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Author Topic: Attempt to repair LCD ribbon with 3M 9703 Tape  (Read 44002 times)
Aerendraca
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« Reply #15 on: January 28, 2013, 09:10:08 PM »

Here's how it looked through the microscope:

* mini-P1170639 a07.jpg (81.64 KB. 800x600 - viewed 1055 times.)


And after a couple of hours of gentle scraping, here's how it looked:

* mini-P1170643 a08.jpg (83.88 KB. 800x600 - viewed 1012 times.)

I am very happy with how this ended up.

Flipping the ffc around now and as mentioned earlier I had to chop off part of the this end too since one of the copper pads had ripped in an awkward place, turns out the offcuts would come in useful later. Here's how it looked after:

* mini-P1170628 a09.jpg (69.49 KB. 800x600 - viewed 831 times.)


I'm not sure why but for some reason I decided to check this end of the ffc under the microscope to check that there were no other problems when I noticed this:

* mini-P1170648 a10.jpg (75.79 KB. 800x600 - viewed 956 times.)

Doh! no idea when this happened but I did not want to give up since I had spent sooooo much time to get this far.

Next up then, fix the broken traces. Here you can see I have applied some clear tape to the underside of the ffc by means of giving some stability and keeping the traces from parting.

* mini-P1170652 a11.jpg (91.06 KB. 800x600 - viewed 837 times.)


After taping I then proceeded to scrape some more of this coating away so as to provide more copper area to work with.

* mini-P1170654 a12.jpg (83.76 KB. 800x600 - viewed 761 times.)

Once again very pleased with this so far.

« Last Edit: January 28, 2013, 09:32:48 PM by Aerendraca » Logged
Aerendraca
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« Reply #16 on: January 28, 2013, 09:22:48 PM »

Since I was happy that enough copper was stripped back I decided to see if I could use silver circuit trace repair paint to bridge the gaps (3 in total that had broken).

* mini-P1170659 a13.jpg (81.55 KB. 800x600 - viewed 799 times.)

The idea was, once dry, I would scrape away the bits between the copper and lovely clean traces would be left behind. This didn't work, the silver paint did not want to adhere to the ffc and the whole lot more or less peeled away.

So, I thought, perhaps I can used the 3M tape over the top of the breaks, and carefully place ontop some of the offcut from earler. So I cut a small piece of 3M tape and cautiously placed it over the breaks.

* mini-P1180677 a14.jpg (98.29 KB. 800x600 - viewed 831 times.)


I then painstakingly cut a piece of the offcut so that just 4 copper traces were present, and once again with a great deal of caution I laid them ontop of the tape.

* mini-P1180686 a15.jpg (73.02 KB. 800x600 - viewed 795 times.)


once in place I pressed it down with the blunt end of the scalpel and sealed it with some more clear tape.

* mini-P1180690 a16.jpg (90.71 KB. 800x600 - viewed 695 times.)

Don't know where that thread type stuff came from or how it got caught under the tape but it's not really in the way so no matter.

And to give some idea of how small this thing is and how tricky the repair was, here it is with a ballpoint pen for reference.

* mini-P1180697 a17.jpg (82.54 KB. 800x600 - viewed 1488 times.)

« Last Edit: January 28, 2013, 09:37:07 PM by Aerendraca » Logged
Aerendraca
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« Reply #17 on: January 28, 2013, 09:30:49 PM »

The final piece!

* mini-P1180695 a18.jpg (84.27 KB. 800x600 - viewed 822 times.)

That took alot of time and patience!

So now the prepping of the circuit board. Once again more scraping with a scalpel.

* mini-P1180692 a19.jpg (87.43 KB. 800x600 - viewed 870 times.)


Tape cut and placed onto the clean pads of the glass and driver circuit. I know I know, I have the tape oriented the wrong way on the circuit part this was a silly oversight due to excitement of an end in sight. Hopefully this wont be a problem as I've sort of stuck it down now, oops. Embarrassed

* mini-P1180702 a20.jpg (104.69 KB. 800x600 - viewed 791 times.)


And like I said, the repaired part stuck down.

* mini-P1180727 a21.jpg (106.09 KB. 800x600 - viewed 846 times.)



* mini-P1180730 a22.jpg (116.4 KB. 800x600 - viewed 864 times.)


This is as far as I have got today, tomorrow I test!! Fingers crossed.

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Chocochan
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« Reply #18 on: January 28, 2013, 10:02:27 PM »

You're very bold. Use a rounded tool like a pen or pencil or the of a paintbrush handle and give the places where the tape is a good rub (like you're burnishing it). The tape is pressure sensitive and relies on it to get a good contact. Was the tape the right way the first time round? I hate seeing other people (and myself) fail, so I'm rooting for you!  Wink
« Last Edit: January 28, 2013, 10:04:25 PM by Chocochan » Logged
Aerendraca
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« Reply #19 on: January 28, 2013, 10:15:09 PM »

Great tip and thanks for the encouragement!

I believe that the tape was the correct way around the first and second time around. Also, I got the same diagram with my tape too I'm guessing from the same seller, though that picture just shows a side profile of the tape and doesn't differentiate if it's preferential to have it oriented width or lengthways, just that the tape conduct through the thickness.
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Chocochan
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« Reply #20 on: January 28, 2013, 10:21:11 PM »

By the way, I forgot to mention. You CAN test it now if you want. The 24 hours thing is so it will have maximum adhesion in terms of how much force is needed to pull it apart, but the signals should still pass. I did so and then left it alone. After rubbing it down well, carefully connect it up and see to save a night of worry!

MAJOR EDIT: I just saw something more on the PDF! It says that the minimum "overlap area" is 3.2mm! This is the "Minimum recommended conductor overlap area (pad area) in the interconnection of individual circuit lines to ensure Z-Axis conduction". My contacts were long so it didn't really matter for me, but I hope it doesn't affect you since your pieces are so thin....
« Last Edit: January 28, 2013, 10:31:06 PM by Chocochan » Logged
Aerendraca
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« Reply #21 on: January 28, 2013, 10:29:44 PM »

Unfortunately I can't test it tonight as the panel is at my work, but I've come this far with patience so leaving it for the night is fine. I'll  let you know how it goes tomorrow. Cheers for the advice by the way.
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Aerendraca
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« Reply #22 on: January 29, 2013, 09:12:35 PM »

Hmmm, well I tried it today and it didn't seem to make a difference at all, still got a big black bar up the side of the screen where the ribbon was 'repaired'. Immediately thinking back to the conversation yesterday I peeled of the circuit board end and re-taped it with the tape rotated 90degrees to see if that would work. I applied the new tape to the circuit board first and looked through the microscope to check where the specks lay prior to placing the ffc ontop. I then checked that the ffc was aligned properly under the scope before applying pressure along the length to ensure a decent seal. Still no joy.

So once again I peeled back the glass end of the ffc happy that the circuit end was perfectly situated, I then rubbed off the old tape and cleaned it up with ethanol. Following this I then placed a clean piece of tape on the glass part traces and once again carefully placed the ffc on top using the microscope to align. Powered it all up again and nope, still not working.

I think I'm up for one more surgery on this and then I'm calling it quits, but before this I think I will try applying some heat to ffc at either end to see if it will give a better bond and therefore hopefully better connection. I have to say though that I think the biggest problem and the reason that this probably isn't likely to ever work is that the pitch of the glass end is far too small for this tape, for example I think the tip of the ballpoint pen is 0.5mm in the image above.
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Chocochan
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« Reply #23 on: January 29, 2013, 10:21:49 PM »

Hmmm.

That is definitely a sign of poor contact (grey screen with 1 or more black lines. I know this after trying to make a breakout board for a 30 pin FFC). I guess maybe it is the pitch that's failing you after all. Can you tell me how many pins there are and how wide the ribbon cable is? There's something I want to check out. Still I don't know how they attached it, as I haven't seen any other tapes that can go below 0.4mm. There are conductive films that can heat bonded, but I don't know what their minimum pitch is. LCD screens are more complicated that we thought.

I wonder if applying two layers may help to add more conductive particles? I dunno. If it was me, I'd probably mess and mess with it until I finally kill it! Tongue
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Aerendraca
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« Reply #24 on: January 31, 2013, 04:06:41 PM »

Okay so here's the info about the pitch of the ffc using the equipment I have available:


* P1190744 (size of smaller end).jpg (116.55 KB. 831x438 - viewed 833 times.)



* P1200760 (0.15mm micrometer).jpg (191.23 KB. 944x516 - viewed 923 times.)



* P1190746 (size of larger end).jpg (135.84 KB. 884x387 - viewed 790 times.)



* P1200770 (0.2mm micrometer).jpg (180.95 KB. 944x515 - viewed 878 times.)


Measurement tools used:
Micrometer to measure pitch +/- 0.01mm
Vernier callipers to measure FFC/FPC width +/- 0.1mm

« Last Edit: January 31, 2013, 06:01:27 PM by Aerendraca » Logged
Chocochan
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« Reply #25 on: January 31, 2013, 07:13:37 PM »

Could you measure the gap between the pins? That's the pitch. Smiley

73 pins?! Holy crap. I was thinking of trying to cobble up something myself and see if I can get something working with the remaining tape I have, but it's looking pretty fine. I'll need to know the pitch first though.
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Aerendraca
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« Reply #26 on: January 31, 2013, 08:39:12 PM »

Despite the way it looks on the images the space between is the same. A quick calculation therefore is 19.5/145 equals 0.134mm for the smaller end.
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Chocochan
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« Reply #27 on: January 31, 2013, 10:30:38 PM »

So it's 0.2mm on one end and 0.15mm on the other? I don't think I could make something like that. I hoped it would be the same all the way down. Hmmm... The only thing I would try in desperation before I give in is to see if the cable can be quickly soldered. Use a lower temp lead solder (lead-free tends to have a higher temp due to less tin and doesn't flow as well) and LOTS of flux (I prefer liquid) and hope you can get them to join without bridging via capillary action. That was how I was able to solder a 30 pin 0.5mm pitch ZIF connector to my little breakout board. There were no bridges or breaks (tested with multimeter), but I think the only reason my board didn't work was because of inconsistency in the cables I was connecting to it. Even though they were all the same length, something was wrong with the connections. I did check and confirm the pinouts. Here's a pic of what I did:


* SANY0051.JPG (27.06 KB. 655x369 - viewed 865 times.)


Here's a guide on something similar:

http://www.instructables.com/id/How-to-remove-and-re-attach-LCD-Ribbon-from-a-PCB-/step1/Remove-Old-Ribbon-Connection/

Of course this is a last resort, mind you. Only other thing is to quickly solder really thin solid core kynar wires to each contact. Lol, that would probably be mindnumbing. I did do something like that to extend a DVI to HDMI adapter (took it out of the housing and soldered wires to the pins), but it was nowhere near 73! I guess it depends on how badly you want to try and fix the screen. Sorry I can't be of more help (I'm not an expert or a McGuyver). I'm not getting anywhere with my build since the screen I want to use is so new, so even with a borked screen you're better off than me!


  

« Last Edit: January 31, 2013, 10:40:19 PM by Chocochan » Logged
Aerendraca
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« Reply #28 on: February 01, 2013, 10:47:16 AM »

 Cheesy No fret, I have another identical panel which I will use for my build. This endevour was more a journey of exploration with a new material to see what it's limitations were, and I think we found them!
Thank you so much for your help with this though, your suggestions and advice were well received and greatly appreciated.

I'm not ready to put this panel on the tip just yet as I have an idea - based on a wierd dream that I had - which involves using some powdered metal (Copper or Aluminium probably) and a carefully selected glue.
My idea is that it might be possible to produce a glue containing conductive particles - much the same as the 9703 tape - whereby if you keep the thickness of the glue spread thinner than the pitch would be conductive in the z-axis only. I was wondering about finding a glue which contracts as it dries but that is rubbery so that it can pull the FFC/FPC down without loss of adhesion. I would hope that there might be a ratio of metal dust to glue which would be good for this, and I would imagine this to be very little metal powder to a relatively larger amount of glue.

As a slight side note for anyone wondering: I haven't given up on my build, I have been working the shadows to investigate the RFI noise by getting a better understanding of the circuitry. When I have something which is not garbled nonsense and scatter-shot thoughts I will update my build log.

P.S. Chocochan, that's awesome and some very tight soldering!
« Last Edit: February 01, 2013, 10:49:53 AM by Aerendraca » Logged
Chocochan
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« Reply #29 on: February 01, 2013, 06:28:45 PM »

Conductive glue huh?

That already exists, but it's not that great. Search for "wire glue". I once had some and it is NOT a good replacement for solder! Its lack of strength is its weakness. I suppose you could slather epoxy over the top, but then if you ever need to get to the connection, it's a mission! Hot glue might be good, but it all depends in how well it will stick to the PCB. It if existed, a ZIF connector would be best. I don't understand why that cable has so many contacts. I guess that's how it is with old panels. Undecided

Have you tried the silver conductive paint perhaps? I hear it's very good, but I don't know about its shear strength. I have a tiny vial of the stuff and never did really use it. Before deciding on PCB etching, I was going to make a stencil and use the paint over that, but I doubt I would've been able to get tracks as small and neat as the custom board I made. Personally I don't think it's that great. I was so sure it would work but all I could get was the backlight on and a grey screen with a black line. I keep thinking maybe the screen is faulty (bought it REALLY cheap on eBay), but I have no way to test it.

I want to use the screen from the Kindle Fire HD (has a max resolution of 1920 x 1200. Nice for a 8.9" screen), but there's no datasheet available so I don't know if there's a controller for it as I'm sure it's LVDS. It'll be a bit smaller (5mm) than the active area of the tablet I want to use (which I plan to buy next week), but that shouldn't matter too much. It would be awesome if there was a way to modify or flash new firmware to a DisplayLink USB display controller so that it can support higher resolutions, but no one has tried yet. Or maybe they have and failed. I don't even know if I can safely change the ZIF connector on the controller anyway. Cry

What about TEENY strips of copper tape and making an adhesive ribbon cable of your own? Use a sharp blade and ruler and cut strips to fit, lay the panel and PCB flat and carefully joint them and check the gaps. Once you see nothing is touching that could cause a short, stick overlapping pieces of electrical tape to hold the copper tape strips in place. Cover both sides and you're done! A custom cable! Unless the copper tape isn't conductive through the adhesive side, it may work? I have a little bit if tape, I should find out...

EDIT: Crap, it's not conductive through the adhesive. Boo. That would've been so easy to do. Angry
« Last Edit: February 01, 2013, 06:34:22 PM by Chocochan » Logged
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