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I am working on a project where we are using 28 - 30 AWG wire with the Molex picoblade and Molex picolock connectors. Does anybody have any recommendations for strain relief for wires and connectors that are very tiny? The wires themselves should not expect any strain, but the device itself will be moving, and I'm worried about possible reliability issues if the wires are flexed near the connector.

I've already popped out a bunch of wires just connecting and disconnecting the connectors. (During actual use, the connectors should never need to be disconnected).

Thanks.

Picolock Connector with 28AWG broken wire Broken Wire from Picolock connector

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    \$\begingroup\$ If the connectors never need to be disconnected, can you cover them with hot glue? \$\endgroup\$
    – tcrosley
    Commented Oct 19, 2015 at 17:55
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    \$\begingroup\$ That is odd that you have wires popping out. Do you mean the wires are coming out of the crimp contact? I've never had this issue with properly crimped picoblade connectors. One thing I have done on a board before is drill 2 small holes on the board with the connector, and tie the wire down with bare wire. It's nothing fancy, but worked for the strain relief I needed on 3 conductor 26 AWG wire. I use hot glue as tcrosley mentioned when I'm making test wiring that should never be unplugged and receives lots of abuse in manufacturing. \$\endgroup\$
    – I. Wolfe
    Commented Oct 19, 2015 at 19:31
  • \$\begingroup\$ @I.Wolfe I added two pictures to the question which show what I mean by the wire coming out of the connector. It looks to me like the wires are breaking right at the point where they meet the connector (and there is still part of the wire left in the crimp insert when this happens). I tried tcrosley's solution of adding hot glue this morning, but it looks to me like the issue will remain just now at the location where the wire meets the glue. I have ordered some silicone to try the same idea with a material that is less hard than the hot-glue. \$\endgroup\$
    – Skaevola
    Commented Oct 19, 2015 at 20:12
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    \$\begingroup\$ End goal is to get the strain on the insulated portion of the wire, and away from where it crimps into the contact. Where it crimps into the connector, it has NO insulation, and is therefore much weaker, since it only has some really thin copper strands holding it in place. If you put up picture of the hot glue job, I could tell you if it looks good. \$\endgroup\$
    – I. Wolfe
    Commented Oct 19, 2015 at 20:21
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    \$\begingroup\$ Are you using a legit crimp tool, which should grab insulation as well as conductor? My experience with the smaller Molex pin inserts is that you have best success using the right tool for the right job. \$\endgroup\$
    – Scott Seidman
    Commented Oct 19, 2015 at 21:48

2 Answers 2

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Wires often break the way you show if they are not properly crimped. This can create a pinch point near the edge of the crimp and cause them to break easily. Are you using the correct Molex Picoblade crimper with the correct AWG pins and wire? Is your strip-length correct? Is the wire insulation diameter small enough to be captured by the crimp? (I am having this problem presently)

One thing I like to do is braid or twist the wires making more of a cable. This helps the strands act as a larger, stiffer piece of cable rather than a bunch of tiny wires.

My picoblade power cable

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I would get some water thin cyanoacrylate(crazy glue) and put a drop in each connection. It is non-conductive and should not corrode the wires but will bind them to the casing fairly well.

The advice above about better crimping should be taken. If done right you should not need the glue.

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    \$\begingroup\$ Though if doing that be careful the glue doesn't get wicked down into the connector and on to the contacts. A cold-melt glue gun would probably better than CA as it won't which into the contacts and is more flexible (CA dries solid so isn't brilliant for strain relief). \$\endgroup\$
    – Tom Carpenter
    Commented Oct 22, 2015 at 1:27

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