Soldering

Soldering (pronounced sod-der-ing in the United States) is a method for joining two pieces of metal. It can be used to join different types of metals and creates strong bonds with copper, tin, brass, and steel. It is an ancient technique that has been adapted to modern times; soldering is commonly used to join components of electronic circuitry such as those in computers and other high-tech devices. It is accomplished by heating a filler metal, known as solder. The solder is heated to an appropriate temperature with a tool called a soldering iron and then used to span the distance between the two metals to be joined, filling in the space and forming a permanent bond. Soldering is a form of brazing, another technique for joining metals, but both soldering and brazing are different from welding.

Background

The word solder comes from the Latin solidus, which means "solid." That became the Latin solidare, which means "fasten together." When the Latin was adopted into Old French, it became souder, which was Anglicized to solder with the contemporary meaning about the year 1350, and entered the English language during the nineteenth century. While some English-speaking countries pronounce the l, it is silent in the United States.

The origins of soldering are unknown, but the process became possible when lead was discovered as a by-product of silver manufacturing. Archaeological evidence indicates that the Mesopotamians were using lead to join other metals about 3000 B.C.E., and the Egyptians were known to use soldered tin about 2000 B.C.E.

Archaeologists have found numerous artifacts that indicate the use of soldering during the time of the Roman Empire from around the first century B.C.E. to the fifth century C.E. Pipes and pumps used in water systems with evidence of soldering with tin and lead have been found. Some soldering has also been identified in the joints of posts used in construction.

While many crafts and forms of technology disappeared for a time during the Middle Ages, soldering remained in use. It was very important in the construction of the elaborate stained glass windows that decorate and served as a form of religious education in huge medieval churches. Historical records indicate the existence of tinsmiths and other trades that would have involved soldering during this time as well.

Soldering remained a useful trade as the Middle Ages gave way to the Renaissance and the Age of Discovery. It was important in many early technological inventions such as the steam engine. The development of electronics in the latter part of the twentieth century provided a new use for soldering as it was the best way to fasten small electrical components in new devices such as telephones and computers. Soldering continues to be important in the twenty-first century. It is used in many situations when different types of metals have to be joined. It also continues to be an important process in the manufacture of electronics.

Overview

Soldering is one of three forms of joining pieces of metal that involve heat. These are known as welding, brazing, and soldering. Each has specific applications for which they are best suited.

Welding uses high heat to join the metals, which must be of similar composition. The welder applies the heat that melts the metals and presses them together so that when they cool, they are joined. While welding can use a filler metal to help create the bond, it is most often accomplished by melting the two metal pieces to be joined. Welded joints are very strong because welding effectively reforms the joint into one solid piece. Welding can also be used to cut metal; the metal is heated until it melts, creating a separation or opening in the metal.

Brazing creates a joint between two metals by applying heat to a filler metal that seals the gaps between the two metals and forms a bond. Unlike welding, the two metals can be different types. Brazing also causes less damage because the filler metal melts at a lower temperature than either of the two metals being joined. This prevents any damage to the original metal surfaces and provides a strong bond, though not as strong as a welded joint.

Soldering is a form of brazing. It can also join two dissimilar metals and also uses a filler metal. The difference between brazing and soldering is in the temperature needed to melt the filler material. Soldering can be accomplished at lower temperatures of less than 840 degrees Fahrenheit (about 450 degrees Celsius), while brazing requires higher temperatures. The joints created by soldering are not as strong as those created by either welding or brazing. However, it is a preferred method where the connection itself, rather than its strength, is the primary consideration. This is why soldering is often used in electrical components. It provides a satisfactory connection that, with the right form of solder, also conducts electricity (or allows electricity to pass through it). This can often be accomplished with a comparatively low temperature solder.

The several types of soldering are categorized by the degree of heat and type of metal alloy used as a filler. They are soft soldering, hard soldering, and silver soldering.

Soft soldering uses a gas torch to heat the tin-lead alloy used as the filler, or solder. This melts at a temperature below 752 degrees Fahrenheit (400 degrees Celsius). It can be used for small, intricate connections where the materials to be joined have lower melting temperatures and high heat cannot be used.

Hard soldering is used with materials that can handle a higher temperature of around 840 degrees Fahrenheit (450 degrees Celsius). The filler material, which is also appropriate for use with higher heat, flows into the small pores of the pieces to be joined. This helps create the bond between the pieces.

Silver soldering uses a filler material made with silver, as the name implies. In some cases, the heat will be applied indirectly to the back of one of the surfaces to be joined. This melts the thin strip of silver fill laid against the joint and allows it to flow across the open joint. The silver fills the gaps and pores, creating a joint. This type of soldering is most often used for making small fittings for electronics and other devices and in jewelry making.

Bibliography

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