Electronic – What type of solder to use with unregulated 25W soldering iron

What’s the proper soldering iron temperature for standard .031" 60/40 solder?

There is no proper soldering iron temperature just for a given type of solder - the iron temperature should be set for both the component and the solder.

When soldering surface mount components, a small tip and 600F (315C) should be sufficient to quickly solder the joint well without overheating the component.

When soldering through hole components, 700F (370C) is useful to pump more heat into the wire and plated hole to solder it quickly.

A negative capacitor lead to a heatsinking solid pour ground plane is going to need a big fat tip at a much higher temperature.

However, I don't micromanage my soldering temperature, and simply keep mine at 700F (370C). I'll change the tips according to what I'm soldering, and the tip size really ends up determining how much heat gets into the joint in a given period of contact.

I think you'll find that very few soldering jobs will really require you to change your tip temperature.

Keep in mind that the ideal situation is that the soldering iron heats up the joint enough that the joint melts the solder - not the iron. So the iron is expected to be hotter than the melting point of the solder so that the entire joint comes up to the melting point of the solder quickly.

The more quickly you bring the joint temperature up and solder it, the less time the soldering iron is on the joint, and thus the less heat gets transferred to the component. It's not a big deal for many passive or small components, but it turns out that overall a higher tip temperature results in faster soldering and less likely damage to the component being soldered.

So if you do use higher tip temperatures, don't leave them on components any longer than necessary. Apply the iron, apply the solder, and remove both - it should take just a second or maybe two for surface mount, and 1-3 seconds for a through hole part.

Please note that I'm talking about prototyping, hobbyist, and one-off projects. If you are planning on doing final assembly with the iron, repair work for critical projects, etc, then you'll need to consider what you're doing more carefully than this general rule of thumb.

After doing plenty of research and asking some electrical engineers who use them, I've found some points that were helpful in deciding.

Benchtop desoldering or rework stations tend to have the most accurate temperature controls, best thermal recovery, and extra features like programmable timing and hot-air, etc.

For example, if you plan to remove surface mount IC's on a regular basis, a hot-air rework unit may be ideal. They have nozzles for just about every IC package, and the higher end units can be programmed to pre-heat for a specific number of seconds, then heat for a number of seconds, and some have a vacuum nozzle to pick up the now-free part. (For example, see the Hakko FR-803B, a $1300 unit.) You have to weigh the cost heavily with the amount of desoldering or repair work you expect to do. For the occasional removal of parts, on a hobby level, this is likely overkill.

If you're just looking for a step up (or two) from the soldering iron and vacuum pump or solder braid, self-contained desoldering guns like the Hakko 808 can be found for about $200. While it has less fine control over temperature than a bench unit, it does have several benefits: self-contained vacuum pump, replaceable filters, and highly portable. Unless you have specific requirements for performing repair work, it will probably handle any through-hole work.

There are many online videos and tutorials about surface-mount desoldering. It is more tricky than through-hole for a variety of reasons. If you have to desolder SMT, you will want to check some of them out first. Some irons have tips specifically designed for multi-pin SMD packages, there are also hot tweezers and of course the aforementioned hot-air rework systems.

To recap, here are some solutions for desoldering through-hole and their relative price ranges:

The old desoldering pump, for about $15-20. Works "ok" but requires both hands and sometimes creative angles.

$12 at Radio Shack, requires one-and-a-half hands. I've not used one, so I'm not sure if it would be more or less convenient than a separate iron and pump.

Between $50 and $200. I found some for $50-100 online, but I have actually tried a Hakko 808 and can attest to the performance. Great for through-hole.

$400 and up. Lots of brands to choose from, Metcal, OKI, Hakko, Weller, etc. Once you start looking at stations, a variety of features and use-case scenarios start to emerge. Definitely geared more for commercial and industry use where soldering rework is an everyday occurrence.

One important thing to look for in soldering or desoldering equipment is the availability and price of consumables. Filters, tips and nozzles. They will need replacement. If you find an off-brand version, can you find parts for it later? If you get a quality station for cheap, do the replacement parts cost a fortune? Can they only be ordered from a foreign country?

Many manufacturers provide documentation and videos of desoldering equipment. Take some time to go through them, realistically evaluate what you will use (and what you can afford).

When I started looking, I thought I wanted a dual-port station (one solder, one desolder). Such stations are about $600. I probably am not going to desolder daily. I went instead with a single-port soldering station for $300, and a desoldering gun for $200. For my shop, the portability of the desoldering gun is worth the $100 saved and then some.