The present invention relates to thermally conductive interface structures generally, and more particularly to a thermally conductive interface incorporating one or more oriented thermally conductive compressive members which are compressive at least along a thickness direction of the interface structure.
Modern electronic devices involve a wide variety of operating electronic components mounted in close proximity with one another. Demand for increased performance and decreased size for such electronic components, has resulted in elevated levels of heat generation. For many electronic components operating efficiency is decreased at elevated temperatures, such that mechanisms are desired for heat transfer away from the electronic components. Accordingly, it is known in the art to utilize heat transfer aids such as cooling fans for moving air across the devices, cooling fluid conductor pipes, and large surface area heat sinks for removing thermal energy from in and around the respective electronic components.
A common technique for removing excess thermal energy from the heat-generating electronic components involves thermally coupling the electronic component to a relatively large surface area heat sink, which is typically made of a highly thermally conductive material, such as metal. Heat transfer away from the heat sink typically occurs at the interface between the heat sink and a cooling media such as air. In some cases, heat transfer efficiency is increased through the use of fans to direct a continuous flow of air over the heat exchanging surfaces of the heat sink.
In some instances, an interfacial material, such as a thermally conductive paste or gel, may be interposed between the heat-generating electronic component and the heat sink in order to increase heat transfer efficiency from the electronic component to the heat sink. Interfacial voids caused by uneven surfaces at the interface between the electronic component structure and the heat sink introduce thermal barriers which inhibit passage of thermal energy thereacross. The interfacial material minimizes such voids to eliminate thermal barriers and increase heat transfer efficiency.
Thermally conductive pastes or gels used in this application commonly exhibit relatively low bulk modulus, and may even be “phase changing” in that the interfacial material becomes partially liquidous and flowable at the elevated temperatures consistent with the operation of the heat-generating electronic component. Although the use of such interfacial materials has proven to be adequate for many applications, certain drawbacks nevertheless exist. For example, some of such interfacial materials may be difficult and messy to handle and install due to their low modulus/flowability characteristics. In addition, limitations have been observed on the thermal conductivity obtainable with such thermal interface materials. Given the ever-increasing demand for removal of thermal energy from electronic components, known thermal interface pastes and gels may be inadequate for certain thermal transfer applications.
In addition to the thermally conductive interfacial materials described above, other types of thermal interface structures are known in the art. For example, solid and semi-solid interface structures have been secured in place between the electronic component and the heat sink through thermally conductive adhesives and the like. While such interface structures typically exhibit high thermal conductivity values, their lack of conformability to adjacent surfaces reduces their overall thermal pathway efficiency.
Accordingly, it is a primary object of the present invention to provide a thermally conductive interface structure that is both highly thermally conductive and conformable to opposed surfaces through compressibility along at least a thickness dimension of the interface structure.
It is a further object of the present invention to provide a thermally conductive interface structure that is highly thermally conductive, compressible along the thickness direction, and may be easily handled and installed.
By means of the present invention, thermal energy may be efficiently transported away from a heat-generating electronic component through a compact and neat arrangement. To carry out the heat transfer described above, a thermally conductive interface structure is provided which is compressible along a thickness direction parallel to the desired direction of heat transfer. The present interface structure has a relatively low compressive modulus along this thickness direction, wherein the compressive modulus is less than about 200 psi. Moreover, the interface structure is highly thermally conductive, and may have a thermal conductivity value of between about 5 and 50 W/m·K.
In a particular embodiment, the thermally conductive interface structure has a length, a width, and a thickness, and includes a matrix material and a thermally conductive compressive member which defines a respective plane extending through the thickness and the width of the interface structure. The thermally conductive compressive member includes reticulated apertures having respective axes which extend perpendicularly therethrough and which are oriented substantially along the length. The compressive member is compressible along a thickness direction.
In some embodiments, the reticulated apertures of the compressive member are substantially diamond-shaped, and define a long dimension between a first pair of opposed apices and a short dimension between a second pair of opposed apices. A length ratio between the long dimension and the short dimension may be about 2 when the compressive member is in a non-compressed condition. The apertures may make up about 40 area percent of the compressive member.
In some embodiments, the thermally conductive interface structure includes a plurality of compressive members that are disposed in substantially parallel relationship along the length. The compressive members may comprise between about 10 and about 50 volume percent of the interface structure.
In another embodiment, the thermally conductive interface structure includes a polymer matrix and a plurality of compressive members disposed along a length of the interface structure, wherein at least some of the compressive members each extend throughout a width and a thickness of the interface structure. The compressive members include strands formed into a mesh defining reticulated apertures. Moreover, the mesh is oriented such that the compressive members are compressible along a thickness direction.
In another aspect, an electronic component assembly of the invention includes a heat-generating electronic component and a thermally conductive interface structure having a length, a width, and a thickness, wherein the thickness is defined between first and second surfaces of the interface structure. At least a portion of the first surface is thermally coupled with the electronic component. The thermally conductive interface includes a polymer matrix material and one or more thermally conductive compressive members each including reticulated apertures having respective axes extending perpendicularly therethrough so as to be oriented substantially along the length. The compressive members each have a compressive bulk modulus along a thickness direction of less than about 200 psi.
A still further embodiment of the interface structure includes a polymer matrix and a thermally conductive compressive member substantially spirally wound about a first axis that is parallel to a thickness direction. The compressive member includes first and second opposed major surfaces which are oriented substantially parallel to the thickness direction and include a plurality of reticulated apertures disposed therein, the compressive member being compressible along the thickness direction.
The objects and advantages enumerated above together with other objects, features, and advances represented by the present invention will now be presented in terms of detailed embodiments described with reference to the attached drawing figures which are intended to be representative of various possible configurations of the invention. Other embodiments and aspects of the invention are recognized as being within the grasp of those having ordinary skill in the art.
With reference now to the drawing figures, and first to
Heat-generating electronic component 12 is schematically illustrated in
In the arrangement illustrated in
An enlarged isolation view of thermally conductive interface structure 14 is illustrated in
As further illustrated in
An end view of interface structure 14 in
In one embodiment, and as illustrated in
An important aspect of the present invention is in the compressibility of compressive members 32 at least along a thickness direction “z”. To that end, strands 34 of compressive members 32 are preferably fabricated of materials and dimensions capable of deformation under relatively light loads. In particular, it is desirable to provide interface structure 14 with a compressive bulk modulus along thickness direction “z” of between about 10 and 200 psi. This range of modulus values may also be pertinent to compressive members 32 themselves, as the compressive members 32 may represent the stiffest elements in interface structure 14. As a consequence, compressive members 32, as operably oriented, may have a compressive modulus along thickness direction “z” of no more than about 200 psi.
In some embodiments, compressive members 32 may be fabricated from a ductile metal or other deformable material. Compressive members 32 may be thermally conductive such that materials selected for use in the manufacture of compressive members 32 have thermal conductivities of at least about 5 W/m·K. As such, materials such as metals, metal-coated fabric, carbon fibers, and the like are example materials useful in the construction of compressive members 32. Particular example materials for compressive members 32 include copper, aluminum, nickel, and titanium.
Compressive members 32 may utilize a variety of cross-sectional configurations for strands 34, including, for example, square, rectangular, round, oblong, and the like. Dimensions for strands 34 may be divided into strand widths “Sw” and strand thickness “St”. In some embodiments, strand width may between about 1 and about 10 mils, while strand thickness may be between about 2 and about 15 mils. Such size ranges render between about 1,500 and about 11,000 apertures 36 per square inch of compressive members 32. It has been found that such dimensions, along with the aperture dimensions described above, yield an overall open area in the compressive members 32 of about 40 area percent, and which provide a desired degree of compressibility along thickness direction “z”. It is to be understood, however, that other dimensions for strand width “Sw”, strand thickness “St”, and apertures 36 may be useful in compressive members 32, while retaining desired levels of compressibility along thickness direction “z”.
Strands 34 of compressive members 32 may refer to (i) the mesh structure of compressive members 32 as a whole, (ii) portions of an integral mesh structure such as that shown in
In addition to compressive members 32, interface structure 14 may further include a material for bonding compressive members to one another and/or securing compressive members 32 substantially in place at interface structure 14. Alternatively, such material may simply be incorporated into interface structure as a medium to fill gaps in interface structure 14. In some embodiments, such material may be thermally conductive in order to aid in the transfer of thermal energy through interface structure 14 at least along thickness direction “z”. The material may also exhibit a relatively low modulus, such as below about 20-30 psi, so as to maintain a relatively low compressive modulus for interface structure 14, at least along thickness direction “z”. Such material is referred to herein as a “matrix” which is intended to be broadly construed as any material, compound, mixture, emulsion, or the like, within which one or more compressive members may be embedded, and/or which may itself be impregnated into voids defined by and between the compressive members of the interface structure. No specific meaning for the term “matrix”, therefore, is intended herein.
In some embodiments, the matrix material may be a polymer having a relatively low compressive bulk modulus, such as below 20-30 psi. Example polymer materials useful in the matrix material of the present invention include, but are not limited to, silicones, polyurethanes, polyisobutylenes, as well as copolymers of silicone with epoxies, acrylics, or polyurethanes. It is desired that the matrix material be relatively stable at operating temperatures of electronic component assembly 10, including temperatures up to about 150-200° C. For the purposes of this application, the term “stable” is intended to mean substantially form-stable, wherein viscosity of the matrix material changes by less than about 10% between room temperature and the operating temperatures of electronic component assembly 10. More importantly, however, the matrix material does not cause the overall compressive bulk modulus of the interface structure at least along thickness direction “z” to exceed a predetermined maximum value, such as about 350 psi.
In some embodiments, the matrix material may be filled with thermally conductive and/or viscosity-modifying particulate fillers. Such particulate filler may be a ceramic material such as alumina, aluminum nitride, aluminum hydroxide, boron nitride, silica, and the like, as well as other inorganic materials and metals. Most typically, the particulate fillers are present at a loading concentration of between about 50 and 90% by weight, and have a particulate size distribution with a mean particle size of about 30-50 microns. Most typically, such particulate filler materials are included in the matrix material to enhance the thermal conductivity thereof. Thermally conductive filled polymer materials are well understood in the art as an interfacial media in heat transfer applications.
The matrix material is identified in
A further example embodiment of an interface structure of the present invention is illustrated in
Interface structure 114 may also be similar to interface structure 14, in that polymer matrix 152 may be impregnated therein, such that polymer matrix 152 is disposed within reticulated apertures 136, and possibly between respective portions of compressive member 132.
Non-polygonal configurations for interface structure 114 other than that illustrated in
Although a variety of techniques for manufacturing the interface structures of the present invention are contemplated herein, the following sets forth example methods for making the interface structures. A construction technique of interface structure 14 is illustrated in
In somewhat similar fashion, interface structure 114 may be constructed through the technique illustrated in
The following sets forth example arrangements for interface structures of the present invention. The following examples, however, are intended to be exemplary only, and not restrictive as to the arrangements and materials useful in the present invention.
A thermally conductive interface structure having a thickness dimension of between about 100 and about 200 mil was prepared with a plurality of aluminum compressive members. The compressive members included a strand width of 5 mil and a strand thickness of 1.5 mil, which non-woven strands defined regular, reticulated, diamond-shaped apertures having a ratio of long dimension to short dimension of about 2. The long dimension of the reticulated apertures was aligned parallel to the thickness direction, and the compressive members defined an open area percent of about 38.
A vinyl terminated polydimethyl siloxane polymer with a viscosity at 25° C. of about 100 cP was mixed with a hydride crosslinker of similar viscosity in an approximately 10:1 ratio along with a 1% platinum catalyst in a 1000:1 ratio. Once cured, the neat polymer had a compressive modulus of about 20 psi at a maximum operating temperature of about 200° C. The uncured composition was impregnated into the mesh arrangement by vacuum impregnation and allowed to cure for 24 hours at 25° C. Once cured, the compressive members were present at about 35 volume percent of the overall structure.
This interface structure exhibited a compressive modulus along the thickness direction of about 75 psi and a thermal conductivity of 22 W/m·K.
A thermally conductive interface structure having a thickness dimension of between about 100 and about 200 mil was prepared with a plurality of aluminum compressive members. The compressive members included a strand width of 5 mil and a strand thickness of 1.5 mil, which non-woven strands defined regular, reticulated, diamond-shaped apertures having a ratio of long dimension to short dimension of about 2. The short dimension of the reticulated apertures was aligned parallel to the thickness direction, and the compressive members defined an open area percent of about 38.
Vinyl siloxane polymer as in Example 1 was impregnated into the mesh arrangement and cured such that the compressive members were present at about 35 volume percent of the overall structure.
This interface structure exhibited a compressive modulus along the thickness direction of about 50 psi and a thermal conductivity of 16 W/m·K.
A thermally conductive interface structure having a thickness dimension of between about 50 and about 200 mil was prepared with a wound aluminum compressive member. The compressive member included a strand width of 5 mil and a strand thickness of 1.5 mil, which non-woven strands defined regular, reticulated, diamond-shaped apertures having a ratio of long dimension to short dimension of about 2. The long dimension of the reticulated apertures was aligned parallel to the thickness direction, and the compressive member defined an open area percent of about 38.
Vinyl siloxane polymer as in Example 1 was impregnated into the mesh arrangement and cured such that the compressive member was present at about 15 volume percent of the overall structure.
This interface structure exhibited a compressive modulus along the thickness direction of about 150 psi and a thermal conductivity of 13 W/m·K.
A thermally conductive interface structure having a thickness dimension of between about 100 and about 200 mil was prepared with a plurality of copper compressive members. The compressive members included a strand width of 5 mil and a strand thickness of 1.5 mil, which non-woven strands defined regular, reticulated, diamond-shaped apertures having a ratio of long dimension to short dimension of about 2. The long dimension of the reticulated apertures was aligned parallel to the thickness direction, and the compressive members defined an open area percent of about 38.
Vinyl siloxane polymer as in Example 1 was impregnated into the mesh arrangement and cured such that the compressive members were present at about 20 volume percent of the overall structure.
This interface structure exhibited a compressive modulus along the thickness direction of about 130 psi and a thermal conductivity of 26 W/m·K.
The 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 can be carried out by specifically different devices and that various modifications can be accomplished without departing from the scope of the invention itself.