Thermomechanical Reliability of Lead Free Solder Joint in SMT Assembly

This conference paper focuses on the practical measurement of the reliability of the LF solder connection SMT mounted components on PCB. For measuring of the reliability a special printed boards with various footprints and Sn - HAL, immerse Sn and galvanic Au surface finishing were designed. Printed boards with vapour and wave soldered components underwent temperature cycling and failures (cracks) were evaluated. A temperature cycling +100 °C/0 °C without dwell was applied. The electrical connection was measured continuously during the entire thermomechanical loading. This was done by connecting of a powered LED diode parallel to the examined solder joint. There was original equipment designed for the temperature cycling. The Peltier semiconductor cells were used for cooling and heating of the copper plate. On this plate the printed boards with components were placed. This solution had a low temperature capacity and it enabled relatively short temperature cycles.