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Soldering Irons, Soldering Pencils and Soldering Stations.

A Cheap Soldering Iron

A Cheap Soldering Iron

In the last post “Soldering – Construction of Electronics” posted a video about the skills of soldering.   In this post I will talk about the tool necessary to do the job.  I really do not have a recommendation, because the iron I currently use I would not recommend.  I will however, tell you the ones I am looking at and what I consider important.

First, we will describe what soldering is.   Soldering and brazing join metal together using a filler material that melts at a lower temperature than the base material where welding actually melts the base material.   The break-point between soldering and brazing is if the filler material melts below 450 deg C (840 deg F).  The old traditional solder used in electronics was called 60/40 solder because it contains 60% lead and 40% tin.  There is a push to remove lead from everything and newer solders contain no lead at all.

The term soldering iron comes from an old tool that was simply a hunk of copper metal on the end of a rod with a wooden handle.  This tool would be placed in a fire and allowed to heat up and then moved over to the job at hand to melt the solder.   Later this iron was made with an electrical heating element built in the tool.  Smaller versions used for electronics work are sometimes called soldering pencils, but most refer to those as soldering irons also.

A simple iron like the one in the picture is nothing more than a handle, a heating element and a pointed metal end called the tip.   The tip is brought to contact the metals to be joined with the solder.  Even on the inexpensive versions of these the tip is copper coated with iron to provide a shiny surface. This surface is very important to keep the tip from oxidizing and eroding away.   As you can see in the photograph the tip on my soldering iron is oxidized and eroded.  It no longer has any coating or a point on it.

In the low-cost versions of soldering irons the temperature of the tip is not controlled at all.  The heater is “pumping” heat into the tip and the temperature of the tip will increase until it gets to the point where the heat loss to the outside air is equal to the heat gain produced by the heater.

Good soldering stations monitor the temperature of the tip and control the power to the heater to maintain the tip at the desired temperature.  This has the advantage  of increasing the tip life and also of not overheating the iron, solder, and solder flux.   Beware, some soldering stations advertise the wattage is variable and do not monitor the temperature.

One of the specifications of a soldering iron is the wattage of the heater.  On a simple soldering iron this is important because a higher wattage iron will reach a higher temperature and overheat the tip.  On these a 20 or 30 watt iron is the recommended value.  On temperature controlled irons the higher the wattage the better, assuming the tip size and iron size is the same.  While the iron is setting in the stand the wattage will be decreased to maintain the same temperature, but once the iron is used the wattage will increase to maintain the same temperature with the increased heat load.
A higher wattage unit will initially get up to temperature quicker and will recover when being used quicker than a low wattage unit.

The term soldering station is used to describe soldering irons with temperature control units.   However, like everything with marketing involved there may be people that use that term to describe simple irons with a stand.  Always look at the specifications and if you are buying a soldering station make sure it has temperature control. Higher end soldering stations also have a sensor that determines the iron has been placed in the stand and will automatically lower the temperature until the iron is removed and this increases tip life.

Some other things to look for.  Some electronics is very sensitive to static discharge.  I will look for a soldering iron that is grounded to ensure the tip cannot be at a potential other than ground potential.  Some irons advertise the heater element is turned off and on at zero-crossing points.  This means that the AC electricity is switched from off to on while the sine wave is at zero volts and is good for many reasons because it does not introduce fast changing pulses.   However, it is hard to imagine these pulses would affect a grounded electrical tip.

Some other soldering options are butane soldering irons and even butane torches.   I would not consider either of these for electronic work.   However the butane soldering iron is very handy if you are working on an automobile so something similar where a power outlet is not easily available.   I have used torches when working with very large wires and it was impossible for the iron to provide enough heat to get the joint up to a temperature necessary to melt the solder.   This was more electrical type work than electronics.

The final option is a cold tip iron that was widely advertised on a TV infomercial a while back.   From what I understand this uses a voltage applied across two separated points and I would not consider it for anything I would do in electronics.

Currently I use a very inexpensive iron but as you can see from picture the tip is no good and since I have got back into electronics I will be purchasing something better.  The cheap irons can be purchased for less than $5.00 from many sources including the big box stores.  Initially I was considering a 40 watt temperature controlled soldering station which can be found new for less than $50.  However, after some thought I probably will go on up to a higher wattage unit so I will have the “headroom” to work with larger wires if needed.  The brands I am looking at are Weller, Xytronic, Tenma, and Hakko. I understand a Weller model is available with the automatic temperature decrease when the iron is put in the stand, but I have yet to find that model and that brand seems to be the highest priced brand.  (It also has been around a long time and is probably the best supported brand.)   The best prices I have found so far has been with MCM electronics,  but there may be other options such as even E-bay.

The final type of soldering unit to talk about is something called SMD rework stations.   These are expensive units and include a hot air gun to de-solder all the pins of a surface mounted device, SMD, at one time.  Personally, I don’t see me working with that kind of electronics in the near future and see no need to purchase something that I will very likely never use.

I hope this description of soldering equipment has been useful to you.

Gary

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