| The development of lead-free solder has been an urgent task for material scientists due to the lead content of conventional solders is harm to health and environmental. SnAgCu solder is concerned for its excellent combination property. Along with Surface Mount Technology (SMT) has been applied widely in the electronic industry. The fine powders of the solder alloy is one of the key materials in the SMT. With the supersonic atomization device designed by our laboratory, we study on the process parameter about atomizing free-lead solder powder of Sn-Ag-Cu system.The results indicate that Ag, Cu has influence on the solidus temperature, spreading property, electrical conductivity of alloy. The solder showes more favorable combination property as content of Ag is 3% and content of Cu is 2.8%. The spreadability of Sn-3Ag-2.8Cu solder is almost same with Sn37Pb solder, its electrical coductivity is higher than Sn37Pb solder. Cu element can make crystal grain of alloy finer. The thickness of the intermetallic layers of Sn-Ag-Cu with copper plate is thicker than that of Sn37Pb.The creep- rupture life of Sn-3Ag-2. 8Cu solder joint at room temperature could be remarkably increased by minute amount of Ce, even up to 9 times morethan that of Sn-3Ag-2. 8Cu solder joints when content of Ce is 0.1% . Ce element can make crystal grain of alloy finer. The RE compounds appeared in the solder when RE added up to 0. lwt%. It is assumed that Ce will deteriorate the mechanical properties of the solder as content of Ag overrun . Summarily, the most suitable content of Ce is within 0. 05wt. %~0.1wt. % .The optimal processing parameters of atomizing SnAgCu solder powder: way of air draft: two ways, superheat of alloy: 250℃, atomizing agent: N2, the protrusion: h=5mm; inner diameter of delivery tube: 3mm, atomizing gas pressure: 0. 7Mpa. The degree of sphericity of the solder powder is excellent , its surface is smooth, distribution of size is narrow, oxygen content is lower.The optimal processing parameters of atomizing SnAgCuCe solder powder: way of air draft: two ways, superheat of alloy: 200℃, other processing parameters is same with SnAgCu.At the same superheat of alloy , the degree of sphericity of Sn3Ag2. 8Cu solder powder is favorable.It is compared with the SnPb solder powder, and its surface is smoother, compared with the SnPb solder , it possesses higher efficient atomization efficiency and lower oxygen content. Oxygen content of SnAgCuCe solder powder is higher than other powder , its efficient atomization efficiency is higher than SnPb , but lower than SnAgCu.With the superheat increasing, the powder size is gradually decreased,but the oxygen content of powder is rapidly increased.Influences of inner diameter of delivery tube on the properties of solder powder: when inner diameter of delivery tube is 3.0mm , better results have been got in the efficient atomization efficiency, size distribution, particle shape and dispersion. Less than 3.0 mm with the internal diameter decreasing, the powder size significantly reduces and efficient atomization efficiency increases, but size distribution becomes worse. Over 3.0 mm with inner diameter of delivery tube increasing, efficient atomization efficiencyof powder is significantly decreases, size distribution get bad and powder surface becomes coarser and irregularer.Influences of atomizing agent on the properties of solder powder: with helium as the atomization agent, the free-lead solder powder is best in the efficient atomization efficiency, size distribution and particle shape. With nitrogen as the atomizing agent , synthetical property of the powder is favorite . With argon as the atomizing agent, synthetical property of the powder is inferior than nitrogen and helium. With air as the atomizing agent ,the powder is better in the efficient atomization efficiency, but they is coarse in size and their surface is rough .
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