Study of copper barrel plating dissolution of printed circuit board with multiple exposure thermal stress testing

The copper barrel plating dissolution of printed wiring boards (PWB) occurring with multiple thermal stress testing had been studied in this paper. The thickness reduction of copper barrel plating and related copper dissolution rate were measured and compared for test specimens under the conditions of multiple thermal stress cycles (1X-6X) with two test temperatures (288°C / 260°C) in accordance with IPC-TM-650, Test Method 2.6.8, modified. Before all thermal stress tests, the solder alloy element concentration (wt%) of the lead-free solder pot in-use had been tested by a solder paste vendor and the result was acceptable and normal as compared with IPC new released guidelines for diagnosing contamination of SAC305 solder pots / baths. Moreover, the practical affecting factors of copper dissolution during thermal stress and lead-free soldering process had been discussed in this paper, including the direct relevance of copper dissolution to printed circuit board performance and reliability.