Subj:   Re: [TN] SMT, replace solder with conductive epoxy?
Date:   26/03/99
To:     [log in to unmask]

In a message dated 24/03/99  11:43:52PM, you write:

> What if... you took all your standard SMD devices, threw them in an etchant
>  to get rid of the tin/lead, immediately took them out and threw them in an
>  immersion "flash" gold bath, then used conductive epoxy to mount them to a
>  flash gold/nickel PCB rather then solder?
>
>  Does this seem feasible? (technically at least)
>
>  Resp.
>  Phil Hersey, Carson City Nevada USA


You would have a very easily printable material instead of the solder paste. A
lower processing temp to cure off the glue and no cleaning problems.
And that's the good news in production
The other production news is, you may have some co planarity problems, need to
redesign some joint configuarations, there are some Health and safety issues
to be run through, adheisve storage and shelf life issues and  so on.
Beyond production
you would also have to look at long term product reliability and check out
service environments and accept that the term conductive when applied to
adhesive means relative to other adhesives. Relative to metals - even
relatively poor conductors like solder - conductive epoxies are very poor
indeed so current carrying capacity and  thermal design would need to be
looked at and so on.
I think you are getting the picture by now. HAving said all this there are
solder ALTERNATIVE adhesives out there and they are being used in certain
specific applications - check put with some major suppliers of conductive
adhesives like Ablestik for more info.

Mike  Fenner.
++++

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