JP4296864B2 - High-speed signal stubless through-hole multilayer printed wiring board manufacturing method, multilayer printed wiring board - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a method for manufacturing a high-speed signal stubless through-hole multilayer printed wiring board and a high-speed signal stubless through-hole multilayer printed wiring board manufactured by this manufacturing method.
[0002]
[Prior art]
In response to the demand for high-density integration of multilayer printed wiring boards, multilayer printed wiring boards with improved electrical characteristics that can handle high-speed signals are required. That is, in the multilayer printed wiring board, as shown in FIG. 3, a plurality of printed wiring boards 11 having wirings 12 formed on the surface are laminated to form the multilayer printed wiring board 1, and the through-hole plating layer 14 is formed on the multilayer printed wiring board. A through-hole 13 having a signal line is formed and a wiring 12A formed therein is connected to form a signal path. The through-hole plating layer 14 and the end 121 of the wiring 12A are electrically connected, and a land 141 is formed on the outermost part of the substrate, for example, a component such as an LSI is mounted.
[0003]
A portion below the through-hole plating layer 14 of the through-hole 13, that is, a portion that is not useful for forming a signal path causes an inconvenience described later as a surplus portion (Stub).
[0004]
Such a signal path formed by the through-hole plating layer 14 and the wiring 12A is shown as an equivalent circuit in FIG. That is, the resistance of the wiring 12A is indicated as Rw, and the resistance formed by tan δ of the printed wiring board 11 is grounded in parallel. Further, the capacitors C ₁ and C ₂ formed by the stub are grounded in parallel.
[0005]
In such an equivalent circuit, as shown in FIG. 4 (B), the substantially square wave from LSI is input, is degraded by the capacitance C ₁ by a stub formed on the input side waveform a next, resistance Rw after being attenuated by the like, the waveform b becomes the capacitance C ₂ of the output side, resulting in a phenomenon that a sinusoidal square wave digital signal or signal attenuation on the way the signal path is deteriorated in a high-speed signal.
[0006]
As a technique for preventing such signal attenuation and deterioration, as shown in FIG. 5, the excess portion (stub) of the through-hole plating layer 14 is scraped off from the back surface of the multilayer printed wiring board 11 to form a capacitance as a stubless structure. It has been proposed to reduce the influence of C (for example, see Patent Document 1, Patent Document 2, Patent Document 3, etc.).
[0007]
[Patent Document 1]
International Publication No. WO 01/56338 A1
[Patent Document 2]
Japanese Patent Laid-Open No. 8-153973 [Patent Document 3]
[Patent Document 1] Japanese Patent Laid-Open No. 2003-158381
[Problems to be solved by the invention]
When only the surplus through-hole plating layer formed on the inner wall of the through-hole is scraped off using a drill having a through-hole formed by the stubless method, for example, the diameter of the multilayer printed wiring board having a thickness of 6 mm is reduced to 0. When a through hole having a diameter of 0.3 mm is formed using a 3 mm cone, and the inner wall of the through hole is plated with 50 μm, the inner diameter of the through hole becomes 0.2 mm. However, when the countersink is applied to the through hole using the cone, the cutting edge provided at the tip of the cone may dig through the through hole plating layer and may be countersunk from the center line of the through hole. It was recognized that problems such as excessively cutting through holes or leaving a through hole plating layer on the inner wall of the through hole were caused.
[0009]
This problem can be solved by cutting with a drill with a diameter sufficiently larger than the diameter of the through-hole. However, in the lower wiring layer formed in a stubless manner, the through-hole should not be exposed on the counterbore inner wall. A margin 15 (see FIG. 5) having a diameter larger than the hole diameter has to be provided, and it has not been possible to sufficiently respond to the trend of high-density wiring.
[0010]
An object of the present invention is to solve such a problem, and an object of the present invention is to provide a multilayer printed wiring board that simultaneously satisfies the high density wiring of the multilayer wiring board and the stubless through hole that can cope with high-speed signals.
[0011]
[Means for Solving the Problems]
In order to solve the above-mentioned problems, the present invention provides a cutting tool having a guide hole at the tip, which has a diameter substantially the same as the diameter of the through-hole, in the method for manufacturing a high-speed signal stubless through-hole multilayer printed wiring board. A manufacturing method that completely removes the through-hole plating layer without being eccentric from the center line of the through-hole by using a spot facing process, and a high-speed signal stubless through-hole multilayer printed wiring board manufactured by this manufacturing method are provided.
The high-speed signal stubless through-hole multilayer printed wiring board used in the present invention is (1) a printed wiring board capable of handling high-speed signals, and (2) an excess portion of the through-hole plating layer formed in the through-hole ( (3) means a multilayer printed wiring board formed by laminating a plurality of printed wiring boards provided with a wiring layer on the surface.
[0012]
DETAILED DESCRIPTION OF THE INVENTION
A method for manufacturing a high-speed signal stubless through-hole multilayer printed wiring board according to the present invention will be described below with reference to FIG. 1A and 1B are diagrams for explaining a manufacturing process of a high-speed signal stubless through-hole multilayer printed wiring board according to the present invention. FIG. 1A shows a through-hole forming process, and FIG. (C) is a longitudinal cross-sectional view which shows typically after a layer formation process and after a spot facing process.
[0013]
First, a multilayer printed wiring board is formed by laminating a plurality of printed wiring boards 11 provided with wiring 12 on the surface. A through hole 13 is drilled at a predetermined position of the multilayer substrate using a drill 30. As the drill 30 used here, a drill usually used for forming a through hole can be used. The end portion 121 of the wiring 12A drawn out to the outside by the through hole 13 is exposed in the through hole 13 (FIG. 1A).
[0014]
Next, a conductive material is plated on the inner wall of the opened through hole 13 by a known method to form the through hole plating layer 14. By forming the through-hole plating layer 14, the end 121 of the wiring 12 </ b> A is electrically connected to the through-hole plating layer 14. Here, on the outermost printed wiring board 11a, a land 141 that is integrated with the through-hole plating layer 14 and on which a mounting component or the like is mounted can be formed (FIG. 1B).
[0015]
Thereafter, the unnecessary through-hole plating layer (stub) 14 in the through-hole 13 is scraped off from below the through-hole 13 by using, for example, a cutting tool 50 (FIG. 1C). As the cutting tool 50, a through hole 13 having a hole diameter, that is, a diameter substantially the same as that of the drill 30 having a through hole formed therein, and having a shape in which a guide portion is provided at a tip end portion can be used.
[0016]
In the high-speed signal stubless through-hole multilayer printed wiring board 1 obtained by this method, the tip of the cutting tool 50 is guided to the hole 142 formed in the through-hole plating layer 14 of the through-hole 13 in the step of scraping the stub. Even if the inside of the through hole 13 is slightly bent, the through hole plating layer 14 can be evenly cut by digging along the bending, and the through hole plating layer 14 can be removed without leaving the inner wall of the through hole 13.
[0017]
In the through hole 13a shown on the right side of FIG. 1, an example in which the through hole 13a is bent and drilled in the middle by the first drilling process is exaggerated.
[0018]
Since the outer dimension of the cutting tool 50 is a small diameter of about 0.3 mm, which is generally equal to the outer dimension of the drill 30 used in a multilayer wiring board, it is easily elastically deformed. Since the cutting tool 50 has a structure in which a guide portion is provided at the tip portion, the tip portion has a low function of making a new hole, and proceeds along the previously drilled through hole. Therefore, even if the through-hole 13a by the first drilling is bent, the surplus portion of the plating layer can be evenly cut along the bent through-hole.
[0019]
In the multilayer printed wiring board obtained by this process, the stub formed in the through hole is surely removed, so that the parasitic capacitance caused by the stub can be reduced and high-speed signals can be handled. Further, since the diameter of the cutting tool 50 for scraping off the stub can be made substantially the same as the outer diameter of the drill 30, the high-density wiring of the multilayer wiring board 1 is not hindered.
[0020]
FIG. 2 is an explanatory view showing details of the cutting tool of the present invention.
[0021]
A cutting tool denoted by reference numeral 50 as a whole has a cylindrical shank portion 51 held by a chuck of a processing apparatus and a cutting blade portion 52 provided with a drill-like cutting blade, and is provided at the tip of the cutting blade portion 52. The guide part 53 is provided.
[0022]
The outer diameter dimension of the cutting edge portion 52 is formed to be approximately the same diameter as the hole diameter dimension of the through hole. The guide part 53 is formed in a cylindrical shape having a smaller diameter than the cutting edge part 52. That is, the guide part 53 does not have a cutting edge and serves as a guide when the cutting edge part 52 of the cutting tool is smoothly inserted into the through hole in which the plating layer is formed. The length dimension of the guide portion 53 is selected as appropriate, and the tip of the guide portion 53 may be formed in the tapered portion 54.
[0023]
In the present embodiment, the diameter dimension of the cutting edge portion 52 is approximately the same as the hole diameter dimension of the drilled through hole, and thus, for example, the diameter is as small as 0.3 mm. Therefore, this cutting edge portion is easily elastically deformed. For example, even if the through hole by the first drilling is bent in the middle, the excess plating layer is effectively scraped along the bent through hole. be able to.
[0024]
【The invention's effect】
As described above, according to the present invention, when a high-speed signal stubless through-hole multilayer printed wiring board is manufactured by scraping off an excessive portion of the through-hole plating layer of the through hole provided in the multilayer printed wiring board, the multilayer wiring board has a high density. It is possible to provide a manufacturing method capable of eliminating a stub by scraping without leaving a through-hole plating layer formed on an inner wall surface of a through-hole without hindering wiring.
[0025]
In addition, this manufacturing method can provide a high-speed signal stubless through-hole multilayer printed wiring board that sufficiently responds to the trend of high-density wiring and that reliably removes stubs in the through-holes.
[Brief description of the drawings]
FIG. 1 is a diagram for explaining a manufacturing process of a high-speed signal stubless through-hole multilayer printed wiring board according to the present invention. FIG. 2 is a diagram for explaining a cutting tool according to the present invention. FIG. 4 is an equivalent circuit of a signal path via a through hole in the multilayer printed wiring board shown in FIG. 3. FIG. 5 is a diagram for explaining the correspondence by a conventional counterbore.
DESCRIPTION OF SYMBOLS 1 High-speed signal stubless through hole multilayer printed wiring board 11 Printed wiring board 12 Printed wiring 121 Printed wiring edge part (exposed part)
13 Through-hole 14 Through-hole plating layer 141 Land 142 Hole 15 Margin 30 Drill 50 Cutting tool

Claims (2)

A method for producing a multilayer printed wiring board in which a plurality of printed wiring boards having a wiring layer provided on the surface is laminated,
Forming a through hole at a predetermined position of the multilayer printed wiring board; and
Forming a through-hole plating layer on the inner wall surface of the through-hole;
A cutting tool having a diameter substantially the same as the hole diameter of the through hole and using a cutting tool as a guide portion without forming a cutting edge at the tip portion, and a step of scraping off an excess portion of the through hole plating layer in this order. A high-speed signal stubless through-hole multilayer printed wiring board manufacturing method. In a high-speed signal stubless through-hole multilayer printed wiring board in which multiple printed wiring boards with a wiring layer provided on the surface are stacked,
High-speed signal stubless through, characterized in that a surplus part of the through-hole plating layer is cut off using a cutting tool that does not form a cutting edge at the tip having the same diameter as that of the through-hole, but serves as a guide. Hole multilayer printed circuit board.

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