JPH0441113A - Drill shape for multilayer printed wiring board - Google Patents

Abstract

PURPOSE:To form a high-reliability through-hole with the inner wall of less roughness by making up a drill with the end portion allowable to make a bore 0.1mm or more smaller than that of a finished hole, 1.5mm or less, and the finishing portion allowable to machine the bore of the finished hole. CONSTITUTION:A drill has the end portion 2 to make a bore 0.1mm or more smaller than that of a finished hole and the finishing portion 3 to machine the bore of the finished hole. In a process of drilling a multilayer printed wiring board 1 with two or more layers laminated and connected, such a drill is used. At first, the end portion 2 of the drill machines a hole specified in the multilayer printed wiring board 1 and then the finishing portion 3 machines the bore of the finished hole to smooth the inner wall 4 of the through-hole. As a result, the inner wall 4 of the through-hole which is made rough by the end portion 2 in making the bore 0.1mm or more smaller than the bore of the finished hole is formed into a smooth face by the finishing portion 3 in machining the bore of the finished hole, then to apply plating thereto uniformly in the through- hole in a steel plating process so as to improve the reliability of through-hole.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a drill shape that provides a highly reliable finish when forming through holes in a multilayer printed wiring board.

[Conventional technology] Copper-clad laminates are the material for multilayer printed wiring boards.

It is made by laminating copper foil on a laminate made of thermosetting resin (phenol resin, epoxy resin Wl) and base material (paper, glass cloth, etc.). A copper-clad laminate of 100% is obtained. Further, in order to electrically connect the layers of the multilayer printed wiring board, holes are formed from the top to the bottom of the multilayer board to form through holes.

Failures in multilayer printed wiring boards primarily occur at through-hole connections, printed contacts, and solder connections. For example, in electronic switching equipment, approximately 1000 through holes are provided per printed wiring board, and the entire device has 1 through hole.
Reaching 500,000 pieces.

Therefore, in order to ensure the reliability of such a large electronic device, it is necessary to pay sufficient attention to the reliability of the through-hole connections of the printed wiring board.

Traditionally, a drill is used to pass through a multilayer printed wiring board.
It forms a through hole.

However, with conventional drills, the inner wall of the through-hole in a multilayer printed wiring board becomes rough because the hole is machined all at once to the finished hole diameter.
Since the thickness of the copper plating in the rough areas becomes thinner, the reliability of the through-hole is significantly reduced.

Conventionally, the drill shape used for drilling holes in multilayer printed wiring boards is, for example, the drill shape described in Japanese Patent Application Laid-Open No. 61-50706. In the drill described in the above publication, improvements have been made in the helix angle of the drill, the depth of the drill groove, etc. In other words, as shown in Figure 4, in order to improve the discharge of chips when rotating the drill and cutting, the angle of the teeth (α) is made steeper, or the depth of the groove (β) is increased. Was.

However, even if the removal of chips is improved, the reliability of through-holes does not improve much.

[Problems to be Solved by the Invention] As mentioned above, when a conventional drill is used to drill a hole in a multilayer printed wiring board and copper plating is performed to form a through hole, the inside wall of the through hole is damaged by the drill during drilling. Since the surface becomes rough and copper plating is applied in that state, the thickness of the plating becomes thinner in the roughened area, significantly reducing the reliability of the through-hole. This is because, as mentioned above, the copper-clad laminate used as the material for multilayer printed wiring boards is composed of thermosetting resin, paper, glass cloth, and other base materials, so the glass cloth portion is extremely thin. Rotate the drill at high speed (approximately 50,000
(rotation), the through hole 11 will open as shown in FIG.
The wall surface becomes rough and uneven. Defects occur frequently in multilayer printed wiring boards, especially those with eight or more layers.

In this case, the distance γ from the wall surface 10 is called roughness, and 12 is the base material of the copper-clad laminate.

As described above, there is a strong demand to reduce the roughness of the inner wall of the through hole to prevent a decrease in reliability.

An object of the present invention is to solve such conventional problems and provide a drill shape for a multilayer printed wiring board that can form highly reliable through holes by reducing the roughness of the inner wall inside the through holes. There is a particular thing.

Means for Solving Problem C] In order to achieve the above object, the drill shape for a multilayer printed wiring board according to the present invention has a drill shape number and a diameter of 1.5.
It is characterized by a two-stage configuration: a tip part that can be machined to a size smaller than the finished hole diameter by 0.1 mm or less, and a finishing part that can be machined to a finished hole diameter of 0.1 mm or less.

[For production]

In the present invention, the shape of the drill used for drilling holes in multilayer printed wiring boards is such that the diameter of the drill is 1°5 mm or less (
(finished hole diameter) and O,1 from this finished hole diameter.
It consists of two stages: a tip part that can be machined to a depth of 1 mm or more. Normally, the roughness of the wall surface is caused by the first drilling, so in the present invention, the first hole is drilled at the tip with a diameter that is at least 0.1 mm smaller than the finished part, and the roughness of the wall surface that occurs at that time is corrected in the next step. It is removed by drilling holes in the finished part of the
The hole is finished to the finished hole diameter. As a result, the inner wall of the through hole is processed neatly, and the copper plating is uniformly plated inside the through hole. As a result, a highly reliable through hole is formed.

〔Example〕

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

FIG. 2 is a side view of a drill showing an embodiment of the present invention.

As shown in Fig. 2, the drill used in the present invention has a tip 2 that is machined to be 0.1 mm or more smaller than the finished hole diameter.
and a finishing part 3 for machining the finished hole diameter. In addition, 5
is a drill shank added to the rear end of the drill, and is a part that the operator holds by hand. The ratio of the two-stage configuration according to the present invention is that the length of the tip part 2 is 1 to 1.5 mm out of the length of the drill of 4 to 6 mm (excluding the shank part 5).
mm, and the length of the finished portion 3 is set to the remaining 3 to 5 mm.

FIG. 1 is a cross-sectional view of the process of making holes in a multilayer printed wiring board according to the present invention.

In FIG. 1, 1 is a multilayer printed wiring board, 2 is a tip, 3 is a finished part, and 4 is an inner wall of a through hole.

In the step of drilling a hole in a multilayer printed wiring board 1 in which two or more layers are laminated and connected, a drill as shown in FIG. 2 is used. First, as shown in FIG. 1(a), the drill tip 2 drills a designated hole in the multilayer printed wiring board 1, and then the finishing section 3 drills the hole to the finished hole diameter to form the inner wall of the through hole. Process 4 smoothly.

In this way, the inner wall 4 of the through hole, which has become rough due to the tip portion 2 which is machined to be 0.1 mm or more smaller than the finished hole diameter, becomes a smooth surface due to the finished portion 3 which is machined to the finished hole diameter, and thereafter, In the copper plating process, the reliability of the through hole is improved because the plating is uniformly deposited inside the through hole.

FIGS. 5(a) and 5(b) are diagrams showing two types of shapes of the drill of the present invention.6 As for the shape of the drill of the present invention,
), the boundary between the tip portion 2 having a diameter of 1.4 mm or less and the finished portion 3 having a diameter of 1.5 mm or less forms a step. In addition, although the processing technology is difficult,
As shown in FIG. 5(b), it is also possible to form a shape in which the boundary between the tip portion 2 having a diameter of 1.4 mm or less and the finished portion 3 having a diameter of 1.5 mm gradually changes.

Note that processing methods that have the same effect as processing with the drill of the present invention include a first drill that has the same diameter as the tip part 2 of 1.4 mm or less, and a drill that has the same diameter as the finished part 3 of 1.5 nm or less. Prepare in advance two second drills with
If the hole is first drilled with the first drill and then finished with the second drill, the same drilling effect as in the present invention is obtained. However, in the present invention, it is not necessary to drill holes twice, and the roughness of the wall surface of the through hole can be reduced by performing the drilling process once.

〔Effect of the invention〕

As explained above, according to the present invention, the tip part of the drill can be machined to be smaller than the finished hole diameter by 0.1 mm or more;
Since there are two stages of finishing parts that are processed to the finished hole diameter, it is possible to reduce the surface roughness of the inner wall within the through hole, and it is possible to form a highly reliable through hole.

[Brief explanation of the drawing]

Fig. 1 is a cross-sectional view of the process of drilling a hole in a multilayer printed wiring board showing an embodiment of the present invention, Fig. 2 is a side view of a drill showing an embodiment of the present invention, and Fig. 3 is an inner wall surface of a through hole. FIG. 4 is a structural diagram of a conventional drill, and FIG. 5 is a sectional view of two types of drills of the present invention. 1: Multilayer printed wiring board, 2. Nitrile tip, 3. Drill finish, 4. Through-hole inner wall, 5. Drill shank part, 10: Wall surface, 11: Through-hole, 12: Base material. (a) Figure 1 to L5 rrm 3 to 5 rrm Figure Figure Figure γ Figure (a) (b) Below and below

Claims (1)

[Claims] 1. In the drill shape used for drilling through holes in multilayer printed wiring boards, the diameter of the drill is 1.
．． A shape of a drill for a multilayer printed wiring board, characterized in that it is composed of two stages: a tip part that can be machined to a diameter of 0.1 mm or more smaller than a finished hole diameter of 5 mm or less, and a finishing part that can be machined to the finished hole diameter.