Testing methods for magnetic heads and magnetic storage devices assembled with the magnetic heads

• US 8,552,716 B2
• Filed: 12/08/2010
• Issued: 10/08/2013
• Est. Priority Date: 12/09/2009
• Status: Expired due to Fees

• Current Assignee: Western Digital Technologies Incorporated (Western Digital Corporation)
• Original Assignee: HGST Netherlands B.V. (Western Digital Corporation)
• Inventors: Ono, Makoto, Ueda, Fumiomi
• Primary Examiner(s): Aurora, Reena
• Application Number:
  US12/963,551
• Publication Number:
  US 20110134559A1
• Time in Patent Office: 1,035 Days
• Field of Search: 324/210, 324/262
• US Class Current: 324/210
• CPC Class Codes: G11B 5/455 Arrangements for functional testing of heads; Measuring arrangements for heads
• CPC Class Codes: Y10T 29/49032 Fabricating head structure or component thereof

Abstract

In one embodiment, a manufacturing method for magnetic heads includes classifying magnetic heads into one of: a first tested head class, and a non-test-candidate head class, determining characteristic values of the magnetic heads classified in the first tested head class, estimating characteristic values of the magnetic heads classified in the non-test-candidate head class, wherein the estimating is based on the characteristic values of the magnetic heads classified in the first tested head class, classifying each of the magnetic heads classified in the non-test-candidate head class into one of: a second tested head class, and a non-test head class based on the estimated characteristic values, determining characteristic values of the magnetic heads classified in the second tested head class, and screening magnetic heads in the second tested head class based on the determined characteristic values of the magnetic heads classified in the second tested head class.

Claims

1. A method for testing magnetic heads, comprising:

classifying each of a plurality of magnetic heads into one of;

a first tested head class, and a non-test-candidate head class, such that at least two magnetic heads in each rowbar are classified into the first tested head class and remaining magnetic heads in each rowbar are classified into the non-test-candidate head class, each rowbar comprising a linear arrangement of a plurality of magnetic heads;

determining characteristic values of the magnetic heads classified in the first tested head class via magnetic head testing;

determining estimated characteristic values of the magnetic heads classified in the non-test-candidate head class, wherein the estimated characteristic values are based on the characteristic values of the magnetic heads classified in the first tested head class near to the magnetic heads in the non-test-candidate head class in each rowbar;

classifying each of the magnetic heads classified in the non-test-candidate head class into one of;

a second tested head class, and a non-test head class, wherein the classifying is based on a comparison between standard characteristic values of a magnetic head and the estimated characteristic values of the magnetic heads classified in the non-test-candidate head class, such that any magnetic heads which do not have estimated characteristic values equivalent to or better than the standard values are classified into the second tested head class and remaining magnetic heads are classified into the non-test head class; and

determining characteristic values of the magnetic heads classified in the second tested head class via magnetic head testing.

2. The method as recited in claim 1, wherein the characteristic values comprise at least one of:

a resistance of a playback element of a magnetic head (MRDCR), an amplitude of a voltage output from terminals of a magnetic head due to a magnetic field received by the playback element (AMP), and an asymmetry of the voltage (ASYM).

3. The method as recited in claim 1, further comprising screening magnetic heads in the first tested head class based on a comparison between the standard characteristic values and the determined characteristic values of the magnetic heads classified in the first tested head class, wherein magnetic heads in the first tested head class which do not have determined characteristic values equivalent to or better than the standard values are classified as scrap, wherein classifying each of the plurality of magnetic heads comprises using criteria that are different from criteria used for screening the magnetic heads in the first tested head class, and wherein the criteria used for screening comprises at least one of a direct current (DC) measurement test and an alternating current (AC) measurement test.

4. The method as recited in claim 1, further comprising screening magnetic heads in the second tested head class based on a comparison between the standard characteristic values and the determined characteristic values of the magnetic heads classified in the second tested head class, wherein magnetic heads in the second tested head class which do not have determined characteristic values equivalent to or better than the standard values are classified as scrap, and wherein classifying the magnetic heads classified in the non-test-candidate head class comprises using criteria that are different from criteria used for screening, and wherein the criteria used for screening comprises at least one of a direct current (DC) measurement test and an alternating current (AC) measurement test.

5. The method as recited in claim 1, wherein determining estimated characteristic values of the magnetic heads classified in the non-test-candidate head class further comprises using characteristic values of the magnetic heads classified in the first tested head class in a rowbar along with characteristic values of other magnetic heads in the rowbar to interpolate characteristic values of the magnetic heads classified in the non-test-candidate head class.

6. The method as recited in claim 1, wherein determining estimated characteristic values of the magnetic heads classified in the non-test-candidate head class further comprises using a difference between pairs of characteristic values corresponding to one position in the rowbar of the magnetic heads classified in the first tested head class in a rowbar and of a profile of characteristic values of other magnetic heads produced previously, wherein the rowbar comprises a linear arrangement of a plurality of magnetic heads.

7. The method as recited in claim 1, further comprising:

applying flag information indicating that a component is to be tested to the characteristic values of the magnetic heads classified in the first tested head class and the magnetic heads classified in the second tested head class;

applying flag information indicating that a component is not to be tested to the characteristic values of components of magnetic heads in the non-test head class which are estimated from the characteristic values of magnetic heads in the tested head class; and

reading out the characteristic values of the tested components and the non-tested components and the corresponding flag information of these components by using serial numbers applied to each of the magnetic heads as search keys.

8. A manufacturing method for magnetic storage device assembled with one or more magnetic heads, the method comprising:

preparing a substrate for forming a plurality of magnetic heads thereon;

forming the plurality of magnetic heads on the substrate;

assembling the plurality of magnetic heads into magnetic storage devices;

testing at least some of the plurality of magnetic heads to obtain characteristic values;

determining estimated characteristic values of non-tested magnetic heads on which testing is not performed using the characteristic values of the tested magnetic heads;

classifying the non-tested magnetic heads based on the estimated characteristic values;

assembling the magnetic heads classified as non-tested magnetic heads into the magnetic storage devices according to assembly rules;

measuring performance of the magnetic storage devices assembled with the non-tested magnetic heads; and

screening the magnetic storage devices assembled with the non-tested magnetic heads,

wherein the characteristic values comprise at least one of;

a resistance of a playback element of a magnetic head (MRDCR), an amplitude of a voltage output from terminals of a magnetic head due to a magnetic field received by the playback element (AMP), and an asymmetry of the voltage (ASYM).

9. A system, comprising:

a processor adapted for executing logic;

logic adapted for classifying each of a plurality of magnetic heads into one of;

a first tested head class, and a non-test-candidate head class, such that at least two magnetic heads in each rowbar are classified into the first tested head class, each rowbar comprising a linear arrangement of a plurality of magnetic heads;

logic adapted for determining characteristic values of the magnetic heads classified in the first tested head class via magnetic head testing;

logic adapted for determining estimated characteristic values of the magnetic heads classified in the non-test-candidate head class, wherein the estimated characteristic values are based on the characteristic values of the magnetic heads classified in the first tested head class;

logic adapted for classifying each of the magnetic heads classified in the non-test-candidate head class into one of;

a second tested head class, and a non-test head class, wherein the classifying is based on the estimated characteristic values of the magnetic heads classified in the non-test-candidate head class; and

logic adapted for determining characteristic values of the magnetic heads classified in the second tested head class via magnetic head testing.

10. The system as recited in claim 9, wherein the logic adapted for classifying the magnetic heads classified in the non-test-candidate head class comprises using criteria that are different from criteria used for screening, and wherein the characteristic values comprise at least one of:

a resistance of a playback element of a magnetic head (MRDCR), an amplitude of a voltage output from terminals of a magnetic head due to a magnetic field received by the playback element (AMP), and an asymmetry of the voltage (ASYM).

11. The system as recited in claim 9, further comprising logic adapted for screening magnetic heads in the first tested head class based on the determined characteristic values of the magnetic heads classified in the first tested head class.

12. The system as recited in claim 9, further comprising logic adapted for screening magnetic heads in the non-test-candidate head class based on the estimated characteristic values of the magnetic heads classified in the non-test-candidate head class.

13. The system as recited in claim 9, wherein the logic adapted for determining estimated characteristic values of the magnetic heads classified in the non-test-candidate head class further comprises using characteristic values of the magnetic heads classified in the first tested head class in a rowbar along with characteristic values of other magnetic heads in the rowbar to interpolate characteristic values of the magnetic heads classified in the non-test-candidate head class, wherein the rowbar comprises a linear arrangement of a plurality of magnetic heads.

14. The system as recited in claim 9, wherein the logic adapted for determining estimated characteristic values of the magnetic heads classified in the non-test-candidate head class further comprises using a difference between pairs of characteristic values corresponding to one position in the rowbar of the magnetic heads classified in the first tested head class in a rowbar and of a profile of characteristic values of other magnetic heads produced previously, wherein the rowbar comprises a linear arrangement of a plurality of magnetic heads.

15. The system as recited in claim 9, further comprising:

logic adapted for applying flag information indicating that a component is to be tested to the characteristic values of the magnetic heads classified in the first tested head class and the magnetic heads classified in the second tested head class;

logic adapted for applying flag information indicating that a component is not to be tested to the characteristic values of components of magnetic heads in the non-test head class which are estimated from the characteristic values of magnetic heads in the tested head class; and

logic adapted for reading out the characteristic values of the tested components and the non-tested components and the corresponding flag information of these components by using serial numbers applied to each of the magnetic heads as search keys.

16. A computer program product, the computer program product comprising:

a non-transitory computer readable medium having computer readable code stored thereon, the computer readable medium comprising;

computer readable code adapted for classifying each of a plurality of magnetic heads into one of;

a first tested head class, and a non-test-candidate head class, such that at least two magnetic heads in each rowbar are classified into the first tested head class and remaining magnetic heads in each rowbar are classified into the non-test-candidate head class, each rowbar comprising a linear arrangement of a plurality of magnetic heads;

computer readable code adapted for determining characteristic values of the magnetic heads classified in the first tested head class via magnetic head testing;

computer readable code adapted for determining estimated characteristic values of the magnetic heads classified in the non-test-candidate head class, wherein the estimated characteristic values is based on the characteristic values of the magnetic heads classified in the first tested head class;

computer readable code adapted for classifying each of the magnetic heads classified in the non-test-candidate head class into one of;

a second tested head class, and a non-test head class, wherein the classifying is based on a comparison between the standard characteristic values and the estimated characteristic values of the magnetic heads classified in the non-test-candidate head class, such that any magnetic heads which do not have estimated characteristic values equivalent to or better than the standard values are classified into the second tested head class and remaining magnetic heads are classified into the non-test head class; and

computer readable code adapted for determining characteristic values of the magnetic heads classified in the second tested head class via magnetic head testing.

17. The computer program product as recited in claim 16, further comprising computer readable code adapted for screening magnetic heads in the first tested head class based on a comparison between the standard characteristic values and the determined characteristic values of the magnetic heads classified in the first tested head class.

18. The computer program product as recited in claim 17, wherein the computer readable code adapted for classifying the magnetic heads classified in the non-test-candidate head class comprises using criteria that are different from criteria used for screening.

19. The computer program product as recited in claim 16, further comprising computer readable code adapted for screening magnetic heads in the non-test-candidate head class based on a comparison between the standard characteristic values and the estimated characteristic values of the magnetic heads classified in the non-test-candidate head class, wherein magnetic heads in the second tested head class which do not have determined characteristic values equivalent to or better than the standard values are classified as scrap.

20. The computer program product as recited in claim 16, wherein the computer readable code adapted for determining estimated characteristic values of the magnetic heads classified in the non-test-candidate head class further comprises using characteristic values of the magnetic heads classified in the first tested head class in a rowbar along with characteristic values of other magnetic heads in the rowbar to interpolate characteristic values of the magnetic heads classified in the non-test-candidate head class, wherein the rowbar comprises a linear arrangement of a plurality of magnetic heads.

21. The computer program product as recited in claim 16, wherein the computer readable code adapted for determining estimated characteristic values of the magnetic heads classified in the non-test-candidate head class further comprises using a difference between pairs of characteristic values corresponding to one position in the rowbar of the magnetic heads classified in the first tested head class in a rowbar and of a profile of characteristic values of other magnetic heads produced previously, wherein the rowbar comprises a linear arrangement of a plurality of magnetic heads.

22. The computer program product as recited in claim 16, further comprising:

computer readable code adapted for applying flag information indicating that a component is to be tested to the characteristic values of the magnetic heads classified in the first tested head class and the magnetic heads classified in the second tested head class;

computer readable code adapted for applying flag information indicating that a component is not to be tested to the characteristic values of components of magnetic heads in the non-test head class which are estimated from the characteristic values of magnetic heads in the tested head class; and

computer readable code adapted for reading out the characteristic values of the tested components and the non-tested components and the corresponding flag information of these components by using serial numbers applied to each of the magnetic heads as search keys.