JPH04296046A - Resin-sealed semiconductor device - Google Patents

Abstract

PURPOSE:To reduce the stress of a sealing resin and to improve the adhesion of the sealing resin to an insert in a resin-sealed semiconductor device which is formed by sealing with an epoxy resin composition. CONSTITUTION:A methyl methacrylate-butadiene-styrene copolymer and a silica- containing silicone rubber are used together and blended in an epoxy resin composition for semiconductor sealing use containing an epoxy resin, a phenolic resin curing agent and a silica filler as components to contribute to a reduction in a stress. As a sealing resin, which is low in the stress and has a high adhesion to an inert, is obtained, a resin-sealed semiconductor device, which is superior in thermal shock resistance and humidity resistance, can be realized.

Description

DETAILED DESCRIPTION OF THE INVENTION [Object of the Invention] [0001] The present invention relates to a resin-sealed semiconductor device sealed with an epoxy resin composition. [0002] Epoxy resin compositions have long been widely used as encapsulating resins for semiconductor devices, and their cured products have excellent moisture resistance, high-temperature electrical properties, moldability, etc. It has become the mainstream resin for molds. Incidentally, as semiconductor devices have become highly integrated in recent years, each functional unit on the semiconductor device has become finer and the size of the semiconductor device pellet itself has rapidly increased. Due to such changes in semiconductor element pellets, conventional sealing resins are no longer able to satisfy requirements such as thermal shock resistance. That is, when this type of resin composition is used to seal a large pellet with a fine surface structure, the phosphosilicate glass film or silicon nitride film that protects the aluminum wiring pattern on the pellet surface cracks. or cause cracks in the sealing resin. This tendency is particularly significant when a thermal cycle test is performed. As a result, the appearance of the semiconductor device is poor and reliability is lowered. [0004] Furthermore, when surface-mounting a semiconductor device, when soldering it to a board, the entire device has a heat resistance of 200 to 260
They undergo severe thermal shock by being exposed to a high-temperature atmosphere at ℃ for about 5 to 90 seconds. At this time, the main cause is vaporization of moisture taken into the package, which may also cause cracks in the sealing resin. As a countermeasure to these problems, active efforts are being made to develop low-stress sealing resins that have excellent crack resistance when subjected to thermal shock. Conventionally, it has been known that incorporating silicone oil or silicone rubber into the resin composition is effective in reducing the internal stress of the sealing resin. In this case, the silicone oil bleeds off during molding or curing, often resulting in poor appearance and staining of the mold. Furthermore, when silicone rubber is blended, the melt viscosity of the resin composition increases, resulting in problems such as decreased moldability of the sealing resin and poor appearance of the resulting cured product. Further, in JP-A No. 63-245426, the internal stress of the sealing resin is reduced by using silica surface-treated with 0.15 to 3.00% by weight of silicone rubber as an inorganic filler. The technology has been disclosed. However, with such a sealing resin, although the increase in the melt viscosity of the resin composition as described above is not so problematic, the effect of reducing the internal stress of the sealing resin is also small. Furthermore, in resin-sealed semiconductor devices sealed with the above-mentioned sealing resin, the adhesion between the internal filler (insert) and the sealing resin is insufficient, and further improvement in thermal shock resistance is required. It was getting worse. [0007] As mentioned above, as semiconductor devices have become highly integrated in recent years, semiconductor devices encapsulated with conventional encapsulation resins are no longer able to satisfy thermal shock resistance, etc. It's coming. The present invention solves these problems and provides a resin seal with low stress in the sealing resin, good adhesion between the sealing resin and the insert, and excellent thermal shock resistance and moisture resistance. The purpose is to provide a static semiconductor device. [Structure of the Invention] [Means and Effects for Solving the Problems] The resin-sealed semiconductor device of the present invention comprises: (a) an epoxy resin having two or more epoxy groups in the molecule; (b) curing; (c) methyl methacrylate-butadiene-styrene copolymer (d) silicone rubber powder containing 30% to 95% silica by weight (e) silica powder An epoxy resin composition containing as an essential component The epoxy resin composition is characterized in that a silicone rubber powder containing 30% or more and 95% or less of silica by weight is blended. The present invention will be explained in more detail below. In the present invention, the component (a), which is the first essential component of the epoxy resin composition, may be any epoxy resin having two or more epoxy groups in the molecule. However, in consideration of heat resistance, an epoxy resin having an epoxy equivalent of 250 or less is preferable. Specific examples of such epoxy resins include phenol novolac type epoxy resins, cresol novolac type epoxy resins, naphthol type novolac type epoxy resins, bisphenol A novolac type epoxy resins, and combinations of phenol or alkylphenols and hydroxybenzaldehyde. Tris(hydroxyphenyl)alkane-based epoxidized products obtained by epoxidizing condensates, epoxidized products of tetra(hydroxyphenyl)alkanes, 2,2',4,4'-tetraglycidoxybenzophenone, triglycidyl of para-aminophenol Ether, polyallyl glycidyl ether, 1,
3,5-triglycidyl etherbenzene, 2,2',
4,4'-tetraglycidoxybiphenyl, 4,4'-
Bis(2,3-epoxypropoxy)-3,3',5,
Examples include epoxidized products of 5'-tetramethylbiphenyl. One or more of these epoxy resins may be used. [0012] The above epoxy resin used in the present invention is
In order to suppress corrosion of metal materials such as wires of semiconductor devices, the content of chlorine ions is preferably 10 ppm or less, and the content of hydrolyzable chlorine is preferably 0.1% by weight or less. In the present invention, the component (b), which is the second essential component of the epoxy resin composition, includes those generally known as curing agents for epoxy resins, such as phenol resins, organic acid anhydrides, and amines. Although any resin can be used without particular limitation, phenolic resin is most preferred. Specific examples of such phenolic resins include:
Novolac-type phenolic resins such as phenol novolak resin, cresol novolac resin, tert-butylphenol novolak resin, nonylphenol novolak resin, bisphenol F novolak resin, bisphenol A novolak resin, naphthol novolak resin,
Polyoxystyrene such as polyparaoxystyrene, 2,
Examples include phenol aralkyl resins such as condensation polymerization compounds of 2'-dimethoxy-p-xylene and phenol monomers, and tris(hydroxyphenyl)alkane-based compounds represented by the following structural formula. [0014] [0015] (In the formula, R1 and R2 represent a hydrogen atom or an alkyl group having 1 to 20 carbon atoms, and these groups may be the same or different. R3 is a single bond, Or represents an alkylene group such as methylene or ethylene.)
One or more of these phenolic resins may be used. From the viewpoint of heat resistance, mechanical properties, and moisture resistance, the amount of the curing agent blended is 0.5 to 1.5, particularly 0.8 to 1.2, based on 1 part of the epoxy resin in terms of chemical equivalent. Preferably within this range. In the present invention, the above component (c), which is the third essential component of the epoxy resin composition, is a vinyl copolymer type rubber powder usually called MBS resin, such as latex styrene-butadiene. It is manufactured by graft polymerizing monomers whose main components are methyl methacrylate and styrene onto rubber, polybutadiene rubber, etc. Specific examples of such methyl methacrylate-butadiene-styrene copolymers include B-22 (Kanebuchi Chemical Co., Ltd., SBR component approximately 45%), B-28 (Kanebuchi Chemical Co., Ltd., SBR component approximately 45%), B-56 (
Kanebuchi Chemical Industry Co., Ltd., SBR content approximately 65%), 68K4
(Japan Synthetic Rubber Co., Ltd., SBR content approximately 55%), BTA
731 (Kureha Chemical Industry Co., Ltd.), BTA751 (Kureha Chemical Industry Co., Ltd.), KCA501 (Kureha Chemical Industry Co., Ltd.)
Co., Ltd.)), etc. Among these methyl methacrylate-butadiene-styrene copolymers, those with a butadiene composition of 7
0% by weight or less, methyl methacrylate composition is 15% by weight
The above are preferred. This is because outside this range, the appearance of the molded product will be impaired. In order for the methyl methacrylate-butadiene-styrene copolymer used in the present invention to be uniformly dispersed in the epoxy resin composition, the average particle size must be 10.
It is preferably blended in the form of particles or powder with a size of 0 μm or less, and the amount added is preferably 0.1 to 10% by weight in the resin composition. If the amount added is less than 0.1% by weight, sufficient thermal shock resistance may not be obtained and burrs generated during molding may become longer. Conversely, 10% by weight
If it exceeds this, the melt viscosity of the resin composition will increase and the moldability will be poor. Furthermore, the amount of the methyl methacrylate-butadiene-styrene copolymer added is more preferably 0.2 to 5% by weight. [0020] When using a phenolic resin as a curing agent in the present invention, the methyl methacrylate-butadiene-styrene copolymer is added to the phenol resin which has been heated and melted in advance, and the mixture is stirred and mixed in an appropriate manner. The methacrylate-butadiene-styrene copolymer can be uniformly dispersed in the resin composition, and better mechanical strength can be imparted to the sealing resin. Stirring and mixing methods at this time include stirring using a mixing blade within a flask, stirring using a universal mixer, and using a homogenizer within a melting pot. In the present invention, the above-mentioned component (d), which is the fourth essential component of the epoxy resin composition, can be any substance as long as the silicone rubber powder contains 30% by weight or more and 95% by weight or less of silica. For example, the surface of silica particles may be coated with silicone rubber, or fine silica particles may be dispersed in silicone rubber. The reason why the silica content is limited to the above range is that if the silica content is outside this range, it is not possible to effectively improve the thermal shock resistance without impairing the mechanical strength of the sealing resin. This is because it becomes difficult. The silica-containing silicone rubber powder used in the present invention preferably has a maximum particle size of 75 μm or less. This is because if the particle size of the silicone rubber powder exceeds 75 μm, when the silicone rubber powder comes into contact with the surface of a semiconductor element, it will apply a large stress locally, which may cause malfunction of the semiconductor element. Further, the particle size of the silica contained in the silicone rubber powder is not particularly limited as long as the particle size of the silicone rubber powder can be suppressed to 75 μm or less. For example, fine particles on the order of mμm, such as fumed silica, may be dispersed in silicone rubber, or the surface of silica particles on the order of several tens of μm may be coated with silicone rubber. In the present invention, the silicone rubber powder containing silica may be added by treating it with a coupling agent together with the silica powder as a filler and then mixing it with the resin component. It is more preferable to treat it in the same way as a styrene copolymer. That is, when using a phenolic resin as a curing agent, the mechanical strength of the resulting sealing resin can be increased by first mixing it with the phenolic resin and then incorporating it into the resin composition. In the present invention, the desirable blending amount of the silicone rubber powder containing silica varies depending on the silica content, but the amount of the silicone rubber component is 0.1 to 5% by weight in the epoxy resin composition. % is preferable. Furthermore, it is more preferable that the total amount of this silicone component and the aforementioned methyl methacrylate-butadiene-styrene copolymer be 0.2 to 10% by weight of the resin composition. The reason for this is that if the total amount of these is less than 0.2% by weight, the reduction in internal stress will be small and there is a risk that sufficient thermal shock resistance will not be obtained. Conversely, 10% by weight
If it exceeds this, the mechanical strength of the sealing resin will decrease significantly. Furthermore, when the amount of the silicone rubber component is less than 0.1% by weight, the reduction in internal stress of the sealing resin is small, and the adhesion between the sealing resin and the insert may be insufficient. %, the moldability of the sealing resin is poor and the mechanical strength is greatly reduced. The methyl methacrylate-butadiene-styrene copolymer and silica-containing silicone rubber powder used as essential components in the present invention both lower the elastic modulus of the resin composition and reduce the internal stress of the sealing resin. It is something that contributes. In addition, the former in particular has the effect of suppressing burrs that occur during molding of the sealing resin and improving workability.
The latter is an effective component for improving the adhesion between the sealing resin and the insert. Therefore, if only methyl methacrylate-butadiene-styrene copolymer is used among these essential components, sufficient adhesion between the sealing resin and the insert cannot be obtained, and the melt viscosity of the resin composition is high. This results in a decrease in moldability. On the other hand, when only silicone rubber powder containing silica is used, burrs generated during molding of the sealing resin become long, resulting in poor workability. That is, in the present invention, a well-balanced resin composition can only be obtained by using a methyl methacrylate-butadiene-styrene copolymer and a silicone rubber containing silica together. In the present invention, the above component (e), which is the fifth essential component of the epoxy resin composition, may be any of those commonly used as fillers for sealing resins, such as fused silica and crystalline silica. Anything is acceptable. However, if the shape of the silica powder is crushed, and the particle size of the silica powder is large, the sharp edges of the silica powder will come into contact with the surface of the semiconductor element and apply a large stress locally, resulting in damage to the semiconductor element. may cause malfunction. Furthermore, if silica powder with a large particle size is present, the silica powder used during molding may block the gate portion of the mold, which may impede moldability. Therefore, the maximum particle size of silica powder is 7
The thickness is preferably 5 μm or less. Furthermore, from the viewpoint of preventing soft errors, it is preferable that the total content of U in all the silica powders is 0.5 ppb or less. [0027] The preferred blending amount of the silica powder used in the present invention is such that, together with the silica contained in the silicone rubber powder, the silica in the resin composition is 50 to 95% by weight, more preferably 65 to 90% by weight. It is quantity. If the silica content is less than 50% by weight, the coefficient of thermal expansion of the resin composition is large, making it impossible to obtain a resin-sealed semiconductor device with excellent thermal shock resistance.On the other hand, if the silica content exceeds 95% by weight, the resin This is because the melt viscosity of the composition increases and the moldability of the sealing resin may decrease. Generally, in epoxy resin compositions, silica has the effect of adjusting the thermal expansion coefficient of the resin composition, but in the present invention, by using a silicone powder containing the silica and silica powder together, thermal shock resistance is improved. A resin-sealed semiconductor device with excellent mechanical strength of the sealing resin can be realized. Further, in the present invention, the above (a) to (e)
) In addition to the essential components, it is preferable to incorporate a curing accelerator into the epoxy resin composition. Any curing accelerator may be used as long as it promotes the reaction between the epoxy resin and the curing agent, and specific examples include 2-methylimidazole, 2,4-dimethylimidazole, and 2-methylimidazole.
Ethyl-4-methylimidazole, 2-phenylimidazole, 2-phenyl-4-methylimidazole, 2-
Imidazole compounds such as heptadecylimidazole; tertiary amine compounds such as triethylamine, benzyldimethylamine, α-methylbenzylmethyldiamine, 2-(dimethylaminomethyl)phenol, 2,4,6-tris(dimethylaminomethyl)phenol; Organic phosphine compounds such as triphenylphosphine, tricyclohexylphosphine, tributylphosphine, and methyldiphenylphosphine; diazabicycloundecene, and the like. One or more types of these curing accelerators may be used. [0029] Since the activity of the curing accelerator varies depending on the type, the amount added cannot be determined unconditionally, but it is preferably in the range of 0.1 to 5% by weight based on the total amount of the epoxy resin and curing agent. preferable. This is because if the amount is less than 0.1% by weight, curing cannot be sufficiently promoted, whereas if it exceeds 5% by weight, there is a tendency for the moisture resistance of the resin composition to decrease. Furthermore, in the present invention, in addition to the above-mentioned components, coupling agents such as silane, borane, and titanate; flame retardants containing phosphorus compounds, bromine, chlorine, etc.; carbon black, etc. Pigments/dyes; release agents such as natural waxes, synthetic waxes, and metal salts of straight chain fatty acids may also be blended. Furthermore, when particularly high moisture resistance is required, it is effective to add various ion scavengers. A specific example of the ion scavenger is DHT-4A (manufactured by Kyowa Chemical Co., Ltd.)
, IXE-600 (manufactured by Toagosei), and the like. The resin composition according to the present invention can be prepared by melt-kneading the above-mentioned components using a heated roll, kneader or extruder, or by mixing them using a special mixer capable of pulverizing them, or by using any of these methods as appropriate. It can be easily manufactured by combining them. The resin-sealed semiconductor device of the present invention is manufactured by resin-sealing a semiconductor element using the resin composition. In this case, low-pressure transfer molding is most commonly used, but sealing can also be achieved by injection molding, compression molding, casting, or the like. It is desirable that heat curing after sealing be performed at a temperature of 150° C. or higher. Note that in the present invention, the semiconductor element sealed with the resin sealant is not particularly limited. [Examples] Examples of the present invention will be explained in detail below. Examples 1 to 9 and Comparative Examples 1 to 5 First, epoxy resin compositions containing the components shown in Tables 1 and 2 in the proportions shown in the same tables were prepared as follows ( (The amounts in the table indicate parts by weight)
. That is, first, silica powder as a filler and silicone rubber powder containing silica were treated with a silane coupling agent in a Henschel mixer, and then other components were blended, kneaded with heated rolls at 60 to 110 °C, and cooled. By post-pulverizing, the epoxy resin composition was obtained. At this time, the methyl methacrylate-butadiene-styrene copolymer was used after being dispersed in the phenol resin as a curing agent, and the silica-free silicone rubber powder blended in Comparative Example 2 was the same as the silica-containing silicone rubber powder in each example. It was treated in the same way as silicone rubber powder. In addition, as each component shown in Table 1, those shown below were used. Epoxy resin; orthocresol novolac type epoxy resin (base resin) (ESCN-195
XL, manufactured by Sumitomo Chemical, epoxy equivalent weight 197)
Brominated epoxy resin; Bisphenol A type brominated epoxy resin (flame retardant)
(AER-755, manufactured by Asahi Kasei, epoxy equivalent: 460) Phenol resin; Phenol novolak resin
(hardening agent)
(BRG-557, manufactured by Showa Kobunshi, equivalent weight 104)
Triphenylphosphine; (PP-360, manufactured by K.I. Kasei Co., Ltd.) (hardening accelerator) Silicone rubber powder A containing silica;

Disperse 1 part by weight of Mudosilica, average particles

Diameter 3μm

〃B: 1 part by weight of silicone rubber contains

Disperse 1 part by weight of Mudosilica, average particles

Diameter 3μm

〃
C; Hue in 1 part by weight of silicone rubber

2 parts by weight of Mudosilica dispersed, average particles

Diameter 3μm

〃
D; Hue in 1 part by weight of silicone rubber

2 parts by weight of Mudosilica dispersed, average particles
Diameter 10μm

〃
E: 9 parts by weight of crushed silica and silicone
Coating 1 part by weight of rubber, average
Particle size 15
μm
〃
F: 49 parts by weight of crushed silica and silicone
Coating 1 part by weight of rubber, average

Particle size: 15 μm Silica-free silicone rubber powder; Average particle size: 3 μm Methyl methacrylate-butadiene-styrene copolymer; MBS resin powder

(BTA731, Kureha


(Manufactured by Gaku Kogyo) Carnauba wax; (Carnauba 1
No., manufactured by Arakawa Hayashi Chemical) (Mold release agent) Antimony trioxide; (Mikuni Seiring) (Flame retardant aid) Carbon black; (CB#30, manufactured by Mitsubishi Yuka)
(Pigment) γ-glycidoxypropyltrimethoxysilane; (
A-187, (silane coupling agent)
(manufactured by Nippon Unicar) Fused silica A: crushed silica (average particle size 15 μm) (filler) Fused silica B: spherical silica (average particle size 15 μm)
(Filler) Next, the following evaluation tests were conducted on each of these epoxy resin compositions. [1] Melt viscosity at 175° C. was measured using a Koka type flow tester to evaluate fluidity. [2] Using each epoxy resin composition, test pieces were created by transfer molding at 175°C for 3 minutes.
After-curing was carried out at 80° C. for 8 hours. [0038] At this time, the length of the slit extending from the 10 μm slit provided in the mold was measured at the same time. Further, for these test pieces, the thermal expansion coefficient, flexural modulus, flexural strength, and adhesive strength with the copper alloy that is the frame material were measured. [3] In order to investigate thermal shock resistance, the following thermal cycle test (TCT test) was conducted. That is,
After sealing a large heat resistance test device (8 mm x 8 mm) using each epoxy resin composition, it was subjected to a cooling/heating cycle of -65°C → room temperature → 150°C for 50 to 50 minutes.
The failure rate was investigated by repeating 400 cycles and checking the operating characteristics of the device. [4] In order to examine the solder immersion resistance, the following pressure cooker test (PCT test) was conducted. That is, each epoxy resin composition was used at 175°C.
The evaluation element was sealed under conditions of , 3 minutes, and after-cured at 180° C. for 8 hours. Next, it was left in an atmosphere of 85° C. and 85% relative humidity for 72 hours to perform a moisture absorption treatment, and then immersed in a solder bath at 260° C. for 5 seconds. At this point, the crack occurrence rate of the package was investigated. Furthermore, this solder immersion package was placed in a pressure cooker at 127°C in a saturated steam atmosphere at 100 to 400°C.
The moisture resistance was evaluated by leaving it for a while and checking the incidence of defects (leak defects, open defects). The above measurement results are summarized in Tables 3 and 4. [Table 1] [Table 2] [Table 2] [Table 3] [Table 4] [0045] As is clear from Table 3, in Examples 1 to 9, the resin composition A reduction in the elastic modulus of the material and an improvement in adhesion to the insert have been achieved. Furthermore, it has low melt viscosity, excellent moldability, good mechanical strength, and TC
It can be seen that there were almost no defects in the T test and PCT test, and excellent thermal shock resistance and moisture resistance were obtained. Effects of the Invention As described in detail above, in the resin-sealed semiconductor device of the present invention, the epoxy resin composition, which is the material for encapsulating the semiconductor element, has a small elastic modulus and a low-stress seal. The semiconductor element is sealed with a sealing resin. Furthermore, the adhesiveness between the sealing resin and the insert is good, and the thermal shock resistance is extremely excellent.Even after surface mounting, the subsequent moisture resistance is good, and it has very high reliability.

Claims (1)

[Claims] Claim 1: (a) Epoxy resin having two or more epoxy groups in the molecule (b) Curing agent (c) Methyl methacrylate-butadiene-styrene copolymer (d) 30% to 95% by weight A resin-sealed semiconductor device characterized in that a semiconductor element is sealed with an epoxy resin composition containing silica powder (e) as an essential component.