HOW-TO GUIDE
How to Solder Small Gauge Stranded Wire to a Connector
By the OhmSavvy Research Team ·
Before you heat a connector
- Connector shells and pins hold heat for a while. Let them cool before touching or flexing the joint.
- Clamp the connector in a vise or helping hands so both your hands stay free and away from the tip.
- Ventilate the bench, and wash your hands after handling leaded solder.
Solder cups, pins and turrets: the terminal types
Solder cup
A half-open tube on D-sub, XLR, DIN and many circular connectors. The wire sits inside it.
Pin terminal
A straight post, as on headers, banana sockets and some panel jacks. The wire lies along or wraps it.
Turret or eyelet
A grooved post or ring, common on amplifier boards and tag strips. The wire wraps the post.
Each type takes the same prep but a slightly different joint. Check the connector datasheet for the largest wire its cups accept; forcing a wire that is too thick into a small cup leaves strands outside.
1Slide parts onto the cable first
Thread everything that goes over the wire before any soldering: the backshell or boot, the cable clamp, and a short sleeve of heat-shrink for each conductor. Forgetting one of these means desoldering every joint to fit it. Push the heat-shrink well back along the wire so the heat does not shrink it early.
2Strip without nicking strands
Fine wire may have only seven to nineteen thin strands, so losing a couple is a real loss of strength. Use the stripper notch for your exact gauge, or one size larger if it bites, and pull the insulation straight off without twisting. Avoid scoring with a blade. Strip just the cup depth, or the pin wrap length, plus about 0.5 mm to 1 mm. Look closely: a strand with a bright nick will break first.
3Twist and tin the wire
Give the strands a light twist in their original lay direction, then tin the bare end with a little solder so it becomes a single smooth conductor. Hold the wire tip-down so solder runs to the end.
Keep the solder on the bare part
4Fill the solder cup
Turn the connector so the open side of the cup faces up. Rest the tip against the back of the cup and feed solder in until it is about two-thirds full and fully molten. Slide the tinned wire into the pool until it touches the bottom, then lift the iron and hold the wire still for a few seconds. The finished joint is a smooth fillet level with the cup opening, with the strand outlines faintly visible.
On multi-pin connectors, work from the middle row outward, or from the far side toward you, so the iron never has to reach past joints you have already made.
5Pin and turret terminals
| Terminal | How the wire sits | Watch for |
|---|---|---|
| Solder cup (D-sub, XLR) | Inside the cup, bottomed | Overflow bridging to the next cup |
| Straight pin | Laid along the pin, or one wrap | Wire pulling off before the solder sets |
| Turret post | Wrapped half to three-quarters round the groove | Overlapping turns hiding a void |
| Eyelet or tag | Hooked through the hole, then crimped lightly | Too much solder filling the hole |
For posts, make the mechanical connection first so the solder only has to bond, not hold the wire in place. The solder should outline the wire, not bury it.
How to prevent insulation shrink-back
Thin PVC insulation softens and pulls away from a hot joint, leaving bare copper exposed between cups. Leave a small gap, keep each joint short, and use a hot, clean tip so the joint melts quickly rather than slowly cooking the wire. Silicone and PTFE insulations tolerate the heat much better. Our guide to soldering wires without overheating insulation covers heat sinks and dwell time in more detail.
Heat-shrink and strain relief
Once every joint has cooled, slide each heat-shrink sleeve down over its cup until it just covers the joint and a few millimeters of insulation, and shrink it with a heat gun. On D-sub and XLR connectors this also insulates neighboring cups from each other. Finally, tighten the connector's cable clamp on the outer jacket, not on the individual wires.
01
Thread parts
Shell, clamp, heat-shrink
02
Strip
Correct notch, no nicks
03
Tin
Bare length only
04
Fill + insert
Cup two-thirds, wire in
05
Shrink + clamp
Cover joint, grip jacket
Iron and tip choice for connectors
A chisel tip around 2 mm to 3 mm wide touches the back of a cup with enough area to heat it quickly; see soldering iron tip types. Thin solder, typically 0.5 mm to 0.8 mm, gives finer control of the fill, as the solder diameter guide explains. New to soldering? Start with how to use a soldering iron.
Irons from our soldering reviews
100W station driving a 65W FX-8801 iron; one of its five temperature presets can hold a hotter setting for brass connector cups.
60W with an adjustable dial, 5 tips and a stand. Suited to beginners and occasional use.
As an Amazon Associate I earn from qualifying purchases. Prices and availability are shown on Amazon.
Frequently asked questions
How much solder should go in a solder cup?
Enough to fill the cup roughly level with its open edge once the wire is in, so the strands are fully surrounded with a smooth fillet along the open face. Solder bulging over the rim or running down the outside is too much and can short to the next cup, especially on closely spaced D-sub connectors.
Should I tin stranded wire before soldering it to a connector?
Yes, for solder cups and pin terminals. Tinning holds the strands together so none splay out of the cup, and it means the wire and the cup only need to melt together briefly. Tin just the stripped length. Do not tin wire that goes into a screw terminal, where solder can creep and loosen the clamp.
Why do strands break next to a soldered connector?
Solder turns the wire into a stiff rod, so bending concentrates at the spot where the solder stops. Nicked strands from stripping fail first. Prevent it by stripping cleanly, keeping solder off the wire under the insulation, and clamping the cable in the connector's strain relief so flexing happens away from the joint.
What temperature should I use for connector solder cups?
Typically about 330 °C to 360 °C for leaded solder and a little higher for lead-free, with a chisel tip large enough to touch the cup body. A larger cup on a metal shell needs more heat input, which is better supplied by a bigger tip than by turning the setpoint up and lingering.
Which wire insulation handles soldering heat best?
Silicone and PTFE insulation tolerate soldering temperatures far better than standard PVC, which softens and shrinks back from the joint. For fine connector work where the insulation sits right next to the cup, PTFE-insulated wire is a common choice. With PVC, leave a small gap and keep each joint short.
