JP5353042B2 - Printed wiring board - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To suppress an interference level between a plurality of power supply systems in a high frequency band of 1 GHz or more, and to enable a high-density packaging instrument utilizing the high frequency band to be made. <P>SOLUTION: Power supply planes 4, 5 isolated by a slit 6 are formed inside the same layer through an insulating layer 3 on a grounding layer 2, a grounding plane 8 is formed on the side opposite to the grounding layer 2 with respect to a power supply layer and across an insulating layer 7 with respect to the power supply layer so as to coat the slit 6 completely, and the grounding layer 2 is connected to the grounding plane 8 by a plurality of vias 9 disposed so as to have an appropriate interval therebetween. <P>COPYRIGHT: (C)2010,JPO&amp;INPIT

Description

  The present invention relates to a printed wiring board capable of suppressing / reducing electromagnetic interference in a printed circuit board in a high frequency region, particularly related to a power supply layer and a ground layer.

  In recent years, printed wiring boards constituting electronic devices tend to have higher frequencies and higher density mounting. Accordingly, a part of the power supplied to the IC or the like is lowered in voltage, and a plurality of power supplies are required for consistency with other logic. In recent years, devices with built-in wireless circuits are also increasing, and printed circuit boards in which digital circuits and analog circuits are mixed are used in the devices. In such printed circuit boards, it is possible to separate digital and analog power supplies. It is common.

  In a printed circuit board mounted on an electronic device, when there are a plurality of power supply systems, conventionally, it has been common to form a plurality of power supply planes in the same power supply layer and separate them by slits (for example, Patent Documents) 1). In conventional equipment, the frequency is not as high as that of current circuits, and in a relatively low frequency region, if the power supply system is separated by a slit or the like, it is not so much a problem, and so far no major problem has been seen. However, in recent years, especially in digital circuits, higher frequencies have progressed, and a large influence is appearing between analog circuits and digital circuits in the operating frequency band of wireless analog circuits, which is problematic as electromagnetic interference in equipment. ing.

The power switching noise components of LSIs and ICs constituting digital circuits on a printed circuit board increase in strength as the operating frequency increases. The frequency component whose strength has increased flows into the power supply system of the digital circuit and propagates directly to the analog power supply system, or noise radiated from the end of the digital power supply layer of the printed circuit board affects the analog system.
JP-A-11-261238

Usually, as a method of suppressing interference between an analog circuit and a digital circuit, a method of enclosing the analog circuit part with a metal shield cover or the like is common. Noise radiated from the RF part of the substrate can be suppressed and reduced with a metal shield cover or the like. However, it is difficult to suppress the influence of noise due to mutual electromagnetic interference between the digital circuit portion and the analog circuit portion inside the substrate with the surface-mounted metal shield cover. In the current board configuration, the digital power supply system and the analog power supply system in the board are separated from each other by power supply or ground. That is, most of the analog power supply system and the digital power supply system are separated by slits in the power supply layer or ground layer. In addition, as a method of connecting while suppressing interference noise between different power supply systems, when slits similar to the power supply layer are formed in the ground layer, and components such as capacitors and ferrite beads are used to connect the ground layers There is also. The method of using components to connect different power supply systems depends on the component characteristics. Generally, the higher the frequency, the higher the parasitic capacitance and inductance, and the higher the possibility that the desired characteristics cannot be obtained. .
Conventionally, the power supply system separation method using only slits has a problem that the effect of suppressing electromagnetic interference due to high frequency noise between the analog and digital power supply systems is limited as shown below. there were. In a printed circuit board in which two or more power supply systems are formed by providing slits in the power supply layer, interference between power supply systems can be reduced by widening the slit interval in the frequency band of 1 GHz or less. If a resonance phenomenon that occurs between the power supply and the ground or a common mode resonance phenomenon in the ground layer creates a band where the electromagnetic interference between the power supply systems cannot be suppressed, and the frequency band falls within the signal band of the wireless device, electromagnetic interference There arises a problem that noise cannot be reduced.

  As a result of analysis by the present inventors, in a high frequency region of 1 GHz or more, a plurality of frequency regions and slits that can suppress the interference degree by increasing the interval of the slits for separating the power supply wiring patterns provided in the power supply layer It has been found that there are a plurality of frequency regions in which the degree of interference does not change even when the interval is changed, and these frequency regions mainly depend on the size of the substrate (more precisely, the sizes of the power supply layer and the ground layer). In the frequency region where the degree of electromagnetic interference does not change with respect to the change in the slit interval, it is shown that a resonance phenomenon with a size in which the power supply systems are combined is likely to occur in the high frequency region due to interference between the power supply systems. Therefore, depending on the size of the substrate or the size of the power supply system wiring pattern, electromagnetic interference cannot be suppressed by a normal method in a necessary frequency band, particularly in a high frequency region such as a microwave or millimeter wave band.

  An object of the present invention is to solve the above-mentioned problems of the prior art, and the object thereof is a printed circuit board in the case where there are a plurality of types of power supply systems or a mixture of digital power supplies and analog power supplies. When there are a plurality of power supply wiring patterns and ground layers in the same layer of the power supply layer, a plurality of power supply wirings in the same layer are compared with the case of using only a separation structure by a power supply interlayer slit which is conventionally used. An effect of suppressing interference noise between patterns is to be obtained.

In order to achieve the above object, according to the present invention, a power supply layer in which a plurality of power supply planes separated from each other by a slit are formed, and disposed on one surface of the power supply layer via an insulating layer. A ground plane formed on the side of the power supply layer opposite to the side on which the ground layer is provided so as to cover the slit through an insulating layer; and the ground layer and the ground plane are connected to each other. A plurality of vias , wherein the vias are formed along the slits of the power supply layer through both sides of the slits, and an interval between the vias passing through the same power supply layer is a target frequency. Provided is a printed wiring board characterized in that it is one sixth or less of the effective wavelength corresponding to the upper limit frequency of the band .

  In the printed wiring board according to the present invention, facing the ground layer, the inner layer has two or more types of power planes separated by the slits in the same layer, and the four slits dividing the different power planes are: Surrounded by a conductor having the same potential as the ground layer. According to the embodiment of the present invention, a ground plane is formed above the slit so as to cover the slit, and the ground layer and the ground plane are connected by a via formed along the slit. According to this configuration, it is possible to suppress propagation of electromagnetic waves having a certain wavelength or more (for example, resonance noise) between the power supply planes. Therefore, the resonance noise between the power supply and ground layers consisting of multiple power supply types affects the other, that is, a great effect can be obtained when suppressing interference with other power supply systems, and between different power supply planes in the high frequency region. As compared with the structure in which only the slits provided for separating the two are formed, it is possible to provide a printed wiring board capable of suppressing interference between power supply systems that is larger.

Hereinafter, embodiments of the printed wiring board of the present invention will be described in detail with reference to the drawings.
[First Embodiment]
FIG. 1 is an exploded perspective view showing the structure of a power supply system in the printed wiring board according to the first embodiment of the present invention. However, in FIG. 1, the via 9 does not actually exist in the illustrated part, but merely shows the position of the projected via. 2A and 2B are top views (third insulating layer) of the printed wiring board in the vicinity of slits provided to separate different power wiring patterns in the same layer in the printed wiring board of FIG. 7 is seen through, which is the same in other top views) and a cross-sectional view. FIG. 3 is a perspective view illustrating only a power supply system (power supply layer and ground layer) in a printed wiring board having a plurality of conventional power supply systems (assuming that there are two types of power supply systems in the figure).

1 to 3, 1 is a first insulating layer, 2 is a ground layer, 3 is a second insulating layer, 4 is a first power plane, 5 is a second power plane, and 6 is a first power plane 4 and a first power plane. 2 is a slit separating the power plane 5, 7 is a third insulating layer, 8 is a ground plane formed on the slit 6 so as to completely cover the slit 6, and 9 is a slit 6 on both sides of the slit 6. Are vias connected to the ground layer 2 and the ground plane 8. As shown in FIG. 3, in the conventional power supply system, only the slit 6 is provided between the power supply planes 4 and 5 in order to separate different power supply systems. On the other hand, in the printed wiring board of the present embodiment shown in FIGS. 1 and 2, a ground plane 8 is provided on the opposite side of the power supply layer from the ground layer 2 so as to completely cover the slit 6 of the power supply layer. Vias 9 connecting the ground layer 2 and the ground plane 8 are arranged at regular intervals on both sides of the slit 6. The maximum distance between adjacent vias should be at least one-sixth or less of the effective wavelength in the substrate corresponding to the frequency band to be used in order to obtain a higher interference degree suppressing effect.
In the present embodiment, the via 9 is formed in the same manner with the slit 6 interposed therebetween. That is, the via 9 is arranged symmetrically with respect to a center line passing through the center of the slit 6.
In FIG. 1 and FIG. 2, the signal wiring is not shown, but the ground plane 8 on the back surface side of the first insulating layer 1 and the front surface side of the third insulating layer 7 is not formed in the signal wiring. Formed in the region. The same applies to other embodiments.

In order to confirm the effect of the printed wiring board of the present invention, the results of three-dimensional electromagnetic field analysis are shown below. FIG. 4 shows the S21 amplitude of the S parameter obtained by analysis in order to evaluate the degree of interference between different power supply systems when the slit interval provided for separating the power supply systems by the conventional method is 0.2 mm. It is a calculation result. 4, when the degree of interference of the problem, S21 the peak value of the amplitude is important, and to assess the degree of interference with a peak value at S ₂₁ magnitude.

  FIG. 5 shows a model in which there is only a slit formed between power supply wiring patterns conventionally used for separating power supply systems when a plurality of power supply systems exist, and the slit interval is 0.2 mm. , 0.5mm and 1.0mm, the values at each peak frequency are shown for the degree of interference between one power supply system and the other power supply system (here, S parameter transmission characteristics between power supply systems) It is a thing. FIG. 5 shows that when the slit interval is changed, the interference degree tends to be reduced as the slit interval is larger in a region of 1 GHz or less and in a part of the frequency (for example, around 1.5 GHz). On the other hand, in other frequency regions (for example, near 1 GHz, near 2.5 GHz, or 3-4 GHz region), it can be seen that the change in the interference degree is extremely small even if the slit width is changed. Therefore, when the conventional method is used, there is a high possibility that a relatively large interference occurs in a region where electromagnetic interference is a problem depending on the size of the substrate and the size of the power supply system.

  FIG. 6 shows the analysis result of the degree of interference between two power supply systems when the maximum interval between adjacent vias is changed in the structure according to the first embodiment of the present invention shown in FIGS. It is a figure. If the maximum distance between adjacent vias is wide, the interference level may be suppressed if the frequency domain is fixed compared to the slit alone, but there is also a frequency domain that increases, and all frequencies below 5 GHz. The peak value that maximizes the degree of interference with the region is almost unchanged. On the other hand, when the via interval is narrowed, the maximum peak value can be suppressed in addition to the fact that the interference is reduced in the frequency region in the figure compared to the case of only slits in all regions below about 5 GHz. I understand that. As a result of further analysis, if the effective wavelength in the substrate with respect to the upper limit of the frequency range where the maximum distance between adjacent vias is desired to be reduced to about 1/6 or less, a suppression effect on the interference degree can be expected in that frequency range. I understood.

[Second Embodiment]
FIGS. 7A and 7B are a top view and a cross-sectional view showing the vicinity of the slit portion provided to separate different power supply planes of the printed wiring board according to the second embodiment of the present invention. is there. The configuration of the printed wiring board according to the present embodiment is basically the same as that of the first embodiment, and a difference is that vias are additionally arranged. That is, in the printed wiring board according to the present embodiment, the vias 9 that connect the ground layer 2 and the ground plane 8 are also arranged inside the slit in addition to those arranged on both sides of the slit 6.

  Results obtained by performing a three-dimensional electromagnetic field analysis for confirming the effect on the printed wiring board having the structure of FIG. 7 showing the second embodiment are shown below. The structure of the printed wiring board is the same as that of the first embodiment shown in FIG. 2, and is a via that connects the wiring pattern disposed on the opposite side of the ground layer with the power supply layer as the center, and the ground layer. In this case, for example, a plurality of vias are provided at the center of the slit of the power supply layer. When the degree of interference between the power supply systems including the two power supply layers and the ground layer in the same layer of the printed wiring board shown in FIG. 7 was calculated, the result shown in FIG. 8 was obtained. FIG. 8 also shows a calculation result using a model of a structure in which a via is provided only at the center of the slit formed in the power supply layer. In this case, the effect of suppressing the interference degree is insufficient. On the other hand, as shown in FIG. 8, in addition to the configuration of the first embodiment, by adding the via 9 to the inside of the slit 6 (in the calculation, the center of the slit), a further effect of suppressing the interference can be obtained. I understand that. Thus, it has been found that if the structure of FIG. 7 is used, an effect of reducing the interference degree can be expected in substantially the same frequency range as in the first embodiment.

[Third Embodiment]
FIGS. 9A and 9B are a top view and a sectional view showing the vicinity of a slit portion provided for separating different power supply planes of a printed wiring board according to the third embodiment of the present invention. is there. The printed wiring board according to the present embodiment has the same structure as that of the first embodiment shown in FIG. 2 except that a slit 2a is provided in the ground layer 2 in the present embodiment. . That is, in the printed wiring board according to the present embodiment, the slit 2a having the same width is formed in the power supply layer 2 at the same position as viewed in projection from the slit 6 formed in the power supply layer. This is the same as the first embodiment.

  The result of conducting a three-dimensional electromagnetic field analysis for confirming the effect on the printed wiring board having the structure of FIG. 9 showing the third embodiment is shown below. The structure of the printed wiring board is the same as that of the first embodiment shown in FIG. 2, but a model of a structure in which a slit is formed in the ground layer as in the power supply layer was analyzed. When the interference degree between the two power supply layers formed in the same layer and the power supply system including the ground layer shown in FIG. 9 is calculated, as shown in FIG. It was found that the effect of reducing the interference degree can be expected in the same frequency range even in the structure of FIG. 9 which is obtained in the same manner as the second embodiment and is the third embodiment.

  In addition, the width of the ground plane 8 arranged with the third insulating layer 7 separated from the power supply layer on the opposite side to the ground layer with the power supply layer as the center is similarly arranged on both sides of the slit between the power supply planes. A three-dimensional electromagnetic field analysis was also performed when the dimensions were sufficiently larger than a plurality of via positions. In this case, when the interference degree was the wiring pattern width of the structure shown in the first and second embodiments. In comparison, it has been found that there is a frequency region where the suppression effect on the interference degree deteriorates. Therefore, in order to make the effect of suppressing the interference degree more effective, it is desirable that the width of the ground plate formed at the position where the power supply layer is sandwiched between the ground layers is made large enough to cover the position of the via.

[Fourth Embodiment]
11A and 11B are a top view and a cross-sectional view showing the vicinity of a slit portion provided for separating different power supply planes of a printed wiring board according to the fourth embodiment of the present invention. is there. The printed wiring board according to the present embodiment is different from that of the first embodiment in the planar shape of the vias, and there is no other change. In the first embodiment shown in FIG. 2, the via 9 has a cylindrical shape. However, in the printed wiring board of the present embodiment, the via is formed into a rectangular via 10 having an elongated planar shape. ing.
When a three-dimensional electromagnetic field analysis is performed on the printed wiring board having the structure of the fourth embodiment shown in FIG. 11, the same effect as that obtained when the via interval is reduced in the first embodiment can be obtained. I understood that.
Note that the fourth embodiment shown in FIG. 11 is a modification of the first embodiment, but similar changes are made to the vias of the second and third embodiments. May be added. Furthermore, the planar shape of the via may be an elliptical shape or a shape obtained by rounding the four corners of the rectangle instead of the rectangle.

[Fifth and sixth embodiments]
12A and 12B are a top view and a partially enlarged view showing the vicinity of a slit portion provided to separate different power supply planes of a printed wiring board according to the fifth embodiment of the present invention. FIG. 13 is a top view showing the vicinity of the slit portion provided for separating different power supply planes of the printed wiring board according to the sixth embodiment of the present invention. Up to the fourth embodiment, only the structure in which the slit provided to separate different power planes in the power supply layer in the printed wiring board crosses the board has been shown. In practice, it is often seen that the slit does not cross the substrate linearly when forming the power supply layer.
In the printed wiring board according to the fifth embodiment shown in FIG. 12, the first power plane 4 and the second power plane 5 are separated by the slit 6 formed in an L shape. On the power supply layer, an L-shaped ground plane 8 is formed so as to completely cover the slit 6 via an insulating layer, and the via 9 connecting the ground plane 8 and the ground layer has an L-shaped slit. 6 on both sides. In the printed circuit board according to the sixth embodiment shown in FIG. 13, the first power plane 4, the second power plane 5, and the third power plane 11 are separated by the slit 6 formed in a T shape. ing. On the power supply layer, a T-shaped ground plane 8 is formed so as to completely cover the T-shaped slit 6 via an insulating layer, and a via 9 connecting the ground plane 8 and the ground layer is formed by T It is formed on both sides of the letter-shaped slit 6.

In the above embodiment, an example related to a printed wiring board has been shown as an embodiment of the present invention. However, a similar structure has a wiring structure in a semiconductor package such as SIP (System in Package) or SOP (System on Package), and SOC. Needless to say, the present invention can be applied to a chip level wiring structure such as (System on Chip) and is effective.
Further, in the above embodiment, a pair of ground layer and power supply layer has been described as a four-layer multilayer wiring board. However, the present invention has several pairs of ground layer and power supply layer, and several tens of layers exist. This can also be applied to multilayer wiring boards. In that case, the present invention can be applied only to a pair of a ground layer and a power supply layer, and the present invention can also be applied to a plurality of pairs of ground layers and power supply layers.

1 is a schematic perspective view showing a configuration of a printed wiring board according to a first embodiment of the present invention. 1 is a schematic top view and cross-sectional view showing a configuration of a printed wiring board according to a first embodiment of the present invention. The schematic perspective view which shows the structure of the printed circuit board for isolate | separating the several power supply system used conventionally. The figure which shows the calculation result of the electromagnetic interference degree between two power supply systems in the structure of the printed circuit board for isolate | separating the several power supply system used conventionally. The figure which shows the calculation result of the electromagnetic interference degree at the time of changing the slit space | interval between two power supply systems by the structure of the printed circuit board for isolate | separating the several power supply system used conventionally. The figure which shows the electromagnetic interference degree between two power supply systems in the structure of the printed circuit board which concerns on the 1st Embodiment of this invention. The top view and sectional drawing in the slit part vicinity of the printed wiring board which concerns on the 2nd Embodiment of this invention. The figure which shows the electromagnetic interference degree between two power supply systems in the structure of the printed circuit board which concerns on the 2nd Embodiment of this invention. The top view and sectional drawing in the slit part vicinity of the printed wiring board concerning the 3rd Embodiment of this invention. The figure which shows the electromagnetic interference degree between two power supply systems in the structure of the printed circuit board which concerns on the 3rd Embodiment of this invention. The top view and sectional drawing in the slit part vicinity of the printed wiring board concerning the 4th Embodiment of this invention. The top view in the slit part vicinity of the printed wiring board which concerns on the 5th Embodiment of this invention. The top view in the slit part vicinity of the printed wiring board which concerns on the 6th Embodiment of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 1st insulating layer 2 Ground layer 2a Slit 3 2nd insulating layer 4 1st power plane 5 2nd power plane 6 Slit 7 3rd insulating layer 8 Ground plane 9 Via 10 Rectangular via 11 3rd power plane

Claims (5)

A power supply layer in which a plurality of power supply planes separated from each other by a slit are formed; a ground layer disposed opposite to one surface of the power supply layer via an insulating layer; and the ground layer of the power supply layer a ground plane formed as the opposite side through an insulating layer overlying said slit to be side, a plurality of vias for connecting the ground plane and the ground layer, the printed wiring board having the Vias are formed along the slit of the power supply layer and through both sides of the slit, and the interval between vias passing through the same power supply layer is 1/6 of the effective wavelength corresponding to the upper limit frequency of the target frequency band. A printed wiring board characterized by the following . The printed wiring board according to claim 1 , wherein the vias are arranged symmetrically with respect to a center line passing through a center of the slit. In addition to the sides of the via of the slit, printed according to claim 1 or 2, characterized in that vias for connecting the ground plane and the ground layer is formed through the interior of the slit Wiring board. Printed circuit board according to any one of claims 1 to 3, characterized in that the slits of the same pattern as the slits are also formed on the ground layer. The ground plane, printed circuit board according to any one of claims 1 to 4, characterized in that it is locally formed along the slit.

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