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Analysis of Technological Properties and Influencing Factors of Electronic Solder (Part I)
The technological properties of solder refer to its performance in use. According to the investigation, the main technical problems encountered in the process of electronic brazing are the behavior of liquid solder. Wetting, flowing, filling and spreading of liquid solder on the surface of solid base metal is the premise of brazing. Without this premise, even if the physical, mechanical properties and micro-structure of solder are good, it will be futile. From melting to solidification and crystallization, the properties of solder are interrelated and influenced.
For example, the melting temperature of solder determines the temperature range of brazing, and the difference between solidification temperature and liquidus temperature determines the speed of solidification or solidification; the oxidation of the surface of liquid solder hinders the bonding of interfacial atoms to achieve the required atomic spacing, thus affecting its wettability, flow, filling and spreading ability; the capillary wetting effect of liquid solder on base metal will determine the solder and base metal. The bonding ability of materials also affects the filling ability; the spreading or overflowing of liquid solder on the base metal surface affects the filling ability on the one hand, and on the other hand, the separation ability of solders between dense solder joints; when the interfacial atoms exist certain solubility and diffusion, it is beneficial to wetting and expanding, but too large mutual solubility or diffusion will produce too many intermetals at the interface. Compounds, on the contrary, are not conducive to wetting and spreading; at a certain brazing temperature, the lower the melting point of solder, the smaller the difference between solid and liquidus temperatures, the better the wettability and fluidity.
