JPH0446049A - Composite body - Google Patents

Abstract

PURPOSE:To obtain a composite sintered body having enhanced strength by dispersing a dispersed phase having a lower rate of filling of powder than a matrix phase in the matrix phase, molding and firing them. CONSTITUTION:An unsintered composite body having a structure obtd. by dispersing a dispersed phase having a lower rate of filling of powder than a matrix phase in the matrix phase is molded and fired to obtain a composite body. Since the generation of stress due to the difference in shrinkage between the phases is controlled during firing by the difference in the rate of filling of powder, the strength of the composite body is easily enhanced and a composite sintered body having high mechanical strength can easily be produced. Especially in the case of electronic ceramics, the size, especially the thickness of the product can further be reduced and the utilization range of structural ceramics can be extended.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a composite used for electronic materials or structural materials and a method for manufacturing the composite sintered body, and in particular, to a method for manufacturing the composite sintered body, in which the filling rate of raw material powder is controlled. In particular, the present invention relates to a composite sintered body with increased strength and a method for preparing the same.

[Problems to be solved by the prior art and the invention 1 Among various structural materials, as exemplified by electronic ceramics or structural ceramics, the required mechanical conditions are as follows:
With the recent improvement in technological standards, the requirements have become more severe, and improvements in the strength of sintered structures are desired.

From this point of view, in order to improve the strength or toughness of the sintered structure, conventional methods include reducing the grain size of raw material powder to submicron sizes, or strictly controlling impurities at grain boundaries. etc. are being carried out.

However, in order to control the structure organization by making the particles finer and reduce the sources of destruction, a special raw material preparation method or a sintering method under high temperature and pressure such as HIP method is required. . Recently, there have also been attempts to add whiskers such as SiC to general-purpose ceramic materials such as alumina to obtain a strength reinforcing effect. In particular, the nanometer-level local stress of the SiC dispersed phase particles causes the dispersed particles to
Attempts to improve the strength by controlling the internal structure between the matrices include, for example, alumina-3tC composite χ
In the above case, the strength was increased by 1''2, and when it was annealed, the strength was further increased by approximately 1.5 times, resulting in a strength of approximately 1540 MPa. Also, this strength is 1200℃
It has been found that it can be maintained even at high temperatures up to a certain degree.

In addition, methods to control porosity, grain boundaries, defects, internal stress, etc. within the matrix, or fiber reinforcement methods, that is, methods to improve strength by achieving a pull-out effect by interaction with a second phase such as whiskers or fibers, are also conducted. It is.

However, nanometer-sized composite structural ceramics made of SiC etc. require the use of SiC whiskers to homogeneously disperse the dispersed phase within the matrix crystal, which poses difficulties in manufacturing technology and restrictions on materials. There is.

Furthermore, in particular, alumina substrates are rapidly becoming larger and more precise, and stronger alumina substrates are desired, which are essential for the automation of manufacturing thick film hybrid ICs and packages.

In order to solve the above-mentioned problems, the present invention composes five dispersed matrix phases with different powder filling rates, fires them, and controls the shrinkage rate, thereby creating a stress field at the interface between the dispersed phase and the matrix phase. The purpose of this invention is to improve the mechanical strength of not only ceramic materials but also various structural materials.

[Structure of the Invention] [Means for Solving the Problems] The gist of the present invention is to
This is a composite having a structure in which a dispersed phase with a powder filling rate smaller than that of the matrix phase is dispersed in the matrix phase. Then, by dispersing a dispersed phase having a diameter of 100 μm or less and having a smaller filling factor than the matrix phase into a matrix phase having a larger filling factor to form a composite, and molding and sintering the composite, , a method for manufacturing a composite fired body.

For example, when creating a ceramic composite, when two materials with different powder filling rates are combined as a dispersed phase and a matrix phase, each shrinkage rate is determined by each powder filling rate. .

The present inventors have focused on the fact that internal stress is generated at the bonding interface between two or more materials having different firing shrinkage rates.

In other words, by combining two or more materials with different firing shrinkage rates, a stress field is generated at the boundary between the dispersed phase and the matrix phase in the sintered body, making it possible to increase the strength. According to the invention, a reinforced composite sintered body can be manufactured by such a method.

In order to apply a stress field to the boundaries of each material, it is possible to apply a material with a large firing shrinkage rate to the dispersed phase and a material with a small firing shrinkage rate to the matrix phase.

The firing shrinkage rate of each can be arbitrarily controlled by controlling the powder filling rate of each raw material.

A molded body is obtained by mixing a binder, a solvent, etc. with raw material powder, molding, and drying.The shrinkage rate of the sintered body obtained by firing this molded body is determined by the particle size of the raw material powder, as well as the particle size of the raw material powder. It depends on the powder filling rate of the green compact.

That is, the inventors have determined the relationship between the firing shrinkage rate and the powder filling rate (
Formula) was considered as follows.

The apparent specific gravity ρ1 is ρ, -ga, /V, ・ ・A However, ρ is the apparent density of the powder, is the weight of the powder in the molded body, and is the weight of the molded body. is the volume of

Assuming that the volume is V and the weight of the substrate is W, the theoretical density ρ of the substrate is expressed in mg by the following formula.

ρ-W/V, ・・・・・・・・・B The powder filling rate is expressed by the following formula C from formulas A and B.

p */ p − (ws/v+)/(w/v+>-w+
/w-・c The firing line shrinkage rate in the x, y, and z directions of the molded body is α
8, α1 and α2, the sintered density ρ of the substrate can be expressed by equation D.

(ρr/ρ)− (ρ, /ρ)/((1−αx)x (t−αy)x (
t-α2))...D Therefore, the powder filling rate (ρ1/ρ) is (ρ, /ρ)- (ρ, /ρ)X ((1-α x)x (i
-α vex (t-α 2))...E Here, (ρf/ρ> is the relative ratio of the sintered density to the theoretical density. If the firing shrinkage of the molded body is isotropic, α8
−αarα2, which is as follows. That is, (ρ, /ρ)/(ρt/ρ)-(1-α8)1αx-1
-''J(ρS/ρ)/(ρr/ρ)------F Therefore, it can be seen that if the powder filling rate and relative density are determined, the linear shrinkage rate can be uniquely obtained.

The sintering properties of a powder material depend on the powder properties of the material and the inherent properties of the material. In other words, in terms of powder characteristics, its particle size,
Depends on particle size distribution, shape, etc. In addition, the inherent properties of the material such as sintering temperature and reactivity are also considered.

That is, a composite material is obtained by dispersing a powder having a powder filling rate smaller than that of the matrix in the dispersed phase, molding it, and sintering it. The strength of the composite sintered body can be increased by bending or stopping the direction of crack propagation due to the stress field at the interface caused by the difference in firing shrinkage rate between the dispersed phase and the matrix phase.

The present invention was developed based on this theory, and it is possible to integrally mold materials having arbitrary different controlled powder filling ratios, that is, a dispersed phase and a matrix phase having different powder filling ratios. The present invention provides a method for strengthening the strength of a sintered body by integrally firing the sintered body by a stress field acting on the interface of the region of the powder filling ratio.

That is, by inducing internal strain stress, the strength of the sintered body is increased by changing or stopping the propagation direction of the crack.

These composites, even if they have the same composition or different compositions, can be used to control the filling rate and sintering properties (powder particle size control, powder surface activity control - powder manufacturing method, This is possible through control using thermal history differences).

◆Shrinkage rates determined from different powder filling rates are as shown in Table 1 when calculated using the F formula with the relative density being ioo and 99.98.96%. That is, as seen in the values in Examples described later, in actual cases, there is a slight difference from the theoretical values. This is probably because the firing shrinkage rate of the molded body in actual examples is not completely uniform shrinkage, and also because it depends on factors such as the molding method or the shape of the powder. However, in sheet forming methods using the doctor blade method, for example, shrinkage in the area method may be regulated by factors such as drying. in this case,
Shrinkage in the thickness direction is not so regulated.Therefore, according to the method of the present invention, there is no problem in arbitrarily setting the shrinkage difference between matrices and dispersed phases with different filling rates.Therefore, the shrinkage The difference generates a stress field, which has a sufficient effect to strengthen the strength of the folded body.

Table 1 Relationship between linear shrinkage rate (%) and filling rate (%) determined from 2F The method for manufacturing a composite sintered body according to the present invention includes- Then, It is as follows.

That is, after mixing arbitrary amounts of the dispersion raw material, binder, and solvent, the mixture is treated by a spray dryer method, or an Iha microemulsion method, and the mixture is heated to a ratio of 1 to 100%.
A dispersed phase of a spherical molded body with a diameter of 1 m is obtained. In order to increase the mechanical strength of a composite sintered body, it is effective to reduce the particle size of the dispersed phase as much as possible, and the method for producing the dispersed phase is to produce monodisperse microspheres using a microemulsion method, etc. suitable. Further, the powder filling rate of the dispersed phase can be adjusted by appropriately selecting the amount of constituent particles or binder, and the amount of solvent. The dispersed phase produced in this way is put into a matrix phase adjusted to have a powder filling rate larger than that of the dispersed phase, and is molded using a general ceramic forming method. Obtain a fired composite.

Next, when this unfired composite is fired at a predetermined temperature, the first
A composite sintered body having the structure shown in the figure is obtained. That is, it has a structure in which a dispersed phase 1 with a small powder filling rate is dispersed in a matrix phase 2 with a large powder filling rate. During this sintering process, the shrinkage rate of the dispersed phase 1 is large and the shrinkage rate of the matrix phase 2 is small. Therefore, as shown by the arrow, the matrix phase around the dispersed phase 1 has a shrinkage rate due to each sintering. The difference results in a tensile force 3. On the other hand,
Since the dispersed phase 1 has a large shrinkage upon firing, a repulsive force 4 is generated in response to the tensile force 3. Therefore, a stress field due to the tensile force 3 and the repulsive force 4 is generated at the interface between the dispersed phase 1 and the matrix phase 2. As a result, when the composite sintered body breaks,
By inducing internal strain stress, the crack propagation direction is changed or stopped.

Furthermore, in the present invention, as in the prior art, the dispersed phase is
Uniform dispersion in the matrix phase is important. Therefore, it is desirable that the dispersed phase be produced in a uniform size and shape. A generally known method for producing a dispersed phase is a spherical molded product using a spray dryer method. 1-10
A spherical molded body with a diameter of about 0 μm is obtained.

In order to increase the strength or toughness of the resulting composite sintered body, it is effective to further reduce the size of the dispersed phase, and methods for producing such a dispersed phase include the production of monodispersed micro-spheres by the microemulsion method, etc. is suitable. Spherical molded bodies on the order of submicron to micron can be manufactured arbitrarily.

The powder filling rate of these molded bodies can be adjusted by arbitrarily selecting the amount of constituent particles, binder, and solvent.

In this way, the powder is poured into the matrix phase, which has a powder filling ratio smaller than that of the dispersed phase, and is used for general ceramic molding such as the doctor blade method, slurry casting method, and press method. By this method, a matrix composite molded body having a dispersed phase dispersed therein is obtained. The method of mixing and dispersing can be the same as the method used for ordinary ceramic molding.

The present invention makes full use of such sintering control technology to obtain a composite sintered body. As a means for this purpose, a molded body with a controlled powder filling rate can be created.

In the powder sintering technique described above, a matrix phase with a large powder filling rate is created, and a spherical dispersed phase as described above with a relatively small powder filling rate is created separately. The spherical dispersed phase is mixed and dispersed in a matrix phase with a relatively small powder filling rate, a molded body is molded from the obtained composite, and the molded body is fired to form a composite sintered body. obtain.

The method for producing the composite sintered body of the present invention is to obtain a spherical green body that has been shaped in advance by a spray drying method or a chemical synthesis method (microemulsion), and then disperse it in a matrix phase and shape it. It is. This matrix phase differs depending on the molding method; in the doctor blade method and slurry casting method, it is used in the form of a slurry, and in the press method, it is used in the form of powder, that is, granulated powder.

Furthermore, although the present invention will be described in this specification and in the examples using a doctor blade method, other methods such as a slurry casting method may also be used.

Next, a method for producing a sintered powder composite according to the present invention will be explained using specific examples, but the present invention is not limited by the explanation.

[Example] As the alumina powder, AL-45 manufactured by Showa Denko Co., Ltd.
-IR alpha alumina (purity 99.5% by weight, average particle size 0
．． 8μm) with a specific surface area of 20m"7g and 4% by weight of flux was used.To this alumina powder, 2.5% by weight of polyvinyl alcohol as a binder and 0.6% ammonium polycarboxylate as a dispersant were used. After adding % by weight to create a slurry, it was dried with a spray dryer manufactured by Yamato Scientific Co., Ltd., and granulated.
~20 μm spherules were obtained. The powder filling rate of this unfired body for the dispersed phase was 60.1%, and the linear shrinkage rate when fired alone at 1600°C was about 14.8%.

The matrix phase was created as follows. That is, a powder was used in which 4% by weight of flux with a specific surface area of 1.0"7 g was added to the same alumina raw material with an average particle size of 1.1 μm. Polyvinyl as a binder was added to this alumina powder. A mixed solvent of 5% by weight of butyral, 3% by weight of butylbenzyl phthalate as a plasticizer, 17% by weight of n-butanol and 83% by weight of xylene as a solvent was used at 55% by weight.
% by weight was added and mixed in a ball mill to obtain a ceramic raw material slurry. The powder filling rate of this unsintered matrix material was 61.8%, and the linear shrinkage rate when fired alone at 1600°C was about 13.3%.

The above-mentioned slurry for dispersed phase was added in an amount of 60 to 90% by weight to the matrix phase thus prepared to obtain an unfired composite slurry.

Next, a molded body having a width of 5° and a thickness of 0.6° was formed from such a composite slurry by a doctor blade method.

The composite molded body was punched out with a die into a size of 34.73 x 42.26 cm to prepare a fired sample.

The composite molded body was fired in a high-speed heating furnace (Cantar Gabrius, RT-2). When firing, initially 450
The temperature was raised to 300°C at a heating rate of °C/hour and held for 1 hour, then the temperature was raised to 1200°C at a heating rate of 900°C/hour, and then 4.5°C/minute. The specified temperature (16
The temperature was raised to 00°C) and held for 1 hour to sinter. Cooling was performed by in-furnace cooling (cooling rate: 7°C/min).

As described above, a composite sintered body having a dispersed phase and a matrix phase was obtained.The strength of this composite sintered body was measured as follows.

For comparison, the strength is shown when molded and fired using a single alumina raw material.

Composite sintered body of the present invention: 470-950 Single alumina sintered body 250-500 [Effects of the invention] The ceramic composite of the present invention and its manufacturing method are as follows. It produced remarkable technical effects.

First, when a ceramic composition or a different type of composition is molded and the molded body is fired, stress generation due to the firing-shrinkage difference can be controlled by the difference in the powder filling rate, making it easy to create a molded body. , it was possible to easily produce a composite sintered body with increased strength and a composite sintered body with high mechanical strength.

Second, especially in the field of electronic ceramics, it is possible to further reduce the size of the product, especially to make the layers thinner, and the range of use of structural ceramics can be expanded.

[Brief explanation of the drawing]

FIG. 1 is a schematic diagram for explaining the structure of a ceramic composite according to the present invention. [Explanation of symbols of main parts] 1...Dispersed phase 2...Matrix phase 3...Tension due to firing shrinkage

Claims (1)

[Claims] 1. 1. A composite material obtained by molding and firing an unsintered composite material having a structure in which a dispersed phase having a powder filling ratio smaller than that of a matrix phase is dispersed in a matrix phase.