Plasma Atomization Technology


The Sn phase responded with the Cu path and was completely consumed in 5 minutes, leaving the only Cu6Sn5 intermediate phase in the joint. Such intermetallic interconnections can therefore be used at high temperatures (over 400 ° C). Many researchers found ways to obtain the joints at a high melting temperature in a relatively short time. Cu substrates connected with a Sn layer of 50 μm (Cu / Sn / Cu sandwich structure) at 260 ° C for 4 hours, leaving the Cu6Sn5 and Cu3Sn phases at the joint. Yin et al. selected the 10 μm Sn layer as the weld layer and obtained the entire Cu3Sn joint at a high temperature of 500 ° C for 3 minutes. Hu et al. used the Sn-coated Cu core scales mixed with flow as the weld layer and then obtained the joints consisting of Cu6Sn5 and Cu3Sn phases for 12 minutes at 250 ° C.

In Figure 5c, the internal microstructure of the strip-shaped powder showed the characteristic of directional growth from surface to center and was relatively uniform in size. Similarly, the internal microstructures of powders with a diameter of 38 μm, 34 μm and 22 μm were basically the same as those with a size of 82 μm, 70 μm and 59 μm respectively. From a combustion perspective, the atomizing current is not consumed in the combustion process, but is kept at high temperature during the residence time.

Furthermore, the speed of air flow changes more diversified due to the existence of many vertebrae on a small scale. Only within the 16mm length from the recirculation zone, the air flow rate underwent three changes, first increasing and then decreasing. Compared to drops of approximately 82 μm and 43 μm, the growth of the Cu3Sn nucleus of the 37 μm drops was relatively limited because the flight distance was further from the nozzle and the temperature gradient was lower. For example, the Cu3Sn nucleus could grow to a certain size along the surface and in the fall until the temperature was reduced to TP, followed by incomplete peritectural coagulation and coagulation of eutectics η + β.

Because the atomization process ensures a complete mixture of fuel and air droplets, the combustion process is characterized by low soot formation, low flame radiation, and clean combustion products. This form of fall formation is associated with a reduction in the influence of surface tension and a greater effectiveness of aerodynamic forces. At even higher speeds, the atomization process is reinforced by the effect of relative movement between the beam surface and the surrounding air. This aerodynamic interaction causes irregularities in the previously smooth liquid surface. These irregularities or ruffles on the surface of the beam are amplified and eventually separated from the surface of the liquid, as illustrated in Figure 1c.

The distribution of the size of the powder produced varies from 0 to 150 µm with a large majority between 0 and 106 µm or from 0 to 75 µm, depending on the configuration and provides excellent flow. In addition, our powder is sieved according to the requirements of each client and each batch is tested, mixed for homogeneity and certified for packaging. During the gas boron nitride ceramic, molten steel is atomized, for example, into fine metal droplets, which cool during its fall into the atomizer.

Based on 45 years of field experience, the author assesses the range of methods available for this purpose, their benefits and limitations, and the likely areas of application. The swivel hood is a common atomizer for large industrial paint stores due to its increased efficiency. As we learned with the pneumatic gun, the amount of air applied and the geometry of the hood is critical to atomization. For a rotary call atomizer, the diameter of the bubble glass, the speed of the rotating bell, and even the type of bell glass edge geometry will have a major impact on atomization.

The air in the cartridge can also be applied to shape the aerosol, allowing better axial spray coverage on the tablet bed. Atomizing water at ultra high pressure, as the name implies, involves the use of very high water pressure, typically in the 100-200 MPa range. At such pressures, the water jets are supersonic, moving at speeds of 400–500 ms – 1, and the atomization is due in part to the shock waves surrounding the water jets. It is normally performed in a gas-inert atomizing chamber and allows the production of very fine steel powders with average particle sizes of around 10 μm.

Water atomization is widely used for stainless steel, but superalloys require vacuum inert gas atomization . The pure Cu6Sn5 powders obtained can be used in many areas, such as additive production and three-dimensional electronic packaging. Here, these Cu6Sn5 intermetallic powders were used for high temperature interconnection to replace traditional Sn-based welding alloys with low service temperatures. The entire construction was placed in a tube oven under an inert gas atmosphere at 240 ° C for 5 minutes. The SEM image of the cross section of the interconnection is shown in Figure 9b.

At higher flow rates, the ligaments form along the entire periphery and then break down into droplets according to the Rayleigh mechanism. With a further increase in flow, the state is finally reached where the ligaments can no longer absorb fluid flow, and a thin, continuous sheet forms that extends beyond the edge of the disc. This sheet eventually breaks down into ligaments and drops, but because the ligaments form from a frayed edge, the resulting spray is characterized by a wide range of drop sizes. The three liquid properties relevant to atomization are density, surface tension, and viscosity.