US20110155360A1

US20110155360A1 - Surface mount heat sink apparatus

Info

Publication number: US20110155360A1
Application number: US12/655,334
Authority: US
Inventors: Kechuan Kevin Liu
Original assignee: Individual
Current assignee: Individual
Priority date: 2009-12-29
Filing date: 2009-12-29
Publication date: 2011-06-30

Abstract

A surface mountable heat sink apparatus for use with surface mount electronic components comprises a heat dissipating body and a plurality of solderable feet complying with Surface Mounting Technology (SMT). The heat dissipating body and the solderable feet are made of different materials and of unitary construction. The solderable feet project partially beyond one edge of the heat dissipating body. The surface mount heat sink apparatus and surface mount electronic component are touchlessly sandwiched and simultaneously soldered onto the solder drain pads on the printed circuit board. Heat dissipated from the surface mount electronic component is conductively transferred to the heat sink body through the solder drain pad, printed circuit board and solderable feet, and finally rejected to surroundings thereafter. Like all the SMT electronic components, the surface mount heat sink apparatus can be placed onto the printed circuit board manually or automatically by a pick-&-place automation equipment.

Description

CROSS-REFERENCE TO RELATED APPLICATIONS

None

STATEMENT REGARDING FEDERAL SPONSORED RESEARCH OR DEVELOPMENT

Not Applicable

FIELD OF THE INVENTION

This invention generally relates to the art of heat sink apparatus, particularly, to a surface mount heat sink apparatus having solderable feet and heat dissipating body which are made of different materials and of unitary construction.

BACKGROUND OF THE INVENTION

Surface mount heat sink apparatus or surface mount heat sink assemblies of a limited variety of designs have been employed to dissipate heat generated by SMT electronic components or devices surface mounted (or soldered) on printed wiring or circuit boards to prevent the electronic components or devices from failure. More than ever before, today's electronic products are reducing the size and cost, increasing power dramatically, and upgrading frequently with new technologies. So that the surface mount heat sinks or heat sink assemblies used on printed wiring or circuit boards must be smaller in size, larger in surface areas and lower in cost to meet the trends.
Generally a heat sink is a piece of part made of any thermally conductive materials, such as Copper, Aluminum and Steel, etc. For better performance and higher heat transfer rate in a confined space, a heat sink usually has extended surface areas, called fins. In addition, for a surface mountable heat sink, the heat sink must be able to be soldered on a printed wiring or circuit board like any other surface mounting electronic components.
In order to meet the requirements of a surface mount heat sink, some stamped heat sinks with copper sheet material have been made available and used on the printed wiring or circuit boards with some SMT electronic components. An example of the latter may be seen in U.S. Pat. No. 5,311,395, this surface mount heat sink is formed with copper or copper alloy sheet which can be soldered on a printed wiring or circuit board. However this SMT heat sink or the like has at least three distinct disadvantages. First the copper material is expensive and heavy; second the sheet metal formed or stamped heat sink body has very limited surface areas within the specified volume, therefore the heat transfer rate is limited; third, the finish of the heat sink has to be solderable plating or coating, like tin plated, and can not be black anodized or painted, therefore it is limited to radiation heat transfer. Another example of the SMT heat sink is from AAVID Thermally, called Slalom Surface Mount Heat Sink. This SMT heat sink combines the copper solderable tags with stamped, pre-black anodized aluminum sheet by staking or self-riveting. This heat sink has the advantage of low cost in manufacturing and light in weight. However, it has, at least, two distinct disadvantages. First, the stamped aluminum heat sink body has very limited surface areas within the confined space; second, the staking joints for the solderable tags and the heat sink legs leave a “big” air gap and lower pressure in the contact areas between the two parts which creates huge thermal resistance in the contact interface areas of the two parts. Therefore it produces the lower heat transfer rate and increases higher temperature rise on the electronic component due to the “bottle-neck” thermal resistance.
Accordingly, what is needed is in the art of larger surface areas, lower cost, lighter weight and higher heat transfer rate heat sink apparatus which incorporates the advantages of different material properties, lower manufacturing cost and automated assembly operations.

SUMMARY OF THE INVENTION

A surface mountable heat sink apparatus for use with SMT electronic components comprises a heat dissipating body and a plurality of solderable feet. The heat dissipating body and the solderable feet are made of different materials and of unitary construction. The solderable feet project partially beyond one edge of the heat dissipating body. The surface mount heat sink apparatus and the SMT electronic component are touchless sandwiched and simultaneously soldered onto the solder drain pad on a printed circuit or wiring board. Heat dissipated from the surface mount electronic component is conductively transferred to the heat dissipating body through the solder drain pad, printed circuit board and solderable feet, and finally rejected into surroundings. Like all the SMT electronic components, the surface mount heat sink apparatus can be placed onto a printed circuit board manually or automatically by pick-&-place automation machines.
The unitary construction of the surface mount heat sink apparatus according to the present invention improves size, weight and power (SWaP) for thermal management products.
It is a further object of the present invention to provide higher heat transfer rate in a specified volume or form factor than those similar heat sinks on market by increasing the surface areas and surface emissivities of the heat sink body and reducing the interface thermal resistance between the solderable feet and the heat dissipating body.
It is yet a further object of the present invention to provide a lower cost and robust method for attaching the solderable feet into the heat dissipating body to minimize the interface thermal resistance in the contact areas of the two parts.
The foregoing has outlined, rather broadly, preferred and alternative features of the present invention so that those skilled in the art may better understand the detailed descriptions of the invention that follows. Additional features of the invention will be described hereinafter that form the subject of the claims of the invention. Those skilled in the art should appreciate that they can readily use the disclosed conception and specific embodiment as a basis for designing or modifying other structures for carrying out the same purposes of the present invention. Those skilled in the art should also realize that such equivalent constructions do not depart from the spirit and scope of the invention in its broadest form.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is an ISO view of an embodiment of the present invention in use with a SMT electronic component soldered on the drain pads of a printed circuit board.

FIG. 2A is an ISO view of an embodiment of the present invention; FIG. 2B is a 2-D drawing of the top and end views of an embodiment of the heat dissipating body, and FIG. 2C is a 2-D drawing of an embodiment of a solderable foot according to the present invention.

FIGS. 3A and 3B are the perspective views and FIG. 3C is a 2-D drawing showing how the solderable feet are installed into the heat dissipating body to create an embodiment of the present invention.

FIG. 4 is an ISO view showing a ramified or derived embodiment of the present invention in use with multiple SMT electronic components soldered on the drain pads of a printed circuit board.

FIGS. 5A and 5B are the projective, exploded views showing how the embodiment of present invention and an SMT component are assembled and soldered on the drain pads of a printed circuit board. FIG. 5C is a 2-D end view of an embodiment of the present invention in use with a SMT component after being assembled and soldered on a printed circuit board.

DETAILED DESCRIPTION OF THE INVENTION

FIG. 1 is ISO view of an embodiment of the present invention in use with a SMT electronic component soldered on the drain pads of a printed circuit board, which illustrates a typical application of the embodiment of the present invention in a printed circuit or wiring board assembly (PCBA or PWBA) 400. In FIG. 1, a PCBA 400 comprises a PCB 300 having solder pads 310, a SMT electronic component 200 and a surface mount heat sink apparatus 100 having heat dissipating body 120 with at least one U-shaped channel 126 and a plurality of solderable feet 110. SMT component 200 touchlessly fits in the U-shaped channel 126 of heat sink apparatus 100 and both SMT component 200 and heat sink apparatus 100 are soldered on solder pads 310 of PCB 300 simultaneously. It is easy to understand from this application that the heat generated by component 200, transferred through solder pads 310, PCB 300 and solderable feet 110 to heat dissipating body 120, and finally rejected by heat dissipating body 120 to its surroundings.
FIG. 2A is an ISO view of an embodiment of the present invention, FIG. 2B is the 2-D drawing of the top and end views of an embodiment of the heat dissipating body, and FIG. 2C is a 2-D drawing of an embodiment of a solderable foot. FIG. 2A shows that the unitarily constructed surface mount heat sink apparatus 100 comprises a heat dissipating body 120 and a plurality of identical solderable feet 110. As shown in FIG. 2B, heat dissipating body 120 is configured to have a length “l” and, at least, one U-shaped channel 126 with two opposite sidewalls 125, each having a circular aperture 124 at its free end, with an internal diameter “d” and an arc “α”. The arc “α” of the circular aperture 124 is defined as 180°<α<360°, preferred to be 270°. Heat dissipating body 120 is further configured to have extended surface areas or fins 122 attached or born to outside surfaces 128 of U-shaped channel 126 and may also be attached or born to inside surface 127, for better heat dissipating and higher heat transfer rate. Heat dissipating body 120 and fins 122 may be fabricated as one part or an assembly of a plurality of parts. Heat dissipating body 120 and fins 122 are preferably constructed of an inexpensive and better thermal conductive material, such as aluminum, and fabricated by extrusion, casting, machining and the like, preferably extrusion. As shown in FIG. 2C, solderable foot 110 is configured as a solid cylinder, wire or rod, having diameter “D” and length “L”, for being mated with circular apertures 124 of heat dissipating body 120 and being soldered on the solder pads on a printed circuit board. To facilitate mating, diameter “D”<“d” and length “L”>“l”, and to facilitate soldering attachment, solderable foot 110 is preferably constructed of solderable material, such as copper with tin-plated.
FIGS. 3A and 3B are the perspective views and FIG. 3C is a 2-D drawing showing how the solderable feet 110 are being installed into heat dissipating body 120 fixedly to create an embodiment of the present invention—surface mount heat sink apparatus 100. FIG. 3A shows that solderable feet 110 are aligning with circular aperture 124 axially. FIG. 3B shows that the solderable feet 110 are mated with heat dissipating body 120. As defined, “L”>“l”, so that there is a small portion of solderable foot 110 sticking out of the both ends of heat dissipating body 120. However the small stick-out portion of solderable foot 110 meant to be flushed with the end of heat dissipating body 120 by compressing on both ends of solderable foot 110 with forces “F”. FIG. 3C shows that forces “F” applying on both ends of solderable foot 110 by hammering or forging to shorten the “L” to “L1”, so that “L1”=“l”, meanwhile, solderable foot 110 expands radially from “D” to “D1”, so that “D1”=“d” to create tight and perfect contact between circular surfaces of solderable foot 110 and circular aperture 124, so as to reduce the interface thermal resistance between solderable feet 110 and heat dissipating body 120. Another method for easy installing solderable foot 110 into circular apertures 124 of heat dissipating body 120 and creating tight and perfect contact between may be utilizing the Thermal Expansion Coefficient (TEC) of the two materials. In other words, before installation of the two parts, heat the heat dissipating body 120 to certain temperature so that “d” becomes “larger”, and cool solderable foot 110 to certain temperature so that “D” becomes “smaller”. After assembly, both are at the same temperature then D=d, therefore tight and perfect contact can be created. After assembly with either method, solderable feet 110 must be confined within to heat dissipating body 120 fixedly and partial body of solderable feet 110 projects beyond the boundary (or edge) of heat dissipating body 120 for solder interaction and build-up.
FIG. 4 is ISO view of an ramified (or derived) embodiment of the present invention in use with multiple SMT electronic components soldered on the drain pads of a printed circuit board, which illustrates that the embodiment of the present invention can be ramified or derived to cool multiple SMT electronic components in a printed circuit or wiring board assembly (PCBA or PWBA) 400. In FIG. 4, a PCBA 400 comprises a PCB 300 having solder pads 310, three SMT components 200 and a surface mount heat sink apparatus 100 having heat dissipating body 120 with three U-shaped channels 126 and four solderable feet 110. SMT components 200 touchlessly fit in the U-shaped channels 126 of heat sink apparatus 100, and all SMT components 200 and heat sink apparatus 100 are soldered on solder pads 310 of PCB 300 simultaneously. It is easy to understand from this application that the heat generated by all components 200, transferred through solder pads 310, PCB 300 and solderable feet 110 to heat dissipating body 120, and finally rejected by heat dissipating body 120 to its surroundings

Operation

For operation, one can use surface mount heat sink apparatus 100 in a normal manner by first placing a SMT electronic component 200 onto solder pads 310 on PCB 300, them placing a surface mount heat sink apparatus 100 over SMT electronic component 200, so that SMT electronic component 200 fits in the U-shaped channel of heat sink apparatus 100. Meanwhile solderable feet 110 are resting on solder pads 310 on PCB 300 as shown in FIGS. 5A, 5B and 5C. The placements or assembly steps can be accomplished manually by human being or automatically by a pick & place equipment. After finishing the placement, the whole assembly 400 will go though a re-flow oven so that solderable feet 110 and SMT component 200 are simultaneously soldered on solder pads 310 of a printed circuit or wiring board 300.
Obviously the present invention provides the surface mount heat sink apparatus with advantages as listed below:
1). Larger surface areas in a confined space
2). Lower interface thermal resistance between solder feet and heat sink body
3). Ease of manufacturing
Although only a few embodiments of the present invention have been described, it should be understood that the present invention be embodied in many other specific forms without departing from the spirit or the scope of the present invention. The present examples are to be considered as illustrative and not restrictive, and the invention is not to be limited to the details given herein, but may be modified within the scope of the appended claims along with their full scope of equivalents.

Claims

1. A surface mount heat sink apparatus for use with at least one SMT electronic component; the apparatus comprising:

(a) a heat dissipating body; and

(b) a plurality of solderable feet;

said heat dissipating body and said solderable feet being made of different materials and of unitary construction; said solderable feet configured having fixed and tight connection with said heat dissipating body;

2. A surface mount heat sink apparatus for use with at least one SMT electronic component as recited in claim 1 wherein said heat dissipating body configured being a U-shaped member having two side walls or legs with continuous interior and exterior surfaces.

3. A surface mount heat sink apparatus for use with at least one SMT electronic component as recited in claim 2 wherein said continuous exterior surfaces of said U-shaped member usually having fins attached or born thereto, and said continuous interior surfaces maybe having fins attached or born thereto;

4. A surface mount heat sink apparatus for use with at least one SMT electronic component as recited in claim 2 wherein said the two side walls or legs, each having a circular aperture close to its free end;

5. A surface mount heat sink apparatus for use with at least one SMT electronic component as recited in claim 4 wherein said circular aperture having a length “l”, an internal diameter of “d” and an arc “α” defined to be 180°<α<360°, preferred to be 270°.

6. A surface mount heat sink apparatus for use with at least one SMT electronic component as recited in claim 1 wherein said solderable feet configured being a solid rod or wire having a length “L” and a diameter of “D”;

7. A surface mount heat sink apparatus for use with at least one SMT electronic component as recited in claim 6 wherein said diameter (D) of said rod is slighter smaller than said internal diameter (d) of said circular aperture on said side wall or leg, expressed as D<d;

8. A surface mount heat sink apparatus for use with at least one SMT electronic component as recited in claim 6 wherein said length (L) of said rod may be slighter longer than said length (l) of said circular aperture on said side wall or leg, expressed as L>l;

9. A surface mount heat sink apparatus for use with at least one SMT electronic component as recited in claim 1 wherein said unitary construction being that said solderable feet configured to cooperatively engage a corresponding said circular aperture in said heat dissipating body fixedly and tightly;

10. A surface mount heat sink apparatus for use with at least one SMT electronic component as recited in claim 9 wherein said solderable feet configured to cooperatively engage a corresponding said circular aperture in said heat dissipating body including partial body of each said foot projects beyond the boundary of said heat dissipating body;

11. A surface mount heat sink apparatus for use with at least one SMT electronic component as recited in claim 1 wherein said fixed and tight connection configured to minimize the thermal resistance of the interfaces between said solderable feet and said heat dissipating body;

12. A surface mount heat sink apparatus for use with at least one SMT electronic component as recited in claim 1 wherein said different materials referring to said heat dissipating body being made of conductive material, like aluminum, and said solderable feet being made of solderable material, like copper;

13. A surface mount heat sink apparatus for use with at least one SMT electronic component; the apparatus comprising:

(a) a heat dissipating body;

(b) a plurality of solderable feet; and

(c) means for joining said solderable feet inside;

said heat dissipating body and said solderable feet being made of different materials and of unitary construction; said solderable feet configured having fixed and tight interface connection with said heat dissipating body; said means for said unitary construction or joining of said heat dissipating body and said solderable feet together being very economical;

14. A surface mount heat sink apparatus for use with at least one SMT electronic component as recited in claim 13 wherein said economical means of joining ensuring tight contact and minimizing the thermal resistance at the interface;

15. A surface mount heat sink apparatus for use with at least one SMT electronic component as recited in claim 13 wherein said economical means including machiningless, weldingless and fixtureless assembly operations;

16. A surface mount heat sink apparatus for use with at least one SMT electronic component as recited in claim 15 wherein said assembly operations including deforming, pressing and swaging, etc. simple mechanical work;

17. A surface mount heat sink apparatus for use with at least one SMT electronic component as recited in claim 15 wherein said assembly operations including taking the advantage of TEC (thermal expansion coefficient) of material properties of the two parts, and using temperature differentials in the assembly operation.