Electronics Forum | Thu Jul 02 16:01:57 EDT 2009 | ewchong
thanks kpm. agree the cause of those pads lifting. all of them were no connects so they cannot be the cause of the electrical failure. when the bga was removed, all the solder balls on the pcb turned into conical shape due to the separation, except
Electronics Forum | Wed Apr 13 12:10:47 EDT 2022 | winston_one
Hello! We have a strange effect. Some pads of big trough-hole DDR slot just dessapear. Initialy it was soldered with selective soldering process (leaded, 290 degrees, ImSn finish, very short storage). Then some connectors with poor barrel fill we hav
Electronics Forum | Thu Jul 02 13:10:22 EDT 2009 | kpm135
On first glance it looks like those particular pads were not attached to any traces. If I had to guess I would say that your rework profile got hot enough to melt away the glue holding the pads to the board and they came away with your part when you
Electronics Forum | Tue Jul 07 08:42:49 EDT 2009 | ewchong
kpm, you are probably right. under magnification those two pads show some exposed copper which means that they were contaminated or had insufficient solder paste before reflow.
Electronics Forum | Tue Jul 07 05:55:34 EDT 2009 | kpm135
I agree with your assessment of the two pins with irregular solder. The head-in-pillow or broken joint are both probable events for your defect. At this point in the process it will probably be difficult to pinpoint the exact cause. If it was a broke
Electronics Forum | Mon Apr 18 12:39:57 EDT 2022 | winston_one
Thanks for all comments. Process was adjusted normally, problem was in PCBs. Microsection of bare boards confirm that the copper thickness in troughholes was unsuffient, sometimes below 10 microns, on soldered boards where there were a problems durin
Electronics Forum | Fri Apr 15 09:56:17 EDT 2022 | winston_one
Thank's Dennis. I'm also now think in this direction. Process was adjusted and soldering are good. But one from five boards can have this effect with bubbles and strange uneven distribution of solder inside the barrel. Probably copper is too thin and
Electronics Forum | Wed Apr 13 21:17:18 EDT 2022 | stephendo
If it was ROHS, I would say that the pads are definitely dissolved away. And it sounds like that is the case here. Your best bet is if it is class 2 and the barrels are at least 50% then push for them to be accepted. If you are trying for more barr
Electronics Forum | Thu Apr 14 15:27:05 EDT 2022 | ppcbs
If it was ROHS I would suspect copper migration. In my experience an acceptable copper finish should last up to at least 6 reflow cycles. If you have bubbles or blow holes in the solder joint, that is a sign of voids in the walls of the copper barre
Electronics Forum | Thu Apr 14 14:00:44 EDT 2022 | winston_one
Also at few boards we see excessive voiding, extremily excessive. During solderind some bubbling can be observed near the soldering point. Boards was dried before assembly. May be we have a problem with too thin metallisation - that's why poor adhesi
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