Au/Al接合部における接合信頼性と支配要因

抄録

In order to clarify the reliability of Au wire bonds to Al pads, failure causes such as void formation and corrosion behavior of Au-Al intermetallics were investigated in accelerated tests. The effects of annealing environments, temperatures and bonding conditions on bond reliability were also examined.
The molding resin has a great influence on the corrosion behavior, GC-MASS (gas chromatography) analyses of outgasses produced from the resin revealed that a major Br-containing species was methyl bromide (CH₃, Br). The corrosion reaction between the intermetallics and bromides produced minute Au precipitates and amorphous Al oxides. This corrosion behavior caused significant fluctuations in electrical resistivity.
Non-uniform formation of intermetallics at the bonds accelerated the corrosion behavior. It was confirmed that initial conditions at the bond interface affected bond failure.
Activation processes of void-induced and corrosion-induced failures were compared in the respect of bond lifetime. The void formation was controlled by an interdiffusion process, whereas the corrosion behavior was controlled by a decomposition process of the resin. Au/Al bond failure could be governed by the intermetallic corrosion at higher temperatures and by void formation at lower temperatures.