Printed wiring board and electronic control device using same

Abstract

A printed wiring board comprising: a first wiring board 300 on which a plurality of semiconductor devices 40 and connectors 50 are mounted as electronic components; a second wiring board 310 which is fixed to a region on a part of the first wiring board 300 and in which the dielectric constant and the dielectric loss tangent of an insulating layer are low in comparison to those of the first wiring board; high-speed signal wiring 100 which is formed on the second wiring board 310 and transmits some signals transmitted between the plurality of electronic components; and signal wiring 110 which is formed on the first wiring board 300 and transmits other signals transmitted between the plurality of electronic components.

Description

Printed Wiring Board and Electronic Control Device Using the Same

[0001] The present invention relates to a printed wiring board on which electronic components are mounted to form an electronic circuit, and more particularly to a printed wiring board suitable for use in an electronic circuit where high-speed signal transmission is performed, and an electronic control device using the same.

[0002] In recent years, from the viewpoints of reducing traffic accidents caused by automobiles and reducing the burden of driving operations by drivers, development has been promoted toward further sophistication of driving support systems and realization of autonomous driving systems. Electronic control devices used in advanced driving support systems, autonomous driving systems, etc. have an increasing amount of data to be processed as the functions become more sophisticated, and high-speed networks are also being used for sensors such as cameras and radars for taking in external information and for data transfer between other electronic control devices. Under such circumstances, signal transmission on the printed wiring board constituting the electronic control device is also being accelerated, and the demand for a low-loss printed wiring board suitable for high-speed signal transmission is increasing.

[0003] As an example of such a printed wiring board for high frequencies, for example, in Patent Document 1, an insulating layer made of a high-frequency compatible low-loss material is laminated on the outermost surfaces of the front and back of a core board having conductor layers on the front and back surfaces via an adhesive layer, and a printed wiring board in which a conductor layer is formed on the insulating layer made of a high-frequency compatible low-loss material is disclosed.

[0004] Japanese Patent Application Laid-Open No. 2021-27293

[0005] Generally, high-frequency compatible low-loss materials are more expensive than general printed wiring board materials such as FR4. Since the printed wiring board disclosed in Patent Document 1 has an insulating layer of a high-frequency compatible low-loss material laminated on the outermost layer of the core board, it is possible to suppress the cost to some extent by using a general substrate material as the core board. However, when a printed wiring board is formed by laminating substrates of different materials, there is a risk of delamination between layers due to differences in the thermal expansion coefficients of the respective materials, which may reduce the reliability of the printed wiring board and, by extension, the electronic device that employs such a printed wiring board. Such problems become more prominent as the size of the printed wiring board increases.

[0006] In view of the above-mentioned technical problems in the conventional era, the object of the present invention is to provide a highly reliable, low-loss, and inexpensive printed circuit board and an electronic control device using the same.

[0007] In one preferred embodiment, the printed circuit board according to the present invention includes a first circuit board on which a plurality of electronic components are mounted, a second circuit board fixed to a portion of at least one surface of the first circuit board and having a lower dielectric constant and dielectric loss tangent of the insulating layer compared to the first circuit board, a first signal wiring formed on the second circuit board for transmitting some of the signals among a plurality of signals transmitted between the plurality of electronic components, and a second signal wiring formed on the first circuit board for transmitting the other signals among the plurality of signals.

[0008] Furthermore, in another preferred embodiment, the printed circuit board according to the present invention includes: a first circuit board on which a plurality of first electronic components are mounted; a second circuit board having a lower dielectric constant and dielectric loss tangent of the insulating layer compared to the first circuit board, on which a plurality of second electronic components are mounted and fixed to a portion of at least one side of the first circuit board; a first signal wiring formed on the second circuit board for transmitting signals transmitted between the plurality of second electronic components; and a second signal wiring formed on the first circuit board for transmitting signals transmitted between the plurality of first electronic components or between the first electronic components and the second electronic components.

[0009] Furthermore, from another perspective, in one preferred embodiment, the electronic control device according to the present invention is an electronic control device mounted on a vehicle for controlling equipment provided in the vehicle, and comprises a printed circuit board according to any of the above embodiments, a plurality of electronic components mounted on the printed circuit board, a housing for housing the printed circuit board on which the plurality of electronic components are mounted, and a cover that together with the housing forms a space for housing the printed circuit board.

[0010] According to the present invention, it is possible to realize low-loss and inexpensive printed circuit boards, and to provide high-performance and inexpensive electronic control devices. Other problems solved by the present invention and novel features will become apparent from the description and drawings herein.

[0011] Figure 4 is a schematic exploded perspective view showing the configuration of one embodiment of an electronic control device to which the present invention is applied. This is a schematic diagram showing a printed circuit board as viewed from the side where electronic components are mounted. This is a schematic partial cross-sectional view showing a cross-section obtained by cutting along the extension direction of the high-speed signal wiring at the portion where the second circuit board is fixed on the first circuit board. This is a schematic partial enlarged view showing the connection portion between the high-speed signal wiring and the auxiliary signal wiring at the end of the second circuit board as viewed from above the printed circuit board 30. This is a schematic partial cross-sectional view showing the cross-section of the portion indicated by the dashed line A-A in Figure 4. This is a schematic partial cross-sectional view showing the cross-section of the portion indicated by the dashed line B-B in Figure 4. This is a schematic partial cross-sectional view showing a cross-section obtained by cutting along the extension direction of the high-speed signal wiring at the fixing portion of the second circuit board in the second embodiment. This is a schematic partial enlarged view showing the connection portion between the high-speed signal wiring and the auxiliary signal wiring at the end of the second circuit board as viewed from above the printed circuit board. This is a schematic partial cross-sectional view showing the cross-section of the portion indicated by the dashed line C-C in Figure 8. This is a schematic partial cross-sectional view showing the cross-section of the portion indicated by the dashed line D-D in Figure 8. This is a schematic partial cross-sectional view showing the cross-section of the fixing portion of the second wiring board in the third embodiment, cut along the extension direction of the high-speed signal wiring. This is a schematic diagram showing the printed wiring board in the fourth embodiment as viewed from the side where the electronic components are mounted.

[0012] Hereinafter, representative embodiments of the present invention will be described with reference to the drawings. The embodiments and drawings described below are illustrative examples for explaining the present invention, and have been omitted or simplified as appropriate for clarity of explanation. Furthermore, please note that in order to facilitate understanding of the invention, the position, size, shape, and extent of each component shown in the drawings may not necessarily represent them precisely. In each drawing, parts having the same configuration and / or function are denoted by the same reference numeral. In addition, in the following description, unless particularly necessary, redundant explanations of parts having the same configuration and / or function will be omitted.

[0013] Figure 1 is a schematic exploded perspective view showing the configuration of one embodiment of an electronic control device to which the present invention is applied.

[0014] The electronic control unit 10 may be, for example, an ECU for an automated driving system or an ECU for an advanced driver assistance system that communicates with various control units that control multiple sensing devices and equipment such as the engine, brakes, and steering, and controls the operation of these devices, or it may be a so-called integrated ECU that aggregates and integrates information from zone ECUs located in various parts of the vehicle to perform integrated control.

[0015] The electronic control device 10 of this embodiment is configured by housing a printed circuit board 30, on which an electronic circuit is formed on at least one side, within a space inside a housing composed of, for example, a metal base housing 20 and a cover 25. The base housing 20 and cover 25 do not necessarily have to be made of metal and may be made of, for example, a resin material, but it is desirable that electromagnetic shielding be provided at least in the parts where high-speed signals are handled.

[0016] The printed circuit board 30 has semiconductor devices 40, such as a microcontroller unit (MCU) and a communication LSI, which constitute the electronic control device, as well as other electronic devices (not shown) that form an electronic circuit together with the semiconductor devices 40. These semiconductor devices 40 and other electronic devices are interconnected by signal wiring formed on the printed circuit board 30 to form an electronic circuit that realizes the function of the electronic control device 10.

[0017] The printed circuit board 30 may also have a connector 50 attached to it, which is an electronic component to which signal lines from sensors mounted on the vehicle and communication lines for sending and receiving data with other ECUs are connected.

[0018] Figure 2 is a schematic diagram showing the printed circuit board 30 as viewed from the side on which electronic components are mounted. The printed circuit board 30 has a first wiring board 300 on which an insulating layer is made of a material commonly used for printed circuit boards, such as FR4, on which electronic components are mounted. On top of this, second wiring boards 310a and 310b, on which a portion of the signal wiring is formed as described later, are fixed.

[0019] The first wiring board 300 is mounted with a mixture of semiconductor devices: a semiconductor device 40a that transmits signals at a transmission speed of 500 Mbps or more (hereinafter referred to as the first transmission speed), a semiconductor device 40b that transmits signals at a transmission speed lower than the first transmission speed (hereinafter referred to as the second transmission speed), and a semiconductor device 40c that transmits signals between both of these semiconductor devices 40a and 40b.

[0020] The semiconductor device 40c may be, for example, an MCU that includes an arithmetic unit and memory, and executes a program stored in the memory using the arithmetic unit to realize various functions of the electronic control unit 10 while using the functions of the semiconductor device 40a and semiconductor device 40b.

[0021] The semiconductor device 40b and the semiconductor device 40c are connected by signal wiring 110a formed on the first wiring board 300. The semiconductor device 40b may be a semiconductor device having a communication interface for communication via a network such as CAN (Controller Area Network), which is commonly used for communication between conventional electronic control devices and various devices in a vehicle. In such a case, the semiconductor device 40b may be connected to a connector 50b by signal wiring 110b formed on the first wiring board 300, and configured to communicate with other electronic control devices and devices in the vehicle via the connector 50b.

[0022] The semiconductor device 40a and the semiconductor device 40c are connected by a high-speed signal wiring 100a capable of transmitting signals at a first transmission speed. The semiconductor device 40a may be a semiconductor device having a communication interface for communication over a high-speed network such as Gigabit Ethernet. In such a case, the semiconductor device 40a can be connected to a connector 50a by a high-speed signal wiring 100b capable of transmitting signals at a first transmission speed, and can be configured to connect to a high-speed network via the connector 50a.

[0023] At least a portion of the high-speed signal wiring 100a is formed on the second wiring board 310a, which is fixed to the first wiring board 300. Similarly, the high-speed signal wiring 100b is formed on the second wiring board 310b, which is fixed to the first wiring board 300. In the following description, when it is not necessary to distinguish between the second wiring boards 310a and 310b, the alphabetical subscript may be omitted and they may be referred to as the second wiring board 310. Similarly, when it is not necessary to distinguish between the high-speed signal wiring 100a and 100b, they may be referred to as the high-speed signal wiring 100.

[0024] The second wiring board 310 can be made of a material with a lower dielectric constant and dielectric loss tangent than that of the first wiring board 300, such as a polyphenylene ether (PPE)-based material, a polyphenylene oxide (PPO)-based material, or a polytetrafluoroethylene (PTFE)-based material, as its insulating layer. As a result, the high-speed signal wiring 100 formed on the second wiring board 310 is capable of transmitting high-speed signals with low loss.

[0025] Figure 3 is a schematic partial cross-sectional view showing a cross-section obtained by cutting along the extension direction of the high-speed signal wiring 100a at the portion where the second wiring board 310 is fixed on the first wiring board 300. This structure is also common to the second wiring board 310b by replacing the semiconductor device 40c with the connector 50a.

[0026] The high-speed signal terminals of the semiconductor device 40 are connected to auxiliary signal wiring 120 formed on the first wiring board 300. The auxiliary signal wiring 120 continues to the end of the second wiring board 310, which is fixed to the first wiring board 300, and at the end of the second wiring board 310, it is connected to high-speed signal wiring 100 formed on the second wiring board 310. The high-speed signal wiring 100 is formed, for example, as a stripline in an intermediate wiring layer, which is an internal wiring layer of the second wiring board 310 sandwiched between insulating layers.

[0027] Figure 4 is a schematic enlarged view of the connection between the high-speed signal wiring 100 and the auxiliary signal wiring 120 at the end of the second wiring board 310, as seen from above the printed circuit board 30. In Figure 4, reference numbers are only assigned to the portion related to the central high-speed signal wiring 100, and reference numbers are omitted for the portions related to the high-speed signal wiring 100 on both sides.

[0028] In Figure 4, the first surface of the second wiring board 310, which is on the near side, is covered with ground wiring 200. As will be described later, the ground wiring 200 is connected to the ground wiring of the first wiring board 300 via via 210.

[0029] The high-speed signal wiring 100 formed in the intermediate wiring layer is connected to via 220, and via via 220 is connected to auxiliary signal wiring 120. Also in the same intermediate wiring layer as the high-speed signal wiring 100, ground wiring 230 is formed so as to sandwich the connection between via 220 and high-speed signal wiring 100 from a direction perpendicular to the extension direction of the high-speed signal wiring 100. The high-speed signal wiring 100, via 220, and ground wiring 230 are formed in the inner layer of the second wiring board 310, and are therefore shown by dashed lines in Figure 4. In Figure 4, the ground wiring 230 sandwiching adjacent high-speed signal wiring 100 is connected to each other, but they may be formed separately from each other. The shape of the ground wiring 230 shown in Figure 4 is merely an example, and any shape is acceptable as long as it allows for impedance matching at the connection between the high-speed signal wiring 100 and auxiliary signal wiring 120.

[0030] Figure 5 is a schematic partial cross-sectional view showing the cross-section of the portion indicated by the dashed line A-A in Figure 4, and Figure 6 is a schematic partial cross-sectional view showing the cross-section of the portion indicated by the dashed line B-B in Figure 4.

[0031] As described above, the high-speed signal wiring 100 is formed in the intermediate wiring layer of the second wiring board 310 and is connected at one end of a via 220 formed along the thickness direction of the second wiring board 310, connecting the intermediate wiring layer of the second wiring board 310 to the second surface (the surface facing the first wiring board 300) at the end of the second wiring board 310. At the other end of the via 220, it is connected, for example, to an auxiliary signal wiring 120 formed on the first wiring board 300 by a solder ball 250. Together with the high-speed signal wiring 100, the via 220 constitutes the signal wiring formed on the second wiring board 310.

[0032] As described above, the first surface of the second wiring board 310 is covered by ground wiring 200. Similarly, the second surface of the second wiring board 310 is also covered by ground wiring 240, except around the via 220. Ground wiring 200 and ground wiring 240 are connected to each other by via 210, which is formed to penetrate the second wiring board 310 in the thickness direction. Ground wiring 230, which is formed in the intermediate wiring layer, is also connected to via 210.

[0033] On the other hand, in the portion of the first wiring board 300 corresponding to the via 210, a via 510 is formed that penetrates the first wiring board 300 in the thickness direction and connects to a ground wire 500 formed on the back surface of the first wiring board 300 (the surface opposite to the mounting surface on which the semiconductor device 40 etc. are mounted). On the mounting surface of the first wiring board 300, a ground wire 520 is formed so as to correspond to the ground wire 230 formed in the intermediate layer of the second wiring board 310, and the ground wire 500 and the ground wire 520 are interconnected via the via 510.

[0034] The via 210 on the second wiring board 310 and the via 510 on the first wiring board 300 are connected, for example, via a solder ball 260. As a result, the ground wires 200, 230, 240, 500, and 520 are interconnected via via 210, the solder ball 260, and via 510. Note that the positions of via 210 and via 510 do not necessarily have to coincide; they may be formed at offset positions from each other.

[0035] Furthermore, by connecting the auxiliary signal wiring 120 to the high-speed signal wiring 100, and the ground wirings 500 and 520 to the ground wirings 200, 230 and 240 using the solder balls 250, the second wiring board 310 is fixed to the upper surface of the first wiring board 300 (the first surface facing the second wiring board 310).

[0036] In this embodiment of the printed circuit board, the signal wiring, which transmits high-speed signals, is formed on a second wiring board made of a material with a lower dielectric constant and dielectric loss tangent than a general substrate material such as FR4, thus enabling signal transmission with reduced transmission loss. The size of the second wiring board is kept to the size necessary to form the high-speed signal wiring, thus suppressing the occurrence of delamination (damage to the joint) caused by the difference in thermal expansion coefficients between the first and second wiring boards. Furthermore, since the high-speed signal wiring 100 is formed in the inner layer of the second wiring board 310 and the outer layer is covered with ground wiring, an electromagnetic shielding structure is formed by the ground wiring, which is advantageous in terms of electromagnetic compatibility (EMC).

[0037] Figure 7 is a schematic partial cross-sectional view showing a cross-section of the mounting portion of the second wiring board in the second embodiment of the present invention, cut along the extension direction of the high-speed signal wiring. The electronic control device in this embodiment differs from the electronic control device in the first embodiment described using Figures 1 and 2 in that the high-speed signal wiring is formed as a microstrip line, and other parts are configured in the same way as in the first embodiment. For this reason, in each drawing referred to in the following description, including Figure 7, parts corresponding to parts described in Figures 1 to 6 are given the same reference numbers as those used in Figures 1 to 6, and their descriptions are omitted unless particularly necessary.

[0038] As shown in Figure 7, in this embodiment, the high-speed signal wiring 101 (corresponding to the high-speed signal wiring 100 in the first embodiment) is formed as surface wiring on the first surface of the second wiring board 311 (the surface opposite to the first wiring board 300). Similar to the first embodiment, the high-speed signal wiring 101 is connected at the end of the second wiring board 311 to the auxiliary signal wiring 120 extending from the semiconductor device 40 on the first wiring board 300. In this embodiment, since the high-speed signal wiring 101 is formed on the surface of the second wiring board 311, the inner layers do not need to have wiring layers. By forming the high-speed signal wiring 101 on the surface of the second wiring board and eliminating the inner layer wiring, the thickness of the second wiring board 311 can be reduced, and the amount of substrate material equivalent to approximately one layer can be reduced, thereby reducing costs. Furthermore, by using surface wiring, the electrical length is shorter than that of inner layer wiring, contributing to faster signal transmission and lower loss.

[0039] Figure 8 is a schematic enlarged view of the connection between the high-speed signal wiring 101 and the auxiliary signal wiring 120 at the end of the second wiring board 311, as seen from above the printed circuit board, and corresponds to Figure 4 in the first embodiment. In Figure 8, as in Figure 4, reference numbers are only assigned to the portion related to the central high-speed signal wiring 101, and reference numbers are omitted for the portions related to the high-speed signal wiring 101 on both sides.

[0040] In this embodiment, the high-speed signal wiring 101 is formed as surface wiring on the first surface of the second wiring board 311, as described above. The high-speed signal wiring 101 is connected to vias 221 at the end of the second wiring board 311. Ground wiring 231 is formed around the vias 221 so as to sandwich the connection between the vias 221 and the high-speed signal wiring 101 from a direction perpendicular to the extension direction of the high-speed signal wiring 101. Each of the ground wirings 231 is connected to a plurality of vias 211.

[0041] In Figure 8, the ground wires 231 flanking the adjacent high-speed signal wires 101 are connected to each other, but they may be formed separately from each other. Furthermore, the shape of the ground wires 231 is merely an example, and any shape is acceptable as long as it allows for impedance matching at the connection point between the high-speed signal wires 101 and the auxiliary signal wires 120.

[0042] Figure 9 is a schematic partial cross-sectional view showing the cross-section of the portion indicated by the dashed line C-C in Figure 8, and corresponds to Figure 5 in the first embodiment. Figure 10 is a schematic partial cross-sectional view showing the cross-section of the portion indicated by the dashed line D-D in Figure 8, and corresponds to Figure 6 in the first embodiment.

[0043] As described above, the high-speed signal wiring 101 is connected to via 211 at the end of the second wiring board 311. Via 211 is formed to penetrate the thickness direction of the second wiring board 311, with the high-speed signal wiring 101 connected to one end and the other end connected to auxiliary signal wiring 120 formed on the first wiring board 300 by a solder ball 250.

[0044] The second surface (the surface facing the first wiring board 300) of the second wiring board 311 is covered with a ground wiring 241 except around the via 211. In the present embodiment, the ground wiring 241 has the shape shown by the thick shading in FIG. 8. That is, the ground wiring 241 is an annular region surrounding the via 221 inside the region corresponding to the ground wiring 231 formed on the first surface on the second surface of the second wiring board 311, and continues from this annular region in the direction opposite to the extending direction of the high-speed signal wiring 101, and is formed so as to cover the second surface except for the region facing the auxiliary signal wiring 120. This shape is the same as that of the ground wiring 240 in the first embodiment.

[0045] The ground wiring 241 is connected to the via 211 formed by penetrating the second wiring board 311 around the via 221. One end of the via 2¹¹ is connected to the ground wiring 231 formed on the first surface of the second wiring board 311, and the other end is connected to the ground wiring 241 covering the second surface of the second wiring board 311. Further, the via 211 is connected to the ground wiring 520 and / or the via 510 formed on the first wiring board 300 via the solder ball 260. As a result, the ground wirings 231, 241, 520, and 500 are interconnected via the via 211, the solder ball 260, and the via 510. Similar to the first embodiment, the second wiring board 310 is fixed to the first surface of the first wiring board 300 by the solder balls 250 and 260.

[0046] In the printed wiring board in the present embodiment as well, it is possible to perform high-speed signal transmission with reduced transmission loss. Also, similar to the first embodiment, the size of the second wiring board can be suppressed to the size necessary for forming the high-speed signal wiring, so that the occurrence of delamination due to the difference in the coefficient of thermal expansion between the first wiring board and the second wiring board can be suppressed.

[0047] FIG. 11 is a partial cross-sectional view schematically showing a state of a cross-section obtained by cutting the mounting portion of the second wiring board in the third embodiment of the present invention along the extending direction of the high-speed signal wiring;

[0048] The electronic control device in the present embodiment is different from the electronic control device in the first embodiment described using FIGS. 1 and 2 in the structure of the attachment portion of the second wiring board to the first wiring board, and the other parts are configured in the same manner as in the first embodiment.

[0049] In the present embodiment, similar to the first embodiment, high-speed signal wirings 100 are formed in the inner layer of the second wiring board 310, and the first surface and the second surface are each covered with ground wirings.

[0050] In the present embodiment, the second wiring board 310 is fixed on the first wiring board 300 by a connection pedestal 600. A connection wiring 610 for connecting between the auxiliary signal wiring 120 and the high-speed signal wiring 100 is formed inside the connection pedestal 600. The connection pedestal 600 may be formed of, for example, the same material as the first wiring board 300 or the second wiring board 310. In this case, the connection wiring 610 can be formed as a via penetrating the connection pedestal 600 in the vertical direction.

[0051] The connection pedestal 600 does not necessarily have to be formed of the same material as the first wiring board 300 or the second wiring board 310, and may be formed of other materials. Alternatively, as the connection pedestal 600, a component such as a so-called connector for connecting the high-speed signal wiring 100 and the auxiliary signal wiring 120 may be used.

[0052] The first wiring board 300 and the second wiring board 310 are fixed while being separated by the connection pedestal 600. Therefore, a space is formed between the first wiring board 300 and the second wiring board 310. Electronic components 620 constituting an electronic circuit may be arranged in the space between the first wiring board 300 and the second wiring board 310, that is, on the first wiring board under the second wiring board 310.

[0053] According to the present embodiment, in addition to obtaining the same effects as those of the first and second embodiments described above, the space that can be formed under the second wiring board 310 can be used for mounting electronic components, and the mounting density of the electronic components can be increased.

[0054] Figure 12 is a schematic diagram showing a printed circuit board in the fourth embodiment as viewed from the side where electronic components are mounted.

[0055] In the second wiring board 320, which uses a substrate material with lower dielectric constant and dielectric loss tangent compared to the first wiring board 300, high-speed signal wiring 100 for transmitting signals at the first transmission speed is formed, similar to the embodiments described above. In this embodiment, electronic components such as semiconductor devices 40a and 40c that transmit and receive signals at the first transmission speed using the high-speed signal wiring 100 are further mounted on the second wiring board 320.

[0056] In this embodiment, since electronic components are mounted on the second wiring board 320, the area of ​​the second wiring board 320 is larger than that of the second wiring board in other embodiments, for example, the second wiring board 310 in the first embodiment. Therefore, although this is less cost-effective than other embodiments, since only high-speed signal wiring 100 is used for high-speed signal transmission between electronic components, it is possible to further reduce signal transmission losses between electronic components.

[0057] According to the embodiments described above, by locally employing a second wiring board capable of transmitting high-speed signals with low loss on a base first wiring board, a wiring board that suppresses the loss of high-speed signals transmitted between electronic components can be realized at low cost. Furthermore, since the second wiring board is employed locally, its area can be reduced, and the reliability of the connection with the first wiring board, which is made of a different material, can be improved.

[0058] In the embodiments described above, an electronic control device mounted on a vehicle was used as an example. However, the wiring board according to the present invention is not limited to electronic control devices for vehicles, but can be widely applied to electronic devices such as communication equipment, in which high-speed signal transmission is performed by at least some signal wiring on a printed wiring board.

[0059] The present invention has been described above using representative embodiments as examples, but the present invention is not limited thereto and can be implemented in various ways without departing from the spirit of the invention as described in the claims. For example, in the embodiments described above, the second wiring board is provided on the same side of the first wiring board as the side on which the electronic components are mounted, but the second wiring board may be provided on the side opposite to the side on which the components are mounted (the back side). In this case, signals from the terminals of the electronic components that transmit high-speed signals are guided to the back side of the first wiring board via vias and connected to high-speed signal wiring formed on the second wiring board on the back side. Also, although the electronic components were mounted on one side of the first wiring board, electronic components may be mounted on both sides of the first wiring board. In this case, the second wiring board may be provided on one side or both sides of the first wiring board.

[0060] Furthermore, the embodiments described above have been explained in detail for the purpose of clearly illustrating the present invention, and the present invention is not necessarily limited to those comprising all the configurations described.

[0061] 10...Electronic control unit, 20...Base housing, 25...Cover, 30...Printed circuit board, 40, 40a, 40b, 40c...Semiconductor equipment, 50, 50a, 50b...Connector, 100, 100a, 100b...High-speed signal wiring, 110a, 110b...Signal wiring, 120...Auxiliary signal wiring, 200, 230, 240, 241, 500, 510...Ground wiring, 210, 211, 220, 221, 510...Via, 250, 260...Solder ball, 300...First wiring board, 310, 310a, 310b, 311, 320...Second wiring board, 600...Connection base, 610...Connection wiring

Claims

1. A printed circuit board comprising: a first wiring board on which a plurality of electronic components are mounted; a second wiring board fixed to a portion of at least one surface of the first wiring board, the second wiring board having a lower dielectric constant and dielectric loss tangent of the insulating layer compared to the first wiring board; a first signal wiring formed on the second wiring board for transmitting some of the signals among a plurality of signals transmitted between the plurality of electronic components; and a second signal wiring formed on the first wiring board for transmitting the other signals among the plurality of signals.

2. The printed circuit board according to claim 1, further comprising a third signal wiring formed on the first wiring board, which connects the first signal wiring to an electronic component among the plurality of electronic components that performs input and output of some of the signals.

3. The printed circuit board according to claim 2, wherein the first signal wiring is formed in the wiring layer inside the second wiring board, and ground wiring is formed on both sides of the second wiring board.

4. The printed circuit board according to claim 2, wherein the first signal wiring is formed on one side of the second circuit board, and a ground wiring is formed on the other side of the second circuit board.

5. The printed circuit board according to claim 2, wherein the second wiring board is fixed to the first wiring board via a base fixed on the first wiring board, and a space is formed between the first wiring board and the second wiring board on which some of the plurality of electronic components can be mounted.

6. The printed circuit board according to claim 5, wherein the base is a connector for connecting the first signal wiring and the third signal wiring.

7. A printed circuit board comprising: a first wiring board on which a plurality of first electronic components are mounted; a second wiring board having a lower dielectric constant and dielectric loss tangent of the insulating layer compared to the first wiring board, on which a plurality of second electronic components are mounted and fixed to a portion of at least one surface of the first wiring board; a first signal wiring formed on the second wiring board for transmitting signals transmitted between the plurality of second electronic components; and a second signal wiring formed on the first wiring board for transmitting signals transmitted between the plurality of first electronic components or between the first electronic components and the second electronic components.

8. An electronic control device mounted on a vehicle for controlling equipment provided on the vehicle, comprising: a printed circuit board as described in any one of claims 1 to 7; a plurality of electronic components mounted on the printed circuit board; a housing for housing the printed circuit board on which the plurality of electronic components are mounted; and a cover that together with the housing forms a space for housing the printed circuit board.

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