I finally got around to printing a replacement cable chunk… AND IT WORKED! The reason for this was a fellow forum member attempted the solder repair, but damaged the end of the cable beyond repair. Earlier in this thread I posted that I designed a near 1:1 copy of the cable, which is what I used for this. It certainly wasn’t as easy as repairing it correctly in the first place… but wasn’t too bad, and worked first try. Sorry, I didn’t really take pictures along the way, but I think you can kinda get the idea from the pics. Here’s a rundown of the process.
I printed the chunk of cable that I wanted (on Pyralux), etched it, and then tinned it (to keep the copper from oxidizing). I then cut the existing cable back behind the damaged area, exposed the copper, and then soldered that to the newly etched cable. This is where I almost messed up. I wasn’t really paying attention and when I started to solder, I had my iron set to 700F (normal soldering temp). The VB cables shrivel and melt at high temperatures, so on the end I started on, I had to heat it and use tweezers and pull the individual traces back in line after a few of them began to curl inward. Then I bumped my soldering iron down just below 600F and finished soldering the cable without issue (the cable still kinda melts at 600F, but if you’re quick, it’s fine). Because of the lower temp, and trying to minimize the heat to the cable, the solder job doesn’t look great… but it works, which is more imporant than looks. 😉
Then I verified continuity between the new and old half, and made sure there were no shorts (visibly, under the microscope, as well as electrically, with the multimeter). Once I was happy with that, I put a piece of Kapton tape on both sides of the cable to protect and reinforce the newly spliced cable. Then I put a small piece of carpet tape (very thin double-sided tape) on the display PCB and aligned then stuck the cable to it. Then it was just a matter of soldering the new half of cable to the display, which was easy (Pyralux is far less heat sensitive than the OEM cable). Once I did that, I again verified a good connection, and then wrapped that in a thin strip of Kapton tape to make sure it doesn’t peel away from the display and cause stress on the solder joints. After that, it was just a matter of hooking it up and testing. 🙂
Yes, I could have printed an entire cable, but I chose to reuse the good part of the cable for several reasons. The part that goes in the LIF socket should really have a finish other than bare copper… and simply tinned with solder isn’t very good for that either. It also needs a stiffener (that thin piece of plastic attached to the cable that makes it easy to insert/remove), which I probably would have taken from the original cable. Also, the cable at the display PCB end would have been upsidedown from how I wanted it, since my cable is single sided (bare copper would have been facing down, meaning the copper wouldn’t be exposed for soldering, and it’d be easy to short out pins if you don’t have it perfectly aligned).
We’ve also talked about getting new cables professionally made (here: http://imall.iteadstudio.com/open-pcb/pcb-prototyping/2layer-flexible-printed-circuits-fpc-10cm-x-10cm-max.html ). I sent my design to verify that they could manufacture it, and I didn’t hear back, and shortly after, it changed to “Back Order”, and has been for several months. Not sure if that means they’re done offering that service, or if they will actually resume sometime in the future. Most of those places are probably still closed for Chinese New Year, but maybe we’ll know more in a week or two.
DogP
