Films and coatings having anisotropic conductive pathways therein

• US 5,851,644 A
• Filed: 07/25/1996
• Issued: 12/22/1998
• Est. Priority Date: 08/01/1995
• Status: Expired due to Fees

• Current Assignee: Loctite (R&D) Limited
• Original Assignee: Loctite (R&D) Limited
• Inventors: McArdle, Ciaran B., Burke, Joseph
• Primary Examiner(s): LAM, CATHY FONG FONG
• Application Number:
  US08/686,987
• Time in Patent Office: 880 Days
• Field of Search: 428/900, 428/323, 428/328, 428/329, 428/356, 428/213, 252/510, 252/503, 252/506, 252/511, 252/512, 252/62.51, 252/62.52, 252/62.53-62.56
• US Class Current: 428/213
• CPC Class Codes: H01F 41/16 the magnetic material being applied in the form of particles, e.g. by serigraphy , to form thick magnetic films or precursors therefor H01F41/18 -H01F41/24 take precedence
• CPC Class Codes: H01R 4/04 using electrically conductive adhesives
• CPC Class Codes: H05K 2201/083 Magnetic materials
• CPC Class Codes: H05K 2203/104 Using magnetic force, e.g. to align particles or for a temporary connection during processing
• CPC Class Codes: H05K 3/323 by applying an anisotropic conductive adhesive layer over an array of pads
• CPC Class Codes: Y10S 428/90 Magnetic feature
• CPC Class Codes: Y10T 428/2495 Thickness [relative or absolute]
• CPC Class Codes: Y10T 428/25 Web or sheet containing structurally defined element or component and including a second component containing structurally defined particles
• CPC Class Codes: Y10T 428/257 Iron oxide or aluminum oxide

Abstract

An anisotropically-conductive film or a substrate having a surface coated with an anisotropically-conductive coating, said film or coating being formed by solidifying a composition comprising

(i) a solidifiable ferrofluid composition, the ferrofluid comprising a colloidal suspension of ferromagnetic particles in a non-magnetic carrier, and

(ii) a plurality of electrically-conductive particles, dispersed in the ferrofluid,

the electrically-conductive particles having been arrayed in a non-random pattern by application of a substantially uniform magnetic field to the composition in a liquid state and having been locked in position by solidification of the composition. The composition is solidified in an A-stage, usually involving a primary cure. In end-use application of the film or coating, the composition usually undergoes a B-stage or secondary cure. The film or coated substrate is an article of manufacture for bonding conductors in the electronics industry.

Claims

1. An anisotropically-conductive film or a substrate having a surface coated with an anisotropically-conductive coating, said film or coating having been formed by solidifying a solidifiable ferrofluid composition, the solidifiable ferrofluid composition comprising

(i) a colloidal suspension of ferromagnetic particles in a non-magnetic carrier, and

(ii) a plurality of electrically-conductive particles dispersed in the ferrofluid composition, said electrically-conductive dispersed particles having an average particle size which is about 10 times or more than the particle size of said ferromagnetic particles,

said electrically-conductive particles having been arrayed in a non-random pattern by application of a substantially uniform magnetic field to the composition in a liquid state and having been locked in position by solidification of the composition.

2. A film or coated substrate according to claim 1 wherein the solidifiable ferrofluid composition was curable and comprised at least a primary cure system which had been activated to solidify said composition.

3. A film or coated substrate according to claim 2 wherein the composition contains a latent cure system which is activatable to further cure said film or coating at a time subsequent to solidification of the composition.

4. A film or coated substrate according to claim 1 wherein the electrically conductive particles have substantially uniform sizes and shapes.

5. A film or coated substrate according to claim 4, wherein said film or coating has a thickness is substantially equal to the average diameter of the electrically-conductive particles.

9. A substrate having conductors thereon, and having an anisotropically conductive film or coating as defined in claim 1 applied to said conductors.

10. A substrate according to claim 9 wherein the anisotropically-conductive coating contains a latent cure system which is activatable to cure said film or coating.

11. A film or coated substrate according to claim 1 wherein the electrically conductive particles are arrayed in a monolayer.

14. A film or coated substrate according to claim 1 wherein the electrically conductive particles are substantially non-magnetic.

17. A film or coated substrate according to claim 1 wherein the composition contains a latent cure system which is activatable to cure said film or coating at a time subsequent to solidification of the composition.

6. An anisotropically-conductive film or substrate coating formed by

(a) applying to a substrate, a layer of a solidifiable ferrofluid composition comprising a colloidal suspension of ferromagnetic particles in a non-magnetic carrier liquid, and a plurality of electrically-conductive particles, dispersed in the ferrofluid composition, the electrically-conductive particles having an average particle size about 10 times or more than that of said ferromagnetic particles;

(b) exposing the solidifiable ferrofluid composition to a magnetic field to array the electrically-conductive particles in a non-random pattern;

(c) concurrent with or subsequent to step (b), exposing the solidifiable ferrofluid composition to solidifying conditions for the composition; and

(d) optionally removing the layer of solidified ferrofluid composition from the substrate to form a film.

12. A film or substrate coating according to claim 6 wherein the electrically conductive particles are arrayed in a monolayer.

15. A film or substrate coating according to claim 6 wherein the electrically conductive particles are substantially non-magnetic.

7. A solid-form anisotropically-conductive film or a substrate having a surface coated with a solid-form anisotropically-conductive coating, said film or coating comprising a composition containing colloidal ferromagnetic particles and a plurality of electrically-conductive particles having an average particle size which is about 10 times or more than that of the ferromagnetic particles arrayed in the composition in a non-random pattern.

8. A film or coated substrate according to claim 7 wherein the composition contains a latent cure system which is activatable to cure said solid-form anisotropically-conductive film or coating.

13. A film or coated substrate according to claim 7 wherein the electrically conductive particles are arrayed in a monolayer.

16. A film or coated substrate according to claim 7 wherein the electrically conductive particles are substantially non-magnetic.

18. An anisotropically-conductive film or a substrate having a surface coated with an anisotropically-conductive coating, said film or coating having been formed by solidifying a solidifiable ferrofluid composition, the solidifiable ferrofluid composition comprising

(i) a colloidal suspension of ferromagnetic particles in a non-magnetic carrier, and

(ii) a plurality of electrically-conductive substantially non-magnetic particles dispersed in the ferrofluid composition,

said electrically-conductive particles having been arrayed in a non-random pattern by application of a substantially uniform magnetic field to the composition in a liquid state and having been locked in position by solidification of the composition.