JPH11145349A - Heat sink for forced cooling - Google Patents

Abstract

PROBLEM TO BE SOLVED: To increase the heat transfer of a collision surface by reducing the height of a part of fins standing almost in parallel on a metallic plate, and constituting a structure in which an eddy is generated in a fin widthwise direction, in the vicinity of the metallic plate which is in contact with a heat generating member. SOLUTION: In a heat sink on a heat generating member 2, a plurality of fins composed of aluminum having high thermal conductivity which are different in height are laminated in a plurality of layers at specified intervals, and high fins 4 and low fins 10 are formed alternately. A blowing means has a structure which sends cooling air blown by a fan or the like to a high heat generating member 2 via a nozzle 3, in the direction almost perpendicular to a board 1. Cooling air 21 at this time flows in from the upper part of the fins via the nozzle 3 and collides against a fin base 5 in a perpendicular direction, along the fins 4. Between the fins 4, the cooling air 21 flows in the direction of a flow 22. In the vicinity of a fin base 5, the flow 23 is disturbed by the fins 10 and flows out. As a result, the cooling air 21 flows in eddy in the vicinity of the fin base 5, so that heat transfer near the fin roots is increased.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a jet cooling structure for an electronic device having a heat generating member such as an electronic device, which is disposed on one or more substrates stacked in the housing of the electronic device. The present invention relates to a heat sink for forced cooling that efficiently cools a plurality of heat generating members mounted thereon.

[0002]

2. Description of the Related Art In recent years, in electronic devices such as computers,
There is a strong demand for improvements in processing capacity, miniaturization, cost reduction, and the like, and the amount of heat generated by electronic elements mounted in electronic devices and the number of mounted electronic elements are increasing. On the other hand, as the size of the housing has been reduced, the heat generation density inside the housing has been increasing. In addition, in order to reduce the signal propagation delay time, a mounting form of a multi-chip module in which a large number of chips are mounted on a substrate such as a ceramic and cooled collectively is used for the electronic element for arithmetic processing. The multi-chip module has a very large heat value and heat generation density, and it is very difficult to cool them.

It is necessary to keep the heat-generating members in the housing at or below the rated temperature in order to prevent damage or malfunction of the elements due to excessive temperature rise. Therefore, for cooling electronic equipment,
There are many structures using a heat sink that increases the heat radiation area and improves the cooling performance. In particular, in an electronic element that generates high heat, various heat sinks for forced cooling are installed on the surface of the member according to the heat generation density and the specified temperature.

The heat sink is made of a material having high thermal conductivity, for example, aluminum or copper. Generally, a flat fin type heat sink in which a plurality of parallel flat plates are arranged on a single metal flat plate at an interval of about 1 to 3 mm or a metal is used. A pin fin-type heat sink having a large number of prisms or cylinders arranged on a flat plate is often used. Flat fin heat sinks have the advantage of being relatively easy and inexpensive to manufacture and of having a small pressure loss for a large heat dissipation area.

In the forced air cooling structure, cooling air is sent to each heat generating member mainly using a fan or a blower. There are two types of cooling systems: a parallel flow type cooling structure that blows the substrate from a substantially horizontal direction and a jet flow type cooling structure that blows the substrate from a substantially vertical direction. In this case, a jet-type cooling structure having a large exchange heat quantity is effective. The jet cooling structure has the advantages that the heat transfer on the collision surface is much higher than the former, and that each heat-generating member can be individually cooled, so that it can be cooled regardless of the position of the heat-generating member.

FIG. 5 shows the experimental results of the temperature distribution of the fins and the air between the fins during jet cooling. The heat sink shown has a width W, a height W / 2 and a thickness 1 mm, and a nozzle width W / 3,
This is a case where the inlet flow velocity is 12 m / s. As for the temperature distribution on the fin surface, the temperature is low near the jet port from the nozzle,
The temperature is high near the root of the fin. Further, it can be seen that the air temperature between the fins is high near the stagnation point and near the root of the fin, and most of the air flows out of the air outlet portion (right side of the fin) in a region that is less than half of the fin.

Further, in a portion where the main flow does not flow between the fins (upper right of the fins), an increase in the temperature of the air due to the circulating flow is confirmed. As can be seen from these temperature distributions, in the impinging jet, heat transfer is very large near the root of the fin (near the collision surface), and there is a region with a small cooling effect above the fin (upper right in the figure). Can improve the heat sink performance.

[0008] Jet cooling is effective for a high heat generating member such as a multi-chip module having a high heat generation density. However, a conventional heat sink is installed on the high heat generating member, and the cooling inflow amount is simply increased according to the cooling capacity. In this case, only the pressure loss increases beyond the cooling performance, and it cannot be said to be an effective cooling means. In this case, there are also new problems due to the downsizing of the housing, such as an increase in the size of the blower and an increase in wind noise at the fins.

Even when a jet cooling structure having a large exchange heat quantity is used, a low-pressure-drop and high-performance heat sink is required for downsizing. However, in the conventional jet cooling, the dimensions of the pin fins and the plate fins are optimized and used in many cases. A conventional jet cooling structure example shown in FIG. 6 (Japanese Patent Laid-Open Publication No. Hei 6-12087) optimizes the jet inlet side to improve the cooling performance.

[0010]

Many conventional jet cooling structures use a flat fin or a pin fin to cool a multi-chip module or the like having a high heat generation density. The performance was not considered. As a means of improving the heat radiation performance, there are cases where the flow rate can be increased by increasing the flow rate. However, there is a problem that the size of the air blower (blower, fan) occupying the housing becomes large for electronic devices that are becoming smaller and lighter. For this reason, a cooling structure (high-performance heat sink) that can sufficiently cool the high heat generating member with a low air flow (low pressure loss) is required.

It is an object of the present invention to provide a heat sink structure capable of efficiently cooling a heat generating member having a high heat generation density under low pressure loss.

[0012]

Means for attaining the object of the present invention, which is the object of the present invention, is to improve the heat transfer at the collision surface and to effectively utilize the fin surface, based on the results shown in FIG. For this reason, in the present invention, the height of a part of the fins set substantially parallel to the metal flat plate is reduced, and a vortex is formed in the fin width direction in the vicinity of the metal flat plate in contact with the heat generating member. Increased surface heat transfer.

Alternatively, the fins are made about half the maximum fin height to allow air to flow through the entire fins, thereby increasing the heat exchange amount of the entire fins.

[0014]

FIG. 1 is a perspective sectional view showing a first embodiment of a heat sink for forced cooling according to the present invention. The inside of the housing of the electronic device has a mounting configuration in which a plurality of substrates are stacked, and various components are mounted on the substrate 1. Among them, a member having a large calorific value, for example, a multi-chip module or the like, often uses jet cooling having a large heat exchange amount. A heat sink is provided on the heat generating member 2 via, for example, a heat conductive adhesive or a heat conductive grease.
A nozzle 3 for ejecting cooling air is provided on the upper part.

The heat sink on the heat generating member 2 is made of a material having high thermal conductivity, for example, aluminum or copper. A plurality of parallel flat plates having different heights are laminated on a metal flat plate at intervals of about 0.5 to 3 mm. It is a thing. In this embodiment, the high fins 4 and the low fins 10 are alternately manufactured, but the arrangement may be different. This structure
Since the fins are set up in parallel with the plane direction, the fins are as easy to make as the conventional flat plate fins.

The air blowing means of the present embodiment transmits cooling air blown by a fan or a blower to a high heat generating member (for example, a multi-chip module) 2 through a nozzle 3 and a substrate 1.
This is a structure that blows air in a substantially vertical direction. Explaining the air flow at this time, the cooling air 21 flows from the upper part of the fin through the nozzle 3 and collides with the fin base 5 in the vertical direction along the fin 4. In the direction of the flow 22 between the fins 4, the fins 10 near the fin base 5
This disturbs the flow 23 and flows out. As can be seen from the above-described experimental results in FIG. 5, the heat flows near the fin base 5 at a higher flow velocity than in the upper part of the fin 4, so that the heat transfer near the root of the fin increases.

FIGS. 2A to 2D show another embodiment. This is a modification of the shape of the low fin in FIG. FIGS. 2A and 2B show the case where the lower fins 11 and 12 between the higher fins 4 are inclined with respect to the fin base 5. 2 (c) and (d)
The cross section of the fins 13 and 14 is changed to a rectangular shape. When jet cooling is performed on them in the same manner as in the embodiment of FIG. 1, turbulence is likely to occur near the fin base 5, and the cooling performance of the heat sink can be improved.

FIG. 3 is a perspective view of a third embodiment of the present invention. A heat generating member 2 is mounted on a substrate 1, a heat sink of the present invention is installed on the heat generating member, and a cooling structure similar to that of FIG. Has become. The fins 4 of the height H of this embodiment are alternately provided with the fins of the height x. The fin heights have a relation of x <0.5H, and the fin 15 provides a flow path resistance between the inflow portion of the cooling air 21 and the surface of the fin base 5 to promote heat transfer characteristics at the upper end of the fin outlet side. It is to let.

In this embodiment, the cooling air 21 induces a flow 26 near the fin base as well as a flow 26 above the fins. For this reason, the stagnation portion of the air between the fins, which is seen in the experimental results of FIG. 5, is reduced, and the fin portions can also exchange heat efficiently.

FIG. 4 is a perspective view of a fourth embodiment of the present invention. A heat generating member 2 is mounted on a substrate 1, a heat sink of the present invention is installed on the heat generating member, and cooling air 21 flows from a nozzle 3 into a fin base 5 from a direction substantially perpendicular to FIG. 1 and FIG. It has a jet structure. In the present embodiment, the heights of the fins 16 are changed on the fin base 5 surface, and when the heat generating member 2 has a heat distribution,
They can be adjusted on the fin base surface, such as when the temperature in the center is high.

FIG. 6 shows the results of measuring the static pressure distribution on the fin surface using the heat sink of the present invention (one example) and the conventional flat fin heat sink. The dimensions of the flat fins are fin width W, height W / 2, and nozzle width 0.44 W. In the shape of the heat sink of the present invention, a fin having a height W / 9 is formed in the center between the flat fins. I have. The fin surface static pressure distribution when the same flow rate flows from the nozzle is shown on the right side of the figure.
In the drawing, the positions of the nozzle portion pressure loss P and the circulation area A are shown.

In the heat sink of the present invention, P ₁ / P ₂ =
Around 1.1, the circulation area is A ₁ > A ₂ , the shape of the entire pressure loss is small, and the high static pressure portion in the heat sink extends over the entire fin. Therefore, when the heat sink of the present invention is used in the jet structure, the entire heat generating member is used as a heat radiating surface as compared with the conventional heat sink, so that the target heat generating member can be efficiently cooled.

[0023]

According to the present invention, in an electronic device having a heat generating member such as an electronic element, a plurality of heat generating members mounted on one or a plurality of substrates stacked in an electronic device housing can be efficiently cooled. be able to.

[Brief description of the drawings]

FIG. 1 is a perspective view of a heat sink for forced cooling according to a first embodiment of the present invention.

FIG. 2 is a partial front view of a fin in FIG. 1;

FIG. 3 is a perspective view of a heat sink for forced cooling according to a third embodiment of the present invention.

FIG. 4 is a perspective view of a heat sink for forced cooling according to a fourth embodiment of the present invention.

FIG. 5 is a diagram showing an example of a heat sink temperature distribution of a jet structure.

FIG. 6 is a diagram showing a comparison between static pressure distributions of a conventional example and a heat sink of the present invention.

FIG. 7 is a perspective view of a conventional cooling heat sink.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Substrate, 2 ... Heating member, 3 ... Nozzle, 4 ... Fin, 5
... fin base, 10 ... fin, 21 ... cooling air.

Continued on the front page (72) Inventor Tadakatsu Nakajima 502 Kandachicho, Tsuchiura-shi, Ibaraki Pref. Machinery Research Laboratories, Hitachi, Ltd. Inside

Claims (1)

[Claims] 1. A structure having a plurality of first fins standing substantially in parallel on a metal flat plate in contact with a semiconductor element surface, and blowing a cooling medium in a direction substantially perpendicular to the metal flat plate. A forced fin heat sink having a second fin lower than the height of the first fin between the adjacent first fins.