Patent Application
20190343020
Embodiments of the invention relate generally to cooling devices for electronics modules and, more particularly, to a fluid cooled heat sink having an integral electromagnetic shielding structure.
The electrical system performance of electronic components is limited by the rate at which the heat it produces is removed. In the field of electronics, and power electronics in particular, there is a generally continuous demand for enhanced performance capabilities and increased package density all within a smaller and smaller footprint. These combined demands increase operating temperatures and thereby erode the performance capabilities of the electronic device. Heightened operating temperatures are especially prevalent in power electronics modules since they are designed to operate at increased power levels and generate increased heat flux as a result.
Thermal management of a heat generating component, such as a power electronics module, may be accomplished with a heat sink that enhances heat transfer from the heat generating component and lowers the operating temperature thereof. The heat transfer capabilities of conventional fluid cooled heatsink designs are currently limited by the capabilities of the casting and machining processes used to manufacture them. Large metal heat sinks can also be quite heavy, even when fabricated from relatively light-weight aluminum.
In addition to thermal management, electromagnetic interference (EMI) suppression is an important part of the design of power electronics systems. With the emergence of wide-bandgap power electronics devices, such as SiC and GaN, for example, EMI suppression becomes more critical due to the extremely fast switching speeds of the devices. Therefore, reducing EMI generated during switching events is an important consideration for optimizing performance of power electronics systems.
Therefore, it would be desirable to design an improved electronics packaging solution that suppresses EMI and provides enhanced thermal management for heat generating components such as power devices.
In accordance with one aspect of the invention, a heat sink for cooling an electronic component includes a substrate comprising an electrically non-conductive material and an inlet port and an outlet port extending outward from the substrate. The inlet and outlet ports are fluidically coupled to a fluid flow surface of the heat sink by passages that extend through a portion of the substrate. The heat sink also includes a shield comprising an electrically conductive material. The shield is disposed atop or within the substrate.
In accordance with another aspect of the invention, a method of manufacturing a heat sink for an electronics component includes forming a heat sink substrate from an electrically non-conductive material using an additive manufacturing process, the heat sink substrate comprising a fluid inlet port, a fluid outlet port, and a fluid flow surface fluidically coupled to the fluid inlet port and the fluid outlet port. The method also includes disposing a shield layer on a surface of the heat sink substrate during the additive manufacturing process, the shield layer comprising an electrically conductive material.
In accordance with another aspect of the invention, a thermal management assembly includes a heat sink comprising a substrate comprising an electrically non-conductive material, the substrate having a fluid flow surface fluidically coupled to a fluid inlet port and a fluid outlet port. The heat sink also includes a shielding structure comprising an electrically conductive layer disposed on or within the substrate. A heat generating component is coupled to a mounting surface of the heat sink. The shielding structure suppresses electromagnetic interference generated by the heat generating component.
These and other advantages and features will be more readily understood from the following detailed description of preferred embodiments of the invention that is provided in connection with the accompanying drawings.
The drawings illustrate embodiments presently contemplated for carrying out the invention.
In the drawings:
Embodiments of the present invention provide for a cooling device for one or more heat generating components. The cooling device is a fluid cooled heat sink formed as a molded component or using an additive manufacturing technique (e.g., stereolithography or three-dimensional (3D printing) that facilitates forming the heat sink as a unitary structure having a complex geometry of internal fluid passages. The cooling device or heat sink also includes a metallic shielding structure that is configured to suppress or mitigate electromagnetic interference (EMI). The electromagnetic shield is either embedded within the core substrate of the heat sink itself or coupled to a top surface of the core substrate. The electromagnetic shielding fluid cooled heat sink may be designed for attachment to a single heat generating component or module, or may be designed as a multi-module heat sink having a generally planar or three-dimensional geometry, as described in more detail below.
Referring now to
Shield 14 is an electrically conductive material such as copper, silver, nickel, or aluminum nitride as non-limiting examples. Shield 14 may be formed by applying a conductive paint, electroplating, performing a sputtering process, or as part of an additive manufacturing technique such as stereolithography, 3D printing, or other known additive technique. Shield 14 may be a single conductive layer or a stack of conductive layers. In some embodiments, shield 14 includes one or more layers of electrically conductive material (e.g., copper) that define the core structure of shield 14 and an optional barrier layer or plating layer 20 (e.g., titanium, nickel, or an alloy thereof) that is disposed atop the core structure to mitigate corrosion. When heat sink 10 is coupled to a heat generating component such as the power module 84 of
Shield 14 conforms to the underlying surface topology of the top side 16 of substrate 12, which includes a component mounting surface 22 and a fluid flow surface 24 of the heat sink 10. The fluid flow surface 24 is recessed below the component mounting surface 22 and forms the bottom surface of a recess or well 26 of the heat sink 10. The shield 14 extends across the component mounting surface 22 and extends into the well 26, coating the sidewalls of the well 26 and the fluid flow surface 24. Shield 14 may maintain substantially the same thickness across the top side 16 of substrate 12, or have some areas thinner than others (e.g., on the vertical sidewalls of the well 26).
Referring to
In operation, a cooling medium is directed into the inlet fitting 38 and exits from the outlet fitting 42. Inlet fitting 38 and outlet fitting 42 may include coupling devices such as valves, nozzles, and the like, to enable the heat sink 10 to be coupled to inlet and outlet fluid reservoirs (not shown). The cooling medium may be part of a closed loop or open loop system. The cooling medium may be water, an ethylene glycol solution, an alcohol, or any other material having a desirable thermal capacity to remove heat from a heat generating component coupled to the heat sink 10.
The inlet orifice 28 and outlet orifice 32 may be sized similarly, as shown in
In the illustrated embodiment, the inlet fitting 38 and outlet fitting 42 are arranged generally orthogonal to the fluid flow surface 24. The supply passage 36 defines a generally linear pathway for fluid to flow between the inlet end of the inlet fitting 38 and the inlet orifice 28. Likewise, the exhaust passage 40 defines a generally linear pathway for cooling medium to flow between the outlet orifice 32 and the outlet end of the outlet fitting 42. In alternative embodiments, supply and exhaust passages 36, 40 may define more complex and non-linear passageways through substrate 12 to obtain even fluid flow distribution over the fluid flow surface 24 and minimize pressure loss.
In the illustrated embodiment, the inlet and outlet orifices 28, 32 are generally aligned along the centerline of the well 26 such that the cooling medium is directed across the fluid flow surface 24 in a direction generally perpendicular to the long axis of each of the raised surface features 76. In alternative embodiments, either or both of the inlet and outlet orifices 28, 32 may be positioned off-center (e.g., proximate a corner). In such case the raised surface features 76 may reoriented to be generally orthogonal to the flow direction across fluid flow surface 24.
In one embodiment, substrate 12 and inlet and outlet fittings 38, 42 are formed from an electrically non-conductive material such as a polymer, plastic, ceramic, or composite including fillers and/or additives. Substrate 12 and inlet and outlet fittings 38, 42 may be thermally conductive or thermally non-conductive. In a preferred embodiment, substrate 12 and inlet and outlet fittings 38, 42 are a high-temperature ceramic-plastic composite such as, for example, Accura® Bluestone™, which can handle steady-state operating temperatures (e.g., temperatures at or above 250° C.), has a rigid structure that is able to support limiting machining such as hole drilling and tapping, has sufficient strength to handle high mechanical loadings from hose clamps and nominal fluid pressures during operation. One skilled in the art will recognize that substrate 12 and inlet and outlet fittings 38, 42 are not limited to the listing of materials described herein and that alternative materials may be used to form substrate 12 and inlet and outlet fittings 38, 42 depending on the specific application and design of the heat sink.
The component mounting surface 22 of heat sink 10 may optionally be formed having a recessed groove 102 that surrounds the well 26 and is sized to receive a portion of an O-ring or gasket 104 (shown in
In some embodiments, heat sink 10 may include one or more additional mounting features 46 (shown in phantom in
Although the heat sink 10 is illustrated having a generally rectangular, box-like shape, embodiments are not limited thereto. For example, the bottom side 48 of the heat sink 10 may be a generally planar surface or have a curved surface topology to facilitate arranging heat sink 10 relative to other external structures. In other embodiments, the top side 16 of heat sink 10 may have a curved surface topology that mirrors a curved mounting surface of a heat generating component.
In a preferred embodiment, substrate 12 and inlet and outlet fittings 38, 42 are manufactured as a unitary structure using an additive manufacturing process such as 3D printing or stereolithography (SLA). Substrate 12 and inlet and outlet fittings 38, 42 may also be manufactured as a unitary structure by a known molding or machining process or a combination of known manufacturing processes including, but not limited to, molding, machining, additive manufacturing, stamping, a known material removal process (e.g., milling, grinding, drilling, boring, etching, eroding, etc.), and/or an additive process (e.g., printing, deposition, etc.). In yet other embodiments, substrate 12 may be formed as a multi-layer structure with inlet and outlet fittings 38, 42 provided as separate components bonded or coupled together by an adhesive, fasteners, or other known joining means.
In the embodiment illustrated in
Referring first to
In the embodiment shown in
The fluid flow surface 24 of any of the heat sink configurations described with respect to
In the illustrated embodiment, raised surface features 76 are discrete curved, arcuate, or crescent-shaped ridges that are arranged in alternating or offset rows across the fluid flow surface 24. In such an arrangement, cooling medium that passes through a gap formed between two adjacent ridges in one row impinges upon a ridge in the next row. The raised surface features 76 function as ramps to direct coolant upward toward the surface of an adjacent heated component. Additionally, the height and spacing of the raised surface features 76 serve to accelerate and decelerate the flow of cooling medium across the fluid flow surface 24 to further augment the convective coefficient of heat transfer from the adjacent heated surface. The raised surface features 76 thus function to form an array of flow velocity distributed jets (referred hereafter as “pseudo jets”) within the cooling medium flow. These pseudo jets enhance heat transfer between the fluid and an adjacent heated surface, resulting in high local convective coefficients within the immediate zone of impact between the heated surface and a respective pseudo jet.
While the peak local heat transfer coefficients produced by the raised surface features 76 may be comparatively lower than those produced by known impinging jet technologies, the combined effect of the entire array of pseudo jets results in an average convective heat transfer coefficient on an adjacent heated surface that is significantly higher than that produced by the discrete impinging jets of the prior art. A heat sink 10 having the raised surface features 76 also operates at relatively low pressure drop and at channel flow velocities that are well below the threshold normally associated with erosion.
In one exemplary and non-limiting embodiment, the raised surface features 46 are ridges that have a height of approximately 1.0 mm, a width or thickness of approximately 1.0 mm, and a length of approximately 4 mm. In such an embodiment, the well 20 may have a width of approximately 45 mm and a length of approximately 105 mm, with the depth of the well 20 spaced approximately 1.5 mm away from the top surface of the raised surface features 46. The dimensions of the well 20 and the dimensions of the raised surface features 46 may be modified in alternative embodiments to enhance heat transfer based on the design specifications of a particular application.
While illustrated herein as crescent-shaped ridges, it is contemplated that the raised surface features 76 may have numerous other geometries that similarly function to form pseudo jets within the flow of cooling medium. For example, raised surface features 76 may have other curved or arcuate geometries, may be a series of dashed straight line segments, or may have an open waffle pattern formed from a series of bisecting dashed lines.
In the embodiment illustrated in
Referring now to
While heat generating component 84 is described herein as a power electronics package, it is understood that heat sink 10 can be configured to facilitate thermal management of any number of alternative types of heat generating components and/or alternative types of electronics packages or components than that described above. Thus, embodiments of the invention are not limited only to the specifically illustrated devices and arrangements thereof. As used herein the term “electrical component” may be understood to encompass various types of semiconductor devices, including without limitation, IGBTs, MOSFETs, power MOSFETs, and diodes, as well as resistors, capacitors, inductors, filters and similar passive devices and/or combinations thereof. In such instances, the position, geometry, spacing, and/or number of surface mounting features 98 may be modified to facilitate mounting the heat sink 10 to the heat generating component 84.
In the embodiment illustrated in
Referring now to
The unitary substrate 114 can be generally described as including three main portions: a first mounting plate portion 116 on the first side 118 of the multi-module heat sink 112, a second mounting plate portion 120 on the second side 122 of the multi-module heat sink 112, and a coolant passage portion 124 positioned between the first and second portions 116, 120. The first mounting plate portion 116 includes three (3) generally co-planar mounting locations 126. Similarly, the second mounting plate portion 120 includes three (3) generally co-planar mounting locations 128. Thus, multi-module heat sink 112 provides discrete mounting locations for six (6) heat generating components in the configuration shown. It is contemplated that heat sink 112 may be modified to provide mounting locations for more or less components than shown herein.
A conformal shielding structure 130, 132 is formed over the outward-facing surfaces of the first and second mounting plate portions 116, 120. Conformal shields 130, 132 may be formed similar to and include any of the same materials as shield 14 of
In one embodiment the conformal shields 130, 132 may be replaced by shielding structures embedded within the first mounting plate portion 116 and second mounting plate portion 120 in a similar manner as shield 56 of
As best shown in
Referring now to
Cooling medium is directed into the fluid inlet manifold 134 through an inlet fluid fitting 152 and exits multi-module heat sink 112 through an outlet fluid fitting 154 coupled to fluid outlet manifold 136. Inlet and outlet fittings 152, 154 may be located on opposing ends of the multi-module heat sink 112 as shown, on the same end, or in any alternative configuration that facilitates connections to external fluid reservoirs (not shown).
Inlet and outlet orifices 140, 142, 146, 148, inlet branch passages 138, outlet branch passages 150, and fluid inlet and outlet manifolds 134, 136 are sized relative to one another to optimize flow uniformity throughout the coolant passage portion 124. In one embodiment, the inlet orifices 140 on first mounting plate portion 116 are sized larger than the outlet orifices 142 on first mounting plate portion 116, as shown in
As disclosed herein, multi-module heat sink 112 is configured to supply cooling medium in parallel to three pairs of mounting locations 126, 128, with each of those three pairs of mounting locations 126, 128 coupled together in series. However, the coolant passage portion 124 may be designed to define alternative fluid paths and to couple all or select groupings of mounting locations 126, 128 in alternative series and/or parallel arrangements. As one example, all of the mounting locations 126, 128 may be connected in series, with the inlet fitting 152 coupled to the inlet orifice 140 of one of the mounting locations 126 and the outlet fitting 154 coupled to one of the outlet orifices 148. In yet another non-limiting example, all of the inlet orifices 140, 146 may be coupled to a common manifold thereby defining a parallel flow path across all mounting locations 126, 128. In yet other alternative configurations, the coolant passage portion 124 may be designed to provide one or more individual mounting locations 116 with a dedicated fluid inlet passage or include multiple inlet passages, with each passage configured to optimize the fluid flow rate and/or pressure drop for a particular type of heat generating component.
Coolant passage portion 124 also includes one or more support structures 156 that extend between first mounting plate portion 116 and second mounting plate portion 120 and provide structural support for multi-module heat sink 112. In the illustrated embodiment, heat sink 112 includes two structural supports 156 that each span the approximate width of the heat sink 112. It is contemplated that the size, shape, number, and position of structural supports may vary from that shown in alternative multi-module heat sink configurations depending on a number of factors, including the overall heat sink size and geometry, material properties of substrate 114, application, environmental conditions, and the like. In yet other embodiments, support structures 156 may be omitted entirely, with the structural support being provided instead by fluid passageways that extend between the first and second mounting plate portions 116, 120.
Each mounting location 126 includes one or more surface mounting features 158 sized and positioned to facilitate mounting a heat generating component to the multi-module heat sink 112 above the respective mounting location 126. In the embodiment shown, the mounting features 158 are through holes formed through a thickness of the respective mounting plate portion 116, 120. However, it is to be understood that the position, size, shape, and overall geometry of mounting features 158 may be modified to facilitate the mounting of different types of heat generating components. For example, mounting features 158 may be formed as flanges or other types of structures that extend outward from the respective mounting plate portion 116, 120.
Multi-module heat sink 112 may also include one or more additional mounting features 160 (shown in phantom) to facilitate mounting multi-module heat sink 112 to one or more external components. Similar to mounting features 158, external mounting features 160 may be extended structures, such as flanges, or simple through holes formed through a portion of the substrate 114.
While multi-module heat sink 112 is illustrated and described as a unitary two-sided structure, the general concept of a multi-module heat sink described herein may be extend to single-sided multi-module heat sink configurations or multi-module heat sinks formed from two or more individual structures bonded together using known bonding materials and/or techniques. For example, a two-sided multi-module heat sink may be formed from two for a first side of the multi-module heat sink and the second plate including one or more mounting locations for a second side of the multi-module heat sink 112.
In the illustrated embodiment, the mounting locations 126 are configured to cool similar types of heat generating components (e.g., power module 84 of
The multi-module heat sink concept may further be extended to heat sink configurations having non-planar fluid flow surfaces.
Substrate 164 includes a number of discrete mounting locations 166, 167 formed on outward-facing surfaces of the non-planar multi-module heat sink 162. As shown, the fluid flow surface 24 of mounting location 166 is non-coplanar with the fluid flow surface 24 of mounting location 167. While illustrated as including two discrete mounting locations 166, 167, alternative embodiments of heat sink 162 may include three or more mounting locations with non-coplanar fluid flow surfaces. In the illustrated embodiment, the fluid flow surface 24 at each mounting location 166, 167 includes two raised rows of jet orifices 168 configured for impinging-jet cooling. However, it is contemplated that mounting locations 166, 167 may be configured in a similar manner as the mounting locations 126 described above, and having any of raised surface feature designs described with respect to
In the illustrated embodiment, multi-module heat sink 162 includes a conformal shielding structure 170 that defines the outward facing surface of each mounting location 166, 167. In alternative embodiments, the conformal shield 170 at each mounting location 166, 167 may be replaced with any of the shielding structure configurations described with respect to
In the illustrated embodiment, heat sink 162 includes a dedicated fluid inlet passage 172, 173 for each mounting location 166, 167. Fluid inlet passages 172, 173 supply cooling medium in parallel to the rows of jet orifices 168 at each mounting location 166. Cooling medium is directed upward out of the jet orifices 168 and exits the well 20 through a respective outlet orifice 157, 159.
In an alternative embodiment, multi-module heat sink 162 may include a single fluid inlet and a single fluid outlet and an internal fluid passage formed within substrate 164 to fluidically couple the outlet orifice 32 of one of the mounting locations 166, 167 to an inlet orifice of the other mounting location 167, 166. In yet other alternative embodiments, multi-module heat sink 162 may be designed having multiple inlet and outlet manifolds (to couple select subsets of mounting locations 166, 167 in parallel flow arrangements), include dedicated inlet and outlet supplies for some or all of the mounting locations 166, 167, or be configured to define serial flow paths through some or all of the mounting locations 166, 167 of heat sink 162. Similar to that described relative to multi-module heat sink 112, the relative sizing of inlet and outlet orifices, inlet and outlet passages, and inlet and outlet manifold is selected to optimize fluid flow and maintain a desired pressure drop through non-planar multi-module heat sink 162.
Beneficially, embodiments of this invention provide electromagnetic shielding and cooling functionality in a common heat sink structure. The core substrate of the heat sink may be manufactured using an additive manufacturing technique such as 3D printing. The fluid flow surface of the heat sink and the internal fluid flow passages formed therein during the additive manufacturing technique have a relatively complex geometry that enhance heat transfer. Heat transfer is further enhanced in the direct cooling heat sink designs disclosed herein that enable direct contact between the cooling medium and the base plate of the electronics module being cooled. This direct contact eliminates the thermal resistance from thermal interface materials used when coupling a heat sink to an electronics module in prior art constructions. Additionally, the heat sink configurations disclosed herein can be produced at lower cost than conventional aluminum heat sinks, at a comparatively lighter overall weight, and may include structural mounting features that are not supported by conventional heat sink techniques. Accordingly, the embodiments described herein provide a low-cost thermal management and electromagnetic shielding solution with enhanced heat transfer and design flexibility as compared to prior art approaches.
Therefore, according to one embodiment of the invention, a heat sink for cooling an electronic component includes a substrate comprising an electrically non-conductive material and an inlet port and an outlet port extending outward from the substrate. The inlet and outlet ports are fluidically coupled to a fluid flow surface of the heat sink by passages that extend through a portion of the substrate. The heat sink also includes a shield comprising an electrically conductive material. The shield is disposed atop or within the substrate.
According to another embodiment of the invention, a method of manufacturing a heat sink for an electronics component includes forming a heat sink substrate from an electrically non-conductive material using an additive manufacturing process, the heat sink substrate comprising a fluid inlet port, a fluid outlet port, and a fluid flow surface fluidically coupled to the fluid inlet port and the fluid outlet port. The method also includes disposing a shield layer on a surface of the heat sink substrate during the additive manufacturing process, the shield layer comprising an electrically conductive material.
According to yet another embodiment of the invention, a thermal management assembly includes a heat sink comprising a substrate comprising an electrically non-conductive material, the substrate having a fluid flow surface fluidically coupled to a fluid inlet port and a fluid outlet port. The heat sink also includes a shielding structure comprising an electrically conductive layer disposed on or within the substrate. A heat generating component is coupled to a mounting surface of the heat sink. The shielding structure suppresses electromagnetic interference generated by the heat generating component.
While the invention has been described in detail in connection with only a limited number of embodiments, it should be readily understood that the invention is not limited to such disclosed embodiments. Rather, the invention can be modified to incorporate any number of variations, alterations, substitutions or equivalent arrangements not heretofore described, but which are commensurate with the spirit and scope of the invention. Additionally, while various embodiments of the invention have been described, it is to be understood that aspects of the invention may include only some of the described embodiments. Accordingly, the invention is not to be seen as limited by the foregoing description, but is only limited by the scope of the appended claims.
