JP6765361B2 - Hard coatings and drills for cutting tools - Google Patents

Description

The present invention relates to a hard coating for a cutting tool coated on a cutting tool such as an end mill or a drill, and a drill coated with the coating.

Conventionally, TiN, TiCN or TiAlN has been used as a hard wear-resistant film to be coated on a cutting tool. In particular, the TiAlN-based coatings represented by Patent Documents 1 and 2 have improved hardness and heat resistance by adding Al to TiN, and are widely used because of their excellent wear resistance.

Further, an AlCrN film as disclosed in Patent Document 3 and the like in which heat resistance is improved as compared with the TiAlN film by using CrN instead of TiN has also been proposed.

By the way, as disclosed in Patent Document 4, in recent years, printed wiring boards have been made smaller, thinner and lighter, and have been made more heat resistant and more rigid in order to improve reliability. PCBs are becoming more difficult to cut as the strength and density of the glass fiber resin contained in the contained printed wiring board (hereinafter referred to as "PCB") increases and the filling amount of the filler increases.

Therefore, even if a drilling tool coated with an AlCrN film is used, deterioration of hole position accuracy is unavoidable, and further improvement in wear resistance to PCB is required.

Japanese Unexamined Patent Publication No. 62-56565 Japanese Patent Application Laid-Open No. 2-194159 Japanese Patent No. 3039381 Japanese Unexamined Patent Publication No. 2014-21314

In view of the above-mentioned current situation, the present inventors have studied the film layer structure of a hard coating for cutting tools and found that the above problems can be solved by adding a third element to the AlCrN coating. It is a product obtained and completed, and provides an extremely practical hard film for cutting tools and a drill capable of improving wear resistance to PCB and suppressing deterioration of hole position accuracy as compared with a conventional AlCrN film.

The gist of the present invention will be described.

A hard film for cutting tools formed on a base material, with a metal component of atomic%.
Al _(100-XY) Cr _(X) Cu _(Y)
However, 30 ≦ X ≦ 67,0 <Y ≦ 5
The present invention relates to a hard coating for cutting tools, which is represented by the above and has a surface coating layer containing at least N as a non-metal element and containing unavoidable impurities.

Further, in the hard coating for cutting tools according to claim 1, one or more elements formed on the surface of the base material and selected from the group consisting of Group 4A, Group 5A, Group 6A, Al and Si. It is characterized by being composed of a nitride, carbonitride or carbide having a thickness of 0.1 μm or more and 1.0 μm or less, and the surface film layer formed on the base film layer. It relates to a hard coating for cutting tools.

Further, in the hard coating for cutting tools according to claim 1, the metal component is atomic%.
Al _(100-z) Cr _(z)
However, 30 ≤ Z ≤ 70
A hard material for cutting tools, which is composed of a base film layer containing at least N as a non-metal element and containing unavoidable impurities, and the surface film layer formed on the base film layer. It is related to the film.

Further, the hard film for a cutting tool according to any one of claims 2 and 3, wherein the base film layer has a NaCl-type crystal structure.

Further, in the hard film for cutting tools according to any one of claims 1 to 4, the hard film for cutting tools is characterized in that the crystal structure observed from the fracture surface of the surface film layer has columnar crystals. It is related.

The hard film for a cutting tool according to any one of claims 1 to 5, wherein the hard film for a cutting tool has a total film thickness of 1 μm or more and 10 μm or less.

Further, in the hard coating for cutting tools according to any one of claims 1 to 6, the base material is a cemented carbide composed of hard particles containing tungsten carbide (WC) and a binder containing cobalt (Co). It relates to a hard film for a cutting tool, which is characterized by being present.

Further, it is a drill for processing a glass fiber-containing printed wiring board having a chip discharge groove, and is coated with the hard film for a cutting tool according to any one of claims 1 to 7, and this hard film is a drill. The present invention relates to a drill, which is not provided on the tip surface of the drill and the inner surface of the chip discharge groove.

Since the present invention is configured as described above, it is an extremely practical hard coating for cutting tools and a drill capable of improving wear resistance to PCB and suppressing deterioration of hole position accuracy as compared with the conventional AlCrN coating.

It is a graph which shows the relationship between the wear resistance of AlCrN film with respect to PCB, and the Cr amount of hole position accuracy. It is an electron micrograph of the fracture surface of the AlCrCuN film of Al / (Al + Cr) = 0.6 showing the Cu amount dependence of the crystal structure of the film. It is a graph which shows the relationship between the wear resistance of the AlCrCuN film of Al / (Al + Cr) = 0.6 with respect to PCB, and the amount of Cu of hole position accuracy.

Embodiments of the present invention which are considered to be suitable will be briefly described by showing the operation of the present invention.

By adding a predetermined amount of Cu to the AlCrN film, both hardness and toughness can be achieved, and damage to the cutting tool (drill) coated with the hard film during PCB cutting can be suppressed. Therefore, the wear resistance of the cutting tool to the PCB can be improved, and deterioration of the hole position accuracy can be suppressed.

Specific examples of the present invention will be described with reference to the drawings.

This embodiment is a hard coating for a cutting tool formed on a base material, and has a surface coating layer containing at least Al, Cr, and Cu as metal components and at least N as a non-metal element and containing unavoidable impurities. It is a thing.

Each part will be described in detail.

As the base material, one made of a cemented carbide composed of hard particles containing WC and a binder containing Co is adopted. Specifically, those in which the average particle size of the WC particles is set to 0.1 μm or more and 2.0 μm or less and the Co content is set to 5 or more and 15% or less in mass% are adopted.

Immediately above this base material (base material surface), it is composed of a nitride, carbon nitride or carbide of one or more elements selected from the group consisting of Group 4A, Group 5A, Group 6A, Al and Si. A base film layer having a thickness of 0.1 μm or more and 1.0 μm or less is provided. The element of Group 4A in this example is titanium (Ti), zirconium (Zr) or hafnium (Hf), and the element of Group 5A is vanadium (V), niobium (Nb) or tantalum (Ta). The element of Group 6A is chromium (Cr), molybdenum (Mo) or tungsten (W).

On this base film layer, the metal component is atomic%,
Al _(100-XY) Cr _(X) Cu _(Y)
However, 30 ≦ X ≦ 67,0 <Y ≦ 5
A surface coating layer containing at least N as a non-metal element and containing unavoidable impurities is provided.

The reason for adopting the above configuration and the action and effect of the above configuration will be described below.

First, the reason why the composition of the surface film layer (AlCrCuN film) is set within the above range will be described.

The present inventors studied AlCrN films having different metal component ratios, and found that the amount of Cr (content ratio of Cr and Al) greatly affects the hole position accuracy and wear resistance in processing with respect to PCB (Fig.). 1).

Therefore, the present inventors considered that in the AlCr-based film, an increase in the amount of Al indicates an increase in hardness and a decrease in toughness, and an increase in the amount of Cr indicates a decrease in hardness and an improvement in toughness. That is, when drilling a PCB with a tool coated with an AlCrN film, it was considered that the toughness of the film contributed to the improvement of wear resistance and the hardness contributed to the improvement of the hole position accuracy.

However, if the above relationship depends on the hardness and toughness of the film, there is a trade-off between hole position accuracy and wear resistance, and as long as the AlCrN film is used, both can be improved at the same time. difficult. Therefore, the present inventors have attempted to improve hardness and toughness by adding a third element to the film and controlling the grain boundaries thereof.

That is, by arranging a material having a high toughness value at the grain boundary, the toughness of the entire system was improved, and at the same time, the grain boundary suppressed the crystal growth of the matrix phase and attempted to improve the hardness by microcrystallization. ..

Specifically, a high wear resistance improving effect was observed by adding Cu, which does not have a NaCl-type crystal structure and is the most difficult to nitride among practical metals. More specifically, the effect of improving wear resistance was exhibited by adding 0.1% or more of Cu as the atomic% of the metal only. However, if the amount added is too large, the wear resistance may drop sharply.

That is, the amount of Cu added when the wear resistance sharply decreases depending on the content ratio of Al and Cr is slightly different, but when the amount of Cu added exceeds 10%, the resistance to any Al and Cr content ratio Abrasion is reduced. It is considered that this is because the amount of Cu added is too large and the stress relaxation of the NaCl structure as the matrix and the structure is transformed from the NaCl type to the wurtzite type (see FIGS. 2 and 3). ). Specifically, as shown in FIG. 2, when the amount of Cu added exceeds 10 at.%, The crystal structure changes, and the columnar crystals seen at 3 at.% And 5 at.% disappear, resulting in diameter reduction and weight loss. Both hole position accuracy deteriorates significantly. Therefore, the Cu content was set to 5 atomic% or less. It is preferably 1 atomic% or more and 4 atomic% or less.

Further, in the processing of a PCB drill coated with an AlCrCuN film, if the Cr in the film is less than 30% in terms of atomic% of the metal alone, the wear resistance and hole position accuracy deteriorate sharply (see the experimental example described later). ). It is considered that this is because the amount of Al added to CrN exceeds the solid solution limit, and it is preferable that Cr is contained in an amount of 30 atomic% or more. However, if the metal elements are only Cr and Cu and Al is not contained, the hardness thereof is excessively lowered and good hole position accuracy cannot be obtained. Therefore, the Cr content was set to 30 atomic% or more and 67 atomic% or less.

Next, the reason for providing the base film layer and the reason for its selection will be described.

Although the degree varies depending on the amount of Cu added, if the above-mentioned AlCrCuN film is provided directly on the base material, the wear resistance and hole position accuracy may be worse than those of the conventional AlCrN film, probably because of poor adhesion. On the other hand, when a nitride film, a carbonized film or a carbonized film having the same NaCl type structure was formed as a base film layer directly on the substrate and an AlCrCuN film was provided on the film, an improvement tendency was observed (described later). See experimental example).

However, although the appropriate film thickness differs depending on the selected base film layer, if the film thickness is too thin, the adhesion will not be improved, and the wear resistance and hole position accuracy will be the same as when there is no base film layer. It may be inferior to the conventional AlCrN film. On the contrary, when the film thickness is too thick, the characteristics of the base film layer appear deeply, and the characteristics of the AlCrCuN film as described above cannot be seen. In particular, when the film thickness exceeds 50% of the total film thickness of the hard film, the characteristics of the underlying film layer appear deeply regardless of the selected film type, and the characteristics of achieving both hardness and toughness are not observed. It was. Therefore, for example, when the total film thickness of the hard film is 1 μm to 10 μm, the thickness of the surface film layer is 0.9 μm to 9.9 μm, the thickness of the base film layer is 0.1 μm or more and 1.0 μm or less, and the hard film layer. It is recommended to set the value not to exceed 50% of the thickness.

Further, when AlCrN was used as the base film, good wear resistance and hole position accuracy were obtained in the widest range, although there was an optimum combination of composition ratios. However, if the amount of Cr in AlCrN is less than 30% in terms of metal atom ratio, the NaCl type structure cannot be maintained, and regardless of the composition ratio of the AlCrCuN film, both wear resistance and hole position accuracy are both. It got worse. Furthermore, if the amount of Cr in AlCrN exceeds 70% in terms of metal atom ratio, the hardness will be too low, and unless the film thickness of the base film is extremely thin, good hole position accuracy cannot be obtained. .. Therefore, the amount of Cr in the AlCrN film of the base film layer is preferably 30% or more and 70% or less in terms of metal atomic ratio.

Next, the coating form on the drill will be described.

The base material of this embodiment is a drill, and when processing a glass fiber-containing printed wiring board, the hole position accuracy greatly contributes to the hole position accuracy when biting into the backing plate. Therefore, by not covering the cutting edge existing at the intersection ridge between the flank of the tool tip and the rake face, the blade angle is kept sharp and the biting property is improved, so that the hole position accuracy at the time of biting to the backing plate is improved. Improved (see Patent No. 5702431). That is, it is preferable that the hard film is not provided on the tip surface (relief surface) of the drill, which is the base material, and the inner surface of the chip discharge groove, but is provided only on the outer peripheral surface of the drill.

Since this embodiment is configured as described above, it is possible to achieve both hardness and toughness, and it is possible to suppress damage during PCB cutting of a cutting tool (drill) coated with the hard film. Therefore, the wear resistance of the cutting tool to the PCB can be improved, and deterioration of the hole position accuracy can be suppressed.

Therefore, this embodiment is extremely practical because the wear resistance to PCB is improved and the deterioration of hole position accuracy can be suppressed as compared with the conventional AlCrN film.

Hereinafter, experimental examples that support the effects of this example will be described.

An arc discharge type ion plating apparatus used as a film forming apparatus, installed in the film forming apparatus a target having a predetermined composition as evaporation sources of metal, by introducing N ₂ gas into the film forming apparatus as a reaction gas, super A sample in which an AlCrCuN film was formed on a hard alloy drill was prepared, and the total film thickness was about 5.0 μm.

After measuring the diameter of the drill, the PCB was drilled under the cutting conditions shown below. After that, the diameter of the drill after machining is measured again, and the amount of change in diameter is calculated to evaluate the wear resistance (diameter reduction), and the deviation between the machine coordinates set in the drilling program and the actual hole position. The hole position accuracy was evaluated by measuring the amount on the back side of the bottom substrate. Table 1 shows the test results when the base film layer is not provided, and Table 2 shows the test results when the base film layer is provided.

The pass / fail judgment is x for those with a diameter reduction of 2.00 μm or more, or a diameter reduction of 0.90 μm or more and a hole position accuracy of 50 μm or more, and one of the diameter reduction or hole position accuracy is the same as the conventional example and the other. Those that are improved or both are improved are marked with 〇, × and those that do not correspond to 〇 are marked with Δ, and those that are particularly preferable among 〇 are marked with ⊚.

[Cutting conditions]
Drill: Diameter 0.25 mm, Groove length 4.7 mm
Work material (PCB): FR-4 halogen-free material Thickness 1.2 mm 6-layer copper foil Number of layers: 2 Plates: Aluminum plate (thickness 0.15 mm)
Discard plate: Bake plate (thickness 1.5 mm)
Rotation speed: 120,000min ^-1
Feed rate: 1.8 m / min
Spindle climbing speed: 25.4m / min
Number of holes: 2,500 hits

From Table 1, each experimental example relating to the composition (coating composition) of the surface coating layer of this example is capable of achieving both diameter reduction and hole position accuracy as compared with the conventional AlCrN coating (conventional example) and the comparative example. It is recognized that

From Table 2, by setting the film thickness (undercoat film thickness) of the undercoat film layer within the above-mentioned numerical range, improvement in diameter reduction is particularly observed regardless of the film type (undercoat film composition). In addition, improvement by the base film layer is observed regardless of the film composition of the surface film layer.

Claims (8)

A hard film for cutting tools formed on a base material, with a metal component of atomic%.
Al _(100-XY) Cr _(X) Cu _(Y)
However, 30 ≦ X ≦ 67,0 <Y ≦ 5
A hard film for a cutting tool, which has a surface film layer containing at least N as a non-metal element and containing unavoidable impurities. In the hard coating for cutting tools according to claim 1, the nitride of one or more elements formed on the surface of the base material and selected from the group consisting of Group 4A, Group 5A, Group 6A, Al and Si. It is characterized in that it is composed of a material, a carbonitride or a carbide, and is composed of a base film layer having a thickness of 0.1 μm or more and 1.0 μm or less and the surface film layer formed on the base film layer. Hard coating for cutting tools. In the hard coating for cutting tools according to claim 1, the metal component is atomic%.
Al _(100-z) Cr _(z)
However, 30 ≤ Z ≤ 70
A hard material for cutting tools, which is composed of a base film layer containing at least N as a non-metal element and containing unavoidable impurities, and the surface film layer formed on the base film layer. Film. The hard film for a cutting tool according to any one of claims 2 and 3, wherein the base film layer has a NaCl-type crystal structure. The hard film for a cutting tool according to any one of claims 1 to 4, wherein the crystal structure observed from the fracture surface of the surface film layer has columnar crystals. The hard film for a cutting tool according to any one of claims 1 to 5, wherein the total film thickness is 1 μm or more and 10 μm or less. In the hard coating for cutting tools according to any one of claims 1 to 6, the base material is a cemented carbide composed of hard particles containing tungsten carbide (WC) and a binder containing cobalt (Co). A hard coating for cutting tools that features. A drill for processing a glass fiber-containing printed wiring board having a chip discharge groove, wherein the hard film for a cutting tool according to any one of claims 1 to 7 is coated, and this hard film is the tip of the drill. A drill characterized in that it is not provided on the surface or the inner surface of the chip discharge groove.