GB2197983A

GB2197983A - Heat sink

Info

Publication number: GB2197983A
Application number: GB8625926A
Authority: GB
Inventors: Peter Mark Law
Original assignee: Marston Palmer Ltd
Current assignee: Marston Palmer Ltd
Priority date: 1986-10-30
Filing date: 1986-10-30
Publication date: 1988-06-02
Anticipated expiration: 2006-10-30
Also published as: GB2197983B; GB8625926D0

Abstract

A metallic heat sink formed from a sheet of metal, particularly intended for use in cooling electronic devices, in which the edges of the sheet 1 of metal are slit and bent to form a series of fins (2-6), the fins being untwisted but lying in a series of three or more different planes to enhance heat transfer by thermal convection when the heat sink is operating. <IMAGE>

Description

Heat Sink This invention relates to heat sinks and has particular, but not exclusive, reference to heat sinks for use in the cooling of electronic devices.

It is well known that electronic devices produce heat which has to be dissipated to reduce the tendency of the devices to overheat. A conventional method of dissipating heat is to mount the device onto a heat sink which essentially comprises a metallically conducting structure with enhanced surface area which conducts heat into the surrounding air to cool the device. Numerous designs of heat sink have been made available to the public, many of which are based on a sheet of metal which is cut and bent to form a series of fins which enhance heat transfer, particularly by convection.

The need to transfer as much heat as possible into the surrounding air has led to a series of complex designs of heat sinks and in particular it is desirable that the greatest area possible of heat sink be presented to the air to lower the temperature of the electronic device.

In previously proposed heat sinks formed from metal a number of proposals relating to the design of the fins have been suggested. In many cases the fins are bent at right angles to the plane of the base and may be twisted to enhance turbulence of air flowing over the device. Thus in British Patent Specification 1 334 173 there is described a metallic heat sink formed from a sheet of metal in which the fins are simultaneously slit and twisted to produce a heat sink of generally U cross-section with a base attachable to the electronic component and a series of fins to enhance convection.

It has also been proposed to use a series of staggered fins, see for example British Patents Specifications 971 052 and 1 048 923.

In all of these arrangements the area of the fins is the maximum that can be obtained commencing with a rectangular blank as no metal is lost in the cutting operation. However, in the case of twisted fins the root of the fins does not lie at the optimum angle for dissipating heat by convection.

By the present invention there is provided a heat sink having a substantially planar base and a plurality of fins, the fins having been formed by cutting and displacement out of the plane of the base to lie in planes substantially at angles to the plane of the base, characterised in that the fins are formed by the action of turning up the metal between the cut slits without twisting and in that there are three or more than three fins lying in three or more different non-parallel planes.

The fins may lie in planes substantially at right angles to the plane of the base.

The heat sink may be generally rectangular in plan view with fins arranged down one pair of opposed sides. The fins may be arrayed down the longer sides of the rectangle. Some at least of the fins may be wider at the top than at the root. Some at least of the fins may be formed of metal which, prior to displacement, lies beyond the pair of opposed sides on which the fins are not arrayed.

Some at least of the fins may be provided with tabs to enhance mounting of the heat sink onto a printed circuit board or other support. The fins may be of identical height after displacement or of different height after displacement. The fins on one side of the generally rectangular heat sink may be a mirror image of the fins on the other side. The top of the fins may be wider than the root of the fins in some at least of the fins.

By way of example embodiments of the present invention will now be described with reference to the accompanying drawings, of which: Figure 1 is a plan view of a heat sink showing the position of the fins prior to displacement in dotted lines; and Figure 2 is a plan view of a heat sink manufactured in accordance with the present invention.

Referring to Figure 1 this shows a heat sink assembly and illustrates the position and displacement of the fins. The heat sink comprises a base 1 and a series of fins 2, 3, 4, 5 and 6. It will be seen that the fins on the left hand side as illustrated in the drawing are a mirror image of those on the right hand side and have been given the same numbers. The heat sink is made from a blank illustrated by the dotted outline for each of the fins together with the solid line shown as 7, 8, 9, 10, 11 and 12. The fin 2 is formed by displacing the metal in the region 13 from the plane of the base 1 to lie at right angles to the plane along the line 14. Similarly the fin 3 is formed by displacing the metal in the area 15 to lie at 3 along the line 16. The other fins 4, 5 and 6 are formed in the same way.

It can be clearly seen that the fins 3, 4 and 5 are wider at the top than at the bottom. This is because the fins are formed not by simply bending parallel strips but by providing metal from a greater area than would be possible using a simple parallel edged design as is, for example, illustrated in British Patent Specification 1 334 173.

Referring to Figure 2 it can be seen that the area of the fins 3, 4 and 5 is clearly greater than the area of the fins 2 and 6. In fact in a typical embodiment fins of 12.5mm height were formed such that the fins 2 and 6 were 7.5mm high and the fins 3 and 4 were 7.5mm wide at the root and lOmm wide at the top.

This means that the total area of fins was 1,031.25mm2. By comparison a straight edged rectangular heat sink of the type described and illustrated in British Patent Specification 1 334 173 has a fin area of only 950mm2. Thus in the case of the heat sink of the present invention there is over a e3.58 increase in fin area compared to the design illustrated in the prior art.

It will be appreciated that the exact arrangement of fins can be varied and the number of fins is not limited to five on each side. Furthermore the angle of the fins can be adjusted and tabs may be provided on some at lest of the fins to permit mounting of the heat sink on a printed circuit board.

The base may be provided with one or more holes to assist in securing of the heat sink to an electronic device.

Claims

CLAIMS:

1. A heat sink having a substantially planar base and a plurality of fins, the fins having been formed by cutting and displacement out of the plane of the base to lie in planes substantially at angles to the plane of the base, characterised in that the fins are formed by the action of turning up the metal between the cut slits without twisting and in that there are three or more than three fins lying in three or more different non-parallel planes.

2. A heat sink as claimed in Claim 1 in which the fins lie in planes substantially at right angles to the plane of the base.

3. A heat sink as claimed in Claim 1 or 2 which is generally rectangular in plan view with fins arranged down one pair of opposed sides.

4. A heat sink as claimed in any one of Claims 1 to 3 in which some at least of the fins are wider at the top than at the root.

5. A heat sink as claimed in Claim 4 when appended to Claim 3 in which some at least of the fins are formed of metal which, prior to displacement, lies beyond the pair of opposed side on which the fins are not arrayed.

6. A heat sink as claimed in any one of Claims 1 to 5 in which some at least of the fins are provided with tabs to enhance mounting of the heat sink onto a printed circuit board or other support.

7. A heat sink as claimed in any one of the preceeding claims in which the fins are of identical height after displacemet.

8. A heat sink as claimed in any one of Claims 1 to 6 in which the fins are of different height after displacement.

9. A heat sink as claimed in Claim 4 or any one of Claims 5 to 8 when appended to Claim 3 in which the fins on one side of the generally rectangular heat sink is of a mirror image of the fins on the other side.

10. A heat sink substantially as herein described with reference to and as illustrated by Figure 2 of the accompanying drawings.