JP2001217358A - Air-cooling structure for multi-chip module - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an air-cooling structure for a multi-chip module excellent in cooling performance by, when a cooling fin is fitted to a large multi-chip module through a heat-conductive material, crushing the entire surface of the heat-conductive material to thin for raised heat-conductive efficiency so that a heat-conductive compound is prevented from being extruded or peeled due to repeated expansion and contraction of a part due to temperature difference of the module caused by power on/off. SOLUTION: The heat of multiple semiconductor devices 2 is introduced to a cap 4 of high heat-conductivity, with a cooling fin 7 placed on the upper surface of the cap 4 with the heat-conductive compound 6 in between. The cooling fin 7 is, with recessed surface formed in the channel direction of the fin as well as in the vertical direction related to a fin base part lower-surface 7b, fitted by mechanically pressurizing the central-part upper surface of the cooling fin 7 with a leaf spring 9.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a cooling mechanism for a multi-chip module, and more particularly to a large-sized air-cooled module, such as an electronic computer for cooling by interposing a heat conductive material between an air-cooled fin and the module. The present invention relates to a cooling structure for a multichip module to be used.

[0002]

2. Description of the Related Art Higher speed and higher integration of semiconductor devices have been achieved with an increase in arithmetic processing speed and an increase in storage capacity of electronic computers. However, on the other hand, heat generation of the chip due to an increase in power consumption of the semiconductor device has become a problem in connection with a reliability problem in the stable operation of the semiconductor device. In particular, in a multi-chip module in which a large number of semiconductor chips are mounted on a high-density wiring board, this heat dissipation problem, that is, the cooling structure of the multi-chip module is taken up as a major issue. Examples of such important cooling structures for multi-chip modules are described below. 1992 ELECTRONIC COMPONENTS & TECHNOLOGY CONFER
"The Thermal Management of" published in ENCE (P997)
IBM's ES / 9000 Advanced Thermal Conduction Module "
Discloses a multi-chip cooling structure as shown in FIG.

[0003] A large number of semiconductor devices 402 are mounted on a wiring substrate 401 made of a ceramic substrate. Cap 404 made of copper or aluminum having high thermal conductivity
A flange 405 and a cap 404 are fastened by bolts 410 via a C-ring 408 between the base plate and the wiring board 401 and a cushion 409 below the wiring board 401 to seal the module. Heat conducting means called a piston 403 is provided between the semiconductor device 402 and the cap 404 so as to correspond to each semiconductor device 402, so that heat generated by the semiconductor device 402 is transmitted to the cap 404. Screw holes 411 are provided at regular intervals on the upper surface of the cap 404 so as to avoid right above the conductor device 402, and a water-cooled heat sink 407 is connected to the bolts 412 via a heat conductive sheet 406 which is a heat conductive material. And the heat of the semiconductor device 402 that has passed through the cap 404 is exhausted.

[0004] As another example, Japanese Patent Application Laid-Open No. 4-4964 is disclosed.
No. 3 discloses a cooling structure for a multi-chip module as shown in FIG. A large number of semiconductor devices 50 are placed on the wiring substrate 501 held by the flange 505.
2 is mounted. A thermally conductive cap 504 is placed over the semiconductor device 502, and the cap 504 is provided.
Together with the water-cooled heat sink 506 are fastened to the flange 505 with bolts 507. Water-cooled heat sink 506
And the cap 504 are precisely processed so as to be in close contact with each other. The heat generated from the semiconductor device 502 is transmitted to the cap 504 via the heat conductive compound 503 corresponding to the upper surface and the side surface of the semiconductor device 502, and is transmitted to the water-cooled heat sink 506 which is in close contact with the cap 504 to exhaust the heat. Further, the water-cooled heat sink 506 in FIG. 5 may be replaced with an air-cooled fin.

From the above two examples, a conventional example as shown in FIG. 6 can be considered. In the conventional example of FIG. 6, air cooling fins 607 are mounted in place of the water cooling heat sink 506 of FIG. 5, and a heat conductive sheet 406 is interposed between the cap 404 and the water cooling heat sink 407 of the prior art of FIG. This is a structure in which a heat conductive compound 606 is interposed between a cap 604 and an air-cooled fin 607. That is, many semiconductor devices 602 are mounted on the wiring board 601 held by the flange 605. Semiconductor device 6
02 is covered with a thermally conductive cap 604,
The cap 604 and the air-cooled fin 607 are
05 with a bolt 608. Air-cooled fins 60
Since the heat conductive compound 606 is interposed between the surfaces facing the cap 7 and the cap 604, excellent cooling performance can be obtained without requiring strict precision processing for bringing the air-cooling fin 607 and the cap 604 into close contact as shown in FIG. be able to.

[0006]

The above-described cooling structure for a multi-chip module has the following problems from the viewpoint of cooling performance.

In the conventional example shown in FIG. 6, an air-cooling fin is mounted on a top surface of a cap via a heat-conductive compound, and a peripheral portion of the air-cooling fin is fastened together with a flange with a bolt to reduce the thickness of the heat-conductive compound. It is thinned to several tens of μm or less to reduce the thermal resistance. However, in recent years, the module size has been increasing, and if the periphery of the air-cooling fin of 150 mm ^square size is fastened with bolts, the reaction force when crushing the heat-conductive compound will increase, and the thermal conductivity near the center of the air-cooling fin will increase. There is a problem that the compound cannot secure a thickness of several tens of μm or less, and the thermal resistance of the thermally conductive compound increases. In addition, as shown in FIG. 7, the cap 704 near the center of the air-cooling fin 707 and the deformation of the air-cooling fin 707 are increased by the repetition of expansion and contraction of the component due to the temperature difference at the time of power on / off of the module. Greatly fluctuates, and the heat conductive compound 706 interposed therebetween may peel off or be pushed out from the peripheral portion 707a of the air-cooling fin 707. From this, the cap 704
The thermal resistance between the air-cooling fins 707 increases and the temperature of the module increases, making it difficult to ensure reliability.

In the structure shown in FIG. 4, screw holes for bolts are provided at certain intervals on the upper surface of the cap so as to avoid right above the semiconductor device, and a heat conductive sheet is interposed between the air-cooling fins and the cap. Therefore, even in the case of a large-sized module, the heat conductive sheet can be uniformly and thinly crushed in all regions. However, if the material of the cap is
In the case of a brittle material such as ceramics having high thermal conductivity, FIG.
In the structure in which a screw hole is formed in the cap and the bolt is fastened with a bolt, the cap may be damaged by stress at the time of fastening the bolt, and it is difficult to ensure reliability.

SUMMARY OF THE INVENTION An object of the present invention is to provide a cooling structure for a multi-chip module having excellent cooling performance by improving the above-mentioned problems of the prior art and attaching air-cooling fins to a large-sized multi-chip module via a heat conductive material. To provide.

[0010]

According to the present invention, there is provided a semiconductor device comprising: a plurality of semiconductor devices; a wiring board on which the semiconductor devices are mounted; a high thermal conductive cap for covering the semiconductor devices; Heat conduction means for guiding heat generation to the cap is provided between the semiconductor device and the cap, and air cooling fins are mounted on the upper surface of the cap via a heat conductive material such as a heat conductive compound or a heat conductive sheet. The lower surface of the fin base of the air-cooling fin has a concave surface in the direction perpendicular to the groove direction of the air-cooling fin, assuming that the multi-chip module has a means for fixing the center part to the cap by mechanically pressing the center with a spring or the like. And a cooling structure for a multi-chip module.

[0011]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment according to the present invention will be specifically described with reference to FIGS. FIG. 1 is an XZ sectional view of an embodiment of the present invention. FIG. 2 is a YZ sectional view of the embodiment of the present invention. FIG. 3 is a perspective view showing only the air-cooled fins 7 according to the embodiment of the present invention and viewing the fin base lower surface 7b upward. A large number of semiconductor devices 2 are mounted on a wiring board 1 made of ceramic or the like. Heat generated by the semiconductor device 2 is transmitted to the cap 4 via the heat conductive compound 3. The cap 4 is made of a material having excellent heat conductivity, and the semiconductor device 2 is sealed together with the cap 4 by a flange 5 for fixing the wiring substrate 1 and the peripheral portion of the wiring substrate 1. A heat conductive compound 6 is provided on the upper surface of the cap 4.
The air-cooling fins 7 are mounted via the air-cooling fins 7, and as shown in FIG. 1 and FIG. Thinly, improving the heat transfer efficiency. Also,
Both ends of the leaf spring 9 are fixed by a bracket 10, and the bracket 10 and the flange 5 are fastened by bolts 11.

The fin base 7a shown in FIG. 3 has a thickness as small as several millimeters to reduce the thermal resistance, and the lower surface 7b of the fin base is oriented in a direction perpendicular to the fin groove direction (Y direction) (X direction). ) Is processed so as to form a concave surface of about 10 μm to 300 μm. The air-cooling fin 7 has a structure in which the fin base 7a has a small thickness and thus has high rigidity in the fin groove direction, but low rigidity in the direction perpendicular to the fin groove direction. As shown in FIG. 1 and FIG.
When the spacer 8 on the upper surface of the center portion of the fin base is pressed, first, the outermost projection 2 on the lowermost surface 7b of the fin base shown in FIG.
The thermally conductive compound 6 near the sides 7b1 and 7b2 is greatly crushed. When the pressing is further continued, the fin base lower surface 7
b receives the reaction force that crushes the heat conductive compound 6 and deforms the air-cooling fin 7 so that the low-rigidity concave surface in the X direction becomes flat. As a result, even in a large-sized module, the heat conductive compound 6 at the center of the lower surface 7b of the fin base is thinly crushed without any problem.

If the fin base lower surface 7b has a convex structure, when the upper surface of the central portion of the air-cooling fin 7 is pressed, the heat conductive compound 6 immediately below the pressed fin 7 is sufficiently thin and crushed by receiving a large load. The heat conductive compound 6 near the outer periphery of the air-cooling fin 7 cannot be crushed thinly because the crushing load is not sufficiently transmitted. According to this embodiment, the thickness of the heat conduction compound 6 interposed between the air-cooling fins 7 and the cap 4 is reduced to reduce thermal resistance, improve heat conduction efficiency, and ensure excellent cooling performance. By pressing the upper surface of the central portion of the air-cooling fin 7 shown in FIG. 1, the gap between the air-cooling fin 7 and the central portion of the cap 4 due to the repetition of expansion and contraction of the component due to the temperature difference at the time of power on / off of the module. 12 The heat conductive compound 6 which keeps the fluctuation small and intervenes
Of the air-cooling fins 7 and extrusion from the peripheral edge of the air-cooling fins 7 is prevented. As a result, an increase in thermal resistance between the cap 4 and the air-cooling fins 7 is suppressed, and excellent cooling performance can be secured.
The module reliability can be improved.

[0014]

According to the present invention, in the large-sized multi-chip module, the lower surface of the fin base of the air-cooled fin is perpendicular to the groove direction (Y direction) of the fin (X direction).
Applying a concave shape processing to the center of the air-cooling fin, pressing the upper surface of the air-cooling fin, thinning the thickness of the heat conductive compound interposed between the cap and the air-cooling fin, reducing the thermal resistance, An increase in thermal resistance between the cap and the air-cooled fins is suppressed by preventing the thermal conductive compound from being extruded or peeled due to repeated expansion and contraction of the component due to a temperature difference between when the module is turned on and off. Thereby, excellent cooling performance is ensured, and the effect of improving the reliability of the module is obtained.

[Brief description of the drawings]

FIG. 1 is an XY cross-sectional view of an embodiment of the present invention.

FIG. 2 is a YZ sectional view of the embodiment of the present invention.

FIG. 3 takes out only the air-cooled fins of the embodiment of the present invention,
It is the perspective view which looked at the fin base lower surface up.

FIG. 4 is a cross-sectional view of a conventional multi-chip module.

FIG. 5 is a cross-sectional view of a conventional multi-chip module.

FIG. 6 is a cross-sectional view of a conventional multi-chip module.

FIG. 7 is a cross-sectional view illustrating a deformation of the conventional multi-chip module of FIG. 6 when the power is turned on / off.

[Explanation of symbols]

 1, 401, 501, 601: Wiring board 2, 402, 502, 602: Semiconductor device 3, 503, 603: Thermal conductive compound 4, 404, 504, 604, 704: Cap 5 , 405, 505, 605 ... Flange 6, 606, 706 ... Thermal conductive compound 7, 607, 707 ... Air-cooled fin 7a ... Fin base 7b ... Fin base lower surface 8 ... Spacer 9 ... leaf spring 10 ... bracket 11, 410, 507, 608 ... bolt 12, 701 ... gap 403 ... piston 406 ... heat conductive sheet 407, 506 ... water-cooled heat sink 408 C-ring 409 Cushion 411 Screw hole 412 Bolt 707a Peripheral edge of air-cooled fin

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Munehiro Oguro, 1st Horiyamashita, Hadano-shi, Kanagawa Prefecture, Hitachi, Ltd. Enterprise Server Division (72) Inventor Takeshi Yamaguchi 1st, Horiyamashita, Hadano-shi, Kanagawa, Hitachi, Ltd. (72) Inventor Takahiko Matsushita Inventor Takahiko Matsushita 1 Horiyamashita, Hadano-shi, Kanagawa Prefecture In-house Enterprise Server Div. F term in the server division (reference) 5F036 AA01 BB05 BB21 BC03 BC09

Claims (3)

[Claims] 1. A semiconductor device comprising: a wiring board on which a number of semiconductor devices are mounted; a thermally conductive cap for covering the wiring board; and a heat conducting means for guiding heat generated by the semiconductor device to the cap. An air-cooling fin mounted on the upper surface of the cap via a heat conductive material, and a means for mechanically pressing a central portion of the air-cooling fin with an elastic member to attach the air-cooling fin to the cap. An air cooling structure for a multi-chip module, wherein a lower surface of a fin base portion of the air cooling fin has a concave shape in a direction perpendicular to a groove direction of the air cooling fin. 2. The cooling performance of the air-cooling fin is improved by pressing a central upper surface of the air-cooling fin to reduce the thickness of the heat conductive material interposed between the cap and the air-cooling fin. The air-cooled structure of a multi-chip module according to claim 1. 3. The heat-conducting material interposed between the cap and the air-cooled fins is kept at a certain thickness or less by pressing the upper surface of the central portion of the air-cooled fins with a constant load, and The air cooling structure of a multi-chip module according to claim 1, wherein the conductive material is not peeled off.