JP4385753B2 - Printed wiring board - Google Patents

Description

  The present invention relates to a printed wiring board, and more particularly to a printed wiring board used in an electronic device such as a personal computer, a copying machine, a printer, and a facsimile.

  For transmission of digital signals on a printed circuit board used in the electronic equipment as described above, it is necessary to be able to sufficiently transmit a harmonic component that is usually 5 times or more the frequency of the fundamental wave of the binary pulse. That is, in order to transmit a high-speed digital signal having a base clock of several hundred MHz or more, harmonic components in the order of GHz must be considered.

  It is known that there are dielectric loss and skin effect as an obstacle to signal transmission on the printed circuit board in the order of GHz. Furthermore, the loss when a signal passes through a plurality of layers through via holes for connecting different layers in the multilayer substrate cannot be ignored.

  According to the analysis by the present inventors, for example, attenuation when a signal passes through a plurality of layers such as a power supply layer and a ground layer sandwiched between two signal wiring layers via via holes is particularly significant. This is due to the following reason. In other words, in the transmission of signals on the printed wiring board, the mirror image current of the signal current flowing through the signal wiring apparently flows symmetrically on the reference plane such as the power supply layer and the ground layer adjacent to the signal wiring layer. The return current flows in a distributed manner on the reference surface according to the spread of the electric lines of force between the mirror image current. When signal wirings wired on both sides of the printed wiring board are connected so as to penetrate through multiple reference surfaces by via holes, the signal current is obstructed when the return current cannot flow across these reference surfaces. It is attenuated. In addition, when the return current cannot flow through the reference surface, the return current becomes incomplete and the far electromagnetic field is not canceled, so that it is clear from the analysis by the present inventors that common mode radiation occurs. It has become. Note that the smaller the coupling between the two reference planes, the greater the attenuation of the signal. That is, the signal loss increases as the distance between the two reference planes increases.

  In Patent Document 1, the power supply layer is divided into a main power supply surface and a sub power supply surface, so that the return current path of the current flowing through the signal wiring is cut off. And a technique for bypassing the high-frequency return current to the ground layer is disclosed.

  However, in the technique described in Patent Document 1, the main power supply surface and the sub power supply surface arranged in the same layer are connected at a high frequency by using two capacitors to bypass the return current. In addition to the inductance component, the via hole for connecting the capacitor between the power supply layer and the ground layer and the inductance component of the pad for connecting the via hole and the wiring are inserted in series in the return current path. For example, a sufficiently low inductance cannot be achieved in a high frequency region of 1 GHz or higher. Therefore, there is a problem that a signal having a frequency component of 1 GHz or more cannot be bypassed because the inductance component becomes dominant.

  Patent Document 2 by the inventors proposes a printed wiring board that can reduce unnecessary electromagnetic radiation and prevent the return current from being hindered. Specifically, in a printed circuit board including a signal wiring layer for wiring signal wiring and a ground region made of a conductor and two ground layers having at least one power supply wiring, the ground regions of the two ground layers They are connected by a plurality of conductive interlayer connection means.

  Further, Non-Patent Document 1 has a structure similar to the printed wiring board described in Patent Document 2 in a region including a CPU, a bridge, a DDR memory, and the like, that is, two ground planes that are tightly coupled with via holes. The structure is described.

  In such a printed wiring board, a via hole connecting two ground layers is disposed in the vicinity of a signal transmission via hole, and therefore, there is a problem between a power plane and a ground plane that are a problem in a general multilayer printed wiring board. Since radiation due to resonance between the two ground layers can be suppressed, and a return current path is secured by a via hole connecting the two ground layers, it is suitable for high-speed transmission.

  However, although details will be described later, even in such a printed wiring board, the effects of suppression of electromagnetic wave radiation and high-speed transmission in the GHz order are limited.

  Electromagnetic noise radiated from various electronic devices such as information devices, which has been a problem in the past, is mainly caused by the clock signal on the printed circuit board and the signal line of the digital signal synchronized with the clock signal. For this reason, various countermeasures against electromagnetic radiation have been taken for the signal lines on the printed wiring board and the wire harnesses connected to the signal lines.

  For example, adding a damping resistor or filter to the signal output line to smooth the rise and fall of the output signal, or arranging a guard pattern with a ground potential near the signal line to reduce the feedback current loop, etc. Countermeasures are widely taken.

  In addition, some electromagnetic waves observed on a printed circuit board have a frequency distribution different from that predicted from the current distribution on the signal line, and have a sharp peak at a specific frequency regardless of the nature of the signal line. . As described in Patent Document 3, the main cause of the generation of electromagnetic waves is not the signal line of the printed wiring board but the power supply system, and the electrical resonance generated in the opposing power supply layer and ground layer. It has been known.

  On the other hand, in Patent Document 3, in order to reduce the reflectance of the resonance current at the end of the printed wiring board, a plurality of first capacitors are arranged at the end of the printed wiring board. A second capacitor for suppressing a loop current flowing between the capacitor and an active element such as an IC mounted on the printed wiring board is connected to the power supply terminal of the active element or between the power supply layer and the ground layer in the vicinity thereof. A technique for connecting between them is disclosed.

  However, in the technique described in Patent Document 3, since there is an inductance due to the capacitor itself and the mounting of the capacitor, for example, there is no effect on a high-frequency resonance current whose frequency exceeds about 1 GHz, and a low frequency band. However, there is a problem that the resonance current cannot be completely eliminated, and the electromagnetic wave radiated from the end portion of the printed wiring board cannot be completely suppressed.

  Further, in Patent Document 4, in order to improve the wiring density of a printed wiring board, a via hole has a double structure, that is, a coaxial structure, whereby a plurality of wirings are connected to each other while minimizing the diameter of the via hole. Techniques to do this are disclosed. Specifically, for example, an outer through-hole is drilled with a mechanical drill, a plating layer is formed on the outer through-hole, a resin filler is filled, a wiring layer is formed, an insulating resin layer is laminated, and photolithography technology is used. After the via hole is formed and the resin filler is thermally cured, a laser pulse is irradiated by a cycle pulse method to penetrate the insulating resin layer and the resin filler to form an inner through hole.

  However, in the technique described in Patent Document 4, since the signal wirings are double-structured, there is a problem in that adverse effects such as increased crosstalk or unstable impedance may occur. there were.

  As described above, when a signal is transmitted at a high speed on the order of GHz, the loss when the signal passes through a plurality of layers through a via hole cannot be ignored. Also, the influence of common mode radiation due to the interruption of the return current is great. The inventors of the present invention analyzed the attenuation of a signal traveling back and forth between two via holes when the distance between the two reference surfaces is 900 μm. As a result, it became clear that the signal component with a frequency of 2 GHz is expected to be attenuated by 2.5 dB, and it was found that the transmission on the order of GHz is not practical. In a printed wiring board having a structure in which two ground layers are sandwiched between signal wiring layers, a connection via hole for connecting a plurality of ground layers is provided in the vicinity of a signal via hole, and a return current passes through a plurality of ground layers. It can be improved to some extent by allowing it to flow through. However, even when the connection via hole is provided in the vicinity of the signal via hole, for example, at a distance of 1.5 mm, the return current does not circulate in the GHz order, and the improvement effect is small.

  As described in Patent Document 1, in a printed wiring board having a structure including a power supply layer and a ground layer as inner layers, a return current is bypassed by a capacitor, but due to the inductance of the capacitor itself and a via hole connecting the capacitor. The bypass effect of frequency components exceeding 1 GHz is significantly limited.

  In the four-layer substrate described in Non-Patent Document 1, the core thickness is set to 1.2 mm in order to reduce the impedance of the wiring and increase the speed. Since signal attenuation depends on the interlayer distance between two layers through which the signal flows, the above four-layer substrate has the effect of signal quality degradation and increased common mode radiation due to the signal flowing through multiple layers. Seems to be even bigger.

  By the way, printed circuit boards based on metals such as aluminum have been put into practical use in recent years. Let's prevent the temperature rise of mounting parts and the board itself by heat conductivity, and prevent electromagnetic interference by the electromagnetic shielding property of the base itself. That's it.

Further, as shown in Non-Patent Document 2, in order to perform high-speed signal driving on a printed circuit board, it is desirable that the impedance of the power source connected to the device is sufficiently low and matches the impedance of the driven wiring. It is known in recent years.
JP-A-11-233951 JP 2003-163467 A Japanese Patent No. 3036629 JP 2001-203458 A Intel, `` Intel Pentium (R) 4 Processor in 478-Pin Package and Intel 845 Chipset Platform for DDR-Design Guide '' The Institute of Electronics, Information and Communication Engineers, “Study of transmission line type power supply to replace power supply bypass capacitor with high-speed signal”, IEICE 2003 Annual Meeting 12C-07, p85-86

  However, in a conventional substrate having a power supply layer and a ground layer, it is difficult to control the power supply impedance, and it is difficult to perform high-speed signal driving.

  The present invention has been made to solve the above-described problems, and suppresses electromagnetic wave radiation caused by a power supply layer and a ground layer, and can be applied to a circuit board operating at high speed with a base clock of 1 GHz or more at a low cost. It is an object of the present invention to provide a printed wiring board that can be made by slightly changing the structure of a general printed board.

In order to achieve the above object, according to a first aspect of the present invention, there is provided a printed wiring board in which a wiring layer, a first ground layer, and a second ground layer are laminated, the first ground layer and the second ground layer. A power supply wiring provided so as to straddle a signal wiring provided in the wiring layer when viewed in plan on at least one of the ground layers, and connected to the wiring layer, the first ground layer and the second ground layer Conductive interlayer connection means penetrating the ground layer, and provided between the first ground layer and the second ground layer, and electrically connecting the first ground layer and the second ground layer. A conductive layer having at least a periphery of the power supply wiring and the periphery of the interlayer connection means, and a first dielectric member that is provided around the power supply wiring and insulates the power supply wiring from the conductive region And before It provided around the interlayer connecting member, characterized by comprising a second dielectric member which insulates the conductive region provided on the periphery of the interlayer connecting means and the interlayer connecting member.

  According to the present invention, a conductive region is provided between two ground layers. The conductive region includes a conductive layer provided at least around the power supply wiring provided on the ground layer and around the interlayer connection means. Dielectric members are provided around the wiring and the interlayer connection means.

  In this way, since the two ground layers are configured to be conducted by the conductive layer, the return current can be prevented from being interrupted, and even a signal in the order of GHz can be prevented from being attenuated. Generation of electromagnetic radiation due to the common mode current can be suppressed. This enables high-speed driving of signals.

In addition, since a dielectric member is provided between the power supply wiring and the ground layer and the power supply wiring and the ground layer are insulated by this dielectric member, a low impedance power supply with respect to the ground via the dielectric member, That is, a power supply that enables high-speed signal driving can be obtained. Moreover, since it is possible to capacitive coupling strongly the power line with respect to the ground potential, when the signal wires are present so as to straddle the power wiring of the ground layer adjacent to the wiring layer, the GHz order in the signal line Even when a high-frequency signal flows, the return current for the signal is not interrupted, and the signal transmission characteristics can be improved.

  In addition, as described in the second aspect, the conductive region may be provided over the entire conductive layer. In this case, the first ground layer and the second ground layer can be electrically conductively connected. Further, it is not necessary to process the dielectric layer to create a large number of regions of the conductive material, and the processability is improved.

  According to a third aspect of the present invention, the first ground layer, the conductive layer, and the second ground layer may be integrated with a single conductive member. . Thereby, the structure of the printed wiring board can be simplified and can be manufactured at low cost.

  The invention according to claim 4 is characterized in that the outer diameter of the interlayer connecting means is such that the characteristic impedance relating to the conductive region around the interlayer connecting means and the interlayer connecting means is substantially the same as the characteristic impedance relating to the wiring of the wiring layer. And at least one of the inner diameters of the conductive regions around the interlayer connection means is adjusted.

  According to the present invention, by adjusting at least one of the outer diameter of the interlayer connection means and the inner diameter of the conductive area around the interlayer connection means, the characteristic impedance and the wiring layer relating to the conductive area around the interlayer connection means and the interlayer connection means The characteristic impedances related to the wirings are made substantially the same. Thereby, it is possible to suppress the deterioration of signal quality due to signal reflection or the like, or the generation of electromagnetic wave radiation due to the occurrence of standing waves.

  The invention according to claim 5 is characterized in that the characteristic impedance relating to the interlayer connection means and the conductive region around the interlayer connection means is substantially the same as the characteristic impedance relating to the wiring of the wiring layer. The dielectric constant is adjusted.

  According to the present invention, by adjusting the dielectric constant of the second dielectric member, it is possible to adjust the interlayer connection similarly to adjusting at least one of the outer diameter of the interlayer connection means and the inner diameter of the conductive region around the interlayer connection means. The characteristic impedance relating to the conductive region around the means and the interlayer connection means and the characteristic impedance relating to the wiring in the wiring layer can be made substantially the same. Thereby, it is possible to suppress the deterioration of signal quality due to signal reflection or the like, or the generation of electromagnetic wave radiation due to the occurrence of standing waves.

  As described above, according to the present invention, low-cost and general printed circuit board can be applied to a circuit board that suppresses electromagnetic wave radiation caused by the power supply layer and the ground layer and operates at a high speed with a base clock of 1 GHz or more. The structure can be made possible by a slight change to the structure.

(First embodiment)
Hereinafter, a first embodiment of the present invention will be described.

  FIG. 1A shows a schematic cross-sectional view of a printed wiring board 10 according to the present embodiment. As shown in FIG. 1A, the printed wiring board 10 includes a first signal wiring layer 12, a first ground layer 14, a conductive layer 15, a second ground layer 16, and a second signal wiring layer 18. It is a laminated multilayer substrate. The first signal wiring layer 12 and the first ground layer and the second ground layer 16 and the second signal wiring layer 18 are insulated by an insulating material 20.

  FIG. 1B shows a plan view of the printed wiring board 10 as viewed from the first ground layer 14 side. In the figure, for the sake of convenience, the insulating material 20 is shown as being transmitted. 1A is a cross-sectional view taken along the line AA of FIG.

  As shown in FIGS. 1A and 1B, the printed wiring board 10 is provided with a cylindrical conductive through hole 100 penetrating the board. The first signal wiring layer 12 is formed with a conductive first signal wiring 102, and the second signal wiring layer 18 is formed with a conductive second signal wiring 104. 102 and the signal wiring 104 are connected (conductive) through the through hole 100.

  The conductive first ground layer 14 and the second ground layer 16 are arranged so as to face each other with the conductive conductive layer 15 interposed therebetween. Therefore, the first ground layer 14 and the second ground layer 16 have substantially the same potential (ground potential). As a result, the first ground layer 14, the conductive layer 15, and the second ground layer 16 constitute a ground layer 17.

  The conductive layer 15 can be made of, for example, a filler-based conductive resin in which metal fine particles are diffused or a metal material such as aluminum. Note that the material is not limited to these materials, and other materials may be used as long as they have conductivity.

  A power line 26 is provided on the first ground layer 14. The power line 26 is connected to a power line (not shown) provided on the first signal wiring layer 12 through a through hole (not shown), for example. The power supplied to the power supply wiring is supplied to various components such as an IC mounted on the substrate.

  A dielectric member 110 is filled around the power line 26. The dielectric member 110 insulates the power line 26 from the first ground layer 14 and the conductive layer 15.

  Similarly, a power line 30 is provided on the second ground layer 16, and a dielectric member 111 is provided around the power line 30. The dielectric member 111 insulates the power line 30 from the second ground layer 16 and the conductive layer 15.

  Further, in the ground layer 17 composed of the first ground layer 14, the conductive layer 15, and the second ground layer 16, as shown in FIG. The inner diameter r2 of the through hole 106 is larger than the outer diameter r1 of the through hole 100. That is, the through hole 100 is surrounded by the ground layer 17, thereby forming a coaxial transmission line that penetrates the substrate. A dielectric member 112 is filled between the through hole 100 and the through hole 106. Thereby, the through hole 100 and the ground layer 17 are insulated.

  As the dielectric members 110, 11, and 112, for example, general glass epoxy, high-speed glass ceramic, a glass cloth base material that is an ultrahigh-speed dielectric constant material, or the like can be used.

  FIG. 7 shows a conventional printed wiring board 200. As shown in FIG. 7, when the first ground layer 202 and the second ground layer 204 are not connected, a signal flowing through the signal wiring 206 is transmitted to the first ground layer 202 and the second ground through the first through hole 208. When the current flows across the ground layer 204 to the signal wiring 210 side, the return current is interrupted. As a result, signal transmission characteristics particularly in the GHz order are deteriorated, the signal is attenuated by the signal flowing across the first ground layer 202 and the second ground layer 204, and the return current is interrupted. Electromagnetic radiation is generated by the induced common mode current.

  On the other hand, in the printed wiring board 10 according to the present embodiment, the conductive layer 15 is provided between the first ground layer 14 and the second ground layer 16, and the first ground layer 14 and the second ground layer 16 are provided. Since the layer 16 is configured to conduct, it is possible to prevent the return current from being interrupted, to prevent the signal from being attenuated even by a signal in the GHz order, and to generate electromagnetic radiation due to the common mode current. Can be suppressed. This enables high-speed driving of signals.

  In addition, since the dielectric member 110 is provided between the power supply line 26 and the first ground layer 14 and the power supply line 26 and the first ground layer 14 are insulated by the dielectric member 110, the dielectric member Through 110, a power source having a low impedance with respect to the ground, that is, a power source that enables high-speed driving of signals can be obtained. Further, since the power supply line 26 is strongly capacitively coupled to the ground potential, when a signal wiring that straddles the power supply line 26 exists on the first signal wiring layer 12, the signal wiring is connected to GHz. Even when a high-frequency signal of the order flows, the return current for the signal is not interrupted, and the signal transmission characteristics can be improved. A dielectric member 111 is also provided between the power supply line 30 and the second ground layer 16, and this is also the same as described above.

  By the way, by changing the outer diameter r1 of the through hole 100 and the inner diameter r2 of the through hole 106, the characteristic impedance Z relating to the transmission line having the coaxial structure including the through hole 100 and the through hole 106 having the ground potential can be controlled. . The characteristic impedance Z is expressed by the following equation.

  Here, μ is the magnetic permeability of the dielectric member 112 between the through hole 100 and the through hole 106, and ε is the dielectric constant of the dielectric member 112 between the through hole 100 and the through hole 106.

  That is, when the magnetic permeability μ and the dielectric constant ε are constant, the characteristic impedance relating to the through hole 100 and the through hole 106 depends on the outer diameter r1 of the through hole 100 and the inner diameter r2 of the through hole 106.

  Therefore, the characteristic impedance relating to the through hole 100 and the through hole 106 is the characteristic impedance obtained in advance from the input / output characteristics of the first signal wiring 102, the second signal wiring 104, and the devices connected to these signal wirings. It is preferable to set the outer diameter r1 of the through hole 100 and the inner diameter r2 of the through hole 106 so as to be substantially coincident with each other. As is clear from the equation (1), when the characteristic impedance Z is desired to be increased, the outer diameter r1 of the through hole 100 may be decreased or the inner diameter r2 of the through hole 106 may be increased, and the characteristic impedance Z may be decreased. For this purpose, the outer diameter r1 of the through hole 100 may be increased or the inner diameter r2 of the through hole 106 may be decreased. In this way, by adjusting at least one of the outer diameter r1 of the through hole 100 and the inner diameter r2 of the through hole 106 to match the impedance of the signal transmission path, the signal quality deteriorates due to signal reflection even for signals in the GHz order. Can be further suppressed.

  When the magnetic permeability μ, the outer diameter r1 of the through hole 100, and the inner diameter r2 of the through hole 106 are constant, the characteristic impedance relating to the through hole 100 and the through hole 106 depends on the dielectric constant ε.

  Therefore, the characteristic impedance relating to the through hole 100 and the through hole 106 is the characteristic impedance obtained in advance from the input / output characteristics of the first signal wiring 102, the second signal wiring 104, and the devices connected to these signal wirings. A dielectric member 112 having a substantially constant dielectric constant may be used. For example, by reducing the dielectric constant, the characteristic impedance Z can be increased in the same manner as when the outer diameter r1 of the through hole 100 is reduced or the inner diameter r2 of the through hole 106 is increased, and by increasing the dielectric constant. The characteristic impedance Z can be lowered in the same manner as the outer diameter r1 of the through hole 100 is increased or the inner diameter r2 of the through hole 106 is decreased. In this way, by adjusting the dielectric constant of the dielectric member 112 between the through hole 100 and the through hole 106 to match the impedance of the signal transmission path, the signal quality deteriorates due to signal reflection even for signals in the GHz order. Can be further suppressed.

  As a method for manufacturing the printed wiring board 10, first, a concave portion for filling the dielectric member 110 is formed in the conductive layer 15 using a known method such as etching or cutting, and the dielectric member 110 is filled. The dielectric member 110 may be formed by any method of thermal means, chemical means, and mechanical means. Here, the thermal means is means for supplying heat to the filled dielectric member 110 and thermosetting it when, for example, a thermosetting conductive resin is used for the conductive layer 15. Is a means for curing the dielectric member 110 by a chemical reaction, and mechanical means include, for example, a means for fitting the dielectric member 110 into a recess formed in the conductive layer 15 when the solid dielectric member 110 is used. Say. The same applies to the dielectric member 111.

  After the dielectric members 110 and 111 are formed on the conductive layer 15, the metal forming the two first ground layers 14 and the second ground layer 16 is made conductive in the same manner as a conventional general printed wiring board manufacturing method. Formed on both sides of the layer 15, unnecessary portions of the metal are removed by means such as etching, and power lines 26 and 30 are formed.

  For example, the method described in Patent Document 4 can be used to form the through holes 100 and 106. In addition to this method, after the ground layer 17 is formed, a first through hole is formed by a cutting means such as a drill or a laser, and the through hole 106 is formed by plating the first through hole. After filling the through hole 106 with the dielectric member 112, the first prepreg layer and the first signal wiring layer 12 are formed on the first ground layer 14, and the second prepreg layer and the second ground layer 16 are formed on the second ground layer 16. The signal wiring layer 18 is laminated, a second through hole is formed by the cutting means in a region filled with the dielectric member 112, and the through hole 100 is formed by plating the second through hole. By forming the first signal wiring 102 on the first signal wiring layer 12 and the second signal wiring 104 on the second signal wiring layer 18 so as to be connected to the through hole 100, the printed wiring board 10. Make Door can be.

  As described above, the printed wiring board 10 can be manufactured without a large increase in cost by a process almost the same as that of the conventional multilayer printed wiring board.

  The present invention can also be applied to a printed wiring board as described in, for example, Patent Document 2 and Non-Patent Document 1, but two ground layers like the printed wiring board described in Patent Document 2 are used. There is no need for a large number of via holes connecting the two.

  FIG. 2 shows a specific example of a printed wiring board to which the present invention is applied. As shown in FIG. 2A, in the printed wiring board 160, the first signal wiring layer 12, the first ground layer 14, the second ground layer 16, and the second signal wiring layer 18 are made of the insulating material 20. Thus, a four-layer substrate having a multilayer structure is provided.

  FIG. 2B shows a plan view of the first ground layer 14. Note that FIG. 2A is a cross-sectional view taken along the line AA in FIG.

  As shown in FIGS. 2A and 2B, a conductive layer 15 is provided between the first ground layer 14 and the second ground layer 16. Thereby, the first ground layer 14 and the second ground layer 16 can be set to substantially the same potential.

  As shown in FIGS. 2A and 2B, a ground pattern 24 and a linear power supply line 26 are separately and independently formed on the first ground layer 14. In the second ground layer 16, a ground pattern 28 and a linear power supply line 30 are formed separately and independently.

  Further, the power supply line 26 and the power supply line 30 are formed on the inner side of the ground pattern 24 from the end of the substrate.

  A dielectric member 110 is provided between the power supply line 26 and the ground pattern 24 and the conductive layer 15, and a dielectric member 111 is provided between the power supply line 30 and the ground pattern 28 and the conductive layer 15. It has been.

  The power supply line 26 and the power supply line 30 are connected to each other through a via hole 32. For example, a positive terminal of a DC voltage power supply 34 mounted on the first signal wiring layer 12 is connected to the power supply line 26 via a via hole 35. The negative terminal of the DC voltage power supply 34 is connected to the ground pattern 24 via the via hole 37. As a result, a predetermined DC voltage Vcc is applied from the DC voltage power supply 34 to the power supply line 26 and the power supply line 30.

  The first signal wiring layer 12 is mounted with ICs (for example, digital ICs) 36, 38, 40, and 42 whose operating frequency and signal frequency are high frequencies (for example, several GHz). The power supply terminal 36V of the IC 36 is connected to the power supply line 26 via the connection pattern 44 and the via hole 46, and the ground terminal 36G of the IC 36 is connected to the first ground layer 14 via the via hole 48. As a result, the DC voltage Vcc is supplied from the power supply line 26 to the power supply terminal 36V, and the IC 36 becomes operable.

  The power supply terminal 38V of the IC 38 is connected to the power supply line 30 via the connection pattern 50 and the via hole 52, and the ground terminal 38G of the IC 38 is connected to the first ground layer 14 via the via hole 54. As a result, the DC voltage Vcc is supplied from the power supply line 30 to the power supply terminal 38V, and the IC 38 becomes operable.

  The power terminal 40V of the IC 40 is connected to the power line 26 via the connection pattern 56 and the via hole 58, and the ground terminal 40G of the IC 40 is connected to the first ground layer 14 via the via hole 60. As a result, the DC voltage Vcc is supplied from the power supply line 26 to the power supply terminal 40V, and the IC 40 becomes operable.

  The power supply terminal 42V of the IC 42 is connected to the power supply line 30 via the connection pattern 62 and the via hole 64, and the ground terminal 42G of the IC 42 is connected to the first ground layer 14 via the via hole 66. As a result, the DC voltage Vcc is supplied from the power supply line 30 to the power supply terminal 42V, and the IC 42 becomes operable.

The signal terminal 36S ₁ of IC36 is connected to one end of the second signal wiring layer 18 linear signal wiring 70 formed through the through hole 100A. The other end of the signal wiring 70 is connected to the signal terminal 38S _{1 of the} IC 38 through the through hole 72.

The through hole 100A is covered with a cylindrical through hole 106A formed in the ground layer 17, and a dielectric member 112A is filled between the through hole 100A and the through hole 106A. Similarly, the through hole 100B is covered with a cylindrical through hole 106B formed in the ground layer 17, and a dielectric member 112B is filled between the through hole 100B and the through hole 106B. For this reason, for example, signals are output across a plurality of layers from the signal terminal 36S _{1 of} the IC 36 to the signal terminal 38S ₁ of the IC 38 via the through hole 100A, the signal wiring 70, and the through hole 100B. Even when it flows, signal quality can be prevented from deteriorating and electromagnetic radiation can be suppressed.

IC36 signal terminal 36S ₂ is connected to one end of the second signal wiring layer 18 which is formed in linear signal lines 76 via the through hole 74. The other end of the signal wiring 76 is connected to the signal terminal 38S _{2 of the} IC 38 through the through hole 78. As a result, signals can be exchanged between the IC 36 and the IC 38.

Further, the signal terminal 40S ₁ of the IC 40 is connected to the signal terminal 42S ₁ of the IC 42 by the signal wiring 80, and the signal terminal 40S ₂ of the IC 40 is connected to the signal terminal 42S ₂ of the IC 42 by the signal wiring 82. As a result, signals can be exchanged between the IC 40 and the IC 42.

  As described above, the printed wiring board 10 does not have a power supply layer facing the first ground layer 14 and the second ground layer 16, and the power supply line 26 is provided on the first ground layer 14. Since the power supply line 30 is formed in 16, electromagnetic wave radiation due to resonance between the power supply layer and the ground layer does not occur, and since the power supply line is provided in the inner layer, the mounting density of the signal wiring layer is reduced. Can be increased. Further, a dielectric member 110 is provided between the power supply line 26 and the ground pattern 24 and the conductive layer 15, and a dielectric member 111 is provided between the power supply line 30, the ground pattern 28 and the conductive layer 15. Therefore, it is possible to obtain a power source having a low impedance with respect to the ground and to drive a signal at high speed. In addition, since the power supply line and the ground pattern are strongly capacitively coupled, even if the signal current flowing through the signal wiring is high frequency, the return current is not interrupted, and electromagnetic radiation can be more effectively prevented. Further, unlike the technique disclosed in Patent Document 2, it is not necessary to avoid the signal wiring straddling the power supply wiring, and the degree of freedom in wiring design can be increased.

  In the present embodiment, the conductive layer 15 includes the first ground layer 14 and the second ground layer in all regions except the portion where the dielectric members 110 and 111 are formed when the printed wiring board 10 is viewed in plan. The case where the conductive region is formed so as to be connected to the layer 16 has been described. However, like the printed wiring board 10A illustrated in FIG. 3, the periphery of the power supply lines 26 and 30 when the printed wiring board 10 is viewed in plan view and The conductive region 120 that connects the first ground layer 14 and the second ground layer 16 may be formed only around the through hole 106, and the other region may be configured by the insulating material 20. Thereby, the conductive region of the conductive layer 15 can be reduced, and it can be manufactured at low cost.

  Further, as in the printed wiring board 10B shown in FIG. 4, the conductive layer 15 is formed using a conductive member having a predetermined rigidity, and the first ground layer 14 and the second ground layer 14 are omitted. Also good. Thereby, the conductive layer 15 functions as a ground layer. Such a printed wiring board 10B can be manufactured by a manufacturing method substantially similar to the manufacturing method described above by omitting the step of forming the first ground layer 14 and the second ground layer 14. For this reason, the structure of the printed wiring board can be simplified and can be manufactured at low cost.

  In the present embodiment, the case where the signal current flows across the two ground layers via the through hole 100 has been described. However, the present invention can be applied not only to the signal current but also to the power supply current. The effects of the present invention can be obtained.

(Example)
Next, examples of the present invention will be described. FIG. 5 shows a simulation of the relationship between signal attenuation and frequency in the printed wiring board 10 shown in FIG. 1 and the conventional printed wiring board 200 shown in FIG. 7 by the FDTD (Finite Difference Time Domain Method) method. Results are shown. Further, FIG. 6A shows a result of a simulation of a far electric field in the printed wiring board having the conventional structure shown in FIG. 7 by the FDTD method, and FIG. 6B shows a result in the printed wiring board 10 shown in FIG. The results of simulating the far electric field by the FDTD method are shown.

  As a simulation condition in the printed wiring board 10, the distance between the first ground layer 14 and the second ground layer 16 is 0.9 mm, the first signal wiring 102 on the first signal wiring layer 12, the second The second signal wiring 104 of the signal wiring layer 18 has a width of 0.5 mm, and the distance between the signal wiring 102 and the first ground layer 14 and the distance between the signal wiring 104 and the second ground layer 16 are 0.3 mm. A microstrip line was used. The outer diameter of the through hole 100 was 0.5 mm, and the inner diameter of the through hole 106 was 2 mm. The dielectric constant ε of the dielectric material such as the insulating material 20 was 4.7, and the metal parts such as the wiring were all perfect conductors. The same applies to the conditions of other printed wiring boards.

  The “conventional structure” shown in FIG. 5 is a simulation result of the printed wiring board 200 shown in FIG. The “neighboring via” is a via hole having the same diameter as the through hole 208 at a position 2.5 mm away from the through hole 208 of the printed wiring board 200 shown in FIG. 7, and is formed between the first ground layer 202 and the second ground layer 204. It is a simulation result of the printed wiring board provided between. “Single plane” is a simulation result of a printed wiring board having a structure in which a single ground layer is sandwiched between a first signal wiring layer and a second signal wiring layer. The through hole has a hole diameter of 2 mm, the width of the microstrip line, that is, the signal wiring formed in the first signal wiring layer and the signal wiring formed in the second signal wiring layer is 0.5 mm, the microstrip line. , That is, the distance between the first signal wiring layer and the ground layer and the distance between the second signal wiring layer and the ground layer are both 0.3 mm. The “new structure” is a simulation result of the printed wiring board 10 according to the present invention shown in FIG.

  Note that the simulation was performed on the ends of the wiring and the ground layer as Mur1st absorption boundary conditions.

  FIG. 5 shows the relationship between the signal attenuation and the frequency when a signal flows from the first signal wiring layer to the second signal wiring layer through the through hole.

  As shown in FIG. 5, in the “conventional structure”, the signal frequency is attenuated by about 1.4 dB at the maximum at 2 to 3 GHz, and when the signal reciprocates and passes through two through holes, the attenuation becomes 2.8 dB. It can be said that the signal transmission in the GHz order is not practical.

  Although the “neighboring via” is improved as compared with the “conventional structure”, the effect is only about 0.2 dB.

  On the other hand, in the “new structure” which is the simulation result of the printed wiring board 10 according to the present invention, the attenuation is reduced as compared with the “conventional structure” and “neighboring via”, and a single ground layer is used. Compared with a “single plane” which is a simulation result of a printed wiring board having a structure in which the return current is not interrupted, the attenuation is almost the same.

  As a result of analysis by the inventors, it has been found that the amount of signal attenuation in the printed wiring board having the conventional structure shown as “conventional structure” increases substantially in proportion to the interval between the two ground layers. That is, there is no problem with a single ground layer, but when there are two ground layers, the amount of signal attenuation changes depending on the interval between them. On the other hand, the printed wiring board according to the present invention indicated by “new structure” has two grounds as shown in the comparison with the simulation result of the printed wiring board provided with the single ground layer indicated by “single plane”. Good signal transfer characteristics are obtained regardless of the layer spacing.

  That is, if the distance between the first signal wiring layer and the first ground layer, which is the outer layer, or the distance between the second signal wiring layer and the second ground layer is reduced in order to reduce the impedance of the signal wiring, In order to avoid the influence of heat caused by the warpage of the board and the solder at the time of component mounting, the interval between the first ground layer and the second ground layer must be increased in a general printed circuit board. A printed wiring board has no adverse effect on signal transmission characteristics, and can be said to be suitable for high-speed transmission in the order of GHz.

  FIG. 6 (A) shows horizontal polarization and vertical polarization of a far electric field as representing changes in electromagnetic wave radiation when a signal flows across a plurality of layers in the printed wiring board 200 having the conventional structure shown in FIG. FIG. 6B shows the result of simulating the wave, and the result of simulating the horizontal polarization and the vertical polarization of the far electric field in the printed wiring board 10 described in the first embodiment in the same manner as described above. . In both cases, a printed wiring board was installed horizontally, and a 1 GHz far electromagnetic field observed from the horizontal direction was simulated.

  As shown in FIGS. 6A and 6B, in the conventional printed wiring board, the electric field strength in the horizontal polarization plane is about 11 dB larger than that of the printed wiring board 10 according to the present invention. This is because the horizontal common mode current generated by the interruption of the return current when a signal flows across a plurality of ground layers is dominant for electromagnetic radiation.

  In order to prevent the calculation from being diverged in this simulation, Mur1 order absorption boundary conditions are used at the ends of the two ground layers, and an electromagnetic field due to a via hole for signal transmission is provided as an inner layer, for example. In the actual case of coupling with the electromagnetic field between the layer and the ground plane, the difference from the printed wiring board according to the present invention is further increased. For example, as shown in "Relationship between via wiring and unwanted radiation in multilayer printed circuit boards" (Electronic Information and Communication Society General Conference, B-4-2 2002-3) Since resonance between the provided power supply layer and the ground layer is excited, electromagnetic wave radiation is increased. However, such a bad influence does not occur in principle in the printed wiring board according to the present invention.

  That is, according to the present invention, signal quality deterioration is suppressed by through holes penetrating a plurality of ground layers, and it is possible to cope with ultra-high-speed transmission on the order of GHz on a printed wiring board. At the same time, further suppression of common mode noise is possible, contributing to low EMI. Further, the present invention does not require a large change in the structure of the printed wiring board itself from a general one, can reduce electromagnetic wave radiation countermeasure components, and can reduce the cost.

  Furthermore, according to the present invention, since the power supply wiring can be configured with a very low impedance, it becomes possible to supply a high-speed transient current with a low impedance to a device that drives a signal at a high speed. Suitable for order signal processing. Further, since the power supply wiring according to the present invention is closely capacitively coupled to the ground layer, the feedback current of the high-speed signal wiring straddling the power supply wiring is not interrupted in high frequency, and the signal quality can be improved. . Further, there is no need to provide via holes for connecting a large number of grounds as in the printed wiring board described in Patent Document 2, and there is no need to place signal wiring avoiding power supply wiring. There is an advantage that the degree of freedom of wiring is not impaired.

  Furthermore, according to the present invention, it is not necessary to greatly change the structure of the printed wiring board itself from a general one, and the number of electromagnetic wave radiation countermeasure parts can be rather reduced, so that the cost can be reduced.

  The above simulation result applies not only to signal transmission but also to high-speed transient current transmission characteristics of the power source.

(A) is AA sectional drawing of the printed wiring board which concerns on this invention shown to (B), (B) is a schematic plan view of (A). (A) is AA sectional drawing of the printed wiring board which concerns on the specific example of this invention shown to (B), (B) is a schematic plan view of (A). It is sectional drawing of the printed wiring board which concerns on the modification of this invention. It is sectional drawing of the printed wiring board which concerns on the modification of this invention. It is a diagram which shows the result of having simulated about the relationship between the attenuation amount of the signal in each printed wiring board, and a frequency. (A) is a diagram which shows the result of having simulated about the far electric field in the printed wiring board of a conventional structure, (B) is a diagram which shows the result of having simulated about the far electric field in the printed wiring board concerning the present invention. (A) is AA sectional drawing of the conventional printed wiring board shown to (B), (B) is a schematic plan view of (A).

Explanation of symbols

10, 10A, 10B Printed wiring board 12 First signal wiring layer 14 First ground layer 15 Conductive layer 16 Second ground layer 17 Ground layer 18 Second signal wiring layer 20 Insulating material 26, 30 Power supply line 100, 106 through-hole 102 first signal wiring 104 second signal wiring 110, 111, 112 dielectric member

Claims (5)

In the printed wiring board in which the wiring layer, the first ground layer, and the second ground layer are laminated,
A power supply wiring provided on at least one of the first ground layer and the second ground layer so as to straddle a signal wiring provided in the wiring layer when viewed in plan ;
Conductive interlayer connection means connected to the wiring layer and penetrating the first ground layer and the second ground layer;
A conductive region provided between the first ground layer and the second ground layer and conductively connecting the first ground layer and the second ground layer includes at least a periphery of the power supply wiring and the A conductive layer provided around the interlayer connection means;
A first dielectric member provided around the power supply wiring and insulating the power supply wiring and the conductive region;
A second dielectric member provided around the interlayer connection means and insulating the interlayer connection means and a conductive region provided around the interlayer connection means;
A printed wiring board comprising:   The printed wiring board according to claim 1, wherein the conductive region is provided over the entire conductive layer.   The printed wiring board according to claim 2, wherein the first ground layer, the conductive layer, and the second ground layer are integrated by a single conductive member.   The outer diameter of the interlayer connection means and the circumference of the interlayer connection means are set so that the characteristic impedance related to the conductive region around the interlayer connection means and the interlayer connection means and the characteristic impedance related to the wiring of the wiring layer are substantially the same. The printed wiring board according to any one of claims 1 to 3, wherein at least one of the inner diameters of the conductive regions is adjusted.   The dielectric constant of the second dielectric member is adjusted so that the characteristic impedance related to the interlayer connection means and the conductive region around the interlayer connection means is substantially the same as the characteristic impedance related to the wiring of the wiring layer. The printed wiring board according to any one of claims 1 to 3, wherein

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