FYI

Someone (Trikeman?) told me that about 10,000 papers exist about whiskers.
Of course most of them are echoes.

Inge


On 12 June 2013 07:26, greg <[log in to unmask]> wrote:

> There have been several papers published at APEX on the topic. But whether
> they address the specific issues raised today I leave to wiser heads than
> mine.
>
> APEX 2007:
>
> Effect of Conformal Coating on Tin Whisker Growth, Vijay Kumar and Linda
> Woody, Lockheed Martin
>
> Parylene as a Suppressant for Tin Whiskers Growth on Printed Circuit
> Boards, Rakesh Kumar
> Specialty Coating Systems
>
> Whisker Penetration into Conformal Coating, Stephen McKeown, Joseph Kane,
> Dr. Stephan Meschter
> BAE Systems, Johnson City, NY
>
>
> APEX 2008:
>
> Effects of Tin Mitigation Processes on Whisker Growth and Solder Joint
> Reliability
> for Chip and Small-Outline Package Components, Tom Lesniewski and Tom
> Higley, Northrop Grumman Network Communications, San Diego, CA 92128
>
> APEX 2010:
>
> Conformal Coatings for Tin Whisker Risk Management, William Fox and Linda
> Woody
> Lockheed Martin Missiles and Fire Control, Ocala, Florida
>
>
> And Chris Hunt did publish also but the APEX papers of his do not talk
> about conformal coating. (He may have published somewhere else on
> whiskers/coatings. Dave who published on tin coated braided wire may want
> to weigh in after he returns.)
>
> Having done the file search on the above whiskers/coatings APEX papers and
> read their summaries the answer to "Does it help?" seems (to me) to be
> somewhere between "yes/no/maybe/it depends." (i.e. it's "above my pay
> grade.")
>
> Greg Munie
> IPC Director of Design Programs
>
>
> >  -------Original Message-------
> >  From: Mike Fenner <[log in to unmask]>
> >  To: [log in to unmask]
> >  Subject: Re: [TN] minimum thickness of Type UR Conformal coat and tin
> whiskers
> >  Sent: 12 Jun '13 09:07
> >
> >  Richard, slightly tongue in cheek I ask: How does soldering with
> tin/lead
> >  prevent tin finish on PCB whiskering?
> >
> >  Phil I recall Chris Hunt of NPL in UK did some work on this. You can
> >  probably download a copy of paper from their WWW.
> >
> >  Best Wishes
> >
> >
> >
> >  Mike
> >
> >
> >
> >  -----Original Message-----
> >  From: TechNet [mailto:[log in to unmask]] On Behalf Of Stadem, Richard D.
> >  Sent: Wednesday, June 12, 2013 2:22 PM
> >  To: [log in to unmask]
> >  Subject: Re: [TN] minimum thickness of Type UR Conformal coat and tin
> >  whiskers
> >
> >  Not only can the whiskers grow through the conformal coating, they can
> grow
> >  under it like weeds in a stream. NASA has some good pictures of this on
> >  their website.
> >  The best tin whisker mitigation scheme is called tin/lead solder.
> >
> >  -----Original Message-----
> >  From: TechNet [mailto:[log in to unmask]] On Behalf Of Douglas Pauls
> >  Sent: Wednesday, June 12, 2013 8:10 AM
> >  To: [log in to unmask]
> >  Subject: Re: [TN] minimum thickness of Type UR Conformal coat and tin
> >  whiskers
> >
> >  Phil,
> >  While this is an answer I "should" know, I don't.  Dave Hillman
> regularly
> >  attends and presents at the CALCE yearly conference on whiskers and so
> he
> >  keeps up on all of that.  At present, my esteemed colleague is bumping
> his
> >  head on rocks, kayaking upside down, on some white water in North
> Carolina.
> >  He should be back in the office on Monday and will no doubt answer then.
> >
> >  From our discussions, the general rule is still "no conformal coating
> >  prevents whiskers".  A thicker coating may cause the whisker to expend
> more
> >  energy punching through and yet more energy to punch through an adjacent
> >  coating on a lead (usually resulting in buckling), but I have yet to
> hear
> >  about some magic thickness of any kind of coating that completely
> mitigates
> >  whiskers.  But I could be wrong.
> >
> >  Dave?
> >
> >  Doug Pauls
> >
> >
> >
> >  From:   Phil Bavaro <[log in to unmask]>
> >  To:     <[log in to unmask]>
> >  Date:   06/11/2013 02:26 PM
> >  Subject:        [TN] minimum thickness of Type UR Conformal coat and tin
> >  whiskers
> >  Sent by:        TechNet <[log in to unmask]>
> >
> >
> >
> >  Doug et al,
> >
> >  Is there a disagreement in the industry as to what minimum thickness of
> >  urethane is required in order to mitigate tin whisker concerns?
> >
> >  I am hearing that the .003+/-.002" does not provide enough of a minimum
> >  thickness and that the number is as high as .004".   I can understand
> >  wanting the minimum being raised to .002" but higher than that would
> seem to
> >  make the process much more difficult to control.
> >
> >  I have a potential customer asking if we measure the thickness on the
> >  individual component leads which is another can of worms it seems.  We
> >  always used flat samples to document our thicknesses.
> >
> >  I did not get to attend this years APEX so I might have missed the
> latest
> >  data.
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