Jeremy, I'm gonna make a couple of assumptions by "reading in between the lines" of your email: 1. You're using no-clean paste. 2. This is only happening on the second side. You tell me if I'm wrong about this... First thing, if you're only experiencing the problem on the second side, it sounds to me like they've coated the boards with CU-56 entek, instead of CU-106 like they should have used with boards that will be seeing multiple thermal excursions. The CU-56 wil pretty much take a hike after the first reflow cycle...hasta la vista baby! It's gone! Although I heard a while back that IBM used CU-56 on a lot of their boards when OSP's first came out, and discovered that if you printed the second side, got the parts on, and reflowed right away, it would work...you had to do that within just a couple of hours after the first reflow occured. I HEARD that, I've not tried it myself though.... If it's happening on both sides, then there could be two possible things to look at: 1. If you are using no-clean paste, then possibly the activity in the flux just ain't got the "grunt" it needs to get through the entek...no-cleans only have about 1/4 the activity that a water soluble paste does...some pastes even less. 2. The vendor is slapping the entek on too thick. There's a lot of board vendors out there that don't have the OSP process automated and controlled the way they should. Think about it for a second, this is a new process for them. In the past, the way the solderable surfaces have been finished has either been through a HASL, or some sort of electroplating method. With OSP's all they need is basically a tank filled with the OSP that they can dip the boards into, and viola' they're doing OSP coated boards! Other than that, you sound like you know what you're doing with reflow profiles...just make sure you're not too hot though...you'll waste all the flux activity before the solder becomes molten and has a chance to wet. I hope maybe this helps! -Steve Gregory-
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