JPH03170216A - Miniature drill of rigid surface layer coated cemented carbide - Google Patents

Abstract

PURPOSE:To improve the cutting ability and breakage resistance by coating a rigid layer on the whole surfaces of flanks and side surfaces for a specified length from an outer circumferential corner to a shank part. CONSTITUTION:The body part of a miniature drill base body 6 of cemented carbide having back taper is inserted into a cylinder, it is installed in a vacuum container with a forward end protruded a little, and physical deposition is applied under normal conditions, so a rigid layer 5 is formed on the surface of the forward part of the base body 6. For the forward end part of this miniature drill of rigid surface layer coated cemented carbide, a rigid layer 5 is formed from a forward end 1 of the base body 6 along the whole surface of an outer circumferential corner 4 and from the outer circumferential corner 4 toward a shank part 3 reducing its thickness gradually for a length of A: 0.1-10mm. By forming the rigid layer 5 for a miniature drill base body 7 of cemented carbide having no back taper similarly, the back taper effect can be achieved apparently, and a good result can be obtained in actual cutting and in discharging cutting chips.

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention provides a long-life and excellent breakage-resistant material for use in making small diameter holes of 31III1 or less in printed circuit boards and other metal substrates. This invention relates to a miniature drill made of cemented carbide whose tip surface is coated with a hard layer.

[Conventional technology]

BACKGROUND ART Conventionally, a miniature drill made of cemented carbide is generally used as a cutting tool when drilling a small hole with a diameter of 3 mm or less in a printed circuit board or the like.

The above cemented carbide miniature drills are generally classified into straight type and undercut type, and the diameter of these cemented carbide miniature drills decreases as the blade approaches the shank continuously from the lip. It comes with a pack taber, and the undercut type has a step on the blade. The straight type has a pack taper of about 1 ttm/1 mm, and the undercut type often has no pack taper in the margin length. Furthermore, the whole of these ordinary cemented carbide miniature drills,
In the margin part or the margin part and the flute part, carbides, nitrides, carbonitrides, carbonates, carbonitrides, and aluminum oxides of metals of groups 4a, 5a, and 6a of the periodic table, and two or more of these metals are added. One type of single layer or a multilayer of two or more types selected from the group consisting of solid solutions of It is also known that the material is coated to improve machinability (Japanese Patent Laid-Open No. 56-3119). The specific composition of the hard layer includes carbides, nitrides, and carbonitrides of metals in groups 4a, 5a, and 6a of the periodic table, and solid solutions of two or more of these metals, such as Tic and Ti.
N, TiCN, ZrC, HfN, V C= T a C
, N b C, N b N, Cra c2, M
O 2 C, W C, Z r C N, V C N
, T a C N, (TI.Nb)C, (Ta,
Cr)CN, (Nb,WAN,(Ti.Ta.W)
CN, (Hf, V, Mo)C, etc. Carbonates and carbonitrides of metals in groups 4a and 5a of the periodic table include T i Co, T i CNO, TaCO, TaC
NO, ZrCO, ZrCNO, HfCO, HfCNO,
and aluminum oxide or diamond.

[Problem to be solved by the invention]

However, the toughness of surface-coated cemented carbide miniature drills coated with the above-mentioned hard layer decreases, and they are more likely to break than cemented carbide miniature drills without a hard layer coating.
Surface-coated cemented carbide coated with the above-mentioned hard layer is rapidly progressing toward smaller drill diameters to improve the degree of integration inside semiconductor substrates and high-speed machining to further increase productivity. This makes miniature drills more likely to break.

[Means to solve the problem]

Therefore, the present inventors conducted research to develop a miniature drill made of surface-coated cemented carbide that has excellent breakage resistance without reducing cutting performance, and discovered the above-mentioned miniature drill made of surface-coated cemented carbide. It was found that the breakage points were statistically concentrated in the part of the drill body close to the shank, which has a length of more than 10 mm from the outer corner to the shank. In order to maintain this, a hard surface layer is coated from the outer corner toward the shank part to the side surface with a length of 0.1 to 10 mm, and the other side surfaces near the shank part are left uncovered. In terms of durability, it is as good as a conventional cemented carbide miniature drill whose entire surface is coated with a hard layer, and its breakage resistance is on the same level as a conventional cemented carbide miniature drill whose surface is not coated with a hard layer. We obtained the knowledge that it is possible to do this.

5 This invention was made based on the above knowledge, and provides a surface hard metal miniature drill coated with a hard metal layer, which is formed by coating the surface of a cemented carbide miniature drill base with a normal hard layer. The hard layer covers the entire flank surface from the tip of the cemented carbide miniature drill base to the outer corner, and the length from the outer corner to the shank: 0, {~1
This is a miniature drill made of cemented carbide whose tip end surface is coated with a hard layer and whose side surfaces are coated over a length of 0 mm.

Here, the hard surface layer coverage range is the entire flank surface from the tip of the drill to the outer corner, and the length of the side surface from the outer corner to the shank: 0.1 to 10 mm. The reason for this is that the flank surface from the tip to the outer corner And the length from the outer corner to the shank is 20. The side surface extending from l to 10 mm is the part that receives the most severe cutting load, so it is necessary to cover the entire surface.On the other hand, the length from the outer corner to the shank part: The side surface close to the shank part, which exceeds LO mm, is covered with the surface. Hard Layer Covered Cemented Carbide Miniature Drill 6 Since this is a location where the probability of breakage is high, a hard layer was not formed on the surface. The length from the outer peripheral corner to the shank portion is preferably as short as possible, and more preferably 0.1 to 3 ml.

Next, the present invention will be specifically explained based on the drawings.

FIG. 1 is a plan view of a miniature drill made of cemented carbide coated with a hard layer on the tip end surface of the present invention; FIG. FIG. 3 is an explanatory cross-sectional view of another miniature drill made of cemented carbide whose tip end surface is coated with a hard layer. In Figures 1 to 3, 1 is the tip, 2 is the flank, 3 is the shank, 4 is the outer corner, 5
is the hard layer, and A is the hard layer covering length from the end of the lip toward the shank.

A miniature drill base 6 made of cemented carbide with a back taper as shown in FIG. 2 is prepared, and a part of the body of the miniature drill base 6 made of cemented carbide with a back taper is pushed into a tube (not shown). Then, the tip is hidden in a tube or placed in a vacuum container with the tip exposed just barely or slightly, and physical vapor deposition is performed under normal conditions to form the hard layer 5 on the back-tapered cemented carbide miniature drill base 6. A shape was formed on the surface of the tip. The tip of the miniature drill made of cemented carbide coated with a hard layer on the tip surface was prepared in this way.
The hard layer covering length A: 0.1 to 10 is formed so that the thickness gradually decreases from the tip 1 to the outer corner 4 of the base body 6 and from the outer corner 4 to the shank part 3, and back taper. Even if the miniature drill base 6 is made of cemented carbide and does not have a back taper, the back taper is further promoted.

Furthermore, if a hard layer 5 is similarly formed on the cemented carbide miniature drill base 7 without a back taper as shown in FIG. Good results can be obtained both in the process and in the removal of chips.

FIG. 1 shows the external appearance of the miniature drill made of cemented carbide whose tip end surface is coated with a hard layer according to the present invention, which is thus formed.

〔Example〕

Next, the present invention will be specifically explained based on examples.

First, a set equivalent to KIO of JIS-B4104, and outer diameter: 0.911111% blade length: 17mm
Prepare a miniature drill base made of WC-based cemented carbide and a cylinder with an inner diameter of 11 mm, and insert the miniature drill base made of WC-based cemented carbide into the inside of the cylinder, and insert the shank from the tip of the drill from the outer corner. The tip of the WC-based cemented carbide miniature drill base is charged into a normal physical vapor deposition device or an artificial diamond vapor deposition device with the tip protruding from the tip end, and the coating length shown in Table 1 is applied only to the tip surface of the WC-based cemented carbide miniature drill base. A hard layer having a certain thickness and film thickness was formed, and miniature drills 1 to 20 of the present invention and comparative miniature drills 1 to 5 were produced. Furthermore, for comparison, the above JI
WC-based cemented carbide miniature drill base having a composition equivalent to KIO of S・B 4104 and dimensions of outer diameter: 0.9 mm and blade length: I7m+i Covering length shown in Table 1 over the entire blade length and Conventional miniature drills 1 and 2 each having a hard layer having a thickness of 9 mm were manufactured. Note that the above film thickness indicates the film thickness near the outer peripheral corner of the miniature drill base made of WC-based cemented carbide.

Using these miniature drills, we constructed a 3.2 mm thick printed circuit board with two sets of double-sided sandwich bodies made of glass epoxy FRP boards and Cu boards between which the board and top board were made of Bakelite and pure aluminum, respectively. , Drill rotation number: 80000r. p. m. sending
Drilling was performed under conditions of: 90 μre/rev, and the number of holes drilled until the miniature drills broke was measured. The measurement results are shown in Table 1.

From the measurement results shown in Table 1, it can be seen that the miniature drills of the present invention and the comparative miniature drills with a hard layer formed only on the tip surface are less likely to break than the conventional miniature drills, and that the miniature drills of the present invention are more difficult to break than the comparative miniature drills. It turns out that it is excellent.

〔Effect of the invention〕

The miniature drill made of cemented carbide coated with a hard layer on the tip end of the present invention has the following features: (1.) Compared to conventional miniature drills made of cemented carbide whose entire surface is coated with a hard layer, the cutting performance is not reduced; Furthermore, the breakage resistance can be made comparable to that of a conventional miniature drill made of cemented carbide without a hard surface coating.

(2) In this invention, by forming the above-mentioned hard layer only on the surface of the tip of the drill, the effect is apparently the same as that of having a back taper, so it is not necessary to back taper the cemented carbide miniature drill. It is easy to manufacture, does not require a machine tool with special numerical control to attach the pack taber, and has excellent effects such as low cost because the area covered by the hard surface layer is small. .

[Brief explanation of the drawing]

FIG. 1 is a plan view of a miniature drill made of cemented carbide coated with a hard layer on the tip end surface of the present invention, FIG. FIG. 3 is an explanatory cross-sectional view of another cemented carbide miniature drill whose tip end surface is coated with a hard layer according to the present invention. 1... Tip, 2... Flank surface, 3...
...Shank part, 4...Outer corner 5
...Hard layer, 6...Cemented carbide miniature drill base with back taper, 7...Cemented carbide miniature drill base without back taper, A...From the outer corner toward the shank part hard layer covering length. Applicant: Mitsubishi Metals Co., Ltd. agent Kazuo Akida and 1 other person14

Claims (3)

[Claims] (1) In a surface hard layer-coated cemented carbide miniature drill in which the surface of a cemented carbide miniature drill base is coated with a normal hard layer, the hard layer is coated from the tip of the cemented carbide miniature drill base to the outer periphery. The entire flank surface leading to the corner and the length from the outer corner to the shank: 0.
A miniature drill made of cemented carbide coated with a hard layer on the tip surface, characterized in that the side surface is coated over a length of 1 to 10 mm. (2) The miniature drill base made of cemented carbide is made of cemented carbide with a hard layer coated on its tip end surface as set forth in claim 1, wherein the miniature drill base made of cemented carbide has no back taper over the entire length of the blade. miniature drill. (3) The cemented carbide miniature drill base is a cemented carbide miniature drill base having a back taper over the entire length of the blade, the tip surface of which is coated with a hard layer. Made miniature drill.