What Is Solder Made Of?

Solder is not the name of a particular metal. Solder is any soft metal used to join two harder metals together via melting and fusing to the parts of the joint. Many different alloys and pure, elemental metals are used for soldering. Many of the alloys combine some other metal with lead, as lead is very soft and is easy to shape.

Although lead is the most common component of the various kinds of solder, it is not the only kind of metal commonly used. Tin is also a very common component of solder alloys, as it is easy to shape, is stronger than lead, and lacks lead’s toxic properties. Silver and copper are other common metals, especially for brazing, a method that produces corrosion-resistant joints at high temperature. Most solder alloys contain at least one of those four metals; many possess them in combination. Zinc is another common component; zinc alloys are especially used as solders for aluminum and steel.

One of the most common solder alloys in use is composed of 60 percent tin and 40 percent lead. An alloy of 63 percent tin and 37 percent lead is commonly used for electrical work. Prior to 1986, the most popular solder used for joining plumbing pipes in the United States was an alloy made of half tin and half lead. Due to legal restrictions on this solder with high lead content, lead-free alloys have become more popular in plumping applications since then.