Rigid adhesive underfill preform, as for a flip-chip device

• US 6,399,178 B1
• Filed: 06/22/1999
• Issued: 06/04/2002
• Est. Priority Date: 07/20/1998
• Status: Expired due to Fees

• Current Assignee: Amerasia International Technology, Inc.
• Original Assignee: Amerasia International Technology, Inc.
• Inventors: Chung, Kevin Kwong-Tai
• Primary Examiner(s): Copenheaver, Blaine
• Assistant Examiner(s): Paulraj, Christopher
• Application Number:
  US09/338,477
• Time in Patent Office: 1,078 Days
• Field of Search: 174/254, 174/255, 174/256, 439/67, 428/131
• US Class Current: 428/131
• CPC Class Codes: H01L 21/563 Encapsulation of active face of flip-chip device, e.g. underfilling or underencapsulation of flip-chip, encapsulation preform on chip or mounting substrate
• CPC Class Codes: H01L 2224/05571 the external layer being disposed in a recess of the surface
• CPC Class Codes: H01L 2224/05573 Single external layer
• CPC Class Codes: H01L 2224/05624 Aluminium [Al] as principal constituent
• CPC Class Codes: H01L 2224/05644 Gold [Au] as principal constituent
• CPC Class Codes: H01L 2224/05655 Nickel [Ni] as principal constituent
• CPC Class Codes: H01L 2224/05666 Titanium [Ti] as principal constituent
• CPC Class Codes: H01L 2224/05684 Tungsten [W] as principal constituent
• CPC Class Codes: H01L 2224/13111 Tin [Sn] as principal constituent
• CPC Class Codes: H01L 2224/16225 the item being non-metallic, e.g. insulating substrate with or without metallisation
• CPC Class Codes: H01L 2224/274 by blanket deposition of the material of the layer connector
• CPC Class Codes: H01L 2224/27438 the preform being at least partly pre-patterned
• CPC Class Codes: H01L 2224/29099 Material
• CPC Class Codes: H01L 2224/29111 Tin [Sn] as principal constituent
• CPC Class Codes: H01L 2224/29199 Material of the matrix
• CPC Class Codes: H01L 2224/2929 with a principal constituent of the material being a polymer, e.g. polyester, phenolic based polymer, epoxy
• CPC Class Codes: H01L 2224/29299 Base material
• CPC Class Codes: H01L 2224/29386 with a principal constituent of the material being a non metallic, non metalloid inorganic material
• CPC Class Codes: H01L 2224/73103 Bump and layer connectors
• CPC Class Codes: H01L 2224/73203 Bump and layer connectors
• CPC Class Codes: H01L 2224/73204 : the bump connector being embedded into the layer connector
• CPC Class Codes: H01L 2224/81801 : Soldering or alloying
• CPC Class Codes: H01L 2224/83101 : as prepeg comprising a layer connector, e.g. provided in an insulating plate member
• CPC Class Codes: H01L 2224/83856 : Pre-cured adhesive, i.e. B-stage adhesive
• CPC Class Codes: H01L 24/29 : of an individual layer connector
• CPC Class Codes: H01L 24/81 : using a bump 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 2924/00013 : Fully indexed content
• CPC Class Codes: H01L 2924/00014 : the subject-matter covered by the group, the symbol of which is combined with the symbol of this group, being disclosed without further technical details
• CPC Class Codes: H01L 2924/01005 : Boron [B]
• CPC Class Codes: H01L 2924/01006 : Carbon [C]
• CPC Class Codes: H01L 2924/01007 : Nitrogen [N]
• CPC Class Codes: H01L 2924/01012 : Magnesium [Mg]
• CPC Class Codes: H01L 2924/01013 : Aluminum [Al]
• CPC Class Codes: H01L 2924/01014 : Silicon [Si]
• CPC Class Codes: H01L 2924/01015 : Phosphorus [P]
• CPC Class Codes: H01L 2924/01019 : Potassium [K]
• CPC Class Codes: H01L 2924/0103 : Zinc [Zn]
• CPC Class Codes: H01L 2924/01033 : Arsenic [As]
• CPC Class Codes: H01L 2924/01039 : Yttrium [Y]
• CPC Class Codes: H01L 2924/01049 : Indium [In]
• CPC Class Codes: H01L 2924/0105 : Tin [Sn]
• CPC Class Codes: H01L 2924/01074 : Tungsten [W]
• CPC Class Codes: H01L 2924/01075 : Rhenium [Re]
• CPC Class Codes: H01L 2924/01079 : Gold [Au]
• CPC Class Codes: H01L 2924/01082 : Lead [Pb]
• CPC Class Codes: H01L 2924/01087 : Francium [Fr]
• CPC Class Codes: H01L 2924/0132 : Binary Alloys
• CPC Class Codes: H01L 2924/014 : Solder alloys
• CPC Class Codes: H01L 2924/04642 : SiC
• CPC Class Codes: H01L 2924/05032 : AlN
• CPC Class Codes: H01L 2924/0532 : 2nd Group
• CPC Class Codes: H01L 2924/0542 : 12th Group
• CPC Class Codes: H01L 2924/05432 : Al2O3
• CPC Class Codes: H01L 2924/0665 : Epoxy resin
• CPC Class Codes: H01L 2924/07802 : not being an ohmic electrical conductor
• CPC Class Codes: H01L 2924/10253 : Silicon [Si]
• CPC Class Codes: H01L 2924/14 : Integrated circuits
• CPC Class Codes: H01L 2924/1579 : with a principal constituent of the material being a polymer, e.g. polyester, phenolic based polymer, epoxy
• CPC Class Codes: H01L 2924/19041 : being a capacitor
• CPC Class Codes: H01L 2924/19042 : being an inductor
• CPC Class Codes: H01L 2924/19043 : being a resistor
• CPC Class Codes: H01L 2924/30105 : Capacitance
• CPC Class Codes: H01L 2924/30107 : Inductance
• CPC Class Codes: H01L 2924/351 : Thermal stress
• CPC Class Codes: H01L 2924/3512 : Cracking
• CPC Class Codes: H01R 4/04 : using electrically conductive adhesives
• CPC Class Codes: H05K 2201/0129 : Thermoplastic polymer, e.g. auto-adhesive layer; Shaping of thermoplastic polymer
• CPC Class Codes: H05K 2201/0209 : Inorganic, non-metallic particles
• CPC Class Codes: H05K 2201/10378 : Interposers
• CPC Class Codes: H05K 2201/10424 : Frame holders
• CPC Class Codes: H05K 2201/10674 : Flip chip
• CPC Class Codes: H05K 2201/10977 : Encapsulated connections
• 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 3/3436 : having an array of bottom contacts, e.g. pad grid array or ball grid array components
• CPC Class Codes: H05K 3/3485 : Applying solder paste, slurry or powder thick film methods for applying conductive paste or ink patterns H05K3/12
• CPC Class Codes: Y02P 70/50 : Manufacturing or production processes characterised by the final manufactured product
• CPC Class Codes: Y10T 428/24273 : including aperture

Abstract

An electronic device comprises one or more electronic components, including flip-chip semiconductor devices, chip resistors, capacitors and inductors and other components, electrically interconnected to an electronic substrate by solder bump interconnections and having a rigid adhesive underfill bonding between the electronic component and the substrate. The rigid adhesive underfill is a preform of an insulating thermoplastic and/or thermosetting resin, or a combination thereof, having a high modulus of elasticity and high glass transition temperature. Preferably, insulating adhesives having a higher melt-flow index are employed to facilitate formation of a void-free bond between the component and the substrate and of a fillet around the edges of the flip-chip or other component, thereby to provide a moisture barrier and additional mechanical strength. The high rigidity and high glass transition temperature of the insulating underfill preform material in combination with the high flow index thereof tend to reduce strain in the solder bumps and other internal stresses, and so improve long-term bonding and contact reliability. Preferably, a number of the rigid adhesive underfill preforms are fabricated together and are applied to a number of the electronic components, e.g., on a wafer, or of the substrates in a panel, before they are separated into individual items.

Claims

1. A rigid adhesive underfill preform for adhesively attaching an electronic device to a substrate having a pattern of contact sites thereon corresponding to a pattern of contacts of the electronic device, and to include solder bumps, said rigid adhesive underfill preform comprising:

a layer of adhesive material having a pattern of holes therethrough corresponding to the pattern of contact sites of the substrate, said layer of adhesive material having a thickness substantially similar to a height of the solder bumps, and wherein said adhesive material is rigid when cured and has a flow index greater than about 1.2 at a temperature T and a pressure P, wherein the flow index is the ratio of the area covered by the adhesive material after curing at a temperature T and a pressure P to the area of the adhesive material before curing.

2. The rigid adhesive underfill preform of claim 1 further comprising solder substantially filling the holes in said layer of adhesive material, wherein the substrate includes the solder bumps on the contact sites thereof, and wherein said layer of adhesive material is laminated to the substrate with the solder bumps of the substrate positioned in the holes of said layer of adhesive material.

3. The rigid adhesive underfill preform of claim 1 further comprising solder substantially filling the holes in said layer of adhesive material, whereby said solder is the solder bumps.

4. The rigid adhesive underfill preform of claim 3 wherein said solder substantially filling the holes in said layer of adhesive material is in the form of a solder paste or a solder cream.

5. The rigid adhesive underfill preform of claim 4 wherein said solder paste or solder cream is reflowed in the holes in said adhesive layer.

6. The rigid adhesive underfill preform of claim 1 wherein said layer of adhesive material is formed by depositing said adhesive material with a stencil, said stencil including a plurality of covers positioned for defining the holes in said layer of adhesive material.

7. The rigid adhesive underfill preform of claim 1 wherein said layer of adhesive material is formed by depositing said adhesive material onto a flat surface of a mold, said mold having a pattern of features projecting from the flat surface thereof for defining the holes in said layer of adhesive material.

8. The rigid adhesive underfill preform of claim 1 wherein said adhesive material when cured has a modulus of elasticity of at least 1,000,000 psi at temperatures below its glass transition temperature.

9. The rigid adhesive underfill preform of claim 8 wherein the glass transition temperature of said adhesive material is not less than 85°

C.

10. The rigid adhesive underfill preform of claim 1 wherein said adhesive material is selected from the group consisting of thermoplastic and thermosetting materials, and blends and combinations thereof.

11. The rigid adhesive underfill preform of claim 1 wherein the difference between the thickness of said layer of adhesive material and the height of the solder bumps is less than twenty percent (20%).

12. The rigid adhesive underfill preform of claim 1 in combination with the substrate having the pattern of contact sites thereon and with a next-level substrate having a corresponding pattern of contact sites thereon, wherein opposing surfaces of said rigid adhesive underfill preform are bonded to said substrate and to said next-level substrate, respectively, and wherein the respective corresponding contact sites of said substrate and said next-level substrate are connected together by the solder bumps.

13. The rigid adhesive underfill preform of claim 1 wherein the flow index of said adhesive material is at least 1.5.

14. The rigid adhesive underfill preform of claim 1 wherein the temperature T is in the range of 150-250°

C. and the pressure P is less than 30 psi.

15. The rigid adhesive underfill preform of claim 1 wherein the temperature T is less than the reflow temperature of solder and the pressure P is less than 100 psi.

16. A rigid adhesive underfill preform for a substrate having a pattern of contact sites thereon and to include solder bumps comprising:

a layer of adhesive material having a pattern of holes therethrough corresponding to the pattern of contact sites of the substrate,

said layer of adhesive material having a thickness substantially similar to a height of the solder bumps, and

wherein said adhesive material is rigid when cured and has a flow index greater than about 1.2 at a temperature T and a pressure P,

wherein the flow index is the ratio of the area covered by the adhesive material after curing at a temperature T and a pressure P to the area of the adhesive material before curing,

wherein said layer of adhesive material has a network of channels in at least one surface thereof.

17. The rigid adhesive underfill preform of claim 16 wherein said layer of adhesive material is formed by depositing said adhesive material with a stencil, said stencil including a plurality of covers positioned for defining the holes in said layer of adhesive material and having tie bars holding said covers in position, wherein said tie bars define said channels.

18. A rigid adhesive underfill preform for a substrate having a pattern of contact sites thereon and to include solder bumps comprising:

a layer of adhesive material having a pattern of holes therethrough corresponding to the pattern of contact sites of the substrate,

said layer of adhesive material having a thickness substantially similar to a height of the solder bumps, and

wherein said adhesive material is rigid when cured and has a flow index greater than about 1.2 at a temperature T and a pressure P,

wherein the flow index is the ratio of the area covered by the adhesive material after curing at a temperature T and a pressure P to the area of the adhesive material before curing,

wherein said layer of adhesive material is formed by depositing said adhesive material with a stencil,

said stencil including a plurality of covers positioned for defining the holes in said layer of adhesive material and tie bars holding said covers in position, wherein said tie bars define channels in a surface of said layer of adhesive material.

19. A rigid adhesive underfill preform for a substrate having a pattern of contact sites thereon and to include solder bumps comprising:

a layer of adhesive material having a pattern of holes therethrough corresponding to the pattern of contact sites of the substrate,

said layer of adhesive material having a thickness substantially similar to a height of the solder bumps, and

wherein said adhesive material is rigid when cured and has a flow index greater than about 1.2 at a temperature T and a pressure P,

wherein the flow index is the ratio of the area covered by the adhesive material after curing at a temperature T and a pressure P to the area of the adhesive material before curing,

wherein said layer of adhesive material is formed by depositing said adhesive material onto a flat surface of a mold,

said mold having a pattern of features projecting from the flat surface thereof for defining the holes in said layer of adhesive material, and

wherein said mold has a pattern of raised ridges on the flat surface thereof, the height of the ridges being less than that of the pattern of features thereon, wherein the raised ridges define channels in a surface of the layer of adhesive material.

20. A rigid adhesive underfill preform for a substrate having a pattern of contact sites thereon and to include solder bumps comprising:

a layer of adhesive material having a pattern of holes therethrough corresponding to the pattern of contact sites of the substrate,

said layer of adhesive material having a thickness substantially similar to a height of the solder bumps, and

wherein said adhesive material is rigid when cured and has a flow index greater than about 1.2 at a temperature T and a pressure P,

wherein the flow index is the ratio of the area covered by the adhesive material after curing at a temperature T and a pressure P to the area of the adhesive material before curing,

wherein said adhesive material includes particulate filler selected from the group consisting of quartz, silica, glass silicates, alumina, aluminum nitride, boron nitride, silicon carbide, zinc oxide, magnesium oxide and diamond, and combinations thereof.

21. A rigid adhesive underfill preform for adhesively attaching an electronic device to a substrate having a pattern of contact sites thereon corresponding to a pattern of contacts of the electronic device, and to include solder bumps, said rigid adhesive underfill preform comprising:

a layer of rigid adhesive material for adhering to the substrate and having a pattern of holes therethrough corresponding to the pattern of contact sites of the substrate,

said layer of rigid adhesive material having a thickness substantially similar to a height of the solder bumps,

wherein said rigid adhesive material includes;

(a) a rigid thermoplastic adhesive having a flow index greater than about 1.2 when melt-flowed at a temperature T and a pressure P,

(b) a rigid thermosetting adhesive having a flow index greater than about 1.2 when cured at a temperature T and a pressure P, or

(c) a blend of (a) and (b), and

wherein the flow index is the ratio of the area covered by the rigid adhesive material after curing at a temperature T and a pressure P to the area of the rigid adhesive material before curing.

22. The rigid adhesive underfill preform of claim 21 wherein the temperature T is in the range of 150-250°

C. and the pressure P is less than 30 psi.

23. The rigid adhesive underfill preform of claim 21 wherein the temperature T is less than the reflow temperature of solder and the pressure P is less than 100 psi.

24. The rigid adhesive underfill preform of claim 21 wherein said layer of rigid adhesive material has a network of channels in at least one surface thereof.