Browse Prior Art Database

Using Magneto-Resistive Head Transducers as Lapping Transducers and a Parallel Resistor System to Calculate Lapping Constants

IP.com Disclosure Number: IPCOM000105716D
Original Publication Date: 1993-Sep-01
Included in the Prior Art Database: 2005-Mar-20
Document File: 4 page(s) / 124K

Publishing Venue

IBM

Related People

Church, MA: AUTHOR [+3]

Abstract

Disclosed is a parallel magneto-resistive (MR) head transducer design which provides a means for precise MR stripe height control by way of using the MR device as a lapping transducer and its specific design for in-line transducer calibration.

This text was extracted from an ASCII text file.
This is the abbreviated version, containing approximately 50% of the total text.

Using Magneto-Resistive Head Transducers as Lapping Transducers and a Parallel Resistor System to Calculate Lapping Constants

      Disclosed is a parallel magneto-resistive (MR) head transducer
design which provides a means for precise MR stripe height control by
way of using the MR device as a lapping transducer and its specific
design for in-line transducer calibration.

      When using MR devices as lapping transducers, two unknown
variables must be determined to calibrate the transducer resistance
to stripe height.  One variable is the combined lead resistances (R1)
of the MR device and the other is a constant (K) which relates to the
track width of the MR device and sheet resistance of the MR stripe.
One method of determining these two variables requires wafer
measurements of the MR stripe height windage and the resistance of
the completed MR device (MR stripe plus combined leads).  Using a
repeating pattern of paired MR devices having two different stripe
heights, both unknown variables can be calculated for each pair of MR
stripes [*].

      There are several inadequacies in using this approach.  One
inadequacy is that lead resistance (R1) can only be calculated for a
pair of devices.  The precision of calibration would be improved if
lead resistance could be calculated for each individual MR device.
Another inadequacy is where it would be most desirable to obtain a
windage value for each MR device, it is only practical to provide an
average stripe height windage, generally for the entire wafer.
Because of the practicality aspect of having to use the less
desirable average windage, the ability to accurately calculate the
two unknowns is degraded.  And still another inadequacy is in
accuracy of making the windage measurement.  Whether making windage
measurements directly or estimating them by electrical test
structures, exact correlation to the resistance of the MR transducers
and the lapping electronics must be maintained.  This measurement can
not only be costly but further degradation in calibration can be
expected to the extent of the capability of maintaining exact
correlation.

      To provide a more direct approach for the calculation of (R1)
and making the calculation of the two unknowns more accurate, pairs
of alternating height MR devices 1 and 2 of Fig. 1 are "interleaved
throughout the row" as in reference [*], but in this case, each MR
device would have a parallel second stripe 3 and 4 placed below its
corresponding MR transducing stripe 1 and 2.  In the preferred
embodiment, both parallel stripes 3 and 4 are identical to their
corresponding MR transducing stripes and the small section of
extended leads 5, 6, 7 and 8 are designed and made to have negligible
or accountable resistance.

      The position of the secondary parallel MR stripes 3 and 4 are
such that, after initial machining but before throat height lapping,
the secondary parallel stripes 3 and 4 are removed while the eventual
MR...