Thermosetting and thermoplastic bisphenol A epoxy/phenoxy resin as encapsulant material

Polymer materials have found extensive applications as encapsulants in the microelectronics packaging industry, especially the epoxy resin systems for die attach adhesive, glob top, underfill, etc. However, normally only thermosetting systems have been widely employed, which could transform into infusible 3D networks during the curing process. In this paper, we explore the possibility of using thermoplastic materials and their combination with thermosetting materials as encapsulants for some specific end microelectronic products, as they would demonstrate some process/property advantages over the fully thermosetting counterparts, a potentially tremendous economic/cost concern. Both thermosetting and thermoplastic epoxy resins were studied for their adhesion as well as adhesion durability capability. The chemistry is based on poly(bisphenol A-co-epichlorohydrin), including the basic liquid resin and the advanced solid resin of different molecular weight, and the so-called phenoxy resin of very high molecular weight. In order to target a practically feasible formulation that would operate with an actual industrial line, the development work was implemented by combining the thermosetting basic liquid epoxy resin with the thermoplastic free radical polymerizable system, which appeared to be a quite promising approach for both product processibility and application performance.