JP4051187B2 - Multi-chip module sealing structure - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a multi-chip module sealing structure which is superior in cooling performance and sealing reliability. SOLUTION: A semiconductor device 2 is mounted on a wiring board 1, the top surface of the wiring board 1 is fixed by soldering 8 to the undersurfaces of first frames 5 of which each thermal expansion coefficient conforms to that of the wiring board 1. Each of the upper parts of the first frames 5 is extended outside of the edges of the wiring board 1, the lower part of the air-cooling heat sink 7 and the top surfaces of the second frames 10 are fastened by bolts 9 through the intermediary of an O-ring between a large air-cooling heat sink 7 covering the frames 5 sufficiently and the first frames 5, and through the intermediary of plastic pieces 6 between the inner middle stages of second frames 10 of which each thermal expansion coefficient conforms to that of the air-cooling heat sink 7 and the outer middle stage of the first frames 5.

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a sealing cooling mechanism for a multichip module, and more particularly to a sealing structure for a multichip module used in an electronic computer or the like equipped with a high-performance semiconductor device.
[0002]
[Prior art]
With the increase in the processing speed of electronic computers and the increase in storage capacity, semiconductor devices have been increased in speed and integration. However, on the other hand, heat generation of the chip accompanying an increase in power consumption of the semiconductor device is a problem in connection with a reliability problem in 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 waste heat problem, that is, the cooling structure of the multi-chip module is taken up as a big problem.
[0003]
On the other hand, in order to maintain the reliability of the semiconductor device with respect to the environment and the cooling performance as a module over a long period of time, a sealing mechanism for confining the semiconductor device and the cooling structure inside the multichip module is also an important technical issue.
[0004]
Examples of such important sealing structures for multi-chip modules are described below. A sealing structure as shown in FIG. 4 is disclosed in “MCM-D / C Application for high Performance Module”, Proceeding of 1996 International Conference on Multi-chip Modules, p69.
[0005]
A large number of semiconductor devices 402 are mounted on a wiring board 401 made of alumina ceramic. Input / output pins 403 are provided on the back surface of the wiring board 401, and a cap plate 405 made of a material having high thermal conductivity is covered so as to cover the wiring board 401, and solder fixing 408 is performed at the peripheral edge of the wiring board 401. Thus, the inside of the module is hermetically sealed. Between the semiconductor device 402 and the cap plate 405, heat conduction means called a heat conductive compound 404 is provided corresponding to each semiconductor device 402, and heat generated by the semiconductor device 402 is transmitted to the cap plate 405. An air-cooled heat sink 407 is attached to the upper surface of the cap plate 405 to dissipate heat generated by the semiconductor device 402 via the cap plate 405.
[0006]
As yet another example, Japanese Patent Laid-Open No. 2000-349211 discloses a multi-chip module sealing structure as shown in FIG.
In FIG. 5, a large number of semiconductor devices 502 are mounted on a wiring substrate 501 such as ceramic. The wiring substrate 501 is a material having a thermal expansion coefficient that matches the thermal expansion coefficient of the semiconductor device 502. Input / output pins 503 are provided on the back surface of the wiring board 501.
[0007]
A frame body 505 made of an iron-nickel alloy, which is a material having a thermal expansion coefficient that matches the thermal expansion coefficient of the wiring board 501, is solder-bonded 508 to the surface of the wiring board 501 on which the semiconductor device 502 is mounted. ing.
[0008]
The upper part of the frame body 505 extends to the outside of the wiring board 501, and the upper surface of the frame body 505 is a flange surface provided with an O-ring groove. The upper and lower surfaces of the peripheral edge of the air-cooled heat sink 507 are flange surfaces, and a rubber O-ring 511 having excellent elasticity is interposed between the flange lower surface and the O-ring groove on the upper surface of the frame 505.
[0009]
In addition, the upper surface of the peripheral portion of the air-cooled heat sink 507 is interposed with a plastic 506 excellent in relative sliding, and the upper surface of the plastic 506 is pressed at the inner middle stage of the upper frame 510 so that the space between the lower portion of the upper frame 510 and the frame 505 Are tightened with bolts 509 to crush the rubber O-ring 511 and perform hermetic sealing.
[0010]
A gap in consideration of assembly accuracy and thermal expansion difference is provided between the inner middle side surface of the upper frame 510 and the outer peripheral side surface of the air cooling heat sink 507, and the upper surface of the frame body 505 and the lower surface of the peripheral edge of the air cooling heat sink 507 are A minute gap is provided so as to avoid contact while maintaining airtightness by the rubber O-ring 511. Between the air-cooled heat sink 507 and the semiconductor device 502, a thermally conductive compound 504 is provided corresponding to each semiconductor device 502, and heat generated by the semiconductor device 502 is transmitted to the air-cooled heat sink 507.
[0011]
[Problems to be solved by the invention]
The sealing structure of the multichip module as described above has the following problems in terms of (1) sealing part connection reliability and (2) cooling performance.
In the structure of FIG. 4 described in “MCM-D / C Application for high Performance Module”, Proceeding of 1996 International Conference on Multi-chip Modules, p69, a cap plate and a heat sink are used to ensure cooling performance. High metals such as aluminum and copper are used.
[0012]
On the other hand, the wiring board employs ceramics such as alumina ceramics in order to provide fine multilayer wiring. Aluminum and copper used for cap plates and heat sinks are mismatched to a greater extent than the thermal expansion coefficient of ceramics, so if the amount of heat generated by the entire module increases or the size of the wiring board increases, the space between the cap board or heat sink and the wiring board increases. The difference in thermal expansion increases. In the structure, since the cap plate and the wiring board are fixed via solder, when the difference in thermal expansion between them increases, horizontal deformation is restrained by the solder fixing portion, and a large stress is generated. As a result, the ceramics or solder portion of the wiring board may be destroyed, and it becomes difficult to ensure the reliability of the sealing connection.
[0013]
Further, when horizontal deformation is constrained by the above-described solder fixation, the module undergoes vertical bending deformation due to the bimetal effect, and as a result, the gap between the cap and the wiring board changes greatly. That is, the thickness of the thermally conductive compound applied between the cap and the semiconductor device may increase or peel off, making it difficult to ensure the reliability of the cooling performance.
[0014]
As a sealing portion structure for improving this point, there is a structure disclosed in Japanese Patent Laid-Open No. 2000-349211. In the structure of FIG. 5, an O-ring or a plastic with good slidability is interposed between an air-cooled heat sink that does not match the thermal expansion coefficient of the wiring board and a frame or upper frame that matches the thermal expansion coefficient of the wiring board. Thus, it is possible to seal without restraining the deformation in the horizontal direction due to the difference in thermal expansion between the air-cooled heat sink and the frame or upper frame. For this reason, the stress which generate | occur | produces in the solder fixed part of a frame and a wiring board is reduced significantly, and sealing connection reliability can be ensured.
[0015]
Further, since no vertical bending deformation occurs, there is no problem of an increase in the thickness of the heat conductive compound and a decrease in cooling performance due to peeling. However, in the above structure, since the air cooling heat sink is provided inside the frame, the area of the cooling fin of the air cooling heat sink is inevitably smaller than the inner frame size of the frame, leading to a decrease in cooling performance. . For this reason, with the increase in the amount of heat generated in the entire module, it becomes difficult to ensure the cooling performance of the module with the air-cooled heat sink having the above structure.
[0016]
An object of the present invention is to provide a multichip module sealing structure that improves the problems of the prior art described above and (1) improves sealing connection reliability and (2) has excellent cooling performance.
[0017]
[Means for Solving the Problems]
In order to achieve the above object, according to the present invention, a first frame is provided on the peripheral edge of a wiring board on which a plurality of semiconductor devices are mounted, and a large and wide cooling region is provided so as to cover the first frame. A cooling body cover is provided, and the first frame is fastened between the second frame and the cover through a member having excellent slidability and a member having a large amount of elastic deformation.
[0018]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, each embodiment according to the present invention will be specifically described with reference to FIGS. 1, 2, and 3.
[Example 1]
FIG. 1 is a cross-sectional view of a multi-chip module sealing structure showing the configuration of the first embodiment of the present invention. In FIG. 1, a large number of semiconductor devices 2 are mounted on a wiring substrate 1 such as ceramic. The wiring substrate 1 has a thermal expansion coefficient that matches that of the semiconductor device 2. Input / output pins 3 are provided on the back surface of the wiring board 1.
[0019]
The lower surface of the first frame 5 made of an iron-nickel alloy has a thermal expansion coefficient that matches the thermal expansion coefficient of the wiring board 1 and is soldered 8 to the surface on which the semiconductor device 2 of the wiring board 1 is mounted.
[0020]
The upper part of the first frame 5 extends to the outside of the wiring board 1, and the upper surface of the first frame 5 is a flange surface provided with an O-ring groove.
[0021]
The lower surface of the peripheral portion of the air-cooled heat sink 7 is a flange surface, and a rubber O-ring 11 having excellent elasticity is interposed between the flange surface and an O-ring groove provided on the upper surface of the first frame 5.
[0022]
The second frame 10 has a coefficient of thermal expansion matched to the coefficient of thermal expansion of the air-cooled heat sink 7, and slides relative to the inner middle stage of the second frame 10 and the outer middle stage of the first frame 5. The rubber O-ring is fastened with a bolt 9 between the lower part of the air-cooling heat sink 7 and the second frame 10 while the lower surface of the plastic 6 is pushed up by the second frame 10 through the plastic 6 excellent in 11 is crushed and hermetically sealed.
[0023]
A gap in consideration of assembly accuracy and thermal expansion difference is provided between the inner middle side surface of the second frame 10 and the outer peripheral side surface of the first frame 5, and the upper surface of the first frame 5 is air-cooled. The lower surface of the peripheral portion of the heat sink 7 is provided with a minute gap so as to avoid contact while maintaining airtightness by the rubber O-ring 11, so that the air-cooled heat sink 7 and the second frame 10 are connected to the first frame 5 and the wiring. By not restraining the relative thermal deformation in the horizontal direction with respect to the substrate 1, the vertical deformation of the module is suppressed.
[0024]
Between the air-cooled heat sink 7 and the semiconductor device 2, a thermally conductive compound 4 is provided corresponding to each semiconductor device 2, and the thickness of the thermally conductive compound 4 is suppressed by suppressing deformation in the module vertical direction. Can be kept constant and stable cooling performance can be obtained. Further, by fastening the module sealing bolt 9 from the lower surface of the second frame 10 and providing cooling fins on the entire upper surface of the air-cooling heat sink 7 , high cooling performance by the large heat sink can be ensured. Further, since the structure does not restrain the thermal deformation generated between the air-cooled heat sink 7 or the second frame 10 and the first frame 5 or the wiring board 1 as described above, the first frame 5 and the ceramic wiring It is possible to reduce the stress generated at 8 parts of the solder fixing of the substrate 1 and to secure high sealing part connection reliability.
[0025]
FIG. 2 is a sectional view of a sealing structure for a multichip module according to a second embodiment of the present invention. The second embodiment is the same as the first embodiment except that a module sealing bolt 9 is provided on the upper surface of the peripheral edge of the air-cooled heat sink 4 and fastened.
Example 3
Hereinafter, an embodiment according to the present invention will be described with reference to FIG.
[0026]
FIG. 3 is a cross-sectional view of a sealing structure for a multichip module according to a third embodiment of the present invention. This third embodiment is implemented except that an O-ring groove is provided in the outer middle stage of the first frame 5 and the rubber O-ring 11 is interposed between the first frame 5 and the second frame 10. Same as Example 1. That is, a rubber O-ring 11 is used instead of the plastic 6 in FIG.
[0027]
【The invention's effect】
According to the present invention, a multi-chip module sealing structure that enables high sealing connection reliability and high cooling performance of a high heat-generating semiconductor device has been realized.
[Brief description of the drawings]
FIG. 1 is a cross-sectional view of a multichip module sealing structure according to a first embodiment of the present invention.
FIG. 2 is a cross-sectional view of a multichip module sealing structure showing a second embodiment of the present invention.
FIG. 3 is a cross-sectional view of a sealing structure of a multichip module showing a third embodiment of the present invention.
FIG. 4 is a cross-sectional view of a conventional multichip module sealing structure.
FIG. 5 is a cross-sectional view of a conventional multichip module sealing structure.
[Explanation of symbols]
1, 401, 501... Wiring board 2, 402, 502... Semiconductor device 3, 403, 503... Input / output pins 4, 404, 504. ... First frame 6, 506 ... Plastic 7, 407, 507 ... Air-cooled heat sink 8, 408, 508 ... Solder fixing 9, 509 ... · Bolt 10 ········· Second frame 11, 511 ··· Rubber O-ring 405 ··········· Cap plate 505 ··· .... Frame body 510 ... Upper frame body

Claims (5)

A wiring board in which a plurality of semiconductor devices are mounted on one side and input / output pins are arranged on the other side, heat conduction means for discharging heat generated by the semiconductor device to the outside, and solder fixing to the upper surface of the peripheral edge of the wiring board A first frame body having an upper portion extending outside the wiring substrate and having a middle stage; a thermally conductive lid body provided to cover the entire surface of the semiconductor device and the first frame body; and the lid A second frame body provided on the lower surface of the peripheral edge of the body and having a middle step on the inside ; and a member having excellent elasticity between the lid body and the upper surface of the first frame body, and the second frame body a sealing structure of a multi-chip module is composed of a unit, for fastening through the superior member sliding properties or elasticity between the inner middle and the outer middle of the first frame of the The outer size of the lid is the mounting area of the semiconductor device. Sealing structure of a multi-chip module, characterized in that also provided widely.   The multi-chip module sealing structure according to claim 1, wherein the lid is an air-cooled heat sink.   2. The sealing structure for a multi-chip module according to claim 1, wherein the lid body constitutes heat conduction means, and an air-cooled heat sink is attached to the outside of the lid body. The member having excellent elasticity interposed between the second frame body and the lid body and the first frame body is an elastically deformable material including at least rubber. The sealing structure of the multichip module of 1. 2. The member having excellent slidability interposed between the second frame and the first frame is a member capable of relative sliding including at least plastic. Multi-chip module sealing structure.

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