I have two papers that I used a little of when I made special studies of
Tin Whiskers. They are available in Dropbox/Whiskers, but nobody seem to
have been interested, however one of the papers page 23 has a very  useful
(and intelligent) Report form,  that you can use for possible upcoming
observations.

1. JESD22A121  Measuring Whisker Growth on Tin and Tin Alloys
2. JP002 Current Tin Whisker Theory and Mitigation Guidelines

Both are rather old, and I do not plan to update either. But good enough
for learning a little about Tin whiskers

Inge


On 17 June 2013 10:00, David D. Hillman <[log in to unmask]>wrote:

> Hi Steve - Yes, XY is in the matrix although the question of coverage for
> XY is not an issue. There are a number of studies that show tin whisker
> can grow thru XY conformal coating too. The IPC task has XY in the matrix
> primary for comparison purposes against the other conformal coating types
> - AR, UR, SR, ER. Again, the test is not a tin whisker test but a test to
> understand/characterize conformal coating/application method on components
> in terms of coverage/thickness.
>
> Dave
>
>
>
> From:   Steven Creswick <[log in to unmask]>
> To:     <[log in to unmask]>
> Date:   06/17/2013 11:45 AM
> Subject:        Re: [TN] minimum thickness of Type UR Conformal coat and
> tin whiskers
> Sent by:        TechNet <[log in to unmask]>
>
>
>
> Dave,
>
> Probably a dumb question, but is parylene in the test matrix somewhere?
>
>
> Steve Creswick
> Sr Associate - Balanced Enterprise Solutions
> http://www.linkedin.com/in/stevencreswick
>                          616 834 1883
>
>
>
> -----Original Message-----
> From: TechNet [mailto:[log in to unmask]] On Behalf Of David D. Hillman
> Sent: Monday, June 17, 2013 11:02 AM
> To: [log in to unmask]
> Subject: Re: [TN] minimum thickness of Type UR Conformal coat and tin
> whiskers
>
> Hi gang - sorry for the late reply but as Doug detailed, I was enjoying
> the
> SE US whitewater for the last week. As for tin whiskers and conformal
> coating mitigation, a conformal coating material captures and contains tin
> whiskers but does not eliminate them. There currently is some
> investigative
> work in progress under the SERDP organization contracts by Celestica/BAE
> and
> Rockwell Collins which will provide some insight on how conformal coating
> can alter the tin surface interface reactions thus impact tin whisker
> initiation/growth. The 4 mil thickness value that Phil mentioned is from
> the
> IPC JSTD 001E Space Addendum criteria and is based on a 12+ year ongoing
> investigation by NASA Goddard with a urathane conformal coating material.
> There is no consensus on what is the minimum thickness necessary for tin
> whisker risk mitigation by a conformal coating material yet -  although
> the
> published data does show thicker is better.
> There is also an IPC JSTD 001 task group working on a "State of the
> Industry" conformal coating  assessment effort that is ongoing right now
> which should provide the industry a baseline of typical coverage/thickness
> for various conformal coating materials types/application methods. This
> baseline could be used in an effort to develop what conformal coating
> minimum thickness would be adequate for tin whisker risk mitigation. So
> the
> short answer for Phil's question is there is a flurry of industry activity
> trying to provide an answer to his question. Good information takes time.
>
> Dave Hillman
> Rockwell Collins
> [log in to unmask]
>
>
>
> From:   Douglas Pauls <[log in to unmask]>
> To:     <[log in to unmask]>
> Date:   06/12/2013 08:12 AM
> Subject:        Re: [TN] minimum thickness of Type UR Conformal coat and
> tin whiskers
> Sent by:        TechNet <[log in to unmask]>
>
>
>
> 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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