Friday 16 July 2021

Third Hand

A problem I often face hand soldering surface mount components is keeping them in the correct position while soldering the first end. The surface tension of the solder invariably moves the component.  When using paste and an oven the surface tension is the same on both ends and pulls the component into position. Solder paste and hot air works similarly but it is easy to blow the component away.

One solution is to tin the pad and the end of the component first and then use tweezers to hold the component on the pad while applying the soldering iron to the tinned end. However that requires a steady hand and today, after having two strong cups of coffee, my hands are far from steady!

Some time ago I bought a PCBite probing kit from Elektor. This consists of a steel base, four magnetic clamping posts to hold a PCB and four sharp tip probes with magnetic bases and flexible swan necks intended for making measurements. It works well for its intended purpose although I think the flexible necks would be better if they were stiffer.

I found they make an excellent third hand for holding SMT components in place while soldering.

Here it is holding an 0805 resistor, they are the smallest parts I am comfortable soldering by hand.


  1. Interesting. Does it not take a while to set it up though? Just tin the pad then hold the component with 90degree tweezers, then just touch the iron to the junction.

  2. Yes that is the conventional way to do it but as I get older my hands are not steady enough.

  3. Would a pogo pin test probe help here to apply some downward pressure to compensate for flex in the arms?

  4. The probes are tiny pogo pins with sharp points. The weight of the head compresses them, so the arms just stop the head falling over and allow it to balance on its point. You have to arrange them so the head is vertical or it will fall over.