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.
Conformal photoresist coating for critical dimension improvement
3D surface topography of read / write head fabrication is difficult for lithography process. Photoresist deposition by using the conventional spin coating method is troubled. Spray coating is a replacement technique that eliminates the problem by producing micro-resist droplets that adhere firmly to the deposition location; thus, spray coating with optimal parameters from designed experiment is a suitable method for photoresist deposition on structures with high aspect ratio. By using proper nitrogen flow rate to spread out AZ4999 resist to be micro-droplet in the same time with proper traveling nozzle speed, the photoresist turbulence will perform good resist coverage over all surfaces. From design of experiment show the optimum condition for conformal deposition is 0.8 Bar at 117mm/s for nitrogen pressure and nozzle speed, respectively. Photoresist thickness was dropped at 30um far away from groove or edge of the head.
Micro-porous P(VDF-HFP)-based polymer electrolyte filled with Al2O3 nanoparticles
Abstract A micro-porous poly(vinylidenefluoride-co-hexafluoropropylene)[P(VDF-HFP)]-based electrolyte (MPE) is prepared by the phase inversion technology using N, N-dimethyl formamide (DMF) as solvent and distilled water as non-solvent. In order to enhance the porosity of polymer membrane, glycerin is added to the polymer solution as plasticizer as well as non-solvent. Various amounts of alumina (Al 2 O 3 ) nanoparticles are used as fillers in the preparation of porous polymer membrane. The crystallinity of polymer matrix decreases with addition of Al 2 O 3 nanoparticles and the amorphous phase expands accordingly. The resulting MPE has 2.11 × 10 − 3 S·cm − 1 of ionic conductivity, 0.66 of the lithium ions transference number and 4.816 kJ·mol − 1 of the activation energy for ions transport when the polymer matrix contains 10% of the mass fraction of Al 2 O 3 nanoparticles. Effect of Al 2 O 3 on the electrochemical properties of polymer electrolyte has been investigated in this paper. Analysis of FTIR spectra shows that there is an interaction between Al 2 O 3 nanoparticles and C F bonds of polymer chain.