HK1147578B - Thermal interface with non-tacky surface - Google Patents

Description

Thermal interface with non-tacky surface

Technical Field

The present invention relates to thermal interfaces for aspects related to heat dissipation layouts that include heat-generating electronic devices, and more particularly to thermal interface members that include a substantially transparent, conformable, and non-tacky surface layer that maintains the above characteristics above solder reflow temperatures.

Background

Thermal interfaces are widely used in heat dissipation applications where it is desirable to transfer excess thermal energy from one location to another. The thermal interface is typically placed between these locations in a manner that provides the desired heat transfer in an efficient and mechanically useful manner. An example application of such a thermal interface is in the electronics industry where electronic devices must be cooled in some way to maintain minimum threshold performance characteristics. One common method of cooling such electronic devices is by dissipating heat from the thermionic device. Such heat dissipation may be achieved, for example, by thermally coupling the electronic device to a heat sink, which typically has a relatively high heat dissipation capacity. Common heat sinks exhibit high heat dissipation characteristics through, for example, materials, surface area, and exposure to a cooling medium.

Thermal coupling of a heat generating component (e.g., an electronic device) to a heat sink may be facilitated by thermal interface materials and structures. For example, direct physical coupling between the heat generating element and the heat sink may be difficult due to relative external geometries, materials, and space limitations near the heat generating element. In this case, the thermal interface may act as a physical connection mechanism between the heat-generating component and the heat sink without significant resistance to heat transfer. Furthermore, since heat transfer may be significantly impeded at a thermal barrier (thermal barrier), a thermal interface may increase the efficiency of heat transfer to a heat sink by minimizing the presence of a thermal barrier where thermal energy must pass through a medium of relatively low thermal conductivity. For example, a thermal interface having a relatively low modulus value may "conform" to surface irregularities (irregularities) of the heat-generating component and the heat sink, thereby minimizing and/or eliminating voids between the surfaces, which may be filled with a relatively low thermal conductivity medium (e.g., air). Thus, thermal interfaces have been found to significantly improve heat transfer from various heat-generating devices.

In some applications, thermal interfaces have utilized relatively low modulus materials such as microcrystalline waxes and silicone grease (silicone grease), silicone gel (silicone gel), and silicone wax (silicone wax) to provide "conformability" characteristics to the thermal interface. The conformability of the interface may be achieved by a material having a low modulus value at room temperature, or alternatively may be achieved as a result of a "phase change" material that softens significantly at or below the operating temperature of the heat-generating device to which the interface is coupled. The relative softening of the interface material may cause surface adhesion that may impede such processing of such interfaces (e.g., when a thermal interface is assembled to components).

To overcome this problem, it has been found that providing an "anti-blocking" or release layer formed on at least one external surface of the thermal interface facilitates the production, assembly and handling of the thermal interface. In addition, such an outer non-stick release layer serves to provide significant protection from contamination of the rest of the thermal interface. In some cases, the anti-stiction or release layer may include a liner film (liner film) that must be removed before the point when the thermal interface is placed in contact with the heat generating device. Such removal operations often prove cumbersome and time and labor consuming. In other cases, the anti-blocking or release layer may be integrally formed or permanently secured to the remainder of the thermal interface. However, in this case, the anti-adhesion layer significantly inhibits the overall integrity of the interface.

In addition to the above, the thermal interfaces are typically installed in a heat dissipation layout in a particular order, where the thermal interfaces are first secured to a heat sink, and the resulting combination is then secured to a previously built package (e.g., an integrated circuit board). This protocol is followed primarily because the installation of components that thermally interface to the electronic package is difficult and cumbersome to handle during its construction. Even for thermal interfaces with an anti-stiction layer, the temperatures reached in the reflow soldering process to secure the electronic component to the package compromise the effectiveness of the anti-stiction layer.

In view of the above, it is therefore a primary object of the present invention to provide a thermal interface comprising one or more highly thermally conductive surfaces that remain non-tacky at or above solder reflow temperatures, while also being capable of good overall conformability to adjacent surfaces.

It is another object of the present invention to provide a thermal interface member having a non-tacky surface layer that is highly thermally conductive, conformable, and remains non-tacky at or above solder reflow temperatures.

It is another object of the present invention to provide a method of constructing a thermal interface in which a surface layer of such an interface is deposited on a release substrate and subsequently placed in registration with a bulk layer of the interface.

It is yet another object of the present invention to provide a method of constructing a package by securing a thermal interface to a package assembly prior to reflow soldering and subsequently securing the combination to a heat sink.

Disclosure of Invention

By means of the invention, excess thermal energy generated by the electronic component can be efficiently dissipated to a heat sink or other heat spreader. In particular, the present invention provides a thermal interface that is highly conformable but remains non-tacky at or above solder reflow temperatures. Thus, the thermal interface of the present invention facilitates handling and thermal package assembly operations while providing a high thermal conduction path from the heat-generating electronic device to the heat sink.

In one particular embodiment, the thermal interface member of the present invention comprises a bulk layer having a thermal conductivity of at least about 0.5W/m-K, and a surface layer disposed on at least a portion of at least one surface of the bulk layer. The surface layer includes a maximum cross-sectional thickness of less than about 10 microns, a thermal conductivity of at least about 50W/m-K along at least the thickness dimension, and a melting point that exceeds the solder reflow temperature. In some cases, the surface layer has a melting point of at least about 300 ℃.

In another embodiment, the thermal interface member of the present invention comprises a thermally conductive polymer-based bulk layer and a metallic surface layer disposed on at least a portion of at least one of the first surface and the second surface of the bulk layer. The metal surface layer has a maximum cross-sectional thickness dimension of less than about 10 microns.

An apparatus for use in a heat dissipation arrangement includes a heat-generating component and a thermal interface member thermally coupled to the heat-generating component and having a thermal conductivity of at least about 0.5W/m-K. The thermal interface member includes a bulk layer and a surface layer disposed on at least a portion of a surface of the bulk layer. The surface layer has a maximum cross-sectional thickness dimension of less than about 10 microns, a melting point above a solder reflow temperature, and greater than about 10⁷Pa modulus.

In another aspect of the invention, a method for constructing a thermal interface member is provided by depositing a thermally conductive material on a substrate to a thickness of less than about 10 μm to form a coated substrate and placing the coated substrate in registration with a surface of the bulk layer such that the thermally conductive material of the coated substrate is in contact with the surface of the bulk layer. Finally, the substrate is separated from the thermally conductive material such that the thermally conductive material remains in contact with the bulk layer surface as the surface layer.

In another aspect, a package includes a support structure having a first surface, an electronic component having a mounting portion and a heat dissipation surface, wherein the mounting portion is coupled to the first surface of the support structure, and a thermal interface member thermally coupled to the heat dissipation surface of the electronic component. The thermal interface member includes a bulk layer having a thermal conductivity of at least about 0.5W/m-K and a surface layer having a maximum cross-sectional thickness of less than about 10 μm. Further, the surface layer has a thermal conductivity of at least about 50W/m-K and a melting point that exceeds a solder reflow temperature.

A method of constructing an electronic component package includes providing a thermal interface member having a bulk layer with a thermal conductivity of at least about 0.5W/m-K and a surface layer disposed on at least a portion of a surface of the bulk layer, the surface layer having a maximum cross-sectional thickness of less than about 10 μm, a melting point above a solder reflow temperature, and a thermal conductivity of at least about 50W/m-K. The method also includes providing a support structure having a first surface and providing an electronic assembly having a mounting portion and a heat dissipation surface. The thermal interface member is thermally coupled to the electronic component by contacting the bulk layer of the thermal interface member with a heat dissipation surface of the electronic component. The mounting portion of the electronic component may be mounted to the first surface of the support structure before or after the thermal coupling. Subsequent to mounting the mounting portion of the electronic component to the first surface of the support structure, the heat sink is thermally coupled to the thermal interface member.

According to an aspect of the present invention, there is provided a package including:

(a) a support structure having a first surface;

(b) an electronic component having a mounting portion and a heat dissipation surface, the mounting portion being coupled to the first surface of the support structure; and

(c) a thermal interface member thermally coupled to the heat dissipation surface of the electronic component and having a bulk layer and a surface layer, wherein:

(i) the bulk layer has a thermal conductivity of at least about 0.5W/m-K; and

(ii) the surface layer has a maximum cross-sectional thickness of less than about 10 μm, a thermal conductivity of at least about 50W/m-K, and a melting point above a solder reflow temperature, the surface layer being disposed on at least a portion of a surface of the bulk layer.

Preferably, the support structure is a circuit board.

Preferably, the electronic component is a semiconductor device.

Preferably, the bulk layer of the thermal interface member is in contact with the heat dissipation surface of the electronic component.

Preferably, the surface layer is aluminum or copper.

Preferably, the package includes a heat sink secured to the surface layer of the thermal interface member.

According to another aspect of the present invention, there is provided a method for constructing an electronic component package, the method comprising:

(a) providing a thermal interface member, comprising:

(i) a bulk layer having a thermal conductivity of at least about 0.5W/m-K; and

(ii) a surface layer disposed on at least a portion of a surface of the bulk layer, the surface layer having a maximum cross-sectional thickness of less than about 10 μm, a melting point exceeding a solder reflow temperature, and a thermal conductivity of at least about 50W/m-K;

(b) providing a support structure having a first surface;

(c) providing an electronic component having a mounting portion and a heat dissipation surface;

(d) thermally coupling the thermal interface member to the electronic component by contacting the bulk layer of the thermal interface member with the heat dissipation surface of the electronic component;

(e) mounting the mounting portion of the electronic component to the first surface of the support structure before or after step (d); and

(f) after step (e), thermally coupling a heat sink to the thermal interface member.

Preferably, the thermal interface portionThe bulk layer of the article has less than about 10⁶Pa modulus.

Preferably, the surface layer of the thermal interface member has a melting point of at least about 300 ℃.

Preferably, the support structure is a circuit board.

Preferably, the method comprises mounting the heat sink to the surface layer of the thermal interface member.

According to yet another aspect of the present invention, there is provided a thermal interface member comprising:

(a) a bulk layer having generally opposed first and second surfaces and a thermal conductivity of at least about 0.5W/m-K; and

(b) a surface layer on at least a portion of at least one of the first and second surfaces of the bulk layer, the surface layer having:

(i) a maximum cross-sectional thickness of less than about 10 μm;

(ii) a thermal conductivity of at least about 50W/m-K along at least a thickness dimension of the surface layer; and

(iii) melting point above the solder reflow temperature.

Preferably, the bulk layer has less than about 10⁶Pa modulus.

Preferably, the surface layer has a melting point of at least about 300 ℃.

Preferably, the surface layer comprises a metal or metal complex.

According to yet another aspect of the present invention, there is provided a thermal interface member comprising:

(a) a thermally conductive polymer-based bulk layer having generally opposed first and second surfaces; and

(b) a metal surface layer on at least a portion of at least one of the first and second surfaces of the bulk layer, the metal surface layer having a maximum cross-sectional thickness dimension of less than about 10 μm.

Preferably, the bulk layer has a thermal conductivity of at least about 0.5W/m-K.

Preferably, the bulk layer has less than about 10⁶Pa modulus.

Preferably, the bulk layer comprises a thermosetting polymer.

Preferably, the bulk layer is a thermoplastic or phase change material.

Preferably, the bulk layer includes thermally conductive particulate matter dispersed therein.

Preferably, the particulate matter is selected from the group consisting of alumina, aluminum nitride, boron nitride, graphite, and combinations thereof.

Preferably, the surface layer is selected from aluminium and copper.

According to yet another aspect of the present invention, there is provided an apparatus for use in a heat dissipation arrangement, the apparatus comprising:

(a) a heat generating component; and

(b) a thermal interface member having a thermal conductivity of at least about 0.5W/m-K and thermally coupled to the heat-generating component, the thermal interface member comprising:

(i) a bulk layer;

(ii) a surface layer on at least a portion of a surface of the bulk layer, the surface layer having a maximum cross-sectional thickness dimension of less than about 10 μm, a melting point above a solder reflow temperature, and greater than about 10⁷Pa modulus.

Preferably, the bulk layer has less than about 10⁶Pa modulus.

Preferably, the bulk layer is a phase change material.

Preferably, the bulk layer comprises a silicone polymer.

Preferably, the thermal interface member is disposed on a surface of the heat-generating component.

Preferably, the surface layer has a melting point of at least about 300 ℃.

Preferably, the surface layer is a metal or metal complex.

Preferably, the surface layer has a thermal conductivity of at least about 50W/m-K.

According to yet another aspect of the present invention, there is provided a method for constructing a thermal interface member having a bulk layer and a surface layer disposed on at least a portion of a surface of the bulk layer, the method comprising:

(a) depositing a thermally conductive material on a substrate to a thickness of less than about 10 μm to form a coated substrate;

(b) placing the coated substrate in registration with the bulk layer surface such that the thermally conductive material is in contact with the bulk layer surface; and

(c) separating the substrate from the thermally conductive material, the thermally conductive material remaining in contact with the bulk layer surface as the surface layer, wherein the bulk layer is thermally conductive and has less than about 10⁶Pa modulus.

Preferably, the surface layer has a thermal conductivity of at least about 50W/m-K.

Preferably, the bulk layer has a thermal conductivity of at least about 0.5W/m-K.

Preferably, the thermally conductive material is deposited on the substrate by vapour deposition.

Drawings

FIG. 1 is a perspective view of a thermal interface member of the present invention;

FIG. 2 is a cross-sectional side view of a thermal interface member of the present invention;

FIG. 3A is a side view of a portion of a process for constructing a thermal interface member of the present invention;

FIG. 3B is a side view of a portion of a process for constructing a thermal interface member of the present invention;

FIG. 3C is a side view of a portion of a process for constructing a thermal interface member of the present invention;

FIG. 4 is a flow chart illustrating the process steps for constructing the thermal interface member of the present invention;

FIG. 5 is a cross-sectional side view of the electronic package of the present invention;

FIG. 6 is a cross-sectional side view of the electronic assembly package of the present invention; and

fig. 7 is a flow chart depicting the process steps for constructing the electronic component package of the present invention.

Detailed Description

The objects and advantages enumerated above, together with other objects, features and developments illustrated by the present invention, will be demonstrated in accordance with specific embodiments described with reference to the accompanying drawings, which are intended to be representative of various possible configurations of the present invention. Other embodiments and aspects of the invention are considered to be within the purview of one of ordinary skill in the art.

Referring now to the drawings, and initially to FIG. 1, thermal interface member 10 includes a bulk layer 12 and a surface layer 14 disposed on a first surface 16 of bulk layer 12. As described above, the surface layer 14 acts as an "anti-blocking" or "release" layer for the thermal interface member 10. In most embodiments, thermal interface member 10 is thermally conductive, and thermally conductive at least along the "z" axis. However, in many embodiments, thermal interface member 10 is thermally conductive along all axes. Typically, surface layer 14 has a thermal conductivity of at least about 50W/m-K, and bulk layer 12 has a thermal conductivity of at least about 0.5W/m-K. It should be understood that the overall thermal conductivity of thermal interface member 10 is intermediate the thermal conductivities of surface layer 14 and bulk layer 12. "bulk" thermal conductivity refers to the thermal conductivity measured from the first surface 18 to the second surface 20 (or from the second surface 20 to the first surface 18) of the thermally conductive assembly 10. It should be understood that the local thermal conductivity value at a point between the first and second surfaces 18, 20 may actually be less than the above-described values. However, the net thermal conductivity of thermal interface member 10, at least along the "z" axis, is as described above.

Bulk layer 12 preferably conducts heat at least along the "z" axis and may be a conformable material. In certain embodiments, bulk layer 12 may be a phase change material. For example, bulk layer 12 may include microcrystalline wax or a silicon-based polymer including silicone wax, silicone grease, and silicone gel. Other examples of formulations useful in bulk layer 12 include those described in U.S. Pat. Nos. 5,950,066 and 6,197,859, which are incorporated herein by reference. In embodiments where bulk layer 12 is a phase change material, bulk layer 12 may have a melting point in the range of about 40 ℃ to about 80 ℃. Thus, bulk layer 12 may become at least partially liquid at temperatures encountered during normal operation of one or more heat-generating devices connected using thermal interface member 10. This phase change characteristic provides a highly integrated interface for making good thermal contact with various heat dissipating surfaces (e.g., surfaces of a heat generating device). As is known in the art, phase change thermal interface materials allow for relatively easy processing at room temperature while being highly integrated at operating temperatures.

In certain embodiments, bulk layer 12 may further include thermally conductive particulate matter dispersed therein to increase the thermal conductivity of body 12. Various thermally conductive particulate materials may be used to promote thermal conductivity of bulk layer 12, including, for example, alumina, aluminum nitride, boron nitride, graphite, silicon carbide, diamond, metal powders, and combinations thereof, with average particle sizes up to about 200 microns. In an exemplary embodiment, the particulate filler material may be provided in bulk layer 12 at a concentration of between about 10 and 95 percent (by weight). Loading level (loadin) of particulate fillerg-level) may affect the overall modulus of bulk layer 12. Accordingly, it is desirable to maintain the operating temperature modulus of bulk layer 12 to not more than about 10⁶Pa. However, in some applications, the modulus value of bulk layer 12 is greater than 10⁶Pa is also permissible.

Bulk layer 12 may be formed to have a thickness dimension "a" of between about 50 and 500 microns, with a thickness in the range of about 100 to 150 microns being most commonly employed.

Surface layer 14 is preferably a high thermal conductor comprising one or more thermally conductive materials. Surface layer 14 may be disposed on all or a portion of first and/or second surfaces 16, 20 of bulk layer 12, for example. In the embodiment shown in fig. 1, surface layer 14 is disposed along substantially the entire area of first surface 16 of bulk layer 12. However, surface layer 14 may be provided on one or more surfaces of bulk layer 12 in any of a variety of continuous or discontinuous patterns. It is contemplated that surface layer 14 acts as a non-stick surface upon which manipulation of thermal interface member 10 may be focused. For example, a "pick and place" assembly operation may move the thermal interface member from the assembly line to an operating position of the heat-generating device package via automated equipment. Such a device may be removably engaged with thermal interface member 10 at surface layer 14. Without non-stick surface layer 14, such automated equipment may foul (fog) due to, for example, the stickiness of bulk layer 12. Thus, the use of automated assembly equipment typically requires some form of non-stick surface upon which the equipment can effectively removably engage the thermal interface member. Since the equipment used during assembly may require a non-stick area, surface layer 14 may cover less than the entire area of, for example, first and second surfaces 16, 20 of bulk layer 12, which is less than the area presented by, for example, first surface 16 of bulk layer 12.

An additional aspect of facilitating handling of thermal interface member 10 during manufacturing and assembly operations is providing surface layer 14 that exhibits a "non-tacky" surface. Such properties may be achieved by various mechanisms, such as material type and material phase. Accordingly, it is an aspect of the present invention to provide surface layer 14 with a non-stick upper surface 18. For some applications, it is desirable that surface layer 14 be non-tacky at both room temperature and at elevated temperatures, such as above the solder reflow temperature. For example, thermal interface assembly 10 may be used in connection with package assembly processes involving high temperatures, including temperatures at which reflow soldering occurs to secure components of the package to one another. Accordingly, it is desirable that surface layer 14 remain substantially unaffected at such high temperatures while maintaining non-tacky surface characteristics.

To achieve the above objectives, surface layer 14 may be solid and have a melting point that exceeds the respective solder reflow temperature. For typical applications, the solder reflow temperature is in the range of about 200 to about 260 ℃, depending on the type of solder used. It is therefore desirable that surface layer 14 have a melting point temperature that is higher than the solder reflow temperature of the respective solder used. In some cases, the melting point of surface layer 14 is greater than about 300 ℃. Table 1 below shows exemplary solder alloy compositions, and their respective phase transition temperatures:

alloy composition	Liquefaction temperature (. degree.C.)	Reflux temperature (. degree.C.)	Melting Range # (° C)
				Sn.-2Ag			221-226
Sn.-3.5Ag	221	240-250
				Sn.-0.7Ag	227	245-255
Sn.-3.0Ag-0.5Cu	220	238-248
				Sn.-3.2Ag-0.5Cu	218	238-248	217-218
Sn.-3.5Ag-0.75Cu	218	238-248
				Sn.-3.8Ag-0.7Cu	220	238-248	217-210
-4Ag-0.5Cu			217-219
				Sn.-4Ag-1.0Cu	220	238-248	217-220
Sn.-4.7Ag-1.7Cu	244	237-247

To maximize the efficiency of the thermal interface member 10, the surface layer 14 is preferably thermally conductive and may be substantially "thermally transparent", and the thermal conductivity of the surface layer 14 may be significantly higher than the thermal conductivity of the bulk layer 12. In certain embodiments, surface layer 14 may have a thermal conductivity of at least about 50W/m-K, and may typically have a thermal conductivity between about 200 and 800W/m-K. The thermal conductivity identified above refers to thermal conductivity at least along the "z" axis, but may also be true along all directions.

An additional aspect of the present invention is the overall integrity of the thermal interface member 10. As mentioned above, an important feature of a thermal interface is that the interface integrates well with the surface against which it is mounted, thereby minimizing thermal barriers and thereby increasing thermal conductivity. Conventional thermal interfaces that include an "anti-blocking" or release layer typically require that such layer be manually removed prior to installation, or that such layer, when left in place at the interface, degrade the thermal performance of the interface due to lack of conformability of the layer and/or the relatively low thermal conductivity of the layer material itself. Accordingly, surface layer 14 may be both highly thermally conductive (as described above) and highly integrated. Thus, surface layer 14 may have a thickness of less than about 10 microns. Even when the modulus is greater than 10 due to thinness⁶Pa, the surface layer 14 is also effective.

Applicants have determined that one way to achieve the above-described integration in surface layer 14 is by providing a very small thickness dimension "b" of surface layer 14. Depending on the material used for surface layer 14, thickness dimension "b" may be less than about 10 microns, and may typically be between about 2 and 6 microns. The thickness dimension "b" of surface layer 14 may refer to the maximum cross-sectional thickness of surface layer 14.

Surface layer 14 may comprise one or more of a variety of materials compatible with the above-described aspects. Applicants have found that a particular class of materials useful for the surface layer of the present invention are metals and/or metal complexes that can be deposited as a thin layer, for example, less than about 6 microns in thickness. Example materials for surface layer 14 include aluminum, copper, silver, and copper-tungsten. However, it is contemplated that other materials and material combinations are also useful for surface layer 14. An additional example of a useful material is graphite.

FIG. 2 is an example of an embodiment of thermal interface member 30 in which surface layer 14 is disposed on only a portion of bulk layer 12. Various layouts of surface layer 14 relative to bulk layer 12 are contemplated within the scope of the present invention. For example, surface layer 14 may be disposed at one or both of first and second surfaces 16, 20 of bulk layer 12, and may be disposed along at least a portion of such one or more surfaces. In this way, surface layer 14 may cover all or a portion of first and/or second surfaces 16, 20 of bulk layer 12.

It is contemplated that first surface 14 may be provided on bulk layer 12 by one of a variety of processes including, for example, vapor deposition, plasma polymerization, spraying, sputtering, and the like. One method of applying surface layer 14 to bulk layer 12 that will be described herein by way of example only is to vapor deposit a metallic material as surface layer 14.

As shown in fig. 3A-3B, a metal vapor (e.g., aluminum) is deposited on the release liner substrate 42 as follows:

the release liner substrate 42 may be placed in a vacuum chamber and transferred between a unwind roll and a wind-up roll, both within the vacuum chamber. The aluminum spool (spool) is then placed at the container within a vacuum chamber where it is heated to the evaporation temperature of the aluminum while the vacuum chamber is substantially evacuated. The aluminum in vapor state is then emitted from the aluminum spool and deposited on a moving substrate approximately 12 inches from the aluminum container.

The thickness "b" of the surface layer 14 at the release liner substrate 42 may be controlled by the speed of the substrate within the vapor deposition chamber. Typically, the substrate 42 is operated between the unwind and wind-up rolls at a speed between about 400-. Once the substrate 42 has been exposed to the metal vapor, the chamber is brought back to atmospheric pressure. In certain embodiments, the vapor deposited substrate may pass over a chill roll to change the metal in a vapor state on the substrate to a solid state prior to being rolled by the take-up roll.

Once the deposited material reaches a predetermined minimum thickness, such as between about 2 and 6 microns, the coated substrate 44 is transferred to a calendaring operation as shown in fig. 3C so as to be placed in registration with the bulk layer 12. The calendaring operation system control block 50, as shown in fig. 3C, places surface layer 14 in registration with first surface 16 of bulk layer 12 at registration location 52, where surface layer 14 is adhered to bulk layer 12 by pressure generated at each roller pair 54-54, 56-56. A separator 58 is used to remove the release liner 42 from the surface layer 14, keeping the surface layer 14 in contact with the bulk layer 12. To prevent the bulk layer 12 from undesirably adhering to the components of the calender molding system 50 (e.g., shafts 54, 56), a release liner 46 may be provided at the second surface 20 of the bulk layer 12. Such release liner 46 may be removed from bulk layer 12 at a desired point in time prior to installation of thermal interface member 10 in, for example, a thermal device package.

FIG. 4 is a flow chart illustrating the processing steps of thermal interface member fabrication as described above in FIGS. 3A-3C. In particular, the material for the surface layer 14 is deposited to a predetermined thickness on a release liner, thereby forming a coated substrate. As noted above, this material or these materials are preferably thermally conductive and may be, for example, a metal, metal complex, and/or other material capable of being deposited on the release liner 42. In some embodiments, the material may be applied to the substrate to a predetermined thickness of less than about 6 microns. Release liners are well known in the art, and it is contemplated that a conventional release liner capable of being relatively easily removed from surface layer 14 may be used in the thermal interface member production process. One example release liner 42 for receiving the deposited surface layer 14 and subsequently being removed therefrom is polyethylene terephthalate (PET).

The coated substrate is then placed into a calendaring operation with the release liner starting in contact with a calendaring (calendaring) roller and the surface layer exposed for orientation in registration with the bulk layer 12. The registration of the surface layer with the bulk layer causes the surface layer to adhere to the bulk layer with a strength greater than the strength of the coupling between the surface layer and its respective release liner substrate. As a result, the substrate is then removed from the surface layer, while the surface layer remains in contact with the bulk layer. Each thermal interface member may then be die cut to the desired size. In this form, the thermal interface member has opposing non-adhesive surfaces so as to be easily handled during shipping and package assembly steps. Typically, the release liner located at, for example, second surface 20 of bulk layer 12 is removed immediately prior to the thermal interface member being installed in a heat-generating device.

The thermal interface member 10 can be used in connection with dissipating heat from a heat-generating component package. As shown in fig. 5, package 70 includes a heat-generating electronic component 72 disposed on a first surface 74 of a support structure 76. The electronic assembly 72 includes a mounting portion 78 coupled to the first surface 74 of the support structure 76 and a heat dissipation surface 80 thermally coupled to the thermal interface member 10. In certain embodiments, the heat dissipation surface 80 may be thermally coupled to the bulk layer 12 of the thermal interface member 10. Such thermal coupling may be in the form of physical contact between bulk layer 12 of thermal interface member 10 and heat dissipation surface 80 of electronic component 72. With this arrangement, heat generated by the electronic component 72 is transferred to the thermal interface member 10 through its thermal coupling at the heat dissipation surface 80. Although heat dissipation surface 80 is shown in FIG. 5 as being substantially opposite mounting portion 78, it should be understood that heat dissipation surface 80 may be any surface of electronic component 72 that is convenient and/or effective in thermally coupling electronic component 72 to thermal interface member 10. Further, it should be understood that the electronic component 72 may be thermally coupled to the thermal interface member 10 by means other than a direct physical connection, such as by means of an indirect interface medium (secondary interface media) or other connection device to the thermal interface member 10.

In the embodiment shown in fig. 5, bulk layer 12 of thermal interface member 10 may be adhered directly to heat dissipation surface 80 due to the inherent adhesive properties of bulk layer 12. However, in other embodiments, thermal interface member 10 may be secured to electronic assembly 72 by, for example, a thermally conductive adhesive material, fasteners (fastener), or the like. Further, the thermal interface member 10 may be oriented such that the surface layer 14 is in contact or facing relationship with the heat dissipation surface 80 of the electronic component 72.

Electronic device 72, as used herein, is a broad sense electronic device intended to include elements included in a variety of electronic systems (e.g., data processing, communications, power systems, etc.). Example devices contemplated as electronic components 72 include semiconductor devices such as transistors and diodes, and passive components (passive components).

The electronic assembly 72 is secured to a circuit board 76, which may be a dielectric material having conductive traces on the first surface 74, or may contain other types of electrical connections, in the embodiment shown in fig. 5. In some embodiments, the support structure 76 may be a thermally conductive material having a dielectric layer at the first surface 74, wherein the electronic component 72 is mounted on the first surface 74. Various layouts and materials are contemplated as being useful for the support structure 76.

As shown in fig. 6, heat sink 92 may be thermally coupled to package 70 (e.g., at thermal interface member 10). In some embodiments, thermal coupling of heat sink 92 to package 70 is achieved by physical contact between first surface 94 of heat sink 92 and first surface 18 of thermal interface member 10 such that surface layer 14 is in thermal contact with first surface 94. As described above, thermal interface member 10 (and in particular surface layer 14) is integral to operatively integrate with first surface 94. This conformity improves the heat transfer efficiency between thermal interface member 10 and heat sink 92. As shown in fig. 6, the heat sink 92 may have a configuration including a relatively high surface area, for example, by way of fins (fin) 96. The use of heat sinks in heat dissipation applications is well understood and it is contemplated that conventional heat sink designs may be used in the inventive arrangements. The heat transfer in the layout of fig. 6 is in the direction indicated by arrow "y" and specifically from heat-generating component 72 through thermal interface member 10 to heat sink 92, and ultimately to the ambient of heat sink 92.

The layout shown in fig. 6 may be constructed in accordance with the flow chart depicted in fig. 7. In particular, thermal interface member 10 may be mounted to heat dissipation surface 80 of electronic component 72, and mounting portion 78 of electronic component 72 may then be mounted to first surface 74 of support structure 76, with the resulting combination then being coupled to heat sink 92 (e.g., at first surface 18 of thermal interface member 10). Alternatively, electronic component 72 may be first mounted to first surface 74 of support structure 76, and thermal interface member 10 is then mounted to heat dissipation surface 80 of electronic component 72. The heat sink 92 may then be thermally coupled to this combination as shown in fig. 6.

The above process is different from the conventional one of manufacturing a package of an electronic assembly in that the conventional technique first mounts the thermal interface member to the heat sink and then connects the electronic assembly/support structure combination to the heat sink/thermal interface member combination. Typically, this final assembly step is undertaken by the original equipment manufacturer that sells the complete electronic component package. However, this final assembly step requires a processing step to remove the release liner from the thermal interface member (e.g., to remove release liner 46 from bulk layer 12) prior to connecting the thermal interface member/heat sink combination to the electronic component. This processing step is time consuming and can sometimes cause damage to the thermal interface member, resulting in product loss and/or reduced product performance. The thermal interface member of the present invention enables the thermal interface member to be coupled to an electronic component/support structure combination at the package manufacturer. In the case where the thermal interface member is mounted to the electronic component prior to mounting the electronic component to the support structure, the thermal interface member of the present invention can withstand the solder reflow temperatures required to secure the electronic component to the support structure. In addition, surface layer 14 protects bulk layer 12 from contamination during the reflow soldering process. Electronic components may also be carried in current Surface Mount Technology (SMT) formats without concern for thermal interface members adhering to SMT tapes and reels, as surface layer 14 presents a non-tacky surface prior to coupling to heat sink 92.

This invention has been described herein in considerable detail in order to comply with the patent statutes and to provide those skilled in the art with the information needed to apply the novel principles and to construct and use embodiments of the invention as required. However, it is to be understood that the invention may be carried out by specifically different equipment and that various modifications may be made without departing from the scope of the invention itself.

Claims (27)

1. A package, comprising:

(a) a support structure having a first surface;

(b) an electronic component having a mounting portion and a heat dissipation surface, the mounting portion being coupled to the first surface of the support structure; and

(c) a thermal interface member thermally coupled to the heat dissipation surface of the electronic component and having a bulk layer and a surface layer, wherein:

(i) the bulk layer has a thermal conductivity of at least about 0.5W/m-K; and

(ii) the surface layer has a maximum cross-sectional thickness of less than about 10 μm, a thermal conductivity of at least about 50W/m-K, and a melting point above a solder reflow temperature, the surface layer being disposed on at least a portion of a surface of the bulk layer.

2. The package of claim 1 wherein the support structure is a circuit board.

3. The package of claim 1 wherein the electronic component is a semiconductor device.

4. The package of claim 1 wherein the bulk layer of the thermal interface member is in contact with the heat dissipation surface of the electronic component.

5. The package of claim 1 wherein the surface layer is aluminum or copper.

6. The package of claim 1, comprising a heat sink secured to the surface layer of the thermal interface member.

7. A method for building an electronic component package, the method comprising:

(a) providing a thermal interface member, comprising:

(i) a bulk layer having a thermal conductivity of at least about 0.5W/m-K; and

(ii) a surface layer disposed on at least a portion of a surface of the bulk layer, the surface layer having a maximum cross-sectional thickness of less than about 10 μm, a melting point exceeding a solder reflow temperature, and a thermal conductivity of at least about 50W/m-K;

(b) providing a support structure having a first surface;

(c) providing an electronic component having a mounting portion and a heat dissipation surface;

(d) thermally coupling the thermal interface member to the electronic component by contacting the bulk layer of the thermal interface member with the heat dissipation surface of the electronic component;

(e) mounting the mounting portion of the electronic component to the first surface of the support structure before or after step (d); and

(f) after step (e), thermally coupling a heat sink to the thermal interface member.

8. The method of claim 7, wherein the bulk layer of the thermal interface member has less than about 10⁶Pa modulus.

9. The method of claim 7, wherein the surface layer of the thermal interface member has a melting point of at least about 300 ℃.

10. The method of claim 7, wherein the support structure is a circuit board.

11. The method of claim 7, comprising mounting the heat sink to the surface layer of the thermal interface member.

12. A thermal interface member, comprising:

(a) a bulk layer having generally opposed first and second surfaces and a thermal conductivity of at least about 0.5W/m-K; and

(b) a surface layer on at least a portion of at least one of the first and second surfaces of the bulk layer, the surface layer having:

(i) a maximum cross-sectional thickness of less than about 10 μm;

(ii) a thermal conductivity of at least about 50W/m-K along at least a thickness dimension of the surface layer; and

(iii) melting point above the solder reflow temperature.

13. A thermal interface member as in claim 12 wherein said bulk layer has a small bulkAt about 10⁶Pa modulus.

14. A thermal interface member as in claim 12 wherein said surface layer has a melting point of at least about 300 ℃.

15. A thermal interface member as in claim 12 wherein said surface layer comprises a metal or metal complex.

16. A device for use in a heat dissipation arrangement, the device comprising:

(a) a heat generating component; and

(b) a thermal interface member having a thermal conductivity of at least about 0.5W/m-K and thermally coupled to the heat-generating component, the thermal interface member comprising:

(i) a bulk layer;

(ii) a surface layer on at least a portion of a surface of the bulk layer, the surface layer having a maximum cross-sectional thickness dimension of less than about 10 μm, a melting point above a solder reflow temperature, and greater than about 10⁷Pa modulus.

17. The apparatus of claim 16, wherein the bulk layer has less than about 10⁶Pa modulus.

18. The apparatus of claim 16, wherein the bulk layer is a phase change material.

19. The device of claim 18, wherein the bulk layer comprises a silicone polymer.

20. The apparatus of claim 16, wherein the thermal interface member is disposed on a surface of the heat-generating component.

21. The device of claim 16, wherein the surface layer has a melting point of at least about 300 ℃.

22. The device of claim 16, wherein the surface layer is a metal or metal complex.

23. The device of claim 16, wherein the surface layer has a thermal conductivity of at least about 50W/m-K.

24. A method for constructing a thermal interface member having a bulk layer and a surface layer disposed on at least a portion of a surface of the bulk layer, the method comprising:

(a) depositing a thermally conductive material on a substrate to a thickness of less than about 10 μm to form a coated substrate;

(b) placing the coated substrate in registration with the bulk layer surface such that the thermally conductive material is in contact with the bulk layer surface; and

(c) separating the substrate from the thermally conductive material, the thermally conductive material remaining in contact with the bulk layer surface as the surface layer, wherein the bulk layer is thermally conductive and has less than about 10⁶Pa modulus.

25. The method of claim 24, wherein the surface layer has a thermal conductivity of at least about 50W/m-K.

26. The method of claim 24, wherein the bulk layer has a thermal conductivity of at least about 0.5W/m-K.

27. The method of claim 24, wherein the thermally conductive material is deposited on the substrate by vapor deposition.