Defect analysis of ultrasonic al wire bonds on Ni-plated package leads

Hybrid integrated circuits used in automotive applications often use surface-mounted thick film circuits on ceramic substrate. The electrical interconnection of the respective contact areas of such circuit modules are typically made by wire bonding techniques, in which thin electrically conductive wires, about 25-300 μm in diameter, are bonded from the chip to bond pads on the substrate, and from the substrate to the leads of the metal case of the package. Typically 25-50 μm gold wire ball-wedge thermosonic bonding is used for interconnecting the chip to the substrate, while 100-300 μm thick aluminium wire wedge-wedge ultrasonic bonding from the substrate to the leads. The interconnection materials such as the wire, the bonding pads and surfaces, as well as, the bonding techniques and process parameters play important role in the quality and the reliability of the wire bonds, and finally of the circuit. Our research has dealt with the analyzes of the defects occurring at the aluminium wire bonding from thick film pads to the nickel-plated stainless steel - Ni leads of the component case.