Organic brightner with residue ionic trapped in the plating layer would causes Tin Whisker grow. Question: if you see the traped brightner and ionic species on surface, it is imply the plating was not done properly, and most likely (a) current density too high, (b) plating layer exhibit high stress (hardness usually high). Does that indicate the ionic assist the whisker growth, or the stress? The whisker initiate from trapped organic has been seen before. Is organic is the nucleation site? Or it just a stress relief location, perfect for whisker to grow? Never got a clear answer. I was lazy, every time think about it until my head hurt, I just drop it altogether. I think all the Guru will answer my question and don't need me to worry about it.
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----- Original Message -----
From: TechNet <[log in to unmask]>
To: [log in to unmask] <[log in to unmask]>
Sent: Thu Mar 25 08:40:22 2010
Subject: Re: [TN] Tin Whiskers
Hi Graham - there are three papers - authored by Foresite, Celestica, and
Atotech - which show that high levels of ionic residues from improperly
processed no clean soldering processes resulted in tin whiskers growing
out of the solder joints. There are several current investigations
(including one here at Rockwell Collins) which are examining the role that
ionics/corrosion could be playing in tin whisker initiation. The
influence of corrosion and tin whisker initiation/growth is also a topic
that has been discussed as part of the JESD201 specification committee
activities. I'll send ya the references when I get a chance.
Dave
Graham Naisbitt <[log in to unmask]>
03/25/2010 06:23 AM
To
TechNet E-Mail Forum <[log in to unmask]>, [log in to unmask]
cc
Subject
Re: [TN] Tin Whiskers
Hi Dave
Despite my close involvement with this topic, I had not heard about
reports of whiskering due to "excessive ionic cleanliness levels" and do
you mean too clean or not clean enough.
We have a new project on this topic that looks to become a recipient of EU
funding on this side of the pond. It would be very helpful if I could get
a copy of such findings - as when they become available. Can you help?
Regards
Graham Naisbitt - KBO
Gen3 Systems - Engineering Reliability in Electronics
Email: [log in to unmask]
Phone: +44 (0)12 5252 1500
Web: www.gen3systems.com
On 24 Mar 2010, at 20:40, David D. Hillman wrote:
> Hi Steve - my comments:
>
> 1) There are ImSn pwb surface finish formulations that will produce tin
> whiskers and there are ImSn pwb surface finish formulations that will
not
> produce tin whiskers. Conduct testing and don't completely believe the
> Marketing literature.
>
> 2) There are only a handful of published reports (3) which show a tin
> whisker growing out of SAC305 solder. The reports show that excessive
> ionic cleanliness levels were the root cause of the tin whiskers. There
> are several industry investigation currently in progress on the specific
> topic of ionic cleanliness levels and tin whiskers. Best guess is that
> some of the investigations will be published later this year.
>
> Dave Hillman
> Rockwell Collins
> [log in to unmask]
>
>
>
>
> Steve Kelly <[log in to unmask]>
> Sent by: TechNet <[log in to unmask]>
> 03/24/2010 12:30 PM
> Please respond to
> TechNet E-Mail Forum <[log in to unmask]>; Please respond to
> Steve Kelly <[log in to unmask]>
>
>
> To
> [log in to unmask]
> cc
>
> Subject
> [TN] Tin Whiskers
>
>
>
>
>
>
> Hi All,
>
> Two questions today:
>
> 1) Any known instances of tin whiskering when the finish is
Immersion
> Tin
>
> 2) Any known instances of tin whiskering after the immersion tin is
> soldered with a RoHS compliant solder such as SAC 305.
>
> Thanks. Steve Kelly
>
>
>
>
>
>
>
>
>
>
>
>
>
> PFC_2col.png
>
> CREATING A FLEXIBLE FUTURE
>
>
>
> Steve Kelly
>
> (416) 750-8433 (work)
>
> (416) 750-0016 (fax)
>
> (416) 577-8433 (cell)
>
>
>
>
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