Flip chip packages

摘要

A flip chip and a flip chip package are shielded from alpha particles emitted by lead in the solder bumps used to form the electrical connection between the flip chip and a substrate. This is accomplished by coating the solder bumps with a layer of alpha particle absorbing material or by providing a suitable amount of alpha particle absorbing material in the underfill material between the flip chip and the substrate. Methods of forming the coating the solder bumps include electroless coating, as well as a method involving a) the deposition of a layer of thick resist in a pattern suitable for the formation of solder bumps; b) the deposition of a layer of alpha particle absorbing material; c) the deposition of a layer of solder; d) removal of excess solder and alpha particle absorbing material; and e) the removal of the thick resist layer.