JP2006303020A - Capacitor built-in printed wiring board - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a capacitor built-in printed wiring board wherein first and second signal wires are hard to interfere each other or no change occurs in impedance of a transmission path because of downsizing and high density, even if a second signal wire is close to an electrode of a built-in capacitor connected to the first signal wire. <P>SOLUTION: The capacitor built-in printed wiring board is provided with a first insulating layer wherein a signal wire is provided on its surface, a capacitor which is provided in contact with the first insulating layer, and a second insulating layer which is provided in contact with the capacitor. In this case, the ground layer of the capacitor is in contact with the first insulating layer, and the capacitor electrode of the capacitor is in contact with the second insulating layer. The signal wire is electrically connected with the capacitor electrode through a via penetrating the first insulating layer, the ground layer and the capacitor layer, and the via is electrically insulated from the ground layer by a gap made of an insulating material. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a printed wiring board with a built-in capacitor, and more particularly to a printed wiring board used in a high-frequency device and having a built-in capacitor connected to a high-frequency signal line.

  Conventionally, in a printed wiring board with a built-in capacitor, a signal line is provided on the surface of the wiring board, and a capacitor including a dielectric layer and a pair of electrodes sandwiching the dielectric layer is formed inside the wiring board. A capacitor built in the wiring board is connected to the signal line and is used for removing noise generated in the signal line. (For example, refer to Patent Document 1).

Japanese Patent No. 3033972 (second page, FIG. 2)

As the size and density of the printed wiring board with a built-in capacitor are reduced, the interval between the wirings is becoming narrower. In addition, with the diversification of electronic devices, the built-in capacitors are also diversifying. In particular, the area of the capacitor electrode is increasing with the demand for higher capacity of the capacitors.
For this reason, in a printed wiring board with a built-in capacitor used in a high-frequency device, the distance between the electrode of the built-in capacitor connected to the first signal line that transmits a high-frequency signal and the second signal line adjacent to the first signal line. Is close. For example, the second signal line is provided on the wiring board surface immediately above the electrode of the built-in capacitor to which the first signal line is connected.
As a result, the amount of electromagnetic coupling between the first signal line and the second signal line increases, the first signal line and the second signal line interfere with each other, and a device connected to these signal lines malfunctions. There was a problem to do.
Furthermore, since the capacitor electrode exists immediately below the second signal line, the characteristic impedance of the transmission line composed of the second signal line and the ground fluctuates, resulting in a problem that the signal transmission efficiency deteriorates.

  The present invention has been made to solve the above-described problems. The purpose of the present invention is to reduce the size and increase the density of the built-in capacitor electrode connected to the first signal line and the second signal line. To obtain a printed wiring board with a built-in capacitor in which the first signal line and the second signal line do not interfere with each other even when they are close to each other, and the impedance of the transmission line by the second signal line does not fluctuate. .

  The printed wiring board with a built-in capacitor according to the present invention is provided with a first insulating layer having a signal line on the surface thereof, and in contact with the first insulating layer, and a ground layer, a capacitor layer, and a capacitor electrode are laminated. And a second insulating layer provided in contact with the capacitor, wherein the ground layer is in contact with the first insulating layer. The electrode is in contact with the second insulating layer, and the signal line is electrically connected to the capacitor electrode through a via penetrating the first insulating layer, the ground layer, and the capacitor layer; A via is electrically insulated from the ground layer by a gap formed of an insulating material.

  The printed wiring board with a built-in capacitor according to the present invention is provided with a first insulating layer having a signal line on the surface thereof, and in contact with the first insulating layer, and a ground layer, a capacitor layer, and a capacitor electrode are laminated. And a second insulating layer provided in contact with the capacitor, wherein the ground layer is in contact with the first insulating layer. The electrode is in contact with the second insulating layer, and the signal line is electrically connected to the capacitor electrode through a via penetrating the first insulating layer, the ground layer, and the capacitor layer; A via is electrically insulated from the ground layer by a gap formed of an insulating material, and a second insulating layer is provided on the surface of the first insulating layer provided with a signal line (referred to as a first signal line). The faith It is provided a line, and a capacitor electrode connected to the first signal line electromagnetically coupled to the second signal line is suppressed. That is, electromagnetic coupling between the first signal line and the second signal line is suppressed, and malfunction of a circuit connected to the second signal line can be prevented.

Embodiment 1.
1 is a cross-sectional view showing a printed wiring board with a built-in capacitor according to a first embodiment of the present invention. As shown in FIG. 1, the capacitor-embedded printed wiring board 20 of the present embodiment has a first signal line 10 and a first signal line on the surface (E surface) of the first insulating layer 5 in the printed wiring board 20. And a second signal line 12 through which a signal different from the signal flowing through the signal line flows. As shown in FIG. 1, the number of the second signal lines 12 may be not only one but also a plurality. The first signal line 10 is paired with the ground layer 2 provided on the surface (F surface) facing the E surface of the first insulating layer 5 to form a first transmission line. The second signal line 12 is also paired with the ground layer 2 provided on the F surface of the first insulating layer 5 to form a second transmission line.
The capacitor layer 1 is provided in contact with the surface of the ground layer 2 that faces the F surface, and the capacitor electrode 4 is provided on the surface of the capacitor layer 1 that faces the ground layer 2. ing. The capacitor electrode 4, the capacitor layer 1, and the ground layer 2 form a built-in capacitor 9. A second insulating layer 3 is provided in contact with the surface of the capacitor layer 1 on which the capacitor electrode 4 is provided. That is, the first insulating layer 5 provided with the first and second signal lines, the built-in capacitor 9 composed of the ground layer 2, the capacitor layer 1, and the capacitor electrode 4, and the second insulating layer 3 are laminated. Thus, a printed wiring board 20 with a built-in capacitor is formed.
In the printed wiring board 20 with a built-in capacitor according to the present embodiment, the first signal line 10 penetrates the first insulating layer 5, the ground layer 2, and the capacitor layer 1 and is insulated from the ground layer 2. The internal capacitor 9 is electrically connected to the capacitor electrode 4 through the via 6, and the built-in capacitor 9 is used, for example, to remove high-frequency noise of a signal flowing through the first signal line 10.

2 is a top view of each of the AA plane (a), the BB plane (b), and the CC plane (c) in the capacitor-embedded printed wiring board of FIG.
As shown in FIGS. 1 and 2, the first signal line 10 and the via 6 are connected by a land 15 provided in the first signal line 10. The ground layer 2 is provided with a hole larger than the via 6, an insulating material is present in the gap 7 between the via 6 and the ground layer 2, and the via 6 and the ground layer 2 are electrically insulated. . The insulating material may be the first insulating layer 5 or the dielectric of the capacitor layer 1.
By configuring the capacitor-embedded printed wiring board in such a structure, the ground layer 2 is shielded even if the projection area of the capacitor electrode 4 on the E surface of the first insulating layer 5 overlaps the second signal line 12. The electromagnetic coupling between the capacitor electrode 4 connected to the first signal line 10 and the second signal line 12 is suppressed. That is, electromagnetic coupling between the first signal line 10 and the second signal line 12 is suppressed, and malfunction of a circuit connected to the second signal line can be prevented. In addition, fluctuations in the characteristic impedance of the transmission line formed by the second signal line 12 and the ground layer 2 are prevented, and transmission efficiency is improved.

In the printed wiring board 20 with a built-in capacitor according to the present embodiment, when the width of the gap 7 formed of an insulating material is at least twice the thickness (t1) of the capacitor layer 1, the via 6 and the ground layer 2 It is preferable to prevent the capacitance of the built-in capacitor 9 from becoming unstable due to the electromagnetic coupling. The upper limit of the outer diameter of the gap 7 is preferably 2/3 below the diagonal of the surface of the capacitor electrode 4 because the electromagnetic shielding effect by the ground layer 2 is not lowered. It is preferable that the projected area of the gap portion 7 on the E plane of the first insulating layer 5 does not overlap the second signal line 12 because the electromagnetic shielding effect by the ground layer 2 is high. When the distance from the outer periphery of the gap 7 to the second signal line is equal to or greater than the half power of the thickness (t5) of the first insulating layer 5, the second signal line 12, the capacitor electrode 4, The ground layer 2 always exists on the line connecting the two, and the electromagnetic shielding effect of the electromagnetic coupling by the ground layer 2 is further enhanced, which is more preferable.
In the printed wiring board 20 with a built-in capacitor according to the present embodiment, there is nothing on the surface (denoted as H surface) opposite to the surface (denoted as G surface) on which the capacitor electrode 4 of the second insulating layer 3 is provided. The third signal line or circuit may be provided at a position sufficiently separated from the capacitor electrode 4, and a substrate layer provided with a circuit may be provided at a position sufficiently separated from the capacitor electrode 4.

Hereinafter, a method for manufacturing the printed wiring board 20 with a built-in capacitor according to the present embodiment will be described.
First, a core substrate to be the second insulating layer 3 in which the capacitor electrode 4 is formed by photolithography is prepared. On the surface of the core substrate on which the capacitor electrode 4 is provided, the capacitor layer 1 having adhesiveness and the copper foil to be the ground layer 2 are laminated in this order. The copper foil is processed by the photoengraving method to form the ground layer 2, and the gap 7 is formed in the ground layer 2.
Next, a base material to be the first insulating layer 5 and a copper foil to be a signal line are laminated in this order on the surface of the ground layer 2. The copper foil at the position where the via 6 is formed is removed by photolithography, and a hole reaching the capacitor electrode 4 is opened at this position. At this time, the hole penetrates the gap 7.
Next, for example, panel copper plating is performed on the hole to form a via 6 made of copper. The via 6 may be formed of a conductive material such as a conductive resin other than copper plating.
Finally, the copper foil laminated on the E surface of the first insulating layer 5 is processed by photolithography to form the first signal line 10, the land 15, and the second signal line 12.
Thus, the printed wiring board 20 with a built-in capacitor according to the present embodiment is obtained.

In the present embodiment, a general double-sided copper-clad plate can be used for the core substrate to be the second insulating layer 3. For example, R1766 (insulating layer thickness: 0.2 mm, copper) manufactured by Matsushita Electric Works, Ltd. A foil thickness of 0.012 mm) can be used.
Moreover, a general insulating adhesive film can be used for the capacitor layer 1, and for example, R1661 (thickness 0.1 mm) manufactured by Matsushita Electric Works, Ltd. can be used. In order to obtain a capacitor having a large capacity per unit area, an adhesive film having a thickness of 0.1 mm or less is preferably used, and an adhesive film having a thickness of 0.02 mm or less is more preferably used. Further, a material having a high relative dielectric constant may be used.
For the first insulating layer 5, a general base material for a multilayer printed wiring board can be used. For example, R1661 (thickness 0.2 mm) manufactured by Matsushita Electric Works, Ltd. can be used.
A general material for a printed wiring board can be used for the copper foil. For example, F3-WS (thickness 0.012 mm) manufactured by Furukawa Electric Co., Ltd. can be used.

Embodiment 2.
FIG. 3 is a sectional view showing a printed wiring board with a built-in capacitor according to the second embodiment of the present invention. As shown in FIG. 3, the capacitor built-in printed wiring board 30 according to the present embodiment is the same as the surface (G) of the second insulating layer 3 in the capacitor built-in printed wiring board 20 according to the first embodiment (G The second ground layer 32 and the third insulating layer 35 are laminated in this order on the surface (H surface) facing the surface), and the second ground layer 32 of the third insulating layer 35 is in contact therewith. The third signal line 11 is provided on the surface (J surface) opposite to the surface (I surface). In the present embodiment, the ground layer 2 in the first embodiment is the first ground layer 2b.
With such a configuration, even if the third signal line 11 is provided in the projection region of the capacitor electrode 4 onto the J plane in the third insulating layer 35, the third signal line 11 is connected to the first signal line 10. Electromagnetic coupling between the capacitor electrode 4 and the third signal line 11 is suppressed. That is, the electromagnetic coupling between the first signal line 10 and the third signal line 11 is suppressed, and the malfunction of the circuit connected to the third signal line can be prevented. In addition, variation in characteristic impedance of the transmission line formed by the third signal line 11 and the ground layer is prevented, and transmission efficiency is improved.

Embodiment 3.
FIG. 4 is a cross-sectional view illustrating a printed wiring board with a built-in capacitor according to the third embodiment of the present invention. As shown in FIG. 4, the capacitor built-in printed wiring board 40 of the present embodiment has the second capacitor electrode 44 on the H surface of the second insulating layer 43 in the capacitor built-in printed wiring board 20 of the first embodiment. Is provided. Further, the second capacitor layer 41 and the second ground layer 42 are laminated in this order on the H surface of the second insulating layer 43 provided with the second capacitor electrode 44, and the second capacitor 49 Is formed. Furthermore, a third insulating layer 45 is provided on the surface of the second ground layer 42 that faces the surface in contact with the second capacitor layer 41.
Further, the second insulating layer 43 is provided with a second via 46 that electrically connects the first capacitor electrode 4 b and the second capacitor electrode 44.

  With this configuration, the capacity of the built-in capacitor can be increased. Further, the third signal line 11 is provided in the projection region of the second capacitor electrode 44 on the surface (J plane) where the third signal line 11 is provided in the third insulating layer 45. In addition, the electromagnetic coupling between the second capacitor electrode 44 connected to the first signal line 10 and the third signal line 11 is suppressed. That is, the electromagnetic coupling between the first signal line 10 and the third signal line 11 is suppressed, and the malfunction of the circuit connected to the third signal line can be prevented. In addition, variation in characteristic impedance of the transmission line formed by the third signal line 11 and the ground layer is prevented, and transmission efficiency is improved.

A method for manufacturing the capacitor built-in printed wiring board 40 of the present embodiment will be described below.
First, a core substrate to be the third insulating layer 45 in which the second ground layer 42 is formed by photolithography is prepared.
Next, each surface of the substrate including the copper foils on both sides is processed by a photoengraving method to prepare a second insulating layer 43 including a first capacitor electrode 4b and a second capacitor electrode 44. A hole is formed in the electrode portion of the core substrate, the second via 46 is formed by the method described in the first embodiment, and the first capacitor electrode 4b and the second capacitor electrode 44 are electrically connected. To do.
Next, the second capacitor layer 41 having adhesiveness on the surface of the second ground layer 42 provided on the third insulating layer 45, and the first capacitor electrode 4b electrically connected as described above. And a second insulating layer 43 including the second capacitor electrode 44 are laminated in this order.
Next, the first capacitor layer 1b, the first ground layer 2b, the first insulating layer are formed on the second insulating layer 43 provided with the first capacitor electrode 4b in the same manner as in the first embodiment. 5, the first via 6b, the first signal line 10 and the second signal line 12 are provided to obtain the capacitor built-in printed wiring board 40 of the present embodiment.

  Next, the effect of the printed wiring board with a built-in capacitor according to the present invention will be described in detail in Examples.

Example 1.
The capacitor built-in printed wiring board 20 of the first embodiment, that is, the capacitor built-in printed wiring board 20 having the structure shown in FIG. 1 was prepared.
Specifically, the first insulating layer 5 was a substrate of a printed wiring board having a thickness of 0.2 mm, and the ground layer 2 was a copper foil for a printed wiring board having a thickness of 0.012 mm. The capacitor layer 1 is an adhesive film having a thickness of 0.1 mm, the second insulating layer 3 is a base layer having a core substrate thickness of 0.2 mm, and the capacitor electrode 4 is a copper foil having a thickness of 0.012 mm. did. The capacitor electrode 4 was a 4 mm square.
The first signal line 10 and the second signal line 12 were wirings having a width of 0.286 mm obtained by processing a copper foil having a thickness of 0.012 mm by a photoengraving method.
The diameter of the via 6 was 0.1 mm, the distance from the center of the via 6 to the signal line 12 was 1 mm, and the outer diameter of the gap 7 was 2.3 mm.

  A high-frequency signal of 1 GHz having an intensity of S1 is input to the first signal line 10 of the printed wiring board 20 with a capacitor having such a structure, and the intensity S2 of the signal output generated on the second signal line 12 by electromagnetic coupling And the amount of electromagnetic coupling C1 (dB) was determined from the ratio between S1 and S2. The obtained electromagnetic coupling amount C1 is shown in Table 1 together with the outer diameter D (mm) of the gap 7.

Examples 2-7.
A capacitor-embedded printed wiring board 20 similar to that in Example 1 was prepared except that the outer diameter D (mm) of the gap 7 was changed to that shown in Table 1.
For each printed wiring board 20 with a built-in capacitor, the electromagnetic coupling amount C1 (db) was determined in the same manner as in Example 1 and shown in Table 1.

Comparative Example 1
FIG. 5 is a printed wiring board with a built-in capacitor of Comparative Example 1 compared with the printed wiring boards with a built-in capacitor of Examples 1 to 7.
As shown in FIG. 5, the capacitor built-in printed wiring board 50 of Comparative Example 1 is provided with the capacitor electrode 4 on the surface of the first insulating layer 5, the ground layer 2 on the surface of the second insulating layer 3, The built-in capacitor 9 of Example 1 is formed except that the capacitor layer 4 is sandwiched between the capacitor electrode 4 provided in the first insulating layer 5 and the ground layer 2 provided in the second insulating layer 3 to sandwich the capacitor layer 4. It is the same as a printed wiring board.
And about the printed wiring board 50 with a built-in capacitor of the comparative example 1, it carried out similarly to Example 1, calculated | required electromagnetic coupling amount C1 (db), and showed in Table 1.

As is apparent from Table 1, the capacitor-embedded printed wiring boards of Examples 1 to 7 have the first signal line 10 and the second signal line 12 as compared with the conventional capacitor-embedded printed wiring board of Comparative Example 1. The amount of electromagnetic coupling C1 was reduced.
That is, in the printed wiring board with a built-in capacitor according to the first to seventh embodiments, the first ground layer 2 acts as an effective shield for electromagnetic coupling to the second signal line 12.
In particular, the capacitor-embedded printed wiring board according to Examples 2 to 7 in which the projected area of the gap 7 on the E surface of the first insulating layer 5 does not overlap the second signal line 12 has the electromagnetic coupling amount C1. Becomes even smaller.
In Examples 3 to 7 in which the distance from the outer periphery of the gap 7 to the second signal line is equal to or more than a half power of the thickness (t5) of the first insulating layer 5, the electromagnetic coupling amount C1 is further increased. Even smaller.

Example 8 FIG.
A capacitor built-in printed wiring board 30 according to the second embodiment, that is, a capacitor built-in printed wiring board having the structure shown in FIG. 3 was prepared.
In this example, that is, in the printed wiring board 30 with a built-in capacitor according to the second embodiment, the part corresponding to the printed wiring board with a built-in capacitor 20 according to the first embodiment is the same as that in the sixth example. The second ground layer 32 is a copper foil for a printed wiring board having a thickness of 0.012 mm, the third insulating layer 35 is a substrate for a printed wiring board having a thickness of 0.2 mm, and a third signal The line 11 was a wiring having a width of 0.286 mm obtained by processing a copper foil having a thickness of 0.012 mm by a photoengraving method.
A high frequency signal of 1 GHz having an intensity of S1 is input to the first signal line 10 of the printed wiring board 30 with a built-in capacitor according to the present embodiment, and the signal output intensity S2 generated on the second signal line 12 by electromagnetic coupling The intensity S3 of the signal output generated on the third signal line 11 was measured. Then, the electromagnetic coupling amount C1 (dB) was obtained from the ratio between S1 and S2, and the electromagnetic coupling amount C2 (dB) was obtained from the ratio between S1 and S3. The obtained electromagnetic coupling amounts C1 and C2 are shown in Table 2 together with the outer diameter D (mm) of the gap 7.

Example 9.
A capacitor built-in printed wiring board 40 of Embodiment 3, that is, a capacitor built-in printed wiring board having the structure shown in FIG. 4 was prepared.
In the present example, that is, the printed wiring board 30 with a built-in capacitor according to the third embodiment, the second capacitor electrode 44 is 0.012 mm thick and 4 mm square copper foil, and the second capacitor layer 41 is 0 mm thick. A 1 mm adhesive film was used, and the second via 46 was the same as the first via 6b. The material configuration of the other parts was the same as in Example 8.

  The electromagnetic coupling amounts C1 and C2 of the printed wiring board 40 with a built-in capacitor according to this example were obtained in the same manner as in Example 8, and are shown in Table 2 together with the outer diameter D (mm) of the gap 7.

Comparative Example 2.
The printed wiring board with a built-in capacitor of this comparative example was the same as the printed wiring board with a built-in capacitor 30 of Example 8 except that the second ground layer 32 was not provided.
About this printed wiring board with a built-in capacitor, the electromagnetic coupling amounts C1 and C2 were determined in the same manner as in Example 8, and are shown in Table 2 together with the outer diameter D (mm) of the gap 7.

As is apparent from Table 2, the electromagnetic coupling amount C1 between the first signal line 10 and the second signal line 12 is the same as that of the printed wiring board with a built-in capacitor in the eighth and ninth embodiments. The wiring board was the same and was small enough. However, the amount of electromagnetic coupling C2 between the first signal line 10 and the third signal line 12 was smaller in the printed wiring board with a built-in capacitor in Example 8 and Example 9 in which the second ground layer 32 was provided. .
That is, in the printed wiring board with a built-in capacitor in the eighth and ninth embodiments, the second ground layer 32 or 42 acts as an effective shield for electromagnetic coupling to the third signal line 11.

FIG. 3 is a cross-sectional view illustrating the printed wiring board with a built-in capacitor according to the first embodiment. It is each a top view of AA surface (a), BB surface (b), and CC surface (c) in the printed wiring board with a built-in capacitor shown in FIG. FIG. 6 is a cross-sectional view showing a printed wiring board with a built-in capacitor according to a second embodiment. FIG. 6 is a cross-sectional view illustrating a printed wiring board with a built-in capacitor according to a third embodiment. 6 is a cross-sectional view illustrating a printed wiring board with a capacitor according to Comparative Example 1. FIG.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Capacitor layer, 1b 1st capacitor layer, 2 Ground layer, 2b 1st ground layer, 3,43 2nd insulating layer, 4 Capacitor electrode, 4b 1st capacitor electrode, 5 1st insulating layer, 6 Via, 6b First via, 7 Gap, 9 Capacitor, 9b First capacitor, 10 First signal line, 11 Third signal line, 12 Second signal line, 20, 30, 40, 50 Capacitor Built-in printed wiring board, 32, 42 Second ground layer, 35, 45 Third insulating layer, 41 Second capacitor layer, 44 Second capacitor electrode, 46 Second via, 49 Second capacitor

Claims (4)

  A first insulating layer having a signal line on the surface, a capacitor provided in contact with the first insulating layer and formed by stacking a ground layer, a capacitor layer, and a capacitor electrode; A printed circuit board with a built-in capacitor having a second insulating layer provided in contact therewith, wherein the ground layer is in contact with the first insulating layer, and the capacitor electrode is in contact with the second insulating layer. And the signal line is electrically connected to the capacitor electrode by a via passing through the first insulating layer, the ground layer, and the capacitor layer, and the via is formed of an insulating material. A printed wiring board with a built-in capacitor, wherein the printed wiring board is electrically insulated from the ground layer.   The width of the gap between the outer periphery of the via and the inner periphery of the hole in the ground layer through which the via passes is at least twice the thickness of the capacitor layer and not more than 2/3 of the diagonal of the capacitor electrode surface. The printed wiring board with a built-in capacitor according to claim 1.   A second ground layer stacked on a surface facing the capacitor in the second insulating layer, and a third insulating layer stacked on the second ground layer. Item 8. A printed wiring board with a built-in capacitor according to Item 1. A second capacitor formed by laminating a second capacitor electrode, a second capacitor layer, and a second ground layer in this order on a surface of the second insulating layer facing the surface in contact with the capacitor; 2. A third insulating layer formed in contact with the second ground layer, and a second via for electrically connecting the capacitor electrode and the second capacitor electrode. The printed wiring board with a built-in capacitor described in 1.

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