Introduction to Soldering

The Basics

Learning Objectives

• To know how to use a soldering iron to achieve perfect soldered joints;

• To understand and put into practice all safety rules when using a soldering iron.

What is soldering?

Soldering is a method of joining metals using heat to melt a filler metal with a lower melting point.

• Solder is an alloy

• It used to be tin and lead, but lead is poisonous

• It is now tin and copper (sometimes also silver or nickel or antimony)

• Melting point 210 – 2300C

• Has a hollow core filled with FLUX - a chemical cleaning agent

What is solder?

The quick guide to perfect soldering

•The parts must be clean and grease free.

•Hold the parts securely in a clamp.

•Clean the tip of the iron.

•Heat both parts of the joint equally.

•Apply just enough solder to make the joint.

•Remove and return the iron to the safety stand.

•Do not move the joint until cooled.

WORK SAFE

•Soldering irons work at 350°C. This is very hot (boiling water is 100°C). The soldering iron will give you a severe burn if touched.

•Wear goggles when soldering.

•Never fool around with the soldering iron.

•Store the soldering iron in the stand when in use.

THINK SAFE

Basics One - Begin

• Plug in and switch on the soldering iron. It will now begin to heating up

• Lightly wet the sponge

Basics Two – Stripping the wire

• Use the side cutters to lightly grip the wire

• Twist the side cutters and the wire gently in opposite directions. Until…

• …you begin to see a gap in the rubber insulation and bare silver wire appears.

• Now use the wire strippers to remove the rubber insulation from the wire.

Basics Three - Twisting

• Twist the bare wire strands together

• The wire will look like this

• Now twist the wire around one of the L.E.D light legs

Basics Four – STOP HOT!!!

• REMEMBER: The soldering iron is extremely HOT. It has been on for the entire time you have been preparing to solder. So make sure you ONLY handle it by the HANDLE and not by the metal areas.

Basics Five – Soldering

• Safely handle the soldering iron. Place a small amount of solder on the tip of the soldering iron until it begins to melt.

This is called tinning and helps the transfer of heat from the soldering iron to the components.

• Place the soldering iron against the wire and leg of the LED light - hold it there for a few seconds.

•Touch the solder against the heated area, so that just enough solder runs onto both. Then remove.

Basics Six - Good and Bad Soldering

Poor joints are usually the result of one of the following:

• Not heating the joint for long enough • Not cleaning the soldering iron and tinning• Poor soldering iron contact• Moving the components before the joint has

cooled

Solder

Correctly soldered Poor soldering(dry joint)

Components

LED - long wire is positive, short wire is negative

Twist the LED short wires together

Put LEDs in wooden mounting blocksTwist long legs together with the resistor

Solder the long leads and resistor together

Resistor

Cut off the small connector

Solder the red wire to the resistorSolder the black wire to the short legs

Tips and Tricks

1. Keep the iron tip clean. A clean iron tip means better heat conduction and a better joint. Use a wet sponge to clean the tip between joints.

2. Double check joints. It is a good idea to check all soldered joints before moving on.

3. Use the iron properly. This will ensure that you are safe.

Plenary

1. At what temperature does water boil at?2. What is the temperature of the soldering

iron?3. What is an alloy?4. 3 safety rules when soldering 5. What two things, other than the solder,

must the soldering iron touch when you are soldering?

6. What makes a bad soldered joint?