Advanced Materials Research Vol. 497

Abstract: Micro-electrode preparation is the key technology in micro-machining of micro- mechanics and micro-parts. In this research, the machining method of micro-pin using micro-electrochemical machining (micro-ECM) was proposed. The principle of micro-pin fabrication is introduced and the studies are focused on the effects of varies parameters on the shape of the micro-pin. The theoretic model between the shape of micro-pin and the parameters including power, voltage, duty ratio of pulse power, immerge depth of electrode is built up and then verified by experimentations. Experimental results denote that the micro-electrode with desirable shape and size could be prepared by controlling applied parameters. When the immersing depth is deeper, the pulse power, low voltage and duty ratio is proper selected. On the contrary, the DC power or pulse power with higher voltage and duty ratio should be applied. Finally, micro-pin with diameter of 5μm and 60μm long was fabricated when the DC power of 1.8V voltage and immersing depth of 1mm is applied.

Abstract: This research is aiming at exploring a feasible machining method for ultra-high slope surface with deterministic figuring technology. We first successfully realize the nanometer-precision machining of optical hemispherical surface by using ion beam figuring (IBF) under the guidance of the reconstructed three-dimensional (3D) surface error. For figuring such a high-slope surface, we proposed some technical details, the modified algorithm for dwell time, the nonlinear developing method of surface error and the stitching machining technology, to address some important problems in process. Simultaneity a fused silica hemispherical surface is figured with our proposed method on the experimental installation IBF700-5V developed by ourselves. The root-mean-square (RMS) surface error of this sample is reduced from 19.6 nm to 9.6 nm after four iterations and about 37.8min. The experimental results indicate that IBF is a technique of high efficiency for the nanometer-precision machining of high-slope surface.

Abstract: Microburrs have great influence on printed circuit board’s quality. PCB is composed of glass fiber plastic reinforcement material and copper foil. The PCB microburrs are generated in copper foil drilling process. These burrs are generated by copper extrusion and accumulation around the micro-hole. Enter burr and exit burr is quite different. Enter burrs are lower than exit burrs. The burr formation experienced three stages: First, Copper foil extrudes with the feed of microdrill; Second, Most of the Materials are cut off by drill tip and the rest of material; At last, rollover burrs appear when drill enters or exits uncut chip rolls.

Abstract: A femtosecond pulsed Nd:YAG laser was used to micromachine polycrystalline diamonds (PCD) and study the ablated microstructure characteristics under different irradiation parameters. With high laser intensity and low traverse speed, a micro cone with very smooth surface and clear edge can be obtained. There was almost no recast layer around the cone and no phase transition on the ablated surfaces was found. By contrast, the use of low laser intensity and high traverse speed could ablate only the grain boundaries without any damage to the diamond grits. These results suggest a need for further research in femtosecond laser micromachining of PCD for potential applications in fabricating new types of micro grinding wheels or diamond pencils.

Abstract: There is an increasingly growing demand for fabrication of micro-structured surfaces such as micro lens arrays and micro prism arrays. Micro end milling is one of the most efficient machining technologies for fabricating these microstructures. In this paper, micro electrodischarge machining (EDM) was applied to fabricate single flute micro end mills on polycrystalline diamond (PCD). Using the fabricated end mills, micro end milling tests of dimple arrays were performed on tungsten carbide (WC) molds and the machining characteristics were investigated.

Abstract: Car camera lens is widely used for the safety system of all kinds of vehicles. The car lens should have very wide field angle, strong ability to endure vibration and thermo-mechanical instability as well as erosion. According to these requirements, a new car lens is designed based on the aspheric glass lenses. The whole structure of car lens contains six separated glass lenses including two aspheric lenses. To reduce the cost, the aspheric lenses are made from low-Tg glass which is adaptable for mass production by glass molding press. The total track of lens is less than 30mm. For the enhancement of night vision, the F-number is set to be 2.4. The full FOV (field of view) of 160 is wide enough to capture all the dangerous information around the car. The imaging resolution is designed to be 3 Mega pixels. The designed result proves that the new car lens features high imaging quality. Its MTF (modulation transfer function) value is not less than 0.15 at the Nyquist frequency as for the field angle of 160. At the half Nyquist frequency, the MTF values of the most field angles are not less than 0.5. Therefore, the new lens could be used in the front of car to monitoring the dangerous cases around the corner.

Abstract: Glass molding press (GMP) was applied to the fabrication of 3 kinds of microgrooves with different pitches on the glass surface. The size effects of microgroove fabrication on the Nickel Phosphorous (Ni-P) plating layer by diamond cutting were experimentally tested, and then, the size effects of microgroove fabrication by GMP using the Ni-P mold were experimentally tested. Finally, the changes of the Ni-P mold after GMP by 100 shots were compared with the microgroove mold before GMP, and the size effects of the mold change were discussed. By the comparison research of microgroove fabrication with different pitches, it suggests a way to create microgrooves with even smaller size.

Abstract: Glass molding is a high-volume fabrication method for producing optical components. Non-isothermal glass molding press (NGM) was proposed to fabricate optical glass, and its characteristics were studied by finite element method (FEM) simulation. The coupled thermo-mechanical analysis was carried out to analyze the key factors such as temperature distribution, stress distribution and strain distribution. The non-isothermal and isothermal glass molding (IGM) was studied, and optimal temperature match between glass and mold was obtained.

Abstract: Glass lens molding is a high-volume fabrication method for producing optical components. In this paper, combined with the orthogonal test method and finite element method (FEM) simulation, the coupled thermo-mechanical analysis was carried out to analyze the key process factors. In order to reduce the testing time, an orthogonal test with three sets of level factors and three parameters is conducted to obtain the optimal molding process parameters. The result shows that the most significant parameter is molding velocity, the other effect parameters are molding temperature and friction coefficient. According to the previous analysis of orthogonal experiment, it is shown that the best optimal finishing process parameters were A2B1C1.

Abstract: SiC crystal substrate has been widely used in the area of microelectronics, photonics and new materials, such as semiconductor lighting, integrated circuits, and so on. In this paper, the influences of the polishing slurry composition, such as the pH value, the abrasive size and its concentration, the dispersant and the oxidants, the rotational speed of the polishing platen and the workpiece and the polishing pressure on the material removal rate (MRR) of SiC crystal substrate (0001) C surface based on the alumina abrasive in chemical mechanical polishing (CMP). This study results will provide the reference for developing the slurry, optimizing the process parameters and researching the material removal mechanism in CMP of SiC crystal substrate.