On Thu, 08 Apr 2010 17:11:39 +1000, Franc Zabkar
wrote:
I came across a reference to this Russian forum thread in a WDC forum:
http://maccentre.ru/board/viewtopic....70953&start=15
Here is Google's translator:
http://translate.google.com/translate_t?sl=ru&tl=en
A better way to do this is to drag the English translation tool to the
tool browser bar:
http://translate.google.com/translate_tools
The browser will automagically ask if you want to translate any
foreign language web page that you view.
The thread discusses oxidisation of contact pads in current Seagate
and Western Digital hard drives.
It's not oxidation. Oxides of both tin and lead are white in color.
My guess(tm) is lead sulphide (galena), as lead sulphate and tin
sulphate are usually white.
http://en.wikipedia.org/wiki/Lead%28II%29_sulfide
It's difficult to tell from the photos if the PCB contacts are gold or
tin-silver. It's also difficult to tell if there was a mix of contact
materials. Mixing gold and tin contacts usually results in black crud
and fretting:
http://www.tycoelectronics.com/documentation/whitepapers/pdf/p316-90.pdf
http://www.tycoelectronics.com/documentation/whitepapers/pdf/p154-74.pdf
(see Fig 3). Contact material galvanic mismatch is another
possibility.
The drives were used in typical
office and home environments, and are about a year old.
Another possible culprit is a contaminated or poorly washed PC board.
The typical kitchen environment will also cause a problem. I see it
on machines and drives fairly often. If necessary, I just clean the
contacts with a pink pencil eraser, and reassemble. I've NEVER had a
drive failure that was directly attributed to such contact corrosion.
It's usually something else that kills the drive.
The thread has
several detailed photos. All except the older tinned PCB appear to
show evidence of serious corrosion.
Is this the fallout from RoHS? Surely it's not the result of some cost
saving measure?
Nope. If the contacts were tin-silver, 5% lead, or one of the other
low lead alloys, the corrosion would probably be white or light gray
in color. The dark black suggests there's at least some lead involved
or possibly dissimilar contact material.
--
Jeff Liebermann
150 Felker St #D http://www.LearnByDestroying.com
Santa Cruz CA 95060
http://802.11junk.com
Skype: JeffLiebermann AE6KS 831-336-2558