Is crimping or soldering safer?
Crimping is preferred on vehicle and machinery installations subject to vibration. On a stranded conductor, solder wicks between the strands by capillary action; a stiff-to-flexible transition forms where the solder ends, and vibration stress concentrates exactly there and breaks the conductor by fatigue. In the heat-affected zone the copper also hardens and loses its ductility.
The difference is mechanical, not electrical. Both connections, when well made, are low resistance; what separates them is durability over time.
- The problem with solder: molten solder travels between the strands of a stranded conductor. Once this zone solidifies it behaves like a single piece. At the cross-section where the solder ends, the cable suddenly becomes flexible; the whole vibration or bending load concentrates at that cross-section and the conductor fatigues and breaks there. The soldering heat also hardens the surrounding copper and makes it brittle.
- The advantage of crimping: a crimp made with the correct die compresses the conductor strands with a gas-tight contact similar to a cold weld. There is no heat input, no hardening, and the insulation grip of the lug provides strain relief that takes the load off the conductor.
- High current: on power and lug connections, a crimped lug or a solid connector is the standard for reliability under high vibration and acceleration.
The condition for crimping is the right tool: use a crimping tool with a die matched to the lug and the cross-section, do not squash it with pliers. After crimping, pull the cable to check the mechanical strength and seal the connection against moisture with heat-shrink sleeving.
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