Research And Development Of Solder Wetting Balancer Based On Solder Globule Wetting Balance Method

In the brazing process,the solderability of the solder is critical to the quality of the solder joint.And the solderability of the solder is highly dependent on the wettability between the solder and the surface of the sample.The wettability is usually determined by the solder composition,the brazing temperature,the surface oxide film condition,the flux,and etc.At present,methods for judging the wettability of solders include wetting balance method,solder ball method,spreading area method,broadening method,etc.Wherein the solder ball method has the advantages of light structure,low solder cost,low cost,and simple operation,it received extensive attention from the industry.Therefore,this paper is based on solder globule wetting balance method.The specific research contents are as follows:The task of this paper is to design an instrument for testing the solder wetting curve based on the solder globule wetting balance method.The instrument includes a force measuring part,a three-dimensional moving part,and a heating part.The force measurement part is composed of the sensor of force measurement,A/D conversion module and serial communication module.Firstly,the sensor of force measurement is deeply analyzed,and the structure and working principle of the sensor are described in detail.The displacement monitoring device is designed and analyzed.The structure of double magnetic steel and magnetic circuit structure are designed,and its structural parameters are optimized.Then,the A/D conversion module is built,the ADC chip is selected for sampling,and the driver is programmed by the AC620 development board to correctly control the ADC chip.Finally,the module of serial communication is set up,which using AC620development board to build a serial port transceiver and dual-port storage RAM system,send and receive tested data,and then transfer the data to PC.The three-dimensional motion portion controls the positional movement of the solder ball,which can align the center of the solder ball with the sample,and it also control the rate when the sample immersing in the solder ball.The heating section controls the heating temperature of the solder balls and ensures that the solder balls and the heating stage are wetted.At last,this paper also proposes a standard for evaluating the performance of the wetting curve-the point model standard and the area model standard.The point model is simple and quick,it evaluates the three basic components of the wetting curve(T₁?s?,T_2/3?s?,F_max?mN/mm?),and extracts the wettability as a single value to judge the wettability.The area model is more accurate,it uses the basic values of the curve,and approximately calculate the area between the wetting curve and the x-axis.The correctness and accuracy of the area model are verified by comparison with the point model and the actual area model.