Saturday, January 12, 2008

Learn To: Solder

Learning to solder (pronouned "sodder", not "sold-er") is essential for anyone who wants to do home-brew electronics work. When one solders, one uses a heating element to melt a spool of wire onto two or more components. Today was my first attempt at soldering, as taught by a good friend. See the accompanying figures and text.

I used wire strippers, some wire, a spool of soldier, and a 12-watt soldering pencil. The wire in question was used for my initial attempt. My next attempt would be to connect three wires together in an RJ45-DB9 connector. Details on this second attempt later in this post.

The first thing to do was strip the wire with the wire strippers. The wire strippers shown belong to my friend, and are appropriate for stripping the wires shown. For the wires in the RJ45-DB9 connector, I had to buy a wire stripper that could strip wire whose diameters are 0.4 square millimeters.

Stripping wires takes some effort, especially if you have never done it before. To be successful at this, you need to cut just the plastic insulation, not the wires themselves. You then pull the insulation off. Using an X-acto knife or your fingernails to strip wires is a less than optimal method.

Heat up the iron. This can take a while, so you might want to start this off first. The iron can warm up to hundreds of degrees, so watch where you put it, your hands, arms, paper, and so on. I brought the top of my hand above the iron, and moved it downwards slowly until I felt warmth. As the iron warms, you will have to move your hand further away. I found that when I had to keep my hand two inches away, the iron didn't warm up past that point.

Once the iron is warmed, place the end of the solder spool on it, letting a bead of solder melt onto it. Move the iron to the wire, coming into contact, allowing the wire to warm up.

Since I was dealing with skinny wires and tiny beads of solder as my first attempt, I found myself looking very closely at the point where the soldering iron met the wire. The wire will warm up after a few seconds, and you can start tapping the solder end to the wire. You know the wire will be warm enough after the wire begins to take on solder, by melting the solder. The wire will suck up the solder like a paper towel sucks up water.

Put just enough solder onto the wire to produce a solder weld, such that the wire and whatever it is that you are soldering it to (another wire, a circuit board, etc), produces a single connection. Do not put enough on to encapsulate the wire; that would be too much. Pull the soldering spool away from the wire, and then pull the soldering iron away. The connection will begin to cool immediately.

I think the first attempt went well, because the solder appeared to bond the wires together, producing a single connection. The wires were not covered in solder.

My second attempt involved soldering even smaller wires. I was trying to solder three wires in total, such that a wire from the RJ45 side of the connector would "split" into two wires towards the DB9 side.

I put a drop of solder on the iron, and moved the iron towards the three wires. I had hand-twisted the three wires together to form a temporary connection. I pressed the bead of solder against the bundle of three wires, waited one second, and then gently tapped the end of the solder spool against the bundle. The wires took on the solder almost immediately, and I pulled away quickly.

The connection cooled, and seemed a success. It was stiff, and solid.

Unfortunately, one of the wires began to pull out of its insulation as I tried to insert one of the DB9 pins into the DB9 end. By the time I had inserted the pin, the wire had broken off, nullifying the desired effect of the soldered connection I had made a minute earlier.

Clearly, more practice at minute soldering is called for, before I attempt at building another RJ45-DB9 connector. The reason for building this connector will be brought up at a later date.

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