International Business Machines Corporation

Other

Donald E Horne

Glen A Garfunkel

Steven Robert Hetzler

Chih-Kung Lee

John Stewart Best

Karl Arthur Flechsig

Prakash Kasiraj

Michael Paul Salo

Sylvia Lui Lee

Robert Langland Smith

David Malcolm Hannon

Fior D Sargent

Vincent Marrello

Wen-Wei Chiang

Walter Gerald Woodworth

A method for assessing write element performance in a combined magnetic head that also includes a magneto-resistive (MR) read element for a data storage drive includes exciting the write element with a square wave immediately after lapping the head during manufacture, before mounting the head for operation in the drive. The write element generates an output signal, and the output signal is detected by the read element and then used to determine whether the write element is defective. By using a square wave, temperature gradients in the head and inductive pick up is avoided, thereby facilitating the use of the read element as a test sensor.

System and method for testing a write head in a combined magnetic head

A glide height test signal processor and method using increased high frequency components is disclosed. The processor is more sensitive to smaller asperities, maintains the positive characteristics of being monotonic and can be easily calibrated. The system includes a circuit for converting asperity contact to an electrical signal, a first bandpass circuit coupled to the first circuit, the first bandpass circuit having a first amplifier for amplifying the electrical signal by a first gain to generate a first amplified signal and a first filter for filtering the first amplified signal at a high frequency to generate a first filtered signal, wherein the first gain is selected for detection of asperities having a diameter of less than or equal to five microns and a processing circuit, coupled to the first bandpass circuit, for processing the first filtered signal to generate an indication of contact with an asperity having a diameter of less than or equal to five microns. A second bandpass circuit may be coupled to the first circuit, wherein the second bandpass circuit has a second amplifier for amplifying the electrical signal by a second gain to generate a second amplified signal and a second filter for filtering the second amplified signal at a low frequency to generate a second filtered signal, wherein the ratio of the first gain and the second gain is substantially at least thirty to one.

Glide height test signal processor and method using increased high

A non-invasive servo-write system for use in a data recording disk drive. The system measures actuator position and generates a reference clock using semiconductor lasers. Internal position references are provided by reflective diffraction gratings affixed to the actuator arm and the spindle hub. Wavefront reconstruction optics correct for aberrations in the gratings. Optical sensors detect differential changes in the diffraction patterns created by the gratings, eliminating sensitivity to frequency drift. Decode electronics convert optical sensor data into an actuator position measurement. Control electronics drive the voice coil motor within the disk drive, which positions the write transducer to record servo information provided in a servo pattern generator. Transparent windows in the head-disk-assembly cover allow the servo-writer to write drives which are completely assembled and sealed.

Servo-writing system for use in a data recording disk drive

The present invention provides a test circuit and method for testing for short circuits in an MR head, merged MR head or piggyback MR head without contacting either of the shield layers. This is accomplished by a bridge circuit which employs part of the components of the head. The bridge circuit has four consecutively arranged branches which are interconnected by four consecutively arranged terminals. The first terminal comprises the substrate or one of the write pads and the second and fourth terminals comprise the first and second read pads. A signal generator is connected across the first and third terminals and a detector, such as a differential amplifier, is connected across the read pads. With this arrangement the first branch of the bridge circuit includes a capacitance which is formed by one of the gap layers between one of the shield layers and a first one of the leads and the second branch of the bridge circuit includes a capacitance which is formed by said one of the gap layers between said one of the shield layers and a second one of the leads. The differential amplifier detects any impedance imbalance in the bridge circuit which indicates that coupling between one or more of the shields and one or more of the leads has changed. Most likely the head has a shield short circuit and can be discarded.

Non-contact method for testing for MR shield short circuits

At the wafer level, a conventional write signal is applied to a pre-selected thin film head. Thereafter, first and second constant amplitude, differing frequency sine wave signals are applied to the head along with a DC bias signal whose magnitude is varied. The level of frequency mixing in the output signal of the head is detected at each level of magnitude of the DC bias signal and this data is utilized in predicting the level of noise in the read-back signal of the thin film head during normal read and write operations in connection with a rotating storage disk.

Method and apparatus for measuring nonlinearity in thin film heads

A capacitive sensor for detecting capacitive contrast servo information on a disk in a data recording disk file includes a center-tapped inductor connected to a high frequency oscillator, a sensing probe formed on the back side of the slider and electrically coupled to one end of the inductor, and a dummy probe also formed on the back side of the slider and electrically connected to the other end of the inductor. The center-tapped inductor forms a primary coil of a transformer so that variations in capacitance sensed by the sensing probe provide a differential output signal in the inductor which is sensed by the transformer secondary coil. The probes, and their electrically conductive leads and terminal pads, are formed by thin film deposition techniques on the back side of the slider and are located with respect to the inductive read/write head so as to equally receive any noise generated by the read/write head. The dummy probe is spaced away from the air bearing surface of the slider so that the variation in capacitance due to the capacitive contrast pattern on the disk is received only by the sensing probe.

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San Jose, CA, United States of America

Donald E Horne