JP3154895B2 - Ceramic mud and green sheet for forming green sheet - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a ceramic slurry for forming a green sheet and a green sheet obtained by using the same.

[0002]

2. Description of the Related Art Ceramic circuit boards are widely used for electronic components. This type of ceramic circuit board is generally manufactured through the following steps.

[0003] First, a ceramic powder is added to a solution containing a binder resin and a plasticizer, uniformly mixed and defoamed to prepare a ceramic slurry. Next, the ceramic slurry is applied on a peelable support, heated and dried, and then peeled from the support to obtain a green sheet.

[0004] Then, the green sheet is punched into a predetermined shape, a predetermined circuit is printed on the surface thereof, and a plurality of the circuits are laminated and thermocompression-bonded if necessary, and the binder resin is heated at a high temperature to remove the binder resin. It is decomposed and heated at a high temperature to sinter the ceramic powder to obtain a ceramic circuit board.

[0005] This kind of green sheet is required to have good flexibility in order to improve handling properties. In order to improve such performance, it is known to use a water-soluble or organic solvent-soluble (water-insoluble) polyvinyl acetal resin, for example, a polyvinyl butyral resin, as a binder resin used for preparing the ceramic slurry. For example, JP-A-3-197511,
JP-A-3-200805, JP-A-4-17526
No. 1 and JP-A-4-178404).

[0006]

In recent years, as electronic devices have become smaller, there has been a demand for ceramic circuit boards to be smaller and have larger capacities. As a measure, use of a thin green sheet (for example, 10 μm or less) obtained by using a ceramic powder having a finer particle size (for example, particle size of 1 μm or less) than the conventional one has been attempted.

However, in order to manufacture such a thin green sheet, when a ceramic powder having a fine particle size is mixed with a water-soluble or organic solvent-soluble (water-insoluble) polyvinyl acetal resin, the ceramic powder is not used. Of the green sheet is not sufficient, and the strength of the green sheet is not sufficient to cause cracks, so that it is difficult to obtain a uniform thin green sheet.

The present invention solves the above problems,
An object of the present invention is to provide a ceramic slurry and a green sheet for forming a green sheet, which can enhance the dispersibility of the ceramic powder, maintain the strength of the green sheet without cracks, and have good coating workability. It is in.

[0009]

In order to achieve the above object, the ceramic slurry for forming a green sheet according to the present invention comprises at least two kinds of polyvinyl acetal resins having different degrees of polymerization mixed with each other. Degree 3
A mixed polyvinyl acetal resin that is from 00 to 1200,
Alternatively, a mixed polyvinyl alcohol obtained by mixing at least two or more kinds of polyvinyl alcohols having different polymerization degrees is acetalized, and the apparent polymerization degree is 300 to 1
It contains a polyvinyl acetal resin of 200, a ceramic powder, and a plasticizer (the invention of claim 1).

The green sheet of the present invention is obtained by shaping the above-mentioned ceramic slurry for forming a green sheet into a sheet and then drying the sheet (the invention of claim 2).

The polyvinyl acetal resin used in the present invention may be obtained by blending at least two kinds of polyvinyl acetal resins having different degrees of polymerization, or blending at least two kinds of polyvinyl alcohols having different degrees of polymerization to form an acetal. Alternatively, at least two or more polyvinyl alcohols having a certain degree of polymerization are acetalized in separate systems and then blended,
The apparent degree of polymerization is 300 to 1200. When the degree of polymerization is less than 300, the synthesized polyvinyl acetal resin has no sheet strength at the time of forming a green sheet and easily cracks. On the other hand, when the degree of polymerization exceeds 1200, the solution viscosity of the slurry becomes too high and the dispersibility is poor and the homogeneity is poor. No mud is obtained. The blending ratio is not particularly limited as long as the apparent degree of polymerization of the finished polyvinyl acetal resin is in the range of 300 to 1200.

[0012] Such a polyvinyl acetal resin is
It can be synthesized by adding various aldehydes to an aqueous solution of polyvinyl alcohol and performing an acetalization reaction by a known method.

The polyvinyl alcohol used preferably has a degree of polymerization of 200 to 3500 and a degree of saponification of 75 to 99.8 mol%. If the degree of polymerization is less than 200, it becomes difficult to synthesize polyvinyl alcohol. Conversely, if the degree of polymerization exceeds 3500, the viscosity of the resulting aqueous solution becomes too high. On the other hand, if the saponification degree is less than 75 mol%, the solubility in water is not sufficient, and if the saponification degree exceeds 99.8 mol%, the synthesis of polyvinyl alcohol becomes difficult.

Examples of the aldehyde used for acetalization of polyvinyl alcohol include formaldehyde (including paraformaldehyde), acetaldehyde (including paraacetaldehyde), propionaldehyde, butyraldehyde, amylaldehyde, hexylaldehyde, heptylaldehyde, and 2-ethylhexylaldehyde. , Cyclohexylaldehyde, furfural, glyoxal, glutaraldehyde and the like. These aldehydes are used alone or in combination of two or more. In particular, those obtained by acetalization with acetaldehyde and / or butyraldehyde are preferable.

[0015] The degree of acetalization of the polyvinyl acetal resin is generally 3 to 80 mol% in total acetalization degree, regardless of whether a single aldehyde or a mixed aldehyde is used.
Is preferable. If the total acetalization degree is less than 3 mol%, the flexibility of the resin becomes poor, and if the total acetalization degree exceeds 80, on the other hand, the residual hydroxyl groups decrease and the dispersibility with the ceramic powder decreases. Here, when the total acetalization degree is generally 55 mol% or less, the resin becomes water-soluble. When the total acetalization degree is generally 55 mol% or more, the resin becomes water-insoluble and becomes organic solvent-soluble.

An example of the method for producing the polyvinyl acetal resin used in the present invention will be described more specifically. First,
The polyvinyl alcohol is dissolved in water. Then, in the presence of an acid catalyst such as hydrochloric acid, after reacting with a predetermined amount of aldehyde, preferably acetaldehyde and / or butyraldehyde so as to give the degree of acetalization,
Neutralize with an alkali such as sodium hydroxide, wash with water and dry. Thus, the polyvinyl acetal resin used in the present invention is obtained.

The ceramic slurry for green sheet molding of the present invention comprises a polyvinyl acetal resin having the above-mentioned specific degree of polymerization, a ceramic powder, and a plasticizer, which are uniformly mixed with water or an organic solvent by a conventional method. It is prepared by dissolving in

The polyvinyl acetal resin is preferably blended in the ceramic slurry in an amount of 3 to 15% by weight. If the amount of the resin is more than 15% by weight, the viscosity of the ceramic slurry becomes too high to lower the dispersibility, and the shrinkage ratio of the obtained green sheet when firing is increased. Conversely, if the amount of the resin is less than 3% by weight,
Insufficiently to disperse the polyvinyl acetal resin throughout the ceramic powder, the resulting green sheet is not sufficiently flexible, and cracks and the like tend to occur after firing.

As the ceramic powder, a ceramic powder conventionally used for producing a ceramic green sheet is used. Examples of such ceramic powders include powders of alumina, zirconia, aluminum silicate, titanium oxide, zinc oxide, barium titanate, magnesia, sialon, spinel mullite, crystallized glass, silicon carbide, silicon nitride, aluminum nitride, and the like. Is mentioned.

In addition, MgO is added to these ceramic powders.
—SiO ₂ —CaO system, B ₂ O ₃ —SiO ₂ system, PbO
—B ₂ O ₃ —SiO ₂ system, CaO—SiO ₂ —MgO—
B ₂ O ₃ system or _{PbO-SiO 2 -B 2 O 3} -CaO
A glass frit such as a system may be added.

In particular, a thin green sheet (for example, 10
In order to obtain (μm or less), it is preferable to use ceramic powder having a finer particle size (for example, a particle size of 1 μm or less).

The above-mentioned ceramic powder is preferably incorporated in the ceramic slurry in an amount of 30 to 80% by weight. When the amount of the ceramic powder exceeds 80% by weight,
The viscosity of the ceramic slurry becomes too high and the kneadability is reduced. Conversely, if the amount of the ceramic powder is less than 30% by weight, the viscosity of the ceramic slurry becomes too low, and the handling properties when forming a sheet deteriorate.

As the plasticizer, any plasticizer can be used as long as it has excellent compatibility with the polyvinyl acetal resin. When the resin is water-soluble, ethylene glycol, diethylene glycol, triethylene glycol, polyethylene glycol, glycerin, hexamethylene glycol or the like is used as a plasticizer.

When the resin is soluble in an organic solvent (water-insoluble), as a plasticizer, phthalate esters such as dibutyl phthalate, dioctyl phthalate, diisodecyl phthalate and butyl benzyl phthalate, tricresyl phosphate, tributyl phosphate , Phosphate esters such as triethyl phosphate,
Resin acid esters such as methylacetyl ricinoleate, dibutyl sebacate and dioctyl adipate, and glycol derivatives such as butylphthalyl glycolate and triethylene glycol-2-ethylbutyrate are used.

The above plasticizer is added to the ceramic slurry at a concentration of 0.1%.
It is preferable to mix in the range of 1 to 10% by weight. If the compounding amount of the plasticizer exceeds 10% by weight, the handleability at the time of forming the sheet is deteriorated. Conversely, if the amount of the plasticizer is less than 0.1% by weight, the flexibility of the sheet due to the addition of the plasticizer cannot be sufficiently obtained.

The water or organic solvent dissolves the polyvinyl acetal resin and imparts appropriate kneading properties to the ceramic slurry, and is preferably used in an amount of 20 to 80% by weight in the ceramic slurry. When dissolving with an organic solvent, ketones such as acetone and methyl ethyl ketone, alcohols such as methanol, ethanol and butanol, and aromatic hydrocarbons such as toluene and xylene are used.

When water is used as a solvent, there is an advantage that fire and environmental problems do not occur as compared with the case where an organic solvent is used as a solvent. Further, when an organic solvent is used as a solvent, there is an advantage that drying of the ceramic slurry can be performed faster than in a case where water is used as a solvent, and the productivity of green sheets is improved.

The ceramic slurry of the present invention includes:
If necessary, a lubricant, a deflocculant, a wetting agent, an antistatic agent, an antifoaming agent, a drying accelerator, and the like may be contained as long as the object can be achieved.

The thus-obtained ceramic slurry for forming a green sheet is defoamed, if necessary, applied to a support such as a peelable polyester film, and heated,
The water or organic solvent is removed by drying, and then the green sheet is peeled off from the support to produce a green sheet.

In order to obtain a hybrid type multilayer ceramic circuit board using the green sheet, the green sheet is punched into a predetermined shape and size, and a circuit is printed on the surface thereof. Ten sheets are laminated, and they are integrated by thermocompression bonding to obtain a laminated body. Then, the laminate is heated to a high temperature (for example, about 600 ° C.) to almost completely decompose the binder resin,
Further, the ceramic powder is heated at a high temperature (for example, about 1600 ° C.) to sinter the ceramic powder to obtain a hybrid type multilayer ceramic circuit board.

[0031]

The at least two binder resins described above
Blend polyvinyl acetal resins with different degrees of polymerization of at least two types, or blend at least two types of polyvinyl alcohols with different degrees of polymerization to form an acetal, and increase the apparent degree of polymerization to 300 to 1200, that is, to broaden the molecular weight distribution. By lowering the solution viscosity with a low degree of polymerization, the dispersibility of the slurry can be increased, and the strength of a green sheet molded with a high degree of polymerization can be improved to prevent cracking.

Furthermore, since crystallization and formation of intermolecular hydrogen bonds between hydroxyl groups due to steric hindrance of the acetal ring are suppressed, the viscosity of the ceramic slurry for green sheet molding of the present invention hardly changes over time. A ceramic slurry for forming a green sheet and a green sheet having good coating workability can be obtained.

[0033]

EXAMPLES Examples and comparative examples of the present invention will be described below.

(Example 1) Production of polyvinyl acetal resin 81 g of polyvinyl alcohol having a polymerization degree of 300 and a saponification degree of 98 mol%, and 112 g of polyvinyl alcohol having a polymerization degree of 1000 and a saponification degree of 98 mol% were added to 2900 g of pure water (apparent). The mixture was stirred at a temperature of 90 ° C. for about 2 hours and dissolved. The solution was cooled to 28 ° C., and 201 g of hydrochloric acid having a concentration of 35% by weight and n-butyraldehyde 11 were added thereto.
2 g was added, the liquid temperature was lowered to 20 ° C., and this temperature was maintained to carry out an acetalization reaction to precipitate a reaction product.
Thereafter, the liquid temperature was maintained at 30 ° C. for 5 hours to complete the reaction, and neutralization, washing with water and drying were performed by a conventional method to obtain a white powder of a polyvinyl acetal resin.

The obtained polyvinyl acetal resin was treated with DM
Was dissolved in SO-d ₆ (dimethylsulfoxide), ¹³ C
When the degree of acetalization (degree of butyralization) was measured using -NMR (nuclear magnetic resonance spectrum), the degree of butyralization was 67 mol%.

Production of Ceramic Slurry 10 parts by weight of this polyvinyl acetal resin was added to a mixed solvent of 30 parts by weight of toluene and 15 parts by weight of methyl ethyl ketone and dissolved by stirring. To this resin solution, 5 parts by weight of dibutyl phthalate as a plasticizer was added and dissolved by stirring. To the resin solution thus obtained, 100 parts by weight of alumina powder (average particle size: 0.3 μm) was added as a ceramic powder, and mixed by a ball mill for 48 hours to obtain a ceramic slurry in which the alumina powder was dispersed.

Production of Green Sheet This ceramic slurry was applied to a release-treated polyester film to a thickness of about 12 μm, air-dried at room temperature for 30 minutes, and further dried at 60-80 ° C. for 1 hour with a hot air drier. The organic solvent was evaporated to obtain a thin green sheet having a thickness of 8 μm.

Table 1 shows the results of performance evaluation of the flexibility, dispersibility, and the presence or absence of cracks of the ceramic slurry and the green sheet.

The performance evaluation was performed according to the following criteria.

The presence or absence of cracks The presence or absence of cracks in the green sheet is visually inspected.
(No crack) and x (with crack) were evaluated on two levels.

The flexibility of the flexible green sheet was examined by touch and evaluated on four levels of ◎ (very good), （(good), good (△), and × (bad).

Dispersibility The dispersibility of the ceramic slurry was visually inspected and evaluated on four levels of ◎ (very good), （(good), good (△), and × (bad).

(Examples 2-3, Comparative Examples 1-3) Degree of polymerization of polyvinyl alcohol, degree of saponification, kind of aldehyde,
A ceramic slurry and a green sheet were produced in the same manner as in Example 1 except that the acetalization degree, the resin blending method, and the average particle size of the ceramic powder were changed as shown in Table 1. Table 1 shows the performance evaluation results of the substance.

Example 4 Production of Polyvinyl Acetal Resin 193 g of polyvinyl alcohol having a polymerization degree of 300 and a saponification degree of 98 mol% was added to 2900 g of pure water, and stirred at a temperature of 90 ° C. for about 2 hours to dissolve. This solution was cooled to 28 ° C., and 201 g of hydrochloric acid having a concentration of 35% by weight and 112 g of n-butyraldehyde were added thereto, and the temperature of the solution was lowered to 20 ° C .. The substance was deposited. Thereafter, the liquid temperature was maintained at 30 ° C. for 5 hours to complete the reaction, and neutralization, washing with water and drying were performed by a conventional method to obtain a white powder of a polyvinyl acetal resin.

The obtained polyvinyl acetal resin was treated with DM
Was dissolved in SO-d ₆ (dimethylsulfoxide), ¹³ C
When the degree of acetalization (degree of butyralization) was measured using -NMR (nuclear magnetic resonance spectrum), the degree of butyralization was 67 mol%.

Similarly, a polyvinyl acetal resin having a degree of polymerization of 1000 and a degree of saponification of 98 mol% was used to obtain a polyvinyl acetal resin having a degree of butyralization of 67 mol%.

Next, a polyvinyl acetal resin having a polymerization degree of 300 and a polyvinyl acetal resin having a polymerization degree of 1000 were blended at a weight ratio of 42:58 to give an apparent polymerization degree of 600.
Was obtained.

The production of the ceramic slurry and the production of the green sheet were carried out in the same manner as in Example 1. Table 1 shows the results.

Examples 5 to 6 Except that the degree of polymerization of polyvinyl alcohol, the degree of saponification, the type of aldehyde, the degree of acetalization, the method of blending the resin, and the average particle size of the ceramic powder were changed as shown in Table 1. Produced ceramic slurry and green sheets in the same manner as in Example 4. Table 1 shows the performance evaluation results of the above substances.

[0050]

[Table 1]

Example 7 Production of polyvinyl acetal resin 84 g of polyvinyl alcohol having a polymerization degree of 300 and a saponification degree of 98 mol%, and a polymerization degree of 1000, and 116 g of polyvinyl alcohol having a saponification degree of 98 mol% were added to 1600 g of pure water to obtain 9
The mixture was stirred and dissolved at a temperature of 0 ° C. for about 2 hours.

The solution was cooled to 45 ° C.
50 g of 5% by weight hydrochloric acid was added, and the mixture was further cooled to 35 ° C., and 20 g of 99% pure n-butyraldehyde and 25 g of 99% pure acetaldehyde were added dropwise over 2 hours, and acetalized at 35 ° C. for 3 hours. The reaction was performed. Thereafter, the liquid temperature was cooled to 20 ° C., and 192 g of a 10% by weight aqueous sodium hydroxide solution was added with stirring to obtain a transparent solution of a polyvinyl acetal resin.

The transparent solution of the obtained polyvinyl acetal resin was applied on a polyethylene film and dried to prepare a transparent film.
Was dissolved in ₆ (dimethylsulfoxide), ¹³ C-NMR
When the degree of acetalization (degree of butyralization and degree of acetoacetalization) was measured using (nuclear magnetic resonance spectrum), the degree of butyralization was 10 mol% and the degree of acetoacetalization was 15 mol%.

Production of Ceramic Slurry 60 g of a transparent solution (concentration: 20% by weight) of this polyvinyl acetal resin was mixed and dissolved in 120 g of pure water, and polyethylene glycol (average molecular weight: 20
0) 4 g and 200 g of alumina powder (average particle size 0.3 μm) as a ceramic powder were added and mixed for 15 hours by a ball mill to obtain a ceramic slurry in which the alumina powder was dispersed.

Production of Green Sheet This ceramic slurry was defoamed under a reduced pressure of 5 mmHg with stirring, adjusted to a viscosity of 10 poise, and applied to a release-treated polyester film to a thickness of about 15 μm. The resultant was air-dried at room temperature for one day, further dried in a hot-air dryer at 110 ° C. for 3 hours, and water was evaporated to obtain a thin green sheet having a thickness of 8 μm.

The above ceramic slurry and green sheet were evaluated for the presence or absence of cracks, flexibility and dispersibility in the same manner as in Example 1.

Table 2 shows the results.

(Examples 8 to 9 and Comparative Examples 4 to 6) Table 2 shows the degree of polymerization of polyvinyl alcohol, the degree of saponification, the type of aldehyde, the degree of acetalization, the resin blending method, and the average particle size of the ceramic powder. A ceramic slurry and a green sheet were produced in the same manner as in Example 7, except that the modification was made as shown. Table 2 shows the results. In Comparative Examples 5 and 6, the dispersibility of the ceramic powder was poor, and the firing shrinkage of the green sheet was not measured.

(Example 10) Degree of polymerization: 300, degree of saponification: 9
200 g of 8 mol% polyvinyl alcohol is added to pure water 160
0 g, and dissolved by stirring at a temperature of 90 ° C. for about 2 hours.

The solution was cooled to 45 ° C.
50 g of 5% by weight hydrochloric acid was added and further cooled to 35 ° C., 20 g of 99% pure n-butyraldehyde and 25% of acetaldehyde of 99% were added dropwise over 2 hours, and the acetal was added at 35 ° C. for 3 hours. The reaction was carried out. Thereafter, the liquid temperature was cooled to 20 ° C., and 192 g of a 10% by weight aqueous sodium hydroxide solution was added with stirring to obtain a transparent solution of a polyvinyl acetal resin.

The transparent solution of the obtained polyvinyl acetal resin was applied on a polyethylene film and dried to prepare a transparent film.
Was dissolved in ₆ (dimethylsulfoxide), ¹³ C-NMR
When the degree of acetalization (degree of butyralization and degree of acetoacetalization) was measured using (nuclear magnetic resonance spectrum), the degree of butyralization was 10 mol% and the degree of acetoacetalization was 15 mol%.

Similarly, a polyvinyl acetal resin having a degree of polymerization of 1000 and a degree of saponification of 98 mol% was used to obtain a polyvinyl acetal resin having a degree of butyralization of 10 mol% and a degree of acetoacetalization of 15 mol%.

Next, a polyvinyl acetal resin having a polymerization degree of 300 and a polyvinyl acetal resin having a polymerization degree of 1000 were blended at a solid content weight ratio of 42:58 to give an apparent polymerization degree of 60.
No. 0 polyvinyl acetal resin was obtained.

Thereafter, the same procedure as in Example 7 was carried out to obtain a ceramic slurry and a green sheet. Table 2 shows the results.
Shown in

Examples 11 to 12 In the same manner as in Example 10 except that the values of polyvinyl alcohol, aldehyde, and ceramic powder were changed as shown in Table 2,
A ceramic slurry and a green sheet were obtained. Table 2 shows the results.

[0066]

[Table 2]

[0067]

The ceramic slurry for forming a green sheet according to the present invention is obtained by mixing at least two kinds of polyvinyl acetal resins having different degrees of polymerization or mixing at least two kinds of polyvinyl alcohols having different degrees of polymerization. Since the mixed polyvinyl alcohol is acetalized and contains a polyvinyl acetal resin having an apparent degree of polymerization of 300 to 1200, a ceramic powder, and a plasticizer, that is, by increasing the molecular weight distribution, a solution having a low degree of polymerization has a low solution viscosity. By lowering it, the dispersibility of the slurry can be increased, and for those with a high degree of polymerization, the strength of the molded green sheet can be improved, making it difficult for cracks to occur, and as a result, a flexible, homogeneous thin layer Green sheet can be manufactured.

Further, the action of the acetal ring suppresses the intermolecular association and crystallization of the polyvinyl acetal resin, so that the ceramic slurry for forming a green sheet according to the present invention hardly undergoes a change in viscosity over time, and There is an advantage that a uniform thin green sheet having good properties can be easily produced.

Claims (2)

(57) [Claims] 1. A mixed polyvinyl acetal resin having an apparent degree of polymerization of 300 to 1200 or a mixture of at least two kinds of polyvinyl acetal resins having different polymerization degrees, or at least two kinds of polyvinyl alcohols having different degrees of polymerization. Is mixed to form acetal, and apparent polymerization degree is 3
A ceramic slurry for forming green sheets, comprising a polyvinyl acetal resin having a particle size of from 00 to 1200, a ceramic powder, and a plasticizer. 2. A green sheet obtained by shaping the ceramic slurry for forming a green sheet according to claim 1 into a sheet and drying it.