Substrate-less hybrid power module assembly and method of manufacturing same

Abstract

The embodiments herein disclose a method for manufacturing a substrateless hybrid power module assembly. The method includes providing a PCB (1302). The method further includes assembling a control circuit component on the PCB (1302). The method further includes mounting a power device on the control circuit component. The method also includes performing device interconnection on the device using SMT, wire bonding, and / or copper strap. The method further includes mounting a bus bar on the bottom of the PCB (1302). The method further includes mounting an insulating layer (1312) below the bus bar mounted on the bottom of the PCB (1302). The method further includes mounting a heat dissipation layer (1314) below the insulating layer (1312). The method further includes mounting one of a plastic molded case (2702) and a potting compound on the heat dissipation layer (1314).

Description

[Technical Field]

[0001] TECHNICAL FIELD The embodiments disclosed herein relate to power module assemblies, and more particularly to flexible, substrateless, high current power module assemblies and methods for assembling / manufacturing substrateless hybrid power module assemblies. [Background technology]

[0002] Emerging industrial, automotive, and consumer electronics applications demand high power density and efficiency for systems at reasonable cost. Flexibility in design and assembly is important to meet diverse product demands. A central criterion for reliable electronic design is thermal management. To improve the reliability of electronic devices, peak component temperatures need to be kept as low as possible.

[0003] A common approach to designing high-power, high-current electronic modules is to use highly thermally conductive materials, such as ceramic substrates, to mount power devices. This ensures an improved thermal path for heat dissipated by the electronic devices to the surroundings. Common materials used for this purpose are aluminum oxide (Al2O3), aluminum nitride (AlN), aluminum silicon carbide (AlSiC) ceramic substrates, or aluminum metal-core printed circuit boards (PCBs). Ceramic substrates have higher thermal conductivity than flame-retardant 4 (FR4) PCBs, but they are expensive and require a complex sintering process to print the circuit patterns. The thickness of copper traces that can be economically printed on ceramic substrates is limited to approximately 100 μm. This thickness may not be sufficient to reliably carry the high currents required by the system. Users can attach copper lead frames of any thickness to meet their needs. However, this process increases the number of components, complexity, and system cost.

[0004] Implementing power devices such as metal-oxide-semiconductor field-effect transistors (MOSFETs), insulated-gate bipolar transistors (IGBTs), and diodes on FR4 PCBs is the simplest and most economical method. However, FR4 material has incredibly low thermal conductivity (0.24 W / m-°K), significantly limiting the utilization of power device capabilities. FR4's low melting point also imposes further limitations. As the current in the system increases, the required copper trace thickness also becomes a constraint. Although aluminum-core PCBs have better thermal conductivity than FR4 PCBs, they also have limitations on the thickness of the copper traces. Printing thicker copper traces increases manufacturing costs. Alternatively, thicker copper lead frames can be attached to increase current carrying capacity. However, this method has the same drawbacks (e.g., component count, complexity, and system cost).

[0005] Alternatively, system users can use discrete semiconductors mounted directly on a heat sink to improve performance. However, as voltage and current increase, assembly complexity, variability, and increased parasitic effects decrease manufacturability and reliability. As power ratings increase, it may be necessary to connect several power devices in parallel, which increases system complexity and reduces reliability. For such applications, the use of integrated power modules (PMs) and intelligent power modules (IPMs) is recommended. They make system integration easier, reduce variability, and improve system reliability.

[0006] Figures 1 and 2 are example diagrams (100 and 200) showing surface mount technology (SMT) devices mounted on an FR4 PCB. FR4 PCBs have very low thermal conductivity. This reduces the performance of power devices, and designers must therefore use many devices in parallel to achieve the desired performance specifications. Copper trace thickness is limited to approximately 200 microns. This presents a challenge for conducting the large currents required by the system. Using multiple layers (>2 layers) increases the complexity and cost of manufacturing the FR4 PCB.

[0007] Figure 3 is an example diagram (300) showing an SMT device mounted on a metal-core PCB. Metal-core PCBs are typically single-layer, making it difficult to mount both power and control circuits on the same board. The thickness of the copper trace is limited to approximately 200 microns. For higher current systems, additional copper lead frames must be attached, resulting in system complexity and reduced reliability.

[0008] Figure 4 shows a cross section of a metal core PCB 400. As shown in Figure 4, an insulating layer is provided on a portion of the Al core, and a copper layer is provided on a portion of the insulating layer.

[0009] Figure 5 shows a cross-sectional view (500) of a module with a ceramic substrate. Figure 6 shows a cross-sectional view (600) of a ceramic substrate. Ceramic substrates are precisely engineered components and are expensive. Ceramic substrates are useful in systems with voltages exceeding 1200V. Ceramic substrates are typically single-sided, making it difficult to place both power devices and control circuitry on the same substrate. The thickness of the copper traces is limited to approximately 200 microns. For higher current systems, additional copper lead frames must be attached, resulting in system complexity and reduced reliability. As shown in Figure 6, a top copper layer is provided on a portion of the ceramic insulating layer. The ceramic insulating layer is provided on the bottom copper layer. The ceramic insulating layer is disposed between the top and bottom copper layers.

[0010] Figures 7a-7c are exemplary diagrams (700a-700c) showing insert molded lead frame design concepts. This approach does not use a ceramic substrate. Instead, the lead frame is molded directly into a plastic base. This is a low-cost option that allows for the use of thicker lead frames. Disadvantages of this method include the difficulty of keeping the lead frame flush against the heat sink, the risk of moisture leakage through the gap between the lead frame and the plastic molding, and the difficulty of embedding the very fine traces required to embed control circuit components alongside the power devices.

[0011] It would therefore be desirable to address the above-mentioned deficiencies and others, or at least provide a useful alternative. Summary of the Invention

[0012] [the purpose] The primary objective of the embodiments herein is to disclose a method for assembling / manufacturing a flexible substrateless hybrid power module assembly.

[0013] Another object of embodiments herein is to improve the availability, reliability, and manufacturability of power electronics systems assembled using discrete power devices and / or bare die in high power electronic systems.

[0014] Another object of embodiments herein is to create custom high current power modules (PMs) and intelligent power modules (IPMs) without using expensive ceramic substrates.

[0015] Another objective of embodiments herein is to enable high density integration while eliminating complex processes, expensive and long lead time materials, and improving thermal performance of flexible substrateless hybrid power module assemblies.

[0016] Another objective of embodiments herein is to seamlessly combine control and power circuits to improve the power density, thermal performance, and reliability of flexible substrateless hybrid power module assemblies while enabling advanced integration of electronic systems.

[0017] Another objective of embodiments herein is to enable the fabrication of circuits using conventional SMT mounting techniques, aluminum wire bonds, copper strap bonding solderable interconnect methods, or any interconnect method. These features enable the proposed method to enable a wide range of products and applications. It also maximizes the utilization of power device capabilities and reduces the cost of power supplies. This method allows for flexible design and fast time-to-market, achieving an optimized cost of the solution.

[0018] These and other aspects of the embodiments herein will be better appreciated and understood when considered in conjunction with the following description and the accompanying drawings. It should be understood, however, that the following description, while indicating at least one embodiment and numerous specific details thereof, is given by way of illustration and not limitation. Many changes and modifications can be made within the scope of the embodiments herein without departing from the spirit thereof, and the embodiments herein include all such modifications. [Brief explanation of the drawings]

[0019] Embodiments herein are illustrated in the accompanying drawings, in which like reference characters indicate corresponding parts in the various drawings throughout, and will be better understood from the following description with reference to the drawings.

[0020] [Figure 1] FIG. 1 is an exemplary diagram showing an SMT device mounted on an FR4 PCB according to the prior art. [Figure 2] FIG. 2 is an exemplary diagram showing an SMT device mounted on an FR4 PCB according to the prior art.

[0021] [Figure 3] FIG. 3 is an exemplary diagram showing an SMT device mounted on a metal core PCB according to the prior art.

[0022] [Figure 4] FIG. 4 shows a cross section of a prior art metal core PCB.

[0023] [Figure 5] FIG. 5 shows a cross-sectional view of a module with a ceramic substrate according to the prior art.

[0024] [Figure 6] FIG. 6 shows a cross-sectional view of a ceramic substrate according to the prior art.

[0025] [Figure 7a] FIG. 7a is an exemplary diagram illustrating an insert molding leadframe design concept according to the prior art. [Figure 7b] FIG. 7b is an exemplary diagram illustrating an insert molding leadframe design concept according to the prior art. [Figure 7c] FIG. 7c is an exemplary diagram illustrating an insert molding leadframe design concept according to the prior art.

[0026] [Figure 8]FIG. 8 is an exemplary diagram illustrating a substrateless hybrid power module having SMT power devices according to embodiments disclosed herein.

[0027] [Figure 9] FIG. 9 is another schematic circuit diagram of a substrateless hybrid power module having power devices according to embodiments disclosed herein.

[0028] [Figure 10] FIG. 10 is an exemplary diagram illustrating a substrateless hybrid power module with chips and wire bonding according to embodiments disclosed herein.

[0029] [Figure 11] FIG. 11 is an exemplary diagram illustrating a substrateless hybrid power module with copper strap interconnects using a solderable front metal (SFM) die according to embodiments disclosed herein.

[0030] [Figure 12] FIG. 12 is an example diagram showing PCB windows of a substrateless hybrid power module cut out below the power devices according to embodiments disclosed herein.

[0031] [Figure 13] FIG. 13 illustrates a cross-sectional view of a substrateless hybrid power module according to embodiments disclosed herein.

[0032] [Figure 14] FIG. 14 is an exemplary diagram illustrating a substrateless hybrid power module with an integrated embossed heat sink according to embodiments disclosed herein.

[0033] [Figure 15] FIG. 15 illustrates a cross-sectional view of a hybrid power module having a substrate according to embodiments disclosed herein.

[0034] [Figure 16] FIG. 16 is an exemplary diagram illustrating a substrateless hybrid power module having SMT power devices according to embodiments disclosed herein.

[0035] [Figure 17] FIG. 17 is another exemplary diagram illustrating a substrateless hybrid power module with chips and wire bonding according to embodiments disclosed herein.

[0036] [Figure 18] FIG. 18 is another exemplary diagram illustrating a substrateless hybrid power module with copper strap interconnects using SFM die according to embodiments disclosed herein.

[0037] [Figure 19] FIG. 19 is an exemplary diagram showing a PCB window of a substrateless hybrid power module cut out under the power devices according to embodiments disclosed herein.

[0038] [Figure 20] FIG. 20 shows a cross-sectional view of a substrateless hybrid power module with chips and wire bonding according to embodiments disclosed herein.

[0039] [Figure 21] FIG. 21 is an exemplary diagram of a substrateless hybrid power module according to embodiments disclosed herein.

[0040] [Figure 22]FIG. 22 is an exemplary diagram illustrating a substrateless hybrid power module having SMT power devices according to embodiments disclosed herein.

[0041] [Figure 23] FIG. 23 is an exemplary diagram illustrating a substrateless hybrid power module with chips and wire bonds according to embodiments disclosed herein.

[0042] [Figure 24] FIG. 24 is another exemplary diagram illustrating a substrateless hybrid power module with copper strap interconnects using SFM die according to embodiments disclosed herein.

[0043] [Figure 25] FIG. 25 is an example diagram showing a PCB of a substrateless hybrid power module with cutouts according to embodiments disclosed herein.

[0044] [Figure 26] FIG. 26 illustrates a cross-sectional view of embossed copper bus bars of a substrate-less hybrid power module according to embodiments disclosed herein.

[0045] [Figure 27] FIG. 27 illustrates a cross-sectional view of a substrateless hybrid power module according to embodiments disclosed herein.

[0046] [Figure 28] FIG. 28 is an exemplary diagram illustrating a substrateless hybrid power module with a molded plastic case according to embodiments disclosed herein.

[0047] [Figure 29]FIG. 29 is a schematic circuit diagram of a three-phase inverter power supply circuit according to embodiments disclosed herein.

[0048] [Figure 30] FIG. 30 is an exemplary diagram illustrating the concept of a three-phase inverter power module having SMT devices and separately mounted power terminals according to embodiments disclosed herein.

[0049] [Figure 31] FIG. 31 is an exemplary diagram illustrating a three-phase inverter power module having SMT devices and integrated power terminals according to embodiments disclosed herein.

[0050] [Figure 32] FIG. 32 is an example diagram of a three-phase inverter power module having chips and wires with separately attached power terminals according to embodiments disclosed herein.

[0051] [Figure 33] FIG. 33 is an exemplary diagram of a three-phase inverter power module having bare die or chip and wire bonding and integrated power terminals according to embodiments disclosed herein.

[0052] [Figure 34] FIG. 34 is an exemplary diagram illustrating a full bridge topology with bare die / chip and wirebonds according to embodiments disclosed herein.

[0053] [Figure 35] FIG. 35 is a circuit diagram of a full-bridge topology with bare die / chip and wirebonds according to embodiments disclosed herein.

[0054] [Figure 36]FIG. 36 is an exemplary diagram illustrating a half-bridge topology with bare die / chip and wirebonds according to embodiments disclosed herein.

[0055] [Figure 37] FIG. 37 is a circuit diagram of a half-bridge topology with bare die / chip and wirebonds according to embodiments disclosed herein.

[0056] [Figure 38] FIG. 38 is an exemplary diagram illustrating a bidirectional switch with bare die / chip and wirebonds according to embodiments disclosed herein.

[0057] [Figure 39] FIG. 39 is a circuit diagram of a bidirectional switch with bare die / chip and wirebonds according to embodiments disclosed herein.

[0058] [Figure 40] FIG. 40 is a front view of a lead frame assembly according to an embodiment disclosed herein.

[0059] [Figure 41] FIG. 41 is a side view of a lead frame assembly with details according to an embodiment disclosed herein.

[0060] [Figure 42] FIG. 42 is an exemplary diagram illustrating a lead frame assembly on an FR4 PCB according to an embodiment disclosed herein.

[0061] [Figure 43] FIG. 43 is a cross-sectional view of a detail of an assembly stack of a bidirectional switch according to an embodiment disclosed herein.

[0062] [Figure 44]FIG. 44 is a flowchart illustrating a method for assembling a substrateless hybrid power module assembly according to embodiments disclosed herein. [Figure 45] FIG. 45 is a flowchart illustrating a method for assembling a substrateless hybrid power module assembly according to embodiments disclosed herein. [Figure 46] FIG. 46 is a flowchart illustrating a method for assembling a substrateless hybrid power module assembly according to embodiments disclosed herein. [Figure 47] FIG. 47 is a flowchart illustrating a method for assembling a substrateless hybrid power module assembly according to embodiments disclosed herein. [Figure 48] FIG. 48 is a flowchart illustrating a method for assembling a substrateless hybrid power module assembly according to embodiments disclosed herein. DETAILED DESCRIPTION OF THE INVENTION

[0063] The embodiments herein, as well as their various features and advantageous details, will be more fully described with reference to the non-limiting embodiments shown in the accompanying drawings and described in detail in the following description. Descriptions of well-known components and processing techniques are omitted so as not to unnecessarily obscure the embodiments herein. The examples used herein are merely intended to facilitate understanding of how the embodiments herein can be implemented and to enable those skilled in the art to further implement the embodiments herein. Therefore, the examples should not be interpreted as limiting the scope of the embodiments herein.

[0064] Embodiments herein provide a method for assembling / manufacturing a substrateless hybrid power module assembly. The method includes providing a PCB. The method further includes assembling at least one control circuit component on the PCB. The method further includes attaching at least one SMT power device to the at least one control circuit component. The method also includes performing at least one device interconnection on at least one die using at least one of wire bonding and copper strapping. The method further includes attaching at least one bus bar to a bottom of the PCB. The method further includes attaching at least one insulating layer below the at least one bus bar attached to the bottom of the PCB. The method further includes attaching a heat dissipation layer below the at least one insulating layer. The method further includes attaching one of a plastic molding case and a potting compound over the heat dissipation layer.

[0065] This method can be used in high-power electronic systems to improve the effectiveness, reliability, and productivity of power electronics systems assembled using discrete power devices and / or bare die. This method can be used to make custom high-current power modules (PMs) and intelligent power modules (IPMs) without using expensive ceramic, metal cores, IMS, or other such substrates. This method can be used to eliminate complex processes, expensive, and long-lead-time materials, enabling high-density integration while improving the thermal performance of the system.

[0066] The method can be used to seamlessly combine control and power circuitry, enabling advanced integration of electronic systems while improving system power density, thermal performance, and reliability. The method can be used to fabricate substrateless hybrid power module assemblies using traditional SMT mounting techniques, solderable interconnect methods such as aluminum wire bonding and copper strap bonding, or any interconnect method. These features enable the proposed method to enable a wide range of products and applications. It also maximizes the utilization of power device capabilities and reduces the cost of power supplies. The method allows for flexible design and rapid time-to-market, achieving optimized solution costs.

[0067] The method can be used to fabricate systems for electric vehicles, traction inverters, chargers, DC-DC converters, industrial drives, solar inverters, up / down inverters, and for any high power conversion application.

[0068] In the proposed method, the method can be used to assemble high-power electronic modules using FR4 PCBs, or other suitable grade PCBs, and highly thermally conductive materials such as aluminum, copper, or ceramic substrate plates or any other suitable material. The poor thermal performance of PCBs is overcome by cutting windows in the PCB below the busbars housing the power devices (e.g., SMT or bare die) and placing highly thermally conductive materials within the windows below the busbars. These highly thermally conductive materials provide an efficient thermal path from the power devices to the heat sink and thus to the ambient. The overall structure thereby improves the thermal path to the ambient and maximizes the performance of the power devices (e.g., MOSFETs, IGBTs, SiC devices, GaN devices, diodes, etc.) used in the substrateless hybrid power module assembly. A suitable insulating layer with high conductivity (TIM—thermal interface material) is inserted between the conductors housing the power devices and the highly thermally conductive material placed in the PCB window to provide the necessary electrical insulation between the power devices and the heat dissipation layer.

[0069] This method can be used to eliminate the need for expensive ceramic substrates for building high-power, high-current electronic modules. Also, the FR4 PCB used to house the conductors for mounting power devices can be used to integrate control circuit blocks such as microcontrollers, power supplies, and gate drivers. This method therefore makes it easier to customize products and maximize the utilization of production tools and systems. It also eliminates the need for multiple interconnect systems between the power devices and the control circuitry.

[0070] In the proposed method, copper or any other such highly conductive busbars / pads of sufficient cross section are used to mount the power devices (e.g., SMT or bare die) and to route the circuit paths to reduce electrical resistance and therefore power loss. These thick metal busbars / pads used to mount the power devices (e.g., SMT and / or bare die) also improve the module's thermal performance and system reliability. By providing high thermal capacity, the busbars / pads help reduce the peak junction temperatures of the power devices during transient operating conditions. Reduced peak junction temperatures are known to improve the reliability and lifetime of substrateless hybrid power module assemblies. Thick busbars / pads can also be used to form interconnect terminals. These terminals also function as heat pipes, helping to dissipate heat, thereby further reducing device temperatures.

[0071] This combination of PCB and highly thermally conductive plate inserted into the PCB cutout is housed in a plastic case to provide mechanical stability and protection from moisture and conductive dust. Insert-molded interconnect elements such as input / output terminals, control connectors, and sensor elements are incorporated into the module system assembly. To improve the thermal performance of the electronic system, cast aluminum or similar heat dissipation elements are attached to the plastic case / power module assembly.

[0072] The processes and concepts described herein allow the entire assembled module to meet the humidity and temperature cycling needs of the application. The method proposes to build power modules (PMs) and intelligent power modules (IPMs) without the use of expensive and complex ceramic and similar substrate materials.

[0073] Furthermore, the proposed method allows a high degree of integration and flexibility to configure custom functions without major design changes, which allows modular functions to be reconfigured without major changes to the tooling and production process, improving productivity and reducing waste.

[0074] This method also aims to reduce import dependency and time-to-market for complex power electronics systems. This method of assembling flexible power assemblies allows end users to select gate drivers and related components to meet their cost / performance needs. End users can select gate drivers from the supplier of their choice with multiple supply chain options. End users can also use existing, tested and tried-and-tested gate driver blocks in their own products. The modular assembly can house microcontrollers, sensors, and other control components, thus reducing the footprint and also providing original equipment manufacturers (OEMs) with short assembly cycles, high throughput, and protection against design piracy.

[0075] The proposed module structure provides a low thermal resistance path from the device junction to the ambient. This improves device capacity utilization and therefore reduces the number of power devices connected in parallel to supply the current required by the system. This method can be used to reduce complexity and errors when using power devices in high-current systems. The resulting module assembly eliminates mismatches in systems built with discrete power devices, thus improving system reliability. This method can be used to enable end users to create custom configurations and optimize system design and cost. The module assembly can be adapted to different circuit and system topologies. This method aims to provide end users with flexibility and an alternative to expensive PMs and IPMs built using ceramic substrates.

[0076] In the proposed method, a PCB with two or more layers forms a structural element that provides mechanical and dimensional stability to the busbars on which the devices are mounted. The same PCB can be used to house the control circuitry, gate driver circuitry, and other circuit elements that make up the system. This saves expensive and space-consuming interconnections between the control and power elements of the system.

[0077] In the proposed method, modules with PCB inserted lead frames are used, eliminating the substrate and increasing current ratings. The proposed method does not rely on PCB traces to carry the current. Bus bars housing the devices carry the current. Thick bus bars (>2500 μm) can be used in the assembly. This reduces the internal resistance of the module and power losses within the assembly. Thick bus bars under the devices increase the thermal mass, resulting in higher peak junction temperatures during transient conditions. Lower peak junction temperatures improve module reliability and lifetime.

[0078] The method can also be used with SMT devices, bare die with wedge bonding, ball bonding with copper or aluminum wire, ribbon bonding with aluminum or copper ribbon, and soldered interconnects. The method can be used to reduce the number of thermal interface layers between the device that dissipates power and the surroundings that absorb the dissipated power. Reducing the number of interfaces reduces thermal resistance and therefore reduces the temperature rise of the device. Reducing the temperature rise improves the reliability and lifespan of the module. Thermal interface material (TIM) properties can be matched to the system's voltage rating and the insulation level required by the system. By selecting the appropriate insulation and molding materials, the module's voltage rating can be increased to 1200V or more.

[0079] The bus bars used to house the devices can be used to form the power terminals, which reduces the number of elements in the system, space, and cost, and the method reduces the internal resistance and inductance of the system.

[0080] Through interconnects, the cables connecting the module terminals (busbars housing the devices) to external elements (battery / source and load) also act as heat pipes, carrying some of the power dissipated by the devices away from the module, thus reducing the device's temperature rise. Lower temperature rise improves module reliability and lifespan.

[0081] Referring now to the drawings, and more particularly to Figures 8-48, wherein like reference characters indicate corresponding features consistently throughout the views, embodiments are shown.

[0082] FIG. 8 is an exemplary diagram (800) illustrating a substrateless hybrid power module (e.g., a substrateless hybrid power module assembly, etc.) with SMT power devices according to embodiments disclosed herein. As shown in FIG. 8, a top bus bar (1304) houses power devices (1306) (e.g., individual devices, dies, chips, etc.). A PCB (1302) has windows cut out below the bus bar that house the power devices (1306). Additionally, a bottom bus bar with embossed inserts (1310) is inserted into the PCB window to provide a direct thermal path to the heat sink. Additionally, a thermal interface material (e.g., electrical insulation) is added between the bottom bus bar (1310) and the heat sink. An exemplary schematic circuit diagram (900) of a substrateless hybrid power module with parallel-connected power devices is shown in FIG. 9.

[0083] Figure 10 is an example diagram (1000) showing a substrateless hybrid power module with chip and wire bonding. Figure 11 is an example diagram (1100) showing a substrateless hybrid power module with copper strap interconnects using solderable front metal (SFM) die. Figure 12 is an example diagram (1200) showing a PCB window of a substrateless hybrid power module cut out under the power devices.

[0084] FIG. 13 shows a cross-sectional view (1300) of a substrateless hybrid power module according to an embodiment disclosed herein. As shown in FIG. 13, there is a PCB (1302), a top copper bus bar (1304) (e.g., control circuit components), and the top copper bus bar is assembled on a portion of the PCB (1302). Power devices (1306) (e.g., SMT, die, etc.) are attached onto the top copper bus bar (1304) using a solder layer. Device interconnection is performed on the die using wire bonding or copper straps. A bottom copper bus bar (1310) with embossed PCB inserts is attached to the bottom of the PCB (1302) through a window cut therein. An insulating layer (1312) is attached below the bottom copper bus bar (1310) attached to the bottom of the PCB (1302). A heat dissipation layer (1314) is attached under the insulating layer (1312). A plastic molded case (2702) and potting compound are attached over the heat dissipation layer (1314).

[0085] FIG. 14 is an exemplary diagram (1400) illustrating a substrateless hybrid power module with an integrated embossed heat sink according to an embodiment disclosed herein. As shown in FIG. 14, the bottom copper bus bar (1310) is omitted. Instead, a heat sink with appropriate embossed ridges is used, which contacts the top copper bus bar (1304) through appropriately prepared cutout windows in the PCB. A thermal interface material (e.g., electrical insulation) is added between the top copper bus bar (1304) and the embossed heat sink ridges. The heat sink is molded into the plastic and becomes part of the module. This method eliminates multiple thermal interfaces, thus resulting in better utilization of silicon devices. This method also reduces the assembly cost of the substrateless hybrid power module.

[0086] Figure 15 shows a cross-sectional view (1500) of a hybrid power module with a substrate according to an embodiment disclosed herein. There is a PCB (1302), control circuit components (e.g., top copper bus bar (1304)), and the control circuit components are fabricated on a portion of the PCB (1302). Power devices are attached to the control circuit components. Device interconnections are performed on the die using SMT, wire bonding, and copper straps. The bottom copper bus bar / lead frame (150 4 ) is a substrate (e.g., ceramic, metal core, IMS, etc.) (150 2 ) and connected within the PCB (1302). In this method, a ceramic substrate can be used. The ceramic substrate used in this method has a significantly lower size and volume, improving heat dissipation within the assembly and extending the operating voltage range. The heat dissipation layer (1314) is attached to the substrate (150). 2 A suitable thermal interface material (TIM) (1312) is attached to the bottom of the bottom substrate (150). 2 ) and the heat dissipation layer (1314), and a plastic molded case (2702) and potting compound are attached onto the heat dissipation layer (1314).

[0087] FIG. 16 is an exemplary diagram (1600) showing a substrateless hybrid power module with SMT power devices according to embodiments disclosed herein. Copper bus bars house the power devices (e.g., individual devices, dies, chips, etc.). The bus bars have inserts on the underside to pass through windows cut out in the PCB (1302). The PCB (1302) has windows cut out below the bus bars that house the power devices. The bus bars are inserted into the PCB windows to provide a direct thermal path to the heat dissipation layer. Thermal interface material (1312) (e.g., electrical insulation) is added between the bottom bus bars and the heat dissipation layer.

[0088] Figure 17 is another exemplary diagram (1700) showing a substrateless hybrid power module with chip and wire bonding. Figure 18 is another exemplary diagram (1800) showing a substrateless hybrid power module with copper strap interconnects using SFM die. The embodiments described in Figures 16-18 use the assembly method as described in the paragraphs above.

[0089] Figure 19 is an example diagram (1900) showing a PCB window of a substrateless hybrid power module cut out under the power devices. Figure 20 shows a cross-sectional view (2000) of a substrateless hybrid power module having SMT, chip and wire bond, and copper strap interconnects according to embodiments disclosed herein. Figure 20 also shows a top bus bar (1310) with an embossed PCB insert on its underside. Figure 21 shows a cross-sectional view (2100) of a substrateless hybrid power module.

[0090] FIG. 22 is an example diagram (2200) showing a substrateless hybrid power module with SMT power devices according to embodiments disclosed herein. Bus bars house the power devices, and the bus bars have inserts on their top sides to pass through windows cut out in the PCB (1302). The PCB (1302) has windows cut out so that the bus bars are on top of the surface of the PCB (1302). The devices are attached to the top side of the bus bars. The bus bars have a direct thermal path to the heat sink. Thermal interface material (e.g., electrical insulation) is added between the bottom bus bar and the heat sink.

[0091] Figure 23 is an exemplary diagram (2300) showing a substrateless hybrid power module with chips and wire bonds. Figure 24 is another exemplary diagram (2400) showing a substrateless hybrid power module with copper strap interconnects using SFM die. The embodiments described in Figures 22-24 use the assembly method as described in the paragraphs above.

[0092] FIG. 25 is an example diagram (2500) showing a PCB of a substrateless hybrid power module with cutouts.

[0093] Figure 26 shows a cross-sectional view (2600) of a PCB insert for a substrateless hybrid power module embossed on the upper copper busbar. Figure 27 shows a cross-sectional view (2700) of a substrateless hybrid power module. Figure 28 is an exemplary diagram (2800) showing a substrateless hybrid power module with a molded plastic case.

[0094] Figures 29-43 illustrate example implementations of different circuit topologies using embodiments disclosed herein. Figure 29 is a schematic circuit diagram (2900) of a three-phase inverter power supply circuit according to embodiments disclosed herein.

[0095] FIG. 30 is an exemplary diagram (3000) illustrating the concept of a three-phase inverter power module having SMT devices and separately mounted power terminals according to embodiments as disclosed herein.

[0096] FIG. 31 is an exemplary diagram (3100) illustrating a three-phase inverter power module having SMT devices and integrated power terminals according to embodiments disclosed herein.

[0097] 32 is an example diagram 3200 of a three-phase inverter power module with chips and wires and separately attached power terminals according to embodiments disclosed herein. Other embodiments using copper strap interconnects or other methods are possible.

[0098] 33 is an example diagram (3300) of a three-phase inverter power module with bare die or chip and wire bonding and integrated power terminals according to embodiments disclosed herein. Other embodiments using copper strap interconnects or other methods are possible.

[0099] Figure 34 is a circuit diagram (3400) of a full-bridge topology used in various system block implementations.

[0100] 35 is an example diagram 3500 showing a full-bridge topology with bare die / chip and wire bonds according to embodiments disclosed herein. Other embodiments with chip / die, SMT devices using copper strap interconnects can be implemented using the assembly methods disclosed herein.

[0101] Figure 36 is a circuit diagram (3600) of a half-bridge topology used in various system block implementations.

[0102] 37 is an example diagram 3700 showing a full-bridge topology with bare die / chip and wire bonds according to embodiments disclosed herein. Other embodiments with chip / die, SMT devices using copper strap interconnects can be implemented using the assembly methods disclosed herein.

[0103] 38 is an exemplary diagram 3800 showing a bidirectional switch with bare die / chip and wirebonds according to embodiments disclosed herein. Other embodiments exist.

[0104] Chip / die, SMT devices using copper strap interconnects can be implemented using the assembly methods disclosed herein.

[0105] Figure 39 is a circuit diagram (3900) of a bidirectional switch topology used in various system block implementations.

[0106] Figure 40 is a front view (4000) of a lead frame assembly for a bidirectional switch according to embodiments disclosed herein. Figure 41 is a side view (4100) of an example lead frame assembly with details according to embodiments disclosed herein.

[0107] FIG. 42 is an exemplary diagram (4200) illustrating a lead frame assembly on an FR4 PCB according to an embodiment disclosed herein.

[0108] FIG. 43 is a cross-sectional view of a detail of a bi-directional switch assembly stack (4300) according to an embodiment disclosed herein.

[0109] 44-48 are flow charts illustrating methods (4400-4800) for assembling / manufacturing high power electronic modules using FR4 or suitable grade PCBs according to embodiments disclosed herein.

[0110] As shown in FIG. 44, at 4402, the method includes providing appropriate cutouts in a bare PCB. To provide the appropriate cutouts, windows are marked via an electrical / mechanical computer-aided design (CAD) tool for the exact location and size of the windows. The windows can be cut out using a milling operation during PCB fabrication. At 4404, the method includes assembling a top busbar control circuit component on the bare PCB. At 4406, the method includes placing a device (e.g., SMT, bare die, chip, etc.) on the top busbar control circuit component. At 4408, the method includes performing device interconnection using SMT, wire bonding, and / or copper strapping. At 4410, the method includes attaching a bottom busbar to the bare PCB. At 4412, the method includes attaching a TIM / insulator below the bottom busbar. At 4414, the method includes attaching a heat sink or heat spreader below the TIM or insulator. At 4416, the method includes attaching a plastic case and / or potting compound or applying a plastic molding onto the heat sink or heat spreader.

[0111] As shown in FIG. 45, at 4502, the method includes providing appropriate cutouts in a bare PCB. At 4504, the method includes assembling top busbar control circuit components on the bare PCB. At 4506, the method includes attaching devices (e.g., SMT, bare die, chips, etc.). At 4508, the method includes making device interconnections using SMT, wire bonding, and copper straps. At 4510, the method includes attaching or applying a TIM or insulator to the embossed heat sink. At 4512, the method includes attaching the embossed heat sink to the PCB. At 4514, the method includes applying a plastic molding or attaching a plastic case and potting compound.

[0112] As shown in FIG. 46, at 4602, the method includes providing an appropriate cutout in a bare PCB. At 4604, the method includes assembling top busbar control circuit components on the PCB. At 4606, the method includes attaching a device (e.g., SMT, bare die, chip, etc.). At 4608, the method includes making device interconnections using SMT / wire bonding / copper strapping. At 4610, the method includes attaching a substrate with a copper leadframe within the PCB cutout. In one embodiment, the copper leadframe includes either milled / machined copper busbars to form embossed inserts. They can also be die-cast / formed to the required specifications. The copper busbars / leadframes can be attached to the FR4 PCB by a soldering process or mechanical attachment using clips, screws, or other suitable means for fastening to the FR4 PCB. At 4612, the method includes attaching a heat sink to the bottom of the substrate. At 4614, the method includes applying a plastic molding or attaching a plastic case and potting compound.

[0113] As shown in FIG. 47, at 4702, the method includes providing appropriate cutouts in a PCB. At 4704, the method includes assembling a bus bar with an embossed PCB insert on the underside. At 4706, the method includes placing a device (e.g., SMT, bare die, chip, etc.) on the top side of the bus bar. At 4708, the method includes performing device interconnection using SMT, wire bonding, or copper strap. At 4710, the method includes attaching a TIM / insulator to the underside of the bottom of the bus bar. At 4712, the method includes attaching a heat sink or heat spreader below the TIM or insulator. At 4714, the method includes applying plastic molding or attaching a plastic case or potting compound over the heat sink or heat spreader.

[0114] As shown in FIG. 48, at 4802, the method includes providing appropriate cutouts in a bare PCB. At 4804, the method includes assembling a bus bar with a PCB insert embossed on the top side of the bus bar. At 4806, the method includes placing a device (e.g., SMT, bare die, chip, etc.) on the top side of the bus bar. At 4808, the method includes performing device interconnection using SMT, wire bonding, or copper strap. At 4810, the method includes attaching a TIM / insulator under the bus bar. At 4812, the method includes attaching a heat sink or heat spreader under the TIM or insulator. At 4814, the method includes applying plastic molding or attaching a plastic case or potting compound over the heat sink or heat spreader.

[0115] This method can be used in high-power electronic systems to improve the effectiveness, reliability, and productivity of power electronics systems assembled using discrete power devices and / or bare die. This method can be used to create custom high-current PMs and IPMs without the use of expensive ceramic substrates. This method can be used to eliminate complex processes, expensive, and long-lead-time materials, enabling high-density integration while improving the thermal performance of the system.

[0116] The method can be used to seamlessly combine control and power circuitry, enabling advanced integration of electronic systems while improving power density, thermal performance, and system reliability. The method can be used to fabricate circuits with traditional SMT mounting techniques, solderable interconnect methods such as aluminum wire bonding and copper strap bonding, or any interconnect method. These features enable the proposed method to enable a wide range of products and applications. It also maximizes the utilization of power device capabilities and reduces the cost of power supplies. The method allows for flexible design and rapid time-to-market, achieving an optimized cost of the solution.

[0117] In one embodiment, the method can be used to assemble high-power electronic modules using an FR4 PCB, or a suitable grade PCB, and a high thermal conductivity material, such as an aluminum, copper, or ceramic substrate plate or any other suitable material. The PCB's poor thermal performance is overcome by cutting windows in the PCB below the busbars housing the power devices (SMT or bare die) and placing a high thermal conductivity material within the windows below the busbars. These high thermal conductivity materials provide an efficient thermal path from the power devices to the heat sink and thus to the ambient. The overall structure thereby improves the thermal path to the ambient and maximizes the performance of the power devices (MOSFETs, IGBTs, SiC devices, GaN devices, diodes, etc.) used in the system. An appropriate thermal interface material is inserted between the conductors housing the power devices and the high thermal conductivity material located in the PCB window to provide the necessary electrical isolation between the power devices and the heat dissipation system.

[0118] This method can be used to eliminate the need for expensive ceramic substrates for building high-power, high-current electronic modules. Also, the FR4 PCB used to house the conductors for mounting power devices can be used to integrate control circuit blocks such as microcontrollers, power supplies, and gate drivers. This method therefore makes it easier to customize products and maximize the utilization of production tools and systems. It also eliminates the need for multiple interconnect systems between the power devices and the control circuitry.

[0119] In the proposed method, copper or any other such highly conductive busbars / pads of sufficient cross section are used to mount the power devices (SMT or bare die) and to route the circuit paths to reduce electrical resistance and therefore power loss. These thick metal busbars / pads used to mount the power devices (SMT and / or bare die) also improve the thermal performance of the module and system reliability. By providing high thermal capacity, the busbars / pads help reduce the peak junction temperature of the power devices during transient operating conditions. Reduced peak junction temperatures are known to improve system reliability and lifetime. Thick busbars / pads can also be used to form interconnect terminals. These terminals also function as heat pipes, helping to dissipate heat, thereby further reducing device temperatures.

[0120] This combination of PCB and highly thermally conductive plate inserted into the PCB cutout is then housed in a plastic case to provide mechanical stability and protection from moisture and conductive dust. Insert-molded interconnect elements such as input / output terminals, control connectors, and sensor elements are incorporated into the module system assembly. To improve the thermal performance of the electronic system, cast aluminum or similar heat dissipation elements can be attached to the plastic case / power module assembly.

[0121] The processes and concepts described herein allow the entire assembled module to meet the humidity and temperature cycling needs of the application. The method proposes to build power modules (PMs) and intelligent power modules (IPMs) without the use of expensive and complex ceramic and similar substrate materials.

[0122] Furthermore, the proposed method allows a high degree of integration and flexibility to configure custom functions without major design changes, which allows modular functions to be reconfigured without major changes to the tooling and production process, improving productivity and reducing waste.

[0123] In the proposed method, a PCB with two or more layers forms the structural element that provides mechanical and dimensional stability to the busbars on which the devices are mounted. The same PCB can be used to house the control circuitry, gate driver circuitry, and other circuit elements that make up the system. This saves expensive and space-consuming interconnections between the system's control and power elements.

[0124] The proposed method uses a module with an insert-molded lead frame, eliminating the substrate and increasing the current rating. The proposed method does not rely on PCB traces to carry the current. The busbars housing the devices carry the current. Thick busbars (>2500 μm) can be used in the assembly. This reduces the internal resistance of the module and power losses within the assembly. The thick busbars underneath the devices increase the thermal mass, resulting in higher peak junction temperatures during transient conditions. Lower peak junction temperatures improve module reliability and lifetime.

[0125] The method can also be used with wedge bonding, ball bonding with copper or aluminum wire, rebonding with aluminum or copper ribbon, and soldered interconnects.

[0126] This method can be used to reduce the number of thermal interface layers between the device that dissipates power and the surroundings that absorb the dissipated power. Reducing the number of interfaces reduces the thermal resistance and therefore the temperature rise of the device. Reducing the temperature rise improves the reliability and lifespan of the module. Thermal interface material (TIM) properties can be matched to the system voltage rating and the insulation level required by the system. By selecting appropriate insulation and molding materials, the module voltage rating can be increased to 1200V or more. Bus bars used to house the device can be used to form the power terminals. This reduces the number of elements, space, and cost of the system. This method also reduces the internal resistance and inductance of the system.

[0127] Through interconnects, the cables connecting the module terminals (busbars housing the devices) to external elements (battery / source and load) also act as heat pipes, carrying some of the power dissipated by the devices away from the module, thus reducing the device's temperature rise. Lower temperature rise improves module reliability and lifespan.

[0128] The method also aims to reduce import dependency and reduce time to market for complex power electronic systems.

[0129] Embodiments herein allow end users to select gate drivers and associated components to meet their cost / performance needs. End users can select gate drivers from the supplier of their choice, with numerous supply chain options. End users can also use existing gate driver blocks that have been tested and tried in their own products. The module assembly can house microcontrollers, sensors, and other control components, thus reducing footprint and providing OEMs with protection against design piracy.

[0130] The proposed module structure provides a low thermal resistance path from the device junction to ambient, which reduces the number of power devices connected in parallel to supply the current required by the system. Additionally, embodiments herein aim to reduce the complexity and errors involved in using power devices in high-current systems. As a result, the module assemblies described herein eliminate mismatches in systems built with discrete power devices, thus improving system reliability. Additionally, embodiments herein allow end users to create custom configurations, ratings, and optimize system design and cost. The module assembly can be adapted to different circuit and system topologies. This approach provides end users with flexibility and an alternative to expensive PMs and IPMs built using ceramic substrates.

[0131] The assembly process is flexible and not limited to the examples shown in this application. Other topologies can be assembled using the proposed method. Silicon MosFETs, IGBTs, diodes, SiC MosFETs, SiC diodes, and GaN devices can be assembled using the proposed method.

[0132] Power devices with voltage ratings from 30V to 1700V or more can be assembled using the proposed method with appropriate insulation techniques. Power devices with current ratings from 10A to 1000A or more can be assembled using the proposed method with appropriate busbar and interconnection techniques. Both high-power devices and low-power control devices can be assembled using the proposed method in the same package to improve performance and reduce volume. The method also reduces interconnects within the system, improving reliability.

[0133] The various actions, acts, blocks, steps, etc. in the methods (4400-4800) may be performed in the order presented, in a different order, or simultaneously. Furthermore, in some embodiments, some of the actions, acts, blocks, steps, etc. may be omitted, added, modified, skipped, etc., without departing from the scope of the embodiments herein.

[0134] The foregoing description of specific embodiments fully reveals the general nature of the embodiments herein, such that, by applying current knowledge, such specific embodiments can be readily modified and / or adapted for various uses without departing from the general concept. Accordingly, it is intended and should be understood that such adaptations and modifications are to be understood within the meaning and range of equivalents of the disclosed embodiments. It should be understood that the phraseology or terminology used herein is for the purpose of description and not of limitation. Thus, while the embodiments herein have been described in terms of embodiments and examples, those skilled in the art will recognize that the embodiments and examples disclosed herein can be practiced with modifications within the spirit and scope of the embodiments described herein.

Claims

1. A method (4400-4800) for manufacturing a substrateless hybrid power module assembly, comprising: Assembling (4404-4804) at least one control circuit component on a printed circuit board (PCB) (1302); Mounting at least one power device on the at least one control circuit component (4406-4806); performing at least one device interconnection on the at least one power device using at least one of surface mount technology (SMT), wire bonding, ribbon bonding, and copper strapping (4408-4808); Attaching (4610) a substrate (1502) having a copper lead frame (1504) to a cutout associated with the PCB (1302); attaching (4612) a heat dissipation layer (1314) to the bottom of the substrate (1502); attaching (4614) one of a plastic molding case (2702) and a potting compound onto the heat dissipation layer (1314); A method comprising:

2. The method comprises: Attaching (4410) at least one bus bar to the bottom of the PCB (1302); attaching (4412) at least one insulating layer (1312) beneath the at least one bus bar attached to the bottom of the PCB (1302); attaching (4414) a heat dissipation layer (1314) beneath the at least one insulating layer (1312); and attaching (4416) one of a plastic molded case (2702) and a potting compound over the heat dissipation layer (1314).

3. The method comprises: attaching (4510) at least one insulating layer (1312) to the embossed heat dissipation layer (1314); attaching (4512) the embossed heat dissipation layer (1314) to a cutout associated with the PCB (1302); and attaching (4514) one of a plastic molded case (2702) and a potting compound over the heat dissipation layer (1314).

4. The method of claim 1 , wherein the substrate (1502) comprises at least one of a ceramic substrate, a metal core PCB, and an IMS substrate.

5. The method of claim 1 , wherein the at least one control circuit component comprises one of a top busbar control circuit component (1304) and a bottom busbar control circuit component (1310).

6. A method (4400-4800) for manufacturing a substrateless hybrid power module assembly, the method comprising: Assembling (4404-4804) at least one control circuit component on a printed circuit board (PCB) (1302); Mounting at least one power device on the at least one control circuit component (4406-4806); performing at least one device interconnection on the at least one power device using at least one of surface mount technology (SMT), wire bonding, ribbon bonding, and copper strapping (4408-4808); Including, The method, wherein the top busbar control circuit component (1304) comprises at least one embossed PCB insert and the bottom busbar control circuit component (1310) comprises at least one embossed PCB insert.

7. 10. The method of claim 1, wherein the at least one power device comprises an SMT, a bare die, a chip, a discrete device, a metal-oxide-semiconductor field-effect transistor (MOSFET), an insulated-gate bipolar transistor (IGBT), a diode, and a gallium nitride (GaN) device.

8. 4. The method of claim 2 or 3, wherein the at least one insulating layer (1312) comprises at least one of a TIM and an insulator, and the heat dissipation layer (1314) comprises a heat sink and a heat spreader.

9. 2. The method of claim 1, wherein the PCB (1302) includes a window cut out below the busbar, the window being marked via a computer-aided design (CAD) tool for a precise location and size of the window cutout, and the window being cut out using a milling operation during manufacturing of the PCB.

10. 10. The method of claim 1, wherein the copper lead frame (1504) comprises at least one of a milled copper bus bar and a machined copper bus bar to form an embossed insert, the copper lead frame (1504) is die-cast or formed to a required specification, and the at least one of the copper bus bar and the lead frame is attached to the PCB via a soldering process or a mechanical fixture using a connection unit to secure the lead frame to the PCB, the connection unit comprising clips and screws.

11. a printed circuit board (PCB) (1302); At least one control circuit component assembled on said PCB (1302); at least one power device mounted on the at least one control circuit component; at least one device interconnection performed on at least one surface mount technology (SMT) and die using at least one of wire bonding, ribbon bonding, and copper strapping; a substrate (1502) mounted with a copper lead frame (1504) within the PCB (1302) cut out from the bottom; a heat dissipation layer (1314) attached to the bottom of the substrate (1502); one of a plastic molding case (2702) and a potting compound mounted on the heat dissipation layer (1314); 1. A substrate-less hybrid power module assembly comprising:

12. At least one bus bar attached to the bottom of the PCB (1302); at least one insulating layer (1312) attached below the at least one bus bar attached to the bottom of the PCB (1302); a heat dissipation layer (1314) attached below said at least one insulating layer (1312); one of a plastic molding case (2702) and a potting compound mounted on the heat dissipation layer (1314); 12. The substrateless hybrid power module assembly of claim 11, comprising:

13. at least one insulating layer (1312) attached to an embossed heat dissipation layer (1314); the embossed heat dissipation layer (1314) mounted within the PCB (1302); one of a plastic molding case (2702) and a potting compound mounted on the heat dissipation layer (1314); 12. The substrateless hybrid power module assembly of claim 11, comprising:

14. 12. The substrateless hybrid power module assembly of claim 11, wherein the substrate (1502) comprises at least one of a ceramic substrate, a metal core PCB, and an IMS substrate useful for extending a system's voltage rating.

15. The substrateless hybrid power module assembly of claim 11 , wherein the at least one control circuit component comprises one of a top busbar control circuit component (1304) and a bottom busbar control circuit component (1310).

16. A substrateless hybrid power module assembly, comprising: a printed circuit board (PCB) (1302); At least one control circuit component assembled on said PCB (1302); at least one power device mounted on the at least one control circuit component; At least one device interconnection performed on at least one surface mount technology (SMT) and die using at least one of wire bonding, ribbon bonding, and copper strapping; Equipped with wherein said at least one control circuit component comprises one of a top busbar control circuit component (1304) and a bottom busbar control circuit component (1310); the top busbar control circuit component (1304) comprises at least one embossed PCB insert, and the bottom busbar control circuit component (1310) comprises at least one embossed PCB insert; The substrate-less hybrid power module assembly.

17. 12. The substrateless hybrid power module assembly of claim 11, wherein the at least one power device comprises an SMT, a bare die, a chip, a discrete device, a metal oxide semiconductor field effect transistor (MOSFET), an insulated gate bipolar transistor (IGBT), a diode, and a gallium nitride (GaN) device.

18. 14. The substrateless hybrid power module assembly of claim 12 or 13, wherein the at least one insulating layer (1312) comprises at least one of a TIM and an insulator, and the heat dissipation layer (1314) comprises a heat sink and a heat spreader.

19. 12. The substrateless hybrid power module assembly of claim 11, wherein the PCB (1302) comprises windows cut out below bus bars, the windows being marked via a computer-aided design (CAD) tool for precise location and size of the window cutout, and the windows being cut out using a milling operation during fabrication of the PCB.

20. 12. The substrateless hybrid power module assembly of claim 11, wherein the copper lead frame (1504) comprises at least one of a milled copper bus bar and a machined copper bus bar to form embossed inserts, the copper lead frame (1504) is die cast or formed to required specifications, and the at least one of the copper bus bar and the lead frame is attached to the PCB via a soldering process or mechanical fixtures using a connection unit to secure the lead frame to the PCB, the connection unit including clips and screws.

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