Contaminant Sources Causing Non-Stick-On-Pad During Die Bonding

A common problem in die bonding is the non-stick-on-pad (NSOP) when the bond does not pass the pull test. Contaminants are a possible cause of NSOP, particularly if an undesired thick film is developed on the bond pads, Such films effectively diminish the bondability of the pads resulting in a NSOP problem. In one such case Fourier Transform Infra-Red (FTIR) spectroscopy was used to fingerprint the contaminant formed on the bond pads. The contaminant was an aluminum-oxygen-fluorine compound that was very resistant. FTIR showed AL-F bonds and wa;er of hydration. The distinctive chemical signature was critical in solving the NSOP problem quickly. This war; accomplished by growing tile resistant film under accelerated conditions, thus recreating the compound in the laboratory, Although the chemical compound was not fully identified, the FTIR signature provided confirmation of the compound for various conditions under which it was formed on bond pads. The source of the fluorine was identified and eliminated.