JPS61131804A - Drilling method of spot facing of internal layer reference section in multilayer circuit substrate - Google Patents

Abstract

PURPOSE:To make the depth of a spot face accurate by detecting it by conduct by constituting a unit to perform spot facing up to the internal conductor pattern face of a multilayer circuit substrate in such a way that an end of an electrode is connected to the conductor pattern layer of the side face of the substrate and another end is connected to a spot facing drill. CONSTITUTION:One end of the metallic shaft 9 in which an electrode 8 is passed through is connected to a motor controller 11, and another end is fixed to the base 10 made of insulator. And the electrode 8 is positioned at the height to be ion contact only with the internal conductor pattern layer of a multilayer circuit substrate 3. And when the multilayer circuit substrate 3 is made to be pressed to the electrode 8 and be slidden, the internal conductor pattern layer 1b, the electrode 8, and the metallic shaft 9 are conducted. The drive of a vertical feed motor 12 in this condition rotates and lowers a spot facing drill 4 through a gear 13 and a rack 14 for vertical feed. When the spot facing drill 4 is brought into contact with the conductor pattern layer 1b, the electrode 8, the metallic shaft 9, and the spot facing drill 4 are conducted causing the controller 11 to stop the motor 12.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention 1] The present invention relates to a method for drilling a counterbore hole in an inner layer reference portion of a multilayer circuit board.

[Technical Background of the Invention] In general, a multilayer circuit board includes, as shown in an enlarged cross section in FIG. - Conductor pattern layers 1b, 1c between each insulating layer.

...is provided.

These conductor pattern layers 1a, ib, ... 1n 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, 1b, .

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

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

When this multilayer circuit board is used for mounting various electrical components, it is possible to connect the conductor pattern with the outside by applying gold plating (through-hole plating) to the inner surface of the hole drilled from the outside in the conductor pattern of the predetermined layer. The patterns 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.

The drilling of the inner layer reference hole is carried out in two steps using a conventional method.

That is, ■ As shown in Fig. 3, use a counterbore drill 4 with a diameter slightly larger than the inner layer reference hole to drill a hole near the inner layer reference hole 6;
When the counterbore drill 4 reaches the inner conductor pattern layer 1b, stop the drill and pull up the drill to drill the counterbore hole 5.
complete.

■ As a result, the conductor pattern layer 1b becomes visible at the bottom of the counterbore hole 5, so while visually checking the inner layer reference hole 6 of the exposed conductor pattern layer 1b, penetrate the entire multilayer circuit board at a predetermined position and insert the inner layer reference hole 6 into the exposed conductor pattern layer 1b. Drill a hole.

Among these processes, in the counterbore hole machining process,
When the counterbore drill reaches the inner conductor pattern layer, it is necessary to stop the drill from descending, and this is currently done by a method.

(a) This is a method in which a descending stopper is set at the part of the drill that moves up and down to prevent the drill from descending below that level. The position of this stopper is determined arithmetically from the thickness of the inner layer.゛(b) As shown in Figure 4 in advance,
A small piece of vinyl chloride resin film 7 is pasted with an adhesive onto the inner layer reference hole 6 of the conductor pattern layer 1b, so that even after the multilayer circuit board 3 is completed, the position of the inner layer reference hole 6 of the conductor pattern layer 1b remains visible from the outside. This is a way to make it easy to find. In this method, a counterbore hole is drilled at the location of this small piece of film 7 using a counterbore drill, and when the tip of the drill reaches the small piece of film, the drill winds up this small piece and a clear shock occurs when it is ejected to the top. , at this time, stop the drill.

[Problems with Background Art] However, these methods (a,) and (b) have the following problems.

In other words, method (a) is theoretically easy to work with and can be automated, but in reality it is a layered process.

The position of the conductor pattern layer in the thickness direction may fluctuate due to variations in molding pressure during the process, partial thickness of the constituent materials, etc., and even if the drill is stopped at a fixed position, the inner conductor pattern layer may be cut too much. Conversely, a problem arises in that an insulating layer remains on the conductor. Therefore, if the insulating layer remains, it is necessary to roughly scrape it off manually, and if it is scraped off too much, there is a risk that the product will be completely defective.

In addition, method (b) relies on the intuition of the counterbore operator, making it difficult to automate, and requires the extra work of having to go to the trouble of pasting small pieces of vinyl chloride resin film on the conductor pattern layer. bawl.

[Object of the Invention] The present invention has been made to solve these conventional problems, and it is an object of the present invention to provide a method for accurately and efficiently drilling counterbored holes.

[Summary of the Invention] That is, the method of drilling a counterbore hole in an inner layer reference portion of a multilayer circuit board according to the present invention includes bringing one electrode into contact with a conductive pattern layer of an inner layer exposed on a side surface of a multilayer circuit board, and connecting the other electrode. The counterbore drill is lowered to the position of the inner layer reference hole of the multilayer circuit board to drill the hole, and the counterbore drill is stopped when it is detected that the two electrodes are electrically connected.

[Embodiments of the invention] Next, an embodiment of the present invention will be described based on FIG.

In the figure, reference numeral 8 designates one electrode made of a conductor ring with a knurled outer periphery. A metal shaft 9 is inserted through the ring hole of this electrode, and one end of this metal shaft 9 is made of an insulator. It is fixed in a hole formed in the stand 10. The metal 1lIII9 is also connected to the motor controller 11.

The electrode 8 has a height such that it contacts only the inner conductor pattern layer of the multilayer circuit board 3, and the multilayer circuit board 3 placed on the stand 10 can be pressed against the electrode 8 to prevent it from slipping and the inner conductor pattern layer 1b. The electrode 8 and the metal shaft 9 are electrically connected to each other. When the vertical feed motor 12 is driven in this state, the counterbore drill 4 gradually descends while rotating via the gear 13 and the vertical feed rack 14. When the counterbore drill 4 contacts the conductor pattern layer 1b, the electrode 8, metal shaft 9, and counterbore drill 4 are electrically connected, and the motor controller 1
A and 8 of Ili11 are electrically closed.

As a result, the 1tilJ lit device 11 stops the motor 12 and then reverses the rotation, so that the counterbore drill 4 rises and leaves the counterbore hole.

[Effects of the Invention] As explained above, according to the method of the present invention, since the counterbore drill is controlled by detecting the electrical contact between the inner conductor pattern layer and the counterbore drill, the inner conductor pattern layer This eliminates the possibility of the insulating layer remaining on the conductive pattern layer due to the counterbore drill not reaching a certain point, or the excessive cutting of the conductive pattern layer caused by the drill descending too far.

Additionally, the extra work of applying small pieces of vinyl chloride resin film is no longer necessary, and automation is possible.

[Brief explanation of the drawing]

Fig. 1 is a partial cross-sectional view for schematically explaining the method of the present invention, Fig. 2 is a cross-sectional view of a multilayer circuit board, and Fig. 3 is a multilayer circuit showing a state in which countersunk holes have been bored up to the inner layer reference hole. FIG. 4 is a cross-sectional view of a multilayer circuit board in which small pieces of vinyl chloride resin film are embedded. 1 a, 1 b, -..., 1n... Conductor pattern layers 2a, 2b... Insulating layer 3... Multilayer circuit board 4...
・・・・・・・・・・・・Countersboring drill 5・・・・・・
・・・・・・・・・Counterbore hole 6・・・・・・・・・
・・・・・・Inner layer reference hole 7・・・・・・・・・・・・・・・
...Film piece 8...Electrode 9...Metal shaft 10...
......Insulator stand 11...
......Motor controller 12...
......Vertical feed motor 13...
・・・・・・Gear 14・・・・・・・・・・・・
・・Patent attorney for racks for vertical feeding Satoshi Suyama - Fig. 1 Fig. 2 Fig. 3 Fig. 4

Claims (1)

[Claims] (1) A counterbore drill with one electrode in contact with the inner conductor pattern layer exposed on the side surface of the multilayer circuit board and the other electrode connected is lowered to the position of the inner layer reference hole of the multilayer circuit board. A method for drilling a counterbore hole in an inner layer reference portion of a multilayer circuit board, characterized in that the counterbore drill is stopped when it is detected that both the electrodes are electrically connected.