Coating of high-efficiency lead-free soldr particles with antioxidation film and its evaluation

球形铜颗粒被用作无铅焊料颗粒的模型颗粒。通过使用球磨机的干式机械方法用蜡粉涂覆铜颗粒，并且在铜颗粒的表面上形成抗氧化膜。使用通过对单个颗粒的无侧限压缩试验测量的铜颗粒的压缩能和应变之间的关系来评估在膜形成处理期间施加到铜颗粒的机械能。以铜颗粒不易变形的能量为依据，确定了球磨机在加工过程中的最佳操作条件。将涂有蜡的铜颗粒浸泡在稀硝酸溶液中的洗脱试验证明，颗粒上的蜡膜阻止了铜洗脱到硝酸溶液中。锡锌合金颗粒是无铅焊料的代表性颗粒之一 ...更多信息 使用相同的方法用蜡粉涂覆的铜颗粒比铜颗粒更软。通过将助焊剂与蜡涂覆的合金颗粒捏合来制备焊膏，并在低温和室温下储存给定的时间段。将浆料在铜板上熔融以评价润湿性。结果表明，蜡膜的存在有效地防止了合金颗粒的氧化，使含蜡合金颗粒的焊膏具有良好的润湿性，并采用毛细管流变仪对焊膏的流动性进行了评价。为了研究浆料中的颗粒含量、蜡涂层和颗粒形状（颗粒的应变）对流动性的影响，在各种条件下测量浆料从毛细管的出口速度，然后确定粘度系数。结果表明，即使颗粒含量为89.5重量%（对应于50体积%），流动性也得到保持，并且随着颗粒变形（应变）的增加而降低。含应变小于0.1的颗粒和膜厚小于1μm的涂蜡颗粒的浆料的粘度系数几乎与未处理的球形颗粒的粘度系数相等。事实证明，本研究开发的机械加工方法能够实现高效无铅焊料颗粒的粉末设计。少

Spherical copper particles were used as model particles of lead-free solder particles. The copper particles were coated with wax powder by means of a dry mechanical method using a ball mill and the antioxidation film was formed on the surface of copper particles. The mechanical energy applied to the copper particles during the film formation processing was evaluated using the relationship between the compressive energy and the strain of a copper particle, which was measured by the unconfined compression test for a single particle. The optimal operating conditions of the ball mill in the processing were determined based on the applied energy in which the copper particles hardly deformed. The elution test in which the wax-coated copper particles were soaked in a dilute nitric acid solution proved that the wax film on the particles prevented the elution of copper to the nitric acid solution. The alloy particles of tin and zinc which were one of the representative lead-free solder particle … More s and were softer than the copper particles were coated with the wax powder using the same method. The solder paste was prepared by kneading the flux with the wax-coated alloy particles and stored at low and room temperatures for a given period of time. The pastes were melted on a copper plate to evaluate the wettability. The results showed that the wax film prevented the oxidation of the alloy particles and the paste including the wax-coated alloy particles had the satisfactory wettability.The flowability of the solder pastes was evaluated with a capillary rheometer. In order to investigate the influence of the particle content in the paste, the wax coating and the particle shape (the strain of particles) on the flowability, the exit velocity of the paste from the capillary was measured under various conditions and then the viscosity coefficient was determined. The results showed that the flowability was maintained even though the particle content was 89.5 wt% (corresponding to 50 vol%) and decreased with increasing in the particle deformation (the strain). The viscosity coefficients of the pastes including the particle having the strain less than 0.1 and the wax-coated particles in which the film thickness was less than 1μm were almost equal to that of untreated spherical particles. It has been proved that the mechanical processing method developed in this study enables the powder design of high-efficiency lead-free solder particles. Less