| Has anyone seen a problem with solder under chip components, in-between the glue and the component or in-between the mask and the component? We seen both. | What could be causing this? This has only been detected on one of our products. All the rest which use the same materials and profiles seem to be good. | | John | I must assume that the chips are glued to the PCB, cured, then wave soldered. If you are seeing solder shorts under the chips this is probably an indication of outgassing. Epoxy is hydroscopic-that is it readily ablorbs moisture from the atmosphere. The moisture expands forming steam in your curing oven. The steam evaporates, leaving chambers or cavities to which liquid solder easily enters. Typically this problem occures when stencil printing epoxy. Here is a simple test for all epoxies. Dispense epoxy in between two glass slides. Sandwich them together and cure in your oven. If moisture is present you will EASILY see the cavities made from the steam. Heraus makes some anti-hydroscopic epoxies (PD44). Also, check your cure schedule. It is helpful to stay below the boiling point of water and slowly evaporate the water rather than vaporize it instantly. This may slow your line down if your oven is a multi-zone linear type. Phillip Hunter Laughlin-Wilt Group Inc. 503-672-4388
reply »