JPS61260906A - Surface coated cemented carbide drill - Google Patents

Abstract

PURPOSE:To increase life by composing a single layer or the innermost layer from tungsten carbide in a surface coated cemented carbide drill having a tip surface coated with one or more layers of which thickness amounts to 0.1-10mu. CONSTITUTION:For example, each 1mu thickness of various hard materials is coated by a high frequency magnetron spattering equipment to a cemented carbide small size stepped twist drill of 0.95mm as a base material and 3 pieces of glass epoxy printed circuit boards are laminated and subjected to drilling test at a cutting speed of 208m/min with a feed rate of 0.05mm/rev. to drill a hole of 0.95mm dia. and 4.8mm depth with a result that a drill coated with WC has the longest life and a coated film thickness of 0.1-10mu is effective. Thus, the drill can make a hole through a laminated printed circuit board effectively with long life.

Description

[Detailed Description of the Invention] [Technical Field] The present invention provides a surface coating that extends the life of drills for drilling holes in printed circuit boards, particularly laminated printed circuit boards, whose usage has increased significantly with the recent development of the electronic industry. Regarding.

[Technical Background] A small-diameter stepped twist drill made of cemented carbide is usually used to drill holes for mounting components on printed circuit boards used in electronic devices.

Printed circuit boards are usually made of a glass epoxy board with a copper plate on both sides or one side, but in recent years, with the rapid development of the electronics industry, the degree of integration has increased, the parts used have become smaller, and components have been mounted on printed circuit boards. Due to the increase in volume, printed circuit boards are also becoming laminated from the conventional one layer to two or four layers. Glass epoxy plates originally have poor machinability, so even if the glass epoxy plates are laminated in areas where drill wear is severe, the wear will further increase. In addition, by laminating printed circuit boards, the number of copper plates that must be cut per hole increases more than ever before. It is known that copper reacts with cemented carbide at high temperatures, and cutting copper is known to cause significant diffusion wear on cemented carbide. The increase in cutting amount has significantly shortened drill life.

An object of the present invention is to provide a tool for efficiently drilling holes in this laminated printed circuit board with a long life.

Small-diameter stepped cemented carbide drills are used to drill holes in printed circuit boards, but in order to improve their wear resistance, it has been proposed to coat part or all of their surfaces with various hard materials ( JP-A-56-31 Kan 7.
3118.3119). The coating materials proposed by this proposal include carbides of metals from groups 4a, 5a, and ea of the periodic table;
It is one type of base metal selected from the group consisting of nitrides, carbonitrides, carbonates, carbonate nitrides, aluminum oxide, and solid solutions of two or more of these, or a multilayer of two or more layers. However, as an example of these proposals, 'r+c
, 'riN, etc., all of which use cemented carbide (WC-C) as the base material.
It is assumed that the coating is coated with a material that has higher wear resistance than o).

However, even this hard-covered drill is increasingly not suitable for use in drilling holes in glass epoxy printed circuit boards.

The inventor has arrived at the present invention as a result of searching for a coating material for drills that has a longer lifespan.

[Disclosure of the Invention] As mentioned above, we realized that the reaction between copper and cemented carbide is a problem when using a cemented carbide drill to drill holes in printed circuit boards, and cobalt, which is the bonding metal phase of cemented carbide, We thought that copper might react with copper at high temperatures, and tried coating it with various materials on the premise of choosing a hard material that does not contain cobalt as the covering material. It has been found that a small twist trill made of cemented carbide coated with tungsten carbide (WC), which is the main component of WC, can stably have a long life when drilling holes in printed circuit boards.

This is contrary to the conventional idea that coating with a material with high hardness improves wear resistance, and that coating with tungsten carbide, which has the lowest hardness among hard materials, is the most effective. I understand.

If the thickness of the coating layer is less than 0.1μ, the coating effect will be poor, and if it exceeds Iθμ, the strength will be extremely reduced, which is not preferable.

The present invention will be described in detail below with reference to Examples.

Example 1 Commercially available cemented carbide (ISO, P-30) with a diameter of 0.951
A small-sized stepped twist drill made by Co., Ltd. was used as a base material, and 1 μm of each of the various hard substances shown in Table 1 was coated using a high-frequency magnetron sputtering device. Using this coated cemented carbide drill, G! Using three stacked glass epoxy printed circuit boards equivalent to 0, cutting speed: 208.9+*/win, feed: 0.05 mm/rev, machined hole diameter: 0.95 m,
The hole drilling test was conducted under the condition that the hole depth was 4.8 m.

The results are shown in the right column of Table 1. 20.00 for each material
The life of the epoxy board was determined by drilling holes up to 0 points and measuring the hole diameter of the epoxy board.

Table 1 As can be seen from the results, it can be seen that the WC coating is the most effective. On the contrary, it can be seen that the lifespan of AQ 203, which has the highest hardness, is actually shorter than that of the uncoated one. In other words, this proves that glass epoxy plates, which are difficult-to-cut materials, are different from the conventional wisdom.

Example 2 Next, in order to investigate the effect of coating film thickness, the same cemented carbide drill as in Example 1 was used as a base material, and WC was coated to various thicknesses over the entire cutting edge using a high-frequency blade magnetron sputtering device. A test was conducted under the same conditions as in Example 1 to determine the lifespan.

The results are shown in Table 2.

Table 2 This table shows that the effect is small when the thickness is less than 0.1μ, and 10
It can be seen that the life is extremely shortened when the thickness exceeds μ.

[Effects of the present invention] The coated cemented carbide drill of the present invention not only has a long lifespan but also has stable performance even when used on glass materials, which are the most difficult to cut materials among epoxy substrates, making it easy to drill holes. It is also extremely effective for automation.

In addition, as a coating method, the sputtering method in the example is used.

Claims (1)

[Claims] In a surface-coated cemented carbide drill in which part or all of the surface cutting edge of the cemented carbide drill is coated with one or more coating layers with a total thickness of 0.1 to 10μ, one layer of the coating layer. Or a surface-coated cemented carbide drill whose innermost layer is tungsten carbide.