Electronics Forum | Mon Jun 25 03:52:24 EDT 2012 | awtm
Our Customer had detected tarnished pad on ImAg PCBA and had conducted several SEM-EDX test at the soldermask below some of the chip resistors. High concentration of sulfur was found and it can be significantly reduced after further chemical cleaned
Electronics Forum | Mon Jun 25 11:33:20 EDT 2012 | davef
The immersion silver is an active surface and readily combines with sulfur from the environment. Silver sulfide tarnishes the surface and creates doubt about the integrity of the finish at inspection. [uyemura.com/library-4.htm] Your customer's boar
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
