The reliability evaluation of the bonding wire in the DC/DC power under the environment of humidity

Aluminum is an active metal; it can form aluminum oxide (Al₂O₃) when left exposed to air. Aluminum oxide can dissolve in either acid or alkaline solutions, and lead to Corrosion failures on bonding-pad or internal line. In order to evaluate the reliability of bonding wires inside the DC/DC power, the reliability test structure of bonding wire in the DC/DC power has been designed, which has been made by connecting several bonding wire in series, all these bonding wires are bonded on the surface of the Aluminum slice, and all the Aluminum slice is mounted on the surface of ceramic substrate. Two ampere electrical current has been put into the test structure chain to simulate the bonding wire working condition under the operation environment, so the reliability of the DC/DC power under the humidity condition can be assessed. The resistor degradation process of the bonding wire have been conducted through the accelerating of temperature and humidity under the 85 °C/85%RH environment. After 2185 hours accelerating lifetime experiment, the reliability of the DC/DC power under the humidity condition has been evaluated. The result is that if the process is well controlled, the bonding wires are robust to the humidity environment, no failure take place even if there is 5000PPM water vapor existing in the package.