TA.TEC Consulting
More Wires or Larger Wire Diameter?
How aluminium bond-wire diameter and wire count influence power-cycling reliability – and why 4 × 15 mil outperformed 3 × 20 mil in the investigated test.
Two bond-wire configurations with identical current-carrying capability were compared: 3 × 20 mil and 4 × 15 mil aluminium wires. Under the investigated power-cycling conditions, wire lift-offs occurred in the 3 × 20 mil configuration before 5,000 cycles, whereas the 4 × 15 mil configuration exceeded 15,000 cycles. The coupled thermo-mechanical FEM analysis showed lower accumulated equivalent plastic strain for the 4 × 15 mil configuration, consistent with the longer experimentally observed lifetime. The results apply to the module design and test conditions investigated in the paper.
In the investigated module, the configuration with four 15-mil aluminium wires showed higher power-cycling reliability than the configuration with three 20-mil wires.
The FEM analysis showed approximately 36% lower accumulated plastic strain per cycle for the 4 × 15 mil configuration. This is consistent with the experimentally observed higher number of cycles to failure.
The results show that, in addition to wire diameter, the number of bond wires can have a significant influence on thermomechanical loading and reliability.
The results apply to the power module investigated in the paper, the heavy aluminium bond wires used, the two configurations 3 × 20 mil and 4 × 15 mil, and the described power-cycling and simulation conditions.
The study investigated an ACEPAK-SMIT module with four silicon diodes on a DBC substrate. The bond wires were produced using ultrasonic wedge bonding. In the power-cycling test, the junction-temperature swing was ΔTj = 80 °C.
The results therefore do not establish a general rule that a larger number of thinner wires is inherently more reliable. Other wire materials, wire diameters, wire counts, bond geometries, modules, load profiles, and boundary conditions must be evaluated separately.
Research Source
Boutaleb, M., Roqueta, F., Moreau, F., Brenet, Y., Barreau, L.
Thermomechanical Reliability of Bond Wires in Power Modules subjected to Power Cycling
2025 26th International Conference on Thermal, Mechanical and Multi-Physics Simulation and Experiments in Microelectronics and Microsystems (EuroSimE), IEEE
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