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. > > ________________________________ > > This message and any attachments are solely for the use of the addressee > > and may contain L-3 proprietary information that may also be defined as > USG > > export controlled technical data. If you are not the intended > recipient, any > > disclosure, use or distribution of its content is prohibited. 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