Cracking of plastic packages during PCB mounting is a serious customer concern as VLSI plastic packages house ever-increasing die sizes and are made thinner. Evolutionary improvements in package materials cannot prevent package cracking in the short term, especially in thin packages. A novel design termed the 'window flag' employs a central hole punched in the die pad to minimize the metal-polymer interface and maximize the silicon-mold compound interface in the die pad region. This window flag design results in crackfree performance following Level 1 preconditioning in QFPs, TQFPs and SOJs. This solution stems from the key discovery that the silicon-mold compound interface is intrinsically very strong under preconditioning stresses.
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