Basic Soldering Instructions

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Having basic soldering skills will help you adapt many toys/appliances and make switches for use by individuals who have disabilities.  This handout provides general information about the tools used for soldering, the basic steps for soldering, and possible solutions for common soldering problems.

What is Soldering?

Soldering allows you to join electrical parts together to form an electrical connection, using a molten mixture of lead and tin (solder) with a soldering iron.  For assistive technology projects, most of your soldering will involve connecting wires to jacks or plugs.  The soldering iron melts solder onto the joint between the wires and jacks/plugs to hold them securely in place and ensure that power can flow through. 

Don’t let the word “electrical” scare you!  You’ll only solder switches, toys, or appliances that use batteries.  You should never solder anything that uses electricity from a wall outlet!

Basic Materials:

Protected work surface for soldering

Soldering iron – 15 to 25 watt (Radio Shack #64-2070 or equivalent)

Standard 60/40 rosin-core solder (Radio Shack #64-009 E or equivalent)

22-gauge 2-conductor speaker wire (Radio Shack #278-1385 or equivalent)

Wire stripper

Masking tape

Scissors

Needle-nose pliers

Damp sponge

1/8” mono jacks or plugs, as described in the next section

Standardization of Jacks and Plugs in Assistive Technology:

The assistive technology industry uses a standard system for putting jacks and plugs on switches, toys, and appliances.  If you follow the accepted procedure, your homemade equipment will always plug in nicely with other components without the use of adapters.

1/8” female inline mono phone jack (Radio Shack #274-333)

Female jacks are used on toys, appliances, and battery interrupters.  1/8” is the standard size.

      

1/8” male mono phone plug (Radio Shack #274-286)

Male plugs are used on switches.  1/8” is the standard size.

 

Soldering Safety Precautions:

  • Always work on a protected surface.
  • Never touch the metal end of a hot soldering iron.
  • Never touch a hot component that you’ve just finished soldering.
  • Wear eye protection in case solder splatters.
  • Use rubber-handled needle-nose pliers if you need to touch components while you’re soldering them.
  • Pregnant women and children should never handle solder due to the lead content.
  • Keep hair and clothing away from the solder and iron.
  • Keep components stable while soldering by using masking tape or a vice.
  • Never solder equipment that plugs into a wall outlet. 
  • Replace soldering irons if the cords get burned or worn.

About the Soldering Iron:

The soldering iron is like a curling iron…the metal end gets hot!!  Most soldering irons need to heat up for about 5 minutes to reach the proper temperature for melting solder.  The wattage doesn’t have anything to do with how hot the soldering iron gets.  Instead, the wattage governs the size of the joint the iron can heat.  For small assistive technology projects, a 15 to 25 watt iron should be fine.

Different tips are available for soldering irons so bigger tips can be used for thick wires and very small tips can be used for very small wires and delicate circuitry.  For most switches, toys, and appliances, the standard tip that comes with your iron will be fine.  If your tip becomes very crusty, you can purchase a new one without buying a new iron. 

About the Solder:

Solder is usually 60% lead and 40% tin.  It looks like a thin, flexible wire and it melts when it touches the hot soldering iron.

                                                   

About the Wire:

22-gauge 2-conductor speaker wire works well for most assistive technology projects. The wire has 2 strands (bundles) of copper wire that are separated from each other by being w rapped in plastic insulation.  When you separate the 2 strands and snip the plastic off, you’ll see the exposed copper wire inside. 

Basic Soldering Steps:

  • Follow all safety precautions.
  • Heat your soldering iron for at least 5 minutes.
  • Tape the components you’re soldering down securely or hold them in a vice.
  • Cut a piece of solder about 6” to 10” long. 
  • Hold the plastic handle of your hot soldering iron like a pencil in your dominant hand.
  • “Tin” the iron by touching solder against the tip briefly to coat it. 
  • Touch the tip of the soldering iron against the connection you want to solder.  Keep it in place for several seconds to ensure that the entire joint heats up to a fairly uniform temperature.
  • Pick up the solder with your other hand and bring in towards the tip of the iron on the joint.  Don’t move the iron – leave it in place.  Only move the solder.
  • When the solder gets near the tip, it will melt off onto your joint.  It should flow like icing and be shiny.  It shouldn’t be dull or clumpy.
  • Remove the solder first, then remove your iron.
  • If necessary, use the tip of your needle-nose pliers to hold the wires down in the solder until it cools.
  • Wipe the tip of your hot soldering iron on a damp sponge frequently. 
  • Un-tape your components or remove them from the vice when the joint is cool.

Troubleshooting:

Common Problems

Possible Solutions

Solder sticks to the iron but not to the joint.  Solder beads up on the tip of the iron.

The joint isn’t heated well enough.  Hold the soldering iron against it longer before introducing the solder.

The tip of the iron is too dirty.  Either clean it with steel wool or replace it.  Wipe it on a damp sponge often while soldering.

The component you’re soldering is dirty or corroded.  Rub fine sandpaper or steel wool on it, and then brush off any residue.

Solder doesn’t melt when it touches the tip of the iron.

Soldering iron isn’t hot enough.  Let it heat longer, or replace it if the heating element is out.

Solder is old and should be replaced.

The wires pop up out of the solder when you remove the iron.

Use needle-nose pliers to hold the wires in place after you’ve soldered them until they cool. 

I don’t have enough free hands!

Try the alternate soldering method.

Alternate Soldering Method:

This method works well if you’re having trouble juggling the iron, solder, and pliers.  Or, it may be helpful if you’re soldering to a very small joint and want to prevent soldering from running onto an area it shouldn’t touch.  This method doesn’t work when soldering wires that have to be threaded through a hole.

  • Follow all safety precautions.
  • Heat your soldering iron for at least 5 minutes.
  • Tape the components you’re soldering down securely or hold them in a vice.
  • Cut a piece of solder about 6” to 10” long. 
  • Hold the plastic handle of your hot soldering iron like a pencil in your dominant hand.
  • “Tin” the iron by touching solder against the tip briefly to coat it. 
  • Hold the tip of the soldering iron against the wires to heat them.
  • Tin the wires by touching solder to them against the tip of the iron until they’re coated.  They should be covered thoroughly but shouldn’t be a “clumpy.”  They should be roughly the same size as before they were tinned, and should look like they’re coated in chrome.
  • With your iron, heat the joint area where you need to attach the wires.
  • Hold the tinned wires in your needle-nose pliers.
  • Press the wires against the heated area and hold your iron against them.
  • The solder on the tinned wires should melt and run against the joint.
  • Remove the soldering iron but leave the wires pressed against the joint with your pliers.
  • Remove the pliers when the joint is cool.

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