JP2509888B2 - Reference position display mark for inner layer circuit Mark exposure method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial field of application) The present invention relates to a reference position indicating mark of an inner layer circuit in a multilayer printed wiring board in which a conductor and an insulator form a plurality of layers alternately. Regarding the exposure method.

(Prior Art) In the manufacturing process of a multilayer printed wiring board, for example, in the case of a four-layer multilayer printed wiring board as shown in FIGS. 3 (a) and 3 (b), the outer layer copper foils 1a and 1d with no circuit are formed. The inner layer copper foils 1b and 1c on which the circuit is formed are insulating base materials 2a, 2b and 2c, respectively.
The multi-layer printed wiring board 3 laminated via the above is sequentially subjected to processing such as drilling, through hole plating, and circuit formation of the outer copper foils 1a and 1d. Since this hole formation and the circuit formation process of the outer layer copper foil must be performed in a state where the relative positional relationship is accurately maintained with respect to the circuits of the inner layer copper foils 1b and 1c, prior to these processes. A reference hole is provided in the multilayer printed wiring board 3. The reference hole is usually drilled in the following two steps.

(1) With a spot facing cutter having a diameter slightly larger than the reference hole, a reference position display mark 4 is provided near the reference position display mark attached to the inner copper foil 1b as shown in FIGS. 4 (a) and 4 (b). Countersink until exposed.

(2) Next, the exposed reference position display mark 4 is visually inspected, and as shown in FIGS. 5A and 5B, the reference hole 5 penetrating the whole is accurately drilled.

However, in the spot facing step (1), it is necessary to stop the descent of the cutter when the cutter reaches the inner copper foil 1b so as not to damage the reference position display mark. However,
In general, a copper clad laminate is obtained by hot press forming, and thus the thickness varies and the counterbore depth is not constant.
Therefore, it is difficult to automate the vertical movement of the cutter,
Conventionally, this counterbore work is performed visually by a skilled person, or a release sheet is attached to the reference position display mark before multilayer press molding, and when the counterbore reaches the reference position display mark, the release sheet is used. The method of stopping by feeling the difference in cutting resistance by hand is performed. As a method for improving this, as disclosed in Japanese Patent Laid-Open No. 58-33896, the blade tip of the cutter is divided into two parts with different sizes with respect to the rotation axis, and they are electrically insulated to form a blade. There is also a method to stop the cutting by detecting the electrical continuity between the cutting edges when touches the reference position display mark, but the cutting is stable because the cutting tool is divided into two parts and they are bonded again with an insulator. In addition, there is a problem in terms of manufacturability and structure as a cutter, such as the fact that there is no gap and the insulating layer between the large and small cutting edges is small, so that there is electrical continuity due to cutting chips and erroneous stoppage during cutting. Further, as disclosed in Japanese Patent Laid-Open No. 61-90851, there is also a method of determining the difference in the cutting resistance of the cutter between the copper foil layer of the wiring board and the insulating base material as a change in the current value and stopping the judgment. If the insulating base material is thick, or if the resin of the insulating base material and the glass fiber composition are different from each other and a uniform cutting resistance cannot be obtained, a malfunction occurs and there is a problem in that a counterbore cannot be formed.

(Problems to be Solved by the Invention) The present invention has been made in view of the above circumstances, and a stable counterbore work can be automatically performed without erroneous detection due to conduction caused by copper foil chips and cutting. It is an object of the present invention to provide a method of exposing an inner layer circuit reference position display mark of a multilayer printed wiring board, which enables continuity detection without special processing of the cutting edge itself of the tool and can easily re-polish the cutting edge.

[Structure of the Invention] (Means for Solving the Problems) As a result of intensive studies to achieve the above object, the present inventor has provided an electric contact at a position apart from the cutting edge of the cutting tool. The present invention has been completed by finding out that the above object can be achieved. That is, the present invention is
In the method of exposing the reference position indication mark of the inner layer circuit by cutting the multilayer printed wiring board with a rotating cutting tool, the cutting tool main body is electrically connected to the cutting tool main body within the cutting edge outer circle excluding the cutting center and the cutting edge of the cutting tool. Provided with an electrical contact that is insulated and that slides in the direction of the cutting tool's rotation axis and that has a restoring force that protrudes from the cutting edge, when the cutting edge and the electrical contact reach the reference position indication mark of the inner layer circuit, A method of exposing a reference position indicating mark of an inner layer circuit in a multilayer printed wiring board, which is characterized in that the electrical continuity generated through a contact is detected to stop the cutting.

(Operation) When the electric contact reaches the reference position display mark of the inner layer circuit after cutting with a cutting tool, the electric contact comes into contact with the reference position display mark by the contact pressure of the restoring force. Even if the progress of the electrical contact is stopped, the cutting tool still continues cutting, and only when the cutting edge of the cutting tool reaches the reference position display mark, the cutting edge and the electrical contact are electrically connected by the copper foil of the reference position display mark. And the cutting stops. Depending on the exposed state of the display mark, it is possible to perform cutting by feeding several pulses. Since the blade tip is separated from the electrical contact located within the outer circumference of the blade tip, malfunctions due to copper foil chips are eliminated, and a blade tip capable of stable cutting is obtained.

(Example) Next, one example of the method of the present invention will be described with reference to the drawings.

FIG. 1 shows a perspective view of the cutting tool used in this example. A groove (may be a hole) 9 along the rotation axis direction is machined in the cutting edge outer peripheral circle excluding the cutting center of the cutting tool 6 and the cutting edge, and an electrical contact 8 electrically insulated by an insulating layer 7 is provided and fixed. is there. This electric contact 8 is in the direction of the rotation axis (arrow
The contact probe has a restoring force in a direction in which it slides in the direction) and protrudes from the cutting edge by a spring or the like, and is fixed so as to slightly project from the cutting edge in the free state. The shape of the tip of the electrical contact 8 is preferably spherical so as not to damage the cutting surface. The electric contact 8 used in this embodiment has a sliding stroke of 5 mm and a spring pressure of 100 g. The stroke and the spring pressure can be of the required magnitude depending on the situation. Since there is little wear of the electrical contacts and it can be used up to 1000 holes or more, which is the limit of use of a normal carbide tip cutter, it can be replaced when the cutting edge of the cutting tool is re-polished, and the replacement is easy.

Next, a cutting device for exposing the reference position display mark of the inner layer circuit will be described with reference to FIG. The cutting device includes a cutting tool 6 grasped by an insulating chuck 14 and a chuck 17.
When a cutting tool rotating motor 15 for rotating the cutting tool 6 via a belt driving unit 10 for lowering-raising the cutting tool 6
Pressing the, a position detector 11 for detecting the position of the cutting tool 6, the descent of the cutting tool 6 on the basis of the detection result of the position detection unit 11, a control unit 12 for controlling the lifting operation, the multilayer printed wiring board 3 It is constituted by a clamp device (not shown). Positioning is performed by moving the multilayer printed wiring board 3 so that the rotation axis of the cutting tool is located right above the reference position display mark of the multilayer printed wiring board 3. Next, when the start switch 13 of the device is pressed, the clamp is lowered and the cutting tool 6 is lowered while rotating, and the cutting edge of the cutting tool 6 and the electrical contact 8 are brought into contact with the outer layer copper foil 1a to generate an electrical conduction signal, This conduction signal passes through the slip ring 16 and the descending / ascending operation control unit
It is added to the counter circuit in 12 and the deceleration signal of the descending speed is output by the control of the pulse motor of the drive unit 10. Next, the insulating base material 2a is spotted, the cutting edge and the electrical contact come into contact with the reference position indicating mark 4 on the inner layer copper foil 1b, and the second conduction signal is added to the counter circuit. When the count number of the counter circuit matches the layer set number set by the layer setting switch 18, the motor control / reverse drive circuit stops and raises the cutting tool. The cutting tool 6 can be immediately stopped and raised when there is a conduction signal that matches the set number of layers, but it is also possible to send several more pulses depending on the state of the exposure mark. When the cutting tool 6 rises, the clamp rises and the counterbore cycle ends. In this way, the reference position display mark can be exposed neatly.

[Effects of the Invention] As described above, the method for exposing the reference position display mark of the inner layer circuit in the multilayer printed wiring board according to the present invention is to provide the electrical contacts in the outer circumference of the cutting edge excluding the center of the cutting edge and the cutting edge. Continuity can be detected without the need to machine the cutting edge of the cutting tool, which does not reduce the cutting durability of the cutting tool. There is little false detection due to conduction by powder, and therefore stable spot facing can be automatically performed. Further, the cutting edge can be easily re-polished by connecting the electrical contact to the socket and removing it when re-polishing the cutting edge.

[Brief description of drawings]

FIG. 1 is a perspective view of a cutting tool showing an embodiment of the present invention, and FIG.
The drawings conceptually show a reference position display mark exposing device for an inner layer circuit of the present invention, FIGS. 3 (a) and (b), 4 (a) and (b), and 5 (a) and (B) is a perspective view or a sectional view showing a step of forming a reference hole in a multilayer printed wiring board. 1a, 1d …… Outer layer copper foil, 1b, 1c …… Inner layer copper foil, 2a, 2b, 2c ……
Insulating substrate, 3 ... Multilayer printed wiring board, 4 ... Reference position mark, 5 ... Reference hole, 6 ... Cutting tool, 7 ... Insulating layer, 8 ... Electrical contact, 9 ... Groove or hole , 10 …… Drive unit,
11 …… Position detection part, 12 …… control part, 13 …… start switch, 14 …… insulation chuck, 15 …… cutting tool rotary motor, 16 …… slip ring, 17 …… chuck, 18 …… layer setting switch .

Claims (1)

(57) [Claims] 1. A method of exposing a reference position indicating mark of an inner layer circuit by cutting a multilayer printed wiring board with a rotating cutting tool, wherein the cutting tool is provided within a cutting edge outer circumference circle excluding a cutting center and a cutting edge of the cutting tool. An electric contact that is electrically insulated from the main body, slides in the direction of the rotating shaft of the cutting tool, and has a restoring force that protrudes from the cutting edge is provided, and the cutting edge and the electric contact have reached the reference position display mark of the inner layer circuit. A method for exposing a reference position indicating mark of an inner layer circuit in a multilayer printed wiring board, wherein cutting is stopped by detecting electrical continuity that occurs through a cutting edge and an electrical contact.