Method and apparatus for immersion cooling or an electronic board

• US 5,305,184 A
• Filed: 12/16/1992
• Issued: 04/19/1994
• Est. Priority Date: 12/16/1992
• Status: Expired due to Fees

• Current Assignee: International Business Machines Corporation
• Original Assignee: International Business Machines Corporation
• Inventors: Andresen, Rolf, Bellar, Robert J., Kim, Sung J., Murphy, Alan L.
• Primary Examiner(s): Tolin, Gerald P.
• Application Number:
  US07/992,287
• Time in Patent Office: 489 Days
• Field of Search: 361/382, 361/385, 361/395, 361/689, 361/699, 361/701, 361/702, 361/704, 361/720, 361/736, 361/752, 174/252, 62/259.2, 62/418, 165/80.4, 165/80.5, 165/104.33, 257/713, 257/714
• US Class Current: 361/699
• CPC Class Codes: H01L 23/44 the complete device being wholly immersed in a fluid other than air H01L23/427 takes precedence
• 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 2924/0002 Not covered by any one of groups H01L24/00, H01L24/00 and H01L2224/00
• CPC Class Codes: H05K 7/20236 by immersion
• CPC Class Codes: H05K 7/20872 Liquid coolant without phase change

Abstract

A liquid heat sink is provided that employs natural convection of a liquid coolant (18'"'"') to cool a printed circuit board (14) on which are mounted a plurality of heat-generating components (12). In particular, the spacing d between the heat-generating components and a cold plate (20) used to cool the liquid must be such as to provide a Rayleigh number of at least about 1700 in the Rayleigh equation: ##EQU1## In the above equation, g is the acceleration of gravity, β is the volumetric coefficient of expansion of the liquid coolant, T₁ is the temperature of the cold plate, T₂ is the temperature of the component to be cooled, ν is the kinematic viscosity of the liquid coolant, and α is the thermal diffusivity of the liquid coolant. The novel heat sink of the present invention allows complete immersion of the component in the liquid to provide maximum heat transfer, while at the same time providing a mounting/packaging scheme that allows full utilization of the desired heat transfer properties.

Claims

1. Liquid heat sink apparatus for cooling electronic components mounted on a printed circuit board, comprising:

(a) a cold plate mounted opposite said electronic components and substantially parallel to said printed circuit board;

(b) means for containing a liquid coolant between said printed circuit board and said cold plate;

(c) said liquid coolant contained between said printed circuit board and said cold plate and in thermal contact with said printed circuit board said electronic components mounted thereon, and said cold plate,

wherein said cold plate is maintained a distance d from said electronic components sufficient to provide a Rayleigh number of at least 1700 in the equation ##EQU4## where g is the acceleration of gravity, β

is the volumetric coefficient of expansion of said liquid coolant, T₁ is the temperature of said cold plate, T₂ is the temperature of the component to be cooled, ν

is the kinematic viscosity of said liquid coolant, and α

is the thermal diffusivity of said liquid coolant;

(d) means for maintaining said cold plate said distance d from said printed circuit board, comprising a sealed housing supporting said cold plate and surrounding said printed circuit board and attached thereto to thereby provide a sealed space for maintaining said liquid coolant herein; and

(e) said sealed housing including means for accommodating expansion of said liquid coolant during thermal cycling.

2. The liquid heat sink apparatus of claim 1 wherein said liquid coolant i selected from the group of fluorocarbon liquids having the formal C_n F_2n-2.

3. The liquid heat sink apparatus of claim 1 wherein said printed circuit board is maintained in a substantially horizontal position.

4. The liquid heat sink apparatus of claim 1 wherein id cold plate is attached to said printed circuit board with a gasket to thereby provide said sealed space for maintaining said liquid coolant therein.

5. The liquid heat sink apparatus of claim 4 further including at least one connector for interfacing said printed circuit board to other electronic components, said connector passing through a portion of said sealed housing and sealed thereto.

6. The liquid heat sink apparatus of claim 1 wherein said means for accommodating expansion comprises at least one flexible wall of said sealed housing.

7. The liquid heat sink apparatus of claim 1 wherein said means or accommodating expansion comprises a sealed chamber fluidically communicating with said liquid coolant and having an air space therein.