Thin film compass and method for manufacturing the same

• US 5,199,178 A
• Filed: 10/23/1991
• Issued: 04/06/1993
• Est. Priority Date: 10/23/1991
• Status: Expired due to Fees

• Current Assignee: Hing S. Tong
• Original Assignee: APAC, Inc. (CRH PLC)
• Inventors: Tong, Hing S., Lam, Fai-Loy P.
• Primary Examiner(s): Will, Thomas B.
• Assistant Examiner(s): FULTON, CHRISTOPHER W
• Application Number:
  US07/781,743
• Time in Patent Office: 531 Days
• Field of Search: 33/361, 33/355 R, 324/260, 324/246
• US Class Current: 33/361
• CPC Class Codes: G01C 17/30 Earth-inductor compasses
• CPC Class Codes: G01R 33/05 in thin-film element

Abstract

A thin film magnetic fluxgate compass having a supporting substrate on which a layer of high permeability material, and at least two layers of nonmagnetic conducting materials are deposited; the high permeability material is fabricated to form a magnetic core or cores; a portion of the non-magnetic conducting layers is fabricated to form an excitation coil, magnetically coupled to the core or cores, which is to be connected to a pulse generator; the remainder of the non-magnetic conducting layers is fabricated into at least two sensing coils, or two pairs of sensing coils wound around the core or cores in opposite pairs, which are used to generate output signals. A method for the fabrication of the thin film compass is disclosed. The compass can be used for the determination of the direction of the geomagnetic field, and, because of its miniature size, for instrumentation that requires a very small magnetic field sensor.

Claims

1. A thin film magnetic compass comprising:

a substrate;

a plurality of layers on said substrate forming a first group of at least two sensing coils, at least a first excitation coil, and a first magnetic core in said sensing and excitation coils, wherein said at least two sensing coils have axes that are transverse to one another, so that when said compass is placed in a geomagnetic field and when said core is driven into magnetic saturation by means of said excitation coil, said sensing coils will provide signals for determining the direction of said geomagnetic field;

wherein said core is in the shape of a polygon having an even number of sides or a circle, said compass comprising a first and a second pair of sensing coils surrounding said core, wherein the two sensing coils in each of the two pairs have axes that are substantially parallel to each other but transverse to those of the axes of the other pair;

said compass further comprising;

a least a substantially flat additional second magnetic core substantially coplanar with and surrounding said first magnetic core; and

at least two additional pairs of sensing coils surrounding said second core.

2. The compass of claim 1, wherein said first and second cores are in the shape of octagons.

3. A thin film magnetic compass comprising:

a substrate;

a plurality of layers on said substrate forming a first group of at least two sensing coils, at least a first excitation coil, and a first magnetic core in said sensing and excitation coils, wherein said at least two sensing coils have axes that are transverse to one another, so that when said compass is placed in a geomagnetic field and when said core is driven into magnetic saturation by means of said excitation coil, said sensing coils will provide signals for determining the direction of said geomagnetic field, wherein said plurality of layers include;

a first conducting layer over said substrate, said conducting layer having a predetermined pattern to form bottom portions of said excitation and sensing coils;

a first insulating layer over said first conducting layer and said substrate;

a magnetic layer over said first insulating layer forming said magnetic core;

a second insulating layer over said magnetic layer and the first insulating layer;

a second conducting layer over said second insulating layer and having a predetermined pattern to form top portions of said excitation and sensing coils; and

vias means through the first and second insulating layers and connected to the top and bottom portions of said excitation-coil and sensing-coils to form the coils.

4. The compass of claim 3, wherein said first and second conducting layers are each in the shape of an array of strips, wherein the strips in the array of the first conducting layer are oriented transverse to the strips in the array of the second conducting layer.

5. The compass of claim 3, further comprising:

a third insulating layer over said second conducting layer, said third insulating layer having therein a pad opening to allow electrical connection between said compass and external circuits.

6. The compass of claim 3, further comprising additional sensing and excitation coils which comprise:

a second group of sensing coils, each sensing coil in the second group surrounding a sensing coil in the first group; and

a second excitation coil surrounding the first excitation coil

7. The compass of claim 6, the additional sensing and excitation coils comprising:

a third conducting layer between the first conducting layer and the substrate, said third conducting layer having a predetermined pattern to form bottom portions of said additional sensing and excitation coils;

a third insulating layer between the first and third conducting layers;

a fourth insulating layer over the second conducting layer;

a fourth conducting layer over the fourth insulating layer, said fourth conducting layer having a predetermined pattern to form top portions of said additional sensing and excitation coils; and

via means through the insulating layers connecting the third and fourth conducting layers to form said additional sensing and excitation coils.

8. The compass of claim 3, further comprising a third insulating layer between the substrate and the first conducting layer.

9. A thin film magnetic compass comprising:

a substrate;

a plurality of layers on said substrate forming a first group of at least two sensing coils, at least a first excitation coil, and a first magnetic core in said sensing and excitation coils, wherein said at least two sensing coils have axes that are transverse to one another, so that when said compass is placed in a geomagnetic field and when said core is driven into magnetic saturation by means of said excitation coil, said sensing coils will provide signals for determining the direction of said geomagnetic field, wherein said core has been tempered by having been heated for a period of 0.5 to 10 hours at a temperature in a range between 200°

to 500°

C., in a magnetic orienting field applied to the core in a direction along a surface of said core, so that said core exhibits an easy axis of magnetization in the direction of the orienting field.

10. The compass of claim 9, wherein the magnetic orienting field of the core has a strength of at least 3 mT.