GB2270862A

GB2270862A - Heat sink manufacture

Info

Publication number: GB2270862A
Application number: GB9317917A
Authority: GB
Inventors: Peter Martin Law
Original assignee: Denso Marston Ltd
Current assignee: Denso Marston Ltd
Priority date: 1992-09-24
Filing date: 1993-08-27
Publication date: 1994-03-30
Anticipated expiration: 2013-08-27
Also published as: GB9317917D0; GB2270862B

Abstract

A two part heat sink comprising a plate and corrugated heat dissipation layer secured together using an epoxy resin brazing or other securing technique. The heat dissipation layer may then be cut sharply by spark erosion or other technique e.g. high speed saw, water or abrasive jet which has low fin compression. Thus, the dissipation layer does not collapse about the cut inhibiting air flow and heat dissipation.

Description

Heat Sinks The present invention relates to heat sinks and more particularly heat sinks fabricated from plate and corrugated elements.

Typically heat sinks have been manufactured either by extrusion or stamping. However, these techniques inhibit to varying degrees the performance and structural features that may be designed into a heat sink. Furthermore, these fabrication techniques limit the types of material that can be used in heat sinks.

A heat sink has two main elements, a surface from which heat can be dissipated and a surface or means of securing a heat generating device such as an integrated circuit device to the heat sink. The surface from which heat is dissipated usually is maximised to ensure heat loss through convection etc to surrounding air is as large as possible. The device securing surface is typically flat or securing means may be included in the heat sink to enable the device to be screwed to it or held in a slot.

Previously, it has been known to secure a corrugated element to a plate in order to create a two part heat sink. The corrugated element and plate typically were secured by brazing or similar technique. It will be appreciated that the corrugated element provides a large heat dissipation area whilst, the plate can be readily configured to facilitate device securing prior to manufacture of the heat sink.

A problem with such 'two part' heat sinks is that during manufacture it is very easy to damage the corrugated element thereby causing inhibitation of air flow during use of the heat sink. Furthermore, if the heat sink is to be cut or shaped after manufacture the corrugations may be crushed and so air flow prevented in use.

It is an objective of the present invention to provide a heat sink and more particularly a method of manufacturing heat sinks that substantially relieves the above mentioned problems.

In accordance with a first aspect of the present invention there is provided a method of manufacture of a heat sink comprising: 1. Securing a corrugated heat dissipation layer to a plate using conductive means; 2. Allowing the conductive means to cure or set; and, 3. Removing edges of the heat sink by spark erosion to ensure substantially un-inhibited air flow through the corrugated heat dissipation layer.

Preferably, the conductive means is an adhesive such as a nickel loaded epoxy resin or a vacuum braze.

In accordance with a second aspect of the present invention there is provided a heat sink comprising a plate element suitable for securing a heat generating device and a heat dissipation element including corrugations, the plate element and heat dissipation element being secured in electrically conductive contact to enable edges about the heat sink to be defined by spark erosion.

In accordance with a third aspect of the present invention there is provided a heat sink comprising a heat dissipation element including corrugations secured to a plate element with an adhesive.

Preferably, the plate element and heat dissipation element are secured together using an adhesive loaded with conductive filaments of a material such as nickel.

The plate element and heat dissipation element may be formed of copper or aluminium.

In accordance with a fourth aspect of the present invention there is provided a method of manufacture of a heat sink comprising: 1. Securing a corrugated heat dissipation layer to a plate using conductive means; 2. Allowing the conductive means to cure or set; and, 3. Removing edges of the heat sink by a high speed saw or water jet cutter or abrasive jet cutter to ensure substantially un-inhibited air flow through the corrugated heat dissipation layer.

Preferably, the conductive means is vacuum brazing or conductive adhesive.

In accordance with a fifth aspect of the present invention there is provided a heat sink comprising a plate element suitable for securing a heat generating device and a heat dissipation element including corrugations, the plate element and heat dissipation element being secured in electrically conductive contact to enable edges about the heat sink to be defined by a high speed saw or water jet cutter or abrasive jet cutter.

Preferably, the plate element and heat dissipation element are secured together using a vacuum brazing technique or adhesive.

Embodiments of the present invention will now be described by way of example only with reference to the accompanying drawings in which: Figure 1 illustrates in plan view a heat sink after securing a plate to a heat dissipation element; Figure 2 illustrates the heat sink of Figure 1 in end view as seen in the direction X-X and with its edge removed along dotted line Y-Y; and, Figure 3 illustrates the heat sink of Figures 1 and 2 in end view as seen from direction X-X and with edges removed along both dotted lines Y-Y and Z~Z .

Considering the Figures, a plate 3 is secured to a layer 1 of highly corrugated material using a conductive adhesive or braze 5. The corrugated layer 1 acts as a heat dissipation element such that heat can be removed by conventive air currents about the layer 1. In order to enhance such heat loss, the corrugations in the layer 1 are staggered such that each corrugation does not extend along the whole length of the layer 1 but is broken into several spans. The ends of each of these spans is open to allow air ingress and flow.

It will be appreciated that the adhesive or braze 5, or any other securing means used, secures the layer 1 to the plate 3 through the peaks/troughs of the layer 1. Thus, it is quite common for the adhesive or braze to clog the corrugations about the edge and so inhibit air flow and heat loss.

Furthermore, in order to create desired shapes or to enable economic production it is usual to cut the assembly illustrated in Figure 1. This act of cutting will damage the corrugations if undertaken with a normal saw technique or compressive cutters or without great care.

In the present invention, the assembly illustrated in figure 1 is cut along dotted lines Y-Y and Z-Z using a spark erosion technique or high speed saw or water jet cutter or abrasive jet cutter. Such cutting does not distort or crush the corrugations and so leaves them open to ensure suitable air circulation.

It can be seen that excess adhesive or braze 7 has been expelled from the junction between the layer 1 and the plate 5. The excess adhesive or braze 7 will harden and clog the corrugations and so is removed by spark erosion or a high speed saw or a water jet cutter or an abrasive jet cutter through dotted lines Y-Y and Z-Z in the heat sink assembly to the form illustrated in Figure 3. Similar techniques can be used to cut specific heat sink shapes with sharp edges to allow good air flow about the assembly illustrated in Figure 3.

The method of manufacture of a heat sink in accordance with the present invention is: 1. Secure a corrugated heat dissipation layer 1 to a plate 3 using a conductive adhesive or weld or braze. If adhesive is used, preferably it is a nickel loaded epoxy resin.

2. Allow the adhesive to cure or the weld or braze to cool; and, 3. Remove those edges of the assembly from which the corrugations extend using spark erosion or a high speed saw or a water jet cutter or an abrasive jet cutter technique such that the corrugations of the layer 1 are left substantially open.

The plate 1 may be curved and is suitable for securing a heat generating element such as a transistor or electronic device to it.

Water jet cutting and abrasive jet cutting are techniques using a forced stream/jet of water or abrasive to cut elements by abrasion.

Claims

CLAIMS: 1. A method of manufacture of a heat sink comprising:

1. Securing a corrugated heat dissipation layer to a plate using conductive means;

2. Allowing the conductive means to cure or set; and,

3. Removing edges of the heat sink by spark erosion to ensure substantially un-inhibited air flow through the corrugated heat dissipation layer.

2. A method as claimed in claim 1 wherein the conductive means is an adhesive such as a nickel loaded epoxy resin or vacuum brazing.

3. A heat sink comprising a plate element suitable for securing a heat generating device and a heat dissipation element including corrugations, the plate element and heat dissipation element being secured in conductive contact to enable edges about the heat sink to be defined by spark erosion.

4. A heat sink comprising a heat dissipation element including corrugations secured to a plate element with an adhesive.

5. A heat sink as claimed in any proceeding claim wherein the plate element and heat dissipation element are secured together using an adhesive loaded with conductive filaments of a material such as nickel.

6. A heat sink as claimed in any proceeding claim wherein the plate element and heat dissipation element are formed of copper or aluminum.

7. A method of manufacture of a heat sink comprising:

2. Allowing the conductive means to cure or set; and,

3. Removing edges of the heat sink by a high speed saw or water jet cutter or abrazive jet cutter to ensure substantially un-inhibited air flow through the corrugated heat dissipation layer.

8. A heat sink as claimed in claim 7 wherein the conductive means is vacuum brazing or conductive adhesive.

9. A heat sink comprising a plate element suitable for securing a heat generating device and a heat dissipation element including corrugations, the plate element and heat dissipation element being secured in conductive contact to enable edges about the heat sink to be defined by a high speed saw or water jet cutter or abrasive jet cutter.

10. A heat sink as claimed in claim 9 wherein the plate element and heat dissipation element are secured together using a vacuum brazing technique or adhesive.

11. A heat sink as claimed in claims 9 or 10 wherein the plate element and heat dissipation element may be formed of copper or aluminium.

12. A method of forming a heat sink substantially as hereinbefore described with reference to the drawings.

13. A heat sink substantially as hereinbefore described with reference to the drawings.