Gold–aluminium intermetallic

Gold–aluminium intermetallic have different properties from the individual metals, such as low conductivity and high melting point depending on their composition.

[3] Au5Al2 typically forms at 95% of Au and 5% of Al by mass, its melting point is about 575 °C, which is the lowest among the major gold-aluminum intermetallic compounds.

AuAl2 is a brittle bright-purple compound, with a composition of about 78.5% Au and 21.5% Al by mass.

At lower temperatures, about 400–450 °C, an interdiffusion process takes place at the junction, leading to formation of layers of different gold-aluminum intermetallic compounds with different growth rates.

This process is known as the Kirkendall voiding, which leads to both increased electrical resistance and mechanical weakening of the wire bond.