Soldering Iron Wattage: Powering Up Your Soldering Skills.

The watts of a soldering iron express more than its power consumption. In this article, I will tell you all about soldering irons’ wattage and how it affects their performance.

Understanding Wattage in Soldering Irons

Wattage expresses the soldering iron’s power consumption and indicates the tool’s capacity to generate heat. Simply put, the electric current entering the soldering iron flows through a resistor that heats up and generates heat. Bigger resistors produce more heat but consume more electricity. Smaller resistors allow the current to flow more freely and, of course, produce less heat.

In essence, high-power soldering irons with higher wattage generate more heat than those with lower wattage.

How Does It Work?

The concept is pretty straightforward, and it is simple physics. When electricity flows through a resistor in the soldering iron, the resistance converts electrical energy into heat, following Joule’s Law, also known as the Joule effect.

Jule’s first law states that the power of heating is directly proportional to the electrical current passing through the resistor and the resistance itself.

The fancy name for the resistor inside the soldering irons is “heating element”, and varies depending on the model and quality of the tool. That’s why not all soldering irons with the same wattage have the same heating times. Other factors like the shape and composition of the heating element and even the soldering tip affect the heating times and thermal efficiency.

So, considering all the above, when talking about soldering irons wattage, you should know that it’s directly related to:

• Power consumption: Indicates the soldering iron’s power consumption expressed in Watts.
• Heat generation: High-power soldering irons can produce more heat than low-power ones. For example, a 100W soldering iron reaches significantly higher temperatures than one with 20W. However, when comparing an 85W iron with another with 100W, the differences are slight and vary depending on the heating element of each device.
• Thermal Stability: High-wattage soldering irons can hold the temperature efficiently and don’t face noticeable temperature drops when you are soldering.
• Heat-up time: High-power soldering irons usually have shorter heat-up times than lower-power irons, but once again, the quality and composition of the heating element can also affect heat-up times.

Are High Wattage Solders Better?

Unlike other tools or machines where more power is usually better, it’s not the case with soldering irons. Some elements are sensitive to heat, and using a high-wattage tool will probably damage them.
Higher wattage means more heat dissipation, which can affect nearby components, especially when it comes to electronic items.

Besides, excessive heat can desolder or damage PCB’s circuit traces and nearby components when working with high-density circuit boards.
As you are about to see, the best wattage for a soldering iron depends on its intended use.

Practical Insights: Choosing the Right Wattage

As we’ve seen, high-wattage soldering irons are not always better. To illustrate this, let’s consider a couple of practical examples.

• Situation-1: Imagine you’re working on a vintage radio repair. The radio circuits are old, delicate, and filled with small components. Using a high-wattage soldering iron, like a 100W iron, could generate too much heat and risk damaging these small, sensitive components.
  For such delicate tasks, a lower-wattage soldering iron, say a 25W or 30W iron, would be more appropriate.
• Situation-2: Let’s say you’re installing a heavy-duty outdoor lighting system. You’re working with thick cables that require sturdy and secure solder joints. A low-wattage soldering iron might not generate enough heat to melt your solder effectively in this case.
  Instead, a high-wattage soldering iron, like an 80W or 100W iron, would make the job much easier and more efficient, creating strong and reliable joints for your outdoor lighting system.

What Wattage Soldering Iron for Automotive?

A 60W soldering iron is practical for multiple automotive jobs, allowing you to work with wiring, some electrical and electronic components, and even weld plastics.

Solder for Control Units

A 60W soldering iron can be too much for jobs involving dealing with delicate parts like control modules, the ECU (Electronic Control Unit), and others. For that jobs, a 25W or 30W soldering iron is most appropriate. This power is insufficient to solder thick wires or work with other elements like fuse and relay boxes, where a 60W is more appropriate.

Thick Wires

If you plan to work with thick wires or repair heavy-duty parts like starter motors, you will need a 100W soldering iron as the solder used in those parts has a high melting point, and you will need enough heat to melt it and work efficiently.

Note that the choice of soldering iron wattage is not only determined by the task at hand but also by the type of solder being used. Different solders have different melting points, and this should be taken into account when choosing the wattage of your soldering iron.

In my experience as a car repair garage owner, I started with a standard and average 60W soldering iron for general use and a beautiful 35W solder for precision jobs. With time, and because of my work, I purchased a portable 25W iron powered by the vehicles’ 12V outlet, which was very practical for working with delicate parts that were difficult to remove from the vehicles.
The 100W soldering iron arrived later when we started repairing starter motors in-house.

This is my personal experience and based on my shop’s needs. Still, the point is that there isn’t a “Swiss-army soldering iron”; the closest to that is the 60W soldering iron. If you wonder about soldering irons with temperature control, trust me, they are great for use in your home garage but need a lot of care and maintenance. In the rush of a shop’s working day, you don’t usually have the time to do fiddle with the varying temperature control, mostly when you use it in a populated shop. I leave a door open for soldering stations; they deserve their own chapter.

Wattage for Electronics

For electronic use, 25 to 35-Watt soldering irons are the best suited for soldering electronic circuits without risks of damaging the components. When you work with high-power devices such as audio amplifiers, RC transmitters, power supplies, and others, 40W soldering irons will allow you to deal with most stubborn components, such as large capacitors and transistors.

With enough practice, you could perform almost every electronic job with a 40W soldering iron without damaging the components or the PCB.

Safety Precations

Safety should always be a priority when using soldering irons, especially those of higher wattages. Keep in mind that these tools can reach high temperatures and may cause burns or fires if not handled correctly.
For a detailed guide on safety, please refer to our soldering safety guide.

FAQ

Is a 40W Soldering Iron Sufficient?

A 40W soldering iron is suitable for most electronic jobs, and if you fit a larger tip, with patience, you can do jobs that you would do with a standard 50W soldering iron.
However, 40W is not enough power for working with thick copper wires used in domestic electrical installations or heavy-duty use such as repairing electric motors or desoldering large heat sinks.

Is a 25-watt Soldering Iron Good Enough?

A 25-watt soldering iron is not good enough for most jobs. It’s ok if you are starting to explore the soldering world and electronics as a hobby. It will be ok to do some tests and build your first boards with the peace of mind that you won’t burn them or the parts.
These solders take some time to heat up, giving you enough time to work, but they can’t hold temperature efficiently, so you may experience some trouble like cold joints if you are learning. In any case, they are suitable for some, but not all, electronic applications.

To Wrap It Up

The wattage, soldering tip, and iron quality are crucial factors to consider before purchasing one or starting a job. It’s important to think about what you will be soldering the most and in what field.

If unsure, a 60W soldering iron offers a good balance between heat generation and power. However, if you work in more than a field or with multiple components, it’s best to consider having at least a low-power soldering iron of 30 or 35W and another of 80W or more.

As a rule of thumb, 40W or less is good for most electronic jobs and delicate circuits, and more than 60W is best for heavy-duty jobs, joining thick cables, and jobs that require much heat or dealing with hard-to-melt solder.
Last but not least, soldering irons are not very expensive, so it’s best to buy a high-quality product and invest in a good tip or set of tips for the best results and a great soldering experience.