Advanced Materials Research Vols. 97-101

Abstract: This paper discusses the effect of two similar gold wire (wire A and wire B) used mainly as a wire bonding material for Quad Flat Nolead (QFN) package. Both wires with diameter of 25.4 μm were bonded using automatic wire bonder by maintaining the temperature at 200°C. The effect of trace elements on the mechanical properties of 4N gold wire has not been widely investigated for some years despite the important of wire-bonding and the move towards fine pitch applications. Due to the element analysis, atomic percentage of Ca in wire B is higher than wire A. Pull strength increase with the increasing of the trace element. The higher pull strength of wire B could improve the yield strength, elastic modulus and recrytallization temperature.

Abstract: This paper presents Time Dependent Dielectric Breakdown (TDDB) testing of gate oxide on 0.5µm BiCMOS Technology. The gate oxide quality for the technology has been investigated and furthermore to qualify the whole set up of the foundry from the process, equipment, cleanroom control and raw material used to produce high quality gate oxide and hence good quality of BiCMOS devices. TDDB test is the most widely used testing to check the quality of gate oxide and in this paper the TDDB test done on MOS capacitors fabricated using 0.5 µm BiCMOS Technology. Seven consecutive qualification lots have been tested and the data shown that TDDB measurement is capable to differentiate between accepted wafer and rejected wafer. The data also shown that TDDB test was capable to characterise 0.5 µm BiCMOS gate oxide with higher yield and comparable with reference lot from other foundry fab.

Abstract: In recent years, wire sawing is considered to be a potentially better technology of slicing brittle crystals especially semiconductor, owing to the unmatched advantages of slicing large ingot into thin wafers with high efficiency, fine quality and less kerf loss. This paper analyses the dynamic effect on wire from a variety of excitation and mechanical structure in the process of cutting on the basis of the effects of vibration on slicing wafer quality. A suitable model is built according to Hamilton principle, closed form expressions is present for the steady state response using finite element method. The relation between inherent characteristics of wiresaw and different system parameters is obtained.

Abstract: The study aimed at improving the problems of warpage occurring in the mold injection of battery lower cases. Firstly, the effects of variations of molding parameters are investigated in order to minimize the warpage. Secondly, Moldflow software is employed to simulate the molten plastic flow inside the cavity, and followed by the holding pressure analysis. Moreover, Taguchi method is applied to find the optimum distribution of mold temperature, and its results are used to design cooling tubes. Finally, different cooling systems are parametrically simulated and the optimum combinations will be found. The analytical results indicate that the optimum parameters can reduce the warpage problem occurring during mold injection. Therefore, the yield rate of the products can be effectively raised.

Abstract: Magnesium alloy is the lightest metal that can be used as structural material at present. As a novel forming process for magnesium alloys, thixomolding can result in a product with few defects and superior dimensional accuracy, and it is suited to manufacture the thin wall products especially. In this paper, the samples of mobile phone housing were fabricated by 220Tons thixomolding machine made by Japan Steel Works. The effects of barrel temperature, screw rotate rate and injection velocity on the mechanical properties were studied. The relationship between process parameters and mechanical properties was investigated. The results show that the effects of barrel temperature and screw rotate rate on the mechanical properties can be divided to low temperature and high temperature stage. The high tensile strength are corresponding to the best injection velocity.

Abstract: Due to those disadvantages of the cycloidal-pin wheel transmission, such as low efficiency, low bearing capacity and poor rigidity, a new kind of axis-fixed cycloid transmission is proposed after generalizing those advantages of axis-fixed drive, cycloid drive and oscillating-tooth drive. Special output mechanism is unnecessary here because the motion is exported directly by the cycloid gear. Thus, there are many advantages of this new transmission-simple structure, small size, high transmission efficiency and large torsional stiffness. The transmission theory and basic structure are analyzed and the formula for the transmission efficiency is derived. A prototype is manufactured and the efficiency experiment is carried out on the test bed. The experimental result verifies the correctness of the therotical analysis.

Abstract: High- precision and large scale are the developing trend for injection molding machine clamping system .This paper compared the characteristics of three-platen toggle and dual-platen hydraulic clamping system. The key impact factors that effecting plastic parts` precision from clamping system were discussed systematically first time. Based on these analyses, a new clamping system has been proposed and manufactured to improve the plastics parts` precision, including three new technologies: new type dual-platen structure, parallelism adaptive correction technology and numerical controlled hydraulic servo system technology. It has been applied in practical machine successfully, and experiment result proves that it is effective enough to satisfying the high-precision molding of large plastics parts.

Abstract: In this paper, a new method considering the combination of tension and deformation curvature which results in less deformation energy under a certain elongation is presented at the first time. The calculation results show that when the elongation is less than 1 %, the tension which is about 1/6 yield stress will consume less energy. If the tension decreases from 1/4 to 1/8 yield stress, the deformation energy of strip with yield stress of greater than 450 MPa decreases significantly. This study can help determine the processes parameters of strip tension levelling effectively.

Abstract: Both experimentation and calculation of the Yada model modulus of casting AZ31 magnesium alloy are provided in this paper. Based on revised Yada model, the microstructure simulation of precision forming inner gear is performed using Superform software. On the basisi of result analysis, the microstructure transformation of the casting magnesium alloy in the hot-forming process is forecasted in terms of revised Yada model.

Abstract: Strip shape control during cold rolling of thin strip is a challenge in rolling practice. In the paper, finite element model of strip shape during cold rolling of thin strip in asymmetrical rolling case was successfully developed, and the strip shape such as the thickness distribution along the strip width have been obtained. The developed finite element model has been verified with the experimental value, which shows they are in good agreement. The obtained results are applicable to control the rolled thin strip shape in practice.