Crimping for wire terminations — an alternative to soldering: part 2

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December 20, 2023 By Bill Schweber Leave a Comment

Soldering is a well-known and reliable technology for terminating wires, but crimping is a widely used alternative.

As much as I enjoy soldering and producing a quality, attractive solder joint, I also recognize that there are times when soldering is not the right way to join wires to each other or their terminations. As noted in “What are the five connector contact termination styles used for?” there are five ways to terminate a cable or wire: soldering, press fit, clamp, crimp, and insulation displacement. Depending on the specifics of the situation, some of these are better suited to terminating a group or cluster of wires, while others are more suitable for individual wires as well as groups.

I faced this challenge when I helped a friend upgrade his home’s three-zone heating system from one with basic, unpowered, dumb thermostats to instead using smart, Wi-Fi- enabled units (Figure 1).

My original plan was to simply solder uninsulated spade lugs to the ends of the various wire connections, including the signal/power interface relays, and then attach the lugs to a standard screw-terminal barrier strip (Figure 2).

I soon realized that it would make more sense to use screw-terminal sockets for the relays as well. This would ease making the physical connections, allow for disconnection if required for troubleshooting or maintenance, and provide a nice, clean way to organize the arrangement for the long term.

While there were some wires I could conveniently pre-solder to their spade lugs “off-site” at my bench, many would have to be done on-site in the basement at the heating system electrical panel (a large piece of plywood). However, the more I thought about it, I realized this was a bad idea, as properly soldering the several dozen wires to their spade lugs in an awkward, cramped basement setting is never easy, neat, or consistent.

From soldering to crimping That’s when I remembered an alternative. I had a basic manual crimping tool in my toolbox which offered another solution (Figure 3). This tool looks like a large pair of pliers with a designated area at the tip of the jaws for crimp barrels of three sizes, along with other wire-stripping and screw-shearing functions.

What is crimping? Crimping is a pressure-based mechanical joining method that connects two components with each other by means of a defined pressing procedure. The method forms a secure connection between the conductor and contact and has replaced the soldering process in many cases. Crimping can be used with many types of connectors, including wire-end ferrules, which are then inserted into mating receptacles or connector bodies (Figure 4).

Even if you are an admirer of a well-done solder joint (as I am), there are many reasons to use crimping. A good crimp is mechanically rugged, electrically consistent, and forms a gas-tight contact between the wire and termination which prevents ingress of moisture and subsequent corrosion.

Unlike soldering, it is quick and easy to set up and start, temporarily interrupt, or stop entirely; there are no hazardous fumes or materials; and there’s no heat to distort insulation or even cause ignition and fire. Crimping is not limited to individual wires. Barrel connectors allow you to easily splice and extend a single wire, and with the appropriate tool and connectors, it can be used for multiwire cable for terminations such as the Ethernet RJ-45 connector; there are even crimpers for optical fiber.

I bought a box of spade lugs with red insulated barrels, practiced crimping on about ten of them to make sure I could do it right, and then did the actual installation (Figure 5). It all went smoothly, and the system was up and running after resolving some minor wire-routing problems.

However, while crimping the spade lugs, I found that it was tricky to make consistent crimps, as my tool was a manual, uncalibrated one dependent on how I placed to spade lug in the jaws and how much pressure I exerted. Depending on the consistency of the user (me, in this case), it was easy to be “off-target” in the final crimp position and pressure more than I liked. For example, some spade-lug barrels were crimped too little, some too much, and some had insulation partially under the crimp zone.

What I now wish I had was a crimping tool like the Weidmüller PZ 6 ROTO ADJ (Figure 6); many similar tools are available from other vendors. It reliably and consistently crimps wire-end ferrules over a wide range of wire cross-sectional areas from 0.14 mm2 to 6 mm2 (roughly 26 AWG to 10 AWG.) It works with wire-end ferrules, with and without plastic collars. Its ratchet guarantees precise crimping and a release option in the event of incorrect operation.

Crimping is not just for plain wires. There are special connectors and corresponding tools for crimping RF coaxial cables, which are impossible to solder due to their miniscule size, shielding, and other mechanical factors. A poorly soldered RF cable presents not only a simple continuity problem but will also have adverse RF performance as well.

Related Content What are the five connector contact termination styles used for? The first undersea transatlantic cable: An audacious project that (eventually) succeeded, Part 1 The first undersea transatlantic cable: An audacious project that (eventually) succeeded, Part 2 Portfolio of crimp termination options simplify on-site assembly Crimp pins and receptacles for wire termination New Right Angle Solder Cup Holders Solder Cup Headers Deliver 25 Percent Height Reduction New Press-Fit PCB Pins for Plated-through Holes

References SparkFun, “Working with Wire” Weidmüller, “Crimping: A permanent connection” NASA, “Rapid and Verified Crimping for Critical Wiring Needs”

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Crimping for wire terminations — an alternative to soldering: part 2 - Electrical Engineering News and Products