How hot does a soldering iron get

Maximum soldering temperature?

Again and again I am asked which soldering temperature should be used for soldering. Or much more what the maximum temperature may be. In short: I solder with a temperature of about 325 ° C. Relatively seldom a little more. The exact temperature at which you should solder depends on many factors, such as the soldering station.

 

But why does this question arise about the soldering temperature?

I can tell my story myself. When I started soldering many years ago when I was around 6 years old, I assembled many soldering sets that I bought from Conrad and the electronics store in my hometown. In these sets there was often a soldering instruction. In these soldering instructions I was advised that active components such as transistors and IC (integrated circuits) are temperature-sensitive and can easily be destroyed during soldering.
Therefore it was always a stress for me to solder these components. I had cold solder joints and burned my fingers. Overall, the soldering results were anything but satisfactory. Maybe it was because I didn't have good equipment, but also because I didn't know exactly what the solder and flux was. Therefore, I recommend that interested parties read my two articles on solder and flux first.

 

Do components break if the soldering temperature is too high?

 

In order to answer this question, I have to go back a little further. In the 25 years that I have already soldered, I have not yet destroyed a single component at too high a temperature. And I honestly have to admit that I've done a lot of crap with all kinds of components. At this point I would like to add that the conductor or the pad is more likely to detach from the circuit board, the more likely that a component is destroyed by heat.

Many components are designed in such a way that they function without any problems even at a temperature of 100-200 ° C. Components also have to withstand high temperatures in industrial and machine soldering. So you don't have to worry about destroying such a component.

And if something does happen, nothing bad has happened either. Resistors, capacitors or diodes only cost 5-10ct, simple ICs cost 50ct and microcontrollers cost 1-5 € each. Unless you are soldering an FPGA for € 1,000, the costs and therefore the risk are quite manageable.

Just for the sake of completeness, I would like to mention that there are components that are actually temperature-sensitive. And that's quartz. Crystals indicate the timing of controllers and processors. If the temperature is too high, a quartz can actually be destroyed or its tack can be influenced.

thermodynamics

In order to understand what soldering temperature is required, there are a few factors to consider. First of all, it is the melting temperature of the solder. The melting temperature of lead-free solder is 180-200 ° C, with lead-free solder it is 218-230 ° C. If you now want to solder a component, you place the soldering tip in such a way that it touches and heats both the soldering pad and the leg of the component.

At this moment, the heat flows from the soldering iron to the component and the soldering pad. Both spots get warmer while the soldering iron cools down. As soon as the pin and the solder pad have reached the melting temperature of the solder, a connection with the solder can be established. The hotter the soldering iron, the faster the heat flows to the pin and the soldering pad and the faster you can solder it. The soldering speed depends on the temperature!

As we just noted, the hot soldering tip cools down during soldering because it gives off its heat. It is usually not a problem with small components, but as soon as the components or the solder pad have a high thermal capacity, it is no longer that easy. The smaller the heat difference between the soldering tip and the soldering point, the slower the heat will flow over. Therefore, the electronics of the soldering iron must start up at that moment and heat the soldering tip again. However, it shouldn't cause a shootover either - that is, that the temperature becomes far too high.

But even the best soldering station cannot help in some cases, when the heat capacity is very large and forms a large area. The soldering tip then heats the component, but the circuit board does not get hot enough because too much heat is dissipating. In such a situation you can then increase the temperature or use a preheater to preheat the circuit board. This lowers the temperature difference between the soldering tip and the soldering point and less heat flows away.

Why my soldering temperature is 325 ° C.

I always solder with a JBC soldering station at a temperature of 325 ° C, because this temperature works for me for all applications. Regardless of whether it is a lead-free or lead-containing solder. Regardless of whether the component has a high or low thermal capacity. The control of the amount of heat that is transferred to a solder joint is determined by the pace of work. Then it takes half a second longer if I solder a point with a high heat capacity without lead.

This 325 ° C has proven itself for me with all high-quality soldering stations. However, you should see 325 ° C as a guideline and find your own soldering temperature in the range of plus minus 20 ° C, which suits your soldering station and the pace of work.

Please do not underestimate the quality of the solder or the flux. A good solder is easy to work with, and a good flux also makes soldering a lot easier. So if you have problems or difficulties with soldering, it may be worth investing in a different solder or in a better flux.