Faulty Manufacure of PCBS, Non-Wetting etc - Page 1
Forum section: electronics / general

author: stephen Jones
author_rank: Newbie
timestamp: July 13, 2023, 12:57:40 pm
content: We are having PCB manufacturing issues with a new supplier. I think there are signs of non wetting and also most pads to me are not sufficiently covered in solder. What could cause this, I attach some pictures to show the issues.. These boards are from our new manufacture and are examples of failed boards, and its ENIG plating

author: jmelson
author_rank: Super Contributor
timestamp: July 13, 2023, 02:27:30 pm
content: Are you assembling these boards yourself, or are these assembled by an assembly house? The problem may not be the blank boards themselves, but the quality of the solder paste or the reflow temperature profile. It could possibly be out-of-date paste.If an assembly house is doing the reflow, then this is THEIR QC problem!Jon

author: wraper
author_rank: Unknown
timestamp: July 13, 2023, 02:57:15 pm
content: It's often a combination of things. First photo looks like misaligned stencil during solder paste application. Second photo looks like as reflow temperature might be a problem as well. Lead-free solder by itself wets significantly worse than leaded. So quality of surface, flux, and application alignment become more important. In addition it could be not good enough PCB plating in combination with too weak solder paste which did not allow it to flow sideways and fix misalignment. For example I had some wetting issues with JLCPCB ENIG and GC10 solder paste. However the same GC-10 worked fine on PCBs from another supplier. And the same PCBs had no issues with SMD291SNL50T3 solder paste.

author: ajb
author_rank: Super Contributor
timestamp: July 13, 2023, 04:59:32 pm
content: If those are ENIG pads (looks like, but color is tricky in photos and could be copper+OSP?) then the board probably isn't the problem.All of the pads with poor wetting look to be attached to copper pours, so that's a big hint. It looks like the heavy thermal mass of those pours is keeping the pads from getting up to temperature. You might be able to improve things by adjusting your reflow profile (more soak time, or more time in the reflow region?), or you might need to increase the thermal isolation of the pads from the pours (fewer spokes, or thinner/longer spokes). The issue could also be compounded by surrounding placement, for example if there are lots of large/heavy components around these joints, those could also make it harder to get these pads up to temperature. The other issues that have been mentioned (like bad solder paste) could be compounding the problem, but I don't think are the main cause.

author: Matt-Brown
author_rank: Regular Contributor
timestamp: July 19, 2023, 07:05:01 pm
content: The 2 caps look to me like this is apaste issue. there doesnt seem to be any solder, and all flux.I would say it is pure reflow related, but not seeing a bare board it could also be black pad.I would try a finger on one pad, if the pad changes color then the plating is not correct

author: mushu326
author_rank: Newbie
timestamp: July 20, 2023, 09:08:59 pm
content: If you're assembling the PCBA, try using a burnishing pen and rub off whatever oxidation is on the surface of the pads before paste printing.

author: wraper
author_rank: Unknown
timestamp: July 20, 2023, 10:20:31 pm
content: Quote from: mushu326 on July 20, 2023, 09:08:59 pm