A capacitor integrated in a printed circuit board

Abstract

The present subject matter relates to a printed circuit board (100) for use in an electric vehicle application. The printed circuit board (PCB) (100) includes a plurality of laminate layers (102) and a capacitor (106) integrated within said plurality of laminate layers (102). These plurality of laminate layers (102) include traces (104) for electric conduction. The capacitor (106) includes at least two conductive plates (108a; 108b) separated by dielectric medium (110). The at least two conductive plates (108a; 108b) are arranged in parallel to the plurality of laminate layers (102). Accordingly, the capacitor (106) is integrated in the PCB (100) therefore permitting a smaller overall footprint of such a PCB 100 in automobile applications.

Description

Title of Invention: A CAPACITOR INTEGRATED IN A PRINTED CIRCUIT BOARDFIELD OF INVENTION

[0001] The present subject matter relates to a capacitor arrangement in a printed circuit board. More specifically, this invention pertains to a capacitor integrated in a printed circuit board, the arrangement of which is particularly useful in on-board chargers for electric vehicles.BACKGROUND

[0002] The rapid growth in vehicle electrification has driven the need for compact, efficient, and reliable onboard charging systems to enable convenient charging of EV battery packs. These onboard chargers often employ resonant converter topologies, such as the LLC resonant converter, which utilize a resonant tank circuit consisting of an inductor and capacitor. Multilayer ceramic capacitors (MLCCs) are commonly used as the resonant capacitor in these circuits due to their small size, high capacitance, and low equivalent series resistance (ESR), and have therefore become a critical component in the design of modem electric vehicles (EVs) and their supporting electronics systems. However, the limited space available within EVs creates a strong demand for even more compact MLCC designs to minimize the overall size and weight of the onboard charger system. Conventional MLCC designs, while offering significant advantages over other capacitor technologies, may not be optimized for the stringent space constraints of EV applications. There is a need for alternate solutions that can further reduce the footprint and height of these components without compromising their electrical performance and reliability.

[0003] Moreover, high AC voltages and currents experienced by MLCCs in resonant tank circuits can lead to significant self-heating within the component, which can degrade its electrical performance and reliability. Conventional MLCC designs may not be adequate to mitigate the self-heating problem in these high-power, high-frequency applications. Moreover, the limited space within EVs necessitates highly compact, components to minimize system size and weight.

[0004] Therefore, there is a need for improved MLCC design that can address the limitations of MLCCs in resonant tank circuits for power electronics. This would allow for the development of more advanced power electronics solutions that can meet the stringent requirements of vehicle electrification.

[0005] The technical problem to be solved is how to provide an alternative to conventional MLCCs (i.e., capacitors) that has is significantly reduced in size and profile while maintaining their suitability for use in high-frequency, high-power resonant tank circuits of onboard EV battery charger. Such an alternative solution that further addresses self-heating limitations of conventional capacitors in resonant tanks. Accordingly, the invention disclosed herein aims to contribute to the advancement of power electronics solutions for vehicle electrification, ultimately leading to more convenient and accessible EV charging infrastructure.SUMMARY OF THE INVENTION

[0001] The present subject matter seeks to solve the above mentioned technical problem in conventional capacitor arrangement in printed circuit boards.

[0002] The present subject matter relates to printed circuit board (PCB) for use in an electric vehicle application, the printed circuit board(PCB) comprising: a plurality of laminate layers comprising traces for electric conduction; and a capacitor integrated within the plurality of laminate layers, the capacitor comprising at least two conductive plates separated by dielectric medium, wherein the at least two conductive plates are arranged in parallel to the plurality of laminate layers. Accordingly, by embedding the capacitor within the PCB, the need for discrete surface mount components is eliminated, allowing for a more compact PCB with a smaller overall footprint. This is particularly effective in automotive application applications. Moreover, embedding the capacitors within the PCB layers can improve heat dissipation compared to surface mount components, enhancing the overall thermal management of the PCB. Therefore, using such type of capacitors in resonant tanks of on-board chargers, for instance, can enhance thermal management of the on-board charger and improve its performance in an electric vehicle application. Moreover, integrating the capacitors directly into the PCB structure provides better mechanical stability and protection from environmental factors, improving the long-term reliability of the electronic system due to its possible exposure to environmental factors in an automobile environment.

[0003] According to an example of the present subject matter, the dielectric medium between the at least two conductive plates is a FR- 4 material having a glass transition temperature (Tg) value more than 150°C.

[0004] According to an example of the present subject matter, the capacitor is a multi-layer ceramic capacitor (MLCC) embedded within the plurality of laminate layers.

[0005] According to an example of the present subject matter, the capacitor is formed by depositing conductive plates and dielectric mediums within the plurality of laminate layers.

[0006] The present subject matter relates also to a method of manufacturing a capacitor within a PCB. According to the present subject matter, the method comprising: forming a plurality of laminate layers from electrically insulating material; depositing a first conductive layer within the plurality of laminate layers; depositing a dielectric medium on the first conductive layer; depositing a second conductive layer on the dielectric medium, forming a capacitor structure within the plurality of laminate layers, wherein the first conductive layer and the second conductive layer are two plates from at least two conductive plates; connecting the first conductive layer to a trace; connecting the second conductive layer to said trace. The capacitor is thereby embedded directly within the plurality of laminate layers. The conductive plates of the capacitor is connected to traces without using via holes. Further, the capacitor is placed very close to the components it is decoupling on the PCB.

[0007] The present subject matter relates also to a system comprising: a printed circuit board (PCB); and a resonant tank circuit comprising: an inductive element integrated within plurality of laminate layers of the PCB and configured to provide inductance; a capacitor integrated within the plurality of laminate layers, the capacitor comprising at least two conductive plates separated by dielectric material, wherein the at least two conductive plates are arranged in parallel to the plurality of laminate layers. The inductive element and the capacitor is embedded within the PCB, thereby enabling increased design flexibility of on-board chargers. This translates to space savings, better thermal management, and enhanced reliability - allcritical factors for modern high-performance electronics, particularly for electric vehicle applications.

[0008] According to an aspect of the present subject matter, the inductive element is selected from the group consisting of an inductor, a choke, and a transformer.

[0009] According to yet another aspect of the present subject matter, the system further comprises a power semiconductor device connected to the resonant tank circuit and configured for soft-switching operation.

[0010] According to yet another aspect of the present subject matter, the power semiconductor device is selected from either gallium nitride (GaN) or silicon carbide (SiC) MOSFET.

[0011] According to an example, either an on board charger, or an inverter, or an rectifier bridge.BRIEF DESCRIPTION OF DRAWINGS

[0012] The features, aspects, and advantages of the present invention will be better understood with regard to the following description and accompanying figures. The description refers to the annexed drawings, wherein:

[0013] FIG. 1 illustrates a capacitor embedded in laminate layers of a substrate, configured in accordance with an example of the present subject matter;

[0014] FIG. 2 illustrates the capacitor in another perspective, configured in accordance the present subject matter;

[0015] FIG. 3 illustrates an inductive element, configured in accordance with an aspect of the present subject matter;

[0016] FIG. 4 illustrates a schematic configuration of a resonant circuit, configured in accordance with an example of the present subject matter; and

[0017] FIG. 5 illustrates a flowchart depicting a method of manufacturing a capacitor within a PCB.

[0018] The figures are not necessarily to scale, and the size of some parts may be exaggerated to more clearly illustrate the example shown. Moreover, the drawings provide examples and / or examples consistent with the description, however, the description is not limited to the examples and / or examples provided in the drawings.BRIEF DESCRIPTION OF DRAWINGS

[0019] In the description that follows, reference is made to accompanying drawings, which form part thereof, and in which is shown by way of illustration specific implementations in which the invention maybe practiced. These implementations are described in sufficient detail to enable that skilling in the art to practice the invention, and it is to be understood that the implementations may be combined, or that other implementations may be utilized, and that structural and logical changes may be made without departing from the scope of the present invention. The following detailed description is, therefore, not to be taken in a limiting sense, and the scope of the present invention is defined by the appended claims and their equivalents.

[0020] FIG. 1 sets forth a cross sectional plan view of an example PCB in which a capacitor is integrated therein, the PCB being particularly for use in electric vehicle applications. Particularly, FIG. 1 shows a printed circuit board (PCB) 100 that includes a plurality of laminate layers 102. These plurality of laminate layers 102 include traces 104 for electric conduction. The PCB 100 further includes acapacitor 106 integrated within the plurality of laminate layers 102. The capacitor 104 includes at least two conductive plates 108a, 108b that are separated from each other by dielectric material 110. The at least two conductive plates 108a, 108b are arranged in parallel to the plurality of laminate layers 102.

[0021] The PCB 100 is a flat panel of non-conductive substrate material that interconnects electronic components using the traces 104, the traces 104 being a pattern of flat conductors laminated onto the PCB 100. The PCB 100 in the example of FIG. 1 is composed of four laminate layers 102. In said example, the capacitor 106 includes four plates 108a, 108b, two being outer plates 108a and the other two being inner plates 108b arranged between the two outer plates 108a. These four plates 108a, 108b lie parallel to the laminate layer 102 and do not traverse said laminate layers 102. Further, the capacitor 106 is provided with dielectric medium 110 between the two inner plates 108b and between the inner plates 108b and the adjacent outer plate 108b. This dielectric material 110 is a non conducting substance, having a permittivity with respect to an electric field. The permittivity of the dielectric material 110 may be selected, along with the physical dimensions of the capacitor 106, to set the capacitor 106 to some particular level of capacitance. In an example, the dielectric material 110 is FR4 that is filled during manufacture. It is preferred that the dielectric material 110 is FR4 having a glass transition temperature (Tg) value of more than 150°C.

[0022] FIG. 2 sets forth another perspective view of the capacitor 106, configured in accordance with the present subject matter. These traces 104 are electrically conductive pathways formed upon two or more laminate layers 102 of the PCB 100. The traces 104 may be provided, for instance, on top 112a and bottom 112b surfaces of the PCB 100, and / or or in laminate layers 102 through the middle of thePCB 100. The traces 104 couple the conductive plates 108a, 108b of the capacitor 106 to other components of the PCB 100, and operate as either input or output termination to pass alternating current. In FIG. 1 , the other component so coupled for conductance of alternating current signals is an integrated circuit C. The inclusion of this integrated circuit C in this example is intended for clarity and should not be seen as a limitation of the invention. Integrated circuits C are likely to frequently utilize capacitors embedded in the PCB 100. However, it should be noted that capacitors106 integrated into the PCB 100 can be coupled to a wide range of electronic components, including resistors, other capacitors, inductors, transistors, and more. Components like the integrated circuit C can be connected to the PCB 100 using various methods, such as through-hole mounting technology, surface mount technology, or any other techniques familiar to those skilled in the field.

[0023] The PCB 100 features traces 104 that are aligned horizontally, running parallel to the orientation of the conductive plates 108a, 108b embedded within the laminate layers 102. These horizontal traces 200 may extend from embedded components, such as the capacitor 106 or the integrated circuit C, facilitating direct electrical connections within the PCB 100 structure. Perpendicular to these horizontal traces, are vertical traces 202 positioned to traverse the laminate layers 102. This vertical alignment of the vertical traces 202 allows for effective interconnection between different layers of the PCB 100, enabling signals to be routed vertically through the laminate layers 102. The vertical traces 202 connect embedded components to other laminate layers 102 of the PCB 100, enhancing overall design flexibility. In some examples, where the signal reach a vertical trace 202, it can transition to another horizontal trace 200 that connects to components, such as the integrated circuit C, mounted on either the top 112a or bottom 112bsurface of the PCB 100. The application of horizontal traces 200 and vertical traces 202 facilitate seamless communication between the capacitor 106 and surface-mounted devices, such as resistors, additional capacitors, or integrated circuits.

[0024] FIG. 3 presents a perspective view of an inductive element 300 integrated within the laminate layers 102 of the PCB 100. A looped conductor 302 arranged in a series of loops that traverse all four laminate layers 102 of the PCB 100. The looped conductor 302 is designed to enhance the inductance of the element, allowing it to effectively interact with the capacitor 106 via the traces 104. This multilayered configuration not only optimizes the inductive coupling between the capacitor 106 and the inductive element 300 but also contributes to improved electrical performance within the circuit. The visual representation in FIG. 3 underscores the seamless integration of the inductive element 300 within the PCB 100, showcasing how the looping structure of the conductor spans across all four laminate layers 102 of the PCB 100 shown in figures. This design is suitable for applications such as onboard charging systems in automobiles, where the combined functionality of the capacitor 106 and inductive element 300 is for managing energy flow, stabilizing voltage levels, and ensuring efficient power transfer. In an onboard charging application, the capacitor and the inductive element work in tandem to manage energy flow efficiently. The capacitor 106 serves as a local energy reservoir, capable of quickly releasing stored energy to stabilize voltage levels during charging and discharging cycles. This is crucial in electric vehicles (EVs) where rapid changes in power demand can occur. The inductive element 300, on the other hand, provides inductance that helps in filtering and smoothing the electrical signals. It can mitigate voltage spikes and noise that may arise from the switching operations of the charging system. The inductive element’s300 ability to resist changes in current complements the capacitor's 106 function of smoothing voltage fluctuations, creating a more stable power supply. The looped conductor 302 spanning across the four laminate layers 102 of the PCB 100 enhances the inductance of the inductive element 300, optimizing its interaction with the capacitor 106 integrated within the laminate layers 102. This configuration allows for the design of compact and efficient power management systems within the limited space of a PCB 100, which is essential in modem automotive designs that prioritize space and weight savings while maintaining high performance.

[0025] FIG. 4 illustrates a system 400, and more closely a resonant tank circuit 402 within the PCB 100 which consists the plurality of laminate layers 102. This configuration combines the capacitor 106 and the inductive element 300 (an inductor, for instance) in series, both of which are integrated within the PCB 100 structure. The capacitor 106 is integrated into the PCB 100, occupying multiple layers 102, and the capacitance value of the capacitor 106 is designed to work in conjunction with the inductive element 300 to create the resonant tank circuit 400. The inductive element 300, which can be selected from the group consisting of an inductor, a choke, and a transformer, is also embedded within the PCB 100, spanning across the plurality of laminate layers 102.

[0026] According to an aspect, two switches Q1 and Q2, are provided as shown in FIG. 4. These switches Q1 and Q2 are power semiconductor devices configured for soft-switching operation, which enhances the efficiency of the circuit by minimizing switching losses. These switches Q1 and Q2, are typically MOSFETs, that operate alternatively to generate a waveform voltage (for instance, of a square waveform) that excites the resonant tank circuit 402. These power semiconductor devices Q1 and Q2 may be either gallium nitride (GaN)or silicon carbide (SiC) MOSFET. In addition, a rectifier 404 may be provided to convert AC output into a DC voltage. This rectified output can be used for various applications, such as charging batteries. Further, a battery source 404 may also be provided, to serve as the energy storage element. The rectified output from the resonant tank can be used to charge this battery, making the entire arrangement suitable for applications like onboard charging systems in EVs.

[0027] According to the system 400 shown in FIG. 4, the resonant tank circuit 402, formed by the capacitor 106 and the inductive element 300, integrated within the PCB 100, is excited by the square waveform generated by the switches Q1 and Q2. The resonant frequency of the resonant tank circuit 402 is determined by the values of the capacitor 106 and inductive element 300. When driven at this resonant frequency, the resonant tank circuit 402 filters out higher harmonics and produces a clean sinusoidal current. The embedded nature of the resonant components (i.e., the capacitor 106 and the inductive element 300) within the PCB 100 allows for a compact and efficient design, optimizing the energy transfer and conversion processes. The half-bridge configuration enables effective control of the energy flow through the resonant tank circuit 402, ensuring efficient charging of the battery source.

[0028] The system 400 therefore integrates the resonant tank circuit 402 with key components integrated or embedded within the laminate layers 102 of the PCB 100, making it suitable for applications such as on board charging systems in EVs, where high efficiency and compact design are crucial requirements.

[0029] The present subject matter relates also to a method 500 for manufacturing the PCB 100 that incorporates the capacitor 106 configured in accordance with the present subject matter. Accordingto the present subject matter, this method 500 involves several key steps aimed at creating a capacitor 106 within a plurality of laminate layers 102 made from electrically insulating material. The process begins with the formation of these laminate layers 102, which serve as the foundation for the PCB 100. The first step 502 involves forming a plurality of laminate layers 102 from electrically insulating material, which provides the necessary support and insulation for the conductive components. Next in step 504, a first conductive layer of the at least two conductive plates 108a, 108b is deposited within these laminate layers 102, establishing the initial conductive pathway for the capacitor 106. Following this, in step 506, a dielectric medium 110 is deposited on the first conductive layer. This dielectric medium 110 is crucial as it separates the two conductive plates 108a, 108b of the capacitor 106, allowing it to store electrical energy. Subsequently, a second conductive layer of the at least two conductive plates 108a, 108b is deposited on the dielectric medium 110, completing the capacitor 106 structure embedded within the laminate layers 102 of the PCB 100. In the final step 508, the first conductive layer is connected to a trace 104 (configured in a manner previously described) and connecting the second conductive layer to said trace 104. These connections enable the capacitor 106 to interact with other components on the PCB 100, facilitating its functionality within the circuit. This method 500 allows for the efficient integration of capacitor 106 directly into the PCB 100, enhancing the overall performance and compactness of electronic devices. According to an example, the system 400 is either an on board charger, an inverter, or a rectifier bridge, for use in automobile applications.

[0030] Various modifications of the disclosed embodiments, as well as alternate embodiments of the subject matter, will become apparent to persons skilled in the art upon reference to the description of thesubject matter. It is therefore contemplated that such modifications can be made without departing from the scope of the present subject matter is defined.

Claims

We Claim:

1. A printed circuit board (PCB) (100) for use in an electric vehicle application, the printed circuit board (PCB) (100) comprising: a plurality of laminate layers (102) comprising traces (104) for electric conduction; and a capacitor (106) integrated within the plurality of laminate layers (102), the capacitor (106) comprising at least two conductive plates (108a; 108b) separated by dielectric medium (110), wherein the at least two conductive plates (108a; 108b) are arranged in parallel to the plurality of laminate layers (102).

2. The printed circuit board (PCB) (100), as claimed in claim 1 , wherein the dielectric medium (110) between the at least two conductive plates (108a; 108b) is a FR-4 material having a glass transition temperature (Tg) value more than 150°C.

3. The PCB (100), as claimed in claims 1 or 2, wherein the capacitor (106) is a multi-layer ceramic capacitor (MLCC) embedded within the plurality of laminate layers (102).

4. The PCB (100), as claimed in any one of the preceding claims, wherein, the capacitor (106) is formed by depositing conductive plates (108a; 108b) and dielectric mediums (110) within the plurality of laminate layers (102).

5. A method (500) of manufacturing a capacitor (106) within a printed circuit board (PCB) (100), comprising: forming a plurality of laminate layers (102) from electrically insulating material; depositing a first conductive layer within the plurality of laminate layers (102);depositing a dielectric medium (110) on the first conductive layer; depositing a second conductive layer on the dielectric medium (104), forming a capacitor (106) structure within the plurality of laminate layers (102), wherein the first conductive layer and the second conductive layer are two plates from at least two conductive plates (108a; 108b); connecting the first conductive layer to a trace (104); connecting the second conductive layer to said trace (104).

6. A system (400) comprising: a printed circuit board (PCB) (100); and a resonant tank circuit (402) comprising: an inductive element (300) integrated within plurality of laminate layers (102) of the PCB (100) and configured to provide inductance; a capacitor (106) integrated within the plurality of laminate layers (102), the capacitor (106) comprising at least two conductive plates (108a; 108b) separated by dielectric material, wherein the at least two conductive plates (108a; 108b) are arranged in parallel to the plurality of laminate layers.

7. The system (400), as claimed in claim 6, wherein the inductive element is selected from the group consisting of an inductor, a choke, and a transformer.

8. The system (400), as claimed in claims 6 or 7, wherein the system (400) further comprises a power semiconductor device (Q1 ; Q2) connected to the resonant tank circuit (402) and configured for soft-switching operation.

9. The system of claim 8, wherein the power semiconductor device is selected from either gallium nitride (GaN) or silicon carbide (SiC) MOSFET.

10. The system as claimed in any one of claims 6 to 9, being either an on board charger, or an inverter, or a rectifier bridge.

Images