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AssigneeInternational Business Machines Corporation
InventorsGlen A. Garfunkel, Donald E. Horne, Robert L. Smith
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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.
A test circuit for testing for short circuits in a combined thin film MR read head and write head, the combined head having an MR sensor which is interconnected between first and second read pads by first and second leads, the MR sensor and the leads being sandwiched between first and second gap layers which are in turn sandwiched between first and second shield layers which are in turn sandwiched between a substrate and an insulation stack, a coil being embedded in the insulation stack and the coil being connected to first and second write pads, the test circuit comprising:
A bridge circuit for testing a thin film merged MR head, the merged MR head having an MR sensor which is interconnected between first and second read pads by first and second leads, the MR sensor and the leads being sandwiched between first and second gap layers which are in turn sandwiched between first and second shield layers which are in turn sandwiched between a substrate and an insulation stack, a coil being embedded in the insulation stack and the coil being connected to first and second write pads, the bridge circuit comprising:
A bridge circuit for testing for short circuits in a thin film MR head which is mounted on a substrate, the MR head having an MR sensor which is interconnected between first and second read pads by first and second leads, the MR sensor and the leads being sandwiched between first and second gap layers which are in turn sandwiched between first and second shield layers, the bridge circuit comprising:
A circuit for testing for short circuits in a thin film MR head which is mounted on a substrate, the MR head having an MR sensor which is interconnected between first and second read pads by first and second leads, the MR sensor and the leads being sandwiched between first and second gap layers which are in turn sandwiched between first and second shield layers, the circuit comprising:
A circuit for testing for short circuits in a thin film MR head which is mounted on a substrate, the MR head having an MR sensor which is interconnected between first and second leads, the leads extending from the MR sensor to first and second read pads respectively, the MR sensor and the leads being sandwiched between first and second gap layers which are in turn sandwiched between first and second shield layers, the circuit comprising:
A method for testing a combined thin film MR read head and write head for short circuits, the combined head having an MR sensor which is interconnected between first and second read pads by first and second leads, the MR sensor and the leads being sandwiched between first and second gap layers which are in turn sandwiched between first and second shield layers which are in turn sandwiched between a substrate and an insulation stack, a coil being embedded in the insulation stack and the coil being connected to first and second write pads, the method comprising:
Dependencies are inferred from the claim text.