Cooling structure for electronic components

Abstract: The invention comprises a cooling structure for electronic components. The structure may comprise a substrate (4); at least one heat generating member (1, 3a) fixed on said substrate; a heat radiation member (8a) provided above said heat generating member which is provided with grooves (11a) at least on the surface opposite said heat generating member; and an elastic heat transfer sheet (12a) which is provided between said heat generating member and said heat radiating member for conducting heat from said heat generating member to said heat radiating member. To another aspect the invention may comprise a substrate; at least one heat generating member fixed on said substrate which is provided with grooves at the top; a heat radiating member provided above said heat generating member and an elastic heat generating member and said heat radiating member for conducting the heat generated from said heat generating member to said heat radiating member. To a still another aspect the invention may comprise a substrate at least one heat generating member fixed on said substrate; a heat radiating member provided above said heat generating member; and an elastic heat transmitting sheet provided between said heat generating member and said radiating member for conducting the heat generated from said heat generating member to said heat radiating member. The radiating member is formed with grooves at least either one of the surface opposing said heat generating member and the surface opposing said heat radiating member.

Description: The invention relates to a cooling structure as mentioned in the introductory part of claim 1. An example of prior art cooling structures for cooling electronic components is disclosed in US-A-4,685,211. In the structure disclosed, a silicone rubber sheet 32 is inserted between a piston 15 and chips 11 to absorb the gap if the chips 11 are mounted on a substrate 12 with an inclination. In order to absorb such a gap, the thickness of the silicone rubber sheet 32 should be increased to increase thermal resistance, and this results in the deteriorated heat radiation efficiency. In accordance with the present invention said object is obtained with the features of the characterizing part of claim 1. Preferred embodiments of the invention are mentioned in the subclaims. Features and advantages of the present invention will become more apparent from the following description when taken in conjunction with the drawings: FIG. 1 is a cross-sectional view of a first embodiment of the invention; FIGs. 2A and 2B are cross-sectional views for explaining the effect of a heat transfer rubber sheet used in the first embodiment; FIGs. 3A and 3B are a top view and a bottom view of a piston used in the first embodiment, respectively; FIGs. 4A through 4D show plane views for showing different grooves formed on the piston; FIG. 5 is a cross-sectional view of a second embodiment of the invention. FIG. 6 is a plane view for showing a heat transfer plate used in the second embodiment. FIGs. 7A through 7D are plane views for showing different grooves formed on the heat transfer plate. In the drawings, the same references numerals represent the same structural elements. Detailed Description of the Preferred Embodiments of the Invention Referring now to FIG. 1, a first embodiment of the invention comprises a plurality of semiconductor components 1 and a heat transfer plate 3a of an LSI case 2 attached on the components 1. The plate 3a may be made of a material which has a thermal expansion coefficient almost identical to that of the semiconductor components 1 and has a high thermal conductivity such as a Cu/W alloy. The case 2 is mounted on a printed wiring substrate 4 so as to have the plate 3a facing the direction opposite to the substrate 4. A cold plate 5 is fixed on the substrate 4 to oppose the substrate 4 via a spacer 6. A cylinder hole 7 is bored through the cold plate 5 at a position corresponding to the case 2, and a piston 8a is inserted through the cylinder hole 7. As shown in FIG. 3A, the piston 8a is slit to have a slot 9, and the piston 8a can be snugly attached on the side thereof onto the wall surface defining the hole 7 by tightening a screw 10 inserted in the slit 9. Grooves lla are formed on the surface of the piston 8a opposing the case 2 as shown in FIG. 3B. A heat transfer sheet 12a is placed between the piston 8a and the plate 3a, and when the piston 8a is fixed with a force applied on the side of the case 2, the sheet 12a is held in elastic deformation between the piston 8a and the plate 3a. The heat generated from the components 1 is transferred to the plate 3a, the heat transfer rubber sheet 12a, and the piston 8a, and then removed by coolant 13 circulating in the plate 5 via the hole 7 to thereby cool the components 1. In this embodiment, it is necessary to reduce the thickness of the sheet 12a which has a lower heat transfer coefficient than other heat conductive members and to improve the contact between the piston 8a, the plate 3a and the sheet 12a in order to lower the thermal resistance. However, this embodiment is structured to absorb the inclination of the plate 3a with respect to the opposing surface of the piston 8a caused by fluctuation in assembly and dimension of parts with the deformation of the sheet 12a to increase the contact area. The sheet 12a needs to have a certain degree of thickness in order to absorb the inclination on the plate 3a with the deformation thereof. FIGs. 2A and 2B show the difference in contact between the piston 8a, the plate 3a and the sheet 12a depending on absence/presence of the grooves 11a. If there are no grooves 11a formed on the piston 8a, it evenly presses a thin rubber sheet 12a in a wider area, and little deformation occurs laterally. Since there is little deformation in the lateral direction, the deformation of the sheet 12a is small, and as shown by the contact area S1 in FIG. 2a, the contact area becomes small. If the piston 8a is formed with grooves 11a, on the other hand, when the heat transfer rubber sheet 12a is pressed, the sheet 12a becomes deformed to rise inside the grooves 11a to thereby increases the deformation of the sheet 12a, and as shown in S2, the contacting area increases. Simply by forming the grooves 11a at the end of the piston 8a, a wider contacting area can be secured between the piston 8a, the plate 3a and the sheet 12a. It also reduces the thermal resistance thereof because the thickness of the heat transfer rubber sheet 12a can be reduced. So far as the grooves 11a of the piston 8a are provided evenly on the surface corresponding to the LSI case, the shape thereof is not necessarily limited to the form of grooves as shown in FIG. 3B. A similar effect can be attained by providing the grooves in parallel lines 111a, a concentric form 112a, a spiral form 113a, a radial form 114a or a combination of any of them. Cross section of the grooves is not limited to a rectangle, but may be a triangle or semicircular. Referring now to FIG. 5, a second embodiment of the invention comprises a plurality of semiconductor components 1 and a heat transfer plate 3b of an LSI case 2 mounted on the components 1. The plate 3b has a thermal expansion coefficient nearly identical to that of the semiconductor components 1 and is made of a material having a high heat conductivity, such as Cu/W alloy. Grooves 11b are formed on the surface of the plate 3b opposite the side where it is attached to the semiconductor components 1 in the form of a grid as shown in FIG. 6, to thereby roughen the surface. The case 2 is mounted on a printed substrate 4. The plate 3b is attached on the side opposite the substrate 4 of the case 2. A cold plate 5 is provided to oppose the substrate 4 and is fixed on the substrate 4 via a spacer 6. The cold plate 5 is bored with a cylinder hole 7 at a position corresponding to the LSI case while a piston 8b is inserted inside the cylinder hole 7. So far as the grooves 11b are provided evenly on the surface of the plate 3b opposing the piston 8b, they do not necessarily have to take the form of a grid. They may take the form of parallel grooves 111b, concentric grooves 112b, spiral grooves 113b, radial grooves 114b, or a combination of any of them as shown in FIGs. 7A through 7D to achieve the same effect. The cross section of the grooves is not limited to a rectangle, but may be a triangle or a semicircle.

Claims: A cooling structure for cooling electronic components comprising: at least one electronic component as a heat generating member (1), said electronic component having a heat transfer plate (3a; 3b), a heat radiating member (8a, 8b) for removing heat generated in said heat generating member (1), a flat elastic heat transfer sheet (12a) provided between said heat transfer plate (3a; 3b) and said heat radiating member (8a; 8b) for conducting heat generated in said heat generating member (1) to said heat radiating member (8a; 8b), said heat transfer plate (3a; 3b) and said heat radiation plate (8a; 8b) being in pressed contact with said elastic heat transfer sheet (12a) characterized in that grooves (11a; 111a; 112a; 113a; 114a; 11b; 111b; 112b; 113b; 114b) are formed in the face of said heat radiating member (8a; 8b), which is in contact with said elastic heat transfer sheet (12a) or in the face of said heat transfer plate (3a; 3b) which is in contract with said elastic heat transfer sheet, said elastic heat transfer sheet (12a) being deformed such that parts of it rise inside said grooves (11a; 111a; 112a; 113a; 114a; 11b; 111b; 112b; 113b; 114b). A cooling structure according to claim 1, wherein a cross section of said grooves (11a; 111a; 112a; 113a; 114a; 11b; 111b; 112b; 113b; 114b) is rectangular, triangular or semicircular. A cooling structure according to claim 1, wherein said grooves have the form of a grid (11a; 11b) or are parallel (111a; 111b), concentric (112a; 112b), spiral (113a; 113b), or radial grooves (114a; 114b). A cooling structure according to claim 2, wherein said heat transfer plate (3a; 3b) has a thermal expansion coefficient almost identical to that of said heat generating member (1).

Inventors: SANO TOSHIFUMI, SANO, TOSHIFUMI
Applicants: NIPPON ELECTRIC CO, NEC CORPORATION
Application year: 1989
Main classification: H01L23
IPC codes: H01L23