JPH0715965B2 - Semiconductor cooling device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial field of application] The present invention is designed to bring a flexible refrigerant flow path into contact with a heating element of an electronic component typified by a semiconductor chip or the like, and to provide a refrigerant in the refrigerant flow path. The present invention relates to a semiconductor cooling device suitable for cooling a semiconductor chip by flowing a gas.

[Conventional technology]

The conventional device is an example of a refrigerant in which a cooling fin is attached to the back surface of a semiconductor chip, which is a heating element, as described in, for example, JP-A-59-200495 and JP-A-58-200945. The semiconductor chip is cooled by flowing cooling water. In general, a plurality of semiconductor chips are arranged on a wiring board via solder balls (flip chip method), and the wiring of the semiconductor chip and the wiring of the wiring board are connected by the solder balls to exchange signals. .

Further, on the back surface side of the semiconductor chip, a flexible structure having a coolant supply port and a coolant discharge port formed by a flexible bellows such as a bellows is arranged, and the flexible structure is attached to an O-ring or a solder on a coolant header. Are joined by. As a result, the stress due to the displacement of the refrigerant header is absorbed by the flexible structure, and the stress does not directly act on the semiconductor chip. The cooling water flowing in the flexible structure cools the semiconductor chip via the cooling fins, but the cooling fins and the semiconductor chip are metallically joined by solder or the like, or have good thermal conductivity. For example, there is a case where they are joined by interposing silicon oil or grease, and in any case, measures are taken to improve heat conduction.

[Problems to be solved by the invention]

As described above, in the semiconductor cooling device targeted by the present invention, the refrigerant header and the wiring board are hermetically sealed so that, for example, air having a relatively high temperature does not enter. In this case, for example, the wiring board is mullite, ceramics,
The refrigerant header is made of Kovar or the like, and the constituent materials of the wiring board and the refrigerant header are different. In terms of temperature, the semiconductor chip and the wiring board side have a high temperature due to heat generation of the element, and the coolant header side has a low temperature because cooling water flows. Therefore, even if the bellows is not stressed at the time of assembly, a relative displacement occurs between the wiring board and the refrigerant header due to the different constituent materials of the wiring board and the refrigerant header and the temperature difference. The product of this displacement and the spring constant of the bellows acts as a force. In particular, since the solder ball that connects the semiconductor chip and each wiring of the wiring board is mechanically weaker than other parts, the solder ball-wiring board connection part or the solder ball-semiconductor chip connection part is mechanically It is weaker than other parts and often breaks at each connection.

Such breaking does not occur because the acting force becomes small if the spring constant of the bellows is made extremely small. To reduce the spring constant of the bellows, the wall thickness of the bellows material should be made thin so that the bellows has a soft structure. However, if this is done, the cooling water will flow inside the bellows for a long time, which may cause corrosion. The bellows may have holes and may cause an accident. Therefore, it is impossible to make the wall thickness thinner than a certain extent, and the spring constant cannot be made too small.

An object of the present invention is to provide a semiconductor cooling device in which the spring constant of a bellows is reduced so that thermal stress applied to a semiconductor chip can be suppressed even when a wiring substrate and a refrigerant header are deformed by thermal strain. To do.

[Means for solving problems]

In order to achieve such an object, according to the present invention, one end of a flexible bellows is attached to each of a plurality of semiconductor chips mounted on a wiring board via solder balls, and the other end of the bellows is attached to a refrigerant header. The semiconductor chip is attached to each of a plurality of formed communication holes, the solder ball is pressed by the elastic force of the bellows onto the wiring board through the semiconductor chip, and the coolant is flown to the coolant header to remove the semiconductor chip. In a semiconductor cooling device for cooling, the axis of the bellows is bent and attached.

[Action]

According to the above configuration, the relative displacement generated by the temperature difference between the wiring board and the refrigerant header is absorbed by the bellows,
Further, the spring constant of the bellows can be reduced. This relieves the thermal stress acting on the solder balls and prevents the solder balls from breaking.

〔Example〕

 Hereinafter, the present invention will be described based on embodiments shown in the drawings.

FIG. 1 relates to a first embodiment of the present invention and relates to a semiconductor cooling device 1
Is provided with a refrigerant header 2 and a plurality of bellows 3.
The refrigerant header 2 is made of Kovar or the like, and has a lower member 6 placed on the wiring board 5, an intermediate member 8 placed on the lower member 6, and an intermediate member 8 placed on the intermediate member 8. The upper member 9 and the lower member 6 are integrally fixed by sandwiching the intermediate member 8 between the lower member 6 and the upper member 9. The wiring board 5 is formed of mullite, ceramics or the like, and a plurality of semiconductor chips 10 are mounted on the wiring board 5 via solder balls 11 in a horizontal row or in a grid pattern. The solder balls 11 are wiring boards. 5 is a connection body having a minute diameter for connecting the wiring of 5 and the wiring of the semiconductor chip 10.

The lower member 6 includes a side wall portion 12 placed on the wiring board 5,
A curved partition 13 is arranged across the side wall 12 so as to face the semiconductor chip 10. The curved surface 13a of the partition 13 has, for example, a central portion of the wiring board 5 and the wiring board 5 has a curved surface 13a. Farther from the wiring board 5, the wiring board 5 is formed so as to sequentially approach the wiring board 5 toward both ends thereof, that is, to be convex upward. A plurality of communication holes 15 are formed on the curved surface 13a so as to face the semiconductor chip 10.
Is set on the same center line with respect to the semiconductor chip 10 arranged in the central part of the wiring board 5, and with respect to the semiconductor chips 10 arranged toward both ends apart from the central part of the wiring board 5. Are set so as to be offset from the center line of the semiconductor chip 10 toward the end of the wiring board 5. This deviation amount is set to be larger sequentially from the central portion to the end portion of the wiring board 5. Further, the lower member 6 has a drain port 16 formed in the side wall portion 12 above the partition portion 13.

The intermediate member 8 is composed of a partition wall portion 18 and a plurality of water supply pipes 19 which are integrally formed so as to stand upright on the partition wall portion 18 so as to extend downward. The axis of the water supply pipes 19 coincides with the center line of the semiconductor chip 10. The water supply pipes 19 are inserted into the communication holes 15, respectively. The upper member 9 is composed of a top wall portion 20 and a side wall portion 21 extending upright downward from an end portion of the top wall portion 20, and a water supply port 22 is formed in the side wall portion 21. The plurality of bellows 3 are respectively joined by soldering or the like to the cooling block 23 whose one end is joined to the upper surface of the semiconductor chip 10 by soldering or the like, and the other end is provided with an O-ring 25 in each communication hole 15, for example. It is fixed with a bolt or the like.

The upper member 9 and the upper surface of the partition wall portion 18 of the intermediate member 8 and the inner peripheral surface of the water supply pipe 19 serve as a water supply portion 26, and the lower surface of the partition wall portion 18 of the intermediate member 8 and the outer peripheral surface of the water supply pipe 19 and the side wall portion 12 of the lower member 6.
The drainage section 2 is formed by the inner surface and the upper surface of the curved section 13a and the bellows 3.
8 are airtightly formed.

A cooling fin (not shown) is placed on the cooling block 23 to improve heat conduction.

Next, the operation of the first embodiment of the present invention will be described.

The cooling water, which is an example of the refrigerant flowing from the water supply port 22, is supplied to the water supply unit 26.
Then, the semiconductor chip 10 is cooled through the cooling fins, passes through the drainage section 28, and is discharged from the drainage port 16. In this case, the constituent materials of the refrigerant header 2 and the wiring board 5 are different as described above, and in terms of temperature, the wiring board 5 and the semiconductor chip 10 side are high in temperature due to the heat generated by the elements, and the refrigerant header 2 side is The temperature is low due to the flow of cooling water. Due to the difference in the constituent materials of the refrigerant header 2 and the wiring board 5 and the temperature difference, the semiconductor cooling device 1 assembled at room temperature causes a relative displacement between the refrigerant header 2 and the wiring board 5.
The wiring board 5 may expand and the refrigerant header 2 may contract, or vice versa.

By the way, the shear spring constant of the bellows 3 varies depending on how the bellows 3 is bent. In other words, when the bellows shaft is bent and supported and a lateral load is applied to the other end (bellows shaft bending fixed type), the bellows shaft is made linear and both ends are fixed.
Comparing with a case where a load is applied in the direction perpendicular to the bellows shaft (bellows shaft linear fixed type), the bellows shaft linear fixed type has a relatively large load to obtain the same amount of displacement, and the spring constant is large. Regarding the spring constant characteristics of the bellows 3 described here, for example, MWKELLOGG COMPANY “Des
ign of Piping Systems ", pages 210 to 230, the shear spring constant obtained from the calculation formula cited in the same book is shown in FIG. In the figure, when the diameter of the bellows 3 is D and the length is L, the horizontal axis represents the aspect ratio (D / L).
And the vertical axis shows the shear spring constant (g / μm),
Curve A is the case where the bellows shaft is bent and fixed, and curve B is the case where the bellows shaft is straight and fixed.

According to the present embodiment, the bellows 3 is bent in the axis line except for the bellows 3 that faces the central portion of the wiring board 5, and the cooling block is formed.
It is fixed to 23 and the communication hole 15, and has a bellows shaft bending fixed type structure. Therefore, as described above, the spring constant of the bellows 3 is comparatively small even if thermal stress due to the difference in material and temperature difference acts between the refrigerant header 2 and the wiring board 5 during operation, so that the semiconductor chip 10 has a relatively small spring constant. The acting stress is small.

Here, the action of the bellows 3 of the bellows shaft bending fixing type is
It will be described with reference to the drawings. It is assumed that the refrigerant header 2 and the wiring board 5 had zero thermal stress at the time of assembly, but the thermal stress acts in the direction of arrow D (D ') due to the difference in material and the difference in coefficient of thermal expansion due to temperature difference. To do. This force D (D ') can be considered by dividing it into two component forces E (E') and F (F '). The component force E (E ′) is a force in the vertical direction with respect to the bellows 3, and the force in this direction is absorbed by the vertical displacement of the bellows 3. Bellows 3 for component force F (F ')
Is expanded and contracted in the directions of arrows G and H so that the contraction allowances are different, and is absorbed by the displacement of the bellows 3.

In this way, the force applied to the bellows shaft in the shearing direction is
It is absorbed by the expansion and contraction movement of the bellows 3. That is,
The relative displacement between the refrigerant header 2 and the wiring board 5 is absorbed without applying a large shearing force to the bellows 3. This relative displacement is greatest near the edge of the wiring board 5, but the amount of deviation between the center line of the communication hole 15 and the semiconductor chip 10 is greatest near the edge, and is absorbed by this. In this way, the stress acting on the semiconductor chip 10 can be suppressed to a small level, and the solder balls 11 can be prevented from breaking.

Note that the deviation amounts of the communication holes 15 and the center line of the semiconductor chip 10 may be set to be the same.

FIG. 4 relates to the second embodiment of the present invention, and is different from the first embodiment in that the shape of the curved surface 13a of the partition portion 13 is different. The curved surface 13a of the partition portion 13 is formed so as to be close to the wiring board 5 in the central portion of the wiring board 5 and to be gradually distant toward both ends of the wiring board 5, that is, to be concave upward. There is. Further, the center lines of the plurality of communication holes 15 are set on the same center line with respect to the semiconductor chip 10 arranged in the central part of the wiring board 5, and are arranged toward both ends apart from the central part of the wiring board 5. The semiconductor chip 10 thus formed is set so as to be offset from the center line of the semiconductor chip 10 toward the central portion of the wiring board 5.

Other configurations and operations are similar to those shown in the first embodiment.

5 and 6 relate to a third embodiment of the present invention, in which a plurality of semiconductor chips 10 are arranged in parallel, and the refrigerant header 2 is formed by a partition wall 30 corresponding to each semiconductor chip 10. The water supply section 26 and the drainage section 28 that are provided, and the communication holes 15A and 15 that communicate with the water supply section 26 and the drainage section 28 on the curved surface 13a.
B and are provided. The upper end of the bellows 3A is fixed to the outside of the communication holes 15A and 15B with a bolt or the like via an O-ring 25, and the lower end of the bellows 3A is joined to the cooling block 23 by solder or the like. The mounting position of the upper end of the bellows 3A is set according to that shown in the first embodiment. Inside the communication holes 15A, 15B, the upper end of the bellows 3B is fixed with a bolt or the like via an O-ring 25, and the bellows 3A, 3B form a water supply passage 31 and a drainage passage 32. Other configurations and operations are similar to those shown in the first embodiment.

FIG. 7 and FIG. 8 relate to the fourth embodiment of the present invention,
The difference from the embodiment is that the partition 13 is formed in a planar shape, and a mounting surface 32 for mounting the upper end of the bellows 3 is formed around the communication hole 15 on the inner surface of the partition 13.

When the center lines of the semiconductor chip 10 and the communication hole 15 are on the same straight line as shown in FIG.
Is set on the horizontal plane with respect to the semiconductor chip 10 arranged in the central part of the wiring board 5, and the central part side is upward with respect to the semiconductor chip 10 arranged from the central part of the wiring board 5 toward the end part. The angle is set to a certain angle θ with respect to the horizontal plane.

The inclination angle θ of the mounting surface 32 may be set so as to gradually increase from the central portion of the wiring board 5 toward the end portion.

Also, as shown in FIG. 8, the center line of the communication hole 15 is the wiring board 5.
Of the semiconductor chip 10 arranged on the same center line with respect to the semiconductor chip 10 arranged in the central portion of the wiring board 5 and arranged toward the end portion apart from the central portion of the wiring board 5. When it is set so as to be deviated from the center line in the direction of the end of the wiring board 5 by e, all the mounting surfaces 32 are set on the horizontal plane.

Note that the deviation amount e of the communication hole 15 may be set to increase sequentially from the central portion of the wiring board 5 toward the end portion.

FIG. 9 relates to a fifth embodiment of the present invention, and is different from the above-mentioned embodiment in that the bellows 3 is molded with the bellows shaft bent before being mounted.
Applies to any of the above embodiments.

〔The invention's effect〕

As described above, according to the present invention, since the axis of the bellows that connects the refrigerant header and the semiconductor chip is bent and attached, the relative displacement due to the difference in the constituent materials of the refrigerant header and the wiring board and the temperature difference. Is absorbed, the spring constant of the bellows is reduced, the thermal stress acting on the solder balls is relieved significantly, and the breakage of the solder balls can be prevented.

[Brief description of drawings]

FIG. 1 is a vertical cross-sectional view of a semiconductor cooling device according to a first embodiment of the present invention, FIG. 2 is a diagram showing calculated values of shear spring constants of bellows, and FIG. 3 shows the action of the bellows of the present invention. Explanatory drawing, FIG. 4 is a longitudinal sectional view of a semiconductor cooling device according to a second embodiment of the present invention, FIG. 5 is a partial longitudinal sectional view according to a third embodiment of the present invention, and FIG. 6 is shown in FIG. Schematic plan view of what is shown, No. 7.
FIG. 8 and FIG. 8 are partial longitudinal sectional views according to the fourth embodiment of the present invention, and FIG. 9 is a front view of the bellows according to the fifth embodiment of the present invention. 1 ... Semiconductor cooling device, 2 ... Refrigerant header, 3 ... Bellows,
5 ... Wiring board, 10 ... Semiconductor chip, 11 ... Solder ball, 13
… Partition, 13a… Curved surface, 15… Communication hole.

Claims (8)

[Claims] 1. A plurality of semiconductor chips mounted on a wiring board via solder balls, one end of a flexible bellows is attached to each of the semiconductor chips, and the other end of the bellows is formed in a plurality of refrigerant headers. A semiconductor cooling device which is attached to each of the communication holes, presses the solder balls onto the wiring board through the semiconductor chips by the elastic force of the bellows, and cools the semiconductor chips by flowing a refrigerant into the refrigerant header. In the semiconductor cooling device, the axis of the bellows is bent and attached. 2. The bellows according to claim 1, wherein both end surfaces of the bellows are not parallel to each other when the bellows is attached.
The semiconductor cooling device according to the paragraph. 3. The inclination of the other end of the bellows with respect to the horizontal plane is set to be larger sequentially from the central portion of the wiring board toward the end with the central portion facing upward.
The semiconductor cooling device according to the paragraph. 4. The semiconductor cooling device according to claim 1, wherein the other end of the bellows is attached to each of a plurality of communication holes formed in a curved partition. 5. When the curved surface of the partitioning portion is formed so as to be far from the wiring board in the central portion of the wiring board and to gradually approach the wiring board toward the end portion of the wiring board, The center line of the communication hole is set on the same center line with respect to the semiconductor chip arranged in the central portion of the wiring board, and the semiconductor is arranged away from the central portion of the wiring board toward the end. The semiconductor cooling device according to claim 4, wherein the chip is set so as to be offset from a center line of the semiconductor chip toward an end portion of the wiring board. 6. The communication hole when the curved surface of the partition portion is formed so as to be close to the wiring board in the central portion of the wiring board and to be gradually farther toward the end portion of the wiring board. The center line of is set on the same center line for the semiconductor chips arranged in the central portion of the wiring board, and for the semiconductor chips arranged from the end portion of the wiring board toward the central portion. The semiconductor cooling device according to claim 4, wherein the semiconductor cooling device is set so as to be deviated from a center line of the semiconductor chip toward a central portion of the wiring board. 7. The semiconductor cooling device according to claim 4, wherein the setting position of the communication hole with respect to the semiconductor chip is set to be gradually deviated from the central portion toward the end portion. 8. The semiconductor cooling device according to claim 1, wherein the axis of the bellows is preliminarily bent and molded.