Hi Steve - yes, you can peel copper away from solder as solder is not a structural material. IMHO your solder coverage is outstanding. My guess is that the product team is having circuit functional issues and thinking they have a grounding/thermal issue which is not the case given the amount of solder coverage you achieved. Dave Hillman Rockwell Collins [log in to unmask] On Thu, Aug 13, 2015 at 2:56 PM, Steve Gregory <[log in to unmask]> wrote: > Hi All, > > So here's the story; we're building a board that has a Linear Technology > LT3652 12-pin MSOP device on it, and it has a belly or grounding pad on it. > The board is designed with five 20-mil via's beneath it (bad idea), and > they are through via's not cap plated or tented. So they start having > problems with the part. The footprint on the board has the belly aperture > much larger that the pad on the device itself. I have a 5-mil thick stencil > because there are 20-mil pitch QFP's on the board, and I print 100% of the > area of the belly pad on the board (which is .160" X .082"). My reflow > profile peaked out at 228 C. and I was above reflow for 63/37 for > 112-seconds. While I did not have a thermocouple on that part, I did have > it nearby because there are some large D-Packs in the vicinity and I wanted > to be sure I was getting adequate reflow on those. > > So the complaint is that we're getting insufficient solder on the belly > pad. It was told to to us that there is less than 50% coverage on the belly > pad. We x-rayed many boards and while we could see that sometimes the vias > didn't fill, we saw evidence of solder on almost 100% of the area of the > pad. We could tilt the board and under high magnification see beneath the > part and tell that solder had wet to the belly pad on the part, but what we > could not tell was how much it actually covered the pad. We removed parts > with hot air and could not find one part that did not have solder wet to > 100% of the pad. > > So my boss asked me to take a board and physically pry one off to see what > it looked like. So I got a heavy exacto blade and slipped it beneath the > edge of the part and pried. The corner broke and then the top half part > with all the guts split off, a couple of leads in the corners broke off > too, but the belly pad stayed on the board. I was able to get the exacto > blade under a corner of the belly pad and I could slowly peel it away from > the solder joint, and this is what it looked like: > > http://stevezeva.homestead.com/LT3652_Belly_Pad.jpg > > So I saw a few small voids (which was not unexpected), but to my untrained > eye I don't see much wrong. I do wonder a little about me being able to > peel away the belly pad like that, should I have been able to do that? Or > does the solder fracture along the intermetallic layer when you apply > peeling forces like that? > > Thanks in advance for any input... > > Steve > > -- > > > This email and any attachments are only for use by the intended > recipient(s) and may contain legally privileged, confidential, proprietary > or otherwise private information. Any unauthorized use, reproduction, > dissemination, distribution or other disclosure of the contents of this > e-mail or its attachments is strictly prohibited. If you have received this > email in error, please notify the sender immediately and delete the > original. > > > ______________________________________________________________________ > This email has been scanned by the Symantec Email Security.cloud service. > For more information please contact helpdesk at x2960 or [log in to unmask] > ______________________________________________________________________ > ______________________________________________________________________ This email has been scanned by the Symantec Email Security.cloud service. For more information please contact helpdesk at x2960 or [log in to unmask] ______________________________________________________________________