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Reliable BGA Assembly Using Plasma Chemical CleaningRobert Hagen, Thomas Zeiler, Bernd Goller, Siemens AG Semiconductors AbstractThe influence of plasma chemical cleaning (PCC) on wire bonding and molding was investigated. Bonding was performed via the bond pads of semiconductor chips (Al-Si-Cu) and by Au metallization of ball grid arrays (BGA) from different suppliers. In comparison to untreated reference substrates, plasma cleaning typically improved the strength and quality of the bond. For some of the BGA carriers, plasma treatment was even necessary to achieve bondability. Destructive tests as well as metallographic investigations before and after the conventional reliability tests, demonstrate the positive effect of plasma cleaning. Other investigations showed that plasma treatment improves the mold adhesion on BGA substrates. Different solder resists and mold compounds were investigated. The influence of the process parameters on adhesion and the long-term effect of the plasma treatment was studied. The adhesion of the mold compound was investigated by peel-off tests and scanning acoustic microscopy. Additional contact angle measurements of plasma treated samples demonstrate remarkable improvement of adhesion.
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