Abstract:
A metal thermal interface structure for dissipating heat from electronic components comprised a heat spreader lid, metal alloy that is liquid over the operating temperature range of the electronic component, and design features to promote long-term reliability and high thermal performance.

Description:
[0001]     The present application is a continuation-in-part of, and claims priority from, U.S. patent application Ser. No. 11/004,107, filed Dec. 3, 2004, and still pending. 
     
    
     TECHNICAL FIELD  
       [0002]     This invention relates to the field of heat transfer structures between electronic components and their associated heat exchangers and, more particularly, to a thermal interface system which utilizes a metal alloy interface, materials and design features to stabilize the alloy while exposed to various environmental conditions.  
       BACKGROUND OF THE INVENTION  
       [0003]     Today&#39;s electronic components generate significant amounts of heat which must be removed to maintain the component&#39;s junction temperature within safe operating limits. Failure to effectively conduct away heat leaves these devices at high operating temperatures, resulting in decreased performance and reliability and ultimately failure.  
         [0004]     The heat removal process involves heat conduction between the electronic component and heat exchanger, or heat sink, via a thermal interface material. Small irregularities and surface asperities on both the component and heat sink surfaces create air gaps and therefore increase the resistance to the flow of heat. The thermal resistance of the interface between these two surfaces can be reduced by providing an interface material which fills the air gaps and voids in the surfaces.  
         [0005]     An ideal medium for transferring heat from one surface to another should have low interfacial or contact thermal resistance, high bulk thermal conductivity and the ability to achieve a minimum bond-line thickness. Additional desirable qualities include product stability, ease of deployment, product reworkability, low cost and non-toxicity.  
         [0006]     Liquids have low interfacial resistance because they wet a surface forming a continuous contact with a large area. Most liquids do not, however, have very high conductivity. Solids, and in particular metals, have very high conductivity but high interfacial resistance. Most common heat transfer materials combine highly conductive particles with a liquid or plastic in order to exploit both characteristics. Examples of the former are greases and gels while the latter include filled epoxies, silicones and acrylics.  
         [0007]     Greases have been developed with thermal conductivities significantly better than the corresponding conductivities of filled adhesives. Typical problems with greases include pumping and dry out, both of which can cause the conducting medium to lose contact with one or both of the heat transfer surfaces. Pumping occurs when the structure is deformed, due to differential thermal expansion or mechanical loads, and the grease is extruded. The oils contained in a grease can be depleted by evaporation or by separation and capillary flow.  
         [0008]     Liquid metal alloys (liquid at the operating temperature of the electronic component), such as alloys of bismuth, gallium and indium, potentially offer both low interfacial resistance and high conductivity. Several alloys of gallium with very low melting points have also been identified as potential liquid metal interface materials. Thermal performance of such an interface would be more than one order of magnitude greater than many adhesives typically in use.  
         [0009]     Although liquid metal alloys offer both low interfacial resistance and high conductivity, they have historically suffered from various reliability issues including corrosion/oxidation, intermetallic formation, drip-out, dewetting, and migration. Unless mitigated, these mechanisms will continue to degrade the interface, resulting in a thermally related catastrophic failure of the actual electronic component.  
         [0010]     The ability to contain an electrically conductive liquid within an electronic package presents significant challenges. The liquid must be reliably retained in the thermal interface throughout the life of the package if shorting is to be avoided and effective resistance is to be minimized. To solve the problems of liquid metal migration, various seal and gasket mechanisms have been disclosed.  
         [0011]     Although, these various mechanisms mitigate liquid metal migration, some disclosures include elastomeric or polymeric components in the thermal path which is thermally undesirable. Other disclosures include various seals which increase the bondline thickness (BLT) of the liquid metal, thereby, increasing the bulk thermal resistance of the interface. These elastomeric components are not hermetic and therefore do not prevent air or moisture from entering the thermal joint.  
         [0012]     In addition, corrosion will propagate through the thermal interface should any air gaps be present. Surface asperities of the heat source and heat exchanger increase the potential for voids. This is further exacerbated when the metal changes between the liquid and the solid state within the temperature range of the package.  
         [0013]     U.S. Pat. No. 5,323,294 and 5,572,404, granted to Layton, et al. on Jun. 21, 1994 and Nov. 5, 1996, respectively, and U.S. Pat. No. 5,561,590, granted to Norell, et al. on Oct. 1, 1996 disclose a heat transfer module in which a compliant, absorbent body containing liquid metal is surrounded by a seal, said body is spaced apart from the seal area. As the module is clamped between a heat source and heat exchanger, liquid metal is squeezed out of the porous structure to fully fill the space within the seal area.  
         [0014]     U.S. Pat. No. 4,915,167, granted to Altoz, et al. on Apr. 10, 1990 discloses a low melting point thermal interface material which is contained between the heat source and heat exchanger by applying a sealant to completely encapsulate the exposed interface material.  
         [0015]     U.S. Pat. Nos. 6,761,928, 6,617,517, 6,372,997, granted to Hill, et al. on Jul. 13, 2004, Sep. 9, 2003, and Apr. 16, 2002, respectively, and U.S. Pat. No. 6,940,721, granted to Hill on Sep. 6, 2005 disclose a low melting point alloy coating both sides of a surface enhanced metallic foil, thereby providing a carrier to support and contain the liquid metal alloy. The low melt alloy on the foil carrier, placed between a heat source and heat exchanger, will become molten during the operational temperatures of the heat source.  
         [0016]     U.S. Pat. No. 6,849,941, granted to Hill, et al. on Feb. 1, 2005 discloses a liquid metal interface material in which the material is bonded (in solid form) to a solid base member and includes a sealing material set into a annular groove (within the base member) surrounding the periphery of the bonded interface.  
         [0017]     U.S. Pat. No. 6,037,658, granted to Brodsky, et al. on Mar. 14, 2000 discloses a heat transfer surface in which a thermally conductive fluid is contained by both an absorbent medium and a seal to inhibit migration.  
         [0018]     U.S. Pat. No. 6,016,006, granted to Kolman, et al. on Jan. 18, 2000 discloses a method for applying thermal interface grease between an integrated circuit device and a cover plate in which a seal encloses the region of the device. Thermal grease is injected into the cavity region via an inlet port in the cover plate thereby filling the interface between device and plate.  
         [0019]     U.S. Pat. No. 5,909,056, granted to Mertol on Jun. 1, 1999 discloses a thermal interface structure in which a phase change thermal interface material is contained within a protrusion on a heat spreader and a dam ring, which is attached to the backside of a semiconductor chip.  
         [0020]     U.S. Pat. No. 6,891,259, granted to Im, et al. on May 10, 2005 and U.S. patent application No. 20030085475, filed by Im, et al. on Oct. 10, 2002 disclose a semiconductor package in which a dam substantially surrounds the thermal interface material. The package lid includes injection holes for the dispensation of the dam and interface material.  
         [0021]     U.S. Pat. No. 6,292,362, granted to O&#39;Neal, et al. on Sep. 18, 2001 discloses a thermal interface material module in which a flowable interface material is deposited in the center opening of a picture-frame carrier and a gasket is mounted to the carrier. With the application of heat, the reservoir area between the interface material and gasket is filled.  
         [0022]     U.S. Pat. No. 6,097,602, granted to Witchger on Aug. 1, 2000 discloses a thermal interface structure in which a phase change interface material is surrounded by a fabric carrier dike structure. The dike is adhesively attached to both the electronic circuit package and heat sink, thereby preventing interface material from migrating from the joint.  
         [0023]     U.S. Pat. Nos. 6,281,573 and 6,656,770, granted to Atwood, et al. on Aug. 28, 2001 and Dec. 2, 2003, respectively, disclose both a solder-based seal (between the ceramic cap/heat exchanger and package substrate) and an elastomeric gasket (between the ceramic cap/heat exchanger and chip) to “near hermetically” seal the cavity containing a Gallium alloy liquid metal interface material and thereby limit oxidation and migration.  
         [0024]     U.S. Pat. No. 6,665,186, granted to Calmidi, et al. on Dec. 16, 2003 discloses a liquid metal interface material held in place by a flexible seal, such as an O-ring, which also accommodates expansion and contraction of the liquid. The seal also allows for air venting and filling of liquid metal.  
         [0025]     U.S. patent application No. 20030173051, filed by Rinella, et al. on Mar. 12, 2002 discloses a method of forming a thermal interface in which a semi-solid metal, injected through an inlet on a heat spreader plate, fills the gap between a die and the cavity formed in the heat spreader plate.  
         [0026]     U.S. patent application No. 20030183909, filed by Chiu on Mar. 27, 2002 discloses a method of forming a thermal interface in which a thermal interface material is dispensed through and inlet in a heat spreader in order to fill the interface between the spreader and the chip.  
         [0027]     U.S. patent application No. 20040262766, filed by Houle on Jun. 27, 2003 discloses a liquid metal interface contained within a cold-formed o-ring barrier positioned directly on the chip. Once the barrier is established between the heat spreader and chip, liquid metal is introduced into the interface via a channel in the spreader.  
         [0028]     U.S. patent application No. 20050073816, filed by Hill on Jan. 7, 2004 discloses a liquid metal interface assembly in which an o-ring or shim sealing member surrounds the liquid metal interface material to shield the interface from the atmosphere.  
         [0029]      FIGS. 1 through 3  show various methods of forming a void-free, high thermal performance thermal interface within electronic assemblies  100 .  FIG. 1A  illustrates an electronic assembly  100  comprised of a thermal interface structure  102  positioned between a heat spreader lid  104  and electronic component  106 , which is comprised of an IC chip  108 , package substrate  110  and electrical interconnection vias  112 . The interface structure  102  is comprised of a metallic core  120  encapsulated by a metallic interface composition  122 . An adhesive layer  114  bonds the heat spreader lid  104  to the electronic component package substrate  110 . It can be seen in  FIG. 1B  that the lid  104  has now been mounted to the package substrate  110  with an adhesive layer  114  located on the lid flange  116 . During operation of the electronic component  106 , the resultant heat will cause excess metallic interface composition  122  to flow out of the thermal interface, thereby creating a fillet outside the IC chip perimeter. Unfortunately, oxidation, present on the surface of the metallic interface  122  prior to heating and flowing, creates a “skin” and prohibits filling of the surface asperities present on the lid  104  and IC chip  108 .  FIG. 1   c,  a magnified sectional view of  FIGS. 1   a  and  1   b,  illustrates the resultant air gaps  123  due to the layer of oxidation  125  inhibiting flow of interface material. The non-hermetic interface allows oxygen and moisture to penetrate into these air gaps  123  and continue oxidation/corrosion of the metallic interface composition 122  within the interface between chip  108  and lid  104 .  
         [0030]     Within  FIG. 2 , it can be seen that a metallic thermal interface composition is injected (by a dispenser  124 ) through a hole  126  in the heat spreader lid  104  to yield a filled thermal interface joint  128 . Without a barrier or seal, interface material would have the tendency to migrate out of the joint. The use of a seal will promote full filling of the thermal joint as well. Additionally, the hole  126 , filled with the interface composition would certainly possess lower thermal conductivity than the typical materials (copper, aluminum) comprising heat spreader lids.  
         [0031]      FIG. 3 , similar to  FIG. 2 , illustrates an electronic assembly  100  comprised of a thermal interface structure  130  sandwiched between an IC chip  108  and heat spreader lid  104 . The lid  104  includes at least one gas permeable plug  132  located within holes  134  in the lid  104 . A barrier or seal  136  is placed near the perimeter of the IC chip  108 , thereby creating a seal and space between the lid  104  and IC chip  108 . Liquid interface material  138  is injected into the holes  134  in the lid  104 , thereby filling the space comprising the thermal interface joint. Should the barrier be of polymeric composition, heat transfer would be reduced near the perimeter of the chip. A metallic barrier would require a bonding and hermetic seal in order for the gas permeable plugs to be effective. Barrier bonding may induce unwanted stresses between the IC chip  108  and the lid  104 . Additionally, the holes  134  in the lid would also created undesirable thermal impedance between the chip  108  and lid  104 .  
       SUMMARY OF THE INVENTION  
       [0032]     Accordingly, it is the overall feature of the present invention to provide an improved thermal interface system in order to more effectively transfer thermal energy from an electronic component to a heat exchange structure.  
         [0033]     An additional feature of the present invention is to provide an improved metal thermal interface system which is liquid over the operating temperature of the electronic component, thereby minimizing the stresses placed on the electronic component by the heat exchange structure.  
         [0034]     Yet, another feature of the present invention is to provide a corrosion resistant interface system in which the metallic interface composition flows and fills the surface asperities on both the electronic component and heat exchanger thereby sealing the interface from moisture and oxygen.  
         [0035]     A further feature of the present invention is to provide an improved metal thermal interface system which includes materials and design features, such as moisture seals, encapsulants, desiccants and corrosion inhibitors, to promote long-term stability and reliability by mitigating corrosion.  
         [0036]     Still another feature of the present invention is to provide an improved metal thermal interface system which includes barrier structures to preclude metal interface migration and preserve high heat transfer.  
         [0037]     One additional feature of the present invention is to provide a metallic interface composition including oxygen gettering elements to promote wetting to oxide layers present on the surface of the electronic component chip and heat exchanger.  
         [0038]     Lastly, it is a feature of the present invention to combine all of these unique design aspects and individual fabrication techniques into effective and manufacturable thermal interface system for electronic components, including Flip Chip integrated circuit (IC) packages. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0039]      FIGS. 1   a  through  1   c,  sectional views, illustrate an electronic assembly including a foil-based thermal interface structure deployed between an IC chip and heat spreader lid, as known in the art.  
         [0040]      FIG. 2 , a sectional view, illustrates an electronic assembly in which thermal interface material is injected through a hole in the heat spreader lid, as known in the art.  
         [0041]      FIG. 3 , a sectional view, illustrates an electronic assembly in which thermal interface material is added though a vent to fill the space inside of a barrier formed between the IC chip and lid, as known in the art.  
         [0042]      FIGS. 4   a  through  4   d,  sectional views, illustrate the sequence of flowing, filling, and sealing of metallic interface material within a thermal interface joint of the present invention.  
         [0043]      FIGS. 5   a  and  5   b,  sectional views, illustrate another sealing embodiment of the present invention.  
         [0044]      FIGS. 6   a  and  6   b,  an isometric and sectional view, respectively, illustrate a metallic interface composition formed as a metallic seal in the present invention.  
         [0045]      FIGS. 7   a  and  7   b,  an isometric and sectional view, respectively, illustrate a coating layer encapsulating the metallic interface composition in all faces with the exception of the inner perimeter within the present invention.  
         [0046]      FIG. 8 , a sectional view, illustrates another embodiment of the present invention in which the coating layer forms a border around the metallic seal outer perimeter.  
         [0047]      FIGS. 9A and 9B , an isometric and sectional view, respectively, illustrate the coating layers partially encapsulating the top and bottom faces of the metallic seal.  
         [0048]      FIGS. 10A and 10B , an isometric and sectional view, respectively, illustrate another embodiment of the present invention including a solid metallic core disposed within the metallic interface composition.  
         [0049]      FIG. 11 , a sectional view, illustrates another solid metallic core embodiment of the present invention.  
         [0050]      FIG. 12 , a sectional view, illustrates diffusion and wetting layers deposited on the metallic core in the present invention.  
         [0051]      FIG. 13 , an isometric view, illustrates an embodiment of the present invention in which an additional metallic interface composition island is added within the inner perimeter of the metallic seal.  
         [0052]      FIG. 14 , a sectional view, illustrates an electronic assembly, including one interface material structure embodiment of the present invention, in which the cavity of the heat spreader lid includes a corrosion inhibiting structure.  
         [0053]      FIG. 15 , a sectional view, illustrates one interface material structure embodiment of the present invention adhesively attached to the heat spreader lid.  
         [0054]      FIG. 16 , a sectional view, illustrates one interface material structure embodiment of the present invention between an IC chip and heat sink.  
         [0055]      FIG. 17 , a sectional view, illustrates one interface material structure embodiment of the present invention positioned between an IC chip and heat spreader lid and between the lid and heat sink. 
     
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0056]     Described below are several embodiments of the present invention which illustrate various ways the present invention can be implemented. In the descriptions that follow, like numerals represent like numerals in all figures. For example, where the numeral  100  is used to refer to a particular element in one figure, the numeral  100  appearing in any other figure refers to the same element.  
         [0057]      FIGS. 4   a  through  4   d  illustrate a sequence of the present invention in which the thermal interface structure  140  flows and fills the space between the electronic component and heat exchanger to yield a highly conductive and hermetic thermal interface joint. An electronic assembly  100  includes a heat exchanger  104  (depicted as a heat spreader lid), a thermal interface structure  140  positioned between the lid  104  and an electronic component  106 . The component  106  is comprised of an IC chip  108 , package substrate  110  and electrical interconnection vias  112 .  
         [0058]     Within  FIG. 4   a,  a thermal interface structure  140  includes a metallic seal member  142  (comprised of an inner and outer perimeter) which is positioned near the perimeter of the IC chip  108  and is comprised of a metallic interface composition. A coating layer  144  encapsulates the metallic seal member on all faces with the exception of the inner perimeter of the member  142 . The coating layer  144  may be of metallic or polymeric composition. The interface structure  140 , when disposed between the lid  104  and IC chip  108 , creates an interface space  146  between the electronic component and heat spreader and a seal to each of their respective surfaces. With the application of heat (from the electronic component  106  or external source), the metallic seal member  142  will flow (flow arrows  148 ) into the space  146  and fill all the surface asperities of both heat spreader lid and IC chip.  
         [0059]      FIG. 4   b  illustrates the melting and flowing of the metallic interface composition comprising the metallic seal member  142 . Pressure applied external to the lid  104  or the weight of the heat exchanger  104  also promotes the flowing of the melting metallic seal member  142  and filling of the interface space  146 . As the seal member  142  continues to melt, the space  146  between the lid  104  and IC chip  108  is reduced in volume.  
         [0060]     As seen in  FIG. 4   c,  the interface space  146  between the lid  104  and IC chip  108  has been fully filled with the metallic interface composition, comprising the metallic seal member  142 . The coating layer  144  assists in containing the flowing interface composition within the perimeter of the metallic seal member  142 . Due to the collapse of the metallic seal member  142  during melting, the adhesive layer  114 , applied to the heat spreader lid  104  at the outer lid flange  116  and package substrate  110 , is now bonded to the electronic component package substrate  110 . Seal materials include silicones, polysulphides, polyurethanes, polyimides, polyesters, epoxides, cyanate esters, olefins and sealing glasses. A continuous seal between the heat spreader lid flange  116  and package substrate  110  greatly reduces the amount of moisture ingression within the lid cavity, resulting in reduced film formation and corrosion on the thermal interface structure  140 .  
         [0061]      FIG. 4   d,  a magnified view of  FIGS. 4   a  through  4   c,  illustrates the filling of surface asperities  152  present on the IC chip  108  and heat spreader lid  104 .  
         [0062]     The metallic interface composition (comprising the metallic seal member  142 ) may be comprised of the metallic elements of bismuth, gallium, indium and tin and their alloys.  
         [0063]     It is desirable for the composition to be liquid over the operating temperature of the electronic component. This allows the metal to adequately flow into all surface asperities of the heat spreader lid  104  and IC chip  108 .  
         [0064]     In another embodiment of the present invention, “reactive” elements or intrinsic oxygen gettering elements are added to the metallic interface composition to further facilitate wetting to the lid  104  and IC chip  108 . The resulting composition has a higher affinity for surface oxides and promotes oxide to oxide bonding, thereby reducing the thermal impedance at the lid  104  and chip  108  contact interfaces. Oxygen getter elements include alkali metals (Li, Na, and K), alkaline-earth metals (Mg and Ca), zinc, refractory metals (Ti, Zr, Hf, Ta, V, and Nb), rare earth metals (La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy and Yb), and mixtures and alloys thereof.  
         [0065]     Within  FIGS. 5   a  and  5   b,  another thermal interface structure of the present invention is illustrated as a sequence of interface formation.  
         [0066]      FIG. 5   a,  a similar electronic assembly structure  100  to  FIGS. 4   a - 4   c,  includes a thermal interface structure  150  comprised of a metallic seal member  142  (comprised of a metallic interface composition) with an inner and outer perimeter. A coating layer  144  is shown surrounding the outer perimeter of the metallic seal member  142 .  
         [0067]      FIG. 5   b  illustrates the fully flowed thermal interface structure  150  in which the interface space  146  between the IC chip  108  and lid  104  has been filled with the metallic interface composition comprising the metallic seal member  142 .  
         [0068]      FIGS. 6A  (an isometric view) and  6 B (a sectional view of  FIG. 6   a  on lines  6 B- 6 B) illustrate a thermal interface structure  139  comprised of a metallic seal member  142  (comprised of a metallic interface composition) and inner perimeter  143  (and therefore outer perimeter) seen in  FIGS. 4   a  through  4   c  and  FIGS. 5   a  and  5   b.    
         [0069]     The thermal interface structure  140  of  FIGS. 7A  (an isometric view) and  7 B (a sectional view of  FIG. 7   a  on lines  7 B- 7 B) includes a metallic seal member  142  and inner perimeter  143 ; however, a coating layer  144  encapsulates all surfaces of the metallic seal member with the exception of the inner perimeter  143 .  
         [0070]     Similar to  FIGS. 7A and 7B , the thermal interface structure  141  of  FIG. 8  includes a coating layer  144  which extends a distance from the outer perimeter of the metallic seal member  142 , thereby forming a boundary region  152  which facilitates adhesive attachment to a variety of heat exchangers.  
         [0071]     As seen in  FIG. 9A  (a sectioned isometric view) and  FIG. 9B  (a side view), the thermal interface structure  142  includes coating layers  144  which partially encapsulate the top and bottom faces of the metallic seal member  142 . This increases the volume of the metallic interface composition without increasing the surface area contact between the coating layer  144  and the IC chip  108  and heat spreader lid  104 .  
         [0072]     Within  FIG. 10A  (a sectioned isometric view) and  FIG. 10B  (a side view), the thermal interface structure  145  includes a solid metallic core  154  which is disposed within the metallic interface composition, comprising the metallic seal member  142 . The metallic core  154  includes two faces wherein the metallic interface composition (comprising the metallic seal member  142 ) flows onto at least one face of the solid metallic core  154  when the metallic seal member  142  is melted. The core  154  may be comprised of a high conductivity metal or metal alloy such as copper or aluminum. In another embodiment, the metallic core  154  is comprised of at least one metallic element comprising the metallic interface composition such as indium, tin or bismuth.  
         [0073]      FIG. 11 , similar to  FIG. 10B , illustrates another thermal interface structure embodiment  147  wherein the metallic core  154  and coating layer  144  extends a distance from the outer perimeter of the metallic seal member  142 , thereby forming a boundary region  152  which facilitates bonding of the individual coating layers as well as adhesive attachment to a variety of heat exchangers.  
         [0074]     As seen in  FIG. 12 , a thermal interface structure  149  (similar to  FIG. 11 ) is illustrated wherein the solid metallic core  154  includes a diffusion barrier layer  156  and wetting layer  158  (over the diffusion barrier layer). In one embodiment of the present invention, the metallic interface composition (comprising the metallic seal member  142 ) is applied to the solid metallic core  154  prior to melting of the metallic seal member  142  in order to further facilitate wetting and flowing of the metallic interface composition on the core  154 .  
         [0075]     Now, within  FIG. 13 , metallic interface composition “islands”  160  (disposed onto each face of the metallic core  154 ) are included with the thermal interface structure  139  also seen in  FIG. 10A . The islands  160  are comprised of both the metallic interface composition (comprising the metallic seal layer  142 ) and coating layer  144  positioned near the perimeter of the interface structure  151 . Similarly, the islands&#39; interface composition will melt and flow into the space between a heat exchanger and IC chip, thereby providing additional interface material for filling the space.  
         [0076]      FIG. 14  illustrates a corrosion inhibiting material  162 , such as a moisture desiccant, vapor phase or liquid phase corrosion inhibitor, is disposed within the heat spreader lid cavity  164 . These materials, in powder or granular form, may be first applied to an absorbent or adhesive substrate/medium to facilitate deployment within the lid cavity  164 .  
         [0077]     Moisture desiccants can adsorb significant amounts of water even at low humidity levels. The reduction of humidity within the lid cavity  164  results in greatly reduced corrosion rates on the thermal interface structure  140 .  
         [0078]     Vapor phase corrosion inhibitors are compounds transported in a closed environment to the site of corrosion by volatilization from a source. The vapors protect metallic surfaces through the deposition or condensation of a protective film or coating. Upon contact with the thermal interface structure  140 , the vapor of these salts condenses and is hydrolyzed by any moisture to liberate protective ions, thus mitigating any corrosion.  
         [0079]     As seen in  FIG. 15 , another thermal interface structure embodiment  153  of the present invention, a boundary region  152 , located outside of the outer perimeter of the metallic seal (illustrated as the space  146 ), includes an adhesive layer  166  which facilitates attachment of the interface structure  140  to the heat exchanger (lid  104 ).  
         [0080]      FIG. 16  illustrates an electronic assembly  170  including an electronic component  106  (comprised of an IC chip  108 , package substrate  110 , and electrical interconnection vias  112 ), heat exchanger (heat sink)  168 , and thermal interface structure  172 . The thermal interface structure  172  includes a metallic seal member (comprised of a metallic interface composition), illustrated as the space  146 , coating layer  144 , and facilitates a thermal path between the IC chip  108  and heat sink  168 . As another embodiment of  FIGS. 4A through 4D ,  FIG. 16  illustrates the thermal interface structure  172  after the metallic seal member has melted and flowed into space  146  between the lid  104  and chip  108 .  
         [0081]     Within  FIG. 17 , it can be seen that the electronic assembly  180  includes two heat exchangers, a heat spreader lid  104  (with a thermal interface structure  140  between the lid  104  and IC chip  108 ) and a heat sink  168  with a thermal interface structure  174  between both heat exchangers. The resultant electronic assembly, providing an all metal heat path from the IC chip  108  and heat sink  168 , would possess high thermal performance with a high degree of reliability and ease of deployment.  
         [0082]     Several embodiments of the present invention have been described. A person skilled in the art, however, will recognize that many other embodiments are possible within the scope of the claimed invention. For this reason, the scope of the invention is not to be determined from the description of the embodiments, but must instead be determined solely from the claims that follow.