JPS6150713B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a small-diameter solid drill made of cemented carbide having a narrow drill blade with a drill diameter of 2 mm or less and around 0.1 mm, and a method for manufacturing the same.

The small-diameter solid carbide drill (also referred to as a microdrill) is mainly used for drilling holes in printed circuit boards for ICs, and its use has increased significantly in recent years as demand for electronic devices increases. Holes in IC boards are increasingly required to have smaller diameters and higher precision, and usage conditions have become stricter in order to improve production efficiency, so solid carbide drills with high rigidity and high wear resistance are increasingly being used. As shown in Fig. 1, this solid carbide drill has a cutting edge part 1 of 0.1 to 0.2 mmφ and a body part 2 of 2 to 0.2 mmφ.
The blade is made of cemented carbide, which has a diameter of 3 mm in one piece, and has less toughness than conventional high-speed steel, so there is a problem that stress is applied to the cutting edge and it easily breaks. Especially IC
Since a large number of small holes can be drilled in a board, a broken drill will significantly reduce the efficiency of the drilling operation. Moreover, cemented carbide solid drills are expensive both in terms of raw materials and processing, and there is a problem in that breakage of the drill greatly affects the manufacturing cost of IC boards.

As a result of considering the reuse of broken or used solid drills that had previously been discarded, the inventors of the present invention abutted a cemented carbide that would become the cutting edge on the tip of the body of a carbide drill. By irradiating high-energy beams such as electron beams and laser beams on the parts and welding the cemented carbide pieces together, it is possible to obtain a small-diameter carbide drill that has the same performance as a solid drill made entirely of one piece. I found it. In the above welding, cemented carbide may be directly welded together, but
When beam irradiation is applied to a welded part, the temperature rises abnormally, causing grain growth of the WC phase and reducing the strength of the cemented carbide, which is especially fatal for small-diameter solid carbide drills that are used under severe conditions.

As a result of various studies to solve this problem, as shown in Fig. 2, a thin metal plate 5 with a thickness of 0.2 to 2 mm was inserted into the contact surface of the cemented carbide body 4 and the cutting edge 3, and an appropriate pressure was applied. When pressurized in the axial direction with a jig and irradiated with a high-energy beam 6 to weld the thin plate, excess molten metal is pushed out to the outer periphery, and when it cools and solidifies, it is completely joined and bonded to the cemented carbide of the main body. It has been found that a small diameter solid carbide drill can be obtained in which no abnormal tissue is generated and the strength is not reduced at all.

The metals to be inserted into the contact surface include so-called iron group metals such as Co, Ni, and Fe, which are used as bonding metals in cemented carbide, and alloys and carbides of these metals, which are used as hard particles in cemented carbide. The material may be selected from metals of groups 4a, 5a, and 6a, such as W, Ti, and Ta, or alloys of two or more, based on the welding part or usage conditions. Since these metals are constituent components of cemented carbide, they have excellent compatibility with cemented carbide and can provide stable bonding strength.

As the high-energy beam, an electron beam or a laser beam that can irradiate a fine beam is useful in the present invention.

FIG. 3 is a micrograph at 200x magnification of a cross section of a joint welded using the method of the present invention described above by inserting a W thin plate into the contact surface.
In No. 4, no abnormal growth of WC or a brittle layer was observed, indicating complete bonding.

High-energy beams irradiate and melt in a short period of time, so if gas is generated and voids occur in the bonding layer, hot-static pressure treatment (HIP) should be performed at the liquid phase generation temperature of the cemented carbide after welding. By completely removing voids and diffusing the cemented carbide phase WC into the welding phase, a completely integrated small-diameter solid drill can be manufactured.

In addition, if wear resistance and toughness of the joint are strongly required, the liquid phase formation temperature of the cemented carbide (approximately 1320
By resintering (heating) at a temperature higher than 30°F (°C), WC can diffuse into the joint, creating a joint layer with the same structure as the cemented carbide.

The small-diameter solid carbide drill of the present invention is not only reusable after breakage or use, but also allows the body portion 4 and the cutting edge portion 3 shown in Fig. 2 to be manufactured separately and welded together by the method of the present invention. As shown in FIG. 1, these drills can be manufactured in a shape that is easier to manufacture than the one-piece drill, and they can be combined to form the required solid drill when necessary, which is advantageous in terms of production control.

Furthermore, the solid drill of the present invention provides a small-diameter solid carbide drill that is superior to conventional integrated small-diameter drills by combining cemented carbide alloys with different material compositions in the body and the cutting edge depending on the conditions of use. It has high industrial value.

Next, an example will be explained.

Example 1 As shown in Fig. 2, a body part 4 was machined from a broken or used cemented carbide drill, and a separately manufactured cemented carbide cutting edge part 3 was attached to the end face of the body part 4, and a Co plate 5 with a thickness of 0.6 mm was attached.
was inserted, and the contact portion was irradiated with an electron beam 6 while being pressurized in the axial direction. The electron beam
The test was carried out under the conditions of 60 KV, 10 mA, vacuum degree of 10 ^-2 Torr, and time of 2 seconds.

The joint surfaces were completely joined as shown in the photograph in Figure 3. This is set to the specified dimensions (d: 0.8 mm, D ₁ ;
0.8, D ₂ : 3.2 mm, L: 38.1 mm, L ₁ : 8 mm), and a printed circuit board drilling test was performed, and it showed exactly the same performance as a conventional integrated solid carbide drill.

Example 2 When the drill jointed in Example 1 was heat-treated in argon gas at 1350°C and 2 atm for 30 minutes, the cross-sectional structure of the joint was indistinguishable from the structure of the cemented carbide of the body. WC was diffused throughout Co. And it showed exactly the same performance as a conventional solid carbide drill.

[Brief explanation of the drawing]

Fig. 1 is a front view of a conventional integrated small-diameter solid carbide drill, Fig. 2 is a front view for explaining the manufacturing method of the solid drill of the present invention, and Fig. 3 is a 200 mm front view of the joint part of the embodiment of the product of the present invention. It is a cross-sectional tissue diagram taken with a microscope at double magnification. 1, 3: cutting edge, 2, 4: body, 5: thin metal plate, 6: high energy beam, 5': joint weld, d: drill diameter, D ₁ : neck diameter, D ₂ : body diameter, L: Total length, _L1 : Blade length.

Claims (1)

[Claims] 1. A solid drill made of cemented carbide,
Co, Ni or Fe on the contact surface between the cutting edge and body
Alternatively, one or more alloy plates or metal plates selected from metals in groups 4a, 5a, and 6a of the periodic table are sandwiched, and the thin plate portion is irradiated with an electron beam or a laser beam under pressure in the axial direction. A small-diameter solid carbide drill that is characterized by being melted, solidified, and joined. 2 In the manufacturing method of solid drills made of cemented carbide, Co and Ni are added to the contact surface between the cutting edge and the body.
Or sandwich Fe or one or more alloy plates or metal plates selected from metals in groups 4a, 5a, and 6a of the periodic table, and apply an electron beam or laser beam to the thin plate part under pressure in the axial direction. A method for producing a small-diameter solid carbide drill, which is characterized by irradiating, melting and solidifying the cemented carbide, and then re-sintering or hot static pressure treatment at the liquid phase formation temperature of the cemented carbide.