acid, maleic acid, fumaric acid, itaconic acid, citraconic acid, and butenedicarboxylic acid are preferably used. Further, as its derivatives, alkyl esters, glycidyl esters, acid anhydrides, imides, etc. are preferably used. Preferred specific examples include methyl acrylate, ethyl acrylate, propyl acrylate, butyl acrylate, methyl methacrylate, ethyl methacrylate, glycidyl acrylate, glycidyl methacrylate, glycidyl ethacrylate, diglycidyl itaconate, and citraconic acid. diglycidyl ester, butene dicarboxylic acid diglycidyl ester, butene dicarboxylic acid monoglycidyl ester, maleic anhydride,
Itaconic anhydride, citraconic anhydride, maleic acid imide, N-phenylmaleic acid imide, itaconic acid imide,
Examples include citraconic acid imide, among which glycidyl methacrylate, maleic anhydride, N-phenylmaleic acid imide, and maleic acid imide are preferably used. Two or more of these unsaturated carboxylic acids or derivatives thereof may be used in combination depending on the application.

The amount of the unsaturated carboxylic acid or its derivative in the grafting reaction ranges from 0.01 to 10% in terms of improving soldering heat resistance.
% by weight is preferred, and 0.05-5% by weight is particularly preferred. Note that the graft reaction here means that an unsaturated carboxylic acid or a derivative thereof is chemically bonded to a styrenic block copolymer.

The modified styrenic block copolymer (D) can be prepared by a known method, for example, by combining the styrenic block copolymer and an unsaturated carboxylic acid or a derivative thereof in a molten state or solution state in the presence of a radical initiator or It can be obtained by grafting a styrenic block copolymer with an unsaturated carboxylic acid or a derivative thereof in the absence of the unsaturated carboxylic acid. Preferably, it can be produced by melt-kneading at 100 to 350° C. using a melt-kneading device such as a single-screw or twin-screw extruder, a Banbury mixer, a kneader, or a roll. Moreover, if an organic peroxide is added as a radical initiator during melt-kneading, the graft reaction can be carried out more effectively. Examples of organic peroxides include benzoyl peroxide, 1,1-bis-tert-butylperoxy-3,
3,5-trimethylcyclohexane, n-butyl-4,
4-bis-tert-butyl peroxybalate, te
rt-butylcumyl peroxide, dicumyl peroxide, tert-butyl peroxybenzoate, di-tert-butyl peroxide, di(tert-butylperoxy)diisopropylbenzene, 2,5-dimethyl-2,5-di( Examples include tert-butylperoxy)hexane, 2,5-dimethyl-2,5-di(tert-butylperoxy)hexyne-3, and tert-butylperoxycumene. The amount of organic peroxide added is 0 to 100 parts by weight of the styrenic block copolymer.
．． 001 to 1 part by weight is preferred.

The amount of the modified styrenic block copolymer (D) added is preferably 0.1 to 10% by weight, and 1 to 10% by weight in the epoxy composition for encapsulating semiconductor devices, from the effect of improving soldering heat resistance.
6% by weight is particularly preferred.

Furthermore, a styrenic block copolymer can be added to the epoxy composition for encapsulating a semiconductor device of the present invention. The amount added is preferably 10% by weight or less. Further, the modified styrenic block copolymer (D) and the styrenic block copolymer may be used after being pulverized in advance by pulverization, crosslinking or other methods. Any procedure can be used for blending the modified styrenic block copolymer (D) and the styrenic block copolymer. For example, epoxy resin (A) or curing agent (B)
Examples include a method in which the epoxy resin (A), curing agent (B), filler (C), and other components are blended simultaneously.

The epoxy composition for semiconductor encapsulation of the present invention contains a flame retardant such as a halogen compound such as a halogenated epoxy resin or a phosphorus compound, a flame retardant aid such as antimony trioxide, and a coloring agent such as carbon black or iron oxide. , silicone rubber, silicone oil, modified nitrile rubber, modified polybutadiene rubber, thermoplastic resins such as polyethylene,
Long chain fatty acids, metal salts of long chain fatty acids, esters of long chain fatty acids, amides of long chain fatty acids, mold release agents such as paraffin wax, and crosslinking agents such as organic peroxides can be optionally added.

The epoxy composition for semiconductor encapsulation of the present invention is preferably melt-kneaded using a known kneading method such as a Banbury mixer, kneader, roll, single-screw or twin-screw extruder, or co-kneader. Manufactured by:

[0044]

[Examples] The present invention will be specifically explained below with reference to Examples. In addition, the number of parts in an example shows a part by weight, and % shows a weight %, respectively.

Reference Example 1 (Production of modified styrenic block copolymer I) 3 parts of maleic anhydride and 2,5-dimethyl-2,
5-di(tert-butylperoxy)hexane 0.1
The parts were dry blended. This mixture was melt-kneaded using a 30 mmφ single screw extruder at a screw rotation speed of 50 rpm and a cylinder temperature of 230° C. to obtain a modified styrenic block copolymer I.

This modified styrenic block copolymer I was subjected to Soxhlet extraction with an acetone solvent to remove unreacted maleic anhydride, and then the infrared absorption spectrum and ultraviolet absorption spectrum were measured to determine the graft reaction amount of maleic anhydride. Quantitated. As a result, maleic anhydride was 1.2
It was found that % graft reaction occurred.

Reference Example 2 (Production of modified styrenic block copolymer II) Similarly to Reference Example 1, 2 parts of glycidyl methacrylate and 2,5-dimethyl were added to 100 parts of the styrenic block copolymer II shown in Table 1. Using 0.1 part of -2,5-di(tert-butylperoxy)hexane, a modified styrenic block copolymer II in which 1.1% of glycidyl methacrylate was grafted was obtained.

Examples 1 to 4, Comparative Examples 1 to 4 The modified styrenic block copolymers (D) of Reference Examples 1 and 2 and the styrenic block copolymers shown in Table 1 were added to the formulations shown in Table 2. The polymers were dry blended using a mixer at the composition ratios shown in Table 2. This was heated and kneaded for 5 minutes using a mixing roll with a roll surface temperature of 90° C., then cooled and pulverized to produce an epoxy composition for semiconductor encapsulation.

[0049]

[Table 1]

[0050]

[Table 2]

[0051] Using this composition, molding was performed at 175°C for 2 minutes by a low-pressure transfer molding method, followed by molding at 180°C for 2 minutes.
After post-curing for 5 hours, the physical properties and moldability of each composition were measured using the following physical property measuring method.

Soldering heat resistance: 160 pin chip size 12 x 12 mm equipped with a simulated element with Al vapor deposited on the surface
Mold 20 QFPs, post cure, 85℃/85%
After humidifying at RH for 50 hours, it was placed in a solder bath heated to 260°C.
The chips were immersed for 0 seconds, and the presence or absence of peeling at the interface between the chip and the resin was examined using an ultrasonic flaw detector. As failure rate, QF where peeling occurred
The percentage of P was determined.

Moisture resistance reliability: Using QFP after soldering heat resistance evaluation, under PCT conditions of 121° C./100% RH, Al
The time required for the cumulative failure rate to reach 50% was determined by assuming that the disconnection of the wiring was a failure, and was defined as the life span.

[0054] Low stress: 160 equipped with a dummy chip
Mold 20 pinQFPs, post-cure, and store at -65°C.
Q where cracks occurred in the temperature cycle test at ~150℃
Assuming that the FP was a failure, the time required for the cumulative failure rate to reach 50% was determined and defined as the life span.

The results of these evaluations are shown in Table 3.

[0056]

[Table 3]

As seen in Table 3, the epoxy compositions for semiconductor encapsulation of the present invention (Examples 1 to 4) are excellent in soldering heat resistance, moisture resistance reliability, and low stress properties.

On the other hand, Comparative Examples 1 to 3, which do not contain the modified styrenic block copolymer (D), and Comparative Example 4, which does not contain the epoxy resin (A), have excellent soldering heat resistance, moisture resistance reliability, and low stress properties. inferior to everything.

[0059]

Effects of the Invention The epoxy composition for semiconductor encapsulation of the present invention has excellent soldering heat resistance, moisture resistance reliability, and low Excellent stress resistance.

Claims (1)

[Claims] Claim 1: Epoxy resin (A), curing agent (B),
Filler (C) and modified styrenic block copolymer (
D) as an essential component, wherein the epoxy resin (A) has the following formula (I) [Chemical formula 1] (However, two of R1 to R8 are 2,3-epoxy represents a propoxy group, and the others represent a hydrogen atom, a halogen atom, or an alkyl group having 1 to 4 carbon atoms.) Contains an epoxy resin (a) as an essential component, and the proportion of the filler (C) is 60 to 90% by weight of the total, and the modified styrenic block copolymer (D) is a styrenic block copolymer copolymerized or grafted with an unsaturated carboxylic acid or a derivative thereof. An epoxy composition for semiconductor encapsulation.