What You Will Need. In addition to a mains powered soldering iron, rated at around 15-18 watts, and some resin-cored electrical solder, you will require some or all of the following:
1. A pair of side cutters, for removing excess lengths of lead
2. A pair of wire strippers
3. A piece of emery cloth or fine sandpaper
4. A suitable workholder ( a "helping hands" is ideal)
5. A soldering iron stand with iron tip cleaning sponge
6. An optional de-soldering pump, a useful tool for sucking away unwanted solder from poorly soldered or dry joints.
Getting Started. Plug in the soldering iron, and wait for it to reach its full working temperature (this should take about three minutes or so).
When using the iron for the first time, it will be necessary to "tin" the iron tip (i.e. give it a coating of solder) to enable the iron to do its job more efficiently. When the iron is hot, apply a small amount of solder to the tip (Fig. 1). If the solder does not flow evenly over the surface, clean it with the emery cloth, and if you have an iron stand with a damp sponge tip cleaner, wipe it on this (or a damp rag) and try again, until the tip is clean and bright.
Your First Soldered Joint. Let us assume that you wish to solder a piece of solid-core wire to a tag on a switch (the method is the same when using multi-strand wire). First, strip the plastic insulation on the wire back by about 12mm. Clean the tags of the switch with emery cloth if they are not clean and bright. This will ensure that the solder flows cleanly and evenly over the joint when the iron is applied. Next, insert the bared wire end through the hole in the solder tag, and wrap the wire around it a couple of times. This will ensure a mechanically sound joint (Fig. 2). Note that only one tag is shown for clarity.
Now comes the tricky part! Apply the iron to the tag and the wrapped wire AT THE SAME TIME, whilst feeding the solder against both (Fig. 3). The solder should then flow evenly over the tag and wire. This may seem to require more hands than the average human being is endowed with, but it can be achieved if you hold the work securely in a vice, helping hands tool, or similar, and apply the iron and solder with your free hands. DO NOT attempt to carry the solder to the joint, or the flux in the solder will vaporise, giving a "dry joint", one which is mechanically unsound and electrically high in resistance.
Finally, snip off any remaining wire lead with your cutters, and inspect the joint. It should look shiny and bright, with the outline of the wire faintly visible beneath the solder. If it is dull and crystalline in appearance, the joint may be "dry". If this is the case, remove the solder, clean up the parts more thoroughly, and start again.
That’s all there is to it! Happy soldering....