We have been manufacturing boards with immersion silver for 8 years, six
of those we have supplied plugged vias.
The process works best BEFORE the immersion silver process.  It should not
be done after immersion silver because of the possibility of contaminating
the silver.
There NEVER should be anything in the via holes that could etch the hole
walls.  They must have a very marginal via plugging process.  Best pick
another fabricator until they improve their via plugging.  Open vias could
increase assembly problems and cost you more money.

Happy Holden
Westwood Associates




Kanaiyalal Patel <[log in to unmask]>
Sent by: TechNet <[log in to unmask]>
06/10/2005 05:23 PM
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[TN] Immersion Silver - Via Plugging






Our supplier is recommending against plugging via holes the immersion
silver boards and here is their explanation. Need some input into how you
guys are managing.

"We can not plug before silver because chemicals used during the silver
process may become trapped. Over time these chemicals can eat away at the
hole wall copper creating voids.
2. Because the boards have passed through rout and are in piece form when
silver is applied the board can not be plugged in panel form as are the
gold boards.
3. Immersion silver is soft and easily damaged. It is our last
manufacturing process and we avoid handling it as much as possible after
being coated, this particularly applies for the plug process."

Appreciate your feedback.
re,
Hemant


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