[Elecraft] Solder

[Ron D'Eau Claire]

Mike S wrote:

There are real concerns that lead-free solders are less reliable. Lead 
free solder joints are more fragile - 
http://www.pcbrc.com/dev/PDFs/WhitePaper-SACfragility1.pdf  Little is 
known about how to avoid the "tin whisker" problem, and the 
corresponding reliability issues - 
http://ap.pennnet.com/Articles/Article_Display.cfm?Section=ARTCL&ARTICLE_ID=
233627&VERSION_NUM=2&p=95

It's interesting to note that many life critical systems (medical, 
aerospace, military) are exempted from RoHS. 

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I hadn't seen that report on the fragility of lead-free solder joints. Thank
you.  It reinforces the point that ordinary solder containing lead has
worked very well for nearly a century with an insignificant failure rate
when joints are soldered properly. 

When we move into new technology we are breaking new ground no less than the
day the Titanic sailed to New York. 

I was aware that the tin whisker problem is a real issue that has no
immediate solution. However, from what I've read, the whisker problem is not
an issue with the solder. It's an issue with using pure tin to coat the
leads on some RoHS parts. The parts themselves are subject to growing deadly
whiskers no matter what solder is used. A number of photos I've seen point
out that the soldered part of the connection is free of whiskers while the
pure tinned portions of the lead that were not subjected to solder grew the
whiskers. 

The whiskers can grow weeks, months or even years after a part is installed
and the whiskers can reach several  mm in length, producing shorts between
adjacent solder pads. Here's some pictures of the whiskers:

http://nepp.nasa.gov/whisker/anecdote/20year/index.html

The whiskers aren't getting the play in the press one might imagine because
the consumer electronics industry isn't too concerned about them. They plan
on your Ipod, computer, personal digital assistant, TV, cell phone or other
personal electronics being discarded every year or two anyway, before the
whiskers will render them useless. 

It's the military, space and other high-reliability applications who are
concerned, and they aren't the ones to make the "front page" of the morning
paper.

I'm inclined to put my Elecraft rigs up there in reliability objectives with
a satellite or missile. I don't plan to trash the rig in a year or two (my
K2 is already going on 7 years old already!). 


Ron AC7AC