Methods for potting connectors?

Depending on the temperature and opperating conditions, I have had good luck with hot melt glue in ordinary conditions. The hot melt is simi flexable. Plummers Goop also is a much stronger and less flexable glue. I do use a flexable epoxy sometimes. Hardman 04007

greg

You can do low volume production with gravity pour casting instead of injection molding. You can get the potting material put up in bipacks that you use with a gun and mixing nozzle. The mold can be made from plastic.

You can also use heat shrunk boots instead of potting.

A 2-part pourable silicone is ideal. Get the official stuff, or go to Tap Plastics or equivalent and get the hobbyist mold-making liquid silicone. There are some cheaper rubberey arylic casting compounds, too.

Master Bond is a good source for official electronic casting stuff. They are helpful.

I'd avoid electrical tape; the adhesive might react with the potting stuff. Maybe wrap some mylar to form the tube, and tape that.

John

John

Temperature is about 25-60 degrees C. Hot melt glue (same thing as hot glue, right?) is too rigid for our purposes and also makes a lousy connection with the Harwin crimp housing.

How flexible is the Hardman epoxy? I'm hoping to find something as flexible as the PVC jacket of the cable.

Thanks!

-Michael

Its pretty flexible, and I would say very similar to PVC.

I have done some stuff with Sylgard a silicone product, but it takes a long time to set up. The Hardman stufff is pretty thick, and I add heat to speed cure. Its does not run too much, but sometimes I make a little form out of tape to control flow.

greg

Last time I got into stress relief I was doing stuff like: springs plastic or rubber tubes silicone molding using high strand count wire doubling up stranded wires using rubber insulated wire using a guitar string plastic clamps

D from BC British Columbia Canada.

I've used test points and tied the cable bundle to the test point with small-sized lacing tape or a tie-wrap. Mount this test point with the long dimension parallel to the cable run. This prevented pullout and wire breakage on these very Harwin connectors. The pcb footprint for this test point can be made smaller than recommended.

Helpful hint with these Harwin connectors: On your test cables, cut the little latch knobs off the connector body with an Xacto knife. This will prevent the metal latch on the pcb connector from getting bent out of shape when you do repeated unmates. The metal latch is fragile.

So you're saying you put a hard right angle bend in the connector (assuming you're using vertical connectors like us) and then tied it down to the PCB? Seems like a decent way of handling it, though in our application if the cables were mounted to the PCBs in such a manner it would be hard to remove the PCBs from their enclosures...

We do exactly that on our test and programming cables. It also helps since some of the Harwins are in incredibly hard to reach places. The metal latch problem is one that I found a half decent workaround for: I replace them when they break. You can actually order just the latches themselves. Removing the remains of the old ones are hard, but once you get the hang of it is not terrible. Installing the new ones just takes a careful application of pressure.

-Michael

Part of the problem may be that you crimpers are crimping too tightly. The reason I say this is because you related that you wire breaks are occurring at the crimp location. Over crimping is the common reason for this.

The wire may pass some lame, undeterministic "pull test", but that doesn't mean the crimping was done right. In a crimped connection, the crimp has to walk the fine line between being tight enough for a connection that won't be bothered by oxygen, and being so tight that the wire itself gets damaged, even if it is not visibly apparent.

Backfilling a connector is not easy as the connector system usually has to be designed for the purpose. Otherwise you will undoubtedly end up with a connector that has been populated with conductors, but the back fill has invaded the mating area.

Also, you would have to choose a potting compound that will stick to the wires. This is because a simple potting compound will likely NOT stick to the wires, which would thereby NOT provide any real strain relief.

It still sounds to me as if the crimps are too tight, because you should not be having broken wires at the crimp, and all your broken wires being there is a strong indicator that the crimp tool is not adjusted properly.

Reasonable choices. Personally i would thixotropic silicone rubber baked at 85C for 45 minutes.

With some careful use of hot air you can combine the methods.

We used the right angle versions with the idea I mentioned above.

It just occurred to me, is the insulation of your wire sliding into the connector pin a tad? If I remember correctly, this is necessary for strain relief. The strip-length and max insulation diameter is critical for Harwin pins.

Didn't realize you could replace the latch. Good to know.

Yes, good of you to mention that, as it is true of most crimp contacts and lugs.