Patents by Inventor Hokei LAM
Hokei LAM has filed for patents to protect the following inventions. This listing includes patent applications that are pending as well as patents that have already been granted by the United States Patent and Trademark Office (USPTO).
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Patent number: 9899046Abstract: A method of testing anti-high temperature performance of a magnetic head comprises applying a plurality of second magnetic fields with different intensities in a second direction to the magnetic head, and measuring a second output parameter curve, and judging whether a variation that is beyond an allowable value is presented on the second output parameter curve, therein the second direction passes through the ABS and at an angle whose absolute value is an acute angle to the ABS. The present invention can screen out defective magnetic heads that possess poor anti-high temperature performance without heating the magnetic head.Type: GrantFiled: April 29, 2011Date of Patent: February 20, 2018Assignee: SAE Magnetics (H.K.) Ltd.Inventors: Cheukman Lui, Chiuming Lueng, Hokei Lam, Mankit Lee, Kwokkam Leung, Cheukwing Leung, Juren Ding, Rongkwang Ni
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Patent number: 9355660Abstract: A testing method of a magnetic head includes: applying a first magnetic field with a constant intensity in a first direction that is the same with that of the longitudinal bias field to the magnetic head, simultaneously applying a second magnetic field with variant intensities in a second direction traversing the air bearing surface, and measuring a first noise; applying a third magnetic field with a constant intensity in a third direction that is opposite to the first direction to the magnetic head, simultaneously applying the second magnetic field with variant intensities in the second direction, and measuring a second noise; and analyzing noise change between the first noise and the second noise. The invention can screen out defective magnetic heads that possess poor noise characteristic and unstable performance.Type: GrantFiled: June 21, 2013Date of Patent: May 31, 2016Assignee: SAE MAGNETICS (H.K.) LTD.Inventors: Hokei Lam, Mankit Lee, Cheukman Lui, Wahchun Chan, Juren Ding, Rongkwang Ni, Cheukwing Leung, Wanyin Kwan
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Patent number: 9121888Abstract: A method of testing anti-high temperature performance of a magnetic head comprises applying a second magnetic field with different intensities in a second direction and the changing first magnetic fields in a first direction, and measuring a plurality of second output parameter curves; and judging whether a variation that is beyond an allowable value is presented on the second output parameter curves, thereby screening out a defective magnetic head, therein the first direction is perpendicular to the air bearing surface of the magnetic head, and the second direction is perpendicular to the shielding layers of the magnetic head. The present invention can screen out defective magnetic heads that possess poor anti-high temperature performance without heating the magnetic head and with high precision.Type: GrantFiled: April 29, 2011Date of Patent: September 1, 2015Assignee: SAE MAGNETICS (H.K.) LTD.Inventors: Chiuming Lueng, Cheukman Lui, Mankit Lee, Hokei Lam, Kwokkam Leung, Cheukwing Leung, Juren Ding, Rongkwang Ni
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Patent number: 8935132Abstract: A spectral simulation method during a noise testing for a magnetic head, includes steps of (a1) detecting several first noise profiles for several magnetic head samples under a first frequency bandwidth range by a dynamic testing machine; (b1) separating each first noise profile into at least two noise curves including a first noise curve and a second noise curve at a predetermined frequency bandwidth, wherein the first noise curve has a frequency bandwidth range lower than that of the second noise curve; (c1) fitting several mathematical equations according to the second noise curves; and (d1) establishing a correlative equation among the mathematical equations, so as to simulate the second noise curve for each magnetic head. The present invention can simulate a second noise curve of the noise profile in a higher frequency bandwidth and establishing the correlative equation according to the second noise curve.Type: GrantFiled: February 8, 2012Date of Patent: January 13, 2015Assignee: SAE Magnetics (H.K.) Ltd.Inventors: Hokei Lam, Cheukman Lui, Chiuming Lueng, Kaichiu Cheung, Wahchun Chan, Juren Ding, Rongkwang Ni
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Publication number: 20140334279Abstract: A testing method of a magnetic head includes: applying a first magnetic field with a constant intensity in a first direction that is the same with that of the longitudinal bias field to the magnetic head, simultaneously applying a second magnetic field with variant intensities in a second direction traversing the air bearing surface, and measuring a first noise; applying a third magnetic field with a constant intensity in a third direction that is opposite to the first direction to the magnetic head, simultaneously applying the second magnetic field with variant intensities in the second direction, and measuring a second noise; and analyzing noise change between the first noise and the second noise. The invention can screen out defective magnetic heads that possess poor noise characteristic and unstable performance.Type: ApplicationFiled: June 21, 2013Publication date: November 13, 2014Inventors: Hokei LAM, Mankit LEE, Cheukman LUI, Wahchun CHAN, Juren DING, Rongkwang NI, Cheukwing LEUNG, Wanyin KWAN
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Patent number: 8664950Abstract: A method for measuring longitudinal bias magnetic field in a tunnel magnetoresistive sensor of a magnetic head, the method includes the steps of: applying an external longitudinal time-changing magnetic field onto the tunnel magnetoresistive sensor; determining a shield saturation value of the tunnel magnetoresistive sensor under the application of the external longitudinal time-changing magnetic field; applying an external transverse time-changing magnetic field and an external longitudinal DC magnetic field onto the tunnel magnetoresistive sensor; determining a plurality of different output amplitudes under the application of the external transverse time-changing magnetic field and the application of different field strength values of the external longitudinal DC magnetic field; plotting a graph according to the different output amplitudes and the different field strength values; and determining the strength of the longitudinal bias magnetic field according to the graph and the shield saturation value.Type: GrantFiled: July 1, 2011Date of Patent: March 4, 2014Assignee: SAE Magnetics (H.K.) Ltd.Inventors: Siuman Mok, Hokei Lam, Cheukwing Leung, Juren Ding, Rongkwang Ni, Wanyin Kwan, Cheukman Lui, Chiuming Lueng
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Publication number: 20130204590Abstract: A spectral simulation method during a noise testing for a magnetic head, includes steps of (a1) detecting several first noise profiles for several magnetic head samples under a first frequency bandwidth range by a dynamic testing machine; (b1) separating each first noise profile into at least two noise curves including a first noise curve and a second noise curve at a predetermined frequency bandwidth, wherein the first noise curve has a frequency bandwidth range lower than that of the second noise curve; (c1) fitting several mathematical equations according to the second noise curves; and (d1) establishing a correlative equation among the mathematical equations, so as to simulate the second noise curve for each magnetic head. The present invention can simulate a second noise curve of the noise profile in a higher frequency bandwidth and establishing the correlative equation according to the second noise curve.Type: ApplicationFiled: February 8, 2012Publication date: August 8, 2013Applicant: SAE Magnetics (H.K.) Ltd.Inventors: Hokei LAM, Cheukman LUI, Chiuming LUENG, Kaichiu CHEUNG, Wahchun CHAN, Juren DING, Rongkwang NI
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Publication number: 20120274317Abstract: A method of testing anti-high temperature performance of a magnetic head comprises applying a second magnetic field with different intensities in a second direction and the changing first magnetic fields in a first direction, and measuring a plurality of second output parameter curves; and judging whether a variation that is beyond an allowable value is presented on the second output parameter curves, thereby screening out a defective magnetic head, therein the first direction is perpendicular to the air bearing surface of the magnetic head, and the second direction is perpendicular to the shielding layers of the magnetic head. The present invention can screen out defective magnetic heads that possess poor anti-high temperature performance without heating the magnetic head and with high precision.Type: ApplicationFiled: April 29, 2011Publication date: November 1, 2012Applicant: SAE Magnetics (H.K.) Ltd.Inventors: Chiuming Lueng, Cheukman Lui, Mankit Lee, Hokei Lam, Kwokkam Leung, Cheukwing Leung, Juren Ding, Rongkwang Ni
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Publication number: 20120275047Abstract: A method of testing anti-high temperature performance of a magnetic head comprises applying a plurality of second magnetic fields with different intensities in a second direction to the magnetic head, and measuring a second output parameter curve, and judging whether a variation that is beyond an allowable value is presented on the second output parameter curve, therein the second direction passes through the ABS and at an angle whose absolute value is an acute angle to the ABS. The present invention can screen out defective magnetic heads that possess poor anti-high temperature performance without heating the magnetic head.Type: ApplicationFiled: April 29, 2011Publication date: November 1, 2012Applicant: SAE Magnetics (H.K.) Ltd.Inventors: Cheukman Lui, Chiuming Lueng, Hokei Lam, Mankit Lee, Kwokkam Leung, Cheukwing Leung, Juren Ding, Rongkwang Ni
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Publication number: 20120249130Abstract: A method for measuring longitudinal bias magnetic field in a tunnel magnetoresistive sensor of a magnetic head, the method includes the steps of: applying an external longitudinal time-changing magnetic field onto the tunnel magnetoresistive sensor; determining a shield saturation value of the tunnel magnetoresistive sensor under the application of the external longitudinal time-changing magnetic field; applying an external transverse time-changing magnetic field and an external longitudinal DC magnetic field onto the tunnel magnetoresistive sensor; determining a plurality of different output amplitudes under the application of the external transverse time-changing magnetic field and the application of different field strength values of the external longitudinal DC magnetic field; plotting a graph according to the different output amplitudes and the different field strength values; and determining the strength of the longitudinal bias magnetic field according to the graph and the shield saturation value.Type: ApplicationFiled: July 1, 2011Publication date: October 4, 2012Applicant: SAE Magnetics (H.K.) Ltd.Inventors: Siuman MOK, Hokei LAM, Cheukwing LEUNG, Juren DING, Rongkwang NI, Wanyin KWAN, Cheukman LUI, Chiuming LUENG