A simulation of air bearing surface materials with copper substrate for corrosion investigation
Corrosion defect is one of the important defects found in hard disk drive manufacturing. Fail to detect this defect might lead to fatal hard disk drive failure. In general, corrosion defect was found after the end of process. The fundamental methodology used to measure corrosion defect in head magnetic process of hard disk drive manufacturing is Electrochemical impedance spectroscopy (EIS). This method applies a low frequency voltage to a chemical cell in order to measure corrosion rate which is defined as a reaction of material in aqueous solution. The data obtained from EIS measurement method are complex and thus hard to analyze. Furthermore, EIS method is destructive materials measurement and the obtained results cannot well predict corrosion behavior of the system. However, head magnetic materials/slider is a stack of three materials in layers i.e. soft magnetic layer, diamond like carbon (DLC) layer, and photoresist layer respectively. These three stack layer of slider can be replaced by R-C equivalent circuit. Nyquist plot and Bode plot are used to observe the frequency response of the equivalent circuit. This observation can help in prediction of corrosion behavior before starting of mass fabrication or transferring to new materials. This work shows that the results obtained from an equivalent R-C circuit model of copper substrate coated with photoresist and the one obtained from EIS method are comparable. It should be noted that the parameters of R-C equivalent circuits are modified for corrosion behavior studying according to two different types of photoresists.
Polymer film selection for corrosion protection of data storage magnetic material
The prevention of soft magnetic material from corrosion in hard disk drive is very concern due to high magnetic moment come with high corrosion sensitivity. Photoresist that is used for read/write head fabrication is important to protect magnetic element. Good photoresist should not found porosity and low water adsorption. This investigation was methodology to classify 5 conditions of photoresist which is used in fabrication at lithography process. Potentiostat/Galvanastat is selected technique by applying external voltage for current response. The result suggested proper photoresist was wet photoresist type, AZP4999. There is no degradation after lithography process had finished. Chemical wear resistance still maintain at same level of magnitude since first step (coating) till last step (developing).
Investigation of large strain extrusion machining (LSEM) of pure magnesium (Mg)
Abstract Large strain extrusion machining (LSEM) is used to produce pure magnesium strips directly from as-cast billets. LSEM reduces manufacturing steps and the special shear direction inclines the unfavorable strong basal texture of Mg. Finding suitable parameter ranges to control geometry and properties of the produced strip is a great challenge. In the present research, a finite element model is proposed and verified with experiments and previous findings. Next, effects of process parameters (temperature and pressure) on geometrical and microstructural properties of the produced strips are investigated. Studying the involved failure micro-mechanisms shows that the process temperature and hydrostatic pressure have adverse effects on the production of a flawless strip. To reduce the temperature and hydrostatic pressure throughout the LSEM process many different conditions are tested by the FEM model. Among all the examined conditions, 0.85 m m R e v feed and 530 R e v m i n rotation speed yields the most promising results it terms of low temperature, low hydrostatic pressure, and stable machining force. The proposed conditions are applied in the experimental setup and a uniform and flawless strip is obtained.