In
electronicsElectronics is a branch of science and technology that deals with the controlled flow of electrons. The ability to control electron flow is usually applied to information handling or device control. Electronics is distinct from electrical science and technology, which deals with the generation,...
,
desoldering is the removal of
solderA solder is a fusible metal alloy with a melting point or melting range of 90 to 450 °C , used in a process called soldering where it is melted to join metallic surfaces. It is especially useful in electronics and plumbing...
and components from a
circuitAn electrical network is an interconnection of electrical elements such as resistors, inductors, capacitors, transmission lines, voltage sources, current sources, and switches....
for
troubleshootingTroubleshooting is a form of problem solving most often applied to repair of failed products or processes. It is a logical, systematic search for the source of a problem so that it can be solved, and so the product or process can be made operational again. Troubleshooting is needed to develop and...
, repair purposes and to salvage components. Electronic components are often mounted on a
circuit boardA printed circuit board, or PCB, is used to mechanically support and electrically connect electronic components using conductive pathways, or traces, etched from copper sheets laminated onto a non-conductive substrate. It is also referred to as printed wiring board or etched wiring board...
and it is usually desirable to avoid damaging the circuit board, surrounding components, and the component being removed.
Specialized tools, materials, and techniques have been devised to aid in the desoldering process.
Desoldering tools and materials include:
- Desoldering braids
- Heat gun
A heat gun is a device used to emit a stream of hot air. They are superficially similar in shape and construction to a hair dryer, though they run at much higher temperatures...
s
- Vacuum plungers (solder sucker
A solder sucker is a device which is used to remove solder from a printed circuit board , as opposed to a desoldering bulb or solder wick. It is usually a small, spring-loaded device that "sucks", as the name implies, the solder off the soldered connection...
s)
- Removal alloys
- Removal fluxes
- Vacuum and pressure pumps with specialized heater tips and nozzles
- Rework stations, used to repair printed circuit boards that fail factory test.
Desoldering requires application of heat to the solder joint and removing the molten solder so that the joint may be separated.
In
electronicsElectronics is a branch of science and technology that deals with the controlled flow of electrons. The ability to control electron flow is usually applied to information handling or device control. Electronics is distinct from electrical science and technology, which deals with the generation,...
,
desoldering is the removal of
solderA solder is a fusible metal alloy with a melting point or melting range of 90 to 450 °C , used in a process called soldering where it is melted to join metallic surfaces. It is especially useful in electronics and plumbing...
and components from a
circuitAn electrical network is an interconnection of electrical elements such as resistors, inductors, capacitors, transmission lines, voltage sources, current sources, and switches....
for
troubleshootingTroubleshooting is a form of problem solving most often applied to repair of failed products or processes. It is a logical, systematic search for the source of a problem so that it can be solved, and so the product or process can be made operational again. Troubleshooting is needed to develop and...
, repair purposes and to salvage components. Electronic components are often mounted on a
circuit boardA printed circuit board, or PCB, is used to mechanically support and electrically connect electronic components using conductive pathways, or traces, etched from copper sheets laminated onto a non-conductive substrate. It is also referred to as printed wiring board or etched wiring board...
and it is usually desirable to avoid damaging the circuit board, surrounding components, and the component being removed.
Specialized tools, materials, and techniques have been devised to aid in the desoldering process.
Desoldering tools and materials include:
- Desoldering braids
- Heat gun
A heat gun is a device used to emit a stream of hot air. They are superficially similar in shape and construction to a hair dryer, though they run at much higher temperatures...
s
- Vacuum plungers (solder sucker
A solder sucker is a device which is used to remove solder from a printed circuit board , as opposed to a desoldering bulb or solder wick. It is usually a small, spring-loaded device that "sucks", as the name implies, the solder off the soldered connection...
s)
- Removal alloys
- Removal fluxes
- Vacuum and pressure pumps with specialized heater tips and nozzles
- Rework stations, used to repair printed circuit boards that fail factory test.
Technique
Desoldering requires application of heat to the solder joint and removing the molten solder so that the joint may be separated. Desoldering may be required to replace a defective component, to alter an existing circuit, or to salvage high value components for possible re-use. Excess application of heat may damage electronic components, or destroy the bond between a
printed circuitPrinted circuit may refer to:* Printed circuit board* Printed Circuit, a synthpop artist* Printed Circuit Corporation, an electronics manufacturer...
trace and the underlying substrate.
A single joint can usually be quickly undone with a soldering iron and use of either vacuum bulb, plunger, or desoldering braid. Once the solder has been melted, the vacuum device is applied to withdraw solder from the joint by a rapid movement of air. Desoldering braid draws up the molten solder by capillary action; the braid usually contains the same
fluxIn metallurgy, a flux is a chemical cleaning agent which facilitates soldering, brazing, and welding by removing oxidation from the metals to be joined. Common fluxes are: ammonium chloride or rosin for soldering tin; hydrochloric acid and zinc chloride for soldering galvanized iron ; and borax for...
as solder.
Multiple-lead devices require special care in removal. For through-hole mounted devices, special soldering bits that facilitate even distribution of heat over all the leads at one time can be used. For factory re-work, a temperature controlled rework station may contain such bits, hot-air systems, and a vacuum system to facilitate removal of the part. Large surface-mounted components require special tooling for production desoldering, although various and improvised methods can be successfully applied for field service. In some instances it is better to destroy the part by cutting off its leads and removing the leads individually, instead of risking damage to the printed circuit board.
Hobbyists may even use a torch or hot air gun to rapidly heat all parts on a board and remove them; such methods are extremely difficult to apply without damaging parts or boards, and may result in toxic fumes. Of course, all soldering work (with flux) involves some amount of toxic fumes, which is why ventilation is important.
Desoldering is used for removal of solder and component from the circuit for troubleshooting repair purposes.
Quad Flat Packs (QFP)
QFPA QFP or Quad Flat Package is an integrated circuit package with leads extending from each of the four sides. It is used primarily for surface mounting ; socketing is rare, and hole mounting is not possible. There are versions having from 32 to over 200 pins with a pitch ranging from 0.4 to 1.0 mm...
chips have thin leads closely packed together protruding from the four sides of the
integrated circuitIn electronics, an integrated circuit is a miniaturized electronic circuit that has been manufactured in the surface of a thin substrate of semiconductor material...
(IC); usually a square IC. Removal of these chips can be problematic. It is impossible to heat all of the leads at once with a standard soldering iron. It is possible to remove them with the use of a razor blade or a high-rpm craft tool, simply by cutting off the leads. The stubs are then easy to melt off and clean with a soldering iron. Obviously this technique entails the destruction of the IC. Another method is to use a heat gun or pencil butane torch and heat up a corner, and gently pry it off, working the torch down the leads. This method often leads to traces getting lifted off the PCB where a lead did not get heated enough to cause the solder to flow.
A system under the JBC brand uses extractor shields that concentrates heat where it needs to be, protect surrounding components and avoids damage to the board or the
QFPA QFP or Quad Flat Package is an integrated circuit package with leads extending from each of the four sides. It is used primarily for surface mounting ; socketing is rare, and hole mounting is not possible. There are versions having from 32 to over 200 pins with a pitch ranging from 0.4 to 1.0 mm...
. The system takes advantage of the properties of
solderA solder is a fusible metal alloy with a melting point or melting range of 90 to 450 °C , used in a process called soldering where it is melted to join metallic surfaces. It is especially useful in electronics and plumbing...
by melting it with hot air. The extractor has an internal spring system that gently pulls the IC when the liquid stage of solder has been reached. The IC is held by a vacuum nozzle similar to the ones used in Pick & Place machines. This system prevents damage to the pads on the
PCBA printed circuit board, or PCB, is used to mechanically support and electrically connect electronic components using conductive pathways, or traces, etched from copper sheets laminated onto a non-conductive substrate. It is also referred to as printed wiring board or etched wiring board...
, the IC, avoids over-heating surrounding components and blowing them off and also removes the risk of having operator errors by using tweezers or other tools that damage the PCB or IC.
Another way to remove one of these devices is to use
Field's metalField's metal, or Field's alloy , is a fusible alloy that becomes liquid at approximately . It is a eutectic alloy of bismuth, indium, and tin, with the following percentages by weight: 32.5% Bi, 51% In, 16.5% Sn....
. Take some of the Field's metal wire, and solder it into all the leads of the chip. Fields metal melts at around 140°F (62°C) — less than water's boiling point. Once it's applied to all the leads, it stays molten, and the chip can simply be lifted off the board. This has the advantage of not damaging the PCB or the IC.