The laser welding technique have he applying to joining of photonic packages because of its high precision and productivity [I]. In many cases, stainless steel (SST) and low carbon steel (LCS) are used as the welding materials. There exists solidification crack tendency because of no welding filler and the fast cooling rate [2]. In this study, we present the study ofthe micro-cracks formation of the joint formed by laser welding. We discuss the failure mechanisms and propose recommendations for avoiding the micro-crack formation of welding SSTand LCS system. SEMEDX, 01M (Orientation Image Microscope) were used in the present study.
The calling for smaller form factor, higher I/O density, higher performance and lower cost has made fan-out wafer level packaging (FOWLP) technology the trend. Good control of die position accuracy and molded wafer warpage are some of the keys to achieve high-yield production for FOWLP. In this study, 10mm×10mm test chips were fabricated and attached (chip-first and die face-up) onto 12 inch glass wafer carriers using die-attach-film (DAF). These reconfigured wafers were compression-molded with selected epoxy molding compounds (EMC). Cu bumps (contact-pads) were revealed by grinding, and redistribution layers (RDLs) were fabricated by lithography and electroplating process. The fan-out wafers were evaluated and characterized after each process step with main focus on the die-misplacement/die shift, re-configured wafer warpage, compression molding defects and RDL fabrication defects. The root causes of these defects were investigated and analyzed, while the possible solutions to overcome the defects were proposed and discussed.
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