KR20210119009A - Ceramic composite and method of fabricating thereof - Google Patents

Abstract

A ceramic composite according to an embodiment of the present invention is a sintered body including alumina (Al2O3) and niobium-doped yttria-stabilized zirconia (Nb-doped YSZ). A ceramic composite according to the present invention can have excellent mechanical strength and good thermal conductivity.

Description

CERAMIC COMPOSITE AND METHOD OF FABRICATING THEREOF

The present invention relates to a ceramic composite and a method for manufacturing the same, and more particularly, to a ceramic composite for an insulating substrate for dissipating heat and a method for manufacturing the same.

As electronic devices are miniaturized, digitized, high-speed, and multifunctional, miniaturization and high-integration of electronic components are also progressing. Since heat generated from electronic components shortens not only the performance of the electronic component but also the lifespan, a heat dissipation package having high heat dissipation performance is required. To this end, an insulating substrate having high heat dissipation performance and high mechanical strength is required.

_{Alumina (Al 2} O ₃ ) is mainly used as a material for an insulating substrate for dissipating heat generated from various electronic components. In addition, nitrides such as aluminum nitride (AlN) and silicon nitride (Si ₃ N ₄ ) have been developed and used as materials for insulating substrates.

In order to use alumina as an insulating substrate, sintering is usually required at a high temperature of 1600° C. or higher, and a general alumina substrate manufactured in this way usually exhibits thermal conductivity of 20 to 30 W/mK, and flexural strength is mostly 250 to It is limited to the range of 350 MPa. For this reason, it has been required to improve the properties of alumina materials, and it is developing in the direction of lowering the thickness of the heat dissipation package through the improvement of the mechanical strength of alumina. This is because the thinner the thickness of the heat dissipation package, the better the heat dissipation characteristics of the package. The high mechanical strength of the heat-dissipating ceramic substrate has the advantage that it can reduce the thickness of the heat-dissipating package and contribute to the improvement of process reliability.

Aluminum nitride (AlN) has the advantage of very high thermal conductivity of 170-230 W/mK, but raw material powder is very expensive, and in order to obtain a dense sintered body, a high temperature of about 1700° C. or higher is required, and nitrogen gas or hydrogen- Since sintering is performed in a reducing atmosphere using a nitrogen mixed gas, the manufacturing cost is also very high.

Silicon nitride (Si ₃ N ₄ ) also has the advantage of having very good flexural strength and thermal conductivity, but like AlN, expensive raw material powder and high temperature and high pressure atmosphere sintering are required, so the manufacturing cost is high.

Therefore, there is a need for a material for a heat dissipating ceramic substrate that does not significantly decrease in thermal conductivity compared to conventional alumina and can be manufactured at low cost while having improved mechanical strength than an alumina material.

An object of the present invention is to provide a ceramic composite having excellent mechanical strength and good thermal conductivity, and capable of being sintered at a low temperature.

An object of the present invention is to provide a method for manufacturing a ceramic composite capable of sintering a ceramic composite having excellent mechanical strength and good thermal conductivity at a low temperature.

The ceramic composite according to an embodiment of the present invention includes alumina (Al ₂ O ₃ ) and niobium-doped yttria-stabilized zirconia (Nb-doped YSZ).

In the ceramic composite, niobium-doped yttria-stabilized zirconia particles having a size of 1 μm or less may be formed between alumina grains having a size of 5 μm or less.

In the ceramic composite, the content of niobium-doped yttria-stabilized zirconia may be 9 vol.% or more and 16 vol.% or less.

The ceramic composite may have a thermal conductivity of 20 W/mK or more and a flexural strength of 500 MPa or more.

A method of manufacturing a ceramic composite according to an embodiment of the present invention, _{high energy milling of alumina (Al 2} O ₃ ) powder and niobium oxide (Nb ₂ O ₅ ) powder using yttria-stabilized zirconia (YSZ) balls After mixing, and after the mixing is completed, it may include a step of atmospheric pressure sintering.

The atmospheric pressure sintering may be performed at a temperature range of 1450°C to 1600°C.

Prior to the mixing step, the method may further include pulverizing at least one of alumina powder and niobium oxide powder.

The ceramic composite according to the present invention may have good thermal conductivity while having excellent mechanical strength.

According to the method for manufacturing a ceramic composite according to the present invention, a ceramic composite having excellent mechanical strength and good thermal conductivity can be sintered under atmospheric pressure at a low temperature of 1450°C.

According to the method for manufacturing a ceramic composite according to the present invention, a ceramic composite having excellent mechanical strength and good thermal conductivity can be manufactured at low cost.

1 is a flowchart illustrating a method of manufacturing a ceramic composite according to embodiments of the present invention.
2 is a graph showing an XRD analysis result of a ceramic composite according to an embodiment of the present invention.
3 is a scanning electron microscope (SEM) photograph of the ZTA sintered body prepared at a sintering temperature of 1450° C. in the present invention.
4 is a scanning electron microscope (SEM) photograph of the ZTA sintered body prepared at a sintering temperature of 1600° C. in the present invention.
5 is a view showing a scanning transmission electron microscope (STEM) analysis results of the ceramic composite according to an embodiment of the present invention.

Hereinafter, preferred embodiments according to the present invention will be described in detail with reference to the accompanying drawings. In the drawings, the same reference numerals are used to indicate the same or similar components.

An alumina-zirconia composite is being considered as an insulating substrate material that can replace alumina (Al ₂ O ₃ ), and the alumina-zirconia composite is referred to as Zirconia Toughened Alumina (ZTA).

Zirconia-reinforced alumina (ZTA) has _{similar thermal conductivity to alumina (Al 2} O ₃ ) material, but has higher mechanical strength (flexural strength). As the addition ratio of zirconia in zirconia-reinforced alumina (ZTA) increases, the flexural strength of zirconia-reinforced alumina (ZTA) increases, while thermal conductivity tends to decrease due to the low thermal conductivity of zirconia (about 4 W/Mk).

Therefore, zirconia-reinforced alumina (ZTA) is required to improve mechanical strength while minimizing a decrease in thermal conductivity compared to _{alumina (Al 2} O _{3 ).}

The present invention provides a ceramic composite having improved mechanical strength (eg, flexural strength) while having good thermal conductivity.

The ceramic composite according to an embodiment of the present invention is _{a sintered body including alumina (Al 2} O ₃ ) and niobium-doped yttria-stabilized zirconia (Nb-doped YSZ).

In the ceramic composite according to an embodiment of the present invention, niobium-doped yttria-stabilized zirconia particles may be formed between the sintered alumina grains. The alumina grains may have a size of 5 μm or less, and the niobium-doped yttria-stabilized zirconia particles may have a size of 1 μm or less.

In the ceramic composite according to an embodiment of the present invention, the content of niobium-doped yttria stabilized zirconia may be 2 vol.% or more and 16 vol.% or less, preferably 9 vol.% or more and 16 vol.% may be below.

The ceramic composite according to an embodiment of the present invention may have a thermal conductivity of 20 W/mK or more and 38 W/mK or less, and may have a flexural strength of 300 MPa or more and 740 MPa or less. When the content of niobium-doped yttria-stabilized zirconia in the ceramic composite is 9 vol.% or more and 16 vol.% or less, the thermal conductivity of the ceramic composite is 20 W/mK or more and 29 W/mK or less, and the ceramic composite The flexural strength of the composite may be 500 MPa or more and 740 MPa or less.

Although the ceramic composite according to an embodiment of the present invention has a small content of niobium-doped yttria-stabilized zirconia of 16 vol.% or less, it has high flexural strength compared to alumina and may have thermal conductivity similar to that of alumina. The ceramic composite according to an embodiment of the present invention may have a high flexural strength compared to alumina and thermal conductivity similar to that of alumina while being composed of alumina crystal grains having a size of 5 μm or less.

1 is a flowchart illustrating a method of manufacturing a ceramic composite according to an embodiment of the present invention. Referring to FIG. 1 , in the method of manufacturing a ceramic composite according to an embodiment of the present invention, alumina (Al ₂ O ₃ ) powder and niobium oxide (Nb ₂ O ₅ ) powder are mixed with yttria-stabilized zirconia (YSZ) balls. ) may include a step of mixing by high-energy milling using, and, after the mixing is completed, atmospheric pressure sintering.

The step of mixing alumina (Al ₂ O ₃ ) powder and niobium oxide (Nb ₂ O ₅ ) powder by high energy milling using yttria stabilized zirconia (YSZ) balls is, for example, 0.1 to 0.1 to After adding the niobium oxide powder of 2.0 at.%, using a planetary ball mill, for example, it may be carried out at 150 rpm for 1 hour to 8 hours. The rpm and time of the planetary ball mill are not limited to the above, and the time may vary depending on the rpm conditions.

In one embodiment of the present invention, in the process of mixing alumina powder and niobium oxide powder using high energy milling, by using the phenomenon that yttria stabilized zirconia (YSZ) balls are worn by alumina powder, yttria stabilized zirconia ( A powder mixture in which alumina powder, niobium oxide powder, and yttria-stabilized zirconia (YSZ) powder are uniformly mixed can be prepared without separately adding YSZ) powder.

Alternatively, the step of mixing the alumina powder and the niobium oxide powder may be performed using general ball milling instead of high energy milling. In this case, the primary particle size (primary particle size) in the step of mixing the alumina powder and niobium oxide powder size) of 1 μm or less, YSZ and ZrO ₂ powder, or a precursor containing zirconium (Zr) may be added.

The atmospheric pressure sintering may be performed in the atmosphere at a temperature range of 1450 to 1600 °C. The atmospheric pressure sintering may be performed for several hours (eg, 2 hours), but is not limited thereto.

In an embodiment of the present invention, by adding niobium oxide as a low-temperature sintering aid (liquid sintering additive) and mixing the powders by high-energy milling, sintering can be easily performed even at 1450°C.

In this embodiment of the present invention, since the ceramic composite can be formed by atmospheric pressure sintering at a temperature range of 1450 to 1600° C. for several hours (eg, 2 hours), HIP (Hot Isostatic Press) or SPS that applies high temperature and high pressure The sintering process that requires special equipment such as (Spark Plasma Sintering) is unnecessary. Therefore, the ceramic composite of the present invention can be manufactured at low manufacturing cost.

In the method for manufacturing a ceramic composite according to an embodiment of the present invention, before the mixing step, in order to similarly control the particle size of the alumina powder and the niobium oxide powder, at least one of the alumina powder or the niobium oxide powder is oiled. It may further include the step of pulverizing through a method such as a ball mill (planetary ball mill). For example, before mixing the alumina powder and the niobium oxide powder, the particle size of the niobium oxide powder may be adjusted by pulverizing the niobium oxide powder through a method such as a planetary ball mill. Accordingly, the alumina powder and the niobium oxide powder can be mixed more uniformly.

The method of manufacturing a ceramic composite according to an embodiment of the present invention may include a step of forming before the step of sintering. In the forming step, the powder mixture mixed through high-energy milling may be molded into a disk shape for, for example, measuring thermal conductivity, and may be molded into a rectangular parallelepiped shape with a predetermined pressure for measuring flexural strength. It is appropriate that the forming form and method of the material for sintering be determined by the specifications required by the application. For example, when used as an insulating substrate for dissipating heat in an electronic component package, that is, a heat dissipation substrate, the powder mixture may be molded into a thin plate shape.

Hereinafter, embodiments of the present invention will be described. However, the following examples are provided to help the overall understanding of the present invention, and the present invention is not limited only to the following examples.

Example

Examples 1 to 8 are zirconia-reinforced alumina (ZTA) ceramic composites prepared by mixing 0.25 at.% niobium oxide powder with alumina powder, and then changing the planetary milling time and sintering conditions. In Examples 1 to 4, or Examples 5 to 8, the planetary milling time was changed from 1 hour to 8 hours. Examples 1 to 4 were sintered at 1450° C. under atmospheric pressure for 2 hours, and Examples 5 to 8 were sintered at 1600° C. for 2 hours under atmospheric pressure.

The sintered specimens were measured for flexural strength and thermal conductivity, respectively. Three-point flexural strength was measured using specimens of 3.0 mm x 4.0 mm x 36.0 mm in size according to KS L ISO 14704. The thermal diffusivity was measured using a laser flash technique: LFA 467 Hyperflash, NETZSCH Instruments Co., and the thermal conductivity value was calculated by multiplying this by the density and specific heat of the specimen. Specific heat was measured using a differential scanning calorimeter (NETZSCH DSC204, NETZSCH Instruments Co.), and density was measured using a water immersion method.

Table 1 below summarizes the manufacturing conditions and physical properties for Examples.

Example 1 Example 2 Example 3 Example 4 Example 5 Example 6 Example 7 Example 8 Sintering conditions 1450℃, 2 hours 1600℃, 2 hours Planetary Milling
hour (hour) One 2 4 8 One 2 4 8 YSZ content
(at.%) 1.7 2.9 6.3 10.3 1.7 2.9 6.3 10.3 YSZ content (vol.%) 2.8 4.7 9.7 15.0 2.8 4.7 9.7 15.0 thermal conductivity
(W/mK) 32.7 37.4 28.8 22.8 34.4 30.4 27.9 27.5 flexural strength
(MPa) 327 429 533 626 182 307 502 732

Referring to Table 1, as the planetary milling time increased from 1 hour to 8 hours, the YSZ content in the ceramic composite increased from 2.8 vol.% to 15.0 vol.%. And, as the YSZ content increases from 2.8 vol.% to 15.0 vol.%, it can be seen that the flexural strength increases. Example 8 with a sintering temperature of 1600° C. and a YSZ content of 15.0 vol.% had the highest flexural strength of 732 MPa. Example 4 with a sintering temperature of 1450° C. and a YSZ content of 15.0 vol.% had a flexural strength of 626 MPa. On the other hand, as the YSZ content increases from 2.8 vol.% to 15.0 vol.%, it can be seen that the thermal conductivity tends to decrease. Example 8 with a sintering temperature of 1600° C. and a YSZ content of 15.0 vol.% had a thermal conductivity of 27.5 W/mK. Example 4 with a sintering temperature of 1450° C. and a YSZ content of 15.0 vol.% had the smallest thermal conductivity of 22.8 W/mK.

Example 4 with a sintering temperature of 1450° C. and a YSZ content of 9.7 vol.% had a thermal conductivity of 28.8 W/mK and a flexural strength of 533 MPa. Example 8 with a sintering temperature of 1600° C. and a YSZ content of 9.7 vol.% had a thermal conductivity of 27.9 W/mK and a flexural strength of 502 MPa.

FIG. 2 shows the results of XRD analysis of Zirconia Toughened Alumina (ZTA) (Example 4) sintered at 1450° C. for 2 hours by way of example. Referring to FIG. 2 , it can be seen that the zirconia-reinforced alumina (ZTA) sintered at 1450° C. for 2 hours according to Example 4 of the present invention is made of alumina and zirconia.

FIG. 3 shows an SEM photograph of Zirconia Toughened Alumina (ZTA) (Example 4) sintered at 1450° C. for 2 hours by way of example. FIG. 4 shows an SEM photograph of Zirconia Toughened Alumina (ZTA) (Example 8) sintered at 1600° C. for 2 hours by way of example. Referring to FIG. 3 , although some pores are present, it can be confirmed that microstructure densification and particle growth have progressed. Referring to FIG. 4 , as the sintering temperature increases, as compared to the specimens sintered at 1450° C., an increase in the size of alumina grains and a dense microstructure can be confirmed.

FIG. 5 shows an STEM (Scanning Transmission Electron Microscopy) analysis result of zirconia toughened alumina (ZTA) (Example 4) sintered at 1450° C. for 2 hours by way of example. Referring to FIG. 5 , it can be seen that yttria-stabilized zirconia (YSZ) is formed between the alumina grains. It can be seen that the added niobium oxide exists in a doped state in the yttria-stabilized zirconia (YSZ) particles formed between the alumina grains after sintering.

Referring to the analysis results of FIGS. 2 to 5 together, the zirconia-reinforced alumina (ZTA) ceramic composite according to embodiments of the present invention has a smaller size niobium-doped yttria-stabilized zirconia (Nb-) between alumina grains. doped YSZ) particles are distributed, the size of the alumina grains is 5 μm or less, and it can be confirmed that the size of the niobium-doped yttria stabilized zirconia (Nb-doped YSZ) particles is 1 μm or less.

Among the examples of the present invention, when the content of niobium-doped yttria-stabilized zirconia is 9 vol.% or more and 16 vol.% or less (Examples 3, 4, 7, 8), the ceramic composite is 20 W/mK or more It has excellent thermal conductivity and has excellent flexural strength of 500 MPa or more.

In particular, the ceramic composites according to some embodiments (Examples 3 and 4) sintered at 1450° C. have excellent thermal conductivity of 20 W/mK or more, and excellent bending of 500 MPa or more, despite the presence of some pores. have strength

In the above, although the embodiment of the present invention has been mainly described, various changes or modifications may be made at the level of those skilled in the art. Accordingly, it will be understood that such changes and modifications are included within the scope of the present invention without departing from the scope of the present invention.

Claims (7)

A ceramic composite comprising alumina (Al ₂ O ₃ ) and niobium-doped yttria-stabilized zirconia (Nb-doped YSZ). According to claim 1,
A ceramic composite in which niobium-doped yttria-stabilized zirconia particles having a size of 1 μm or less are formed between alumina grains having a size of 5 μm or less. According to claim 1,
The content of niobium-doped yttria-stabilized zirconia is greater than or equal to 9 vol.% and less than or equal to 16 vol.%. According to claim 1,
Ceramic composite with a thermal conductivity of 20 W/mK or more and a flexural strength of 500 MPa or more. mixing alumina (Al ₂ O ₃ ) powder and niobium oxide (Nb ₂ O ₅ ) powder by high-energy milling using yttria-stabilized zirconia (YSZ) balls; and
After the mixing is completed, atmospheric pressure sintering; Method for producing a ceramic composite comprising a. 6. The method of claim 5,
The atmospheric pressure sintering step is a method of manufacturing a ceramic composite is performed at a temperature range of 1450 ℃ to 1600 ℃. 6. The method of claim 5,
Prior to the mixing step, the method of manufacturing a ceramic composite further comprising the step of pulverizing at least one of alumina powder and niobium oxide powder.

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