Molded underfill development for flipstack CSP

The current standard for flipchip encapsulantion is a two step process. Following flipchip attach, a liquid underfill material is dispensed along the die edge and allowed to flow, via adhesive capillary force, through the gap between the flipchip die and the PCB. Upon cure of the liquid underfill, complete die encapsulation is achieved with a standard transfer mold process using preformed epoxy pellets. When applied to a FlipStack™ CSP product, a matrix of die on the substrate are individually underfilled and cured. The transfer molding process then encapsulates all die in a single transfer of the molding compound.