possible to repair 0.2 mm spacing flat flex cable?

[SArepairman]

I have a tape drive head with a ripped flat flex cable. It is an expensive drive but the problem is that I would need to repair something along the lines of 100 conductor 0.2 mm spacing flat flex which tore.


I assume this is completely impossible. Its a weird cable assembly (comes off the head in two arcs)

[c4757p]

Nothing is impossible if you just believe in yourself!


OK, yeah, it's completely goddamn impossible, about an order of magnitude worse than the also impossible 0.5mm.

[SArepairman]

I was thinking about maybe using some kind of slow cure conductive epoxy under a microscope using a thin wire to apply but I would like to hear a success story before I start buying expensive epoxies

[amyk]

I was thinking about maybe using some kind of slow cure conductive epoxy under a microscope using a thin wire to apply but I would like to hear a success story before I start buying expensive epoxies

Assuming you can sacrifice a bit of length (several mm should be sufficient), cutting a piece of the cable out and inverting it on top could work. Expose the conductors on all 3 mating surfaces and use anisotropic conductive film to glue it all together under a press. You'll definitely need a microscope for alignment.

[flolic]

It probably can be done, but it's not easy...


Resistor is 0805, for size comparison.

[SArepairman]

Hmm. I like the film idea.

If I can do this it would mean a cool 500$ in my pocket so I might give it a try.

[ablacon64]

It probably can be done, but it's not easy...

That was a fine job! Congrats! How did you do it? Maybe scratching the surface where you wanted the solder to bind?

[flolic]

Yes, you need to scratch protective coating from the ends to expose copper tracks. And then "just" solder two ends of flex cable together with the help of flux. But most important thing is to precisely adjust the ends, and to fix them with the Kapton tape while soldering.
After soldering everything must be carefully taped over with the Kapton tape to give mechanical strength.

[ablacon64]

Very interesting, I have an iphone 4 LCD with a broken touch cable, I'll see what I can do. That image was inspiring, thank you!

[robrenz]

Very nice job flolic   My only suggestion IF the joint is actually going to flex, is to expose the copper for a short distance on opposite sides of the film and then overlap the joint a small amount (forming a lap joint instead of a butt joint). Tin both sides and then reflow it together.  Then use kapton tape to even the lap joint on both sides then a kapton strip over both sides of the actual joint. The butt joint is only a solder bridge and the solder may fatigue over time and become open or intermittent.

[brainwash]

I would be interested if something like this can be accomplished with FFC containing carbon-based tracks.
I tried to do that same thing once but any temperature on the iron that was able to melt the solder was also melting the substrate as well. Conductive silver paint might be better but not sure how well would that be modeled on 0.2mm.

[krivx]

Is replacing the flex an option? Itead now do flex pcbs in small quantities...

[SArepairman]

This is a weird cable connected to weird connectors (it has like 100 pins in a connector that's like 1 inch by 3mm. I don't think I can get that custom made.

Plus soldering it to the head (4 cables total of like 300 pins?) is probobly a night mare in itself.

That is a good idea, to tin and put together.

I will be most impressed with my self if I can do this job.

The picture IS very inspiring btw. 

[brainwash]

Can you post a pic?

[SArepairman]

I would be interested if something like this can be accomplished with FFC containing carbon-based tracks.
I tried to do that same thing once but any temperature on the iron that was able to melt the solder was also melting the substrate as well. Conductive silver paint might be better but not sure how well would that be modeled on 0.2mm.

I will post a picture some time soon.

So I figure tin both, lay them down on microscope glass, align them under microscope, ppress down with another glass and then heat both sides of the glass (while its clamped) so the solder melts and the two pieces fuse, test for continuity with a bee's dick probe then put kapton strain relief. 

I figure it should come out to 25$ an hour, if its a 500$ unit.... 
Or maybe 250$ an hour if the gods look down upon me....

[amyk]

I would be interested if something like this can be accomplished with FFC containing carbon-based tracks.
I tried to do that same thing once but any temperature on the iron that was able to melt the solder was also melting the substrate as well. Conductive silver paint might be better but not sure how well would that be modeled on 0.2mm.

Anisotropic conductive film sounds like it'd be ideal for this, since it conducts only in one direction. Rather expensive for a roll of it, although you don't need to use much.