Application of FPGA units in combined temperature cycle and vibration reliability tests of lead-free interconnections

According to the European Directive 2002/95/EC RoHS solders that contain lead have to be replaced with lead-free equivalents. Replacing well-known materials with new materials not only force technological adaptations but also force necessity of reliability investigations, especially new failure modes. In case of lead-free solders, the main problem is reduction of solder joint strength. Lower strength of lead- free solder joint in comparison with SnPb is the result of defects that occur in the joint structure. Because of local defects, the joints are much more sensitive for stresses, Stress inducted within the area of solder joint can lead to joint fractures. Despite the crack occurrence, the solder joint can still conduct electrically. Nevertheless cracked joint should be treated as failed because it does not fulfill its constructional function. Such failures can be difficult to detect in static conditions, but can be easy detected, when the tested joint is subjected to vibrations. During vibrations short opens of the joint can occur. Additional high temperature or temperature cycles loadings can make detection easier by acceleration of crack occurrence. To detect short opens of solder joints subjected to vibrations, continuous fast measurements of resistance changes during the test are required. Within the article, the essence of fast multi-channel measurements and the construction of dedicated data storage system will be described. As a summary expected results of measurements will be shortly presented.