Size Determination of Voids in the Soldering of Automotive DC/DC-Converters via IR Thermography

Abstract

In this work, a method for the size determination of voids in the solder layer between the leadframe of a discrete semiconductor in an SO-8FL package and the underlying circuit board is proposed. The devices under test are heated by a short high-power pulse and the thermal response of the surrounding copper layers close to drain and source is observed by an infrared camera. The heat flow from the junction to the drain and source copper layers is affected by voids in the solder layer. Specially, the heat flow towards the drain copper layer is impeded and a surge in the heat flow towards the source copper layer is expected. Experimental data show that the ratio of the source and drain temperature rise is related to the void share in the solder layer, which is determined prior to the investigation via x-ray examination. Disturbance factors are evaluated and a suitable approach for the usage of the findings of this work in end-of-line-testing is suggested.