Method for refining and homogeneously distributing alloying partners and for removing undesirable reaction products and slags in or from soft solder during the production of fine solder powder

摘要

The invention relates to a method for refining and homogeneously distributing alloying partners and for removing undesired reaction products such as oxides and/or slag in or from soft solder during the production of fine solder powder, in which the solder alloy is melted in a high temperature-resistant plant and/or animal oil, the melt is moved to another container of oil with a temperature of at least 20° C. greater than the liquidus temperature, stirred there, and subjected to multiple shear treatments using rotors and stators for forming a dispersion comprising solder balls and oil, from which dispersion the solder balls are separated by means of subsequent sedimentation. The object of the invention is to prevent with certainty reaction of the lanthanoids with oxygen, nitrogen, and other reaction partners during processing of lead-free soft solder alloys into fine solder powders, to avoid agglomeration of the reaction products in the matrix of the solder balls, and to distribute the alloying partners finely dispersed and homogeneously in the matrix of the solder balls. The inventive method includes the following steps: a) Use of the oil as a separating medium for melt and reaction products and/or slag and for releasing the latter when the solder is melted; b) Build-up of the released reaction products and/or slag in the oil due to differences in density between melt and reaction products and/or slag in accordance with step a); c) Separation of the oil with the reaction products and/or slag by draining the melt into the other oil container at a temperature of at least 20° C. greater than the liquidus temperature and suctioning of the oil with the reaction products and/or slag; d) Driving out the reaction products and/or slag still present in the interior of the solder melt by enlarging the surface area of the solder melt during shearing with stators at a circumferential speed of 15.0 to 25 m/s while maintaining a melt-to-oil volume ratio of 1:20 to 1:50; e) Build-up in the oil of the reaction products and/or slag from the interior of the solder melt during shearing due to differences in density in accordance with step b); f) Turbulent mixing of the remaining solder melt during a cycle period of 10 to 30 minutes for homogeneous distribution of the alloying partners in the solder, g) Separation of the built-up reaction products and/or slag in accordance with steps c) and e) together with the oil after the solder balls have settled.