JPH043676B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for manufacturing a multilayer printed circuit board, and more particularly to a method for manufacturing a multilayer printed circuit board that streamlines the drilling process of a high-density multilayer printed circuit board.

Conventionally, in a multilayer printed circuit board (hereinafter referred to as a "multilayer printed circuit board"), when electrically connecting between internal conductor pattern layers and between external and internal conductor pattern layers, as shown in FIG. A terminal 1 is provided at a position where the pattern layer is desired to be connected, a hole 2 is made with a drill, and the inside of the hole 2 is plated. In addition, as shown in Fig. 2, plates 3 with pre-drilled holes and plating are laminated.
Gluing is also practiced. However, all of the above-mentioned methods have the serious problem of requiring a large number of man-hours for drilling.

The present invention has been made in view of the above circumstances, and its purpose is to solve the above-mentioned problems in the production of conventional multilayer printed boards, reduce the number of man-hours required for drilling holes, and reduce the diameter of the holes. It is an object of the present invention to provide a method for manufacturing a multilayer printed board that enables improvement in wiring density.

The above object of the present invention is to provide a method for manufacturing a multilayer printed circuit board comprising a plurality of conductor layers and a resin layer provided between the conductor layers, in which the lowest layer of the conductor layers to be electrically connected is This is achieved by making a hole in the upper conductor layer in advance, irradiating a laser beam from above through the hole, and removing the resin layer between the conductor layers from the uppermost layer to the lowermost layer.

The key point of the present invention is that there is a significant difference in the absorption of lasers, especially carbon dioxide lasers, between the resin and copper that make up the multilayer printed board, and copper reflects most of the carbon dioxide laser. The point is that the hole for making the electrical connection can be opened in a short time by selectively disassembling and removing it.

Embodiments of the present invention will be described in detail below with reference to the drawings.

FIGS. 3a to 3e are diagrams showing a method of connecting an outer layer and an inner layer according to an embodiment of the present invention. First, as shown in FIG. 3a, a hole slightly smaller than the beam diameter of the carbon dioxide laser that will be used later for drilling is formed at the center position 6' of the terminal 6 in the outer layer copper foil 4 by etching. Next, as shown in Figure 3b,
The substrate surface is scanned with a carbon dioxide laser L having an intensity and irradiation time such that only the resin layer is removed, and the resin layer 8 at the positions of the holes provided by the etching is removed.
Make a hole. Thereafter, as shown in FIG. 3c, after removing the resin layer in the holes provided in the resin layer 8 using a plasma smear removal device or the like, copper plating (the results are shown in FIG. 3d), etching ( The results are shown in FIG. 3e) to form a wiring pattern 9 and a terminal 6.

In FIG. 3b, since the inner layer terminal 5 does not have a hole, the laser does not penetrate inside the inner layer terminal 5 (downward in the figure) and can connect the outer layer and the desired inner layer. .

FIG. 4 shows another embodiment of the present invention, in which an outer layer and a plurality of inner layers 5 and 7 are connected. In this case, it is necessary to form the above-mentioned small hole by etching at the center position of the terminal 6 provided on the outer layer and the center position of the terminal 7 provided on the inner layer, respectively, and the laminated structure of these is laser processed. Accordingly, the connection can be made by making a hole reaching the terminal 5 in the inner layer and plating the hole.

In the above embodiment, a carbon dioxide laser was used as the laser, but the present invention should not be limited to this.

Further, holes provided in the conductor at positions where electrical connections are to be made may also be made by methods other than etching.

As described above, according to the present invention, in the production of a multilayer printed board having a plurality of inner conductor pattern layers and in which holes for making electrical connections between the conductor pattern layers are made by laser processing, the electrical Holes are pre-drilled in the conductor at the locations where physical connections are to be made, and only the resin is removed by laser processing. This allows the characteristics of laser processing to be maximized and reduces the time required to drill the holes. It is possible to provide a method for manufacturing a multilayer printed board that has excellent effects such as being able to shorten the size of the holes and improving wiring density because the hole diameter can be reduced to 0.1 to 0.2 mm.

[Brief explanation of drawings]

1 and 2 are cross-sectional views showing the connection of conventional conductor pattern layers; FIGS. 3 a to e are cross-sectional views showing a method of connecting an outer layer and an inner layer according to an embodiment of the present invention; and FIG. FIG. 3 is a sectional view showing another embodiment of the present invention. 4: outer layer copper foil, 5, 6, 7: terminal, 8: resin layer, 9: wiring pattern, L: laser.

Claims (1)

[Claims] 1. In a method for manufacturing a multilayer printed circuit board comprising a plurality of conductor layers and a resin layer provided between the conductor layers, the lowest layer of the conductor layers to be electrically connected A multilayer printed circuit board characterized in that a hole is made in advance in the upper conductor layer, and a laser is irradiated from the upper side through the hole to remove the resin layer between the conductor layers from the uppermost layer to the lowermost layer. manufacturing method. 2. The method of manufacturing a multilayer printed circuit board according to claim 1, wherein the holes in the conductor layer are formed by etching to form holes having a diameter smaller than the beam diameter of the laser. 3. The method of manufacturing a multilayer printed circuit board according to claim 1, characterized in that a carbon dioxide laser is used as the laser.