Make sure to specify that there be absolutely no silver content in the
carbon ink. Been there, done that.  You don't want to live through that
electromigration problem.

I'd encourage you to require supplier ongoing verification that product is
silver free. We've had ink suppliers provide silver free ink to pwb fabs
that was mixed/prepped in vessels that still had traces of silver from
previous lower resistance inks (silver is often used to lower the ink
ohm/sq). That ppm level of silver was enough to make fast failures on
keypads used in high humidity, constant bias applications.

dw


At 11:37 AM 1/20/2005, you wrote:
>Currently we use gold for all of our keypads.  I want to reduce the cost
>of a product and thought about switching to a carbon keypad.  I am not
>familiar with the process and wanted to know a few things.  We mostly use
>a water-soluble process and our entire product is washed.  Some boards are
>a mixed technology using SnPb currently.
>
>?  Are there any Reflow solder concerns I should be aware of?
>?  Are there any Wave solder concerns I should be aware of, like masking
>pads during wave solder?
>?  Are there any other concerns period that I should be addressing.
>
>Thank you,
>
>Scott
>
>
>
>
>
>
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