Characterization of Al wire wedge bonding in power electronics package

Heavy Al wire wedge bonding is a dominant technique for power packages with high voltage. The parameters that impact the wedge bonding quality are mainly bonding process related and material related. Possible failure modes for wire bonding are non-stick of bond wire to the pad, die surface cratering or peeling of pad metallization, and wire break. In this paper, the dielectric damage under the top metal of the silicon die is investigated during the Al wire wedge bonding process for a power module package with 20 mil Al bond wires. FEA 3-D modeling is conducted to simulate the wedge bonding process. The high compressive stress in the dielectric layer is determined to cause the dielectric damage, by comparing the FEA simulation results and practical FA analysis results. To shorten the simulation time, DoEs with FEA 2-D models are performed to study the impact of bonding parameters, thickness of top metal and barrier metal of silicon die, and die tilt. With the guidance of the FEA simulation results, some practical tests are performed for the same parameters. The samples are further analyzed for cross sectional measurements by SEM, chemical etching/de-cap analysis. It is found that the FA results match well with the FEA modeling results.