Soldering

Soldering is a method of joining metal parts using a filler metal of low melting point (solder). Heat is applied to the metal parts, and the soft filler metal is pressed against the joint, melts, and is drawn into the joint by capillary action. After the metal cools, the resulting joints are not as strong as the base metal, but have adequate strength, electrical conductivity, and water-tightness for many uses. Soldering is an ancient technique that has been used practically as long as humans have been making articles out of metal.

Related Topics:
Melting point - Solder - Capillary action

~ ~ ~ ~ ~ ~ ~ ~ ~ ~

Soldering can be done in a number of ways, including passing parts over a bulk container of melted solder, using an infrared lamp, or by using a point source such as an electric soldering iron or brazing torch. A flux is usually used to assist in the joining process. This flux can be manufactured as part of the solder in single or multi-core solder. It does not matter whether you use single-or multi-core solder.

Related Topics:
Infrared - Electric - Soldering iron - Brazing - Flux

~ ~ ~ ~ ~ ~ ~ ~ ~ ~

One application of soldering is making connections between electronic parts and printed circuit boards. Another is in plumbing. Joints in sheet-metal objects such as cans for food, roof flashing, and drain gutters were also traditionally soldered. Jewelry and small mechanical parts are often assembled by soldering. Soldering can also be used as a repair techniqe to patch a leak in a container or cooking vessel.

Related Topics:
Printed circuit board - Plumbing - Jewelry

~ ~ ~ ~ ~ ~ ~ ~ ~ ~

Soldering is distinct from welding in that the base materials to be joined are not melted, though the base metal is dissolved somewhat into the liquid solder much as a sugar cube into coffee - this dissolution process results in the soldered joint's mechanical and electrical strengths. A "cold solder joint" with poor properties will result if the base metal is not warm enough to melt the solder and cause this dissolution process to occur.

~ ~ ~ ~ ~ ~ ~ ~ ~ ~

Due to the dissolution of the base metals into the solder, solder should never be reused; once the solder's capacity to dissolve base metal has been achieved, the solder will not properly bond with the base metal and a cold solder joint with a hard and brittle crystalline appearance will usually be the result. It is good practice to remove all used solder from a joint prior to resoldering - desoldering wicks or vacuum desoldering equipment can be used.

~ ~ ~ ~ ~ ~ ~ ~ ~ ~

The lower melting point of solder means it can be melted away from the base metal, leaving it mostly intact though the outer layer will be "tinned" with solder which can only be removed by abrasive or chemical processes. This tinned layer will later flow into a new joint, resulting in a satisfactory base metal concentration in the joint, as well as making the new solder flow very quickly and easily.

~ ~ ~ ~ ~ ~ ~ ~ ~ ~

Brazing is similar to soldering but uses higher melting temperature alloys, based on copper, as the filler metal.

~ ~ ~ ~ ~ ~ ~ ~ ~ ~

"Hard soldering", or "silver soldering" (performed with high-temperature solder containing up to 40% silver) is also a form of brazing, even though the term "soldering" is more often used, even though it is incorrect.

~ ~ ~ ~ ~ ~ ~ ~ ~ ~

Since lead used in traditional solder alloys is toxic, much effort in industry has been directed to adapting soldering techniques to use lead-free alloys for assembly of electronic devices and for potable water supply piping.

~ ~ ~ ~ ~ ~ ~ ~ ~ ~