Development Of Measurement And Control System Of Laser Trimming Machine

Electronic and information technology is in a period of the rapid development,at the same time,electronic devices are developing in the direction of miniature,represents the trend of the times,developing the thick-film hybrid IC is very meaningful,because it can miniaturize electronic equipment effectively.And thick-film resistor is a kind of very important component of the thick-film hybrid IC.Due to its manufacturing techniques,there is a large error in the resistance of thick-film resistor,and the laser trimming machine is a kind of very ideal automation equipment to adjust the resistance of thick-film resistor.The measurement and control system plays an pivotal role in the laser trimming machine,and it is responsible for collecting relevant data and controlling each subsystem in the process of trimming the resistor,its performance directly affects the accuracy and efficiency of the laser trimming machine.The system includes the constant current source board,AD acquisition card,the probes board and the matrix control board.In this dissertation,several studies and designs are made concentrating on the measurement and control system.At first,this paper analyzes the basic principle of two methods of Measuring resistance,and analyzes the main functions of the measurement and control system,then we put forward an overall planning.Secondly,we analyze the basic principle of constant current source,and put forward the suitable scheme based on this project.Then we finished the hardware& software design,and thermal isolation design.Thirdly,according to the demands of the laser trimming machine,the right AD acquisition card was chosen for this project,and the probes board was designed for this system.In order to meet the need of trimming multiple resistors in once load,the matrix control board was designed.And this project reduces the volume of the PCB through introducing CPLD technology.RS-485 interface is designed for the constant current source board and the matrix control board,and selecting PIC18F4580 belonging to Microchip as the core unit for both of them.Finally,in order to improve the reliability of the control board,we desigened the quality inspection platform.