Design Limits When using Gold-Aluminum Bonds

Gold-aluminum wire bonds form intermetallic phases with any elevated temperature treatment. Intermetallic formation alone does not cause bond failure. However, certain failure modes--open metallization in the bond area, lifted wire bonds after aging, and heel breaks after thermal cycling--may be related to intermetallic formation. Specific causes of these failure modes are discussed. These form the basis for the recommendations presented as design limits when using gold-aluminum wire bonds in circuits.