Effect of thermal shock conditions on reliability of chip ceramic capacitors

Different size X7R MLCCs have been subjected to three types of thermal shock testing: terminal solder pot dip test, ice water test, and liquid nitrogen drop test. Electrical characteristics of the parts were measured through various test conditions to determine critical temperatures that result in fracturing and electrical failures. Optical examinations and cross-sectional analysis were used to confirm the presence of cracks. Mechanisms of fracturing and the effectiveness of different thermal shock methods are discussed. It is shown that the heat conduction and direction of temperature changes (heating or cooling) are critical factors of thermal shock testing of MLCCs. The probability of fracturing depends also on the level of residual mechanical stresses, mostly in terminal areas of ceramic capacitors.