Toughened thermosetting resin compositions useful as underfill sealants

A thermosetting resin composition capable of sealing underfilling between a semiconductor device and a circuit board to which said semiconductor device is electrically connected, said composition comprising:

• (a) about 92 parts by weight of an epoxy resin component comprising bisphenol F epoxy resin;
• (b) about 8 parts by weight of latent hardening component, of which 4 parts is comprised of (i) a cyanate ester component comprising 1,3-bis[4-cyanatophenyl-1-(methylethylidene)]benzene and 4 parts is comprised of (ii) an imidazole component comprising 2-ethyl-4-methylimidazole;
• and
• (c) about 8 parts of a polysulfide-based toughening component comprising LP-3.

A thermosetting resin composition capable of sealing underfilling between a semiconductor device and a circuit board to which said semiconductor device is electrically connected, said composition consisting essentially of:

• (a) about 100 parts of an epoxy resin component;
• and
• (b) a latent hardener component in an amount up to about 30 parts comprising
• (i) a cyanate ester component in an amount up to about 15 parts, and
• (ii) an imidazole component in an amount up to about 15 parts;
• and
• (c) a polysulfide-based toughening component in an amount up to about 20 parts;
• and
• (d) optionally, a filler;
• (e) optionally, a defoaming agent;
• (d) optionally, a leveling agent;
• and
• (e) optionally, a dye.

A thermosetting resin composition having a gel time at a temperature of about 150° C. of about two minutes or less, and capable of sealing underfilling between a semiconductor device and a circuit board to which said semiconductor device is electrically connected, said composition comprising:

• (a) an epoxy resin component;
• (b) a latent hardener component comprising
• (i) a cyanate ester component, and
• (ii) an imidazole component;
• and
• (c) a polysulfide-based toughening component.

A process for fabricating semiconductor devices, said process comprising the steps of:

• electrically connecting a semiconductor device comprising a semiconductor chip mounted on a carrier substrate, to a circuit board;
• infiltrating a thermosetting resin composition into the space between the carrier substrate of said semiconductor device and said circuit board, wherein the composition comprises an epoxy resin component;
• a latent hardener component comprising a cyanate ester component, and an imidazole component;
• and a polysulfide-based toughening component;
• and
• curing the composition by the application of heat.