JP2001031474A - Production of ceramic green sheet - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for producing a ceramic green sheet having a low fraction defective of sheet by a foreign matter in a slurry. SOLUTION: This method for producing a ceramic green sheet has a first process for mixing ceramic powder with a solvent and a plasticizer to give an initial slurry, passing the initial slurry through a first filter to give a first slurry and transporting the first slurry to a slurry preparation apparatus 14, a second process for passing the first slurry prepared by the slurry preparation apparatus 14 through a second filter 16 to give a second slurry and transporting the second slurry to a fixed amount feeder 17 of slurry and a third process for passing the second slurry through a third filer 18 by the fixed amount feeder 17 of slurry to give a third slurry and transporting the third slurry to a ceramic green sheet molding machine 19.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing a green sheet of a ceramic substrate used for an IC package substrate or the like.

[0002]

2. Description of the Related Art Conventionally, a doctor blade method has been used for manufacturing a ceramic thin plate such as a ceramic substrate for an IC package. The doctor blade method is a manufacturing method in which a slurry obtained by mixing a solvent, a binder, and a plasticizer with ceramic powder is formed on a carrier film using a doctor blade, and dried to obtain a ceramic green sheet. . When producing a slurry by mixing a solvent, a binder and a plasticizer with ceramic powder, undissolved solids of the organic polymer resin used as the binder, aggregates of uncrushed ceramic powder, coagulation of the slurry Foreign substances such as solids due to the above-mentioned matter often exist in the slurry. These foreign substances, when manufacturing the ceramic green sheet,
As it causes defects such as swelling, pinholes and cracks,
It is collected before entering the doctor blade device. Specifically, an organic polymer resin is dissolved in a solvent,
A method of dispersing ceramic powder in a solution in which undissolved solid matter of an organic polymer resin has been removed in advance, or a filter installed in front of a quantitative supply device for transporting a slurry to a ceramic green sheet molding machine to remove the foreign matter And the like.

[0003]

However, even when the conventional method for removing foreign matter is used, defects such as swelling, pinholes and cracks due to foreign matter still occur in the production of ceramic green sheets. This fact indicates that foreign matter is newly generated or mixed in the process from the quantitative supply device to the ceramic green sheet molding machine, and the conventional foreign matter removing method removes foreign matter originally present in the slurry. This is an effective method for removing, but it is not an effective method for removing foreign matter newly generated throughout the manufacturing process. The present invention has been made in view of such circumstances, and has as its object to provide a method for manufacturing a ceramic green sheet having a low sheet defect rate due to foreign matter in slurry.

[0004]

According to the present invention, there is provided a method for manufacturing a ceramic green sheet according to the present invention, wherein an initial slurry obtained by mixing a solvent, a binder and a plasticizer with ceramic powder is passed through a primary filter. A first step of transporting the primary slurry to a slurry adjusting device as a primary slurry, and a secondary slurry of the primary slurry adjusted by the slurry adjusting device through a secondary filter; A second step of transporting the slurry to the slurry quantitative supply device, and the secondary slurry being converted into a third slurry through a third filter by the slurry quantitative supply device, and transporting the third slurry to the ceramic green sheet forming machine; And a third step. As a result, in addition to the removal of foreign substances originally present in the slurry, it is also possible to remove foreign substances newly generated during the manufacturing process, which cannot be performed by the conventional foreign substance removal method,
A ceramic green sheet having a low sheet defect rate due to foreign matter in the slurry can be manufactured. In the method for manufacturing a ceramic green sheet according to the present invention, the tertiary filter can be installed immediately before the ceramic green sheet forming machine. As a result, the third material containing no foreign matter
The next slurry can be directly used for the production of ceramic green sheets, and the production of ceramic green sheets with a much lower sheet failure rate due to foreign matter in the slurry becomes possible.

[0005]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Next, embodiments of the present invention will be described with reference to the accompanying drawings to provide an understanding of the present invention. Here, FIG. 1 is a block diagram of a ceramic green sheet manufacturing facility applied to the method for manufacturing a ceramic green sheet according to one embodiment of the present invention. As shown in FIG. 1, a ceramic green sheet manufacturing equipment 10 to which a method for manufacturing a ceramic green sheet according to an embodiment of the present invention is applied includes pipes 11 a to 11 d for connecting respective devices and allowing slurry to pass therethrough. Machine 1
2, a primary filter 13, a slurry adjusting device 14, a slurry storage tank 15, a secondary filter 16, a slurry quantitative supply device 17, a tertiary filter 18, and a ceramic green sheet molding machine 19. Less than,
These will be described in detail.

A feature of the ceramic green sheet manufacturing equipment 10 is that, when the manufactured slurry is transported to the ceramic green sheet forming machine 19, foreign matter generated corresponding to each process is appropriately removed. The ceramic green sheet manufacturing equipment 10 includes a solvent,
It has a mixer 12 comprising, for example, a ball mill, a vibration mill and the like, which mixes a binder and a plasticizer to produce an initial slurry while pulverizing aggregates of ceramic powder. Furthermore, a primary filter 13 such as a centrifuge or a 32-200 mesh sieve is provided in the middle of the pipe 11a connected to the mixer 12, and used as a foreign substance in the initial slurry, for example, as a binder. Undissolved solids of organic polymer resin and aggregates of uncrushed ceramic powder are collected and removed to form a primary slurry.

[0007] The slurry adjusting device 14 installed at the tip of the pipe 11a uses a vacuum stirrer or the like to reduce the first pressure under reduced pressure.
By removing bubbles in the secondary slurry and evaporating the solvent, the viscosity of the slurry is adjusted to adjust the primary slurry to an optimal state for forming a ceramic green sheet. A slurry storage tank 15 is provided in the slurry adjusting device 14 via a pipe 11b, and supplies the adjusted primary slurry to the next step in accordance with the forming speed of the ceramic green sheet. Slurry storage tank 15
In the middle of the pipe 11c connected to the
A secondary filter 16 such as a ~ 200-mesh sieve is provided, and the solids and coarse particles of the ceramic powder due to the solidification of the primary slurry, which is foreign matter in the adjusted primary slurry flowing into the slurry quantitative supply device 17, are provided. The particles are collected to form a secondary slurry.

[0008] The continuous slurry supply device 17 is of a type that transports slurry by utilizing a pressure difference due to vacuum, a plunger type, or the like.
A predetermined amount of the secondary slurry is transported to the ceramic green sheet forming machine 19 via the. Immediately before the ceramic green sheet molding machine 19, a centrifugal separator or 32 to 20
A tertiary filter 18 such as a 0-mesh sieve is provided, and foreign matters in the secondary slurry flowing from the slurry constant-quantity supply device 17 are collected to form a tertiary slurry. The foreign matter collected by the tertiary filter 18 is a solid substance resulting from the coagulation of the secondary slurry.
The amount and size of the foreign matter collected in step 6 are smaller than those of the foreign matter collected in step 6. A ceramic green sheet forming machine 19 such as a doctor blade device once receives the tertiary slurry in a liquid dam 19a which is a slurry reservoir in the ceramic green sheet forming machine 19, and manufactures a ceramic green sheet.

Next, a description will be given of a tertiary filter 18 for collecting foreign substances in the secondary slurry and supplying a slurry containing no foreign substances to the ceramic green sheet forming machine 19, which is a feature of the present invention. . The third filter 18 is not provided, and the pipe 11c from the secondary filter 16 to the slurry quantitative supply device 17 and the ceramic green sheet molding machine 19 from the slurry quantitative supply device 17
When a ceramic green sheet is manufactured by using a sufficiently cleaned unused one for the pipe 11d up to the liquid dam 19a, no defect is generated due to foreign matter in the secondary slurry for a while after the pipe replacement. That was confirmed. However, after that, the pipes 11c, 11d
Solid matter was generated inside the slurry by solidification of the slurry. Therefore, in order to manufacture a ceramic green sheet free from defects, it is necessary to install a tertiary filter 18 immediately before the liquid dam 19 a of the ceramic green sheet forming machine 19 in addition to the secondary filter 16. Conceivable.

Next, a method for manufacturing a ceramic green sheet according to an embodiment of the present invention will be described in detail. First, a ceramic powder, a solvent, a binder, and a plasticizer are charged into the mixer 12 and mixed for a predetermined time to produce an initial slurry. This initial slurry is mixed with the primary filter 13.
, And transported to the slurry adjusting device 14 (first step). As the ceramic powder, for example, an oxide ceramic powder such as alumina is used. For the binder used to improve the strength of the formed ceramic green sheet, an organic polymer resin such as polyvinyl butyral is used, and the solvent is an alcohol, xylene, an organic solvent such as toluene, or an alcohol, A mixed organic solvent containing xylene, toluene and the like can be used, and dioctyl acetate and the like can be used as a plasticizer for improving the plasticity of the ceramic green sheet. In the produced initial slurry, undissolved solids of the organic polymer resin used as the binder and aggregates of uncrushed ceramic powder in the ceramic powder are present. For this reason, the initial slurry is filtered using the primary filter 13 to remove undissolved solids of the organic polymer resin and aggregates of the uncrushed ceramic powder, and the primary slurry free of foreign matter is removed. Then, the primary slurry is transported to the slurry adjusting device 14.

Next, the primary slurry adjusted by the slurry adjusting device 14 is transported to the slurry storage tank 15 for storage, and the secondary filter 16 is transferred from the slurry storage tank 15 in accordance with the forming speed of the ceramic green sheet. Into a secondary slurry through the slurry constant feeder 17
(2nd step). The primary slurry contains a large amount of air mixed during the initial slurry production,
When a ceramic green sheet is formed using this slurry, a large number of bubbles are formed in the sheet, resulting in defects. In addition, the primary slurry is produced in a state in which the amount of the solvent is somewhat excessive in order to enhance the mixing effect of the mixer 12, and the viscosity of the slurry is generally too low to form the ceramic green sheet. When the primary slurry having an excessive amount of solvent is used, the dimensional change in the drying process of the formed ceramic green sheet becomes large, so that the ceramic green sheet is easily deformed or cracked. For this reason, the primary slurry is agitated under reduced pressure using the slurry adjusting device 14 to remove bubbles, and the viscosity of the slurry is adjusted by evaporating the solvent. However, since the viscosity of the slurry is adjusted while evaporating the solvent, the solidification of the slurry occurs locally during the stirring of the primary slurry, and as a result, there is also a problem that solid matter is mixed into the slurry. In addition, the ceramic powder often contains a small amount of coarse particles that are smaller in particle size than the aggregates of the powder but largely deviate from the particle size distribution of the powder. When the coarse particles are present in the ceramic green sheet, the amount of dimensional shrinkage is locally different from that of the surroundings, so that it is likely to cause a crack. For this reason, in order to remove solid matter generated during solidification of the slurry during the solidification of the slurry and coarse particles in the ceramic powder, the secondary slurry is passed through the secondary filter 16 to form a secondary slurry free of foreign matter. Is transported to the slurry quantitative supply device 17.

Then, a predetermined amount of the secondary slurry supplied from the slurry quantitative supply device 17 is supplied to the third filter 1.
8 to form a third slurry, which is transported to the ceramic green sheet forming machine 19 (third step). During the continuous operation of ceramic green sheet molding, the secondary filter 1
In the pipes 11c and 11d from 6 to the ceramic green sheet forming machine 19 and in the slurry stagnation portion of the slurry quantitative supply device 17, solids are likely to be generated due to solidification of the secondary slurry. For this reason, the solid matter due to solidification of the secondary slurry is removed by the tertiary filter 18 installed immediately before the ceramic green sheet forming machine 19 to obtain a tertiary slurry free of foreign matter. The green sheet is transported to a green sheet forming machine 19 to form a ceramic green sheet.

The condition of the tertiary filter 18 is, of course, that foreign matter can be collected, but the supply of the slurry corresponding to the forming speed of the ceramic green sheet forming machine 19 depends on the capacity of the slurry quantitative supply device 17. It is guaranteed within the range. Therefore, a case where a sieve is used as the third filter 18 will be described in more detail. In using a sieve, it is the opening width of the sieve that affects the permeability of the slurry. Therefore, a 32, 100, 150 and 200 mesh sieve is applied to the same secondary slurry as the tertiary filter 18, and a ceramic green sheet is actually formed using a doctor blade device. The relationship between the width of the opening and the percentage of defectives was determined.
The defect rate was evaluated based on the number of sheets having defects such as blisters, pinholes, and cracks per 1000 sheets having a side of 100 mm. Table 1 shows the results. Table 1 also shows the percentage of defects when no sieve is used. 32 used as the third filter 18;
The four types of sieves of 100, 150 and 200 mesh are used for the ceramic green sheet forming machine 1 in any of the sieves.
The supply of the slurry corresponding to the molding speed of 9 was possible using the slurry quantitative supply device 17. The detection of defects was performed using an optical microscope, and the case where swelling, pinholes, cracks, and the like were present was regarded as a defective sheet.

[0014]

[Table 1]

From the results shown in Table 1, the number of defective sheets is substantially constant regardless of which sieve is used, and within the range of the opening width of the used sieve, the effect of removing foreign substances is not related to the opening width of the sieve. It has been found.

[0016]

EXAMPLE A mixed solution of 8% by weight of polyvinyl butyral as a binder, 2% by weight of dioctyl acetate as a plasticizer, 30% by weight of xylene, 40% by weight of butanol, and 30% by weight of toluene was mixed with 40 kg of alumina. And prepared using a ball mill having a volume of 100 liters.
Mixing for 0 hours produced an initial slurry. The initial slurry was made a primary slurry through a 100 mesh sieve and transported to a vacuum stirrer.

Using a vacuum stirrer, the mixture is stirred for 3 hours under reduced pressure, and the viscosity of the slurry is reduced to 200 simultaneously with the defoaming of the primary slurry.
It was adjusted to be 0 cps. The adjusted primary slurry was stored in a slurry storage tank. Subsequently, the adjusted primary slurry in the slurry storage tank was converted into a secondary slurry through a 200-mesh sieve, and was transferred to a plunger type pump.

Using a plunger type pump, the secondary slurry was made into a tertiary slurry through a 100-mesh sieve and transported to a liquid dam of a doctor blade device (ceramic green sheet molding machine). Using this tertiary slurry, a sheet is formed into a 100 mm wide strip,
Drying was performed under the conditions of a drying temperature of 150 ° C. and a drying speed of 0.5 m / min to produce an alumina green sheet. The obtained green sheet was cut into a length of 100 mm, and the number of defective sheets having defects such as swelling, pinholes and cracks was measured. As a result, the failure rate for 100,000 sheets was 3% for the swelling, 2% for the cracks, and the failure rate (blowing) when the 100 mesh sieve (third filter) was not used. , A defect rate of 5%, and a crack rate of 3%). Although the embodiment of the present invention has been described above, the present invention is not limited to this embodiment. For example, in the present embodiment, a tertiary filter is installed immediately before a ceramic green sheet forming machine. However, any position may be used as long as foreign matter can be removed between the slurry quantitative supply device and the ceramic green sheet molding machine.

[0019]

According to the method for producing a ceramic green sheet according to the first and second aspects of the present invention, an initial slurry obtained by mixing a solvent, a binder and a plasticizer with ceramic powder is converted into a primary slurry through a primary filter. , First
A first step of transporting the next slurry to the slurry adjusting device;
The primary slurry adjusted by the slurry adjusting device is
A second step of transporting the secondary slurry to a quantitative slurry supply device through a secondary filter, and a secondary slurry of the secondary slurry through a tertiary filter with the quantitative slurry supply device. A third step of transporting the slurry to the ceramic green sheet molding machine, which is effective for removing foreign substances newly generated in all manufacturing steps, which cannot be handled by the conventional foreign substance removing method, and It becomes possible to manufacture ceramic green sheets having a low rate. In particular, in the method for manufacturing a ceramic green sheet according to claim 2, since the tertiary filter is installed immediately before the ceramic green sheet forming machine, foreign matters can be removed from the slurry immediately before the formation of the ceramic green sheet. Thus, it is possible to manufacture a ceramic green sheet having a much lower failure rate.

[Brief description of the drawings]

FIG. 1 is a block diagram of a ceramic green sheet manufacturing facility to which a method for manufacturing a ceramic green sheet according to an embodiment of the present invention is applied.

[Explanation of symbols]

10: Ceramic green sheet production equipment, 11a-1
1d: piping, 12: mixer, 13: primary filter,
14: slurry adjusting device, 15: slurry storage tank,
16: Secondary filter, 17: Slurry quantitative supply device, 18: Tertiary filter, 19: Ceramic green sheet molding machine, 19a: Liquid dam

Claims (2)

[Claims] 1. A first step in which an initial slurry obtained by mixing a solvent, a binder, and a plasticizer with ceramic powder is converted into a primary slurry through a primary filter, and the primary slurry is transported to a slurry adjusting device. A second step of converting the primary slurry adjusted by the slurry adjusting device into a secondary slurry through a secondary filter, and transporting the secondary slurry to a slurry quantitative supply device; Converting the secondary slurry to a tertiary slurry through a tertiary filter, and transporting the tertiary slurry to a ceramic green sheet forming machine. 2. The method for producing a ceramic green sheet according to claim 1, wherein the tertiary filter is installed immediately before the ceramic green sheet forming machine.