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June 2013

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Subject:
From:
Steven Creswick <[log in to unmask]>
Reply To:
TechNet E-Mail Forum <[log in to unmask]>, Steven Creswick <[log in to unmask]>
Date:
Tue, 18 Jun 2013 05:52:49 -0400
Content-Type:
text/plain
Parts/Attachments:
text/plain (253 lines)
Inge,

Sorry, but was not me.  I can imagine there being a great deal of
non-published work out there, however.

Smooth skies!

Steve C

-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Inge Hernefjord
Sent: Tuesday, June 18, 2013 1:27 AM
To: [log in to unmask]
Subject: Re: [TN] APEX Papers on Conformal coat and tin whiskers

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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> > be defined as
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> recipient, any
> >  disclosure, use or distribution of its content is prohibited. 
> > Please
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> > any  attachments.
> >
> >  
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