From Schmo to Pro: Soldering 101

Soldering is both a key part of electronics building, and one of the tasks that keeps many people from getting involved in the pursuit. Soldering really isn't hard, it just takes a bit of practice, and knowledge of some key points.

There are loads of soldering tutorials around; this one will focus on quickly getting up to speed and avoiding the mistakes that make soldering a frustrating process.

First, what are we trying to accomplish by soldering? Soldering is the process of heating metal parts, applying flux and solder, to form a good electrical and mechanical connection between the parts.

Four Key Points of Doom

In my experience, there are four key points to soldering effectively:

 

Your Iron

This is the key to soldering: you need to use a good soldering iron. First off, anything from Radio Shack is complete crap. I cannot stress this enough. Radio Shack sells the world's worst soldering irons. They are poorly constructed, do not transfer heat well, and are made with shoddy metals that wear out very quickly.

Given the choice between a Radio Shack iron and a Bic lighter, I'd take the Bic lighter. This is a shame since so many people fail at soldering because they start out with a Radio Shack iron. So the first rule of Solder Club is: never buy a Radio Shack Iron.

Another important note: Don't use a soldering gun. These are too hot and too clumsy for electronics work.

The good news is that there plenty of good, inexpensive soldering irons out there. Before looking at specific models, let's identify the key soldering iron characteristics.

  • Form Factor: The most common beginner form factor is a pencil iron. The pencil iron is simply a handle, heating element, tip, and cord all in one unit. These are generally inexpensive, and you would purchase a separate stand and cleaner. A more convenient and easy-to-use form factor is the soldering station. In this configuration, the pencil plugs into a base unit, and the base unit usually has some type of temperature control. Soldering stations also include a separate stand with some type of integrated cleaner. Recommendations here will focus on soldering stations.
     
  • Wattage: A soldering iron's wattage does not correlate to how hot it will get. Rather, it defines how quickly the soldering iron will recover from heat loss caused by contact between the soldering iron tip and other surfaces. Low-wattage irons will take longer to heat back up after losing heat. Larger wattage irons will recover quickly. In general, I like to use irons in the 40-80 watt range.
     
  • Temperature Control: A good soldering station will have built-in electronic temperature control. This is achieved by incorporating a thermostat circuit. Dial in your temperature and the iron will work to keep itself as close to that temperature as possible.

With the basic list of characteristics under our belt, let's look at some options:

Good: Circuit Specialists Stations

This unit is incredible bang for the buck action. I've used this myself for many years. At around $40, it is a great value in an adjustable temp soldering iron. It includes a metal stand that also holds a cleaning sponge.

Circuit Specialists has a wide selection of irons, and some great money-saving bundles as well. They also carry a wide range of replacement tips, solder and other consumables for your soldering pleasure.

Check them out: 
 
http://www.circuitspecialists.com/level.itml/icOid/6388

 

Better: Weller Soldering Irons and Soldering Stations

Weller has been consistently making some of the best soldering gear since the beginning of time. You pay more for a Weller, but it will last a lifetime of properly cared for.

An excellent choice in the Weller line is the WES51 Analog Soldering Station. It is a 50 watt iron with electronic temperature control .

Note that many Weller soldering stations do not come with a soldering tip (which is whack as far as I'm concerned). A good general purpose tip for the kind of through-hole soldering you'll be doing is the Weller ETO 1/32"long Conical(eto) Weller Et-series.

You can get great prices on Weller gear at online tool sites or at Amazon.com: http://www.amazon.com/Weller-WES51-Analog-Soldering-Station/dp/B000BRC2XU

Best: Hakko Irons

As far as I'm concerned, Japanese-based Hakko offers some of the best engineering when it comes to soldering stations. They sit at the higher end of the price scale, but are well worth it.

I currently use the Hakko 936 soldering station and it is rock solid and well made.

If money is no object, you can end up spending thousands of dollars on Hakko gear!

 

 

Consumables

For solder, you want 60/40 Tin/Lead mix, rosin flux core. The thickness or diameter of the solder should be in the range of 1mm to 1.5mm. Anything bigger or smaller will make soldering tougher. Do not use plumber solder or any type of acid-core, you'll make a mess and probably go blind.

Other useful consumables include:

  • Replacement cleaning sponges or,
  •  wire wool cleaners
  • De-soldering braid

 

Soldering Technique

Proper soldering technique can be distilled down to a basic sequence of operations.

  1. Turn on your soldering iron and let it reach the desired operating temperature.
     
  2. Clean the tip using either a damp sponge cleaner or a brass wire mesh cleaner.
     
  3. Tin the tip by applying a small amount of solder. You don't want a big glob on the end, just a thin film coating.
     
  4. Apply heat to the part to be soldered.
     
  5. Apply solder: Once the part is heated, apply a small amount of solder while the iron tip is still on the part.
     
  6. Observe the solder joint: as soon as the solder flows cleanly and forms a non-flaky shiny bond, remove the iron.
     
  7. Place the iron back in its stand.
     
  8. For additional solder joints, return to step 2.

This sounds rather simple, and once you get the hang of it, it really is. Remember to clean your tip just before you use it, not after. The other key is to heat the parts first, then apply the solder.

Common Soldering Tasks, Illustrated

Figure 1: Connecting two wires

 

Figure 2: Board-mounting a component

 

 

Figure 3: Ideal solder amount

 

 

Hints and Tricks

Here are some useful tips for a more enjoyable soldering experience.

  • Temperature: A soldering iron tip of between 800 and 900 degrees Fahrenheit is ideal for electronics soldering.
     
  • Do not solder while wearing shorts.
     
  • If your soldering iron should start to fall from your work surface, do not attempt to catch it. Let it hit the ground, then go after it.
     
  • Don't solder transistors, integrated circuits, or very expensive parts to a PCB. Instead, solder in a socket. This will save you many incidents of frustration over the long run. (i.e. there is nothing more frustrating than looking at a soldered-in backwards transistor or integrated circuit :))
     
  • Take your time, your soldering will be better for it.
     
  • Don't try to re-surface your tip with sandpaper or filing. That will just grind off the coating that makes the tip solder well. If your tip won't clean or re-tin, get a new tip.

Safety

No soldering how-to article would be complete without a discussion of the safety.

  1. Stuff can leap off your iron right into you one good eye. Wear eye protection!
     
  2. Nasty ass fumes that are spewed about when you solder. You should always solder in a well-ventilated area, and away from children or pets. It is also a wise investment to acquire a fume extractor. The fume extractor is a device which uses a fan to pull air from immediately around your soldering area through a filter, thereby severely reducing the amount of noxious compounds put off by melting solder and rosin. If you don't have a fume extractor, you should at least use a fan to blow any smoke or vapors away from your soldering area.

Have fun soldering.

 



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