[aprssig] Kenwood TH-D7A(G) Retired - wiskers (off-topic)

Derek Koonce derek at dkoonce.com
Mon Oct 13 20:32:12 EDT 2008

Few statements I'd like to add over the flurry of email...

1. Military, space, and other key critical electronics are still using 
Pb based solder due to tin wisker problems. The recent reports I have 
read that there is something about the lead that minimized wisker 
growth. Even a few percent helps. As stated before, studies are continuing.

2. Joint pictures: Pb joints tend to be shiny when done. Pb-free tend to 
be dull in color.

3. As for China's ROHS, be careful since China could configure their 
requirements to eliminate outside electronics that do not conform to 
"their" standard. US is slow to adopt due to wisker problems.

Derek Koonce

Shanon KA8SPW wrote:
> My fellow hams:
> Don't be so fast to replace what works.  Another case of a law to 
> replace or reduce something before the technology is there to provide 
> a solution.
> Take a read about growing "tin whiskers" and lead free solder.  Big 
> problem in RoHS circuits.  And it don't take long to show up.
> "There is electrical risk posed by the other major component of 
> solder, tin. For reasons that remain somewhat obscure, tin used in 
> electronic devices can form what are called "tin whiskers 
> <http://nepp.nasa.gov/whisker/>," thin filaments of the metal up to 
> 10mm long that sprout from surfaces covered in the metal. Although the 
> causes of the whiskers are obscure, the consequences aren't: whiskers 
> that bridge two conducting areas can cause short circuits, causing 
> erratic behavior or ultimately destroying the equipment. NASA 
> maintains a list <http://nepp.nasa.gov/whisker/failures/index.htm> of 
> various military, orbital, and medical failures that have been 
> attributed to tin whiskers. Presumably, many failures in equipment 
> that is not significant enough to warrant a post-failure analysis are 
> also the product of tin whiskers."

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