Evaluating Desorption Baking Cycles for Moisture Sensitive Integrated Circuits
Baking moisture sensitive ICs requires matching package thickness and carrier heat ratings to balance desorption speed against intermetallic lead oxidation risks.
Gold Aluminum Wire Bond
Connection Integrity
An electrical connection formed between a gold wire and an aluminum contact pad provides the conductive path within a semiconductor package. During assembly, gold aluminum wire bond processes utilize ultrasonic energy and heat to create a solid-state weld at the terminal pad. This junction must maintain low electrical resistance and high mechanical strength throughout the operational lifespan of the integrated circuit.
Mechanical Strength
The strength of the finished connection is evaluated using destructive and non-destructive pull testing methods to measure the force required to break the wire or lift the bond. Pull testing ensures that the bond has been properly formed without causing excessive deformation of the wire. If the welding parameters are poorly adjusted, the wire may shear at the neck or peel away from the pad.
Thermal Aging
Elevated temperatures accelerate the diffusion of gold and aluminum across the interface, leading to the formation of multiple intermetallic phases. This diffusion process can create microscopic voids that reduce the cross-sectional area of the contact and eventually cause electrical failure. The thermal stability of this interface is critical for devices operating in harsh environments where temperature spikes are common.
Failure Mechanism
Over time, the differing diffusion rates of the two metals lead to voiding, which can cause the connection to detach completely. This structural separation leads to intermittent electrical open circuits or complete device failure.