Papers by Author: Jia Xi Du

Abstract: In view of characteristics of involute helical gear profile, analyzed the multi-axis machining process for helical gear. Focused on the processing characteristics of helical gear for multi-axis machining, discussed tool path generation, machining program, tool path simulation, cutter interference and collision detection for machine tool and gear profile, seeking out the optimal method and process of helical gear for multi-axis machining. Applying this machining technology in manufacture, it can improve performance of gear, while it can also improve efficiency of manufacture.

Abstract: Based on PID controller, the closed-loop model of instantaneous torque for automotive brake test-bench was established, and then the instantaneous torque and the deviation function were calculated, furthermore, the genetic algorithm was adopted in order to get a global optimal solution and to optimize the parameters of the PID control system. So that the deviation function can be reduced or improved. By comparing the effect of control function, the causes for error volatility of the PID control system were derived, and the fitness function of genetic algorithm was determined reasonably. This algorithm can improve the reliability and accuracy of the control model effectively, and provide an effective method for testing the merits and integrated performance of automotive brake design.

Abstract: According to the law of rigid body around fixed axis rotation, established the mathematical model of motor drive current and instantaneous rotational speed. From the ideal situation of the simulation, according to the same discrete interval of time equal to the same increment of spindle angular velocity conditions, established the discrete closed-loop control system model. In allusion to the disadvantage of calculating corresponding braking current by the instantaneous speed and the instantaneous braking torque measured during the last interval, proposed the control method of calculating braking current by the instantaneous speed and the instantaneous braking torque measured all discrete intervals before current time. Discussed emphatically the computer controlled method based on the discrete closed-loop and phase-locked loop theory which can be used to design the braking current. Evaluated the advantages and disadvantages of the model, and proposed the improved direction.

Abstract: Chemical mechanical polishing (CMP) has become the most widely used planarization technology in the metal and hard-brittle crystal substrate manufacturing process. In this paper, the distinguish method of lubricating behavior in CMP had been analyzed in theory firstly. Then, the tests of CMP with silicon wafer and deposited copper wafer at different polishing pressure had been done. By the test results, the Stribeck curves obtained showed obvious smooth. But in normal CMP conditions, the friction coefficient of polishing area was above 0.1. By analyzing the experimental results, it was concluded that the lubrication state in CMP interface is belong to the boundary lubrication and the material removal is the process of bringing and removed of the chemical reaction boundary lubricating film on hard-brittle crystal substrate surface constantly. The contact form between the workpiece and the polishing pad is the solid-solid contact. These results will provide theoretical guide to further understand the material removal mechanism of in hard-brittle crystal substrate CMP.

Abstract: In this paper, the finite element model for the cabinet of a drum washing machine and the model for testing vibration of the cabinet were developed in ANSYS software and PULSE™, respectively. A series of tests were conducted. The natural frequencies and mode shapes were obtained by finite element analysis and modal experiment, which revealed weak parts of the cabinet. Meanwhile, the computational modes were in good agreement with experimental ones and this could provide an available method by which it was convenient to improve the design of the cabinet.

Abstract: The friction force on wafer surface plays an important role in removing material of wafer surface and the friction force on wafer surface may have a direct influence on non-uniformity of material removal in wafer CMP process. In this paper, models of friction force on wafer surface were built according to the CMP process. It is proved that the model of the friction force on the wafer surface is correct by the silicon wafer CMP Friction experiment. Then the data fitting of friction model has been done with the experimental data. By the friction force model, the within wafer nonuniformity (WIWNU) of friction force distribution on wafer surface has been obtained with different rotational speed of wafer and polishing pad. The research of this paper is helpful to further understanding the material removal mechanism in wafer CMP.

Abstract: In order to understand the material removal mechanism in the process of chemical mechanical polishing (CMP), the states of abrasives in the slurry and on the polishing pad in CMP process have been studied by testing. It was concluded that although the abrasive in the slurry is in the form of agglomeration, but the abrasive on the polishing pad are in approximately uniform layer distribution. The different CMP slurries had been designed for CMP test of MRR. According to analyzing the test results, it was concluded that the mechanical action produced by the abrasive is the main mechanical action in wafer CMP process and the MRR mainly results from the interaction between the mechanical action of the abrasives and the chemical action of slurry. These results will provide a reliable basis for the building of abrasive trajectory model and a theoretical guide to further understanding the material removal mechanism in wafer CMP.

Abstract: Chemical mechanical polishing (CMP) has already become a mainstream technology in global planarization of wafer. The nonuniformity of material removal on wafer surface has a main influence on surface profile of silicon wafer in CMP process. However, the formation mechanism of nonuniformity in wafer CMP has not been fully understood and the influences of CMP process variables on nonuniformity are not fully clear. The nonuniformity of material removal on wafer surface has not been fully understood and the influences of CMP process variables on nonuniformity are not fully clear in CMP process. In this paper, firstly, the equation of particle movement trajectories on wafer surface was built by the movement relationship between the wafer and the polishing pad on a single head CMP machine with line oscillation of carrier. Then the distribution of abrasive trajectories on wafer surface was analyzed at different rotational speed. By the analysis, the relationship between the movement variables of the CMP machine and the With-In-Wafer Nonuniformity (WIWNU) of material removal on wafer surface had been derived. Last, the WIWNU tests were conducted on CP-4 machine. The analysis results are in accord with experimental results. The results will provide some theoretical guide for designing the CMP equipment, selecting the movement variables in CMP and further understanding the material removal mechanism in wafer CMP.

Abstract: Right getting hold of the contact form between the wafer and the pad is the precondition of fully understanding the material removal mechanism in wafer chemical mechanical polishing (CMP) process. In this paper, according to friction and abrasion theory, the differentiating method of contact form between the wafer and the pad has been obtained firstly. Then, the material removal rate (MRR) produced by mechanical action, chemical action and their interaction has been achieved by test results of MRR. According to analysis on test results of MRR, it is concluded that the mechanical action produced by abrasives is the main mechanical action, the MRR produced by the interaction between the mechanical action of abrasives and chemical action of slurry is the main MRR and the contact form between the wafer and the pad is solid-solid contact in wafer CMP. These results will provide theoretical guide to further understand the material removal mechanism of in wafer CMP.