Skills · skill
Crimping and Wire Termination
Electronics · Beginner
- Difficulty
- Beginner
- Safety
- Live circuits: isolate first. Undersized wire for the current heats and starts fires — the crimp is not the weak point, the choice is.
- Done When
- It passes a hard pull, reads a few milliohms, and stays cool at full current.
- Tools
- Ratcheting crimper with the correct dies for the terminal, wire strippers, terminals sized to the wire gauge, heat-shrink, heat gun.
- Category
- Electronics
Steps
Strip exactly the length of the terminal barrel; no nicked strands.
Twist the strands lightly and insert until they show at the far end but not into the mating area.
Crimp in the ratchet die for that terminal until it releases; a half-crimp is no crimp.
Pull test: a firm tug should not move it.
Inspect: the barrel is uniformly formed, insulation grip holds the jacket, strands visible at the end.
Heat-shrink over the joint.
The Science
A proper crimp deforms both terminal and strands past their yield point into a single cold-welded mass with no air gaps — no oxide can form, so the resistance stays low for decades. Solder in a crimp is worse: it wicks up the strands, makes a hard point where the flexible wire becomes rigid, and it fatigues and breaks there. Contact resistance is what heats a bad joint: a tenth of an ohm at 30 A is 90 W in a connector.
How It Fails
Strands pulled out because the wire was too small for the terminal. Insulation crimped instead of copper. Pliers instead of a ratchet die — a squashed barrel that loosens with heat cycling.
Summary
Joining a wire to a terminal by cold-forming the metal around it — done right, a gas-tight joint better than solder; done wrong, the most common electrical fault there is.
Referenced by
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