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Analysis of Technological Properties and Influencing Factors of Electronic Solder (Part 2)
Therefore, the technological properties of solders include many aspects. It is necessary to make a dialectical and comprehensive analysis of these properties, not only emphasizing one property but neglecting other properties. From the use point of view, according to the behavior of solder in brazing process, the technological properties and influencing factors of electronic solder are analyzed and summarized as follows:
(1) Melting/Curing Temperature
That is, the solidus and liquidus temperatures of solder alloys and the temperature difference between them. During the brazing thermal cycle, in the heating stage, the solid phase line is the temperature at which the solder begins to melt, and the liquid phase is the temperature at which the solder begins to interact with the solid base metal, while the liquid phase is the temperature at which the solder begins to solidify, while the solid phase line is the temperature at which the solidification ends and the liquid solder stops interfacial reaction. The solder is pasty between solids and liquids. The smaller the temperature difference between solids and liquids is, the faster the solidification or melting rate is, the better the brazing operation is. The melting temperature of solder is determined by the composition of alloy. Tin-based alloys are commonly used in electronic solders. When low melting point metal components are added to tin, the melting temperature will decrease, but when high melting point metal is added, the melting temperature will generally rise. The closer the composition of the alloy is to the eutectic point, the lower the melting temperature and the smaller the temperature difference between solid and liquid lines. When the composition of solder reaches the eutectic point, the lowest melting temperature is obtained, and the temperature difference between solid and liquid lines is zero.
