Learning how to solder using proper techniques is a fundamental skill every ham should master. Whether you’re attaching connectors to a coaxial cable or constructing a balun, knowing how to solder will come in handy.
Grab a roll of solder, soldering iron, stand, and a tip cleaner. Let’s get started.
Soldering Safety
Safety first! There are a few things we should consider before firing up that soldering iron.
Soldering irons can reach temperatures approaching 900 degrees F, so it’s very important to know where your iron is at all times. Use a soldering iron stand to help prevent accidental burns or damage. Handle with care—always hold the soldering iron close to the base. If it smells like chicken, you’re probably holding it wrong.
Clear the area, giving yourself room to work. You don’t want to accidentally burn anything, especially yourself or your favorite radio.
Wear protective eyewear. Hold wires to be heated with tweezers, pliers or clamps to avoid receiving burns from objects you heat.
When solder is heated, fumes are released that can be harmful to your eyes and lungs. Solder in a well-ventilated area or use a fume extractor. Another option—use those leftover Covid masks.
Even though you have turned off and unplugged your soldering iron, it will be hot for some time. Never leave a hot soldering iron unattended. Also, wash your hands when done soldering, especially if you’re using lead solder.
Prep and Clean
Tinning the tip will increase the surface contact area, allowing more heat to be transferred to the metal you’re trying to solder. Do this by applying a small amount of solder on the tip of the soldering iron before trying to solder anything. You should tin the tip of your iron before and after each soldering session to extend its life. Eventually, every tip will wear out and will need replacing when it becomes rough or pitted.
Clean the tip frequently to remove oxidation. The most common ways are using a damp sponge or a brass wire ball.
Never scrape your tip with sandpaper, a knife, or other abrasives. This will take the outer layer off the tip, allowing dirt to build up and cause performance issues.
Choose the Right Tools
One of the biggest mistakes is choosing an underpowered soldering iron. A thermostatically controlled soldering iron can be set to a temperature suitable for each soldering job. These can be simple 20-60W irons or a full-featured soldering station with temperature control. If you’re building antennas, making ground connections or preparing feedlines, a 100W soldering gun is a good choice.
A helping hand is a device that has two or more alligator clips and sometimes a magnifying glass and light attached. These clips will assist you by holding the things you are trying to solder and help prevent burns. Circuit board holders keep your circuit boards in place and allow you to rotate the board for easy access.
Solder Choices
Solder is a metal alloy material that’s melted to create a solid bond between electrical parts. It comes in both lead and lead-free variations with diameters of .032″ and .062″ commonly available. Inside the solder core is flux, a material which helps improve electrical contact and mechanical strength.
Thicker diameter solder is good for soldering larger joints more quickly, but it can make soldering smaller joints difficult. For this reason, it’s a good idea to have both sizes on hand for your different projects.
Manufacturers are moving toward lead-free rosin core solder for health and environmental reasons. This type of solder is usually made up of a tin/copper alloy and has a higher melting point, making it a bit harder to work with. You can also use a 60/40 tin/lead rosin core solder. If you do use lead solder, make sure you have proper ventilation and that you wash your hands after use.
Solid Connections
Whenever possible, make a good mechanical connection before soldering. This will make a stronger contact.
Touch the tip to the metal you’re trying to solder, whether it’s a terminal or a solder pad. Slowly add some solder until you see the solder run to the metal. Once you see the solder moving onto the metal, you can add the solder a little faster until you have a good amount of solder and the connection is made. Leave the tip on for an additional second.
Once you have made the solder connection, you’ll want to remove the soldering iron and not disturb the connection until the solder has hardened. If you move a connection too soon, it will either fall apart or cause a cold solder joint. A proper solder joint is smooth, shiny and looks like a volcano or cone shape. You want just enough solder to cover the entire joint but not too much so it becomes a ball or spills to a nearby lead or joint.
Oops
Soldering is forgiving, which makes it relatively easy to fix most any mistakes. If you apply a little too much solder or position a component incorrectly, you can reheat the joint, melt the solder and then reposition it correctly. Solder can be heated and cooled as many times as you need to get your joint properly fixed. If you don’t get the outcome you were trying for, don’t get discouraged—try again.
Desoldering is the process of removing solder at the joint to disconnect two items that have been soldered, or removing an accidental solder bridge. Desoldering may become necessary if you want to replace a component that is defective, or if you want to change something about your design after it has already been soldered. To desolder wires you can usually just heat them up and pull them apart. To remove excess solder, you can use a desoldering station, desoldering braid, or a desoldering pump.
