JPH0278259A - Semiconductor cooling device - Google Patents

Abstract

PURPOSE:To contrive relaxation of a stress, which is generated by a vibration, by a method wherein cooling structures coupled with one another by flexible bellows are respectively restrained by a press plate having a rubber layer. CONSTITUTION:A thermal stress, which is generated in each constituent material due to a temperature difference between heating elements 2 and a refrigerant liquid, is absorbed by the deformation of flexible bellows 7, 8 and 12. If a vibration 19 parallel to a substrate 1 acts, moments shown by arrows 20 and 21 work. As each cooling structure 6 is fixed on the substrate 1 by solder balls 3, the fulcrums of the moments are the balls 3. In the case of the moment 20, a tensile force 22 works on the ball 3 on the side of the left end part and a compressive force 23 works on the ball 3 at the right end part. In the case of the moment 21, the above forces each work reversely. A press plate 13 restrains softly the structure 6 to prevent it from moving. In particular, when the number of natural oscillations of each bellows is close to that of the bellows at the time of an earthquake and the time of transportation, the moments 20 and 21 are further increased and the effect of the plate 13 is more increased. By a such a way, a stress due to a vibration can be relaxed.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention is directed to a flexible cooling channel that is brought into contact with a heating element of an electronic component such as a semiconductor element, and cooling water is introduced into the cooling channel. The present invention relates to a semiconductor cooling device that cools a heating element by flowing water.

[Conventional technology]

A conventional device, as described in Japanese Patent Application Laid-Open No. 61-226946, is a zero heating element chip in which a cooling fin is attached to the back side of a heating element (for example, a semiconductor chip) and the heating element is cooled by flowing cooling water. Generally, a plurality of chips are arranged on a board, and the wiring inside the chip and the wiring inside the board are connected by a flip-chip method to exchange signals. The cooling fins may be metallically joined to the heating element by soldering or the like, or may be filled with silicone oil, grease, or the like having good thermal conductivity. If the heating element generates a large amount of heat, it should be joined by soldering or the like. On the other hand, the structure that guides cooling water to the cooling fin portion is made of a flexible structure such as a bellows. What is the role of this flexible structure?

The purpose is to minimize the direct influence of pressurizing force during assembly or thermal stress during operation on the heating element side.

When the cooling fin portion is metallically joined to the heating element, the cooling fin portion and the flexible structure are joined by an O-ring or the like. When silicone oil, grease, or the like is inserted between the cooling fin portion and the heating element, the cooling fin portion and the flexible structure are joined metallically.

[Problem to be solved by the invention]

When the amount of heat generated by the heating element is large, the cooling fin part and the heating element are joined metallically, and the cooling fin part and the flexible structure are connected by an O-ring.

When a large number of heating elements are arranged on a substrate, the cooling water passes through one heating element and then is guided to an adjacent heating element. Therefore, the soft, flexible structure becomes a connection body with a ring connection paired with the heating element to be cooled.

A large number of these connected bodies are arranged in parallel on the substrate. The parallel flow of cooling water to each connection is accomplished by a common header.

The role of the flexible bellows is to connect the signal line between the heating element (semiconductor chip) and the substrate, for example, by applying stress to the heating element 5 due to pressure during assembly of the structure or thermal stress during operation. The purpose is to prevent damage to solder balls etc.

However, the prior art does not take measures against vibrations of the structure, such as during an earthquake or movement of the structure.

An object of the present invention is to construct a cooling structure using a connected body of flexible bellows, to alleviate the pressure force during assembly of the structure or the thermal stress during operation, and to reduce the amount of heat generated even when the structure vibrates. The purpose is to reduce the stress applied to the body.

[Means to solve the problem]

In order to achieve the above object, the cooling structure has the following structure.

If several cooling structures are connected by flexible bellows, the cooling structures have their own weight, so when they vibrate, the solder connecting the signal line between the heating element and the board, for example, Force is applied to the ball.

Therefore, from the side opposite to the substrate, a plurality of cooling structures connected by flexible bellows are held down by a spongy holding plate made of, for example, a mesh band. by this,
Alleviates the stress that occurs when the cooling structure vibrates.

[Effect]

Cooling structures metallically bonded to a plurality of heating elements on a substrate are each connected by flexible bellows. This flexible bellows has the function of allowing a refrigerant liquid to flow within the flexible bellows in order to cool each heating element, and also functions to relieve the pressurizing force generated during assembly and the thermal stress generated during operation.

By the way, when this structure vibrates during an earthquake or during transportation of the structure, the following phenomenon occurs. The board and the cooling structure are connected via the heating element by multiple solder balls, so if the board vibrates in a direction parallel to the board, the center of gravity of the cooling structure is used as a fulcrum, and the cooling structure The weight of Therefore, at this time, a moment acts on the structure using the joint surface between the cooling structure and the substrate as a fulcrum. When a moment is applied, tensile force or compressive force is applied to each of the plurality of solder balls. In that case, the solder balls near the end face of the heating element tend to receive, for example, a tensile force, while the solder balls at the other end tend to receive a compressive force. When compressive force and tensile force are applied to the solder ball, the half FtJ ball may be crushed, or the half FtJ ball may be peeled off from the board surface or the mature solder ball, resulting in a defect.

On the other hand, in a structure in which each cooling structure is connected by a flexible bellows, resonance may occur if the vibration frequency of the structure is close to the natural frequency of the flexible bellows. In that case, the force applied to the solder ball increases, making it more likely that the solder ball will be defective or damaged. Therefore, especially when using flexible bellows, the structure must be designed to reduce the force exerted on the half-I sphere that is generated by vibration.

The cooling structure is covered with a rubber or spongy holding plate.
By holding it in place, it is possible to prevent displacement of the vibrating cooling structure, and it is possible to suppress the compressive force and tensile force acting on the solder balls to a small level. This device attempts to absorb displacement due to thermal stress with a flexible bellows during one operation.

The displacement due to this thermal stress is slow;
Even if the rubber-like or spongy-like holding plate holds down the cooling structure, it does not impede its displacement absorption ability. On the other hand, when vibration occurs during an earthquake or during transportation, a sudden force is applied, and this can be absorbed by a rubber-like or spongy holding plate. In this way, it is possible to prevent solder balls from being defective or damaged during an earthquake or during transportation.

〔Example〕

An embodiment of the present invention will be described below with reference to FIGS. 1 to 4. A large number of heating elements 2 (semiconductor chips, etc.) are mounted on a wiring board 1, and signal lines therein are connected by solder balls 3. FIG. 2 shows an example of a structure in which nine heating elements 2 are arranged in nine rows in parallel. The back side of heating element 2 (
A cooling part 4 having cooling fins inside is disposed on the side opposite to the surface connected by the solder balls 3, and an introduction part 5 for guiding cooling water to the cooling fin part is disposed in the cooling part 4, A cooling structure 6 corresponding to each heating element 2 is formed. A plurality of introduction parts 5 corresponding to each heating element 2 are connected by flexible bellows 7, respectively.

5. In the example shown in FIG. 2, both ends of each row of nine heating elements are connected to a common ladder 9 via flexible bellows 8, similarly to between each heating element.

The common header 9 is divided into an inner structure 10 and an outer structure -1, and the flexible bellows 8 is joined to the outer structure 11 by silver soldering or the like. The inner structure 10 is fixed to the substrate 1.

Each inner structure 10 is connected by a flexible bellows 12. Further, the four corner common header is provided with an outlet 18 after the refrigerant.

And the height of each cooling structure 6 and common ladder 8 is.

It is constructed to be uniform. 11 with common headers 9 provided at both ends of nine heating elements as shown in Figure 2.
The upper surface (
A holding plate 13 is attached to the opposite side of the substrate 1, as shown in FIGS. 1 and 2. For hold-downs 1-3,
A rubber layer 15 is attached to one surface of the flat plate 14, and the rubber layer 15 faces the cooling structure 6 side. Holding board 13
is in the shape of a large flat plate, approximately the same size as the board 1.

As shown in FIG. 1, the cooling structure 6 is sandwiched between a holding plate 13 and a substrate 1. Then, by sandwiching the fixed frame 16 from four directions and tightening the holding plate 13 with the screws 17,
Hold down the cooling structure 6.

Next, the operation will be explained. A refrigerant liquid for removing heat generated by one heating element when the semiconductor device is in operation flows into the common header from at least one of the refrigerant liquid outlets 18 attached to the common header in the four corners. As it flows through each common header 8 and flexible bellows 1.2, it branches at each common header into nine rows of nine cooling structures connected by flexible bellows 7. The branched refrigerant liquid is guided from the introduction part 5 of the cooling structure 6 to the cooling part 4, and as it flows inside, it absorbs the heat generated by the heating element 2, is heated, and then flows back to the adjacent cooling structure. and flow,
It is ultimately led to the common header at the other end. At each common header section at the other end, the warmed refrigerant liquid joins together and flows out from the other one of the refrigerant liquid outlet ports 18 .

The above is the explanation of the cooling mechanism.

By the way, in such a cooling device, 1
The heating element has a temperature of approximately 60 to 150°C, and the refrigerant liquid has a temperature of approximately 10 to 50°C. Therefore, this temperature difference causes a difference in thermal expansion of the constituent materials of each part. The flexible bellows 7.8.12 functions to absorb thermal stress by deformation of the bellows, even if thermal stress occurs due to such an expansion difference. In normal times, this semiconductor device functions as described above.
When vibration occurs during an earthquake or during transportation, a moment of force acts on the cooling structure 6 or the common header 8.
FIG. 4 shows a case where parallel vibration 19 acts on the substrate, taking one cooling structure as an example. In this case, the cooling structure 6, on which a moment as indicated by the arrow 20.21 acts, is fixed to the substrate 1 via the solder ball 3, so the fulcrum of the moment 20.21 is at the solder ball 3. Become.

Therefore, for example, taking the case of moment 2o,
In FIG. 4, a tensile force 22 acts on the solder ball 3 on the left end side, and a compressive force 23 acts on the solder ball 3 on the right end side.

The opposite is true for moment 21. The holding plate 13 provided with a rubber layer on the tip side of the cooling structure (on the side opposite to the heating element) is
By pressing the cooling structure 6 to a certain degree of softness, movement of the cooling structure 6 can be prevented. In other words, it acts to supply a force of moment 20.21.

In particular, when the natural frequency of the flexible bellows is close to the frequency during earthquakes or transportation, this moment 20° 21 becomes even larger, and the effect of the holding plate 13 becomes even greater.

As explained above, a cooling device equipped with a flexible bellows and a presser plate reduces the pressing force during assembly.

This reduces the tensile and compressive forces that are applied to the solder ball due to thermal stress during operation, or moments that act during earthquakes or during transportation, thereby minimizing damage and defective solder balls.

Another embodiment is shown in FIG. 5, the tip 2 of the cooling structure 6.
In addition to suppressing only 4 with a rubber layer, the side surface 2 on the tip side
It has a structure in which a rubber layer is also provided on the 5th side. With the flexible bellows 7 as a support, the moment in the direction in which the nine cooling structures run is small, and in this case, on the contrary, the moment in the direction perpendicular to the nine cooling structures becomes large. Therefore, FIG. 5 shows a case in which nine cooling structures run in a direction perpendicular to the plane of the paper, and a rubber layer is inserted into the gap 26 of each nine cooling structure. With this configuration, the tensile force and compressive force acting on the solder balls due to the moment in the direction perpendicular to the nine cooling structures can be kept small.

FIG. 6 shows another embodiment. A support plate 27 is configured to protrude from the side of the support plate 14 between nine rows of cooling structures. A rubber layer 15 is provided between the support plate 27 and the cooling structure 6.
is provided. By providing the support plate 27, the moment in the direction perpendicular to the nine cooling structures can be reduced to the fifth
It can be kept much smaller than the case shown in the figure. Furthermore, regarding the strength of the support plate 13, the rust resistance in the direction in which the support plate 27 runs is stronger than in the case of a simple plate-like structure as shown in FIG. This is because it is fixed not only to the support plate 13 but also to the substrate 1 via the fixing frame 16, and the rust resistance of the substrate 1 in the direction in which the support plate 27 runs becomes stronger.

FIG. 7 shows another embodiment. Only the rubber layer 15 is inserted between nine rows of cooling structures.

This rubber layer also functions to reduce the moment in the direction perpendicular to the nine-unit cooling structure. In this case, there is no need to provide the holding plate 13, and the structure can be simplified.

FIG. 8 shows another embodiment. A frame 28 is provided on the front side of the holding plate 13 (the side opposite to the supporting plate 27). The direction of this frame 28 is perpendicular to the support plate 27. As mentioned above, the support plate 27 has made the support plate 13 more resistant to rust in the direction in which the support plate 27 runs, but according to this embodiment, the rust resistance on the side perpendicular thereto can also be increased. FIG. 9 shows an external view of a cooling structure assembled using such a holding plate. In addition to strengthening the rust resistance of the holding plate 13 in the two orthogonal directions, by assembling the cooling structure using the fixed frame 16 in this way, the two orthogonal directions of the board 1
The rust resistance in the direction is also increased - Fig. 10 shows another embodiment. When a block 30 is a board 1 on which a large number of heat generating elements 2 are mounted, a plurality of blocks are mounted on a large board 29 to constitute a cooling device. In the example shown in FIG. 10, four blocks 30 each having six rows of cooling structures connected by flexible bellows are mounted on the large substrate 29. In this case, a relatively large holding plate 13 will be used. How to fix the holding plate 13.

It is fixed to a large board 29. Holding board 13 and large board 2
A fixing plate 31 with holes as shown in FIG.
A total of three bolts are inserted between the holding plate 13 and the large board 29, in the example shown in FIG. Fix it.

〔Effect of the invention〕

Since the present invention is configured as described above, it has the effects described below.

By attaching a pressure plate with a rubber layer to the substrate side from the tip side of the cooling structure connected by flexible bellows, the moment of force applied to the cooling structure during earthquakes or transportation is suppressed, and the substrate and heating element are By reducing the tensile or compressive force applied to the solder balls in between, it is possible to prevent them from breaking or becoming defective. And to provide a rubber layer.

The rust resistance of the board is improved by fixing the board and a holding plate that holds down the structure made of the holding board and the rubber layer on the tip side of the cooling structure with a fixing frame.

Furthermore, simply by providing only the rubber layer between the cooling structures, the moment of force due to vibration can be reduced. In this case, the structure can be made simpler during comparison.

By providing a support plate to the support plate and inserting it between the cooling structures, the moment of force applied to the cooling structure that occurs during earthquakes or transportation can be further suppressed, and the support plate can prevent corrosion of the support plate. Strengthen your sexuality. By integrating it with the board using a fixed frame, the rust resistance of the board is further strengthened. Further, in the holding plate, a frame is provided on the opposite side of the holding plate in a direction perpendicular to the holding plate, thereby increasing the rust resistance of the holding plate and the substrate in two orthogonal directions.

[Brief explanation of the drawing]

Fig. 1 is a perspective view showing the overall configuration of an embodiment of the present invention, Fig. 2 is a perspective view showing one element of the invention, Fig. 3 is a sectional view of Fig. 1, and Fig. 4 shows the operation. 5 is a sectional view showing another embodiment, FIG. 6 is a sectional view showing another embodiment, FIG. 7 is a sectional view showing another embodiment, and FIG. 8 is a sectional view showing another embodiment. FIG. 9 is a perspective view of the overall structure of another embodiment; FIG. 10 is a sectional view of another embodiment; FIG. 11 is a perspective view of another embodiment. FIG. 3 is a perspective view of an example element. 1... Board, 2... Heating element, 3... Solder ball, 4...
...Cooling part, 5...Introduction part, 6...Cooling structure, 7
...Flexible bellows, 9...Common header, 12...
・Flexible bellows, 13... Pressing plate, 14... Flat plate, 15... Rubber layer, 16... Fixed frame, 17...
-Screw, 27...Support plate, 28...Frame. Broom 1 Fig. 2 Fig. 3 Fig. 4 z l u I4 S Fig. bl ￥l No. 7 concave No. δ Fig. q Also, broom 10 Fig. Y 1) 1 concave

Claims (1)

[Claims] 1. Arrange multiple semiconductor chips, which are heat generating elements, on a substrate in a lattice pattern, bond a cooling structure to the back side of the heat generating element on the side opposite to the substrate, and connect each cooling structure with a flexible bellows. In a device that cools a heating element by flowing a refrigerant liquid into each cooling structure, the cooling structure is cooled by a holding plate consisting of a rubber layer and a flat plate so that the rubber layer faces the cooling structure side. A semiconductor cooling device characterized by having a structure in which it is pressed against a substrate side.