US20040076408A1 - Method and apparatus for removeably coupling a heat rejection device with a heat producing device - Google Patents

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
• 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.[0001]
FIELD OF THE INVENTION
• 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.[0002]
BACKGROUND OF THE INVENTION
• 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.[0003]
• 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.[0004]
• 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.[0005]
• 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.[0006]
• 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.[0007]
• 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.[0008]
• 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.[0009]
SUMMARY OF THE INVENTION
• 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.[0010]
• 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.[0011]
• 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.[0012]
• 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.[0013]
BRIEF DESCRIPTION OF THE DRAWINGS
• FIG. 1A illustrates a Copper heat rejection device attached to the backside of a Silicon chip with a layer of thermal grease in between.[0014]
• 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.[0015]
• 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.[0016]
• 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.[0017]
• 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.[0018]
• FIG. 3A illustrates a schematic of a preferred coupling method in accordance with the present invention.[0019]
• FIG. 3B illustrate a schematic of a preferred coupling method in accordance with the present invention.[0020]
• FIG. 4 illustrates a flow chart describing the method of coupling the heat rejecting device with the heat producing device.[0021]
• FIG. 5 illustrates a flow chart describing the method of removing the heat rejecting device with the heat producing device.[0022]
DETAILED DESCRIPTION OF THE PRESENT INVENTION
• 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.[0023]
• In particular, FIG. 2A shows a[0024]heat producing device100, such as an electronic device that is coupled to acircuit board99 by an array of pins or bumpbonds98. FIG. 2A also illustrates a thin film ofthermal interface102 applied to atop surface101 of theelectronic device100. As shown in FIGS.2A-2B, theheat rejecting device104 or heat rejector is configured to be coupled to theelectronic device100 via thethermal interface102. As stated above, theheat rejector104 is preferably a heat sink which allows heat to transfer from theelectronic device100 through thethermal interface102. Alternatively, theheat rejector104 is any other heat exchanger. Alternatively, theheat rejector104 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, theheat rejector104 is coupled to thethermal interface102, whereby heat produced by theelectronic device100 is transferred by convection and conduction through thethermal interface102 to theheat rejector104.
• The[0025]thermal interface102 is preferably a phase change material, such as solder, whereby an attachlayer103 and thethermal interface102 preferably undergoes a phase change from solid to liquid when a sufficient amount of heat is applied to it. Alternatively, the entirethermal interface102 undergoes a phase change from solid to liquid when a sufficient amount of heat is applied to it. Thethermal interface102 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 thethermal interface102 although any other material which has a small thermal resistance and allows theheat rejector104 to be easily removeable therefrom.
• As shown in FIGS. 2A and 2B, the[0026]heat rejector104 preferably includes a series ofheating elements106 in thebottom surface108 of theheat rejector104. Alternatively, as shown in FIGS. 2A and 2B, theheating element106′ is on theupper surface112 of theheat rejector device104, whereby heat applied from theheating element106′ propagates through theheat rejector device104 to theinterface108. Alternatively, as shown in FIGS. 2A and 2B, theheating element106″ is within theheat rejector device104, whereby heat applied from theheating element106″ propagates through theheat rejector device104 to theinterface108. Alternatively, theheating elements106 are configured within, on thetop surface112, on thebottom surface108, or in any combination thereof, of theheat rejection device104.
• It is preferred that the[0027]heating elements106 are electronic circuits having one or more resistors, such as polysilicon resistors. Alternatively, theheating elements106 are wire heaters. Alternatively, theheating elements106 utilize any other appropriate components which produce an adequate amount of heat, as discussed below. Althoughseveral heating elements106 are shown in FIGS. 2A and 2B, any number ofheating elements106 are contemplated within the present invention.
• In addition, as shown in FIGS.[0028]2-3, theheat rejection device104 includes two electrical contacts orterminals110 on one of its surfaces which allow current to flow to theheating elements106. Theseelectrical contacts110 preferably have a dimension of approximately 100 microns, although othersized contacts110 are contemplated. Theseelectrical contacts110 allow a brief, high-current to flow to theheating element106, whereby theheating element106 generates heat which passes to thethermal interface102. The heating ofheating element106 sufficiently melts or “softens” theinterface material106 without heating the entireelectronic device100. As a result, theheat rejector device102 is able to be coupled to theelectronic device100 without subjecting theelectronic device100 to unacceptable temperatures which may damage the system.
• Alternatively, the[0029]electrical contacts110 are in thebottom surface108 or side surfaces or a combination of surface on theheat rejecting device104, as shown in FIGS.2A-2B. Although only twoelectrical terminals110 are shown in FIGS. 2 and 3, any number of electrical contacts are alternatively present in theheat rejection device104. Theheating elements106 are preferably manufactured into the surface of theheat rejector device104 using standard bonding technology or other semiconductor wafer manufacturing methods which will not be discussed in detail here. In addition, theelectrical contacts110 are manufactured on or in theheat rejector device104 using started deposition and lithography techniques. Alternatively, theelectrical contacts110 are manufactured on or in thedevice104 using screen printing, solder re-flow or any other conventional process known by one skilled in the art.
• To couple the[0030]heat rejection device104 to thethermal interface102 and eventually to theelectronic device100, a current is applied to theheating element106 through theelectrical terminals110. The current causes theheating element106 to heat up to a temperature which is preferably slightly higher than the melting point or phase change temperature of thethermal interface106 material. Alternatively, the temperature of theheating element106 is substantially higher than the phase change temperature of thethermal interface102. Thus, the present invention utilizes theheat rejection device104 as a source of heat which causes theheat rejection device104 to form the engagement with the interface. In addition, the characteristics of thethermal interface104 cause thethermal interface104 to undergo a reverse phase change or “harden” when it is cooled or returns to its equilibrium state. The hardening of thethermal interface104 thereby secures and holds theheat rejection device104 to theheat producing device102.
• In the preferred embodiment, the[0031]heating element106 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 theheater element104 depends on, but is not limited to, the type ofthermal interface material102 used, the amount of thermal interface material between theelectronic device100 andheat rejector104 and the desired strength of the engagement between theelectronic device100 andheat rejector device104. Additionally, the time period of heating the thermal interface depends on, but is not limited to, the type ofthermal interface material102 used between theelectronic device100 andheat rejector104; the amount of current applied to theheater element106; and the heat output capacity of theheater element106. Nonetheless, theheating element106 is heated to the predetermined temperature before theelectronic device100 or thepins99 andcircuit board98 become warm.
• In the preferred embodiment, current is steadily applied to the[0032]heating element106 for an appropriate amount of time, depending on several factors, some of which are discussed above, to heat theheating element106 to slightly above the phase change temperature of theinterface102. Thus, the steadily increasing temperature of theheating element106 is sufficiently large enough to melt the attachlayer103 of theinterface102 without allowing the heat to spread to the underlying package and the surrounding components on thecircuit board99. Alternatively embodiment, current is applied to theheating element106 via theelectrical terminals110, whereby theheating element106 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 theheating element106 is slow enough to heat the attachlayer103 of theinterface102. However, the heat pulse is brief enough and low-enough in total energy that the active regions of theelectronic device100 do not exceed their thermal budget and thereby overheat. It should be noted that the nature of theheat rejection device104 dissipates the heat created by theheating elements106. Thus, the timing of the heating pulse is set such that thethermal interface102 is sufficiently heated to undergo a phase change without theelectronic device100 andheat rejector device104 reaching an excessively high temperature. In other words, the temporal duration of the heating pulse is substantially shorter than the thermal diffusion time from thethermal interface102 to thetop surface101 of theelectronic device100, which is approximately 1 second.
• It is preferred that the[0033]heating elements106 are all heated to the same temperature for the same amount of time. This method causes theinterface material102 to uniformly undergo the phase change across the entire surface of the attachlayer103 of thethermal interface102. Alternatively, theheating elements106 heat the attachlayer103 of theinterface102 in zones, such as quadrants. This alternative method allows theentire interface103 to then be formed incrementally in zones. This alternative method also allows large amount of heat to be applied to a particular zone of theinterface102 in a single pulse, whereby the single pulse of heat has a temperature that is far below the amount that would overheat theelectronic device100.
• 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[0034]tool201 is in electrical contact with theterminals210 on thelower surface208 of theheat rejection device204. Alternatively, as discussed above and shown in FIGS. 2A and 2B, the electrical terminals are positioned on the side and/or top surfaces of theheat rejection device204. In addition, a pair ofspring members208 are shown in FIGS. 3A and 3B, whereby the spring members allow the mountingtool200 to press the heat rejection device212 to thethermal interface202 and theelectronic device200. Similarly, thespring members208 allow the mountingtool201 to easily remove theheat rejection device204 from thethermal interface202 and theelectronic device200, as will be discussed below. It should be noted that the mountingtool201 shown in FIGS. 3A and 3B is only for exemplary purposes and any different type of geometric arrangements of the mountingtool201 to removeably couple theheat rejector device204 to theelectronic device200 is contemplated.
• 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[0035]heat rejector device204 itself, along with theelectrical contacts210 andheating elements206 is manufactured using known methods, as discussed above. Initially, in the preferred method, theelectronic device200 is coupled to thecircuit board99, whereby the array ofpins98 hold theelectronic device200 into the circuit board99 (step300). Alternatively, theelectronic device200 is coupled to thecircuit board99 after thethermal interface202 is applied to theelectronic device200 and theheat rejection device204 is also coupled thereto.
• Following, the[0036]thermal interface202 is preferably applied to the top surface of the electronic device200 (step302). Alternatively, thethermal interface202 is applied to the bottom of theelectronic device200. Alternatively, thethermal interface202 is applied to the top surface and the bottom surfaces, individually or in combination on theheat rejection device204. As stated above, thethermal interface202 is applied to theelectronic device200 using technologies and methods known in the art. Thethermal interface202, preferably solder, is in a solid state and is susceptible to phase change when heated to its phase change temperature.
• Once the[0037]electronic device200 is prepared to engage theheat rejector device204, the external mounting tool201 (FIGS. 3A and 3B) moves theheat rejector device204 to an predetermined position to couple theheat rejector device204 to the electronic device200 (step304). Preferably, the appropriate position of theheat rejector device204 is above theelectronic device200. Alternatively, the appropriate position of theheat rejector device204 is adjacent or below theelectronic device200.
• The mounting[0038]tool201 utilizes apower source220 to move and position theheat rejector device204 as well as engage theheat rejector device204 with thethermal interface202. In addition, the mountingtool201 is coupled to a heatingelement power source224 which supplies a current to theheating element206 via theelectrical contacts208. Theelectrical contacts208 complete the electrical circuit to heat theheating elements206 and thereby engage theheat rejector device204 with theelectronic device200. Alternatively, theelectrical contacts210 are positioned on the top surface or adjacent surface of theheat rejection device204 as discussed above. The heatingelement power source220 is preferably coupled to acontrol circuit222 which activates and controls theheating element206. In addition, thecontrol circuit222 controls the amount of time that theheating element206 is activated as well as whether theheating element206 heats thethermal interface202 gradually or in brief pulses.
• As shown in FIG. 4B, the[0039]electronic device200 is coupled to thecircuit board99 when theheat rejection device204 is removed therefrom. Alternatively, theelectronic device200 is first removed from thecircuit board99 and theheat rejection device204 is removed thereafter. the mountingtool201 positions theheat rejector device204 in contact with the attach layer203 of the thermal interface202 (step306). Power is supplied from the heatingelement power source224 and controlled by thecontrol circuit222, whereby current is supplied to theheating element206 for an appropriate amount of time, depending on the factors discussed above (step308). The current flowing through theheating element206 causes theheating element206 to produce a sufficient amount of heat to raise the temperature of thethermal interface202 to above its phase change temperature (step310). The rise in temperature causes thethermal interface202 to undergo a phase change from a solid to a liquid. However, theheating element206 produces the adequate amount of heat in a brief enough period of time such that the heat does not pass to and thereby damage theelectronic device200,circuit board99 orheat rejector device204. As stated above, the heat produced by theheating element206 may be controlled by thecontroller circuit222 to be a gradual, uniform heating. Alternatively, the heat produced by theheating element206 may be controlled by thecontroller circuit222 to be a brief pulses of a predetermined time duration. In addition, as discussed above, theheating element206 may be configured to heat thethermal interface202 directly or alternatively in quadrants or zones.
• The[0040]heat rejector device204 is then pressed against theelectronic device200 utilizing thesprings208, whereby theheating element206 is at least partially embedded in the thermal interface material202 (step312). Thethermal interface202, after transforming into the liquid or softened state, allows the bottom surface of theheat rejector device204 to be easily pressed into contact with thethermal interface202. After the appropriate amount of time of heating, thecontrol circuit222 terminates supply of current to theheating element206, thereby allowing theheating element206 to cool (step314). The termination of current in effect lowers the temperature of thethermal interface202 below the phase change temperature. As the temperature of thethermal interface202 drops below its phase change temperature, thethermal interface202 undergoes a reverse phase change from a liquid back to a solid, preferably within a matter of seconds (step316). It should be noted that the cool down time period varies depending on the type ofthermal interface202, thickness of thethermal interface202 layer, as well as other factors discussed above. Alternatively, thethermal interface202 rapidly cooled by a fan or other cooling device (not shown).
• Once the[0041]thermal interface202 cools back into the solid state, theheat rejection device204 becomes engaged with and secured to theelectronic device200. The properties of the solid phasethermal interface202 securely hold theheat rejection device204 in place and allows heat to easily transfer from theelectronic device200 to theheat rejection device204 due to the low thermal resistance of thethermal interface202. Thereafter, thetool200 releases theheat rejector device204, whereby the rest of the assembly of the system proceeds (step316).
• The process of removing the[0042]heat rejector device204 from theelectronic device100 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 theheat rejector device104 from theheat producing device200, the mountingtool201 moves and positions itself to engage theheat rejector device204, as shown in FIG. 3B (step400). Once thetool201 engages theheat rejector device104, the electrodes211 on the engaging arms of thetool201 come into contact with theelectrical terminals210 shown on the bottom surface of theheat rejector device204. Power is then supplied to thetool201 from thepower source224, whereby current passes through the electrodes211 to theheating element206 via the electrical terminals110 (step402).
• The current flowing through the[0043]heating element206 causes theheating element206 to produce enough heat to raise the temperature of thethermal interface202 above the phase change temperature (step404). As stated above, the heat produced by theheating element206 may be controlled by thecontroller circuit222 to be a gradual, uniform heating. Alternatively, the heat produced by theheating element206 may be controlled by thecontroller circuit222 to be a brief pulses of a predetermined time duration. In addition, as discussed above, theheating element206 may be configured to heat thethermal interface202 directly or alternatively in quadrants or zones.
• The rise in temperature causes the[0044]thermal interface202 to undergo a phase change from solid to liquid state. However, as stated above, theheating element206 produces enough heat in a brief enough period of time such that the heat minimally passes or does not pass to theelectronic device200 orheat rejector device204. The phase change of thethermal interface202 into the liquid or softened state thereby releases theheat rejector device204 from the secured engagement (step406). The springs shown in FIGS. 3A and 3B along the mounting arms of thetool201 in effect pull theheat rejector device204 from thethermal interface202, thereby disengaging the hearrejector device204 from theelectronic device200. Once theheat rejector device204 is removed from theelectronic device200, theheating element206 is no longer in contact with thethermal interface202. Alternatively, after the appropriate amount of time that thethermal interface102 has become liquid, thecontrol circuit206 terminates supplying the current to theheating element106 and disengages theheat rejector device104 from theelectronic device100. The termination of heat supplied to thethermal interface102 lowers the temperature of thethermal interface102, whereby thethermal interface102 undergoes a phase change from a liquid back to a solid preferably within a matter of seconds (step408).
• 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.[0045]

Claims (36)

What is claimed is:

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 toclaim 1 further comprising positioning the heat rejecting device at a predetermined location with respect to the heat producing device.

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

7. The method according toclaim 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 toclaim 1 wherein the at least one heating element is positioned within the heat rejecting device.

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

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

11. The method according toclaim 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 toclaim 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 toclaim 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 toclaim 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 toclaim 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 toclaim 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 toclaim 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 toclaim 13 wherein the at least one heating element is positioned within the heat rejector device.

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

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

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

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

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

32. The heat rejector device according toclaim 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 toclaim 24 wherein the at least one heating element is positioned within the heat rejector device.

34. The heat rejector device according toclaim 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.

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