Circuit boards and electronic equipment.

Abstract

This technology provides advantages in improving the electrical characteristics of circuit boards. [Solution] The device comprises a wiring board 1 having wiring 16 and wiring 17, and an inductor component 8 mounted on the wiring board 1, wherein the electrode 81 of the inductor component 8 is connected to wiring 16, and the electrode 82 of the inductor component 8 is connected to wiring 17, and wiring 17 includes a test pad 4.

Description

Technical Field

[0001] The present invention relates to a circuit board.

Background Art

[0002] A circuit board may be provided with a test pad (check pad) for easily testing (checking) the functional state.

[0003] Patent Document 1 discloses that a test pad is connected to a transmission line via a branch transmission line that branches off from a position on the transmission line.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problem to be Solved by the Invention

[0005] There is a problem that providing a test pad may deteriorate the electrical characteristics of the circuit board.

Means for Solving the Problem

[0006] One object of the present disclosure is to provide a technique that is advantageous for improving the electrical characteristics of a circuit board.

[0007] One aspect of the present disclosure is a circuit board comprising: a wiring board having a first wiring and a second wiring; and an inductor component mounted on the wiring board, wherein a first electrode of the inductor component is connected to the first wiring, a second electrode of the inductor component is connected to the second wiring, and the second wiring includes a test pad.

[0008] One aspect of the present disclosure is a circuit board comprising a first signal wiring section and a second signal wiring section constituting a differential signal line, a first signal pad which is an open end, a second signal pad which is an open end, a third signal wiring section branching from the first signal wiring section, a fourth signal wiring section branching from the second signal wiring section, a fifth signal wiring section extending from the first signal pad, a sixth signal wiring section extending from the second signal pad, a first inductor component, and a second inductor component, wherein the third signal wiring section and the fifth signal wiring section are connected via the first inductor component, and the fourth signal wiring section and the sixth signal wiring section are connected via the second inductor component. [Effects of the Invention]

[0009] According to one aspect of this disclosure, a technique advantageous for improving the electrical characteristics of a circuit board can be provided. [Brief explanation of the drawing]

[0010] [Figure 1] A diagram illustrating a circuit board. [Figure 2] A diagram illustrating a circuit board. [Figure 3] A diagram illustrating a circuit board. [Figure 4] A diagram illustrating a circuit board. [Figure 5] A diagram illustrating a circuit board. [Figure 6] A diagram illustrating the probe. [Figure 7] A diagram illustrating electronic devices. [Figure 8] A graph showing the results of the examples and comparative examples. [Figure 9] A diagram illustrating the circuit board of the comparative example. [Modes for carrying out the invention]

[0011] Hereinafter, embodiments for carrying out the present invention will be described with reference to the drawings. However, the embodiments described below are only one embodiment of the invention and are not limited thereto. Common components will be described with reference to multiple drawings, and components with common reference numerals will be omitted from description as appropriate. Different items with the same name can be distinguished by adding "item number ○," such as "item number 1," "item number 2," etc.

[0012] <First Embodiment> The configuration of the circuit board 30 will be explained using Figure 1. Figure 1(a) is a schematic diagram of the planar layout of the circuit board 30, and Figure 1(b) is a schematic diagram of the cross-sectional layout of the circuit board 30. The circuit board 30 includes a wiring board 1. The wiring board 30 has wiring 16 and wiring 17. The circuit board 30 includes an inductor component 8 mounted on the wiring board 1. The inductor component 8 has electrodes 81 and 82. An inductor is provided between electrodes 81 and 82 in the inductor component 8. Electrode 81 of the inductor component 8 is connected to wiring 16, and electrode 82 of the inductor component 8 is connected to wiring 17. Wiring 17 includes a test pad 4.

[0013] The test pad 4 is open-ended relative to the inductor component 8. By making contact with the test pad 4, the circuit board 30 can be tested (inspected) via the probe.

[0014] The circuit board 30 may further include electronic components 26 and 27 mounted on the wiring board 1. Electronic component 26 is, for example, an integrated circuit component, but may also be other electronic components such as passive components. Electronic component 27 is, for example, a passive component, but may also be other electronic components such as integrated circuit components.

[0015] The wiring 16 includes a connection pad 21, a connection pad 22, and a connection pad 23. A portion of the wiring 16 other than the connection pads 21, 22, and 23 is a wiring portion 20. The wiring portion 20 can be composed of a plurality of wiring sections, and the plurality of wiring sections can also be composed of a plurality of wiring patterns. The wiring 17 includes a connection pad 24. A portion of the wiring 17 other than the connection pad 24 and the test pad 4 is a wiring portion 25. The connection pad 21 is bonded to the electronic component 26. The connection pad 22 is bonded to the electronic component 27. The connection pad 23 is bonded to the inductor component 8 (electrode 81). The connection pad 24 is bonded to the inductor component 8 (electrode 82). These bonding methods are typically solder bonding, but bonding using an anisotropic conductive material is also possible.

[0016] As shown in FIG. 1(b), the wiring board 1 has a front surface 101 which is a first main surface, and a back surface 102 which is a second main surface. The back surface 102 is the surface opposite to the front surface 101. In the example of FIG. 1(b), the electronic component 26 is arranged on the front surface 101 side. The electronic component 27 is arranged on the front surface 101 side, but may also be arranged on the back surface 102 side. The test pad 4 and the inductor component 8 are arranged on the back surface 102 side, but may also be arranged on the front surface 101 side.

[0017] The electronic component 26 is, for example, an integrated circuit component that outputs a signal to the wiring 16, and the signal output from the electronic component 26 is transmitted via the wiring 16 and input to the electronic component 27. The electronic component 27 is, for example, a connector component or a wiring component, but may also be a resistor component, a capacitor component, or the like. In this case, the wirings 16 and 17 serve as signal wirings, but the present invention is not limited thereto, and the wiring 16 may be a power wiring that transmits electric power, or a wiring that transmits both electric power and a signal. The wiring 16 may be a signal wiring constituting a differential signal line. That is, another wiring may be arranged in the vicinity of the wiring 16 with capacitive coupling, and each wiring may transmit a differential signal.

[0018] The wiring path from the connection pad 21 to the connection pad 23 may be longer than the wiring path from the test pad 4 to the connection pad 24. The wiring path from the connection pad 22 to the connection pad 23 may be longer than the wiring path from the test pad 4 to the connection pad 24. Arranging the inductor component 8 closer to the test pad 4 to make the wiring path from the test pad 4 to the connection pad 24 shorter is advantageous for improving test accuracy. The wiring path from the connection pad 21 to the connection pad 23 may be shorter or longer than the wiring path from the connection pad 22 to the connection pad 23. For example, when an integrated circuit component is connected to the connection pad 21 and a passive component is connected to the connection pad 22, the branch portion is preferably closer to the connection pad 22 in order to suppress the influence on the integrated circuit component. Therefore, when an integrated circuit component is connected to the connection pad 21 and a passive component is connected to the connection pad 22, the wiring path from the connection pad 21 to the connection pad 23 is preferably longer than the wiring path from the connection pad 22 to the connection pad 23. In this manner, by connecting the wiring 17 including the test pad 4 and the wiring 16 via the inductor component 8, the adverse effect of the test pad 4 on the electrical characteristics of the wiring 16 can be reduced. As a result, the electrical characteristics of the circuit board 30 are improved.

[0019] <Second Embodiment> Figure 2 is a perspective view showing an embodiment to which the circuit board 30 according to the present invention is applied. The circuit board 30 has signal wiring sections 2 and 3 that constitute a differential signal line, signal pads 4 and 5 for easily testing the functional state of the differential signal, and signal wiring sections 6 and 7 that branch off from signal wiring sections 2 and 3, respectively. The wiring including signal wiring sections 2 and 6 and connection pads (not shown) corresponds to the wiring 16 of the first embodiment. Similarly, the wiring including signal wiring sections 3 and 7 and connection pads (not shown) corresponds to the wiring 16 of the first embodiment. Electronic components are connected to the connection pads on one end 1a and the other end 1b of signal wiring section 2. Electronic components are connected to the connection pads on one end 2a and the other end 2b of signal wiring section 3. For example, connectors are connected to the one end 1a and 2a, and integrated circuit components are connected to the other end 1b and 2b. In this case, the branching section is located closer to the other end 1b, 2b than to the other end 1a, 2a. The branched signal wiring sections 6 and 7 are connected to inductor components 8 and 9, respectively, and the other end of inductor component 8 is connected to signal wiring section 10, which is connected to an open signal pad 4. Similarly, the other end of inductor component 9 is connected to signal wiring section 11, which is connected to an open signal pad 5. The wiring including signal wiring section 10, an unillustrated pad, and signal pad 4 corresponds to wiring 17 in the second embodiment. Similarly, the wiring including signal wiring section 11, a connection pad (not shown), and signal pad 5 corresponds to wiring 17 in the second embodiment.

[0020] Here, we consider the inductance L1 of the inductor component 8 and the branched signal wiring sections 6 and 10, and the capacitance C1 formed by the signal pad 4. Similarly, we consider the inductance L2 of the inductor component 9 and the branched signal wiring sections 7 and 11, and the capacitance C2 formed by the signal pad 5. With respect to L1 and C1 or L2 and C2, the transmission characteristics can be improved by lowering the LC resonant frequency f determined by Equation 1 and moving it outside the frequency band of the transmitted signal. More specifically, the transmission characteristics can be improved by determining the values ​​of L and C respectively so that the cutoff frequency is one-quarter of the frequency of the fundamental wave of the transmitted frequency.

[0021]

number

[0022] This makes it possible to improve the transmission characteristics that have been degraded by branch wiring leading to the check pad of the differential wiring.

[0023] <Third Embodiment> The circuit board 30 according to this embodiment will be described with reference to Figure 3. The circuit board 30 according to this embodiment differs from the first embodiment in that the signal pads 4 and 5 and inductor components 8 and 9 are located on the back surface (conductor layer 402) of the circuit board 30, and the signal wiring sections 6 and 7 branched from the differential wiring in the conductor layer 401 and the signal wiring sections 12 and 13 connected to the inductor components 8 and 9 in the conductor layer 402 are connected by via conductors 14 and 15, respectively.

[0024] Thus, even when the branch wiring leading to signal pads 4 and 5 includes the length of the via, which is equivalent to the thickness of the circuit board, and thus further degrades the signal transmission characteristics, it is possible to improve the transmission characteristics.

[0025] Furthermore, since the inductances of via conductors 14 and 15 can be added together, the LC resonant frequency can be made even lower, making it possible to avoid overlap with the frequency band of the transmission signal even when the lowest-order frequency of the transmission signal is low.

[0026] <Fourth Embodiment> The circuit board 30 according to this embodiment will be described with reference to Figures 4 and 5. The circuit board 30 according to this embodiment differs from the first and second embodiments in that it has a plurality of differential wirings 201, 202, 203, and 204.

[0027] Figure 4 is a top view of the circuit board 30 as seen from the front surface (the conductor layer 401), and Figure 5 is a top view as seen from the back surface (the conductor layer 402).

[0028] As shown in Figure 4, the circuit board 30 according to this embodiment is provided with a plurality of differential wirings 201, 202, 203, and 204 for connecting a transmitting IC (not shown) that transmits differential signals and a connector pad 101 of a connector that connects cables. The differential wirings 201, 202, 203, and 204 are connected from the left and right sides of the connector pad 101, and the wiring area can be made smaller in the direction perpendicular to the wiring direction compared to when the wiring is connected from one side of the connector pad 101.

[0029] Here, as shown in Figure 5, when considering the placement of the inductor components 301, 302, 303, and 304 on the back side relative to the differential wirings 201 and 202 on the left side of the connector pad 101, if the differential wirings 201 and 202 are placed in opposite directions, there is a risk that the inductor components and signal pads placed on the right side will interfere with the wiring of the differential wirings 203 and 204 that connect to the right side of the connector pad 101. Also, if both inductor components 301, 302, 303, and 304 for differential wirings 201 and 202 are placed on the left side of the connector pad 101, attempting to place the two pairs of inductor components in the same location will cause the wiring area of ​​the differential wiring to expand in the direction of the shorter side of the inductor components.

[0030] In this embodiment, the placement of each pair of inductor components of differential wiring 201 and 202, which are located to the left of the connector pad 101, is offset so that they do not overlap when viewed from the short side direction of the inductor components, making it possible to arrange them without expanding the wiring area.

[0031] Furthermore, by arranging the test ground pads parallel to the long side of the inductor component, the expansion of the wiring area can be further suppressed. The above arrangement configuration can also be similarly implemented for differential wiring 203 and 204 on the back surface of the printed circuit board 1 (the conductor layer 402).

[0032] <Fifth Embodiment> The method for manufacturing the circuit board 30 includes the steps of preparing the circuit board 30 and testing the circuit board 30 by bringing a probe into contact with the test pad 4. Such a method for manufacturing the circuit board 30 can also be adopted as one of the manufacturing processes for electronic equipment having a circuit board 30. Figure 6 shows an example of a probe 501 that is brought into contact with the test pad. The probe 501 has a structure that allows its tip to make contact at multiple points in order to ensure a reliable connection with the test pad.

[0033] The tip of the probe, which is used to test the functional state by contacting the signal pad, has a crown-like shape as shown in Figure 6, and is designed to reliably make contact at multiple points, with an outermost diameter of approximately φ1 mm. Therefore, the shape of the signal pad must be at least φ1 mm or larger. In this way, even when the probe tip is large and requires connection at multiple points, the structure of this embodiment makes it possible to reliably test the functional state while improving the transmission characteristics.

[0034] <Sixth Embodiment> Figure 7 is a schematic diagram illustrating an electronic device 80 to which the circuit board 10 is applied. The electronic device 80 comprises a circuit board 30 and a housing that houses the circuit board 30. The electronic device 80 may also comprise an electrical device 40, an electrical device 50, and an electrical device 60. Figure 6 shows a case where the electrical device 50 includes the circuit board 30, but the electrical device 40 or the electrical device 50 may include the circuit board 30. The electrical devices 40 and 60 are connected to the electrical device 50. The electrical device 40 may be a control device that controls the electrical device 50, or a power supply device that supplies power to the electrical device 50. The electrical device 50 may be a control device or a processing device. The electrical device 60 may be an image forming apparatus. The image forming apparatus may be, for example, an imaging device, a display device, or a printing device. The electrical device 50 may be an image processing device that processes an image formed by an image forming apparatus as an imaging device. The electrical device 50 may be an image processing device that processes an image displayed by an image forming apparatus as a display device. The electrical device 50 may be an image processing device that processes images to be printed by an image forming apparatus as a printing device.

[0035] In electronic devices such as photocopiers, high-speed transmission of large amounts of digital signals within the device is necessary to achieve faster printing speeds and higher image resolution. Therefore, differential signal transmission methods, which enable high-speed transmission of large amounts of data, are becoming widely used.

[0036] In recent high-speed differential signal transmission, data encoded using conversion tables or formulas is transmitted so that the logic transition rate between high and low levels is 50%. Therefore, there are no consecutive low or high levels of 4 bits or more. Consequently, 4 consecutive bits of data represent the lowest frequency required for data transmission, and the bandwidth required for signal transmission is at least one-quarter of the frequency of the fundamental wave, which is half the data transmission rate.

[0037] Differential wiring, which is used for high-speed transmission, requires test pads to easily test its functional status. However, test pads are sometimes placed on the same layer as the differential wiring. Therefore, if the size of the test pads increases, placing them on the same layer as the differential wiring necessitates branching the differential wiring and placing the test pads separately from it, which degrades the signal transmission characteristics.

[0038] Furthermore, if the test pads are located on the back side of the circuit board, opposite to the differential wiring that is routed on the front side, the branch wiring leading to the test pads will include the length of the vias, which are equivalent to the thickness of the circuit board, further degrading the signal transmission characteristics. Therefore, conventionally, test pad wiring has been made as short as possible to avoid degrading the signal transmission characteristics.

[0039] However, because the test pads are large and need to be positioned away from the differential wiring, it is difficult to shorten the branch wiring leading to the test pads.

[0040] Furthermore, to improve testing efficiency, test pads must be concentrated on one side. If multiple differential traces are routed on both the front and back surfaces of the board, the test pads will have to be placed on the side opposite to the differential traces, making it impossible to shorten the branching routes leading to the test pads.

[0041] In this embodiment, these problems can be solved by the inductor component 8. [Examples]

[0042] <Examples> This section describes the results of a simulation conducted to verify the effectiveness of the printed circuit board shown in Figure 2. The signal transmission characteristics (Sdd21) were calculated when the sum of the inductances of inductor component 8 and its branched signal wiring sections 6 and 10, and the sum of the inductances of inductor component 9 and its branched signal wiring sections 7 and 11, were each 200 nH, and the capacitance formed by each signal pad 4 and 5 was 0.7 pF. The simulation used 4-port S-parameter calculation, with the reference impedance of each port (1a, 2a, 1b, 2b) set to 50 Ω and the frequency range for calculation set to 100 MHz to 10 GHz. The results are shown in Figure 2.

[0043] <Comparative Example> The comparative example shown in Figure 9 will now be explained. Figure 9 differs from the embodiment in that it does not have an inductor component. The inductance of each branched signal wiring section 6 and the inductance of signal wiring section 7 were set to 6nH, while all other values ​​were the same as in the embodiment. The results of the comparative example are shown by the dotted line in Figure 8.

[0044] <Evaluation Results> As shown in Figure 8, in the comparative example, the LC resonance frequency is 2.5 GHz, so the signal transmission characteristic is that the signal does not transmit at 2.5 GHz but is attenuated. On the other hand, when the transmission frequency of a differential signal is 5 Gbps, the fundamental frequency is half that frequency, 2.5 GHz, so the frequency bandwidth required for data transmission is from 625 MHz, which is one-quarter of the fundamental frequency, to 7.5 GHz, which is the third harmonic of the fundamental frequency. Therefore, in the transmission characteristic of the comparative example, the resonance overlaps with the frequency bandwidth required for data transmission, resulting in degraded transmission characteristics.

[0045] In contrast, in the configuration of the embodiment where the signal pads are connected via an inductor, the LC resonant frequency is lower than 625MHz, thus avoiding overlap with the frequency band required for data transmission. Furthermore, up to the cutoff frequency of the transmission characteristics at 625MHz, i.e., the characteristic at which there is a 3dB attenuation, there is no deterioration in data transmission, and therefore the present invention is effective within this range.

[0046] As described above, in this embodiment, instead of shortening the length of the branch wiring from the differential wiring to the signal pad, it is intentionally made longer, that is, in the direction of increasing the inductance, so that the frequency band required for data transmission and the attenuation band due to resonance do not overlap.

[0047] Furthermore, attempting to adjust the inductance by changing the wiring length would result in an unrealistically long wiring area, making it impossible to secure sufficient wiring space. Therefore, by installing a small inductor component, it becomes possible to achieve both equivalent improvements in transmission characteristics and miniaturization of the wiring area.

[0048] The embodiments described above can be modified as appropriate without departing from the technical concept. Furthermore, the previously described embodiments may be combined with each other. Also, some aspects of at least one embodiment can be deleted or replaced. Moreover, new aspects can be added to at least one embodiment.

[0049] The disclosures in this specification include the following aspects:

[0050] [Aspect 1] A wiring board having a first wiring and a second wiring, The circuit board includes an inductor component mounted on the aforementioned wiring board, The first electrode of the inductor component is connected to the first wiring. The second electrode of the inductor component is connected to the second wiring. The second wiring includes a test pad. A circuit board characterized by the following features.

[0051] [Aspect 2] With respect to the inductor component, the test pad is an open end. A circuit board according to embodiment 1, characterized by the features described above.

[0052] [Aspect 3] The circuit board comprises a first electronic component and a second electronic component mounted on it. The first wiring includes a first pad, a second pad, and a third pad. The second wiring includes the fourth pad, The first pad is bonded to the first electronic component, The second pad is bonded to the second electronic component, The third pad is bonded to the first electrode, The fourth pad is bonded to the second electrode. A circuit board according to embodiment 1 or 2, characterized by the features described herein.

[0053] [Aspect 4] The aforementioned wiring board has a first main surface and a second main surface which is the opposite surface of the first main surface. The first electronic component is located on the first main surface side, The test pad and the inductor component are arranged on the second main surface side. The circuit board according to embodiment 3, characterized by the features described herein.

[0054] [Aspect 5] The second electronic component is located on the first main surface side. The circuit board according to embodiment 4, characterized by the features described herein.

[0055] [Aspect 6] The first electronic component is an integrated circuit component, and the second electronic component is a passive component. A circuit board according to any one of embodiments 3 to 5, characterized by the features described herein.

[0056] [Aspect 7] The wiring path from the first pad to the third pad is longer than the wiring path from the test pad to the fourth pad. A circuit board according to any one of embodiments 3 to 6, characterized by the features described herein.

[0057] [Aspect 8] The wiring path from the first pad to the third pad is longer than the wiring path from the second pad to the third pad. A circuit board according to any one of embodiments 3 to 7, characterized by the features described herein.

[0058] [Aspect 9] The first wiring is a signal wiring section. A circuit board according to any one of embodiments 1 to 8, characterized by the features described herein.

[0059] [Aspect 10] The first wiring is a signal wiring that constitutes a differential signal line. A circuit board according to any one of embodiments 1 to 9, characterized by the features described herein.

[0060] [Aspect 11] A first signal wiring section and a second signal wiring section that constitute a differential signal line, The first signal pad is an open end, The second signal pad is an open end, A third signal wiring section branching off from the first signal wiring section, The fourth signal wiring section branches off from the second signal wiring section, A fifth signal wiring section extending from the first signal pad, A sixth signal wiring section extending from the second signal pad, The first inductor component, The second inductor component, In a circuit board equipped with, The third signal wiring section and the fifth signal wiring section are connected via the first inductor component. A circuit board characterized in that the fourth signal wiring section and the sixth signal wiring section are connected via the second inductor component. [Aspect 12] The circuit board according to embodiment 11, characterized in that the capacitance value of the first signal pad, the third signal wiring section, the fifth signal wiring section, the inductance value of the first inductor component, and the capacitance value of the second signal pad, the fourth signal wiring section, the sixth signal wiring section, and the inductance value of the second inductor component have a frequency of one-quarter of the fundamental frequency of the transmission frequency that is less than or equal to the cutoff frequency.

[0061] [Aspect 13] The circuit board according to embodiment 11 or 12, characterized in that the first signal wiring section, second signal wiring section, third signal wiring section, and fourth signal wiring section are arranged on a first conductor layer, the first signal pad, second signal pad, first inductor component, second inductor component, fifth signal wiring section, and sixth signal wiring section are arranged on a second conductor layer, and the seventh signal wiring section and eighth signal wiring section, which are connected to the other terminals of the first inductor component and the second inductor component via the second conductor layer, and the third signal wiring section and fourth signal wiring section are connected by a first via conductor and a second via conductor, respectively.

[0062] [Aspect 14] The circuit board according to embodiment 13, wherein the differential signal line is designated as the first differential signal line, and the ninth and tenth signal wiring sections constituting the second differential signal line, and the eleventh and twelfth signal wiring sections branching from the ninth and tenth signal wiring sections are arranged on the first conductor layer, and the third and fourth signal pads, the third and fourth inductor components, the fourth inductor component, the thirteenth signal wiring section connected to the third signal pad, and the fourteenth signal wiring section connected to the fourth signal pad are arranged on the second conductor layer, and the fifteenth and sixteenth signal wiring sections connected to the other terminal of the third and fourth inductor components in the second conductor layer, and the eleventh and twelfth signal wiring sections are connected by the third via conductor and the fourth via conductor, respectively, and the first inductor component, the second inductor component, the third inductor component, and the fourth inductor component are arranged so as not to overlap when viewed from the short side direction of the components.

[0063] [Aspect 15] The first signal pad and the second signal pad are test pads. The circuit board described in embodiment 11.

[0064] [Aspect 16] A circuit board as described in any one of the embodiments 1 to 15, A housing for the circuit board, Electronic devices equipped with these features.

[0065] [Aspect 17] A first electrical device including a circuit board as described in any one of the embodiments 1 to 15, A second electrical device connected to the first electrical device, Electronic devices equipped with these features.

[0066] [Aspect 18] The second electrical device is an image forming apparatus. The electronic device according to embodiment 17, characterized by the features described herein.

[0067] [Aspect 19] The second electrical device is an imaging device, a display device, or a printing device. The electronic device according to embodiment 17, characterized by the features described herein.

[0068] [Aspect 20] A step of preparing a circuit board as described in any one of the embodiments 1 to 10 or embodiment 15, A step of testing the circuit board by bringing the probe into contact with the test pad, A method for manufacturing a circuit board, characterized by having the following:

[0069] Furthermore, the disclosures in this specification include not only those explicitly stated herein, but also all matters that can be inferred from this specification and the drawings attached thereto.

[0070] Furthermore, the disclosures in this specification include the complements of the individual concepts described herein. That is, if this specification contains a statement such as "A is greater than B," then even if it omits a statement such as "A is not greater than B," it can be said that this specification discloses "A is not greater than B." This is because the statement "A is greater than B" presupposes that the case where "A is not greater than B" is being considered. [Explanation of Symbols]

[0071] 30 circuit board 16, 17 Wiring 4 Test pads 8 Inductor Components

Claims

1. A wiring board having a first wiring and a second wiring, The circuit board includes an inductor component mounted on the aforementioned wiring board, The first electrode of the inductor component is connected to the first wiring. The second electrode of the inductor component is connected to the second wiring. The second wiring includes a test pad. A circuit board characterized by the following features.

2. With respect to the inductor component, the test pad is an open end. The circuit board according to claim 1.

3. The circuit board comprises a first electronic component and a second electronic component mounted on the aforementioned circuit board, The first wiring includes a first pad, a second pad, and a third pad. The second wiring includes the fourth pad, The first pad is bonded to the first electronic component, The second pad is bonded to the second electronic component, The third pad is bonded to the first electrode, The fourth pad is bonded to the second electrode. The circuit board according to claim 1.

4. The aforementioned wiring board has a first main surface and a second main surface which is the opposite surface of the first main surface. The first electronic component is located on the first main surface side, The test pad and the inductor component are arranged on the second main surface side. The circuit board according to claim 3, characterized in that it is a circuit board.

5. The second electronic component is located on the first main surface side. The circuit board according to feature 4.

6. The first electronic component is an integrated circuit component, and the second electronic component is a passive component. The circuit board according to claim 3, characterized in that it is a circuit board.

7. The wiring path from the first pad to the third pad is longer than the wiring path from the test pad to the fourth pad. The circuit board according to claim 3, characterized in that it is a circuit board.

8. The wiring path from the first pad to the third pad is longer than the wiring path from the second pad to the third pad. The circuit board according to claim 3, characterized in that it is a circuit board.

9. The first wiring is a signal wiring. The circuit board according to claim 1.

10. The first wiring is a signal wiring that constitutes a differential signal line. The circuit board according to feature 4.

11. A first signal wiring section and a second signal wiring section that constitute a differential signal line, The first signal pad is an open end, The second signal pad is an open end, A third signal wiring section that branches off from the first signal wiring section, The fourth signal wiring section branches off from the second signal wiring section, A fifth signal wiring section extending from the first signal pad, A sixth signal wiring section extending from the second signal pad, The first inductor component, The second inductor component, In a circuit board equipped with, The third signal wiring section and the fifth signal wiring section are connected via the first inductor component. A circuit board characterized in that the fourth signal wiring section and the sixth signal wiring section are connected via the second inductor component.

12. The circuit board according to claim 11, characterized in that the capacitance value of the first signal pad, the third signal wiring section, the fifth signal wiring section, the inductance value of the first inductor component, and the capacitance value of the second signal pad, the fourth signal wiring section, the sixth signal wiring section, and the inductance value of the second inductor component have a frequency of one-quarter of the fundamental frequency of the transmission frequency that is less than or equal to the cutoff frequency.

13. The circuit board according to claim 11, characterized in that the first signal wiring section, second signal wiring section, third signal wiring section, and fourth signal wiring section are arranged on a first conductor layer, the first signal pad, second signal pad, first inductor component, second inductor component, fifth signal wiring section, and sixth signal wiring section are arranged on a second conductor layer, and the seventh signal wiring section and eighth signal wiring section, which are connected to the other terminals of the first inductor component and the second inductor component via the second conductor layer, and the third signal wiring section and fourth signal wiring section are connected by a first via conductor and a second via conductor, respectively.

14. The circuit board according to claim 13, wherein the differential signal line is designated as the first differential signal line, and the ninth and tenth signal wiring sections constituting the second differential signal line, and the eleventh and twelfth signal wiring sections branching from the ninth and tenth signal wiring sections are arranged on the first conductor layer, and the third and fourth signal pads, the third and fourth inductor components, the fourth inductor component, the thirteenth signal wiring section connected to the third signal pad, and the fourteenth signal wiring section connected to the fourth signal pad are arranged on the second conductor layer, and the fifteenth and sixteenth signal wiring sections connected to the other terminal of the third and fourth inductor components in the second conductor layer, and the eleventh and twelfth signal wiring sections are connected by the third via conductor and the fourth via conductor, respectively, and the first inductor component, the second inductor component, the third inductor component, and the fourth inductor component are arranged so as not to overlap when viewed from the short side direction of the components.

15. The first signal pad and the second signal pad are test pads. The circuit board according to claim 11.

16. A circuit board according to any one of claims 1 to 15, A housing for the circuit board, Electronic devices equipped with these features.

17. A first electrical device including a circuit board according to any one of claims 1 to 15, A second electrical device connected to the first electrical device, Electronic devices equipped with these features.

18. The second electrical device is an image forming apparatus. The electronic device according to feature 17.

19. The second electrical device is an imaging device, a display device, or a printing device. The electronic device according to feature 17.

20. A step of preparing a circuit board according to any one of claims 1 to 10 or claim 15, A step of testing the circuit board by bringing the probe into contact with the test pad, A method for manufacturing a circuit board, characterized by having the following:

Images