Patent Application
20120327603
The invention relates generally to cooling devices, and more particularly, to a cooling device having integrated millichannels for a power module.
Power electronics refers to the application of solid-state electronics related to the control and conversion of electrical power. This conversion is typically performed by silicon, silicon carbide, and gallium nitride devices that are packaged into power modules. One of the factors associated with the power modules is the generation of heat. While the heat generated by the power modules is due to many factors, it generally relates to the fact that the power module efficiency is always less than 100 percent, and the efficiency loss is typically generated as heat. Unfortunately, the power module performance tends to erode with increased temperatures.
An additional factor for thermal management relates to the packaging of a number of devices in small footprints. The power density, at which the devices, and thus the module can operate, therefore depends on the ability to remove this generated heat. The common form of thermal management of power electronics is through heat sinks. Heat sinks operate by transferring the heat away from the heat source of the power module, thereby maintaining the heat source at a lower relative temperature. There are various types of heat sinks known in the thermal management field including air-cooled and liquid-cooled devices.
One example of the thermal management of a power module includes the attachment of a heat sink with embedded tubes to provide liquid cooling of the power module. The heat sink is typically a metallic structure, such as aluminum or copper. A cooling medium such as water is passed through the tubes to cool the power module. The heat sink is typically coupled to the power module base with a thermal interface material (TIM) dispersed there between. The thermal interface material may comprise thermal greases, compliant thermal pads, or the like. The conventional cooling devices have large thermal gradients and high-pressure drops across the devices. Also, the conventional cooling devices have large thermal resistance, which limits operation levels of the power module.
There is a need for an improved cooling device.
In accordance with one exemplary embodiment of the present invention, a cooling device for a power module having an electronic module disposed on a base plate via a substrate is disclosed. The cooling device includes a heat sink plate having at least one cooling segment. The cooling segment includes an inlet plenum for entry of a cooling medium. A plurality of inlet manifold channels are coupled orthogonally to the inlet plenum for receiving the cooling medium from the inlet plenum. A plurality of outlet manifold channels are disposed parallel to the inlet manifold channels. An outlet plenum is coupled orthogonally to the plurality of outlet manifold channels for exhaust of the cooling medium. A plurality of millichannels are disposed in the base plate orthogonally to the inlet and the outlet manifold channels. The plurality of milli channels direct the cooling medium from the plurality of inlet manifold channels to the plurality of outlet manifold channels.
In accordance with another exemplary embodiment of the present invention, a power module having an exemplary cooling device is disclosed.
In accordance with another exemplary embodiment of the present invention, a method includes directing a cooling medium via an inlet plenum of at least one cooling segment of a heat sink plate. The method further includes directing the cooling medium from the inlet plenum to a plurality of inlet manifold channels coupled orthogonally to the inlet plenum in the at least one cooling segment of the heat sink plate. The method also includes directing the cooling medium from the plurality of inlet manifold channels to a plurality of outlet manifold channels disposed parallel to the inlet manifold channels in the at least one cooling segment of the heat sink plate via a plurality of millichannels disposed in the base plate orthogonally to the inlet and the outlet manifold channels so as to cool an electronic module mounted on a base plate via a substrate. The method further includes exhausting the cooling medium from the plurality of outlet manifold channels via an outlet plenum coupled orthogonally to the plurality of outlet manifold channels.
In accordance with another exemplary embodiment of the present invention, a method for manufacturing an exemplary cooling device for a power module is disclosed.
These and other features, aspects, and advantages of the present invention will become better understood when the following detailed description is read with reference to the accompanying drawings in which like characters represent like parts throughout the drawings, wherein:
As discussed in accordance with the embodiments discussed herein, a cooling device for a power module is disclosed. In certain embodiments, the cooling device includes a heat sink plate having at least one cooling segment. The cooling segment includes an inlet plenum for entry of a cooling medium. A plurality of inlet manifold channels are coupled orthogonally to the inlet plenum for receiving the cooling medium from the inlet plenum. A plurality of outlet manifold channels are disposed parallel to the inlet manifold channels. An outlet plenum is coupled orthogonally to the plurality of outlet manifold channels for exhaust of the cooling medium. A plurality of millichannels are disposed in the base plate of the power module orthogonally to the inlet and the outlet manifold channels. The plurality of millichannels direct the cooling medium from the plurality of inlet manifold channels to the plurality of outlet manifold channels. It should be noted herein aspects of the present invention relate generally to heat sinks, stacks, and apparatuses using the heat sinks, and more particularly to millichannel heat sinks. It should be noted herein, that a “millichannel” has a width and a height on the order of millimeters in each dimension.
Referring to
The substrate 15 is provided to avoid electrical short circuits and to perform heat exchange between the base plate 14 and the electronic module 12. In one embodiment, the substrate 15 is an electrically isolating and thermally conductive layer, such as a ceramic layer. Non-limiting examples of the ceramic layer may include aluminum oxide, aluminum nitride, beryllium oxide, and silicon nitride. In a specific embodiment, the ceramic layer 15 may be bonded to the base plate 14 and the electronic module 12 via top and bottom conductive layers (for example, copper layers), i.e. substrate 15 may have either a direct bonded copper (DBC), or an active metal braze (AMB) structure. In other words, a top conductive layer may be disposed between the electronic module 12 and the ceramic layer 15 and a bottom conductive layer may be disposed between the ceramic layer 15 and the base plate. In a particular embodiment, an aluminum layer, a gold layer, a silver layer, or an alloy layer may be preferred instead of the copper layer. In another embodiment, the base plate 14 may be directly bonded to the substrate 15. The substrate 15 may be coupled to the base plate 14 and the electronic module 12 using a number of techniques, including but not limited to, brazing, bonding, diffusion bonding, soldering, or pressure contact such as clamping to provide a simple assembly process. It should be noted herein that the exemplary arrangement in
Referring to
In the illustrated embodiment, the heat sink plate 16 includes a plurality of cooling segments 26 disposed in the heat sink surface 18. In one embodiment, the plurality of cooling segments 26 are recessed in the heat sink surface 18 of the heat sink plate 16. The base plate 14 includes sets of millichannels 28 disposed in the plate surface 20. Each set of millichannels 28 is positioned to overlap the corresponding cooling segment 26. In embodiments of the invention, each of the millichannels 28 are recessed into the plate surface 20 of the base plate 14 to form trenches in the plate surface 20. In the illustrated embodiment, the heat sink plate 16 has a rectangular shape. It should be noted that the exemplary heat sink plate 16 in
The heat sink plate 16 may include at least one thermally conductive material, non-limiting examples of which may include copper, aluminum, nickel, molybdenum, titanium, and alloys thereof. In some embodiments, the heat sink plate 16 may include metal matrix composites such as aluminum silicon, aluminum silicon carbide, aluminum graphite, and copper graphite. In other embodiments, the heat sink plate 16 may include ceramics such as aluminum oxide and silicon nitride ceramic. Alternatively, the heat sink plate 16 may include at least one thermoplastic material.
For the exemplary arrangement in
Referring to
In certain embodiments of the invention, the millichannels 28 may have a rectangular or square cross-section. Non-limiting examples of the cross sections of the millichannels 28 may further include circular, triangular, trapezoidal, and u-shaped cross-sections. The millichannels 28 may be cast, machined, or etched, and may be smooth or rough in the base plate. The rough millichannels may have relatively larger surface area to enhance turbulence of a cooling medium 40 so as to augment thermal transfer therein. In non-limiting examples, the millichannels 28 may employ features such as dimples, bumps, or the like therein to increase the roughness thereof. Similarly to the millichannels 28, the manifold channels 34, 36 may also have a variety of cross-sectional shapes, including but not limited to, round, circular, triangular, trapezoidal, and square/rectangular cross-sections. The geometry of the plenums 32, 38, the manifold channels 34, 36, and the millichannels 28 may be designed based on the application, type of cooling medium used, and also the ambient temperature. The number of manifold channels 34, 36, and millichannels 28 may vary depending on the application.
In an exemplary operation, the cooling medium 40 enters the inlet manifold channels 34 via the inlet plenum 32. A supply source (not shown) is used to pump the cooling medium 40 into the inlet plenum 32. The cooling medium 40 is then directed from the inlet manifold channels 34 to the outlet manifold channels 36 via the millichannels 28 of the base plate. Thereafter, the cooling medium 40 is exhausted from the outlet manifold channels via the outlet plenum 38. It should be noted herein that entry of the cooling medium 40 into the inlet plenum 32 and exhaust of the cooling medium 40 from the outlet plenum 38 are along a same direction 42. In one embodiment, the cooling medium 40 includes a mixture of propylene glycol and water. In a specific embodiment, the cooling medium 40 may include 60 percent by weight of propylene glycol and 40 percent by weight of water. The cooling medium 40 may also include other electrically conductive or non-electrically conductive liquids. In another embodiment, the cooling medium 40 may include a gaseous medium. Accordingly, when the electronic module 12 and the base plate 14 are disposed on the heat sink plate 16, the cooling medium 40 flowing through the heat sink plate and the millichannels 28 of the base plate enable cooling of the electronic module.
The configuration of the cooling segment 26 discussed herein, specifically relating to parallel arrangement of the inlet manifold channels 34, and outlet manifold channels 36, tapered cross-sections of the channels (34, 36), orthogonal arrangement of the plenums (32, 38), and the millichannnels 28 provide a relatively large flow area resulting in constant flow velocity and low pressure drop across the segment 26. The thermal gradient across the segment 26 is minimized. The thermal resistance and thermal resistivity of the power module is minimal enabling the power module to be operated at higher power levels. As noted below:
Thus, the power level of the module is increased with lower thermal resistance and higher changes in temperature.
Referring to
Accordingly, for the exemplary arrangement, when the heat sink plate is coupled to the base plate, and the cooling medium 40 is directed sequentially through the inlet plenum 32, the plurality of inlet manifold channels 34, the set of millichannels 28, the plurality of outlet manifold channels 36, and the outlet plenum 38, heat exchange between the base plate and the heat sink plate results so as to cool the electronic module. The seal provides a liquid tight seal about the cooling segment of the heat sink plate.
Referring to
While only certain features of the invention have been illustrated and described herein, many modifications and changes will occur to those skilled in the art. It is, therefore, to be understood that the appended claims are intended to cover all such modifications and changes as fall within the true spirit of the invention.
