Cracking remains the major reason of failures in multilayer ceramic capacitors (MLCCs) used in space electronics. Due to a tight quality control of space-grade components, the probability that as manufactured capacitors have cracks is relatively low, and cracking is often occurs during assembly, handling and the following testing of the systems.
Cracks in ceramic chip capacitors can be introduced at any process step during surface mount assembly. Thermal shock has become a “pat” answer for all of these cracks, but about 75 to 80% originate from other sources.
Cracks in ceramic capacitors might cause life test failures. Acceleration testing of various lots of commercial ceramic capacitors was performed in . Some correlation between the life test results and the presence of delaminations in MLCCs was observed. Increased leakage currents in MLCCs having cracks might be due to various mechanisms.
At relatively low ΔTf temperatures, the probability of cracking is extremely small. The effect of preheating of ceramic capacitors having sizes 1206 and 0805 at temperatures ranging from 155 oC to 100 oC on results of wave reflow soldering at 235 oC did not reveal any thermal cracking or leakage current failures .
Index terms: Electric breakdown, ceramic capacitors, defects, reliability. Most failures of ceramic capacitors are caused either by degradation of insulation resistance that results in unacceptably high leakage currents in the circuit or by electrical breakdown that causes catastrophic failure of the part and can damage the board.
After a number of temperature excursions, for example due to circuit operation, the crack may propagate (Figure 3), creating an open-circuit device. In severe cases, the body of the capacitor may even fall out, leaving just remnants of ceramic surrounded by termination and solder joints.