Soldering Basics

Soldering has always appeared like a simple process. However, it couldn’t be further from the truth. To get a good solder joint, you need to take the proper procedures. Having experience in industrial/robotic soldering and nearly 30 years hobby solder experience, I hope I can make life easier for a few people.

I REALLY wanted to make this quick and to the point, However there is actually a lot to keep in mind while soldering.

Contents:

  1. Equipment and Accessories
  2. Protecting the Tip
  3. Temperature Control
  4. Flux it up
  5. Tinning
  6. Soldering Procedure

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1. Equipment and Accessories

Must haves:

  • Quality Soldering Iron
    • 60 watts is more than enough for hobbyists
    • Adjustable temperature control is a must
    • Aoyue, X-Tronic, and Weller are good names
    • Make sure replacement tips are readily available
    • If you spend more than $30-$60, you are wasting your money
  • 60/40 Rosin core solder like this one from Alpha Fry
  • Paste Flux. Best I have used is the Rectorseal Nokorode Regular Paste Flux
    • Flux is the key to making great solder joints
    • The rosin flux in the solder evaporates rather quickly, especially at high temps
    • The Rectorseal label says not for electronics use. This is OK, we will get to that later
  • Contact cleaner such as Max Professional Contact Cleaner
  • A wet sponge for cleaning the solder iron tip
    • The metal “brillo” type tip cleaners end in premature tip wear (although they claim it doesn’t). Solder tips should never be scraped over a metal surface
    • Never use sandpaper to clean off the tip

Optional:

  • Fume extractor such as this one from Aoyue
  • The Infamous Helping Hands
    • As a side tip – put some shrink tube on the jaws of one of the alligator clips to prevent them from biting into and damaging items:
Soldering 02
Prevent alligator tears in your wire – cover the jaws with shrink wrap

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2. Protecting the Tip

  • Oxidation is the enemy in all aspects of soldering and heat accelerates this process
  • Keep the tip protected by always keeping a small amount of solder on the tip. Even when turning it off, leave a blob of solder on the tip

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3. Temperature Control

  • Never crank the temp all the way up. The more heat, the more oxidation and the greater the chance of overheating your electronics, etc
  • Use a temperature according to the size of the components being soldered. For example, the dial on the Aoyue that I have, the dial ranges from 1 to 8. I use 2 for 30ga wire, 4-5 for 20ga to 18ga wire, and 6-8 for 14ga to 12ga wire

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4. Flux it up

  • If you have never used flux before, get some
  • Flux cleans surfaces and prevents the oxidation of the surfaces as they are being soldered
    • Metal oxides form rapidly at solder temps
    • Solder does not like metal oxides
  • After soldering, clean the components with contact cleaner. Excess flux will slowly corrode wires

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5. Tinning

  • With the exception of very small wires (30ga and below), wires and solder surfaces should always be tinned (but doesn’t hurt to tin small wire)
  • Tinning is the process of adding solder to wires and/or surfaces before the two components are soldered together
  • The tinning process will be shown in the next section

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6. Soldering Procedure

  1. Prep the wire(s) and or surfaces to be soldered by putting a little flux on them
    • For large wires, apply flux liberally since the higher iron temp tends to evaporate the flux quite quickly.Soldering 03
  2. Clean the solder tip by wiping it across a wet sponge (this might take several wipes to clean it completely).
    • Cleaning the tip should be done often – the solder on a hot iron will have a build up of oxides formed on it within a few minutes.
  3. Add some solder to the tip of the iron.Soldering 05
  4. Apply solder to the work piece.
    • For small wires 16ga and smaller: The solder tip should be able to have enough solder on it to tin the wire/surface. Touch the tip to the wire/surface. The solder should immediately flow onto the wire/surface. This shouldn’t take more than 2 seconds.
    • For larger wires and large connectors: The tip cannot hold enough solder. Touch the tip (with solder on it) to the wire/surface. Once you see the solder flowing onto the wire/surface, keep the tip on the work piece and add more solder with your other hand by applying more solder from the solder spool.
    • NOTE: Many people will say to heat up the wire/surface with the soldering iron tip (with no solder on it yet) before adding the solder. This is a SEVERELY backwards idea. This might be fine for a house or car, but not for electronics. Having solder on the tip before hand will provide a much greater surface area for transferring heat to the work piece which results in faster soldering and this is what we want. This allows less time for the heat to travel to any nearby electrical components that might be sensitive to high heat.Soldering 06_Soldering 07
  5. After removing the solder tip from the piece, double check to make sure the solder flowed nicely onto the wire/surface – this is especially important for larger wires. Many times it looks like a large wire is tinned nicely until you look at the other side. Often times the solder did not flow all the way through.Soldering 08
  6. Add a little more flux to one of the two pieces you are joining.
  7. Add more solder to the tip of the iron.
  8. While the two pieces are in contact with each other, apply the iron tip until you see the solder melt and flow between the two pieces.
    • For small pieces, you can remove the iron almost immediately.
    • For larger pieces, it may take several seconds for all the solder to flow together.Soldering 9
  9. Add solder to the iron tip (if needed) before putting it back in the holder.
  10. Using contact cleaner, clean off any residual flux. An old toothbrush sometimes helps with this.
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