JP2022120475A - Drill for forming through hole in magnetic substance - Google Patents

Abstract

To provide a drill which can inhibit surface roughness of a side wall of a through hole near a penetration side end of a magnetic substance.SOLUTION: A drill for forming a through hole in a magnetic substance is used to form a through hole in a magnetic substrate used for a printed wiring board. A drill tip includes four flat surfaces. Two surfaces of the four flat surfaces are tip flanks which extend from a center of the drill tip to a drill side surface and respectively form tip cutting edges with ridge lines with two spiral chip discharge grooves on the drill side surface. The other two surfaces of the four flat surfaces are belt-like extrusion surfaces which extend from the center of the drill tip to the two spiral chip discharge grooves along the tip flanks and have a constant width.SELECTED DRAWING: Figure 1

Description

TECHNICAL FIELD The present invention relates to a drill for forming a through hole in a magnetic material used for a power supply through hole or the like of a printed wiring board.

In general, through-holes for power supply in printed wiring boards for servers are filled with magnetic cores for the necessity of strengthening the power supply. The magnetic core is formed by mixing a resin and a magnetic material. A through-hole is drilled in the magnetic core, and a conductor layer is formed as a through-hole conductor by plating on the side wall of the through-hole. As a result, current loss in the through-hole conductor is suppressed by electromagnetic induction of the magnetic material.

2. Description of the Related Art As a conventional drill for drilling a through hole in a printed wiring board, for example, the one disclosed in Patent Document 1 is known. This drill has improved breakage resistance by forming an outer peripheral cutting edge with a ridge line between a margin of the outer peripheral surface of the tip of the drill body and a helical chip discharge groove.

JP-A-06-344212

By the way, as shown in the front view of FIG. There are two sets of a flat tip flank 3 forming the tip cutting edge 2 and a convex second flank 4 connected to the tip flank 3, and the tip flank 3 and the second flank 4 The pairs with the flanks 4 are separated by a chisel 5 which crosses the pairs obliquely in the middle.

However, in the above-described conventional drill, the chisel 5 has a sharp ridgeline shape toward the tip of the drill. In 4, it is presumed that the portion remaining near the lower end) is crushed. Therefore, the surface of the through-hole side wall 6a near the through-hole side end becomes rough, making it difficult to form the conductor layer 7 with a constant thickness or a constant radial cross-sectional area by plating. However, there is a problem that the power supply cannot be stabilized.

An object of the present invention is to provide a drill for forming a through hole in a magnetic material used for a power supply through hole or the like of a printed wiring board. To provide a drill that can be suppressed.

The drill for forming a magnetic through-hole of the present invention is a drill for forming a through-hole in a magnetic material used for a printed wiring board,
The drill tip has four flat surfaces,
Two of the four flat surfaces extend from the center of the tip of the drill to the side surface of the drill, and form a tip cutting edge at the ridge line with the two spiral chip discharge grooves on the side surface of the drill. is the tip flank,
The other two of the four flat surfaces are strip-shaped extrusion surfaces of constant width extending from the center of the drill tip along the tip flank to the two spiral chip discharge grooves. be.

The width of the extruded surface is preferably 10 μm to 50 μm.

It is preferable that the tip of the drill is provided with two second flanks that are convex curved surfaces connected to the two tip flanks.

BRIEF DESCRIPTION OF THE DRAWINGS Fig. 1 is a front view showing an embodiment of a drill for forming a through-hole of a magnetic material according to the present invention; FIG. 4 is an enlarged cross-sectional view showing a printed wiring board in which a through-hole is formed in a magnetic material by the drill for forming a magnetic-material through-hole according to the embodiment, and a conductor layer is formed on the side wall surface of the through-hole; It is a front view which shows an example of the conventional drill for magnetic material through-hole formation. FIG. 4 is an enlarged cross-sectional view showing a printed wiring board in which a through hole is formed in a magnetic material with the conventional magnetic material through hole forming drill, a conductor layer is formed on the side wall surface of the through hole, and the printed wiring board is formed.

An embodiment of a drill for forming a magnetic through-hole according to the present invention will be described below with reference to the drawings. FIG. 1 is a front view showing an embodiment of a magnetic through-hole forming drill of the present invention. FIG. 2 is an enlarged cross-sectional view showing a printed wiring board in which a through hole is formed in a magnetic material by the magnetic material through hole forming drill of the above embodiment and a conductor layer is formed on the side wall surface of the through hole.

The magnetic through-hole forming drill of this embodiment is used to form a through-hole in a magnetic core 6 as shown in FIG. It is.

The magnetic core 6 is made of a mixture of ordinary resin and a magnetic material such as ferrite. A conductor layer 7 serving as a hole conductor is formed to suppress the current loss of the through-hole conductor by electromagnetic induction of the magnetic material.

Although not shown, the drill of this embodiment includes a shank gripped by a chuck or the like of a machine tool, and a drill body arranged on the same axis as the shank and integrally coupled to the shank. The body may be of an undercut type having, for example, a cutting edge portion on the tip side of the drill and a neck portion connected to the proximal end of the cutting edge portion and having a smaller diameter than the cutting edge portion. It may be a straight type with an outer diameter.

As shown in FIG. 1, the tip of the cutting edge of the drill of this embodiment has four flat surfaces. , extends from the center of the drill tip (drill axis) O to the side of the drill, and the tip cutting edge 2 is formed by the ridge line with the two helical chip discharge grooves 1 on the side of the drill.

The other two of the four flat surfaces are defined as extruding surfaces 8, and these extruding surfaces 8 form two spiral chip discharge grooves 1 extending from the center O of the drill tip along the tip flank 3. , extending in a strip shape with the same constant width. The width of this extrusion surface 8 is preferably 10 μm to 50 μm. If the thickness is less than 10 μm, the effect of smoothing the side wall of the hole is not sufficiently good as compared with the ridge-shaped chisel 5 of the conventional drill.

The extruding surface 8 can be easily formed, for example, by polishing the chisel 5 of the conventional drill shown in FIG. 3 to flatten it.

The tip of the cutting edge portion of the drill of this embodiment may further have two ordinary secondary flanks 4, which are convex curved surfaces respectively connected to the two tip flanks 3, as in the shape of a conventional drill. By doing so, the drilling resistance can be made smaller, so that the breakage resistance of the drill can be improved.

As shown in FIG. 2, the drill of this embodiment was used to drill the through-hole of the magnetic core 6, and the side wall 6a of the through-hole was plated to form the conductor layer 7 as a through-hole conductor. The surface of the through-hole side wall 6a near the through-side end (lower end in FIG. 2) of the magnetic core 6 was formed smooth with a surface roughness smaller than that of the conventional drill shape. This is because, in the final stage of forming the through-hole, the remaining portion of the magnetic core 6 near the end of the through-hole is not crushed and is pushed out from the hole toward the through-hole (downward in FIG. 2) by the extrusion surface 8 as it is. It is assumed that there is.

Therefore, according to the drill of this embodiment, the surface roughness of the through-hole side wall 6a near the through-side end of the magnetic core 6 is suppressed from becoming rough, and the plating has a constant thickness or a constant radial cross-sectional area. The formation of the conductor layer 7 can be facilitated, and the current loss of the through-hole conductor made of the conductor layer 7 can be sufficiently suppressed, and the power supply can be stabilized.

REFERENCE SIGNS LIST 1 Chip discharge groove 2 Tip cutting edge 3 Tip flank 4 Second flank 5 Chisel 6 Magnetic core 6a Through hole side wall 7 Conductor layer 8 Extruded surface O Center of drill tip (drill axis)

Claims (3)

A magnetic material through-hole forming drill for forming a through-hole in a magnetic material used in a printed wiring board,
The drill tip has four flat surfaces,
Two of the four flat surfaces extend from the center of the tip of the drill to the side surface of the drill, and form a tip cutting edge at the ridge line with the two spiral chip discharge grooves on the side surface of the drill. is the tip flank,
The other two of the four flat surfaces are strip-shaped extrusion surfaces of constant width extending from the center of the drill tip along the tip flank to the two spiral chip discharge grooves. be. A drill for forming a magnetic through-hole according to claim 1,
The width of the extrusion surface is 10 μm to 50 μm. The drill for forming a magnetic through-hole according to claim 1 or 2,
The tip of the drill has two secondary flanks, which are convex curved surfaces that are continuous with the two tip flanks.

Images