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Lead-Free Solders

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nuckolls.bob(at)cox.net
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Posted: Mon Jun 16, 2008 5:58 pm Post subject: Lead-Free Solders

 	  Quote: 	
		  Comments/Questions: I enjoyed reading the information in your article on 

crimping vs. soldering.  One thing that I did not see addressed was the 

problem of tin whiskers growing on soldered connections and causing shorts:


	


   Tin whiskers occur in very selective environments and

   only from tin-lead alloys with every low lead levels. At

   the present time, there are no lead-free alloys that have

   been embraced by the aviation industry . . . and I would

   presume the military isn't really enthusiastic about low-lead

   or lead-free solders either. In addition to the tin-whisker

   problems, lead-free falls short in a number of performance

   characteristics.



   Bob . . .

        ----------------------------------------

        ( IF one wishes to be "world class" at )

        ( anything, what ever you do must be   )

        ( exercised EVERY day . . .            )

        (                  R. L. Nuckolls III  )

        ----------------------------------------

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jmcburney(at)pobox.com
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Posted: Tue Jun 17, 2008 4:57 am Post subject: Lead-Free Solders

I agree with you, Bob, that lead-free isn't the best way to go.  However,

it's getting harder and harder to get past the "tree-huggers".  Notice how

often you see "RoHS" in the catalogs anymore.



Do not archive



Blue skies and tailwinds



Jim

CH-801

DeltaHawk diesel

Augusta GA

90% done, 90% left

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nuckolls.bob(at)cox.net
Guest

Posted: Tue Jun 17, 2008 7:57 am Post subject: Lead-Free Solders

At 08:53 AM 6/17/2008 -0400, you wrote:

 	  Quote: 	
		  



I agree with you, Bob, that lead-free isn't the best way to go.  However,

it's getting harder and harder to get past the "tree-huggers".  Notice how

often you see "RoHS" in the catalogs anymore.



Do not archive



Blue skies and tailwinds


	


  Yes, but the RoHS components solder down very nicely

  with good ol' 63/37. I probably have a lifetime supply

  of the "good stuff" on my shelves.



  Now, this DOES raise the specter of tin-whiskers on

  components that are built to RoHS standards even when

  they're assembled to the product with 63/37.



  Fortunately, these experiences are rare. We've had

  hot tin dipped, closely spaced relay terminals on our

  GA aircraft for decades. 99.9% of the time, any whisker

  that might have offered a potential for system malfunction

  simply gets burned away.



  Of course, not the case with micro-electronics. In this

  case, it appears that conformal coatings have held the

  Whisker Dragon at bay.



  Bob . . .

        ----------------------------------------)

        ( . . .  a long habit of not thinking   )

        ( a thing wrong, gives it a superficial )

        ( appearance of being right . . .       )

        (                                       )

        (                  -Thomas Paine 1776-  )

        ----------------------------------------

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info(at)mtfind.com
Guest

Posted: Thu Jun 19, 2008 1:38 pm Post subject: Lead-Free Solders

One additional point. The tin-whisker problem is a major concern in 

aerospace etc. where the life of the circuitry is important. Your statement 

about external coating can prevent (external to the device) whisker growth 

is correct. The concern in the industry is internal whisker growth with 

expected lifetimes of only a few years (before lead removal the life was 

several decades). Consumer electronics have an average useful life of only a 

few years (due to technology etc. improvements) and it is not a large issue 

there.  It is a large issue in aerospace where the needed lifetime is 

typically tens of years. This is a major reason for the exemption of RoHS 

requirement in aerospace among other long life systems.



Paul

---

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nuckolls.bob(at)cox.net
Guest

Posted: Thu Jun 19, 2008 5:44 pm Post subject: Lead-Free Solders

At 02:36 PM 6/19/2008 -0700, you wrote:

 	  Quote: 	
		  



One additional point. The tin-whisker problem is a major concern in 

aerospace etc. where the life of the circuitry is important. Your 

statement about external coating can prevent (external to the device) 

whisker growth is correct. The concern in the industry is internal whisker 

growth with expected lifetimes of only a few years (before lead removal 

the life was several decades). Consumer electronics have an average useful 

life of only a few years (due to technology etc. improvements) and it is 

not a large issue there.  It is a large issue in aerospace where the 

needed lifetime is typically tens of years. This is a major reason for the 

exemption of RoHS requirement in aerospace among other long life systems.


	




   Yeah, that and the lack of toughness in lead-free joints. Seems

   that re-flowed joints of lead-free products don't get the

   wetting or structural integrity that we've enjoyed in 63/37

   all these years. One of my clients has tried several lead-free

   solder systems and decided he wasn't going to change over soon . . .

   not at least with his present warranty policy!



   Bob . . .

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