Method of making anisotropic conductive elements for use in microelectronic packaging

• US 6,518,091 B1
• Filed: 09/05/2000
• Issued: 02/11/2003
• Est. Priority Date: 03/04/1997
• Status: Expired due to Term

• Current Assignee: Tessera, Inc. (Adeia Inc.)
• Original Assignee: Tessera, Inc. (Adeia Inc.)
• Inventors: Haba, Belgacem
• Primary Examiner(s): Niebling, John F.
• Assistant Examiner(s): LATTIN, CHRISTOPHER W
• Application Number:
  US09/655,300
• Time in Patent Office: 889 Days
• Field of Search: 438/107, 204/164
• US Class Current: 438/107
• CPC Class Codes: B29C 70/62 the filler being oriented during moulding for short fibres B29C70/14
• CPC Class Codes: B29C 70/882 partly or totally electrically conductive, e.g. for EMI shielding conductive floors or floor coverings H05F3/025; EMI shielding in general H05K9/00
• CPC Class Codes: G02F 1/1339 Gaskets; Spacers; Sealing of cells
• CPC Class Codes: H01L 21/568 Temporary substrate used as encapsulation process aid H01L21/4832 and H01L21/566 take precedence
• CPC Class Codes: H01L 21/6835 using temporarily an auxiliary support
• CPC Class Codes: H01L 2224/27438 the preform being at least partly pre-patterned
• CPC Class Codes: H01L 2224/29101 the principal constituent melting at a temperature of less than 400°C
• CPC Class Codes: H01L 2224/2919 with a principal constituent of the material being a polymer, e.g. polyester, phenolic based polymer, epoxy
• CPC Class Codes: H01L 2224/29499 Shape or distribution of the fillers
• CPC Class Codes: H01L 2224/83101 as prepeg comprising a layer connector, e.g. provided in an insulating plate member
• CPC Class Codes: H01L 2224/83192 wherein the layer connectors are disposed only on another item or body to be connected to the semiconductor or solid-state body
• CPC Class Codes: H01L 2224/83851 being an anisotropic conductive adhesive
• CPC Class Codes: H01L 23/49827 Via connections through the substrates, e.g. pins going through the substrate, coaxial cables H01L23/49822, H01L23/49833, H01L23/4985, H01L23/49861 take precedence
• CPC Class Codes: H01L 24/27 Manufacturing methods
• CPC Class Codes: H01L 24/29 of an individual layer connector
• CPC Class Codes: H01L 24/83 using a layer connector
• CPC Class Codes: H01L 2924/00 Indexing scheme for arrangements or methods for connecting or disconnecting semiconductor or solid-state bodies as covered by H01L24/00
• CPC Class Codes: H01L 2924/01005 Boron [B]
• CPC Class Codes: H01L 2924/01006 Carbon [C]
• CPC Class Codes: H01L 2924/01029 Copper [Cu]
• CPC Class Codes: H01L 2924/01033 : Arsenic [As]
• CPC Class Codes: H01L 2924/01047 : Silver [Ag]
• CPC Class Codes: H01L 2924/01322 : Eutectic Alloys, i.e. obtained by a liquid transforming into two solid phases
• CPC Class Codes: H01L 2924/014 : Solder alloys
• CPC Class Codes: H01L 2924/0665 : Epoxy resin
• CPC Class Codes: H01L 2924/0781 : being an ohmic electrical conductor
• CPC Class Codes: H01L 2924/12044 : OLED
• CPC Class Codes: H01L 2924/14 : Integrated circuits
• CPC Class Codes: H05K 2201/0133 : Elastomeric or compliant polymer
• CPC Class Codes: H05K 2201/0248 : Needles or elongated particles; Elongated cluster of chemically bonded particles
• CPC Class Codes: H05K 2201/083 : Magnetic materials
• CPC Class Codes: H05K 2201/09536 : Buried plated through-holes, i.e. plated through-holes formed in a core before lamination
• 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 2203/105 : Using an electrical field; Special methods of applying an electric potential
• CPC Class Codes: H05K 3/323 : by applying an anisotropic conductive adhesive layer over an array of pads
• CPC Class Codes: H05K 3/368 : parallel to each other H05K3/361 takes precedence
• CPC Class Codes: H05K 3/4623 : the circuit boards having internal via connections between two or more circuit layers before lamination, e.g. double-sided circuit boards H05K3/462 takes precedence

Abstract

A method of making an anisotropic conductive element for use in microelectronic packaging includes providing a layer of material having a pair of oppositely-directed major faces, the layer incorporating a curable dielectric material in a fluid condition and electrically conductive particles in the curable dielectric material and applying a magnetic field to the layer of a material so as to alter the configuration of the particles and so as to form areas of high particle concentration defining a plurality of conductive paths extending between the major faces of the layer of a material. After applying the magnetic field, the dielectric material is cured. The layer may be compressed for moving the conductive particles together to provide lower resistance electrical paths through the layer. In certain embodiments, at last some of the conductive particles are elongated so that when the magnetic field is applied to the layer of a material, the magnetic field turns the axes of elongation of at least some of the elongated particles towards the vertical direction. In other embodiments, the magnetic field moves at least some of the conductive particles in horizontal directions.

Claims

1. A method of making an anisotropic conductive element for use in microelectronic packaging comprising the steps of:

(a) providing a layer of a material having a pair of oppositely-directed major faces, said layer incorporating a curable dielectric material in a fluid condition and electrically conductive particles in said curable dielectric material;

(b) applying a magnetic field to said layer of a material so as to alter the configuration of said particles and so as to form areas of high particle concentration defining a plurality of conductive paths extending between the major faces of said layer;

(c) compressing said layer for moving said conductive particles together to provide lower resistance electrical paths through said layer; and

(d) after the applying a magnetic field step, curing said dielectric material.

2. The method as claimed in claim 1, further comprising applying an electrical field to said layer of a material.

3. The method as claimed in claim 1, wherein said curable dielectric material sets to a non-fluid condition during the curing said dielectric material step.

4. The method as claimed in claim 1, wherein said layer of a material includes an anisotropic conductive material.

5. The method as claimed in claim 1, wherein said layer has the pair of oppositely-directed major faces and a vertical direction between said major faces, at least some of said particles being elongated and the applying a magnetic field step including turning the axes of elongation of at least some of said elongated particles toward the vertical direction.

6. The method as claimed in claim 5, wherein the applying a magnetic field step includes biasing said major faces with opposing magnetic fields on at least some regions of said faces.

7. The method as claimed in claim 1 wherein said layer has a pair of oppositely-directed major faces, a vertical direction between said major faces and horizontal directions parallel to said major faces, wherein the applying a magnetic field step includes moving at least some of said particles in horizontal directions.

8. The method as claimed in claim 7 wherein said magnetic field moves at least some of said particles in said horizontal direction so as to form said areas of high particle concentration interspersed with areas of low particle concentration.

9. The method as claimed in claim 8, further comprising the step of compressing said layer in said vertical direction to provide low-resistance electrical paths between said particles in said areas of high particle concentration.

10. The method as claimed in claim 1, wherein said curing step includes the step of heating said curable dielectric material.

11. The method as claimed in claim 10, wherein said curable dielectric material has a viscosity which is reduced during the heating step.

12. The method as claimed in claim 10, wherein said heating step and said applying a magnetic field step occur simultaneously.

13. The method as claimed in claim 5, further comprising the step of providing a substrate over at least one of said oppositely-directed major faces.

14. The method as claimed in claim 13, wherein said substrate includes a flexible dielectric film.

15. The method as claimed in claim 14, wherein said flexible dielectric film includes a polymeric material.

16. The method as claimed in claim 14, wherein said substrate includes a microelectronic element having a plurality of electrical contacts.

17. The method as claimed in claim 16, wherein said microelectronic element includes a semiconductor chip having a plurality of electrical contacts on the front face thereof.

18. The method as claimed in claim 1, wherein said dielectric material is curable to a silicone elastomer.

19. The method as claimed in claim 1, wherein said electrically conductive particles include one or more metals.

20. The method as claimed in claim 1, wherein said electrically conductive particles include non-conductive central cores coated with a conductive material.

21. The method as claimed in claim 20, wherein said non-conductive cores include a material selected from the group consisting of polymers and glass.

22. A method of making a microelectronic package comprising the steps of:

(a) providing a microelectronic element including a plurality of electrical contacts on a first surface thereof;

(b) providing a layer of a material over said first surface of said microelectronic element, said material in said layer incorporating a dielectric material in a fluid condition and electrically conductive particles in said dielectric material;

(c) applying a magnetic field through said contacts to said layer of a material so as to alter the configuration of said electrically conductive particles; and

(d) compressing said layer for moving said conductive particles together to provide lower resistance electrical paths through said layer.

23. The method as claimed in claim 22, wherein the applying a magnetic field step includes moving at least some of said particles into substantial alignment with one or more of said contacts so as to form areas of high particle concentration aligned with said contacts interspersed with areas of low particle concentration.

24. The method as claimed in claim 23, further comprising the step of setting said dielectric material to a non-fluid condition after the moving step.

25. The method as claimed in claim 24, wherein said layer of a material has a first major face and a second major face, further comprising the step of abutting a second microelectronic element having a plurality of electrical contacts with said second major face of said layer so that said contacts of said first and second microelectronic elements confront one another and are in substantial alignment with one another, said particles in said areas of high particle concentration electrically interconnecting one or more of said confronting contacts.