JPS62158399A - Position detection of reference mark of multilayer printed board - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION (A) Field of Industrial Application The present invention relates to a method for detecting the position of a reference mark on a multilayer printed circuit board.

(b) Conventional technology When creating a multilayer printed circuit board, it is necessary to align the patterns on the inner layer and the pattern on the outer layer.
Usually, a pattern on the outer layer is printed to match the fiducial marks on the inner layer. However, the reference marks on the inner layer are covered with a copper foil layer and cannot be visually confirmed from the outside.

For this reason, conventionally, in order to make the reference mark visible, the area where the reference mark is thought to be located has been counterbored using a counterboring device to expose the reference mark. Another method that does not use a counterboring device is to use X-rays and perform image processing to find the center position of the reference mark and then drill the hole.

(c) Problems to be Solved by the Invention However, the method of spot boring requires a lot of man-hours and is difficult to automate. Furthermore, methods using X-rays are not convenient because of legal regulations regarding the handling of X-rays, and x1/9 transmission inspection equipment is very expensive and does not have good workability. The present invention aims to solve these problems.

(d) Means for Solving the Problems The present invention detects reference marks under the copper foil layer using an eddy current position sensor. Solve the above problems. That is, the method for detecting the position of a reference mark on a multilayer printed circuit board according to the present invention moves an eddy current position sensor a predetermined distance S from the copper foil layer on the surface of the multilayer printed circuit board, and detects a change in the output voltage or current of the eddy current position sensor. The purpose is to detect the position of the reference mark from the top of the multilayer printed circuit board.If the eddy current position sensor is moved parallel to and above the multilayer printed circuit board, it will detect the position of the reference mark even if it is covered with a copper foil layer. The current changes when it passes through. Therefore, by reciprocating the eddy current type position sensor once in each of the X and Y directions, the center positions in the X and Y directions can be detected. Since the center position of the reference mark is thereby detected, the drill can be moved to this center position to drill the reference hole.

(F) Embodiments Hereinafter, embodiments of the present invention will be described based on FIGS. 1 to 9 of the accompanying drawings.

FIGS. 1 and 2 show a reference hole machining apparatus for a multilayer printed circuit board for carrying out the method of the present invention. A drill head 14 provided with an eddy current position sensor 10 and a drill 12 includes:
It is attached to a table 18 movable in the X direction by a servo motor 16, and this table 18 is further provided on a table 22 movable in the Y direction perpendicular to the X direction by a servo motor 20. The operation of servo motor 16 and servo motor 20 is controlled by controller 24, and the operation of servo motor 16 and servo motor 20 is controlled by controller 24.
, i.e., the X direction and Y direction of the drill head 14
A signal corresponding to the directional coordinates is detected by, for example, a pulse detector provided therein, and is input to the controller 24. A detection signal from the eddy current position sensor 10 is also input to the controller 24 .

Next, the method of the present invention using this apparatus will be explained. First, as shown in FIG.
(Point A in Figure 3). For example, the multilayer printed circuit board 3o has a four-layer structure as shown in the enlarged view in FIG. copper mark 32
There is. Each layer is partitioned off by a prepave 30b. Therefore, although the copper mark 32 on the second layer from the top is not visible from the outside, its approximate position can be known in advance, and point A does not necessarily have to be located on the copper mark 32.

However, the farther the point A is from the copper mark 32, the longer the time required for detection becomes. Next, the servo motor 16 is activated to reciprocate the eddy current position sensor 10 in the X direction as shown by the broken line in Figure 7g3. When moving to the right in FIG. 3 through point B, the eddy current position sensor 10
The output current detected by changes as shown in FIG.

The coordinate value indicated by the pulse signal from the servo motor 16 at the point where the current rises to a predetermined value (that is, this corresponds to point B) is stored in the controller 24. Further, the output current of the eddy current position sensor 10 when moving to the left in FIG. 3 after passing through point C also changes as shown in FIG. 5, and the coordinate value C at point C is memorized. Ru. Controller 24
Then, the calculation x=(b+c)/2 is performed, and this X indicates the coordinate value of the center position of the copper mark 32 in the X direction. Next, the servo motor 20 is operated to reciprocate the eddy current position sensor 10 in the Y direction, and the center position of the copper mark 32 in the Y direction is calculated by the same operation as above. This means that the center position of the copper mark 32 has been detected. Next, the servo motor 16 and the servo motor 20 are operated to move the drill 12 to this center position. That is, from the state where the eddy current position sensor 10 matches the center position of the detected copper mark 32, the servo motor 16 is operated to move the drill head 14 by the distance R12 between the eddy current position sensor 10 and the drill 12. The state will be as follows. Thereby, the drill 12 is aligned with the center position of the copper mark 32. Next, the drill 12 is lowered and the reference hole is machined. Due to the stiffness, a reference hole is accurately formed in the center of the copper mark 32.

The eddy current type position sensor 10 is of a type that detects eddy current that changes depending on the presence of a copper mark, etc. However, even if the copper mark 32 is covered with a layer 30a, The method of the present invention was made possible by discovering that the current changes depending on the presence of the substance. Experimental results showing this are shown in FIG. FIG. 7 shows that the peak value of the output voltage when there is no copper mark 32 and the peak value of the output voltage when there is a copper foil layer 30a on the surface
This figure shows a state that changes depending on the thickness of the prebrave 30b between the copper mark 32 and the copper mark 32. Since the presence of the copper mark 32 causes such a difference in output voltage, the center position of the copper mark 32 can be determined even from above the copper foil layer 30a. Moreover, from this FIG. 7, even if the thickness of the BRIB RAVE 30b is about 900 μm, the copper mark 32
It can be seen that the position of can be detected.

In the experiment shown in FIG. 7, the eddy current position sensor 1
The diameter of 0 is 5.4 mm, the thickness of the copper foil layer 30a is 18 μm,
The thickness of the copper mark 32 is 35 μm, and the diameter of the copper mark 32 is 5 mm.
, and the distance between the eddy current type position sensor 10 and the copper layer 30a is 390 μm.

Note that if the thickness of the copper foil layer 30a exceeds 100 μm,
As shown in FIG. 8, the change in output voltage becomes small, making detection difficult. Note that FIG. 8 is a diagram showing changes in the peak value of the output voltage when the thickness of the copper foil layer 30a is changed. Also, an eddy current position sensor 10 and a copper foil layer 30
With respect to the distance from a, a sufficient change in output voltage can be obtained if it is in the range of 0 to 1700 μm, but detection becomes difficult in a range other than this. FIG. 9 shows the change in output voltage when the distance is changed.

(G) As described in detail, according to the present invention, the center position of the reference mark on the inner layer of the multilayer printed circuit board is detected using an eddy current position sensor, so that visual confirmation is not possible. The center position of the copper mark can always be detected accurately and efficiently with simple work.

[Brief explanation of drawings]

Figure 1 is a plan view showing the reference hole processing device, Figure 2 is a view seen in the direction of arrow 11 in Figure 1, Figure 3 is a diagram showing the trajectory of the copper mark and the eddy current position sensor, and Figure 4. 5 and 5 are diagrams showing changes in the output current of an eddy current type position sensor, FIG. 6 is an enlarged cross-sectional view of a multilayer printed circuit board, FIG. 7 is a diagram showing changes in output voltage due to the presence of copper marks, and FIG. FIG. 8 is a diagram showing the change in output voltage depending on the thickness of the copper foil layer, and FIG. 9 is a diagram showing the change in the output voltage depending on the distance of the eddy current type position sensor. 10... Eddy current position sensor, 12... Drill,
30...Multilayer printed circuit board, 30a...Copper foil layer,
30b...Blibrave, 32...Copper mark (reference mark).

Claims (1)

[Claims] A method for detecting the position of a fiducial mark on a multilayer printed circuit board, which detects the position of the fiducial mark on a multilayer printed circuit board in which another copper foil layer is provided on the layer on which the steel fiducial mark is provided. A multilayer printed circuit board, characterized in that an eddy current position sensor is moved a predetermined distance from a copper foil layer on the surface of the multilayer printed circuit board, and a reference mark position is detected from a change in the output voltage or current of the eddy current position sensor. A method for detecting the position of the fiducial mark.