Abrading – Accessory – Abradant supplying
Reexamination Certificate
1999-10-01
2001-03-06
Scherbel, David A. (Department: 3723)
Abrading
Accessory
Abradant supplying
Reexamination Certificate
active
06196907
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The invention relates to an improved polishing slurry delivery system for polishing electroless nickel plating used to manufacture hard disk drives. This slurry delivery system is for use with Wittig style machines
2. Description of the Prior Art
Polishing machines for polishing disk drives are known in the art. For example, U.S. Pat. No. 4,930,259 to Kobylenski et al. discloses a Magnetic Disk Substrate Polishing Assembly. In this case, the polishing assembly comprises a polish roller having a continuously fed polish cloth or polish tape. In addition, U.S. Pat. No. 4,845,816 to Nanis discloses a burnishing head for burnishing memory surfaces of computer memory disks.
With regard to the field of the present invention, Seagate Recording Media in Anaheim, California manufactures computer hard drives using a Wittig Polisher. Hans Wittig, of Seagate developed a polisher that is used to planorize or make flat, and polish electroless nickel plating which has been deposited on aluminum substrates This polishing process can be accomplished in two steps. Step one uses a very aggressive polishing process to planorize the nickel plating. Step two involves a less aggressive polishing technique that polishes the nickel to a mirror finish. The resultant substrate has a surface that is flat to within a few millionths of an inch, and has virtually no scratches when viewed with a laser inspection machines. The polishing media is a slurry of very fine aluminum oxide, each particle being less than 0.1 micron in size, and de-ionized water. De-ionized water is corrosive to ferric metals, and will thus cause rapid oxidation to most iron carrying metals.
The Wittig design has one problem in that the slurry and the de-ionized water must travel through more than a total of 20 feet of iron carrying metals per machine to reach the substrate surface. This results in iron oxide (rust) being mixed with the fine slurry and de-ionized water. Since the particles of rust can be several orders of magnitude larger than the very fine particles of the aluminum oxide polishing compound, the rust causes unacceptable scratches in the surface of the substrates.
SUMMARY OF THE INVENTION
It is therefore, an object of the invention to provide a slurry delivery system for a Wittig type polishing machine that can be assembled into a Wittig machine with little adjustment.
It is another an object of the invention to provide a slurry delivery system for a Wittig type polishing machine that reduces the exposure of de-ionized water and slurry to ferrous metals.
It is a further object of the invention to provide a slurry delivery system for a Wittig type polishing machine that reduces the amount of oxide impurities in an applied slurry.
It is still a further object of the invention to provide a slurry delivery system for a Wittig type polishing machine that improves the polishing surface of disk drives and thus reduces the failure rate of disk drives to below 10%.
These and other objects are achieved by providing a slurry delivery system for a Wittig machine comprising an extended length drive shaft made from type 416 stainless steel having a longitudinally extended inner channel. The heat treated type 416 stainless steel drive shaft provides the rugged high strength bearing journals required for this Wittig machine element. The relatively high tensile strength of the type 416 stainless steel will allow for long drive shaft life and improved durability. Type 416 stainless steel is a martensitic stainless steel containing 12-14% chromium as an alloying agent. Because stainless steels derive their resistance to corrosion from the presence of chromium, increasing the chromium content in steel progressively enhances the resistance to rusting. There is a slurry delivery tube made from type 316 stainless steel disposed within the drive shaft. Type 316 stainless steel has a chromium content of about 16-18% that is noticeably higher than type 416 stainless steel. In addition, type 316 stainless steel contains between 10-14% nickel which can be used to greatly improve the delivery tubels resistance to nonoxygenating media such as the abrasive slurry. Type 316 stainless steel also contains a higher level of manganese, which does not alter the corrosion resistance of the chromium, and molybdenum that improves resistance to solutions of halogen salts and pitting in seawater. Thus, this slurry delivery tube is less prone to corrosion than the type 416 stainless steel used for the drive shaft. In this way, the slurry delivery tube contained within the drive shaft eliminates the possibility that de-ionized water will contact and oxidize any iron based metal.
The de-ionized water is fed through a type 316 stainless steel slurry delivery tube in the central core of the drive shaft, which attaches to a type 316 stainless steel cross tube, within the drive shaft, that connects to a suitable manifold assembly that is inert to de-ionized water. The slurry leaves the manifold and continues through a modified slurry bowl and U-Joint to the type 316 stainless steel hub. After the de-ionized water and slurry passes through the hub -t flows into a large urethane plate attached to the upper Meehanite Platen. The slurry and de-ionized water flows through this urethane plate and down into type 316 stainless steel delivery tubes inserted into the Meehanite Upper Platen. A thin urethane pad with adhesive backing isolates the slurry from the top surface of the Meehanite Upper Platen.
This new design mimics the spring rate and stiffness of the current platen support so as not to introduce any unknown variables that could effect the polishing process.
Thus, this type design provides a corrosion free path for the transition of slurry, de-ionized water, and air to the substrate surfaces. In this case, the entire tool upgrade can be delivered on site and installed reasonably quickly in a Wittig type polishing machine resulting in minimum tool downtime. This design provides a complete low cost, long term effective solution for Wittig serviceability for a long time.
REFERENCES:
patent: 3848366 (1974-11-01), David
patent: 4048763 (1977-09-01), Janssen
patent: 4272924 (1981-06-01), Masuko et al.
patent: 4433510 (1984-02-01), Katagiri et al.
patent: 4490948 (1985-01-01), Hanstein et al.
patent: 4502252 (1985-03-01), Iwabuchi
patent: 4674236 (1987-06-01), Kawakami et al.
patent: 4845816 (1989-07-01), Nanis
patent: 4930259 (1990-06-01), Kobylenski et al.
patent: 5533923 (1996-07-01), Shamouilian et al.
patent: 5554064 (1996-09-01), Breivogel et al.
patent: 5582540 (1996-12-01), Su et al.
patent: 5658185 (1997-08-01), Morgan, III et al.
patent: 5779525 (1998-07-01), Boller
patent: 5816900 (1998-10-01), Nagahara et al.
patent: 5876271 (1999-03-01), Oliver
patent: 6045437 (2000-04-01), Tandon et al.
Collard & Roe P.C.
Nguyen George
Scherbel David A.
U.S. Dynamics Corporation
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