# US 2014/0154951 A1 · Common ground for electronic lapping guides

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- Number: US 2014/0154951 A1
- Document ID: US20140154951A1
- Status: Published application
- Kind: A1
- Application number: 13/690,657
- Filed: 2012-11-30
- Published: 2014-06-05
- Earliest claimed: 2012-11-30
- Assignees: HGST Netherlands B.V.
- Applicants: Hgst Netherlands B.V.
- Inventors: Glen P. Gee; Edward H.P. Lee; David J. Seagle; Darrick T. Smith
- Web page: https://patentgrep.com/patent/US20140154951A1

## CPC

- B24B 37/00: Lapping machines or devices; Accessories (B24B3/00 takes precedence)
- B24B 37/005: Control means for lapping machines or devices
- G11B 5/1871: {Shaping or contouring of the transducing or guiding surface}
- G11B 5/3166: {Testing or indicating in relation thereto, e.g. before the fabrication is completed}
- G11B 5/3169: {Working or finishing the interfacing surface of heads, e.g. lapping of heads}
- Y10T 29/49004: including measuring or testing of device or component part
- Y10T 29/49032: Fabricating head structure or component thereof
- B24B: MACHINES, DEVICES, OR PROCESSES FOR GRINDING OR POLISHING (grinding of gear teeth B23F, of screw-threads B23G1/36; by electro-erosion B23H; abrasive or related blasting B24C; tools for grinding, buffing or sharpening B24D; polishing compositions C09G1/00; abrasives C09K3/14; electrolytic etching or polishing C25F3/00; grinding arrangements for use on assembled railway tracks E01B31/17); DRESSING OR CONDITIONING OF ABRADING SURFACES; FEEDING OF GRINDING, POLISHING, OR LAPPING AGENTS
- G11B: INFORMATION STORAGE BASED ON RELATIVE MOVEMENT BETWEEN RECORD CARRIER AND TRANSDUCER (recording measured values in a way that does not require playback through a transducer G01D9/00; recording or playback apparatus using mechanically marked tape, e.g. punched paper tape, or using unit records, e.g. punched or magnetically marked cards G06K; transferring data from one type of record carrier to another G06K1/18; circuits for coupling output of reproducer to radio receiver H04B1/20; gramophone pick-ups or like acoustic electromechanical transducers or circuits therefor H04R)
- Y10T: TECHNICAL SUBJECTS COVERED BY FORMER US CLASSIFICATION

## Abstract

Embodiments described herein generally relate to connecting Electronic Lapping Guides (ELG) to a lapping controller such that the number of wire bonds from the controller to a row of read heads is minimized. When lapping the air bearing surface of the read heads, the electrical resistances of the ELGs are monitored to adjust the lapping process and set the stripe height for read sensors in the read heads. Once the resistance corresponds to the desired stripe height, the lapping process is stopped. To measure the resistance, each ELG may be electrically coupled to the same substrate—i.e., share the same common ground. The lapping controller applies a voltage potential across the ELGs using a wire bonded to a pad in the respective read head and one or more connections to the grounded substrate. This configuration avoids having to bond two wires onto each read head.

## Claims

### Claim 1

A device, comprising:
a substrate; and
a plurality of read heads disposed on the substrate, a first one of the plurality of read heads comprising:
a read sensor configured to detect magnetic orientation changes in a magnetic media,
an electronic lapping guide (ELG) configured to indicate, based on a resistance of the ELG, a stripe height of the read sensor, wherein the ELG is electrically coupled to the substrate, and
a first bonding pad electrically coupled to the ELG, wherein the first bonding pad, the ELG, and the substrate are part of a current path permitting current to flow through the ELG.

### Claim 2 (depends on 1)

The device of claim 1, further comprising a second bonding pad electrically coupled to the substrate and part of the current path permitting current to flow through the ELG.

### Claim 3 (depends on 2)

The device of claim 2, wherein the second bonding pad is disposed on a second read head of the plurality of read heads that is different from the first read head comprising the ELG.

### Claim 4 (depends on 2)

The device of claim 2, wherein the second bonding pad is disposed on a portion of the substrate that does not include one of the plurality of read heads.

### Claim 5 (depends on 1)

The device of claim 1, wherein the plurality of read heads is arranged in a row on the substrate.

### Claim 6 (depends on 1)

The device of claim 1, wherein the substrate is one of: alumina and titanium carbide.

### Claim 7 (depends on 1)

The device of claim 1, wherein the ELG is not electrically connected to a second bonding pad in the first read head.

### Claim 8 (depends on 1)

The device of claim 1, wherein the read sensor is one of a tunneling magnetoresistance sensor and a giant magnetoresistance sensor.

### Claim 9

A system, comprising:
a substrate comprising a plurality of read heads, each read head comprising:
a read sensor configured to sense data stored in a magnetic media,
an ELG configured to indicate, based on a resistance of the ELG, a stripe height of the read sensor, wherein the ELG is electrically coupled to the substrate, and
a bonding pad electrically coupled to the ELG, wherein the bonding pad, the ELG, and the substrate are part of a current path permitting current to flow through the ELG,
a lapping unit configured to simultaneously lap an air bearing surface on the plurality of read heads, wherein the substrate is mounted on the lapping unit; and
a lapping controller electrically coupled to the bonding pad and the substrate, the lapping controller configured to measure the resistance of the ELG using the current path and transmit instructions to the lapping unit based on the measured resistance.

### Claim 10 (depends on 9)

The system of claim 9, further comprising a substrate access pad electrically coupled to the substrate, wherein the lapping controller is electrically coupled to the substrate via the substrate access pad.

### Claim 11 (depends on 10)

The system of claim 10, wherein the lapping controller is electrically coupled to a first bonding pad in a first one of the plurality of read heads and a second bonding pad on a second one of the plurality of read heads, wherein the lapping controller uses a first current path from the first bonding pad to the substrate access pad to measure a resistance of a first ELG in the first read head and a second current path from the second bonding pad to the substrate access pad to measure a resistance of a second ELG in the second read head.

### Claim 12 (depends on 10)

The system of claim 10, wherein the substrate access pad is disposed on one of the plurality of read heads.

### Claim 13 (depends on 9)

The system of claim 9, wherein the lapping controller is physically coupled to at most one bonding pad in a first one of the plurality of read heads when measuring the resistance of an ELG in the first read head.

### Claim 14

A method, comprising:
attaching a first wire to a bonding pad on a first one of a plurality of read heads disposed on a substrate, the first read head comprising:
a read sensor configured to detect magnetic orientation changes in a magnetic media, and
an ELG configured to indicate, based on a resistance of the ELG, a stripe height of the read sensor, wherein the ELG is electrically coupled to the substrate, and wherein the bonding pad is electrically coupled to the ELG;
attaching a second wire to a substrate access pad electrically coupled to the substrate; and
applying a voltage potential across the first and second wires such that current flows through the substrate and the ELG.

### Claim 15 (depends on 14)

The method of a claim 14, further comprising:
attaching a third wire to a second bonding pad on a second one of the plurality of read heads; and
applying a voltage potential across the second and third wires such that current flows through the substrate and an ELG in the second read head.

### Claim 16 (depends on 15)

The method of claim 15, further comprising, during a same lapping period, switching between applying the voltage potential across the first and second wires to applying the voltage potential across the second and third wires.

### Claim 17 (depends on 14)

The method of claim 14, wherein the substrate access pad is not disposed on the first read head.

### Claim 18 (depends on 14)

The method of claim 14, wherein the voltage potential across the first and second wires is applied while lapping an air bearing surface on the plurality of read heads.

### Claim 19 (depends on 14)

The method of claim 14, further comprising, while applying a voltage potential across the first and second wires:
measuring a resistance of the ELG based on the current flow; and
correlating the measured resistance to the stripe height of the read sensor.

### Claim 20 (depends on 19)

The method of claim 19, further comprising, upon determining the stripe height of the read is at a predetermined value, instructing a device to cease lapping an air bearing surface of the first read head.