Sona, the electroplated tin is used instead of tin/lead electroplate and it
is stripped from the panels after etch. Solder mask over bare copper
-SMOBC-. You cannot leave the tin on the etched panels and solder mask over
the tin-it will lose adhesion upon thermal excursion. That being said, we
use Electrochemicals Tinbrite 3. We have had no issues with slivering or
breakdown. Like any other process, if properly controlled, bright acid tin
is trouble-free.



At 08:19 AM 10/14/2005, you wrote:
>Hi Technetters:
>Now that Leadfree is here or close to, we would like to change the
>electrolytic tinlead plating tank to electrolytic tin tank.
>I would like to know if the other fab houses have done this and if so which
>vendors tin chemistry has a wider window of operation. Are they seeing any
>tin whiskers/sliver problems etc..especially if the boards are stored for
>few months.
>Also it is my understanding that you can mask over this plated tin since it
>does not flow. In this case you can totally avoid stripping the tin and tin
>levelling.
>We currently do offer other finishes including electroless tin , immersion
>nickel/gold, silver....
>If there are other consideration in making this change I would appreciate
>your input.
>Franklin, like you I would like to see more fab houses participating but I
>would like to remain with technet.
>Thanks
>
>Sona Sitapara
>Fineline Circuits Inc.
>
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