Introduction to Soldering

Soldering is the process of mechanically and electrically binding together two or more metal components through the introduction of an additional metal alloy, that is applied in a molten state.

Plainly stated, it is metallic hot glue!

Effective soldering requires good heat transfer from the iron to the components to be soldered. Any kind of contamination, corrosion or oxidization – either on the irons’ tip or on the components to be soldered, introduces “thermal resistance” into the process, making the task more difficult (if not impossible) – and time consuming. Remember – the longer heat is applied, the greater the risk of heat damage to to the wire or component, so it’s important to get the job wrapped up quickly.

Copper, steel, silver and gold can be easily soldered. For all practical purposes, aluminum , Iron and stainless steel cannot be soldered with conventional materials and techniques.

Sometimes, there are technical exceptions, but that is a subject beyond the scope of this discussion.

TOOLS

You’ll need the following:

  • A pencil soldering iron – 25 to 40 watts.
  • A soldering iron holder – to safely secure the iron while it’s hot, and not in use.
  • Tip cleaner. I prefer the “metal wool” type. A moist paper towel will do in a pinch.
  • Solder. 60/40 is OK. I prefer 63/37. It melts a little faster.
  • FLUX – a.k.a. soldering paste. An absolute must! Be absolutely sure it is rated for electronic use.
  • Wire cutters – large and small sizes.
  • Wire strippers. A razor or knife will do.
  • Hemostats: Get an assortment of straight, curved, different sizes. An indispensable tool!
  • Razor knife, sand paper, and common jewelers screwdrivers – for scraping and cleaning.
  • An eraser, alcohol, and paper towels
  • Heat shrink tubing assortment.
  • Electrical tape
  • A scrap piece of board or plywood to work on.
  • Good lighting
  • Magnification – glasses, or better yet – a mag light. You need to see the details.

Safety

Soldering is not particularly dangerous – so long as you use your common sense. You can hurt yourself if you are not careful, and fail to pay full attention to your situation. Solder contains lead, so don’t eat, drink or smoke while soldering. Wash your hands when your done soldering. Make sure you have reasonably good ventilation. Secure your iron when it’s not in your hand. Unplug it as soon as you’re done. Don’t solder anything connected to energized equipment.

Most of all, Pay attention! Use your brain.

Four Basic Rules For Effective Soldering:

  1. It’s got to be CLEAN! And that means everything – the iron’s tip, the circuit board pad, the components leads, and the wires. If you intend to apply solder to it, clean it first. Anything gray, black or crusty will NOT accept solder, so before you get started, inspect everything, and clean up as necessary. A pencil eraser, followed by a wipe down with alcohol will take care of most cleaning efforts. If the problem is severe, you may need to scrape or sand the surface until bright and shiny metal is exposed. A final wipe down with alcohol is useful to remove any skin oils or chemical contamination.
  2. It’s got to be STABLE! If any of the components move – especially during the cooling phase, the crystalline structure of the solder will fracture – resulting in a unreliable solder joint, that has a dull appearance.
  3. Use “Flux” (a.k.a. “Soldering Paste”) – it makes a HUGE difference. Flux helps to clean the 1. metal components as they are heated, it helps to prevent oxidization during the soldering process, and it helps to facilitate the flow of the liquified solder. A little goes a LONG way! Be sure to get Flux that is rated for electronics. Flux used to solder copper plumbing is not suitable, and may harm electronic components. Even if your solder has a “rosin core” flux in side, USE MORE FLUX!
    I cannot stress this strongly enough – use flux, EVERY time and the soldering process will be almost effortless!
  4. It’s got to be HOT! You’ve got to use the right iron for the job. A 25 to 40 watt pencil iron is fine for most jobs, but A 100+ watt soldering gun or even a propane torch may be necessary for soldering larger objects such as PL-259’s or anything with a large amount of copper. Insufficient heat will prevent the proper bonding of the solder to the components, and will result in a poor, unreliable connection – known as a “cold” solder join – for obvious reasons. The larger the metal surface, the more heat is required – even if you only intend to solder just one small spot. The remaining metal will “sink” the heat away, preventing the target area from reaching the proper temperature. Sometimes you can make very effective use of a pencil iron, if you preheat the work area with a heat gun or even a blow dryer!

NEXT TIME WE WILL FOCUS ON THE PROCESS OF SOLDERING WIRES

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