Comparison of Experimental and Estimated Fusing Current of Gold (Au) and Copper (Cu) Bonding Wires in Semiconductor IC Packages

In this paper, fusing current experiments and simulation were made over a range of bonding wire diameters used in semiconductor packaging from 18-50um for Au and 23-50um for Cu. Comparing the measured fusing current for Au and Cu wires, the deviation ranged from 14-28% with largest deviation for thicker wires. This correlates well with the prediction of ~25% more current carrying capacity of Cu given its higher electrical conductivity and thermal conductivity than Au. Prediction estimates from the modified Preece equation showed 6-33% higher values when compared with the experimental results. Finite element analysis simulation under condition with both ends insulated showed 23-35% higher value than the experimental measurements for Au wire. This increased further to 35-41% under the condition with both ends connected to heat sink. For Cu wire, maximum current values from simulations were 16-33% and 38-40% higher than the experimental values under the same insulated and with heat sink configurations, respectively. The temperatures used under the condition with wire ends connected to heat sink were simulated under extreme conditions. The maximum current from the FEA simulation calculations can be used as a guideline to estimate the required number and sizes of wire that can be used for specific device and package application requirements.