James,
I have used silver epoxies for 20 years and support all the concerns all
ready raised. I have found that curing at a lower temp does improve the life
of a Ag epoxy/solder interface but it is still poor... as others mentioned,
increased DC resistance over time. As Jim mentioned, I would give it maybe 6
mo in a benign lab evironment at best and immediate at worst. Ag epoxy to
ENIG is certainly fine for table top, room temp lab environment and is even
reliable especially with Ni/Au plate and is probably why Bill is having
success with Ag epoxy (solder is on the other side and I know he's not wire
bonding to a tin or solder coat). If you don't have humidity control, Ag
migration should be a concern and conformal coat recommended. Board
flexure opening interfaces is definitely a problem. Bottom line: I avoid
solder-Ag epoxy interfaces, period.
Good Luck,
Bruce
> ----------
> From: Marsico, James[SMTP:[log in to unmask]]
> Reply To: TechNet E-Mail Forum.;Marsico, James
> Sent: Tuesday, January 23, 2001 3:34 PM
> To: [log in to unmask]
> Subject: [TN] silver epoxy & solder coated parts
>
> Hello, Technet...
>
> Here is an unusual situation. We have to assemble a surface mount
> assembly
> using silver epoxy. Some of the components will be solder coated. I
> know,
> don't bother asking... this is the way it has to be. The good thing is
> that
> this assembly is a prototype for bench-top laboratory use only. There is
> no
> harsh environment and needs to operate 1, maybe 2, years. The question is
> does anyone foresee any problems? What happens when one mixes toe two
> technologies?
>
> Thanks,
> Jim Marsico
> EDO Electronic Systems Group
> [log in to unmask] <mailto:[log in to unmask]>
>
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