Cris,

Don't forget to mention how they should address the adhesion problems after
immersion tin.

Yes, prep for solder mask is critical, but this is true of all final finish
processes.

In order for them to prevent adhesion failures is the use of enhanced
hardeners for the solder mask the final cure prior to symbolization.

Currently we cure at 180 F for 40 minutes. We have reduced our plating time
to 6 minutes without adverse solderability and still maintaining good
coverage.

Some more things to consider.

Franklin D Asbell
Network Circuits, Inc.
Irving, Texas




----- Original Message -----
From: <[log in to unmask]>
To: <[log in to unmask]>
Sent: Wednesday, November 03, 1999 5:29 PM
Subject: Re: [TN] immersion tin as a surface finish


> Ryan,
>
> I have a significant amount of experience with the white tin (Dexcoat FST)
> and I can share the following experiences with you. Surface prep for LPSM
is
> critical, whether it is our process or the competition. A good pumice
scrub/
> acid rinse or one of the new oxide alternative processes ( micro-etch) is
> mandatory for a wide process latitude. The biggest issue customers find
> initially is with the adhesion of many LPSM's. Good chem lab support is
also
> mandatory (just like immersion gold). I would suggest that you run parts
> through your process up to surface finish and the send them out for
coating.
> This will give you a heads up if there are any issues in your existing
> process.
>
> Good Luck,
> Chris McGary
> Dexter
> 1800-877-9871 ext209
>
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