JPH0583511B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Application Field) The present invention relates to an artificial ruby used as a bonding capillary, an optical connector, a wire guide, or an ornament, and a method for producing the same.

(Prior Art) Polycrystalline synthetic rubies have been used as carriers for gold wires connecting electrodes on the surface of semiconductor chips and fingers of lead frames.

Such polycrystalline artificial ruby is made of aluminum oxide and chromium oxide, MgO, SrO, Y ₂ O ₅ and La ₂ O ₃
etc. were mixed as a sintering aid, and the mixture was molded and then sintered in a predetermined atmosphere, but it was difficult to control the atmosphere and a large number of sintering aids were required.
JP-A-59-97572 proposes a method in which a mixture of aluminum oxide, chromium oxide and magnesium oxide is molded and then sintered at a temperature of 1400 to 2000°C in a vacuum of 10 ^-1 Torr or more.

(Problems to be Solved by the Invention) The artificial ruby obtained by the conventional method described above has a large average crystal grain size and is inferior in light transmittance.
In addition, the hardness is difficult to exceed 200 HV, so there are problems in terms of workability and durability.

(Means for Solving the Problems) In order to solve the above problems, the present invention provides 0.7 to 3wt%
A fine mixed powder of chromium oxide, 0 to 0.05 wt% magnesium oxide, and the balance aluminum oxide is prepared, an organic binder is added to this fine mixed oxide powder, and it is molded into a predetermined shape. After the body was sintered at 1280-1350°C, it was subjected to hot isostatic pressing at 1300-1310°C and 1000-2000 atm.

(Effect) By performing the process under the above conditions, the average crystal grain size can be reduced.
An artificial ruby with a pore size of 2.0 μm or less, free of coarse particles of 4 μm or more, and a pore diameter of 0.1 μm or less, excellent in translucency, hardness, and bending strength is produced.

(Example) Examples of the present invention will be described below with reference to the accompanying drawings.

FIG. 1 is a block diagram showing the method of the present invention in the order of steps. In the present invention, aluminum salt, which becomes aluminum oxide with a purity of 99.99% or more when thermally decomposed after spray drying, is used as a starting material. Chromium salt that becomes chromium oxide with a purity of 99.99% or more and purity when thermally decomposed after spray drying
Prepare a magnesium salt that becomes 99.99% or more magnesium oxide. For example, as an aluminum salt, ammonium alum or aluminum ammonium carbonite hydroxide (AACH: NH ₄ AlCO ₃ (OH) ₂ ) is used.
Chromium nitrate Cr (NO ₃ ) is used as the chromium salt.
_{3.9H 2} O, and magnesium nitrate Mg(NO ₃ ) _{3.6H 2} O is used as the magnesium salt.

Then, each of the above salts was weighed and suspended in a resin pot containing a resin ball, and dried by spray drying.
The product is thermally decomposed at a temperature of 1050°C to obtain a fine powder mixture of aluminum oxide, chromium oxide, and magnesium oxide, which is a uniform mixture of oxides. Then, this mixed fine powder is further wet-pulverized in a solvent such as ethanol to loosen aggregates, and dried again by spray drying to obtain a fine powder. Here, the proportion of each oxide constituting the mixed fine powder is chromium oxide, 0.7 to 3wt
%, magnesium oxide is 0-0.05wt%, and aluminum oxide is the balance. In other words, it is not necessary to add magnesium oxide at all.

In addition, to obtain a mixed fine powder of oxides, as shown in Figure 2, each salt is thermally decomposed to form aluminum oxide, chromium oxide, and magnesium oxide separately, and then these are weighed and mixed. Good too.

Once the mixed fine powder of the oxide is obtained as described above, an organic binder mainly composed of a thermoplastic resin is added to the mixed fine powder, and the mixture is molded into a desired shape by injection molding.

Next, the molded body obtained by injection molding is degreased and then sintered. Sintering conditions are 1280-1300℃
The test shall be carried out in an atmosphere of 1280 to 1300°C and a vacuum of 10 ^-3 to ^{10 -6} Torr, or in an atmosphere of N ₂ , Ar or H ₂ at 1300 to 1350°C. The heating rate was set to 200°C/h, and the temperature was maintained at 800°C and 1295°C for 1 hour each.

The sintered body obtained as described above is subjected to hot isostatic pressing. The conditions at this time are 1300~
It is carried out for 1 hour at 1310°C and a pressure of 1000 to 2000 atm in an argon atmosphere. The product thus obtained is subjected to diamond precision grinding and precision polishing to obtain a final product.

(Effect of the invention) Figure 3 is a diagram showing the durability, etc. of the products of the present invention (Nos. 1 to 6) and comparative examples (Nos. 7 to 9) manufactured by changing the ratio of chromium oxide and magnesium oxide. be.
In addition, only for the comparative example (No. 9), the starting material was aluminum oxide of the Bayer method, and for this material
Vacuum sintering was performed at 1575℃×1hr, then 1500℃×
Hot isostatic pressing was performed under conditions of 1000 atm x 1 hr (in Ar).

In addition, for durability testing, we prototyped an ultrasonic type bonding capillary, and after repeating wire bonding 20,000 times, we cleaned it with aqua regia and observed the condition of the tip using an electron microscope (400x magnification), and found no changes at all. The case where there was no damage was rated A, the case where there was some wear was rated B, and the case where falling off or chipping was observed was rated C.

In addition, for the workability test, the following precision grinding and polishing were performed by applying a load of 500 g to a sliding precision grinding/polishing machine rotating at 60 rpm.

Grinding Water/wet method 200# metal bond diamond/grinding wheel 10min Polishing Oil/wet method 8μm diamond paste/on ceramic plate 10min Grinding Oil/wet method 1μm diamond paste/on copper plate 20min Polishing Oil/wet method 0.5μm diamond paste on buff 10min And precision grinding/ A case where the surface became a mirror surface after precision polishing was rated A, a case where some scratches remained was rated B, and a case where chipping was significant was rated C.

In addition, regarding the quality of translucency, the obtained sintered body was sliced and polished to a thickness of 0.3 mm.
The test was based on whether the characters on the newspaper surface 1 cm away were visible.

As is clear from Figure 3, chromium oxide is 0.7
~3.0wt% and magnesium oxide is 0 to 0.05wt%, an artificial ruby with excellent various properties can be obtained.

To summarize the above, the present invention exhibits the following effects.

First, by using a metal salt as a starting material, sintering can be performed at a low temperature. That is, since the high purity oxide obtained by thermally decomposing a metal salt has an activated surface, sintering can be completed at a low temperature. If the sintering temperature is low, even if magnesium oxide is not added, abnormal grain growth is less likely to occur, resulting in uniform and fine crystal grains. Therefore, although magnesium oxide is not an essential material, its addition improves sinterability.

Furthermore, since a spray drying method is used as a mixing method, various oxides, etc. can be mixed uniformly, and since hot isostatic pressing is performed, the hardness of the product can be increased. Especially when the sintering temperature is 1280℃ or higher,
Because the hot isostatic press was performed at a temperature of 1300℃ or higher and 1000atm or higher, no pores larger than 0.1μm remain.
Sintering temperature below 1350℃, hot isostatic press at 1310℃
Since the temperature was below ℃ and below 2000 atm, there was no abnormal grain growth of 4 μm or more.

In addition, hot isostatic pressing causes mechanical lattice strain in the crystal, which increases the hardness of the product.

Further, in the present invention, chromium is added, and this chromium easily self-diffuses onto the surface of the material, forming a chromium-rich oxide film on the surface of the ceramic, thereby preventing carbon adhesion and improving hardness and corrosion resistance. However, if the proportion of chromium oxide is less than 0.7wt%, the desired hardness and corrosion resistance cannot be obtained, and if it is more than 3wt%, pores of 0.1μm or more will remain in the product after hot isostatic pressing, resulting in the desired toughness and strength. Therefore, the ratio of chromium oxide (converted to chromium oxide in the case of chromium salt) (aluminum oxide,
100% mixture of chromium oxide and magnesium oxide
) is preferably 0.7 to 3 wt%.

Since the radius of the chromium ion and the radius of the aluminum ion are almost equal (about 12% difference), the chromium ion and aluminum ion replace each other during sintering, resulting in lattice strain in the crystal. As above, the hardness of the product is improved.

Therefore, according to the method of the present invention, it is possible to obtain an artificial ruby that has excellent light transmittance, has a uniform crystal grain size, has a dense and fine structure, and has excellent strength, hardness, durability, and workability.

[Brief explanation of drawings]

Fig. 1 is a block diagram showing the method of the present invention in the order of steps, Fig. 2 is a drawing showing the steps of another embodiment, and Fig. 3 is a chart comparing strength, hardness, etc.

Claims (1)

[Claims] 1. Crystals with an average particle size of 2.0 μm or less in which 0.7 to 3.0 wt% of chromium oxide is dissolved in aluminum oxide, or 0.7 to 3.0 wt% of chromium oxide in aluminum oxide and
It consists of crystals with an average particle size of 2.0 μm or less in which 0.05 wt% or less of magnesium oxide is dissolved, the internal pore diameter is 0.1 μm or less, there are no coarse particles of 4 μm or more, and the hardness is 2000 Hv or more. , a polycrystalline artificial ruby characterized by having translucency. 2 Chromium oxide obtained by thermally decomposing chromium salt is 0.7
~3.0wt%, 0 to 0.05wt% of magnesium oxide obtained by thermally decomposing a magnesium salt, and the balance being aluminum oxide obtained by thermally decomposing an aluminum salt, and an organic binder is added to the desired powder. This molded body is sintered at 1280-1350℃, and then this sintered body is heated at 1300-1310℃ and 1000℃.
A method for producing polycrystalline artificial ruby, characterized by applying hot isostatic pressing under conditions of ~2000 atm. 3 The mixed powder of the oxide contains an aluminum salt,
The method is characterized in that a chromium salt and a magnesium salt are weighed to form a homogeneous suspension solution, this suspension solution is dried by a spray drying method to form a fine powder, and this fine powder is obtained by thermal decomposition. A method for producing a polycrystalline artificial ruby according to claim 2. 4 The molded body is sintered in the atmosphere at 10 ^-3 to 10 ^-6
3. The method for producing polycrystalline artificial ruby according to claim 2, wherein the method is carried out in a Torr vacuum or in an atmosphere of N ₂ , Ar or H ₂ .