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Subject: Re: [Homebrew_PCBs] Re: Tinning the board? silver/tin solder or copper/tin so...

From: ron amundson <mnphysicist@...>
Date: 2005-11-21

Alan King <alan@...> wrote: JanRwl@... wrote:

>"Tinpest" is NOT a problem with "tin solders" with other metals ALLOYED in
>with the tin, even when only 1% or so! Only "pure tin" can get tinpest below
>freezing!
>
When SAC solder is already shown to have problems with tin pest, chances are SA has a probability of having problems, and SC would be worse. The 1%Pb as mentioned earlier will alleviate the problem, and its hoped that contaminants within SAC other than lead will do the same. (Notice the term hoped). The EU directive comes into effect in mid year 2006, and CA here in the US is probably going to adopt something similiar.

There are other problems with SAC that are also starting to show. Strange unexplained fractures, that are not a function of low temperature has the medical community really concerned. The probability is low, really low, so it may not be a big deal for stuff we do, but for those in high volume, or mission critical apps, its going to be a major concern.

I know I would not want to be in consumer electronics customer service for the next couple years.Its going to be a nightmare, but then again when politics rules over science and economics, that tends to happen.

The only good part is that perhaps the solder metallurgists have this solved, and are just keeping quiet on it, until ∗∗it hits the fan for their competition.

Ron

Here are some references off google
http://www.semiconfareast.com/pbfree.htm
http://www.indium.com/drlasky/files/TinPestPaper0723Final.pdf




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