Delamination from process induced sources

Former studies on delamination have seldom addressed the issue of delamination caused by contamination in terms of what the contaminants are and where they originate. It is however imperative that process engineers involved in the assembly of electronic packaging understand these problems so they can minimize yield loss and reject rates. With the aid of time-of-flight secondary ion mass spectrometry (TOF-SIMS), five delaminated units from different Asian factories were all diagnosed to be contaminated with polydimethylsiloxane (PDMS). PDMS is a widely used chemical agent that has extremely low surface tension and viscosity, which makes it very mobile on surfaces. Possible sources of PDMS from materials used in the assembly line are identified by TOF-SIMS in this paper. The ability of PDMS to transfer to wafer surfaces is revealed by TOF-SIMS analysis. Also, PDMS can cause delamination in molded units as checked with the aid of scanning acoustic microscopy.