Browse Prior Art Database

Reed Microloop Transducer

IP.com Disclosure Number: IPCOM000115150D
Original Publication Date: 1995-Mar-01
Included in the Prior Art Database: 2005-Mar-30
Document File: 4 page(s) / 116K

Publishing Venue

IBM

Related People

Cain, W: AUTHOR [+7]

Abstract

Microloops are thin metal leads, closed at one end, fabricated onto transparent (usually glass) substrates. The loop dimensions are typically 1-2 microns. By bringing the loop into close proximity to a magnetic field source such as a recording head, time varying magnetic fields can be sensed from the voltage developed across the loop due to the flux intercepted by the loop. The spatial characteristics of the magnetic field are determined by precision translation of the microloop over the film head while maintaining constant separation between the loop and the magnetic field source.

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Reed Microloop Transducer

      Microloops are thin metal leads, closed at one end, fabricated
onto transparent (usually glass) substrates.  The loop dimensions are
typically 1-2 microns.  By bringing the loop into close proximity to
a magnetic field source such as a recording head, time varying
magnetic fields can be sensed from the voltage developed across the
loop due to the flux intercepted by the loop.  The spatial
characteristics of the magnetic field are determined by precision
translation of the microloop over the film head while maintaining
constant separation between the loop and the magnetic field source.

      The microloop position is verified by observing the test sample
through the transparent substrate on which the loop is fabricated.
Microloop separation is maintained by clamping the loop-substrate
unit to the test sample.  This clamping operation is repeated for
each repositioning of the loop.  Since a glass substrate is not
compliant, variability of the pressure applied in the clamping
operation causes changes in the loop separation from the test sample.
Excessive pressure may damage either the sample or the microloop.

      In principle, the microloop structure can also be used to
locally generate magnetic fields and thus excite the test sample.
This requires applying large currents (100 ma) through the microloop
which can only be accommodated if the loops are thick (>  2 &mu.m)
and if the loop dimension is narrow (<  2 &mu.m).  Processing such
structures is made difficult because the uniformity and ruggedness of
glass substrates are poor.  Lack of substrate uniformity limits
lithography.  Fragile substrates result in breakage during thick
plating operations.

      Because of the positioning and compliance issues required by
the microloop and processing challenges, we propose a new type of
microloop transducer which consists of a precision loop embedded in a
flexible alumina reed shape.  The reed microloop is fabricated on a
release or sacrificial layer allowing the use of a uniform and rigid
substrate suitable for fine line lithography and for thick film
plating operations.  Fig. 1 shows this reed structure within the
microloop.  Typical dimensions are 15 mm length, 1 mm width, and 20
&mu.m thickness.  It is shaped with a contact pad on which the loop
is formed.  The mechanical characteristics can be optimized to allow
for nondestructive contact between the reed and the test device.  The
mass and physical size of the transducer allow for straight forward
positioning of the loop relative to any test device.  The reed
microloop has compliant mechanical properties.

      The microloop is processed on a sac...