Re: What to use as crimp tool?

A proper crimping tool, applied as directed, is intended to produce a gas-tight electrical contact, that is corrosion resistant at the point of contact. This is supposedly impervious to fluids, as well.

Vibration does not affect either a crimp or a solder joint directly. It affects the body of the wire as it exits the contact area. Unsoldered stranded wire has better vibration performance than the same stranded wire after consolidation by soldering.

Vibration resistance near the joint can be improved through the judicious use of strain relief.

RL

Soldering a crimp joint makes it weak. If you want a joint that lasts for decades, crimping (a.k.a. cold welding) is the only way to go. But you'll need to spend $$$ to get the right tools. Crimping is an art.

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fancy

Agreed. Even a lonely Christmas gets better with a good DIY meal.

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I spent 5 weeks in China correcting assembies that were made with that theory. They spent the large amounts of money on the tools. The crimp joints started failing in under a year.

Soldering the crimp lug after it is crimped is a science. I'd rather trust it than "an art" that I have seen fail so many times.

It does wick into the side you solder from and seals it up and improves the strength of the joint. Even if it did wick to the far side that would only move the point of failure slightly if the wire doesn't have a good strain relief.

Yes, letting stress get to any electrical connection on a wire is bad. This is why connectors almost always have some way of taking hold of the wire some short distance from the joint.

The supposedly part of that theory points out one of its weaknesses. I have seen crimp lugs turn green in the environment. The process of crimping always leaves defects in the tin plating that can be where the corrosion will start. A little solder closes these up and leaves a joint with a smooth surface of only one metal.

Right at the point of the crimp, the stands are either (A) pushed together so tightly that they act like a solid or (2) not pushed together that tightly.

If (A) is the case, the area of the joint acts like the solid wire case. If (2) is the case, any flex will work the wires loose. Either will cause failure.

Yes, there must be a strain relief. This should ne be just bundling of the wires together. It should be anchored to something that doesn't move.

I find plenty of crimps that do get warm. Then its a loosing battle. Some get so hot they break apart. It makes jobs for me. Sometimes welding is the only acceptable method.

greg

This is where use of the proper crimping tool comes into play. The use of the correct tool will often result in a recognizable signature impression on the joint that is used for inspection/compliance and quality control.

Bare stranded copper grounding wires are used regularly in contact with and buried in the natural environment . In this specific application, the crimped contact is documented and demonstrated regularly to outlast the conductors' lifetime.

The simple presence of soldered crimp connections may be enough to justify pulling equipment out of service in many safety-critical applications (military, biomedical and avionics) until all such contacts can be re-examined and reworked for integrity.

In situations where the correct tool is not available for an urgent repair, the use of alternatives, including soldering, should be recorded and flagged for the earliest possible correction.

The procedure, of course, is covered generally by MIL-TD-1111. :)

RL

Good crimps are really good. Consumer equipment is laden with bad crimps.

greg

These crimpers made an impression that was inspected and everything was just fine by eye. When put to use in the environment, they failed. The best way to tell by looking is to look to see if it is soldered. If it is not soldered, the joint will fail.

100% of the joints that failed in China were crimped, 0% failures were seen with soldered. This still applies today. I have seen no failures in the crimp lugs that are soldered.

Because the soldered ones are 100% reliable and simply never fail, I will continue with the method I use now. There really is no point in your continuing to argue the point because I will continue to believe the evidence of my experience.

Have you taken up this issue with your supplier, or are you simply satisfied to receive the defective parts because they're still cheaper, even after the shoddy rework is performed?

RL

That crimp tool or wire supplier was doing something wrong, a proper crimp is a gas tight seal and will never fail. There are an uncountable number of crimps in use in high current industrial applications that continue to last forever, and this covers the full spectrum of vibration, corrosive atmosphere, temperature, everything...quite a few high temp heater connections use a crimp, usually stainless steel, several thousand degrees, they last forever, try soldering those-)

Another problem may have been insufficient derating of the connector current rating. A lot of suppliers will advertize say 25Amp capability but fail to mention that is at a 55oC temperature rise with 'perfect' crimps- I doubt they even test for it in production, especially the el cheapo near counterfeit stuff of unknown origins. You're up against a runaway condition if the surface contact area starts to oxidize.

On Apr 15, 8:03 am, "Michael A. Terrell" wrote: [....]

Many will pass pull tests, burn in tests and cold soak tests and then fail in a few months time under vibration and exposure to the envirnment. I think the physical motion somehow helps the chemistry of failure get started.

The parts are not defective in any way that we can detect. These are not just parts from one batch or one supplier. The trip to China was mostly for unsoldered Panasonic crimp lugs. More recent failures were on an "american" brand who's name escapes me and some from somebody in the far east. Someone in production "who knew better" decided to stop soldering the lugs and the failure rate came back.

If we assume: (1) One that never fails is proper. (2) A proper one never fails.

Now how do we ensure that 100% of the crimps are proper without waiting for failure? There is no known way to tell by simple inspection. Soldering can be checked by inspection.

Caterpiller (at last report) solders their crimps. I solder mine. I don't seee failures of the soldered crimps but I do see failures of the unsoldered ones.

If the metal just outside the contact area starts to grow green fur, the joint will fail in time. I think it is a "crevice corrosion" that gets going in the area between the metal of the jug and the metal of the wire.

I take it that fellow was not voicing what he probably knew quite well (that going back to soldering would probably fix the problem) based on hoping you'd come up there and find another problem? (I mean, a better person who thought they knew better would have just admitted the mistake and corrected the problem themselves without you having to fly halfway around the world, wouldn't they?)