JPH0149039B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field] The present invention relates to a device for punching reference holes in a multilayer printed wiring board.

[Background Art] Multilayer printed wiring boards used in electronic devices and the like are generally manufactured as follows. First, metal foil is pasted on both sides or one side of the inner layer prepreg,
An inner layer circuit is formed on this to create an inner layer circuit board. Then, prepregs for the outer layer are superimposed on the top and bottom of the inner layer circuit board or a plurality of inner layer circuit boards arranged in a plane, and metal foil is further superimposed on the outside of these, followed by heating and pressure forming. . After that, for one inner layer circuit board or a plurality of inner layer circuit boards arranged in a plane, rough cutting is performed for each inner layer circuit. By the way, in the intermediate product of the multilayer printed wiring board produced after the above-mentioned molding, the hole mark displayed on the surface of the inner layer circuit board for indicating the position of the reference hole is detected from the outermost layer metal foil side. A spot with a hole mark is counterbored from above to expose the hole mark, and a reference hole is drilled in the center of this hole mark. Then, by forming an outer layer circuit on the outermost layer of metal foil using this reference hole as a reference, a multilayer printed wiring board is completed.

However, the above method has the following problems. This is because a. In intermediate products of multilayer printed wiring boards that are made up of multiple inner layer circuit boards arranged side by side, the inner layer circuit boards are hidden from view due to the outermost layer of metal foil, so rough cutting is required. b. When trying to find the hole mark, the hole mark is blocked by the outermost layer of metal foil and cannot be seen, so the exact position cannot be determined; and c. Hot pressure molding. The problem is that sometimes misalignment occurs between the outer layer and the inner layer circuit board, making it increasingly difficult to determine the exact position of the hole mark.

Therefore, in order to solve the above-mentioned problems, the following hole mark detection method has been devised. In other words, after forming the inner layer circuit C and hole mark B on the inner layer prepreg, with a patch (guide mark) pasted on the hole mark B in advance, the outer layer prepreg D and metal foil E are stacked and heated and pressed. The intermediate product of the completed multilayer printed wiring board is raised by the thickness of the patch, and the part on the metal foil is visually determined to be slightly shiny. Thereafter, counterbore the determined position to make a counterbore hole A as shown in Fig. 8a, and then peel off the patch to expose the hole mark B as shown in Fig. 8b.
In this method, the adhered resin is further polished to clearly expose the peel-off hole mark B, and the center position X of the hole mark B is determined using a magnifying scope.

However, this method also requires a patching process. Moreover, since the counterbore position is detected visually, it is difficult to drill the counterbore in an accurate position.
Moreover, the depth t ₀ of the counterbore hole A was determined by the operator's intuition, so it required considerable skill to counterbore it to the appropriate depth. Therefore, there was a problem in that the accuracy of the spot facing and drilling positions was low and reliability was lacking. Furthermore, as described above, the resin adheres to the hole mark surface, which not only poses an aesthetic problem but also causes a decrease in the accuracy of the hole drilling position. Furthermore, in addition to the patching process to indicate the hole mark position as described above, manual work such as spot boring, polishing to remove adhering resin, and hole drilling is required.
There were problems with the starting accuracy and quality of each, and it was extremely labor-intensive and difficult to ensure final accuracy. In other words, it was difficult to automate the process while ensuring accuracy, so we relied on the manual process described above, but this ended up being unreasonable in terms of quality and cost.

[Object of the Invention] The present invention has been made in view of the above-mentioned problems, and its purpose is to provide a device for drilling reference holes in a multilayer printed wiring board that is automated at low cost and has high precision in the position of drilling reference holes. is to provide.

[Disclosure of the Invention] The present invention provides a circuit pattern in which a hole mark indicating the position of a reference hole is formed at an appropriate location on an inner layer circuit board, and an edge mark is formed on the surface of the inner layer circuit board to predict the formation position of the hole mark. a multilayer printed wiring board formed of metal foil on the peripheral edge thereof; an edge mark detection means for scanning the surface of the multilayer printed wiring board to detect the position of the edge mark based on a change in eddy current loss; a prediction means for predicting the position of the hole mark from the detection position of the multilayer printed wiring board; and a counterbore hole of a constant depth is drilled at a predetermined position on the upper and lower surfaces of the multilayer printed wiring board based on the prediction result of the prediction means. Upper and lower end mills, a light projection means that irradiates a light beam to either the upper or lower counterbore hole of the multilayer printed wiring board drilled by the end mill, and the countersink hole is arranged from the opposite side of the light emitter. an image processing means for determining the center position of the hole mark from the image obtained by the imaging means;
The present invention is characterized by comprising a drill device that is moved to the center position of the hole mark determined by the image processing means and drills a reference hole in the multilayer printed wiring board.

This will be explained below using examples.

Embodiment FIG. 1 shows an inner layer circuit board 1 used in this embodiment, and the inner layer circuit board 1 has hole marks 1b, 1b, 1b at three locations on the periphery of the circuit pattern 1a having the hole mark 1b. Metal edge marks 8a, 8b, and 8c, which serve as standards for determining the coordinates of the circuit pattern 1a, are formed at the same time as the circuit pattern 1a. These edge marks 8a, 8b, 8c are for determining the xy coordinate axes of the inner layer circuit board 1, as shown in FIG. perpendicular to the axis,
The x-axis is a straight line passing through the center point of the edge mark 8c. Each hole mark 1 according to these xy coordinate axes
Determine the coordinate position of b. For the edge marks 8a, 8b, and 8c, as shown in FIG. 2, an eddy current sensor 9 is mounted inward (in the direction of the arrow, also shown in FIG. 1) while keeping a certain distance from the surface of the outer metal foil 5. The position is measured by scanning. Electric conductors are detected by utilizing the fact that the impedance of the sensor coil changes due to eddy current loss. In this embodiment, since the eddy current loss due to the outer layer metal foil is constant, the change in eddy current loss when the outer layer metal foil and the metal edge mark overlap is detected. As shown in the graph of FIG. 2, when the eddy current sensor 9 that scans the surface of the outer metal foil 5 reaches the edge marks 8a, 8b, and 8c where the first magnetic field change occurs, the sensor output reaches the first waveform peak. It is designed to form point A. Therefore, the eddy current sensor 9
Based on the output change to form the first waveform peak point A, each of the plurality of edge marks 8a,
8b and 8c are measured, and the xy coordinate axes defined on the inner layer circuit board 1 appear on the surface of the outer layer metal foil 5. Therefore,
The position of each hole mark 1b whose coordinates have been determined in advance along the xy coordinate axes can also be automatically determined on the surface of the outer metal foil 5.

Once the position of the hole mark is detected, counterbore processing is then performed at that position. During the counterboring process, the xy coordinates of the hole mark 1b on the inner layer circuit board 1 are matched with those on the outer layer metal foil. If you automatically replace it at the corresponding position by calculation processing etc.,
This is a classification where automation can be realized for counterbore processing.

For example, as shown in FIG. 3, the XY coordinate axes are placed on the outline representing the outer shape of the rough-cut multilayer printed wiring board 7 whose outermost layer is a metal foil for forming an outer layer circuit. The X-axis is taken on one side of the outer shape, and the Y-axis is taken on the side perpendicular to said one side. And now Etsuji Mark 8
Let each coordinate of a, 8b, 8c on the XY coordinate system be (Xa,
Ya), (Xb, Yb), (Xc, Yc), the inclination θ between the xy coordinate axes of the inner layer circuit board 1 and the outer shape of the multilayer printed wiring board 7 can be determined by the following formula.

θ=tan ^-1 (Xb-Xa/Yb-Ya) ... Also, the coordinates (X ₀ , Y ₀ ) on the XY coordinate system of the origin of the xy coordinates of the inner layer circuit board 1 are determined by the following formulas and formulas. .

X ₀ = Xb ^{cos 2} _θ −Yb sin ^θ cos θ ⁺ Hole mark 1b to be found
The XY coordinates (Xi, Yi) of is determined by the following formula and.

Xi=X ₀ +xi cosθ+yi sinθ … Yi=Y ₀ −xi sinθ+yi cosθ … The hole mark 1b obtained as above
By inputting the XY coordinates (Xi, Yi) into an arithmetic control means such as a computer, and controlling the counterbore means provided to move relatively according to the XY coordinates based on the information, the counterbore A hole is automatically formed at a position on the outer metal foil 5.

In the above embodiment, the number of metal edge marks 8a, 8b, 8c formed is not particularly limited, and the positions of the edge marks 8a, 8b, 8c do not have to be located on the xy coordinate axes.

FIG. 4 shows the configuration of a counterbore means consisting of a counterbore positioning NC feeding device, in which a multilayer printed wiring board 7 is placed on an XY table (not shown) that operates based on an XY coordinate system. . The multilayer printed wiring board 7 is moved to the counterbore location using this XY table. At this spot facing portion, end mills 12a12b serving as counter boring means are provided on both upper and lower sides of the pedestal 11.
A hole 11a is formed in the pedestal 11 to receive the lower end mill 12b. Then, the end mill 12a is lowered from above to counterbore the hole 1.
2c is formed as shown in FIG. At this time, the counterbore depth t ₁ is controlled using the downward displacement of the end mill or the passage of time after the contact signal between the metal foil 5 and the end mill 12a is output by the continuity detector 28. Next, the lower end mill 12b is raised at the same position to form the counterbore hole 12c, and the counterbore depth _t2 is controlled in the same manner as the upper end mill 12a.
At this time, the bottom of the upper counterbore hole 12c and the hole mark 1
It is preferable that the distance t ₃ from the groove b is about 0.1 to 0.3 mm, and the counterbore depths t ₁ and t ₂ are about 0.25 mm. The airtight chamber 13 is communicated with a dust collection path 13b for collecting dust, etc. inside, and a rubber material 14 is provided at the periphery of the opening to improve airtightness. Contact pin 15 and pin 15a for connection with end mill 12a
and springs 16 and 16a that bias the contact pin 15 and pin 15a downward. A brush 17 connected to a continuity detector 28 is in sliding contact with a rotor 18 which is rotationally driven by a timing belt 19 and rotates an end mill 12a, and this brush 17 is held by a brush holder 17a.

Now, when the counterbore processing from the front and back sides of the multilayer printed wiring board 7 is completed, the above-mentioned upper counterbore hole 12c portion of the multilayer printed wiring board is moved below the ITV camera 21 as shown in FIG. 6 using the XY table. let
At this time, illumination by optical fibers 20, 20 is applied obliquely from below the lower counterbore hole 12c, and a light transmission image appearing on the bottom surface of the upper counterbore hole 12c is imaged by the ITV camera 21 as shown in FIG. If this light transmission image is image-processed, the center point 26 of the hole mark 1b
Since this is directly derived, the drilling position of the reference hole can be detected with high precision without error.

The image processing device 29 then binarizes the video signal obtained by capturing the image, and uses the binarized image data using conventionally known methods such as the centroid measurement method and the long side 1/2 division method. The center coordinates of the hole mark 1b are determined by , and the multilayer printed wiring board 7 is moved by controlling the XY table (not shown) so that the drill 22 is located below the center coordinates. After that, the actual drilling begins. As a result, a reference hole with extremely high positional accuracy can be obtained. In this case, the drill rotating part is attached to another fine-movement XY table (not shown), and by controlling and driving the fine-movement XY table, the central axis of the drill 22 is aligned with the hole mark 1b.
It may be arranged to align with the center point of . When drilling the holes, the multilayer printed wiring board 7 is placed on the pedestal 11 and is held down from above by the holding member 23.
The surface side is set to a sealed state. Holding member 23
A transparent glass 23b is fitted on the upper surface of the ITV camera 21, and the ITV camera 21 captures a light transmission image through the transparent glass 23b. In addition, the chips generated when drilling a hole with the drill 22 are removed from the air jet passage 23a.
The dust is blown away through the air circulation hole 23e for improving the dust collection effect, and is collected through the dust collection paths 25 and 25'.

As described above, by automatically detecting the position of the hole mark 1b, drilling the counterbore holes 12c, 12c, detecting the center point of the hole mark 1b, and drilling the reference hole, high accuracy is achieved. However, as a method for detecting the position of the hole mark 1b, in addition to the method of detecting the edge marks 8a, 8b, 8c using the eddy current sensor 9 as described above, there are other methods for detecting the position of the hole mark 1b. The method of capturing a light transmission image in the same way as detecting the center point, and the method of capturing the edge mark 8
The edge marks 8a, 8b, 8c may be formed of a magnetic material, and the edge marks 8a, 8b, 8c may be detected from the surface of the outer metal foil 5, which is a non-magnetic material, by a magnetic sensor.

[Effects of the Invention] The present invention provides a circuit pattern in which a hole mark indicating the position of a reference hole is formed at an appropriate location on an inner layer circuit board, and an edge mark for predicting the formation position of the hole mark is formed on the surface of the inner layer circuit board. edge mark detection means for detecting the position of an edge mark without contact by scanning the surface of the multilayer printed wiring board using a multilayer printed wiring board formed of metal foil on the peripheral edge of the multilayer printed wiring board;
Since it is equipped with a prediction means for predicting the hole mark position from the detection position from the edge mark detection means,
The position of the hole mark can be automatically detected with high accuracy, and based on the prediction result of the prediction means, the hole mark is moved to a predetermined position on the top and bottom surface of the multilayer printed wiring board, and a counterbore hole of a constant depth is drilled. Moreover, since it is equipped with a lower end mill, it is possible to automatically drill a counterbore, and in addition to obtaining a counterbored hole of a certain depth, the finish of the bottom of the counterbore hole can be uniformized without variation, and the appearance is improved. The appearance of the multi-layer printed circuit board is improved, and in addition, there is a light projection means that irradiates a light beam to the counterbore holes on either the top or bottom of the multilayer printed circuit board drilled with these end mills, and a counterbore hole is drilled from the opposite side of the light projection side. The center point of the hole mark is automatically detected with high precision because it is equipped with an imaging means arranged correspondingly to take a light transmission image, and an image processing means that determines the center position of the hole mark from the image obtained by the imaging means. Therefore, a reference hole can be drilled at a highly accurate position by a drill device that is moved to the center position of the hole mark determined by the image processing means, and as mentioned above, everything is automated. , it is possible to obtain precision that cannot be obtained from manual or visual work, significantly improve productivity, and improve the quality of the finished product.Moreover, it eliminates the need for patching, which eliminates scratches and foreign matter contamination caused by patching work. This has the effect that the occurrence of major defects in multilayer printed wiring boards, such as wire breaks and shorts, which occur due to these factors, is significantly reduced, and highly reliable products can be obtained.

[Brief explanation of drawings]

FIG. 1 is a plan view showing an embodiment of an inner layer circuit board of a multilayer printed wiring board used in an embodiment of the present invention, FIG.
The figure is an explanatory diagram of a method for automatically replacing the detected hole mark position with the position on the outer layer metal foil,
Fig. 4 is a cross-sectional view of the same end mill section, Fig. 5 is a cross-sectional view of the counterbore hole part of a multilayer printed wiring board obtained by the same end mill, and Fig. 6 is an ITV for detecting the hole mark as above. 7 is an enlarged plan view of the counterbore hole according to the above, and FIG. cross section,
1 is a plan view, 1 is an inner layer circuit board, 1a is an inner layer circuit, 1b is a hole mark, 5 is an outer layer metal foil, 7 is a multilayer printed wiring board, 8a, 8b, 8c are edge marks,
12a and 12b are end mills, 12c is a counterbore hole, 20 is an optical fiber, 21 is an ITV camera, 2
6 is the center position of the hole mark, and 29 is an image processing device.

Claims (1)

[Claims] 1 Hole marks indicating the positions of reference holes are formed at appropriate locations on the inner layer circuit board, and edge marks for predicting the formation positions of the hole marks are formed on the surface of the inner layer circuit board. edge mark detection means for scanning the surface of the multilayer printed wiring board to detect the position of the edge mark without contact; and predicting the position of the hole mark from the detection position from the edge mark detection means. upper and lower end mills that are moved to predetermined positions on the upper and lower surfaces of a multilayer printed wiring board to drill counterbore holes of a constant depth based on the prediction results of the prediction means; and these end mills. A light projection means that irradiates a light beam to a counterbore hole on either the upper or lower side of the multilayer printed wiring board drilled in the multilayer printed wiring board, and a light projection means that is arranged corresponding to the counterbore hole from the opposite side of the light projection side and captures a light transmission image. an imaging means; an image processing means for determining the center position of the hole mark from the image obtained by the imaging means; and a reference hole moved to the center position of the hole mark determined by the image processing means on a multilayer printed wiring board. 1. A reference hole drilling device for a multilayer printed wiring board, comprising: a drill device for drilling holes in a multilayer printed wiring board.