Method for surface mounting electrical components to a substrate

• US 5,820,716 A
• Filed: 02/25/1997
• Issued: 10/13/1998
• Est. Priority Date: 11/05/1993
• Status: Expired due to Term

• Current Assignee: Round Rock Research LLC
• Original Assignee: Micron Technology, Inc.
• Inventors: Tuttle, Mark E.
• Primary Examiner(s): Gallagher, John J.
• Application Number:
  US08/805,561
• Time in Patent Office: 595 Days
• Field of Search: 156/315, 156/85, 156/273.7, 29/832, 361/803, 361/746, 361/734
• US Class Current: 156/85
• CPC Class Codes: C09J 5/02 involving pretreatment of the surfaces to be joined
• CPC Class Codes: H01L 2224/13099 Material
• CPC Class Codes: H01L 2224/16225 the item being non-metallic, e.g. insulating substrate with or without metallisation
• 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 2224/32225 the item being non-metallic, e.g. insulating substrate with or without metallisation
• CPC Class Codes: H01L 2224/73203 Bump and layer connectors
• CPC Class Codes: H01L 2224/8319 Arrangement of the layer connectors prior to mounting
• CPC Class Codes: H01L 2224/838 Bonding techniques
• CPC Class Codes: H01L 24/12 Structure, shape, material or disposition of the bump connectors prior to the connecting process
• CPC Class Codes: H01L 24/32 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 2924/01006 Carbon [C]
• CPC Class Codes: H01L 2924/01013 Aluminum [Al]
• CPC Class Codes: H01L 2924/0665 Epoxy resin
• CPC Class Codes: H01L 2924/07802 not being an ohmic electrical conductor
• CPC Class Codes: H01L 2924/0781 being an ohmic electrical conductor
• CPC Class Codes: H01L 2924/07811 Extrinsic, i.e. with electrical conductive fillers
• CPC Class Codes: H01L 2924/14 Integrated circuits
• CPC Class Codes: H05K 2201/0125 Shrinkable, e.g. heat-shrinkable polymer
• CPC Class Codes: H05K 2203/1105 : Heating or thermal processing not related to soldering, firing, curing or laminating, e.g. for shaping the substrate or during finish plating
• CPC Class Codes: H05K 3/305 : Affixing by adhesive
• CPC Class Codes: H05K 3/321 : by conductive adhesives
• CPC Class Codes: Y02P 70/50 : Manufacturing or production processes characterised by the final manufactured product
• CPC Class Codes: Y10T 29/4913 : Assembling to base an electrical component, e.g., capacitor, etc.

Abstract

A method for surface mounting electrical components to a substrate, such as a printed circuitboard, involves use of an anisotropically conductive adhesive or Z-Axis adhesive between facing conductive surface areas on the component and substrate. Pressure is applied to the conductive adhesive by a nonconducting adhesive that is first cured between oppositely facing nonconductive surface areas of the component and substrate. This fixes the thickness of each layer of the conductive adhesive at a dimension no greater than its design conductive thickness. In a first submethod, the nonconducting adhesive is a fast setting adhesive subjected to mechanical pressure only as it is assembled on the substrate prior to the subsequent curing of the conductive adhesive. In a second submethod, it is a high shrinkage adhesive that applies compressive force between the component and substrate as it cures and shrinks dimensionally while at a temperature below the subsequent curing temperature of the conductive adhesive.

Claims

1. A method for mounting an electrical component to a supporting substrate comprising the following steps:

providing an electrical component, the electrical component having a nonconductive surface and a pair of conductive surfaces adjacent the nonconductive surface, the pair of conductive surfaces of the electrical component being a first conductive surface and a second conductive surface;

providing a substrate, the substrate having a nonconductive surface and a pair of conductive surfaces adjacent the nonconductive surface, the pair of conductive surfaces of the substrate being a third conductive surface and a fourth conductive surface;

applying a nonconductive adhesive in contact with the nonconductive surface of the substrate and in contact with the nonconductive surface of the electrical component, the nonconductive adhesive not being in contact with the first, second, third or fourth conductive surfaces, the nonconductive adhesive curing at a first temperature, the nonconductive adhesive shrinking as it cures;

applying an anisotropically conductive adhesive in contact with the first conductive surface and in contact with the third conductive surface, the anisotropically conductive adhesive curing at a second temperature, the second temperature being higher than the first temperature;

applying the anisotropically conductive adhesive in contact with the second conductive surface and in contact with the fourth conductive surface;

curing the nonconductive adhesive at the first temperature to bond the nonconductive surface of the substrate to the nonconductive surface of the electrical component, the nonconductive adhesive shrinking as it cures, the anisotropically conductive adhesive being compressed between the first and third conductive surfaces and between the second and fourth conductive surfaces as the nonconductive adhesive shrinks; and

after curing the nonconductive adhesive, curing the compressed anisotropically conductive adhesive at the second temperature to

     1) form an electrically conductive path between the first and third conductive surfaces and bond the first conductive surface to the third conductive surface and

     2) form an electrically conductive path between the second and fourth conductive surfaces and bond the second conductive surface to the fourth conductive surface.

2. A method for mounting an electrical component to a supporting substrate comprising the following steps:

providing an electrical component, the electrical component having a nonconductive surface and a pair of conductive surfaces adjacent the nonconductive surface, the pair of conductive surfaces of the electrical component being a first conductive surface and a second conductive surface;

providing a substrate, the substrate having a nonconductive surface and a pair of conductive surfaces adjacent the nonconductive surface, the pair of conductive surfaces of the substrate being a third conductive surface and a fourth conductive surface;

applying a nonconductive adhesive in contact with the nonconductive surface of the substrate and in contact with the nonconductive surface of the electrical component, the nonconductive adhesive curing under first conditions;

applying an anisotropically conductive adhesive in contact with the first conductive surface and in contact with the third conductive surface, the anisotropically conductive adhesive curing under second conditions, but not curing under the first conditions;

applying the anisotropically conductive adhesive in contact with the second conductive surface and in contact with the fourth conductive surface;

curing the nonconductive adhesive under the first conditions to bond the nonconductive surface of the substrate to the nonconductive surface of the electrical component, the nonconductive adhesive being compressed between the nonconductive surfaces of the electrical component and the substrate by external mechanical forces during the curing of the nonconductive adhesive, the anisotropically conductive adhesive being compressed between the first and third conductive surfaces and between the second and fourth conductive surfaces by external mechanical forces as the nonconductive adhesive cures;

after curing the nonconductive adhesive, removing the compressing of the external mechanical forces; and

after curing the nonconductive adhesive and removing the compressing of the external mechanical forces, and while not providing external mechanical forces to further compress the anisotropically conductive adhesive, curing the compressed anisotropically conductive adhesive under the second conditions to

     1) form an electrically conductive path between the first and third conductive surfaces and bond the first conductive surface to the third conductive surface and

     2) form an electrically conductive path between the second and fourth conductive surfaces and bond the second conductive surface to the fourth conductive surface.

3. The method of claim 2 wherein the first conditions comprise exposure to ultraviolet light.