Issue with solder mask on freshly assembled PCB - Page 1
Forum section: electronics / general

author: Hrvoje-CRO
author_rank: Contributor
timestamp: November 28, 2013, 02:32:00 pm
content: Hello!Few weeks ago i've assembled one project (2same pcb's) and what really makes me frustrated is this:http://postimg.org/image/6z4rwswf7/As you can see, solder mask around that joints looks like residues of flux, but it's not a flux! Even worse - it's a solder mask "swelled" but i have no idea why? Only on 2 exactly same PCB's and exactly same parts of PCB.Is it possible that the cause of that issue is kontakt LR spray? Because i used that spray only on that 2 PCB's. But why arround solder joints and not on entire PCB?Thank you in advance!

author: jahonen
author_rank: Super Contributor
timestamp: November 28, 2013, 03:26:31 pm
content: Non-SMOBC-soldermask? If soldermask is not SMOBC (Solder Mask Over Bare Copper), then the solder will easily creep under the solder mask and cause "swelling". Difference is that SMOBC is put on the PCB before pads are plated, (thus no plating between solder mask and copper), but non-SMOBC boards will get plating for whole PCB and solder mask is put there only after plating.Regards,Janne

author: Hrvoje-CRO
author_rank: Contributor
timestamp: November 28, 2013, 04:17:17 pm
content: Hi Janne!PCB is factory made, and it is galvanic tinned. Company that has made for me PCB answered me that is possible on some places issues like mine. But i am still concerned with that. Oh yes, what about temperature of soldering? Perhaps i chose too high temperature of my soldering iron. I do not remember...Regards,Hrvoje

author: Alphatronique
author_rank: Regular Contributor
timestamp: November 28, 2013, 04:28:06 pm
content: Hithat definitively a PCB shop issue ,caused by bad solder mask or shop for save money not strip the tin plating it use as etch resist ..be aware that normally when that happen mask may flake and expose tracethat later oxidise and may cut trace ...so better to change your pcb supplier ...

author: Hrvoje-CRO
author_rank: Contributor
timestamp: November 29, 2013, 11:57:31 pm
content: Believe it or not the cause of my problem was Kontakt LR spray.

author: Alphatronique
author_rank: Regular Contributor
timestamp: November 30, 2013, 01:48:37 pm
content: Hiok but solder mask normally not deteriorate whit normal flux cleaner ;-)was not found MSDN for it was curious what it put on it

author: Hrvoje-CRO
author_rank: Contributor
timestamp: December 02, 2013, 02:33:07 pm
content: Hi again,Yes and i know that! This is why i am frustrated because i am not 100% sure if is LR cause. But obviously it is after use on other PCB from same manufacturer.

author: Kjelt
author_rank: Super Contributor
timestamp: December 02, 2013, 02:53:19 pm
content: The manual of the cleaner does say:QuoteTry flushing with IPA after use, that is what I always do. But I would first test the PCB if this is really the cause, so apply on places where there is no bubbling yet and see if this is really the cause or that it was perhaps a too hot/long soldering that was the cause. Because it is both on a large PCB plane part , so you needed more heat to get the soldering done on that place so that could also be the cause?

author: Hrvoje-CRO
author_rank: Contributor
timestamp: January 03, 2014, 10:23:22 pm
content: Quote from: Kjelt on December 02, 2013, 02:53:19 pmHi Kjelt,Could be main cause of that be alfa fluitin's flux? And no, it is NOT due to usage of spray that i mention as a cause.I ask that because i've noticed on another PCB something strange. One tiny line near solder joint is covered with flux residues and exactly on that part soldermask has "bubbled".

author: Kjelt
author_rank: Super Contributor
timestamp: January 03, 2014, 11:03:31 pm
content: Quote from: Hrvoje-CRO on January 03, 2014, 10:23:22 pmOk if spray is not the cause: the marked places are all ground planes, you needed to apply much more (longer) heat for soldering those spots, could that be the issue?

author: Hrvoje-CRO
author_rank: Contributor
timestamp: January 04, 2014, 03:39:52 am
content: Quote from: Kjelt on January 03, 2014, 11:03:31 pmGood question! Actually, i think, did i maybe put too much heat into those spots? You mean that?Interesting, because, wider lines are also affected, especially where i soldered connectors with thicker pins... there you need to apply more heat.

author: peter.mitchell
author_rank: Super Contributor
timestamp: January 04, 2014, 05:30:10 am
content: I still think it is Non-SMOBC-soldermask, you can check by very gently scraping off some solder mask over a track/plane in a non visible area.

author: Hrvoje-CRO
author_rank: Contributor
timestamp: January 04, 2014, 03:00:42 pm
content: Quote from: peter.mitchell on January 04, 2014, 05:30:10 amIt is non SMOBC, no copper on PCB, just galvanic tined.