An Automatic Thermostatic Control System For Diffusion Furnace

Diffusion furnace is an important technological equipment used tomanufacture the electronic components. It is applicable to the manufacturingprocess of semiconductor devices, such as transistor, thyristor and the solidintegrated circuit. Temperature is the critical factor among the technologicalparameters of a diffusion furnace, so the accuracy of temperature controlgoverns not only the product quality, but also the efficiency of the diffusionfurnace.On the basis of temperature characteristic of the diffusion furnace, wedesigned and implemented a thermostatic control system which adoptedthyristor controlled circuit and cascade PID control algorithm. The systemused SCM AT89S52 as the core. Firstly, the temperature of the diffusionfurnace was measured by sensor thermocouple. After signal processing andA/D, the temperature signal was sent to SCM and handled by cascade PIDcontroller. The thermostatic control of the diffusion furnace was achievedthrough controlling the heating power of the furnace wire driven by zeropassage trigger bidirectional thyristor. Moreover, the system designed human-machine interface with MCGS configuration software and realizedreal-time monitoring from PC to SCM. Finally, we validated the control effectof the system based on the simulation experiment in the lab and MATLABsimulation.During the process of writing this thesis, we obtained the comprehensivematerials and data, and researched the temperature characteristic of thediffusion furnace detailedly. We designed Dahlin cascade PID controlleraccording to the technological requirements for the diffusion furnace, andconducted useful probes for the development trend of high accuracytemperature control of the thermostatic control system.