How to repair/replace graphite track LCD ribbon

Various simple devices with a 7-segment or custom monochrome LCD display have a multi-way graphite track ribbon connecting the LCD to the circuit board. This is attached to the LCD at one end and the circuit board at the other with anisotropic adhesive tape such as 3m 9703. A common fault after a number of years is that this adhesive fails. You can sometimes reattach it with a hot smoothing iron but this may be only a temporary fix if it works at all.

I’ve tried reattaching one on a personal GPS tracker with new 3M 9703 tape but it hasn’t worked (no segments work). Probably I should have thoroughly cleaned off the original adhesive first, or maybe ribbon has failed.

Does anyone know a source of replacement ribbons? The nearest I can find are FFC ribbons with pre-prepared ends designed for push-fit or ZIF ribbon connectors, and all much too long and the wrong number of tracks.

Alternatively, has anyone had any success repairing or reattaching these?

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Are you sure the metal oxide pads on the LCD are still intact? Often times they get lifted, You'll need a microscope with a polarizer and the light source also polarized as the interference of the light through the LCD's connection edge.

Hi Dan - I can’t be sure but I don’t think so because rubbing gently with IPA, I didn’t manage to very effectively remove the old adhesive. In any case, since the oxide is vacuum deposited onto the glass I wouldn’t think the pads would get lifted like a PCB track though rubbing with anything the least bit abrasive could well damage them. Perhaps more likely is that the graphite has been taken off the ribbon. I was wondering if I could cut it back by a millimetre or so in order to expose fresh. Anyway, I need to set aside an hour or so to remove the 3M 9703 I added, and then see what I've got.

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