JP3451940B2 - Miniature drill made of cemented carbide with excellent breakage resistance - Google Patents

Description

Description: BACKGROUND OF THE INVENTION [0001] 1. Field of the Invention [0002] The present invention has a high strength without a decrease in abrasion resistance, thereby exhibiting excellent breakage resistance even when the diameter is further reduced. The present invention relates to a cemented carbide miniature drill. 2. Description of the Related Art Conventionally, in general, a miniature drill made of cemented carbide has a hard dispersed phase occupying 70 to 93 area% as shown in FIG. The hard dispersed phase shows (a) tungsten carbide (hereinafter, referred to as WC), and (b) V precipitated in the binder phase in a cooling process during sintering. Precipitated composite carbide of W and Cr [hereinafter, (V, W, C
r) represented by C], which comprises the above (a) and (b), and both have an average particle size of 1.0 μm or less due to the action of the V component, and further contain Co, Cr, and V in an amount of: weight%
(Hereinafter, simply indicating% indicates weight%), Co: 5-
13%, Cr: 0.2-2%, V: 0.05-0.3
%, WC-based cemented carbide (hereinafter referred to as cemented carbide)
It is well known that, as illustrated in a schematic front view in FIG. 3, it is composed of a cutting edge portion and a shank portion, and drilling is performed by an outer peripheral edge formed on the cutting edge 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. On the other hand, in recent years, the degree of integration of semiconductor devices has been remarkably increased, and accordingly, the diameter of the holes provided therein has also been reduced in diameter. The miniature drill used is also smaller in diameter, but the smaller the hole diameter, the higher the required strength (toughness) of the miniature drill from the viewpoint of preventing breakage. It is necessary to increase the Co content of the cemented carbide. However, if the Co content is increased, the wear resistance is inversely reduced, and it is unavoidable to shorten the service life. [0004] Therefore, the present inventors have proposed:
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. ”.
(W, Cr) C was precipitated in the binder phase upon cooling to form a hard dispersed phase, but after changing the vacuum atmosphere to a pressurized atmosphere as described above and maintaining the pressurized atmosphere for a predetermined time, By rapid cooling, (V, W, Cr) C is reduced to W as shown in FIG.
C is deposited on the surface of C as a full coating thin layer and / or a partial coating thin layer to form a coating WC, which is not deposited in the binder phase, and the resulting (V, W, Cr) C deposition ratio With little change in (V,
The cemented carbide without precipitation of (W, Cr) C has higher strength than the above-mentioned conventional cemented carbide in which (V, W, Cr) C is dispersed and precipitated in the binder phase. Research results show that if a miniature drill is made of cemented carbide, it will show excellent breakage resistance even when the diameter is further reduced, and the reduction in wear resistance will be suppressed by the reduction in diameter. I got it. The present invention has been made on the basis of the above-mentioned research results. According to the structure observation by an electron microscope, the hard dispersed phase occupies 70 to 93% by area, and the remainder consists of the binder phase mainly composed of Co. Shows the following structure, the hard dispersed phase,
A coated WC in which WC is entirely and / or partially coated with a thin layer of (V, W, Cr) C;
m, less than or equal to Co, Cr, and V
Content of Co: 5 to 13%, Cr: 0.2 to 2%,
V: 0.05 to 0.3%, characterized by a cemented carbide miniature drill made of cemented carbide and having excellent breakage resistance. Next, the reason why the composition of the cemented carbide constituting the miniature drill of the present invention and the average particle size of the hard dispersed phase composed of the coated WC are limited as described above will be described. (A) Composition (a) Ratio of Hard Dispersed Phase (Coated WC) If the ratio is less than 70 area%, desired excellent wear resistance cannot be ensured, while the ratio is 93 area%.
If it exceeds, the ratio of the binder phase becomes relatively too small,
Since the strength suddenly decreases, the ratio is set to 70 to 93 area%, preferably 83 to 90 area%. (B) Content of Co The Co component has the effect of improving the sinterability and improving the strength by forming the binder phase, thereby suppressing the breakage of the drill. 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%.
%. (C) Cr content As described above, the Cr component precipitates on the surface of the WC as a thin layer covering the entire surface and / or a partially covering layer (V, W, C)
r) Forming C to improve wear resistance and dissolving in the binder phase to improve heat resistance,
If the content is less than 0.2%, a desired improvement effect on the above-mentioned effect cannot be obtained. On the other hand, if the content exceeds 2%, the solid solution ratio in the binder phase becomes too high, and the strength is reduced. Therefore, the content is determined to be 0.2 to 2%, preferably 0.3 to 1%. (D) Content of V In the V component, (V, W, Cr) C is also formed to improve wear resistance, and also forms a solid solution in a binder phase to form a solid solution during sintering. Although the coating WC has an effect of suppressing the grain growth, if the content is less than 0.05%, the hard (V,
Not only is it difficult to form (W, Cr) C, but even when the average particle size of the WC powder as the raw material powder is 1.0 μm or less, the coated WC exceeds 1.0 μm due to grain growth during sintering. Since the average particle size is reached, the desired strength cannot be secured and the occurrence of breakage cannot be suppressed. On the other hand, if the content exceeds 0.3%, the strength of the binder phase itself decreases. The content is determined to be 0.05 to 0.3%, desirably 0.1 to 0.2%, since breakage easily occurs. (E) Average particle size of coated WC The average particle size of the coated WC constituting the hard dispersed phase is adjusted by the average particle size and the V content of the WC powder as the raw material powder as described above. When the particle size exceeds 1.0 μm, the strength is significantly reduced due to coarsening of the hard dispersed phase particles. Therefore, the average particle size is set to 1.0 μm or less. Next, a cemented carbide miniature drill according to the present invention will be described in detail 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 a quantitative analysis method, and an arbitrary cross section thereof was observed using a transmission electron microscope and an energy dispersive X-ray spectrometer. After confirming that the average particle diameter was obtained, the ratio was calculated by an image analyzer, and the measurement and calculation results shown in Table 1 were shown. From the dimensions shown in Table 1 Produced either two edge geometry invention miniature drill 1-8 respectively by cutting. For the purpose of comparison, the sintering conditions were set to 0.0
After maintaining at a predetermined temperature in the range of 1350 to 1480 ° C. for 1.5 hours in a vacuum atmosphere of 5 torr, the same except that the furnace is cooled (in this case, the cooling rate to 1200 ° C. is about 10 ° C./min) Conventional miniature drills 1 to 8 as shown in Table 2 were manufactured under the conditions. With respect to the miniature drills 1 to 8 of the present invention and the conventional miniature drills 1 to 8 obtained as a result, a printed board having a thickness of 1.6 mm composed of an alternate six-layer laminate of a glass layer, an epoxy resin layer and a copper layer And the number of test pieces: 20 shown in Table 1
A drilling test was performed using the book, and the number of drilling operations and the number of breaks until the outer diameter of the outer peripheral edge of the miniature drill caused 5% wear were measured. The results of these measurements are shown in Tables 1 and 2, and the number of perforations is shown as an average value without breakage. [Table 1] [Table 2] From the results shown in Tables 1 and 2, all of the miniature drills 1 to 8 of the present invention have (V, W, Cr) C
Is deposited as a thin layer of the WC entirely and / or partially coated so that the (V, W, Cr) C is substantially dispersed in the binder phase. It is clear that the abrasion resistance is equal to that of the conventional miniature drills 1 to 8 and that it exhibits a further improved breakage resistance. As described above, the miniature drill of the present invention has a high strength enough to cope with the reduction of the diameter, so that it is excellent for 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 diagram 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.

──────────────────────────────────────────────────の Continuing on the front page (72) Inventor Teruyoshi Tanase 1511 Furamagi, Ishishita-cho, Yuki-gun, Ibaraki Pref. 6 (56) References JP-A-4-289146 (JP, A) JP-A-10-10014 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) C22C 29/00-29 / 18 B23B 51/00

Claims (1)

(57) [Claims 1] Observation of the structure with an electron microscope shows a structure in which the hard dispersed phase occupies 70 to 93 area% and the remainder is composed of a binder phase mainly composed of Co. The dispersed phase is composed of coated tungsten carbide obtained by entirely and / or partially coating tungsten carbide with a thin layer of a precipitated composite carbide of V, W, and Cr, and
It has an average particle size of not more than μm, and further contains Co, Cr and V in weight%, Co: 5-13%, Cr: 0.2-2%, V: 0.05-0. A miniature drill made of a cemented carbide having excellent breakage resistance, characterized in that the drill is made of a tungsten carbide-based cemented carbide of 3%.