Soldering Info

Soldering is spelled like soldering but fyi in American English, this word is usually pronounced like "SOD-der-ring" (IPA: /ˈsɒdərɪŋ/)...the L is silent. Soldering involves joining two pieces of metal together using solder ("SOD-der"). We have soldering irons that look like this:

Note that there is a little stand (on the left) to hold the iron (bottom right), and it connects up via a cable to a little base station (in the middle) where you can turn it on and off or adjust the temperature. The grey pad is the thing you should be holding on to. The metal tip of the iron GETS HOT (it needs to in order to melt the solder), so be really careful not to touch that part; there's a little cushioned/insulated part you should be holding instead.

Creating a solder joint involves a few steps:

• Heat both the part (the pin sticking through) and the pad (the metal contact on the PCB) for a little while (a second or so probably ok) using the iron, making sure you're in contact with both.
• Feed a small amount of solder onto the joint. It should "flow" smoothly into place and make a shape like a little pyramid or cone.
• Continue heating for a little bit to make sure things fall into place, then remove the iron.
• Let the joint cool before moving things around.

The whole process looks like this:

Adafruit also has a good guide to soldering, and in particular a nice page showing several common problems and how to fix them. The following picture from that guide is a summary of some common issues:

We're looking for a nice pyramid- or cone-shaped joint at the end, with no parts of the pad on the board still visible beneath the solder.

Soldering is not edge-of-your-seat daredevil-type stuff, but there are lots of things that can be dangerous here. Be careful, pay attention to what you're doing, and take your time; and we should all have a fun safe time.

Some things to pay attention to:

• Wear safety goggles at all times when soldering and when clipping wires. Getting solder or flux or small pieces of wire in your eyeballs is not fun and can cause serious damage.
• The tip of the iron gets really hot. For the love of all that is holy, don't touch it. There's a perfectly-good handle you should use instead. Minor burns can result if you touch the hot part even for a short while, and if you remain in contact with it, those burns can become serious. Seek immediate medical attention if a burn breaks the skin. The parts you're soldering will also stay hot for a while, so be careful when touching them.
• If you want to, use the little vent fans we have around. The rosin in the solder vaporizes at low temperatures and can cause (usually-mild) eye and respiratory irritation if you're exposed to it for a long time. This is not likely to bother most people especially since we'll only be soldering for a short while; but if you have asthma or something or are at all concerned about possible respiratory irritation, feel free to use a vent fan.
• Be really careful with the iron around power cords. If the iron melts through plastic on a power cord, it can cause electric shock.

So your process is: for every component on the board, grab that component and slide the pins through the board, then flip the board over, solder those joints, then carry on to the next component. If you can think ahead, it's best to solder the shortest components first (the ones that sit closest to the surface of the board).

Questions?

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