JP2011231252A - Resin composition and resin-sealed semiconductor device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a resin composition for sealing a power semiconductor device, which provides the resin-sealed semiconductor device excellent in thermal shock resistance.SOLUTION: The resin composition is obtained by blending a polyfunctional epoxy compound, a curing agent, an inorganic filler, and an aromatic polysulfone resin, and used as a resin composition for sealing a power semiconductor device. The aromatic polysulfone resin preferably used contains ≥6×10hydroxyl groups and/or its salts per 1 g of the aromatic polysulfone resin, and has a reduced viscosity of 0.35 to 0.60 dl/g.

Description

  The present invention relates to a resin composition for sealing a power semiconductor device. The present invention also relates to a resin-encapsulated semiconductor device obtained by encapsulating a power semiconductor device with this resin composition.

  In recent years, in the field of power semiconductor devices such as power semiconductor modules for power control, particularly in the field of small-capacity power semiconductor devices such as inverter modules, the size has changed to conventional metal pressure-welded semiconductor devices and ceramic-encapsulated semiconductor devices. There is an increasing demand for resin-encapsulated semiconductor devices that can be reduced in weight and are inexpensive. This resin-encapsulated semiconductor device is usually obtained by encapsulating a power semiconductor device with a resin composition. For example, Patent Document 1 discloses a polyfunctional epoxy compound, a curing agent, and inorganic as the resin composition. A resin composition containing a filler is disclosed.

JP 11-92624 A

  In a conventional resin composition for encapsulating a power semiconductor device, the resulting resin-encapsulated semiconductor device does not necessarily have sufficient thermal and thermal shock resistance, and, for example, cold heat having a temperature difference of 200 ° C. or more between −65 to 150 ° C. When an impact is applied to the resin-encapsulated semiconductor device, there is a problem that cracks and interfacial delamination are likely to occur in the cured product of the resin composition that is an encapsulant, and the reliability of the resin-encapsulated semiconductor device is likely to be reduced. Therefore, an object of the present invention is to provide a resin composition for encapsulating a power semiconductor device that provides a resin-encapsulated semiconductor device having excellent resistance to thermal shock.

  In order to achieve the above object, the present invention provides a resin composition for sealing a power semiconductor device, comprising a polyfunctional epoxy compound, a curing agent, an inorganic filler, and an aromatic polysulfone resin. Moreover, according to this invention, the resin sealing type | mold semiconductor device formed by sealing a power semiconductor device with this resin composition is also provided.

  The polyfunctional epoxy compound is a compound having two or more epoxy groups in one molecule, and examples thereof include glycidylated polyhydric alcohol (glycidyl ether), glycidylated polyhydric phenol (glycidyl ether), Examples thereof include glycidylated products of carboxylic acids (glycidyl esters), glycidated products of polyvalent amines (glycidylamine), and alicyclic polyfunctional epoxy compounds, and two or more of them may be used as necessary. Among them, glycidylated polyhydric phenol is preferably used, and examples of this polyhydric phenol include bisphenol A, bisphenol F, tetrabromobisphenol A, bisphenol S, dihydroxybiphenyl, dihydroxynaphthalene, dihydroxystilbene, alkyl-substituted hydroquinone and the like. Dihydric phenols; phenolic novolacs, cresol novolacs, naphthol novolacs, bisphenol A novolacs and other novolacs; phenols, alkyl-substituted phenols, naphthols and other phenols and benzaldehyde, hydroxybenzaldehyde, terephthalaldehyde, alkyl-substituted terephthalaldehydes and other aldehydes Condensates; including polyadducts of phenols and cyclopentadiene, if necessary It may be used two or more kinds.

  The curing agent is a compound that reacts with the polyfunctional epoxy compound to function as a curing agent for the polyfunctional epoxy compound. Examples thereof include phenol novolak, cresol novolak, tris (hydroxyphenyl) alkane, and phenol-modified polybutadiene. , Phenolic aralkyl resins, polyphenolic curing agents such as phenols and dicyclopentadiene polyadditions; amine curing agents such as dicyandiamide, diaminodiphenylmethane, diaminodiphenylsulfone; pyromellitic anhydride, trimellitic anhydride Acid anhydride-type curing agents such as acid and benzophenonetetracarboxylic dianhydride may be mentioned, and two or more of them may be used as necessary. Of these, polyhydric phenol-based curing agents are preferably used.

  Although content of a hardening | curing agent is suitably adjusted with the kind, For example, in the case of a polyhydric phenol type hardening | curing agent, the phenolic hydroxyl group is 0.5-0.5 with respect to the epoxy group of a polyfunctional epoxy compound. The amount is preferably 1.5 mole times. Moreover, in the case of an amine type hardening | curing agent, it is preferable that the amino group is the quantity used as 0.5-1.5 mol times with respect to the epoxy group of a polyfunctional epoxy compound. In the case of an acid anhydride-based curing agent, the acid anhydride group is preferably in an amount that is 0.5 to 1.5 mole times the epoxy group of the polyfunctional epoxy compound. If the content of the curing agent is too small, the curing reaction of the resin composition hardly occurs, and if it is too large, the properties of the cured product of the resin composition are likely to be deteriorated.

  Examples of the inorganic filler include silica such as crystalline silica and fused silica, glass such as alumina, boron nitride, aluminum nitride, talc, and quartz glass, calcium carbonate, silicon nitride, silicon carbide, titanium carbide, and tungsten carbide. Two or more of them may be used as necessary. Of these, silica, alumina, boron nitride, and aluminum nitride are preferably used. The shape of the inorganic filler may be, for example, powder or fiber. In terms of heat dissipation performance, alumina, boron nitride, and aluminum nitride are preferable.

  The content of the inorganic filler is preferably 50 to 80% by weight in the resin composition. If the content of the inorganic filler is too small, it becomes difficult to reduce the curing shrinkage of the resin composition and the linear expansion coefficient of the cured product of the resin composition. The property tends to decrease.

An aromatic polysulfone resin is a resin having an aromatic group (residue obtained by removing two hydrogen atoms bonded to the aromatic ring from an aromatic compound) and a sulfonyl group (—SO ₂ —). It is preferable to have a repeating unit represented by 1) (hereinafter sometimes referred to as repeating unit (1)), and further, a repeating unit represented by the following formula (2) (hereinafter referred to as repeating unit (2)) And other repeating units such as a repeating unit represented by the following formula (3) (hereinafter also referred to as repeating unit (2)). The aromatic polysulfone resin preferably has 50 to 100 mol%, more preferably 80 to 100 mol% of the repeating unit (1) with respect to the total of all repeating units.

_{^{-Ph 1 -SO 2 -Ph 2 -O- (}} 1)

(Ph ¹ and Ph ² each independently represent a phenylene group. The hydrogen atoms in the phenylene group may each independently be substituted with an alkyl group, an aryl group, or a halogen atom.)

-Ph ³ -R-Ph ⁴ -O- (2)

(Ph ³ and Ph ⁴ each independently represent a phenylene group. The hydrogen atoms in the phenylene group may each independently be substituted with an alkyl group, an aryl group or a halogen atom. R represents an alkylidene. Represents a group, oxygen atom or sulfur atom.)

-(Ph ⁵ ) _n -O- (3)

(Ph ⁵ represents a phenylene group. Each hydrogen atom in the phenylene group may be independently substituted with an alkyl group, an aryl group or a halogen atom. N represents an integer of 1 to 3. When n is 2 or more, a plurality of Ph ⁵ may be the same or different from each other.)

The phenylene group represented by any of Ph ^{1 to} Ph ⁵ may be a p-phenylene group, an m-phenylene group, or an o-phenylene group. -A phenylene group is preferred. Examples of the alkyl group that may substitute a hydrogen atom in the phenylene group include a methyl group, an ethyl group, an n-propyl group, an isopropyl group, an n-butyl group, an isobutyl group, an s-butyl group, and a t-butyl group. Group is mentioned, The carbon number is 1-5 normally. Examples of the aryl group that may substitute a hydrogen atom in the phenylene group include a phenyl group, a 1-naphthyl group, a 2-naphthyl group, and a p-toluyl group, and the number of carbon atoms is usually 6-15. It is. Examples of the alkylidene group represented by R include a methylene group, an ethylidene group, an isopropylidene group, and a 1-butylidene group, and the number of carbon atoms is usually 1-5.

The aromatic polysulfone resin preferably has 6 × 10 ⁻⁵ or more hydroxyl groups and / or salts thereof (hereinafter sometimes referred to as “hydroxyl groups”) per 1 g of the aromatic polysulfone resin. . Thereby, the intensity | strength of the hardened | cured material of a resin composition can be improved. The content of the hydroxyl groups is preferably 8 × 10 ⁻⁵ or more per 1 g of the aromatic polysulfone resin, and is usually 20 × 10 ⁻⁵ or less, preferably 17 × 10 ⁻⁵ or less. is there.

  All of the hydroxyl groups are preferably hydroxyl groups. In addition, the aromatic polysulfone resin preferably has the hydroxyl groups bonded to an aromatic ring, that is, as a phenolic hydroxyl group and / or a salt thereof, and preferably at the end of the main chain.

  The salt of the hydroxyl group is composed of an oxyanion group in which a proton is dissociated from the hydroxyl group and a counter cation. Examples of the counter cation include alkali metal ions such as lithium ion, sodium ion and potassium ion, magnesium Examples thereof include alkaline earth metal ions such as ions and calcium ions, ammonium ions obtained by protonating ammonia and primary to tertiary amines, and quaternary ammonium ions. When the counter cation is a polyvalent cation such as an alkaline earth metal ion, the counter anion may be composed of a plurality of oxyanion groups, an oxyanion group, a chloride ion, or a hydroxide. It may be composed of other anions such as ions.

  The aromatic polysulfone resin preferably has a reduced viscosity of 0.35 to 0.60 dl / g, and more preferably 0.45 to 0.55 dlg. If the reduced viscosity of the aromatic polysulfone resin is too small, the impact resistance of the cured product of the resin composition tends to decrease, and if too large, the moldability tends to decrease.

  The aromatic polysulfone resin preferably has a 5% weight reduction temperature of 400 ° C. or higher in thermogravimetric measurement from the viewpoint of durability of the resin-encapsulated semiconductor device.

  The aromatic polysulfone resin can be suitably produced by polycondensation of the corresponding bis (halogenophenyl) sulfone compound and divalent phenol in an organic high polarity solvent using an alkali metal carbonate. For example, the resin having the repeating unit (1) is a compound represented by the following formula (4) as a bis (halogenophenyl) sulfone compound, and a compound represented by the following formula (5) as a divalent phenol. It can be manufactured by using it. Moreover, resin which has a repeating unit (1) and a repeating unit (2) uses the compound represented by following formula (4) as a bis (halogenophenyl) sulfone compound, uses the following formula (6) as a bivalent phenol. It can manufacture by using the compound represented by. Moreover, resin which has a repeating unit (1) and a repeating unit (3) uses the compound represented by following formula (4) as a bis (halogenophenyl) sulfone compound, uses the following formula (7) as a bivalent phenol. It can manufacture by using the compound represented by.

_{^{X 1 -Ph 1 -SO 2 -Ph 2}} -X 2 (4)

(X ¹ and X ² each independently represent a halogen atom. Ph ¹ and Ph ² are as defined above.)

HO—Ph ¹ —SO ₂ —Ph ² —OH (5)

(Ph ¹ and Ph ² are as defined above.)

^{HO-Ph 3 -R-Ph 4} -OH (6)

(Ph ³ , Ph ⁴ and R are as defined above.)

HO— (Ph ⁵ ) _n —OH (7)

(Ph ⁵ and n are as defined above.)

  The alkali metal carbonate may be an alkali carbonate that is a normal salt, an alkali bicarbonate (an alkali hydrogen carbonate) that is an acidic salt, or a mixture of both. As the alkali carbonate, sodium carbonate or potassium carbonate is preferably used, and as the alkali bicarbonate, sodium bicarbonate or potassium bicarbonate is preferably used.

  The target reaction is dehydrohalogenation / polycondensation of a bis (halogenophenyl) sulfone compound and a dihydric phenol. If no side reaction occurs, the closer the molar ratio of the two is to 1: 1, that is, The closer the amount of the bis (halogenophenyl) sulfone compound used is to 100 mol% relative to the dihydric phenol, the higher the degree of polymerization and the reduced viscosity of the resulting aromatic polysulfone resin. By-product alkali hydroxide or the like causes a side reaction such as a substitution reaction or depolymerization of a halogeno group to a hydroxyl group. This side reaction reduces the degree of polymerization of the resulting aromatic polysulfone resin and decreases the reduced viscosity. And the content of hydroxyl groups tends to increase. Further, if no side reaction occurs, the larger the amount of alkali metal carbonate used, the faster the target polycondensation proceeds. Therefore, the resulting aromatic polysulfone resin has a higher degree of polymerization and reduced viscosity. However, in actuality, the more the amount of the alkali metal salt of carbonic acid used, the more likely the side reaction similar to the above occurs. Furthermore, if no side reaction occurs, the higher the polycondensation temperature, the faster the target polycondensation proceeds. Therefore, the resulting aromatic polysulfone resin tends to have a high degree of polymerization and a reduced viscosity. However, in fact, the higher the polycondensation temperature, the more likely the side reaction similar to the above occurs. Therefore, in consideration of the degree of this side reaction, the amount of the aromatic dihalogeno compound used or the alkali metal salt of carbonic acid is used so as to obtain an aromatic polysulfone resin having the preferred hydroxyl group content and reduced viscosity. It is preferable to adjust the amount of use and the polycondensation temperature.

  In addition, it replaces with a part or all of a bis (halophenyl) sulfone compound and / or dihydric phenol, and a corresponding hydroxyphenyl (halophenyl) sulfone compound can also be used.

  The content of the aromatic polysulfone resin is preferably 0.5 to 15% by weight in the resin composition, and more preferably 1 to 10% by weight. If the content of the aromatic polysulfone resin is too small, it becomes difficult to improve the toughness of the cured product of the resin composition and the opportunity strength at high temperatures, and if it is too large, the fluidity of the resin composition tends to be lowered, and the work The property tends to decrease.

  The resin composition of the present invention preferably contains a curing accelerator, examples of which include 2-methylimidazole, 2-ethylimidazole, 2-ethyl-4-methylimidazole, 1-benzyl-2-methylimidazole, Imidazole compounds such as 2-heptadecylimidazole and 2-undecylimidazole; 2- (dimethylaminomethyl) phenol, 2,4,6-tris (dimethylaminomethyl) phenol, benzylmethylamine, α-methylbenzyldimethylamine , Piperidine, dimethyllaurylamine, dialkylaminomethanolamine, tetramethylguanidine, 2-dimethylamino-2-hydroxypropane, N, N′-dimethylpiperazine, N-methylmorpholine, 2- (dimethylaminomethyl) phenol, hexamethyle Tertiary amine such as tetramine, 1-hydroxyethyl-2-heptadecylglyoxalidine, 1,8-diazabicyclo (5,4,0) undecene-7, and other amine compounds; phosphorus compounds such as triphenylphosphine Can be mentioned.

  Although content of a hardening accelerator is suitably adjusted with the kind, it is preferable that it is 0.1 to 5 weight% in a resin composition. If the content of the curing accelerator is too small, the impact resistance of the cured product of the resin composition tends to be lowered, and if too much, the moldability of the cured product of the resin composition tends to be lowered.

  The resin composition of the present invention contains other components as necessary, for example, a colorant such as carbon black, a release agent such as carnauba airx or polyethylene wax, a flame retardant such as antimony trioxide, and γ-glycidoxy. In the resin composition, one or more of a coupling agent such as propyltrimethoxysilane, a rubber component such as silicone rubber and fluororubber, an antioxidant, a heat stabilizer, an ultraviolet absorber, and a crystal nucleation agent, Usually, it may be contained within a range not exceeding 10% by weight.

  The resin composition of the present invention can be prepared by mixing a polyfunctional epoxy compound, a curing agent, an inorganic filler, an aromatic polysulfone resin, and other components used as necessary. The mixing order is appropriately adjusted. First, the polyfunctional epoxy compound and the aromatic polysulfone resin are uniformly dissolved in a solvent such as N-methyl-2-pyrrolidone or cyclohexanone, and the solvent is removed from the solution by drying under reduced pressure or the like. Or by adding this solution to a solvent such as an alcoholic organic solvent such as methanol or ethanol, a solvent such as water or a mixture thereof, and then removing the solvent from the precipitate by drying under reduced pressure or the like. A mixture of a functional epoxy compound and an aromatic polysulfone resin is obtained, and then this mixture is pulverized with a hammer mill or the like, if necessary, and then mixed with a curing agent and an inorganic filler, and a mixing device such as a roll, a kneader or a reika machine. It is preferable to prepare a resin composition by mixing. In mixing the polyfunctional epoxy compound and the aromatic polysulfone resin, part or all of the aromatic polysulfone resin may react with the polyfunctional epoxy compound.

  The resin composition of the present invention thus obtained is used as a sealing material for sealing a power semiconductor device. Examples of the sealing method include low-pressure transfer molding, injection molding, compression molding, and cast molding. After covering with a resin composition of a power semiconductor device, the resin composition is cured to be used as a sealing body. That's fine. As a power semiconductor device to be sealed, for example, a power element such as IGBT, thyristor, GTO thyristor, SI thyristor, EST, MCT, IEGT, power MOSFET, MOS thyristor, and its control circuit component such as bi-CMOS. What is installed. In addition, the resin-encapsulated semiconductor device obtained in this way is used, for example, in the manufacture of electric devices and machines such as air conditioners, electronic calculators, and control machines.

(Measurement of hydroxyl group content in aromatic polysulfone resin)
A predetermined amount of aromatic polysulfone resin was dissolved in dimethylformamide, and an excess amount of paratoluenesulfonic acid was added. This solution was titrated with a 0.05 mol / l potassium methoxide / toluene / methanol solution using a potentiometric titrator to neutralize residual paratoluenesulfonic acid, and then neutralize hydroxyl groups. The content of hydroxyl groups in the aromatic polysulfone resin is obtained by dividing the amount of potassium methoxide required for neutralization of the hydroxyl group (converted into moles) by the predetermined amount (g) of the aromatic polysulfone resin. The amount (pieces / g) was determined.

(Measurement of reduced viscosity of aromatic polysulfone resin)
About 1 g of aromatic polysulfone resin was dissolved in N, N-dimethylformamide to make the volume 1 dl. The viscosity (η) of this solution was measured at 25 ° C. using an Ostwald type viscosity tube. Further, the viscosity (η ₀ ) of N, N-dimethylformamide as a solvent was measured at 25 ° C. using an Ostwald type viscosity tube. From the viscosity (η) of the solution and the viscosity (η ₀ ) of the solvent, the specific viscosity ((η−η ₀ ) / η ₀ ) is obtained, and this specific viscosity is calculated as the concentration of the solution (about 1 g / dl). ) To obtain the reduced viscosity (dl / g) of the aromatic polysulfone resin.

[Evaluation of thermal and thermal shock resistance of resin-encapsulated semiconductor devices]
About 20 resin-encapsulated semiconductor devices, after cooling at −65 ° C. for 30 minutes, leaving at room temperature for 5 minutes and then heating at 150 ° C. for 30 minutes, repeated thermal cycle test (TCT) went. About 20 resin-encapsulated semiconductor devices after this thermal cycle test, the number of those in which cracks occurred in the cured product of the resin composition was determined. It is determined that the smaller the number, the better the thermal shock resistance.

[Polyfunctional epoxy compound]
As a polyfunctional epoxy compound, an ortho-cresol novolac type epoxy resin having an epoxy equivalent of 197 (“ESCN-195L” manufactured by Sumitomo Chemical Co., Ltd.) was used.

[Curing agent]
As a curing agent, a phenol novolac resin having a hydroxyl group equivalent of 104 (“BRG-556” manufactured by Showa Polymer Co., Ltd.) was used.

[Inorganic filler]
As the inorganic filler, spherical silica having an average particle size of 0.5 μm (“SO-C2” manufactured by Admatech Co., Ltd.) was used.

Production Example 1 (Production of aromatic polysulfone resin)
In a polymerization tank equipped with a stirrer, a nitrogen introduction tube, a thermometer, and a condenser with a receiver at the tip, 500 g of 4,4′-dihydroxydiphenylsulfone, 576 g of 4,4′-dichlorodiphenylsulfone, and a polymerization solvent 922 g of diphenylsulfone was charged, and the temperature was raised to 180 ° C. while nitrogen gas was circulated in the system. After adding 290 g of potassium carbonate to the obtained solution, the temperature was gradually raised to 290 ° C., and the mixture was further reacted at 290 ° C. for 2 hours. The obtained reaction solution was cooled to room temperature, solidified, finely pulverized, washed with warm water and washed with a mixed solvent of acetone and methanol several times, then heated and dried at 150 ° C. to obtain an aromatic polysulfone resin. Obtained as a powder. As a result of measuring the content of hydroxyl groups in the aromatic polysulfone resin, it was 9.5 × 10 ⁻⁵ units / g. Further, the reduced viscosity of this aromatic polysulfone resin was measured and found to be 0.52 dl / g.

Example 1
13.3 parts by weight of the polyfunctional epoxy compound and 1.5 parts by weight of the aromatic polysulfone resin obtained in Production Example 1 were uniformly dissolved in N-methylpyrrolidone. This solution was dried under reduced pressure to remove N-methylpyrrolidone to obtain a mixture of a polyfunctional epoxy compound and an aromatic polysulfone resin. This mixture was mixed with 6.7 parts by weight of a curing agent, 121.1 parts by weight of an inorganic filler, and 0.2 part by weight of 2-ethyl-4-methylimidazole (curing accelerator) to obtain a resin composition. After covering the power semiconductor device for testing with this resin composition, the resin composition was cured to obtain a resin-encapsulated semiconductor device, and as a result of evaluating the thermal shock resistance, the cured resin composition was obtained. The number of cracks generated was 0 out of 20.

Comparative Example 1
13.3 parts by weight of a polyfunctional epoxy compound, 6.7 parts by weight of a curing agent, 121.1 parts by weight of an inorganic filler, and 0.2 part by weight of 2-ethyl-4-methylimidazole (curing accelerator) are mixed to form a resin composition I got a thing. After covering the power semiconductor device for testing with this resin composition, the resin composition was cured to obtain a resin-encapsulated semiconductor device, and as a result of evaluating the thermal shock resistance, the cured resin composition was obtained. The number of cracks generated was 2 out of 20.

Claims (6)

  A resin composition for sealing a power semiconductor device, comprising a polyfunctional epoxy compound, a curing agent, an inorganic filler, and an aromatic polysulfone resin. The resin composition according to claim 1, wherein the aromatic polysulfone resin has a repeating unit represented by the following formula (1).
_{^{-Ph 1 -SO 2 -Ph 2 -O- (}} 1)
(Ph ¹ and Ph ² each independently represent a phenylene group. The hydrogen atoms in the phenylene group may each independently be substituted with an alkyl group, an aryl group, or a halogen atom.) 3. The resin composition according to claim 1, wherein the aromatic polysulfone resin has 6 × 10 ⁻⁵ or more hydroxyl groups and / or salts thereof per 1 g of the aromatic polysulfone resin.   The resin composition according to any one of claims 1 to 3, wherein the reduced viscosity of the aromatic polysulfone resin is 0.35 to 0.60 dl / g.   The resin composition according to any one of claims 1 to 4, wherein the inorganic filler is at least one selected from the group consisting of silica, alumina, boron nitride, and aluminum nitride.   A resin-encapsulated semiconductor device obtained by encapsulating a power semiconductor device with the resin composition according to claim 1.