Study On Supersonic Atomization Theory And Production Of Solder Alloy Fine Powder

Surface Mount Technology(SMT) has been applied abroad in electronic industry.The fine powders of the solder alloy are one of the key materials in the SMT, the requirement as following: the particle diameter is in 5 u m~ 74 u m, the shape is spherical and the distribution of the particle size is uniform. We have developed a set of supersonic atomizing equipment with the base theory of the supersonic atomization and the base characteristic of the solder alloy. The paper studies systematic the production technology and process of the solder alloy fine powders in the equipment, and deduces the gas velocity formula used in supersonic atomization in theory. Then the paper also study the atomizer structure (the protrusion of the delivery tube value h), atomizing gas pressure P, over-heat temperature of alloy A T, the component of solder alloy and atomizing medium and so on.The results indicate: (1) the gas flied of the supersonic atomizer under the delivery tube forms an inverse vortex taper. The negative pressure exists in theinverse vortex taper. The field emerges two-peak distribution of symmetry about axis in two-dimensional space. (2) The atomizing gas velocity formula that has been revised can meet the requirement of the supersonic atomization. (3) The most principal factors that influence the supersonic atomization process include the flow ratio of the gas-liquid metal(GMR)value, the flow of atomizing of gas and the range of the inverse vortex taper. The more of the value of three factors, the more advantage they are for the atomization and the more fine the powders are. (4) the produced powders are the best in efficient atomization efficiency, particle diameter, particle shape and dispersion when the solder alloy is ZHL63A, atomizing medium is N2, the protrusion h=6.0mm, atomizing gas pressure P=100MPa, over-heat temperature △ T=167℃(T=350℃).