Choosing solder

You can make good joints with any kind of solder, though some kinds are easier to work with than others.

It doesn't matter whether you pick leaded or unleaded solder. Leaded solder is a bit easier to work with as it melts at a lower temperature, but it is worse for the environment and can pose (very slight) health risks. Generally, soldering irons can put out enough heat that the difference is easy to overcome by adjusting your iron's temperature.

Solder with a flux core makes soldering much easier. We always recommend using solder with a flux core. Flux is a corrosive chemical which helps to clean oxidation off of the surfaces you're trying to join. It greatly simplifies the soldering process. If your solder has a flux core, you won't have to apply flux to your joints separately.

Oxidation occurs the moment a PCB is exposed to air. Even on PCBs with high quality surface finishes such as ours, a little oxidation does still occur.

The diameter of the solder wire affects control. When soldering, you're feeding solder into the joint. The thicker the diameter, the more solder you're feeding into the joint per length of distance you feed it with. As such, a very small diameter allows for very precise control, at the cost of having to feed a lot more distance into the joint. There are some popular diameters available:

• 0.5mm diameter solder is quite precise and delicate. It's Thomas' personal preference, but can be slow to work with.
• 0.7mm diameter solder is a nice balance between precision and speed. We recommend this for beginners who don't yet have their own preference.
• 1.0mm diameter solder offers a lot of volume per distance, and can greatly speed up your soldering on larger joints such as those for switches. However, smaller joints would require you to feed it much more slowly, making it easy to feed too much solder by accident.

While even smaller or larger diameters are available, we wouldn't recommend using them for our kits. The smaller sizes are nice to use for high-precision soldering, which our kits don't require. Larger sizes are meant to be used for larger joints, which our kits also do not require.

The materials used in solder don't matter much. Leaded solder usually has a 60/40 ratio between tin (Sn) and lead (Pb), while unleaded solder usually has a ratio of 99.3/0.7 between Tin (Sn) and copper (Cu).

Sometimes, you'll see unleaded solder containing a little silver (Ag). Silver decreases the melting point, reduces oxidation, increases conductivity and makes joints a little stronger. It's also more costly and its enhanced technical properties are not required for use in our kits, so we don't recommend buying more expensive solder if all you do is solder keyboard kits.