Adhesion evaluation of adhesiveless metal/polyimide substrate for MCM and high density packaging

Directly metallized polyimide films are being widely used as advanced high-density packaging substrates. Adhesion of metal to polyimide is a key performance requirement of the film. Excellent initial adhesion and good retention after severe process steps and reliability stresses are required. In this paper, the adhesion performances of films with different types of polyimide and tie layer from multiple vendors have been evaluated. The interface failure mechanisms are also examined via SEM micrographs and XPS survey scans. Peel strength and its retention behaviour are characterized in term of tie layer materials, environmental stresses and surface analysis results. The object of this work is to select the proper base material for high-density flexible multilayer substrates, a technology which is under development by FCPT.