Application of molybdenum in electronic industry
Molybdenum was used in the early electronic industry. With the emergence of solid-state electronics, a new application field is gradually formed; the current application depends on the metal's high melting point, high heat transfer, machinability, strength and sinter ability. Some of these applications are equipment and tools for manufacturing electronic components.
Manufacturing equipment and tools
Molybdenum tile is used as sintered ceramic substrate and multilayer ceramic circuit. Molybdenum is processed to close to tolerance and keeps its smoothness at high sintering temperature, so that the size of sintered product is within tolerance.
Another important application of manufacturing equipment is the arc cavity of ion implantation device. Various ions including B, P, O and As can be deposited by this method. The arc cavity is a part of the implanter. It must resist the influence of temperature and sputtering to produce ions, so that the geometry of the chamber must be stable, and the ion beam will not be polluted by the chamber material. Molybdenum, with high melting point and good mechanical properties, is the primary structural material of various devices.
Multilayer ceramic (MIC) package
In the mid-1960s, IBM introduced MIC packaging technology as a way to improve the performance and maintainability of its host computer. The manufacturing process starts from the unfired alumina sheet, which is cut into a single package layer, and then perforated to form a vertical annular joint cavity or pass between the two layers. By filling the channel and shielding with molybdenum, the circuit which only exists in each layer is deposited on the raw ceramic. The ink used in the process is a mixture of molybdenum powder and organic binder.
Once the unprocessed sheet metal is dried, the layers are overlapped to form a three-dimensional circular arrangement, which is compressed and layered, and sintered at > 1500 ℃ to make the structure dense and adhesive. During sintering, the delamination undergoes a linear shrinkage of up to 17%, while each single layer and the circular track of the channel passing through each layer remain straight. At present, MC package is being manufactured with more than 70% special layer.
Heat treatment in electronic package
Because molybdenum has good thermal conductivity and low coefficient of thermal expansion. The thermal expansion coefficient of molybdenum and silicon is well matched, the cost of molybdenum is lower, and the plasticity is better than that of tungsten, so it is used in many semiconductor components. The higher thermal conductivity of molybdenum can also better heat removal, so that the equipment can operate at higher power and prolong its service life.
The hundreds of millions of small diodes used in the rectifier bridge are made of molybdenum heat sink. The powder treatment technology is the key factor for the powder produced for special purpose.
Recently, Cu Mo composites have attracted people's attention. The impregnation, infiltration, liquid sintering and powder compaction of pre sintered molybdenum framework are all used by different manufacturers to produce this composite. This kind of structure is more mechanically stable than that of copper clad molybdenum and is easy to process due to its good thermal stability when the Cu / Mo ratio is high. One disadvantage of this composite component is that the properties of the finished product are sensitive to the manufacturing method. Therefore, the copper / molybdenum ratio on the surface of products from different manufacturers is the same, but the physical properties may be different.
Film metallization (spray plating)
Molybdenum is also used in various electronic components, including metal spray plating of ceramic substrates, deposition of multiple modules and metallization of silicon components. The emergence of high-capacity memory chips has promoted the development of ultra-high-purity molybdenum and tungsten, and eliminated several parts per million of radioactivity and the performance degradation caused by metal spray coating diffusion into silicon components. The requirements for the target are as follows: (1) no defect. The porosity and the second phase particles reduce the uniformity and purity of the coating, thus reducing the productivity.② High purity. Impurity elements will reduce the conductivity of the circuit track, thus reducing the performance of the device. It may also affect the performance of semiconductor contacts.
Flat panel display (FPD)
Molybdenum also plays an important role in FPD technology. There are several forms of FPD on the market. The most common type is active matrix liquid crystal display (LCD). However, field emission display (FED), electro fluorescence display (EFD), plasma display panel, thin cathode ray tubes (RTs) and vacuum fluorescent display (VFD) are the most common types.
Optical display has the advantages of low power consumption such as clarity, brightness, portability and durability. At present, the annual sales volume of the display market is about 10 billion US dollars, and the standard display size is more than 400 mm < 400 mm. Experiments show that FPDs can be used to make large high definition TV screen.
The key to feds is the electronic power supply of the so-called field emitter. This kind of small transmitter belongs to the special or gate electrode whole control column. The transmitter space is much smaller than the screen image size. The display screen is smaller than conventional TV screens using high and low-pressure phosphors. The main difference between CRTs and FPDs is the way in which the display generates electrons. Instead of thermal emitters that require a lot of power, FPD uses a launch system that contains a large number of (up to 500 × 106) endpoints that eject electrons from very close proximity to a flat screen, allowing for minimal shape factor.
Fed combines the advantages of FPDs and traditional CRT display.
(1) The display can switch pixels one by one and control the total image.
(2) The voltage is nonlinear.
(3) Pixels have redundant matrix grids, and if one of the sub components fails, the pixels are still working.
(4) There is no need for heater to reduce heat load and power demand.
(5) Production requires a minimum of processing steps to reduce production costs.
(6) The display has high spatial resolution and high image definition.
(7) The display is not sensitive to the temperature range when the operating range is widened.
(8) The design has high current density capacity.
(9) The extremely thin flat form greatly increases the choice of display development.
At present, the emitter head is made of molybdenum deposition layer, so molybdenum evaporation technology strongly affects the size and quality of FPD. Electron beam evaporation is a line of sight covering method. When combined with emission technology, it is the most suitable method for molybdenum endpoint deposition. The molybdenum coating rate depends on the evaporation power and the distance between the source and the substrate, and it is almost linear with the power for dense and diffused electron beams. According to the increase of FPD size and the requirement of optimum deposition angle of 85 ° to 90 °. The uniformity of the molybdenum coating from the center to the corner is also important to the quality of FPD, which makes the design of electron beam as important as the quality of molybdenum target.
