Solder

- information, tutorial, article about solder, what it is, how it can be used in electronics construction and manufacture and what it is made from.

Solder is an essential material for the electronics industry. Without solder the assembly methods currently used in the manufacture of electronics equipment would need to completely change. Apart from being used in the electronics industry, solder is also used in plumbing and many other areas such as in jewelry, where metals need to be joined together.

The word solder comes from the middle English word "soudur" which in turn came from the Latin "soldare" meaning to make solid.

What is solder?

Solder is a fusible metal alloy. Often it consists of tin and lead, although the use of lead based solders was banned in the European Union on the 1980s. Under the Restriction of Hazardous Substances (RoHS) directive lead free solder is required. (Lead free solder and its use is outlined on another page in the Electronics manufacture section of this website.) However traditional tin lead based solders are still in widespread use in many areas.

The melting point of solder used in electronics is below 450C, often around 200 - 250C for electronics applications, and there are often low melting point solders for special low temperature applications. These typically have melting point temperatures of around 200C.

Solder is able to melt at a point much lower than either of its constituents. The reason for this is that solder is what is known as a Eutectic or eutectic mixture. This is a mixture of two or more elements that has a lower melting point than any of its constituents. The actual mechanism is an involved chemical concept and is beyond the scope of this website.

The traditional form of solder used for electronics manufacture, production and general construction was a 60 / 40 mix of tin and lead respectively. This provided a sufficiently low temperature melting point consistent with a high yield of good joints.