How is indium used in indium bonding?

Indium fundamental properties

Indium is a silver-white and bluish metal, very soft (softer than lead). Its chemical properties are similar to iron, and it can react slowly with oxygen in the air between room temperature and melting point, thus forming a very thin oxide film on the surface. Its melting point is 156.61℃, boiling point is 2080℃, density is 7.3 grams/cubic centimeter, good ductility and conductivity, plasticity, can be pressed into extremely thin sheets.

Indium is a rare metal, and its content in the Earth's crust is similar to that of silver (1× 10-5%), but its yield is only 1% of that of silver. Indium minerals in the Earth's crust mainly include: sulfur indium copper mine, sulfur indium iron mine and water indium ore. In nature, indium minerals are dispersed and associated with other minerals in trace form, so far no single or indium as the main component of natural indium deposits have been found. About 50 kinds of minerals have been found to contain indium, among which the minerals with the highest indium content and industrial recovery value are mainly lead-zinc ores containing sulfur. In addition, cassiterite, wolframite and common amphibole often contain more indium. The content of indium in sphalerite is generally 0.001% ~ 0.1%, sometimes as high as 1%.

High purity indium application fields

Indium has a wide range of applications, especially in the high-tech field. The transparent electrode made of indium-tin-oxide (ITO), the main product of Indium, is widely used in the electronic information industry to make thin-film transistors, liquid crystal displays, plasma displays, etc. More than 50 percent of the world's indium is currently used to make liquid crystal products. Indium antimonide and indium arsenide can be used for infrared detection, optomagnetic devices, magnetoresistors and solar energy converters, etc. Indium phosphide is used in microwave communication, optical fiber communication laser light source and solar cell materials. Selenium-indium-copper polycrystalline films are used to make solar cells, in which indium is added to the anode material to protect against corrosion.

Indium can be alloyed with many metals. Silver-lead-indium alloy can be used to make bearings for high-speed aero-engines; Indium-tin alloy can be used as vacuum sealing material and low melting point alloy contact material, as a binder between glass and glass or glass and metal; Alloys with low melting points, such as Wood alloys, can be lowered by adding indium: alloys of gold, palladium, silver and copper with indium are used to make dentures and ornaments.

Indium telluride powder is used for bonding

At present, the mainstream target binding process adopts the material with low melting point and good electrical conductivity, thermal conductivity, fluidity and infiltration as the binding material. The commonly used material is indium (In), which has a low melting point (156.61℃) and has very good fluidity and infiltration. Using indium binding target material to avoid when the sputtering target material loss, the need to control a certain amount of sputtering power, but in the process of sputtering target materials sputtering power is one of the major influential factors of film-forming rate. 

In these days of coating preparation, using the high speed of sputtering target materials has become the main means to reduce costs, improve requires the sputtering power, sputtering rate Then the surface temperature of the target and the temperature of the coating cavity will also increase. Most of the existing target backplanes are simple in design and have no good cooling system, so the heat of the sputtering surface of the target cannot be taken away through the cooling system, and the target is prone to fall off due to the melting of the binding layer. Therefore, the target used in high temperature environment has higher requirements on the melting point of the binding layer.

Silver and copper are eutectic alloys with mutual solid solution boundaries. Copper exists in the form of solid solution in silver, which has good wettability, good strength, ductility, thermal conductivity, electrical conductivity and corrosion resistance, and has a high melting point (600 ~ 950℃), low price, which is a very good binding material. However, the higher the melting point of the binding material means the higher the temperature of the binding operation, and the conventional binding method usually requires manual operation, which cannot be carried out in such a high temperature environment, and the welding material is easy to oxidize in the high temperature environment, so it is difficult to ensure the binding quality.