Granted Patent B2

US 12,631,445 · App. 18/224,680 · Granted May 19, 2026

Inventor: Shoji Suzuki (San Jose, CA)

Assignee: WESTERN DIGITAL TECHNOLOGIES, INC.

G01B21/08

Abstract

Claims (70)

1 . A method of identifying a substrate suitable for use within a magnetic medium of a data storage device configured for magnetic recording, comprising:

identifying one or more dimensions of a slider of the data storage device to be used in conjunction with the magnetic medium;

determining a measurement length and a localized height threshold as a function of the one or more dimensions of the slider;

measuring a plurality of localized height values of the substrate at a plurality of distances from a center of the substrate, each of the plurality of localized height values measured within the measurement length and at one of the plurality of distances;

comparing the plurality of localized height values and the localized height threshold; and

determining to utilize the substrate for the magnetic medium based on the comparison of the plurality of localized height values and the localized height threshold.

2 . The method of claim 1 , wherein the plurality of localized height values are measured along a plurality of measurement lines on a surface of the substrate, each of the plurality of measurement lines being a straight line directed toward the center of the substrate and having a length equal to the measurement length.

3 . The method of claim 2 , wherein each of the plurality of localized height values is measured based on a difference between a highest point and a lowest point on the surface of the substrate along a respective measurement line of the plurality of measurement lines.

4 . The method of claim 1 , wherein the determining the localized height threshold comprises determining the localized height threshold based on the measurement length, and

wherein the measurement length is based on a length and a width of a rectangular surface of the slider configured to face a surface of the magnetic medium and is further based on a skew angle of the rectangular surface, the skew angle being an angle between a line parallel to the length of the rectangular surface and a data track on the magnetic medium.

5 . The method of claim 4 , wherein the measurement length is a sum of the length of the rectangular surface multiplied by a sine value of the skew angle and the width of the rectangular multiplied by a cosine value of the skew angle.

6 . The method of claim 4 , wherein the localized height threshold is 500 nanometers multiplied by a square of a ratio of the width of the rectangular surface the slider to the measurement length.

7 . The method of claim 4 , wherein the localized height threshold includes a plurality of localized height thresholds respectively corresponding to a plurality of radial distance ranges from the center of the substrate,

wherein the determining the localized height threshold comprises determining the plurality of localized height thresholds based on the measurement length and further based on the plurality of radial distance ranges from the center of the substrate, and

wherein the comparing the plurality of localized height values and the localized height threshold comprises comparing the plurality of localized height values and the plurality of localized height thresholds, wherein each localized height value is compared with a respective one of the plurality of localized height thresholds that corresponds to a respective radial distance range of the plurality of radial distance ranges.

8 . The method of claim 7 , wherein the plurality of radial distance ranges respectively correspond to a plurality of radial distance constants, and

wherein each of the plurality of localized height thresholds is determined based on a respective radial distance constant of the plurality of radial distance constants multiplied by a square of a ratio of the width of the rectangular surface of the slider to the measurement length.

9 . The method of claim 1 , wherein the determining to utilize the substrate comprises:

determining that the substrate is acceptable for the magnetic medium in response to determining that a shortest distance from a center of the substrate corresponding to a localized height value exceeding the localized height threshold is greater than a radial distance threshold; and

determining that the substrate is unacceptable for the magnetic medium in response to determining that the shortest distance from the center of the substrate corresponding to the localized height value exceeding the localized height threshold is less than or equal to the radial distance threshold.

10 . The method of claim 1 , wherein the plurality of localized height values includes a plurality of sets of localized height values respectively corresponding to the plurality of distances from a center of the substrate, each set of localized height values corresponding to a respective one of the plurality of distances, and

wherein the determining to utilize the substrate comprises:

determining a plurality of maximum localized height values respectively for the plurality of sets of localized height values that respectively correspond to the plurality of distances, each maximum localized height value of the plurality of maximum localized height values being a maximum value of localized height values of a respective set of the plurality of sets;

determining that the substrate is acceptable for the magnetic medium when a shortest distance from a center of the substrate corresponding to a maximum localized height value of the plurality of maximum localized height values that exceeds the localized height threshold is greater than a radial distance threshold; and

determining that the substrate is unacceptable for the magnetic medium when the shortest distance from the center of the substrate corresponding to the maximum localized height value of the plurality of maximum localized height values that exceeds the localized height threshold is less than or equal to the radial distance threshold.

11 . The method of claim 1 , wherein the plurality of localized height values include a plurality of sets of localized height values respectively corresponding to the plurality of distances from a center of the substrate, each set of localized height values corresponding to a respective one of the plurality of distances, and

wherein the determining to utilize the substrate comprises:

determining a plurality of average localized height values respectively for the plurality of sets of localized height values that respectively correspond to the plurality of distances, each average localized height value of the plurality of average localized height values being an average value of localized height values of a respective set of the plurality of sets;

determining that the substrate is acceptable for the magnetic medium when a shortest distance from a center of the substrate corresponding to an average localized height value of the plurality of average localized height values that exceeds the localized height threshold is greater than a radial distance threshold; and

determining that the substrate is unacceptable for the magnetic medium when the shortest distance from the center of the substrate corresponding to the average localized height value of the plurality of average localized height values that exceeds the localized height threshold is less than or equal to the radial distance threshold.

12 . The method of claim 1 , further comprising:

identifying a data zone on a surface of the substrate to record data based on the localized height threshold and the plurality of localized height values.

13 . The method of claim 12 , wherein the identifying the data zone comprises:

determining that a localized height value of the plurality of localized height values that corresponds to a distance of the plurality of distances exceeds the localized height threshold; and

excluding, from the data zone, a portion on the surface of the substrate that is beyond the distance of the plurality of distances from the center of the substrate.

14 . The method of claim 12 , wherein the plurality of localized height values include a plurality of sets of localized height values respectively corresponding to the plurality of distances from a center of the substrate, each set of localized height values corresponding to a respective one of the plurality of distances, and

wherein the identifying the data zone comprises:

determining a plurality of maximum localized height values respectively for the plurality of sets of localized height values that respectively correspond to the plurality of distances, each maximum localized height value of the plurality of maximum localized height values being a maximum value of localized height values of a respective set of the plurality of sets;

determining that a maximum localized height value of the plurality of maximum localized height values that corresponds to a distance of the plurality of distances exceeds the localized height threshold; and

excluding, from the data zone, a portion on the surface of the substrate that is beyond the distance of the plurality of distances from the center of the substrate.

15 . The method of claim 12 , wherein the plurality of localized height values include a plurality of sets of localized height values respectively corresponding to the plurality of distances from a center of the substrate, each set of localized height values corresponding to a respective one of the plurality of distances, and

wherein the identifying the data zone comprises:

determining a plurality of average localized height values respectively for the plurality of sets of localized height values that respectively correspond to the plurality of distances, each average localized height value of the plurality of average localized height values being an average value of localized height values of a respective set of the plurality of sets;

determining that an average localized height value of the plurality of average localized height values that corresponds to a distance of the plurality of distances exceeds the localized height threshold; and

excluding, from the data zone, a portion on the surface of the substrate that is beyond the distance of the plurality of distances from the center of the substrate.

16 . The method of claim 1 , wherein the measurement length includes a plurality of measurement lengths and the localized height threshold includes a plurality of localized height thresholds,

wherein each of the plurality of localized height values are measured within a respective one of the plurality of measurement lengths and at one of the plurality of distances, and

wherein the comparing the plurality of localized height values and the localized height threshold comprises comparing the plurality of localized height values and the plurality of localized height thresholds, respectively, wherein each of the plurality of localized height values is compared with a respective one of the plurality of localized height values.

17 . A method of identifying a substrate suitable for use within a magnetic medium of a data storage device configured for magnetic recording, comprising:

identifying one or more dimensions of a slider of the data storage device to be used in conjunction with the magnetic medium;

determining a measurement length and a localized height threshold as a function of the one or more dimensions of the slider;

measuring a plurality of localized height values of the substrate at a plurality of distances from a center of the substrate, each of the plurality of localized height values measured within the measurement length and at one of the plurality of distances;

comparing the plurality of localized height values and the localized height threshold; and

identifying a data zone on the substrate to record data based on the comparison of the plurality of localized height values and the localized height threshold.

18 . The method of claim 17 , wherein the identifying the data zone comprises:

determining that a first localized height value of the plurality of localized height values measured at a first distance of the plurality of distances exceeds the localized height threshold; and

excluding, from the data zone, a portion of a surface of the substrate that is beyond the first distance from a center of the substrate.

19 . The method of claim 17 , wherein the plurality of localized height values includes a plurality of sets of localized height values measured at the respective plurality of distances from a center of the substrate, each set of localized height values corresponding to a respective one of the plurality of distances, and

wherein the identifying the data zone comprises:

determining a plurality of maximum localized height values respectively for the plurality of sets of localized height values that respectively correspond to the plurality of distances, each maximum localized height value of the plurality of maximum localized height values being a maximum value of localized height values of a respective set of the plurality of sets;

determining that a maximum localized height value, of the plurality of maximum localized height values that was measured at a first distance of the plurality of distances, exceeds the localized height threshold; and

excluding, from the data zone, a portion of a surface of the substrate that is beyond the first distance from the center of the substrate.

20 . The method of claim 17 , wherein the plurality of localized height values includes a plurality of sets of localized height values measured at the respective plurality of distances from a center of the substrate, each set of localized height values corresponding to a respective one of the plurality of distances, and

wherein the identifying the data zone comprises:

determining a plurality of average localized height values respectively for the plurality of sets of localized height values that respectively correspond to the plurality of distances, each average localized height value of the plurality of average localized height values being an average value of localized height values of a respective set of the plurality of sets;

determining that an average localized height value of the plurality of average localized height values that corresponds to a first distance of the plurality of distances exceeds the localized height threshold; and

excluding, from the data zone, a portion of a surface of the substrate that is beyond the first distance from the center of the substrate.

21 . The method of claim 17 , wherein the measurement length includes a plurality of measurement lengths and the localized height threshold includes a plurality of localized height thresholds,

wherein each of the plurality of localized height values are measured within a respective one of the plurality of measurement lengths and at one of the plurality of distances, and

wherein the comparing the plurality of localized height values and the localized height threshold comprises comparing the plurality of localized height values and the plurality of localized height thresholds, respectively, wherein each of the plurality of localized height values is compared with a respective one of the plurality of localized height values.

Assignments (3)

Continuity (2)

References Cited (15)