# US 5,769,996 A · Compositions and methods for providing anisotropic conductive pathways and bonds between two sets of conductors > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 5,769,996 A - Document ID: US5769996A - Status: Granted - Kind: A - Application number: 08/464,733 - Filed: 1995-06-29 - Granted: 1998-06-23 - Earliest claimed: 1994-01-27 - Assignees: Loctite (Ireland) Limited - Inventors: Ciaran Bernard McArdle; Joseph Burke - Web page: https://patentgrep.com/patent/US5769996A ## CPC - H05K 3/323: {by applying an anisotropic conductive adhesive layer over an array of pads} - H01F 1/44: of magnetic liquids, e.g. ferrofluids (particles in a bonding agent H01F1/28, H01F1/36, {H01F1/37}) - 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) - H01R 4/04: using electrically conductive adhesives - H01R 12/57: surface mounting terminals - H05K 2201/0221: Insulating particles having an electrically conductive coating - H05K 2201/023: Hard particles, i.e. particles in conductive adhesive at least partly penetrating an electrode - H05K 2201/0233: Deformable particles - H05K 2201/083: Magnetic materials - H05K 2203/104: Using magnetic force, e.g. to align particles or for a temporary connection during processing - H10W 72/325: {Die-attach connectors having a filler embedded in a matrix} - H10W 72/352: {comprising metals or metalloids, e.g. solders} - Y10T 428/12069: Plural nonparticulate metal components - Y10T 428/12347: Plural layers discontinuously bonded [e.g., spot-weld, mechanical fastener, etc.] - H05K: PRINTED CIRCUITS; CASINGS OR CONSTRUCTIONAL DETAILS OF ELECTRIC APPARATUS; MANUFACTURE OF ASSEMBLAGES OF ELECTRICAL COMPONENTS - H01F: MAGNETS; INDUCTANCES; TRANSFORMERS; SELECTION OF MATERIALS FOR THEIR MAGNETIC PROPERTIES - H01R: ELECTRICALLY-CONDUCTIVE CONNECTIONS; STRUCTURAL ASSOCIATIONS OF A PLURALITY OF MUTUALLY-INSULATED ELECTRICAL CONNECTING ELEMENTS; COUPLING DEVICES; CURRENT COLLECTORS - H10W: GENERIC PACKAGES, INTERCONNECTIONS, CONNECTORS OR OTHER CONSTRUCTIONAL DETAILS OF DEVICES COVERED BY CLASS H10 - Y10T: TECHNICAL SUBJECTS COVERED BY FORMER US CLASSIFICATION ## Abstract The invention provides a composition comprising: (i) a ferrofluid comprising a colloidal suspension of ferromagnetic particles in a non-magnetic carrier liquid, and (ii) a plurality of electrically-conductive particles having substantially uniform sizes and shapes, dispersed in the ferrofluid. Various types of substantially non-magnetic electrically-conductive particles are described. Application of a substantially uniform magnetic field by magnet means to the composition causes the electrically-conductive particles to form a regular pattern. The composition is used for providing anisotropic conductive pathways between two sets of conductors in the electronics industry. The composition may be a curable adhesive composition which bonds the conductors. Alternatively or in addition the electrically-conductive particles may have a latent adhesive property e.g. the particles may be solder particles. The ferrofluid may be a colloidal suspension of ferromagnetic particles in a liquid monomer. ## Claims ### Claim 1 A method of providing anisotropic conductive pathways between two sets of conductors which comprises forming said pathways with a plurality of electrically conductive particles having substantially uniform sizes and shapes, said electrically conductive particles having been arrayed in a regular pattern by application of a substantially uniform magnetic field to a composition comprising (i) a plurality of electrically-conductive particles having substantially uniform sizes and shapes dispersed in either (ii) a ferrofluid comprising a colloidal suspension of ferromagnetic particles in a non-magnetic carrier liquid, or (iii) a mixture of a ferrofluid comprising a colloidal suspension of ferromagnetic particles in a non-magnetic carrier liquid and a curable liquid composition. ### Claim 2 (depends on 1) A method according to claim 1 wherein the electrically-conductive particles are arrayed in a regular pattern in a monolayer, in columns, or both. ### Claim 3 (depends on 1) A method according to claim 1 wherein the separation between the respective sets of conductors is substantially equal to or less than the average diameter of the electrically-conductive particles. ### Claim 4 (depends on 1) A method according to claim 1 which includes applying pressure to urge the respective conductors towards one another. ### Claim 5 A method of forming anisotropic conductive pathways between two sets of conductors wherein a layer of a curable composition is applied to one set of conductors and a second set of conductors is brought against the layer of curable composition after which the composition is cured in a composition curing step, the method characterized in that: (a) the curable composition comprises (i) a plurality of electrically-conductive particles having substantially uniform sizes and shapes dispersed in either (ii) a ferrofluid comprising a colloidal suspension of ferromagnetic particles in a curable non-magnetic carrier liquid, or (iii) a mixture of a ferrofluid comprising a colloidal suspension of ferromagnetic particles in a curable or non-curable, non-magnetic carrier liquid and a curable liquid composition; and (b) the method further comprises applying a substantially uniform magnetic field to the curable composition such that interaction between the ferrofluid and the electrically-conductive particles causes the electrically-conductive particles to form a regular pattern before the composition is cured and the composition curing step is performed while the electrically conductive particles are formed into said pattern so as to lock the pattern in position. ### Claim 6 (depends on 5) A method according to claim 5 which includes applying pressure to urge the respective sets of conductors towards one another before, during, or before and during the curing step. ### Claim 7 (depends on 5) A method according to claim 5 wherein the separation between the respective sets of conductors at the time of curing is substantially equal to or less than the average diameter of the electrically-conductive particles. ### Claim 8 A method of making an anisotropically conductive bond between two sets of conductors, wherein a layer of adhesive composition is applied to one set of conductors and a second set of conductors is brought against the layer of adhesive composition after which the composition is cured in a composition curing step, the method characterized in that: (a) the adhesive composition comprises (i) a plurality of electrically-conductive particles having substantially uniform sizes and shapes dispersed in either (ii) a ferrofluid comprising a colloidal suspension of ferromagnetic particles in a curable adhesive non-magnetic carrier liquid, or (iii) a mixture of a ferrofluid comprising a colloidal suspension of ferromagnetic particles in a curable or non-curable, magnetic carrier liquid and a curable adhesive liquid composition; and (b) the method further comprises: exposing the layer of adhesive composition to a substantially uniform magnetic field such that interaction between the ferrofluid and the electrically-conductive particles causes the electrically-conductive particles to form a regular pattern of particles each in electrical contact with an adjacent particle and/or with a conductor in one or both sets of conductors or with both a particle and one or two conductors, whereby conductive pathways are provided from one set of conductors to the other set, each pathway comprising one or more of the electrically-conductive particles, before the adhesive composition is cured; and the composition curing step is performed while the electrically conductive particles are formed into said pattern so as to lock the pattern in position. ### Claim 9 (depends on 8) A method according to claim 8 which includes applying pressure to urge the respective sets of conductors towards one another before, during, or before and during the curing step. ### Claim 10 (depends on 9) A method according to claim 9 wherein the separation between the respective sets of conductors at the time of curing is substantially equal to or less than the average diameter of the electrically-conductive particles. ### Claim 11 (depends on 8) A method according to claim 8 wherein the magnetic field is applied normal to the layer of adhesive composition and the electrically-conductive particles form a regular array of particles in a monolayer, or in columns. ### Claim 12 (depends on 8) A method according to claim 8 wherein the magnetic field is applied parallel to the layer of adhesive composition and the electrically-conductive particles form parallel chains of particles, each in electrical contact with an adjacent particle or particles of the same chain. ### Claim 13 (depends on 8) A method according to claim 8 wherein the separation between the respective sets of conductors at the time of curing is substantially equal to or less than the average diameter of the electrically-conductive particles. ### Claim 14 A method of making an anisotropically conductive bond between two sets of conductors wherein a layer of a composition comprising particles with a latent adhesive property is applied to one set of conductors and a second set of conductors is brought against the layer of the composition after which the latent adhesive property of the particles is activated, the method characterized in that: (a) the particles with a latent adhesive property are electrically-conductive particles having substantially uniform sizes and shapes; (b) the composition comprises (i) a plurality of said particles with a latent adhesive property dispersed in either (ii) a ferrofluid comprising a colloidal suspension of ferromagnetic particles in a non-magnetic carrier liquid or (iii) a mixture of a ferrofluid comprising a colloidal suspension of ferromagnetic particles in a non-magnetic carrier liquid and a curable liquid composition; and (c) the method further comprises: exposing the layer of the composition to a substantially uniform magnetic field such that interaction between the ferrofluid and the electrically-conductive particles causes the electrically-conductive particles to form a regular pattern of particles each in contact with an adjacent particle with a conductor of one or both sets of conductors or with both a particle and one or two conductors; and activating the latent adhesive property of the particles with a latent adhesive property whereby conductive pathways are provided from one set of conductors to the other set, each pathway comprising one or more of the electrically-conductive particles, and the conductors are bonded by the particles. ### Claim 15 (depends on 14) A method according to claim 14 which includes applying pressure to urge the respective sets of conductors towards one another before and/or during activation of the latent adhesive property. ### Claim 16 (depends on 15) A method according to claim 15 wherein the separation between the respective sets of conductors at the time of activation of the latent adhesive property is substantially equal to or less than the average diameter of the electrically-conductive particles. ### Claim 17 (depends on 14) A method according to claim 14 wherein the magnetic field is applied normal to the layer of the composition and the electrically conductive particles form a regular array of particles in a monolayer. ### Claim 18 (depends on 14) A method according to claim 14 wherein the magnetic field is applied parallel to the layer of adhesive composition and the electrically-conductive particles form parallel chains of particles, each in electrical contact with an adjacent particle or particles of the same chain. ### Claim 19 (depends on 14) A method according to claim 14 wherein the electrically-conductive particles are solder particles of an electro-conductive metal alloy. ### Claim 20 (depends on 19) A method according to claim 19 wherein the non-magnetic carrier liquid is a rosin-based flux. ### Claim 21 (depends on 20) A method according to claim 20 which includes the further step of: applying a sealant or encapsulating composition over the ferrofluid composition and curing the sealant or encapsulating composition to seal the ferrofluid composition in place. ### Claim 22 (depends on 20) A method according to claim 20 which includes the further step of: retracting the ferrofluid liquid from between the conductors and injecting an adhesive, sealant or encapsulating composition between the conductors. ### Claim 23 (depends on 14) A method according to claim 14 wherein the separation between the respective sets of conductors at the time of activation of the latent adhesive property is substantially equal to or less than the average diameter of the electrically-conductive particles. ### Claim 24 A composition comprising: (i) a plurality of electrically-conductive particles having substantially uniform sizes and shapes dispersed in either: (ii) a ferrofluid comprising a colloidal suspension of ferromagnetic particles in a curable, non-magnetic carrier liquid, or (iii) a mixture of a ferrofluid comprising a colloidal suspension of ferromagnetic particles in a curable or non-curable, non-magnetic carrier liquid with a curable liquid composition. ### Claim 25 (depends on 24) A composition according to claim 24 wherein the average particle size of the electrically-conductive particles is at least 10 times that of the colloidal ferromagnetic particles. ### Claim 26 (depends on 24) A composition according to claim 24 wherein the electrically-conductive particles are substantially non-magnetic. ### Claim 27 (depends on 26) A composition according to claim 26 wherein the electrically-conductive particles comprise a non-magnetic, non-conductive core coated with an electrically-conductive metal. ### Claim 28 (depends on 27) A composition according to claim 27 wherein the core is selected from plastics material and glass and optionally is hollow. ### Claim 29 (depends on 24) A composition according to claim 24 wherein the non-magnetic carrier liquid is curable and the composition is a curable composition. ### Claim 30 (depends on 29) A composition according to claim 29 wherein the curable composition is an adhesive composition. ### Claim 31 (depends on 30) A composition according to claim 30 wherein the ferrofluid is a dispersion of colloidal magnetic particles in a curable liquid adhesive composition. ### Claim 32 (depends on 24) A composition according to claim 24 wherein the electrically-conductive particles have a latent adhesive property. ### Claim 33 (depends on 32) A composition according to claim 32 wherein the latent adhesive property is activated by heat. ### Claim 34 (depends on 33) A composition according to claim 33 wherein the electrically-conductive particles comprise a fusible metal. ### Claim 35 (depends on 34) A composition according to claim 34 wherein the fusible metal comprises solder particles of an electro-conductive metal alloy. ### Claim 36 (depends on 33) A composition according to claim 33 wherein the conductive particles comprise particles which are of conductive material or which have a conductive coating thereon, and which bear an outer coating of an adhesive which is activatable by heat or pressure. ### Claim 37 (depends on 24) A composition according to claim 24 wherein the electrically-conductive particles comprise a fusible metal. ### Claim 38 (depends on 37) A composition according to claim 37 wherein the fusible metal comprises solder particles of an electro-conductive metal alloy. ### Claim 39 (depends on 24) A composition according to claim 24 wherein the conductive particles comprise particles which are of conductive material or which have a conductive coating thereon, and which bear an outer coating of an adhesive which is activatable by heat or pressure. ### Claim 40 A composition comprising a plurality of electrically-conductive particles having substantially uniform sizes and shapes dispersed in a ferrofluid comprising a colloidal suspension of ferromagnetic particles in a non-curable, non-magnetic carrier liquid wherein the electrically-conductive particles comprise an outer coating of an adhesive which is activatable by heat or pressure.