Design Of Electronic Balance Measuring System For Weldability

With the rapid development of the semiconductor industry,military,medical,industrial production and our daily life in the increasing demand for electronic products,and electronic products are all types of electronic components welded on the PCB board of the assembly,in the welding process of its process has a high quality interconnecting technology needs.In the actual production process,the oxidation degree of the pins of welding components and the performance of welding materials need to be quantitatively evaluated to ensure the high quality and zero defects in the welding process,so the weldability detection is particularly important.The design and research process of a complete weldable electronic balance involves mechanical structure,motor drive,control,data acquisition,display processing and other aspects.In the whole design and research process,the measurement and control board is regarded as the "brain of the instrument",which controls the normal operation of the whole system.It can be said that it is the key technical part.The main research content of this topic is the design of the measurement and control circuit for weldability electronic balance.It aims to continuously detect the buoyancy force borne by the test sample before the infiltration and the vertical force generated by the surface tension after the beginning of the infiltration through this measurement and control circuit and the wetting balance method.The weldability was evaluated by analyzing the relationship curve between the force and time.The solderability electronic balance measurement and control circuit designed in this paper includes hardware circuit and control software.The hardware circuit includes balance position detection circuit,tare excitation and net excitation selfstarting circuit.The digital PID principle and depth PWM automatic feedback control technology are used to realize the fast and stable balance adjustment of the closed-loop system with high precision measurement circuit.The tare compensation,net weight compensation and temperature drift compensation are realized by the combination of program controlled D/A converter and operational amplifier,and the compensation fineness can reach 20 bit.In the software part,STM32F103 chip is used as the main control microprocessor and RS485 interface and RS232 interface are extended for external controller and other equipment communication requirements.In addition,the measurement and control circuit also extends the USB interface for the communication of the upper computer Lab VIEW,using its friendly interface,simple operation and other characteristics,through the design of the virtual control panel to achieve humancomputer interaction.The hardware circuit and related software designed in this paper have been verified by experiments in the prototype equipment,and its range is 0-5g.The resolution is 5mg;Nonlinear error ±1mg;Repeatability 5mg,each index has reached the relevant technical requirements.