| abstract |
The present invention relates to a film-like underfill encapsulant composition that can be a thermoplastic or thermoset B-stage or is preformed for use in the application of electronic components to substrates. The composition includes a thermoplastic or thermosetting resin, expandable microspheres, a solvent, and optionally a catalyst. If desired, other additives such as fixing agents, flow additives, rheology modifiers may also be added. The underfill encapsulant can be dried or B-staged to provide a smooth, tack-free coating on the substrate or component. In other embodiments, the expandable filler expands upon high temperature application to form a closed cell foam structure in the desired portion of the assembly. |