MXPA97010344A - Apparatus for heating and cooling an electrical device - Google Patents

Abstract

The present invention relates to a method and apparatus that maintain the operating temperature of an electronic device within an acceptable operating range for a wide range of ambient temperatures. The apparatus includes a thermal collector and a temperature-dependent charging device that carries the thermal collector in thermal contact with the electronic device when the ambient temperature exceeds an ambient level.

Description

Apparatus for heating and cooling an electronic device of the invention The invention relates to regulating the temperature of an electronic device and specifically to heating and cooling an electronic device having a substantially planar upper surface by thermally selectively coupling the electronic device. with a thermal connector and a thermal pad. BACKGROUND PB THE INVEWCIOM Electronic devices, including integrated circuits, must be maintained during operations at a temperature within an operating temperature range specified by the manufacturer of the electronic device, to operate properly. In the case of commercially available integrated circuits, typically the temperature range is between 0 and 70 * Celsius. With electronic device implements in a given system, for example on a printed circuit board within a computer, features must be included to maintain the electronic device at temperatures within the operating range of the electronic device. Typically, because electronic devices produce heat as a by-product of operation, electronic devices must be cooled. Fans and REF: 25047 thermal collectors have been used to cool electronic devices and keep them within the specified operating range. Fans and thermal collectors work when they are deployed in an environment with narrow temperature limits such as the home. However, when the extreme temperatures of the environment can vary widely, devices for regulating the operating temperature of the electronic device must become more complex, and both have to heat and cool the electronic device. Thermal collectors in close contact with the electronic device tend to shift the operating range of the electronic device downwards to a certain ambient temperature. Therefore, with a single thermal collector, both the upper range and the lower range of acceptable ambient temperatures rise in which the electronic device can operate within its operating range, making thermal collectors alone unsuitable for cold environments. Likewise, the fans are inadequate and even more tend to be expensive and tend to fail. SUMMARY OF THE INVENTION In accordance with the present invention, a method and apparatus for maintaining the operating temperature of an electronic device within a range acceptable to the device have been introduced. The apparatus regulates the temperature of an electronic device rigidly connected to a base and includes a thermal collector having a planar surface. A temperature-dependent charging device is connected to the thermal collector and the base and keeps the thermal collector at a distance away from the electronic device. The temperature-dependent charging device forces the thermal collector towards the electronic device as the temperature increases, so that when the temperature exceeds a threshold, the thermal collector thermally contacts the integrated circuit, cooling it in this way. The method regulates the temperature of an electronic device, and includes supporting a thermal collector at a distance away from the integrated circuit, reducing the distance until the thermal collector thermally contacts the electronic device over a threshold temperature, and increasing the height until the collector thermally detaches the electronic device below a threshold temperature. In a preferred method, the electronic device is heated when the temperature falls below a threshold temperature. BRIEF DESCRIPTION DB THE DRAWINGS These and other characteristic objectives and advantages will be more fully appreciated with reference to the accompanying drawings.

Figure 1 illustrates a preferred embodiment showing the thermal collector raised on an electronic device with bi-metallic strips. Figure 2 illustrates one embodiment of Figure 1, wherein the thermal collector 18 has been brought into thermal contact with the electronic device. Figure 3 illustrates an embodiment of the present invention that further comprises a thermal cushion. Figure 4 illustrates elements of the thermal cushion according to a preferred embodiment of the present invention. Figure 5 illustrates an alternative embodiment of the present invention, which further comprises a pin and a spring for controlling the height of the thermal collector on the electronic device. DESCRIPTION OF THE INVENTION A preferred embodiment of the invention is illustrated in Figure 1. An electronic device for example integrated circuit 10, is connected to a base, for example a printed circuit board (PCB) 12. The circuit 10 contains electrical contacts 14 which are coupled to coupling contacts on the PCB 12. Any method of packing the integrated circuit 10 and connecting the integrated circuit 10 to the PCB 12 can be employed, provided that the integrated circuit 10 already has a substantially larger upper surface. planar 16 or thermally coupled to a substantially planar top surface 16. The connection of the integrated circuit 10 to the PCB 12 can be performed directly by techniques including surface mount technology, tilting chip and automated tape joining ( ). Preferably, however, the integrated circuit 10 is connected to a packet which in turn is connected to the PCB 12. Examples of these packets include dual inline packets (DIPS) four-element flat packets, single chip modules and multiple modules chips The PCB 12 includes electrical conductors coupled to the electrical contacts 14 on the PCB that support power and electrical signals that stimulate the integrated circuit 10 to perform its intended function. The PCB 12 may also contain one or more other integrated circuits 10, electronic devices, discrete logic and installation to connect to other printed circuit boards and peripheral devices such as a monitor. As the integrated circuit 10 performs its intended function, it produces heat as a by-product of the electrical processes that occur there. The heat produced by the integrated circuit 10 rises to the integrated circuit temperature 10. The integrated circuit 10 is in thermal contact with the printed circuit board 12 and the air on the substantial upper surface is planar 16. Therefore, the Ambient temperature of PCB 12 temperature affects the integrated circuit temperature 10.

A thermal collector 18 is disposed on the integrated circuit 10. The thermal collector 18 has a finned portion 20 and portions without fins 22. The finned portion 20 includes fins 24 formed integrally with the thermal collector 18, height, width and pitch of the fins 24 are chosen to provide a certain rate of cooling. The fins 24 increase the surface area of the thermal collector and therefore increase the effective thermal transfer to the surrounding air by convection. Thermal collectors of the described variety are well known in the art and are readily available. Figure 1 illustrates the thermal collector 18 having a substantially planar lower surface 26 disposed on the substantially planar upper surface 16 of the integrated circuit 10. In a preferred embodiment of the invention, a thermally conductive compressible material is disposed against the interior surface 26 of the thermal collector 18. This can be implemented with an elastomeric cushion 28 mounted with an adhesive on the lower surface 26 of the thermal collector 18. Preferably, the elastomeric cushion 28 is .127 to .254 mm (5 to 10 mils) in thickness and has a lower surface of 30 with dimensions similar to the upper surface 16 of the integrated circuit 10. The elastomeric cushion 28 compensates for the surface roughness of the thermal collector 18 and the integrated circuit 10, thereby creating better thermal conductivity between the integrated circuit 10 and the thermal collector 18. The thermal collector 18 is kept in place on the integrated circuit by a temperature-dependent charging device. In a preferred embodiment, the temperature dependent charging device is bi-metallic strips 32. Each bi-metal strip 32 has end portions 34 and a curved portion 36 between the end portions 34. The bi-metal strips 32 are connected at the end portions 34 to the lower surface 26 of the thermal collector 18 and to the PCB 12. The connection is preferably made by riveting or by other conventional techniques including welding glue and clamping. Each bi-metallic strip 32 is constituted by strips of two substantially rectangular, thin pieces of different materials that are laminated together. The different materials must have different coefficients of thermal expansion. Bi-metallic strips are well known in the art. The bi-metallic strips 32 are then folded to form the curved portion 36 and the end portions 34. The bi-metallic strips 32 are folded such that the material with the higher coefficient of thermal expansion is outside the portion of the portion. curved 36. As the ambient temperature increases, the outer strip 38 elongates at a higher speed than the inner strip 40, thereby reducing the radius of curvature. On the contrary, as the ambient temperature is lowered, the outer strip 38 shrinks in length at a faster rate than the inner strip 40, thereby reducing the radius of curvature of the curved portion 36. Conform to the radius of curvature of the the curved portion 36 decreases, the height of the thermal collector 18 on the integrated circuit 10 decreases until the foam cushion 28 contacts the upper surface 16 of the integrated circuit 10. The radius of curvature of the bi-metallic strips 32 and the selected materials to implement the individual strips 38 and 40 must be selected such that the thermal collector 13 comes into contact with the integrated circuit 10 when the temperature of the bi-metallic strip 32 exceeds a threshold level. Similarly, the above parameters should be chosen such that the thermal collector 18 is brought out of thermal contact with the integrated circuit 10 below a certain ambient temperature. The bi-metallic strips 32 have static interfaces 42 and 44 to the thermal collector 18 and the PCB 12 respectively. The interfaces 42 and 44 can be made thermally conductive or thermally insulating in order to make the temperature of the bi-metallic tracking strips 32 at the temperature of the thermal collector 18 or the PCB 12. For example, if the interfaces 42 between the thermal collector 18 and the bi-metallic strip 32 become thermally conductive, while the interfaces 44 between the bimetallic strips 32 and the PCB 12 are made thermally insulating, the temperature of the bi-metallic strips 32 It will always tend to be close to the thermal collector 18. If the bi-metallic strip 32 is thermally non-conductive at both interfaces 42 and 44, the bi-metallic strip will tend to track the ambient temperature of the air. Similarly, if the interfaces 42 are made thermally insulating and the interfaces 44 are made thermally conductive, the temperature of the bi-metal strip will tend to track the temperature of the PCB 12. In an alternate embodiment of the invention, a thermally conductive path is created between the interface 46 between the integrated circuit 10 and the PCB 12. In addition, thermally conductive paths were created on the PCB 12 between the interfaces 46 and 44 and at the interface 44 itself. Then, a thermally conductive path is established between the integrated circuit 10 and the bi-metallic strip 32, which will tend to track the temperature of the integrated circuit 10, particularly if the interface 42 becomes thermally insulating. Figure 2 illustrates the embodiment of the invention illustrated in Figure 1, wherein the radius of curvature of the curved portion 36 of the bi-metallic strips 32 has been reduced such that the elastomeric cushion 28 contacts the upper surface 16 of the integrated circuit 10. The ability to selectively bring the thermal collector 18 into thermal contact with the integrated circuit 10 over a threshold temperature extends the range of ambient temperature over which the integrated circuit 10 can operate 10. In particular, the integrated circuit 10 can operate in this configuration at temperatures lower than would be possible when implementing the integrated circuit 10 with a permanently connected thermal collector 18. FIG. 3 illustrates a preferred embodiment of the present invention, which further includes a thermal pad 50 connected to the upper surface 16 of the integrated circuit 10. The thermal pad 10 can be implemented with the heater commercially available and well-known Kapton. In a preferred embodiment of the present invention, the thermal cushion 10 is substantially planar in the X, Y and very thin divisions in the Z dimension, between .127 to .0508 mm (5 to 2.0 mils) and preferably 0.254 mm ( 1 mil) in order to maintain good thermal conductivity through the thermal cushion 50 when the thermal cushion ns heats up. The connection of the thermal pad 50 to the integrated circuit 16 is achieved for example by adhering with a thermally conductive adhesive or resin. The thermal pad 50 illustrated in Figure 4 includes a conductive element 52 circumscribed within an electrically non-conductive material. The conductive element 52 is arranged such that its surface area covers almost the entire area of the X, Y plane of the thermal cushion 50. The mounting of the conductive element 52 for example is a serpentine pattern as illustrated in Figure 4. The element conductor 52 has ends for connection to a temperature sensor 54. In a preferred embodiment of the invention, the temperature sensor 54 is included within the thermal pad 50. However, the temperature sensor 54 can be located remote, including the PCB 12 or in the thermal collector 18. The temperature sensor 54 is coupled to the conductive element 52 and supplies a voltage through the conductive element 52, when the temperature falls below a predetermined threshold, causing current to flow through the conductive element 52. , thus producing resistive heat. The thermal pad 50 therefore supplies heat to the integrated circuit 10 when the ambient temperature is cold in order to boost the integrated circuit temperature 10 and keep it within the operating range of the integrated circuit 10. The electrically non-conductive material 56 wherein the conductor element 52 is found, preferably it is plastic, but it can be any material that conducts heat but is not a good electrical conductor. The electrically non-conductive material can be formed integrally around the conductive element 52, for example using a molding process. Conversely, the electrically non-conductive material 56 may include a pair of substantially planar cushions, each having an inner surface against which the conductive element 52 is disposed. The pair of substantially planar cushions may then be connected together, for example with adhesive, by fusion or by ultrasonic welding. Figure 5 shows an alternative embodiment of the invention, wherein the thermal collector 18 has a hole 60 drilled or formed in a portion without fins 22. A spring 62 has a longitudinal axis and is disposed against the lower surface 26 of the thermal collector 18 The longitudinal axis of spring 62 is substantially co-linear with the central axis of the orifice 60 and the spring 62 is disposed between the thermal collector 18 and the PCB 12. The spring 62 applies compression force to the thermal collector 18 and tends to force the thermal collector 18 away from the upper surface 16 of the integrated circuit 10. A pin 64 has an upper end 68, a lower end 70. The pin 64 is disposed within the hole 60 and the spring 62, such that the pin 64 is substantially co-linear with the center axis of the hole 60 and the longitudinal axis of the spring 62. The lower end 70 and the pin 64 are connected to the PCB 12. The connection is achieved by many techniques including the forming of a hole in the PCB 12 and coating metal between the pin 64 and the hole, or by connecting the processor 64 to a clamp connected to the PCB 12. Connected to the upper end 68 of the pin 64 is an end 34 of a bi-strip -metical 32. The other end 34 of the bi-metallic strip 32 is disposed against the upper surface 72 of the finless portion 22 of the thermal collector 18. In a preferred embodiment of the invention, the upper end 68 terminates a bulbous region. The bi-metallic strip 32 has holes formed in each of the ends 34 and the pin 64 is disposed within the holes of the bimetallic strip 32. The bi-metallic strip 32 exerts force on the upper end 68 of the pin 64 and the upper surface 72 of the thermal collector 18. The inner strip 40 of the bi-metallic strip 32 has a higher coefficient of thermal expansion than the outer strip 38. Therefore, unlike the embodiment illustrated in Figures 1 to 3, according to the temperature increases, the inner strip 40 expands in length faster than the outer strip 38, thereby increasing the radius of the curved portion 36. This causes the bimetallic strip 32 to exert downward force against the upper surface 72 of the thermal collector 18 and tent to compress the spring 62. The materials used to implement the strips 38 and 40 of the bi-metallic strip 32, and the spring constant for the spring 62, should be chosen in a manner Such that over a certain threshold temperature, the lower surface 30 of the elastomeric cushion 28 contacts the upper surface 16 of the integrated circuit 10. On the contrary, as the temperature falls below the threshold temperature, the spring 62 must overcome the force of compression of the bimetallic strip 32 such that the lower surface 30 of the elastomeric cushion 28 moves away from the upper surface 16 of the integrated circuit 10. A range of motion of approximately .254 mm (10 mils) is preferred for the manifold thermal, however the range can be more or less dependent on the application. In a preferred embodiment of a method according to the present invention, a cooling step is performed in the integrated circuit when the ambient temperature exceeds a threshold level. The cooling step is achieved with a thermal collector 18 which is held at a distance away from an integrated circuit 10. When the temperature exceeds a threshold level, the thermal collector 18 is brought into thermal contact with the integrated circuit 10 as illustrated in FIG. 2. This cools the integrated circuit 10 and extends into the ambient temperature range for which the integrated circuit 10 remains within its range of adequate operating temperature. The thermal contact between the thermal collector 18 and the integrated circuit 10 is improved with an elastomeric cushion 28, "which compensates surface roughness of the upper surface 16 of the integrated circuit 10 and the surface roughness of the lower surface 26 of the thermal collector 18 as shown in FIG. illustrated in Figure 1. In an alternate embodiment, the method further includes a heating step. When the temperature falls below a threshold level, heat is applied to the integrated circuit in this manner by raising its temperature and extending the range of ambient temperatures for which the integrated circuit maintains adequate operating temperature. In a preferred embodiment of the invention, the heating is performed by a thermal cushion 50 which is disposed against the upper surface 16 of the integrated circuit 10. The thermal cushion 50 is coupled to a temperature sensor 54 which activates the thermal cushion 50 once that the temperature falls below a threshold level. Although specific embodiments of the present invention have been described, it will be understood by those of ordinary skill in the art that changes can be made to those specific embodiments without departing from the spirit and scope of the invention. It is noted that in relation to this date, the best method known to the applicant to carry out the aforementioned invention, is that which is clear from the present description of the invention.

Having described the invention as above, property is claimed as contained in the following:

Claims (24)

1. CLAIMS 1. An apparatus for regulating the temperature of an electronic device connected to a base, characterized in that it comprises: a thermal collector having a surface; a temperature dependent charging device, connected to a thermal collector, and the base, holding the thermal collector at a distance from the electronic device; and wherein the temperature-dependent charging device forces the thermal collector towards the electronic device as the temperature increases, such that when the temperature exceeds a threshold, the thermal collector thermally contacts the integrated circuit.
2. 2. The apparatus according to claim 1, characterized in that the temperature dependent charging device comprises: at least one bi-metallic strip having a pair of end portions and a curved portion including a radius between the portions of end, one of the end portions is connected to the thermal collector, the other end portion is connected to the base and in this way holds the thermal collector at an integrated circuit distance; and where the radius changes based on the temperature and the distance varies with the radius, such that when the temperature exceeds a threshold, the thermal collector thermally contacts the integrated circuit.
3. 3. - The apparatus according to claim 2, characterized in that the thermal collector includes a portion with fins.
4. 4. The apparatus according to claim 2, characterized in that the base is a printed circuit board.
5. 5. The apparatus in accordance with the claim 2, characterized in that the base is a simple chip module.
6. 6. The apparatus according to claim 2, characterized in that the base is a multi-chip module.
7. 7. The apparatus according to claim 1, characterized in that the electronic device is an integrated circuit.
8. 8. The apparatus in accordance with the claim 1, characterized in that it also comprises a thermally conductive compressible material disposed against the surface of the thermal collector, for thermally contacting the integrated circuit.
9. 9. The apparatus in accordance with the claim 8, characterized in that the thermally conductive compressible material is elastomeric tape.
10. 10. The apparatus in accordance with the claim 1, characterized in that it also comprises a thermal cushion having upper and lower surface, the lower surface is in thermal contact with the integrated circuit; thermostat means, coupled to the thermal cushion that activate the thermal cushion when the temperature falls below a threshold; and wherein the thermal collector thermally contacts the integrated circuit through the thermal pad when the temperature exceeds a threshold.
11. 11. The apparatus in accordance with the claim 10, characterized in that the thermal pad includes: a conductive element coupled to the thermostat means, disposed within the thermal pad that produces resistive heating in response to activation by the thermostat means.
12. 12. The apparatus in accordance with the claim 11, characterized in that the thermal cushion has a thickness in the range of .0127 to .0508 mm (.5 to 2 mils).
13. 13. Apparatus that regulates the temperature of an integrated circuit rigidly connected to a base, characterized in that it comprises: a thermal collector having upper and lower surfaces, the upper surface includes a portion with fins and a portion without fins, the portion without fins includes a hole extending from the upper surface to the lower surface; a spring having a central axis disposed between the thermal collector and the base; a pin having upper and lower ends, the lower end is connected to the base and the pin extends through the central axis of the spring and the hole in the thermal collector; and a bi-metallic strip having a pair of end portions and a curved portion having a radius between the end portions, one of the end portions being connected to the upper surface of the thermal collector, the other end portion being connects to the upper end of the pin, the bi-metallic strip and the spring in this way holds the thermal collector at a distance from the integrated circuit; and wherein the radius changes based on the temperature and the distance varies with the radius, such that when the temperature exceeds a threshold, the bi-metallic strip acts to compress the spring and the thermal collector thermally contacts the integrated circuit.
14. 14. Method for regulating the temperature of an electronic device, characterized in that it comprises the steps of: supporting a thermal collector at a distance from an electronic device; reduce the distance until the thermal collector thermally contacts the electronic device over a threshold temperature; and increasing the distance until the thermal collector thermally detaches the electronic device below a threshold temperature.
15. 15. The method according to claim 14, characterized in that the electronic device is rigidly connected to a base.
16. 16. - The method according to claim 14, characterized in that an elastomeric cushion facilitates thermal contact between the thermal collector and the electronic device.
17. 17.- The method according to the claim 14, characterized in that it further comprises the step of: heating the electronic device when the temperature falls below a threshold.
18. 18. The method according to claim 17, characterized in that the electronic device includes a substantially planar upper surface; and the heating step is performed by a thermal pad in thermal contact with the upper surface of the electronic device.
19. 19. The method according to claim 14, characterized in that the electronic device is an integrated circuit.
20. 20. The method according to claim 14, characterized in that the support stage is carried out by a bi-metallic strip at a first temperature; the reduction step occurs in response to heating the bi-metallic strip to a second temperature greater than the first temperature; and the step of increasing occurs in response to cooling the bimetallic strip to a third temperature lower than the second temperature.
21. 21. - The method according to claim 20, characterized in that the bi-metallic strip is thermally insulated from the base.
22. 22. The method according to claim 20, characterized in that the bi-metallic strip is thermally isolated from the thermal collector.
23. 23. The method according to claim 20, characterized in that the bi-metallic strip is thermally coupled to the electronic device.
24. 24.- The method of compliance with the claim 23, characterized in that the bi-metallic strip is thermally decoupled from the thermal collector.