John Peavoy@ISL
22/10/97 11:20


Glenn / David,

I believe that Alpha Advanced Products Div. (among others) had a product
with just what you mention i.e. "hard spiky bits"(!) to penetrate through
the oxide layer. I believe that this was/is called Polysolder. Not sure if
it's still on the go, or has been superceded.

Regards,

John Peavoy
Viasystems





[log in to unmask] on 21/10/97 21:33:48

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Subject:  Re: [TECHNET] FAB:  Silver-filled epoxy with tin or solder




Glenn,

The problem with using them with tin or tin-lead is that the quite stable
layer of oxide that forms on tin can result in poor conduction. If you
melt the tin/tin-lead during epoxy cure then the silver filler in the
epoxy may leach into the solder, leaving a silver depleted and therefore
non-conductive layer of adhesive - I have heard of people getting away
with this through very carefull process control, but I think it would be
better not to risk it if possible. I believe the adhesives engineered to
work with tin have "hard spiky bits" to penetrate the oxide layer.

David Whalley


>David,
>Very interesting.  What would be the reasoning for not using silver-filled
>epoxy with tin or solder surfaces?
>
>Glenn Pelkey
>Quality/Reliability Engineer

>| The general rule for using silver filled epoxys is not to
>| use them with tin or
>| solder finishes. Some manufacturers do market materials
>| designed to work with
>| them and I have also talked to people who have had success
>| with other materials
>| by very carefully controlling the curing process so that
>| the solder layer just
>| briefly melts, but if you can switch to another finish on
>| the wire you are less
>| likely to have problems.

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