Thermal stress reduction strategy for high-temperature power electronics with Ag sintering.

Thermal stress caused by the coefficients of thermal expansion (CTE) mismatch of materials is the main failure mechanism in power electronic packaging. High junction temperature (T j) would induce larger thermal stress and accelerate failing process. In this paper, two packaging strategies to reduce thermal stress of power module for high-temperature operation were presented based on organic-free sintered Ag bonding and wireless packaging structuring: reduce elastic modulus of sintered Ag layer by changing sintering parameters; and reduce the CTE mismatch by changing the ribbon material. Finite-element analysis (FEA) simulations confirmed that these strategies can effectively reduce the maximum and average thermal stress in power electronics packaging. Furthermore, by combining these two strategies, high-temperature power cycling test indicated that the wireless packaging with Cu30Mo70 ribbon and 5 MPa sintering pressure exhibited excellent durability and reliability in the temperature swing at the junction (Δ T j ∆T j) over 150 K. • Two packaging strategies to reduce thermal stress for high-temperature operation • FEA results indicate that the maximum thermal stress would decrease by 30–55%. • The lifetime is increased to ~20,000 cycles at the temperature over 200 °C. • Strategies are applied with organic-free Ag sintering and wireless packaging. [ABSTRACT FROM AUTHOR]