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October 12, 2002 Acidic versus Alkaline Post Texture Cleaning in the Disk Drive Industry This is a description of an all media Storage (Disk industry) alkaline cleaning process. See Process Chart here Acid cleaning can fix residues, of oily materials, such as fatty acids, hydrocarbon oils and silicone oils on the surface. That is acid will make them more strongly attached to the surface. As a result, they will be more difficult to remove in the subsequent alkaline cleaning steps, especially when a brush cleaning step is used. In your A/C process, the acidic disks will partially neutralize the alkalinity, making the alkaline cleaner weaker. When the disk is put in the brushing stage, the oily substances will smear, or spread, on the PVA and will not be removed completely with the subsequent alkaline cleaning. If highly alkaline cleaner is used through the whole process, the oily substances will not adhere to the PVA because of the high alkalinity on the PVA. The theory behind acid cleaning is that a mild etch of the disk will remove more completely the contaminants. This may work to some extent on particulates, but not on oils. We can accomplish a mild etch as well, a very good particle removal as well as oil removal with our highly alkaline cleaners such as; NuWet DT 78 or NuWet DT 58. The process: After texturing, the disks go back to the cassette in the holding tank. The holding tank can be D. I. Water, or a 1 % Texturing fluid. Next the disks go into a soak tank. This should be 8 % by volume NuWet DT 78. The disks can stay there 15 to 90 minutes. Ideally, 30 minutes. Next the disks go into the Oliver I, there is no need to rinse in between. Use 2 % by volume NuWet DT 78 spray. Next the disks go into MD07. If there is an ultrasonic or a soak tank, use 5 % by volume of NuWet DT 78. In the spray stage use 2 % by volume NuWet DT 78. After the laser, Oliver II, Use 2 % by volume spray. In the MD08, If there is an ultrasonic or a soak tank, use 5 % by volume of NuWet DT 78. In the spray stage use 2 % by volume NuWet DT 78.
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