Bill,
There is quite a bit of info out there. Talk to your vendors. Your two main
choices are in fact gold
and carbon ink. I've heard of just solder used (cheap toys and phones), also
some of the silver combos. With gold you have two choices selective or
complete board. With complete board
it may be tough to find someone with a deep tank, or if small enough board
that they can use the
same process as for fingers. Many have used immersion gold, there have been
some studies done that this gold is hard enough to withstand the swiping
over time. Also if you do selective you need to supply
connections out the edge for plating of all contacts.
With carbon the actual pattern must be a little looser (wider trace space)
than with gold. YOu will need to talk to your vendor, but we used about .030
track/.030space You need to concider the actual size of the button with
repect to this pattern for optimal contact, 360 Degrees. You must also clear
solder
mask around pattern from this area with same clearances. Also with respect
to your circuit you need
to consider the resistance of the carbon vs gold. The main problem with
carboon is it is a very
operator dependant process. But does work well if controlled.
This is kinda general so if you need more info please feel free to contact
me.we used both finishes
successfully, however carbon took longer to nail down the process control.
Bob
Robert M. Wolfe, C.I.D.
47 Chatfield Drive
Trumbull, CT 06611
203-261-2182
[log in to unmask]
----- Original Message -----
From: "Brooks,Bill" <[log in to unmask]>
To: <[log in to unmask]>
Sent: Friday, September 21, 2001 1:42 PM
Subject: [DC] Gold Plating for push button membrane switches
> Hi - I am creating a board to be used with a membrane switch panel. What
is
> the best surface finish under the switch contact area? I think standard
gold
> like we use with card edge connectors. Has anyone out there done this with
> success before? Any issues you can think of?
> How would you specify the plating callout?
>
> Bill Brooks
> PCB Design Engineer , C.I.D.
> DATRON WORLD COMMUNICATIONS, INC
> 3030 Enterprise Court
> Vista, CA 92083
> Tel: (760)597-1500 Ext 3772 Fax: (760)597-1510
> mailto:[log in to unmask]
> IPC Designers Council, San Diego Chapter
> http://www.ipc.org/SanDiego/
> http://home.fda.net/bbrooks/pca/pca.htm
>
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