Methods for forming and positioning moldable permanent magnets on electromagnetically actuated microfabricated components

• US 5,472,539 A
• Filed: 06/06/1994
• Issued: 12/05/1995
• Est. Priority Date: 06/06/1994
• Status: Expired due to Term

• Current Assignee: General Electric Company
• Original Assignee: General Electric Company
• Inventors: Durocher, Kevin M., Gorczyca, Thomas B., Saia, Richard J., Ghezzo, Mario
• Primary Examiner(s): Simmons, David A.
• Assistant Examiner(s): HELMER, STEVEN JAMES
• Application Number:
  US08/254,725
• Time in Patent Office: 547 Days
• Field of Search: 427/259, 427/271, 427/272, 156/155, 156/252, 156/248, 156/633, 156/668, 156/656
• US Class Current: 156/155
• CPC Class Codes: H01H 2050/007 Relays of the polarised type, e.g. the MEMS relay beam having a preferential magnetisation direction
• CPC Class Codes: H01H 50/005 using micromechanics
• CPC Class Codes: H02K 99/00 Subject matter not provided for in other groups of this subclass

Abstract

A low temperature batch method for forming and positioning permanent magnets on electromagnetically actuated micro-fabricated components, such as electrical switches employs a first adhesive, such as a Siltem/epoxy blend of an epoxy resin and a siloxane polyimide polymer, to releasably attach a mold layer of Kapton polyimide to a substrate, which may be the movable portion of a micromechanical structure, or a precursor to such movable portion. A well-shape cavity is formed in the mold layer, and filled with a slurry of rare earth NdFeB magnetic particles suspended in a second adhesive, which is cured to form the body of a magnet. The second adhesive is an SPI/epoxy blend, also of an epoxy resin and a siloxane polyimide polymer, but with a greater adhesion strength and a higher temperature softening point compared to the Siltem/epoxy blend. The entire structure is heated, and the mold layer is pulled off the substrate, while the body of magnetic material remains firmly attached. Selective etchants may be subsequently employed to remove metal sacrificial layers, while the NdFeB magnetic particles are protected from attack by the etchant by being effectively encased in plastic.

Claims

1. A method for fabricating an electromagnetically actuated micromechanical structure, comprising the steps of:

fabricating a precursor to a micromechanical structure, the precursor including a base, an element subsequently to become moveable relative to the base, and a sacrificial layer separating the base and the element and supporting the base on the element;

employing a first adhesive to releasably attach a mold layer of polymer material to the element;

forming a well-shaped cavity extending through the mold layer of polymer material;

filling the well-shaped cavity with a slurry of magnetic particles in a second adhesive;

curing the second adhesive to form a body of magnetic material;

removing the mold layer of polymer material and the first adhesive while allowing the body to remain adhered to the element; and

releasing the element for movement relative to the base by employing a selective etch to remove the sacrificial layer.

2. The method of claim 1, wherein the first adhesive has a lower adhesion strength than the second adhesive when heated, and wherein the step of removing the mold layer of polymer material comprises heating the precursor, mold layer and adhesives.

3. The method of claim 2, which further comprises the step of magnetizing the body.

4. The method of claim 1, wherein the step of fabricating a precursor to a micromechanical structure comprises fabricating a precursor which includes an electromagnet.

5. The method of claim 1, wherein the step of fabricating a precursor to a micromechanical structure comprises fabricating a precursor wherein the element is an electrical switch contact.

6. The method of claim 1, wherein the first adhesive comprises a blend of an epoxy resin and a siloxane polyimide polymer.

7. The method of claim 1, wherein the second adhesive comprises a blend of an epoxy resin and a siloxane polyimide polymer.

8. The method of claim 6, wherein the second adhesive comprises a blend of said epoxy resin and a second siloxane polyimide polymer.

9. The method of claim 1, wherein the step of forming a well-shaped cavity comprises laser-ablating a predetermined portion of said mold layer of polymer material.

10. The method of claim 9, wherein the step of forming a well-shaped cavity comprises:

providing a metal mask over the mold layer of polymer material, with an opening in the metal mask defining the cavity location; and

ablating with a laser the polymer material where not masked.