Hi Jack

I would not blame Hugo if he'd zap all of that gibberish I've send through
and is hypothetically sitting in IPC archives for the generations to cherish
; but IF it's there; I did answered this one few times stating even cycles
of carbon pill (on silicon membrane) switching onto flash gold pads (
10-20umNi + 0.5umAu ) .
You were told correctly not to bother with selective plating ; unless specs
or standards given will force you to do so .

Keep the Ni up to 20um (micrometers ; not microinches) ; and the gold
optimally 0.8-1.2um to be on safe side ;
however we clocked 1 Million cycles on 0.5umAu on 5.3umNi ; as I wanted to
be as far from embrittlement as possible ;
ITRI states 1.5umAu tops as safe limit for solder ; our internal spec states
top 0.8um .
We go as low as 0.3umAu ( 3.0umNi )  on some batches (yes ; very pale)
without problems and switching resistivity changes .
Tried the Alpha Level (silver) ; lasted only 60K's , cycled with 1/8" carbon
pill ; went through to copper ;
the NiAu dynamic duo is hard to beat ; logically if you see the compatible
characters for this particular application .

And ; in couple of decades on gold and millions of telephones behind living
to tell (previous life) ;
I don't think there's better, cheaper and simpler way .
The only thing is if you did not solder on gold before you'll have to work
harder on process than on tin ;
creeps on pads much slower .

So, check the classics again ; let me know if you'd get stuck .

See you Jack

Paul Klasek
http://www.resmed.com

> ----------
> From:         Jack Olson[SMTP:[log in to unmask]]
> Sent:         Thursday, 18 March 1999 3:58
> To:   [log in to unmask]
> Subject:      [TN] Flash Gold and Switch Contacts
>
> I have just read through about a thousand messages regarding gold plating
> in
> the Technet archive, but still couldn't find exactly what I need to know:
>
> We have a design with one side all contact switch patterns, and the other
> side SMT components. Since we wanted to gold plate the contact patterns,
> we
> were told to just gold plate the whole board.
>
> So the question is:  What gold thickness would be thin enough for the
> SMT's
> and still thick enough for good reliable contacts?  Or is there a better
> way?
>
> thanks in advance,
> Jack
>
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