CN115915628A

CN115915628A - Method for processing multilayer printed wiring board

Info

Publication number: CN115915628A
Application number: CN202210900518.5A
Authority: CN
Inventors: 张瑞良; 时永胜典; 薗田耕平
Original assignee: Via Mechanics Ltd
Current assignee: Via Mechanics Ltd
Priority date: 2021-08-20
Filing date: 2022-07-28
Publication date: 2023-04-04
Also published as: JP2023028658A; TW202310691A; KR20230028149A

Abstract

The invention provides a method for processing a multilayer printed wiring board, which does not cause defective stub removal even if a front hole is inclined. The solution of the present invention is to measure the position coordinates of the back side opening of the front hole formed in the multilayer printed wiring board. And correcting the back drilling processing program by using the measured position coordinates, and carrying out spot facing processing by using the corrected back drilling processing program, wherein the back drilling processing program is manufactured by converting the processing designated position coordinates of the front hole processing program.

Description

Method for processing multilayer printed wiring board

Technical Field

The present invention relates to a method of processing a multilayer printed wiring board, and more particularly, to a method of spot facing (back drilling) for removing a stub of a multilayer printed wiring board.

Background

In order to connect the internal conductor wiring layers of a multilayer printed wiring board (hereinafter referred to as a "board"), a through hole (hereinafter referred to as a "front hole") is formed from the front surface side (hereinafter referred to as a "first surface side") of the board toward the back surface side (hereinafter referred to as a "second surface side"), and conductive plating is performed thereon. However, since the plated portion of the via hole is longer than the distance between the target conductor wiring layers, there is a problem that impedance mismatch, signal delay, and waveform blunting occur unless an excessively long portion (hereinafter referred to as "stub") is shortened.

In order to solve this problem, for example, as disclosed in

patent document

1 or 2, a countersinking process (hereinafter, referred to as "back drilling process") of removing a plating layer serving as a stub is performed from the other surface side of the substrate to the front of the conductor wiring with a drill having a diameter slightly larger than that of the front hole after plating. With the recent increase in the frequency of substrates, the demand for such processing has rapidly increased.

Fig. 1 is a diagram illustrating a conventional back-drilling method, and is a cross-sectional view of a substrate. A conventional general back drilling method will be described with reference to fig. 1. Here, the first conductor layer 2 and the second conductor layer 3 of the substrate 1 are connected by the plating layer 5, and the stub 6 located from the second conductor layer 3 to the other surface side of the substrate is removed as an example.

First, the substrate 1 is placed on a table of a drilling machine (not shown), and as shown in fig. 1 a, a front hole 4 penetrating the substrate 1 from one surface side is formed at a position where the first conductor layer 2 and the second conductor layer 3 are connected, by a front-hole-machining drill 7 held by a spindle 9 (front-hole-machining step). Thus, a part of the first conductor layer 2 and the second conductor layer 3 is exposed to the inner wall surface of the front hole 4. The front hole machining is performed by preparing a machining program (hereinafter, referred to as "front hole machining program") that specifies the position coordinates of a hole to be machined in advance, and following the program. Here, the drilling machine is controlled so that the spindle 9 holding the drill and the table on which the substrate 1 is placed are moved in the XY direction relative to each other, and the rotation center of the drill is positioned at the position coordinates specified by the machining program. A through hole (hereinafter, referred to as a "reference hole"), which is not shown, is formed as a reference at a predetermined position on the substrate 1, and a position coordinate of each hole is specified by setting a specific position of the substrate 1 as an origin from the reference hole.

Next, the substrate 1 is removed from the table, and as shown in fig. 1B, a plating layer 5 having a predetermined thickness is formed on the inner wall of the front hole 4 by a known method (plating process). Thus, the first conductor layer 2 and the second conductor layer 3 are electrically connected by the plating layer 5.

Then, the substrate 1 is placed on the table of the drilling machine again in a state where the X-axis in the front hole machining is reversed as the rotation center. Then, as shown in fig. 1C, back drilling is performed from the other surface side of the substrate 1 to the second conductor layer 3 at a position corresponding to the front hole 4 using a back drilling drill 8 having a diameter slightly larger than that of the front hole (back drilling step). Thereby, the stub 6 of the substrate 1 is removed ((D) of fig. 1).

Here, the back drilling process needs to be performed at a position corresponding to the already formed front hole. Therefore, a back-drilling program is created by converting the value of the Y coordinate into a value multiplied by-1 (a value in which the positive and negative values are exchanged) while maintaining the value of the X coordinate at the machining designated position coordinate of the front hole machining program, and then the back-drilling program is executed in accordance with the program. The coordinate position is converted into (1, -1) and (2, -3) as the designated position coordinates for back drilling, for example, in the case where the first front hole is provided at the position coordinates (1, 1) and the second front hole is provided at the position coordinates (2, 3) in the front hole processing program.

In this way, conventional back drilling is performed by a program that converts the position coordinates of one surface of the substrate into the position coordinates of the other surface. This is premised on the front hole being formed vertically with respect to the horizontal plane of the substrate, and the back-drill processing designation position coordinate is located on the vertical line of the center of the opening on one surface side of the front hole in the substrate (front-hole processing designation position coordinate).

Documents of the prior art

Patent document

Patent document 1: japanese patent laid-open publication No. 2016-122825

Patent document 2: japanese patent laid-open No. 2012-222187

Disclosure of Invention

Problems to be solved by the invention

However, the front hole formed in the substrate is not limited to being formed vertically with respect to the horizontal plane of the substrate, and may be formed obliquely. In the case where the front hole is inclined, there is a problem that a defective pile removal occurs as described below.

Fig. 2 is a diagram illustrating an example of defective stub removal due to diagonal front hole travel, and is a cross-sectional view of a substrate for each processing step corresponding to fig. 1. The front hole 4 may be formed obliquely by a slanting groove or an engagement of the front hole machining drill 7. In this case, as shown in fig. 2 (a), the opening center position on the other surface side of the substrate 1 is shifted from the opening center position on the one surface side. Therefore, after the plating process (fig. 2B), when the substrate 1 is subjected to the back drilling process by reversing the front and back sides, the processing designated position coordinates of the back drilling process program are deviated from the actual opening position on the other surface side. When the back drilling is performed in this state (fig. 2C), the stub 6 near the opening on the other surface side does not contact the back drilling bit 8, and a part of the stub remains without being removed as shown in fig. 2D.

Here, although

patent document

1 or 2 discloses a technique for improving the positional accuracy in the depth direction in the back drilling process, it does not describe a problem of defective pile removal in the front hole formed in an oblique manner. The present invention has been made to solve the above problems, and an object of the present invention is to provide a back drilling method which does not cause defective pile removal even in a deviated front hole.

Means for solving the problems

In order to solve the above problems, the present invention is a method for processing a substrate, including: a front hole processing step of forming a front hole penetrating from one surface side to the other surface side at a position coordinate specified by a pre-made front hole processing program for the multilayer printed wiring board; a plating process step of forming a plating layer on an inner wall of the front hole; and a back drilling process for removing a part of the plating layer from the other surface side by spot facing; the substrate processing method includes: a back drill processing program creation step of creating a back drill processing program in which the position coordinates obtained by converting the processing designated position coordinates of the front hole processing program are designated as a processing position; an opening position measuring step of measuring an opening position coordinate on the other surface side of the front hole after the front hole machining step and before the back drilling machining step; and a back drilling program correcting step of correcting the back drilling program based on the measured opening position coordinates; in the back drilling step, spot facing is performed at the position coordinates specified by the corrected back drilling program.

Effects of the invention

According to the present invention, since the back-drilling designated position coordinates are corrected based on the opening position coordinates on the other surface side of the actually measured front hole, even if the front hole is inclined, the front hole can be machined without generating a defective pile removal.

Drawings

Fig. 1 is a diagram illustrating a conventional general back drilling method;

fig. 2 is a view illustrating an example of defective pile removal due to slant of a front hole;

fig. 3 is a configuration diagram of a drilling device according to an embodiment of the present invention;

fig. 4 is a configuration diagram of a hole position measuring apparatus according to an embodiment of the present invention;

fig. 5 is a diagram illustrating a relationship between the center of the other-surface-side opening of the front hole and the rotation center of the back-drill-processing drill.

Description of the reference numerals

1: multilayer printed wiring board

7: drill bit for processing front hole

8: drill bit for back drilling

9: main shaft

11: working table

12: vertical direction driving part

13: horizontal direction driving part

14: camera with a lens having a plurality of lenses

20: integral control device

21: drilling control unit

22: storage unit

23: back drill processing program creation unit

24: back drill processing program correcting part

30: hole position measuring device

31: light penetration workbench

32: line camera

33: linear guide

34: horizontal direction driving part

40: measuring device control unit

41: image processing unit

Detailed Description

Hereinafter, representative embodiments of the present invention will be described with reference to the drawings. Fig. 3 is a configuration diagram of a drilling device as an embodiment of the present invention. Note that the same components as those described as a conventional example will be described with the same reference numerals. Reference numeral 11 denotes a table on which the substrate 1 is placed, and 9 denotes a spindle for holding and rotating the front-hole-machining drill 7 (or the back-drilling drill 8). Reference numeral 12 denotes a vertical direction driving unit which drives the spindle 9 in the vertical direction. Reference numeral 13 denotes a horizontal direction driving unit which drives the table 11 and the spindle 9 in the X direction and the Y direction relative to each other. Here, for convenience of explanation, only one horizontal direction driving unit 13 is shown, but actually, the horizontal direction driving units are provided in the X direction and the Y direction, respectively. The vertical direction driving unit 12 and the horizontal direction driving unit 13 are controlled by the drilling control unit 21 to move the rotation center of the front-hole drilling bit 7 (or the back-hole drilling bit 8) to the position coordinates specified by the machining program, and lower and raise the spindle 9 to cut the substrate 1. The drilling control unit 21 recognizes a reference hole, not shown, of the substrate 1 based on the image data of the camera 14, sets a specific position of the substrate 1 as an origin, and specifies a specific position coordinate to perform the machining.

Reference numeral 20 denotes an overall control device for controlling the entire drilling device, and the overall control device includes: a drilling control unit 21 for performing drilling; a storage unit 22 for storing a front hole machining program, a back drilling machining program, a correction back drilling machining program, and the like; a back drilling program creation unit 23 for creating a back drilling program based on the front hole processing program; and a back-drilling program correcting section 24. The overall control device 20 is connected to a hole position measuring device 30 described in detail below. The overall control device 20 includes a control unit other than the above, a CPU (central processing unit) not shown in the drawings, and the like, and the CPU includes a control unit and an arithmetic unit, and the control unit controls the flow of interpretation of instructions and control of a program, and the arithmetic unit executes arithmetic operations.

Fig. 4 is a block diagram of the hole position measuring device 30. The hole position measuring device 30 will be described with reference to fig. 4. The hole position measuring device 30 is connected to the overall control device 20, measures the coordinates of the center position of the other-side opening of the front hole formed in the substrate 1, and transmits the measured position coordinates to the overall control device 20.

Reference numeral 31 denotes a light transmission table on which glass or the like of the substrate 1 to be measured is placed. A line camera 32 as an imaging means is disposed below the light-transmitting table 31 so as to image upward. In the in-line camera 32, image pickup elements (not shown) are linearly arranged in the X-axis direction (direction perpendicular to the paper surface).

The line camera 32 is movably held by a linear guide 33 extending in the Y-axis direction (the left-right direction of the drawing), and is movable along the linear guide 33 by a horizontal direction driving unit 34. A linear scale, not shown, is provided on the linear guide 33, and a sensor, not shown, is provided at a position facing the linear scale of the line camera 32. The measuring device control unit 40 accurately controls the position of the linear camera 32 in the Y-axis direction by the linear scale and the sensor.

The measuring device control unit 40 controls the image pickup operation of the line camera 32 and the driving of the horizontal direction driving unit 34. The measuring device control unit 40 is provided with an image processing unit 41, and the image processing unit 41 recognizes the opening position coordinates from the image data and the like sent thereto from the line camera 32. The measuring device control unit 40 includes a CPU, not shown, which includes a control unit and an arithmetic unit, the control unit controlling the flow of interpretation of instructions and control of programs, and the arithmetic unit executing arithmetic operations. The measuring device control unit 40 is connected to the overall control device 20, and controls each unit, not shown, of the hole position measuring device 30 together with the overall control device 20.

The processing method according to the present invention is explained. Further, detailed description of the same steps as those in the conventional art is omitted. First, the substrate 1 is placed on the table 11 of the drilling machine, and a front hole is formed in accordance with a front hole processing program prepared in advance and stored in the storage unit 22 (front hole processing step). Next, a plating layer having a predetermined thickness is formed on the inner wall of the front hole formed in the substrate 1 by a known plating method (plating process).

Then, the opening position on the other surface side of each front hole formed in the substrate 1 is measured in the following manner (opening position measuring step). The substrate 1 is placed on the light-transmitting table 31 of the hole position measuring device 30 in the same front-back direction (direction in which one surface side becomes the upper surface) as in the front hole processing. Then, the line camera 32 is positioned at the moving origin, and then, the imaging of the other surface side of the substrate 1 is started. Further, in the present embodiment, the origin of movement is located at the right end of the straight guide 33 in the figure. Then, the line camera 32 photographs the other surface side of the substrate 1 at every predetermined sampling time while moving on the linear guide 33, and transmits the photographed data to the image processing unit 41. The image processing unit 41 calculates the center position coordinates of each anterior foramen from the captured image data output from the line camera 32, the position of the line camera 32 in the Y-axis direction, and the like.

The image processing unit 41 sets an origin from a reference hole provided in the substrate 1 for the recognized opening center of each front hole, and calculates position coordinates. The measurement position control unit 40 transmits the measurement position coordinates obtained by the calculation of the image processing unit 41 to the overall control device 20. The measurement position coordinates transmitted to the overall control device 20 are stored in the storage unit 22.

Next, a back-drilling program is created from the front-hole machining program (back-drilling program creation step). Specifically, the back-drilling program creation unit 23 of the overall control device 20 creates a back-drilling program for converting the value of the Y coordinate into a value multiplied by-1 (value obtained by exchanging positive and negative values) while maintaining the value of the X coordinate, and sets the obtained position coordinate as the machining designated position coordinate, and stores the machining designated position coordinate in the storage unit 22.

Then, the prepared back-drilling program is corrected in the following manner based on the measurement position coordinates (back-drilling program correction step).

The back-drilling program correcting unit 24 compares the machining designated position coordinates of the back-drilling program with the corresponding measured position coordinates, and calculates the amount of deviation between the two. The measurement position coordinates are those of the opening formed on the other surface side of the front hole of the substrate 1, and therefore, they are in the same XY coordinate system as those of the back-drilling specified position coordinates converted as if the front-hole-machining specified position coordinates were machined from the other surface side. Therefore, each machining-designated position coordinate can be compared with the corresponding measurement position coordinate. Then, when the deviation amount is less than a predetermined value, the machining designated position coordinates are maintained, and when the deviation amount is equal to or greater than the predetermined value, the machining designated position coordinates are replaced with the measurement position coordinates. The machining designated position coordinates included in the back drilling program are compared with the corresponding measurement position coordinates, and are corrected by replacement (hereinafter, the back drilling program after correction is referred to as "corrected back drilling program").

Here, the predetermined value as a reference for the position coordinate replacement determination may be R-R for the following reason when the radius of the front hole is R and the radius of the drill used for the back drilling is R.

Fig. 5 is a diagram illustrating a relationship between the center of the opening on the other surface side of the front hole and the rotation center of the back drill bit. In fig. 5, a circle having a radius r is an opening on the other surface side of the front hole 4, and a hatched portion inside the circle indicates the stub 6 (plating layer 5). The circle having the radius R is the drill 8 for back drilling, and the portion surrounded by the circle is removed by back drilling. C1 is the center of the opening on the other surface side of the front hole 4, and is a point corresponding to the measurement position coordinates. C2 is the rotation center of the back-drill processing drill 8, and is a point corresponding to the back-drill processing designated position coordinates.

As shown in fig. 5, when the deviation D between the aperture center C1 and the drill center C2 is 0 (fig. 5 a), lower than R-R (fig. 5B), or equal to R-R (fig. 5C), the stub 6 is positioned inside the circle of the back drill 8, and can be removed by back drilling. On the other hand, when the deviation amount D exceeds R-R ((D) of fig. 5), a part of the stub 6 exceeds the circle of the back-drilling bit 8, and the portion thus exceeded becomes a residue to be removed. Therefore, when the deviation amount D exceeds R-R, the stubs 6 can be completely removed from all the front holes 4 by correcting the back-drilling designated position coordinates.

When the correction of the back-drilling process program is completed, the substrate 1 is placed on the table 11 of the drilling apparatus in a state where the X-axis in the front hole process is reversed as the rotation center, and the back-drilling process is performed in accordance with the corrected back-drilling process program (back-drilling process step).

According to the above method, the correction back-drilling program corrects the machining position coordinates of the front hole where the defective pile removal occurs due to the diagonal movement to the measured opening position coordinates, and thus the problem of the defective pile removal can be solved.

In the present embodiment, the reference value for determining whether or not to correct the position coordinates of the back drilling program is R-R, but the present invention is not limited to this, and for example, if the reference value is set to be smaller, the problem of defective pile removal can be more reliably solved.

Claims

1. A method for processing a substrate, comprising: a front hole processing step of forming a front hole penetrating from one surface side to the other surface side in the multilayer printed wiring board at a position coordinate designated by a pre-prepared front hole processing program; a plating process step of forming a plating layer on an inner wall of the front hole; and a back drilling process for removing a part of the plating layer from the other surface side by spot facing;

the method for processing a substrate is characterized by comprising:

a back drill processing program creation step of creating a back drill processing program in which the position coordinates obtained by converting the processing designated position coordinates of the front hole processing program are designated as a processing position;

an opening position measuring step of measuring an opening position coordinate on the other surface side of the front hole after the front hole machining step and before the back drilling machining step; and

a back drill processing program correcting step of correcting the back drill processing program based on the measured opening position coordinates;

in the back drilling step, spot facing is performed at the position coordinates specified by the corrected back drilling program.

2. The method for processing a substrate according to claim 1,

in the back drill processing program correcting step, among the processing designated position coordinates of the back drill processing program, a value in which a deviation amount from the measured opening position coordinates corresponding to the processing designated position coordinates exceeds a predetermined value is replaced with the measured opening position coordinates to correct the back drill processing program.