KR102165558B1 - Multi-layered structure for sintering of thin ceramic plate and manufacturing method of thin ceramic plate using the same - Google Patents

Abstract

The present invention is a multilayer structure for firing, which is laminated and heat-treated with a ceramic green sheet made of a thick film from a slurry of ceramic powder particles in a heat treatment means such as a furnace for manufacturing a thin ceramic substrate, and the ceramic green using the same. Disclosed is a firing method for manufacturing a thin ceramic substrate by sintering a sheet. In the present invention, the sintering multilayer structure is plate-shaped hexagonal boron nitride (h-BN) powder particles respectively loaded on the upper and lower surfaces of the ceramic green sheet so as to form different interfaces with the upper and lower surfaces of the ceramic green sheet. A plastic support body configured to support a pair of h-BN green sheet buffers, the h-BN green sheet buffer forming a heterogeneous interface with the lower surface of the ceramic green sheet, and the upper surface of the ceramic green sheet and a heterogeneous interface And a load cover which is loaded on the upper surface of the h-BN green sheet buffer and applies its own gravity load to the ceramic green sheet during the heat treatment. In addition, in the present invention, the organic binder composition in the h-BN green sheet buffer is selected to have a lower thermal decomposition temperature than the organic binder composition in the ceramic green sheet. As a result, as the temperature increases during firing, the voids in which the binder composition of the buffer layer is removed first form a gas circulation path, and then the gas generated as the binder composition of the object to be burned is removed at a higher temperature and the organic matter inside the object to be fired pyrolysis. The residue is easily discharged to the outside through the gas circulation path, so that an increase in the pressure inside the object to be fired is suppressed, whereby physical deformation such as warpage of the sintered substrate is further suppressed.

Description

Multilayer structure for firing of thin ceramic substrate and manufacturing method of thin ceramic substrate using the same {MULTI-LAYERED STRUCTURE FOR SINTERING OF THIN CERAMIC PLATE AND MANUFACTURING METHOD OF THIN CERAMIC PLATE USING THE SAME}

The present invention relates to a sintering multilayer structure that is laminated with a ceramic green sheet made of a thick film from a slurry of ceramic powder particles in a heat treatment means such as a furnace for manufacturing a thin ceramic substrate and heat-treated.

In addition, the present invention relates to a firing method for manufacturing a thin ceramic substrate by sintering the ceramic green sheet using the multilayer structure.

In recent years, according to the design trend of lightening, miniaturization, integration, and high heat dissipation of electronic devices including portable mobile devices, high strength, high heat dissipation and thinning of the substrate constituting the same are increasingly required.

In general, these substrates are glass ceramic-based low temperature co-fired ceramics (LTCC) that can be sintered at temperatures below 1000°C, or metal oxide or nitride-based high-temperature co-fired ceramics that can be sintered at temperatures above 1400°C. High-temperature co-fired ceramics: HTCC). In addition, such a ceramic substrate is a predetermined laminate in which a ceramic green sheet formed with a thickness of approximately several to tens of µm containing an organic binder is manufactured as a plurality of same or different materials according to the design specifications of the substrate or package module. Is formed as and finally produced by sintering this laminate at an appropriate temperature.

However, in general, in the above-described sintering process, the bending phenomenon of the laminated body to be fired is caused by heat treatment, which causes dimensional deformation and flatness of the final sintered substrate. This is usually the result of heat treatment in the sintering process, the deformation of the shrinkage rate due to the dispersion of ceramic particles in the object to be fired and the density unevenness, the difference in shrinkage rate behavior between different ceramic materials, or deformation due to mutual reactions, the object to be fired and the plastic setter arranged to support it from the bottom. This is due to the interfacial distortion due to the difference in surface friction and specific heat between the support layer substrates, the temperature distribution between the upper and lower layers stacked inside the object to be fired, and the difference in the shrinkage of each sintering rate due to the difference in convective heat.

Therefore, in order to suppress such deflection of the substrate, a technique of disposing a ceramic material powder bed having a sintering temperature higher than that of the object to be fired as a so-called firing buffer layer on each upper surface and/or lower surface of the object to be fired (Public Patent No. 10-1990 -0007060, 10-2004-0079504, 10-2006-0112591), or a technique for arranging a ceramic material fired support layer consisting of a single layer or multiple layers (Patent Nos. 10-0302390, 10-0528693 , No. 10-0930176, No. 10-1292040, No. 10-1311387, Patent Publication No. 10-2006-0112591), or use a sintered buffer layer having a different coefficient of thermal expansion in the heterojunction region with the object to be fired during sintering (Patent No. 10-0878399, No. 10-0887112), the sintering process heat treatment by making the firing environment the same between the top and bottom of the fired body or by the effect of gravity load on the fired body by the fired support layer Efforts have been made to suppress the physical deformation caused by.

As examples of the prior art as described above, FIGS. 1A to 1B are diagrams for explaining a setting structure in which a ceramic green sheet laminate, which is a to-be-fired, is disposed in a furnace for general non-pressurization or atmospheric pressure sintering of a thin ceramic substrate. 1a is a schematic diagram showing a setting structure in a furnace of the object to be fired, and FIG. 1B is a photograph of a thin ceramic substrate sintered as the setting structure in a furnace of FIG. 1A.

As shown in Fig. 1A, in the sintering of a thin ceramic substrate, a flat fired support layer substrate 3 made of alumina or zirconia is placed on the upper surface of a firing setter 2 in a furnace, and the fired body 1 is placed on the upper surface thereof. ), and then heat treatment.

However, in this case, warpage occurs severely as shown in FIG. 1B in the final sintered substrate 1 due to the difference in the frictional restraining force and temperature distribution of the upper and lower parts of the fired body 1 during firing.

In addition, FIGS. 2A to 2B are views for explaining a structure in which a ceramic green sheet laminate is set in a furnace for general non-pressurization or atmospheric pressure sintering of a thin ceramic substrate as an example of another prior art. It is a schematic diagram showing the setting structure in the furnace of the object to be fired, and FIG. 2B is a photograph of the thin ceramic substrate which has been sintered as the setting structure in the furnace of FIG. 2A.

As shown in Fig. 2a, in addition to the setting structure of Fig. 1a, a load cover 4 is mounted on the upper surface of the object to be fired 1, and the load cover 4 has the same or different composition as the fired support layer substrate 3 However, the composition has a higher sintering temperature than that of the object to be fired (1). In this way, the gravitational load of the load cover 4 during firing is applied to the object to be fired 1, so that physical deformation due to heat treatment can be suppressed.

As a result, as shown in FIG. 2B, the warpage defects of the final sintered to-be-fired substrate 1 were significantly reduced compared to the case of FIG. 1B, but the substrate 1 is still severely curved, making it difficult to put it into practice.

As described above, the conventional techniques until now still cannot suppress the curvature in the sintered substrate to a level that can be immediately put into practical use.

In particular, the sintering buffer layer, which is used including conventional spherical or amorphous high-temperature firing oxide powders to suppress the bending of the sintered substrate, has a local reaction with the surface of the substrate to be fired, wherein these powders have a similar oxide composition during sintering. Prone to occur

In addition, in particular, after the sintering process is finished, the residual buffer layer or residual high-temperature oxide powder used so far must be removed. For this removal, scratches or cracks are generated on the surface of the laminate by applying a physical impact to the sintered laminate substrate. In addition, since foreign substances may be mixed by the cleaning medium, the surface roughness of the substrate is not good, and additional cleaning is required, which is not preferable in terms of the quality of the substrate as well as the manufacturing cost.

In addition, according to the prior art, there is a problem in that the sintering buffer layer cannot but be disposed of without reuse due to damage and contamination of its particles in the removal step, resulting in severe waste of resources.

Accordingly, the present invention provides a sintering multilayer structure capable of manufacturing a thin ceramic substrate having excellent flatness and surface roughness without bending defects by being laminated with a ceramic green sheet and heat treatment, and a thin ceramic substrate by sintering the ceramic green sheet using the same. It is to provide a firing method to manufacture.

The present invention according to one aspect for achieving the above problem relates to a sintering multilayer structure that is laminated and heat-treated with the ceramic green sheet in a heat treatment means for sintering the ceramic green sheet, wherein the multilayer structure for firing is Can contain:

-A pair of h-BN green sheet buffers composed of hexagonal boron nitride (h-BN) powder particles respectively loaded on the top and bottom surfaces of the ceramic green sheet to form a different interface with the top and bottom surfaces of the ceramic green sheet Wow;

-A firing support for supporting the h-BN green sheet buffer forming a heterogeneous interface with the lower surface of the ceramic green sheet from the lower side;

-A load cover that is loaded on the upper surface of the h-BN green sheet buffer forming a different interface with the upper surface of the ceramic green sheet to apply its own gravity load to the ceramic green sheet during the heat treatment.

In addition, the present invention according to another aspect relates to a sintering multilayer structure that is laminated together with the plurality of ceramic green sheets and heat-treated in a heat treatment means for sintering a plurality of laminated ceramic green sheets, wherein the multilayer structure for sintering May include:

-The upper surface of the ceramic green sheet, which is interposed between the plurality of ceramic green sheets to form a different interface with the upper and lower surfaces of each of the ceramic green sheets, and is located at the highest among the plurality of ceramic green sheets, and the lowest among the plurality of ceramic green sheets. A plurality of h-BN green sheet buffers composed of hexagonal boron nitride (h-BN) powder particles respectively loaded on the lower surface of the ceramic green sheet located at;

-A firing support for supporting the h-BN green sheet buffer forming a heterogeneous interface with the lower surface of the ceramic green sheet located at the lowest among the plurality of ceramic green sheets;

-It is loaded on the upper surface of the h-BN green sheet buffer that forms a heterogeneous interface with the upper surface of the ceramic green sheet located at the top among the plurality of ceramic green sheets, and applies its own gravity load to the plurality of ceramic green sheets during the heat treatment. To cover the load.

In addition, the powder particles of the hexagonal boron nitride (h-BN) have a plate shape, their diameter is in the range of 30 nm to 20 μm, and the shape aspect ratio may be 5 or more.

In addition, the thickness of the h-BN green sheet buffer may range from 10 to 100 μm.

In addition, the h-BN green sheet buffer and the ceramic green sheet each contain an organic binder composition, and the organic binder composition in the h-BN green sheet buffer has a lower thermal decomposition temperature than the organic binder composition in the ceramic green sheet. I can. In addition, the thermal decomposition temperature of the organic binder composition in the h-BN green sheet buffer may be lower than the thermal decomposition temperature of the organic binder composition in the ceramic green sheet by 50 to 100°C. In addition, the organic binder composition in the h-BN green sheet buffer may be pyrolyzed in the range of 300°C or less, and the organic binder composition in the ceramic green sheet may be pyrolyzed in the range of 350 to 400°C.

In addition, the organic binder composition in the h-BN green sheet buffer may be at least one selected from polypropylene carbonate (PPC) and polyethylene carbonate (PEC). In addition, the organic binder composition in the ceramic green sheet is polyvinyl butyral (PVB), polyvinyl alcohol (PVA), polyvinyl acetate, polystylene, hydroxy ethylcellulose ( hydroxy ethylcellulose), polymethyl methacrylic acid (PMMA), and methylcellulose may be at least one selected from the group consisting of.

In addition, the firing support and the load cover may be at least one selected from the group consisting of zirconia, alumina, silica, and magnesia.

In addition, the present invention according to another aspect relates to a method of manufacturing a thin ceramic substrate by sintering a ceramic green sheet made of a thick film from a slurry of ceramic powder particles, the method may include the following steps:

-Loading the plastic support;

-Loading a first h-BN green sheet buffer prepared from a slurry of hexagonal boron nitride (h-BN) powder particles on the firing support;

-Loading the ceramic green sheet on the first h-BN green sheet buffer;

-Loading a second h-BN green sheet buffer manufactured in the same manner as the first h-BN green sheet buffer on the ceramic green sheet;

-Loading a load cover for applying its own gravity load to the ceramic green sheet on the second h-BN green sheet buffer;

-Sintering the ceramic green sheet.

At this time, the powder particles of the hexagonal boron nitride (h-BN) have a plate shape.

In addition, the step of preparing the thick film of each of the first h-BN green sheet buffer and the second h-BN green sheet buffer may include the following:

-preparing a preliminary slurry by mixing h-BN powder particles, a solvent and a dispersant;

-Preparing a slurry of h-BN powder particles by adding an organic binder and a plasticizer to the preliminary slurry;

-Forming a thick film sheet by degassing and molding or casting the slurry of the h-BN powder particles.

In addition, the present invention according to another aspect is a ceramic green sheet made of a thick film from a slurry of ceramic powder particles, and on the upper and lower surfaces of the ceramic green sheet to form different interfaces with the upper and lower surfaces of the ceramic green sheet, respectively. On the top surface of the loaded green sheet buffer, the green sheet buffer forming a different interface with the lower surface of the ceramic green sheet, and a plastic support supporting the green sheet buffer from the lower side, and the green sheet buffer forming a different interface with the upper surface of the ceramic green sheet. A method of manufacturing a thin ceramic substrate comprising heat-treating a multilayer structure including a load cover for applying its own gravitational load to the loaded ceramic green sheet, and sintering the ceramic green sheet. The sheet buffer and the ceramic green sheet each contain an organic binder composition, the organic binder composition in the green sheet buffer is selected to have a lower thermal decomposition temperature than the organic binder composition in the ceramic green sheet, the laminated structure is heat treated and the The step of sintering the ceramic green sheet may include:

-Forming pores in the green sheet buffer as the organic binder composition in the green sheet buffer is thermally decomposed and removed as the applied temperature increases and the pores form a gas circulation path;

-As the applied temperature further increases, gas generated by thermal decomposition of the organic binder composition in the ceramic green sheet is discharged to the outside of the ceramic green sheet through the gas circulation path, and at the same time, an external atmosphere gas is transmitted to the gas circulation path. Flowing into the interior of the ceramic green sheet through;

-Discharging the organic matter pyrolysis residue generated inside the ceramic green sheet to the outside through the gas circulation path.

At this time, after the completion of the step of sintering the ceramic green sheet, the sintering support and the green sheet buffer are separated from the thin ceramic substrate manufactured by sintering the ceramic green sheet, and the green sheet buffer is made of a slurry for recycling. Can be.

In addition, the green sheet buffer may be prepared from a slurry of plate-shaped hexagonal boron nitride (h-BN) powder particles.

In addition, the organic binder composition in the green sheet buffer may be selected to have a lower thermal decomposition temperature in the range of 50 ~ 100 ℃ than the organic binder composition in the ceramic green sheet. In addition, the organic binder composition in the green sheet buffer may be pyrolyzed in the range of 300°C or less, and the organic binder composition in the ceramic green sheet may be pyrolyzed in the range of 350 to 400°C.

According to the present invention, a buffer layer composed of h-BN plate-like powder particles is interposed between the object to be fired and the surrounding medium in the sintering process, thereby effectively suppressing physical deformation such as warpage caused by the difference in shrinkage rate behavior during firing of the object to be fired in the sintering process. do.

In addition, in the sintering process, the buffer layer composed of the h-BN plate-shaped powder particles does not have any reaction with other materials or residual foreign substances, and in particular, the morphology of the h-BN plate-shaped particles constituting the buffer layer is maintained as it is. It can be separated and re-made into a slurry that can be recycled for other sintering processes.

In addition, according to the present invention, the binder composition of the buffer layer is selected so that the thermal decomposition temperature band is relatively lower than that of the binder composition of the object to be fired, and as the temperature increases during firing, the binder composition of the buffer layer is first removed and voids And these voids form a gas circulation path. After that, the gas generated when the binder composition of the fired object is removed at a higher temperature is discharged to the outside through the gas circulation path, and at the same time, the external atmospheric gas is released inside the fired body due to the pressure difference. Flows into. Due to this gas circulation cycle, organic matter pyrolysis residues such as residual carbon inside the fired body are easily discharged to the outside through the gas circulation path, so that the internal pressure of the fired body is suppressed from increasing, thereby preventing physical deformation such as bending of the sintered substrate. More restrained.

According to the above, according to the present invention, a thin ceramic substrate with greatly improved flatness and surface roughness can be manufactured.

1A to 1B are views for explaining a setting structure in which a ceramic green sheet laminate, which is a to-be-fired, is disposed in a furnace for general non-pressurization or atmospheric pressure sintering of a thin ceramic substrate,
1A is a schematic diagram showing a setting structure in a furnace of the object to be fired;
1B is a photograph of a thin ceramic substrate that has been sintered as the setting structure in the furnace of FIG. 1A.
2A to 2B are diagrams for explaining a structure in which a ceramic green sheet laminate is set in a furnace for general non-pressurization or atmospheric pressure sintering of a thin ceramic substrate as an example of another prior art,
2A is a schematic diagram showing a setting structure in a furnace of the object to be fired;
2B is a photograph of a thin ceramic substrate that has been sintered as the setting structure in the furnace of FIG. 2A.
3 is a view showing a setting structure in which an object to be fired is disposed in a furnace for sintering a thin ceramic substrate according to a preferred embodiment of the present invention.
FIG. 4 shows a structure in which a plurality of to-be-fired objects are stacked and set in a furnace for one batch sintering of a plurality of thin ceramic substrates as another embodiment of the present invention, which is a variation of the embodiment shown in FIG. 3. This is the drawing you see
5 is a thermogravimetric differential analysis (TGA) for each pyrolysis behavior of polypropylene carbonate (PPC) and polyvinyl butyral (PB) usable as an organic binder composition in the present invention. It is a graph.
6A to 6D are a structure in which an object to be fired is set in a furnace for sintering of a thin ceramic substrate as already shown in FIG. 3 in another preferred embodiment of the present invention, and in particular, the internal structures of the object to be fired and the buffer layer are mainly shown. As one thing,
6A shows the state before the sintering process;
6B is a gas generated as the sintering process is initiated and the sintering temperature is increased, the binder composition contained in the buffer layer is first pyrolyzed and removed at a relatively low temperature to create a gas circulation path, and then the binder composition of the fired object is pyrolyzed at a higher temperature. Is discharged through the gas circulation path and an external atmosphere gas is introduced into the interior;
6C shows a state in which the binder composition of the object to be fired is sufficiently removed and the gas circulation path is maintained;
6D shows a state in which the thin ceramic substrate is sintered when the sintering process is finished.
7 is a view showing a position to measure the bending strain value of the sintered thin ceramic substrate in the present invention.
8 shows photographs of a thin ceramic substrate sintered by a sintering process as shown in FIGS. 5A-5D according to an embodiment of the present invention.
9A to 9B show the surface roughness of the sintered thin ceramic substrate,
Figure 9a shows the case of the present invention;
9B shows the case of the prior art (FIG. 2).
10A-10B are photographs showing a sintered state according to the present invention,
10A shows a photograph of a thin ceramic substrate that has been sintered;
10B shows photographs of the thin ceramic substrate of FIG. 10A and the separated sintered support and buffer, respectively.

The present invention proposes a structure and method in which an object to be fired is set in a furnace in a general sintering process as a way to greatly improve the warpage defects occurring during sintering of a thin ceramic substrate in the prior art as described above. In the present invention, the to-be-fired body, which is referred to as a sintering target, may be a multilayer body formed by stacking a plurality of ceramic green sheets manufactured by a general thick film process or a single bulk ceramic green sheet. Hereinafter, the present invention will be described in detail with reference to the accompanying drawings.

3 shows a setting structure in which an object to be fired is disposed in a furnace for sintering a thin ceramic substrate according to a preferred embodiment of the present invention. In this embodiment, such a to-be-fired body may preferably be configured as a laminate in which a plurality of ceramic green sheets are stacked.

In this embodiment, as shown in FIG. 3, the sintered object 10 to be sintered is particularly set in the furnace so that the buffer layers 50 are disposed on both sides thereof to form a heterogeneous interface therewith.

In addition, in FIG. 3, the body to be fired 10 is supported by the fired support layer 30 on the fired setter 20 through the buffer layer 50 at its lower side, and the upper side thereof through the buffer layer 50 It is arranged to receive the load by the load cover 40 and is set to maintain a minimum flatness.

In particular, in the present invention, the buffer layer 50 is formed in the shape of a green sheet formed from a slurry of plate-shaped boron nitride particle powder, preferably plate-shaped hexagonal boron nitride (hereinafter "h-BN") particle powder. do.

In general, since boron and nitrogen are bonded to each other through a strong covalent bond (sp ² -hybridized), h-BN does not have an unsaturated bond on the surface and has a flat structure at the atomic level. The h-BN particle powder generally has excellent chemical stability, but has particularly excellent mechanical properties (approximately 675Gpa) and heat conduction properties (~400W/mK).

Therefore, the buffer layer 50 formed in the form of a green sheet from the slurry of the h-BN particle powder and interposed between the upper and/or lower heterogeneous interfaces of the fired body 10 as shown in FIG. And between the upper and/or lower heterogeneous interfaces of the fired body 10 while being chemically stable in a chemically harsh environment (ie, according to FIG. 3, between each interface between the fired support layer 30 and the load cover 40) ), it maintains excellent bending strength against thermal expansion/contraction and exhibits particularly excellent heat dissipation function. Accordingly, the buffer layer 50 effectively suppresses physical deformation such as warpage caused by a difference in shrinkage rate behavior during sintering with the upper and/or lower media of the object 10 during firing.

In the present invention, the diameter of the h-BN plate-shaped powder particles of the buffer layer 50 is in the range of approximately 30 nm to 20 μm, more preferably in the range of 50 nm to 10 μm. In addition, the h-BN plate-shaped powder particles are advantageous in that they have a large shape aspect ratio (ratio of particle diameter/particle thickness) in consideration of flatness, and preferably 5 or more. It is preferable that the thickness of the buffer layer 50 is in the range of approximately 10 to 100 μm, and in one embodiment, depending on the thickness of the object to be fired 10, the buffer layer 50 may be overlapped in plurality.

In addition, in the present invention, the upper side of the fired body 10 is supported by the fired support layer 30 through the buffer layer 50, while the lower side of the fired body 10 is supported by the load cover 40. By being applied, physical deformation due to heat treatment during sintering can also be suppressed. The fired support layer 30 and the load cover 40, and the fired setter 20 generally used for chemical separation between the fired body 10 and the surrounding furnace wall, are relatively It may be a composition having a high sintering temperature, for example, may be a known high-temperature firing composition generally including zirconia, alumina, silica, magnesia, and the like. The firing support layer 30 and the load cover 40 may also be made of a known high-temperature firing composition generally including zirconia, alumina, silica, magnesia, and the like.

Further, in an embodiment of the present invention, the thickness of the thin ceramic substrate is in the range of approximately 10 to 1000 μm.

In addition, FIG. 4 is another embodiment of the present invention, which is a variation of the embodiment shown in FIG. 3, in which a plurality of to-be-baked objects 10 are stacked in multiple layers for sintering a batch of a plurality of thin ceramic substrates. It shows the structure to be set.

Referring to FIG. 4, in this embodiment, a plurality of to-be-fired objects 10 are stacked in multiple layers, and between them and on the upper surface of the fired object 10 located at the top and the lower surface of the fired object 10 located at the bottom, FIG. 4 The buffer layer 50 as described above is interposed, and the uppermost buffer layer 50 and the lowermost buffer layer 20 each have an interface with the load cover 40 and the fired support layer 30 on the fired setter 20. Achieve.

In this case, again, each buffer layer 50 can suppress the occurrence of warpage as much as possible by effectively suppressing the physical deformation caused by the difference in shrinkage rate behavior during sintering with the upper and/or lower media of each to-be-fired 10 during firing, From this sintering process, a plurality of sintered substrates 10 can be obtained in one batch.

On the other hand, the present invention is another embodiment, in addition to the above-described embodiment of the present invention, in order to prevent the occurrence of warpage of the substrate more securely, residual carbon in the green sheet buffer layer and the fired body throughout the entire sintering process. We present a mechanism to keep a small amount of distribution uniform.

The mechanism of this embodiment is that the fired body made of the ceramic green sheet laminate is thermally decomposed during firing, and the organic material decomposition gas generated inside the laminate is not smoothly discharged to the outside, thereby increasing the internal pressure at the center thereof. Accordingly, it is due to consideration of the phenomenon that microcracks occur in the object to be fired. In particular, this phenomenon is more severe in mass manufacturing in one batch by loading a thin ceramic substrate in multiple layers, as in the embodiment of FIG. 4, due to insufficient decomposition (e.g., binder removal) of organic matter in the center of the laminate during sintering. As the grain growth decreases and sintering is suppressed, the microstructure in the substrate becomes non-uniform, which in turn makes the shrinkage of the substrate non-uniform, thereby remarkably causing a warpage of the substrate.

In order to solve this phenomenon, in this preferred embodiment of the present invention, each binder composition generally contained in each of the buffer layer 50 and the object to be fired 10 is fired prior to firing in the basic setting structure shown in FIG. It is designed to be dissipated and removed sequentially according to each temperature band that rises in time.

5 is a thermogravimetric differential analysis (TGA) for each pyrolysis behavior of polypropylene carbonate (PPC) and polyvinyl butyral (PB) usable as an organic binder composition in the present invention. It is a graph.

As shown in FIG. 5, these PPC and PVB exhibit different pyrolysis behaviors, and thus dissipate different temperature bands. That is, in the present invention, if an organic binder composition having different pyrolysis behaviors as described above is included in each of the buffer layer 50 and the object to be fired 10 of FIG. 3, each of these layers increases according to the temperature bands that rise during firing. The organic binder composition may be sequentially and selectively dissipated and removed.

That is, in the present invention, the binder composition of the buffer layer 50 is selected so that the thermal decomposition temperature band is relatively lower than that of the binder composition of the fired body 10. Accordingly, as the temperature in the furnace increases during firing, the binder composition of the buffer layer 50 is first pyrolyzed and removed, so that the voids (ie, pores) function as a gas circulation path to the outside. Then, the gas generated as the binder composition 14 of the object to be fired 10 is pyrolyzed at a higher temperature is discharged to the outside through the gas circulation path, and at the same time, an external atmospheric gas is introduced into the inside, forming a circulation cycle of the gas. do. In addition, through this gas circulation path, organic matter pyrolysis residues such as residual carbon in the to-be-fired 10 can be easily discharged to the outside, and an increase in internal pressure is suppressed.

6A to 6D are, in particular, in a structure in which an object to be fired is set in a furnace for sintering a thin ceramic substrate as already shown in FIG. 3 in another preferred embodiment of the present invention, each of the object to be fired 10 and the buffer layer 50 respectively 6A shows a state before the sintering process, and FIG. 6B shows a binder composition 54 included in the buffer layer 50 at a relatively low temperature as the sintering process is started and the firing temperature increases. ) Is thermally decomposed and removed to create a gas circulation path, and then the gas generated as the binder composition 14 of the to-be-fired 10 is pyrolyzed at a higher temperature is discharged through the gas circulation path and at the same time external atmosphere gas is introduced into the interior. 6C shows a state in which the binder composition 14 of the object to be fired 10 is sufficiently removed and the gas circulation path is maintained. FIG. 6D shows the thin ceramic substrate 10 sintered when the sintering process is completed. Each shows the state.

Typically, as shown in FIG. 6A, the buffer layer 50 and the object to be fired 10 are formed into a thick film by including ceramic fillers 52 and 12 and organic binders 54 and 14, respectively. However, this embodiment is a composition in which the binder composition 54 of the buffer layer 50 has a relatively lower thermal decomposition temperature band than each of the binder compositions 14 of the fired body 10 in the setting structure of the embodiment of FIG. 3. Is selected.

As a result, as shown in FIG. 6B, as the sintering process is started and the firing temperature gradually increases, the binder composition 54 in the buffer layer 50 is thermally decomposed at a relatively low temperature (see FIG. 5), and the spot is formed into pores. ) And these voids form a gas circulation path to the outside. Then, the gas generated as the binder composition 14 of the object to be fired 10 is pyrolyzed at a higher temperature is discharged to the outside through the gas circulation path (A), and at the same time, the atmospheric gas from the outside due to the air pressure difference between the inside and the outside is A circulation cycle of gas flowing into the inside through the gas circulation path (A') is formed. Due to this circulation cycle, organic matter pyrolysis residues such as residual carbon in the inside of the to-be-fired 10 can be easily discharged to the outside through the gas circulation path, thereby suppressing an increase in the internal pressure of the fired body 10.

And, as shown in Figure 6c, in the circulation cycle of the gas through the gas circulation path, the binder composition 14 of the object to be burned 10 is sufficiently removed, and other organic matter pyrolysis residues generated in the object to be burned 10 are It is maintained until it is sufficiently discharged to the outside through the gas circulation path.

In the present invention, the thermal decomposition temperature of the binder compositions 54 and 14 contained in each of the buffer layer 50 and the object to be sintered 10 is selected to have a difference of 50°C or more, more preferably 50-100°C. Can be. In this way, each of the binder compositions 54 and 14 are removed from the inside of the buffer layer 50 and the object to be fired 10 in stages according to the temperature band rising during firing.

As an example, the binder composition included in the buffer layer 50 is removed by thermal decomposition at preferably below 300° C., and polypropylene carbonate is used as a polyalkylene carbonate-based binder. PPC) and polyethylene carbonate (polyethylene carbonate: PEC) may be selected from one or more, most preferably the PPC.

In addition, as an example, the binder composition included in the to-be-fired 10 is preferably thermally decomposed and removed in the range of 350 to 400° C., and polyvinyl butyral (PVB), polyvinyl alcohol: PVA), polyvinyl acetate, polystylene, hydroxy ethylcellulose, polymethyl methacrylic acid (PMMA), and one selected from the group consisting of methylcellulose It may be more than that, most preferably the PVB.

Hereinafter, the present invention will be described in more detail through preferred embodiments of the present invention. However, the examples described below by the present invention are provided to aid in an overall understanding of the present invention, and the present invention is not limited to the following examples.

Preparation of the buffer layer 50

In the setting structure shown in FIG. 3, the buffer layer 50 was manufactured as follows. The buffer layer 50 was prepared as a green sheet by (i) preparing a slurry of h-BN plate-shaped particle powder and then (ii) molding or casting this slurry into a thick film sheet.

(i) Preparation of slurry of h-BN plate-shaped particle powder

First, the diameter of h-BN plate-shaped particles is in the range of about 30 nm to 20 μm, whereas the thickness of the plate-shaped particles is only several to tens of nm, so the specific surface area is relatively large compared to other spherical or amorphous ceramic powders. It is difficult to disperse due to a large amount of agglomeration of particles. Therefore, it is possible to provide a slurry having improved dispersibility over the next two steps.

First, as a first step, add 0.4wt% of Nopco-092 as a dispersant to 43.7wt% of h-BN plate-like powder and 49.2wt% of dimethyl carbonate (DMC) as a solvent, and mix them with a ball mill for 6 hours. A slurry was prepared.

And, as a second step, in the preliminary slurry, 5.9 wt% of a polypropylene carbonate (PPC) binder as a binder, 0.57 wt% of dibuthyl phthalate (DBP) as a plasticizer, and polyethylene glycol (polyetylene glycol: 0.2 wt% of PEG) was added and mixed for 12 hours to prepare a slurry of final h-BN plate-shaped particle powder.

(ii) Preparation of green sheet

Thereafter, the viscosity of the slurry may be adjusted through a remixing process by adding a mixed solvent to the slurry according to the required thickness of the formed sheet to be completed. The thus-finished slurry was stored at room temperature for at least 6 hours through a degassing process to stabilize, and then tape-casted to form a thick film sheet to prepare a buffer layer 50.

Preparation of the object to be fired (10)

In the present invention, all ceramic compositions having a sintering temperature lower than that of the buffer layer composed of h-BN plate-shaped particles may be used, and in particular, all ceramic compositions including alumina and/or zirconia may be used. In this embodiment, the high-strength alumina-based ceramic composition described in Patent Application No. 10-2017-0152740 (filed on November 16, 2017) of the present applicant is used as an example of such an object 10, Of course, it is natural that silver is not limited to this composition. This patent application No. 10-2017-0152740 is incorporated herein by reference in its entirety as an example.

Such a high-strength alumina-based ceramic composition is a ZTA (zirconia toughened alumina) composition in the range of 0.1 to 0.5 wt% of the total amount of ZTA to an alumina composite in which 10 to 25 vol% of stabilized zirconia (YSZ) powder containing 3 mol% yttria is added. ZTA-BNNT-B ₂ O ₃ containing boron nitride nanotube (BNNT) and containing 0.1 to 0.5 wt% of boron oxide as a sintering aid, ceramic filler 12 shown in FIG. 6A It was used as a composition powder for dragon.

In addition, a mixed solvent of toluene and ethanol as a solvent is mixed with the composition powder, where 34% by weight of the total slurry components, toluene 11.2%, ethanol 40.8%, and 1% dispersant are added to the ball mill for 6 hours. After mixing, 9.1% of a polyvinyl butyral (PVB) binder and 3.6% of dibutyl phthalate (DBP) as a plasticizer were added thereto, followed by mixing for 12 hours to complete the slurry for the ceramic filler (12). I did. Thereafter, a mixed solvent was added according to the required thickness of the molded sheet, and the viscosity of the slurry was adjusted through a remixing process.

Then, the slurry was tape-casted, formed into a plurality of thick film sheets, and laminated to prepare a laminated body 10.

Setting and sintering of the object to be fired (10)

As shown in FIG. 3 or 6A, the buffer layer 50 and the material to be fired 10 prepared as described above are in the order of the buffer layer 50-the material to be fired 10-the buffer layer 50 and the zirconia firing support 30 and It was set by interposing between the zirconia load covers 40.

Then, the temperature was gradually raised in a nitrogen, nitrogen + hydrogen or argon atmosphere and sintered at a temperature of 1600° C. for 4 hours to obtain a sintered thin ceramic substrate 10.

In addition, in order to compare the characteristics with this example, the above-prepared body to be fired as Comparative Example 1 was arranged in the order of zirconia fired support (3)-fired body (1) according to the prior art shown in FIG. 1A and sintered as above. Thus, a sintered thin ceramic substrate 1 was obtained (Comparative Example 1).

In addition, as Comparative Example 2, according to the prior art shown in FIG. 2A, the zirconia firing support (3)-the fired body (1)-zirconia load cover (4) was placed in the order of A thin ceramic substrate 1 was obtained (Comparative Example 2).

Measurement of bending deformation of thin ceramic substrate 10

In order to quantitatively evaluate the warpage results of the thin ceramic substrates of Example 1 and Comparative Examples 1 and 2 each sintered as above, the warpage strain value of the substrate was measured with reference to FIG. 7. 7 is a view showing a position to measure the bending strain value of the sintered thin ceramic substrate in the present invention.

As shown in FIG. 7, the warpage strain value was measured at each specific position (a to e) of the thin ceramic substrates 10 and 1 having a shape of 35×35×0.18mm ^{3 in} width×length×thickness, and the reference The thickness was 180 μm as the thickness of the sintered thin ceramic substrates 10 and 1, and the measurement reference point was taken as the center point (a) where the diagonals of the sample intersect. The measured value is to measure the height of the upper part of the substrate at the five measuring points of the substrate 10 and 1 in a state where the floor surface is calibrated to 0 using a micrometer equipped with a flat base, and measure the upper part of the substrate. The value obtained by subtracting the reference thickness of the substrate from the value becomes the bending deformation value. The bending deformation values measured as above are summarized in Table 1 below.

Example Measurement point on the 35×35mm ² substrate in FIG. 7 a (reference point) b c d e Comparative Example 1
(Figure 1) Measured value (㎛) 1,466 1,170 1,270 960 1,299 Bending deformation (±㎛) +1,286 +990 +1,090 +780 +1,119 Comparative Example 2
(Figure 2) Measured value (㎛) 190 260 185 200 190 Bending deformation (±㎛) +10 +80 +5 +20 +10 Example
(Fig. 3) Measured value (㎛) 180 (standard thickness) 180 189 188 180 Bending deformation (±㎛) 0 0 +9 +8 0

Referring to Table 1, the warpage strain value of the sintered substrate 1 according to the prior art Comparative Example 1 (FIG. 1) reached 780 to 1,286 µm, which was very poor, and also according to the other prior art Comparative Example 2 (FIG. 2). The flexural strain value was 5 to 80 μm, which was much reduced than that of Comparative Example 1, but this also did not reach the conventional flexural strain value of ±50 μm or less.

On the other hand, it can be clearly seen that the warpage deformation value of the sintered substrate 10 according to the embodiment (FIG. 3) according to the present invention is only within 0 to 9 μm, so that excellent results with little or no warpage defects are provided.

In addition, FIG. 8 shows a photograph of the thin ceramic substrate 10 sintered by the sintering process as shown in FIGS. 5A to 5D according to the above embodiment of the present invention.

Referring to FIG. 8, it is observed that the substrate 10 is hardly warped. This is in sharp contrast to that of the substrates 1 (FIGS. 1B and 2B) of Comparative Examples 1 and 2 showing a significant warping phenomenon, and it can be seen that the present invention has a remarkably improved effect over the prior art.

On the other hand, another effect of the present invention is a remarkable improvement of the surface roughness of the sintered thin ceramic substrate as above.

9A to 9B show the surface roughness of the sintered thin ceramic substrate, Fig. 9A shows the case of the present invention, and Fig. 9B shows the case of the prior art (Fig. 2). At this time, the surface roughness was measured with a surface roughness meter (Veeco). In addition, FIGS. 10A-10B are photographs showing a sintered state according to the present invention, FIG. 10A is a photograph of the sintered thin ceramic substrate 10, and FIG. 10B is a sintered support separated from the thin ceramic substrate of FIG. 10A ( 30) and the pictures of the buffer 50 are shown, respectively.

9A to 9B, the surface roughness Ra of the thin ceramic substrate 1 manufactured by the prior art (FIG. 2) is 1.047 μm, whereas the thin ceramic substrate manufactured by the present invention (FIG. 3) ( The surface roughness of 10) is 0.191 μm, and it can be seen that in the case of the present invention, an improvement effect of about 548% is obtained compared to the prior art. This is because, unlike conventional spherical or amorphous particle powders, the buffer layer 50 of the present invention is made of nano-thick thin plate-shaped particle powders having a large aspect ratio as described above, thereby lowering the surface roughness.

This is also proved in FIGS. 10A to 10, where the buffer layer 50 has no chemical reaction with the ceramic laminate substrate 10 and the fired support layer 30 during sintering, and the surface is cleanly separated after sintering. That is, the separated buffer layer 50 after the sintering process does not have any reaction with other materials or residual foreign matter, and in particular, maintains the morphology of the h-BN plate-shaped particles constituting the buffer layer 50 as it is, so that the separated buffer layer ( The particle powder of 50) can be made into a slurry again and recycled as a green sheet of the buffer layer 50 for another sintering process.

This is also to solve the problems of the prior art described above. That is, contrary to the present invention, the firing buffer layer of the prior art is made of a conventional spherical or irregular high-temperature firing oxide powder (eg, alumina powder, etc.), thereby causing a local chemical reaction with the surface of the substrate to be fired upon sintering. This is because the reactant particles remain on the surface of the sintered ceramic substrate, making it difficult to remove physically or chemically, and thus the used sintering buffer layer was inevitably discarded and cannot be recycled.

As described above, the present invention proposes a structure and method in which an object to be fired is set in a furnace as a method of greatly improving the warpage defects occurring during sintering of a thin ceramic substrate in the prior art.

That is, in the present invention, a buffer layer composed of h-BN plate-shaped powder particles is interposed between the object to be fired and the surrounding medium (i.e., the fired support and the load cover), and the buffer layer is chemically stable in a thermally and chemically harsh environment such as a sintering process. At the same time, it maintains excellent bending strength against thermal expansion/contraction at each interface between the fired body, the fired support layer and the load cover, and exhibits particularly excellent heat dissipation function. Accordingly, the buffer layer effectively suppresses physical deformation such as warpage caused by a difference in shrinkage rate behavior during firing of the object to be fired.

In addition, in the sintering process, the buffer layer composed of the h-BN plate-shaped powder particles does not have any reaction with other materials or residual foreign substances, and in particular, the morphology of the h-BN plate-shaped particles constituting the buffer layer is maintained as it is, so the sintering process is completed. It is then separated and made into a slurry, so that it can be reused as much as a green sheet of the buffer layer for other sintering processes.

In addition, in the present invention, the binder composition of the buffer layer is selected so that the thermal decomposition temperature band is relatively lower than that of the binder composition of the object to be fired, and as the temperature increases during firing, the binder composition of the buffer layer is first removed to form voids. And these voids form a gas circulation path, and the gas generated when the binder composition of the to-be-fired object is removed at a higher temperature is released to the outside through the gas circulation path, and at the same time, an external atmospheric gas flows into the inside of the fired body due to the difference in atmospheric pressure. do. Due to this gas circulation cycle, organic matter pyrolysis residues such as residual carbon inside the fired body are easily discharged to the outside through the gas circulation path, so that the internal pressure of the fired body is suppressed from increasing, thereby preventing physical deformation such as bending of the sintered substrate. More restrained.

As described above, in the embodiments and examples of the present invention described above, it is common in the field that there may be some variation within the usual error range according to various experimental conditions, such as the purity of the selected raw material, impurity content, and heat treatment conditions. It is absolutely natural to those who have the knowledge of.

In addition, preferred embodiments and embodiments of the present invention are disclosed for the purpose of illustration, and anyone with ordinary knowledge in the field will be able to make various modifications, changes, additions, etc. within the spirit and scope of the present invention. , Changes, additions, etc. should be regarded as belonging to the scope of the claims. That is, as an example, if a person of ordinary skill in the art omits the sintered setter 20, which is generally used for chemical separation between the sintered object 10 and the surrounding furnace wall, in the present invention, It will be readily appreciated that it may also include a case where only the sintered support layer 30 is supported through the buffer layer 50.

Claims (20)

In the sintering multilayer structure that is laminated with the ceramic green sheet and heat-treated in a heat treatment means for sintering the ceramic green sheet,
As long as it is composed of plate-shaped hexagonal boron nitride (h-BN) powder particles each loaded on the top and bottom surfaces of the ceramic green sheet to form a different interface with the top and bottom surfaces of the ceramic green sheet, respectively, and having a shape aspect ratio of 5 or more. A pair of h-BN green sheet buffers;
A firing support for supporting the h-BN green sheet buffer forming a different interface with a lower surface of the ceramic green sheet from a lower side;
Laminate for firing, characterized in that it includes a load cover that is loaded on the upper surface of the h-BN green sheet buffer forming a different interface with the upper surface of the ceramic green sheet to apply its own gravitational load to the ceramic green sheet during the heat treatment. Structure. In the sintering multilayer structure that is laminated together with the plurality of ceramic green sheets in a heat treatment means to sinter a plurality of stacked ceramic green sheets and heat treated,
The upper and lower surfaces of the ceramic green sheets are interposed between the plurality of ceramic green sheets to form a heterogeneous interface, and the upper surface of the ceramic green sheet located at the highest among the plurality of ceramic green sheets, and the lowermost of the plurality of ceramic green sheets. A plurality of h-BN green sheet buffers each of which is loaded on the lower surface of the ceramic green sheet and composed of plate-shaped hexagonal boron nitride (h-BN) powder particles having a shape aspect ratio of 5 or more;
A firing support for supporting the h-BN green sheet buffer, which forms a heterogeneous interface with a lower surface of the ceramic green sheet located at the bottom of the plurality of ceramic green sheets, from a lower side;
It is loaded on the upper surface of the h-BN green sheet buffer that forms a heterogeneous interface with the upper surface of the ceramic green sheet located at the top among the plurality of ceramic green sheets, and applies its own gravity load to the plurality of ceramic green sheets during the heat treatment. A laminated structure for firing, comprising a load cover. delete The method according to claim 1 or 2,
The diameter of the powder particles of the hexagonal boron nitride (h-BN) is in the range of 30nm ~ 20㎛, the laminated structure for firing. delete The method according to claim 1 or 2,
The thickness of the h-BN green sheet buffer is in the range of 10 ~ 100㎛ for firing laminate structure, characterized in that. The method according to claim 1 or 2,
The h-BN green sheet buffer and the ceramic green sheet each contain an organic binder composition, and the organic binder composition in the h-BN green sheet buffer has a lower thermal decomposition temperature than the organic binder composition in the ceramic green sheet. A laminated structure for firing. The method of claim 7,
The thermal decomposition temperature of the organic binder composition in the h-BN green sheet buffer is lower than the thermal decomposition temperature of the organic binder composition in the ceramic green sheet by 50 to 100°C. The method of claim 7,
The organic binder composition in the h-BN green sheet buffer is thermally decomposed in a range of 300°C or less, and the organic binder composition in the ceramic green sheet is thermally decomposed in a range of 350 to 400°C. The method of claim 7,
The organic binder composition in the h-BN green sheet buffer is at least one selected from polypropylene carbonate (PPC) and polyethylene carbonate (PEC). The method of claim 7,
The organic binder composition in the ceramic green sheet is polyvinyl butyral (PVB), polyvinyl alcohol (PVA), polyvinyl acetate, polystylene, hydroxy ethylcellulose. ), polymethyl methacrylic acid (PMMA), and at least one selected from the group consisting of methylcellulose. The method according to claim 1 or 2,
The firing support and the load cover are laminated structure for firing, characterized in that at least one selected from the group consisting of zirconia, alumina, silica and magnesia. In the method of manufacturing a thin ceramic substrate by sintering a ceramic green sheet made of a thick film from a slurry of ceramic powder particles,
Loading the firing support;
Loading a first h-BN green sheet buffer prepared from a slurry of plate-shaped hexagonal boron nitride (h-BN) powder particles having a shape aspect ratio of 5 or more on the firing support;
Loading the ceramic green sheet on the first h-BN green sheet buffer;
Loading a second h-BN green sheet buffer identical to the first h-BN green sheet buffer on the ceramic green sheet;
Loading a load cover that applies its own gravity load to the ceramic green sheet on the second h-BN green sheet buffer;
Sintering the ceramic green sheet to manufacture a thin ceramic substrate;
After the sintering step is finished, the firing support, the first h-BN green sheet buffer, and the second h-BN green sheet buffer are separated from the thin ceramic substrate, and the first h-BN green sheet buffer and the first A method, characterized in that the 2 h-BN green sheet buffer is prepared as a slurry for recycling. delete The method of claim 13,
The step of preparing the thick film of the first h-BN green sheet buffer
Preparing a preliminary slurry by mixing the h-BN powder particles with a solvent and a dispersant;
Preparing a slurry of the h-BN powder particles by adding an organic binder and a plasticizer to the preliminary slurry;
And forming a thick film sheet by degassing and molding or casting the slurry of the h-BN powder particles. The method of claim 13,
The first h-BN green sheet buffer, the second h-BN green sheet buffer, and the ceramic green sheet each contain an organic binder composition, and the first h-BN green sheet buffer and the second h-BN green sheet buffer The organic binder composition contained in is selected to have a lower thermal decomposition temperature than the organic binder composition contained in the ceramic green sheet,
The step of sintering the ceramic green sheet
As the temperature applied for the sintering increases, the organic binder composition in each of the first h-BN green sheet buffer and the second h-BN green sheet buffer is thermally decomposed and removed, and the first h-BN green sheet buffer and Forming pores in each of the second h-BN green sheet buffer and forming a gas circulation path for the pores;
As the applied temperature further increases, gas generated by thermal decomposition of the organic binder composition inside the ceramic green sheet is discharged to the outside of the ceramic green sheet through the gas circulation path, and at the same time, an external atmosphere gas is discharged to the gas circulation path. Flowing into the interior of the ceramic green sheet through;
And discharging the organic matter pyrolysis residue generated inside the ceramic green sheet to the outside through the gas circulation path. delete delete The method of claim 16,
The organic binder composition inside each of the first h-BN green sheet buffer and the second h-BN green sheet buffer is selected to have a lower thermal decomposition temperature in the range of 50 to 100° C. than the organic binder composition inside the ceramic green sheet. How to characterize. The method of claim 16,
The organic binder composition inside each of the first h-BN green sheet buffer and the second h-BN green sheet buffer is pyrolyzed in a range of 300° C. or less, and the organic binder composition in the ceramic green sheet is in the range of 350 to 400° C. Process characterized in that it is pyrolyzed.

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