Patent Publication Number: US-2023139202-A1

Title: Power device assemblies having embedded pcbs and methods of fabricating the same

Description:
TECHNICAL FIELD 
     The present specification generally relates to apparatus and methods for power electronic assemblies and, more specifically, apparatus and methods for power electronic assemblies having low overall thermal resistance while achieving a compact package size. 
     BACKGROUND 
     Due to the increased use of electronics in vehicles, there is a need to make electronic systems more compact. One component of these electronic systems is a power electronic device used as a switch in an inverter. Power electronic devices have large cooling requirements due to the heat generated. 
     Additionally, there has been a trend for power electronic devices conventionally composed of silicon to now be composed of silicon-carbide. The use of silicon-carbide causes a larger heat flux due to it defining a smaller device footprint. For these reasons, and more, there is a need to improve the cooling of power electronic devices while maintaining a compact package size. 
     SUMMARY 
     In one embodiment, an apparatus for a power electronics assembly includes a cold plate assembly and one or more power device assemblies. The cold plate assembly includes a manifold including a heat sink cavity in a first surface and a heat sink. The heat sink includes one or more substrate cavities and the heat sink is positioned in the heat sink cavity. The one or more power device assemblies are positioned within the one or more substrate cavities. Each power device assembly of the one or more power assemblies includes a direct bonded metal (DBM) substrate including a first metal layer directly bonded to an insulator layer and a power device. The DBM substrate includes a power device cavity. The power device is positioned in the power device cavity and the power device is electronically coupled to the first metal layer. 
     In another embodiment, a power device assembly includes a direct bonded metal (DBM) substrate and one or more power devices. The DBM substrate includes a first metal layer directly bonded to an insulator layer and the DBM substrate includes one or more power device cavities. The one or more power devices are each positioned in one of the one or more power device cavities. Each of the one or more power devices are electrically coupled to the first metal layer. 
     In yet another embodiment, a method of forming a power electronics assembly is shown. The method includes positioning a heat sink into a heat sink cavity on a first surface of a cold plate manifold. The heat sink includes one or more substrate cavities. The method further includes embedding one or more power device assemblies within the one or more substrate cavities. Each power device assembly includes a direct bonded metal (DBM) substrate having a first metal layer bonded to an insulator layer. The DBM substrate includes a power device cavity. The method further includes placing a bonding layer at least partially within the power device cavity. The method further includes bonding a power device to the power device cavity via the bonding layer. The power device being electrically coupled to the first metal layer. 
     These and additional features provided by the embodiments described herein will be more fully understood in view of the following detailed description, in conjunction with the drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The embodiments set forth in the drawings are illustrative and exemplary in nature and not intended to limit the subject matter defined by the claims. The following detailed description of the illustrative embodiments can be understood when read in conjunction with the following drawings, where like structure is indicated with like reference numerals and in which: 
         FIG.  1    schematically depicts a perspective view of an illustrative power electronics assembly including a plurality of embedded power devices, according to one or more embodiments shown and described herein; 
         FIG.  2    schematically depicts an exploded perspective view of a cold plate assembly of the power electronics assembly having a heat sink and a manifold, according to one or more embodiments shown and described herein; 
         FIG.  3    schematically depicts an assembled perspective view of a cold plate assembly of a power electronics assembly, according to one or more embodiments shown and described herein; 
         FIG.  4    schematically depicts a side view of a cold plate assembly of a power electronics assembly, according to one or more embodiments shown and described herein; 
         FIG.  5    schematically depicts a side view of the power electronics assembly of  FIG.  1   , taken along cross-section A-A of  FIG.  1   ; 
         FIG.  6    schematically depicts an exploded, perspective view of one of the plurality of embedded power device assemblies, according to one or more embodiments shown and described herein; 
         FIG.  7    schematically depicts an assembled, perspective view of one of the plurality of embedded power device assemblies, according to one or more embodiments shown and described herein; 
         FIG.  8    schematically depicts a perspective view of the power device assembly of  FIG.  1   , taken along portion B-B of  FIG.  5   ; 
         FIG.  9    schematically depicts a side view of a power device assembly embedded into a power device assembly, according to one or more embodiments shown and described; 
         FIG.  10    schematically depicts a side view of a power device assembly embedded into a power device assembly in response to receiving a force according to one or more embodiments shown and described herein; 
         FIG.  11    schematically depicts another perspective view of an illustrative power electronics assembly including a plurality of embedded power device assemblies, according to one or more embodiments shown and described herein; 
         FIG.  12    schematically depicts a side view of the power electronics assembly of  FIG.  11   , taken along cross-section C-C of  FIG.  11   ; and 
         FIG.  13    schematically depicts a perspective view of an illustrative power electronics assembly having a PCB printed upon it, according to one or more embodiments shown and described herein. 
     
    
    
     DETAILED DESCRIPTION 
     Embodiments described herein are generally directed to power electronics assemblies having direct bonded metal (DBM) layers integrated with conductive layers and cold plate assemblies having self-alignment features. The conductive layer has a cavity where a power electronics device is placed. The cavity is designed so that the top surface of the power electronics device is flush with a top surface of the cold plate assembly, while allowing the power electronics device to be electrically coupled to its bottom electrode. The flat surface allows for PCBs to be printed directly upon the cold plate assembly. Since there are less overall layers there is less overall thermal resistance in the power electronics assembly. Additionally, due to the proximity of the heat-generating power electronics device to the cold plate, there is improved cooling. This allows for the power electronics device to output higher power, while maintaining a compact package size. 
     In conventional systems, separate metal components are needed to electrically couple a power electronics device for a power electronics assembly to a bottom electrode of the power electronics device. This results in additional components, increased height of the assembly, and increased thermal resistance. 
     Various embodiments of the power electronics assemblies, method of fabricating power electronic assemblies, and operation of power electronic assemblies are described in more detail herein. Whenever possible, the same reference numerals will be used throughout the drawings to refer to the same or like parts. 
     Referring now to  FIGS.  1 - 3   , an example power electronics assembly  100  is illustrated according to one or more embodiments described herein. Particularly,  FIG.  1    depicts a power electronics assembly  100  including a plurality of power device assemblies  114  with one power device assembly shown in an exploded view.  FIG.  2    illustrates a cold plate assembly  102  of the power electronics assembly  100  in an exploded view.  FIG.  3    illustrates the cold plate assembly  102  of  FIG.  2    in an assembled view. 
     In some embodiments, the power electronics assembly  100  is utilized in an electric vehicle. In other embodiments, the power electronics assembly  100  is used in an electrically-driven device, such as and without being limited to, a hybrid vehicle, any electric motor, generators, industrial tools, household appliances, and the like. The power electronics assembly  100  may be electrically coupled to an electric motor and/or a battery and is configured to receive power from the electric motor and/or battery. 
     The example power electronics assembly  100  includes a cold plate assembly  102  configured to house embedded power devices  114 , while absorbing the heat generated by the power devices  114 . As discussed in greater detail herein, the cold plate assembly  102  receives coolant configured to absorb the heat generated by the power devices  114  and provide that coolant to a downstream cooling system. In this way, the cold plate assembly  102  is able to remove heat from the power electronics assembly  100  in an efficient manner. The cold plate assembly  102  may be machined, forged, extruded, or cast from a block of thermally conductive material. In some embodiments, the cold plate assembly  102  is 3D printed. 
     The cold plate assembly  102  includes a manifold  104  (e.g., a manifold plate). The manifold  104  is configured to receive and provide coolant to remove heat from the power electronics assembly  100 . The manifold  104  has a first surface  106  (e.g., plane). The first surface  106  defines a substantially flat profile. As discussed in greater detail herein, a PCB may be printed upon the first surface  106 . This is advantageous as it reduces the thermal resistance of the power electronics assembly  100 . 
     The manifold  104  includes an inlet  132  (e.g., input port). The inlet  132  is configured to receive coolant from a cooling system (not shown). After interfacing with the heat sink  110 , the coolant is configured to receive heat from the heat sink  110 . The cold plate assembly  102  further includes an outlet  134  (e.g., output port). The warmed coolant exits the cold plate assembly  102  via the outlet  134 . In this way, the cold plate assembly  102  is able to cool the power electronics assembly  100 . 
     The manifold  104  defines a heat sink cavity  108  (see  FIG.  2   ) in the first surface  106 . The cold plate assembly  102  further includes a heat sink  110 . The heat sink  110  is positioned within the heat sink cavity  108 , as shown in  FIGS.  1  and  3   . Due to the heat sink  110  being positioned in the heat sink cavity  108 , elements of the heat sink  110  are self-aligned relative to the cold-plate assembly  102 . In other words, the position of the heat sink  110  is known by fixing the heat sink  110  to a specified position. This reduces the overall assembly tolerances of the power electronics assembly  100 . 
     The heat sink  110  includes a plurality of substrate cavities  112 . As discussed in greater detail herein, each of the plurality of substrate cavities  112  defines a depth large enough that when components are placed into each of the plurality of substrate cavities  112 , a top surface of each of the plurality of substrate cavities  112  is flush (e.g., flat, along the same plane) with the first surface  106 . This is advantageous as it provides a flush surface for the PCB to be printed upon the power electronics assembly  100 . 
     Referring now to  FIG.  4   , a side view of the example cold plate assembly is shown. In some embodiments, the cold plate assembly  102  includes fins  202 . The fins  202  are positioned on a bottom surface of the heat sink  110 . The fins  202  are further positioned between the inlet  132  and the outlet  804 . Additionally, the fins  202  are positioned fluidly downstream of the inlet  132  and fluidly upstream of the outlet  134 . This results in the fins  202  disrupting the coolant flow before exiting the outlet  134 . In this way, coolant entering the inlet  132  has maximum contact with the fins  202  in order to increase the effectiveness of cooling the cold plate assembly  102 . The fins  202  includes a series of channels. In some embodiments, the fins  202  include pin fins or any other suitable type of fins. After entering the inlet  132 , the coolant flows through the channels of the fins  202  in order to increase the effectiveness of cooling the cold plate assembly  102 . 
     Referring now to  FIG.  5   , a side view of the power electronics assembly of  FIG.  1   , taken along cross-section A-A of  FIG.  1   , is shown. As illustrated, the top surfaces of the heat sink  110 , the substrate cavity  112 , and the power device assembly  114  are flush to the first surface  106  of the manifold  104 . 
     Referring now to  FIGS.  6 - 7   , an individual power device assembly  114  of a plurality of power device assemblies  114  for the power electronics assembly  100  is shown.  FIG.  6    shows a power device assembly  114  in an exploded view while  FIG.  7    shows the power device assembly in an assembled view. The plurality of power device assemblies  114  are embedded (e.g. disposed) into the plurality of substrate cavities  112 . As a non-limiting example, the plurality of power device assemblies  114  may define an inverter circuit for powering an electric device, such as an electric motor. 
     Due to each of the plurality of power device assemblies  114  being positioned in one of the plurality of substrate cavities  112 , each of the plurality of power device assemblies  114  is self-aligned relative to the cold-plate assembly  102 . In other words, the position of each of the plurality of power device assemblies  114  is known by fixing each of the plurality of power device assemblies  114  to a specified position. This reduces the overall assembly tolerances of the power electronics assembly  100 . Additionally, a top surface of each of the plurality of power device assemblies  114  are flush to the first surface  106 . 
     Each power device assembly  114  includes a direct bonded metal (DBM) substrate  116 . The DBM substrate  116  provides electrical insulation for the power device assemblies  114  to isolate them from each other. 
     The DBM substrate  116  includes a first metal layer  118  directly bonded to an electrical insulation layer  120 . In an example embodiment, the first metal layer  118  is positioned on the top layer of the DBM substrate  116 . The first metal layer  118  may be composed of copper, aluminum, or any suitable conductor. As discussed in greater detail herein, the first metal layer  118  operates as an “S-cell” for the power electronics assembly  100 . In other words, the first metal layer  118  provides electrical connection to a bottom electrode of the power device. 
     The DBM substrate  116  further includes the insulation layer  120 . As the cold plate assembly  102  is composed of a conductive material, the insulation layer  120  provides electrical insulation for each of the plurality of power device assemblies  114  from one another. The electrical insulation layer may be a ceramic, such as alumina. 
     The DBM substrate  116  further includes a power device cavity  122  within the first metal layer  118  of the DBM substrate  116 . The DBM substrate  116  further includes a bottom metal layer (not shown) on the bottom surface of the electrical insulation layer  120 . 
     As discussed in greater detail herein, the power device cavity  122  is configured such that after components are bonded to the DBM substrate  116 , the top surface of the DBM substrate  116  is flush with the first surface  106 . 
     Each power device assembly  114  further includes a bonding layer  124  (e.g., a solder layer). The bonding layer  124  is positioned on a bottom surface and/or side surfaces of the power device cavity  122  and is configured to bond the power electronics device  126  to the power device cavity  122 . The bonding layer  124  may provide bonding by silver sintering, soldering, transient liquid phase bonding (TLP) or any other suitable bonding method. 
     Each power device assembly  114  further includes the power electronics device  126 . The power electronics device  126  may be insulated-gate bipolar transistors (IGBTs), metal-oxide-semiconductor-field-effect-transistors (MOSFETs), or any other suitable power device. The power electronics device  126  is embedded into the power device cavity  122 . The power electronics device  126  may be bonded, soldered, adhered to the power device cavity  122  via the bonding layer  124 . The power electronics device  126  includes electrical pads  128  to enable power connections for components having high voltage requirements. The power electronics device  126  further includes smaller electrical pads  130  which receives control signals from drivers (e.g., gate drivers) and may provide signals from sensors (e.g., temperature sensors, current sensors,) embedded in the power device assembly  114 . The height of the power electronics device  126  and the thickness of the bonding layer  124  are configured such that they are substantially equal to the depth of the power device cavity  122 . This results in the top surface of the power device assembly  114  to be flush with the first surface  106 . 
     The power electronics device  126  includes a bottom electrode (not shown) that is that is electrically coupled to the first metal layer  118  through the bonding layer  124 . Electrical connection to the bottom electrode is then made through the first metal layer  118 . By providing power the device cavity  122  within the first metal layer  118  to electrically couple the first metal layer  118  to the bottom electrode, a separate conductive component is not required to make this electrical connection. This is advantageous as it reduces the number of components, the height, and the overall thermal resistance of the power electronics assembly  100 . 
     Conventional systems, for example, may require insulation layers and grease. These layers increase the overall thermal resistance of the power electronic systems while also separating the heat source from the cold sink. As discussed in  FIGS.  6 - 7   , the current arrangement facilitates the removal of layers between the power electronics device  126  (e.g., the heat source) and the heat sink  110 . Accordingly, the thermal resistance between the power electronics device  126  and the heat sink  110  is substantially reduced. This is advantageous as it maximizes the cooling of the power electronics devices  126  while creating a compact package size. Additionally, the improved cooling facilitates for the power electronics devices  126  to provide higher power while maintaining a compact package size. 
     Due to each power electronics device  126  being positioned in one of power device cavities  122 , each power electronics device  126  is self-aligned relative to the cold-plate assembly  102 . In other words, the position of each power electronics device  126  is known by fixing each power electronics device  126  to a specified position. This reduces the overall assembly tolerances of the power electronics assembly  100 . 
     Additionally, this arrangement facilitates for PCBs to be 3D printed directly upon the first surface  106 . This is due to each component of the power electronics assembly  100  being flush relative to the first surface  106  and by having each cavity resulting in the respective component to be self-aligned. Additionally, a bonding reflow fixture is not required in the manufacturing process of the power electronics assembly  100 . This is due to there being less components requiring bonding and the improved accuracy of bonding due to the self-alignment features in the power electronics assembly  100 . 
     Referring now to  FIG.  8   , a perspective view of the power device assembly of  FIG.  1   , taken along portion B-B of  FIG.  4   , is shown. The power device assembly  114  defines a channel  802  (e.g., space, open area) between a perimeter of the power device assembly  114  and the heat sink  110 . Before printing a PCB upon the cold plate assembly  102 , the channel  802  is may be first filled such that it is flush with the first surface  106 . The channel  802  may be filled through a manual filling process or is printed upon by the 3D printer. This is advantageous as it allows the first surface  106  to be flush throughout the entire top surface of the cold plate assembly  102 .  FIG.  8    also illustrates the channel-like structure of the fins  202 . As discussed in greater detail above, coolant that has entered the manifold  104  flows through these channels in order to increase cooling. 
     Referring now to  FIGS.  9 - 10   , a side view of a power device assembly  114  embedded into the power device cavity  122  is shown. As illustrated in  FIG.  6   , the power electronics device  126  is positioned beneath the top surface of the power device cavity  122 . This is advantageous as it provides additional surface area between the power electronics device  126  and the bonding layer  124 . This results in superior bonding between the power electronics device  126  and the bonding layer  124 . 
     Due to materials having varying coefficients of thermal expansion (CTE), during cooling a force may be applied onto the bonding layer  124  and the power electronics device  126 . In conventional systems, where the bonding layer  124  and the power electronics device  126  are positioned above the first surface  106 , the force on the bonding layer  124  and the power electronics device  126  is a splitting force (e.g., the bonding layer  124  and the power electronics device  126  are pushed away from each other tangential to the first surface  106 ). This is a concern as the bonding layer  124  and the power electronics device  126  may not be able to handle strong splitting forces. This can cause the power electronics device  126  to separate from the bonding layer  124 . 
     As illustrated in  FIG.  10   , in response to undergoing the force, the bonding layer  124  and the power electronics device  126  experience a compression force. This is advantageous as the bonding layer  124  and the power electronics device  126  are much less likely to separate due to a compression force in comparison to a splitting force. This improves the reliability of the power electronics assembly  100  in production and during operation. 
     Referring now to  FIG.  11   , a perspective view of another power electronics assembly  1100  is shown, according to another embodiment. As illustrated, each channel (e.g., such as channel  802 ) between a perimeter of a power device assembly  1114  (e.g., such as power device assembly  114 ) and a heat sink  1110  (e.g., such as the heat sink  110 ) is filled such that it is flush with a first surface  110  of a cold plate assembly  1102  (e.g., such as cold plate assembly  102 ). In order for a PCB to be printed upon the first surface  1106 , the first surface  1106  should be substantially flat. A substantially flat surface allows for the PCB to have superior electrical connections to power electronic devices and removes the need for a reflow process. As discussed in greater detail above, the power electronics assembly  1100  is configured for its components to be substantially flat with the first surface. This is advantageous as it reduces a step to make the first surface  1106  (e.g., manual or automated filling) to become flat. 
     Referring now to  FIG.  12   , a side view of the power electronics assembly  1100  of  FIG.  11   , taken along cross-section C-C, is shown according to another embodiment. The power electronics assembly  1100  includes an insulation layer  1206  (e.g., such as the insulation layer  120 ) that is 3D printed upon the first surface  1106 . The insulation layer  1206  may be ceramic or any other suitable electrically insulating material. During the printing of the insulation layer  1206 , a substrate cavity  1208  (e.g., such as the substrate cavity  112 ) is formed on a top surface of the insulation layer  1206 . 
     The power electronics assembly  1200  further includes a metal layer  1210  (e.g., such as the metal substrate  118 ) that is 3D printed within the substrate cavity  1208 . The metal layer  1210  may be copper, aluminum or any other suitable electrically conducting material. After the metal layer  1210  is printed, power devices may be sintered, soldered, or adhered to the metal layer  1210 . This is advantageous as it reduces the number of manufacturing steps to create the power electronics assembly  1100 . Additionally, due to the insulation layer  1206  printed directly on the first surface  1106 , a DBM substrate (e.g., such as the DBM substrate  116 ) is no longer required. 
     Referring now to  FIG.  13   , a perspective view of a power electronics assembly  1300  is shown, according to another embodiment. The power electronics assembly  1300  includes a cold plate assembly  1302  (e.g., such as cold plate assembly  102  and cold plate  1202 ). Printed upon the cold plate assembly  1302  is one or more PCBs  1304 . The one or more PCBs  1304  are electrically coupled to a plurality of embedded power devices positioned in the cold plate  1202  and are configured to receive power from the plurality of embedded power devices. Additionally, as a result of the plurality of embedded power devices being positioned within the cold plate assembly  1302 , the power electronics assembly  1300  has superior cooling due to there being less total thermal resistance and a decreased distance between the cold plate assembly  1302  and the plurality of embedded power devices. 
     In some embodiment, the entire power electronics assembly  1300  is 3D printed. Due to the self-alignment of heat sink cavities (e.g., such as heat sink cavity  108 ), substrate cavities (e.g., such as substrate cavities  112 ), and power device cavities (e.g., such as power device cavity  122 ), each component has a respective reference point. This results in lower assembly tolerances through the entire assembly. Accordingly, this facilitates the entire power electronics assembly  1300  to be 3D printed as there is less variability in the system. 
     From the above, it is to be appreciated that defined herein are embodiments directed to power electronics assemblies having DBM layers integrated with conductive layers and cold plate assemblies having self-alignment features. This facilitates for PCBs to be printed upon the cold plate assembly resulting in less overall thermal resistance and improved cooling. 
     It is noted that the terms “substantially” and “about” may be utilized herein to represent the inherent degree of uncertainty that may be attributed to any quantitative comparison, value, measurement, or other representation. These terms are also utilized herein to represent the degree by which a quantitative representation may vary from a stated reference without resulting in a change in the basic function of the subject matter at issue. 
     While particular embodiments have been illustrated and described herein, it should be understood that various other changes and modifications may be made without departing from the scope of the claimed subject matter. Moreover, although various aspects of the claimed subject matter have been described herein, such aspects need not be utilized in combination. It is therefore intended that the appended claims cover all such changes and modifications that are within the scope of the claimed subject matter. 
     It will be apparent to those skilled in the art that various modifications and variations can be made to the embodiments described herein without departing from the scope of the claimed subject matter. Thus, it is intended that the specification cover the modifications and variations of the various embodiments described herein provided such modification and variations come within the scope of the appended claims and their equivalents.