Circuitgrrl,
As one of the “Big Boys” who puts their reputation on the line every time a
new technology is implemented on product, risk doesn’t discourage us nor do
we “put our head in the sand”. We prefer to make data driven “knowledge
based” decisions.
In 1996 we determined a need for a flat solderable surface finish. We had
extensive experience with OSP’s and had shown that periodic solderability
busts are a concern since board fabrication contamination issues couldn’t be
seen prior to component placement and surface mount assembly. Up to this
time our participation in consortia activities associated with surface
finishes indicated that there wasn’t an “ideal” finish that was as flat as
OSP copper and as solderable as SnPb HASL. The “Gray” immersion tin products
available were flat but their solderability degraded rapidly when exposed to
moist heat. As a result, the only available candidates were immersion gold
over electroless nickel (IAuENi) and immersion silver (IAg). The evaluation
methodology we used and the results which lead us to chose IAg as our
surface finish of choice were presented at the IPC Third Annual National
Conference: A Summit on Surface Finishes and PWB Solderability in Irvine, CA
on September 23, 1999. An update of these evaluations will be presented at
SurFin 2000 in Chicago, IL on June 28, 2000.
The “White” immersion tin surface finish was not included in our 1996 – 1998
evaluations because it wasn’t readily available and we had already
implemented IAg into production in 1997. Because of supply chain
considerations (i.e., not every board vendor offers every surface finish)
we’ve run a production trial of surface finishes available from our board
vendors. Although the “White” immersion tin results were markedly better
than the evaluations we made earlier with “Gray” immersion tin, the
immersion tin did not perform as well as immersion silver. Our current
surface finish of choice continues to be immersion silver.
Regards,
George
George M. Wenger DMTS
Bell Laboratories Princeton, Supply Network Solutions
Engineering Research Center FMA / AQA / RCA Lab
(609) 639-2769 (Office); 3210 (Lab); 2343 (Fax)
[log in to unmask]
-----Original Message-----
From: [log in to unmask] [mailto:[log in to unmask]]
Sent: Thursday, June 01, 2000 4:45 PM
To: [log in to unmask]
Subject: Re: [TN] Immersion White Tin
The immersion white tin we have seen requested is Omikron by Florida CirTech
and I have heard of Dexter and Alphametal producing an immersion white tin.
Supposedly assemblers are moving to the IWT because it is more reworkable
than OSP, the surface co-planarity is good and so is the solderability.
We're trying to determine where the industry is going, is anyone else seeing
this happen?
On Thu, 1 Jun 2000 13:38:45 -0700 , Brooks Bill wrote:
> This is going to date me... I used to manufacture boards in my youth, we
> used electroless tin as a coating for boards where heavy hydro-squeegee
> solder coating was not required... Is this what you mean by white tin
> immersion?
> -Bill Brooks
>
> -----Original Message-----
> From: [log in to unmask] [mailto:[log in to unmask]]
> Sent: Thursday, June 01, 2000 12:18 PM
> To: [log in to unmask]
> Subject: [TN] Immersion White Tin
>
>
> I hope to generate some discussion on this subject, since there wasn't
much
> from last weeks questions on immersion white tin...
>
> We (as a PCB fabricator) have had several inquiries about immersion white
> tin from our customers, but we don't see any of the large OEM's making a
> move towards it.
> Any opinions out there?
>
>
>
>
>
>
>
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