JP2001053397A - Double-sided printed wiring board - Google Patents

Abstract

PROBLEM TO BE SOLVED: To enable characteristic impedance control at through-holes of a double-sided printed wiring board, having a wiring circuit of differential signal lines. SOLUTION: This wiring board is composed by providing a wiring circuit which connects parallel differential signal wires 31, 32 on one surface of an insulating board to parallel differential signal wires 33, 34 on the other surface via through-holes 27, 28 for signal wires which pierce both surfaces of this insulating board. In this case, the through-holes 27, 28 for signal wires are surrounded by a cylindrical grounding conductor 25, and grounding wires 35-38 for signal wires arranged outside the differential signal wires are connected to the surface exposed part of the grounding conductor 25.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a double-sided printed wiring board, and more particularly, to a through-hole for matching the characteristic impedance of a differential signal, which needs to control the characteristic impedance of two signal lines between both surfaces, in the through-hole. The present invention relates to a double-sided printed wiring board having a structure.

[0002]

2. Description of the Related Art High-frequency signals are used in communication equipment, and the frequency is increasing. In a printed wiring board on which these communication devices are mounted, a signal wiring pattern is formed into a strip line or a microstrip line in order to transmit a high frequency signal, and characteristic impedance is controlled to prevent deterioration of high frequency characteristics.

However, when a signal input to a signal wiring pattern on one side is transmitted to a signal wiring pattern on the other side of the printed wiring board via a through hole for a signal line, the signal wiring pattern on the other side is not used. A phenomenon where the signal is disturbed is seen. The cause of this phenomenon is that the characteristic impedance of the through-hole is not controlled, so that a mismatch occurs between the signal wiring pattern on the surface and the characteristic impedance of the through-hole. With an increase in the speed of signal transmission of electronic devices such as communication devices, it has become increasingly important for printed wiring boards to match the characteristic impedance of signal wiring patterns.

For this purpose, Japanese Patent Application Laid-Open No. 2-09469 has been proposed.
No. 3 and Japanese Patent Application Laid-Open No. 06-037416 disclose a method of providing a cylindrical outer conductor connected to an inner ground layer around a signal line through hole of a multilayer printed wiring board.

FIG. 5 is a perspective view of a through-hole portion of a printed wiring board showing an example of these techniques. Reference numeral 51 in the figure
Is a multilayer printed wiring board, in this case an example of a three-layer multilayer printed wiring board. Reference numeral 52 denotes an inner ground conductor layer provided in the inner layer, reference numerals 56 and 57 denote signal wiring patterns on the front and back surfaces, reference numeral 54 denotes through holes for connecting signal wiring patterns on the front and back surfaces, and reference numeral 55 denotes a through hole 54. It is a cylindrical ground conductor portion provided around, and is electrically connected to the inner ground conductor layer 52. Reference numeral 53 denotes an insulating layer filled between the ground conductor 55 and the through hole 54. This technique is effective as a method for controlling the characteristic impedance of one signal wiring pattern on the front and back surfaces of a multilayer printed wiring board so as to coaxially surround a through hole with a cylindrical ground conductor 55.

[0006]

Recently, a method of transmitting a differential signal using two signal lines has been put to practical use in a double-sided printed wiring board. As in the case of the board, the control of the characteristic impedance of the signal wiring is important.

In the above-mentioned conventional technique, since only one signal line is provided in the through hole, the differential impedance for controlling the characteristic impedance of the two signal lines of the double-sided printed wiring board between both sides is required. It was difficult to apply for signal lines.

An object of the present invention is to provide a double-sided printed wiring board having a through-hole structure capable of controlling characteristic impedance even in a differential signal.

[0009]

According to the present invention, there is provided a double-sided printed wiring board comprising two parallel differential signal lines disposed at predetermined positions on one surface of an insulating substrate and penetrating both surfaces of the insulating substrate. A double-sided printed wiring board having a wiring circuit connected to two parallel differential signal lines arranged on the other surface of the insulating substrate via the signal line through hole of the two signal lines; A hole is provided inside the insulating substrate, and a part of the hole is surrounded by a cylindrical ground conductor exposed on the surface of the insulating substrate, and exposed portions of the ground conductor on the insulating substrate surface are formed on both surfaces of the insulating substrate. And a wiring structure connected outside to the two differential signal lines and to a signal line ground line arranged in parallel with the two differential signal lines. Configured as.

The differential signal lines on the insulating substrate have a positional relationship of 180 ° with each other, and the signal line through-hole and the cylindrical grounding conductor are connected to the signal line through-hole and the cylindrical grounding. Insulation can be achieved with the first insulating material filled between the conductors.

The differential signal line and the cylindrical grounding conductor can be insulated by a second insulating material provided between the differential signal line and an end of the cylindrical grounding conductor.

In the present invention, two through holes for connecting two differential signal lines on both sides are surrounded by a cylindrical ground conductor, and a ground line for a signal line is arranged outside the differential signal lines on both sides. By connecting this to the cylindrical installation conductor, it is possible to provide a double-sided printed wiring board capable of controlling the characteristic impedance of the surface of the differential signal line and the through-hole.

[0013]

Next, embodiments of the present invention will be described in detail with reference to the drawings.

FIG. 1 is a schematic perspective view showing a through-hole structure of a double-sided printed wiring board according to an embodiment of the present invention. 2A and 2B are a plan view and a cross-sectional view of the double-sided printed wiring board of FIG. 1, wherein FIG. 2A is a plan view, and FIGS. 2B to 2C are lines AA ′ and BB ′ of FIG. And a cross-sectional view along the line CC ′.

In the double-sided printed wiring board of the present invention, as shown in FIG. 1, two differential signal lines 31 and 32 connected to the element 29 are arranged in parallel on the upper surface layer 22, Outside the lines, signal line ground lines 35 and 36 having the same width are arranged at equal distances in parallel with the signal lines. The lower surface layer 23 under the double-sided printed wiring board has the differential signal lines 31,
Two differential signal lines 33 and 34 connected to the element 30 in the directions of 32 and 180 ° are arranged in parallel, and outside of these signal lines, signals of the same width are arranged at equal distances in parallel with the signal lines. Wire ground wires 37 and 38 are provided. The ends of the two differential signal lines on the upper and lower surface layers are electrically connected by two signal line through holes 27 and 28, respectively.
7 and 28 are surrounded by a ground conductor 25 constituting a through hole 24 provided in a cylindrical shape on the outside thereof (FIG. 2).
(A), FIG. 2 (b), FIG. 2 (c)). Ground conductor 25
At least a portion is exposed on the surface of each surface layer, and the exposed portion is electrically connected to a ground line for a signal line of the surface layer (see FIGS. 2A and 2D). .

The insulation between the ground conductor 25 and the differential signal line on the surface layer and between the ground conductor 25 and the signal line through hole are patterned on the first insulator 26a filled in the through hole 24 and the surface layer. It is held by the second insulator 26b.

In the present invention, as described above, the signal line ground line is disposed outside the signal lines on the upper and lower surface layers of the printed wiring board in parallel with the signal line, and the signal line ground line and the ground conductor are provided. The characteristic impedance can be controlled also in the double-sided printed wiring board by connecting the surface exposed portions of the above. Also, since the signal line through holes 27 and 28 are surrounded by the ground conductor 25, they can be treated as coaxial extensions.
The characteristic impedance can be controlled in the through hole, and signal disturbance between the upper and lower differential signal lines can be prevented.

Next, a first example of a method for manufacturing a printed wiring board according to the above embodiment will be described with reference to FIG.

FIG. 3 is a cross-sectional view of a main part of the wiring board for explaining a manufacturing process of the printed wiring board.
It is sectional drawing represented along B '. First, as shown in FIG. 3A, a base material 41 having a thickness of about 0.5 to 1.0 mm to which no copper foil is attached such as an epoxy glass substrate or a polyimide glass substrate is prepared.

Next, a through hole 42 is formed in the base material 41 by drilling or the like. The diameter of the through hole is determined by the diameter of the signal line through hole provided in a later step, and is usually about 1 to 1.5 mm. After the formation of the through-hole 42, a first copper plating film 43 having a thickness of 15 to 35 μm is formed on the surface of the through-hole 42 and the surface of the base material 41 by ordinary electroless copper plating and electrolytic copper plating. The first copper plating film 43 on the wall of the through hole 42 is protected by a resist, and the first copper plating film 43 on the base material 41 is removed by etching, so that the first copper plating 43 is formed on the wall of the through hole 42. Landed or Landless Through Hole 2
4 is formed (FIG. 3B). The first copper plating film may be formed only by electroless copper plating for thickening, and the surface of the base material 41 of the first copper plating film 43 on the wall of the through hole 41 has a width of 50 to 150 μm. May be attached. Further, instead of electroless copper plating for base plating of electrolytic copper plating, a copper film or an organic conductive film by sputtering can be used.

Next, a first insulating material 26a made of a liquid thermosetting epoxy resin is filled into the through-hole 42 by using a squeegee or the like, and after thermosetting, the surface is polished with a buff or the like to form the through-hole 42. Smooth the thermosetting resin on the surface. Next, the substrate 41
After applying a photo-curable epoxy resin having a thickness of about 70 μm to the surface by screen printing or curtain coating, selectively irradiating ultraviolet rays, developing with an aqueous sodium carbonate solution, and forming a differential signal line and a signal line grounding region. Then, a pattern of the second insulating material 26b is formed and thermally cured (FIG. 3C). The connection portion between the first copper plating film 43 and the signal line ground line is exposed without covering the second insulating material 26b.

Next, the first filling material formed inside the through hole 42 is formed.
Two through holes 45 having a diameter of 0.1 mm are formed at predetermined intervals in the insulating material 26a and the second insulating material 26b by a drill, and the entire surface including the through holes 45 is formed to a thickness of 1 by a normal copper plating technique.
A second copper plating film having a thickness of 0 to 20 μm is coated (FIG.
(D)). Note that one through-hole 45 is shown in FIG. 3D because the cross-sectional view is shown along BB ′ in FIG. 2A.

Next, a photoresist (not shown)
By patterning the second copper plating film 44 by etching using, the differential signal lines 32 and 33 are formed as shown in FIG. The differential signal lines 32 and 33 are connected by signal line through holes 28,
The signal line through hole 28 and the first copper plating film 44
(The ground conductor 25 surrounding the signal line through hole 28). By this etching, a ground line for the signal line is also formed in parallel with the outside of the differential signal line, and this ground line is formed by being connected to the ground conductor 25 exposed on the surface (FIGS. 2A and 2D). reference).

Next, a second example of the method of manufacturing the printed wiring board according to the above embodiment will be described with reference to FIG.

FIG. 4 is a cross-sectional view of a main part of the wiring board for explaining the manufacturing process of the printed wiring board of the present invention.
It is sectional drawing represented along BB 'of (a). First,
As shown in FIG. 4A, a base material 41 having a thickness of about 0.5 to 1.0 mm, in which a copper foil 6 having a thickness of 12 to 35 μm is attached to an epoxy glass substrate, a polyimide glass substrate, or the like, is prepared.

Next, a through hole 42 is formed by drilling a hole in the base material 41 with a drill or the like, and a thickness of 15 mm is formed on the through hole 42 and the surface of the base material 41 by ordinary electroless copper plating and electrolytic copper plating.
A first copper plating film 43 having a thickness of about 35 μm is formed, and then the copper foil 46 and the first copper plating film other than the through-holes are removed using an electrodeposition resist or an etching resist of a dry film to form a land or land. First on the wall of the through hole 42
Is formed with the copper plating 43 formed thereon. Note that, instead of electroless copper plating for base plating of electrolytic copper plating, a copper film or an organic conductive film by sputtering can be used.

Next, a first insulating material 26a made of a liquid thermosetting epoxy resin is filled into the through hole 42 by using a squeegee or the like, and thermally cured, and the surface is polished with a buff or the like to polish the surface of the through hole 42. Of the thermosetting resin of the
A photo-thermosetting epoxy resin is applied on the surface by a screen printing method or a curtain coating method to a thickness of about 70 μm, selectively irradiated with ultraviolet rays, and developed with an aqueous solution of sodium carbonate to form a differential signal line and a signal line grounding line. A pattern of the second insulating material 26b is formed in the region and thermally cured (FIG. 4C). The connection portion (the end of the through hole) of the first copper plating film 43 with the signal line ground line is the second insulating material 26.
b is left uncovered and exposed.

Next, two through holes 45 having a diameter of 0.1 mm are formed at predetermined intervals in the first insulating material 16a and the second insulating material 16b filled inside the through holes 24 by a drill. The entire surface including the through hole 45 is coated with a second copper plating film having a thickness of 10 to 20 μm by the copper plating technique (see FIG. 4).
(D)). Note that one through-hole 45 is shown in FIG. 4D because the cross-sectional view is shown along BB ′ in FIG. 2A.

Next, a photoresist (not shown)
By patterning the second copper plating film 44 by etching using, the differential signal lines 32 and 33 are formed as shown in FIG. The differential signal lines 32 and 33 are connected by signal line through holes 28,
The signal line through hole 28 and the first copper plating film 44
(The ground conductor 25 surrounding the signal line through hole 28). By this etching, a ground line for the signal line is also formed in parallel with the outside of the differential signal line, and this ground line is formed by being connected to the ground conductor 25 exposed on the surface (FIGS. 2A and 2D). reference).

[0030]

As described above, in the present invention, two corresponding differential signal lines on both sides of the double-sided printed wiring board are arranged inside the double-sided printed wiring board such that at least a part thereof is exposed on both sides. Two cylindrical through conductors are electrically connected to each other through two through-holes that are electrically insulated from each other, and a ground line for signal lines is arranged outside the two differential signal lines on both sides. The following effects can be obtained by using a structure in which the signal line ground wire is connected to the exposed portion of the cylindrical ground conductor on the surface of the wiring board. Since the characteristic impedance can be controlled in the through hole of the differential signal line, it is possible to prevent the occurrence of the disturbance phenomenon in the through hole of the signal. Since the characteristic impedance at the surface and through holes can be controlled on the double-sided printed wiring board, high-frequency elements for communication equipment can be mounted.

[Brief description of the drawings]

FIG. 1 is a schematic perspective view of a double-sided through-hole wiring board according to an embodiment of the present invention.

FIGS. 2A and 2B are a plan view and a cross-sectional view of a main part of the double-sided through-hole wiring board of FIG. 1, wherein FIG. 2A is a plan view and FIG.
(C) is a cross-sectional view along the line AA ′ of FIG.
FIG. 4D is a cross-sectional view along the line B ′, and FIG. 4D is a cross-sectional view along the line CC ′ in FIG.

FIG. 3 is a cross-sectional view of a main part of a substrate for describing a first method for manufacturing a double-sided through-hole wiring board of the present invention.

FIG. 4 is a cross-sectional view of a main part of a substrate for describing a second method of manufacturing a double-sided through-hole wiring board of the present invention.

FIG. 5 is a sectional perspective view of a through-hole portion of a conventional multilayer printed wiring board.

[Explanation of symbols]

22 Upper surface layer 23 Lower surface layer 24, 54 Through hole 25 Ground conductor 26a First insulator 26b Second insulator 27,28 Signal line through hole 29,30 Element 31,32,33,34 Differential Signal lines 35, 36, 37, 38 Ground lines for signal lines 41 Base material 42, 45 Through hole 43 First copper plating film 44 Second copper plating film 46 Copper foil 51 Multilayer printed wiring board 52 Inner layer ground conductor layer 53 insulating layer 55 ground conductor 56, 57 signal wiring pattern

Claims (6)

[Claims] 1. An insulating substrate comprising: two parallel differential signal lines disposed at predetermined positions on one surface of an insulating substrate; and two signal line through holes penetrating both surfaces of the insulating substrate. In a double-sided printed wiring board having a wiring circuit connected to two parallel differential signal lines disposed on the other surface, the two signal line through holes are provided inside the insulating substrate. A portion of the grounding conductor is surrounded by a cylindrical grounding conductor exposed on the surface of the insulating substrate, and an exposed portion of the grounding conductor on the surface of the insulating substrate is provided on both sides of the insulating substrate outside the two differential signal lines. A double-sided printed wiring board having a wiring structure connected to signal line ground lines arranged in parallel with the differential signal lines. 2. The double-sided printed wiring board according to claim 1, wherein the differential signal lines on the insulating substrate are in a positional relationship of 180 ° with each other. 3. The signal line through hole and the cylindrical grounding conductor are insulated by a first insulating material filled between the signal line through hole and the cylindrical grounding conductor. The double-sided printed wiring board according to claim 1, wherein 4. The double-sided printed wiring board according to claim 3, wherein a thermosetting resin is used as said first insulating material. 5. The differential signal line and the cylindrical grounding conductor are insulated by a second insulating material provided between the differential signal line and an end of the cylindrical grounding conductor. The double-sided printed wiring board according to claim 1, wherein: 6. The double-sided printed wiring board according to claim 3, wherein a photo-thermosetting resin is used as the second insulating material.