Measurement of Ion-Mobility in Copper-Aluminum Wirebond Electronics Under Operation at High Voltage and High Temperature

Transition of ground vehicles to HEV and FEV has necessitated the operation of electronics in automotive underhood at high voltage bias and high temperature for extended period-of-time. Examples include gate drivers and IGBT modules. A typical automotive benchmark is operation for 10 years and 100,000 miles. Simultaneously, the first-level interconnects are migrating to use copper-wire interconnects in place of the previously used gold wire. Copper wire has higher propensity for corrosion and a narrower process-bonding window in comparison with gold wire based systems. Exposure to high temperature, humidity and bias influences the mobility of ions in the EMC and thus the contaminant transport to the WB interfaces. Measurements of diffusion behavior of EMCs at high temperature and high voltage bias are not available for readily being used in models. Prior studies have focused on biased humidity tests on wire bonds with the amplitude of the bias being limited up to 3.5Volts. In this paper, a PWM-controlled-gate drive-based test setup is established to study the effect of high voltage (up to 20Volts) on Cu-Al wire bond interconnects. A migration-diffusion cell experiment is designed to quantify the effect of voltage bias on transport of chlorine in EMCs. Diffusion coefficient and ionic mobility of chlorine at different temperatures are obtained. Resistance spectroscopy measurements show the progression of corrosion induced by voltage bias. A corrosion simulation is used to quantify the effect of voltage bias on corrosion rate of Cu-Al wire bond.