KR100965264B1 - Electromagnetic bandgap structure and printed circuit board - Google Patents

Abstract

Electromagnetic bandgap structure according to an embodiment of the present invention, two power supply layers are located separately on the same plane; A ground layer positioned on a plane different from the two power layers; A dielectric layer interposed between the two power layers and the ground layer; Two first conductor walls formed through the dielectric layer to protrude from each of the two power layers toward the ground layer at positions adjacent to the boundary between the two power layers; And a second conductor wall formed through the dielectric layer to have a shape protruding from the ground layer toward the power supply layer at a position corresponding to the boundary between the two power supply layers. In addition, according to the present invention, a printed circuit board including the electromagnetic bandgap structure may be provided.

Printed circuit board, electromagnetic bandgap structure, switching noise, conductor wall.

Description

Electromagnetic bandgap structure and printed circuit board

The present invention relates to a printed circuit board, and more particularly, to an electromagnetic bandgap structure that suppresses noise transmission in a power network and a printed circuit board including the same.

Recently, as mobility is important, various devices such as mobile communication terminals, PDAs (Personal Digital Assistants), notebook computers, and DMB (Digital Multimedia Broadcasting) devices capable of wireless communication are being released.

The devices include a printed circuit board on which analog circuits (ie RF circuits) and digital circuits are mounted in combination for wireless communication.

Accordingly, electromagnetic waves caused by the operating frequency of the digital circuit and the harmonics are transmitted to the RF circuit, thereby causing a problem that prevents the correct operation of the RF circuit. In particular, SSN (Simultaneous Switching Noise) is one of the major factors causing the performance degradation in modern high-performance systems with a combination of digital and RF circuits. SSNs occurring in digital circuits or systems have a very fatal effect on RF circuits or systems. For this reason, the power of the digital circuit and the RF circuit is separated and used (see FIG. 2A to be described later). However, since the ground is shared by the two circuits, the switching noise is transmitted even in the high frequency region even if the power is disconnected from the printed circuit board.

For this reason, a high-impedance surface has been introduced as an electro-magnetic bandgap structure that can be included in a printed circuit board to prevent transmission of the switching noise. It is generally named coplanar EBG. Such a coplanar EBG structure has a form in which EBG cells having a characteristic of not passing a specific frequency are repeatedly formed in one of a power supply layer and a ground layer.

1A is a perspective view of a printed circuit board including a coplanar EBG structure according to the prior art, and FIG. 1B is a plan view of the coplanar EBG structure shown in FIG. 1A.

1A and 1B, two printed circuit boards including a ground layer 210, a dielectric layer 230, and a power supply layer 220 are illustrated, and the power supply layer 220 has a large area. Metal patch 220a and a plurality of metal branches 220b having a small area. At this time, any two adjacent metal patches 220a are electrically connected through the metal branch 220b, and this form is repeatedly formed over the entire surface of the power supply layer 220.

Here, the large area metal patches 220a on the same plane form a low impedance region, and the small area metal branches 220b form a high impedance region. Therefore, the coplanar EBG structure has a form in which the low impedance region and the high impedance region are alternately arranged, thereby performing a function as a band reject filter that can shield noise of a specific frequency band.

However, the coplanar EBG structure according to the prior art has a wide area and a narrow area over the entire area (total area) of the power layer or ground layer to function as a signal transfer layer. There is a big problem in design constraints in the manufacture of the substrate in that it must be repeatedly arranged and formed.

In addition, in actual printed circuit boards, signal transmission between electronic devices located on the top surface of the substrate, electronic circuits, and the like, and electronic circuits located on the bottom surface thereof passes through the interior in a vertical direction. In this case, since the power supply layer and the ground layer are located in the inner layer of the multilayer substrate, the shape is maintained as in FIG. 1B because of the clearance hole for forming the via. There is a problem that is difficult to do.

In addition, when the signal wiring is placed on the top of the non-uniform conductor pattern such as the EBG structure of FIG. 1B, the characteristic impedance of the signal wiring becomes uneven, which is very disadvantageous for high speed signal transmission.

Therefore, a new EBG structure is required to shield the switching noise while preventing the performance degradation of the EBG structure and the performance degradation of the signal transmission due to the EBG structure.

Accordingly, the present invention provides a printed circuit board in which a digital circuit and an analog circuit (for example, an RF circuit) are mounted in combination, and includes an electromagnetic bandgap structure capable of preventing switching noise in a high frequency region transmitted from a digital circuit. To provide a printed circuit board.

Other objects of the present invention will be readily understood through the following description.

According to an aspect of the present invention, two power layers are separated and positioned on the same plane; A ground layer positioned on a plane different from the two power layers; A dielectric layer interposed between the two power layers and the ground layer; Two first conductor walls formed through the dielectric layer to protrude from each of the two power layers toward the ground layer at positions adjacent to the boundary between the two power layers; An electromagnetic bandgap structure is provided that includes a second conductor wall formed through the dielectric layer to have a shape protruding from the ground layer toward the power supply layer at a position corresponding to the boundary between the two power supply layers.

Here, the two first conductor walls may be formed to have lengths corresponding to the lengths of the edges forming the boundary in the respective power layers along the length direction of the boundary between the two power layers.

Here, the second conductor wall may be formed to have a length corresponding to any one of the lengths of the edges forming the boundary in the respective power layers along the length direction of the boundary between the two power layers.

Here, when the first conductor wall and the second conductor wall are viewed based on a vertical cross section of the electromagnetic bandgap structure, an intersection point of an imaginary straight line in the horizontal direction crossing between the power supply layer and the ground layer is shown. Each can be formed to a height that can exist on both of the conductor walls.

The second conductor wall may extend from the ground layer to the same plane as the power layer through the dielectric layer.

Here, one of the two power layers separated from each other may be used as the power layer for the digital circuit, and the other may be used as the power layer for the RF circuit.

In addition, according to another aspect of the present invention, a printed circuit board including the electromagnetic bandgap structure of the above-described structure can be provided.

According to an electromagnetic bandgap structure and a printed circuit board including the same according to an embodiment of the present invention, a high frequency region transmitted from a digital circuit in a printed circuit board on which a digital circuit and an analog circuit (for example, an RF circuit) are combined. There is an effect that can prevent the switching noise.

Hereinafter, an electromagnetic bandgap structure and a printed circuit board including the same according to embodiments of the present invention will be described in detail with reference to the accompanying drawings. In describing the present invention, when it is determined that the detailed description of the related known technology may unnecessarily obscure the subject matter of the present invention, the detailed description thereof will be omitted. Numbers (eg, first, second, etc.) used in the description of the present specification are merely identification symbols for sequentially distinguishing identical or similar entities.

In general, in the case of a main board or package having a mixed signal design, in order to prevent switching noise (SSN), the power layer or power plane is separated into two layers and grounded. The ground layer or ground plane is designed in a shared manner.

A general form of a printed circuit board having such a power layer separation structure is shown through a perspective view of FIG. 2A and a vertical cross-sectional view of FIG. 2B.

2A and 2B clearly show only a part related to a power supply layer having a separation structure and a grounding layer used in common in a multilayer printed circuit board (which will be described later with reference to FIGS. 3 and 4). The same is true for).

Referring to FIGS. 2A and 2B, a ground layer 110, a dielectric layer 120, and a power supply layer may be included, and the power supply layer may include two of the first power supply layer 130-1 and the second power supply layer 130-2. Separated into dogs. In this case, the first power layer 130-1 may be, for example, for supplying power to the RF circuit corresponding to a position (see reference numeral 300 of FIG. 2A) where the RF circuit is to be mounted through a mixed signal design. The second power source layer 130-2 is used for the purpose of applying power to the digital circuit corresponding to the position (see reference numeral 200 of FIG. 2A) on which the digital circuit is to be mounted.

However, the power layer isolation structure shown in FIGS. 2A and 2B alone is often insufficient to prevent the transfer of switching noise 20 from the digital circuit to the RF circuit. This is especially true in light of recent specifications where signals in the high frequency band are mainly used. Accordingly, the present invention proposes an electromagnetic bandgap structure (EBG) as shown in FIGS. 3 and 4.

The EBG structure proposed in the present invention prevents transmission of switching noise through a structure in which a conductor wall protrudes into the dielectric layer from each power layer separated from the ground layer along the boundary area where the power layer is separated. This will be described in more detail below.

3 is a perspective view of a printed circuit board including an EBG structure according to an embodiment of the present invention, Figure 4 is a vertical cross-sectional view of the printed circuit board shown in FIG. 5 is a diagram showing virtually an inductance component and a capacitance component that will exist through the EBG structure according to the vertical cross-sectional view of FIG. 4.

The printed circuit board of the present invention also basically starts from the same structure as in Figs. 2A and 2B. Referring to the printed circuit board 100 shown through FIGS. 3 and 4, the ground layer 110, the dielectric layer 120, and the power layer are included. As shown in FIG. 2B, the power supply layer separation structure is divided into a first power supply layer 130-1 and a second power supply layer 130-2.

However, in the present invention, in addition to the above configuration, the conductive wall protruding from the first power source layer 130-1 through the dielectric layer 120 toward the direction in which the ground layer 110 is located (hereinafter, referred to as 'left first' for convenience of description). Conductor wall 140-1 ') and another conductor wall penetrating through the dielectric layer 120 from the second power supply layer 130-2 and protruding in the same direction as the left first conductor wall (hereinafter,' The dielectric layer (from the ground layer 110 at a position corresponding to the right first conductor wall 140-2 ') and the two first conductor walls 140-1 and 140-2 on the left and right sides. It further includes a conductor wall (hereinafter, referred to as a 'second conductor wall 150') protruding through the 120 to the direction in which the power supply layer is located.

Here, the left first conductor wall 140-1 and the right first conductor wall 140-2 are formed adjacent to a separation boundary between the first power layer 130-1 and the second power layer 130-2. Can be. Further, the two first conductor walls 140-1 and 140-2 are formed long along the longitudinal direction of the separation boundary between the two power layers. At this time, the left and right first conductor walls 140-1 and 140-2 are edge lengths of the first and second power supply layers 130-1 and 130-2, respectively (reference numeral 10 of FIG. 3). Length in the direction of the burn direction).

In this case, the second conductor wall 150 may be formed at a position corresponding to the separation boundary between the two power supply layers 130-1 and 130-2, and the left first conductor wall 140-1 or the right side thereof. It may have a length corresponding to any one of the first conductor wall 140-2.

As described above, in the power supply layer separation structure, the left first conductor wall 140-1 and the second power supply layer 130-2 protruding and extending from the first power supply layer 130-1 toward the ground layer 110. From the ground layer 110 to the power supply layer between the right first conductor wall 140-2 and the two first conductor walls 140-1 and 140-2 protruding from the ground layer 110. When the second conductor wall 150 protrudes, the second circuit wall 150 may be formed from a digital circuit in one position (for example, reference numeral 200 in FIG. 3) and the RF circuit in another position (for example, FIG. 3). Switching position 20 to be transmitted to (refer to position 300) may be significantly reduced.

As shown through FIG. 5, this is the capacitance component C1 formed by the first and second power layers 130-1 and 130-2, the ground layer 110, and the dielectric layer 120 interposed therebetween. , C4) and capacitance components C2 and C3 formed by the left and right first conductor walls 140-1 and 140-2 and the second conductor wall 150 and the dielectric layer 120 interposed therebetween. ), There are inductance components L1, L2, L3 by each of the conductor walls 140-1, 140-2, 150, and the resistances present in the respective conductor layers and the dielectric layers, although not separately shown in the drawings. This is because the inductance component can function as a kind of band filter that can filter out noise of a specific frequency band.

At this time, the height of the first conductor walls 140-1 and 140-2 (ie, the length in the vertical direction based on the vertical cross-sectional view of FIGS. 4 and 5) and the height of the second conductor wall 150 are not particularly limited. Of course, it can be changed without any change. That is, in the vertical cross-sectional view of FIGS. 4 and 5, when one virtual straight line (see, for example, switching noise 20) in the horizontal direction across the power supply layer and the ground layer is simulated, all of the straight lines correspond to the one straight line. Although the intersection is present in the conductor walls 140-1, 140-2, 150 (i.e., the structure in which the switching noise 20 is blocked by its respective conductor walls), this is not necessarily the case. none.

The structure in which the switching noise 20 is not blocked by the respective conductor walls (ie, referring to the vertical sectional views of FIGS. 4 and 5, the first conductor walls 140-1 and 140-2 and the second conductor wall) Even if the 150 elements do not overlap each other in the horizontal direction, the EBG structure according to the present invention may shield the switching noise 20 due to the presence of the capacitance component and the inductance component as described above. Because it is.

3 to 5 illustrate that the height of the second conductor wall 150 does not completely penetrate through the dielectric layer 120, the height of the second conductor wall 150 is also defined by the first and the second conductor walls 150. It can be freely changed within the limit that can be electrically separated from the second power layer (130-1, 130-2). For this reason, the second conductor wall 150 completely penetrates through the dielectric layer 120 at the boundary position between the two power layers 130-1 and 130-2, thereby providing two power layers 130-1 and 130-. Of course, it may be extended to reach the same plane as 2).

3 to 5, one left first conductor wall 140-1 is provided on the first power supply layer 130-1, and the right power is also formed on the second power supply layer 130-2 for convenience of drawing. Although it is assumed that at least one conductor wall 140-2 is formed and only one second conductor wall 150 is formed in the ground layer 110, the number of conductor walls at this time is also shown in the drawings. Of course, there can be more than this.

FIG. 7 illustrates a comparison of frequency characteristics of the EBG structure according to the exemplary embodiment of the present invention illustrated in FIGS. 3 to 5 and the general power layer separation structure illustrated in FIGS. 2A and 2B.

FIG. 7 is a view reflecting simulation results of frequency characteristics at 0.1 to 20 GHz with respect to the two structures using a 3D field solver. Referring to FIG. 7, in the case of a printed circuit board including an EBG structure according to an exemplary embodiment of the present invention, the shielding rate S21 is improved in all frequency regions as compared with a general case having a power layer separation structure. It can be confirmed that the shielding effect is particularly excellent in the high frequency band. This shows that the EBG structure of the present invention will be very effective for shielding the switching noise of the high frequency band, considering that general switching noise is excellent in the high frequency band.

Hereinafter, a method of manufacturing a printed circuit board including an EBG structure according to an embodiment of the present invention will be described. However, this is only to show that the EBG structure according to the present invention can be easily manufactured through a general manufacturing process of a printed circuit board, and a detailed description thereof will be omitted and will be briefly described for each manufacturing order.

Of course, it will be apparent to those skilled in the art that the EBG structure and the printed circuit board thereof according to the embodiment of the present invention may be manufactured by various methods other than those of FIGS. 6A to 6C to be described below.

FIG. 6A briefly illustrates only a process for fabricating conductor walls, which is a key feature of the present invention, in an example, and illustrates the case in which the fabrication is performed through a buried pattern process. First, the conductor layers 111 and 131 made of a conductive material such as copper (Cu) are prepared (see (a) of FIG. 6A), and the conductor walls 140-1 and 140-2 are positioned at predetermined positions through copper plating or the like. , 150) (see (b) of FIG. 6A). The conductor walls 111, 131 on which the conductor walls 140-1, 140-2, and 150 are fabricated are laminated on both surfaces of the dielectric 121 in a semi-cured state (see (c) of FIG. 6A). After the 140-1, 140-2, and 150 are buried in the dielectric layer 120 (see (d) of FIG. 6A), the conductor layers 111 and 131 existing on both surfaces of the dielectric layer 120 are removed. Etching (see (e) of FIG. 6A).

After fabricating the conductive walls 140-1, 140-2, and 150 embedded in the dielectric layer 120 through the process of FIG. 6A, the power layer having the separation structure through the process of FIG. 6B or 6C. The printed circuit board having a.

6B illustrates an additive process, and FIG. 6C illustrates a process sequence according to a subtractive process. In accordance with the additive method, the dry film 161 is first powered. After laminating at a predetermined separation boundary position for forming the layer separation structure, both surfaces are plated using copper or the like (see FIG. 6B (f)), and the first dry film 161 is removed by a method of removing the dry film 161. And second power layers 130-1 and 130-2 and ground layer 110 (see (g) of FIG. 6B). On the contrary, in the case of the subtractive method, first, double-side plating is performed using copper or the like (see FIG. 6C (h)), and then the dry film 162 is laminated on the portion except for the separation boundary position. (See (i) of FIG. 6C), the first and second power supply layers 130-1 and 130-2 are removed by using a method of removing the copper and the like exposed to the boundary position and then removing the dry film 162 again. ) And the ground layer 110 may be manufactured (see (j) of FIG. 6C).

As described above, the EBG structure according to the present invention can be manufactured very simply using a manufacturing process of a general printed circuit board, while overcoming the problems of the coplanar EBG structure according to the prior art, digital circuits and RF In a printed circuit board on which a circuit is to be mounted, there is an advantage that the problem of switching noise in a high frequency region transmitted from a digital circuit can be greatly improved.

Although the above has been described with reference to a preferred embodiment of the present invention, those skilled in the art to which the present invention pertains without departing from the spirit and scope of the present invention as set forth in the claims below It will be readily understood that modifications and variations are possible.

1A is a perspective view of a printed circuit board including a coplanar EBG structure according to the prior art.

1B is a plan view of the coplanar EBG structure shown in FIG. 1A;

Figure 2a is a perspective view showing a general form of a printed circuit board having a power layer separation structure.

FIG. 2B is a vertical cross-sectional view of the printed circuit board shown in FIG. 2A. FIG.

3 is a perspective view of a printed circuit board including an EBG structure according to an embodiment of the present invention.

4 is a vertical cross-sectional view of the printed circuit board shown in FIG.

FIG. 5 is a diagram showing virtually an inductance component and a capacitance component that will exist through the EBG structure according to the vertical cross-sectional view of FIG.

6A to 6C are flowcharts illustrating a method of manufacturing a printed circuit board including an EBG structure according to an embodiment of the present invention.

7 is a diagram reflecting a simulation result regarding frequency characteristics represented by an EBG structure according to the present invention.

<Description of the symbols for the main parts of the drawings>

110: ground layer 120: dielectric layer

130-1: first power layer 130-2: second power layer

140-1, 140-2: first conductor wall 150: second conductor wall

Claims (7)

Two power layers disposed separately on the same plane; A ground layer positioned on a plane different from the two power layers; A dielectric layer interposed between the two power layers and the ground layer; Two first conductor walls formed through the dielectric layer to protrude from each of the two power layers toward the ground layer at positions adjacent to the boundary between the two power layers; A second conductor wall formed through the dielectric layer to have a shape protruding from the ground layer toward the power supply layer at a position corresponding to the boundary between the two power supply layers; Electromagnetic bandgap structure comprising a. The method of claim 1, The two first conductor walls are formed along the length of the boundary between the two power supply layers, the electromagnetic bandgap structure having a length corresponding to the length of the edge forming the boundary in each power supply layer, respectively. . The method of claim 1, And the second conductor wall is formed to have a length corresponding to any one of the lengths of the edges forming the boundary in the respective power layers along the longitudinal direction of the boundary between the two power layers. . The method of claim 1, When the first conductor wall and the second conductor wall are viewed with respect to the vertical cross section of the electromagnetic bandgap structure, the intersection of each of the conductors with an imaginary straight line in the horizontal direction crossing between the power supply layer and the ground layer is each conductor. Electromagnetic bandgap structures, each formed to a height that can exist on both walls. The method of claim 1, And the second conductor wall extends from the ground layer through the dielectric layer to the same plane as the power layer. The method of claim 1, Either one of the two power layers in separate positions is used as the power layer for the digital circuit, and the other is used as the power layer for the RF circuit. A printed circuit board comprising the electromagnetic bandgap structure according to any one of claims 1 to 6.

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