Etching a substrate: processes – Nongaseous phase etching of substrate – With measuring – testing – or inspecting
Reexamination Certificate
1999-03-08
2001-07-03
Gulakowski, Randy (Department: 1746)
Etching a substrate: processes
Nongaseous phase etching of substrate
With measuring, testing, or inspecting
C451S008000, C451S059000, C216S106000
Reexamination Certificate
active
06254795
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The invention relates to a hard disk plate, and more particularly, to a texture measuring method of a hard disk plate.
2. Description of the Prior Art
A typical hard disk plate is formed by elecrolessly plating a nickel and phosphorus layer on an aluminum baseboard. The surface of the nickel and phosphorus layer is ground to a roughness (Ra) of 8~15 Å followed by mechanical texturing to form circular textures on the surface with a roughness (Ra) of 20~40 Å. The final step of the process of forming the hard disk plate involves forming a sputtered base layer, a magnetic layer, a passivation layer and a lubricating layer of approximately 20 Å on the passivation layer.
The hard disk plate comprises a landing zone where a magnetic head may land and a data storage area for storing data. The landing zone has a great number of circular textures to reduce the contact surface between the magnetic head and the hard disk plate. This reduces stiction between them. The data storage area has a smaller number of circular textures so as to provide a better base for positioning the magnetic layer, facilitate operations of the magnetic head, remove oxide on the surface of the nickel and phosphorus layer, and remove scratches generated when grinding the nickel and phosphorus layer.
Removal of scratches is accomplished by mechanical texturing. The thicker the portion of the nickel and phosphorus layer removed, the more scratches will be removed. However, the removal of scratches will result in a rougher data storage area. This will cause problems in the operation of the magnetic head. There are many factors affecting the formation of the circular textures. They include the type of texturing tape, texturing slurry, and coolant, force imposed on the hard disk plate, speed of rotation of the hard disk plate, texturing time, and vibration frequency of the main axis of the hard disk plate. Thus, it is difficult to determine how to form the circular textures.
Currently, the formation of the circular textures is determined based on two numbers. The first number is the difference between the weight of the hard disk plate before and after the circular textures are formed. This value indicates the amount of the hard disk plate removed. The second number is the roughness of the surface of the hard disk plate. This can be directly measured with a measuring device.
The amount of hard disk plate removed is small making accurate measurement of the difference in weight before and after circular texture formation difficult. Moreover, the process is labor intensive as the hard disk plate must be washed and dried before each weighing. Furthermore, the amount of the hard disk plate removed over different areas of the hard disk plate cannot be accurately assessed using the current method. Thus, the flatness of the hard disk plate after forming the circular textures cannot be effectively determined.
SUMMARY OF THE INVENTION
It is therefore a primary objective of the present invention to provide a texture measuring method of a hard disk plate to solve the above mentioned problems.
Briefly, in a preferred embodiment, the present invention provides a texture measuring method of a hard disk plate comprising:
performing a laser etching process to form a pinhole at each of a plurality of predetermined positions in a predetermined area on the hard disk plate;
measuring the pinhole at each of the predetermined positions to obtain a first measurement value;
performing a mechanical texturing process on the predetermined area of the hard disk plate to form circular textures on the predetermined area; and
measuring the pinhole at each of the predetermined positions to obtain a second measurement value wherein the first and second measurement values are used to determine the extent of texturing performed on the predetermined area of the hard disk plate.
It is an advantage of the present invention that the first and second measurement values are used to determine the extent of texturing performed on the predetermined area of the hard disk plate so that measuring the amount of the hard disk plate being removed takes less work, and the amount of the hard disk plate being removed over different parts of surface of the hard disk plate can be effectively determined.
These and other objects and the advantages of the present invention will no doubt become obvious to those of ordinary skill in the art after having read the following detailed description of the preferred embodiment that is illustrated in the various figures and drawings.
REFERENCES:
patent: 5167096 (1992-12-01), Eltoukhy et al.
patent: 5506017 (1996-04-01), Ranjan et al.
patent: 6123603 (2000-09-01), Tada et al.
Chen Chi-Chih
Tan An-Hung
Wang Han-Ming
Gulakowski Randy
Hsu Winston
Kornakov Michael
Trace Storage Technology Corp.
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