On Tue, 10 Oct 2006 10:25:23 +0100, "Dave Plowman (News)"
wrote:

Excuse the OT post, but there I'm hoping the wealth of knowledge here
about things electronic can help me.

Most will have seen those flexible ribbon type connectors used on some
CDs, etc. It's a thin flexible plastic which is copper clad then etched
into tracks. Pushes into an edge connector.

A similar idea is used for low output contact heating pads which have to
be very thin for physical reasons. Commonly, copper clad Kapton sheet is
used. (Kapton is a thin flexible heat resistant material made by DuPont -
although there will be other similar products.)

They seem to be constructed by etching an element out of the copper clad
sheet material - rather like you'd do with a PCB - then laminated with a
second plain sheet to insulate the element. The end result is perhaps
0.5mm thick, strong and flexible. Connections to it are merely soldered on
high temperature insulated flying leads.

The elements I need are about 110 x 60mm and consume roughly 10 watts at
12 volts. Silicone rubber encased ones of approximately the right
properties are available, but are slightly too thick as well as too
expensive.

I have sourced a supplier of complete units, and although the unit cost is
low the one off setup cost isn't. So ideally I'd like to do the whole job
myself. Anyone any ideas about this process and a supplier of the raw
materials in smallish quantities?

Dave, you can source the copper-clad kapton direct from Dupont

http://www2.dupont.com/Packaging_and...flex_circuits/

Any PCB house ought to be able to do the job of etching whatever
pattern you want into it, and source the right sort of quantities. I
guess you can design a pattern for yourself that results in the right
end-to-end resistance.

d

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Pearce Consulting
http://www.pearce.uk.com

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