JPS6132819B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Application of the Invention] The present invention relates to an apparatus for cooling integrated circuits in large-scale electronic computers.

[Background of the invention]

Since large-scale electronic computers are required to have high calculation speed, circuit chips in which semiconductor elements are integrated on a large scale have been developed in recent years. Furthermore, in order to make the electrical wiring connecting the integrated circuit chips as short as possible, methods have been developed for mounting a large number of integrated circuits on a substrate.

Conventionally, when the integrated circuit has a low packaging density and generates a small amount of heat, a standard air cooling method using forced convection cooling has been used. However, as the amount of heat generated increases due to the increase in the packaging density of the integrated circuits, the air velocity must be increased in order to provide sufficient cooling by air cooling methods. However, in current large electronic computers, noise problems occur due to airflow, and integrated circuits with narrow allowable temperature ranges cannot be maintained within a stable temperature range unless some kind of auxiliary means is provided.

Accordingly, regarding a cooling device for an integrated circuit in a large computer, a heat transfer connection device as shown in FIG. 1 is disclosed in US Pat. No. 4,156,458. That is, an integrated circuit chip 1 is provided on a multilayer circuit board 2 (hereinafter referred to as the board), which is composed of a large number of conductive layers and insulating layers, and has an arbitrary number of connection pins 3 on the back surface.
A plurality of them are installed via Face-Down-Bonding connection parts 9 (hereinafter referred to as connection parts). A cooler 8 through which cold water or air flows is mounted on a cap 4 made of a material with good thermal conductivity and mounted on the substrate 2 and covering the integrated circuit chip 1.

A back plate 6 is attached to the inner surface of the cap 4, and one end of a metal foil bundle 5 is glued into a groove provided in the back plate 6, and the other end of the metal foil bundle 5 is attached to the integrated circuit chip 1. It touches the back at a 45° angle. The integrated circuit chip 1 is therefore cooled via the heat flow path formed by the cooler 8, the cap 4, the back plate 6 and the metal foil bundle 5.

However, in the structure described above, the metal foil bundle 5
Pressure is constantly applied to the connection part 9 due to the spring action. Since the integrated circuit chip 1 generates heat as it is energized, the connections 9 are normally subject to repeated thermal stress. When a load higher than a certain pressure is applied to the connection part 9, the connection part 9
becomes fatigued and breaks. If the load due to the spring action of the metal foil bundle 5 is reduced in order to prevent this, the contact condition between the metal foil bundle 5 and the integrated circuit chip 1 will deteriorate and the contact thermal resistance will increase. As described above, there is a drawback that improvement in cooling performance and improvement in thermal fatigue strength of electrical connections are mutually contradictory.

In addition, a cooling device as shown in Fig. 2 was developed in JP-A-52
It is described in the -53547 publication. A number of cylinders 10 are opened in the cap 4, and a piston 11 for conducting heat from the integrated circuit chip 1 and a spring 12 for applying a pressing force to the piston 11 are inserted into the cylinders 10. A space surrounded by the substrate 2 and the cap 4 is filled with highly thermally conductive helium gas. Heat generated from the integrated circuit chip 1 is transferred to the piston 11 through a helium gas layer interposed at the contact portion between the piston 11 and the integrated circuit chip 1. Further, it is transmitted from the piston 11 to the helium gas layer interposed in the gap 20 between the piston 11 and the cylinder 10, and is guided to the cap 4. In this case, there are limits to the improvement in cooling performance due to the following points.

The thermal conductivity of helium gas is one of the highest among gases, but it is much lower than that of metals. Therefore, in order to keep the thermal resistance of the helium gas layer low and increase the cooling effect of the integrated circuit chip 1, it is necessary to
It is necessary to make the gap 20 between the piston 1 and the cylinder 10 small and to make the piston 11 long. However, for this reason, the piston 11 can hardly tilt within the cylinder 10. The integrated circuit chip 1 is bonded to the substrate 2 through the connections 9.
Usually, the piston 11 is not mounted parallel to the plane of the board 2, but is mounted on the board 2 at a certain angle.
It becomes difficult to follow this slope, and the integrated circuit chip 2
A gap is created between the contact surface of the surface and the end surface of the piston 11. As a result, the piston 11 and cylinder 10
Even if the thermal resistance of the helium gas between them is reduced, the contact thermal resistance between the piston 11 and the integrated circuit chip 2 becomes large, and there is a limit to how much the overall thermal resistance can be reduced.

Further, the earlier application, Japanese Patent Laid-Open No. 56-110249, describes a cooling structure as shown in FIG. Separate thin rectangular heat conductive plates 14 are inserted into a number of parallel grooves 13 provided in the cap 4 facing the integrated circuit chip 1, and the multiple heat conductive plates 14 are inserted by springs 15. It is pressed against the back side of the integrated circuit chip 1. The cooling structure in Figure 3 is
Compared to the cooling structure shown in FIG. 2, the heat exchange area between the heat conductive plate 14 and the side wall of the parallel groove 13 can be easily increased.
Further, the contact state between the heat conductive plates 14 and the integrated circuit chip 1 has been improved to surface contact with the thickness end faces of each heat conductive plate 14. However, even in the case of FIG. 3, there is a limit to the improvement in cooling performance.

Since a large number of heat conductive plates 14 are each separated and independently inserted into the parallel grooves 13, there is almost no mutual heat exchange between the heat conductive plates 14. Since the integrated circuit chip 1 is composed of a large number of electric circuits, it is generally extremely rare for it to generate heat uniformly. The heat distribution within the integrated circuit chip 1 varies over time. Therefore, when heat is generated at the edge of the integrated circuit chip 1, only the heat conductive plate 14 near the heat generating part can remove the heat, and the heat can be removed from the far thin integrated circuit chip from the far away heat conductive plate. Only the heat transmitted through 1 can be carried away. That is, even if a large number of heat conductive plates 14 are placed on the integrated circuit chip 1, almost no heat transfer occurs between the heat conductive plates 14, so that the heat transfer efficiency of each heat conductive plate 14 decreases. In addition, the heat conductive plate 14
The footprint of the integrated circuit chip 1 is limited by the width of the integrated circuit chip 1. Therefore, there is a limit to the improvement in cooling performance.

[Purpose of the invention]

In view of the above, the present invention provides an integrated circuit for effectively cooling an integrated circuit without applying an unnecessarily large load to the connection parts of the integrated circuit, and without being affected by thermal expansion, vibration, or mounting accuracy of the integrated circuit. The purpose is to provide a cooling device.

[Summary of the invention]

In the present invention, a pair of heat conductors each having a plurality of fins is attached to an integrated circuit and a cap covering the integrated circuit, and each fin of the pair of heat conductors is arranged so as to engage with each other with a small gap. It is characterized by this.

[Embodiment of the Invention] An embodiment of the present invention will be described below with reference to the drawings.

In FIGS. 4 and 5, reference numerals 16 and 17 refer to bases 16a and 17a made of a material with good thermal conductivity such as copper or aluminum, and bases 16a and 17a made of a material with good thermal conductivity such as copper or aluminum, and bases 16a and 17a that are integrally molded or bonded to the bases 16a and 17a, respectively. Any number of fins 16 of material
It is a heat conductor formed in the shape of a horsetail. The bases 16a, 17a are fixed to the surface of the integrated circuit chip 1 and the inner surface of the cap 4 via an adhesive or a low melting point metal such as a solder material 12. In addition, as a mounting method, at least one of the bases 16a and 17a may be attached to the inner surface of the integrated circuit chip 1 or the cap 4 instead of being fixed.
The contact may be made using a spring force without applying more load than necessary.

The fins 16b and 17b are combined so as to face each other with a minute gap 19 maintained therebetween. Further, in the space inside the cap 4 and the minute gap 19, a gas having good thermal conductivity such as helium gas,
Filled with hydrogen gas. or minute gap 19
Only the inside may be filled with a liquid such as thermally conductive grease. The rest of the structure is the same as the conventional example, so a description thereof will be omitted.

Since this embodiment is configured as described above, the heat generated in the integrated circuit chip 1 is transmitted from the back side of the integrated circuit chip 1 to the cooler 8 via the pair of thermal conductors 16 and 17 and the cap 4. is cooled. In addition, since the pair of thermal conductors 16 and 17 are installed with a small gap 19 maintained, the chip 1 is only subjected to the weight of one of the thermal conductors 10 or a controlled load from a spring. The connections 9 of the circuit chip 1 are substantially unaffected by thermal expansion and vibrations. Further, the opposing area of the fins 16b and 17b is usually the same as that of the integrated circuit chip 1.
In addition, a gas with good thermal conductivity is provided in the space inside the cap 4 and the small gap 19 between the fins 16b and 17b, or a gas with good thermal conductivity is provided only in the small gap 19. Since each is filled with fluid, a pair of thermal conductors 1
The thermal resistance between 6 and 17 can be significantly reduced. Furthermore, the bases 16a, 17a and the fins 16
b, 17b are integrated, so the base 16
It is also possible to make the area of a, 17a larger than the back surface area of the integrated circuit chip 1, and it is possible to make maximum use of the effect of enlarging the heat transfer area.

In the above embodiment, the fins 1 of the heat conductors 16 and 17
Since the fins 6b and 17b are formed in a thin flat plate shape, when both the fins 16b and 17b are combined, the fins 10b and 11b tend to vibrate from side to side, which reduces the installation accuracy of the heat conductors 10 and 11. There is a fear.

Other embodiments shown in FIGS. 6 and 7 have been made to eliminate the above-mentioned drawbacks, and the fins 16c and 17c in FIG. 6 have a wave shape, and the fins 10d and 11d in FIG. 7 have a bent shape. In Fig. 8, Finn 10
e and 11e are arranged concentrically with the fins 10 in FIG.
f and 11f are each formed in a spiral shape.

Next, an experiment conducted on the embodiment shown in FIG. 4 will be described.

Base 16a, 1 made of copper plate, 1 mm thick and 5 mm square
Copper fins 16b and 17b with a thickness of 0.2 mm, a length of 10 mm, and a width of 5 mm are attached on the top of the heat conductor 7a with a pitch of 0.8 mm to form a pair of thermal conductors 16 and 17, respectively. They were installed in combination so as to face each other with a minute gap 19 of 0.2 mm maintained across the length. Such a thermal conductor 1
6, 17 to integrated circuit chip 1 via adhesive 18.
and cap 4, respectively.

Bases 16a, 17 of the thermal conductors 16, 17
The temperature at the center of a and the amount of heat generated by the integrated circuit chip 1 are measured, and the thermal resistance R is calculated by dividing the temperature difference between the two bases 16a and 17a by the amount of heat generated by the integrated circuit chip 1.
The experimental results are organized and illustrated using (°C/W) as shown in Fig. 10. Curve A in the figure shows the result when the cap 4 is filled with air, and curve B shows the result when the air in the cap 4 is exhausted and helium gas is filled instead. From this figure, it is clear that the cooling effect increases when helium gas, which has better thermal conductivity than air, is sealed.

Next, an embodiment of the method for manufacturing a heat conductive connection device according to the present invention will be described. First, the heat conductor 1
The fins 16b and 17b of 6 and 17 are arranged in a minute gap 19.
The base 16a of one of the thermal conductors 16 is fixed onto the back surface of the integrated circuit chip 1 via a coating layer 18.
Both heat conductors 16, 17 and the integrated circuit chip 1 are then inverted together, allowing the heat conductor 17 to fall freely onto the inner surface of the cap 4. Then, the solder layer 18 previously coated on the base 17a of the heat conductor 17 and the inner surface of the cap 4 is melted and bonded to each other. Thereafter, the space inside the cap 4 and the minute gap 19 between the fins 16b and 17b are filled with a fluid having good thermal conductivity, such as helium gas or hydrogen gas.

〔Effect of the invention〕

According to the present invention described above, thermal conductivity is achieved to effectively cool an integrated circuit chip without applying an undue load to the connection portion of the integrated circuit chip, and without being affected by the mounting accuracy of the integrated circuit chip. can provide a good heat transfer connection device. It goes without saying that the present invention is not limited to the above-described embodiments, but can be similarly applied to various types of integrated circuit heating elements such as integrated circuit packages.

[Brief explanation of the drawing]

1 to 3 are side sectional views of conventional heat transfer connecting devices, FIG. 4 is a side sectional view showing an embodiment of the heat transfer connecting device of the present invention, and FIG. 5 is a side sectional view of a conventional heat transfer connecting device. FIGS. 6 to 9 are perspective views of the conductor, and FIGS.
The figure is a diagram showing the relationship between the amount of heat generated and the thermal resistance of the embodiment according to the present invention. 1...Integrated circuit chip, 4...Cap, 1
6, 17... Heat conductor, 16a, 17a... Fin, 18... Solder layer, 19... Minute gap.

Claims (1)

[Scope of Claims] 1. An integrated circuit comprising a substrate, one or more integrated circuits bonded on the substrate, and a cap covering the integrated circuit, and transmitting heat generated in the integrated circuit to the cap. A cooling device for an integrated circuit comprising: a fin integrated with a base mounted on the integrated circuit, and a fin disposed to engage with the fin with a minute gap mounted on the inner wall surface of the cap. . 2. A cooling device for an integrated circuit according to claim 1, characterized in that a minute gap formed between a pair of fins is filled with a fluid having good heat conduction.