By the way, you can see a nice vew of Tin whiskers on below video clip from
NASA. I wonder if they have used the MCM substrates I shared with them,
looks very alike mine, never mind, funny show....
For those of you that are familiar with SEM, the last sequences needs a
very good and tuned instrument + skilled operator. I have taken photos at
nearly 500,000 times magnification with super LaB6 and 10exp-10, WD=5 mm
and tilt 45, aperture 10 um and Sec det acc 1 kV and EHT= 1 kV (!!). So low
EHT? Normal 20 kV had made the superthin whisker TEM instead.. I never
presented the images, because at that magnification , sub nm, there is
nothing to see. Not until next magnitude, but then you need AFM.
http://www.youtube.com/watch?v=oZATl6Uxtz4
Inge
On 17 June 2013 13:28, Inge Hernefjord <[log in to unmask]> wrote:
> 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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