Key Technology Study On High Performance Machining Microwave Printed Circuit Board

The aluminum base microwave printed circuit board (PCB) is used as a high frequency micro-wave communication device, which is composed of resin, reinforced materials, copper foil and aluminum base. The microwave PCB has wide application foreground in communication, military, instrument and other fields for its excellent performances. The dielectric layer of the microwave PCB has two phase-the polytetraflouroethylene (PTFE) and ceramic powder. It is a typical difficult-to-machine material because the ceramic particle bonded with PTFE has high strength and hardness. Research was carried out on the key technologies of high efficiency milling of microwave PCB, which include green machining mechanics, cutting parameters optimization and cutting database.The main work and the results obtained in this dissertation are as follows:①The research was carried out on the cutting force of high speed milling microwave PCB. The effects of milling parameters, cooling method and tool coating on the cutting force were investigated. The cutting force model was set up based on the polynomial linear regression theory. Cryogenic pneumatic mist jet impinging cooling will improve the machinability of microwave PCB. The high efficiency cooling method improves cooling and the lubricating conditions in the cutting zone, which results in the decrease of the cutting force.②The research was carried out on the dynamic characteristics and chatter stability lobe of the small diameter end mill (diameter less than3mm). The precise3D CAD model of solid carbide end mill was set up by using Pro/E CAD software. The dynamic characteristic of the cutting tool was obtained by numerical simulation method in ABAQUS system. The results show the extended length of milling tool and cutting width has influence on the critical cutting depth. The increasing of extended length and cutting width will result in the decreasing of critical cutting depth.③The research was carried out on the law of heat source and transfer at the condition of cryogenic pneumatic mist jet impinging cooling in allusion to the machining characteristic of high speed milling. By using Ansys software, numerical simulation research is conducted on the3D work piece temperature distribution. The comparison of the results of the finite element simulation and the data of the experiment verifies the accuracy of the finite element model. The relation between cutting temperature and milling parameters is investigated after this. It is found that the cutting temperature increases with the increase of cutting and feeding speed. Simulation results show that when choosing the milling parameters, it’s not suitable to choose a cutting speed with the value below150m/min, or else the cutting temperature of the milling zone would become too high to obtain a good machining quality.④④The experimental research on the wear mechanics and the tool life of TiN coated cemented carbide cutting tool in high speed milling of the aluminum base microwave PCB is carried out. The SEM is used to observe the wear morphology of the rake and flank face of cutting tools. The wear mechanisms of TiN coated tool include abrasive wear, adhesive wear and diffusion wear. It is shown that the abrasive wear is the main reason of cutting the complex material. The tool flank wear standard is commended as40um in the TiN coated cemented carbide milling the microwave PCB. Cryogenic pneumatic mist jet impinging cooling will result in the low cutting temperature and low wear ratio of diffusion wear and adhesive wear.⑤Optimization of milling parameters of microwave printed circuit board is modeled, and the optimization based on genetic algorithm and particle swarm optimization (GA-PSO) was researched. Chosing maximum productivity as the optimization objective and cutting speed and feed as optimization variables, the target function is presented. Cutting constraint functions are also established including the power of machining tool, tool life, surface quality, end miller deformation and the chatter stability. Then the application of GA-PSO on the optimization of milling parameters of microwave printed circuit board is researched. The optimization algorithm flow was established, and the fitness function with engineering significance was presented. Each main parameters of the optimization algorithm was also given. The optimized milling parameters are got. Results shows the improvement in machining efficiency. Based on the parameters, the NC process of milling parameters of microwave printed circuit board is optimized. As a result, the quality and quantity of products are improved evidently.⑥For convenient use of the research results in production, a milling parameters database system based on B/S was researched and developed. Requirement analysis, conceptual design and logic design of the system were carried out respectively. The structures of database tables were obtained, and the system functions were realized. Then the integration between the system and CAM was researched. The function modules and B/S design structure of the system were given. The E-R model was also established. The database tables were designed based on Microsoft SQL Server. And the system functions which can query, show, add, modify and delete milling parameters data effectively were developed by ASP. The integration between the system and the CAM module of Pro/E was realized based on Pro/Toolkit second development interface and MFC, with which the NC programmers can easily query and call the optimized milling parameters database in the CAM module of Pro/E. The system has been applied in the production field.