WLCSP (wafer level chip scale package) has been developed for several years to reduce package size, process cost and to increase product reliability. With the development of high-density, flip chip packages, an underfill process for fine-pitch bump size become more important. WLUF (wafer level underfill) is a technology that applies an underfill material onto a wafer front side and encapsulates the flip chip package without the need for capillarity flow and flux dispensing. Thus, voids from capillarity flow may be avoided and flux-dispensing process is eliminated to prevent potential reliability risks resulting from residual fluxes. In this study, we describe the investigation of a new WLUF technology for fine pitch WLCSP packages and present the lamination and bonding test results using the WLUF materials on our test WLCSP packages.
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