JPH0637416A - Printed wiring board - Google Patents

Abstract

(57) [Summary] [Object] The present invention relates to a printed wiring board, and an object thereof is to improve the accuracy of the characteristic impedance of a through hole. [Structure] The through hole 31 has a first copper plating portion 32 for signals located in the center, a second copper plating portion 34 surrounding the signal and having a ground potential, and a first copper plating portion 3
Insulator part 33 occupying between 2 and the second copper plated part 34
Composed of and. The through hole 31 constitutes a coaxial cable structure.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a printed wiring board,
Particularly, it relates to the structure of the through hole portion.

High-speed signals have come to be used in communication equipment.

Along with this, it is required for printed wiring boards to have further improved electrical characteristics.

The wiring pattern of the printed wiring board is generally of a microstrip line (or shield type strip line) structure, and the characteristic impedance is accurately determined.

Therefore, at the present time, it is required to accurately determine the characteristic impedance of the through hole connecting the wiring patterns.

[0006]

2. Description of the Related Art FIG. 13 shows a conventional printed wiring board 1 as an example.

Reference numeral 2 denotes a printed wiring board body, which is composed of insulating layers 5, 6 and 7 formed with the solid layers 3 and 4 sandwiched therebetween.

Reference numerals 8 and 9 are wiring patterns respectively,
Are formed on the upper surface 10 and the lower surface 11.

A through hole 12 connects the wiring patterns 8 and 9.

The through hole 12 is composed of a copper plating portion 14 formed in a cylindrical shape on the peripheral side surface 13a of the hole 13 of the main body 2.

The wiring pattern 8 faces the solid layer 3 with the insulating layer 6 in between, and constitutes a microstrip line indicated by reference numeral 8A in FIG.

The wiring pattern 9 faces the solid layer 4 with the insulating layer 7 in between, and similarly constitutes a microstrip line indicated by reference numeral 9A in FIG.

Therefore, the accuracy of the characteristic impedance of the wiring patterns 8 and 9 is good.

[0014]

An equivalent circuit of the through hole 12 is as shown by reference numeral 12A in FIG. 14, which has a characteristic impedance different from the characteristic impedance of the pattern and is difficult to control. Is.

As a result, when a high-speed signal is input to FIG. 13 and propagated in the order of the wiring pattern 8 → the through hole 12 → the wiring pattern 9, the signal deteriorates at the through hole 12.

When a simulation is performed, FIG.
15 GHz of the waveform indicated by reference numeral 20 in FIG.
When the signal of is input, the signal extracted from
As shown by reference numeral 21 in FIG. 15B, it was found that the signal had a waveform that was considerably distorted with respect to the input waveform 20.

Therefore, an object of the present invention is to provide a printed wiring board in which the precision of the characteristic impedance of the through hole portion is improved.

[0018]

According to a first aspect of the present invention, there is provided a first conductor portion which connects between wiring patterns and has a signal potential, and a diameter larger than a diameter of the first conductor portion. A second conductor portion surrounding the first conductor portion and having a ground potential;
The structure has a through hole having a structure including an insulator portion that occupies a space between the first conductor portion and the second conductor portion.

According to a second aspect of the present invention, the wiring patterns are connected to each other, and a ground potential is provided at a portion adjacent to the signal through hole having a signal potential to correct the electrical characteristics of the signal through hole. The configuration has a through hole for electrical characteristic correction.

[0020]

The first conductor portion, the insulator portion, and the second conductor portion of claim 1 act so as to form a structure similar to a coaxial cable.

The signal through hole and the correction through hole of the second aspect act so as to form a structure similar to a balanced cable.

[0022]

1 and 2 show a printed wiring board 30 according to a first embodiment of the present invention.

In each figure, the same reference numerals are given to the parts corresponding to those shown in FIG.

Reference numeral 31 is a through hole, which comprises a first copper-plated portion 32 as a first conductor portion, an insulator portion 33, and a second copper-plated portion 34 as a second conductor portion.

The first copper-plated portion 32 has a cylindrical shape with a diameter of d, connects the wiring patterns 8 and 9 and has a signal potential.

The diameter of the second copper-plated portion 34 is D (> d).
Is cylindrical and is concentric with the first copper-plated portion 32,
The solid layers 3 and 4 are connected to each other and have a ground potential.

The insulator portion 33 has a substantially cylindrical shape, occupies a space between the first copper plated portion 32 and the second copper plated portion 34, and has a dielectric constant ε.

As a result, the through hole 31 has the same structure as the coaxial cable.

The through hole 31 is represented by an equivalent circuit in which a capacitance is added to an inductance, as indicated by reference numeral 31A in FIG.

The characteristic impedance Z ₀ of this through hole 31 is

[0031]

[Equation 1]

Is represented by

The characteristic impedance of the through hole 31 can be appropriately determined by changing the three parameters, that is, the diameters D and d and the dielectric constant ε. In the present embodiment, the diameters D and d and the permittivity ε are appropriately determined so that the characteristic impedance Z ₀ of the through hole 31 is equal to the characteristic impedance of the wiring patterns 8 and 9.

A simulation of the printed wiring board 30 shown in FIG. 1 was performed, and as shown in FIG.
When a signal having a waveform indicated by reference numeral 20 is input to (A) and propagated through the wiring pattern 8 → through hole 31 → wiring pattern 9 and is output from, a waveform indicated by reference numeral 21A in FIG. 4 (B) is obtained. I found out. The degree of distortion of the waveform 21A with respect to the waveform 20 remains slightly.

Therefore, according to the printed wiring board 30 described above, a high speed signal can be propagated with a slight signal deterioration.

Next, a method of manufacturing the printed wiring board 30 will be described with reference to FIG.

First, as shown in FIG. 3A, a double-sided solid two-layer printed wiring board 40 is manufactured.

Next, as shown in FIG. 7B, a via having a diameter D is formed in the printed wiring board 40 and copper through-hole plating is performed to form a second copper plated portion 34.

Next, as shown in FIG. 6C, an insulating resin (for example, polyimide) is filled in the via by a usual method to form an insulator portion 33.

Next, as shown in FIG. 3D, insulating layers 6 and 7 are formed on both surfaces of the printed wiring board 40 by pressing to obtain the printed wiring board main body 2A.

Next, as shown in FIG. 6E, wiring patterns 8 and 9 are formed on the upper and lower surfaces of the printed wiring board body 2A.

Finally, as shown in FIG. 6F, a hole having a diameter d is formed in the printed wiring board body 2A so as to pass through the end portions of the wiring patterns 8 and 9 and the center of the insulating portion 33. Through-hole plating of copper is performed to form the first copper-plated portion 32.

As a result, the printed wiring board 30 is manufactured.

Next, a printed wiring board 50 according to a second embodiment of the present invention will be described with reference to FIGS. 6 to 8.

In each drawing, the same reference numerals are given to the portions corresponding to the constituent portions shown in FIG.

Reference numeral 51-1 is a through hole for electrical characteristic correction, which has the same size as the through hole 12 for signals and is formed at a position separated from the through hole 12 by a distance A.

As shown in FIG. 8, the through hole 51-1 is formed in a cylindrical shape on the peripheral side surface 52-1a of the hole 52-1 formed through the solid layers 3 and 4 in the printed wiring board body 2. It is composed of a copper-plated portion 53-1.

The copper-plated portion 53-1 is electrically connected to the solid layers 3 and 4 and has a ground potential.

The copper plated portion 14 has a signal potential.

The through hole 12 cooperates with the through hole 51-1 to form a structure similar to a balanced cable.

Through hole 1 of the printed wiring board 50
The equivalent circuit of the portion 2 is represented as a configuration in which a capacitance is added to the inductance, as indicated by reference numeral 12A in FIG.

Assuming that the radius of the through holes 12 and 51-1 is a, the dielectric constants of the insulating layers 5, 6, and 7 around the through holes 12 are ε, and the magnetic permeability is μ, the characteristics of the through holes 12 are shown. The impedance Z ₀ is given by

[0053]

[Equation 2]

It is represented by

Therefore, once the structure of the printed wiring board is determined, the characteristic impedance Z ₀ can be controlled by changing the distance A.

In the present embodiment, the distance A is appropriately determined, and the impedance Z ₀ of the portion of the through hole 12 has a value equal to the special impedance of the wiring patterns 8 and 9.

Therefore, also in the above-mentioned printed wiring board 50, the signal is propagated through the through hole 12 with almost no signal deterioration.

FIG. 10 shows a printed wiring board 50A which is a modification of the printed wiring board 50 of FIG.

As shown in the figure, the signal through hole 1
The electrical characteristic correcting through hole 51A adjacent to 2 may have an oval shape.

The printed wiring boards 50 and 50A described above are manufactured not by providing the through holes 51-1 and the like from the beginning, but by adding through holes to the design data for which the pattern design is completed.

Next, a method for automatically adding the electrical characteristic correcting through holes 51-1 and the like to the design data for which the pattern design has been completed will be described with reference to FIGS. 11 and 12.

FIG. 11 shows the CAD apparatus 70 as a whole.

The pattern data editing section 71 controls the automatic wiring section 72.

Reference numeral 73 is a characteristic correction through-hole adding section, which adds a correction through-hole as described below based on the data from the pattern data editing section 71 and the data from the structure information input section 74.

The wiring pattern data in which the data of the correction through hole is added to the data from the pattern data editing unit 71 is sent to the manufacturing data output unit 75.

The characteristic correction through-hole adding section 73 is shown in FIG.
As shown in FIG. 2, the characteristic correction through-hole interval calculation circuit 8
0 and a characteristic correction through hole addition circuit 81.

First, data on the printed wiring board structure, material characteristics, and through-hole shape is taken into the circuit 80 from the structure information input unit 74. ) Calculate the value.

Next, a C (capacitance) value for correcting the calculated L value is calculated. Once the C value is determined, C calculated from the dielectric constant of the printed wiring board and the total length of the through hole
The distance A between the through hole and the through hole having the ground potential is calculated so that the value can be obtained.

The data of the through hole distance A determined by the circuit 80 and the wiring pattern data from the pattern data editing unit 71 in FIG. 11 are supplied to the circuit 81.

The circuit 81 has a through hole for correction added to a portion having a distance A to the signal through hole and not short-circuited with other patterns.

The data to which the correction through hole is added is output as wiring pattern data.

The present invention is not limited to the above-described embodiment having a structure applied to a microstrip line, but can be applied to a shield-type strip line or the like and has the same effect.

[0073]

As described above, according to the first aspect of the invention, the characteristic impedance of the through hole can be freely determined, and the characteristic impedance of the through hole can be accurately matched with the characteristic impedance of the wiring pattern. As a result, it is possible to substantially eliminate the signal deterioration at the through-hole portion, and it is possible to propagate the high-speed signal while suppressing the signal deterioration to the minimum.

According to the invention of claim 2, as in the invention of claim 1, it is possible to propagate a high-speed signal while suppressing signal deterioration to a minimum. Furthermore, since only through holes are added, it is possible to add data even to those for which wiring data has been completed, and it is possible to easily manufacture compared to the invention of claim 1.

[Brief description of drawings]

FIG. 1 is a vertical sectional view of a printed wiring board according to a first embodiment of the present invention.

FIG. 2 is a sectional view taken along the line II-II in FIG.

FIG. 3 is a diagram showing an equivalent circuit of the printed wiring board of FIG.

FIG. 4 is a diagram showing the degree of signal deterioration in the printed wiring board of FIG.

5 is a diagram showing a method of manufacturing through holes in the printed wiring board of FIG.

FIG. 6 is a plan view of an essential part of a printed wiring board according to a second embodiment of the present invention.

7 is a cross-sectional view taken along the line VII-VII in FIG.

8 is a cross-sectional view taken along the line VIII-VIII in FIG.

9 is a diagram showing an equivalent circuit of the printed wiring board in FIG.

FIG. 10 is a diagram showing a modification of the printed wiring board of FIG.

FIG. 11 is a diagram showing a CAD device for automatically adding through holes having electrical characteristics.

FIG. 12 is a diagram showing a configuration of a characteristic correction through-hole addition unit in FIG.

FIG. 13 is a diagram showing a conventional printed wiring board as an example.

14 is a diagram showing an equivalent circuit of the printed wiring board in FIG.

15 is a diagram showing the degree of signal deterioration in the printed wiring board of FIG.

[Explanation of symbols]

 2 printed wiring board main body 3,4 solid layer 8,9 wiring pattern 12,31 through hole 13,52-1 hole 13a, 52-1a peripheral side surface 14 copper plated portion 30,50,50A printed wiring board 32 first copper Plated portion (first conductor portion) 33 Insulator 34 Second copper plated portion (second conductor portion) 40 Two-layer printed wiring board 51-1, 51A Through hole for electrical characteristic correction 53-1 Copper plated portion 70 CAD device 71 Pattern data editing unit 72 Automatic wiring unit 73 Characteristic correction through hole addition unit 74 Structural information input unit 75 Manufacturing data output unit 80 Characteristic correction through hole interval calculation circuit 81 Characteristic correction through hole addition circuit

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Maki Kitajima 1015 Kamiodanaka, Nakahara-ku, Kawasaki City, Kanagawa Prefecture, Fujitsu Limited (72) Inventor, Shuichi Tokaibayashi 1015, Kamedotachu, Nakahara-ku, Kawasaki, Kanagawa Prefecture, Fujitsu Limited

Claims (2)

[Claims] 1. A first conductor portion (32) for connecting between wiring patterns (8, 9) and having a signal potential, and a diameter (D) larger than the diameter (d) of the first conductor portion. Then
A second conductor portion (34) surrounding the first conductor portion and having a ground potential, and an insulator portion (33) occupying between the first conductor portion and the second conductor portion. A printed wiring board having a through hole having the following structure. 2. An electrical characteristic for connecting between wiring patterns and having a ground potential at a portion adjacent to a signal through hole (12) having a signal potential to correct the electrical characteristic of the signal through hole. Correction through hole (51-1, 51
-2, 51A) having a configuration having a printed wiring board.