The Basics of Soldering Electronics
Iliya Papoulias
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Soldering can seem like a daunting task at first, but when you get used to soldering circuit boards you get the grasp of it. This article is meant to teach the basics of soldering THT (Through Hole Technology) components and soldering basic wires to get started in the world of soldering electronics. Soldering means electrically connecting components together by melting solder (a type of metal alloy) using a hot iron. Soldering is a useful skill for fixing electronics and hacking electronics to have different purposes.
Useful Tools for Soldering
The iron which is used to solder electronics is called a soldering iron and they come in many brands and models. Also the price will vary depending on what soldering iron is chosen. For example, a 40 dollar one may just plug into your outlet and will heat up without any temperature control. Alternatively, you can pay hundreds of dollars for a soldering station which has adjustable temperature and may even display what temperature the iron is. If you are new to soldering or you just need a soldering iron for a quick fix you can get a cheap one. If you plan to solder continually, and will require more features, you should pay more. The biggest and trusted brands that make soldering irons are Weller or Hakko. You can buy a soldering iron from online websites like Amazon or at retailers like Home Depot or Princess Auto. Soldering irons may come with different tips as each tip is useful for a particular soldering job. I suggest if you are soldering electronics use a conical tip or a chesil tip as those are the easiest to use in soldering electronics.
There are many types of solder you can buy, but make sure you pick an electrical solder, not a plumbing solder as it is meant for fixing pipes and it contains an acid flux which is bad for electronic boards. Electrical solder varies depending which one you buy. There is a lead solder which contains lead (Pb) and was used in older electronics, but is still used by hobbyists as it is good for soldering at a lower temperature. However, when working with lead solder, work in a well ventilated area or use a device called a fume extractor. The purpose of the fume extractor is to suck the solder fumes using a fan and filter out the toxic fumes. Lead-free solder is used nowadays for new electronics. It doesn't contain lead, but you still shouldn’t breath in the fumes. The drawback is that the lead free solder requires a higher temperature and isn’t as easy to solder compared to lead solder which flows easily. Lead free solder contains tin, copper, silver, bismuth, indium, zinc, antimony, and other metals to improve the performance of the solder. While lead solder contains lead (Pb) and tin (Sn) which means it has a lower melting point at 188 degrees celsius compared to lead free temperature which melts at a temperature of around 217 degrees celsius.
One thing that will make soldering easier is if you buy solder which has flux or you buy flux separately as it makes soldering a breeze. Flux is used as it helps prepare copper contacts of a circuit board by cleaning and removing oxides, making it easier for solder to flow. It also prevents metal oxidation on the circuit board pads as it seals out air preventing oxidation creating a perfect solder joint. You can buy flux in many forms, such as flux being inside the solder or buying solder separately in syringes or in a paste. There are many types of flux as well such as rosin flux, rosin substitute, clean/no clean flux, and water soluble flux, but the one I recommend is the rosin core flux as it is found in electrical solder.
One way to clean the tip is to drag your solder iron on a damp sponge, taking the excess solder off of your iron. The drawback is that rubbing your iron tip repeatedly changes the temperature causing your iron to expand or contract and the iron tip to fail. Another way to clean your iron tip is to use metal wool, like steel wool, which is harder, but doesn’t last as long. On the other hand, brass wool is softer/less abrasive on the iron. This is a much better alternative than a sponge as it removes the dirt from the iron, but doesn't reduce the temperature of the tip the way a sponge does. In order to clean your tip using metal wool, dab the tip into the steel wool. For more stubborn dirt, apply pressure to the iron on the wool varying the strokes. You can clean your tip with a tip tinner where you rub your iron into the liquid to remove the oxidation on the iron. You can also use a cold tip soldering bar to clean your iron tip when it is cold. Be careful as a hot iron tip could damage your tip. A clean soldering iron is bright and shiny, so this is how you can tell when you have to clean the iron tip.
Some other items which are useful to buy when soldering are a solder wick/ braid and a solder sucker. These are vital tools as they are used to remove solder off the printed circuit board (PCB) if you make a mistake when soldering. Also, you can purchase a PCB vice and “helping hands” which are devices used to hold what you are soldering. A PCB vice, as the name implies, holds printed circuit boards using adjustable clamps. You can adjust the distance of the clamps to hold the printed circuit board properly. You can get them in many different sizes of vice for the particular PCB, but this may be more expensive. Helping hands are similar to a PCB vice, but can hold wire as well. The helping hands are alligator clips connected to plastic flexible arms which adjust where the clips are while holding the items you are soldering. Helping hands are used for both PCBs, as well as wires. Helping hands are very versatile because of their adjustability. In addition, you can buy wire strippers which are important for stripping the insulation off the wires in order to reveal the copper in the wires. This is necessary to easily solder wires together or put them into a PCB. Pliers are useful to trim off excess leads from soldering. Excess leads can bend and cause a short circuit.
How to Solder
First, you must pick what to solder. This could be an electronics kit where you can solder electronics to a PCB (printed circuit board) or it could be a project to soldering two wires together.
Soldering a wire is the easiest way to make a solder connection. The first step is to use something to hold your wires (such as a helping hand) and position your wires so they are close to each other. Then, twist the two wires together so they are connected to one another. This makes a sturdy electrical connection between the wires and makes it easier to solder together. Next if you have a wall outlet soldering iron, wait until it heats up till the solder is able to melt and for the soldering station adjust the temperature to the correct melting temperature of the solder. Next you should tin your soldering iron which is the process of putting a large amount of solder onto your iron cleaning your iron removing the oxidation giving a coat of solder on the iron preventing oxidation. Next use a steel wool or damp sponge and rub the excess solder to give it a nice shiny and bright look. Now put a small coat of solder on as it helps transfer the heat better from the iron to the board. After that Then place your iron tip at an angle on the wire and head up the exposed wire. Then take your solder with the iron still on the exposed wire strips, put solder onto the wire and it should melt into the wire. Try putting solder on the places that still don’t have solder to create a perfect connection. Now clean off your soldering iron by rubbing it on a sponge or rubbing it with metal wool and now you know how to solder lengths of wires together.
Soldering through hole components on a printed circuit board from a kit is a bit harder but is simple through practice. Like before, tin your iron tip with lots of solder and then rub it on a damp sponge or rub it in metal wool to get a clean iron tip. Put a thin coating of solder on your tip, then put the component lead(metal legs of the components) through the PCB so they are through the copper traces on the back side of the back of the board. Then bend the leads a bit so your component doesn’t fall out when soldering. Next use a vice to hold your board up with the traces facing you to solder and then put your iron tip slanted a bit on both the copper trace and the lead. Then wait a few seconds till the iron heats up the pad and leg. This is important as when solder touches the pad it should flow perfectly onto the race creating a solid electrical connection between the joint and the leg of the component. To tell if you did this correctly is if the solder joint is shiny and smooth, kind of like a cone or volcano shape when the solder is connected to the lead of the component. It shouldn’t look like a round shiny circle as it is a sign you put too much solder or even worse you put too much solder that is connected to another trace on the board that wasn’t intended causing a short circuit. This solder overlap connected to another trace on the board is called a solder bridge. If your solder joint isn’t shiny due to the iron not being hot enough is a dull solder joint preventing a proper electrical connection between the pad or the joint. To fix this you can put your iron back onto the solder joint heating it to make a better electrical connection or adding more solder to make it sturdy. To remove solder from a solder joint you can use a solder sucker by heating up the solder joint with your iron and bringing the desolder pump to the joint. Then push the top button down and to take away the solder click the side button causing the soldering pump to suck the solder on trace and the lead of the component. You can use solder braid/solder wick as well by taking a strip of the solder braid, putting it on the solder joint, putting your iron on top of the solder braid causing the solder braid to absorb the solder. If it isn’t sucking the solder put some solder on your iron that will help absorb the solder. Once you find your solder joint is good, use some piers to clip off the excess leads.
Now that you know about the basics of soldering, you can use your skills to fix many types of electronics or modify them to your liking. You can even build many unique circuits with this skill that can be useful for you, especially with microcontrollers where you can create robots and other devices. Soldering takes a lot of practice so it may take a few times to actually get right and you shouldn’t get frustrated as mistakes often occur if you are new to soldering. Once you have mastered the soldering you can move to more complex soldering such as SMD (surface mount soldering) which are small components that don’t have any leads that go through the board. These components require a good eye and loss of precision as these components are tiny and the components are harder to connect to the traces. With your new found skill of soldering go out there and solder electronics or use your new found knowledge to teach others.
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