Application of Active Thermography for Detection of Soft-Soldered Lap Joints Inner Defects

Abstract

Soft soldiering is a joining technique commonly used in many areas of industry. It is especially useful for joining components susceptible to damage caused by high temperature. One of the vital issues associated with this type of joining is the possibility of the formation of hidden defects, like: cracks, lack of connection, gas voids etc. In the paper, a study of active thermography application for detection of common defects in soft-soldered lap joints is presented. Lap joints of thin copper, aluminum and high-alloy steel palates were made using solder paste in a soldering oven. Internal defects were intentionally introduced into the joints. To reveal defects, an active lock-in thermography method was applied. Various heating parameters, IR images acquisition, and processing methods were tested. In order to compare the obtained defect detection results with a benchmark, tested samples were radiographically analyzed. Results prove that active thermography methods can be applied for the detection of defects in soft-soldered lap joints. Based on the research performed, the size of defects that can be detected was estimated.