JPS60197322A - Method of inner layer reference hole in multi-layer circuit board - Google Patents

Abstract

PURPOSE:To drill reference holes with no locating hole, by smoothly grinding two adjacent sides on the outer periphery of a substrate to expose the outer edge section of a conductive pattern layer formed therein with inner layer reference holes so that the positions of the reference holes are obtained from discontinuous points. CONSTITUTION:All four sides of a multi-layer circuit board 3 are smoothed by grinding them while the outer edge section of a conductive layer 1b of the board 3 is exposed, and the positions of discontinuous points PX, PY on the conductive pattern layer are determined by means of a detector. When the positions of the discontinuous points have been obtained for every side, the positions distant from the discontinuous points PX, PY by known distances X, Y are set as the positions of reference holes, and therefore, the drill positions are determined in accordance with the positions of the reference holes, thereby inner layer reference holes 8 are drilled at predetermined positions.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention] The present invention relates to a method for drilling inner layer reference holes in a multilayer circuit board.

[Technical Background of the Invention] In general, a multilayer circuit board includes a conductor pattern layer 1a on a surface layer and a back layer, and a plurality of insulating layers 2a, 2b, . . . in addition to In, as shown in an enlarged cross section in FIG. Conductor pattern layers 1b, 1c are interposed between each insulating layer through...

...... is provided.

These conductor pattern layers 1a1'lb, . . . 111 are generally made of copper foil, and the insulating layer is made of a composite material such as glass fiber-epoxy resin, paper-epoxy resin, paper-phenol resin, etc. .

These conductor pattern layers 1a, Ib, .

1c, . . . are all etched into a predetermined pattern and embedded between the insulating layers 2a, 12b, .

These intermediate conductor pattern layers 1b, 1c1, . . . are only slightly visible from the outside when the multilayer circuit board 3 is completed, and cannot be completely seen through.

When using this multilayer circuit board with various electrical components installed, metal plating (through-hole plating) is applied to the inner surface of the hole drilled from the outside in the conductor pattern of a predetermined layer. can be electrically connected.

Since it is necessary to make the holes reliably at the desired conductor pattern positions, two or more reference holes (inner layer reference holes) are usually drilled in advance, and the holes are drilled based on the drawing dimensions using the inner layer reference hole positions as a reference. Drilling holes in predetermined locations is performed.

Conventionally, the following method has been used to form the inner layer reference hole.

(b) Based on the pattern of the inner layer reference hole of the intermediate layer that slightly appears on the surface layer, first use a counterbore drill 4 to drill a hole 5 larger than the inner reference hole, as shown in Figure 2. Open accurately to the position of the conductor pattern layer.

As a result, the conductor pattern layer 1b becomes visible at the bottom of the counterbore hole 5, so the exposed conductor pattern layer 1b
The inner layer reference holes are drilled through the entire multilayer circuit board at predetermined positions while visually checking the inner layer reference holes 6.

(b) As shown in FIG. 3, a small piece 7 of vinyl chloride resin film is pasted with an adhesive on the inner layer reference hole portion of the conductor pattern layer 1b, and even after the multilayer circuit board 3 is completed, the conductor pattern layer The position of the inner layer reference hole 6 of the conductor pattern layer 1b is made so that it can be easily seen from the outside, and a counterbore hole is drilled at this position with a counterbore drill as in the case of (a) to set the inner layer reference of the predetermined conductor pattern layer 1b. The position of the hole is exposed, and then the hole is visually drilled at the position of the inner layer reference hole 6 of the conductor pattern layer 1b. With this method, the position of the inner layer reference hole is easy to see from the outside, and by paying attention to the timing when the digging drill ejects the small piece 7 of the PVC resin film when counterboring the hole, it is possible to prevent the hole from being bored too deep by mistake. can.

[Problems in the Background Art] However, in both methods (a) and (b), in order to drill holes at the positions of the inner layer reference holes 6 of the predetermined conductor pattern layer 1b, first, a larger hole is drilled at the approximate position. Make a counterbore hole and make an inner layer reference hole 6 of the intermediate conductor pattern layer 1b.
It requires two steps: exposing the multilayer circuit board 3 and then drilling the inner layer reference hole 6 through the entire multilayer circuit board 3, which is not easy to work with and requires skill especially in drilling the countersunk holes in the previous process, so automation is not possible. The disadvantage was that it was difficult.

Furthermore, as shown in Fig. 4, if the position of the counterbore hole 5 deviates significantly from the position of the inner layer reference hole 6, it becomes difficult to position the drill, and the outline of two connected holes is formed on the top surface, resulting in an external appearance. The problem was that it was not very desirable.

[Object of the Invention] The present invention has been made to solve these conventional drawbacks, and is capable of easily drilling inner layer reference holes at predetermined positions of a conductor pattern in one step without drilling counterbored holes. An object of the present invention is to provide a method for drilling inner layer reference holes in a multilayer circuit board.

[Summary of the Invention] That is, the method for drilling inner layer reference holes in a multilayer circuit board according to the present invention includes: (A) at least two adjacent holes on the outer periphery of a multilayer circuit board;
(B) the step of grinding and smoothing the two sides and exposing the outer edge of the conductor pattern layer in which the inner layer reference hole of the multilayer circuit board is formed; (B) the outer edge of the exposed conductor pattern layer; (C) locating an inner layer reference hole from the position of the detected discontinuity point on the outer edge of the conductor pattern layer and drilling a hole at this position. There is.

[Embodiments of the invention] An embodiment of the present invention will be described below based on the drawings.

FIG. 5 is a plan view conceptually showing the conductor pattern of the multilayer circuit board.

In FIG. 5, the conductor pattern layer 1b of the multilayer circuit board 3
The outer edge of the conductor pattern A, where the inner layer reference hole 6 is normally provided, and the outer edge of the conductor pattern B, which is electrically independent from the outer edge of the conductor pattern A, are exposed at the outer edge of the conductor pattern. In this outer edge, a plurality of portions without a conductor pattern, ie, discontinuous portions C of the conductor pattern usually appear on each side.

Since this discontinuous portion C is determined at the design stage of the multilayer circuit board 3, the relative positional relationship between this discontinuous portion C and the inner layer reference hole 6 is determined in advance.

Note that from a circuit design point of view, two electrically independent
If two conductor patterns cannot be exposed on the same side, or if the discontinuity point is at an inappropriate position, install a separate conductor pattern for position detection at a position extending parallel to the side from the inner layer reference hole 〇. A notch may be formed in this to form a discontinuous portion.

In this embodiment, after the multilayer circuit board 3 is completed, the four sides of the multilayer circuit board 3 are ground, each side is brought to a normal temperature, and the outer edge of the conductor pattern layer 1b of the multilayer circuit board 3 is ground. part is exposed.

Next, the positions of discontinuous points PX and PY of the conductor pattern on each side of the conductor pattern of this multilayer circuit board 3 are detected. As a means for detecting the positions of these discontinuous points Px and Pv, a method using electrical contacts is convenient, but it is not limited to this method.
For example, optical detection is also possible.

FIG. 6 is a plan view showing an example of an inner layer standard measuring device used for detecting such a discontinuous portion, and FIG.

This detection device 8 has a positioning stopper 9 on the top surface.
9, a vacuum suction cup 11.11 for fixing the multilayer circuit board 3, and three sets of discontinuities for detecting discontinuities in the conductor pattern layer exposed on the sides of the multilayer circuit board 3. It is composed of a detection device 12.

The discontinuity detection device 12 includes a fluid cylinder 13 disposed along the side of the multilayer circuit board 3 fixed to a vacuum suction cup 11.11, and a piston 14 of the fluid cylinder 13.
A roller-shaped electrical contact 15 fixed to the tip of the electrical contact 15, a scale plate 16 for measuring the approximate position of the electrical contact 15, and a detection circuit (not shown) for detecting the presence or absence of contact between the electrical contact 15 and the conductor pattern. and a drilling position control circuit that sends a position signal of the electrical contact to a drive control circuit of the drill to move the drill to the drilling position of the inner layer reference hole. Reference numeral 17 indicates an index of the scale plate, and reference numeral 18 indicates an electrode for supplying a detection voltage to the conductor pattern.

In this detection device 8, first, the multilayer circuit board 3 to be drilled into the inner layer reference hole of the conductor pattern has one side attached to the stopper 9.
．． 9 and is positioned, and then suctioned and fixed to the vacuum suction cup 11.

Next, the electrode 18 is brought into contact with an arbitrary position of the conductor pattern A of the multilayer circuit board 3, and the fluid cylinder 13 is actuated to connect the electric contact 15 at the tip of the piston 14 to the exposed surface of the multilayer circuit board 19, as shown in FIG. It is moved along each side of the multilayer circuit board 19 while in contact with the conductive pattern 1b.

At this point, the position where the electrical connection between the electrode 18 and the electrical contact 15 is broken is defined as a discontinuity point.

After the positions of the discontinuous points on each side have been determined in this way, from the discontinuous points Px and Pv in FIG.
, Y is determined to be the position of the single hole in the inner layer M. Therefore, by positioning the drill based on this position data and drilling, it is possible to drill the inner layer reference hole at a predetermined position. Note that if there are many discontinuous points on the side of the target multilayer circuit board, any one of them may be used as a reference.

In addition, if the position of the interior reference hole provided along the side is completely parallel to the side, the two orthogonal holes as described above
It is possible to drill an interior reference hole by simply detecting a discontinuous point on one side, but if necessary, it is also possible to detect discontinuous points on other sides and use this as a reference. good.

Furthermore, it is possible to automatically position the drill based on the position data of this discontinuous point, but if necessary, the position of the discontinuous point can be marked on the multilayer circuit board and the inner layer reference hole can be drawn by drawing. It is also possible to manually drill an inner layer reference hole at this position.

[Effects of the Invention] As explained above, according to the present invention, the inner layer reference hole of a multilayer circuit board can be easily drilled in one step, and the position detection and drilling of the inner layer reference hole can be particularly done manually. Since it can be done without relying on other people, it is possible to automate the entire system.

[Brief explanation of the drawing]

Figure 1 is an enlarged sectional view conceptually showing a multilayer circuit board, Figure 2
The figure is a cross-sectional view showing a state in which a counterbore hole has been drilled up to the inner layer reference hole, Figure 3 is an enlarged cross-sectional view of a multilayer circuit board in which small pieces of vinyl chloride resin used in another conventional method are embedded, and Figure 4 is A plan view showing an inner layer reference hole appearing at the bottom of a counterbore hole in the conventional method, FIG. 5 is a plan view conceptually showing a multilayer circuit board, and FIG. 6 is an inner layer reference type detection used in an embodiment of the present invention. FIG. 7 is a plan view showing the device, FIG. 7 is a side view thereof, and FIG. 8 is a front view showing the electrical contacts and their contact positions on the multilayer circuit board. 1a...1n...Conductor pattern layers 2a, 2b...Insulating layer 3...Multilayer circuit board 4...
・・・・・・・・・・・・Countersboring drill 5・・・・・・
・・・・・・・・・Counterbore hole 6・・・・・・・・・
・・・・・・Inner layer reference hole 7・・・・・・・・・・・・・・・
・・Small piece of vinyl chloride resin film 8 ・・・・・・・・・・・・・・・・・・・・・・・・・・・・・・・・・・・・・・・・・・・・・・・
・・・・・・・・・・・・・・・Vacuum sucker 12・・・・・・
......Discontinuity point detection device 13...
......Fluid cylinder 14...
・・・・・・・・・Piston 15・・・・・・・・・・
...Electrical contacts PX, PY...Discontinuity point Patent attorney Sa Suyama - Figure 1 Figure 2 Figure 3 Figure 4 Figure 5 Garden Figure 7 Figure 10 Figure 8 7

Claims (2)

[Claims] (1) (A) A step of grinding and smoothing at least two adjacent sides of the outer periphery of the multilayer circuit board and exposing the outer edge of the conductor pattern layer in which the inner layer reference hole of the multilayer circuit board is formed; (B) detecting a discontinuous point on the outer edge of the exposed conductive pattern layer; (C) locating the inner layer reference hole from the position of the detected discontinuous point on the outer edge of the conductive pattern layer; A method for drilling an inner layer reference hole in a multilayer circuit board, the method comprising the step of drilling a hole at this position. The multilayer circuit board according to claim 1, wherein (2) (A>) grinding and (B) (7) detection of discontinuous points on the outer edge of the conductor pattern are performed on three sides of the multilayer circuit board. How to drill the inner layer reference hole.