If this is your first-time soldering, let us go over some of the basics of how to solder before we assemble the kit. The best way to learn to solder is by watching. I would suggest watching videos online about the basics of soldering in addition to these instructions, to best prepare yourself.
How Soldering Works
Soldering is the process of joining two or more metal objects by melting and applying some intermediate metal material referred to as solder. It is often used in electronics as it offers a way to connect electrical components with a strong, yet reversible, conductive bond.
Soldering Equipment Names and Usages
Rosin / Flux
Rosin (sometimes called flux) is used in soldering to help the liquid solder flow smoothly and stop the solder or its contact point from oxidizing. Most solder has a rosin core, so there is no need to worry about this. If you are using solder with no rosin core, you will need to add rosin to the board with a rosin pen before soldering.
Helping Hand / Board Holder
To make it easier to solder, many people use a board holder or helping hand. These are tools that will hold your board at a useful angle to make soldering more convenient. While they are not necessary, they do make life a lot easier, especially when you have hundreds of solder connections to make.
Solder Sucker / Solder Plunger
A solder sucker, sometimes called a solder plunger, is used to remove solder from a connection if we want to undo one of our joints. It uses a spring-loaded plunger to suck the liquid solder up inside, away from the board. While it will not get 100% of the solder, it removes a large portion of it.
Usually used after a solder sucker, solder wick removes any remaining solder from an electrical joint. To use it, just place it over the solder and put your soldering iron on top. When the solder melts, it will get wicked up into the solder wick, and the wick will change from a copper-orange to a silver color. Once the wick has solder in it, you need to cut off that section and use a new part of the wick. Be careful, the wick gets very hot very quickly when in use, only hold it from the plastic spool it came on.
This kit will be looking at a style of soldering called through-hole, commonly abbreviated to THT (with the third “T” being for technology). As the name implies, one component will have a lead, or extended metal part, that goes through a hole in the other part. Solder then flows in between the two to make a solid connection. You can tell if a part is THT soldered if there is a bit of metal sticking out the bottom of the PCB. On your Arduino, all of the pin headers will be through-hole soldered.
How to Make a Through-Hole Solder Joint
We will now go through how to make a through-hole solder joint. The same process applies for any package or component. We will go over how to apply this technique to each specific package type as we work through the soldering kit. In general, the entire process of soldering a THT joint should take less than 10 seconds. If you heat the board or component for too long, there is a risk of damage. One thing to keep in mind is that not all pins will take the same amount of time to solder. Specifically, pins connected to copper pours (5V and GND in this kit) will take significantly longer to solder, as the heat will be dissipated to the pour instead of concentrating in the pin.
Troubleshooting Soldering Issues
Tips for Making Soldered Projects Look Better
Even if you solder everything correctly, sometimes your board will come out looking a bit weird. Here are a few tips to make your assembled project look much cleaner and more professional. None of this will have any impact on the operation of the circuit, just how it looks.
- Align similar components. If you have multiple identical components in a row (like the resistors up the left side of the voltmeter), arrange them all to be in the same orientation.
- Keep parts inline with the silkscreen. As you connect a part, make sure that it lines up cleanly with the silkscreen below. My go-to trick to do this is to solder one lead, then re-heat the solder on that pin as I gently push the component perpendicular to the board, so both leads press against the same edge of their respective holes. This will make sure that the part is parallel with the silkscreen, without having to try and line it up by hand. Keep in mind that the part will get hot when you heat up one lead, so be careful!
- Clean around solder joints. The rosin from solder joints will build up in translucent films around solder joints, that catch the light at odd angles. You can remove this with isopropyl alcohol and a toothbrush or Q-Tip.
Looking for more tips on how to solder? I'd suggest reading Sparkfun's guide on THT soldering. It contains a ton of great information!