Lamar:
First, not to be a nit-picker, but you mean "immersion Tin", not electroless Tin, there is a difference...
Immersion Tin plating solutions can be difficult to rinse, and we recommend a warm (110 degree F) stagnant first rinse, followed by cascade cold rinses. If the first rinse is not warm, you can get slow dissolution of remaining Tin salts, which will give exactly the sort of problem you have seen.
The added benefit of a warm stagnant first rinse is that it captures "dragout", which then can be used to replace evaporated water from the hot immersion Tin plating solution, thus saving (expensive) chemistry.
Rudy Sedlak
RD Chemical Company
--- On Thu, 9/15/11, Lamar Young <[log in to unmask]> wrote:
From: Lamar Young <[log in to unmask]>
Subject: [TN] electroless tin
To: [log in to unmask]
Date: Thursday, September 15, 2011, 7:06 AM
Is there something inherent in the manufacturing process of electroless
tin boards that could cause ionics to be continually extracted in an
IPA/DI water solution? Or something to be more aware of?
I'm afraid that this may be too general of a question. But, we have a
customer that says all other board types have no issue with ionics except
their electroless tin boards. They have cleaned and not cleaned the
boards with the same result. It would seem that the ionics is not from a
residue, rather something leaching out.
Yes, they are using a bulk extraction system. No, they have not performed
IC so we don't know what ionic species are present.
Any advice that can be provided would be appreciated since I am not a
board process expert.
Lamar Young
Specialty Coating Systems, Inc.
7645 Woodland Dr.
Indianapolis, IN 46278
(317) 244-1200 Ext. 276
www.scscoatings.com
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