Reliability of Laminated Bond Structure Using (Cu, Ni)/Sn TLP Bonding with Al Interlayer for High Temperature Power Electronics Packaging

摘要

Future automotive power electronics will be using wide band gap (WBG) devices that requires high temperature operation of over 200 °C and current solder material cannot be operated over 150 °C. New bonding technology such as transient liquid phase (TLP) bonding whose melting point is over 400 °C has shown to be one promising high temperature bonding candidate. In this study, reliability of a new laminated bond structure using an Al interlayer is investigated by subjecting the structure to thermal cycling from -40 °C to 200 °C for 500 cycles. The new structure mitigates thermal stress due to CTE mismatch between the copper substrate and the power device. The results show that after 200 °C of thermal storage for 100 h, complete consumption of tin occurs along with formation of (Cu, Ni)/Sn intermetallic compound (IMC). The same samples were thermal cycled from -40 °C to 200 °C, and the confocal scanning acoustic microscopy(CSAM) results display consistent bonding quality. However, micro-level cracking was observed through a further Scanning Electron Microscopy (SEM) check on the cross-section of a sample. The root cause of the crack was identified as excessive thermal stress, especially normal (or peel) stress, through numerical analysis. The study demonstrates the potential and challenges of the new laminated structure for low cost and reliable high temperature bonding material for power devices.