JPH0715960B2 - Semiconductor chip cooling device - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a semiconductor chip cooling device, and more particularly to a semiconductor suitable for cooling heat generated by a large number of semiconductor chips arranged on a circuit board. The present invention relates to a chip cooling device.

[Prior Art] A conventional semiconductor chip cooling device is disclosed in
There is one described in JP-A-60-126853. This prior art will be described with reference to FIGS. 9 to 12.

FIG. 9 is a partial cross-sectional perspective view of the conventional semiconductor chip cooling device described in the above publication, and FIG. 10 is a cross-sectional view of a main part of the heat transfer part of FIG. 9, FIG. FIG. 12 is an enlarged cross-sectional view of the fin fitting portion.

As shown in FIGS. 9 and 10, the semiconductor chip cooling device described in the above publication has a fin 8'formed on the inner surface of the housing 5'and a heat source having a bottom area larger than the heat transfer area of the semiconductor chip 3 '. The fins 7'formed on the base of the transfer element 4'are fitted together with a minute gap kept therebetween, and the base of the heat transfer element 4'is pressed against the semiconductor chip 3'by the spring 21 ', so that the semiconductor chip 3'. It has a structure that makes surface contact with the back surface of.

[Problems to be Solved by the Invention] In the above conventional technology, as shown in FIGS. 9 and 10, a semiconductor chip 3'joined to a circuit board (hereinafter simply referred to as a board) 1'by solder balls 2 '. The generated heat is transmitted from the back surface of the semiconductor chip 3'to the base of the heat transfer element 4 ', which is in contact with the back surface of the semiconductor chip 3', the fins 7'formed on the base of the heat transfer element 4 ', and It is transmitted to the fins 8'on the inner surface of the housing 5'which are fitted with the fins 7 '.

In such a heat transfer path, the heat transfer between the fins 7'on the base of the heat transfer element 4'and the fins 8'on the inner surface of the housing 5'determines the cooling performance.

However, in the above prior art, the fins 7'of the heat transfer element 4 '
The fins 8'of the housing 5'are fitted with each other with a minute gap therebetween. As shown in FIG.
Heat transfer element 4'fitted in groove 11 'of housing 5'
When the clearances δ'on both sides of the fin are equal, as shown in FIG. 12, one clearance δ'n is narrow and the other clearance δ'n is small.
In some cases, w becomes wider, and the state of the gap during fin fitting is not constant. The heat transfer coefficient of the gap is the highest in the contact state without the gap, decreases rapidly with the expansion of the gap, and becomes substantially constant when the gap is separated by a certain amount or more.

Therefore, in the conventional technology in which the gaps between the fins are not constant, there is a problem that the heat transfer performance between the fins varies.

The present invention has been made in order to solve the above-mentioned problems of the prior art. In a transmission structure in which fins are fitted together, the transmission surfaces of the fins fitted together are inevitably in contact with each other due to the fitting of the fins, and a stable fin spacing is achieved. It is an object of the present invention to provide a cooling device for a semiconductor chip capable of performing the heat transfer of the above.

[Means for Solving the Problems] In order to achieve the above object, the structure of the semiconductor chip cooling device according to the present invention transfers the heat generated by the semiconductor chip mounted on the circuit board to the housing for cooling. For this purpose, a plurality of fins formed on the housing and a plurality of fins formed on the heat transfer element are provided, each of which has a heat transfer element that is in contact with the back surface of the semiconductor chip and the other is engaged with the housing side through a minute gap. In a semiconductor chip cooling device adapted to be fitted to each other, a plurality of fins formed in the housing and a plurality of fins formed in the heat transfer element are used as a reference with respect to a surface of the heat transfer element which is in contact with the back surface of the semiconductor chip. It is formed to have a predetermined angle with respect to the perpendicular.

The basic structure of the present invention is shown in FIG.

FIG. 1 is a cross-sectional view of essential parts of a semiconductor chip cooling device showing the basic configuration of the present invention.

As shown in FIG. 1, the above purpose is to provide a heat transfer element 4 that contacts the back surface of the semiconductor chip 3 mounted on the substrate 1 by the solder balls 2 and conducts the heat generated from the semiconductor chip 3 to the housing 5. The fins 7 formed and the fins 8 formed on the housing 5 are achieved by forming an angle θ with respect to the perpendicular 12 of the reference plane 9 of the heat transfer element 4 that contacts the back surface of the semiconductor chip 3.

[Operation] The operation of the above technical means will be described with reference to FIGS. 1 to 6.

Here, FIG. 2 is a sectional view of an essential part showing a state before fitting of the fin portion in the apparatus of FIG. 1, and FIG. 3 is a fin angle θ, a gap δ, an insertion length at the time of fitting the fin portion. FIG. 4, FIG. 5 and FIG. 5 are cross-sectional views of the main part showing the spring insertion portion in the device of FIG. 1, and FIG.
It is a local cross section which shows the relationship between a fin angle and a friction angle.

As shown in FIG. 2, a fin 7 having an angle θ (hereinafter referred to as a fin angle) with respect to a perpendicular 12 to the reference plane 9 of the heat transfer element 4 whose reference plane 9 is a surface in contact with the back surface of the semiconductor chip 3. And a case where a fin 8 having the same fin angle θ as the fin angle of the fin 7 of the heat transfer element 4 is fitted to a perpendicular 13 to the reference plane 10 of the housing 5 formed parallel to the back surface of the semiconductor chip 3. Think

The state shown in FIG. 2 is a state before fin fitting, and the heat transfer surface 8b of the fin 8 of the housing 5 and the heat transfer element 4 are set.
It is assumed that the heat transfer surface 7b of the fin 7 is partially in contact with the heat transfer surface 7b. In such a state, as shown in FIG. 5, a spring insertion portion 20 provided on the heat transfer element 4 and a spring insertion portion formed at a predetermined position of the housing 5 into which the heat transfer element 4 is fitted.
A spring 22 that repels when the heat transfer element 4 is inserted into the housing 5 is mounted between the heat transfer element 21 and the heat transfer element 21. Further, in this state, the heat transfer surface 8a of the fin 8 of the housing 5 and the heat transfer element 4 are
The gap δ between the fin 7 and the heat transfer surface 7a is set in advance. As shown in FIG. 3, the gap δ is defined by the insertion length 1 of the heat transfer element 4 into the housing 5 in the direction perpendicular to the reference plane 10 and the reference plane of the housing 5 and the heat transfer element 4.
It depends on the fin angle θ of the fin 8 and the fin 7 with respect to 10, 9.

It is desirable that the contact of the heat transfer surface occurs before the insertion of the predetermined insertion length, and the setting of the gap δ is also set in consideration of this point.

Under such preparation, the heat transfer element 4 is inserted in a direction perpendicular to the reference plane 10 of the housing 5. A state in which the predetermined insertion length is inserted is shown in FIG.

When the gap δ is set to be small, both the heat transfer surfaces 7a, 8a of the fins 7, 8 come into contact with each other before the predetermined insertion length 1 is inserted, and the heat transfer surfaces 7a, 8a slide by the subsequent insertion. . When the heat transfer element 4 is inserted into the housing 5 to the set position, as shown in FIG. 4, the spring 22 mounted between the heat transfer element 4 and the housing 5 has both heat transfer surfaces 7a and 8a. A displacement equivalent to the displacement in the reference plane 9 direction of the heat transfer element 4, that is, the lateral direction, is applied in accordance with the insertion length 1 after the contact. When a compression coil spring is used as the spring 22, a reaction force generated by applying a lateral displacement to the spring 22 tends to bring the two joint surfaces into close contact with each other, further increasing the reliability of the close contact.

Next, the fin angle θ of the fins 7 and 8 with respect to the reference plane of the housing 5 and the heat transfer element 4 will be described.

The fin angle θ is limited by the coefficient of friction between the heat transfer surface 7a of the fin 7 and the heat transfer surface 8a of the fin 8.

Metals and ceramics are considered as materials of the housing 5 and the heat transfer element 4.

The maximum coefficient of dry friction between metals, between ceramics, between metals and ceramics is about 1.5, and the friction angle λ (see Fig. 6)
When converted to, it becomes approximately 56 °. The relationship between the friction angle λ and the fin angle θ is as shown in FIG. 6 when the load direction 6 of the heat transfer surface 7a with respect to the heat transfer surface 8a is determined, and when the friction angle λ is 60 °, the fin angle θ is 30. It becomes ゜. That is, when the fin angle θ with respect to the reference plane is 30 ° or less, the post-contact slippage occurs between the heat transfer surface 7a of the heat transfer element 4 and the heat transfer surface 8a of the housing 5.

As described above, the fins 7 and 8 having a slight angle θ with respect to the normal line of the reference plane of the heat transfer element 4 and the housing 5 are fitted to each other, and the fins are arranged in the direction perpendicular to the reference plane of the mating fin. By inserting the fins, the heat transfer surfaces of the fins always come into contact with each other, and stable and good heat transfer can be obtained.

[Embodiment] An embodiment of the present invention will be described below with reference to FIGS. 7 and 8.

FIG. 7 is a vertical sectional view showing a semiconductor chip cooling device according to an embodiment of the present invention before fin fitting, and FIG.
FIG. 8 is a vertical cross-sectional view showing a fin fitting state of the device of FIG. 7. In both drawings, the same parts as those in FIG. 1 showing the basic structure are designated by the same reference numerals.

As shown in FIG. 7, a semiconductor chip 3 joined by solder balls 2 is mounted on a substrate 1, and pins 14 are provided on the lower surface of the substrate 1 and held by a holding plate 15.

Heat transfer element 4 arranged in contact with the back surface of the semiconductor chip 3.
The plurality of fins 7 are formed so as to maintain the fin angle θ.

On the other hand, the housing 5 facing this is formed with a plurality of fins 8 and grooves 11 on the inner surface so as to maintain the fin angle θ, and can be fitted to the fins 7 and 8.

A spring is mounted between the heat transfer element 4 and the housing 5 in a direction in which they repel each other. Since the structure is the same as that shown in FIGS. 4 and 5, it is omitted here.

In this embodiment, the fin angle θ of the fin 7 with respect to the perpendicular 12 of the reference plane 9 where the heat transfer element 4 contacts the semiconductor chip 3 is
The fin width was 10 °, and the dimensional difference between the fin width m and the groove width n, that is, the fitting gap δ was 0.5 mm. Similarly, the fin width m of the fin 8 and the groove width n of the groove 11 formed in the housing 5 are the same as those of the heat transfer element 4, and the angle θ of the reference plane 10 of the housing 5 with respect to the perpendicular 13 is 10 °. Further, the insertion length l of the heat transfer element into the housing 5 is set to 7 mm.

As is apparent from FIG. 3, when the fin angle θ is 10 ° and the heat transfer surface gap δ is 0.5 mm, the insertion length l is about 3 mm and both heat transfer surfaces are in contact with each other.

FIG. 8 shows a state in which the heat transfer element 4 is further inserted into the housing 5 by about 4 mm from the state where both heat transfer surfaces are in contact with each other. In this state, both heat transfer surfaces of the heat transfer element 4 and the housing 5 were in close contact with each other, and good heat transfer could be obtained.

As described above, according to the present embodiment, the fins 7 and 8 of the heat transfer element 4 and the housing 5 that are fitted to each other have a fin angle, so that the heat transfer surfaces of the fins 7 and 8 are fitted to each other. Therefore, the heat transfer between the fins is improved and stabilized, and the heat generated in the semiconductor chip 3 passes through the heat transfer element 4 and the housing 5,
It is efficiently transmitted to a cooler (not shown) attached to the housing 5.

[Effects of the Invention] As described above, according to the present invention, in the transmission structure in which the fins are fitted together, the transmission surfaces of the fins fitted together are inevitably in contact with each other due to the fitting of the fins, and stable heat transfer between the fins is achieved. It is possible to provide a cooling device for a semiconductor chip that can perform transmission.

[Brief description of drawings]

FIG. 1 is a cross-sectional view of an essential part of a semiconductor chip cooling device showing the basic structure of the present invention, and FIG. 2 is a cross-sectional view of an essential part of the device shown in FIG. Fig. 3 shows the fin angle, clearance, and
Diagrams showing the relationship of insertion length, FIGS. 4 and 5 are cross-sectional views of a main part showing a spring insertion part in the device of FIG. 1, and FIG.
The figure is a local sectional view showing the relationship between the fin angle and the friction angle,
FIG. 7 is a vertical sectional view showing a semiconductor chip cooling device according to an embodiment of the present invention before fin fitting, and FIG.
FIG. 7 is a vertical cross-sectional view showing a fin fitting state of the apparatus of FIG.
FIG. 9 is a partial cross-sectional perspective view of a conventional semiconductor chip cooling device, and FIG. 10 is a longitudinal cross-sectional view of a main part of the heat transfer element of FIG.
11 and 12 are enlarged cross-sectional views of the fin fitting portion. 1 ... Substrate, 3 ... Semiconductor chip, 4 ... Heat transfer element, 5
...... Housing, 7,8 ...... Fin, 7a, 8a ...... Heat transfer surface,
9,10 …… Reference plane, 12,13 …… perpendicular, θ …… Fin angle.

Claims (2)

[Claims] Claim: What is claimed is: 1. In order to transfer heat generated by a semiconductor chip mounted on a circuit board to a housing for cooling, one of the heat contacts the rear surface of the semiconductor chip and the other heat engages with the housing through a minute gap. A cooling device for a semiconductor chip, comprising: a plurality of fins formed in the housing, and a plurality of fins formed in the heat transfer element fitted to each other; The fins formed on the transmitter are
A cooling device for a semiconductor chip, wherein the heat transfer element is formed to have a predetermined angle with respect to a vertical line of the heat transfer element in contact with the back surface of the semiconductor chip. 2. The device according to claim 1, wherein an angle of each fin of the housing and the heat transfer element is 30 ° or less with respect to a vertical line of the surface of the heat transfer element in contact with the back surface of the semiconductor chip. A semiconductor chip cooling device characterized by the above.