IDC vs. Crimp vs. Spring Connectors

[martincho]

I am working on a design that requires wire splicing.  One set of wires is carrying 400 VAC at about 1 A.  Another set is 100 VDC at 3 to 5 A.  No vibration other than whatever the product might be exposed to during shipping.  No temperature extremes.

The options are:

• Insulation displacement connectors (3M Scotchlok)
• Crimped butt connectors (TE PIDG or Plasti-Grip
• Spring Connectors (Wago)

Here are random examples of the above (these are not selected for my application):

https://www.mouser.com/ProductDetail/3M-Electronic-Specialty/560B-BULK?qs=3gW96gqhLborxsSEYKXv0A%3D%3D

https://www.mouser.com/ProductDetail/TE-Connectivity/34067?qs=2ECNu9wPwy5ix9YN1BeGuA%3D%3D

https://www.wago.com/us/wire-splicing-connectors/splicing-connector/p/222-413

IDC connectors are attractive because they reduce labor.  You don't have to strip the wires and don't have to deal with any of the issues that can arise from stranded vs. solid wire.

Crimp-type butt connectors require stripping.  The advantage I see is that you can use full-cycle tooling to ensure a solid connection.  Generally speaking, crimp connections are very reliable and reasonably resistant to moisture.

The spring-type connector is interesting.  I am less familiar with reliability on these.  They do require wire stripping, so there's that extra step in time and labor.  They seem to be rated for a wide range of wire size and currents.  This could mean stocking a single part number to cover the range I mentioned above.  Not sure how these do with regards to moisture and long-term reliability.

I am looking for general commentary from anyone who might have considered these wire-to-wire joining options in applications with similar requirements.


Thanks,

-Martin

[jpanhalt]

I have done no comparisons, but in  a recent motor installation, I used spring connection like you show instead of wire nuts. 

For anything except telecoms and very low voltage, I do not use IDC.  I like IDC for some narrow pitch signal connectors as it is easier to do than crimp with my cheap tools. 

To me, crimp connection are great for a permanent connection.  They are the most difficult to redo without reducing the conductor lengths.  Wire nuts used to be a standard in the US for such things a household and infrequently re-done connections.  Spring connections are supposed to be a better alternative to wire nuts.

[martincho]

There's also these push-in connectors:

https://www.wago.com/us/wire-splicing-connectors/compact-pushwire-splicing-connector/p/2773-403

They are UL rated for 600 V and 20 A.   Very low cost.  Interesting.

[thm_w]

Surprised that 3M part is rated 7 to 15A. Its basically a vampire tap, which are not known to be terribly reliable.

[martincho]

Here's an interesting set of videos where some of these connectors are tested to brutal limits:







I feel far more confident about standardizing on these now.

[langwadt]

Surprised that 3M part is rated 7 to 15A. Its basically a vampire tap, which are not known to be terribly reliable.

looks like something a sketchy mechanic would use to make questionable and unreliable bodges on a car with

[Berni]

For a permanent connection crimping is usually the most reliable option. The forces involved create cold welding of the wire making it a reliable low resistance connection that is also mechanically strong. Does require a crimping tool but is faster than a screw terminal.

Also if moisture is a big concern it might be worth covering the crimp with heatshrink tubing to seal it in.

Crimped connections also tend to visually look 'more professional' as compared to blocky splice things hanging off cables that give it more of a look that someone DIYed that connection in there garage.

As for stripping insulation you can do it pretty fast with some decent automated stripping pliers, just put the wire in there, squeeze down, release and the wire is stripped. The speed advantage of insulation displacement connectors is not worth the worse reliability, especially at high currents.

[jpanhalt]

Yes, crimp is great for stranded wire.  But what about solid/solid and solid/stranded wire connections?

In my experience, crimp on heavy gauge solid is not very reliable, at least using ordinary crimpers.  Even smaller gauge (e.g., 22 awg) is prone to loosen.  Also, the need to occasionally remove a connection (e.g., with electric motors) or modify it (e.g., household, offices) support something less permanent and/or more appropriate for solid.  That is where wire nuts and the newer "spring" connections come into play.

As I mentioned earlier, my first use of lever-spring connections was quite recent.  So far, I was impressed and have had no problems.  Subjectively, they were a little harder to pack in a connection box than wire nuts, but years of experience v. first-time use makes that a biased observation.

EDIT: I also used WAGO

[JohanH]

Vote for Wago here. I wouldn't use anything else in electrical installations (1.5 mm2 / 16 AWG and larger). They are so good. Solid wire or stranded, both works.

[tooki]

Surprised that 3M part is rated 7 to 15A. Its basically a vampire tap, which are not known to be terribly reliable.

No they’re not. They work like punchdown blocks (but with the movement in reverse): a v-shaped blade that slices the insulation and clamps down on the conductor. This is a very reliable connection.

IDC is a broad term that covers many different contact geometries. Most are the punchdown type. Others just stab little teeth into the wire. Either way, though, IDC is widely used and certainly isn’t considered unreliable.

Yes, crimp is great for stranded wire.  But what about solid/solid and solid/stranded wire connections?

In my experience, crimp on heavy gauge solid is not very reliable, at least using ordinary crimpers.  Even smaller gauge (e.g., 22 awg) is prone to loosen.

Crimping is always a precision operation, and whether solid or stranded, the contact, wire, and tool must all be matched. Anecdotally, I’d say that the vast majority of crimp systems are designed for stranded wire exclusively, but some do work with both. It’s no problem at all with circular indent crimping (the military/aerospace type).

One issue with solid wire and crimping is stripping precision: if a strand is nicked during stripping, on stranded wire it doesn’t cause catastrophic damage: future flexing may break the one nicked strand, but the others will be fine. With solid wire, a nick leaves the only strand weakened, and the crimping process may exacerbate the damage.

Ultimately, again anecdotally, practically all of the crimped solid wire I’ve seen is to specialty wire that can’t be soldered, like nichrome wire in heating appliances.

[jpanhalt]

NASA does not seem to allow an exception for terminations.  I think I know what you mean by circular indent type, but doesn't that induce work hardening and a breaking point for solid wire?

[tooki]

I’m sure it does to an extent. I can certainly understand why NASA would prohibit it since they’re the ultimate high-risk high-vibration environment. For the most part, the question of crimping solid wire is irrelevant since we rarely use solid wire in electronics any more. And certainly crimping solid wire is vastly less forgiving than crimping stranded wire, not that I would call crimping a particularly forgiving technology to begin with!