A HEATSINK AND A METHOD AND AN ASSEMBLY FOR FORMING THE SAME

Abstract: A heatsink (1) is formed from a block-like extruded or machined base member (10) and a number of planar fin members (12). The fin members may comprise "U"-shaped members. The fin members are secured in slots (14) formed in the base member and are preferably formed of the same material as the base member to improve the efficiency of the thermal contact therebetween. The fin members are each preformed to comprise a number of fin portions (12a) which extend upwardly from the base member of the assembled heatsink.

Description: A HEATSINK AND A METHOD AND AN ASSEMBLY FOR FORMING THE SAME The present invention relates to a heatsink and to a method and an assembly for forming the same. The present invention particularly relates to a heatsink having a high fin member to spacing ratio, i.e. high fin members with small gaps therebetween. A heatsink of this type is normally relatively large being designed to have optimum heat dissipating characteristics. It is generally formed from an extruded metal member having integrally formed fin members. The fin members can be machined thus enabling heatsinks with various arrangements of fins, etc. to be provided. However, the arrangement of fins is restricted by dimensional characteristics of the extruded member, for example fin member spacing, which are themselves limited by extrusion technology. The cost of the extruded member often accounts for a sizeable proportion of the total cost of a heatsink manufactured in this manner. One object of the present invention is to provide a method of forming inexpensive heatsinks. Another object of the invention is to provide heatsinks with excellent heat dissipating characteristics. According to a first aspect of the present invention, there is provided a heatsink assembled from a block-like base member and at least one generally planar fin member, said fin member comprising a plurality of fin portions, wherein said fin member is fixed to said base member such that at least the fin portions extend upwardly therefrom and the base member and the fin member are made of thermally conductive material. Preferably, the base member and the fin member are made of the same thermally conductive material. Preferably, the thermally conductive material is a metallic material. Preferably further, the metallic material is aluminium. Preferably, the heatsink includes a plurality of spaced apart fin members. Preferably, pairs of adjacent fin members are preformed as "U"-shaped members which each comprise two generally coplanar fin members integrally joined by a base portion extending between lower edge portions thereof. Preferably also, the fin members or "U"-shaped members are fixed to the base member by engaging the lower edge portions or base portions thereof in respective slots formed in a surface of the base member. Preferably, the ratio of the height of the fin members to the spacing therebetween is substantially greater than 1. The fin portions of each fin member may be equally spaced. The fin portions may be twisted to lie in respective planes angled with respect to a plane in which the fin member lies. The fin portions may be twisted such that they extend outwardly from only one side of their respective fin member. The fin portions may be formed to extend over a greater part of the height of their respective fin member. The fin portions may be formed to extend to an upper edge of their respective fin member. The fin members may each comprise portions displaced from the plane of the fin member which generally lie coplanar with the plane of the fin member. The heatsink may be assembled such that corresponding fin portions of adjacent fin members are aligned in a transverse direction. Alternatively, the corresponding fin portions of adjacent fin members may be staggered. According to a second aspect of the present invention, there is provided a method of assembling a heatsink comprising a block-like base member and at least one generally planar fin member, said fin member comprising a plurality of fin portions, wherein said fin member is fixed to said base member such that at least said fin portions extend upwardly therefrom and the base member and the fin member are made of thermally conductive material. Other features of the method of assembling a heatsink according to the second aspect of the invention correspond to dependent features of the heatsink according to the first aspect of the invention. According to a third aspect of the present invention, there is provided an assembly for forming a heatsink, said assembly comprising a block-like base member and at least one generally planar fin member, said fin member comprising a plurality of fin portions, wherein said base member and said fin member are made of thermally conductive material. Other features of the heatsink assembly according to the third aspect of the invention correspond to dependent features of the heatsink according to the first aspect of the invention. The foregoing and further features of the present invention will be more readily understood from the following description of preferred embodiments, by way of example thereof, with reference to the accompanying drawings, of which: Figure 1 is a plan view of a first embodiment of a heatsink in accordance with the invention; Figure 2 is a section on line A-A of figure 1; Figure 3 is a transverse sectional view of another embodiment of the invention; Figure 4 is a partial end-on view of the embodiment of figure 3; Figure 5 is a plan view of a further embodiment of the invention; Figure 6 is a partial end-on view of the embodiment of figure 5; Figure 7 is a plan view of yet another embodiment of the invention; Figure 8 is a partial end-on view of the embodiment of figure 7; Figure 9 is a partial end-on view of a still further embodiment of the invention: Figure 10 is a plan view of a yet still further embodiment of the invention; and Figure 11 is a partial end-on view of the embodiment of figure 10. A first embodiment of a heatsink 1 according to the present invention is illustrated in figures 1 and 2. This comprises a block-like base member 10 made of a thermally conductive material to which are fixed a plurality of plate-like fin members 12 also made of a thermally conductive material. Each fin member 12 comprises a plurality of fin portions 12a which, in this embodiment, are integral with a lower edge portion 12b of the fin member 12 which locates in a slot 14 (shown in broken outline in figure 2) in the base member 10. The base member 10 and fin members 12 are preferably made of aluminium which exhibits good heat dissipating characteristics. The present invention enables a heatsink 1 to be quickly assembled from a block of aluminium which is machined or extruded to have a plurality of longitudinally extending slots 14 into each of which a fin member 12 as described above is press-fitted. The fin members 12 are formed by press-cutting from a sheet material and thus the form and size of the fin portions 12a is determined by the shape of the die used to cut the fin members 12. The fin members 12 can, as in this embodiment, be identical to provide a heatsink 1 in which the fin portions 12a of adjacent fin members 12 are aligned across the width of the heatsink 1. It will be appreciated, however, that it is a relatively simple task to form and arrange the fin members 12 such that the fin portions 12a of adjacent fin members 12 are staggered with respect to each other across the width of the heatsink 1. The fin portions 12a are arranged to extend over a greater part of the height of their respective fin member 12 and can be formed to extend to adjacent a surface 16 of the block-like base member 10 when the fin members 12 are assembled with said base member 10. The fin members 12 are arranged to be placed closely together to provide a heatsink 1 in which the ratio of the height of the fin portions 12a to gaps between the fin members 12 is substantially greater than 1. It is preferred that the method of fixing the fin members 12 to the block-like base member 10 is by press- fitting without the use of soldering, brasing, etc. to ensure good thermal contact between the base member 10 and the fin members 12. However, it will be appreciated that the fin members 12 can be fixed to the base member 10 by any suitable retaining method or means. It is also preferred that the base member 10 and the fin members 12 are made of the same thermally conductive material in order to avoid bi-metallic bending which can occur when the fin members and the base member are made of different metals. The heatsink 1 formed with fin members 12 and a base member 10 of the same thermally conductive metallic material will have greater corrosion resistance over a heatsink 1 utilising different metals. In the description of other embodiments, like numerals are used to denote like parts. Figures 3 and 4 show a second embodiment of the present invention in which the fin portions 12a comprise pressed- out portions of the fin member 12. These portions 12a extend coplanarly with the plane of their respective fin member 12 but spaced outwardly therefrom. Thus the airflow through the fin members 12 of the heatsink is disturbed by the pressed-out fin portions 12a but the total surface area available for heat dissipation is at a maximum since the fin portions 12a have not been formed, by removal of portions from the fin members 12 as in the first embodiment. The fin portions 12a can be arranged in many different ways and further embodiments are illustrated by figures 5 and 6 and figures 7 and 8, respectively. In figures 5 and 6, it can be seen that the fin portions 12a are twisted to extend outwardly from one side of their respective fin member 12. In figures 7 and 8, it can be seen that the fin portions 12a are twisted so as to extend outwardly from both sides of their respective fin member 12. Yet further embodiments of the invention are illustrated by figure 9 and figures 10 and 11, respectively. In figure 9, it can be seen that adjacent fin members 12 are preformed as "U"-shaped members 13. Each "U"-shaped member 13 comprises two fin members 12 arranged to be coplanar and integrally joined at their lower edges 12b by a base portion 13a extending therebetween. The "U"-shaped members 13 can be press- fitted into respective slots 14 formed in the base member 10 or by any other suitable means. In the embodiment illustrated in figure 9, the "TJ"-shaped members 13 are secured in their respective slots 14 by means of wire-like wedge 15. Each of the fin members 12 comprises a number of fin portions (not shown) in a like manner to the first embodiment of the invention. Figures 10 and 11 show yet another embodiment of figure 9, employing "U"-shaped members 13. However, in this embodiment, the fin portions 12a of the fin members 12 are of a form similar to those of the embodiment of figures 7 and 8. It will therefore be appreciated that the "U"- shaped members 13 of the embodiments of figure 9 and figures 10 and 11, respectively, can be formed with fin portions in accordance with any other embodiment of the invention. One advantage of employing "U"-shaped members 13 rather than separate fin members 12 is that it is easier to automate the handling of the "U"-shaped members 13. A further advantage is that said members have a larger area of contact with the base member when compared to the equivalent number of separate fin members. Thus the thermal contacts between the base member and the "U"-shaped members is more efficient. It will be appreciated that a heatsink according to the present invention may be formed with fin members of an identical form or a combination of fin members having variously configured fin portions. This provides a very wide design freedom in arranging the pattern of fin portions across the width of the heatsink. Thus, heatsinks can be designed with a fin portion formation which optimises the heat dissipating characteristics of a heatsink for a given application. This design freedom is achieved at little extra cost contrary to the situation encountered with known heatsink designs. The present invention thus provides a heatsink having a structure and performance similar to that of the large sized expensive heatsinks machined from extruded members but at a substantially smaller cost.

Claims: CLAIMS 1. A heatsink assembled from a block-like base member and at least one generally planar fin member, said fin member comprising a plurality of fin portions, wherein said fin member is fixed to said base member such that at least the fin portions extend upwardly therefrom and the base member and the fin member are made of thermally conductive material. 2. A heatsink as claimed in claim 1, wherein the base member and the fin member are made of the same thermally conductive material. 3. A heatsink as claimed in claim 2, wherein the thermally conductive material is a metallic material. 4. A heatsink as claimed in claim 3, wherein the metallic material is aluminium. 5. A heatsink as claimed in any proceeding claim, wherein the heatsink includes a plurality of spaced apart fin members. 6. A heatsink as claimed in claim 5, wherein pairs of adjacent fin members are preformed as "U"-shaped members which each comprise two generally coplanar fin members integrally joined by a base portion extending between lower edge portions thereof. 7. A heatsink as claimed in claim 5 or claim 6, wherein the fin members or "U"-shaped members are fixed to the base member by engaging the lower edge portions or base portions thereof in respective slots formed in a surface of the base member. 8. A heatsink as claimed in any one of claims 5 to 7, wherein the ratio of the height of the fin members to the spacing therebetween is substantially greater than 1. 9. A heatsink as claimed in any one of claims 5 to 8, wherein the fin portions of each member may be equally spaced. 10. A heatsink as claimed in any one of claims 5 to 9, wherein the fin portions are twisted to lie in respective planes angled with respect to a plane in which the fin member lies. 11. A heatsink as claimed in any one of claims 5 to 9, wherein the fin portions are twisted such that they extend outwardly from only one side of their respective fin member. 12. A heatsink as claimed in any one of claims 5 to 11, wherein the fin portions are formed to extend over a greater part of the height of their respective fin member. 13. A heatsink as claimed in any one of claims 5 to 12, wherein the fin portions are formed to extend to an upper edge of their respective fin member. 14. A heatsink as claimed in any one of claims 5 to 9, wherein the at least one fin member comprises fin portions displaced from the plane of the fin member which generally lie coplanar with the plane of the fin member. 15. A heatsink as claimed in any one of claims 5 to 14, wherein the heatsink is assembled such that corresponding fin portions of adjacent fin members are aligned in a transverse direction. 16. A heatsink as claimed in any one of claims 5 to 14, wherein the corresponding fin portions of adjacent fin members are staggered. 17. A method of assembling a heatsink comprising a block-like base member and at least one generally planar fin member, said fin member comprising a plurality of fin portions, wherein said fin member is fixed to said base member such that at least said fin portions extend upwardly therefrom and the base member and the fin member are made of thermally conductive material. 18. An assembly for forming a heatsink, said assembly comprising a block-like base member and at least one generally planar fin member, said fin member comprising a plurality of fin portions, wherein said base member and said fin member are made of thermally conductive material.

Inventors: FISHER FRANCIS EDWARD, JOHNSON ROBIN DOUGLAS, JORDAN WILLIAM DAWSON, FISHER, FRANCIS, EDWARD, JOHNSON, ROBIN, DOUGLAS, JORDAN, WILLIAM, DAWSON
Applicants: FISHER FRANCIS EDWARD, JOHNSON ROBIN DOUGLAS, JORDAN WILLIAM DAWSON, REDPOINT THERMALLOY LTD, FISHER, FRANCIS, EDWARD, JOHNSON, ROBIN, DOUGLAS, JORDAN, WILLIAM, DAWSON, REDPOINT THERMALLOY LIMITED
Application year: 1996
Main classification: H01L23
IPC codes: H01L23, H05K7