Improving thermal shock test reliability

The failure rate required of surface mount multilayer ceramic capacitors is so low that testing at use conditions will not detect important shifts in reliability performance. Multilayer ceramic capacitors manufactured from various dielectrics were tested at multiple temperatures to develop a sensitive test and to understand failure mechanisms occurring during wave solder. Test temperatures of the solder wave ranged from 240° to 450°C. Effects of preheat, flux type, and machine differences, as well as various termination and plating parameters, were also evaluated. Results from these production experiments were used to develop test conditions to screen commercial parts to 1 or 2 orders of magnitude lower failure rates and to study production processes and materials to further improve the reliability of ceramic chip capacitors. This paper documents the steps in developing an accelerated thermal shock test.