JPH10209351A - Heat sink - Google Patents

Abstract

PROBLEM TO BE SOLVED: To raise the cooling efficiency at forced air cooling, by retracing the windward end faces of inner fins more than these of both side fins. SOLUTION: On a base 1, a plurality of fins 2 erect parallel in equal pitches. The windward end faces 2a of the inner fins 2 slightly retract more than those of both side fins 2 on the same plane but all the fins have identical shapes and lengths, and hence the leeward end faces of them similarly retract. The end faces of the near center fins retract more than the both side fins in the flow of forced cooling air to reduce the air flowing around the outsides of the fins from the front of a heat sink to increase the air flowing along the near center of the heat sink, thereby improving its radiation efficiency.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a heat sink for radiating heat generated by a semiconductor device, and more particularly to a structure of a finned heat sink suitable for forced air cooling.

In recent years, since the degree of integration of semiconductor integrated circuits has been remarkably increased and the heat generation density in a package has been increased, the importance of heat dissipation of the package has increased. It is generally said that every time the temperature of an electronic component drops by 10 ° C., the reliability of the electronic component doubles. Therefore, in many cases, a heat sink is attached to a package, and a device or the like on which the package is mounted is provided with a fan or the like to perform forced air cooling.

[0003]

2. Description of the Related Art There are various types of heat sinks for semiconductor packages.
A finned heat sink of a type in which a plurality of fins stand upright on one surface of a base is often used because the manufacturing cost is low. Hereinafter, the conventional example will be described with reference to FIG. This heat sink is the base 1
A plurality of fins 2 having the same shape are erected in parallel at the same pitch, and all the end faces 2 a of the fins 2 are
Are on the same plane as the end face of. Base 1 and multiple fins 2
Is integrally formed of a metal having high thermal conductivity such as aluminum.

[0004]

However, as a result of performing a fluid analysis of the forced air cooling airflow with respect to such a conventional heatsink, the airflow heading toward the front of the heatsink does not pass through the space between the fins. It was found that the flow velocity was high near the outer surface, and slowed down near the center of the heat sink.
Since the semiconductor chip, which is a heat source, is generally located at the center of the package, a relatively slow flow rate at the center means that the cooling efficiency is low. The conventional heat sink has such a problem.

[0005] It is an object of the present invention to solve such a problem and to provide a heat sink capable of increasing the cooling efficiency during forced air cooling.

[0006]

To achieve this object, according to the present invention, there is provided a heat sink having a plurality of fins which stand upright on one surface of a base in parallel with each other. The position of the end face is a heat sink in which the fin located closer to the center is retracted from the fins located on both sides.

According to a second aspect of the present invention, at least the outermost fin of the fins is a heat sink having an inwardly inclined end face facing windward during forced air cooling. According to a third aspect of the present invention, the fin is a heat sink having unevenness on a side surface of which the surface area of the side surface increases.

That is, by moving the end face of the fin closer to the center backward from the end faces on both sides in the traveling direction of the forced air cooling airflow, the airflow flowing from the front face of the heat sink to the outer face of the fin is reduced, and the fin passes the center part of the heat sink. The airflow increases and the flow velocity increases, and as a result, the heat dissipation (cooling efficiency) of the heat sink improves. Further, by inwardly tilting the end surfaces of the fins, the airflow flowing from the front surface of the heat sink to the outer surfaces of the fins is further reduced. Furthermore, since the surface area increases if grooves and protrusions are provided on the side surfaces of the fins, the heat dissipation of the heat sink is further improved by a synergistic effect with an increase in the airflow passing near the center of the heat sink.

[0009]

DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described with reference to FIGS. FIG. 1 is a perspective view showing a first embodiment of the present invention. A plurality of fins 2 stand upright on the base 1 at a constant pitch in parallel. The position of one end face 2a of the fin 2 (on the windward side with respect to the forced air cooling airflow) is
The fins 2 on both sides are on the same plane as the end face of the base 1, but the fins 2 on the inner side are slightly receded toward the center. Since all the fins 2 have the same shape and are therefore equal in length, the other end face (on the leeward side) is receded similarly to the end face 2a on the windward side.

FIG. 2 is a perspective view showing a second embodiment of the present invention. In this example, on the leeward side, the fins 2 other than on both sides are retreated as in FIG. 1, but on the leeward side, as in the conventional example, there are no retreated fins 2 and are flush with the end face of the base 1. It is in. Therefore, the length of the fins 2 on both sides is slightly shorter than that of the fins 2 on both sides.

Next, the results of trial calculations of the effects of these examples using thermal fluid analysis software 'FLOTHERM' (manufactured by FLOMERIC, UK) are shown. The analysis conditions were as follows: ambient temperature: 20 ° C., flow rate: 1 m / s, material: aluminum.
The shape is shown in FIG. 3A and 3B are explanatory diagrams of a model used for a trial calculation of the effect of the present invention. FIG. 3A is a top view and FIG. 3B is a front view. In the figure, x = 44 mm, y = 42 mm, z = 4 m
m, s = 4 mm, t = 4 mm, and u = 20 mm are common to each model, and m, n, p, and q differ depending on the model. As a result of the analysis, the thermal resistance value of each model was as shown in the following table.

[0012]

[Table 1]

Model Nos. 1 and 2 correspond to the first embodiment, models Nos. 3 and 4 correspond to the second embodiment, and model No. 5 corresponds to the conventional example. The thermal resistance value of each of the models No. 1 to 4 is smaller than that of the model No. 5. Model No.3
And No. 4 are slightly less effective than the models No. 1 and No. 2 because the side surface area is slightly reduced, but this type has the advantage that the external dimensions are not increased.

FIG. 4 is a top view showing a third embodiment of the present invention. In this example, the windward end face 3a of the fin 3 standing upright in parallel on the base 1 is slightly inwardly inclined, at least for the fins 3 on both sides, so that the outer edge becomes slightly acute. I have. This reduces the airflow flowing around the outer surface of the heat sink. still,
In FIG. 4, the end face 2a in the second embodiment is deformed like the end face 3a, but the end face 2a in the first embodiment may be deformed like the end face 3a.

FIG. 5 is a perspective view showing a fourth embodiment of the present invention. In this example, a groove 4c is provided on the side surface 4b of the fin 4 that stands upright on the base 1 in parallel. This increases the surface area of the side surface 4b. Instead of the groove 4c, for example, a hemispherical small protrusion may be provided in a lattice shape to increase the surface area. Although FIG. 4 shows a modification of the side surface in the second embodiment, the side surface in the first and third embodiments may be modified.

[0016]

As described above, according to the present invention,
A heat sink capable of increasing the cooling efficiency during forced air cooling can be provided.

[Brief description of the drawings]

FIG. 1 is a perspective view showing a first embodiment of the present invention.

FIG. 2 is a perspective view showing a second embodiment of the present invention.

FIG. 3 is an explanatory diagram of a model used for a trial calculation of an effect of the present invention.

FIG. 4 is a top view showing a third embodiment of the present invention.

FIG. 5 is a perspective view showing a fourth embodiment of the present invention.

FIG. 6 is a perspective view showing a conventional example.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Base 2,3,4 Fin 2a, 3a End face 4b Side face 4c Groove

Claims (3)

[Claims] 1. A heat sink provided with a plurality of fins standing upright on one surface of a base in parallel, wherein the fins located on the windward side during forced air cooling have fins located closer to the center on both sides. A heat sink characterized by being receded from the fin. 2. The heat sink according to claim 1, wherein at least an outermost fin of the fins has an inwardly inclined end face facing windward during forced air cooling. 3. The heat sink according to claim 1, wherein the fin has an unevenness on a side surface so that a surface area of the side surface increases.