An epoxy resin composition for encapsulating a semiconductor, which is free from halogen and antimony and has excellent soldering crack resistance and high-temperature storage life without lowering the flame-retardancy, and which comprises as essential components (A) an epoxy resin, (B) a phenol resin curing agent, (C) a curing accelerator, (D) an inorganic filler and (E) a red phosphorus-based flame-retardant, wherein the ratio of (a) the number of epoxy groups of the epoxy resin to (b) the number of phenolic hydroxyl groups of the phenol resin curing agent [(a)/(b)] is 0.8 to 1.2, the amount of the inorganic filler (D) contained in the epoxy resin composition is 70 to 90% by weight based on the total weight of the epoxy resin composition and the cured product of the epoxy resin composition has a glass transition temperature of 100.degree. to 160.degree. C. and a linear expansion coefficient at 25.degree. C. of 0.8 to 1.8.times.10.sup.-5 /.degree.C.
The object of the present invention is to provide an epoxy resin compositions for encapsulating of semiconductors containing no bromine compounds and no antimony oxide and excellent in flame retardancy, moisture resistance, moldability, curability and electric characteristics. This composition is an epoxy resin composition containing (A) an epoxy resin, (B) a phenolic resin, (C) a curing accelerator, (D) an inorganic filler and (E) a red phosphorus-based flame retardant, wherein the improvement comprises the red phosphorus-based flame retardant (E) having a total content of phosphate ion and phosphite ion extracted from the retardant when subjected to extraction with water at 80.degree. C. for 20 hours is not more than 2000 ppm, the amount of the red phosphorus in the red phosphorus-based retardant being 20-40% by weight and the red phosphorus-based retardant being contained in an amount of 0.5-5% by weight in the whole resin composition.
A halogen-free flame retardant epoxy resin composition containing (A) a bisphenol A type epoxy resin, (B) a curing agent, (C) red phosphorus particles each of which is covered with a covering layer, at least the outermost layer of which is formed of a resin, and (D) an inorganic filler.
Despite the frangibility of additive-free granules of brominated anionic styrenic polymer, it has been found possible by use of special mechanical processing to provide pellets of unadulterated brominated anionic styrenic polymer having a bromine content of at least about 50 wt % and in which at least about 70 wt % (preferably at least about 75 wt %) of the pellets are retained on a standard US No. 40 sieve and no more than about 30 wt % (preferably no more than about 25 wt %) are retained on a standard US No. 5 sieve. In preferred embodiments such pelletized anionic styrenic polymer is brominated anionic polystyrene having a bromine content of at least about 67 wt %, e.g., in the range of about 67 to about 71 wt %. Also preferred are pelletized brominated anionic styrenic polymers in which the melt flow index (ASTM D 1238-99) at 220.degree. C., 2.16 kg is at least 4 g/10 min and preferably is at least 5 g/10 min. Another embodiment of this invention is a method of preparing pelletized unadulterated brominated anionic styrenic polymer which method comprises: A) forming strands of molten unadulterated brominated anionic styrenic polymer; B) submitting said strands to cooling and downwardly directed forced air flow on a porous conveyor belt whereby said strands are broken into pellets; and C) causing said pellets to drop into a classifier that removes fines from the pellets.
