JST-Style PCB connector for coax shield - Page 1
Forum section: electronics / projects

author: mzy12
author_rank: Contributor
timestamp: November 11, 2024, 04:43:31 pm
content: Hey!I'm designing a PCB that I want to have disconnect cable, ribbon cable, whatever, on it's edge so I can disconnect some analog cables with coax shield for when I want to/need to repair the board or anything around it.I'm struggling to find the best way to terminate the shield surrounding the cable to a JST style multi-pin connector. Obviously, you can't just crimp it like the rest of the wires in the bundle, as the crimp relies on a standardised wire guage and insulation around the wire, neither of which a shield has. I could obviously use something like a multi pin din or 6.35mm jack and plug and terminate it like a standard audio cable, but that would be pretty bulky for what I am trying to achieve here.If anyone has any thoughts or suggestions, I'd greatly appreciate it

author: reboots
author_rank: Regular Contributor
timestamp: November 11, 2024, 05:32:27 pm
content: Is this for production, or a one-off?I would solder a short length of insulated wire to the braid, suitable for crimping. I would add a piece of adhesive-lined heat shrink tubing over the braid and cable jacket to keep everything from moving around or shorting out.

author: mzy12
author_rank: Contributor
timestamp: November 11, 2024, 10:12:46 pm
content: Quote from: reboots on November 11, 2024, 05:32:27 pmAaaah I knew there was obvious solution I was overlooking. Thanks for the suggestion hahah.QuoteJust something on a small PCB for myself. Nothing crazy, but I still want it to be a reliable solution

author: ZGoode
author_rank: Frequent Contributor
timestamp: November 11, 2024, 10:26:58 pm
content: It really depends how much vibration this device will be under. If you're really worried you could add a little hot glue to the connector to make sure it does not accidentally come unplugged. As long as you do a good job on the crimps themselves, you shouldn't be too worried about them coming undone.

author: ajb
author_rank: Super Contributor
timestamp: November 11, 2024, 10:39:57 pm
content: Crimping the shield (assuming a braided wire shield) isn't necessarily out of the question. It's easier if you have a drain wire, but you can comb the shield wires out and then twist into something approximating a wire, sleeve it with heatshrink, and then crimp normally. Doing that in production would require some care and qualification to make sure it can be done efficiently and reliably in volume, but for a one-off personal thing it's not a big deal. The crimp between the wire strands and the terminal is the most important one and provides most of the pullout strength, the insulation crimp is mainly there for strain relief -- some terminals don't even crimp the insulation. So as long as the effective cross section of the shield wires is within the range of the terminal, and any insulation isn't so thick that it prevents a proper crimp, it's probably fine.

author: mzy12
author_rank: Contributor
timestamp: November 11, 2024, 11:42:38 pm
content: Quote from: ajb on November 11, 2024, 10:39:57 pmI was under the assumption this was a big no no in the world of crimpingI'll give it a shot anyways, it won't kill anyone

author: kmm
author_rank: Regular Contributor
timestamp: November 12, 2024, 02:02:53 am
content: Quote from: mzy12 on November 11, 2024, 11:42:38 pmI've seen this done quite a lot in lower-end products for board-to-board audio interconnects. I recall most of the CD drive audio out to motherboard cables I saw back in the day just twisted up the braid and crimped to it, often with a JST style connector on the CD drive end

author: tooki
author_rank: Super Contributor
timestamp: November 14, 2024, 06:05:46 pm
content: Quote from: mzy12 on November 11, 2024, 11:42:38 pmI have also seen this on a ton of audio/video gear.Ideally, look for a connector with contacts that are available in a wide enough wire size range that you can get contacts suitable for both the conductor and shield. Depending on the connector, there might be different contacts for different wire sizes, or it might be a single contact style. In either case, you’ll just need to use a different crimp die opening for them.Or you can use identical contacts and crimp die for everything, just divide the shield up to multiple contacts to reach the same gauge as the conductor.