JP2000000712A - Miniature drill made of cemented carbide with high strength - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a miniature drill made of cemented carbide with high strength. SOLUTION: A miniature drill is composed of cemented carbide showing texture comprising a first hard dispersed phase: 65-92.5 area %, a second hard dispersed phase: 0.5-5 area % and a connection phase mainly composed of Co and unavoidable impurities: the rest by texture observation by an electron microscope. The first hard dispersed phase comprises coated WC with WC coated over the whole surface or partially with a thin layer of (V, W, Cr) C. The second hard dispersed phase comprises (V, W, Cr) C minutely dispersed and distributed in the connection phase, respectively having the average diameter of 0.7 μm or less, and the content of Co, Cr, V are to be Co: 5-13%, Cr: 0.2-2%, and V: 0.2-1%.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a cemented carbide miniature drill having high strength without abrasion resistance and exhibiting excellent breakage resistance even when the diameter is further reduced. .

[0002]

2. Description of the Related Art Conventionally, in general, a miniature drill made of cemented carbide generally has a structure in which the first hard dispersed phase is 60 to 92 area%, and the second hard dispersed phase is as shown in FIG. : 1 to 10 area%, a binder phase mainly composed of Co and unavoidable impurities: remaining, showing a structure consisting of the following: the first hard dispersed phase is made of tungsten carbide (hereinafter, referred to as WC); The dispersed phase is composed of a precipitated composite carbide of V, W, and Cr [hereinafter, referred to as (V, W, Cr) C] finely distributed in the binder phase. 7 μm
It has the following average particle size, and the content of Co, Cr, and V is expressed in terms of% by weight (hereinafter, simply “%” indicates% by weight), Co: 5 to 13%, Cr: 0.2 ~ 2%, V:
0.2 to 1%, and is composed of a WC-based cemented carbide (hereinafter, referred to as a cemented carbide) and includes a cutting edge portion and a shank portion as illustrated in a schematic front view in FIG. It is well known that drilling is performed by an outer peripheral blade formed on the cutting blade portion. It is also known that these cemented carbide miniature drills are mainly used for drilling a printed circuit board or the like of a semiconductor device.

[0003]

On the other hand, the recent high integration of semiconductor devices is remarkable, and accordingly, the diameter of the holes provided in these devices is also tending to be reduced in size. Therefore, miniature devices used for drilling these holes are required. Drills also have a smaller diameter, but the smaller the drilled hole diameter, the higher the strength (toughness) of the miniature drill is required in order to prevent breakage. The Co content must be increased, but when the Co content is increased, the abrasion resistance decreases in inverse proportion, and it is unavoidable to shorten the service life.

[0004]

Means for Solving the Problems Accordingly, the present inventors have
In view of the above, the above-mentioned conventional cemented carbide miniature drills were focused on, and a study was carried out to improve the strength without impairing the wear resistance of the conventional cemented carbide miniature drills. In the production of a cemented carbide (hereinafter referred to as a conventional cemented carbide) constituting a drill, the sintering is performed in a vacuum atmosphere of 0.01 to 0.1 torr.
Temperature: After holding at 1350 to 1480 ° C for 1 to 2 hours, cool the furnace to at least 1200 ° C (cooling rate in this case is about 1
0 ° C./min), and the sintering is performed in a vacuum atmosphere of 0.01 to 0.1 torr at a temperature of 1350 to 1480 ° C. for 1 to 2 hours, and then the atmosphere is heated to 50 ° C. After changing to a pressurized atmosphere of 150 kg / cm ² for 15 to 60 minutes,
Quenching at a cooling rate of 50 to 100 ° C./min up to 0 ° C. ”.
All of W, Cr) C were dispersed and precipitated in the binder phase upon cooling to form a second hard dispersed phase, but as described above, the vacuum atmosphere was changed to a pressurized atmosphere, and After holding for a predetermined time and then quenching, as shown in the schematic diagram of the structure observation result by the electron microscope in FIG. The first hard dispersed phase composed of the coated WC is formed, and the resulting (V, W, Cr) C precipitation ratio hardly changes.
r) The cemented carbide in which a part of C forms the coating WC has higher strength than the conventional cemented carbide in which (V, W, Cr) C is dispersed and precipitated only in the binder phase. become,
Therefore, if a miniature drill is made of this cemented carbide, it will show excellent breakage resistance even in this one-step reduction in diameter,
In addition, a study result was obtained that a decrease in wear resistance was suppressed even by reducing the diameter.

The present invention has been made based on the results of the above-mentioned research, and the structure of the first hard dispersed phase: 65 to 92.5 area%, the second hard dispersed phase: 0.1 5 to 5 area%, a binder phase mainly composed of Co and unavoidable impurities: remaining, showing a structure consisting of the following, and the first hard dispersed phase completely coats WC with a thin layer of (V, W, Cr) C. And / or a partially covered coating WC, wherein the second hard dispersed phase was finely dispersed and distributed in the binder phase (V, W, C
r) composed of C, each having an average particle diameter of 0.7 μm or less, and further having a Co, Cr and V content of C
o: 5 to 13%, Cr: 0.2 to 2%, V: 0.2 to
1%, which is characterized by a cemented carbide miniature drill having excellent breakage resistance, which is made of a cemented carbide.

Next, in the miniature drill of the present invention, the reason why the composition of the cemented carbide constituting the drill and the average particle size of the hard dispersed phase are limited as described above will be described. (A) Composition (a) Ratio of first hard dispersed phase (coated WC) Existence of (V, W, Cr) C in first hard dispersed phase, that is, (V, W, Cr) C coats the surface of WC It has been empirically found that the strength of the cemented carbide is significantly improved by performing the method. In this case, when the structure is observed by an electron microscope, 50% or more of the total grain boundary length of WC is (V). , W, Cr) C.
Further, the first hard dispersed phase has a function of further improving wear resistance by the coexistence of WC and (V, W, Cr) C coating the surface thereof, but if the ratio is less than 65 area%. However, the desired excellent abrasion resistance cannot be ensured. On the other hand, when the proportion exceeds 92.5 area%, the proportion of the binder phase becomes relatively too small, and the strength rapidly decreases. Therefore, the ratio was determined to be 65 to 92.5 area%, preferably 80 to 89 area%.

(B) Second hard dispersed phase ((V, W, C
r) Ratio of C) The second hard dispersed phase has a function of further increasing the hardness of the cemented carbide and thus improving the wear resistance. If the hardness improvement effect cannot be obtained, and if the ratio exceeds 5% by area, the strength will rapidly decrease.
Area%, desirably 1 to 3 area%.

(C) Content of Co The Co component has the effect of improving sinterability and forming a binder phase to improve strength, thereby suppressing drill breakage. If the content is less than 1, sufficient breakage resistance to elongation cannot be ensured.
If it exceeds 3%, a sharp decrease in wear resistance cannot be avoided, so its content is 5 to 13%, preferably 6 to 10%.
%.

(D) Cr content As described above, the Cr component is deposited on the surface of the WC as a thin film entirely coated and / or a thin layer partially coated (V, W, C)
r) In addition to forming C to improve strength and wear resistance, it also forms a second hard dispersed phase to further improve wear resistance and forms a solid solution in the binder phase. Has the effect of improving the heat resistance, but its content is 0.2
If the content is less than 2%, a desired improvement effect cannot be obtained in the above-mentioned action. On the other hand, if the content exceeds 2%, the solid solution ratio in the binder phase becomes too high, which causes a decrease in strength. The amount was determined to be 0.2-2%, preferably 0.3-1.0%.

(E) Content of V In the V component, (V, W, Cr) C is also formed to improve the strength and wear resistance. Has the effect of suppressing the grain growth of the first and second hard dispersed phases at the time, but if the content is less than 0.2%, it is only difficult to form hard (V, W, Cr) C. However, even if the average particle size of the raw material powder WC powder is 0.7 μm or less, the first hard dispersed phase has an average particle size exceeding 0.7 μm due to grain growth during sintering, and The effect of suppressing the growth of the second hard dispersed phase precipitated in the binder phase is not sufficient, and as a result, a desired high strength cannot be secured, and the occurrence of breakage cannot be prevented. If it exceeds 1%, the strength of the binder phase itself decreases, and breakage tends to occur. Yu amount from 0.2 to 1%, preferably defined 0.2 to 0.5%.

(F) Average particle size of the first and second hard dispersed phases These average particle sizes are as described above for WC as raw material powder.
The average particle diameter is adjusted according to the average particle diameter and the V content. When the average particle diameter exceeds 0.7 μm, the strength is significantly reduced due to the hard dispersed phase coarsening. It is determined as follows.

[0012]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Next, the cemented carbide miniature drill of the present invention will be specifically described with reference to examples. As raw material powders, WC powder having an average particle diameter of 0.8 μm, VC powder having an average diameter of 1.5 μm, and Cr ₃ C having an average particle diameter of 2.3 μm were used.
₂ Powder and Co powder are prepared, and these raw material powders are blended to a predetermined composition, mixed by a wet ball mill for 72 hours, dried under reduced pressure, further mixed with wax and a solvent for 1 hour, and then extruded. And a long molded body having a diameter of 4.4 mm, and these long molded bodies were dewaxed in a vacuum atmosphere of 0.05 torr, and 1350 mm.
After maintaining at a predetermined temperature within the range of １４1480 ° C. for 1.5 hours, the atmosphere is changed to a pressurized atmosphere of a pressure: 60 kg / cm ² , and after maintaining the pressurized atmosphere for 25 minutes, the temperature up to 1200 ° C. is increased to 50 to 100 ° C. By sintering at a predetermined cooling rate in the range of ° C./min under rapid cooling conditions, a long sintered material made of cemented carbide and having a diameter of 3.5 mm is manufactured. , The contents of Co, Cr, and V components were measured by quantitative analysis, and the arbitrary cross section was observed using a transmission electron microscope and an energy dispersive X-ray spectrometer, and the first hard dispersed phase was coated. After confirming that WC and the second hard dispersed phase consisted of (V, W, Cr) C, the average particle diameter of these was measured, and the ratio was calculated by an image analyzer. Shows the measurement and calculation results shown in Table 1, respectively, from the elongated sintered material
The miniature drills 1 to 8 of the present invention each having a two-blade shape were manufactured by cutting to the dimensions shown in Table 1. For the purpose of comparison, the sintering condition was set to 0.05 to
After maintaining at a predetermined temperature in the range of 1350 to 1480 ° C. for 1.5 hours in a vacuum atmosphere of rr, the furnace was cooled (12 in this case).
Conventional miniature drills 1 to 8 as shown in Table 2 were manufactured under the same conditions except that the cooling rate to 00 ° C was about 10 ° C / min).

The resulting miniature drills 1 to 8 of the present invention and the conventional miniature drills 1 to 8 have a 1.6 mm-thick printed circuit board composed of alternately six-layer laminated plates of a glass layer, an epoxy resin layer and a copper layer. Were subjected to a drilling test under the conditions shown in Table 3 and the number of test pieces: 20, and the number of drilling processes until the outer diameter of the outer diameter of the miniature drill became 5% wear and The number of breaks was measured. Table 3 shows the results of these measurements. The number of perforations was shown as an average value without breakage.

[0014]

[Table 1]

[0015]

[Table 2]

[0016]

[Table 3]

[0017]

According to the results shown in Table 3, all of the miniature drills 1 to 8 of the present invention have a part of (V, W, Cr) C as a thin layer and / or a thin layer of WC. By precipitation, the (V, W, Cr) C
Conventional miniature drill 1 in which is dispersed only in the binder phase
It is evident that the abrasion resistance is equivalent to that of Nos. To 8 and that it shows a further improved breakage resistance. As described above, the miniature drill of the present invention has high strength enough to cope with the reduction in diameter, and is excellent over a long period without breakage even when applied to, for example, a highly integrated semiconductor device. It demonstrates its performance.

[Brief description of the drawings]

FIG. 1 is a schematic view showing the results of observation of the structure of a cemented carbide constituting a miniature drill of the present invention by an electron microscope.

FIG. 2 is a schematic view showing a structure observation result by an electron microscope of a cemented carbide constituting a conventional miniature drill.

FIG. 3 is a schematic front view showing a miniature drill.

 ──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Teruyoshi Tanase 1511 Furamagi, Ishishita-cho, Yuki-gun, Ibaraki Pref. Mitsubishi Materials Corporation Tsukuba Works (72) Inventor Taketo Sasama 1-10 Takanodai, Funabashi-shi, Chiba -6 F term (reference) 3C037 AA09 FF06

Claims (1)

[Claims] 1. Structure observation by an electron microscope: first hard dispersed phase: 65 to 92.5 area%, second hard dispersed phase: 0.5 to 5 area%, binder phase mainly composed of Co and unavoidable impurities : The remaining hard dispersed phase is composed of tungsten carbide, V, W and C.
and / or partially coated with a thin layer of the precipitated composite carbide of tungsten carbide, and the second hard dispersed phase contains V dispersed finely in the binder phase.
, W and Cr, each of which has an average particle size of 0.7 μm or less, and further contains Co, Cr, and V in a content of 5% to 13% by weight, : 0.2 to 2%, V: 0.2 to 1%, a high-strength cemented carbide miniature drill comprising a tungsten carbide-based cemented carbide.