But as long as you have a pencil eraser with you Steve, you won't have to
make that long ride back downstairs.
Mike McMaster
RF Product Engineer
Merix Corporation
503-992-4263
----------
From: Stephen R. Gregory [SMTP:[log in to unmask]]
Sent: Wednesday, April 19, 2000 5:17 PM
To: [log in to unmask]
Subject: Re: [TN] Five year storage finish
In a message dated 04/19/2000 6:08:15 PM Central Daylight Time,
[log in to unmask] writes:
> Hello,
> Below is a question sent to me. Does anyone have any
suggestions?
> Thanks
> Rich
>
> I do have a question that you might be able to help me with. We
have a
> customer that is building something like an electronic hotel room
key
> (double sided board) which will be stored for up to 5 years prior
to use...
> and then the key will be used only once. We are trying to figure
out what
> type of surface finish to tell them to use. There is a single
surface
> mount IC mounted to the board... otherwise, there are contacts on
one edge
> that will be used to connect the key to the "lock" when it is
used. In
> your experience of talking to the Tech Net people, have you come
across a
> solution to this type of requirement? My first inclination is to
use Ni /
> Au plating with a thick (20+ microinches) deposition of Au.
Being a cheap
> double sided board, they are really price conscious, so they want
to keep
> it as cheap as possible. I don't know if HASL will provide a
good contact
> after that long on a shelf...
Hi Richard!
This question is pretty unique. Putting a reliability cap on, gold,
because
of it's properties of not oxidizing would seem a good choice. But on
the
other hand, how are these "hotel keys" going to be stored? Also,
does a flash
gold plating drive the costs up that much? I've heard that flash
doesn't cost
any more than HASL...
Are they going to be stored in a protected environment? Or are they
going to
be in a cabinet or drawer at the check-in desk that might be exposed
to the
occasional coffee spill or whatever? Assuming that these are going
to be
throw-away cards, I would opt for using the cheapest finish that you
can use,
and then advise that a mechanical means of cleaning the contacts on
old keys
be used to prevent them from functioning.
I know some people will cringe, but in my Navy days flying on P-3's
(anti-submarine warfare and patrol aircraft) we were loaded with
electronics.
When something didn't work right, the first thing our in-flight
technician
did was pull a suspected board, take a pencil erasure and clean the
finger
contacts and plug it back in. Many times that fixed things...believe
it or
not. Most of the times these boards were finished with gold finger
contacts...
So, from a completely practical point of view, and to keep costs
down, use
the cheapest finish you can (since they are going to be a one time
use only)
and maybe advise some sort of "freshing" of the contacts if the
cards are
really old...
Of course this goes without saying that if I'm a customer at this
hotel, and
I've been put up on the 15th floor and my key doesn't work and I
have to go
all the way down back to the check-in desk that I won't be pissed, I
can't
say that (GRIN).
But from my point of view, if the customer can't control the storing
conditions, it won't matter if the contacts are gold or tin/lead.
Just some random thoughts...
-Steve Gregory-
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