JPH03247548A - Ceramic green sheet and production thereof - Google Patents

Abstract

PURPOSE:To improve the surface smoothness, workability and thermal decomposability of a ceramic green sheet by limiting the evaporation index of an org. solvent used at the time of preparing a slurry as starting material for producing the green sheet. CONSTITUTION:When a slurry consisting of ceramic powder, an org. binder and an org. solvent or further contg. a dispersant and a plasticizer is cast on a polymer film to produce a ceramic green sheet, the org. solvent is used so that the ratio of the evaporation index to the wt.% is regulated to <=450. Powder of at least one among alumina, alumina-glass and zirconia is used as the ceramic powder and at least one among alcohols, ketones, aliphatic hydrocarbon, arom. hydrocarbon and acetic esters is used as the org. solvent. A ceramic green sheet having <=0.1mum average surface roughenss (Ra) along the center line and <=1mum max. height (Rmax) is obtd.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to ceramic substrates, particularly ceramic green sheets that are used as materials for ceramic wiring boards and ceramic substrates for printing precision circuits by vapor deposition. Be careful how you send it.

[Conventional Branch Equilibrium] Conventionally, in the production of ceramic green sheets, a sintering aid is added to inorganic powder such as alumina or alumina glass, an organic binder made of polyvinyl butyral, a dispersant, a plasticizer, and a solvent such as trichloroethylene, methyl ethyl ketone, or toluene are used. A method has been adopted in which a slurry is prepared by dispersing it in a vehicle consisting of the following: This slurry is cast onto a polymer film through a doctor blade, and then the solvent is evaporated to obtain a sheet-like molded product.

Alumina thick film or thin film substrates, laminated substrates, ceramic capacitors, and the like are manufactured using this green sheet method. In particular, in recent years, there has been a trend in multilayer wiring boards to reduce circuits and circuit spacing in order to create finer patterns, and attempts have been made to stack dozens or more layers in order to increase density.

However, in the production of green sheets, the sheet surface roughness deteriorates due to the formation of a dry film on the slurry surface (Japanese Patent Laid-Open Publication No. 17063/1983), and the occurrence of density variations and cracks during forming and drying (Japanese Patent Laid-Open Publication No. 17063/1983). 64-65056
), dimensional stability due to shrinkage during firing (JP-A-1-
There are problems related to the slurry composition and preparation method. Furthermore, fine patterning is greatly influenced by the sheet surface roughness, and the problem becomes more important as the number of layers increases.

Under the above circumstances, JP-A-62-17063 attempts to improve the sheet surface roughness by examining solvents, and the conventional surface roughness (Ra) of 1.1 μm was improved to 0.5 μm. There is. However, the smoothness of the sheet surface is not sufficient for drawing fine patterns and laminating over several tens of layers. Height (R
max) has not been considered. In addition, trichlorethylene is used to improve the explosion-proof properties of solvents, which has a negative impact on the environment.

In addition, polyvinyl butyral v is usually used as a binder.
IUit is used, but in this case, the smoothness of the obtained ceramic green sheet tends to be inferior to that of one using a (meth)acrylate copolymer as a binder, and the center line average roughness ( A sheet having Ra) of 0.5 μm or less cannot be easily obtained. Furthermore, this resin has poor thermal decomposition properties, and when several tens or more layers of ceramic green sheets are laminated, carbon remains even after firing, which is undesirable since there is a problem of impairing insulation properties.

[Problems to be Solved by the Invention] As mentioned above, in order to laminate fine pattern wiring over several dozen layers of conventional ceramic green sheets, it is necessary to improve the surface smoothness, moldability, thermal decomposition properties, etc. of the green sheets. There is a problem.

The present invention solves these problems and also! ! The purpose of the present invention is to provide a ceramic green sheet that does not have a large adverse effect on the working environment for workers, and a method for producing the same.

Means for Solving the RFF Problem] As a result of intensive study by the inventors to solve the above problem, the ceramic green sheet manufactured by the manufacturing method specified in the claims achieves the above object. Based on this finding, we have completed the present invention.

The present invention will be explained in detail below.

In the present invention, the center line average roughness (Ra) of the sheet surface is 0.1
It is a ceramic green sheet with characteristics of less than μm and a maximum height (Rmax) of less than μm, and a slurry consisting of ceramic powder, an organic binder, an organic solvent, and if necessary a dispersant and a plasticizer 1 is made into a polymer. In the method of manufacturing a ceramic green sheet by casting on a film, the sum of the evaporation index to the forming weight ratio of the organic solvent (hereinafter referred to as "evaporation rate index") is 450 or less. This is a method for manufacturing ceramic green sheets using a solvent.

Organic solvents according to the present invention include alcohols such as methanol, ethanol, 2-propertool, 1-butanol and 1-hexanol, ketones such as acetone and methyl ethyl ketone, aliphatic hydrocarbons such as pentane, hexane, and heptane, At least one kind selected from aromatic hydrocarbons such as benzene, toluene, xylene, and ethylbenzene, and acetate esters such as methyl acetate, ethyl acetate, and butyl acetate can be used. Preferably, it is a mixed solvent of two or more selected from 2-propanol, 1-butanol, toluene, methyl ethyl ketone, and ethyl acetate. The evaporability of a solvent, which is usually expressed as the ratio of evaporation rate to butyl acetate (evaporation index: taking the evaporation rate of butyl acetate to 100), greatly affects properties such as the stability and kneadability of the slurry. In selection, the evaporation rate index is adjusted to be 450 or less, preferably in the range of 150 to 400.

If the evaporation rate index exceeds 450, the drying rate of the solvent is fast, resulting in poor green sheet surface smoothness, and the green sheet tends to dry partially, causing unevenness and cracks to occur on the sheet surface. There is. If the evaporation rate index is less than 150, the surface smoothness of the green sheet will not be adversely affected, but the drying rate of the solvent will be slow, resulting in poor workability, which is not practical.

The organic binder used is an alkyl acrylate having an alkyl group having 1 to 10 carbon atoms, and an alkyl acrylate having an alkyl group having 1 to 20 carbon atoms.
A monomer selected from the group consisting of alkyl methacrylates having an alkyl group of 20000 to 100000, more preferably 3
Range from 0000 to 60000! (meta)
It is a copolymer of acrylate. Number average molecular weight (Mn)
This affects the lamination of the green sheet P# layer, and if Mn exceeds 100,000, the green sheet becomes hard and has poor adhesion, and peeling tends to occur near the circuit between the green sheets after lamination pressing. 20
If it is less than 000, the green sheet strength is insufficient and cracks occur on the surface.

Monomers used in the synthesis of (meth)acrylate copolymers include methyl acrylate, ethyl acrylate, propyl acrylate, butyl acrylate, methyl propyl acrylate, cyclohexyl acrylate, 2-ethylhexyl acrylate, and methyl methacrylate, ethyl acrylate, etc. From methacrylate, butyl methacrylate, methylpropyl methacrylate, octyl methacrylate, 2-ethylhexyl methacrylate, decyl methacrylate, dodecyl methacrylate, lauryl methacrylate, cyclohexyl methacrylate, etc.
Two or more types are selected. The selected monomers are solution polymerized,
It is polymerized by known methods such as suspension polymerization and emulsion polymerization, and is used as an organic binder.

It goes without saying that the solvent used during polymerization is preferably the same as the solvent used when producing slurry Fl.

The ceramic powder used is at least one selected from alumina, alumina-glass, and zirconia, but in some cases magnesia, calcia, silica, kaolin, talc, etc. may be added as a sintering aid or particle growth inhibitor. It is also possible to do so. The average particle size of the ceramic powder used is 4 to 5 μm or less, and for glass it is 10 to 1 μm.
The diameter may be 5 μm or less, but it takes time to crush and disperse the powder during slurry tAa. Therefore, the average particle size of ceramic powder is preferably 1 μm or less, and 5 μm or less for glass, and more preferably 0.5 μm or less, and more preferably 1 μm or less for glass. In addition, the glass composition is silica, boric acid,
Alumina, magnesia, calcia, strontina, barrier, zirconia, titania, zinc oxide, and those to which acids (arsenic, etc.) are added are appropriately selected and used.

In addition, aluminum nitride, mullite, cordierite, forsterite, zircon, etc. can also be used as the ceramic powder.

The slurry can be prepared by the usual ball milling method, in which ceramic powder, an organic binder, *lI solvent, and if necessary a dispersant and a plasticizer are added together, or the ceramic powder and an organic solvent are mixed together, if necessary, and a dispersant is added. After predispersion in the mill, an organic binder and optionally a plasticizer are added for at least 1 hour, preferably 1 hour.
Disperse and mix for 2 hours or more to obtain a slurry.

In this case, it is added so that the content of the (meth)acrylic binder in the width of the ceramic green sheet is in the range of 5 to 311%. When the binder content in the green sheet is 5% by weight, the moldability of the green sheet is poor and the strength and flexibility are also insufficient. Also,
When the content exceeds 300/l, the flexibility of the green sheet can be obtained, but the processability is poor and shrinkage due to firing is large, making it impossible to obtain dimensional stability.

Ceramic green sheets are manufactured by known methods such as a doctor blade method or a calendar roll method in which a slurry is cast onto a polymer film.

"Examples" The present invention will be explained in more detail below using reference examples and examples, but the present invention is not limited to these examples as long as the gist of the invention is followed.

Reference Example 1 80 parts by weight of toluene and 1 part of 4 caps of methyl ethyl ketone were placed as a solvent in a separable flask equipped with a stirrer, a thermometer, a cooling tube, a nitrogen introduction tube, a funnel for dipping the monomers into the mixture, and a funnel for starting and dropping during polymerization. , Nitrogen was introduced from the nitrogen inlet tube to create a nitrogen atmosphere inside the flask.Next, the mixed monomers were mixed with 2% by weight of a-tohethyl acrylate, 2-
Ethylhexyl acrylate 381% by weight, methyl methacrylate 4.94% by weight, cyclohexyl methacrylate 25! ! Amount %, lauryl methacrylate 3ON! amount%
100 parts by weight of a mixed monomer consisting of methacrylate and 190.06% by weight were charged, and during polymerization, 0.4 parts by weight of rotoheazobisisobutyronitrile was charged.

While controlling the internal temperature of the flask to 60°C, the mixed monomers and polymerization initiator were added dropwise with stirring over 2 hours, heated at 60°C for 2 hours, then at 80°C for 2 hours, and then cooled to a solid content concentration of 45. % and a number average molecular weight of 40,000 was prepared by Fl.

Reference Example 2 Reference Example 4 except that the monomer repair ratio etc. of Reference Example 1 was changed and only toluene was used as the solvent! l! 1 and rFAm, a binder (b) having a solid content of 50z1 and a number average molecular weight of 5oooo was prepared.

Example 1 Alumina (S-23 manufactured by Nikkei Kako ■) 45% by weight,
Borosilicate glass 55 containing calcia and zirconia and having an average particle size of 5 um! ! Ceramic powder added with amount%
121 parts of the binder (a) obtained in Reference Example 1 was added as a solid content to 100% Ti, and 1 part of a mixed solvent of toluene/methyl ethyl ketone (1 child's ratio 2/■) was added as a solvent.
8 parts by weight were added.

Next, the mixture was kneaded in a ball mill for 24 hours to prepare a slurry. The formation of the solvent in this slurry is toluene 221
ffi parts, 11 parts by weight of methyl ethyl ketone, and the evaporation rate index is 350. This slurry was cast onto a polymer film using the doctor blade method.
It was dried at 80° C. to obtain a green sheet with a thickness of 70 μm.

As for the characteristics of the obtained green sheet, the centerline average roughness (Ra) and maximum height (Rmax) of the green sheet surface were measured using a stylus and a linear scanning type surface profile measuring device. These results are shown in the table and Figure 1. Example 2 Zirconia powder (NS-3Y, manufactured by Nissui Shokubai Kagaku AM) with an average particle diameter of 0.3μ was added to 100 m@Q of the binder obtained in Reference Example 2 (b ) was used in a solid content of 25 parts by weight, and a mixed solvent of toluene/1-butanol (3/l ratio) was used as a solvent at 60 parts by weight. ! A green sheet having a thickness of 300 μm was obtained in the same manner as in Example 1 by adding dibutyl phthalate 1x ME as a plasticizer. The evaporation rate index of the solvent in the slurry is 206.

The properties of the green sheet obtained in the same manner as in Example 1 are shown in the table.

Example 3 A mixed solvent of toluene/2-propertool (!! Takahiro 4/1) was added as a solvent to ceramic powder 1001 type e made by adding magnesia soupDm to alumina powder (Showa Denki $I AL-45). In addition, after kneading in a ball mill for 12 hours, 15 parts by weight of the binder (a) obtained in Reference Example 1 was added as a solid content, and kneading was further carried out in a ball mill for 12 hours to prepare a slurry. The solvent evaporation rate index in this slurry is 290.

Using this slurry, a green sheet with a thickness of 50 μm was obtained in the same manner as in Example 1, and the properties of the green sheet are shown in the table.

Example 4 Alumina powder (AL-45 manufactured by Showa Denko ■) 96% royal weight
To 100 parts by weight of ceramic powder to which 4% by weight of flux consisting of MgO, CaO, and SiO2 was added, 30 parts by weight of a mixed solvent of l-butanol/paraxylene (weight ratio 5/l) was added as a solvent to the powder obtained in Reference Example 2. binder (b)
A green sheet with a thickness of 70 μm was obtained in the same manner as in Example 1 using 10 parts by weight of the solid content. The characteristics of the green sheet are shown in the table.

Note that the evaporation rate index of the solvent in the slurry was 96.

Comparative Example 1 Dityl acetate/methyl ethyl ketone (weight ratio 5
Example 1 except that 24 overlapping parts of a mixed solvent of /l) were used.
In the same manner as above, a green sheet with a thickness of 70 μm was obtained,
The characteristics of the green sheet are shown in the table and FIG.

The evaporation rate index of the solvent in the slurry is 510.

It should be noted that only a portion of this slurry dried during the casting operation, resulting in numerous deep groove-like defects in the product.

Surface smoothness measurement results [Effects of the invention] The ceramic green sheet of the present invention has a center line average roughness (Ra) of 0.1 μM or less and a maximum height (R
max) is 1 μm or less, making it suitable for circuit formation by screen printing or photolithography, and also suitable for producing circuit boards with a circuit width of 50 μm or less and a laminated circuit board of 50 to several hundred layers. .

4. Explanation of the figures Figure 1 shows the surface shape of the green sheet obtained in Example 1, and Figure 2 shows the surface shape of the green sheet obtained in Comparative Example 1. This is the result of height measurement.

Claims (6)

[Claims] (1) Center line average roughness (Ra) of sheet surface is 0.1μ
A ceramic green sheet having a maximum height (Rmax) of 1 μm or less. (2) The ceramic green sheet according to claim (1), containing at least one selected from alumina, alumina-glass, and zirconia. (3) Ceramic powder, organic binder and organic solvent,
A method of manufacturing a ceramic green sheet by casting a slurry comprising a dispersant and a plasticizer as necessary on a polymer film, wherein the sum of the evaporation index to the composition weight ratio of the organic solvent is 450 or less ( 1)
Or the method for producing a ceramic green sheet according to (2). (4) The method for producing a ceramic green sheet according to claim (3), wherein the organic solvent is at least one selected from the group consisting of alcohols, ketones, aliphatic hydrocarbons, aromatic hydrocarbons, and acetic esters. . (5) A copolymer in which the organic binder is made by copolymerizing at least two or more monomers selected from the group consisting of alkyl acrylates having an alkyl group having 1 to 10 carbon atoms, and alkyl methacrylates having an alkyl group having 1 to 20 carbon atoms. The method for producing a ceramic green sheet according to claim 3, wherein the ceramic green sheet is a polymer. (6) The number average molecular weight (Mn) of the organic binder is 200
The method for producing a ceramic green sheet according to claim 5, wherein the ceramic green sheet has a particle diameter of 00 to 100,000.