Putting a 7 segment LCD back in place

[Martini]

Hey !


My $10 "precision" scale gave up the other day. Its only problem is with the LCD screen. Some traces looked broken at their (metaphorical) hinge, so I thought I could unglue the ribbon and move it one millimeter. But the black traces were full of glue and didn't make contact. So I cleaned them, now the ribbon doesn't stick

Any idea about connecting the screen back to the PCB?
(Knowing I don't have conducting glue)

[SeanB]

Normally done with a hot bar sealer, but doable if you have a temperature controlled iron and set it around 150C to melt the plastic back to the clean board.

[amyk]

Anisotropic conductive tape could be an easier solution if you can find some.

[wraper]

Z-axis conductive tape would do the job http://www.ebay.com/itm/262379455349. However it is expensive (that price is for a tiny piece) and won't help anyway. By tearing off that ribbon cable, you destroyed it beyond repair. Conductive traces from the cable remained on the PCB, what left on the cable is insulated from the both side and therefore is not accessible. And you won't be able to remove the insulating layer without damaging the traces anyway. So just buy another scales.

[Martini]

Wow, those tapes look cool, I didn't know such solution existed.

Normally done with a hot bar sealer, but doable if you have a temperature controlled iron and set it around 150C to melt the plastic back to the clean board.

That didn't work at 150°C, I'll try to up the temp a bit tomorrow when I have more light to work.

By tearing off that ribbon cable, you destroyed it beyond repair. Conductive traces from the cable remained on the PCB, what left on the cable is insulated from the both side and therefore is not accessible. And you won't be able to remove the insulating layer without damaging the traces anyway. So just buy another scales.

Resistance of the black traces is a few hundred ohms when the probes are 5 mm apart. Is that congruent with the insulation you're talking about?

[wraper]

Is that congruent with the insulation you're talking about?

Dunno, maybe some super cheap uninsulated type. Few hundred ohms is about right resistance for carbon traces.

[amyk]

Physically hold it in place (firmly) if you want to test whether it will work. If there's any conductivity it should, LCDs don't require much current at all to operate.

[Martini]

Physically hold it in place (firmly) if you want to test whether it will work. If there's any conductivity it should, LCDs don't require much current at all to operate.

Oh, it does. But it's really tricky to align and put pressure on all the contacts at the same time.