Metal-coated polymer encapsulated electronic module and method of manufacturing the same

Abstract

Metal-coated polymer-encapsulated power semiconductor modules, methods of making / using such power modules, and vehicles having traction power inverters containing such power modules are provided. A power electronics assembly includes one or more power semiconductor modules enclosed within an assembly housing. Each power module includes a substrate, a semiconductor device mounted on the substrate, a polymer encapsulant in which the substrate and semiconductor device are encapsulated, and electrical leads connected to the semiconductor device and protruding from the polymer encapsulant. A metal or ceramic coating is applied to selected portions of the exposed outer surface of the polymer encapsulant. The metal / ceramic coating can be a single metal layer covering substantially all of the exposed surface area of the outer surface of the polymer encapsulant. An optional hydrophobic polymer layer, a passivation layer, and / or an oxide layer can cover the outer surface of the metal layer. Alternatively, another metal layer or an embedded layered microstructure can cover the metal layer.

Description

[0001] introduction

[0002] The present disclosure generally relates to polymer-encapsulated electronic devices. More specifically, aspects of the present disclosure relate to polymer-encapsulated power semiconductor modules for use in high-voltage power inverters for electric drive vehicles.

[0003] Current production motor vehicles, such as modern automobiles, are initially equipped with a powertrain that operates to propel the vehicle and power the vehicle's onboard electronics. For example, in automotive applications, the vehicle powertrain is typically represented by a prime mover that transmits drive torque to the vehicle's final drive system (e.g., differential, axles, wheels, etc.) through an automatic or manually shifted power transmission. Historically, automobiles have been powered by reciprocating piston internal combustion engine (ICE) assemblies due to their readily available and relatively inexpensive cost, light weight, and overall efficiency. As some non-limiting examples, such engines include compression ignition (CI) diesel engines, spark ignition (SI) gasoline engines, two-stroke, four-stroke, and six-stroke architectures, and rotary engines. Hybrid electric and all-electric (collectively referred to as "electric drive") vehicles, on the other hand, utilize alternative power sources to propel the vehicle, thereby minimizing or eliminating reliance on fossil fuel-based engines for traction power.

[0004] A full electric vehicle (FEV) (commonly known as an "electric vehicle") is an electrically driven vehicle configuration that completely omits the internal combustion engine and accompanying peripheral components from the powertrain, relying instead on a rechargeable energy storage system (RESS) and traction motors for vehicle propulsion. The engine assembly, fuel supply system, and exhaust system of an ICE-based vehicle are replaced by a single or multiple traction motors, a traction battery pack, and battery cooling and charging hardware in a battery-based FEV. In contrast, a hybrid electric vehicle (HEV) powertrain utilizes multiple traction power sources to propel the vehicle, most commonly operating an internal combustion engine assembly in conjunction with a battery-powered or fuel cell-powered traction motor. Because hybrid electric vehicles are able to derive their power from sources other than the engine, the HEV engine can be fully or partially shut down when the vehicle is propelled by the electric motor.

[0005] The high-voltage (HV) electrical system controls the transfer of power between the traction motors and the rechargeable traction battery pack, which stores and supplies the necessary power for operating many hybrid and all-electric powertrains. Compared to the individual cells of a standard 12-volt starting, lighting, and ignition (SLI) battery pack, modern traction battery packs combine stacks of battery cells into individual battery modules, which are electrically interconnected in series or parallel and mounted to the vehicle chassis, for example, via a battery pack housing or support bracket. The HV electrical system may employ a front-end DC / DC power converter electrically connected to the vehicle's traction battery pack to boost the voltage supply to the HV main DC bus and DC / AC power inverter module (PIM). High-frequency bulk capacitors may be placed across the positive and negative terminals of the main DC bus to provide electrical stability and store supplemental energy. A dedicated electronic battery control module (EBCM) manages the operation of the battery pack and the traction motors by working in conjunction with the powertrain control module (PCM) and the power electronics package for each electric motor.

[0006] Because electric vehicles utilize a direct current (DC) power source and an alternating current (AC) prime mover, a traction power inverter module (TPIM) is employed to convert the DC power output by the traction battery pack into AC power that can be consumed by the multi-phase electric motors. During regenerative braking, the TPIM can operate in reverse, acting as an electrical converter to convert the AC power output from the electric motors via electromagnetic induction (EMI) into DC power that can be stored by the battery pack. A TPIM typically contains the packaging of independent power modules, each of which includes an arrangement of semiconductor devices (also known as "semiconductor chips") supported on a substrate that provides electrical and thermal transfer paths for the semiconductor chips. Each semiconductor device, which can be a metal-oxide-semiconductor field-effect transistor (MOSFET), a semiconductor diode, or an insulated-gate bipolar transistor (IGBT), operates as a power semiconductor switch within an oscillator circuit that filters, rectifies, and boosts the signal. In some power module designs, the semiconductor chips can be sandwiched between two thermally conductive substrates, such as direct-bonded copper (DBC) substrates, allowing heat to be removed from both sides of the semiconductor chip simultaneously. SUMMARY OF THE INVENTION

[0007] This application involves the following:

[0008] [1] A power electronic assembly comprising:

[0009] an assembly housing; and

[0010] A power module is enclosed in an assembly housing and includes a substrate, a semiconductor device mounted on the substrate, a polymer encapsulant encapsulating the substrate and the semiconductor device, electrical leads connected to the semiconductor device and protruding from the polymer encapsulant, and a metal and / or ceramic coating on an outer surface of the polymer encapsulant.

[0011] [2] The power electronic assembly of [1] above, wherein the metal and / or ceramic coating comprises a first metal layer directly mounted to and covering most but not all exposed areas of the outer surface of the polymer encapsulant.

[0012] [3] The power electronic assembly as described in [2] above, wherein the metal and / or ceramic coating further comprises a hydrophobic polymer layer covering an outer surface of the first metal layer opposite to an inner surface of the first metal layer adjacent to the polymer encapsulant.

[0013] [4] The power electronic assembly as described in [3] above, wherein the outer surface of the first metal layer covered by the hydrophobic polymer layer includes an etched or roughened cover layer.

[0014] [5] The power electronic assembly as described in [2] above, wherein the metal and / or ceramic coating further includes a passivation layer and / or an oxide layer on the outer surface of the first metal layer.

[0015] [6] The power electronic assembly as described in [2] above, wherein the metal and / or ceramic coating further includes a second metal layer covering the first metal layer, the first metal layer comprises a first metal material, and the second metal layer comprises a second metal material different from the first metal material.

[0016] [7] The power electronic assembly as described in [6] above, wherein the first metal material comprises zinc and the second metal material comprises steel.

[0017] [8] The power electronic assembly as described in [2] above, wherein the metal and / or ceramic coating further comprises an embedded layered microstructure on the outer surface of the first metal layer.

[0018] [9] The power electronic assembly as described in [1] above, wherein the metal and / or ceramic coating has a thickness of about 1 micrometer (µm) to about 500 µm.

[0019]

[10] The power electronic assembly as described in [1] above, wherein the assembly housing comprises a first polymer material and the polymer encapsulant comprises a second polymer material different from the first polymer material.

[0020]

[11] The power electronic assembly as described in

[10] above, wherein the first polymer material comprises epoxy with silica, polyamide, polyphthalamide and / or polyphenylene sulfide, and the second polymer material comprises an epoxy-based, bismaleimide-based and / or silicone-based molding compound.

[0021]

[12] The power electronic assembly as described in [1] above, wherein the assembly housing includes an elongated body having an inlet port, an outlet port, and a coolant fluid channel fluidly connecting the inlet and outlet ports, the fluid channel extending longitudinally through the housing body between an inner surface of the assembly housing and a major surface of the power module.

[0022]

[13] The power electronic assembly as described in

[12] above, wherein the power module further comprises:

[0023] a thermally conductive heat transfer plate attached to the semiconductor device and defining a major surface of the power module; and

[0024] A heat transfer fin array is mounted on a major surface of the power module and disposed within the fluid channel.

[0025]

[14] An electric vehicle comprising:

[0026] a vehicle body having a plurality of wheels;

[0027] a traction motor mounted to the vehicle body and operable to drive one or more wheels to propel the electrically driven vehicle;

[0028] a rechargeable traction battery pack mounted to the vehicle body and operable to power a traction motor; and

[0029] A traction power inverter module (TPIM) electrically connects a traction battery pack to a traction motor, the TPIM comprising a power module enclosure having an assembly housing, a coolant fluid channel in the assembly housing and through which a coolant fluid passes, and a plurality of power modules enclosed in the assembly housing, each power module comprising a substrate, a plurality of semiconductor devices mounted on the substrate, a polymer encapsulant encapsulating the substrate and the semiconductor devices, a plurality of electrical leads connected to the semiconductor devices and protruding from the polymer encapsulant, and a multi-layer metal coating positioned on an outer surface of the polymer encapsulant and in a spaced, non-contacting relationship with the electrical leads.

[0030]

[15] A method for manufacturing a power electronic assembly, the method comprising:

[0031] forming an assembly housing;

[0032] assembling a power module including a substrate, a semiconductor device mounted on the substrate, and electrical leads connected to the semiconductor device;

[0033] encapsulating the substrate and the semiconductor device in a polymer encapsulant;

[0034] Applying a metal and / or ceramic coating to the outer surface of the polymer encapsulant; and

[0035] A power module encased in a polymer encapsulant with a metal and / or ceramic coating is positioned in the assembly housing.

[0036]

[16] The method of

[15] above, wherein the metal and / or ceramic coating comprises a first metal layer directly mounted on and covering most but not all exposed areas of the outer surface of the polymer encapsulant.

[0037]

[17] The method of

[16] above, wherein the metal and / or ceramic coating further comprises a hydrophobic polymer layer covering an outer surface of the first metal layer opposite to an inner surface of the first metal layer adjacent to the polymer encapsulant.

[0038]

[18] The method as described in

[16] above, wherein the metal and / or ceramic coating further includes a passivation layer and / or an oxide layer on the outer surface of the first metal layer.

[0039]

[19] The method as described in

[16] above, wherein the metal and / or ceramic coating further includes a second metal layer covering the first metal layer, the first metal layer comprises a first metal material, and the second metal layer comprises a second metal material different from the first metal material.

[0040]

[20] The method as described in

[16] above, wherein the metal and / or ceramic coating further comprises an embedded layered microstructure on the outer surface of the first metal layer.

[0041] This document describes metal-coated polymer-encapsulated electronic devices, methods for manufacturing and using such electronic devices, and motor vehicles equipped with high-voltage traction power inverters containing metal-coated polymer-encapsulated power semiconductor modules. To enhance moisture resistance and electromagnetic shielding, for example, a single or multilayer metal coating covers selected surface areas of a polymer encapsulant in which the power semiconductor module is encapsulated. Typically, electronic systems employ active electronic components encapsulated in an electrically insulating polymer, which is coated in a moisture-resistant metal layer. The outermost surface of the polymer encapsulant and / or metal coating can be designed to increase surface energy prior to coating, such as by chemical etching (e.g., with acid) or plasma treatment to increase surface roughness. To improve corrosion resistance, the outer surface of the metal coating can be passivated with multiple oxide layers. An optional hydrophobic polymer coating can be applied to the outermost surface of the metal coating. Densification processes such as thermal shock spraying, powder molding, or laser pinning (e.g., if residual stress is desired) can be applied to the metal coating containing the embedded layered structure to enhance the physical barrier effect to moisture diffusion.

[0042] At least some of the attendant benefits of the disclosed concepts include metal-coated polymer encapsulated electronic modules with direct contact heat transfer between the coolant fluid and the individual power modules to improve system thermal management. In addition, sealing via polymer encapsulation and bonding provides a simplified module manufacturing process to reduce manufacturing time and cost. Other attendant benefits may include improved electromagnetic shielding, wherein the improved electromagnetic shielding is used to improve system performance. The use of a metal coating on the encapsulating polymer provides a moisture barrier and EMI shielding, while also enabling the power module enclosure to be immersed in liquid coolant to provide direct cooling of the internal electronic components. In at least some applications, the disclosed power inverter assembly can achieve at least a 20-25% increase in cooling capacity compared to commercially available TPIM designs, accompanied by a 20-25% reduction in enclosure volume, a 20-25% reduction in mass, and a 35-50% savings in cost.

[0043] Aspects of the present disclosure relate to metal-coated polymer-encapsulated power semiconductor modules, TPIM assemblies employing such power modules, and HV electrical systems incorporating such power modules. By way of example, a representative power electronics assembly includes an assembly housing (e.g., formed as a unitary structure from a dielectric polymer) and one or more power modules enclosed within the assembly housing (e.g., in a stacked or side-by-side arrangement). Each power module is fabricated from a substrate (e.g., formed from epoxy and silicon dioxide) and an array of semiconductor devices (e.g., transistor and diode chips) mounted on the substrate. Both the substrate and the semiconductor devices are encapsulated in a polymer encapsulant (e.g., formed from an epoxy or silicone-based molding compound). One or more electrical leads are connected to the semiconductor devices (e.g., via traces on the substrate) and extend laterally from the polymer encapsulant through the assembly housing. A fluid-tight, corrosion-resistant metal and / or ceramic coating is applied to selected exposed portions of the outer surface of the polymer encapsulant.

[0044] Additional aspects of the present disclosure relate to motor vehicles equipped with an HV TPIM containing any of the metal-coated polymer-encapsulated power semiconductor modules described herein. As used herein, the terms "vehicle" and "motor vehicle" are used interchangeably and synonymously to include any relevant vehicle platform, such as passenger cars (ICE, HEV, FEV, fuel cell, fully and partially autonomous vehicles, etc.), commercial vehicles, industrial vehicles, tracked vehicles, off-road and all-terrain vehicles (ATVs), motorcycles, agricultural equipment, watercraft, aircraft, electric bicycles, electric scooters, and the like. For non-vehicle applications, the disclosed concepts can be used for any logically relevant purpose, including stand-alone power stations and portable power packs, grid-connected inverters, photovoltaic systems, pumping equipment, machine tools, appliances, and the like. In one example, an electrically driven vehicle includes a vehicle body with a passenger compartment, a plurality of wheels mounted to the body, and other standard original equipment. One or more traction motors, operating alone (e.g., for a fully electric powertrain) or in conjunction with an engine assembly (e.g., for a hybrid electric powertrain), selectively drive one or more wheels, thereby propelling the vehicle. The HV electrical system may operatively connect the traction motor to a rechargeable energy storage system resident on the vehicle body.

[0045] Continuing with the discussion of the above example, the vehicle also includes a rechargeable traction battery pack mounted to the vehicle body and operable to supply power to the traction motor. One or more TPIMs connect the battery pack to the motor and electrically convert the power transferred therebetween. The TPIM contains one or more power module enclosures, each power module enclosure having a plurality of power modules enclosed in a fluid-cooled assembly housing. Each power module includes a substrate on which a plurality of semiconductor devices are mounted, and a polymer encapsulant encapsulating the substrate and semiconductor devices. Low-voltage and high-voltage electrical leads are connected to the semiconductor devices and protrude from the polymer encapsulant and through the assembly housing. A multi-layer metal coating covers selected portions of the outer surface of the polymer encapsulant.

[0046] Other aspects of the present disclosure relate to manufacturing processes, control logic, and computer-readable media (CRMs) for manufacturing or using any of the disclosed packaged devices, TPIMs, HV electrical systems, and / or vehicles. In one embodiment, a method for manufacturing a power electronics assembly is provided. The representative method includes, in any order and in any combination with any of the options and features disclosed above and below: forming an assembly housing; assembling a power module comprising a substrate, a semiconductor device mounted on the substrate, and electrical leads connected to the semiconductor device; encapsulating the substrate and the semiconductor device in a polymer encapsulant; applying a metal and / or ceramic coating to an outer surface of the polymer encapsulant; and placing the power module encapsulated in the polymer encapsulant with the metal / ceramic coating in the assembly housing.

[0047] For any of the disclosed devices, systems, and methods, the metal / ceramic coating comprises or consists essentially of a single metal layer, the single metal layer being directly attached to and covering substantially all exposed surface area of the outer surface of the polymer encapsulant. For multilayer configurations, an optional hydrophobic polymer layer may cover the outer surface of the metal layer, the outer surface being opposite the inner surface of the metal layer adjacent to the polymer encapsulant. The outer surface of the metal layer may include an etched or roughened finish. As a further option, a passivation layer and / or an oxide layer may be formed on a portion or all of the outer surface of the metal layer.

[0048] For any of the disclosed devices, systems, and methods, the metal / ceramic coating may include a supplementary (second) metal layer that covers a portion or all of a primary (first) metal layer adjacent to the polymer encapsulant. The two layers may be formed from the same or similar metal materials, or may each be formed from a different metal material. In one non-limiting example, the primary (first) metal layer may be formed in whole or in part from zinc, while the supplementary (second) metal layer may be formed in whole or in part from steel. Alternatively, an embedded layered microstructure may be formed on the outer surface of the primary (first) metal layer, for example, via thermal spraying or powder metallurgy techniques. Each metal layer may be formed via thermal spraying techniques, electroplating, chemical "electroless" plating, anodizing, laser cladding, physical vapor deposition, chemical vapor deposition, and the like.

[0049] For any of the disclosed devices, systems, and methods, the metal / ceramic coating has a thickness of about 1 micrometer (μm) to about 500 μm. Alternatively, the assembly housing is formed entirely or partially from a first polymer material, and the polymer encapsulant is formed entirely or partially from a second polymer material different from the first polymer material. The first polymer material may include epoxy and silica, and the second polymer material may include an epoxy-based and / or silicone-based molding compound. Instead of using a metal coating, the polymer encapsulation may be coated with a ceramic, silicate, phosphate, and / or hydroxyl compound.

[0050] For any of the disclosed devices, systems, and methods, the assembly housing includes an elongated body having an inlet port, an outlet port, and a coolant fluid channel fluidly connecting the inlet and outlet ports. The fluid channel may extend longitudinally through the housing body and be interposed between an inner surface of an upper half or a lower half of the assembly housing and a major surface of the power module. The power module may include one or more thermally conductive heat transfer plates, each of which is attached to a semiconductor device and defines a major surface of the power module. An array of heat transfer fins may be mounted to each major surface of the power module and disposed within the fluid channel. An adhesive material such as epoxy, parylene, or silicone may be used to bond each power module to the assembly housing.

[0051] The above summary does not represent every embodiment or every aspect of the present disclosure. Rather, the above features and advantages of the present disclosure, as well as other features and attendant advantages, will be apparent from the following detailed description of illustrative embodiments and modes for implementing the present disclosure when taken in conjunction with the accompanying drawings and the appended claims. Furthermore, the present disclosure expressly includes any and all combinations and subcombinations of the elements and features described above and below. Summary of the Figures

[0052] Figure 1is a schematic diagram of a representative electric drive vehicle having an all-electric powertrain employing multiple motor / generator units (MGUs) electrically connected to a rechargeable traction battery pack via separate traction power inverter modules (TPIMs) according to aspects of the present disclosure.

[0053] Figure 2 is a perspective view of a representative TPIM power module enclosure containing a plurality of metal-coated polymer-encapsulated power semiconductor modules according to aspects of the present disclosure.

[0054] Figure 3 It is along Figure 2 A longitudinal cross-sectional view of a representative TPIM power module enclosure taken along line 3-3.

[0055] Figure 4 yes Figure 3 An enlarged view of one of the power semiconductor modules in a longitudinal cross-section of a representative TPIM power module enclosure.

[0056] Figure 5 It is along Figure 2 A transverse cross-sectional view of a representative TPIM power module enclosure taken along line 5-5.

[0057] Representative embodiments of the present disclosure are shown in the accompanying drawings by way of non-limiting example and are described in more detail below. However, it should be understood that the novel aspects of the present disclosure are not limited to the specific forms shown in the drawings listed above. On the contrary, the present disclosure is intended to cover all modifications, equivalents, combinations, sub-combinations, permutations, groupings, and substitutions that fall within the scope of the present disclosure, such as those encompassed by the appended claims. Detailed Description of the Invention

[0058] The present disclosure allows for many different forms of embodiments. Representative examples of the present disclosure are shown in the accompanying drawings and described in detail herein, with the understanding that these embodiments are provided as examples of the principles of the disclosure, rather than as limitations on the broad aspects of the present disclosure. To this end, elements and limitations that are described, for example, in the abstract, introduction, overview, illustrations, and detailed description but not explicitly set forth in the claims should not be incorporated into the claims, either individually or collectively, by implication, inference, or otherwise. In addition, the drawings discussed herein may not be to scale and are provided purely for guidance purposes. Therefore, the specific and relative dimensions shown in the figures should not be interpreted as limiting.

[0059] For purposes of this specification, unless specifically disclaimed: the singular includes the plural and vice versa; the words "and" and "or" shall be both conjunctive and disjunctive; the words "any" and "all" shall mean "any and all"; and the words "include," "contain," "includes," "including," "having" and their alternatives shall each mean "including but not limited to." In addition, approximate words such as "approximately," "almost," "substantially," "substantially," "approximately," and the like may each be used herein in a sense such as, for example, "at, approximately, or nearly at," or "within 0-5% of," or "within acceptable manufacturing tolerances," or any logical combination thereof. Finally, directional adjectives and adverbs such as front, rear, inboard, outboard, starboard, port, vertical, horizontal, up, down, front, rear, left, right, and the like may be relative to a motor vehicle, such as the forward driving direction of a motor vehicle when the vehicle is operably oriented on a level driving surface.

[0060] Referring now to the drawings, in which like reference numerals represent like features throughout the several views, Figure 1 A schematic diagram of a representative automobile is shown, generally designated 10, and for purposes of discussion is depicted herein as a sedan-type electric drive passenger vehicle. The illustrated automobile 10 (also referred to herein simply as a "motor vehicle" or "vehicle") is merely an exemplary application in which the novel aspects of the present disclosure may be practiced. Likewise, the incorporation of the concepts of the present invention into an all-electric AWD powertrain should also be understood as a non-limiting embodiment of the disclosed features. Thus, it is to be understood that aspects of the present disclosure may be applied to other powertrain architectures, may be implemented for any logically related type of vehicle, and may be used in automotive and non-automotive applications, among others. Furthermore, only selected components of the motor vehicle and power module enclosure are shown and described in greater detail herein. However, the vehicles and power modules discussed below may include many additional and alternative features, as well as other available peripheral components, to implement the methods and functionality of the present disclosure.

[0061] Figure 1The electrically driven vehicle 10 is an example of a battery electric vehicle (BEV) equipped with a multi-mode, front and rear independent drive (FRID) powertrain that achieves on-demand all-wheel drive capability by simultaneously delivering propulsion torque from independently operable electrified drive units (DUs) to multiple wheels. The AWD BEV powertrain of vehicle 10 is shown as having a split-branch architecture: a front (primary) powertrain (PTF) branch at the front end of vehicle body 15 and a rear (auxiliary) powertrain (PTR) branch behind the front powertrain (PTF) at the rear end of vehicle body 15. In this example, the front powertrain (PTF) can be represented by the front (first) axle 11, which drives the left front (passenger front) and right front (driver front) drive wheels 16 and 17. Similarly, the rear powertrain (PTR) can be represented by the rear (secondary) axle 13, which drives the left rear (passenger rear) and right rear (driver rear) wheels 18 and 19. Figure 1 The vehicle 10 is shown having at least one dual independent drive unit (DIDU) axle at the rear axle 13 ; however, the electrically driven vehicle 10 may utilize multiple DIDU axles, a single DIDU axle at the front axle 11 , etc.

[0062] To propel the vehicle 10 during either FWD or AWD operating modes, a first prime mover—which may be a front (main) drive unit 20—generates tractive torque for driving the two front drive wheels 16, 17. Enclosed within the front drive unit 20 is a traction motor 22, which is mechanically coupled to the left and right front wheels 16, 17 via a front (first) driveline 25. According to the illustrated example, the front driveline 25 utilizes an integrated transmission, differential, and axle (transaxle) unit 26 with independent half-shafts 27 to couple the motor 22 to the wheels 16, 17. A front (first) power inverter module (PIM) 24 electrically connects the drive unit motor 22 to the rechargeable energy storage system (RESS) 14. For a fully integrated drive unit assembly, the motor, inverter, and transmission of the DUs 20, 30, 40 are encapsulated as a monolithic construction with internal cooling and high specific power capabilities.

[0063] Operation of the front drive unit 20 and the associated PIM 24 is provided by a resident vehicle controller 50, which may include a resident storage device 51 and one or more subsystem control modules 53, which may include any one or more of a powertrain control module (PCM), an advanced driver assistance system (ADAS) module, an electronic battery pack control module (EBCM), a brake system control module (BSCM), and the like. The left and right front (disc, drum, or air) friction brakes 28 and 29, respectively, are selectively engaged in response to braking commands, such as from the BSCM, from the vehicle controller 50, to decelerate the front drive wheels 16 and 17. A high-voltage electrical bus 12 connects the vehicle's three drive units 20, 30, and 40 to the RESS 14. In at least some embodiments, the RESS 14 is configured as a multi-cell lithium-ion system capable of charging and discharging under a range of conditions. Although depicted as a single prime mover implemented as a traction motor, the front powertrain PTF may employ multiple traction motors, an engine assembly, or a hybrid combination of an engine and motor.

[0064] To propel vehicle 10 during AWD or RWD (if applicable) operating modes, second and third prime movers—which may essentially be a left rear (first auxiliary) drive unit 30 and a right rear (second auxiliary) drive unit 40—generate tractive torque for independently driving rear drive wheels 18, 19. Enclosed within left rear drive unit 30 is a first auxiliary traction motor 32, which is mechanically coupled to left rear wheel 18 via a left rear driveline 35. Similarly, second auxiliary traction motor 42 is enclosed within right rear drive unit 40 and mechanically coupled to right rear wheel 19 via a right rear driveline 45. Left rear driveline 35 utilizes an independent differential unit 36 and dedicated rear half-shafts 37 to couple motor 32 to left rear drive wheel 18. Similarly, right rear driveline 45 utilizes its own independent differential unit 46 and dedicated rear half-shafts 47 to couple motor 42 to right rear drive wheel 19. For at least some desired applications, each traction motor 22 , 32 , 42 is a multi-phase AC permanent magnet (PM) motor generator unit (MGU).

[0065] A left rear (second) power inverter module 34 electrically connects the left rear drive unit motor 32 to the RESS 14 via bus 12, and a right rear (third) power inverter module 44 electrically connects the right rear drive unit motor 42 to the RESS 14 via bus 12. Independent operation of the rear drive units 30, 40 and their respective PIMs 34, 44 can also be provided by the resident vehicle controller 50. Each PIM 24, 34, 44 is a component of the DU power electronics control (PEC) subsystem, regulating the transfer of electrical energy to and from the traction motors 22, 32, 42 and converting high-voltage DC power to three-phase AC power and vice versa as needed. A traction PIM may include a set of power inverters, high-speed transistors and capacitor-based filters, and motor control hardware to receive motor control commands for providing motor drive and regeneration functions. The left and right rear friction brakes 38 and 39, respectively, are selectively engaged in response to corresponding brake commands, for example, from the vehicle controller 50, to decelerate the left and right rear wheels 18, 19.

[0066] RESS 14 is suitable for storage and supply for pushing Figure 1 The RESS can be a deep-cycle, high-ampere capacity battery system rated, for example, at approximately 350 to 800 VDC or higher, depending on the desired vehicle range, gross vehicle weight, and the various accessory loads drawing power from the RESS. To this end, the RESS can employ one or more high-voltage, high-energy-density battery packs electrically connected to the drive unit motors. Traction battery packs typically consist of an array of lithium-ion rechargeable (secondary) battery modules. These modules can be arranged in rows and columns and supported on a battery support bracket or enclosed within a battery pack housing. Aspects of the disclosed concepts are similarly applicable to other electrical storage cell architectures, including those employing nickel metal hydride (NiMH) batteries, lead-acid batteries, lithium polymer batteries, or other suitable types of rechargeable electric vehicle batteries (EVBs). Each battery module can include a series of electrochemical battery cells, such as stacked pouch-type lithium-ion (Li-ion) or Li-ion polymer battery cells.

[0067] Discussed below are representative power electronics systems having active electronic components encapsulated in an electrically insulating polymer covered with a moisture-resistant metal or ceramic coating. For example, in a power inverter enclosure, delicate semiconductor electronics are encapsulated in an encapsulating polymer to improve environmental protection and electrical isolation. However, over the operating life of the power electronics system, the uncoated polymer encapsulant may degrade and eventually begin to absorb moisture. This absorbed moisture, in turn, may degrade the electrical performance of the assembly and may corrode the embedded electronics, potentially requiring repair or replacement. Some existing designs utilize metal cooling plates to allow the polymer-encapsulated electronics to be immersed in a cooling fluid. However, this approach increases material and manufacturing costs, encapsulation requirements, and the overall mass of the system. Electromagnetic noise is also emitted by the device, which may need to be shielded to prevent interference with other systems.

[0068] To minimize moisture ingress into the power semiconductor module, a metal coating and / or ceramic coating may be applied to the polymer encapsulant. The use of a metal and / or ceramic coating on the polymer encapsulant acts as a moisture barrier and EMI shield while enabling the system to be immersed in a liquid coolant to provide direct cooling of the semiconductor devices. The metal / ceramic layer may have a substantially uniform thickness of about 1 μm to about 500 μm. A predetermined gap (e.g., a gap of about 2-4 mm) may be maintained between the metal coating and the high and low voltage electrical leads of the module to prevent short circuits and electrical interference. The metal / ceramic coating may be applied to additional portions of the power module enclosure to improve the adhesion of the power module to the polymer assembly housing. Moisture ingress into the encapsulated power module may be resisted by applying a structurally designed metal coating system, which modifies the surface properties, such as reducing surface energy and increasing surface roughness, and creates a physical barrier to reduce the diffusion coefficient of absorbed molecules.

[0069] Figure 2 A power module package 100 is shown, which represents a portion of an electronic system that uses metal-coated polymer encapsulated electronic devices to change the electrical power transfer between a source and a load. In electrified powertrain applications, such as Figure 1 In a vehicle 10, two such power module packages 100 can operate in unison as a switching network of a three-phase circuit to provide a DC / AC inverter function, such as in Figure 1 As in PIM 24, 34, 44. Figure 2The power module enclosure 100 is generally comprised of three power semiconductor modules ("power modules") 102 enclosed within a protective assembly housing 104. For ease of manufacturing and simplicity of design, the power modules 102 can be substantially identical to one another, despite inherent manufacturing variations and tolerances. Although depicted as consisting of three power modules 102 aligned side-by-side in a single row, the power module enclosure 100 can contain more or fewer power modules 102, which can be similar or different from one another, and can be enclosed in alternative arrangements, for example, equally spaced apart in a stacked or circular arrangement.

[0070] like Figure 2 and 5 As best shown in FIG, each power module 102 is fabricated with a module body 106 and a plurality of electrical connectors—three high-voltage leads 108 and three low-voltage leads 110—extending laterally from opposite sides of the module body 106. Enclosed within the power module body 106 are a first set of semiconductor devices 112, a second set of semiconductor devices 114, and a substrate 116 on which the semiconductor devices 112, 114 are supported and operatively connected. The first set of semiconductor devices 112 may include two or four IGBT chips, MOSFET chips, and / or thyristor chips. The second set of semiconductor devices 114 may include two or four large-signal or silicon-controlled rectifier diode chips. In the three-phase circuit switching network of the PIM, three pairs of switches may be arranged in series, with a diode connected in antiparallel to each switch to correspond to the three phases of a multi-phase motor. Each pair of series switches may include a first transistor switch (e.g., a "high switch") having a corresponding lead coupled to the positive electrode of a voltage source (e.g., a battery pack in the RESS 14) and a second transistor switch (e.g., a "low switch") having a corresponding lead coupled to the negative electrode of the voltage source. The substrate 116 may be made in whole or in part of a dielectric material such as epoxy and silicon dioxide, and may employ molybdenum spacers for selective electrical isolation and silver sintering paste for electrical connection.

[0071] Mounted to opposing top and bottom sides of the module body 106 are a pair of heat transfer plates 118 and 120 with the semiconductor devices 112, 114 sandwiched therebetween. The two heat transfer plates 118, 120 are at least partially uncovered by the mold compound 105 of the module body 106 such that the top (first) major surface 107 of the body 106 of the power module 102 is at least partially defined by the top (first) heat transfer plate 118 and the bottom (second) major surface 109 of the body 106 is at least partially defined by the bottom (second) heat transfer plate 120. The heat transfer plates 118, 120 may be made of a metal and / or ceramic material that exhibits a high thermal conductivity (e.g., greater than about 20 W / m·K at ambient temperature) and a low coefficient of thermal expansion (e.g., less than about 10 ppm / K at ambient temperature). As used herein, the terms "metal" or "metallic" may refer to elemental metals as well as metal alloys comprising a combination of elemental metals and one or more alloying elements. For example, Figure 4 As shown in FIG, each heat transfer plate 118, 120 may be a direct bonded copper (DBC) sandwich structure having a ceramic core 115 (e.g., alumina or aluminum nitride) and copper skins 117 formed on or bonded to opposing upper and lower surfaces of the core 115. Alternatively, the heat transfer plates 118, 120 may each be in the form of a direct bonded aluminum (DBA) ceramic substrate in which a sheet of copper (Cu) or copper oxide (CuO) is sandwiched between and directly bonded to two layers or sheets of aluminum (Al).

[0072] In the body 106 of the power module 102, semiconductor devices 112 and 114 are mounted on a substrate 116, electrically connected to leads 108 and 110, sandwiched between heat transfer plates 118 and 120, and encapsulated in a polymeric mold compound 105. This mold compound 105 (also referred to herein as the "polymer encapsulant") can contain any suitable polymer material, including epoxy-based, bismaleimide-based, and / or silicone-based polymer materials. Additional encapsulant options may include thermosetting polymers such as polyurethane, phenolic resins, bismaleimides, polyimides, polyesters, silicones, or other amorphous thermosets, as well as thermoplastic polymers such as polypropylene, ABS, PVC, PPS, PA, PPA, PAI, PEEK, PE, or other semi-crystalline thermoplastics. Mold release agents, pigments, silica, phenolic hardeners, cure-accelerating catalysts, and non-conductive fillers (e.g., minerals, glass, fibers, phosphates, hydroxylated compounds, etc.) may also be present in useful mold compound compositions. The free "outside" ends of the leads 108, 110 protrude from the mold compound 105 and through the sidewalls of the assembly housing 104. The outermost exposed surfaces of the mold compound 105 (including outwardly facing surface areas not covered by plates 118, 120 or shielded by the leads 108, 110) may be modified to increase the surface energy, such as by chemical etching or plasma treatment, to improve bonding with the metal or ceramic coating 122, as will be described in further detail below.

[0073] Common Reference Figure 2 and 3 The assembly housing 104 of the power module enclosure 100 electrically insulates the internal electrical components of the power module 102 from the surrounding environment and prevents the unwanted ingress of dust and moisture. In addition, the assembly housing 104 is coupled to the module body 106 to prevent the coolant fluid (indicated by arrows C) flowing through the top (first) and bottom (second) coolant fluid channels 101, 103 of the power module enclosure 100 from being vented. FL ) and the exposed free ends of the leads 108, 110. The assembly housing 104 has an elongated hollow housing 124 having a central longitudinal axis A L , the central longitudinal axis A LThe body 124 is divided into a bottom (half) section 123 and a top (half) section 121 of the body 124. A coolant inlet port 126 is located at the proximal (first) end of the housing 124 and is fluidly connected to a coolant outlet port 128 located at the distal (second) end of the housing 124 via fluid channels 101, 103. The outlet port 128 is opposite the inlet port 126. The two coolant ports 126, 128 are in fluid communication with the two coolant channels 101, 103, so that coolant fluid introduced into the inlet port 126 can be divided between the coolant channels 101, 103 and recombined before being discharged from the outlet port 128 of the housing. The terms "top" and "bottom" or "upper half" and "lower half" used herein in the discussion of the power module enclosure 100 are used for reference purposes only in the illustrated orientation and are interchangeable.

[0074] The assembly housing 104, including the upper and lower halves 121, 123 of the housing and the inlet and outlet ports 126, 128 of the housing, can be integrally formed as a unitary one-piece structure. In such cases, the entire housing 104 can be formed, for example, by secondary injection molding the power module 102 so as to define the internal fluid channels 101, 103 in a single manufacturing step. In other embodiments, the housing 104 can be a multi-part construction formed by multiple discrete components that are positioned around the power module 102 and subsequently joined to each other along the interface therebetween. For example, during assembly of the power module enclosure 100, the portion of the housing 104 that is directly engaged with the outer surface of the power module 102 can be physically attached thereto. An adhesive or sealant can be used to bond the upper and lower halves 121, 123 of the housing 104 to each other and / or to the interfacing outer surfaces of the power module 102. Such adhesives or sealants can be silicone-based polymeric materials, such as epoxies, parylene, or room temperature vulcanizing (RTV) silicones. Assembly housing 104 can be made of a dielectric polymer, which can be a thermoset or thermoplastic polymeric material. Housing 104 can be made of an epoxy / silicon dioxide composition, or any of the polymeric materials identified above with respect to mold compound 105 of power module body 106. Alternatively, housing 104 can be formed of polyamide, polyphthalamide, or polyphenylene sulfide, any of which can be glass fiber, silica, and / or mineral filled.

[0075] In order to increase the flow of coolant fluid C from the power module 102 FLTo facilitate heat transfer in the power module body 106, top (first) and bottom (second) arrays of heat transfer fins 130 and 132 are mounted to the respective top and bottom major surfaces 107, 109 of the power module body 106, respectively, and disposed within the respective fluid channels 101, 103. The top fin array 130 is shown physically mounted along its bottom end to the top major surface 107 of each power module 102, and mounted along its top end to the inner surface of the housing upper half 121. Similarly, the bottom fin array 132 is physically mounted along its top end to the bottom major surface 109 of each power module 102, and mounted along its bottom end to the inner surface of the housing lower half 123. Figure 5 In the embodiment depicted in , each array of heat transfer fins 130, 132 is defined by a discrete, unitary sheet of corrugated metal. In other designs, the heat transfer fins 130, 132 may exhibit alternative configurations, such as a series of discrete pillars, columns, wires, or fins.

[0076] Fluid channels 101, 103 guide the coolant fluid C FL (eg, water, glycol, or both) flows through and directly contacts the two major surfaces 107, 109 of the power module 102. At the same time, the coolant fluid C FL The flow is directed through and in direct contact with the corrugated surfaces of the fins 130, 132 so as to effectively and efficiently transfer heat away from the power module 102 via convection. The top coolant fluid channel 101 extends parallel to the central longitudinal axis A between the top 121 of the housing 104 and the top major surface 107 of the power module 102. L Likewise, the bottom coolant fluid passage 103 extends between the bottom 123 of the housing 14 and the bottom major surface 109 of the module 102 along a longitudinal axis A parallel to the housing 104. L The longitudinal direction extends through the housing 104.

[0077] To minimize moisture ingress into individual power modules 102, moisture-impermeable metal and / or ceramic layers 122 may be added to selected portions of polymer encapsulant 105. For example, Figure 4A metal / ceramic layer 122 is shown, having front (first) and rear (second) portions 122A and 122B, respectively, covering the front (upstream) and rear (downstream) faces of the encapsulant 105. Surrounded by these faces, they cover the top and bottom surfaces of the encapsulant 105 exposed by the heat transfer plates 118, 120 and fins 130, 132. Thus, the front and rear portions 122A, 122B collectively define a longitudinal cross-section having two mirror-imaged U-shaped sections. Also shown is an impermeable metal / ceramic layer 122, having mutually parallel, substantially parallel top (third) and bottom (fourth) portions 122C and 122D, respectively, which are interposed between the top and bottom ends of the fins 130, 132 and physically connect them to the inner surfaces of the upper and lower housing halves 121, 123. Thus, the top and bottom portions 122C, 122D collectively define a longitudinal cross-section having two mirror-imaged straight segments. However, the impermeable metal / ceramic layer 122 does not block the fluid channels 101, 103 or the coolant fluid C FL The encapsulant coating 122 may, for example, only cover the portion of the power module 102 that is immersed in the coolant fluid C. FL The selected portions of the coating are provided to ensure that moisture can exit each module 102 through the uncoated side.

[0078] Continuing with the discussion of the metal / ceramic layer 122, Figure 5 Left (fifth) and right (second) side portions 122E and 122F, respectively, are shown, covering the left and right sides of fins 130 and 132 and surrounding these sides to cover the top and bottom laterally protruding surfaces of encapsulant 105. Thus, top and bottom portions 122C and 122D of impermeable metal / ceramic layer 122 cooperate with side portions 122E and 122F to define a cross-section having two mirror-imaged omega (Ω)-shaped portions. However, impermeable layer 122 does not contact leads 108 and 110, nor does it cover (i.e., expose) the outward-facing surface of encapsulant 105 proximate leads 108 and 110. As shown, impermeable metal / ceramic layer 122 is set back from leads 108 and 110 by at least approximately 1 mm, or, in at least some desired applications, by a clearance distance of, for example, approximately 2-4 mm, to prevent shorting or electrical interference with leads 108 and 110.

[0079] For at least some embodiments, the impermeable metal / ceramic layer 122, including all six of the above-listed portions 122A-122F, can be formed as an integral, one-piece structure. Alternatively, any one or more or all of the above-listed portions 122A-122F can be formed as discrete or connected portions. In addition, the metal / ceramic layer 122 can include a plurality of portions located adjacent to the metal / ceramic layer 122. Figure 4 and 5105 . For example, the top and bottom portions 122C, 122D may be eliminated entirely from the impermeable metal / ceramic layer 122, such that the fins 130, 132 are bonded directly to the assembly housing 104. Alternatively, the side portions 122E and 122F may expose the left and right sides of the fins 130, 132 and thereby cover only the top and bottom laterally protruding surfaces of the encapsulant 105, in order to minimize assembly mass and cost.

[0080] like Figure 4 and 5 As shown in , one or more metal and / or ceramic layers may be applied to the exposed outer surface of the polymer encapsulant 105, such as via thermal spray techniques, electroplating, electroless plating, anodizing, laser cladding, physical vapor deposition, chemical vapor deposition, etc. For example, Figure 5 The illustration shows impermeable layer 122, with primary (first) metal layer 125 adjacent to, abutting, and directly attached to the exposed surface area of the outer surface of polymer encapsulant 105. An optional supplemental (second) layer 127 can be applied over and cover some or all of primary metal layer 125. Similarly, an auxiliary (third) layer 129 can be applied over and cover some or all of supplemental layer 127. It should be understood that impermeable metal / ceramic layer 122 can consist essentially of a single layer, or can include two or more layers. For a multi-layer configuration, all layers can cover the same locations and thus share a common total surface area; alternatively, the individual layers can have different layouts and different surface areas.

[0081] A representative example of a multi-metallic coating may include an impermeable layer 122 having a primary metal layer 125 and a supplemental layer 127, wherein the primary metal layer is formed in whole or in part from a first metallic material and the supplemental layer is formed in whole or in part from a second metallic material different from the first metallic material. In a non-limiting example, primary metal layer 125 is formed from zinc and supplemental layer 127 is formed from steel. Supplemental layer 129 may be formed in whole or in part from a third metallic material that may be the same as or different from the first and / or second metallic materials. Any one or more, or all, of layers 125, 127, and 129 may be formed from other metallic materials, including aluminum, copper, tin, other ferrous metals, or alloys of any of the metallic materials described herein. Optionally, first layer 125 may be a metal / plastic adhesive for bonding second (metal) layer 127 to polymer encapsulant 105, or second layer 127 may be a metal / metal adhesive for bonding third (metal) layer 129 to first (metal) layer 125.

[0082] Rather than being constructed entirely of metal, the impermeable layer 122 may include supplemental and / or auxiliary layers 127, 129 formed from ceramic or polymeric materials. For example, the supplemental layer 127 or auxiliary layer 129 may be formed in whole or in part from a hydrophobic polymer, such as a urethane-based or silane-based sealing coating. As a further alternative, one or both of the optional layers 127, 129 may be formed from silicates, phosphates, hydroxyls, or the like. To increase the contact surface area and bond strength between the adjacent metal and polymer layers, the interfacial surface areas of the exposed outer surface of the polymer encapsulant 105 and / or the primary metal layer 125 may be provided with an etched or roughened finish. Similarly, the contact surface area and bond strength between the adjacent metal layers may be increased by etching / roughening the interfacial surface areas of the exposed outer surface of the primary layer 125.

[0083] As described above, moisture can be prevented from penetrating into the polymer encapsulant 105 by applying a structurally designed coating system 122 that modifies the surface properties of the encapsulant, such as reducing surface energy and increasing surface roughness, and creates a physical barrier to reduce the diffusion coefficient of absorbed molecules. A densification process, such as thermal shock spraying, powder molding, or laser pinning can be applied to the primary metal layer 125 or the secondary metal layer 127, for example to improve stress and energy dissipation characteristics. Densification can be achieved using thermal spraying techniques, powder metallurgy processes, or other suitable metal densification methods. The outer surface of the metal layer, such as the primary and / or supplementary metal layers 125, 127, can be modified to include one or more passivation layers and / or oxide layers. The oxide layer can be formed using a chemical reaction between oxygen and the metal coating to optimize its potential difference.

[0084] Various aspects of the present disclosure have been described in detail with reference to the illustrated embodiments; however, those skilled in the art will recognize that many modifications may be made thereto without departing from the scope of the present disclosure. The present disclosure is not limited to the precise configurations and compositions disclosed herein; any and all modifications, changes, and variations apparent from the foregoing description are within the scope of the present disclosure as defined by the appended claims. Furthermore, the inventive concept expressly encompasses any and all combinations and subcombinations of the aforementioned elements and features.

Claims

1. A power electronic assembly comprising: Assembly housing; and A power module enclosed in an assembly housing and comprising a substrate, a semiconductor device mounted on the substrate, a polymer encapsulant encapsulating the substrate and the semiconductor device, electrical leads connected to the semiconductor device and protruding from the polymer encapsulant, and a metal and / or ceramic coating on an outer surface of the polymer encapsulant; wherein the metal and / or ceramic coating comprises a first metal layer mounted directly onto and covering most but not all exposed areas of the outer surface of the polymer encapsulant, wherein the metal and / or ceramic coating further comprises an embedded layered microstructure on the outer surface of the first metal layer, The metal and / or ceramic coating has a front portion and a rear portion covering the front and rear faces of the polymer encapsulant, respectively, with a top portion and a bottom portion being parallel to each other.

2. The power electronic assembly of claim 1, wherein the metal and / or ceramic coating further comprises a hydrophobic polymer layer covering an outer surface of the first metal layer opposite an inner surface of the first metal layer adjacent to the polymer encapsulant. 3 . The power electronic assembly of claim 2 , wherein the outer surface of the first metal layer covered by the hydrophobic polymer layer comprises an etched or roughened overcoat layer. 4 . The power electronic assembly of claim 1 , wherein the metal and / or ceramic coating further comprises a passivation layer and / or an oxide layer on an outer surface of the first metal layer. 5 . The power electronic assembly of claim 1 , wherein the metal and / or ceramic coating further comprises a second metal layer covering the first metal layer, the first metal layer comprising a first metal material, and the second metal layer comprising a second metal material different from the first metal material. 6 . The power electronics assembly of claim 5 , wherein the first metal material comprises zinc and the second metal material comprises steel. 7 . The power electronic assembly of claim 1 , wherein the metal and / or ceramic coating has a thickness of 1 μm to 500 μm.

8. The power electronics assembly of claim 1, wherein the assembly housing comprises a first polymer material and the polymer encapsulant comprises a second polymer material different from the first polymer material.

9. The power electronic assembly of claim 8, wherein the first polymer material comprises a combination of epoxy and silicon dioxide, polyamide, polyphthalamide, or polyphenylene sulfide, and the second polymer material comprises an epoxy-based, bismaleimide-based, or silicone-based molding compound.

10. The power electronics assembly of claim 1 , wherein the assembly housing comprises an elongated body having an inlet port, an outlet port, and a coolant fluid channel fluidly connecting the inlet port and the outlet port, the fluid channel extending longitudinally through the housing body between an inner surface of the assembly housing and a major surface of the power module.

11. The power electronics assembly of claim 10, wherein the power module further comprises: a thermally conductive heat transfer plate attached to the semiconductor device and defining a major surface of the power module; and A heat transfer fin array is mounted on a major surface of the power module and disposed within the fluid channel.

12. An electric vehicle comprising: a vehicle body having a plurality of wheels; a traction motor mounted to the vehicle body and operable to drive one or more wheels to propel the electrically driven vehicle; a rechargeable traction battery pack mounted to the vehicle body and operable to power a traction motor; and A traction power inverter module (TPIM) electrically connects a traction battery pack to a traction motor, the TPIM comprising a power module enclosure having an assembly housing, a coolant fluid channel in the assembly housing and through which a coolant fluid passes, and a plurality of power modules enclosed in the assembly housing, each power module comprising a substrate, a plurality of semiconductor devices mounted on the substrate, a polymer encapsulant encapsulating the substrate and the semiconductor devices, a plurality of electrical leads connected to the semiconductor devices and protruding from the polymer encapsulant, and a multi-layer metal coating positioned on an outer surface of the polymer encapsulant in a spaced, non-contact relationship with the electrical leads. wherein the metal coating comprises a first metal layer mounted directly onto and covering most but not all exposed areas of the outer surface of the polymer encapsulant, wherein the metal coating further comprises an embedded layered microstructure on the outer surface of the first metal layer, The metal coating has a front portion and a rear portion covering the front and rear surfaces of the polymer encapsulant, respectively, and has a top portion and a bottom portion parallel to each other.

13. A method of manufacturing a power electronics assembly, the method comprising: forming an assembly housing; assembling a power module including a substrate, a semiconductor device mounted on the substrate, and electrical leads connected to the semiconductor device; encapsulating the substrate and the semiconductor device in a polymer encapsulant; applying a metal and / or ceramic coating to the outer surface of the polymer encapsulant; and Positioning a power module encapsulated in a polymer encapsulant with a metal and / or ceramic coating in the assembly housing, wherein the metal and / or ceramic coating comprises a first metal layer mounted directly onto and covering most but not all exposed areas of the outer surface of the polymer encapsulant, wherein the metal and / or ceramic coating further comprises an embedded layered microstructure on the outer surface of the first metal layer, The metal and / or ceramic coating has a front portion and a rear portion covering the front and rear faces of the polymer encapsulant, respectively, and has a top portion and a bottom portion parallel to each other.

14. The method of claim 13, wherein the metal and / or ceramic coating further comprises a hydrophobic polymer layer covering an outer surface of the first metal layer opposite an inner surface of the first metal layer adjacent to the polymer encapsulant.

15. The method of claim 13, wherein the metal and / or ceramic coating further comprises a passivation layer and / or an oxide layer on an outer surface of the first metal layer.

16. The method of claim 13, wherein the metal and / or ceramic coating further comprises a second metal layer covering the first metal layer, the first metal layer comprising a first metal material, and the second metal layer comprising a second metal material different from the first metal material.

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