Flat Flex Cable modification for narrow opening - Page 1
Forum section: electronics / projects

author: k1mgy
author_rank: Regular Contributor
timestamp: April 04, 2019, 08:25:17 pm
content: When I designed an interconnect between two boards, I never imagined they would be separated and joined by a 20mm diameter (narrow) tube that serves as a handle for the product case. So my 40 pin wide ffc, which is 22mm wide obviously won't fit. I might be able to curve the business end to fit through, but this is not a best solution.. and I'm concerned that doing so will damage the cable end.One thought is to very precisely split the cable longitudinally from one end to just above the connector at the other end. At 0.5mm pitch, this will require a microscope and a very steady hand.Has anyone run into this problem? I looked for solutions from the FFC manufacturers, but nothing found.

author: langwadt
author_rank: Super Contributor
timestamp: April 04, 2019, 09:19:48 pm
content: roll it?

author: k1mgy
author_rank: Regular Contributor
timestamp: April 04, 2019, 09:26:17 pm
content: That will work to get it through. I'm looking at something called "slit ffc".

author: jbb
author_rank: Super Contributor
timestamp: April 04, 2019, 09:50:29 pm
content: You could just squeeze the trace and space width, thus making a narrower ‘neck.’ To get the wide connector through the tube you may need to roll it a bit and allow a little extra length.It’s a lot more work, but you could also go for a high density connection (2 row staggered) that would be about 12mm wide. This would unfortunately require PCB spins at both ends.

author: KL27x
author_rank: Super Contributor
timestamp: April 04, 2019, 10:44:14 pm
content: Break it up into 2x 20P FPC ribbon with two connectors on either end?

author: langwadt
author_rank: Super Contributor
timestamp: April 04, 2019, 11:32:23 pm
content: rolled up to a high pitch spiral doesn't bend the ends

author: k1mgy
author_rank: Regular Contributor
timestamp: April 04, 2019, 11:44:46 pm
content: Wish I had the option to spin new board, then I'd change the connector entirely.

author: k1mgy
author_rank: Regular Contributor
timestamp: April 04, 2019, 11:45:58 pm
content: Quote from: langwadt on April 04, 2019, 11:32:23 pmTrue enough. I may get brave (or stupid) and try to cut down the middle to create two half-width sections.

author: Psi
author_rank: Super Contributor
timestamp: April 04, 2019, 11:56:52 pm
content: Quote from: k1mgy on April 04, 2019, 11:45:58 pmDoing that under the microscope should be quite doable.Just need a brand new razor shape blade and go very slowly.

author: langwadt
author_rank: Super Contributor
timestamp: April 05, 2019, 12:03:18 am
content: https://www.ebay.co.uk/itm/332754899933

author: ajb
author_rank: Super Contributor
timestamp: April 05, 2019, 03:47:16 am
content: Looking at the problem from the other way, can you make the handle 25mm instead?

author: Siwastaja
author_rank: Super Contributor
timestamp: April 05, 2019, 01:11:40 pm
content: I have slit FFCs under a microscope: I needed some 50-pin, 0.5mm pitch cables for prototyping but had only 40-pin cables available, so splitting and taping them back together to the rescue (while waiting for the proper cables)! Tidy your workspace, use a sharp model knife under a good stereo microscope, and then carefully pull the cable, keeping the knife steady against the table. Do it slowly and control the pull direction carefully to keep the slit going in the middle of the tracks, avoiding sudden, large corrections.No problem with the result, but this is a very tedious task, so only suitable for very small runs (or expensive products, where manual, skilled labor is required anyway). Expect 5 minutes of skilled, careful work per cable, and expect a poor yield.