Effect of board design and assembly process on leakage currents of ceramic chip capacitors

An experiment designed to study the effects of mounting pad configurations on the tendency toward thermal cracking and/or leakage currents of 1206 and 0805-size SMCs (surface-mounted ceramic chip capacitors) was conducted. The results show that, with the maximum delta temperature of 135 degrees C, vias, traces, long pads, and heat sinks do not cause thermal cracking. No significant differences were found between SMCs mounted on FR-4 boards and FR-2 boards. The differences in capacitor dielectrics were insignificant, except that one particular capacitor designed with a thinner dielectric layer suffered more failures.<
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