The images below show cut-away views of a resistor soldered into a
circuit board. The ideal joint should look like an upside down volcano.  
A perfectly soldered joint
A dry joint
When the wire or circuit board
is dirty a dry-joint can occur.
When this happens the wire
may look like it is soldered in
Place but there is no actual
electrical connection.
Too little solder
If too little solder is applied then
the wire may not be held
Too much solder
When too much solder is
Used then a large blob can
Form. This can cause the tracks
On the circuit board to touch
Together stopping the circuit
From working properly:

This is called a solder bridge.
Soldering Tools

These are the tools we commonly use in school.
Desoldering tool
If we make a mistake and
Put a component in the
Wrong place, or use too much
Solder then we can use a
desoldering tool to “suck”
melted solder off the circuit
Side Cutters
Also know as wire
Wire strippers
Used to remove the
Plastic covering of
wires and cables.
Long nosed pliers
They are used to position
components and to pull
the wires through the holes
In a circuit board
Soldering iron stand
When we are soldering we
Must make sure that the
Soldering iron is returned to
The stand. This prevents
Accidental burning of the
Wire, table and most
Importantly, you!
Soldering iron
Traditionally solder is
an alloy of lead and tin.
Lead is very poisonous
So in school we use a
different type made of
Tin, silver and copper.