selectively flexible chemical vapor deposition (CVD) diamond or other heat spreader

Abstract

A system includes at least one component (108) configured to generate thermal energy, a heat spreader (100) configured to remove thermal energy from the at least one component, and at least one substrate (110) configured to remove thermal energy from the heat spreader. The heat spreader includes a first portion (102) and a second portion (104). The first portion of the heat spreader is coupled to the substrate and the second portion of the heat spreader is coupled to the at least one component. The first portion of the heat spreader includes high aspect ratio structures (106) that are separated from one another. The high aspect ratio structures cause the first portion of the heat spreader to be flexible and to accommodate a mismatch between a coefficient of thermal expansion of a material in the heat spreader and a material in the substrate.

Description

Technical Field

[0001] This disclosure generally relates to heat sinks for integrated circuit devices or other devices. More specifically, this disclosure relates to chemical vapor deposition (CVD) diamond or other heat sinks capable of selective flexing. Background Technology

[0002] Typically, heat sinks are used in electronic devices to remove heat from components such as power amplifiers or other integrated circuit chips. In high-power systems, diamond-based heat sinks formed using chemical vapor deposition (CVD) have been used to remove heat from integrated circuit chips, such as silicon carbide (SiC)-based gallium nitride (GaN) power amplifiers or other high heat dissipation density devices. These types of devices typically require highly efficient and thermally expansion-matched heat dissipation to adequately and reliably manage the device's operating temperature. Unfortunately, high-quality CVD diamond is typically relatively expensive to manufacture and has a low coefficient of thermal expansion (CTE), meaning that CVD diamond does not expand much with increasing temperature. Therefore, this often makes CVD diamond heat sinks incompatible with higher CTE requirements or cost-sensitive packaging technologies. Summary of the Invention

[0003] This disclosure provides chemical vapor deposition (CVD) diamond or other heat sinks that can be selectively flexed.

[0004] In a first embodiment, a device includes a heat sink comprising a first portion and a second portion. The first portion of the heat sink is configured to be coupled to a substrate, and the second portion of the heat sink is configured to be coupled to at least one device to be cooled. The first portion of the heat sink includes a high aspect ratio structure that is separated from each other. This high aspect ratio structure causes the first portion of the heat sink to be flexible and adaptable to a mismatch in the coefficient of thermal expansion between the material in the heat sink and the material in the substrate.

[0005] In a second embodiment, a system includes: at least one component configured to generate heat; a heat sink configured to remove heat from the at least one component; and at least one substrate configured to remove heat from the heat sink. The heat sink includes a first portion and a second portion. The first portion of the heat sink is coupled to the substrate, and the second portion of the heat sink is coupled to the at least one component. The first portion of the heat sink includes a high aspect ratio structure that is separated from each other. This high aspect ratio structure causes the first portion of the heat sink to be flexible and adaptable to a mismatch in the coefficient of thermal expansion between the materials in the heat sink and the materials in the substrate.

[0006] In a third embodiment, a method includes: obtaining a heat sink comprising a first portion and a second portion; attaching the first portion of the heat sink to a substrate; and attaching the second portion of the heat sink to at least one device to be cooled. The first portion of the heat sink comprises a high aspect ratio structure separated from each other. The high aspect ratio structure causes the first portion of the heat sink to be flexible and adaptable to a mismatch in the coefficient of thermal expansion between the material in the heat sink and the material in the substrate.

[0007] Other technical features will readily be apparent to those skilled in the art from the following drawings, description and appended claims. Attached Figure Description

[0008] For a more complete understanding of this disclosure, reference is made to the following description in conjunction with the accompanying drawings, in which:

[0009] Figure 1 Exemplary chemical vapor deposition (CVD) diamond or other heat sinks capable of selective flexibility are shown according to this disclosure;

[0010] Figure 2 An exemplary system for forming a selectively flexible CVD diamond or other heat sink is shown according to the present disclosure;

[0011] Figure 3 An exemplary method for forming a selectively flexible CVD diamond or other heat sink is shown according to this disclosure; and

[0012] Figure 4 An exemplary method for using a selectively flexible CVD diamond or other heat sink is shown according to this disclosure. Detailed Implementation

[0013] The following description Figures 1 to 4 The various embodiments used to describe the principles of the invention in this patent document are merely illustrative and should not be construed as limiting the scope of the invention in any way. Those skilled in the art will understand that the principles of the invention can be implemented in any type of suitably arranged apparatus or system.

[0014] As noted above, diamond-based heat sinks formed using chemical vapor deposition (CVD) can be used to remove heat from integrated circuit chips, such as silicon carbide (SiC)-based gallium nitride (GaN) power amplifiers or other devices. Unfortunately, high-quality CVD diamond is typically relatively expensive to manufacture and has a low coefficient of thermal expansion (CTE), making CVD diamond heat sinks often incompatible with certain packaging technologies that require higher CTE or are cost-sensitive. For example, low-cost radio frequency (RF) modules and other components often require lower-cost heat sinks to control component costs. Furthermore, RF modules and other components are typically mounted on copper or other substrates with a higher CTE than CVD diamond, meaning those substrates expand at a faster rate with increasing temperature than CVD diamond. This can generate significant stresses at the interface between the CVD diamond heat sink and the associated packaging substrate that need to be managed. Typically, the materials used to manage these thermal stresses detract from the thermal benefits of diamond due to their poor thermal conductivity.

[0015] CVD diamond manufacturers have developed a variety of materials in an attempt to find a trade-off between thermal conductivity, cost, and CTE, and to find the "sweetspot" between lower-cost materials (such as beryllium oxide) and pure polycrystalline CVD diamond. These attempts have largely focused on metal / diamond composites (such as aluminum-diamond, copper-diamond, and silver-diamond materials, as well as other more exotic diamond composites). Furthermore, methods have been proposed to "grade" thermal conductivity along the thickness of the heatsink by varying the quality of the CVD diamond during fabrication, in order to optimize performance and cost. However, these attempts have not yet demonstrated the ability to grade CTE, and therefore the continued production of CVD diamond with low CTE.

[0016] This disclosure provides various selectively flexible diamond heat sinks or other heat sinks for use in high-power applications or other applications, wherein the heat sink achieves a customized combination of flexibility, superior thermal performance, and low cost. As described in more detail below, in some embodiments, boron-doped CVD diamond material or other diamond materials (such as wafers) are fabricated or otherwise obtained, and mechanically flexible pillar structures or other high aspect ratio structures are formed in a main surface of the diamond material. The presence of these high aspect ratio structures makes the surface of the diamond material highly flexible, thus enabling it to be coupled to another structure (such as copper or other substrates) with a higher CTE. Because the surface of the diamond material is flexible due to the presence of the high aspect ratio structure, it can accommodate the expansion and contraction of the diamond material and the copper or other substrate at different rates. Therefore, the surface of the diamond material can reduce the additional stress caused by the different expansion and contraction of the diamond material and the copper or other substrate due to their CTE mismatch.

[0017] The other primary surfaces of the diamond material can remain unetched or otherwise solid. This allows the surface to maintain high stiffness and high thermal conductivity in areas where the diamond material is attached to one or more low-CTE integrated circuit chips or other devices to be cooled, such as when bonded to silicon (Si), silicon carbide, or other substrates(s) of a device(s). Therefore, fully dense, high-conductivity diamond is placed closest to the device(s)(s) to be cooled (where the material is most needed), while flexible surfaces with a high aspect ratio structure are located on the opposite side (on which the CTE mismatch needs to be addressed).

[0018] In some instances, using boron-doped diamond materials helps control or reduce costs because boron-doped CVD diamond can grow significantly faster than even the lowest grade of pure CVD diamond and is substantially easier to etch. It is worth noting that if multiple instances of a heat sink are formed on the same wafer, that wafer can be diced or otherwise processed to separate the heat sinks after fabrication, which also simplifies manufacturing operations and increases production yield.

[0019] These approaches can offer a variety of benefits or advantages depending on the implementation method. For example, heat sinks formed using one of these approaches offer superior thermal performance because boron-doped diamond or other diamond materials have very high thermal conductivity, such as between 800 W / m•K and 2000 W / m•K or greater. Furthermore, the selective flexibility of the CVD diamond material on the etched side of the heat sink allows for the application of thin, low-thermal-resistance die-attach materials (such as solder films) to the unetched portions of the diamond material. Additionally, using boron-doped diamond heat sinks or other diamond heat sinks helps create opportunities to reduce the cost of heat sink metallization because boron-doped diamond or other diamond materials provide a degree of conductivity that reduces the reliance on wrap-around metallization for DC and RF grounding.

[0020] Figure 1 An exemplary CVD diamond or other heat sink 100 capable of selective flexibility according to this disclosure is shown. Figure 1 As shown, the heat sink 100 includes a first portion 102 and a second portion 104. The first portion 102 of the heat sink 100 defines a first main surface of the heat sink 100 (on... Figure 1 (Positioned along the bottom of the radiator 100). The second portion 104 of the radiator 100 defines a second main surface of the radiator 100 opposite to the first main surface (in... Figure 1 (Located along the top of radiator 100). The first portion 102 of radiator 100 generally corresponds to the following portion of radiator 100: the portion of radiator 100 has been etched or otherwise treated to form a separated column or other high aspect ratio structure 106. The second portion 104 of radiator 100 generally corresponds to the following portion of radiator 100: the portion of radiator 100 is generally unetched or otherwise solid, and is used to connect radiator 100 to one or more devices to be cooled.

[0021] At least a first portion 102 of the heat sink 100 is formed using CVD diamond. In some instances, the CVD diamond forming at least the first portion 102 of the heat sink 100 may be equivalent to doped CVD diamond, such as boron-doped CVD polycrystalline diamond. In some embodiments, the doping of the first portion 102 of the heat sink 100 is substantially or substantially constant throughout. In other embodiments, the doping of the first portion 102 of the heat sink 100 has a gradient, such as the amount of dopant being greatest at the bottom of the first portion 102 of the heat sink 100 and decreasing with (at...) Figure 1The orientation shown decreases as it moves upward. Such a gradient can facilitate easier etching of the first portion 102 of the heat sink 100 and / or result in a gradient in the thermal conductivity of the first portion 102 of the heat sink 100. The doping gradient can be generated in any suitable manner, such as by changing the growth rate and thus changing the grain size and orientation of the polycrystalline diamond. In other embodiments, the first portion 102 of the heat sink 100 may be undoped CVD diamond.

[0022] The second portion 104 of the heat sink 100 is formed using diamond (such as CVD polycrystalline diamond) and may or may not contain any dopants. In some cases, the first and second portions 104 of the heat sink 100 may initially be formed as a single CVD diamond monolith, and this CVD diamond monolith can then be etched or otherwise processed to form a high aspect ratio structure 106 (thereby distinguishing the first and second portions 104 of the heat sink 100). For example, in some embodiments, the heat sink 100 can be fabricated using a CVD technique in which the first portion 102 of the heat sink 100 (possibly in a gradient manner) is grown using dopants, and then the second portion 104 of the heat sink 100 is grown without dopants. Of course, the reverse is also possible, in which the second portion 104 of the heat sink 100 is grown without dopants, and then the first portion 102 of the heat sink 100 (possibly in a gradient manner) is grown using dopants. Once growth is complete or otherwise formed, the first and second portions 104 of the heat sink 100 can be processed as needed, and the first portion 102 of the heat sink 100 can be etched or otherwise processed to form a high aspect ratio structure 106.

[0023] The two portions 102 and 104 of the heat sink 100 and the heat sink 100 itself can each have any suitable size, shape, and dimensions. In this example, the heat sink 100 is generally rectangular when viewed from the side, and it may also be generally rectangular when viewed from the top. However, this is merely for illustration, and any other suitable regular or irregular shape may be used herein. Moreover, in this example, the first portion 102 of the heat sink 100 has a greater, and possibly much greater, thickness than the second portion 104 of the heat sink 100 (in... Figure 1 (Measured from top to bottom). Furthermore, this is for illustrative purposes only, and each portion 102, 104 of the heat sink 100 can have any suitable thickness. Additionally, in this example, each portion 102, 104 of the heat sink 100 has a substantially constant thickness, although this is not necessary. For example, the high aspect ratio structure 106 in different regions of the first portion 102 of the heat sink 100 can have different heights.

[0024] The high aspect ratio structure 106 in the heat sink 100 generally corresponds to a column or other slender structure with a high aspect ratio, wherein those structures are separated from each other by gaps. High aspect ratio generally indicates that each structure 106 has a certain aspect ratio relative to its width (in... Figure 1 (measured from left to right) compared to a basically larger height (in) Figure 1 (Measurement from top to bottom). The high aspect ratio structures 106 in the radiator 100 can each have any suitable size, shape, and dimension, and the high aspect ratio structures 106 can be arranged in any suitable regular or irregular manner in the radiator 100. Each of the high aspect ratio structures 106 can also have any suitable cross-sectional shape, such as circular, rectangular, or other shapes, and different high aspect ratio structures 106 may or may not have different cross-sectional shapes.

[0025] The high aspect ratio structure 106 can be formed in any suitable manner. Exemplary techniques can include etching the diamond material forming the first portion 102 of the heat sink 100 using a depth reactive ion etching (DRIE) process or other plasma etching process, a water jet etching process, or any other suitable process that removes material from the first portion 102 of the heat sink 100 to form the high aspect ratio structure 106. As noted above, in some embodiments, a doping gradient may be used in the first portion 102 of the heat sink 100 to facilitate easier etching of the first portion 102 of the heat sink 100. However, the use of a doping gradient (at least to facilitate etching) is optional and not required in any particular embodiment of the heat sink 100.

[0026] In this example, heat sink 100 is used to transfer heat energy from one or more devices 108 to at least one substrate 110. Each device 108 corresponds to any suitable integrated circuit chip or other structure that generates (or receives from another source) the heat energy to be removed by heat sink 100. In some embodiments, at least one device 108 corresponds to one or more gallium nitride-on-silicon carbide integrated circuit chips or other high-power integrated circuit chips. As a particular example, at least one device 108 may include one or more power amplifiers or one or more RF modules. Note that although one or more devices 108 are shown herein as extending fully across the width of the second portion 104 of heat sink 100, this is for illustrative purposes only. The main surface of heat sink 100 formed by the second portion 104 of heat sink 100 may be larger (and potentially significantly larger) than the one or more devices 108 to be cooled.

[0027] Each substrate 110 corresponds to any suitable structure that receives heat energy from the heat sink 100 and transports that heat energy to one or more desired destinations (such as for removal). In some embodiments, each substrate 110 corresponds to a copper substrate or another metallic substrate with a high CTE or a highly thermally conductive substrate. In many instances, the CTE of one or more materials forming each substrate 110 will be higher than the CTE of one or more materials forming the heat sink 100. Therefore, under the same temperature change, each substrate 110 will expand and contract more relative to the heat sink 100. Note that the relative size and dimensions of the heat sink 100 relative to the substrate 110 are for illustrative purposes only and can be varied as needed or desired.

[0028] Thermal interface material (TIM) 112 may be positioned between heat sink 100 and each device 108, and thermal interface material 114 may be positioned between heat sink 100 and each substrate 110. Each thermal interface material 112, 114 generally corresponds to a thin layer of material that facilitates heat transfer between components and provides protection for at least one of the components (such as heat sink 100). Each thermal interface material 112, 114 can be formed from any suitable material(s) and in any suitable manner. As a specific example, solder or sintering material may be used to form each thermal interface material 112, 114. Each thermal interface material 112, 114 may also have any suitable size, shape, and dimension. Note that the thickness of thermal interface materials 112, 114 is for illustrative purposes only, and thermal interface materials 112, 114 may typically be much thinner than shown herein.

[0029] As described above, the formation of the high aspect ratio structure 106 allows the first portion 102 of the heat sink 100 to be selectively flexible. Among other things, this flexibility allows the heat sink 100 to be used with at least one substrate 110 having a different (and potentially significantly different) coefficient of thermal expansion compared to the diamond material of the heat sink 100. For example, the CVD diamond in the heat sink 100 may have a CTE of about 1 ppm / K, while the copper in the substrate 110 may have a CTE of about 17 ppm / K. The use of the high aspect ratio structure 106 allows the first portion 102 of the heat sink 100 to accommodate such a large mismatch between the CTE of the CVD diamond and the CTE of the copper. In other words, because the high aspect ratio structure 106 is flexible and therefore can be bent to a certain extent as needed, the high aspect ratio structure 106 allows the material of substrate(s)110(s) to expand and contract at a rate significantly different from that of the material of the heat sink 100.

[0030] Furthermore, the customizable nature of the high aspect ratio structure 106 allows for tailoring the amount of adaptation in different ways for different implementations. Thus, for example, different configurations or arrangements of the high aspect ratio structure 106 can be used to provide different amounts of flexibility. These different configurations or arrangements of the high aspect ratio structure 106 can be used in different regions of the same first portion 102 of the same radiator 100 or in different radiators 100. As a specific example, thicker and / or more high aspect ratio structures 106 can provide lower flexibility, while thinner and / or fewer high aspect ratio structures 106 can provide more flexibility. Therefore, the desired amount of flexibility can be obtained in one or more regions of the first portion 102 of the radiator 100 by appropriately fabricating suitable high aspect ratio structures 106 in one or more regions of the first portion 102 of the radiator 100.

[0031] Furthermore, the second portion 104 of the radiator 100 may remain generally solid and substantially flat to facilitate mounting at least one device 108 and removing heat from at least one device 108. For example, each device 108 may have a CTE much closer to that of CVD diamond when each device 108 has a CTE of approximately 3 ppm / K. This mismatch can typically be accommodated by using thermal interface material 112 or other mechanisms. Thus, the second portion 104 of the radiator 100 is capable of effectively removing heat from one or more devices 108 while accommodating any CTE mismatch.

[0032] Additionally, the optional use of doping can help facilitate easier fabrication and / or improved operation of the heat sink 100. For example, as noted above, boron-doped CVD diamond can be grown much faster than pure CVD diamond and is substantially easier to etch, thereby facilitating easier formation of the high aspect ratio structure 106. As another example, doping can be used to create gradients or otherwise achieve the desired thermal conductivity of the first portion 102 of the heat sink 100.

[0033] Finally, even with the high aspect ratio structure 106 present, the thermal conductivity of the first portion 102 of the heat sink 100 remains sufficiently high, and may be significantly higher than that of the device(s) 108. This is useful because the gaps between the high aspect ratio structures 106 reduce the thermal conductivity of the first portion 102 of the heat sink 100 relative to the thermal conductivity of the second portion 104 of the heat sink 100. Therefore, even with a lower thermal conductivity, the first portion 102 of the heat sink 100 is still sufficient to transfer heat between the device(s) 108 and the substrate(s) 110 in a suitable manner.

[0034] although Figure 1 An example of a CVD diamond or other heat sink 100 capable of selective flexing is shown, but other options are possible. Figure 1 Various modifications can be made. For example, each component of the heat sink 100 can have any suitable size, shape, and dimension, and can be formed from any suitable material(s) and in any suitable manner. Furthermore, while specific examples of materials, fabrication techniques, and thermal conductivity have been provided above, these are for illustrative purposes only and do not limit the scope of this disclosure to these specific materials, fabrication techniques, and thermal conductivity. As a particular example, although generally described as involving the use of a diamond material formed by CVD, the diamond material can be formed in any other suitable manner. Moreover, the heat sink 100 does not need to be formed using a diamond material; instead, it can be formed using other etchable, high thermal conductivity heat sink materials(s) such as silicon carbide or aluminum nitride (AlN). As another particular example, although generally described as involving the use of a boron-doped diamond material, the diamond material can have any other suitable dopant(s) that promotes the etching, growth, or other formation of the high aspect ratio structure 106 or the heat sink 100, or the doping may not be used in conjunction with the diamond material.

[0035] Figure 2 An exemplary system 200 for forming a selectively flexible CVD diamond or other heat sink is shown according to the present disclosure. For ease of explanation, Figure 2 System 200 can be described as being used for making Figure 1 One or more instances of the heat sink 100. However, Figure 1 The radiator 100 can be made using any other suitable system in any other suitable manner. Furthermore, Figure 2 The system 200 can be used to manufacture any other suitable radiator designed in accordance with the teachings of this disclosure.

[0036] like Figure 2As shown, system 200 includes CVD equipment 202, etching / cutting equipment 204, TIM deposition equipment 206, and mounting equipment 208. CVD equipment 202 generally corresponds to at least one deposition chamber and associated equipment for performing one or more chemical vapor deposition processes within the deposition chamber(s). Among other things, CVD equipment 202 can also be used to form boron-doped CVD diamond material or other diamond materials for use in the fabrication of heat sinks. As a specific example, CVD equipment 202 can be used to form wafers of boron-doped CVD diamond material or other diamond materials. In some instances, each wafer of diamond material can be produced by growing the diamond material on a sacrificial substrate and then etching or otherwise removing the sacrificial substrate to obtain a wafer of diamond material. As noted above, in some cases, the diamond material produced by CVD equipment 202 can be polycrystalline. Furthermore, as noted above, the diamond material produced by the CVD equipment 202 may be doped with or without a gradient, which can be accomplished by introducing one or more suitable dopants into the deposition chamber during the growth of the diamond material. The CVD equipment 202 includes any suitable components for forming diamond material or other heat sink material using a chemical vapor deposition process.

[0037] Etching / cutting equipment 204 generally corresponds to equipment used for etching and / or cutting diamond material produced by CVD equipment 202. For example, etching / cutting equipment 204 may include at least one etching chamber and associated equipment for performing a deep reactive ion etch process or other plasma etching process on a wafer of diamond material to form a high aspect ratio structure 106. Etching / cutting equipment 204 may alternatively include equipment for performing a water jet etching process or other suitable etching process to remove material from the wafer of diamond material to form the high aspect ratio structure 106. As noted above, the formation of the high aspect ratio structure 106 can be customized to achieve a desired level of flexibility in the heat sink 100. Different regions of the first portion 102 of the same heat sink 100 may or may not have high aspect ratio structures 106 with different characteristics to achieve different levels of flexibility in those regions. If multiple heat sinks 100 can be fabricated at different portions of a single diamond material wafer, the etching / cutting apparatus 204 may further include apparatus for dicing the diamond material wafer into individual heat sinks 100. The etching / cutting apparatus 204 includes any suitable components for etching, cutting, or otherwise mechanically processing the diamond material or other heat sink material to form a high aspect ratio structure 106 and (if necessary) personalized heat sinks 100.

[0038] TIM deposition apparatus 206 generally corresponds to apparatus for depositing one or more thermal interface materials onto heat sink 100 and / or onto components to be coupled to heat sink 100. For example, TIM deposition apparatus 206 may include apparatus for depositing thermal interface material 112 onto a generally flat surface of a second portion 104 of heat sink 100 and for depositing thermal interface material 114 onto a generally flat surface of a first portion 102 of substrate 110 to be coupled to heat sink 100. Note that the placement of thermal interface materials 112, 114 may vary depending on the implementation and may be deposited in any other suitable manner. TIM deposition apparatus 206 includes any suitable components for depositing one or more thermal interface materials.

[0039] Mounting device 208 is generally equivalent to equipment for attaching heat sink 100 to other components of a larger system. For example, mounting device 208 may include equipment for mounting one or more devices 108 to at least one heat sink 100 and one or more heat sinks 100 to at least one substrate 110. In some cases, mounting device 208 may heat one or more of these components to “reflow” solder or other materials forming thermal interface materials 112, 114, so as to attach each heat sink 100 to (one or more) devices 108 and (one or more) substrates 110. Mounting device 208 includes any suitable components for attaching components to heat sink 100.

[0040] although Figure 2 An example of a system 200 for forming a selectively flexible CVD diamond or other heat sink 100 is shown, but alternatives are possible. Figure 2 Make several changes. For example, Figure 2 The various components shown can be combined, further subdivided, repeated, omitted, or rearranged, and additional components can be added as needed. As a specific example, additional equipment can be used to perform additional operations in system 200, such as any post-formation processing of diamond materials and / or any post-installation processing of the mounted heat sink / device / substrate. As another specific example, the general sequence of operations discussed above is for illustrative purposes only and may vary depending on the equipment used.

[0041] Figure 3 An exemplary method 300 for forming a selectively flexible CVD diamond or other heat sink is shown according to this disclosure. For ease of explanation, Figure 3 Method 300 can be described as being used to make Figure 1 One or more instances of the heat sink 100. However, any other suitable technique may be used to manufacture it in any other suitable manner. Figure 1The radiator is 100. Furthermore, Figure 3 Method 300 can be used to manufacture any other suitable radiator designed in accordance with the teachings of this disclosure.

[0042] like Figure 3 As shown, in step 302, diamond material for one or more heat sinks is fabricated or otherwise obtained. This may include, for example, fabricating or otherwise obtaining a wafer of at least one CVD diamond material. Fabricating the CVD diamond material may involve growing the CVD diamond material to form one or more wafers, wherein suitable one or more dopants may be introduced at one or more suitable times during growth (and optionally with the formation of a doping gradient in the CVD diamond material). If necessary, one or more pretreatment operations may be performed on the diamond material in step 304. This may include, for example, pretreating the wafer of the CVD diamond material to give the diamond material a desired thickness or one or more other properties.

[0043] In step 306, the diamond material is etched or otherwise processed to form a high aspect ratio structure in the main surface of the diamond material. This may include, for example, etching the wafer of each CVD diamond material to form the desired high aspect ratio structure 106 along one main surface of the diamond material. The opposite main surface of the diamond material may remain flat or unetched. As noted above, the properties of the high aspect ratio structure 106 (such as its height, width, or density) can be customized to achieve a desired level of flexibility in the heat sink 100. Moreover, the first portion 102 of a single heat sink 100 may include different regions with the high aspect ratio structure 106, which have different properties (such as different heights, widths, or densities) to achieve different levels of flexibility in the regions. Therefore, the flexibility properties of the heat sink 100 can be customized based on a number of factors to achieve constant or variable flexibility. In step 308, the diamond material is cut (if necessary) to form individual heat sinks. This may include, for example, cutting each wafer of CVD diamond material to form an individual heat sink 100.

[0044] In step 310, each heat sink is attached to another component. This may include, for example, using thermal interface material 112 or other mechanisms, to attach each heat sink 100 (such as the second portion 104 of heat sink 100) to one or more devices 108. This may also include using thermal interface material 114 or other mechanisms to attach each heat sink 100 (such as the first portion 102 of heat sink 100) to at least one substrate 110. Note that these attachments may be accomplished in any other suitable manner and do not necessarily depend on the use of thermal interface materials 112, 114.

[0045] although Figure 3 An example of a method 300 for forming a selectively flexible CVD diamond or other heat sink 100 is shown, but variations are possible. Figure 3 Several changes were made. For example, although shown as a series of steps, Figure 3 Multiple steps can overlap, occur in parallel, occur in different orders, or occur any number of times.

[0046] Figure 4 An exemplary method 400 for using a selectively flexible CVD diamond or other heat sink is shown according to this disclosure. For ease of explanation, Figure 4 Method 400 can be described as involving the use of Figure 1 One or more instances of the heat sink 100. However, it can be used in any other suitable manner. Figure 1 The radiator is 100. Furthermore, Figure 4 Method 400 may involve using any other suitable radiator designed in accordance with the teachings of this disclosure.

[0047] like Figure 4 As shown, in step 402, heat energy is generated or otherwise obtained by the one or more devices to be cooled. This may include, for example, operating one or more devices 108 coupled to at least one heat sink 100. As a particular example, this may include operating one or more power amplifiers or one or more RF modules coupled to at least one heat sink 100.

[0048] In step 404, at least a portion of the thermal energy is transferred from the one or more devices to be cooled to a second portion 104 of at least one radiator. This may include, for example, the flow of thermal energy from the one or more devices 108 through a thermal interface material 112 to a second portion 104 of at least one radiator 100. In some embodiments, the second portion 104 of at least one radiator 100 is not etched or otherwise provided with a flat surface, which may help increase the flow of thermal energy into the one or more radiators 100.

[0049] In step 406, at least a portion of the thermal energy is transferred from the second portion of at least one heat sink to the first portion of at least one heat sink. This may include, for example, thermal energy flowing from the second portion 104 of at least one heat sink 100 to the first portion 102 of at least one heat sink 100. Although the first portion 102 of at least one heat sink 100 includes a high aspect ratio structure 106 separated by gaps (and therefore has a lower thermal conductivity relative to the second portion 104 of at least one heat sink 100), the overall thermal conductivity of at least one heat sink 100 is still more than sufficient for transferring a considerable amount of thermal energy from one or more devices 108.

[0050] In step 408, at least a portion of the thermal energy is transferred from a first portion of at least one heat sink to at least one substrate. This may include, for example, the flow of thermal energy from the first portion 102 of at least one heat sink 100 through a thermal interface material 114 to one or more substrates 110. Here, the overall result of steps 402-408 is that one or more devices 108 are cooled based on the thermal energy transfer that has occurred through at least one heat sink 100 and to (one or more) substrates 110.

[0051] In step 410, the mismatch in thermal expansion and / or contraction between at least one heat sink and at least one substrate is accommodated. This may include, for example, a high aspect ratio structure 106 of the first portion 102 of at least one heat sink 100 bending or otherwise deforming during operation of one or more devices 108. This allows copper or other materials in at least one substrate 110 to expand or contract at a different rate than the diamond material in at least one heat sink 100. Therefore, this helps to avoid generating considerable stress along the boundary between at least one substrate 110 and at least one heat sink 100.

[0052] although Figure 4 An example of a method 400 for using a selectively flexible CVD diamond or other heat sink 100 is shown, but variations are possible. Figure 4 Several changes were made. For example, although shown as a series of steps, Figure 4 The various steps in the process can overlap, occur in parallel, occur in different orders, or occur any number of times.

[0053] It may be advantageous to clarify the definitions of certain words and phrases used throughout this patent document. The terms “comprising” and “including” and their derivatives mean inclusion rather than limitation. The term “or” is inclusive, meaning and / or. The phrase “associated with” and its derivatives may mean including, being included in, interconnected with, containing, being contained within, connected to or connected with, linked to or connected with, capable of communicating with, cooperating with, interleaving, juxtaposing, proximate, demarcated to or bordering with, having, possessing the nature of, relating to or related to, etc. When used with a list of items, the phrase “at least one of” means that different combinations of one or more of the listed items may be used, and that only one item in the list may be required. For example, “at least one of the following: A, B, and C” includes any of the following combinations: A, B, C, A and B, A and C, B and C, and A and B and C.

[0054] The descriptions in this application should not be construed as implying that any particular element, step, or function is a fundamental or critical element that must be included within the scope of the claims. The scope of the patent subject matter is defined solely by the granted claims. Furthermore, no claim invokes 35 USC § 112(f) with respect to any appended claims or claim elements, unless the specific claim expressly uses the exact words “part for…” or “step for…” followed by a participle phrase indicating the function.

[0055] While this disclosure has described some embodiments and generally associated methods, variations and substitutions of these embodiments and methods will be apparent to those skilled in the art. Therefore, the above description of exemplary embodiments does not limit or restrict this disclosure. Other changes, substitutions, and modifications are possible without departing from the spirit and scope of this disclosure, as defined by the appended claims.

Claims

1. An apparatus for thermal management, comprising: a heat spreader, comprising: a first portion configured to be coupled to a substrate, the first portion comprising chemical vapor deposition (CVD) diamond, wherein the CVD diamond in the first portion is doped, and wherein, in the first portion, the doping of the CVD diamond has a gradient, and a second portion configured to be coupled to at least one device to be cooled; wherein the first portion of the heat spreader comprises high aspect ratio structures that are separate from each other, the high aspect ratio structures having a greater height than their width, the high aspect ratio structures causing the first portion of the heat spreader to be flexible and to accommodate a mismatch in coefficient of thermal expansion between a material in the heat spreader and a material in the substrate.

2. The apparatus of claim 1, wherein, the second portion of the heat spreader comprises CVD diamond.

3. The apparatus of claim 1, wherein, the doping in the CVD diamond in the first portion of the heat spreader is greatest along an outer surface of the heat spreader that is adjacent to the substrate, and decreases as moving away from the outer surface.

4. The apparatus of claim 1, wherein, the CVD diamond in the first portion of the heat spreader is doped with boron.

5. The apparatus of claim 1, wherein, the CVD diamond comprises CVD polycrystalline diamond.

6. The apparatus of claim 1, wherein, the apparatus further comprises at least one of: a first thermal interface material on an outer surface of the first portion of the heat spreader; and a second thermal interface material on an outer surface of the second portion of the heat spreader.

7. A system for thermal management, comprising: at least one component configured to generate thermal energy; a heat spreader configured to remove thermal energy from the at least one component; and at least one substrate configured to remove thermal energy from the heat spreader; wherein the heat spreader comprises: a first portion coupled to the at least one substrate, the first portion comprising chemical vapor deposition (CVD) diamond, wherein the CVD diamond in the first portion is doped, and wherein, in the first portion, the doping of the CVD diamond has a gradient, and a second portion coupled to the at least one component; and wherein the first portion of the heat spreader comprises high aspect ratio structures that are separate from each other, the high aspect ratio structures having a greater height than their width, the high aspect ratio structures causing the first portion of the heat spreader to be flexible and to accommodate a mismatch in coefficient of thermal expansion between a material in the heat spreader and a material in the at least one substrate.

8. The system of claim 7, wherein, the at least one component comprises at least one integrated circuit chip.

9. The system of claim 7, wherein at least one of: the at least one component comprises a silicon carbide based gallium nitride device; and the at least one substrate comprises copper.

10. The system of claim 7, wherein, the second portion of the heat spreader comprises CVD diamond.

11. The system of claim 7, wherein, the heat spreader further comprises at least one of: a first thermal interface material on an outer surface of the first portion of the heat spreader; and a second thermal interface material on an outer surface of the second portion of the heat spreader.

12. A method for thermal management, comprising: obtaining a heat spreader, the heat spreader comprising: a first portion comprising chemical vapor deposition (CVD) diamond, wherein the CVD diamond in the first portion is doped, and wherein, in the first portion, the doping of the CVD diamond has a gradient, and a second portion; attaching the first portion of the heat spreader to a substrate; and attaching the second portion of the heat spreader to at least one device to be cooled; wherein the first portion of the heat spreader comprises high aspect ratio structures that are separate from one another, the high aspect ratio structures having a greater height than their width, the high aspect ratio structures causing the first portion of the heat spreader to be flexible and to accommodate a mismatch in coefficient of thermal expansion between the material in the heat spreader and the material in the substrate.

13. The method of claim 12, wherein, The second portion of the heat spreader comprises CVD diamond.

14. The method of claim 13, wherein, Obtaining the heat spreader comprises fabricating the heat spreader by: obtaining a wafer of CVD diamond; etching the wafer to form the high aspect ratio structures; and dicing the wafer to form individual heat spreaders.

15. The system of claim 7, wherein, The doping in the CVD diamond in the first portion of the heat spreader is greatest along an outer surface of the heat spreader that is adjacent to the at least one substrate, and decreases as one moves away from the outer surface.

16. The system of claim 7, wherein, The CVD diamond in the first portion of the heat spreader is doped with boron.

17. The system of claim 7, wherein, The CVD diamond comprises CVD polycrystalline diamond.

18. The method of claim 12, wherein, The doping in the CVD diamond in the first portion of the heat spreader is greatest along an outer surface of the heat spreader that is adjacent to the substrate, and decreases as one moves away from the outer surface.

19. The method of claim 12, wherein, The CVD diamond in the first portion of the heat spreader is doped with boron.

20. The method of claim 12, wherein, The CVD diamond comprises CVD polycrystalline diamond. The CVD diamond comprises CVD polycrystalline diamond.

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