What is Desoldering?

H.R. Childress

Desoldering describes the process of removing solder to separate electrical components. Someone may need to desolder to replace a component or some wiring, or just to remove excess solder from a joint. Either a desoldering pump, sometimes called a "solder sucker," or a solder wick or braid is required to desolder.

Desoldering is a process used to separate items that have been fused together with solder.
Desoldering is a process used to separate items that have been fused together with solder.

To desolder a joint, a person must use a soldering iron as well as one of the desoldering tools. The soldering iron melts the solder so it can easily be removed from the circuit. A 15 to 30 Watt soldering iron usually is best for electronics and circuit boards. Soldering guns should not be used, however, as they could damage circuit boards and electrical components.

Preparation for desoldering is the same no matter which tool is used. The soldering iron should be heated to about 770°F (about 400°C) to desolder electrical components. Its tip should be tinned — that is, coated in fresh solder and then wiped off on a wet sponge.

The hot soldering iron is held to the joint long enough to melt the solder if a desoldering pump is being used. The pump is cocked or primed by pushing down the plunger. It is then held against the joint with melted solder, and when the trigger is pulled, the pump sucks up the solder. If the pump does not get all the solder off the first time, it is sometimes necessary to add fresh melted solder to the joint to loosen the old solder so it will come off with the new.

In one method for using a solder wick or braid, the soldering iron may be used to heat the joint as for a solder sucker, then the wick is placed in the melted solder. Capillary action sucks the solder into the wick material. Alternatively, the solder wick may be placed against the unheated joint, then the soldering iron is pressed against the wick, and the solder is sucked up by the wick material as it melts. This method generally works better for small joints. For either method, the used wick is cut off after it is filled with solder.

A good desoldering job should remove all the old solder so the component can be replaced or so the joint can be resoldered. After the solder is removed, a component may drop off easily or it may need some gentle help from a pair of pliers. Resoldering should be done carefully to prevent the need to desolder again.

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