If you’re into tinkering, at some point you’ll probably find yourself needing to know how to use a soldering iron and how to solder.
Maybe you’ve designed a cool little circuit using a breadboard and you’re ready to solder together the final product.
Or perhaps you found a bad solder joint in a broken circuit.
It could be that some electronics part you ordered did not arrive pre-soldered.
In this post, we’ll explain how soldering works. Here’s everything you need to learn how to use a soldering iron and solder like a pro!
You can check out our video demonstration here and subscribe to our YouTube channel to keep up with new projects.
Or you can also follow the step-by-step instructions below.
What is soldering?
Soldering is what we do to connect metal parts together, such as copper wire, resistors, capacitors, transistors, integrated circuits, PCBs… you get the idea.
The process uses solder (a metal that is easy to melt) to join metal components that do not melt easily. When we solder metal components together, the solder melts and then hardens to form a tight connection with the metal components (which do not melt).
Soldering also requires another material called “flux” to make a strong bond between the metal components.
For a deep dive into the chemistry of soldering, check out Hackaday’s post on this subject.
What is solder made of?
Historically, solder was made of tin and lead.
Because of health and environmental concerns, a variety of lead-free solders have been developed. These lead-free solders most commonly include copper or silver along with tin. Solder may also contain other metals such as bismuth, indium, zinc, and antimony.
Solder is commonly sold with flux in its core to help with bonding.
What is in flux?
Flux has historically been made from the resin of pine trees. It often contains some amount of chemical activator. Non-resin “water-soluble” fluxes are made from organic or inorganic acids and leave behind a water-soluble residue (the fluxes themselves are not water-soluble, despite their name).
How to use a soldering iron
Before starting, make sure your soldering iron is hot.
Get the components ready so they touch each other in the way you want them joined. For example, in our video demonstration, we solder a wire to a speaker contact. So, we arranged the wire so that it was lying against the speaker contact.
It’s okay if, for the moment, the pieces don’t stay in place. You’ll just want to be able to quickly reconstruct this arrangement for Step 4.
Use a damp sponge to wipe the tip of the soldering iron.
Quickly touch the solder wire to the tip of the soldering iron until there’s a small molten bead of solder on the tip of the iron. This will help conduct heat onto the components you are soldering.
Note that in the image below, the soldering iron is *not* yet touching the speaker.
Hold the tip of the iron against your metal components for a couple of seconds. To make a strong connection, it’s important that the components (in our example, the wire and the speaker contact) get as hot as the solder.
Quickly touch the solder to the joint you are soldering, and you should see it flow in and join your components.
Check out all of our cool engineering projects.
We also have a helpful basic electronics page that teaches skills such as how to use a breadboard and multimeter.
If you found this post helpful or have questions, please let us know! Are there projects you’d like us to build? Please leave us a comment!