JPH10218672A - Baking for ceramic sheet - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for baking a ceramic sheet, hardly causing bending of ceramic sheet and unevenness on the surface and capable of eliminating removal of fusion preventing powder after baking and processes for ultrasonic washing and brushing. SOLUTION: A ceramic green sheet 13 is placed on the flat top of a setter 11 not to be reacted with the ceramic green sheet 13 at high temperature during baking and another setter 11 is installed through a spacer 12 at an interval not to bring the setter into contact with the ceramic green sheet 13. The ceramic green sheets 13 are introduced in this state into a baking furnace. The ceramic green sheets 1 to be baked are square or round laminar bodies having a side or a diameter of >=50 times as much as their thickness. The interval δ between the vertical setters 11 is larger than thickness (t) of a ceramic green sheet 4 after baking and <= five times as much as the thickness of the green sheet 13.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a ceramic sheet firing method in which a thin ceramic green sheet is introduced into a firing furnace, heat-treated, and fired to obtain a fired ceramic sheet. In particular, the present invention relates to a method for manufacturing a ceramic sheet that is most suitable for firing a rectangular or circular ceramic sheet having a side length or diameter that is 50 times or more the thickness of the ceramic sheet.

[0002]

2. Description of the Related Art As electronic components have become smaller, there has been an increasing demand for thinner ceramic sheets having a larger area due to a demand for improved productivity. For example, a substrate used for a hybrid integrated circuit substrate is a square sheet having a thickness of 0.5 mm and a square of 150 mm or 200 mm, and a piezoelectric sheet for a piezoelectric buzzer is also 30 mm at a thickness of 0.05 mm.
The size of φ is used. In any case, the sheet is required to be flat.

[0003] Such a ceramic sheet as a sintered body is generally produced by the following method. First, a slurry is prepared by adding and mixing a binder to a ceramic powder, and the slurry is formed by a wet extrusion method, a doctor blade method, or the like, thereby forming a thin ceramic green sheet. Next, the ceramic green sheets are punched into a predetermined shape, and thereafter, as shown in FIG. 5, a plurality of the punched ceramic green sheets 2 are stacked on the setter 1 in a state of being stacked. At this time, in order to prevent the ceramic green sheet 2 from being fused with the setter 1 and the ceramic green sheet 2 at the time of firing, a fusion preventing powder is sprayed between the upper surface of the setter 1 and the ceramic green sheet 2. Finally, the setter 3 is further stacked on the uppermost stage of the ceramic green sheet 2. The setter 3 is placed as a weight so that the ceramic green sheet 2 does not warp during firing. Then, the ceramic green sheet 2 is introduced into a firing furnace such as a tunnel furnace together with the firing sheaths 2 and 3 and subjected to heat treatment. By this heat treatment, the ceramic green sheet 2 is sintered, and a ceramic sheet as a sintered body is obtained.

As the above-mentioned anti-fusing powder, a heat-resistant ceramic powder which does not react with the setters 2 and 3 and the ceramic green sheet 2 even at a high temperature during firing, such as ZrO ₂ powder, is used. After firing of the ceramic sheet, the ceramic sheets 2 and 3 are separated from the setter, and then the ceramic sheet is subjected to ultrasonic cleaning in water, an organic solvent, or the like, so that the anti-fusing powder attached to the ceramic green sheet is removed. Has been washed off. However, ceramic sheets, such as piezoelectric ceramics, which are extremely thin and vulnerable to impact, can be broken or microcracked by ultrasonic cleaning when subjected to ultrasonic cleaning. ing.

[0005]

However, in the above-described conventional method of firing a ceramic sheet, as described above, the setter 3 is placed as a weight on the stacked ceramic green sheets 2 via the anti-fusing powder. However, due to the gravity of the setter 3, the anti-fusing powder penetrates the surface of the ceramic green sheet 2 before firing, and is fired as it is. For this reason, irregularities due to the anti-fusing powder are generated on the surface of the fired ceramic sheet. On the other hand, if firing is performed without placing a setter as a weight, a ceramic sheet that is thin and has a large area tends to warp during firing. Further, since ultrasonic cleaning and brushing steps are required to remove the anti-fusing powder, the number of manufacturing steps is increased by that amount and the cost of the product is increased.

The present invention has been made in view of the above-mentioned problems in the conventional method of firing a ceramic sheet. Therefore, the ceramic sheet is unlikely to be warped or has irregularities on its surface, and it is not necessary to remove the anti-fusing powder after firing. An object of the present invention is to provide a method for firing a ceramic sheet that does not require steps such as cleaning and brushing.

[0007]

According to the present invention, in order to achieve the above object, the ceramic green sheet 13 is placed on a setter 11 which does not react with the ceramic green sheet 13 at a high temperature during firing. The lid on the setter 11 is arranged with a gap wider than the sheet thickness t and not more than 5 times the thickness of the ceramic green sheet 13, and in this state, the ceramic green sheet is introduced into a firing furnace. Firing.

That is, in the method of firing a ceramic sheet according to the present invention, the ceramic green sheet 13 is placed on the flat upper surface of the setter 11 which does not react with the ceramic green sheet 13 at a high temperature during firing, and the ceramic green sheet is The method is characterized in that the ceramic green sheet 13 is introduced into a firing furnace and fired in a state where the lid is disposed on the ceramic green sheet 13 with a gap not in contact with the ceramic green sheet 13.

The fired ceramic green sheet 13 is a square or round plate having a side length or diameter that is 50 times or more the thickness. The setter 11 on which the ceramic green sheet 13 is placed is placed by using another setter 11 on which the ceramic green sheet 13 is placed as a lid and further placing another ceramic green sheet 13 on the setter 11 which is the lid. Multiple layers can be stacked. The gap δ between the setter 11 and the lid thereon is larger than the thickness t of the fired ceramic sheet 14 and is not more than five times the thickness of the ceramic green sheet 13.

In this method of firing the ceramic sheet, the ceramic green sheet 13 is fired with the ceramic green sheet 13 placed on the flat upper surface of the setter 11 which does not react with the ceramic green sheet 13 at a high temperature during firing. Therefore, it is not necessary to spray the anti-fusing powder on the setter 11 and the ceramic green sheet 13. For this reason, the step of removing the anti-fusing powder from the ceramic sheet 14 by ultrasonic cleaning or brushing the fired ceramic sheet 14 becomes unnecessary.

As will be described later, the interval δ between the setter 11 on which the ceramic green sheet 13 is placed and the lid thereon is larger than the thickness t of the fired ceramic sheet 14 and is smaller than the thickness t of the ceramic green sheet 13. By setting it to 5 times or less, it is possible to suppress warpage during firing even for a large-area ceramic green sheet 13 having a side length or diameter 50 times or more the thickness. Further, since the gap is provided between the ceramic green sheet 13 and the lid thereon, it is possible to prevent the evaporation of the binder at the time of firing, that is, the deformation of the ceramic green sheet 13 at the time of removing the binder.

[0012]

Embodiments of the present invention will now be described specifically and in detail with reference to the drawings.
FIG. 1 shows an example of a state in which a ceramic green sheet 13 is introduced into a firing furnace according to the present invention. The ceramic green sheet is made by adding and mixing a binder to a ceramic powder to form a slurry, and forming the slurry by a wet extrusion method, a doctor blade method, or the like. Next, the ceramic green sheet is punched into a predetermined shape to obtain a ceramic green sheet 13 having a predetermined shape. The ceramic green sheet 13 is punched out in consideration of shrinkage during firing so that the fired ceramic sheet 14 has a predetermined size.

A setter 11 made of a heat-resistant material which does not react with the ceramic green sheet 13 at a high temperature during firing and having a flat upper surface having a sufficiently large area than the ceramic green sheet 13 is prepared. For example,
If the ceramic green sheet 13 is mainly composed of a dielectric ceramic such as BaTiO ₃ ,
_A setter 11 made of ₂ O ₃ is used. Also, Al ₂ O ₃
In the case of a ceramic green sheet 13 for a hybrid integrated circuit substrate whose main component is Al ₂ O ₃
Is used. PZT (PbTiO
_{In the case of} a ceramic green sheet 13 mainly composed of a piezoelectric ceramic of ( _3- PbZrO ₃ ), a setter 11 made of MgO is used for those having a large Pb component.

On the other hand, for example, when the ceramic green sheet 13 mainly composed of a piezoelectric ceramic is fired, if the setter 11 made of Al ₂ O ₃ is used, the Pb component contained in the ceramic green sheet 13 during firing is reduced. This is not appropriate because it diffuses into the inside 11 and the ceramic composition of the fired ceramic sheet 14 changes.

A ceramic green sheet 13 is placed on the flat upper surface of the setter 11, and
Another setter 1 as a lid on the
Put one. The spacers 12 are arranged at the four corners of the setter 11 and at the intermediate portion thereof. The spacers 12 form a gap δ between the upper and lower setters 11. This gap δ is larger than the thickness t of the fired ceramic sheet 14 and is not more than five times the ceramic green sheet 13.

Further, a ceramic green sheet 13 is also placed on the upper surface of the upper setter 11, and a spacer 12 is placed thereon.
A different setter 11 is placed via. Thus, the plurality of ceramic green sheets 13 are set while the setters 11 and the spacers 12 are alternately stacked. After stacking several sets of the setters 11 on which the ceramic green sheets 13 are placed, finally, the uppermost setter 11 functioning only as a lid is stacked.

When the interval δ between the upper and lower setters 11 is equal to or less than the thickness t of the fired ceramic sheet 14, the upper setter 11 serving as a lid is brought into contact with the upper surface of the fired ceramic sheet 14. Will be in contact. Then, the lower surface of the upper setter 11 is transferred to the upper surface of the fired ceramic sheet 14 or the ceramic sheet 14 is pressed, so that the surface roughness of the ceramic sheet 14 increases or the thickness t varies. May cause.
When the interval δ between the upper and lower setters 11 exceeds five times that of the ceramic green sheet 13, the warpage of the fired ceramic sheet 14 rapidly increases as described later. In other words, the effect of suppressing the warpage of the ceramic sheet 14 is poor.

With the ceramic green sheets 13 stacked and placed on the setter 11 in this manner, they are introduced into a firing furnace such as a tunnel furnace and heated to fire the ceramic green sheets 13. After these are taken out of the firing furnace and cooled to room temperature, the setter 11 and the spacer 12 are decomposed, and the fired ceramic sheet 14 is taken out.

[0019]

EXAMPLES Next, examples of the present invention will be described specifically and in detail with specific numerical values. To (Example 1) Average particle diameter 1.2μm of Al ₂ O ₃ powder, 6 wt% of MgO-SiO ₂ -CaO as flux, an acrylic binder 16 wt%, the ammonium polycarboxylate as a dispersant 1% by weight, 2% by weight of glycerin and 16% of water were mixed, mixed and uniformly dispersed to form a slurry. This slurry is 0.6m thick
m into a long sheet.
The ceramic green sheet 13 was obtained by punching into a corner.

Purity 99.6, 2 mm thick, 250 mm square
A setter 11 having a flat upper surface made of Al ₂ O ₃ % was prepared, and the ceramic green sheet 13 was placed on the center of the setter 11. Furthermore, height 1mm, 8mm
Corner ceramic pillars were used as spacers 12, which were arranged at the four corners of the setter 11, and another setter 11 was placed thereon. The ceramic green sheets 13 are also placed on this, and the setters 6 are stacked in the same manner as described above to set six ceramic green sheets 13. Finally, the setters 11 are placed on the spacers 12 and did. These were introduced into a tunnel furnace, and the ceramic green sheets 13 were fired at a predetermined temperature and time. In this example, the interval between the upper and lower setters 11 is 1 mm.

After being taken out of the tunnel furnace, the setter 1
1, spacer 12 and fired ceramic sheet 14
After cooling to room temperature, the setter 11 and the spacer 12 were disassembled, and the fired ceramic sheet 14 was taken out.
At this time, when the presence or absence of fusion between the ceramic sheet 14 and the setter 11 was observed, no fusion between the ceramic sheet 14 and the setter 11 was observed.

The fired ceramic sheets 14 to 10
0 sheets were randomly extracted and the thickness t was measured. Further, the 100 ceramic sheets 14 are placed on a flat surface plate, and a plate parallel to the surface plate is lowered from above the ceramic sheet 14 and is applied to the ceramic sheet 14, and the ceramic sheet 14 shown in FIG. Was measured for the maximum height h. Then, a numerical value in which (maximum height h-thickness t of ceramic sheet) / thickness t of ceramic sheet was expressed as a percentage was calculated as a warpage rate. As a result, the average value of the thickness t of the ceramic sheet 14 was 0.5 mm, and the average value of the warpage ratio was 5%. Further, the surface roughness (Ra) of the 100 fired ceramic sheets 14 was measured, and the average value was determined. In this example, the interval between the upper and lower setters 11 during the firing is twice as large as that of the fired ceramic sheet 14. The results are shown in Table 1. 5 is shown.

When the ceramic green sheets 13 are stacked, the spacers 1 inserted between the setters 11 are stacked.
The ceramic green sheets 13 were fired in the same manner as in the above example except that the height of the second setter 2 was changed to change the distance between the upper and lower setters 11. Then, in the same manner as above, the presence or absence of fusion of the ceramic sheet 14 to the setter 11 or the number of fused ceramic sheets 14 was measured to determine the fusion rate. Further, 100 fired ceramic sheets 14 were randomly extracted, their thickness t, warpage rate, and surface roughness (Ra) were measured in the same manner as described above, and their average values were determined. The results are shown in Table 1. 1 to 4 and 6. Further, the sample 1
6, the relationship between the multiple of the thickness t of the ceramic sheet 14 at the interval δ of the setter 11 and the warpage rate of the ceramic sheet 14 is shown in the graph of FIG.

For comparison, the ceramic green sheets 13 were stacked by the conventional method shown in FIG. 5, and the other steps were the same as in the above-described example, and the ceramic green sheets 13 were fired. In the same manner as above, the presence or absence of fusion of the ceramic sheet to the setter 1 or the number of fused ceramic sheets was measured, and the fusion rate was determined. Further, 100 fired ceramic sheets were randomly extracted, and their thickness t, warpage rate, and surface roughness (R
a) was measured and their average was determined. This result
Table 1 shows a comparative example.

[0025]

[Table 1]

As is apparent from the above results, the setter 11
The multiple of the thickness t of the ceramic sheet 14 at the interval δ is 1 to
In the range of 5 times, the warpage rate of the ceramic sheet 14 was suppressed to an extremely low level of 6% or less. Also, there was no fused setter 11 and no fused ceramic sheet 14, and the surface roughness (Ra) was suppressed to a low level of 0.15 μm.

On the other hand, when the multiple of the thickness t of the ceramic sheet 14 at the interval δ of the setters 11 exceeds five times, the warpage rate of the ceramic sheet 14 becomes 6% as is apparent from FIG.
From 20 to 30%. FIG.
The ceramic sheet fired by the conventional method as shown in FIG. 1 has a high warpage ratio of 25%, 1.5% of the fused ceramic sheet, and a surface roughness (Ra) of 0.4 μm.
m and high.

Example 2 PZT having an average particle size of 0.8 μm
A slurry was prepared by mixing, mixing, and uniformly dispersing 4% by weight of methylcellulose, 2% by weight of glycerin, and 10% of water with respect to the ceramic material for the piezoelectric sounding body. The slurry was formed into a long sheet having a thickness of 0.06 mm, and the sheet was punched into a 25 mmφ to obtain a ceramic green sheet 13.

A setter 11 having a flat upper surface made of Y-stable ZrO ₂ having a thickness of 0.8 mm and a square of 100 mm was prepared, and the ceramic green sheet 13 was placed at the center of the setter 11. Ceramic pillars are used as spacers 12, which are arranged at the four corners of the setter 11,
Another setter 11 was placed thereon. A ceramic green sheet 13 is also placed on this, and similarly, 15 steps of setters 11 are stacked and 15 ceramic green sheets 13 are set in the same manner. Finally, the setter 11 is placed on the spacer 12 and a lid is formed. did. These were introduced into a tunnel furnace, and the ceramic green sheets 13 were fired in a Pb atmosphere at a predetermined temperature and time. This step is performed by changing the height of the spacers 12 so that the distance between the upper and lower setters 11 is 0.05 mm, 0.1 mm, 0.2 mm, 0.25 m.
m, 0.4 mm and 0.5 mm.
The thickness t of the fired ceramic sheet 14 was measured to be 0.05 mm in all cases.

For the fired ceramic sheet 14,
In the same manner as in Example 1, the presence or absence of the fusion of the ceramic sheet 14 to the setter 11 or the number of the fused ceramic sheets 14 was measured to determine the fusion rate. Further, 100 fired ceramic sheets 14 were randomly extracted, their thickness t and warpage were measured in the same manner as in Example 1, and the average value was obtained. The results are shown in Table 2. 1 to 6. Further, the interval δ of the setter 11
The relationship between the multiple of the thickness t of the ceramic sheet 14 and the warpage rate of the ceramic sheet 14 is shown in the graph of FIG.

For comparison, the ceramic green sheets 13 were stacked by the conventional method shown in FIG. 5, and the other steps were the same as in the above-described example, and the ceramic green sheets 13 were fired. In the same manner as above, the presence or absence of fusion of the ceramic sheet to the setter 1 or the number of fused ceramic sheets was measured, and the fusion rate was determined. Further, 100 fired ceramic sheets were randomly extracted, their thickness t and warpage were measured in the same manner as described above, and the average value was determined. The results are shown in Table 2 as a comparative example.

[0032]

[Table 2]

As is apparent from the above results, the setter 11
The multiple of the thickness t of the ceramic sheet 14 at the interval δ is 1 to
In the range of 5 times, the warpage rate of the ceramic sheet 14 was suppressed to an extremely low level of 5% or less. Also, there was no fused setter 11 and no fused ceramic sheet 14. On the other hand, when the multiple of the thickness t of the ceramic sheet 14 at the interval δ of the setters 11 exceeds five times, the warp rate of the ceramic sheet 14 increases sharply from 5% to 30 to 42, as is clear from FIG. %. Further, in the ceramic sheet fired by the conventional method as shown in FIG. 5, the warpage rate was as high as 43%, and the fused ceramic sheet was 5%.

[0034]

As described above, according to the present invention, the ceramic sheet is less likely to be warped or uneven, and furthermore, it is not necessary to remove the anti-fusing powder after firing. Step is not required. As a result,
Along with improving the quality of the ceramic sheet, productivity can be improved by reducing the number of steps and improving the yield.

[Brief description of the drawings]

FIG. 1 is a side view showing an example of a setting state of a ceramic green sheet on a setter in a method for firing a ceramic sheet according to the present invention.

FIG. 2 is a side view showing a method for measuring a warpage ratio of a ceramic sheet fired by the method for firing a ceramic sheet according to the present invention.

FIG. 3 is a graph showing an example of the relationship between the ratio of the setter interval of a ceramic sheet fired by the method of firing a ceramic sheet according to the present invention to the thickness of the ceramic sheet and the warpage rate of the ceramic sheet.

FIG. 4 is a graph showing another example of the relationship between the ratio between the setter interval of a ceramic sheet fired by the method for firing a ceramic sheet according to the present invention, the thickness of the ceramic sheet, and the warpage rate of the ceramic sheet.

FIG. 5 is a side view showing an example of a setting state of a ceramic green sheet on a setter in a conventional example of a method of firing a ceramic sheet.

[Explanation of symbols]

 11 Setter 12 Spacer 13 Ceramic Green Sheet 14 Fired Ceramic Sheet

Claims (5)

[Claims] 1. A method for obtaining a ceramic sheet as a sintered body by introducing a ceramic green sheet (13) into a firing furnace, heat-treating and firing the ceramic green sheet, wherein the ceramic green sheet (13) is heated at a high temperature during firing. The ceramic green sheet (13) is placed on the flat upper surface of the setter (11) which does not react with the ceramic green sheet (1).
3) A method for firing a ceramic sheet, wherein the ceramic green sheet (13) is introduced into a firing furnace and fired in a state in which a lid is disposed above the ceramic green sheet (13) with a gap not in contact with the ceramic green sheet (13). . 2. The cover is made of a ceramic green sheet (1).
2. The method for firing a ceramic sheet according to claim 1, wherein the setter is a different setter from the one on which the sheet is placed. 3. The method for firing ceramic sheets according to claim 2, wherein the setters (11) on which the ceramic green sheets (13) are placed are stacked in a plurality of stages. 4. The gap (δ) between the setter (11) and the lid thereon is larger than the thickness (t) of the fired ceramic sheet (14), and is larger than the thickness (t) of the ceramic green sheet (1).
3. The method according to claim 1, wherein the thickness is not more than five times the thickness of the third aspect.
4. The method for firing a ceramic sheet according to any one of claims 1 to 3. 5. The ceramic green sheet (13)
The method for firing a ceramic sheet according to any one of claims 1 to 4, wherein the firing method is a plate-like body having a side length or a diameter that is 50 times or more the thickness.