Electronics Forum | Wed Nov 29 20:54:32 EST 2017 | truthseeker
DAVEF: In "Soldermask - sulfur presence" [http://www.smtnet.com/Forums/index.cfm?fuseaction=view_thread&CFApp=1&Thread_ID=16291&#Message66659], how did you determined that sulfur was coming out of mats onto boards?
Electronics Forum | Mon Feb 26 09:36:08 EST 2001 | blnorman
ASTM E 443 is a test for sulfur by Oxygen Flask Combustion. Other instruments will detect sulfur (I assume a SEM with EDS capability will pick up the sulfur). We had an addition cure silicone potting compound inhibition problem last year that was t
Electronics Forum | Wed Sep 03 11:42:21 EDT 2008 | robinj
If the tarnish is really dark, it is very difficult to remove. Since it is yellowish it is only in the early stages. Replating will definitely work. I have used sulfuric acid based cleaners to remove this yellowish color. But rinse well and dry quick
Electronics Forum | Wed Feb 21 19:55:12 EST 2001 | davef
References on corrosion are: * "ASM Corrosion Handbook No. 13" [0871700077]. * "Electronic Packaging and Corrosion" ME Nicholson [0871702916]. Please explain how you determined that you have silver-sulfide contamination. Where is the silver comin
Electronics Forum | Fri Aug 22 09:07:22 EDT 2008 | blnorman
Sulfur is probably the culprit. Board supplier should be providing boards with anti-tarnish sheets between the individual boards. Also, cardboard is a major source of sulfur and so boards should not be shipped in cardboard.
Electronics Forum | Wed Nov 29 20:57:10 EST 2017 | davef
Jez, you're digging away in the grass on this one. Long time ago. Look at: FED-STD-101, Method 3005 for reducible sulfur. The standard is maintained by some packing material group. Interestingly, it's not uncommon to see it referenced in other elec
Electronics Forum | Mon Aug 04 12:38:25 EDT 2008 | blnorman
Avoid cardboard boxes as well. They are sulfur bearers, and silver has an affinity to form silver sulfide.
Electronics Forum | Mon Apr 26 14:40:07 EDT 2010 | blnorman
We had one product that used immersion silver plating. There were a couple of instances where we saw tarnishing, and elemental analysis confirmed the presence of sulfur. These boards did have the anti-tarnish sheets between boards, but somehow they
Electronics Forum | Sun Feb 23 14:32:42 EST 2003 | davef
Sources of sulphur in PCB fabrication are: * Some locales have high H2S concentrations in the air. * Metal etching steps that use sulfuric acid or a sulfonated buffering compound may result in sulfate residues. * Sulfates can come from contact with
Electronics Forum | Thu Feb 09 20:12:51 EST 2017 | imarkl
Any advise about dewetting defect occurrence during 2nd pass reflow. Commonality on affected PCB having water marks near affected pad(s). Elemental composition found on affected pads without solder paste are Silicon and Sulfur. As well as in pad with
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