PRE-TEXTURING AND TEXTURING OF NI-P DISC USING DIAMOND AS ABRASIVE PARTICLES
Publication Date: 2002-Oct-10
The IP.com Prior Art Database
An improved process to prepare hard drive media disc for the deposition of the magnetic layer, wherein the removal rate and surface texture are controllable and adjustable through pressure and chemical formulation. In this process, a diamond containing slurry is used to accomplish the goal of pre-texturing polish.
PRE-TEXTURING AND TEXTURING OF NI-P DISC
USING DIAMOND AS ABRASIVE PARTICLES
To prepare the hard drive media disc for the deposition of magnetic layer, the Ni-P surface needs to be polished and textured. The conventional process is a two-step process. The surface is polished with a slurry containing hard abrasive particles such as alumina in the presence of strong chemistry to remove the large topographic features with high material removal rate. The second step is to smooth the surface and remove any surface defects with somewhat lower removal rate. In order to achieve atomic level smoothness, small particles such as colloidal silica are typically used in this step. The subsequent texturing is to produce structured and controllable textures on the surface. The texturing step is typically performed with diamond particles in the absence of any chemistry. The process is typical lengthy and materials intense as the removal rate is low.
A current practice in producing a computer hard drive magnetic disc involves a pre-texturing polish and subsequent texturing. A pre-polishing is to smooth the surface to Ra less than 2A (measured by AFM) and texturing is to create more patented scratches with Ra in the order of 6-7A. Texturing is used to reduce stiction (static friction). More irregular surfaces have lower stiction and this leads to the practice of texturing disk surfaces using fixed or free abrasive particles.
Pre-texturing polishing is commonly performed with a slurry containing silica or alumina as abrasive particles, one or more types of carboxylaic acids as complexing, one or more types of chemical oxidizers, and one or more types of surfactants. Texturing operations are known in the art to utilize typically < 0.4 um diamond at a concentration of less than 2 carats/liter in order to achieve approximately 7A Ra by AFM. Alumina also is a common abrasive used in texturing operations. See for following references in this regard: Cooper, et al., “Tapes for Polishing and Texturing Thin-Film Magnetic Disks,” Technical Information Report presented at Discon USA ’96, Texwipe Company LLC; and Bhushan, “Magnetic Slider/Rigid Disk Substrate Materials and Disk Texturing Techniques--Status and Future Outlook,” Adv. Info. Storage Syst., Vol. 5, 1993: 175-209.
We have found an improved / simplified process, wherein the removal rate and surface texture are controllable and adjustable through pressure and chemical formulation. In our process, for the first time, a diamond containing slurry is used to accomplish the goal of pre-texturing polish. The results have a direct implication that the developed slurries can also be used for texturing application that is vastly different from the current practices.
In one embodiment, the slurry is comprised of...