Basic Soldering Technique
This video shows Basic Soldering Technique, and the equipment used to solder.
There are two main types of soldering iron, the iron to the right has a station which shows the temperature on the display. The controls adjust the desired target temperature.
The one on the left works at a fixed temperature, but is used in the same way. If you’re using a digital iron then set the target temperature to around three hundred and fifty degrees C and wait for the iron to heat up.
When you are not soldering remember to keep the iron in the holder. be careful when you are soldering not to put the iron in contact with the lead, some soldering irons have PVC coated leads which will melt through easily and pose a risk of electric shock if touched.
The best leads to use are made from silicon which won’t melt at the temperatures soldering irons reach. The other item you’ll need is of course solder. solder is a low melting point alloy which flows easily when heated to it’s liquid state.
When it cools and solidifies it fuses to the surface of a metal at the molecular level, providing good electrical conductivity between two metal surfaces.
Solder normally contains flux helps the solder to flow, and also helps make a good contact by removing the oxides on the surface of the metals being joined.
Although modern flux is not toxic, when soldering you should always use a fume extractor to prevent the fumes from the flux irritating you lungs.
The fumes are extracted by a High Efficiency Particulate Air Filter or HEPA filter before the air is returned to the room.
Before you handle the components it’s strongly advised that you wear an earthing band to prevent electrostatic damage to the components.
There are two different soldering types: surface mount, and through hole.
Surface mount connections are made by heating components with pre-applied solder in an oven, so that it melts and joins to the surface of the board.
In this tutorial we’ll look at ‘plated through hole soldering’ which done on boards with printed circuits on both sides.
Through hole soldering is where components are pushed through a hole in the board and soldered from the other side. The solder flows through the hole to make the best possible contact.
First take your component and create a bend in the legs with a pair of pliers, so that each leg is at a right angle.
Push the legs through the holes in the board at the appropriate place and push it all the way down. Then turn the board over and bend the legs slightly to lock the component in place.
When the iron is up to temperature, first clean the tip of the iron on the wet sponge on the iron holder to remove any excess solder and flux residue that might be there.
You then apply heat directly to the pad for about a second, before placing the solder in contact with the pad.
When the solder starts to melt feed it in for about a second, take the solder away, but leave the iron on the pad for another second.
Then take the iron away and let the connection cool. Let’s have another look at that. Before you make another connection it’s important to remove any excess solder remaining on the tip of the iron.
This is because any flux in the solder will vaporise until there’s none remaining, if you try to make a connection with solder without any flux in it you risk making a bad connection.
When you turn the board over you should see that the solder has flowed through the hole by capillary action, guaranteeing a good contact.
Trim the leads just above the solder using some wire cutters. When you cut the wires be careful that the cut end is held captive so that it doesn’t fly off.
This can be done by putting your finger on the end when cutting. If you make a bad joint or want to remove a component you can remove the solder by using a de-soldering pump.
This is a spring loaded piston with a trigger which when released creates a vacuum which sucks the solder up.
Cock the pump, use the iron to melt the connection and put the tip of the pump onto the melted solder then release the trigger.
You might have to repeat the operation several times to clear all of the solder.
An ideal solder should look like a cone with slightly concave sides showing that the solder has flowed through the hole. You can see all the solders here look regular.
Bad joints are noticeably different to the concave cones of good joints. If your joint looks like any of these then it would be wise to remake it.
Bad joints can lead to intermittent connections, or no connection at all.