JP3420126B2 - Double-sided printed wiring board - Google Patents

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 the two sides. 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 their frequencies are becoming higher and higher. In a printed wiring board on which these communication devices are mounted, a signal wiring pattern is striplined or microstriplined 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 the signal wiring pattern on one surface is transmitted to the signal wiring pattern on the other surface of the printed wiring board through the through hole for the signal line, the signal wiring pattern on the other surface is The phenomenon that the signal is disturbed can be seen. The cause of this phenomenon is that the characteristic impedance of the through hole is not controlled, so that the mismatch of the characteristic impedance between the signal wiring pattern on the surface and the through hole occurs. With the increase in the speed of signal transmission in electronic devices such as communication devices, it is becoming more and more important to match the characteristic impedance of signal wiring patterns in printed wiring boards.

To this end, JP-A-2-09469
Japanese Unexamined Patent Application Publication No. 3 and Japanese Unexamined Patent Publication No. 6-037416 disclose a method of providing a cylindrical external conductor connected to an inner ground layer around a through hole for a signal line 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 is an inner ground conductor layer provided in the inner layer, 56 and 57 are signal wiring patterns on the front surface and the back surface, 54 is a through hole for connecting the signal wiring patterns on the front and back surfaces, and 55 is a through hole 54. It is a cylindrical ground conductor portion provided around and is electrically connected to the inner-layer ground conductor layer 52. Reference numeral 53 is an insulating layer filled between the ground conductor 55 and the through hole 54. This technique is effective as a method of controlling the characteristic impedance of one signal wiring pattern on the front and back surfaces of the multilayer printed wiring board in order to coaxially surround the through hole with the cylindrical ground conductor portion 55.

[0006]

Recently, in a double-sided printed wiring board, a method of transmitting a differential signal by using two signal lines has been put into practical use. As the signal speed increases, the multilayer printed wiring board can be used. It is important to control the characteristic impedance of the signal wiring as well as the board.

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

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

[0009]

In the double-sided printed wiring board of the present invention, two parallel differential signal lines arranged at predetermined positions on one surface of the insulating substrate penetrate through 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 through the signal line through holes of A hole is provided inside the insulating substrate, a part of which is surrounded by a cylindrical ground conductor exposed on the surface of the insulating substrate, and an exposed portion of the ground conductor on the surface of the insulating substrate is on both sides of the insulating substrate. And a wiring structure that is connected to the signal line ground lines that are arranged in parallel to the two differential signal lines outside the two differential signal lines. Configured as.

Disposed on the one surface of the insulating substrate
Of the two differential signal lines and the insulating substrate
Wherein the positional relationship between each other by 180 ° from the other of the disposed face two differencing Shah <br/> le signal lines, also, the cylindrical of the ground conductor and the through-hole wherein the signal line is the signal line Can be insulated with the first insulating material filled between the through hole for use and the cylindrical ground conductor.

The differential signal line and the cylindrical ground conductor may be insulated by a second insulating material provided between ends of the differential signal line and the cylindrical ground conductor.

In the present invention, the two through-holes connecting the two differential signal lines on both sides are surrounded by the cylindrical ground conductor, and the signal line ground 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 on the surface of the differential signal line and on the through hole.

[0013]

BEST MODE FOR CARRYING OUT THE INVENTION 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. FIG. 2 shows a plan view and a sectional view of the double-sided printed wiring board of FIG. 1, (a) is a plan view, and (b) to (c) are (a) lines AA ′ and BB ′, respectively. 3 is a cross-sectional view taken along the line CC ′ and FIG.

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, and these signal lines are connected. On the outside of the lines, signal line ground lines 35 and 36 having the same width are arranged in parallel to the signal lines at equal distances. Further, the differential signal line 31, on the upper surface layer 22 on the lower surface layer 23 of the double-sided printed wiring board,
Two differential signal lines 33 and 34 connected to the element 30 in the direction of 32 and 180 ° are arranged in parallel, and signals having the same width are equidistantly arranged outside the signal lines in parallel with the signal lines. Grounding wires 37 and 38 for wires are provided. The ends of the two differential signal lines on each of the upper and lower surface layers are electrically connected by two signal line through holes 27 and 28.
7, 28 are surrounded by a ground conductor 25 that forms a through hole 24 provided in a cylindrical shape on the outside (FIG. 2).
(A), FIG. 2 (b), and FIG. 2 (c)). Ground conductor 25
Is exposed at the surface of each surface layer, and the ground wire for the signal line of the surface layer is electrically connected to the exposed portion (see FIGS. 2A and 2D). .

The insulation between the ground conductor 25 and the differential signal line of the surface layer and the insulation between the ground conductor 25 and the through hole for the signal line is 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 ground wire for signal line is arranged outside the signal wire on the upper and lower surface layers of the printed wiring board in parallel with the signal wire, and the ground wire for signal line and the ground conductor. It is possible to control the characteristic impedance even in a double-sided printed wiring board by connecting the exposed surface portion of. Moreover, since the signal line through holes 27 and 28 are surrounded by the ground conductor 25, they can be treated as coaxial extensions.
It is possible to control the characteristic impedance in the through hole, and it is possible to prevent signal disturbance between the upper and lower differential signal lines.

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

FIG. 3 is a sectional view of an essential part of the wiring board for explaining the 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, such as an epoxy glass substrate or a polyimide glass substrate, on which a copper foil is not attached is prepared.

Next, a through hole 42 is formed by making a hole in the base material 41 with a drill or the like. The diameter of the through hole is determined by the diameter of the through hole for the signal line to be provided in a later step, but it is usually about 1 to 1.5 mm. After forming the through holes 42, a first copper plating film 43 having a thickness of 15 to 35 μm is formed on the through holes 42 and the surface of the base material 41 by ordinary electroless copper plating and electrolytic copper plating, and then etching such as electrodeposition resist is performed. The first copper plating film 43 on the wall of the through hole 42 is protected by a resist, the first copper plating film 43 on the base material 41 is removed by etching, and the first copper plating 43 is formed on the wall of the through hole 42. Through hole 2 with land or landless
4 is formed (FIG. 3B). The first copper plating film may be formed only by electroless copper plating for thickening, and the width of the first copper plating film 43 on the wall of the through hole 41 is 50 to 150 μm on the surface of the base material 41. You may attach the land of. Further, instead of the electroless copper plating for the base plating of the electrolytic copper plating, a copper film formed by sputtering or an organic conductive film can be used.

Next, the first insulating material 26a made of a liquid thermosetting epoxy resin is filled in the through hole 42 by using a squeegee or the like, and after heat curing, the surface is polished with a buff or the like to form the through hole 42. Smooth the thermosetting resin on the surface. Substrate 41
After applying a photo-thermosetting epoxy resin with a thickness of about 70 μm on the surface by screen printing method or curtain coating method, selectively irradiate with ultraviolet rays and develop with a sodium carbonate aqueous solution to form a differential signal line and a ground line forming region for the signal line. Then, a pattern of the second insulating material 26b is formed and heat cured (FIG. 3C). The connection portion of the first copper plating film 43 with the signal line ground line is exposed without being covered with the second insulating material 26b.

Next, the first filling member formed inside the through hole 42 is formed.
After forming two through holes 45 having a diameter of 0.1 mm at a predetermined interval in the insulating material 26a and the second insulating material 26b, a thickness of 1 is formed on the entire surface including the through holes 45 by a normal copper plating technique.
A second copper plating film of 0 to 20 μm is coated (FIG. 3).
(D)). It should be noted that one through hole 45 is shown in FIG. 3D, but this is because the cross-sectional view is shown along the line BB ′ in FIG.

Next, photoresist (not shown)
The second copper plating film 44 is patterned by etching using, to form the differential signal lines 32 and 33 as shown in FIG. The differential signal lines 32 and 33 are connected by the signal line through hole 28,
In addition, the signal line through hole 28 and the first copper plating film 44
(It becomes the ground conductor 25 that surrounds the through hole 28 for the signal line) and is insulated. By this etching, a signal line ground line is also formed in parallel to 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 manufacturing method example of the printed wiring board according to the above embodiment will be described with reference to FIG.

FIG. 4 is a cross-sectional view of an essential 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, after forming a through hole 42 by making a hole in the base material 41 with a drill or the like, the through hole 42 and the surface of the base material 41 have a thickness of 15 by ordinary electroless copper plating and electrolytic copper plating.
The first copper plating film 43 having a thickness of up to 35 μm is formed, and then the copper foil 46 and the first copper plating film other than the through holes are removed by using an electrodeposition resist or an etching resist of a dry film to form a landed or landed film. No. 1 on the wall of the through hole 42
The through hole 24 having the copper plating 43 is formed. Instead of electroless copper plating for undercoating of electrolytic copper plating, a copper film formed by sputtering or an organic conductive film can be used.

Next, the first insulating material 26a made of a liquid thermosetting epoxy resin is filled in 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 form the surface of the through hole 42. Smoothing the thermosetting resin of
The surface is coated with a photothermosetting epoxy resin with a thickness of about 70 μm by a screen printing method or a curtain coating method, and is selectively irradiated with ultraviolet rays and developed with an aqueous solution of sodium carbonate to form a differential signal line and a ground line for a signal line. A pattern of the second insulating material 26b is formed in the region and heat-cured (FIG. 4C). The connection portion (through hole end portion) of the first copper plating film 43 to the signal line ground line is formed of the second insulating material 26.
b is exposed without being covered.

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

Next, photoresist (not shown)
The second copper-plated film 44 is patterned by etching using, to form the differential signal lines 32 and 33 as shown in FIG. The differential signal lines 32 and 33 are connected by the signal line through hole 28,
In addition, the signal line through hole 28 and the first copper plating film 44
(It becomes the ground conductor 25 that surrounds the through hole 28 for the signal line) and is insulated. By this etching, a signal line ground line is also formed in parallel to 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, the two corresponding differential signal lines on both sides of the double-sided printed wiring board are arranged inside the double-sided printed wiring board so that at least a part thereof is exposed on both sides. Inside of the cylindrical ground conductor are respectively connected by two through holes that are electrically insulated from each other, and the signal line ground lines are arranged outside the two differential signal lines on both sides. With the 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, the following effects can be obtained. Since the characteristic impedance in the through hole of the differential signal line can be controlled, the disturbance phenomenon of the signal in the through hole can be prevented. Since the double-sided printed wiring board can control the characteristic impedance on the surface and through holes, it is possible to mount a high frequency element for communication equipment.

[Brief description of drawings]

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

2A is a plan view of the double-sided through-hole wiring board of FIG. 1 and FIG. 2B is a cross-sectional view of an essential part thereof, in which FIG. 2A is a plan view and FIG.
Is a cross-sectional view taken along the line AA ′ of FIG.
Sectional drawing which followed the B'line, (d) is sectional drawing which followed the CC 'line of (a).

FIG. 3 is a sectional view of an essential part of a substrate for explaining a first manufacturing method of a double-sided through-hole wiring board according to the present invention.

FIG. 4 is a sectional view of an essential part of a substrate for explaining a second method for manufacturing a double-sided through-hole wiring board according to the present invention.

FIG. 5 is a cross-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 line 35, 36, 37, 38 ground line for signal line 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 grounding conductors 56, 57 signal wiring pattern

Claims (6)

(57) [Claims] 1. An insulating substrate, wherein two parallel differential signal lines arranged at predetermined positions on one surface of the insulating substrate pass through two signal line through holes penetrating both sides of the insulating substrate. In a double-sided printed wiring board having a wiring circuit connected to two parallel differential signal lines arranged on the other surface, the two signal line through holes are provided inside the insulating substrate, and one of the through holes is provided. The portion is surrounded by a cylindrical ground conductor exposed on the surface of the insulating substrate, and the exposed portion of the ground conductor on the surface of the insulating substrate is located on both sides of the insulating substrate and outside the two differential signal lines. A double-sided printed wiring board having a wiring structure connected to ground lines for signal lines arranged in parallel with the differential signal lines of the book. 2. The insulating substrate is arranged on the one surface of the insulating substrate.
And the two differential signal lines and the insulating substrate
Double-sided printed wiring board according to claim 1, wherein said the other the disposed face of the two differential signal lines in the positional relationship between each other by 180 °. 3. The signal line through hole and the cylindrical ground conductor are insulated by a first insulating material filled between the signal line through hole and the cylindrical ground 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 the first insulating material. 5. The differential signal line and the cylindrical ground conductor are insulated by a second insulating material provided between ends of the differential signal line and the cylindrical ground conductor. The double-sided printed wiring board according to claim 1. 6. The double-sided printed wiring board according to claim 5, wherein a photothermosetting resin is used as the second insulating material.