JP2005235963A - Method for forming through hole in printed board - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for forming a through hole which reduces a diameter of the hole formed for suppressing the deterioration of electric characteristics caused by the through hole to the minimum, thereby enhancing the integration of a printed board. <P>SOLUTION: After a hole of a small diameter is formed, a hole of a large diameter is formed up to a layer required for electrically connecting a signal line 30 with a signal line 31, plating 40 is performed therein, and next a plating portion where the electric connection is unwanted is removed by a hole 22, thereby reducing a diameter of the hole 22. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a method for forming a through hole in a printed circuit board.

  Conventionally, it is not necessary to electrically connect a signal or power supply in order to improve the deterioration of electrical characteristics caused by a through hole intended to electrically connect a signal or power supply formed on a printed circuit board. The through-hole portion was removed as shown in FIG. 3 (for example, Patent Document 1). In this method, in order to completely remove a through-hole portion unnecessary for electrical connection, it is necessary to make a hole larger than the through-hole formed first in consideration of manufacturing variation. In this method, the finally formed through hole is limited to either the substrate front surface or the back surface at a specific position.

International Publication No. WO 01/56338 A1

In the conventional structure, the diameter of the hole formed to remove unnecessary portions is larger than the diameter of the through hole formed first, and the hole area cannot be mounted on the wiring, so it can be mounted on the printed circuit board. There is a drawback that the wiring area becomes small and the wiring cannot be integrated at a high density.
In order to solve this problem, it is necessary to reduce the through-hole diameter, but in order to mount a component that inserts a lead into the through-hole, it is not possible to make it smaller than a certain diameter due to physical restrictions. was there.

  An object of the present invention is to provide a method of forming a through hole that can reduce the diameter of a hole for improving the electrical characteristics that are formed after plating is formed on the inner wall of the through hole.

  In the through hole forming means of the present invention, when making a through hole for forming a through hole, the hole diameter is changed in the middle of the thickness direction of the substrate to reduce the diameter of a portion unnecessary for electrical connection. It is characterized by. Thereafter, plating is performed. Since the portion unnecessary for the electrical connection has a small diameter, the diameter of the hole formed for removing the portion unnecessary for the electrical connection can be reduced as compared with the conventional technique.

  On the other hand, when a through hole is made, a through hole is formed on both the front surface and the back surface of the substrate at the same position by making the portion of the hole diameter narrower to be removed later near the center in the thickness direction of the substrate. It is possible.

  According to the present invention, since the degree of integration of the printed circuit board can be increased by reducing the diameter of the hole to reduce the influence of the electrical characteristic deterioration due to the through hole, the electrical characteristic deterioration due to the through hole is reduced and integrated. A multi-layer printed circuit board having a high degree can be provided.

  Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a diagram showing an example of a longitudinal sectional structure of a printed board according to the present invention.

  The printed circuit board 1 in FIG. 1A is composed of four layers, has a through hole 20 penetrating the printed circuit board 1, and a signal provided in an outer layer through a plating 40 formed in the inner wall of the through hole. The line 30 and the signal line 31 provided in the inner layer are electrically connected. The conductor 32 and the conductor 33 are electrically insulated from the conductor 30 and the conductor 31. The hole 22 is a hole formed to remove plating unnecessary for connecting the signal line 30 and the signal line 31 after plating is formed on the inner wall of the through hole. When components are directly mounted in the through holes, the signal line 30 or the signal line 31 may not exist.

  In FIG. 1B, by limiting the hole for removing unnecessary portions to the vicinity of the center in the thickness direction of the substrate, the through hole 20 can be insulated on the front and back surfaces of the substrate. Therefore, it is possible to form through holes on the front and back surfaces of the substrate at the same position.

Next, the manufacturing process of the multilayer printed board according to the present invention will be described with reference to FIG.
A small-diameter hole 21 is formed in the printed circuit board 1 with a small-diameter drill or the like (FIG. 2A). Next, a hole 23 is drilled with a drill having a large diameter to a position where it is necessary to electrically connect through the through hole (FIG. 2B). A plating 40 is formed on the inner walls of the holes 21 and 23 (FIG. 2C). Unnecessary plating is removed by opening holes 22 with a drill or the like (FIG. 2D). As a result, the structure of FIG. 1A is realized.

  In this embodiment, this reduces the area of the hole in the lower part of the through hole, increases the area where wiring is possible on the printed circuit board, and improves the degree of integration.

  On the other hand, in forming a hole having a large diameter, the substrate 40 is opened from the front and back surfaces (FIG. 2E), and plating 40 is formed on the inner walls of the holes 21 and 23 (FIG. 2F), and the thickness of the substrate By removing unnecessary portions near the center of the direction with a hole 22 using a drill or the like, the structure of FIG. 1B is realized.

  In this embodiment, this makes it possible to form through holes on the front and back surfaces of the substrate at the same position, thereby improving the degree of wiring integration.

  In the above-described embodiment, an example of a four-layer printed board has been described. Needless to say, the present invention can be applied to a multilayer printed board other than the four-layer printed board. Moreover, although the case where the signal is transmitted is used in the embodiment, it is needless to say that the signal need not be limited. Further, in the embodiment, the drilling by the hole 20 is one layer, but the depth to be drilled is not limited. It goes without saying that the present invention can also be applied to the case of drilling two or more layers. Also, in the embodiment, the case where the outer layer and the inner layer signal line are connected is used, but the case where the inner layer and the inner layer signal line are connected, and the case where the through hole in which the component is mounted is connected to the inner layer or the outer layer signal line. Needless to say, it can also be applied. Further, the order of opening the hole 23 having the large diameter and the hole 21 having the small diameter and the surface (front surface, back surface) for forming the hole 23 having the large diameter are not limited.

It is a figure which shows an example of the longitudinal cross-section of the printed circuit board which concerns on this invention. It is a figure which shows the manufacturing process of the printed circuit board which concerns on this invention. It is a figure which shows the prior art.

Explanation of symbols

1 ... Printed circuit board, 10 ... Insulating substrate,
20 ... hole, 30 ... signal line,
40 …… Plating

Claims (3)

  In a method for forming a through-hole of a printed circuit board having two or more conductor layers for electrically connecting a signal or a power source, through holes having different hole diameters are formed stepwise in the middle of the thickness direction of the board. A method for forming a through hole in a printed circuit board, comprising: removing a portion having a small hole diameter which is not necessary for electrical connection after plating on a wall surface.   2. The through-hole forming method according to claim 1, wherein the through-hole has a portion having a small hole diameter provided near the center in the thickness direction of the substrate. A printed circuit board manufactured using the through hole forming method according to claim 1.

Images