Thermal Fatigue Resistance Improvement of New Al Bonding Wire

Aluminum (Al) wire has been used for interconnection in power module packaging because of its inherent flexibility and cost advantage. However, its low thermal fatigue resistance increases the risk of device failure at high junction temperatures (<tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$\mathbf{T}_{\mathbf{j}}$</tex>). One of the failure modes of Al wire bond is the thermo-mechanical stress at wire bond contact area due to CTE (coefficient of thermal expansion) difference between Al wire / Al metallization and Si chip, resulting in bond crack. In order to improve the thermal fatigue resistance of Al wire, a high reliability Al wire LX1 has been developed. The objective of this paper is to demonstrate the thermal fatigue performance of LX1 using typical Al metallization and existing bond equipment for power electronics. Active power cycle (APC) tests were performed at challenging high temperature conditions (<tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$\mathrm{T}_{\text{jmax}} \approx 175^{\circ} \mathrm{C}, \Delta \mathrm{T}_{\mathrm{j}} \approx 140 \mathrm{K}$</tex>) with SiC to examine the adaptability of LX1 for the next generation power devices. The results show that LX1 has lower CTE and significantly higher thermal bond reliability than conventional Al wire, realizing three times longer lifetime and efficient suppression of bond crack under the harsh APC test condition.