GB2113470A

GB2113470A - Heat sink

Info

Publication number: GB2113470A
Application number: GB8300795A
Authority: GB
Inventors: Frank Hopkins
Original assignee: REDPOINT Ltd
Current assignee: REDPOINT Ltd
Priority date: 1982-01-14
Filing date: 1983-01-12
Publication date: 1983-08-03
Also published as: GB8300795D0

Abstract

A heat sink comprising a sheet metal member at least one edge portion of which is formed with a plurality of slits to form a plurality of fingers (3) between adjacent slits and at least some of the fingers are bent relative to the remaining fingers so that adjacent fingers are disposed in different planes and the arrangement being such that substantially no metal is removed from the sheet metal member during formation of the fingers. <IMAGE>

Description

SPECIFICATION Heat sink The invention relates to heat sinks more particularly but not exclusively for semi-conductor devices.

It is known to provide heat sinks with a base plate from which a plurality of spaced fingers extend, these fingers being bent at right angles to the base plate. The purpose of bending and spacing the fingers apart is to reduce the amount of cross radiation between the fingers since such radiation lowers the efficiency of the heat sink. A disadvantage of such devices is that in order to space the fingers apart a considerable amount of metal, which could be used for radiating heat, must be removed from the blank and therefore only a limited increase in efficiency is achieved even though the crossradiation between the fingers is reduced.

In our U.K. Patent No. 1334173 there is disclosed a heat sink for a semi-conductor device comprising a metal blank an edge portion of which is slit to define a plurality of parallel-edged fins which are twisted so as to be inclined at an acute angle to the original plane of the blank, the total width of fins between any two slits being substantially equal to the distance between said two slits in the plane of the blank from which the fins have been twisted. In this manner the fins or fingers are spaced apart without the necessity of removing metal from the blank.

Such a heat sink is primarily intended as a U-shaped heat sink and is not readily adaptable to "open box" configuration.

It is an object of the invention to provide a heat sink having spaced apart and non-twisted fins or fingers without the necessity of removing metal from the blank and which is readily adaptable to "open box" configuration.

According to the invention there is provided a heat sink comprising a sheet metal member at least one edge portion of which is formed with a plurality of slits to form a plurality of fingers between adjacent slits and at least some of the fingers are bent relative to the remaining fingers so that adjacent fingers are disposed in different planes and the arrangement being such that substantially no metal is removed from the sheet metal member during formation of the fingers. Preferably the slits are substantially at right angles to an edge of the sheet metal member, and preferably at least some of the slits are parallel to one another.

The sheet metal member may comprise a base portion, the arrangement being such that the fingers extend substantially at right angles to the base portion.

If desired the fingers may be arranged in staggered relationship in two substantially parallel rows.

In a preferred embodiment the heat sink comprises a rectangular base portion the four edges of which carry fingers extending substantially at right angles to the base portion so that the heat sink resembles an open-topped box.

The invention is diagrammatically illustrated by way of example in the accompanying drawings in which Figure 1 is a side view of a heat sink according to the invention; Figure 2 is a plan view of the heat sink shown in Figure 1, and Figure 3 is a perspective view of the heat sink of Figures 1 and 2.

In the drawings there is shown a heat sink 1 made from a single piece of sheet metal e.g. aluminium, the surface of which is preferably blackened in order to improve its heat transfer characteristics. The heat sink 1 is in the form of an open-topped opencornered box comprising a substantially square base member 2 surrounded by upstanding walls formed by heat radiating fingers 3. The adjacent fingers in each wall are staggered so that the fingers are disposed in two rows. The adjacent edges of adjacent fingers lie in common planes at right angles to the major faces of the fingers.

For the purpose of increasing air flow across the heat sink the fingers do not extend to the corners of the base plate.

The heat sink is formed by slitting the edges of a flat blank at right angles to the edges to form a plurality of fingers and bending up the fingers substantially at right angles to the original plane of the blank. Each finger is bent in such a way that the fingers are staggered and are disposed in two rows.

Preferably the inner row of fingers are bent through more than 90% e.g. 92.5 , whereas the outer row of fingers are bent through less than 90% e.g.

86% since in this manner the two rows of fingers diverge one from the other. The greater separation thus achieved between the rows of fingers is beneficial in minimising cross-radiations between the fingers.

It will be appreciated that the invention is also applicable to heat sinks other than square based, for example polygonal, e.g. having three or more sided bases. Also the invention is applicable to heat sinks which in cross section are U shaped e.g. two sided, or L shaped e.g. one sided.

Claims

1. A heat sink comprising a sheet metal member at least one edge portion of which is formed with a plurality of slits to form a plurality of fingers between adjacent slits and at least some of the fingers are bent relative to the remaining fingers so that adjacent fingers are disposed in different planes and the arrangement being such that substantially no metal is removed from the sheet metal member during formation of the fingers.

2. A heat sink according to claim 1 in which the slits are substantially at right angles to an edge of the sheet metal member.

3. A heat sink according to claim 1 or claim 2 in which at least some of the slits are parallel to one another.

4. A heat sink according to any preceding claim in which the sheet metal member comprises a base portion and in which the fingers extend substantially at right angles to the base portion.

5. A heat sink according to any preceding claim in which the fingers are arranged in staggered relationship in two substantially parallel rows.

6. A heat sink according to any preceding claim comprising a rectangular base portion the four edges of which carry fingers extending substantially at right angles to the base portion so that the heat sink resembles an open-topped box.

7. A heat sink substantially as hereinbefore de scribed with reference to and as illustrated in the accompanying drawings.