Abstract
The impact of the contact angle of a droplet, the included angle of a substrate and the droplet volume on the morphology and profile of the droplet is discussed, and the spreading characteristics of lead-free solder on an inverted V-shaped substrate are studied, which provides theoretical guidance and data support for a comprehensive study of the interface reaction and wetting mechanism between solder and substrate, and helps improve the brazing process to adapt to complex welding operations. Based on the method of finite element simulation, different contact angles, included angles of inverted V-shaped substrate, droplet volumes and other variables are entered in the model; the relevant physical parameters are defined according to the surface tension and density of solder Sn-3.0Ag-0.5Cu at temperature of 490K; the theoretical spreading results of the droplet are simulated and calculated by Surface Evolver by using the principle of energy minimization and the method of gradient descent; and the spreading distance, contact area and energy equivalence of the droplet are read out by program, which helps to investigate the spreading behavior and wetting characteristics of the droplet.
Highlights
It is of great value to study the morphology characteristics of the molten solder when it reaches a state of static equilibrium on a V-shaped substrate to accurately measure the geometric and physical parameters related to the wettability and to explore the spreading mechanism of the droplet and how the interface energy changes, which is in line with the requirements of increasingly complex and diverse welding process
In the process of building the model, the coordinates of each vertex of the model should be selected in accordance with the droplet volume, and the volume should be kept unchanged during calculation. The physical parameters such as gas-liquid surface tension and density should be input to display the real-time iterations of the model via different windows
Based on the fact that the droplet reaches a state of stable equilibrium when the energy is minimized, triangular partition of the grid, averaging grid, linear approximation, quadratic approximation, and other calculation methods and the method of gradient descent were used to find the morphology when the energy function of the system was minimized
Summary
It is of great value to study the morphology characteristics of the molten solder when it reaches a state of static equilibrium on a V-shaped substrate to accurately measure the geometric and physical parameters related to the wettability and to explore the spreading mechanism of the droplet and how the interface energy changes, which is in line with the requirements of increasingly complex and diverse welding process. The experimental study on the wettability and spreadability of a solder on a V-shaped substrate at different temperatures can provide theoretical guidance for the application of complex brazing process [3,4] On this basis, some important parameters for the exploration of the three-phase interface characteristics can be obtained through the simulation study on the spreading behavior of the droplets of different volumes on the V-shaped substrates with different included angles and the changes of the droplet morphology, so as to help understand the interaction mechanism between the droplet and the substrate, and systematically analyze the mechanical relationship of the droplet on a special substrate and the change of contour structure characteristics resulting therefrom. It is an effective method to establish a mathematical and physical model by using the method of finite element to simulate and analyze the theoretical spreading morphology of the molten solder Sn-3.0Ag-0.5Cu on the inverted V-shaped substrate under different conditions [5]
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