Fixing a DDR pad: irritating flex cable edition.

April 19, 2013 3:30 PM

It looks thusly. My issue is that, despite the fact that it was originally barely taped down at all, I am unable to successfully, reliably reattach it using the same method. ("it" in this case being the printed black strips on the left). I am reasonably sure that lack-of-contact is my problem, because if I physically hold the cable to the board, it will reliably work when I push a button. Best I can do is that sometimes, after putting it all back together for the Nth time, one button will work. Maybe other buttons on its side will work, maybe not. Maybe it'll work for a few presses and then quit. The cable looks fine, the board contacts look fine, no amount of scotch tape is helping me out here. How do I affix these suckers but good?
posted by curious nu to Technology (7 answers total)

Best answer: I'm guessing that's not the original tape? I don't know about DDR controllers in particular, but where I've encountered similar contact types in equipment they've been applied under pressure & held down by something like Kapton tape (or a simiar polyimide) - the pressure ensures contact, & the tape doesn't stretch & loosen like household Scotch tape does.

Repair can be tricky, but I've had reasonable success by lightly applying either soft conductive silver from a pen, or simpy carbon from a pencil (rub the tracks ently with the side of the lead), to the flexible conductive track. I then use wide Kapton tape - wide enough to hang over the edges & stick 3 sides of the flexible track to the main board - pulling it tight lengthways & rolling it down along each flexible track with a small rubber roller (mine's made from an old tape recorder capstan) and a fair amount of pressure.

It works even better if you can jam a bit of non-conductive rubber between the housing and the flexible strip to keep the pressure on when it's all screwed back together.
posted by Pinback at 3:55 PM on April 19, 2013

Response by poster: I tried a bit of cardboard as a pressure shim, and that seems to have worked. Obviously not ideal for electronics. =p I'll try and find some non-conductive rubber for it instead, and keep an eye out for the special tape. Thanks.
posted by curious nu at 4:35 PM on April 19, 2013

What about that piece of rubber that fell off the lawn mower?
posted by mimo at 4:40 PM on April 19, 2013

Use something like scotch tape to hold it in position, and then install a piece of foam rubber on the back of whatever cover is installed on the other side of it, that will put pressure on the contacts. That's how I've seen every one of those kinds of things installed. (That, or a metal clip that holds it down.) You can get the foam rubber at a home center in the aisle where screens and stuff like that are located. Sometimes it's called truck cap sealing tape.
posted by gjc at 5:29 PM on April 19, 2013

Best answer: Honestly, if the cardboard works fine, then use cardboard - I wouldn't bother with the trouble of getting rubber & opening it up again. It's fine for electronics, the only issue being that it will compress and lose pressure on the contacts much quicker than rubber or tape.

When that happens, go find some rubber or foam sheet ;)

(Oh, beware the black foam similar to weatherstripping, etc - it's often conductive.)
posted by Pinback at 6:18 PM on April 19, 2013

Response by poster: Thanks so much!
posted by curious nu at 6:46 PM on April 19, 2013

they sell plastic 'shims' at (just about) every hardware store (they're super-cheap and look like very very thin doorstops.) you can break or cut them if they're too long. also, plastic toys and junk from the 99-cent store, broken up, work for this kind of thing...container lids, etc...
posted by sexyrobot at 1:46 PM on April 20, 2013