Tin whiskers caused by material stress

[Bob Stern]

"Yong Sun, a mechanical engineering doctoral student at the University of South Carolina’s College of Engineering and Computing ... used a process called digital image correlation to track the deformation of the surfaces and was able to prove the growth of whiskers are caused by high-strain gradient built up inside the device. Sun’s findings were published in the Scripta Materialia, a materials science journal."

http://www.sc.edu/news/newsarticle.p...1#.UQGkFKWAQUV

Hopefully, solder manufacturers now will develop new solder mixtures that minimize the internal stress of the solder joint.

[bear]

Yeah, it's called "Pb".

But seriously, for tin whiskers I think you first need a pot metal cat?

[kouiky]

I completed an in depth report on tin whiskers and silver dendrite four years ago. To this day, there are those who deny the existence of the phenomenon. Thus, I no longer discuss it in any great length.

[sandyK]

Originally Posted by kouiky

I completed an in depth report on tin whiskers and silver dendrite four years ago. To this day, there are those who deny the existence of the phenomenon. Thus, I no longer discuss it in any great length.

Koulky
In my career with Telstra I had to replace hundreds of relay springsets that had springs develop a s/c to the relay frame, and hence caused a failure. Later on I realised that I was able to overcome the problem by connecting an electrolytic capacitor charged to the Exchange voltage of around 52V between the spring and the frame of the relay.
There was rarely anything to see, but the fault was cleared without the need to replace the springset. Some of these springsets had quite expensive metal contacts, so it resulted in quite a saving in both money and time unsoldering and replacing the faulty springset.
Regards
Alex

[djmiddelkoop]

To this day, there are those who deny the existence of the phenomenon

Totally don't understand, as even NASA had to deal with this issue :
NASA Goddard Tin Whisker Homepage

[kouiky]

I know it exists. What I was stating was that people on other forums claim it doesn't exists because their favorite audio guru says so.

[djmiddelkoop]

Ok, thanks for the info.

By the way, I have personally seen it at work on tinned surfaces.

[marce]

The best method of stopping tin whiskers is adding lead to the tin, anything above 3% lead will do if I remember correctly
This is the reason why a lot of electronics (and some enses) only have a 10 year life span claimed by manufacturers, because of the dam things. They were also mentioned in the report NASA did for the Toyota problem.
Cant believe people deny it, in this day andage, a link would be fun...
For some stuff, I have had to specify ALL the components re-tinned with tin/lead solder, and BGA's re-balled at 2.5p per pin, costs soon mount up!