Soldering - Tools

Tools

In principle any type of soldering tool can carry out any work using solder at temperatures it can generate. In practice different tools are more suitable for different applications.

Hand-soldering tools widely used for electronics work include the electric soldering iron, which can be fitted with a variety of tips ranging from blunt to very fine, to chisel heads for hot-cutting plastics rather than soldering. The simplest irons do not have temperature regulation; small irons rapidly cool when used to solder to, say, a metal chassis, while large irons have tips too cumbersome for working on PCBs and similar fine work. Temperature-controlled irons have a reserve of power and can maintain temperature over a wide range of work. The soldering gun heats faster but has a larger and heavier body. Gas-powered irons using a catalytic tip to heat a bit, without flame, are used for portable applications. Hot-air guns and pencils allow rework of component packages which cannot easily be performed with electric irons and guns.

For non-electronic applications soldering torches use a flame rather than a soldering tip to heat solder. Soldering torches are often powered by butane and are available in sizes ranging from very small butane/oxygen units suitable for very fine but high-temperature jewelry work, to full-size oxy-fuel torches suitable for much larger work such as copper piping. Common multipurpose propane torches, the same kind used for heat-stripping paint and thawing pipes, can be used for soldering pipes and other fairly large objects either with or without a soldering tip attachment; pipes are generally soldered with a torch by directly applying the open flame.

A soldering copper is a tool with a large copper head and a long handle which is heated in a blacksmith's forge fire and used to apply heat to sheet metal for soldering. Typical soldering coppers have heads weighing between one and four pounds. The head provides a large thermal mass to store enough heat for soldering large areas before needing re-heating in the fire; the larger the head, the longer the working time. Historically, soldering coppers were standard tools used in auto bodywork, although body solder has been mostly superseded by spot welding for mechanical connection, and non-metallic fillers for contouring.

Toaster ovens and hand held infrared lights have been used by hobbyists to replicate production soldering processes on a much smaller scale.

Bristle brushes are usually used to apply plumbing paste flux. For electronic work, flux-core solder is generally used, but additional flux may be used from a flux pen or dispensed from a small bottle with a syringe-like needle.

Wire brush, wire wool and emery cloth are commonly used to prepare plumbing joints for connection. Electronic joints are usually made between surfaces that have been tinned and rarely require mechanical cleaning, though tarnished component leads and copper traces with a dark layer of oxide passivation (due to aging), as on a new prototyping board that has been on the shelf for about a year or more, may need to be mechanically cleaned.

Some fluxes for electronics are designed to be stable and inactive when cool and do not need to be cleaned off, though they still can be if desired, while other fluxes are acidic and must be removed after soldering to prevent corrosion of the circuits. For PCB assembly and rework, either an alcohol or acetone is commonly used with cotton swabs or bristle brushes to remove flux residue after soldering. A heavy rag is usually used to remove flux from a plumbing joint before it cools and hardens. A fiberglass brush can also be used.

A heat sink, such as a crocodile clip, can be used to prevent damaging heat-sensitive components while hand-soldering. The heat sink limits the temperature of the component body by absorbing and dissipating heat (reducing the thermal resistance between the component and the air), while the thermal resistance of the leads maintains the temperature difference between the part of the leads being soldered and the component body so that the leads become hot enough to melt the solder while the component body remains cooler.