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.
________________________________
 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. Please notify the sender by reply e-mail and immediately 
delete this message and any attachments.

______________________________________________________________________
This email has been scanned by the Symantec Email Security.cloud service.
For more information please contact helpdesk at x2960 or [log in to unmask] 
______________________________________________________________________




______________________________________________________________________
This email has been scanned by the Symantec Email Security.cloud service.
For more information please contact helpdesk at x2960 or [log in to unmask] 
______________________________________________________________________




______________________________________________________________________
This email has been scanned by the Symantec Email Security.cloud service.
For more information please contact helpdesk at x2960 or [log in to unmask] 
______________________________________________________________________