On 11 May, 1998 Todd wrote: | We are having continuous bridging problems with the trailing | leads on a 26-pin D-sub through-hole connector. The pitch is | 0.100". The connector is going through the wave at approximately | a 20 Degree angle. Does anyone have any board layout recommendations for | size,location,spacing, and # of dummy pads/holes to eliminate this bridging | problem. | Thanks. Todd, Dummy pads for a thru-hole component? Hmmmmm,...I don't think I've ever seen dummy pads for thru-hole before. I think mainly because there's a different kind of wetting force going on with PTH leads than what's happening with SMT leads...and to tell ya the truth, I don't know if that would even work. There's gotta be something else going on that's causing you to bridge like that. One thing with the design that could be causing problems is that the leads that are bridging are connected to an internal power or ground plane and not thermally relieved, the internal plane acts like a heat sink and causes the solder to freeze and solidify before the solder has a chance to separate cleanly as it's exiting the wave. When was the last time you had a solder analysis done on yer' pot? It doesn't take a whole lot of contamination of other metals to make the solder behave weird. Just a little too much copper, aluminum, etc. can change the liquidous point and viscosity, not to mention the grain structure of solder joints. Just out of curiosity, what kinda process are you in, no-clean or water soluble? What kinda' wave ya' got, and what sorta set points are ya' runnin? Ya' know, belt speed, pot temp, preheat, yada, yada, yada... -Steve Gregory-
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