Solder, << SOD uhr, >> is a metal alloy used to join metal surfaces together (see Alloy ). It is also used to mend metal objects. To be effective, the solder must melt more easily than the metals to which it is applied and must adhere to the materials being joined.
There are two types of solder, hard and soft. Hard solders will melt only at high temperatures. The advantage of hard solders is their strength and the fact that they can be pressed or hammered into various shapes without breaking. Some hard solders are drawn out into long threads, and others are pressed into sheets. The most common hard solder is silver solder, which consists of silver, copper, and zinc. Many copper alloys also are used as hard solders.
Soft solders will melt at low temperatures. But they are weak and cannot be hammered without breaking. The most common soft solders include various alloys of tin and lead. These alloys also contain other metals, such as antimony, cadmium, bismuth, and silver.
Researchers have developed many special solders for joining unusual material combinations, such as glass and ceramics. These solders combine the chemical element indium with either tin or silver. Gold-based solders are used in the assembly and sealing of semiconductor devices.
