Soldering for DCC – general techniques and equipment.

See Kelsey Parks Electronics Club Soldering Tutorial. You can download a PDF version and print.

When soldering small components onto circuit boards as in hobby electronics projects, wiring in DCC decoders, connecting headlights etc, some special soldering equipment is required that many modellers may not have.

Low wattage soldering irons with smaller tips than the normal general purpose handyman/garage types found around most layouts that are used for general purpose soldering such as layout wiring etc. Also one that has the soldering tip electrostatically isolated so as not to damage small very sensitive components that are part of DCC decoders etc. I would thoroughly recommend if your serious about doing a good job, buying a Temperature controlled Soldering Station.

I have been using the T-2000 from Dick Smith Electronics for years. The new model is the T-2200. This type of soldering iron has replacement tips and the temperature can be adjusted for the particular soldering job, from the lower temperature requirement of soldering white metal loco kits to higher temperature requirements of thicker connections or metal.

If your soldering requirements are very occasional, then use a small 15 – 20 watt soldering iron, the 17 watt is an excellent model. I recommend this one due replacement tips are available.

Similar soldering irons are available from Jaycar Electronics are Temperature controlled soldering station TS1560  and an 18 watt  TS1551 soldering iron.

Temperature of Soldering Iron: For electronics, tin/lead rosin cored solders are normally 60/40 by weight. This solder melts at about 190 degrees C so set the soldering iron to about 200 – 220, no higher otherwise the rosin burns and thus does not do its job. When soldering larger jobs, set the iron to a slightly higher temperature, but for what we want to do, set at 200 – 220 degrees C.

Tip size:  The size of the tip is important. To transfer heat from the iron to the “job” you must keep the tip temperature above the correct temperature for melting the solder but not too high the damage sensitive components and the copper tracks on circuit board. For small electronic components use the smallest conical tip, and larger heat requirement use a chisel tip. The correct temperature is important for a successful solder joint, thus I recommend soldering irons with replacement tips. If you only buy one tip buy the smallest and this tip will be suitable for small electronic work. Your existing general purpose soldering iron can do the heavier work like under layout connections.

Solder: For general purpose soldering, you can use any rosin cored solder but for small electronic soldering use much thinner solder  .56 to .8 mm is ideal. Using the larger diameter needs more heat to melt and it is too much or the job.

Flux is the cleaning agent and allows solder to stick to the job. General purpose rosin cored solder has flux already included in centre and when the solder is melted the flux flows onto the joint.

Soldering Workbench: Working comfortably in a well illuminated area when soldering small components is essential. This really applies to our hobby work bench that should have excellent bright lighting (fluorescent lights), comfortable chair and at the correct height so as not to strain your eyes or arms and some form of magnifier or reading glasses for us with less than perfect, worn out eyes.

Some people use head mounted magnifiers or those cantilevered magnifiers that have a circular fluro tube in it. I have one from Jaycar Electronics but I don’t use it much. I use glasses for reading now, and prefer for close up work on my work bench, a pair of prescribed reading glasses with the shortest focal length, about 7 inches with a twin 40 watt fluorescent light batten, 20 inches above my workbench. Hence I have two pairs of glasses at the bench all the time. I was at a friends place and at his work bench that was illuminated with a couple of the newer quartz halogen 15 watt ceiling lights that are the go now, that provided poor over all lighting and with one of the above cantilevered lights, all he was doing, was swearing and moving the magnifier, till he could see the model clearly. This modeller makes really beautifully detailed models, even won a NMRA model contest in the U.S. with his models. Imagine how much better they would have been, if he could have seen better, with better lighting. I could not even see.

A tidy work bench is a much desired work place, but somehow mine is always cluttered up.

Remember, for soldering, the area should be well ventilated.

Soldering for small electronic components:

1. Use a small low wattage iron as discussed above.

2. Use .56 to .8 mm solder

3. Ensure the surfaces are clean.

4. “Tin” stripped wire ends.

5. Clean the iron tip prior to a really delicate small job and “tin” iron tip.

6. Hold both items to be soldered firmly to prevent any movement while solder is cooling.

7. Hold the iron tip against both surfaces and apply just enough solder to make joint.

8. Only apply the iron long enough to melt the solder and flows to both surfaces.

9. A good joint will be shiny. A bad overheated joint will be grainy and dull.

“Tinning” is applying a little solder to the end of the stripped wire or component lead. This allows for a quicker application of the iron when soldering the joint, due the solder flows quicker. Tinning the iron tip allows for heat transfer quicker due the “liquid” shape of the solder giving more surface area to transfer heat. DO NOT apply to much solder when tinning the iron tip. When both component surfaces that have to be soldered, have been tinned and  with a little solder on the iron tip, this will sometimes all that is needed for a joint. A little more solder may be required to make it flow and be a successful joint.

If soldering a wire lead to a switch terminal with a hole or a circuit board hole, place the UNTINNED wire end in the hole and then solder. Do not tin the wire, it may not fit into the hole after being tinned and secondly, twisting the wire to secure it, prior to soldering will hold it in position while soldering.

I have been soldering for 40 years, so it does come easier with a little bit of practice. Experiment with a few items if this is the first time. It is not that difficult, all of you have had some practice with soldering, if you have a layout.