we've demonstrated electroless Ni/Immersion Au is reliable in our
applications (cell phones).  We send stuff to some nasty parts of the
global (temp, humidity, corrosive atmospheres).   Life tests  good up to 1M
cycles plus lots of environmental testing.

The keypad and keypad contact is a source of greater concern.  if it's a
long life application and your keypad is made of elastomers with a carbon
pill contact better spec a quality pill (e.g. Shin Etsu 3601).  make sure
the cure/post bake cure is sufficient (total extractables <= 3.5%) to
prevent silicone oils from outgassing and insulating your keypad.  other
problem is if the carbon pill is low quality -- then it'll powder and short
your keypad over time.

dwight
staff qe

>To all Technetters,
>
>I think this topic has been covered before and I apologize if this is so
>but I will ask the question again.
>
>I want to use immersion gold over nickel for my PCB.  While this is not
>unusual in itself, I'm more concerned with the use of the gold as keypad
>contacts.  Since the gold is very thin to begin with (around 4-5
>microinches), will this degrade over time to where there is no more gold
>present on the contact pad?
>
>I have read varying articles that state that it is or isn't a problem and
>would like to know what others have experienced with this alternative
>surface finish.
>
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