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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