JP2013254759A - Circuit substrate and electronic apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a circuit substrate that reduces noise propagating to wiring during static noise application and reaching an IC at lower costs.SOLUTION: A circuit substrate has a configuration in which an angular ring-like GND pattern is formed on signal wiring layers relative to a substrate end outer peripheral part to be an intrusion port of noise, and the GND pattern is electrically connected with a substrate GND through a plurality of points of GND veer. Accordingly, electromagnetic noise that is diffracted at a substrate end and intrudes into an interlayer insulating film is reduced.

Description

  The present invention relates to a circuit board and an electronic device on which the circuit board is mounted.

As background art in this technical field, there is JP-A-2006-350243 (Patent Document 1). In this publication, “GND is connected in the middle of GND lines 41 and 42 of a liquid crystal flexible printed circuit board (FPC) 40 for connecting a liquid crystal panel and a main board for signal transmission to the liquid crystal panel (near the metal frame 32). Terminals 41A and 42B are formed, and the liquid crystal FPC 40 is folded and the GND terminals 41A and 42B are connected to the metal frame 32 for housing the liquid crystal panel etc. Thereby, the GND of the liquid crystal driving driver for the liquid crystal panel is strengthened. (Improves impedance) ”. (See summary)
There is also JP-A-10-326868 (Patent Document 2). In this publication, “a high-frequency noise cut circuit composed of a capacitor and a resistor formed in a semiconductor integrated circuit element is formed, and this high-frequency noise cut circuit reduces static noise generated in a signal line from a pad. By covering the signal line, power supply line, transistor, etc. with metal or polycrystalline silicon, the capacitance (capacitor) C is provided to equalize internal fluctuations due to electrostatic noise and prevent malfunctions by protecting it from electromagnetic noise. . " (See summary)

JP 2006-350243 A JP-A-10-326868

  With the recent miniaturization, high density, high speed, and high functionality of electronic devices, ICs mounted on electronic circuits have become more miniaturized, faster, and lower in power and applied during electrostatic discharge. As a result, the circuit malfunction due to electrostatic noise has become a greater problem. To solve this problem, for example, Patent Document 1 proposes that a GND terminal is provided on a flexible printed circuit board and connected to a housing frame to reduce impedance and strengthen GND.

  By strengthening the GND described above, it is possible to suppress the intrusion into the circuit board by escaping the electrostatic noise applied from the connector or the like to the low impedance housing side during electrostatic discharge. Some become electromagnetic noise and propagate in space as electromagnetic waves. In electrostatic discharge to a connector mounted on a circuit board, generated electromagnetic noise propagates on the surface of the circuit board and is combined with signal wiring on the board to generate inductive noise. Since the noise propagates to the IC to which the wiring is connected, the circuit may malfunction depending on the noise level applied to the connector.

  As a method of suppressing this malfunction, there is a method of suppressing inductive noise coupled with signal wiring by forming a circuit board with a stripline structure and forming a wiring vulnerable to noise as an inner layer. However, electromagnetic noise propagating on the substrate surface is diffracted at the edge of the substrate, and part of the noise penetrates into the interlayer insulating film in the circuit board, reaches the signal wiring in the inner layer, and generates inductive noise.

  In order to suppress the above-mentioned noise, it is common to use a method of constructing a high-frequency filter circuit or a noise suppression element to prevent malfunction. However, with the additional circuit configuration and the addition of noise suppression elements, there is a problem that the board area increases. In contrast to the additional mounting area, Patent Document 2 forms a high-frequency noise cut circuit composed of a capacitor and a resistor in a semiconductor integrated circuit element to suppress an increase in substrate area, but causes a problem of further cost increase. Yes.

  Therefore, an object of the present invention is to improve the electromagnetic noise resistance at a low cost and to improve the reliability of the operation of the circuit board and the electronic device.

In order to solve the above problems, for example, the configuration described in the claims is adopted.
The present application includes a plurality of means for solving the above-mentioned problems. To give an example, each signal wiring layer has a square ring shape so as to surround the outer periphery of the circuit board 1 serving as a noise intrusion port. The GND pattern 6 is configured, and the above-described GND pattern 6 is electrically connected to the substrate GND 8 through a plurality of GND vias 2 to be diffracted at the substrate edge and enter the interlayer insulating film 9. It is characterized by reducing electromagnetic noise.

  According to the present invention, improvement in electromagnetic noise resistance can be realized at low cost, and the reliability of the operation of the circuit board and the electronic device can be improved.

It is a figure of the circuit board structural example in Example 1 of this invention. It is a figure of the circuit board cross section in Example 1 of this invention. It is a schematic diagram of the noise propagation situation in the circuit board including the signal wiring in the inner layer. It is a schematic diagram of the noise propagation situation of the circuit board in Example 1 of the present invention. It is the simulation result which verified the effect of the present invention using electromagnetic field analysis. It is a figure which shows the number of GND vias and the induction noise voltage result in Example 1 of this invention. 1 is an external view of a thin TV equipped with a circuit board according to Embodiment 1 of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is an external view of an HDD equipped with a control board that employs a board configuration according to a first embodiment of the present invention. It is a figure of the circuit board structural example in Example 2 of this invention. It is a structural example figure of the circuit board in 3rd Example of this invention. It is a structural example figure of the circuit board in 4th Example of this invention. It is a structural example figure of the circuit board in the 5th Example of this invention. It is a structural example figure of the circuit board in the 6th Example of this invention.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. Note that components having the same function are denoted by the same reference symbols throughout the drawings for describing the embodiment, and the repetitive description thereof will be omitted.

  Below, the circuit board which is Embodiment 1 of this invention is demonstrated. FIG. 1 is a diagram illustrating a configuration example of a circuit board according to the present embodiment, and FIG. 2 is a cross-sectional view of the circuit board according to the present embodiment.

  The circuit board 1 attached to the housing 4 has signal wiring in the inner layer of the board, and a connector 7 for inputting a signal from the outside or outputting a signal to the outside is provided on the surface of the circuit board 1. . A ring-shaped GND pattern 6 formed in each signal wiring layer is provided on the outer peripheral portion of the substrate end serving as an electromagnetic wave entrance. The ring shape of the GND pattern 6 formed in each of the signal wiring layers described above has a shape along the outer periphery of the circuit board 1 and is electrically connected to the substrate GND 8 through the plurality of GND vias 2.

  As shown in FIG. 2, the power wiring layer 9 formed on the circuit board 1 is not electrically connected by the GND via 2, but has a pattern layout in which a clearance is provided for the GND via 2. The ring shape of the GND pattern 6 is not limited to the shape surrounding the outer periphery of the substrate end.

  Next, the effect of reducing electromagnetic noise by the configuration of the present invention will be described.

  FIG. 3 is a schematic diagram of a noise propagation state in the circuit board 1 in which the signal wiring 3 is formed in the inner layer. When noise is applied from the board-mounted connector 7, electromagnetic waves are generated around the tip of the discharge gun 11 and propagate in space on the surface of the circuit board GND8. When the propagating electromagnetic wave reaches the substrate end of the circuit board 1, a part of the electromagnetic wave is diffracted at the substrate end and enters the interlayer insulating film 9 in the substrate as electromagnetic noise. When the substrate structure has a strip structure, the electromagnetic wave that has entered is shielded by the substrate GND 8 formed above and below, so that the intensity of the electromagnetic wave reaches the signal wiring 3 without being attenuated, and noise voltage is generated by inductive coupling. Occur. When an induced noise voltage is generated in this way, it is superimposed on the signal waveform on the wiring and propagated to the signal receiving circuit, resulting in problems such as circuit malfunction.

  On the other hand, FIG. 4 is a schematic diagram of a noise propagation situation in the circuit board 1 according to the first embodiment of the present invention. In Example 1 of the present invention, the outer peripheral portion of the substrate end has a grid-like GND pattern with respect to the cross-sectional direction of the substrate. When a propagation electromagnetic wave generated by applying noise reaches the substrate end of the circuit board 1 and is diffracted and enters the interlayer insulating film 9 in the substrate as electromagnetic noise, the grid-like GND pattern is electrically It functions as an electromagnetic shielding wall that suppresses electromagnetic noise intrusion from the substrate cross-sectional direction. For this reason, compared with the conventional substrate structure, the electromagnetic wave intensity which penetrate | invades into the interlayer insulation film in a board | substrate can be reduced.

  In this manner, by forming a grid-like GND pattern in the cross-sectional direction on the outer peripheral portion of each circuit board 1, electrostatic discharge due to electrostatic discharge or the like is applied to the connector 7 mounted on the circuit board 1. Even when noise is applied and the generated electromagnetic wave propagates in space on the substrate surface and diffracts into the interlayer insulating film 9 at the edge of the substrate, the electromagnetic wave is shielded by the GND pattern 6 and therefore enters the interlayer insulating film 9 Electromagnetic noise can be reduced.

  FIG. 5 is a simulation result in which the effect of the present invention is verified using electromagnetic field analysis. A FR4 board having a 6-layer structure in which a GND via assuming the GND pin of the connector is formed in the center of the board, and a straight wiring having a characteristic impedance value of 50Ω is formed from this GND via under the conditions of a wiring distance of 15 mm and a wiring length of 100 mm. Was modeled. The result of having simulated the noise waveform induced in the wiring edge part when the waveform which simulated the discharge noise of the discharge voltage 8kV by an electrostatic tester is applied with respect to the said circuit board is shown.

  In the substrate structure in which a plurality of GND vias 2 are formed with respect to the circuit board outer peripheral portion, a noise waveform of 0.193 V at the maximum is generated in the negative electrode. On the other hand, for the wiring layer in which the signal wiring 3 is laid out, in the substrate structure in which the square ring-shaped GND pattern 6 is formed on the outer peripheral portion of the substrate and connected to the substrate GND 8 via the plurality of GND vias 2, The maximum amplitude of negative noise is reduced to 0.185V.

  Further, for the three wiring layers excluding the layout layer of the power supply wiring layer, a square ring-shaped GND pattern 6 is formed on the outer peripheral portion of the substrate end, and connected to the substrate GND 8 via a plurality of GND vias 2. The maximum amplitude of negative noise is reduced to 0.163V. The amplitude value can be further reduced by about 15% with respect to the structure in which only the plurality of GND vias 2 are formed on the outer peripheral portion of the circuit board. Thus, by arranging the GND pattern corresponding to each wiring layer, the electromagnetic noise entering from the outer peripheral portion of the substrate end is reduced, and the effect of reducing the noise voltage generated in the signal wiring by inductive coupling with the electromagnetic noise is exhibited. be able to.

  This reduction effect can be increased by increasing the number of GND vias provided on the outer peripheral portion of the substrate end. FIG. 6 shows the relationship between the number of GND vias formed on the outer periphery of the circuit board and the noise voltage induced in the signal wiring. When the four corners of the circuit board are connected only by post-grounding, if the noise voltage induced to the signal wiring is normalized to 0 dB, the voltage level decreases as the number of GND vias increases, and the induced noise voltage level when 28 are provided Is reduced to -17 dB, which is about 1/7.

  By the way, in recent years, consumer electronics have been reduced in weight and cost, and the circuit board and housing frame joints have been reduced and the housing frame has been made non-metallic. Design is gaining importance. On the other hand, the above-described problem can be solved by mounting a circuit board having the configuration of the present invention in various electronic devices.

  FIG. 7 is an external view of a thin TV on which the circuit board of the present invention is mounted. In a thin TV, a front casing 21 and a rear casing 28 are mostly made of a plastic material, and openings 29 for heat dissipation are provided in various places in the casing. A circuit board (main board) 24 in which control circuits such as an HDD 23, an audio unit, a video unit, and a tuner unit are integrated, a power supply board 25, and an inverter board 26 are provided directly below the housing through a frame 22 serving as a base. They are arranged and connected by cables 27. Various connectors 7 that are electromagnetic noise intrusion ports are directly mounted on the main board 24, and the electromagnetic shielding effect by the back housing 28 cannot be obtained. Design is extremely important.

  By applying the implementation structure according to the present invention to the main board, when electrostatic noise flows from the connector 7, electromagnetic noise that propagates in space on the surface of the main board and diffracts at the substrate edge and enters the interlayer insulating film It can be reduced. According to the present invention, it is possible to improve the electromagnetic noise resistance at the product level, and it can be realized at low cost.

As other applicable products, implementation and effects on HDDs that have been installed in various electronic devices and information devices in recent years will be described.
FIG. 8 is an external view of a hard disk drive (HDD) equipped with a control board adopting the configuration of the present invention. Due to the variety and diversification of mounted products, HDDs are required to have high resistance to electromagnetic noise not only in the product mounting state but also in a single HDD product. In response to this requirement, the disk portion is sealed with a metal casing 4 and shielded against electromagnetic waves, but the control board 31 is not shielded for weight reduction and cost reduction. In such a state that it is electrically exposed to the metal casing 4 via the post 5 in a state where it is exposed to the ground. The spindle motor 32 is connected to the control board via the cable 27. Further, the connector 7 serving as an entrance for electrostatic noise is directly mounted on the end portion of the control board, and the mounting design for improving the electromagnetic noise resistance with the control board alone is extremely important as in the case of a thin TV.

  By applying the structure according to the present invention to the control board 31, when electrostatic noise flows from the connector 7, the electromagnetic wave propagates in space on the surface of the control board 31, diffracts at the board edge, and enters the interlayer insulating film Noise can be reduced.

  As a result, noise that reaches and leads to the signal wiring in the inner layer of the control board can be reduced, and malfunction can be prevented. By applying the present invention, it is possible to improve the electromagnetic noise resistance at the product level, and it can be realized at a low cost.

Other applicable products include servers and workstations with metal enclosures. The effects applied to these information processing apparatus devices will be described below.
Conventionally, in information equipment that requires high reliability such as servers and workstations, the internal circuit board (CPU board) is covered with a metal casing, and various connectors that serve as an entrance for electrostatic noise Are electrically connected to the GND portion of the connector and the metal casing. For this reason, when electrostatic noise flows from the connector, the noise is released to the ground through the housing, and electromagnetic waves generated in the vicinity of the connector are shielded by the housing and enter the housing, and the circuit board (CPU board) ) The structure suppresses the propagation of electromagnetic waves on the surface.

  However, power consumption has increased due to recent increases in speed and performance, and a higher level of heat dissipation design is required.Ventilation holes are constructed by installing fans, etc. Intrusion has become a problem. For this reason, even in a server or workstation having a metal casing, an electromagnetic interference suppression design that improves electromagnetic noise resistance is increasing in importance for a mounted circuit board (CPU board).

  Therefore, by applying the implementation structure according to the present invention to the circuit board (CPU board), when electrostatic noise flows in from the connector, electromagnetic waves that have entered from the opening of the housing space on the surface of the circuit board (CPU board). Electromagnetic noise that propagates, diffracts at the substrate edge, and enters the interlayer insulating film can be reduced, and electromagnetic noise resistance can be improved.

  As described above, the application of the present invention can improve electromagnetic noise resistance in various electronic devices and information processing devices on which circuit boards are mounted, and the reliability of circuit devices and electronic devices on which circuit boards are mounted. Can be improved.

  FIG. 9 is a configuration diagram of a circuit board in the second embodiment of the present invention. In the circuit board 1, a square ring-shaped GND pattern 6 is formed on each signal wiring layer with respect to the outer peripheral portion of the board end serving as a noise intrusion opening. The GND pattern 6 formed in each signal wiring layer is electrically connected to the substrate GND8 through the plurality of GND vias 2. In the embodiment, the GND vias are arranged in a staggered manner with respect to each adjacent via.

  The electromagnetic wave shielding effect can be improved by arranging the GND via 2 at a shorter distance between the vias than in the linear arrangement.

FIG. 10 is a configuration diagram of a circuit board in the third embodiment of the present invention. When the circuit board 1 has the opening 12 on the pattern of the substrate GND 8, a ring-shaped GND pattern 6 is formed on each signal wiring layer on the outer periphery of the opening 12. The GND pattern 6 is an embodiment in which the GND pattern 6 is electrically connected to the substrate GND 8 through a plurality of GND vias 2.
By configuring a shield wall in the opening according to this embodiment, it is possible to shield electromagnetic noise that is diffracted and invades at the opening.

  FIG. 11 is a structural diagram of a circuit board in the fourth embodiment of the present invention. In the circuit board 1, the GND pattern 6 including the entire side length on the end face side is formed in each signal wiring layer on the end face of the circuit board 1 that is closest to the mounting position of the connector 7 that is the entrance of the electrostatic noise. The GND pattern 6 is electrically connected to the substrate GND8 through a plurality of GND vias 2.

  The electromagnetic noise intensity that propagates in space on the substrate surface, diffracts at the substrate edge, and enters the interlayer insulating film 9 is highest at the substrate end surface closest to the mounting position of the connector 7 and is a noise voltage that is induced to the signal wiring. Determining the level. By providing the GND pattern corresponding to the signal wiring layer on the end face of the board closest to the connector, a shield wall can be formed and the noise voltage induced in the signal wiring can be reduced.

  FIG. 12 is a diagram showing a configuration example of a circuit board in the fifth embodiment of the present invention. In the circuit board 1, the electrostatic noise is applied, and the GND pattern 6 including the entire side length is provided for each signal on the board end face closest to the mounting position of the connector 7, which is an entry port, and the two end faces orthogonal to the adjacent board end face. Configure in the wiring layer. The GND pattern 6 is electrically connected to the substrate GND8 through a plurality of GND vias 2.

  In addition, about the 2 end surfaces orthogonal to the adjacent substrate end surface, the GND pattern 6 that covers a part of the side length is formed instead of the entire side length, and is electrically connected to the substrate GND 8 through the plurality of GND vias 2. Form may be sufficient.

  FIG. 13 is a diagram showing a configuration example of a circuit board in the sixth embodiment of the present invention. For the signal wiring 3 that is vulnerable to noise in the circuit board 1, a square ring-shaped GND pattern 6 that surrounds the outer periphery of the wiring is formed. The GND pattern 6 formed in each signal wiring layer is electrically connected to the substrate GND8 through the plurality of GND vias 2. By arranging the GND pattern configured in each wiring layer around the configuration vulnerable to noise in this way, it is possible to reduce the cost of mounting the GND pattern and reduce electromagnetic noise.

1 Circuit Board 2 GND Via 3 Signal Wiring 4 Housing 5 Post 6 GND Ring 7 Connector 8 Board GND
9 Power supply wiring 10 Interlayer insulating film 11 Discharge gun 12 Opening

21 Front housing 22 Frame 23 HDD
24 Main board 25 Power supply board 26 Inverter board 27 Cable 28 Rear housing 29 Opening

31 Control board 32 Spindle motor

Claims (7)

A circuit board,
A substrate GND constituting upper and lower layers of the circuit substrate;
Signal wiring provided in an inner layer of the circuit board;
A GND pattern provided in a layer in which the signal wiring is formed;
A GND via for connecting between the substrate GNDs on the upper and lower layers of the circuit board,
The circuit board, wherein the GND pattern is electrically connected to the substrate GND through the GND via. The circuit board according to claim 1,
The circuit board, wherein the GND pattern has a ring shape covering the periphery of the signal wiring. The circuit board according to claim 2,
The GND pattern has a shape along an outer periphery of an end portion of the circuit board, and is arranged on an outer periphery of the end portion of the circuit board. The circuit board according to claim 1,
The circuit board has a connector for connecting to an external device,
A circuit board comprising the GND pattern including the entire side length on the end face side at the end face of the circuit board closest to the connector arrangement position. The circuit board according to claim 4,
The circuit board has a connector for connecting an external device,
A circuit board comprising the GND pattern including the entire length at two end faces orthogonal to a board end face closest to the connector arrangement position. The circuit board according to any one of claims 1 to 5,
A circuit board comprising a plurality of the GND vias and a plurality of GND vias arranged in a staggered manner.   An electronic apparatus comprising the circuit board according to any one of claims 1 to 6.

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