Influence of Wire-Bonding Layout on Reliability in IGBT Module

The wire-bonding layouts influence the profiles of current density, ohmic loss and junction temperature. The temperature profile across IGBT chip is different when the wire-bonding layouts are different. Reasonable wire-bonding layout could reduce the maximum junction temperature ( Tjmax) of the chip and slow down the aging process of the solder and bonding wires. The uniform wire-bonding layout is proposed in this paper to improve the packaging reliability of the power module. To analyze the influence of wire-bonding layouts on reliability, the centralized wire-bonding layout and uniform wire-bonding layout of bonding wires are compared. The results of the electro-thermal simulation show that using uniform wire-bonding layout reduces the Tjmax of the chip by 1~3 °C. What's more, as distance between wire-bonding point and chip center increases, there is a minimum value of Tjmax in the uniform wire-bonding layout. The analytical model is deduced to study the phenomenon. To verify the simulation and theoretical analysis results, the IGBT modules with centralized wire-bonding layout and uniform wire-bonding layout of bonding wire are tested by power cycling tests (PCT). The experimental results show that the Tjmax of the module with uniform wire-bonding layout of bonding wire is 3.3 °C lower than that of the module with centralized wire-bonding layout. Correspondingly, with the help of LESIT lifetime model, the calculated lifetime of the IGBT module with uniform wire-bonding layout increases by 1/3, compared with centralized wire-bonding layout.