JPH035360A - Ceramic green sheet - Google Patents

Abstract

PURPOSE:To obtain a ceramic green sheet excellent in fine wiring pattern printing property, machinability, dimensional stability, thermal decomposition property, etc., and useful as material for multilayered wiring board by blending a specific (meth)acrylic binder with an alumina-containing inorganic powder. CONSTITUTION:A sheet consisting of (A) an inorganic powder (Al2O3 content, >=40wt.%; pH, preferably 5-10; average grain size, <=1mum; soda content, <=0.03% expressed in terms of Na2O) and 5-30wt.% of (B) a (meth)acrylic binder [acid value, 0.1-2.0; mol.wt., 5000-9000; Mn, 2000-40000; degree V of nonuniformity represented by (Mw/Mn)-1, 1-2] and having <=0.5mum surface rougness (Ra) is formed into a ceramic green sheet for multilayered wiring board.

Description

[Detailed Description of the Invention] [Field of Application of the Invention] The present invention relates to a ceramic green sheet that is a material for ceramic substrates, particularly ceramic multilayer wiring boards, and is capable of drawing fine wiring patterns and has excellent machinability, dimensional stability, and heat resistance. This invention relates to a ceramic green sheet that has excellent degradability and is suitable for multi-layering.

[Prior Art] In recent years, devices using ceramic substrates have been frequently used in the manufacture of electronic devices. With the miniaturization of electronic devices, the density of wiring boards is increasing, and ceramic substrates are being manufactured as multilayer wiring boards.

Conventionally, the manufacturing method for multilayer wiring boards uses an alumina content of 9.
A conductive paste of molybdenum or tungsten is used on a 0% or 96% green sheet, and a conductive paste mainly composed of silver, palladium, etc. is used on a low-temperature sinterable green sheet containing 40 to 60% alumina. A laminating method is known, in which a wiring pattern is printed, multiple sheets are laminated and sintered, and in order to achieve high density, the lamination method is
v1 is also increasing, and attempts are being made to laminate dozens of layers or more.

The organic binder used in these green sheets for multilayer wiring boards is usually polyvinyl butyral resin, as described in "Ceramic Multilayer Wiring Boards" by Kanji Otsuka (Uchida Rokaku, published December 10, 1987). In addition, in order to impart flexibility and machinability to the green sheet, a large amount of plasticizer such as phthalate ester is added to the organic binder in an amount of 20 to 50% by weight.

However, polyvinyl butyral resin has poor dispersibility of inorganic powder, probably because it reacts with the glass component added to alumina as a sintering aid, and the surface of the resulting green sheet tends to be rough. Therefore, with the miniaturization of wiring patterns, smoothness of the green sheet surface is required, but when polyvinyl butyral resin is used, it is difficult to obtain a green sheet with a surface smooth enough to draw fine wiring patterns. have. In addition, depending on the conditions, it may be necessary to bake in a reducing atmosphere, but polyvinyl butyral resin has poor thermal decomposition properties, and there are problems such as peeling at the laminated interface and loss of insulation due to residual carbon after baking. be.

Furthermore, since a large amount of plasticizer is added, during thermo-compression bonding during green sheet stacking, the plasticizer oozes out to the surface, causing misalignment of the wiring pattern and insufficient connection between the upper and lower via holes. There are also problems.

Therefore, various studies have been made on organic binders to solve these problems, but the present situation is that an optimal binder has not yet been found.

[Object of the Invention] Therefore, the object of the present invention is to solve the above-mentioned problems of the prior art, and to improve the printability of fine wiring patterns during the production of ceramic substrates, especially ceramic multilayer wiring boards.
An object of the present invention is to provide a ceramic green sheet having excellent properties in terms of printed pattern stability, dimensional stability, and thermal decomposition properties.

[Structure of the Invention] The object of the present invention is to provide a ceramic green sheet comprising an inorganic powder containing 40% by weight or more of alumina and a (meth)acrylic binder, in which the acid value of the (meth)acrylic binder is In the range of 0.1 to 2.0, the weight average molecular weight (Mn) is in the range of 5oooo to 90,000, the number average molecular weight (Mn) is in the range of 20,000 to 40,000,
The degree of non-uniformity (V) expressed by the formula % is in the range of 1 to 2, and the content of the (meth)acrylic binder in the ceramic green sheet is in the range of 5 to 30% by weight. This is achieved by a ceramic green sheet featuring:

Usually, alumina is mainly used in ceramic substrates used for electronic parts and the like, and the inorganic powder according to the present invention also contains 40% by weight or more of alumina.

A suitable inorganic powder is 20 g of inorganic powder and 8 g of water.
For example, if the pH of a 20% water slurry obtained by adding 0g to
It shows weak basicity in the range of .

To specifically illustrate the inorganic powder containing 40% by weight or more of alumina that is suitably used in the present invention, the alumina has an average particle size of 3 μm or less, preferably 1 μm or less, more preferably 0.5 μm or less, The soda content is 0.06% or less, preferably 0.03% or less as Na2O.

In addition, 40 to 60% by weight of the total inorganic powder is alumina, borosilicate glass, β-subodumene (LiAl5i20a)
+ Cordierite (Mg2AIaSisO+s) + Holsterite (Mg2SiO4) + Mullite (MgA
low-temperature sintering type powder with a sintering temperature of 800 to 1200°C, in which 40 to 60% by weight of one or more of calcium and barium-containing glass, etc. ~96% by weight is alumina, clay and talc (Mg3StaO+5(OH)2) + as sintering aids
High-temperature sintering with a sintering temperature of 1500 to 1700°C, in which 4 to 10% by weight of one or more of clay (AhSi20s(OH)n) and glass containing magnesia, calcia, zirconia, alumina, etc. is added. Examples include compacted powder.

The (meth)acrylic binder used in the present invention is based on acrylic acid or methacrylic acid and esters thereof, and has an acid value in the range of 0.1 to 2.0.
Weight average molecular weight (M is in the range of 50,000 to 90,000, number average molecular weight (Mn) is in the range of 20,000 to 40,000, and the degree of heterogeneity (V) expressed by the formula % is limited to the range of 1 to 2. Ru.

The acid value ranges from 0.1 to 2.0, preferably from 0.5 to 1.
0, but if it exceeds 2.0, agglomeration is observed in the slurry, and especially if it exceeds 4.0, the basic points of the inorganic powder and the carboxyl group (-COO-) in the binder
The slurry becomes gelled, which makes it difficult to form a sheet, probably because it becomes easier to form a crosslinked structure. In addition, the acid value is 0.1
When it is less than 100%, no agglomeration is observed in the slurry, but the very small amount of carboxyl groups in the binder makes it difficult to wet the powder, resulting in a slurry with thixotropy, which impairs sheet formability. strength also decreases.

Furthermore, the glass transition temperature of the (meth)acrylic binder is in the range of 50 to 0°C, preferably -40 to -10°C.
is within the range of Within this range, excellent flexibility and pressure bonding properties can be imparted to the green sheet, and there is no need to add a plasticizer. However, a plasticizer may be added to ease conditions such as pressure and temperature during lamination pressing. In this case, it is preferable to mix 2 to 10% by weight of the binder. As the plasticizer, known ones such as phthalate esters such as dibutyl phthalate and dioctyl phthalate can be used.

The (meth)acrylic binders having the above acid value and glass transition temperature range are methyl acrylate, ethyl acrylate, and n-propyl acrylate.

20 to 60% by weight of an acrylic acid ester having an alkyl group having 1 to 10 carbon atoms selected from n-butyl acrylate, isobutyl acrylate, cyclohexyl acrylate, 2-ethylhexyl acrylate, etc., methyl methacrylate, ethyl methacrylate, n-butyl methacrylate, isobutyl methacrylate, n-
1 carbon number selected from octyl methacrylate, n-decyl methacrylate, n-dodecyl methacrylate, lauryl methacrylate, cyclohexyl methacrylate, 2-ethylhexyl methacrylate, etc.
40-80% by weight of methacrylic esters having ~20 alkyl groups and acrylic acid, methacrylic acid,
0.01 to 0.5% by weight of carboxyl group-containing monomers such as maleic acid and itaconic acid are optimally selected as the monomer composition of the binder.

In addition, acrylic acids containing hydroxyl groups such as 2-hydroxyethyl acrylate, 2-hydroxypropyl acrylate, glycerol acrylate, and trimethylolpropane acrylate that can be copolymerized with these acrylic esters, methacrylic esters, and carboxyl group-containing monomers. Alkyl ester monomer or aminoethyl (meth) containing a basic nitrogen atom in the molecule
Acrylate, aminoethyl (meth)acrylamide,
Allylamine, N-methylaminoethyl (meth)acrylate, N-phenylaminoethyl (meth)acrylate, N,N-dimethylaminoethyl (meth)acrylate, N,todimethylaminobrobyl (meth)acrylamide, N-vinylpyrrolidone , acryloylformoline, vinylpyridine, or other basic unsaturated monomers, or aromatic or aliphatic monomers having unsaturated bonds such as styrene, vinyl acetate, allyl alcohol, allyl ether, etc., in an amount not exceeding 10% by weight as a binder. Can be added to the composition.

These monomers have a weight average molecular weight (Mw) of 50 by known polymerization methods such as suspension polymerization, solution polymerization, and emulsion polymerization.
000 to 90,000, preferably 70,000 to 8
0000, the number average molecular weight (Mn) is 20000
~40000 range, preferably 25000-3500
tUa is set to 0 range. However, the heterogeneity (V) expressed by the following formula is in the range of 1 to 2, and it is preferable that the molecular weight distribution has a small spread.

(Mw/Mn) -1 When the weight average molecular weight (Mu) is less than 50,000 and the number average molecular fi (Mn) is less than 20,000, the bonding strength as a binder decreases, resulting in poor formability of the green sheet and the use of the binder. Must be added in large quantities. Also,
When the weight average molecular weight (Mw) exceeds 90,000 and the number average molecular weight fl (Mn) exceeds 40,000, the binder viscosity increases, so the formability of green sheets, especially the formability of thin green sheets with a thickness of 100 μm or less is inferior, and a large amount of solvent must be added for dilution.

Furthermore, when the degree of heterogeneity (V) exceeds 2, the molecular weight distribution broadens, and alumina and borosilicate glass, β
- The surface smoothness of the obtained green sheet becomes poor, probably because the dispersibility with subodumene, talc, clay, etc. becomes poor.

To the thus obtained binder, the above-selected inorganic powder and organic solvent, as well as a dispersant, a plasticizer, etc. are added as necessary, and the mixture is kneaded for a predetermined time using a ball mill or the like to prepare a slurry. A ceramic green sheet is prepared by a known method such as.

In this case, the content of the (meth)acrylic binder in the ceramic green sheet is in the range of 5 to 30% by weight. When the binder content in the green sheet is 5% by weight without grooves, the moldability of the green sheet is poor and the strength and flexibility are also insufficient. On the other hand, when the content exceeds 30% by weight, 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.

[Examples] Hereinafter, the present invention will be explained in more detail by reference examples and examples, but the present invention is not limited to these examples.

Reference Example 1 80 parts by weight of toluene and 40 parts by weight of methyl ethyl ketone as solvents were put into a separable flask equipped with a stirrer, a thermometer, a cooling tube, a nitrogen introduction pipe, a mixing monomer dropping funnel, and a polymerization initiator dropping funnel, and the nitrogen introduction pipe was charged. More nitrogen was introduced to create a nitrogen atmosphere inside the flask. Then, the mixed monomers were added dropwise to the funnel, 2% by weight of ethyl acrylate, 2-
100 parts by weight of a mixed monomer consisting of 38% by weight of ethylhexyl acrylate, 4.94% by weight of methyl methacrylate, 25% by weight of cyclohexyl methacrylate, 30% by weight of lauryl methacrylate and 0.06% by weight of methacrylic acid were prepared. , A polymerization initiator was added dropwise to the funnel, and 0.4 parts by weight of heazobisisobutyronitrile was charged.

While adjusting 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 determine the solid content concentration. 45%, acid fio, 5, glass transition temperature -35°C, weight average molecular weight 75,000, number average molecular 13
A binder (a) named 0000 was prepared.

Reference Example 2 Reference Example 1 except that the monomer composition ratio of Reference Example 1 was changed.
Binders (b) to (h) shown in Table 1 were prepared in the same manner as above.

Table 1 Reference example of physical properties of binder 3 Alumina as inorganic powder (LS-23 manufactured by Kuchigaru Manufacturing Co., Ltd.) 4
Low-temperature sintering type powder (1) in which 55% by weight of borosilicate glass is added to 5% by weight, and alumina (manufactured by Showa Denko f! $1 A)
L-45) 96% by weight of M g O+ Ca O+
A high-temperature sintering type powder (II) to which 4% by weight of flux consisting of S i 02 was added was used.

The pH of a 20% water slurry obtained by adding 20 g of the former powder to 80 g of water and shaking it in a paint shaker for 5 minutes was 9.0. A 20% water slurry of the latter powder obtained in the same manner had a pH of 8.5.

Example 1 100 parts by weight of the low-temperature sintered powder (1) obtained in Reference Example 3 was added with an acid value of 0.5, a glass transition temperature of -35°C, a weight average molecular weight of 75,000, and a number average molecular weight of 30,000. Added 12 parts by weight of binder (a) as a solid content, and added toluene/methyl ethyl ketone (weight ratio 2) as a solvent.
A slurry was prepared by adding 18 parts by weight of a mixed solvent (/l) and then milling in a ball mill for 24 hours. This slurry was cast onto a polymer film by a doctor blade method and dried at 80°C to obtain Greensea (A) with a thickness of 70 μm. Further, a green sheet (K) having a thickness of 70 μm was obtained in exactly the same manner except that the high-temperature sintered powder (II) obtained in Reference Example 3 was used.

The binder content in each green sheet was 11% by weight.

The properties of the obtained green sheets (A) and (K) were determined by measuring the centerline average roughness (Ra) of the green sheet surface using a stylus type and linear scanning method using a surface profile measuring device (Dektak 3030). The tensile stress and elongation of the green sheet until breaking were measured using a strength testing machine (Takasu Seisakusho; Servo Pulsar EHF-ED3-1OL). Furthermore, the flexibility when wound onto an IOwnφ glass rod and the punching performance when punching a 40×40mm area at a pitch of 2mm using an O.15mmφ punch were visually observed, and the results are shown in Table 2. The surface shapes of Green Sea) (A) and (K) are shown in Figures 1 and 2.

Example 2 100 parts by weight of the low temperature sintering type powder (1) obtained in Reference Example 3 was added with the acid value 1.0 obtained in Reference Example 2, glass transition temperature -18°C, weight average molecular weight ii 5oooo, number average molecular weight 27000
A green sheet (B) having a thickness of 50 μm was obtained in the same manner as in Example 1 using the binder (b).

The binder content in this green sheet is 1
It was 1% by weight.

The properties of the obtained green sea) (B) are shown in Table 2.

Example 3 100 parts by weight of the low temperature sintered powder (1) obtained in Reference Example 3 was added with the acid value 1.7 obtained in Reference Example 2, glass transition temperature -9°C, weight average molecular fl 60000, number average molecular weight Added 18 parts by weight of a binder (C) of 25,000 as a solid content, and further added 21 parts by weight of a mixed solvent of toluene/ethyl acetate/isopropanol (weight ratio 6/3/1) as a solvent. 1 weight of dioctyl phthalate as a plasticizer. add 1 part, then 1 part
Knead the slurry in a ball mill for 6 hours and turn it into Sl! lI
! Shita. This slurry was prepared in the same manner as in Example 1 until the thickness was 1
00 μm green sea) (C) was obtained. In addition, a green sheet with a thickness of 90 μm (
L) was obtained. The binder content in each green sheet was 16% by weight.

The properties of the obtained green sheets (C) and (L) are shown in Table-2.

Comparative Example 1 The binder (d) (e) obtained in Reference Example 2 was added to the low temperature sintered powder (1) and the high temperature sintered powder (II) obtained in Reference Example 3.
), (f), (g) and (h) are combined as shown in Table 2, and green sheets (D), (E), (G), (H) with a thickness of 70 μm are prepared in the same manner as in Example 1. )
and (M) were obtained. The binder content in each green sheet was 11% by weight.

Table 2 shows the characteristics of each of the obtained green sheets. In addition, the surface shape of the green sheet (H) is shown in Figure 3.
It was shown to.

Comparative Example 2 Low-temperature sintering type powder obtained in Reference Example 3 (6 parts by weight of the binder (d) obtained in Reference Example 2 as a solid content in parts by weight of Btoo),
Similarly, 11 parts of binder (e) was added, and the same procedure as in Example 1 was carried out to obtain Greensea (1) having a thickness of 70 μm. Further, a green sheet (N) having a thickness of 70 μm was obtained in exactly the same manner except that the high temperature sintered powder (IF) obtained in Reference Example 3 was used.

The binder content in each green sheet was 11% by weight.

The properties of the obtained green sheets (■) and (N) are shown in Table 2.

Comparative Example 3 100 parts by weight of the low temperature sintering type powder (1) obtained in Reference Example 3 was added with polyvinyl butyral (PVB) resin (30% by Denki Kagaku ■).
00-K) 10 parts by weight, and toluene/ethyl acetate/n-butyl alcohol as a solvent (weight ratio 6/
A slurry was prepared by adding 36 parts by weight of a mixed solvent of 3/1) and 4 parts by weight of dioctyl phthalate as a plasticizer, followed by kneading in a ball mill for 36 hours. This slurry was treated in the same manner as in Example 1 to obtain a green sheet (J) with a thickness of 120 μm. Further, a green sheet (0) having a thickness of 150 μm was obtained in exactly the same manner except that the high-temperature sintered powder (II) obtained in Reference Example 3 was used. The binder content in each green sheet was 9% by weight.

The properties of the obtained green sheets (J) and (○) are shown in Table-2.

Example 4 Green sea) (A) and (K) obtained in Example 1
, Te0 for the green sheet (B) obtained in Example 2
．． A through hole was obtained by punching out a 15 maφ hole with a 40×40 mm (1) area and 2 square holes.

These through holes were filled with conductive paste to form via holes, and the same paste was screen printed to create a wiring pattern in an area of 40 x 40 mm, and the amount of dimensional change in the green sheet was determined.

As a result, the green sheet (A,) of 40X40mmC
The deviation on the D diagonal is 0.054 mm, and the green sheet (
The deviation of K) was 0.069 mm, and the deviation of green sheet (B) was 0.057 mm.

Comparative Example 4 Green sea obtained in Comparative Example 1) (D), (E
).

(, G), (H) and (M), green sheets (1) and (N) obtained in Comparative Example 2, and green sheets (J) and (O) obtained in Comparative Example 3 Example 4
The amount of dimensional change was determined in the same manner as above.

As a result, the deviations along the diagonal line of 40×40+nm were all 0.15 mrB or more, which corresponded to the diameter of the via hole, and therefore had the possibility of causing poor conduction.

[Effects of the invention] Green sheets (A), (B), (C) according to the invention
).

(K) and (L) have excellent properties in surface smoothness, machinability, flexibility, tensile strength, dimensional stability, and thermal decomposition. Because it is characterized by stability, it is suitable as a material for ceramic substrates, especially ceramic multilayer wiring boards.

[Brief explanation of drawings]

Figure-1, Figure-2 and Figure-3 are Green Sea respectively)
It is a figure which shows the surface shape of (A), (K), and (H).

Claims (2)

[Claims] (1) Inorganic powder containing 40% by weight or more of alumina and (
meth)acrylic binder, the acid value of the (meth)acrylic binder is in the range of 0.1 to 2.0, and the weight average molecular weight (Mw) is in the range of 50,000 to 90,000; When the number average molecular weight (Mn) is in the range of 20,000 to 40,000, the formula (
The degree of non-uniformity (V) expressed by Mw/Mn)-1 is in the range of 1 to 2, and the content of the (meth)acrylic binder in the ceramic green sheet is in the range of 5 to 30% by weight. A ceramic green sheet characterized by: (2) Center line average roughness (Ra) of the green sheet surface
) is 0.5 μm or less, the ceramic green sheet according to claim (1).