Issue link: https://iconnect007.uberflip.com/i/488725
20 SMT Magazine • April 2015 Because of the number of SIR boards and the test chamber's inability to accommodate all the boards at one time, the SIR testing had to be run in two separate batches, as mentioned ear- lier. An unintended side effect of running mul- tiple batches is the possible occurrence of slight batch to batch variations. The best way to detect these variations is with the controls, as these are bare clean unprocessed (unreflowed) boards. A critical examination of the average SIR values obtained from each scenario seems to indicate that such a variation occurred in this study. The SIR values obtained from Run 2, including those values measured on the controls, were generally lower than those obtained from Run 1. In order to effectively compare all the data as one large data set and reduce the impact of the batch to batch variation, the data was later "normalized." To normalize the data, the author divided the average SIR value from the controls in Run figure 14: Halogen-free solder paste, 235°c peak temperature ramp profile (run 1). figure 16: Halogen-containing solder paste, 235°c peak temperature ramp profile (run 1). figure 15: Halogen-free solder paste, 235°c peak temperature soak profile (run 1). figure 17: Halogen-containing solder paste, 235°c peak temperature soak profile (run 1). ElECTriCal rEliaBiliTy OF NO-ClEaN SOlDEr paSTE Flux rESiDuES continues FeAture