Gold ball-bond mechanical reliability at 40μm pitch: squash height and bake temperature effects

An unusual mechanical failure mode in gold ballbonds at 50μm pitch due to degradation at the Au–Au4Al interface during ageing in air at 175°C

“…[48] assume however that all gold aluminide compounds are formed during ballbonding, which appears inconsistent with the majority of reactive diffusion literature. Such a failure mechanism is not consistent with the experiments reported in this paper that show degradation within Au 4 Al and between The effect of isothermal ageing temperature on the proposed de-bonding mechanism remains an open question except for some limited work in a recent study on 40 lm pitch ballbonding [49], which shows the same HSBL and LSBL failure modes occur after baking at 150°C, 175°C and 200°C and with increased bake temperature both types of failure occur at shorter times. Interestingly however, the same study also shows that for each ageing temperature, the use of a different capillary geometry results in the de-bonding of gold balls at approximately the same time regardless of squash height.…”

Measuring stress next to Au ball bond during high temperature aging

“…While more and more effort and expertise is required to meet existing 175°C HTS reliability requirements for fine pitch, as e.g. 50 lm ball bond pitch (BBP) processes, or ultra-fine pitch (40 lm BBP and below) processes, such bonds fail to survive 1000 h at 200°C [9]. This points out the limits of the conventional Au-Al bonding system.…”