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I have very little soldering experience - nothing harder than resoldering audio wires in headphones or replacing a mechanical switch on a computer mouse circuit board. I used a plain old unregulated 40 watt soldering iron at all times.

Now turns out there're temperature controlled soldering irons - reading that answer was the first time I heard about them. Which makes me suspect that maybe my prior soldering experience might have been better should I have one of those.

How do I know if I need a temperature controlled iron? What are specific scenarios in which a temperature controlled iron will be advantageous?

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You always need a temperature controlled soldering iron. It's one of the first must-haves for the EE, together with a good DMM. Uncontrolled irons heat up to high temperatures while they sit in their holder, so that your first solderings occur at way too high temperatures, which leads to poor quality soldering connections and possible damage to (smaller) components.


When in college we had labs where we soldered, but we were never formally taught how to do it. Many inexperienced hobbyists apply the solder to the soldering iron. Wrong! You heat up the PCB pad/ component's pin with the iron, and apply the solder to the heated surface. Only that way the flux can do its cleaning job on the surfaces.

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  • \$\begingroup\$ I took about a term's worth of electronics - on a physics course - and the statement about 'do not apply solder to the soldering iron' was mentioned, but never enforced. Equipment was the cheapest of the cheap and instruction was sparse, so everybody attempted the stated method once (with no guidance as to how long the heating process was supposed to take), gave up when it didn't work, then carried on melting huge globs of solder onto their workpiece. All in all, I don't feel I got my money's worth in that class. \$\endgroup\$ – Tom W Apr 4 '12 at 22:01
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It's a good thing to have a temperature controlled iron, because you can set it to be beyond the melting point of your specific solder (there are many different, for instance lead-based or lead-free is a common distinction), but still remaining in a safe limit for the components.

Especially with SMD packages, using a too high temperature or holding the iron too long in position (because of too low temperature) may damage the pads, the pins or the package itself. So, while in some cases (hobbyst tinkering) you can just use your simple iron, it's better to have a temperature controlled one, to obtain a quality work.

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  • \$\begingroup\$ Solder paste isn't usually used with a soldering iron. \$\endgroup\$ – Leon Heller Mar 20 '12 at 11:26
  • \$\begingroup\$ @LeonHeller sorry language mistake...hope that "wire" is the word :) \$\endgroup\$ – clabacchio Mar 20 '12 at 12:06
  • \$\begingroup\$ @clabacchio: I guess "solder alloy" would be just fine. \$\endgroup\$ – sharptooth Mar 20 '12 at 12:39
  • \$\begingroup\$ @sharptooth I've checked Wiki and the lab :) and found that "solder" seems to be the choice \$\endgroup\$ – clabacchio Mar 20 '12 at 12:43
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Although expensive, temperature-controlled irons are recommended in two situations:

  1. when soldering fine (small area) pads
  2. when the device being soldered is sensitive to small temperature excursions (typically small devices, ICs, CMOS/MOSFETS)

Excessive heat could fry the delicate device being soldered or warp the PCB tracks/pads that the copper peels off from the board (fine tracks/pads are especially vulnerable). Inconsistent heat can lead to early solder failure: small pockets of poorly melted solder will not bind well.

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Temperature controlled irons are also useful when soldering components to power planes when there is inadequate thermal relief as they can dump extra power into the bit without increasing the temperature. An uncontrolled iron will simply cool down.

You can also tin enamelled copper wire if you have manually adjustable temperature by whacking the temp up to 400°C. Just remember to turn the temperature down afterwards!

I still have a mains powered uncontrolled iron in my too box, but it is only 15W. This can be useful for light work but I would not recommend anything over 25W.

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