Study On Stress In Micro Electrodeposited Coating And Fabrication Of Micro Mould Insert

With the rapid development of MEMS, micro electroforming technology has been applied widely and. become the initial choice in manufacture of microstructure and micro moulds. However, the stress always exists in the electrodeposited coating and has adverse influence on mechanical properties of the coating and devices forming. The size precision and fabrication of micro mould inserts are problems for microfluidic chip products. The primary work of this study is mainly concentrated on the two aspects. The research result is beneficial for improving the stability of micro structures and dimensional precision of electroforming.The method to calculate the internal stress in Ni electrodeposited coating was researched. Based on the theory of bragg's law and elastic theory, a theoretical formula for electrodeposited coating internal stress called sin~2Ψmethod is established. And the stress value could be obtained by the X-ray diffractometer.The influence of ultrasonic vibration on the Ni plating was researched using the ultrasonic vibration equipment. A relationship curve is established between the vibration time and the stress relief effect. The mechanism of stress relief in deposited coating using ultrasonic stress relief is discussed and the influence of additive on the coating is also discussed . Ultrasonic stress relief technology is as well as heat treatment in removing internal stress, it is useful for making the micro devices be qualified products.The processing parameters of micro electrodeposited coating were optimized in terms of internal stress. Based on the 33 factorial orthogonal array technique, the X-ray diffractometer and stress formulae were employed to measure the internal stress of electrodeposited coating under different processing parameters. Employing a neural network technique, a simulative model was established to investigate the influence of process parameters on the internal stress. According to the results of orthogonal experiment, the neural network was trained and the prediction model was built between the internal stress and three main process parameters: current density , electrodeposited temperature and the basement types. The predict results were in good agreement with the experimental results. The internal stress was greatly reduced under the guidance of neural network and micro electrodeposited process could be optimized.The micro mould inserts were fabricated by the UV-LIGA technology. The researches on the the precisions followed were performed. Owing to optimized experiment parameters and auxiliary features, the spin-coating SU-8 resist was more smooth and the swelling displacement was reduced, which improved the consistency of the insert. Further more, over-plating method combined with the following machining process was employed to reform the asymmetry of the insert . Through the improvement of the technology, the precisions of the single inserts' width and height are controlled in±3μm.