Reliable Aluminum Wire-Bonded SiC/Si Diodes With Laminated Al/Cu Stress Buffers

Abstract

Operation temperature of typical wire-bonded power modules, especially for harder silicon carbide (SiC) power chips, keeps increasing. The thermo-mechanical reliability of aluminum (Al) wire-bonds which suffer from the mismatch of coefficient of thermal expansion (CTE) between chip and bonding wires reduces significantly. In this letter, a novel laminated Al/copper (Cu) soft stress buffer was proposed between SiC chip and bonding wires, capable of reducing thermo-mechanical stress of the wires and using soft Al wires with low ultrasonic bonding energy instead sophisticated Cu wires. Lifetime of Al wire bonding on the proposed 10- <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">μ</i> m Al/40- <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">μ</i> m Cu buffer was 5.14 times longer than that on a SiC chip directly under power cycling with constant Δ <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">T</i> <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">j</sub> = 110 °C. In the end, a lifetime prediction model was established to guide the laminated buffer design for enhancing the reliability of Al wire-bonded Si diodes.