Method of eliminating uncontrolled voids in sheet adhesive layer

• US 6,919,230 B2
• Filed: 01/12/2004
• Issued: 07/19/2005
• Est. Priority Date: 04/13/2001
• Status: Expired due to Term

• Current Assignee: STMicroelectronics Incorporated (STMicroelectronics NV)
• Original Assignee: STMicroelectronics Incorporated (STMicroelectronics NV)
• Inventors: Chiu, Anthony M.
• Primary Examiner(s): Lee, Eddie
• Assistant Examiner(s): Gebremariam, Samuel A
• Application Number:
  US10/755,925
• Publication Number:
  US 20040140574A1
• Time in Patent Office: 554 Days
• Field of Search: 438/118, 257/783
• US Class Current: 438/118
• CPC Class Codes: H01L 2224/29011 comprising apertures or cavities
• 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 2224/8319 Arrangement of the layer connectors prior to mounting
• CPC Class Codes: H01L 2224/8385 using a polymer adhesive, e.g. an adhesive based on silicone, epoxy, polyimide, polyester
• 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 2924/01004 Beryllium [Be]
• CPC Class Codes: H01L 2924/01005 Boron [B]
• CPC Class Codes: H01L 2924/01006 Carbon [C]
• CPC Class Codes: H01L 2924/01033 Arsenic [As]
• CPC Class Codes: H01L 2924/01082 Lead [Pb]
• CPC Class Codes: H01L 2924/014 Solder alloys
• CPC Class Codes: H01L 2924/0665 Epoxy resin
• CPC Class Codes: H01L 2924/07802 not being an ohmic electrical conductor
• CPC Class Codes: H01L 2924/12042 LASER
• CPC Class Codes: H01L 2924/14 Integrated circuits

Abstract

A preformed adhesive layer for joining components within integrated circuit packaging includes venting slots for controlling the size and location of voids within an assembled integrated circuit package. Air randomly entrapped between the surfaces of the adhesive layer and adjoining components during assembly will generally release into the venting slots during subsequent assembly and/or mounting steps performed at elevated temperatures, rather than creating internal pressures causing separation of package components or releasing into the encapsulant. Die delamination and encapsulant void problems occurring during reflow or other assembly and mounting processes as a result of entrapped air are avoided.

Claims

1. For use in an integrated circuit package, a method of affixing one package component to another package component comprising:

forming an adhesive material region; and

forming at least one venting slot extending within the adhesive material region from a region proximate to a central region of said adhesive material region towards a side or corner of a periphery of said adhesive material region, the at least one venting slot for controlling a size and location of voids between said adhesive material region and components joined by said adhesive layer during packaging.

2. The method as set forth in claim 1 wherein the step of forming at least one venting slot extending within the adhesive material region for controlling a size and location of voids between said adhesive material region and components joined by said adhesive material region during packaging further comprises:

forming a plurality of venting slots each extending from a region proximate to a side or corner of a cavity hole within the adhesive material region towards a corresponding side or corner of the periphery of the adhesive material region.

3. The method as set forth in claim 2 wherein the step of forming a plurality of venting slots each extending from a region proximate to a side or corner of a cavity hole within the adhesive material region towards a corresponding side or corner of a periphery of the adhesive material region further comprises:

forming each venting slot to extend to a point separated from the periphery of the adhesive material region by a width of adhesive material sufficiently narrow to permit diffusion of gas therethrough; and

forming extensions of each venting slot extending along a periphery of the cavity hole, wherein the extensions are spaced from the cavity hole by adhesive material sufficiently wide to minimize diffusion of gas from the venting slots into the cavity hole.

4. The method as set forth in claim 1 further comprising:

forming a plurality of patterns for the adhesive material region within a sheet, each pattern including the at least one venting slot.

5. The method as set forth in claim 1 further comprising:

affixing a substrate having a die cavity therein to a second package component utilizing the adhesive material region.

6. The method as set forth in claim 5 further comprising:

mounting an integrated circuit die within the die cavity;

affixing the integrated circuit die to the second package component through the cavity hole; and

electrically connecting the integrated circuit die to conductive traces on the substrate.

7. A method of forming a packaging material, the method comprising:

forming one or more instances of a pattern within a sheet of adhesive material for selectively affixing one packaging component to another packaging component, the pattern including at least one venting slot within the adhesive material extending within the pattern from an area proximate to a center of the pattern towards a side or a corner of a peripheral edge of the pattern, the at least one venting slot for controlling a size and location of voids between said adhesive material and components joined by said adhesive material during packaging.

8. The method as set forth in claim 7, wherein the pattern is rectangular and the at least one venting slot comprises four venting slots each extending from an area proximate to the center towards a corner of the pattern.

9. The method as set forth in claim 8, wherein the at least one venting slot further comprises four venting slots each extending from an area proximate to the center towards a side of the pattern.

10. The method as set forth in claim 9, wherein each of venting slots further comprises portions extending from an end of the respective venting slot nearest the center around a periphery of a center region within the pattern.

11. The method as set forth in claim 10, further comprising:

a opening through the adhesive material within the center region, wherein portions of the adhesive material separating the opening from the portions of the venting slots around the periphery of the center region have a width sufficient to inhibit diffusion of gas from the venting slots into the opening.

12. The method as set forth in claim 10, wherein the pattern and the opening are sized to match a printed circuit board substrate having a die cavity therein.

13. A method of packaging an integrated circuit die comprising:

providing a printed circuit board substrate having a die cavity through a central portion thereof and an other packaging component; and

affixing the printed circuit board substrate to the other packaging component with an adhesive layer having

an opening through a center of the adhesive layer and corresponding in size to the die cavity, and

at least one venting slot within the adhesive layer extending from a region proximate to the opening towards a peripheral edge of the adhesive layer.

14. The method according to claim 13, wherein the at least one venting slot is separated from the opening by a region of adhesive layer material having a width greater than a width of adhesive layer material separating the at least one venting slot from the peripheral edge.

15. The method according to claim 13, wherein the adhesive layer and the opening are both rectangular, the adhesive layer further comprising venting slots extending between corresponding corners of the adhesive layer and the opening and between corresponding sides of the adhesive layer and the opening.

16. The method according to claim 13, wherein the other packaging component is a metallic heat spreader.

17. The method according to claim 13, wherein the adhesive layer is one of an epoxy impregnated fiber glass carrier or a polyimide carrier on which is deposited B-staged polyimide.

18. The method according to claim 13, further comprising:

mounting an integrated circuit die within the die cavity and through the opening on a surface of the other heat spreader.

19. The method according to claim 18, further comprising:

forming wire bonds connecting the integrated circuit die to conductive traces leading to solder balls within an array on a surface of the printed circuit board substrate.