Flip chip on circuit board with enhanced heat dissipation and method therefor

• US 6,156,980 A
• Filed: 06/04/1998
• Issued: 12/05/2000
• Est. Priority Date: 06/04/1998
• Status: Expired due to Term

• Current Assignee: Apple Inc.
• Original Assignee: Delco Electronics Corporation (Motors Liquidation Co. GUC Trust)
• Inventors: Berndt, Joanna Christine, Myers, Bruce Alan, Peugh, Darrel Eugene
• Primary Examiner(s): Gaffin, Jeffrey
• Assistant Examiner(s): Cuneo, Kamand
• Application Number:
  US09/090,495
• Time in Patent Office: 915 Days
• Field of Search: 174/261, 174/252, 174/260, 174/263, 174/262, 361/768, 361/719, 438/108, 257/737, 257/778, 257/779, 291/739
• US Class Current: 174/252
• CPC Class Codes: H01L 2224/0401 Bonding areas specifically adapted for bump connectors, e.g. under bump metallisation [UBM]
• CPC Class Codes: H01L 2224/16 of an individual bump connector
• CPC Class Codes: H01L 2224/81801 Soldering or alloying
• CPC Class Codes: H01L 23/3677 Wire-like or pin-like cooling fins or heat sinks
• 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 2924/00014 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 2924/01006 Carbon [C]
• CPC Class Codes: H01L 2924/01013 Aluminum [Al]
• CPC Class Codes: H01L 2924/01029 Copper [Cu]
• CPC Class Codes: H01L 2924/01033 Arsenic [As]
• CPC Class Codes: H01L 2924/01078 Platinum [Pt]
• CPC Class Codes: H01L 2924/01082 Lead [Pb]
• CPC Class Codes: H01L 2924/014 Solder alloys
• CPC Class Codes: H01L 2924/14 Integrated circuits
• CPC Class Codes: H01L 2924/15787 Ceramics, e.g. crystalline carbides, nitrides or oxides
• CPC Class Codes: H01L 2924/30105 Capacitance
• CPC Class Codes: H05K 1/0206 by printed thermal vias
• CPC Class Codes: H05K 2201/066 Heatsink mounted on the surface of the PCB heatsink inserted in the PCB H05K2201/10416
• CPC Class Codes: H05K 2201/0959 Plated through-holes or plated blind vias filled with insulating material
• CPC Class Codes: H05K 2201/10416 : Metallic blocks or heatsinks completely inserted in a PCB metallic supports H05K3/0061
• CPC Class Codes: H05K 2201/10674 : Flip chip
• CPC Class Codes: H05K 3/42 : Plated through-holes or plated via connections

Abstract

A circuit structure and method for conducting heat from a power flip chip. Heat is dissipated from a flip chip mounted to a PCB by conducting heat through conductive vias to the opposite surface of the PCB. The flip chip is equipped with two sets of solder bumps, one of which is registered with conductors on the PCB, while the second is registered with a thermal conductor layer on the PCB surface and electrically isolated from the conductors. A second thermal conductor layer on the opposite surface of the PCB contacts the vials, such that heat is conducted from the flip chip to the second thermal conductor layer through the second set of solder bumps, the first thermal conductor layer, and the conductive vias. A heatsink is embedded in the PCB between the vias and the second thermal conductor layer to further promote heat conduction away from the flip chip. Heat can be conducted from the PCB with a second heatsink, such as a housing that encloses the PCB. The second heatsink either directly contacts the second thermal conductor layer, or makes thermal contact with the second thermal conductor layer through a thermally-conductive lubricant or adhesive.

Claims

1. A circuit board assembly comprising:

a substrate having electrical conductors and a first thermal conductor layer on a first surface thereof and having a second thermal conductor layer on a second surface opposite the first surface;

a surface-mount IC device mounted to the first surface of the substrate, the surface-mount IC device having a first set of solder bumps registered with the electrical conductors and at least one solder bump registered with the first thermal conductor layer;

a via within the substrate between the first surface of the substrate and the second surface of the substrate;

a heat-conductive material within the via and contacting the first thermal conductor layer on the first surface of the substrate; and

a heatsink embedded within the substrate between the via and the second thermal conductor layer and contacting the heat-conductive material within the via, wherein heat is conducted from the surface-mount IC device to the second thermal conductor layer through the at least one solder bump, the first thermal conductor layer, the heat-conductive material within the via, and the heatsink.

2. A circuit board assembly as recited in claim 1, wherein the substrate is a printed circuit board.

3. A circuit board assembly as recited in claim 1, wherein a plurality of vias are present in the substrate, each of the vias having the heat-conductive material therein and contacting the first thermal conductor layer and the heatsink.

4. A circuit board assembly as recited in claim 1, wherein the substrate has a laminate construction and the heatsink is a metal mass placed within the laminate construction.

5. A circuit board assembly as recited in claim 1, further comprising a housing member contacting the second thermal conductor layer.

6. A circuit board assembly as recited in claim 5, further comprising a thermally-conductive lubricant between the housing member and the second thermal conductor layer.

7. A circuit board assembly as recited in claim 5, further comprising a pedestal on the housing member and thermally contacting the second thermal conductor layer.

8. A circuit board assembly comprising:

a printed circuit board having electrical conductors and a first thermal conductor layer on a first surface thereof and having a second thermal conductor layer on a second surface opposite the first surface, the electrical conductors defining a conductor pattern that surrounds the first thermal conductor layer on the first surface of the printed circuit board;

a flip chip mounted to the printed circuit board, the flip chip having a first set of solder bumps registered with the electrical conductors and a second set of solder bumps registered with the first thermal conductor layer, the second set of solder bumps being located on the flip chip at an interior surface region thereof;

vias within the printed circuit board between the first surface of the printed circuit board and the second surface of the printed circuit board;

a heat-conductive material plated within the vias and contacting the first thermal conductor layer on the first surface of the printed circuit board; and

a heatsink embedded within the printed circuit board between the vias and the second thermal conductor layer and contacting the heat-conductive material within the vias, wherein heat is conducted from the flip chip to the second thermal conductor layer through the second set of solder bumps, the first thermal conductor layer, the heat-conductive material within the vias, and the heatsink.

9. A circuit board assembly as recited in claim 8, wherein the printed circuit board has a laminate construction and the heatsink is a metal mass placed within the laminate construction.

10. A circuit board assembly as recited in claim 8, further comprising a housing member contacting the second thermal conductor layer.

11. A circuit board assembly as recited in claim 10, further comprising a thermally-conductive lubricant between the housing member and the second thermal conductor layer.

12. A circuit board assembly as recited in claim 10, further comprising a pedestal on the housing member and thermally contacting the second thermal conductor layer.

13. A method for forming circuit board assembly, the method comprising the steps of:

providing a substrate having oppositely-disposed first and second surfaces, a heatsink embedded within the second surface, and a via within the substrate between the first and second surfaces;

depositing a heat-conductive material within the via and forming electrical conductors and a first thermal conductor layer on the first surface of the substrate, the heat-conductive material contacting the first thermal conductor layer and the heatsink;

forming a second thermal conductor layer on the second surface of the substrate, the second thermal conductor layer contacting the heatsink such that said heat sink is between the via and said second thermal conductor layer; and

mounting a flip chip to the substrate, the flip chip having a first set of solder bumps registered with the electrical conductors and at least one solder bump registered with the first thermal conductor layer, wherein heat is conducted from the flip chip to the second thermal conductor layer through the at least one solder bump, the first thermal conductor layer, the heat-conductive material within the via, and the heatsink.

14. A method as recited in claim 13, wherein the substrate is a printed circuit board.

15. A method as recited in claim 13, wherein a plurality of vias are formed in the substrate, each of the vias having the heat-conductive material therein and contacting the first thermal conductor layer and the heatsink.

16. A method as recited in claim 13, wherein the substrate has a laminate construction and the heatsink is a metal mass placed within the laminate construction.

17. A method as recited in claim 13, further comprising the step of contacting the second thermal conductor layer with a housing member.

18. A method as recited in claim 17, further comprising the step of placing a thermally-conductive lubricant between the housing member and the second thermal conductor layer.

19. A method as recited in claim 17, further comprising the step of forming a pedestal on the housing member so that the pedestal thermally contacts the second thermal conductor layer.

20. A method as recited in claim 13, wherein the electrical conductors are deposited to define a conductor pattern that surrounds the first thermal conductor layer on the first surface of the printed circuit board, and wherein the second set of solder bumps are located on the flip chip at an interior surface region thereof.