Cooling system for IC package

Abstract: A cooling system for an IC package includes a support plate (107) arranged to oppose a wiring board (102) on which a plurality of integrated circuits (101) are mounted. A plurality of cooling plates (103) are fixed to the support plate (107) by support members (109) and each has a coolant channel therein. The cooling plates (103) are arranged in a one-to-one corres­ pondence with the integrated circuits (101). Flexible coolant pipes (106) connect the coolant channels of adjacent cooling plates (103). Heat conduction members (105) are disposed between the cooling plates (103) and the integrated circuits (101) and elastic members (108) disposed between the support plate (107) and the cooling plates (103) urge the cooling plates against the integrated circuits through the respective heat conduction members (105), thereby independently urging the cooling plates (103) against the corresponding integrated circuits (101) so as to independently cool the integrated circuits.

Description: Background of the Invention The present invention relates to a cooling system for an IC package used in electronic equipment such as an information processor. Many conventional cooling systems for an IC package employ a cooling scheme wherein a plurality of printed boards each mounting ICs thereon are accommodated in shelves and are cooled by forced convection of air by cooling fans. A forced air cooling scheme of this type is required to deliver a large quantity of air to electronic equipment since recent electronic equipment has a higher heat generation density due to use of LSIs (Large Scale ICs). When the capacity of the forced air cooling system is increased, a high-power cooling fan used therein poses a noise problem. Therefore, the cooling capacity of the cooling system of this type has almost reached a maximum capacity. In another cooling system, a liquid coolant such as water having a heat capacity larger than that of air is circulated near ICs, and metal parts are located in contact with cases of the ICs to conduct heat from the ICs to the coolant, thereby dissipating heat. A typical example of such a cooling system is disclosed in Special Report "SUPERCOMPUTERS DEMAND INNOVATION IN PACKAGING AND COOLING", ELECTRONICS./September 22, 1982, PP. 142 - 143. In this literature, a plurality of LSIs are brought into contact with a cold plate having a water channel in which a coolant flows, thereby cooling the LSIs. Heights of LSIs are not necessarily identical due to variations in dimensional precision of parts, mounting variations, warping of a printed board, and the like and cannot be aligned on an identical plane. For this reason, a thermal paste sealed in a film is mounted on a surface of a cold plate which is in contact with an LSI, and variations in LSI heights are absorbed by flexibility of the thermal paste. However, when variations in heights of LSIs exceed a predetermined range and cannot be absorbed by a material such as a thermal paste, air which has a poor heat conduction property is present in a heat conduction path between the LSI and the cold plate, thus degrading the cooling effect. Prior US patent US-A-4558395 discloses a cooling system for IC's in which cooling members are urged against corresponding IC's by helical springs. Springs are positioned between the top surface of each cooling member, and a cover plate. Furthermore, coolant enters into the cooling members via pipes connected to their top surfaces. The invention provides a cooling system for an IC package, comprising: a wiring board on which a plurality of integrated circuits are mounted; a support plate arranged to oppose said wiring board; a plurality of cooling plates each having a coolant channel therein, said plurality of cooling plates being arranged in a one-to-one correspondence with said plurality of integrated circuits; flexible coolant pipes each connecting said coolant channels of adjacent ones of said cooling plates; heat conduction members each positioned between a respective cooling plate and the corresponding integrated circuit ; and elastic members disposed between said support plate and said cooling plates to urge said cooling plates against the integrated circuits through said heat conduction members, respectively, thereby independently urging said cooling plates against the corresponding integrated circuits so as to independently cool the integrated circuits, characterised in that said cooling plates are each attached to said support plate by support members, in that said elastic members each comprise a leaf spring, and in that the coolant pipes connect to the coolant channels of the cooling plates through the sides of the cooling plates. Brief Description of the Drawings Fig. 1 is a sectional view of a cooling system for an IC package according to an embodiment of the present invention; Fig. 2 is a sectional view of the cooling system in Fig. 1 along the line A-A thereof; Fig. 3 is a longitudinal sectional view showing a case wherein one of ICs of the embodiment of Fig. 1 is inclined; Fig. 4 is a longitudinal sectional view showing a cooling system for an IC package according to another embodiment of the present invention; and Fig. 5 is a perspective view showing an IC structure shown in Fig. 4. Detailed Description of the Preferred Embodiments The present invention will be described with reference to the accompanying drawings. Fig. 1 is a longitudinal sectional view of a cooling system for an IC package according to an embodiment of the present invention, and Fig. 2 is a sectional view thereof along the line A - A in Fig. 1. Reference numeral 101 denotes an integrated circuit (IC) housed in a package; and 102, a wiring board on which a plurality of ICs are mounted. Reference numeral 103 denotes a metal cold plate serving as a cooling plate, having a coolant channel 104 therein, for cooling the corresponding IC 101. The cold plates 103 are arranged in a one-to-one correspondence with the ICs 101. A heat conduction member 105 is arranged between the IC 101 and the cooling plate 103 to absorb small warping of opposite surfaces of the IC 101 and the cooling plate 103. The heat conduction member 105 may be a paste- or soft sheet-like member (e.g., a material prepared by mixing a metal oxide or boron nitride in silicone rubber or silicone oil). Reference numeral 106 denotes a coolant pipe for connecting coolant channels 104 of the adjacent cooling plates 103. A connection portion 106A of the coolant pipe 106 is connected to the corresponding cooling plate 103 by brazing. A remaining portion 106B of the coolant pipe 106 comprises a flexible tube. As clearly shown in the drawings, the coolant pipes 106 are connected to the coolant channels 104 of the cooling plates 103 through the sides of the cooling plates. Reference numeral 107 denotes a support plate parallel to the wiring board 102 and spaced apart therefrom by a predetermined distance. Leaf springs 108 each having one end fixed to the support plate 107 are interposed between the support plate 107 and the corresponding cooling plate 103 to urge the cooling plate 103 toward the corresponding IC 101. The cooling plate 103 is fixed by support members 109 so as not to be separated from the corresponding support plate 107. Heat generated by the ICs 101 is conducted to the corresponding cooling-plates 103 through the corresponding heat conduction members 105 and is then dissipated to a coolant flowing through the corresponding coolant channels 104. As shown in Fig. 3, even if variations in the dimensional precision of parts, mounting variations, and warping of the wiring board 102 are present, and the ICs 101 are inclined at different angles, the leaf springs 108 are elastically deformed to keep the opposite surfaces of the cooling plate 103 and the IC 101 parallel to each other. The coolant pipe 106 which connects the adjacent cooling plates 103 has a flexible structure. Since all the cooling plates 103 are moved independently of each other, the cooling system can cope with large different heights of the adjacent ICs. Therefore, air which has a poor heat conduction property is not present in a heat conduction path between the IC 101 and the cooling plate 103, and the IC 101 can be effectively maintained at a low temperature. Fig. 4 is a longitudinal sectional view of a cooling system for an IC package according to another embodiment of the present invention. Fig. 5 is a perspective view of the system when an IC 101′ is observed from the side of a wiring board 102. One end of each of Z-shaped leads 111 is connected to a corresponding side surface of the IC 101′, and the other end of each of the leads 111 is connected to the wiring board 102. A stopper 110 is fixed on the surface (i.e., lower surface in Figs. 4 and 5) of the IC 101′ on the side opposite to the wiring board 102. The stopper 110 attached to the IC 101′ can prevent flexture of the leads 111 because the stopper 110 is brought into contact with the wiring board 102 even if forces of the leaf springs 108 which are generated by variations in IC heights are applied to the IC 101′. Therefore, excessive forces do not act on the leads 111. According to the present invention as described above, the leaf springs arranged between each cooling plate having the coolant channel therein and the support plate urge the IC through the corresponding cooling plate. Each coolant pipe which connect the adjacent cooling plates has flexibility, and the cooling plates can be independently displaced. Therefore, even if variations in dimensional precision of parts, mounting variations, warping of the wiring board having ICs thereon are present or the heights and inclinations of the ICs are not uniform, each cooling plate can be in tight contact with the corresponding IC through the corresponding heat conduction member. Therefore, air having a poor heat conduction property is not present in a heat conduction path between each IC and the corresponding cooling plate, and the IC can be efficiently kept at a low temperature.

Claims: A cooling system for an IC package, comprising: a wiring board (102) on which a plurality of integrated circuits (101) are mounted; a support plate (107) arranged to oppose said wiring board; a plurality of cooling plates (103) each having a coolant channel (104) therein, said plurality of cooling plates being arranged in a one-to-one correspondence with said plurality of integrated circuits; flexible coolant pipes (106) each connecting said coolant channels of adjacent ones of said cooling plates; heat conduction members (105) each positioned between a respective cooling plate and the corresponding integrated circuit; and elastic members (108) disposed between said support plate and said cooling plates to urge said cooling plates against the integrated circuits through said heat conduction members, respectively, thereby independently urging said cooling plates against the corresponding integrated circuits so as to independently cool the integrated circuits, characterised in that said cooling plates (103) are each attached to said support plate by support members (109), in that said elastic members (108) each comprise a leaf spring, and in that the coolant pipes (106) connect to the coolant channels (104) of the cooling plates (103) through the sides of the cooling plates. A cooling system according to claim 1, further comprising a stopper (110) mounted on a surface of each of said integrated circuits (101) on a side opposite to said wiring board (102) in accordance with a distance to be maintained between each integrated circuit and said wiring board. A cooling system according to claim 1 or claim 2, in which the heat conduction members (105) are paste-like or soft sheet-like members.

Inventors: UMEZAWA KAZUHIKO, UMEZAWA, KAZUHIKO
Applicants: NIPPON ELECTRIC CO, NEC CORPORATION
Application year: 1988
Main classification: H01L23
IPC codes: H05K7, H01L23