Witchcraft, superstitions are made of this...
That said, the boards are likely to fail again before too long. Maybe they have a bad/dry solder joint that now makes better contact because the board flexed sufficiently to allow the contact to wipe a new path on the pad through the residual flux or a capacitor with a bad internal connection was renewed in the same way... I have personally experienced a PC that worked intermittently, going off into la-la land after 30 min to 2 hrs or longer due to a ram chip lead contact that was sitting on top of a dry joint. When the system was powered down sufficiently long to cool off it renewed itself automatically. Took me three weeks to find it and re-solder it.
Chuck Patten, PMP
Engineer Lead Project
-----Original Message-----
From: Leadfree [mailto:[log in to unmask]] On Behalf Of Gianfranco Scanu
Sent: Wednesday, March 03, 2010 8:31 AM
To: [log in to unmask]
Subject: Re: [LF] video card home baking....
You're right: at 192 °C tin is "rock solid", so there should be some different
mechanism involved, but, as I told you, there are so many similar "reports"
around, and the story just puzzles me a bit.
Regards
On Wed, 3 Mar 2010 17:07:31 +0100, Pascal Oberndorff
<[log in to unmask]> wrote:
>Before everybody starts blaming Pb-free without any evidence: 385 F is
about 192 C, which means there is no remelting of Pb-free solder joints or of
whiskers.
>
>Let's try to keep realistic.
>
>
>
>With kind regards, Met vriendelijke groeten, Mit freundlichen Gruessen,
>
>Pascal Oberndorff
>Manager Materials and Reliability, Operations Back End Innovation,
>NXP Semiconductors
>Gerstweg 2, BY 1.015, 6534 AE, Nijmegen, The Netherlands.
>Tel: +31 24 353 6985, Fax: +31 24 353 3350, Mobile: +31 6 510 24910
>E-Mail: [log in to unmask]
>www.nxp.com
>
>
>-----Original Message-----
>From: Leadfree [mailto:[log in to unmask]] On Behalf Of Gianfranco Scanu
>Sent: 2010 Mar 03 4:29 PM
>To: [log in to unmask]
>Subject: [LF] video card home baking....
>
>http://hardforum.com/showthread.php?t=1421792
>
>This is just one of the many threads discussing this issue on the net.
>Which is your idea?
>Could be related to tin whiskers on lead free products (this kind of video
cards
>are RoHS compliant) or to solder joints issues?
>
>Regards
>
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