Losses, dear Steve, losses.
When we increased the pulse power, however, the whiskers were blown,
But I think our customer didn’t accept that solution ....he-he.
Inge
-----Ursprungligt meddelande-----
Från: Stephen R Gregory [mailto:[log in to unmask]]
Skickat: den 17 oktober 2005 14:39
Till: TechNet E-Mail Forum; Ingemar Hernefjord
Kopia: [log in to unmask]
Ämne: Re: [TN] SV: [TN] Electrolytic Tin Plating
Mornin' Inge and Everyone!
Got your whiskers picture Inge, very remarkable photo! You told me that
this was a picture of whiskers inside a waveguide. How did you know they
were there?
Anyways, go to: http://www. <http://www.stevezeva.homestead.com>
stevezeva.homestead.com
and then go to "Picture
<http://www.stevezeva.homestead.com> Page 2", then look for "Waveguide
Whiskers".
<http://www.stevezeva.homestead.com> Again, very remarkable image!
<http://www.stevezeva.homestead.com> Kind regards,
<http://www.stevezeva.homestead.com> -Steve Gregory-
<http://www.stevezeva.homestead.com> Senior Process Engineer
<http://www.stevezeva.homestead.com> LaBarge Incorporated
<http://www.stevezeva.homestead.com> Tulsa, Oklahoma
<http://www.stevezeva.homestead.com> (918) 459-2285
<http://www.stevezeva.homestead.com> (918) 459-2350 FAX
<http://www.stevezeva.homestead.com>
<http://www.stevezeva.homestead.com> Ingemar Hernefjord
<[log in to unmask]>
<http://www.stevezeva.homestead.com> Sent by: TechNet <[log in to unmask]>
<http://www.stevezeva.homestead.com> 10/17/2005 05:30 AM
<http://www.stevezeva.homestead.com> Please respond to TechNet E-Mail
Forum <[log in to unmask]>; Please respond to Ingemar Hernefjord
<[log in to unmask]>
<http://www.stevezeva.homestead.com>
<http://www.stevezeva.homestead.com> To:
[log in to unmask]@SMTP@Exchange
<http://www.stevezeva.homestead.com> cc: (bcc: Stephen R
Gregory/LABARGE)
<http://www.stevezeva.homestead.com> Subject: [TN] SV:
[TN] Electrolytic Tin Plating
<http://www.stevezeva.homestead.com> Whisker growth is depending on the
base material. Any alloy with Cu and
<http://www.stevezeva.homestead.com> Zn is risky, tin over Ni will not
cause much whiskers, Pt and Pd no
<http://www.stevezeva.homestead.com> whiskers at all etc. Reason is
that whisker growth is mainly caused by
<http://www.stevezeva.homestead.com> diffusion of e.g. Cu into the tin
plate. Cu/Sn IMCs grow and cause
<http://www.stevezeva.homestead.com> stress in the boundaries and. The
stress is in the order 40-100 Mpa at
<http://www.stevezeva.homestead.com> the root of the whisker embryo.
The unique thing is that this can only
<http://www.stevezeva.homestead.com> be created in a specific range of
tin thickness: approx. 2-5 um. 10um
<http://www.stevezeva.homestead.com> thick tin or more is said to
produce no whiskers at all, as well as
<http://www.stevezeva.homestead.com> thinner than 2um. Our company
together with Bosch and ESA have done a
<http://www.stevezeva.homestead.com> study and made tests, probably the
most advanced today to get to the
<http://www.stevezeva.homestead.com> root of the phenomenon, but still
there are work to be done. There are
<http://www.stevezeva.homestead.com> many contradictory facts, e.g. two
bath suppliers can have 'exactly'
<http://www.stevezeva.homestead.com> same chemicals in their soup, one
giving whiskers, the other not. Other
<http://www.stevezeva.homestead.com> questions are about growth speed,
where some claim that whiskers can't
<http://www.stevezeva.homestead.com> grow with more than some um/month,
while I myself have seen whisker grow
<http://www.stevezeva.homestead.com> to 10 mm length in a couple of
weeks! I'll see if I can put a picture up
<http://www.stevezeva.homestead.com> on Steve's wall. Finally, fusion
seems to solve all whisker problems,
<http://www.stevezeva.homestead.com> but how do we know that? Who can
predict what happens after 5 or 10
<http://www.stevezeva.homestead.com> years.
<http://www.stevezeva.homestead.com> Interesting topic, anyway
<http://www.stevezeva.homestead.com> Ingemar Hernefjord
<http://www.stevezeva.homestead.com> Ericsson Microwave Systems
<http://www.stevezeva.homestead.com>
<http://www.stevezeva.homestead.com> -----Ursprungligt meddelande-----
<http://www.stevezeva.homestead.com> Från: TechNet
[mailto:[log in to unmask]] För Franklin Asbell
<mailto:[log in to unmask]> Skickat: den 14 oktober 2005 16:41
<mailto:[log in to unmask]> Till: [log in to unmask]
<mailto:[log in to unmask]> Ämne: Re: [TN] Electrolytic Tin Plating
<mailto:[log in to unmask]> I'm thinking the chemistry involved with
electrolytic tin is going to
<mailto:[log in to unmask]> result
<mailto:[log in to unmask]> in whiskers/growth and I would suggest it not
be used for a final
<mailto:[log in to unmask]> finish. If
<mailto:[log in to unmask]> you are like many shops you use the tin/lead
as an etch resist in
<mailto:[log in to unmask]> process,
<mailto:[log in to unmask]> which is fine, but for final finish immersion
tin would be better.
<mailto:[log in to unmask]> Check out Florida Cirtech's website, they have
a nice study you can
<mailto:[log in to unmask]> download
<mailto:[log in to unmask]> and print regarding the differences between
the two type baths
<mailto:[log in to unmask]> (electrolytic
<mailto:[log in to unmask]> and their Omikron).
<mailto:[log in to unmask]> (and again, this is not an endorsement for any
specific chemistry, the
<mailto:[log in to unmask]> site
<mailto:[log in to unmask]> mentioned offers greater volumes of literature
is all, and I like my
<mailto:[log in to unmask]> literature)
<mailto:[log in to unmask]> I would think storage would not be an issue
with plated tin or tin-lead
<mailto:[log in to unmask]> provided they were sealed properly, but with
the plated tin, some
<mailto:[log in to unmask]> humidity,
<mailto:[log in to unmask]> some contamination, and mild current...these
are all good conditions to
<mailto:[log in to unmask]> cause growth.
<mailto:[log in to unmask]> And I'm thinking tin will indeed flow, it just
takes a higher
<mailto:[log in to unmask]> temperature...
<mailto:[log in to unmask]> Franklin
<mailto:[log in to unmask]>
<mailto:[log in to unmask]> -----Original Message-----
<mailto:[log in to unmask]> From: TechNet [mailto:[log in to unmask]] On
Behalf Of Fineline Circuits,
<mailto:[log in to unmask]> Inc
<mailto:[log in to unmask]> Sent: Friday, October 14, 2005 9:20 AM
<mailto:[log in to unmask]> To: [log in to unmask]
<mailto:[log in to unmask]> Subject: [TN] Electrolytic Tin Plating
<mailto:[log in to unmask]> Hi Technetters:
<mailto:[log in to unmask]> Now that Leadfree is here or close to, we
would like to change the
<mailto:[log in to unmask]> electrolytic tinlead plating tank to
electrolytic tin tank.
<mailto:[log in to unmask]> I would like to know if the other fab houses
have done this and if so
<mailto:[log in to unmask]> which
<mailto:[log in to unmask]> vendors tin chemistry has a wider window of
operation. Are they seeing
<mailto:[log in to unmask]> any
<mailto:[log in to unmask]> tin whiskers/sliver problems etc..especially
if the boards are stored
<mailto:[log in to unmask]> for
<mailto:[log in to unmask]> few months.
<mailto:[log in to unmask]> Also it is my understanding that you can mask
over this plated tin since
<mailto:[log in to unmask]> it
<mailto:[log in to unmask]> does not flow. In this case you can totally
avoid stripping the tin and
<mailto:[log in to unmask]> tin
<mailto:[log in to unmask]> levelling.
<mailto:[log in to unmask]> We currently do offer other finishes including
electroless tin ,
<mailto:[log in to unmask]> immersion
<mailto:[log in to unmask]> nickel/gold, silver....
<mailto:[log in to unmask]> If there are other consideration in making
this change I would
<mailto:[log in to unmask]> appreciate
<mailto:[log in to unmask]> your input.
<mailto:[log in to unmask]> Franklin, like you I would like to see more
fab houses participating but
<mailto:[log in to unmask]> I
<mailto:[log in to unmask]> would like to remain with technet.
<mailto:[log in to unmask]> Thanks
<mailto:[log in to unmask]> Sona Sitapara
<mailto:[log in to unmask]> Fineline Circuits Inc.
<mailto:[log in to unmask]>
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