Abstract:

Surface mount multilayer ceramic capacitors (MLCCs) are susceptible to cracking due to mechanical bending of the printed circuit board on which they have been assembled. Bending stresses are transmitted through the solder fillets to the ceramic body of the capacitor. With the transition to lead-free materials in the electronics industry there is a need to understand the impact of the solder material on flex cracking of MLCCs.

An experimental study was conducted to study susceptibility to flex cracking of MLCCs, in which a comparison was made between identical samples which were assembled using either lead-free (Sn3.0Ag0.5Cu) or eutectic tin-lead (Sn37Pb) solder. Experimental results showed that MLCCs mounted on boards with lead-free solder are less susceptible to flex cracking compared with MLCCs mounted on boards with eutectic tin-lead solder. Flex testing was performed on MLCCs having X7R dielectric and 1812 size from three manufacturers, assembled on printed circuit boards with both lead-free and eutectic tin-lead solders. Test results revealed a significant interaction between manufacturer and the extent of improvement with lead-free over tin-lead solder.

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