Method and apparatus for removeably coupling a heat rejection device with a heat producing device

Abstract

A method and apparatus for removeably coupling a heat rejecting device with a heat producing device, wherein a thermal interface material having a predetermined phase change temperature is between the heat rejecting device and the heat producing device, the method comprising: configuring the heat rejecting device to include at least one heating element; and energizing the at least one heating element for a predetermined amount of time through at least one electrical contact, wherein a current applied to the at least one heating element heats the at least one heating element until the thermal interface material substantially reaches the predetermined phase change temperature. The at least one heating element is located on an interface surface in contact with the thermal interface material, although alternatively on an opposite surface, or within the apparatus.

Description

RELATED APPLICATION

[0001] This Patent Application claims priority under 35 U.S.C. 119 (e) of the co-pending U.S. Provisional Patent Application, Serial No. 60/420,557 filed Oct. 22, 2002, and entitled “VAPOR ESCAPE MICROCHANNEL HEAT EXCHANGER WITH SELF ATTACHMENT MEANS”. The Provisional Patent Application, Serial No. 60/420,557 filed Oct. 22, 2002, and entitled “VAPOR ESCAPE MICROCHANNEL HEAT EXCHANGER WITH SELF ATTACHMENT MEANS” is also hereby incorporated by reference.

FIELD OF THE INVENTION

[0002] The invention relates to a method and apparatus for attaching and detaching two or more devices to one another in general, and specifically, to a method and apparatus for removeably coupling a heat rejection device to a heat producing device.

BACKGROUND OF THE INVENTION

[0003] High power integrated circuits have evolved in recent years towards ever increasing transistor density and clock speed. The result of this trend is a rapid increase in the power and heat density of modern microprocessors and an emerging need for new cooling technologies. One aspect of this problem is addressed by the development of novel heat rejection devices or structures including, but not limited to heat pipes, fin-arrays with fans or microchannel liquid coolers. All of these structures are efficient at transporting the heat to some remote location. In all of these cases, heat is deposited in a liquid, solid or gas medium and that medium provides transport of the heat by conduction or convection.

[0004] A more fundamental aspect of this problem relates to the transfer of the heat from an electronic device through a coupling thermal interface into the heat rejection device. A schematic of this configuration is illustrated in FIG. 1A. The thermal interface between the heat rejection device and the heat producing electronic device is a critical layer in this overall system. In particular, the interface's characteristics can place severe limits on the overall performance of the system, regardless of the heat removing capabilities of the heat rejection device or structure. Typically, thermal interfaces include a thin film of material that is positioned between contacting surfaces of the heat producing device and the heat rejection structure, whereby the heat producing device and the heat rejection structure may or may not be made of the same material having a same thermal expansion coefficient.

[0005] There are cases in which the heat producing device and the heat rejection structure are made of different materials and thus have different thermal expansion coefficients. One example is where the heat producing device is made from Silicon and the heat rejection device is made from Copper. In these cases where the heat rejection structure has a different thermal expansion coefficient than the electronic device, the thermal interface material must be able to maintain contact and allow shear between both of the surfaces. Thermal greases are often used in such applications, as the grease is “liquid” and can be sheared without losing contact with either surface. In addition, the thermal grease has a high viscosity such that the surfaces of the heat producing device and heat rejection device do not separate or slide laterally when the heat producing device is operating. FIGS. 1A and 1B illustrate a Copper heat rejection device attached to the backside of a Silicon chip with a layer of thermal grease in between. As shown in FIG. 1B, the copper is heated and expands due to the temperature being produced from the Silicon chip. Since Copper has a larger thermal expansion coefficient than Silicon, the thermal grease in between the chip and the rejection device allows the heat rejection device to expand without exerting force on the Silicon, as shown in FIG. 1B.

[0006] In addition, it is possible to engineer a high performance heat rejection structure that has a thermal expansion coefficient which matches the heat producing device. Both structures having the same thermal expansion coefficient allows thermal interface material to be used, whereby the thermal interface material does not shear. Examples of these thermal attaches such as thin, solid adhesives, include, but are not limited to metal layers, eutectic, solder and direct fusion bonding. The thermal resistance of these thin solid layers is lower than thermal grease. In addition, the thermal resistance for metal attaches can be significantly lower than thermal grease.

[0007] However, use of a thin, solid adhesive between the Silicon device and the Copper heat rejection device causes the Copper-Silicon sandwich to curl due to the thermal expansion coefficient mismatch between the Silicon heat producing device and the Copper heat rejection device. This is shown in FIG. 1C. As shown in FIG. 1C, the differential thermal expansion between the Copper heat rejection device and the Silicon chip results in a bimetal bending that causes some of the bumpbonds between the Silicon chip and the circuit board to fail.

[0008] An issue with using a metal, eutectic, or fusion bond between the Silicon heat producing device and the metal-type heat rejection device is the high temperature needed to form the bond between the two devices. Melting the metal or the eutectic thermal interface requires temperatures that exceed the thermal limitations of the electronic device or its supporting package. This is a reason that a eutectic or solder bond is not in wide use as a thermal interface attach between an electronic device and a heat rejection device, despite the performance advantages of such an interface. In addition, melting the metal thermal interface renders the thermal interface between the heat producing device and the heat rejecting device to be permanent and non-reworkable. Thus, use of a metal or eutectic as a thermal attach is not currently a preferred material in the industry for applications requiring repeated removal and attachment of a heat rejecting device to a heat producing device.

[0009] What is needed is a method and apparatus for easily coupling a heat rejection device with a heat producing electronic device having a thermal interface therebetween, whereby the thermal interface has a very low thermal resistance. What is also needed is a method and apparatus for enabling a heat rejection device to be removeably coupled with a heat producing electronic device, whereby the heat rejection device is reworkable and can be easily removed from the electronic device using high heating temperatures without damaging the electronic device or the packaging and surrounding electronics.

SUMMARY OF THE INVENTION

[0010] In one aspect of the invention, a method of removeably coupling a heat rejecting device to a heat producing device comprising configuring at least one heating element. The method including applying a thermal interface material between the heat rejecting device and the heat producing device. The thermal interface material is configured to allow engagement and disengagement of the heat rejecting device therewith above a predetermined temperature. The method includes applying a current to the heating element, via at least one electrical contact, for a predetermined amount of time, wherein the heating element heats the thermal interface material above the predetermined temperature. The method further comprises positioning the heat rejecting device at a predetermined location with respect to the heat producing device. The thermal interface material undergoes a phase change between a first temperature below the predetermined temperature and a second temperature above the predetermined temperature. Engagement between the heat rejecting device with the heat producing device further comprises pressing the heat rejecting device and the thermal interface material against one another until the temperature of the thermal interface material is substantially at the first temperature. Disengagement of the heat rejecting device with the heat producing device further comprises removing the heat rejecting device and the thermal interface material against one another when the temperature of the thermal interface material is substantially at the second temperature. The at least one heating element is located on an interface surface in contact with the thermal interface material, although alternatively on an opposite surface, or within the apparatus. The heating element heats the thermal interface material in predetermined zone locations. The heating element applies heat to the thermal interface material in a substantially uniform manner. The heating element applies heat to the thermal interface material by a plurality of heat pulses, each heat pulse being of a predetermined time duration.

[0011] In another aspect of the invention, a heat rejector device is coupled to an interface material. The heat rejector device is secured to the interface material in a first phase state and is configured to be removeable from the interface material in a second phase state. The heat rejector device comprises at least one heating element which applies a predetermined amount of heat to the interface material such that the interface material undergoes a phase change from the first phase state to the second phase state in response to the predetermined amount of heat applied thereto by the heating element. The thermal interface material undergoes a phase change between a first temperature, which is below the predetermined temperature, and a second temperature, which is above the predetermined temperature. The thermal interface material engages the heat rejecting device by being pressed against the heat rejecting device until the thermal interface material reaches to the first temperature. The thermal interface material disengages the heat rejecting device by removing the heat rejecting device and the thermal interface material from one another when the thermal interface material is at the second temperature. The at least one heating element is configured to be in contact with the thermal interface material, although the at least one heating element is alternatively positioned on a surface of the heat rejector device opposite of the thermal interface material or within the heat rejector device. The at least one heating element heats the thermal interface material in predetermined zone locations, in a substantially uniform manner or by a plurality of heat pulses, whereby each heat pulse is of a predetermined time duration. The heat rejector device further comprises at least one electrical contact positioned on a predetermined surface, wherein the current is applied through the at least one electrical contact.

[0012] In another aspect of the invention, an assembly for removeably coupling a heat rejecting device to a heat producing device, wherein a thermal interface material having a predetermined phase change temperature is applied between the heat rejecting device and the heat producing device. The assembly comprises means for holding an interface surface of the heat rejecting device in contact with the thermal interface material, wherein at least one heating element configured on the interface surface is in contact with the thermal interface material. The assembly comprises means for energizing the heating element for a predetermined amount of time, wherein the at least one heating element transforms the thermal interface material to undergo a phase change the thermal interface material substantially reaches the predetermined phase change temperature. The interface material is in the first phase state when it is below a predetermined phase change temperature. The interface material is in the second phase state when it is above the predetermined phase change temperature. The interface material undergoes the phase change between the first phase state and the second phase state within an appropriate amount of time. The at least one heating element heats the interface material in predetermined zone locations, in a substantially uniform manner, and/or a plurality of heat pulses, each heat pulse is of a predetermined time duration. The at least one heating element is configured to be in contact with the interface material, positioned on a surface of the heat rejector device opposite of the interface material, or positioned within the heat rejector device. The heat rejector device including at least one electrical contact positioned on a predetermined surface, wherein the current is applied through the at least one electrical contact.

[0013] In another aspect of the invention, a method of removeably coupling a heat rejecting device with a heat producing device, wherein a thermal interface material having a predetermined phase change temperature is applied between the heat rejecting device and the heat producing device. The method comprising: configuring the heat rejecting device to include at least one heating element. The method comprises energizing the heating element for a predetermined amount of time, wherein a current applied to the heating element heats the heating element until the surface of the thermal interface material substantially reaches the predetermined phase change temperature.

BRIEF DESCRIPTION OF THE DRAWINGS

[0014] FIG. 1A illustrates a Copper heat rejection device attached to the backside of a Silicon chip with a layer of thermal grease in between.

[0015] FIG. 1B illustrates a Copper heat rejection device attached to the backside of a Silicon chip with a layer of thermal grease in between and expanding due to heating.

[0016] FIG. 1C illustrates a Copper heat rejection device attached to the backside of a Silicon chip with a layer of thermal grease in between and undergoing bi-metal bending.

[0017] FIG. 2A illustrates a general schematic of a heat rejector device separated from a heat producing device in accordance with the preferred embodiment of the present invention.

[0018] FIG. 2B illustrates a general schematic of a heat rejector device coupled to a heat producing device in accordance with the preferred embodiment of the present invention.

[0019] FIG. 3A illustrates a schematic of a preferred coupling method in accordance with the present invention.

[0020] FIG. 3B illustrate a schematic of a preferred coupling method in accordance with the present invention.

[0021] FIG. 4 illustrates a flow chart describing the method of coupling the heat rejecting device with the heat producing device.

[0022] FIG. 5 illustrates a flow chart describing the method of removing the heat rejecting device with the heat producing device.

DETAILED DESCRIPTION OF THE PRESENT INVENTION

[0023] FIG. 2A illustrates a general schematic of a heat rejector device separated from a heat producing device in accordance with the preferred embodiment of the present invention. FIG. 2B illustrates a general schematic of a heat rejector device coupled to a heat producing device in accordance with the preferred embodiment of the present invention.

[0024] In particular, FIG. 2A shows a heat producing device 100, such as an electronic device that is coupled to a circuit board 99 by an array of pins or bumpbonds98. FIG. 2A also illustrates a thin film of thermal interface 102 applied to a top surface 101 of the electronic device 100. As shown in FIGS. 2A-2B, the heat rejecting device 104 or heat rejector is configured to be coupled to the electronic device 100 via the thermal interface 102. As stated above, the heat rejector 104 is preferably a heat sink which allows heat to transfer from the electronic device 100 through the thermal interface 102. Alternatively, the heat rejector 104 is any other heat exchanger. Alternatively, the heat rejector 104 is a vapor escape heat exchanger described in co-pending U.S. patent application Ser. No. ______ filed ______ and entitled “______” which is hereby incorporated by reference. As shown in FIG. 2A, the heat rejector 104 is coupled to the thermal interface 102, whereby heat produced by the electronic device 100 is transferred by convection and conduction through the thermal interface 102 to the heat rejector 104.

[0025] The thermal interface 102 is preferably a phase change material, such as solder, whereby an attach layer 103 and the thermal interface 102 preferably undergoes a phase change from solid to liquid when a sufficient amount of heat is applied to it. Alternatively, the entire thermal interface 102 undergoes a phase change from solid to liquid when a sufficient amount of heat is applied to it. The thermal interface 102 has small thermal resistance and allows shear without undergoing bilateral bending. For exemplary purposes, solder is referred to in the present description in relation to the thermal interface 102 although any other material which has a small thermal resistance and allows the heat rejector 104 to be easily removeable therefrom.

[0026] As shown in FIGS. 2A and 2B, the heat rejector 104 preferably includes a series of heating elements 106 in the bottom surface 108 of the heat rejector 104. Alternatively, as shown in FIGS. 2A and 2B, the heating element 106′ is on the upper surface 112 of the heat rejector device 104, whereby heat applied from the heating element 106′ propagates through the heat rejector device 104 to the interface 108. Alternatively, as shown in FIGS. 2A and 2B, the heating element 106″ is within the heat rejector device 104, whereby heat applied from the heating element 106″ propagates through the heat rejector device 104 to the interface 108. Alternatively, the heating elements 106 are configured within, on the top surface 112, on the bottom surface 108, or in any combination thereof, of the heat rejection device 104.

[0027] It is preferred that the heating elements 106 are electronic circuits having one or more resistors, such as polysilicon resistors. Alternatively, the heating elements 106 are wire heaters. Alternatively, the heating elements 106 utilize any other appropriate components which produce an adequate amount of heat, as discussed below. Although several heating elements 106 are shown in FIGS. 2A and 2B, any number of heating elements 106 are contemplated within the present invention.

[0028] In addition, as shown in FIGS. 2-3, the heat rejection device 104 includes two electrical contacts or terminals 110 on one of its surfaces which allow current to flow to the heating elements 106. These electrical contacts 110 preferably have a dimension of approximately 100 microns, although other sized contacts 110 are contemplated. These electrical contacts 110 allow a brief, high-current to flow to the heating element 106, whereby the heating element 106 generates heat which passes to the thermal interface 102. The heating of heating element 106 sufficiently melts or “softens” the interface material 106 without heating the entire electronic device 100. As a result, the heat rejector device 102 is able to be coupled to the electronic device 100 without subjecting the electronic device 100 to unacceptable temperatures which may damage the system.

[0029] Alternatively, the electrical contacts 110 are in the bottom surface 108 or side surfaces or a combination of surface on the heat rejecting device 104, as shown in FIGS. 2A-2B. Although only two electrical terminals 110 are shown in FIGS. 2 and 3, any number of electrical contacts are alternatively present in the heat rejection device 104. The heating elements 106 are preferably manufactured into the surface of the heat rejector device 104 using standard bonding technology or other semiconductor wafer manufacturing methods which will not be discussed in detail here. In addition, the electrical contacts 110 are manufactured on or in the heat rejector device 104 using started deposition and lithography techniques. Alternatively, the electrical contacts 110 are manufactured on or in the device 104 using screen printing, solder re-flow or any other conventional process known by one skilled in the art.

[0030] To couple the heat rejection device 104 to the thermal interface 102 and eventually to the electronic device 100, a current is applied to the heating element 106 through the electrical terminals 110. The current causes the heating element 106 to heat up to a temperature which is preferably slightly higher than the melting point or phase change temperature of the thermal interface 106 material. Alternatively, the temperature of the heating element 106 is substantially higher than the phase change temperature of the thermal interface 102. Thus, the present invention utilizes the heat rejection device 104 as a source of heat which causes the heat rejection device 104 to form the engagement with the interface. In addition, the characteristics of the thermal interface 104 cause the thermal interface 104 to undergo a reverse phase change or “harden” when it is cooled or returns to its equilibrium state. The hardening of the thermal interface 104 thereby secures and holds the heat rejection device 104 to the heat producing device 102.

[0031] In the preferred embodiment, the heating element 106 is heated to a predetermined temperature for a time period of a few microseconds to a few minutes, depending on a variety of factors. The temperature output required from the heater element 104 depends on, but is not limited to, the type of thermal interface material 102 used, the amount of thermal interface material between the electronic device 100 and heat rejector 104 and the desired strength of the engagement between the electronic device 100 and heat rejector device 104. Additionally, the time period of heating the thermal interface depends on, but is not limited to, the type of thermal interface material 102 used between the electronic device 100 and heat rejector 104; the amount of current applied to the heater element 106; and the heat output capacity of the heater element 106. Nonetheless, the heating element 106 is heated to the predetermined temperature before the electronic device 100 or the pins 99 and circuit board 98 become warm.

[0032] In the preferred embodiment, current is steadily applied to the heating element 106 for an appropriate amount of time, depending on several factors, some of which are discussed above, to heat the heating element 106 to slightly above the phase change temperature of the interface 102. Thus, the steadily increasing temperature of the heating element 106 is sufficiently large enough to melt the attach layer 103 of the interface 102 without allowing the heat to spread to the underlying package and the surrounding components on the circuit board 99. Alternatively embodiment, current is applied to the heating element 106 via the electrical terminals 110, whereby the heating element 106 is heat pulsed for a very brief time, ranging from a few microseconds to a few seconds, depending on the factors discussed above. In this embodiment, the heat pulse from the heating element 106 is slow enough to heat the attach layer 103 of the interface 102. However, the heat pulse is brief enough and low-enough in total energy that the active regions of the electronic device 100 do not exceed their thermal budget and thereby overheat. It should be noted that the nature of the heat rejection device 104 dissipates the heat created by the heating elements 106. Thus, the timing of the heating pulse is set such that the thermal interface 102 is sufficiently heated to undergo a phase change without the electronic device 100 and heat rejector device 104 reaching an excessively high temperature. In other words, the temporal duration of the heating pulse is substantially shorter than the thermal diffusion time from the thermal interface 102 to the top surface 101 of the electronic device 100, which is approximately 1 second.

[0033] It is preferred that the heating elements 106 are all heated to the same temperature for the same amount of time. This method causes the interface material 102 to uniformly undergo the phase change across the entire surface of the attach layer 103 of the thermal interface 102. Alternatively, the heating elements 106 heat the attach layer 103 of the interface 102 in zones, such as quadrants. This alternative method allows the entire interface 103 to then be formed incrementally in zones. This alternative method also allows large amount of heat to be applied to a particular zone of the interface 102 in a single pulse, whereby the single pulse of heat has a temperature that is far below the amount that would overheat the electronic device 100.

[0034] The process of coupling the heat rejector device with the electronic device will now be discussed in detail. FIGS. 3A and 3B illustrate a schematic of a preferred coupling method in accordance with the present invention. As shown in FIGS. 3A and 3B, a mounting tool 201 is in electrical contact with the terminals 210 on the lower surface 208 of the heat rejection device 204. Alternatively, as discussed above and shown in FIGS. 2A and 2B, the electrical terminals are positioned on the side and/or top surfaces of the heat rejection device 204. In addition, a pair of spring members 208 are shown in FIGS. 3A and 3B, whereby the spring members allow the mounting tool 200 to press the heat rejection device 212 to the thermal interface 202 and the electronic device 200. Similarly, the spring members 208 allow the mounting tool 201 to easily remove the heat rejection device 204 from the thermal interface 202 and the electronic device 200, as will be discussed below. It should be noted that the mounting tool 201 shown in FIGS. 3A and 3B is only for exemplary purposes and any different type of geometric arrangements of the mounting tool 201 to removeably couple the heat rejector device 204 to the electronic device 200 is contemplated.

[0035] FIG. 4 illustrates a flow chart of the coupling method discussed in relation to FIGS. 3A and 3B according to the preferred embodiment of the present invention. The heat rejector device 204 itself, along with the electrical contacts 210 and heating elements 206 is manufactured using known methods, as discussed above. Initially, in the preferred method, the electronic device 200 is coupled to the circuit board 99, whereby the array of pins 98 hold the electronic device 200 into the circuit board 99 (step 300). Alternatively, the electronic device 200 is coupled to the circuit board 99 after the thermal interface 202 is applied to the electronic device 200 and the heat rejection device 204 is also coupled thereto.

[0036] Following, the thermal interface 202 is preferably applied to the top surface of the electronic device 200 (step 302). Alternatively, the thermal interface 202 is applied to the bottom of the electronic device 200. Alternatively, the thermal interface 202 is applied to the top surface and the bottom surfaces, individually or in combination on the heat rejection device 204. As stated above, the thermal interface 202 is applied to the electronic device 200 using technologies and methods known in the art. The thermal interface 202, preferably solder, is in a solid state and is susceptible to phase change when heated to its phase change temperature.

[0037] Once the electronic device 200 is prepared to engage the heat rejector device 204, the external mounting tool 201 (FIGS. 3A and 3B) moves the heat rejector device 204 to an predetermined position to couple the heat rejector device 204 to the electronic device 200 (step 304). Preferably, the appropriate position of the heat rejector device 204 is above the electronic device 200. Alternatively, the appropriate position of the heat rejector device 204 is adjacent or below the electronic device 200.

[0038] The mounting tool 201 utilizes a power source 220 to move and position the heat rejector device 204 as well as engage the heat rejector device 204 with the thermal interface 202. In addition, the mounting tool 201 is coupled to a heating element power source 224 which supplies a current to the heating element 206 via the electrical contacts 208. The electrical contacts 208 complete the electrical circuit to heat the heating elements 206 and thereby engage the heat rejector device 204 with the electronic device 200. Alternatively, the electrical contacts 210 are positioned on the top surface or adjacent surface of the heat rejection device 204 as discussed above. The heating element power source 220 is preferably coupled to a control circuit 222 which activates and controls the heating element 206. In addition, the control circuit 222 controls the amount of time that the heating element 206 is activated as well as whether the heating element 206 heats the thermal interface 202 gradually or in brief pulses.

[0039] As shown in FIG. 4B, the electronic device 200 is coupled to the circuit board 99 when the heat rejection device 204 is removed therefrom. Alternatively, the electronic device 200 is first removed from the circuit board 99 and the heat rejection device 204 is removed thereafter. the mounting tool 201 positions the heat rejector device 204 in contact with the attach layer 203 of the thermal interface 202 (step 306). Power is supplied from the heating element power source 224 and controlled by the control circuit 222, whereby current is supplied to the heating element 206 for an appropriate amount of time, depending on the factors discussed above (step 308). The current flowing through the heating element 206 causes the heating element 206 to produce a sufficient amount of heat to raise the temperature of the thermal interface 202 to above its phase change temperature (step 310). The rise in temperature causes the thermal interface 202 to undergo a phase change from a solid to a liquid. However, the heating element 206 produces the adequate amount of heat in a brief enough period of time such that the heat does not pass to and thereby damage the electronic device 200, circuit board 99 or heat rejector device 204. As stated above, the heat produced by the heating element 206 may be controlled by the controller circuit 222 to be a gradual, uniform heating. Alternatively, the heat produced by the heating element 206 may be controlled by the controller circuit 222 to be a brief pulses of a predetermined time duration. In addition, as discussed above, the heating element 206 may be configured to heat the thermal interface 202 directly or alternatively in quadrants or zones.

[0040] The heat rejector device 204 is then pressed against the electronic device 200 utilizing the springs 208, whereby the heating element 206 is at least partially embedded in the thermal interface material 202 (step 312). The thermal interface 202, after transforming into the liquid or softened state, allows the bottom surface of the heat rejector device 204 to be easily pressed into contact with the thermal interface 202. After the appropriate amount of time of heating, the control circuit 222 terminates supply of current to the heating element 206, thereby allowing the heating element 206 to cool (step 314). The termination of current in effect lowers the temperature of the thermal interface 202 below the phase change temperature. As the temperature of the thermal interface 202 drops below its phase change temperature, the thermal interface 202 undergoes a reverse phase change from a liquid back to a solid, preferably within a matter of seconds (step 316). It should be noted that the cool down time period varies depending on the type of thermal interface 202, thickness of the thermal interface 202 layer, as well as other factors discussed above. Alternatively, the thermal interface 202 rapidly cooled by a fan or other cooling device (not shown).

[0041] Once the thermal interface 202 cools back into the solid state, the heat rejection device 204 becomes engaged with and secured to the electronic device 200. The properties of the solid phase thermal interface 202 securely hold the heat rejection device 204 in place and allows heat to easily transfer from the electronic device 200 to the heat rejection device 204 due to the low thermal resistance of the thermal interface 202. Thereafter, the tool 200 releases the heat rejector device 204, whereby the rest of the assembly of the system proceeds (step 316).

[0042] The process of removing the heat rejector device 204 from the electronic device 100 will now be discussed. FIG. 5 illustrates a flow chart of the removal method discussed in relation to FIGS. 3A and 3B according to the preferred embodiment of the present invention. To remove the heat rejector device 104 from the heat producing device 200, the mounting tool 201 moves and positions itself to engage the heat rejector device 204, as shown in FIG. 3B (step 400). Once the tool 201 engages the heat rejector device 104, the electrodes 211 on the engaging arms of the tool 201 come into contact with the electrical terminals 210 shown on the bottom surface of the heat rejector device 204. Power is then supplied to the tool 201 from the power source 224, whereby current passes through the electrodes 211 to the heating element 206 via the electrical terminals 110 (step 402).

[0043] The current flowing through the heating element 206 causes the heating element 206 to produce enough heat to raise the temperature of the thermal interface 202 above the phase change temperature (step 404). As stated above, the heat produced by the heating element 206 may be controlled by the controller circuit 222 to be a gradual, uniform heating. Alternatively, the heat produced by the heating element 206 may be controlled by the controller circuit 222 to be a brief pulses of a predetermined time duration. In addition, as discussed above, the heating element 206 may be configured to heat the thermal interface 202 directly or alternatively in quadrants or zones.

[0044] The rise in temperature causes the thermal interface 202 to undergo a phase change from solid to liquid state. However, as stated above, the heating element 206 produces enough heat in a brief enough period of time such that the heat minimally passes or does not pass to the electronic device 200 or heat rejector device 204. The phase change of the thermal interface 202 into the liquid or softened state thereby releases the heat rejector device 204 from the secured engagement (step 406). The springs shown in FIGS. 3A and 3B along the mounting arms of the tool 201 in effect pull the heat rejector device 204 from the thermal interface 202, thereby disengaging the hear rejector device 204 from the electronic device 200. Once the heat rejector device 204 is removed from the electronic device 200, the heating element 206 is no longer in contact with the thermal interface 202. Alternatively, after the appropriate amount of time that the thermal interface 102 has become liquid, the control circuit 206 terminates supplying the current to the heating element 106 and disengages the heat rejector device 104 from the electronic device 100. The termination of heat supplied to the thermal interface 102 lowers the temperature of the thermal interface 102, whereby the thermal interface 102 undergoes a phase change from a liquid back to a solid preferably within a matter of seconds (step 408).

[0045] The present invention has been described in terms of specific embodiments incorporating details to facilitate the understanding of the principles of construction and operation of the invention. Such reference herein to specific embodiments and details thereof is not intended to limit the scope of the claims appended hereto. It will be apparent to those skilled in the art that modification s may be made in the embodiment chosen for illustration without departing from the spirit and scope of the invention.

Claims

1. A method of removeably coupling a heat rejecting device to a heat producing device comprising:

a. configuring the heat rejecting device to include at least one heating element;

b. applying a thermal interface material to an interface surface of the heat producing device, a first surface of the heating rejecting device in contact with the thermal interface material, the thermal interface material configured to allow engagement and disengagement of the heat rejecting device above a predetermined temperature; and

c. applying a current to the at least one heating element for a predetermined amount of time, wherein the at least one heating element heats the thermal interface material above the predetermined temperature.

2. The method according to claim 1 further comprising positioning the heat rejecting device at a predetermined location with respect to the heat producing device.

3. The method according to claim 1 wherein the thermal interface material undergoes a phase change between a first temperature below the predetermined temperature and a second temperature above the predetermined temperature.

4. The method according to claim 3 wherein engagement of the heat rejecting device with the heat producing device further comprises pressing the heat rejecting device and the thermal interface material against one another until the temperature of the thermal interface material is substantially at the first temperature.

5. The method according to claim 3 wherein disengagement of the heat rejecting device with the heat producing device further comprises removing the heat rejecting device and the thermal interface material against one another when the temperature of the thermal interface material is substantially at the second temperature.

6. The method according to claim 1 wherein the at least one heating element is positioned on the first surface of the heat rejecting device.

7. The method according to claim 1 wherein the at least one heating element is positioned on a heat rejecting device surface opposite of the first surface of the heat rejecting device.

8. The method according to claim 1 wherein the at least one heating element is positioned within the heat rejecting device.

9. The method according to claim 1 wherein the at least one heating element heats the thermal interface material in predetermined zone locations.

10. The method according to claim 1 wherein the at least one heating element applies heat to the thermal interface material in a substantially uniform manner.

11. The method according to claim 1 wherein the at least one heating element applies heat to the thermal interface material by a plurality of heat pulses, each heat pulse being of a predetermined time duration.

12. The method according to claim 1 further comprising configuring the heat rejecting device to include at least one electrical contact positioned on a predetermined surface, wherein the current is applied through the at least one electrical contact.

13. A heat rejector device configured to be removeably coupled to a thermal interface material, the thermal interface material configurable to engage and disengage the heat rejector device above a predetermined temperature, the heat rejector device comprising at least one heating element, wherein a current applied to the at least one heating element for a predetermined amount of time produces an adequate amount of heat in the at least one heating element to heat the thermal interface material above the predetermined temperature.

14. The heat rejector device according to claim 13 wherein the thermal interface material undergoes a phase change between a first temperature below the predetermined temperature and a second temperature above the predetermined temperature.

15. The heat rejector device according to claim 14 wherein the thermal interface material engages the heat rejecting device by being pressed against the heat rejecting device until the thermal interface material reaches to the first temperature.

16. The heat rejector device according to claim 14 wherein the thermal interface material disengages the heat rejecting device by removing the heat rejecting device and the thermal interface material from one another when the thermal interface material is at the second temperature.

17. The heat rejector device according to claim 13, wherein the at least one heating element is configured to be in contact with the thermal interface material.

18. The heat rejector device according to claim 13 wherein the at least one heating element is positioned on a surface of the heat rejector device opposite of the thermal interface material.

19. The heat rejector device according to claim 13 wherein the at least one heating element is positioned within the heat rejector device.

20. The heat rejector device according to claim 13 wherein the at least one heating element heats the thermal interface material in predetermined zone locations.

21. The heat rejector device according to claim 13 wherein the at least one heating element applies heat to the thermal interface material in a substantially uniform manner.

22. The heat rejector device according to claim 13 wherein the at least one heating element applies heat to the thermal interface material by a plurality of heat pulses, each heat pulse being of a predetermined time duration.

23. The heat rejector device according to claim 13 further comprising at least one electrical contact positioned on a predetermined surface, wherein the current is applied through the at least one electrical contact.

24. A heat rejector device coupled to an interface material, wherein the heat rejector device is secured to the interface material in a first phase state and configured to be removeable from the interface material in a second phase state, the heat rejector device comprising at least one heating element for applying a predetermined amount of heat to the interface material such that the interface material undergoes a phase change from the first phase state to the second phase state in response to the predetermined amount of heat applied thereto by the at least one heating element.

25. The heat rejector device according to claim 24 wherein the interface material is in the first phase state when below a predetermined phase change temperature.

26. The heat rejector device according to claim 25 wherein the interface material is in the second phase state when above the predetermined phase change temperature.

27. The heat rejector device according to claim 24 wherein the interface material undergoes the phase change between the first phase state and the second phase state within an appropriate amount of time.

28. The heat rejector device according to claim 24 wherein the at least one heating element heats the interface material in predetermined zone locations.

29. The heat rejector device according to claim 24 wherein the at least one heating element applies heat to the interface material in a substantially uniform manner.

30. The heat rejector device according to claim 24 wherein the at least one heating element applies heat to the interface material by a plurality of heat pulses, each heat pulse being of a predetermined time duration.

31. The heat rejector device according to claim 24 wherein the at least one heating element is configured to be in contact with the interface material.

32. The heat rejector device according to claim 24 wherein the at least one heating element is positioned on a surface of the heat rejector device opposite of the interface material.

33. The heat rejector device according to claim 24 wherein the at least one heating element is positioned within the heat rejector device.

34. The heat rejector device according to claim 24 further comprising at least one electrical contact positioned on a predetermined surface, wherein the current is applied through the at least one electrical contact.

35. An assembly for removeably coupling a heat rejecting device to a heat producing device, wherein a thermal interface material having a predetermined phase change temperature is applied between the heat rejecting device and the heat producing device, the assembly comprising:

a. means for holding an interface surface of the heat rejecting device in contact with the thermal interface material, wherein at least one heating element configured on the interface surface is in contact with the thermal interface material; and

b. means for energizing the at least one heating element for a predetermined amount of time, wherein the at least one heating element transforms the thermal interface material to undergo a phase change the thermal interface material substantially reaches the predetermined phase change temperature.

36. A method of removeably coupling a heat rejecting device with a heat producing device, wherein a thermal interface material having a predetermined phase change temperature is between the heat rejecting device and the heat producing device, the method comprising:

a. configuring the heat rejecting device to include at least one heating element; and

b. energizing the at least one heating element for a predetermined amount of time, wherein a current applied to the at least one heating element heats the at least one heating element until the thermal interface material substantially reaches the predetermined phase change temperature.