How to solder a single wire into multiple cups in a D-SUB connector?

Question

The question title says it all: I need one wire in the cable to connect to 3 cups in a D-SUB connector.

How do I best do this?

Do I solder the cups together with a blob of solder?

Do I bridge the cups with additional wires?

Do I split the cable wire in 3 (awfully thin wire already)?

How is shrink wrap insulation applied?

Answer 1

Many quick & dirty alternatives are possible, but I'll try to answer how to do this professionally by the book (IPC).

Make 3 wires then join them with the single incoming wire at a separate solder joint.

• Solder 3 wires to the dsub cups as usual. Peel & prepare them in advance by applying solder to them. Put some solder in the cup, then heat and insert.
• Cut them at some sensible distance from the dsub. Ideally the wires to the dsub should have some mechanical strain relief somewhere, so you should take that in account when deciding how long the wires should be and where to join them. If it's some panel mount dsub then it might not matter.
• If the 3 isolated wires are long enough (>100mm or so) then consider twisting them together.
• Peel the single incoming wire and place a piece of shrink tube on it for later.
• Peel the 3 wires, twist the naked wires together, then twist them with the peeled incoming wire. Solder.
• Drag the shrink tube down from the single wire to cover the joint, then heat it.

Answer 2

If the D cups are side by side, I'd use short pieces of bare wire cut into a U shape. Fit each end into a hole and solder like normal.

For 3 or more, use several pieces of bare wire, and the middle cups get two ends.

When fitting the incoming cable-wire, use one of the cups that has only a single bridging wire into it.

If your cups are all over the D connector then this doesn't work so well - for that situation use longer wires with insulation, and tie them off to prevent shorting.