Information on the clear connection film to an LCD display

Are you referring to elastomeric connectors? Sometimes called Zebra connectors.

Hi Doug,

I haven't seen ty unit yet so I am not sure but I got the impression it was more like clear plastic ribbon.

John

3M Electrically Conductive Adhesive Transfer Tape 9703

https://multimedia.3m.com/mws/media/66235O/3m-electrically-conductive-adhesive-transfer-tape-9703.pdf

Hi Dave,

Thanks for the link. this looks promising.

John

Hi John,

Here is the picture of the remote.

Is it the ribbon to PCB end that is causing the problem ?

I've seen some designs which have a shaped spring clip that applies a downward force to keep the ribbon in contact with the PCB. Looks like you could do something similar here.

Yes, the end attached to the glass seem attached strongly, i am heating and press pressure to the end cable that is attached to PCB. Here is another picture with same remote but something black stuff added but still has the same issues. Have also attached a picture of what the company came up with and fixed the display issue for good ( the pins are metal ).

Yes, the end attached to the glass seem attached strongly, i am heating and press pressure to the end cable that is attached to PCB. Here is another picture with same remote but something black stuff added but still has the same issues. Have also attached a picture of what the company came up with and fixed the display issue for good ( the pins are metal ).

Hi Andrei,

The black material is likely epoxy resin glue. The metal pins are called 'lead frame pins' and are quite common on LCDs, but usually come pre-attached (and often glued, sometimes with a transparent glue and sometimes with opaque) as part of the display, from the LCD manufacturer.

Converting an LCD from the flat flex to the lead frame pins might be manually possible, but you'd need a PCB with the holes in it. I think if the lead frame pins is the option you're aiming toward, then it would be better to purchase the LCD with the lead frame pins pre-attached if this is an option (assuming that the interface board with the holes is also available), otherwise there is the difficulty in trying to source the correct lead frame pins for the thickness of the glass on the LCD, and finding a suitable adhesive etc.

Are the 5 solder pins to the left the only obstructions under the board in the area of the ribbon ?

i.e. could you slide a thin spring clip onto that lower edge of the PCB such that it pressed the ribbon firmly against the PCB.

By this stage, there may be some oxidisation of the contacts, which is making conductivity poor with the adhesive alone. May need to lift it, clean it and try some of that conductive tape Shabaz mentioned, then fit a clip.

Good point, maybe a C-shaped clip could work (like the type used sometimes on the edge of paper for filing) maybe with a 3D printer possibly.

The 5 solder pins is holding the display PCB to main PCB, there is very little tiny space in between, maybe a half size of bank card.

Are there any type of glue that i can lift the film, apply the glue and put the film back?

Yes, an A4 edge binder clip did spring to mind but I don't think that there is enough room here. 3D printing similar to fit the space remaining below could work.

Alternatively something of a similar style of design to breadboard row inserts.

The spring metal sometimes used with EMF screening fingers is very thin yet quite  springy. Would need an insulating layer to prevent it shorting out any tracks.

Hi Andrei,

I think (this is all speculation, I've never tried to repair an LCD) it would be hard to manually apply glue, because conductive glue would be conductive in all directions and could short out the pins.

With generic heat seal connector ribbon cable I presume that the anisotropic conductive glue is manufactured into the length of the cable, so that it can be cut to length and attached as required, so perhaps it is more a case of trimming off the used end and then reapplying heat to a fresh bit of cable. This assumes that you have plenty spare to have another go which doesn't look likely in this case.

With production run cables however, the glue may only be applied sparingly to the very end sections, especially if the bonding mechanisms are different at each end e.g. to glass and to PCB.

This problem of failing heat seal connections appears to be quite common in the automotive industry.

Some repair attempts describe the conductive tracks in the ribbon disintegrating when attempting to expose them, which could be an issue here if attempting to use the conductive tape approach for repair.

I see that you can get special tips for soldering irons 'T-iron' / 'T-tip' which basically look like an oversized DIL package desoldering bit with some silicone rubber facing to prevent overheating of the ribbon.

https://www.amazon.co.uk/CITALL-Soldering-T-iron-Ribbon-Repair/dp/B07BBMD8DW     

Perhaps with such a tool it may be possible to reheat the connection more successfully with less risk of damage.

Aw Andrei, I have had LCDs with flat flex issues too.

I have been able to temporarily fix issues by bending them in a position where they made the LCD work, then taping everyting with normal bureau tape. But that never lasts.

Otherwise, merely glueing it won't work I think, since there is nothing to apply pressure to each contact along the plastic.

You're supposed to use a hot bar (a very very broad soldering iron, as long as the flat flex and as broad as the solder-down contacts). Tricky.

The display looks like the Nokia one used on the older TI MSP320 LCD boosterpack (used it in the first design of the eLoad here on e14). I believe there is no stock left of the source LCD - one of the reasons that the boosterpackis obsolete now.