Steve,
having done the same design for a number of years, you need to work
closely with your customer to meet their expectations for the keypad
contacts. The design is typically not difficult or tightly restrained in any
fashion except for the expected operation at the user level. There are a lot
of issues that relate to the performance which go far beyond the work/no
work issues. (i.e., type of device, key response time, is the button well
restrained physically or does it roll significantly.) I worked for Advanced
Gravis for five years, we did study after study of silicon membrane switches
and developed our own requirements but the demands of a PC gamer are
significantly different from a photocopier, portable CD player or other
devices.
One of your questions about finish, didn't you already answer that
earlier when you mentioned carbon impregnated donut shape? You maybe weren't
too clear there. My initial comment would be, if your boards are
manufactured in SE Asia, gold flash over nickel, in SE Asia this is your
cheapest finish which will work very well for membrane switches (4 - 8 micro
inches gold flash, over 60 - 100 microinches of Nickel, life near infinite,
the silicon will deteriorate before the finish is shot).
Brad Velander,
Lead PCB Designer,
Norsat International Inc.,
#300 - 4401 Still Creek Dr.,
Burnaby, B.C., V5C 6G9.
Tel. (604) 292-9089 direct
Fax (604) 292-9010
website www.norsat.com
> -----Original Message-----
> From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED]]
> Sent: Tuesday, July 24, 2001 12:02 PM
> To: Protel EDA Forum
> Subject: [PEDA] Keypad land pattern design
>
>
>
> I need to design a landing pattern for a rubber key pad
> switch. My customer
> expects high volumes (it's a consumer product). The
> conductive element of the
> switch is carbon impregnated in a donut shape (.360in OD, .260in ID).
>
> In the past, I've simply followed the recommendations of the
> manufacturer;
> however, this manufacturer is located in Taiwan and it's
> difficult to get the
> information I need because any questions must be routed
> through my customer.
> That opens the door to prolonged responses and miscommunication.
>
> As a result, I'm exploring the idea of creating my own
> landing pattern
> design. I'm a bit nervous about it.
>
> I'd appreciate any design recommendations or possible sources
> of information.
> In addition to the landing pattern I need to specify the
> finish of the land
> pattern (gold plated, carbon screen, ??). I need reliability
> and low cost.
>
>
> Thanks,
> Steve Allen
> Project Engineer
> Manufacturing Services, Inc.
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