Thermal enhancement approach using solder compositions in the liquid state

• US 6,281,573 B1
• Filed: 03/31/1998
• Issued: 08/28/2001
• Est. Priority Date: 03/31/1998
• Status: Expired due to Fees

• Current Assignee: International Business Machines Corporation
• Original Assignee: International Business Machines Corporation
• Inventors: Quinones, Horatio, Atwood, Eugene R., DiGiacomo, Giulio, Benenati, Joseph A.
• Primary Examiner(s): Williams, Alexander O.
• Application Number:
  US09/052,296
• Time in Patent Office: 1,246 Days
• Field of Search: 257/706, 257/675, 257/703, 257/704, 257/705, 257/707, 257/710, 257/722, 257/723, 257/738, 257/737, 257/734, 257/779, 257/782, 257/783, 361/6.97, 361/706, 361/708, 361/705, 361/783, 174/260, 165/80.3
• US Class Current: 257/706
• CPC Class Codes: H01L 2224/16225 the item being non-metallic, e.g. insulating substrate with or without metallisation
• CPC Class Codes: H01L 2224/29099 Material
• CPC Class Codes: H01L 2224/32225 the item being non-metallic, e.g. insulating substrate with or without metallisation
• CPC Class Codes: H01L 2224/32245 the item being metallic
• CPC Class Codes: H01L 2224/73204 the bump connector being embedded into the layer connector
• CPC Class Codes: H01L 2224/73253 Bump and layer connectors
• CPC Class Codes: H01L 23/3675 characterised by the shape of the housing
• CPC Class Codes: H01L 23/3736 Metallic materials H01L23/3732, H01L23/3733, H01L23/3735, H01L23/3737, H01L23/3738 take precedence
• CPC Class Codes: H01L 23/4275 by melting or evaporation of solids
• 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 2924/01322 Eutectic Alloys, i.e. obtained by a liquid transforming into two solid phases
• CPC Class Codes: H01L 2924/01327 Intermediate phases, i.e. intermetallics compounds
• CPC Class Codes: H01L 2924/09701 Low temperature co-fired ceramic [LTCC]
• CPC Class Codes: H01L 2924/15311 being a ball array, e.g. BGA
• CPC Class Codes: H01L 2924/16251 Connecting to an item not being a semiconductor or solid-state body, e.g. cap-to-substrate

Abstract

Solder compositions are introduced to interface between an IC chip and its associated heat exchanger cover. The solder compositions have a solidus-liquidus temperature range that encompasses the IC chip operational temperature range. The solder composition has the desired property of absorbing and rejecting heat energy by changing state or phase with each temperature rise and decline that result from temperature fluctuations associated with the thermal cycles of the integrated circuit chips. A path for high thermal conduction (low thermal resistance) from the IC chip to the heat exchanger to the ambient air is provided by an electronic module cover, configured as a cap with a heat exchanger formed or attached as a single construction, and made of the same material as the substrate, or made with materials of compatible thermal coefficients of expansion to mitigate the effects of vertical displacement during thermal cycling. The cap-heat exchanger cover is constructed to be compliant, and to contact both the IC chip and substrate.

Claims

1. An apparatus for maximizing thermal conduction and eliminating the adverse effects of operational thermal cycling comprising:

an integrated circuit chip having a top surface and a bottom surface, and operational within a temperature range;

a bonding composition on a surface of said integrated circuit chip, said bonding composition having a solidus-liquidus temperature range encompassing said integrated circuit chip operational temperature range, such that said bonding composition is in a semi-molten state when power is applied to said integrated circuit chip and said chip is operating within the chip operational temperature range; and

,

an elastomeric gasket, for use with non-hermetically sealed or semi-hermetically sealed electronic modules, of a polymeric ring fitted within a groove in said cover.

2. The apparatus of claim 1 further comprising a substrate with a top surface, having seal bands on said top surface, wherein said integrated circuit chip bottom surface is attached to said substrate top surface.

3. The apparatus of claim 2 further comprising said cover attached to said substrate top surface and said integrated circuit chip top surface, comprised of a ceramic cap cover portion and a heat exchanger cover portion bonded together to form one cover piece, wherein said cover is mounted as a single piece over said integrated circuit chip and said substrate, said heat exchanger cover portion having a bottom surface over said integrated circuit chip top surface.

4. The apparatus of claim 3 further comprising a solder wetable thin film structure over said top surface of said integrated circuit chip, said bottom surface of said heat exchanger cover portion, said bottom surface of said cap over portion, and over said top surface of said substrate.

5. The apparatus of claim 1 wherein said bonding composition comprises a preform Bi—

In composition of 25% Bi by weight, with a liquidus temperature of about 100°

C.

6. The apparatus of claim 1 wherein said bonding composition comprises a preform Bi—

In eutectic of 34% Bi by weight, with a liquidus temperature of about 72°

C.

7. The apparatus of claim 1 wherein said bonding composition comprises preform solder materials that melt at or below room temperature including:

a) Ga—

In composition of 70% In by weight, with a eutectic temperature of about 16.5°

C. and a liquidus of about 90°

C.;

b) Ga—

Zn composition of 85% Ga by weight, with a eutectic temperature of about 29.8°

C. and a liquidus of about 110°

C.;

or,

c) Ga—

Sn composition of 40% Sn by weight, with a eutectic temperature of about 20°

C. and a liquidus of about 100°

C.

8. The apparatus of claim 3 wherein said heat exchanger has a cavity within said bottom surface and over said integrated circuit chip top surface.

9. The apparatus of claim 3 wherein said cover is a ceramic.

10. The apparatus of claim 3 wherein said cap cover portion is about 1 mm to 2.5 mm in thickness, such that said cover is compliant, conforming to vertical displacements caused by different thermal expansions of materials.

11. The apparatus of claim 1 wherein said bonding composition is about 13 to 17 mils in thickness.

12. The apparatus of claim 3 wherein said thin film structure further comprises a deposition or evaporation of Cr—

Ni—

Au layers.

13. The apparatus of claim 12 wherein said thin film structure is comprised of a Cr layer 100 nm thick, a Ni layer 1000 nm thick, and a Au layer 50 nm thick.

14. The apparatus of claim 5 wherein said bonding composition is used at the eutectic composition wherein said composition will melt completely at the eutectic temperature of the alloy.

15. The apparatus of claim 6 wherein said bonding composition is used at the eutectic composition wherein said composition will melt completely at the eutectic temperature of the alloy.

16. The apparatus of claim 7 wherein said bonding composition is used at the eutectic composition wherein said composition will melt completely at the eutectic temperature of the alloy.