Control of Stress Concentration in Surface- Mounted Multilayer Ceramic Capacitor Subjected to Bending

Failure of surface-mounted multilayer ceramic capacitor (MLCC) results mainly from bending of the printed circuit board during handling and applications. Cracking of MLCC normally initiates at the junction of the bottom end of termination and the dielectric ceramics and it would cut through dielectric ceramics and electrodes to result in the capacitance loss and failure of MLCC. The purpose of this study was to mitigate the stress concentration and to shift the stress concentration location toward the side end of MLCC to minimize the number of electrodes cut by cracking. To achieve this, effects of the stiffness and the thickness of the solder and the size of MLCC on the location of crack initiation and the fracture load were examined. Nanoindentation was performed to obtain the mechanical properties of the constituents of the system. Finite element analyses were conducted to simulate the stress field in the surface-mounted MLCC subjected to bending and the results were compared to the observed crack initiation locations and the fracture load. The outcome would provide guidelines in mounting and designing of MLCCs to enhance its reliability and lifetime.