The skill of desoldering is a very useful skill to possess. If you can solder, you will at some point need to know how to desolder components that are wrong or need replacing and you can cause a lot of damage with a hot soldering iron if you don’t do it properly, usually as a cause of applying to much heat.
It’s perfectly possible to remove a component without damaging it either through heat or mechanically by using too much force. Sometimes a part is damaged so damaging it further won’t make any difference but the biggest problem that I have encountered or at least used to in the early days is damaging the board.
You can replace components but PCB damage is more difficult to put right. The reason circuit boards get damaged in desoldering is because of the heat that is used. You must be careful not to apply the iron longer than you would for normal soldering. If you have to, stop and let it cool down and have another go. The copper on a printed circuit board is bonded onto the insulating board material, usually fiberglass or SRBP (synthetic resin bonded paper) with basically a type of glue that gives way if overheated. Once the track or pad has come away from the board the components movement can break the track.
The pad can also get broken when you try to remove a component that hasn’t been completely desoldered. The remaining solder can pull off a pad or part of it.
This is certainly something you DON’T want to do. It can prove very difficult to try to repair a heat damaged circuit board and most methods are at best Heath Robinson and don’t provide long term reliability so don’t damage them in the first place. If a component is damaged or is so cheap as not to bother reusing it can be easier to remove if you essentially damage it first. Things with lots of leads are usually a prime candidate for this method basically if you cut the leads off the component but leave enough in the board it can be a lot easier to remove then if you leave them. This was the first way I was taught to desolder and it can actually be done without using any specific desoldering tools so it’s the first method I’ll discuss.
To remove something such as a resistor you can cut the component lead near to the body. Do this on both sides of the component to get it out of the way them trim the leads close to the board component side. If you turn the board around now to the pad side and apply your soldering iron to the joint along with some fresh solder as the solder and the old joint melts pull the tip of the iron away and the remaining component lead will usually come away with it. Do it quickly as if you were resoldering and you won’t damage the board. This is one of the most basic techniques of how to desolder components.
There are other ways using tools that make removing components easier. one of the most popular is to use a desoldering pump. For a guide on buying and using a desoldering pump read here.
Learning how to desolder components is definitely a skill that will improve with practice so give it a go on old circuit boards first.
One of the safest ways of desoldering is to use solder wick, also known as solder braid, details of this method are shown on the page what is the best desoldering braid.