Using a small pointed iron to solder connections to relatively chunky electrical contacts

I am in the process of soldering up an Arduino circuit using fine bell wire to make the required connections to a couple of rocker switches using a small diameter soldering bit commensurate with the small scale connections involved. The problems comes about with the selected rocker switches with their relatively chunky solder connection tabs which can b a bit of drain on the small soldering iron. Presumable the technique is to tin the as supplied switch contacts with a larger iron before using the small solderring iron to make the final wire connections. Anyone else had this mis matching problem to overcome?

Two factors come in to play with a soldering iron, the bit size and the wattage available to heat the bit. A fine point with a low wattage iron will struggle to heat a large switch terminal. A high wattage (50W) iron that is temperature controlled can run a fine point tip without overheating it or a large tip and be able to keep it up to temperature. I run a Weller temperature controlled iron usually with a fine point. To avoid changing tips for larger one off tasks I let the iron contact as much as possible of a terminal and create a pool of solder to transfer as much heat as fast as possible this has worked for me for 50 years. A good joint will have a smooth shiny finish and the solder should flow freely, an under heated joint will be dull and rough and the solder will not flow freely. Solder for electronic work should be eutectic so that it transitions from liquid to solid almost instantaneously. Personally I do not like lead free solder but it works ok, lead tin is available as it is required for repair work to old spec equipment.

Mike

You need to use the larger iron on the switch (including the bell wire) and smaller iron on the Arduino. By all means, tin the terminals first. No different than large screwdriver for big screws and smaller one for small screws.

Rocker switches often take crimp spade connectors which is easier.

regards Martin

Can I suggest that crimping is for factory work - with accurately controlled presses and precision dies. And the same size wire and connectors every time. Our workshops are quite different. Not only that, the best crimped connection still has holes between the wires, which can fill with water (which is often not pure water). This can cause corrosion inside the fitting, and this is very awkward to rectify.

Soldered joints, with a manual crimp first to hold everything firmly in place, are better in our varied environments (and sometimes out in the snow.)

Only my views, after about 40 years of doing it successfully.

Cheers, Tim

Fairly simple choice. Solder for single strand and crimp for multi-strand if vibration is a possibility.

OP needs to learn that the iron needs to be sized to the largest component, not the smallest. Obvious to most that trying to heat a large, thick, copper sheet with a tiny iron will only result in the heat being dissipated over a large are of the sheet, thus never reaching soldering temperature; applying the iron to a small component and waiting for a larger component to reach soldering temperature may well overheat (and possibly destroy) the smaller component.

You could but crimp tools for insulated spade terminals are available to all. RS do one for £63 and they are less from other sources. I've been doing it professionally all my life and never seen it done on a press. As for water ingress the OP is connecting up an Arduino and doesn't mention the need.

regards Martin

Errrrr, why not solder the wire to the switch FIRST with a gutsy iron and then the dainty connection to the Ardweeny?

Regards Ian.

It's why I own 4 soldering irons! Fine tip for fiddly work, small tip most of the time, big tip for switch contacts and the like, plus a 200W monster for big joints.

You can pre-solder switch contacts and tack wires on with a small iron but it's not ideal. The ideal joint is mechanically sound clean metal to metal before solder is applied. The solder flows over the whole to guarantee good contact throughout by making the joint solid, and then protects the contact from corrosion. Tacking solder to solder is physically weak and electrically inferior. It's OK for simple experimental work, but dubious joints in complex electronics cause hard to diagnose faults.

Dave

I think bell wire is quite a thick wire for making signal interconnections, have a look at some 30AWG or 0.25mm wire, some wires like Kynar are quite easy to solder without stripping back. Bell wire is handy for the matrix type solderless breadboards although a little bit heavier can make life easier.

Mike

Anyone know where I can buy a range of Kynar 30AWG connecting wire in say a a range of 3 or 4 colours in reasonably short (2m) lengths?

Hi, EBay

https://www.ebay.co.uk/itm/122010525608?mkcid=16&mkevt=1&mkrid=711-127632-2357-0&ssspo=h2N0B68PQuS&sssrc=2349624&ssuid=4eI7-dBlT2a&var=421012631750&widget_ver=artemis&media=COPY

Maurice

Edited By Maurice Taylor on 12/12/2022 15:06:40

Its a normal problem, hence the numerous replies.

Spade connectors can be soldered to wires with little irons and can be squeezed to fit anything. As Arduino are not water friendly I assume that would be the quickest, cheapest solution.

If you are sure that the switches have solder tabs then this is a good time for a bigger iron. My unfortunate experience is that they have plastic parts that don't like heat.

You could use a lump of metal as an iron and heat it on the kitchen stove. That's always fun.