JPH0613181U - Circuit board for high-speed signal transmission - Google Patents

Abstract

(57) [Abstract] [PROBLEMS] To provide a circuit board structure for high-speed signal transmission in which the influence of impedance discontinuity between a signal line and a VIA land is suppressed and signal reflection is reduced. [Structure] Reference numerals 1a and 1b denote VIAs for electrically connecting layers of a circuit board for high-speed signal transmission, which is a multi-layer board,
Reference numerals 2a, 2b, and 2c denote the first layer, the second layer, and the third layer, respectively.
It is a VIA land that is generally cross-shaped in layers. VI of each layer
By making the shape of the A land 2 into a cross shape in this way, the area of the VIA land is reduced, and even when a high frequency signal is transmitted in the circuit board for high speed signal transmission, the capacitance component is suppressed and the impedance is not affected. The occurrence of continuous points can be reduced.

Description

[Detailed description of the device]

[0001]

[Industrial applications]

 The present invention relates to a structure of a circuit board that transmits high speed signals.

[0002]

[Prior art]

 FIG. 6 shows the structure of a conventional high-speed signal transmission circuit board. 6A and 6B are top views, and FIG. 6C is a cross-sectional view of a high-speed signal transmission circuit board which is a multilayer board.

In FIG. 1, reference numerals 7a and 7b are VIAs for electrically connecting the layers of a high-speed signal transmission circuit board, which is a multi-layer board, and are filled with a metal such as Au, Cu, or W. Further, reference numerals 8a, 8b and 8c are VIA lands.

In these VIA lands, when the dielectric layers 11a, 11b and 11c are stacked, it is necessary to electrically and surely connect the VIAs 7a and 7b and the signal line 10. For this reason, the VIA lands 8 of each layer are designed to have a size that enables reliable electrical connection even if a stacking error occurs in the manufacturing process of the multilayer substrate.

The VIA land 8a of FIG. 6A has a circular shape, and the VIA land 8a of FIG. 6B has a square shape. Reference numeral 9 is a signal line of the first layer, reference numeral 10 is a signal line of the third layer, and reference numerals 12a and 12b are power supply or ground layers. The signal lines 9 and 10 have a strip line structure, and impedance is controlled by a power supply or GND layers 12a and 12b and dielectric layers 11a and 11b.

[0006]

[Problems to be solved by the device]

 However, when a high-frequency signal is transmitted to the high-speed signal transmission circuit board as shown in FIG. 6, the capacitance component becomes large due to the large area of the VIA land. As a result, a discontinuity of impedance occurs between the signal line and the VIA land, causing a problem of signal reflection, and transmission characteristics are significantly deteriorated. Therefore, in the conventional structure of the circuit board for high-speed signal transmission, only high-speed operation can be performed within a range in which the transmission characteristics are not deteriorated, and stable signal transmission cannot be performed at higher speed.

The present invention solves the above-mentioned drawbacks of the prior art, suppresses the influence at the impedance discontinuity between the signal line and the VIA land, and provides a circuit board for high-speed signal transmission with less signal reflection. The purpose is to do.

[0008]

[Means for Solving the Problems]

 In order to achieve the above object, the present invention provides a high-speed signal transmission circuit board in which a circuit board is formed of two or more signal transmission conductor layers and two or more power or earth layers. The VIA land of the VIA that connects the conductor layers has a size and a shape that can be electrically connected to the VIA even if a stacking error occurs, and the VIA land of the VIA land can be sufficiently connected with the VIA land. It has a shape in which the area is equivalently reduced.

[0009]

[Action]

 According to the circuit board for high speed signal transmission according to the present invention, the capacitance component is suppressed because the area of the VIA land is substantially small even when high speed signal transmission is performed. Therefore, the influence at the impedance discontinuity between the signal line and the VIA land can be reduced, and stable signal transmission without signal deterioration can be performed.

[0010]

【Example】

 Hereinafter, a circuit board for high-speed signal transmission according to the present invention will be described in detail with reference to the accompanying drawings.

FIG. 1 shows an embodiment of a high-speed signal transmission circuit board according to the present invention. (A) is a top view and (b) is a cross-sectional view of the high-speed signal transmission circuit board which is a multilayer board. is there .

In FIG. 1, reference numerals 1a and 1b are VIAs for electrically connecting the layers of a high-speed signal transmission circuit board, which is a multi-layer board, and are filled with a metal such as Au, Cu, or W. Reference numerals 2a, 2b, and 2c denote VIA lands of the first layer, the second layer, and the third layer, respectively, and the VIA lands 2 of each layer have a substantially cross shape. Reference numerals 3 and 4 are signal lines of the first layer and third layer, respectively, and reference numerals 5a and 5b are power source or ground layers of the second layer and fourth layer, respectively. Reference numeral 6a is a first dielectric layer between the first and second layers, reference numeral 6b is a second dielectric layer between the second and third layers, and reference numeral 6c is a third dielectric layer between the third and fourth layers. Of the dielectric layer.

By making the shape of the VIA land 2 of each layer into a cross shape in this way, the area of the VIA land is reduced, and even when a high frequency signal is transmitted in the circuit board for high speed signal transmission, the capacitance component is reduced. It can be suppressed and the occurrence of impedance discontinuity can be reduced.

FIGS. 2A and 2B show a case where a stacking deviation between the dielectric layers 6 a and 6 b or a printing deviation of the signal line 3 occurs in the high-speed signal transmission circuit board of FIG. 1. , (A) is a top view and (b) is a sectional view thereof. In this way, even if the VIA land is formed in the shape of a dove, an electrical open due to the stacking error does not occur, and the problem caused by the shape of this embodiment does not occur.

The shape of the VIA land 2a is not particularly limited to the cross shape, and the VIA land 2a has such a size and shape that it can be electrically connected to the VIA 1a even when a stacking error occurs, and the electrical connection to the VIA 1a is made. The shape may be such that

That is, as a shape that reduces the area of the VIA land 2a to suppress the capacitance component and reduces the occurrence of impedance discontinuities, for example, an X shape as shown in FIG. 3 may be used. Further, although not particularly shown, a shape which reduces the area without changing the maximum length from the conventional one, such as a * -shaped, human-shaped, circular or square VIA land provided with a small number of slits radially, may be considered.

Next, points to be noted when determining the shape of the VIA land 2a will be described with reference to FIG. FIG. 4A shows the land shape shown in FIG. 3, and FIG. 4B shows the land shape in which fine lines are radially formed as compared with FIG.

In FIG. 4, the land area appears to be larger in (a) than in (b), but due to the distribution of the electric field, a coupling effect occurs in adjacent lines in (b), and the land area of Work well. Therefore, in (b), the area is equivalently larger than that in (a). Therefore, the VIA land is suitable for the pattern as shown in FIG. 1 or 3 which is not so delicate.

Further, in order to keep the impedance constant even if the VIA is slightly deviated, at least a length corresponding to the diameter of VIA from the center is required as the conducting portion. That is, the area surrounded by the dotted line in FIG.

Next, the results of analysis of the conventional VIA and the VIA of this embodiment using a three-dimensional electromagnetic field analysis simulator will be shown. FIG. 5 is a simulation model of the circuit board for high-speed signal transmission at that time. That is, FIGS. 5A and 5B are simulation models of a conventional high-speed signal transmission circuit board, FIG. 5A is a top view, and FIG. 5B is a cross-sectional view. 3 (c) and 3 (d) are simulation models of a circuit board for high-speed signal transmission according to one embodiment of the present invention, (c) is a top view and (d) is a cross-sectional view. The results obtained by this simulation are shown in Table 1.

[0021]

[Table 1]

From this simulation result, comparing the return loss of the conventional VIA with that of the VIA of the present invention, a difference appears from a frequency of 1 GHz or higher, and the higher the frequency, the better the characteristic of the VIA of the present invention. .

The applicant of the present application has previously described in Japanese Patent Application No. 3-179237 the distance between the conductor in the signal transmission conductor layer and the power supply or the ground layer, the conductor width in the signal transmission conductor layer, and the signal transmission. We have proposed a high-speed signal transmission circuit board whose impedance is controlled by the thickness of the dielectric between the conductor layer and the power or ground layer. By combining the present invention and this proposed technology, it is possible to provide a circuit board for high-speed signal transmission, which is more reliable.

[0024]

[Effect of device]

 As described above in detail, according to the present invention, the area of the VIA land is equivalently narrowed to reduce the capacitance component and suppress the influence of the discontinuity point of the impedance between the signal line and the VIA land. As a result, the reflection characteristics of high frequency signals can be improved.

[Brief description of drawings]

FIG. 1 is a top view and a sectional view showing an embodiment of a circuit board for high-speed signal transmission according to the present invention.

2A and 2B are a top view and a cross-sectional view showing an example when the VIA is displaced in the embodiment of FIG.

FIG. 3 is a top view showing another embodiment of the circuit board for high speed signal transmission according to the present invention.

FIG. 4 is an explanatory view showing a comparative example of the shapes of VIA lands in the present invention.

FIG. 5 is an explanatory diagram showing a simulation model in the related art and the present embodiment.

6A and 6B are a top view and a cross-sectional view showing the shape of a VIA land in the conventional technique.

[Explanation of symbols]

 1a, 1b VIA 2a, 2b, 2c VIA land 3,4 Signal line 5a, 5b, 5c Power supply or ground layer 6a, 6b, 6c Dielectric layer

Claims (2)

[Scope of utility model registration request] 1. A high-speed signal transmission circuit board in which a circuit board is formed by two or more signal transmission conductor layers and two or more power source or ground layers, and a VIA connecting the signal transmission conductor layers. The VIA land has such a size and shape that it can be electrically connected to the VIA even if a stacking error occurs, and
The above-mentioned VIA within a range in which electrical connection with the IA is sufficiently obtained.
A high-speed signal transmission circuit board having a shape in which the area of the land is equivalently reduced. 2. The circuit board for high speed signal transmission according to claim 1, wherein the VIA land has a substantially cross shape.