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Old Jan 28, 2013, 09:32 PM
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United States, MA, Walpole
Joined Dec 2003
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CMOS Ribbon Cable Extension with "plug union" method

Originally Posted by Gradius View Post
A very simple question: can the tiny camera be easily removed and add an extension cable (50 cm or so) from it to the pcb?
Originally Posted by Isoprop View Post
Originally Posted by HTTom View Post
My soldering skills (and my eyes) are not sufficient to solder the 24 pin connector to the cable.

This might work better:

I placed the cable into the connector, then pressed the lens in as far as I could with my fringertips (nails). It is a very tight fit. I pressed on the area of the redish film that is wider than the copper colored film. Then I locked the latch. I would suggest a bit of Amazing Goop to glue the cable and lens films together.

I used these parts:

You can buy various quantities of the connectors, but I only found one vendor. There are multiple vendors (USA and overseas) for the cables (and multiple price points). You can also get them in various lengths. Mine are 200mm. The longest I saw was 250mm. For longer lengths just join more than one together.
In addition to the above methods of extending a cable, there is another way that involves soldering the ribbon cable socket, but not to the ribbon cable which isn't designed to be soldered. This method uses two of the ribbon cable sockets soldered back-to-back. While this is still a micro-soldering job, with the proper techniques it can be done reliably. I used these "cable-to-plug" tips from Timetec which helped with soldering two plugs together to form a cable union as well (my additional comments in Green):
Pin alignment : use 2 pieces of 'blu-tack' to position and hold the connector in place - use an eyeglass to align the pins precisely with the tracks.
I used plain old masking tape to hold the two plugs in alignment.

Soldering : There should be enough solder already on the both the tracks of the cable and the connector.
Use a very fine iron that is clean - firstly tin the bit and then remove all excess solder from it.

This ensures good thermal contact between the connector pins and the bit. Apply plenty of reflow flux along the full length of connector pins and cable.
I used a good paste flux from Radio Shack

Start at the top and heat 2 or 3 pins at a time - hold the bit on the connector pins for a couple of seconds before proceeding to the next pair.
On no account allow the bit to touch the plastic of the ribbon cable - the connector shell however is heat resistant.

If you still have problems, you can tin the connector - very quickly (add flux first) using a tiny amount of solder in a 'swiping' action.
Pins may join / 'stick' together, but once you reflow this on the connector, joints will separate.
I very lightly tinned the pins on both plugs, then "wiped" the iron along them to remove as much excess solder as possible.

Practice is everything - experiment with pieces of old cable and used connectors to determine the optimum iron temperature and technique for you.
With plugs aligned and the top plug sitting on one layer of masking tape to better level the pins with the plug pins under it, I smeared a lot of paste flux along the aligned pins, then carefully touched my iron (23 Watts) to a couple pins on each end to lock the plugs together while soldering the rest of the pins two at a time. The solder wicked well into individual the pins being connected with the right amount of solder and flux. I had a tiny bit too much solder and could see a solder bridge on a couple of pins. Reflowing the solder worked sometimes, but if not, I laid a piece of copper braid over the pins (again adding more paste flux), and heated the copper braid which neatly wicked excess solder from the entire line of pins.

The "baked-on" flux will stick between pins, so it's necessary to remove it to be sure there are no solder bridges. Soaking in mineral spirits softens the flux, and wiping the pin rows with a sharp wood tooth pick on both sides, followed by washing under hot water removed most of the flux. A couple stubborn spots I poked with a wire kitchen pot scrubbing brush that clean between pins. When done, there should be light visible between all the pins with nothing in between them their full length.

To finish, I first tested the plug union to be sure it worked, then wrapped the plug with masking tape, and with a tooth pick flowed a line of epoxy into the gap between the two plugs, completely filling it to bond with each side and the pins. This is needed to strengthen the connection. The soldered pins are very weak and can easily bend and break the solder connection.

With the epoxy set, I put some blue masking tape on the side of the plug that will have the blue side of the ribbon cable showing when the cable is properly oriented. And finally, I put a small band of thick clear heat shrink tube around the joint. This probably wasn't needed, but I had this stuff laying around and found it makes gripping the plug much easier when sliding the small locking tabs to insert or remove the ribbon cable.

I had a couple of prior failed attempts until I used this procedure, and after the first one I quickly made a couple more with no problems! It would be possible to daisy chain more cable with more plug unions to get a longer extension. I didn't have more ribbon cables to try it, so don't know how long it could be and still work.

I used the same plugs and ribbon cable as mentioned in HTTom's post. Here's some pics of the process:
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Last edited by Tom Frank; Jan 29, 2013 at 09:01 AM.
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