What Is Soldering Iron and Solder?

Soldering skills are helpful for many things, from fixing a tool to assembling complex DIY circuits and more. In this article, I will show you the basics of this process so that you can dive into the wonderful world of soldering.

What is a Soldering Iron?

Soldering Iron 101
A soldering iron is a handheld tool used for building or repairing electric and electronic devices. It features a heated metal tip that melts solder over the elements to be joined, creating a strong and consistent bond between them. These tools are commonly used for working on wires, electronic components, and circuits, among others.

There are three main types of soldering irons:

1. Soldering Pencils

These are the most common type of soldering tools. You can find the simplest models in any hardware store; however, some advanced models are only available in specialized shops or online.
These tools are usually powered by grid AC current; however, some models work with 12V DC, making them ideal for automotive work or other jobs where grid power is unavailable. Inside the handle, a resistor is heated by the current, transferring temperature to the tip.

2. Soldering Guns

These pistol-like tools are powered by grid current and share the same working principles as soldering pencils. The difference is that they feature a trigger that allows users more control over the soldering temperature.
They usually have a high-power output, making them unreliable for high-precision jobs but very practical for electrical and automotive projects.

3. Soldering Stations

These tools consist of a control box and a soldering pen connected to it. The box is connected to the power grid, allowing users to control the temperature and other features, making them ideal for high-precision jobs.

What is Solder?

Solder is a metal alloy with a low melting point used to join or connect two or more metallic components. One of the most common types of solders is a mixture of tin and lead in a 60/40 or 63/37 ratio of tin to lead.
Solder: Tin-Lead
However, tin and lead are not the only materials used for making solder; in the last decade, lead-free alloys made of tin, copper, silver, and other metals have become popular because of the rising awareness of lead toxicity.

For manual soldering, solder usually comes in the form of a thin wire of diameters that vary depending on the application and typically go from .032″ and .062″. This wire often has a rosin core made of a material called “flux”, which improves the alloy’s conductivity and the joint’s mechanical strength.

When heated with a soldering iron, the solder melts and flows onto the metal surfaces being joined. As it cools down and solidifies, it forms a reliable electrical and mechanical connection, creating a stable and secure bond between the components.

Another commonly used allow, popular in electronics, is a type of solder known as “5-core” because of its composition of five elements, tin, lead, silver, copper, and antimony. This solder type has a high melting point and excellent wetting properties, forming a smooth and continuous layer, achieving strong and reliable joints.

How Does Soldering Iron Work?

To solder two or more parts properly, it’s essential to pre-heat them before applying solder. Once they have reached a certain temperature, the solder is melted by the soldering iron and applied to them. After removing the soldering iron, the solder solidifies as it cools down, creating a strong mechanical and electrical bond between the parts.
Soldering method illustration
Below, you will find simple steps to learn how to use a soldering iron:

  1. Plug in the soldering iron and let it heat up for a couple of minutes.
  2. Once the tip of the iron is hot, clean it using a sponge or soldering cleaning brass wire.
  3. Apply solder to the tip, rotating the soldering iron as you leave an even thin coat over the tip. This process, known as “tinning,” ensures a proper heat transfer and protects the soldering iron’s tip.
  4. Clean the tip once again using a sponge or solder-cleaning brass.
  5. Ensure that all the components to be soldered are clean.
  6. Preheat the parts by touching them softly with the tip for about 3 seconds.
  7. Once the parts are properly heated, place the tip against them without applying excessive pressure.
  8. Hold the solder in place and apply enough solder to cover the parts. It’s important not to apply solder excessively.
  9. After applying the solder, set aside allowing it to cool down.
  10. Unplug the soldering iron and let it cool off.

When using a soldering station, instead of plugging in the soldering iron, you will turn the station on, set the desired temperature, and wait until the soldering iron tip reaches that temperature.

Avoiding excessive solder is essential to ensure a proper solder and electrical connection. Too much solder may create undesirable resistance, leading to circuit overheating or malfunctioning.

Common Applications

Let’s take a look at some typical applications and uses of the soldering iron:

  • Electronics: Jobs like repairing or building electronic devices.
  • Electricity Jobs: Repairing electric tools and connecting wires securely, among others.
  • Metalworking: Soldering irons can be used to join a wide variety of metals. It’s used to solder thin sheets of metal, copper pipes, and jewelry, for example.
  • Woodworking: Some artisans use the heated tips of soldering irons as pyrographs, or in other words, create decorative designs and drawings on wood.
  • Hobbies: It is also used in hobbies like model making, for example.

Safety Precautions

Soldering may seem simple, but it involves heat and electricity, so it’s essential always to use soldering irons carefully. I will leave you a list of the most important things to consider when soldering. However, please always check your soldering iron or station user’s manual for safety guidelines.

  • Always wear safety goggles or protective eyewear to protect your eyes from potential solder splatters and/or debris and the fumes of melted solder.
  • Keep flammable materials away from the soldering area to prevent fire hazards.
  • Work in a well-ventilated area or use an air extractor to prevent inhaling potentially toxic solder fumes.
  • Use a heat-resistant work surface or a soldering mat to protect your work area from damage and prevent fires.
  • Keep a fire extinguisher nearby in case of fire.
  • Use a support or a heat-resistant stand to hold the soldering iron when not in use to prevent accidental burns or damage to surfaces.
  • Never leave a heated iron unattended.
  • Unplug the soldering iron when not used and let it cool down before storing it.
  • Always handle the equipment with care and avoid touching the hot tip to prevent burns or injuries.
  • Follow the manufacturer’s instructions and guidelines for your specific soldering iron model.
  • Inspect the electric cord for any sign of damage and replace or fix it if needed.
  • Remember that the soldering iron’s cord carries grid electrical current. That’s why working in a comfortable position is essential to ensure safety. Avoid any contact between the cord and the hot tip or heated surfaces. Keep the cord away from the soldering area to prevent melting the insulation, which could damage the cable and potentially lead to electrical shock.