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Halogen-Free Solder Paste - Part 2

We received a call today from a customer that had tested the halide content of their board and reflowed solder paste, without components, using Ion Chromatography. This was an attempt to get a "baseline" reading for halogen and halide content. Well, they got a suspicious reading and we got the urgent phone call. Halogen-free solder paste is by its very nature also halide-free solder paste, but not necessarily the opposite. Halogens are found everywhere; in some solder pastes, some fluxes, resins and solder masks, and even some surface finishes. A lot of it has to do with temperature and the curing of the boards. This shows up when testing for halogens. Try running a bare un-reflowed board, without solder along with a bare, reflowed board. Sometimes the differences are really concerning. Also, a little cleanliness goes a long way. Repeat the same test with boards that have been cleaned per the IPC recommendations for Surface Insulation Resistance (SIR), try the test again, cleaned versus un-cleaned test boards. Add in the solder paste factor, contamination from fingers, soiled gloves and even alcohol-based marking pens. Please let me know your results, Mario Scalzo. More information may be found at our Online Help: Indium Knowledge Base.