JPH04291751A - Cooling control of multichip module - Google Patents

Abstract

PURPOSE:To collectively cool semiconductor devices such as multichip modules by controlling cooling capacity every semiconductor element. CONSTITUTION:A cooling structure where a cooling jacket 20 is connected via a thermal compound 9 to a multichip module with a semiconductor element 1 mounted on a module board 6: the cooling jacket has a pair of a cooling water inlet 7 and a cooling water outlet 8, and cooling water is distributed to respective nozzles 3 via a header 4. Its flow rate is controlled by changes in pitch of a coil spring 5 consisting of a thermosensitive material provided at the outlet of a nozzle 3. Semiconductors on the board can be cooled discretely so as to develop no ununiformity in temperature distribution, whereby thermal deformation of boards during action can be suppressed.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a cooling device for semiconductor elements used in electronic computers and the like, and more particularly to cooling a multi-chip module that is a high-density semiconductor package.

0002

[Background Art] Semiconductor devices used in electronic computers, etc., generate a large amount of heat during operation due to the high density integration of electronic circuits, and it is essential to efficiently cool these semiconductor devices to maintain normal operation. This has become an issue. In particular, multi-chip modules, which have a large number of high-density semiconductor elements called large-scale integrated circuits (LSI) mounted on a single board in order to shorten signal transmission distances and operate at high speed, generate a lot of heat during operation. big. Cooling technology for such multi-chip modules includes, for example, NIKKEI ELECTRONICS.
Water-cooling techniques are known, such as those described in (Published June 17, 1885). This technology transfers heat generated by a semiconductor element mounted on a substrate to a cooling jacket called a cold plate through which cooling water flows through heat radiation studs and heat conduction blocks. The heat dissipation stud used here is used to maintain good contact at all times against height displacement and inclination of the surface of the semiconductor element caused by warping of the substrate and non-uniform dimensional accuracy during mounting of each semiconductor element. Other examples of structures for absorbing such displacement include using cooling elements such as bellows or pistons with spherical tips, which are brought into contact with semiconductor elements. Furthermore, in order to reduce thermal resistance, a thermally conductive compound is filled into the minute gaps in the contact area that cannot be absorbed by such a flexible structure. However, in this cooling structure in which an intermediate body such as a cooling element is provided between the semiconductor element and the cooling jacket, the thermal resistance increases due to the longer heat transfer distance between the semiconductor element and the cooling jacket and the large number of contact points. growing. Therefore, for example, JP-A-1-11514
A method of reducing thermal resistance by bringing a cooling jacket into direct contact with a semiconductor element, as exemplified in Japanese Patent No. 7, has been proposed. Such a cooling structure has a plurality of semiconductor elements arranged on one substrate, and is suitable for cooling a semiconductor device that generates a lot of heat. However, if heat generation differs from semiconductor to semiconductor, simply cooling the substrate all at once will cause a difference in temperature between the semiconductors on the same substrate, resulting in a decrease in performance. For this reason, JP-A-61-21
Japanese Patent No. 8146 proposes a method in which a semiconductor temperature detection means is provided for each semiconductor element, and the cooling amount of each semiconductor is controlled based on this temperature. Here, as an example, the temperature of the semiconductor element is detected by the voltage change at the junction of the transistor in the electronic circuit, and the opening degree of the flow path control valve provided in the cooling water flow path is controlled by a pulse motor based on the detection signal. A method for adjusting cooling capacity for each flow path is illustrated. Furthermore, as a simple cooling capacity control method, a method using a shape memory alloy as shown in FIG. 12 is exemplified, but the shape memory alloy is simply used to drive the heat transfer control gap 16.

0003

[Problem to be solved by the invention] As mentioned above, the semiconductors used in multi-chip modules generate a high amount of heat.
High cooling performance is required. For this reason, a method is used to cool each semiconductor element by supplying a cooling medium to each semiconductor element. In this case, it is necessary to distribute and supply the cooling electric body that is supplied to the module in bulk according to the heat generation of the semiconductor. This involves controlling the flow rate of the cooling medium for each flow path, and as shown in the conventional example, the structure is generally complicated. In other words, controlling a valve driven by a step motor for each flow path as in the conventional example is practically impossible in the cooling structure of a multi-chip module in which several dozen semiconductor elements are mounted on a 10 to 20 cm square substrate. It is possible. Therefore, an object of the present invention is to enable the cooling performance of a multi-chip module to be controlled for each semiconductor element using a simple mechanism.

0004

[Means for Solving the Problems] In order to solve the above problems, in the present invention, a coil spring is provided in a cooling medium flow path at a position corresponding to a semiconductor element mounted on a substrate. Furthermore, this coil spring takes measures to change the pitch depending on the temperature of the semiconductor element. One method uses a movable element, such as a bimetal or a shape memory alloy, that deforms in response to changes in the temperature of the semiconductor element to press the spring and change the pitch of the coil spring. Another method is to construct the coil spring itself from a temperature-sensitive movable material such as a bimetal or shape memory alloy, and to change its own spring pitch in response to changes in the temperature of the semiconductor element. .

[0005]

[Operation] In the coil spring installed in the cooling medium flow path, the gap between the pitches of the coils becomes a passage for the cooling medium. Therefore, changing this pitch interval means expanding or contracting the flow path of the cooling medium. By changing the cross-sectional area of the flow path, the flow rate of the cooling medium passing therethrough can be changed. This coil spring can be arranged for each cooling section of each semiconductor element, and can control the amount of cooling for each semiconductor element of a multi-chip module in which a plurality of semiconductor elements are arranged on a substrate. The movable element that causes the pitch change of the coil spring senses the temperature of the semiconductor element and acts to compress or expand the coil spring. Further, when the coil spring is made of a temperature-sensitive material, the pitch can be changed in response to the temperature of the semiconductor element, so that cooling can be controlled as described above. Furthermore, even when the sensor and drive element are provided separately,
A drive element such as a piezoelectric element is deformed based on the temperature detected by the sensor, and the generated force is used to change the pitch of the coil spring, whereby the flow rate of the cooling medium can be similarly controlled. As a result, the temperature of each semiconductor element within the module can be kept constant.

[0006]

[Examples] The present invention will be explained below with reference to Examples. Figure 1 shows
1 is a cooling structure of a multi-chip module showing a cross-sectional structure of a typical embodiment of the present invention. A plurality of semiconductor elements 1 are mounted on a module substrate 6. This embodiment shows a cross-sectional structure in which semiconductor elements are arranged in five rows and five columns on a substrate. Pin 2 is used for power supply and signal transmission to these semiconductor elements. In order to cool the semiconductor elements, a cooling jacket 20 is collectively connected to the semiconductor elements on the substrate via a thermal compound 9. Cooling water is collectively supplied to the cooling jacket 20 from the cooling water inlet 7, and the supplied cooling water passes through the header 4 within the cooling jacket to the nozzle 3 for cooling each semiconductor element.
distributed to. Since the cooling water is supplied in the form of a jet to the heat transfer surface of each semiconductor element from this nozzle, high cooling performance can be obtained. The cooling water ejected from each nozzle and having cooled the heat from the semiconductor elements is collectively discharged from the cooling water outlet 8 to the outside of the module. In addition to this configuration, in the present invention, a coil spring 5 is arranged at the nozzle outlet inside the cooling jacket. This may be made using, for example, a shape memory alloy that expands and contracts in response to temperature. This coil spring can be arranged for each nozzle as shown in the figure. Therefore, the cooling water supplied from the nozzle 3 jet-cools the semiconductor element and flows as shown by the arrow in the figure. Thereafter, the cooling water passes through the gap between the pitches of the coil springs and heads toward the cooling water outlet 8. With this structure, when the temperature of the semiconductor element rises, this heat is transmitted to the coil spring, and the coil spring stretches and acts to widen the pitch. This is because the spring is made of a temperature-sensitive material. As a result, the cross section of the cooling water flow path becomes larger, increasing the flow rate of cooling water supplied from the nozzle.
The cooling capacity against heat generated by the semiconductor element structure is increased. Therefore, when the temperature of the semiconductor element decreases, the coil spring contracts and returns to its original pitch, and the cooling water flow rate decreases to the standard flow rate. In this way, the relationship between the cooling water flow rate and the pitch of the coil spring, which determines the cooling capacity for maintaining the temperature of the semiconductor element, is determined by the relationship with the pressure loss of the nozzle portion. Further, the temperature at which the pitch is changed is optimally designed depending on the characteristics of the temperature-sensitive material that constitutes the coil spring and the state of heat transfer from the heat transfer surface to the coil spring. By arranging the coil springs in the cooling water flow path in this manner and changing the pitch thereof, the cooling capacity can be controlled for each semiconductor element. With this optimal design, the temperature of the semiconductor elements on the substrate can be made uniform.

This example shows the case where a shape memory alloy is simply used as the temperature-sensitive material, but in order for this coil spring to expand and contract in response to temperature accurately, the heat from the semiconductor element must be efficiently absorbed into the coil. It is necessary to tell the spring. Therefore, it is desirable to use a material with good thermal conductivity. Figure 2
shows the structure of a coil spring made of a composite material as an example that satisfies this requirement. This is a shape memory alloy with a copper-based interior, such as a Cu-Zn-Al alloy or Cu
A highly thermally conductive shape memory alloy using -Zn-Ni alloy is surrounded by a Ti-Ni type shape memory alloy that has high temperature sensitivity and corrosion resistance. This coil spring has high thermal conductivity from the end surface in contact with the heat transfer surface, and can more accurately transmit the temperature of the semiconductor element to the coil spring. Therefore, when the coil spring of this configuration is used in the above-described embodiment of the cooling module, the precision of pitch control of the coil spring can be improved, and a cooling module with highly accurate temperature control characteristics can be obtained. FIG. 3 further shows an example of a coil spring having a structure with different diameters. This coil spring is used with the larger diameter end in contact with the heat transfer surface. In other words, this embodiment has the effect of increasing the heat transfer area from the heat transfer surface to the spring.
This structure allows the temperature of the semiconductor element to be well transmitted to the coil spring. In this way, since the outer surface of the shape memory alloy made of the composite material shown in FIGS. 2 and 3 that comes into contact with the cooling water is made of a material with high corrosion resistance, long-term reliability can be ensured. Also,
In order to increase the corrosion resistance in this manner, as shown in FIG. 4, a structure in which a copper spring made of a shape memory alloy is coated with fluorine 12 as a surface treatment with water repellent properties, for example, is also possible. The entire spring of such a coil spring is made of a material with good thermal conductivity, and corrosion resistance can be maintained, so a cooling module using this spring can be used as described above.
Highly accurate pitch control becomes possible. FIG. 5 shows the structure of a spring wire when a coil spring is made of a heat pipe made of a shape memory alloy in order to further equalize the temperature of the coil spring. FIG. 6 shows a cross-sectional structure taken along VI-VI in FIG. That is, the coil spring of this structure has a diameter in which the working fluid 13 is sealed inside the pipe 21 made of, for example, a Ti-Ni shape memory alloy under conditions that allow it to be vaporized at the temperature of the semiconductor element, such as water or methanol under reduced pressure. The spring is a 1 to 2 mm micro heat pipe formed into a coil shape. In a coil spring with this structure, the internal working fluid evaporates due to the heat received at the end face of the spring and instantly diffuses throughout the spring, so no temperature gradient occurs in the coil spring. As a result, pitch changes due to changes in the coil spring can be accurately caused at the transformation temperature of the shape memory alloy. Figure 7 is, for example, Figure 2 or Figure 3.
This figure shows an example of the method for manufacturing the coil spring according to this embodiment shown in FIG. This is an example of manufacturing using drawing processing, in which a copper-based shape memory alloy 11 is used as a core wire, and a plate material of a Ti-Ni-based shape memory alloy 10 is surrounded by the core wire while being drawn using a die. In the next step, the composite material is drawn to obtain the required wire diameter. Finally, the strands are bent into a coil shape and heat treated to determine the shape before and after the transformation temperature. The composite material coil spring made of the shape memory alloy thus obtained is used in the cooling structure shown in FIG.

In the above embodiments, the coil spring itself is made of a temperature-sensitive material, and the coil spring itself deforms and changes its pitch due to the heat transmitted from the semiconductor element. However, in the embodiment shown in FIG. 8, the coil spring is constructed using a stainless steel spring that does not have a temperature sensitive function, and the temperature of the semiconductor element is controlled by changing the pitch of the coil spring. Note that FIG. 8 shows the structure of one semiconductor element that is part of a module. In this embodiment, a stainless steel coil spring that does not have a temperature sensitive function is placed at the outlet of the nozzle 3, and a bimetal 17 is inserted between the semiconductor element 1 and the coil spring 5 as shown in the figure to drive this spring. . In this structure, the basic configuration of jet cooling using a cooling medium is the same as the embodiment shown in FIG. 1, but the change in pitch of the coil spring is caused by the bimetal 17 receiving heat from the semiconductor element, loosening the restraint of the coil spring, and causing the spring to expand. The pitch of the coil spring changes. Other structures are conceivable for changing the pitch of a coil spring that does not have a temperature sensitive function in accordance with the temperature of a semiconductor element. For example, FIG. 9 shows an example of the structure of a temperature-sensitive functional element for driving a coil spring. FIG. 10 shows a partial cross-sectional structure of the movable part shown in FIG. In this example, two types of shape memory alloy plates are pasted together, and the peripheral parts that come into contact with the coil springs are processed to look like an assembly of plate springs as shown in the figure. This is because the surface that is hit by the jet is made of corrosion-resistant Ti-Ni.
A copper-based shape memory alloy 11 having good thermal conductivity is used on the heat transfer surface side that receives heat from the semiconductor element. According to this configuration, the leaf spring portion that deforms due to temperature can be deformed with high sensitivity due to the deformation force due to the characteristics of the shape memory alloy and the bimetallic effect resulting from the combination of two types of metals, and the coil spring disposed above this Pitch can be changed easily. Similar to the embodiment described in FIG. 1, these can be used in a cooling module to control the flow rate of cooling water for each semiconductor element.

FIG. 11 shows another embodiment of the present invention, in which the coil spring is made of a material that deforms only in one direction in response to temperature changes. be. In other words, this example uses a shape memory alloy that only deforms in the direction of elongation from its initial length when the coil spring reaches the transformation temperature, and does not return to its original state even if the temperature drops after deformation. . In this case, a bias force is required to compress the coil spring to its original state when the temperature drops, and a rubber ring 22 is used in this embodiment. It is clear that a generally used stainless steel coil spring or the like may be used. The rubber ring arranged as shown is a shape memory alloy coil spring 5.
The coil spring 5 is always pressed against the rubber ring, but when the temperature of the semiconductor element rises, the coil spring 5 expands and compresses the rubber ring. As a result, the pitch of the coil springs widens, the flow rate of cooling water supplied from the nozzle 2 increases, and the cooling efficiency increases. When the temperature of the semiconductor element decreases and returns to its original temperature, the reaction force of the compressed rubber ring 22 increases, compressing the coil spring 5 and returning to its original pitch, reducing the amount of cooling water supplied. do. This operation is repeated as the amount of heat generated by the semiconductor element changes, and the amount of cooling of the semiconductor element can be controlled.

0010

According to the present invention, since the flow rate of the cooling current supplied to each semiconductor element can be controlled using a simple principle and structure, there is an effect of eliminating the effects of uneven flow and non-uniform flow of the cooling medium.

[0011] Furthermore, since multiple semiconductor elements mounted on the module board that generate a large amount of heat can be individually cooled without being affected by the temperature rise of the cooling medium, uniform cooling is possible without unevenness in temperature distribution on the module board. This is effective in minimizing thermal deformation of the board during operation, and allows highly reliable cooling of the module.

[Brief explanation of the drawing]

FIG. 1 is a sectional view of a multi-chip module showing one embodiment of the present invention.

FIG. 2 is an explanatory diagram of a coil spring made of a composite material.

FIG. 3 is an explanatory diagram of a reducing diameter coil spring made of a composite material.

FIG. 4 is an explanatory diagram of a surface-coated coil spring.

FIG. 5 is a cross-sectional view of a wire for a heat pipe type coil spring.

FIG. 6 is a sectional view taken along the line VI-VI in FIG. 5;

FIG. 7 is an explanatory diagram of the manufacturing method of the composite material coil spring of the present invention.

FIG. 8 is a partial cross-sectional view of a cooling structure using a coil spring made of non-temperature-sensitive material.

FIG. 9 is an explanatory diagram of a temperature sensitive element for driving a coil spring.

FIG. 10 is a cross-sectional view taken along the circumference of FIG. 9;

FIG. 11 is a partial cross-sectional view of a cooling structure with a bias structure.

FIG. 12 is a cross-sectional view of an example of a conventional cooling structure using a shape memory alloy.

[Explanation of symbols]

1... Semiconductor element, 2... Pin, 3... Nozzle, 4... Header,
5... Coil spring, 6... Module board, 7... Cooling water inlet, 8... Cooling water outlet, 9... Thermal compound, 20...
cooling jacket.

Claims (10)

[Claims] 1. A semiconductor device in which heat generated from each semiconductor element of a multi-chip module in which a plurality of semiconductor elements are mounted on a substrate is transmitted by conduction to cooling jackets provided facing each other to collectively cool each module. A method for controlling cooling of a multi-chip module, characterized in that a coil spring is provided in a cooling medium flow path in a cooling jacket, and the flow rate of the cooling medium is changed using a pitch change of the coil spring. 2. A semiconductor device in which heat generated from each semiconductor element of a multi-chip module in which a plurality of semiconductor elements are mounted on a substrate is transmitted by conduction to a cooling jacket provided oppositely to cool each module at once, Using a cooling jacket provided with nozzles that can individually supply a cooling medium to the heat transfer surface at a position facing each of the semiconductor elements on the substrate,
A cooling control method for a multi-chip module, in which a coil spring is arranged for each nozzle, and the supply amount of the cooling medium is individually controlled using pitch changes of the coil spring. 3. According to claim 1 or 2, heat generated from each semiconductor element of a multi-chip module in which a plurality of semiconductor elements are mounted on the substrate is conducted to the cooling jacket provided facing each other for each module. In a semiconductor device that is cooled all at once, the temperature of each of the semiconductor elements on the substrate in the cooling medium flow path is individually detected, and the pitch of the coil spring is changed using a movable element such as a piezoelectric element based on the detected temperature. Cooling control method for multi-chip modules. 4. According to claim 1 or 2, in a multi-chip module in which a plurality of semiconductor elements are mounted on the substrate, heat generated from each of the semiconductor elements is transferred by conduction to a cooling jacket provided oppositely to the module. using a shape memory alloy or bimetal that can be cooled at once and deformed by sensing the temperature of the semiconductor elements through a heat transfer surface in the cooling jacket at a position facing each of the semiconductor elements mounted on the substrate. , a cooling control method for multichip modules that changes the pitch of coil springs. 5. A cooling control method for a multi-chip module according to claim 1 or 2, in which the coil spring is made of a bidirectional shape memory alloy for cooling the multi-chip module using pitch changes of the coil spring. . 6. The multi-chip module according to claim 1 or 2, wherein the multi-chip module is cooled by utilizing a pitch change of the coil spring, and the multi-chip module is made of a unidirectional shape memory alloy that applies a bias force to the coil spring. A cooling control method for multi-chip modules made of composite materials of high thermal conductivity materials such as copper and aluminum and shape memory alloys. 7. A cooling control method for a multi-chip module according to claim 6, in which a unidirectional shape memory alloy is made of a composite material with a high thermal conductivity material such as copper or aluminum, and high thermal conductivity is added to a coil spring. . 8. A cooling control method for a multi-chip module according to claim 6 or 7, wherein the bias force is applied using a rubber material. 9. A semiconductor device in which heat generated from each semiconductor element of a multi-chip module in which a plurality of semiconductor elements are mounted on a substrate is transmitted by conduction to a cooling jacket provided oppositely to cool each module at once. Using a cooling jacket with nozzles that can individually supply a cooling medium to the heat transfer surface at a position facing each of the semiconductor elements on the substrate,
A cooling control method for a multi-chip module, characterized in that a flow rate control mechanism is provided on the jet outlet side of each nozzle. Claim 10: Claims 1, 2, 3, 4, 5, 6, 7, 8
or 9, the cooling control method for a multi-chip module, wherein a coil spring is disposed at the jet outlet portion of the nozzle so that a jet flow is jetted into the inside of the coil spring.