JPS6310583B2 - - Google Patents

Description

Claim 1: A plurality of spaced turns, each of said turns having an upper turn of a predetermined length and a relatively short length of turns by a pair of legs. a wire form exhibiting an open T-shaped configuration connected to a lower turn; and a retaining plate formed as a frame-like member with a central opening, said wire form being connected to an upper part of said turn and A lower turn is disposed within the central opening such that a lower turn extends outwardly from each opposing flat surface of the retention plate, and a leg of each turn is adjacent to the central opening of the retention plate. A heat exchange device for an integrated circuit package, wherein the wire mold is attached to the retaining plate so as to form an integral unit.

2. The heat exchange device defined in claim 1, wherein the wire type is a continuous wire of a predetermined length in the shape of a helical coil.

3. The heat exchange device defined in claim 2, wherein the holding plate is a substantially flat rectangular member.

4. The heat exchange device as defined in claim 3, wherein the legs of each of the windings are in contact with edges of two opposing legs of the holding plate adjacent to the central opening. , the edges include a plurality of homogeneous spaced incisions each receiving a leg of the turns, the incisions establishing a spacing between the turns.

5. A heat exchange device as defined in claim 4, wherein each of the lower turns connects the leg of one turn with the opposite leg of the next following turn.

6. The heat exchange device defined in claim 5, wherein the lower winding portion of the wire type is inclined with respect to the upper winding portion,
The upper turn generally conforms to the shape of the retaining plate, and the lower turn is adapted to be attached to a surface of the integrated circuit package during operation of the integrated circuit package.

7. A heat exchange device as defined in claim 6, wherein the upper winding of the wire type has a plurality of windings parallel to the air flow in which the device is arranged to function. It is further characterized in that it appears as spaced cylindrical members.

8. A heat exchange device as defined in claim 7, wherein the respective external surfaces of both the upper and lower turns of the wire form are each parallel to the flat surface of the retaining plate. It is further characterized in that it lies within a plane.

9. A heat exchange device as defined in claim 8, wherein both the wire mold and the holding plate are made of copper.

BACKGROUND OF THE INVENTION An essential requirement for the operation of integrated circuits is the transfer of heat generated by the integrated circuit chip from the package itself to the external environment. The problem of heat dissipation is particularly severe in high density packaging applications where the volume allocation for the heat exchange medium is extremely limited.

Commonly used heat exchange or heat sink devices for integrated circuit packages result from protrusions, asperities, and machined parts formed into various shapes or configurations. However, due to size and volume limitations, none of these methods of manufacturing results in a device that provides the maximum effective cooling area for a given volume. The criteria just described are the most important factors in the performance of any heat exchanger. The heat transfer coefficient factor is related to the effective cooling area of the device. To reiterate here, the device described above does not maximize this property. It is clear that the heat transferred from the package to the surroundings must overcome the thermal resistance of the heat exchanger itself. The largest component of the total resistance offered by a heat exchange device is called the membrane resistance, which is inversely proportional to the surface area of the device. In other words, membrane resistance is the reciprocal of the product of effective surface area and convective heat transfer coefficient. By maximizing the latter factor, the membrane resistance of the heat exchanger is reduced.

The device of the present invention accomplishes the above with a simple, economical, and volume efficient construction.

SUMMARY OF THE INVENTION In accordance with the present invention, a heat exchange device is provided for attachment to the carrier or package of an integrated circuit chip for dissipating heat generated by the chip during circuit operation. The heat exchange device of this invention consists of two basic parts: a wire type and a metal frame retaining plate,
These parts are assembled and joined together to form an integral unit.

In the actual operational embodiment of this device, the wire form consisted of a length of continuous wire shaped into a helical coil with spaced surrounds or turns. Each turn is an open “T”
similar to , with the upper turn connected to a relatively short lower turn by a pair of legs;
These correspond to the horizontal top, vertical sides and horizontal base of the "T", respectively.

The retaining plate is a generally rectangular frame-like member having a plurality of spaced notches or notches along the edges on two sides of its central opening. The periphery of this plate forms a cross section that approximates the volume assigned to this heat exchanger.

In assembling the device, the wire mold is inserted into the opening in the retaining plate. The above-mentioned upper winding part stands up straight and is located above the surface of the retaining plate, while the leg part of this winding is received by the notch. The lower turn functions as a connecting member, connecting the leg of one turn with the opposite leg of the next successive turn. The lower turns therefore exhibit an oblique shape relative to the upper turns, which are oriented in a rectangular manner that matches the shape of the retaining plate. This plate provides both the desired spacing and great stiffness for the coil turns. The wire mold and retaining plate are then joined together by a suitable method such as reflow soldering, dip soldering or spot welding.
As will be explained in more detail below, the retaining plate also serves to enhance the thermal efficiency of the wire mold.

The heat exchanger of the present invention provides significant advantages over commonly used heat exchange media. Thus, its low profile and negligible dimensions make it useful in high density packaging applications. It provides maximum surface area and convective heat transfer coefficient for a given volume. Furthermore, it minimizes restricting air flow in forced air systems and is bidirectional thereto. Also, it can be easily attached to integrated circuit packages, minimizing thermal stresses imposed on the latter as a result of processing and other thermal changes.

Other features and advantages of the heat exchanger of this invention are:
It will become clearer in the detailed description below.

[Brief explanation of the drawing]

FIG. 1 is a plan view of the heat exchanger of the present invention.

FIG. 2 is an end view of the heat exchanger of FIG. 1 shown attached to an integrated circuit package.

3 is a pictorial diagram clearly illustrating a portion of the heat exchanger of FIG. 1; FIG.

DESCRIPTION OF THE PREFERRED EMBODIMENTS Because of the close relationship of the drawings and the relative simplicity of the heat exchanger 10 of the present invention, the following description will refer generally to FIGS. 2 and 3 at the same time. Particular reference should be made to FIG.

The device 10 consists of two parts: a wire mold 12 and a retaining plate 14. In an actual operational example, the wire form 12 consisted of a length of continuous wire shaped into a coil having a plurality of spaced turns. As seen in particular in FIG. 2, each turn of the coil presents a low sided open "T" shape, where the upper turn portion 12a is separated by the lower turn portion 12a of relatively short length.
c by a pair of legs 12b.

The retaining plate 14 is a rectangular, metallic, frame-like member having a plurality of homogeneous spaced incisions 16 along the edges of each of the two opposite sides of the central opening 18 thereof. . The periphery of the plate 14 forms a cross-section approximately equal to the volume occupied by this heat exchanger.

As best seen in FIGS. 2 and 3, the heat exchange device 10 opens the openings 18 in the plate 14 while maintaining the longitudinal axis of its wire form 12 parallel to the planar surface of the plate 14. It is assembled into the retaining plate 14 by inserting the lower wound portion 12c therethrough. The upper winding portion 12a is then supported by a retaining plate 14,
On the other hand, the leg 12b is placed within the notch 16.
It is clear that the notches 16 serve to maintain the spacing of the coils from each other. As seen in particular in FIGS. 1 and 3, the lower winding portion 1
2c act as connecting members, each connecting the leg of one turn with the opposite leg of the next succeeding turn. Therefore, the lower winding portion 12c exhibits a shape that is inclined with respect to the upper winding portion 12a. As seen in FIG. 2, the respective external surfaces of both upper and lower wound portions 12a and 12c are flattened into a flat (as opposed to arcuate) shape. The last-mentioned surfaces are therefore each in a plane parallel to the plane of the holding plate 14. Wire form 12 and retaining plate 14 are then joined together by any suitable method such as reflow soldering, dip soldering, or spot welding. Holding plate 1
4 provides greater rigidity to the wire mold 12.

FIG. 2 shows the heat exchange device 10 of the present invention in a simplified manner mounted on an integrated circuit package 20. FIG. The integrated circuit package 20 includes:
Typically formed from ceramic, it includes a cavity 22 into which a chip 24 is mounted. A metallized element 26 is shown bonded to the exterior surface of package 20. In practice, the element 26 is fitted within the ceramic surface. In either case, element 26
extends across the entire surface of the package or is located near the chip 24.

The heat exchange device 10 includes a metallized element 2
6. This is accomplished by joining the lower turned portion 12c of the wire form 12 to the element 26 by soldering or using a thermally conductive adhesive. The heat generated by the tip 24 is transferred to the lower turned portion 12c of the wire form 12.
and via the legs 12b to the retaining plate 14, which facilitates distributing its heat to all of the upper turns 12a, thereby improving the volume conduction of the device 10. It has been found that while the heat exchange device 10 interfaces with large areas of metallization, it causes minimal thermal stress on the package as a result of processing and other temperature changes.

The heat exchange device 10 of the invention is particularly suitable for forced air cooling, where the upper turns 12a of the wire form 12 offer only a small resistance to air flow. When air passes through a heat exchanger having a substantially flat surface, such as in known protruded, textured, or machined devices, a boundary layer influences the degree of heat dissipation at the heat exchange surface. It should be noted that it is produced next to . In contrast, the upper turn 12a of the wire form 12 of the device of the invention appears as a collection of parallel spaced cylindrical members. The device of this invention is bidirectional with respect to the direction of air flow, but the air flow is wire-type
Optimal results appear when parallel to the two coil axes. This is true since elements of circular cross-section, transverse to the direction of air flow, create a turbulence effect behind each of these elements, thereby improving heat transfer conditions. In short, this turbulence destroys the boundary layer effect mentioned earlier and increases the convective heat transfer coefficient.

In conclusion, it is recognized that the heat exchanger disclosed herein provides a low cost, simple and highly efficient means of heat dissipation in the form of a high density integrated circuit package. The inventive concept described herein is applicable to various fields of application. In the actual operational situation, a copper wire with a diameter of 0.042 inches was used for the wire mold, while the copper retaining plate was 0.80 parallel inches and had a thickness of 0.032 inches. The total height of the heat exchanger was 0.27 inches. It should be understood that in other applications, changes or modifications to the parameters described above may be necessary to suit specific requirements. Such variations are within the skill of the designer and do not depart from the true scope and spirit of this invention.
It is intended to be covered by the following claims.