JPH0581552B2 - - Google Patents

Description

[Detailed description of the invention]

[Field of Application of the Invention] The present invention relates to ceramic substrates, particularly ceramic green sheets that are the material for ceramic multilayer wiring boards. The present invention relates to a suitable ceramic green sheet. [Prior Art] In recent years, devices using ceramic substrates have been frequently used in the manufacture of electronic equipment. and,
With the miniaturization of electronic devices, the density of wiring boards is increasing, and ceramic boards are being made as multilayer wiring boards. Conventionally, the manufacturing method for multilayer wiring boards is to apply molybdenum or tungsten conductive paste on a green sheet with an alumina content of 90% or 96%, or
A lamination method is known in which a wiring pattern is printed on a low-temperature sinterable green sheet containing 60% alumina using a conductive paste mainly composed of silver, palladium, etc., and multiple sheets are laminated and sintered. ing. In order to achieve higher density, the number of laminated layers has also increased, and attempts have been 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, a large amount of plasticizer such as phthalate ester is added to the organic binder in an amount of 20 to 50% by weight to impart flexibility and machinability to the clean sheet. 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.
The surface of the obtained green sheet tends to be rough. Therefore, with the miniaturization of wiring patterns, smoothness of the green sheet surface is required.
When polyvinyl butyral resin is used, it is difficult to obtain a green sheet with a surface smooth enough to draw a fine wiring pattern. 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 insulation properties may be impaired due to peeling or residual carbon at the laminated interface after baking. There are also other problems. 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 and the printed patterns when manufacturing ceramic substrates, especially ceramic multilayer wiring boards. The object of the present invention is to provide a ceramic green sheet having excellent properties such as stability, dimensional stability, and thermal decomposition properties. [Structure of the Invention] The object of the present invention is to provide a ceramic green sheet containing an inorganic powder containing 40% by weight or more of alumina and a (meth)acrylic binder,
The acid value of the (meth)acrylic binder is 0.1~
2.0 range, weight average molecular weight (Mw) from 50000
Range of 90000, number average molecular weight (Mn) from 20000
40000, the degree of heterogeneity (V) expressed by the formula (Mw/Mn)-1 is in the range of 1 to 2,
This is achieved by a ceramic green sheet characterized in that the content of the (meth)acrylic binder in the ceramic green sheet is in the range of 5 to 30% by weight. Usually, alumina is mainly used in ceramic substrates used for electronic parts, and the inorganic powder according to the present invention also contains 40% by weight or more of alumina. Inorganic powder 20 is a suitable inorganic powder.
A water slurry with a concentration of 20% obtained by adding g to 80 g of water and shaking it for 5 minutes in a paint shaker, for example, exhibits weak basicity with a pH in the range of 8 to 10. A specific example of the inorganic powder containing 40% by weight or more of alumina that is preferably used in the present invention is that alumina has an average particle size of 3 μm or less, preferably 1 μm.
The diameter is more preferably 0.5 μm or less, and the soda content is 0.06% or less as Na ₂ O, preferably
It is 0.03% or less. In addition, 40 to 60% by weight of the total inorganic powder is alumina, borosilicate glass, β-spodium (LiAlSi ₂ O ₆ ),
One or two types of cordierite (Mg ₂ Al ₄ sib ₅ O ₁₈ ), holsterite (Mg ₂ SiO ₄ ), mullite (MgAl ₂ O ₄ ), glass containing calcium or barium, etc.
The sintering temperature is 40-60% by weight of seeds or more.
Low-temperature sintering powder at 800-1200℃ and all-inorganic powder
90-96% by weight alumina, clay as sintering aid,
Talc (Mg ₃ Si ₄ O ₁₀ (OH) ₂ ), Clay (Al ₂ Si ₂ O ₅
(OH) ₄ ) and one or more types of glass containing magnesia, calcia, zirconia, alumina, etc., in a high temperature sintering type powder with a sintering temperature of 1500 to 1700°C, in which 4 to 10% by weight is added. The body etc. can be mentioned. The (meth)acrylic binder used in the present invention is based on acrylic acid or methacrylic acid and their esters, and has an acid value of
Range from 0.1 to 2.0, weight average molecular weight (Mw) 50000
~90000 range, number average molecular weight (Mn) ~20000
40,000, the degree of non-uniformity (V) expressed by the formula (Mw/Mn)-1 is limited to a range of 1 to 2. The acid value is in the range of 0.1 to 2.0, preferably in the range of 0.5 to 1.0, but when it exceeds 2.0, agglomeration is observed in the slurry, and especially when it is over 4.0, the basic points of the inorganic powder and the carboxyl in the binder Group (−
Perhaps because it interacts with COO ^- ) and becomes easier to form a crosslinked structure, the slurry turns into a gel, making sheet forming difficult. In addition, when the acid value is less than 0.1, no agglomeration is observed in the slurry, but the slurry becomes thixotropic and has poor sheet formability, perhaps because the binder has a very small amount of carboxyl groups, making it difficult to wet the powder. This also reduces the strength of the green sheet. Furthermore, the glass transition temperature of the (meth)acrylic binder is in the range of -50 to 0°C, preferably -40 to 0°C.
It is in the range of -10℃. 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 binder having the above acid value and glass transition temperature range has a carbon number selected from methyl acrylate, ethyl acrylate, n-propyl acrylate, n-butyl acrylate, isobutyl acrylate, cyclohexyl acrylate, 2-ethylhexyl acrylate, etc. 1
Acrylic esters with ~10 alkyl groups
20-60% by weight, methyl methacrylate, ethyl methacrylate, n-butyl methacrylate,
Isobutyl methacrylate, n-octyl methacrylate, n-decyl methacrylate, n
-Dodecyl methacrylate, lauryl methacrylate, cyclohexyl methacrylate, 2
- 40 to 80% by weight of a methacrylic acid ester having an alkyl group having 1 to 20 carbon atoms selected from ethylhexyl methacrylate, etc., and 0.01% of a carboxyl group-containing monomer such as acrylic acid, methacrylic acid, maleic acid, itaconic acid, etc. ~0.5% by weight
is selected optimally as each 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)acrylate containing a basic nitrogen atom in the molecule, aminoethyl (meth)acrylamide, allylamine, N-methylaminoethyl (meth)acrylate, N-phenylaminoethyl (meth) Acrylate, N,N-dimethylaminoethyl (meth)acrylate, N,N-dimethylaminopropyl (meth)acrylamide, N
-vinylpyrrolidone, acryloylformoline,
Basic unsaturated monomers such as vinyl pyridine or aromatic or aliphatic monomers having unsaturated bonds such as styrene, vinyl acetate, allyl alcohol, allyl ether, etc. may be added to the binder composition in an amount not exceeding 10% by weight. can. These monomers have a weight average molecular weight (Mw) in the range of 50,000 to 90,000, preferably 70,000, by known polymerization methods such as suspension polymerization, solution polymerization, and emulsion polymerization.
~80000 range, number average molecular weight (Mn) 20000
It is adjusted to a range of ~40,000, preferably a range of 25,000 to 35,000. However, it is preferable that the uniformity of loading (V) expressed by the following formula is in the range of 1 to 2, and that the molecular weight distribution has a small spread. (Mw/Mn)-1 When the weight average molecular weight (Mw) is less than 50,000 and the number average molecular weight (Mn) is less than 20,000, the binding strength as a binder decreases, resulting in poor formability of the green sheet and a large amount of binder is required. must be added. In addition, the weight average molecular weight (Mw)
When the number average molecular weight (Mn) exceeds 90,000 and the number average molecular weight (Mn) exceeds 40,000, the binder clay becomes high, so the formability of the clean sheet, especially the formability of thin green sheets with a thickness of 100 μm or less, is poor, and it is necessary to use a solvent for dilution. Must be added in large quantities. 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 due to poor dispersibility with spodium, talc, clay, etc. 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 slurry is prepared by kneading for a predetermined time using a ball mill or the like. A ceramic green sheet is prepared by a known method such as a blade method. In this case, the content of (meth)acrylic binder in the ceramic green sheet is 5 to 5.
Add in a range of 30% by weight. When the content of the binder in the green sheet is less than 5% by weight, the moldability of the green sheet is poor and the strength and flexibility are also insufficient. Moreover, when the content exceeds 30% by weight, the flexibility of the green sheet can be obtained, but the workability 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 using reference examples and examples, but the present invention is not limited to these examples. Reference Example 1 Toluene was added as a solvent to a separable flask equipped with a stirrer, a thermometer, a cooling tube, a nitrogen introduction tube, a mixing monomer dropping funnel, and an aggregation initiator dropping funnel.
Add 80 parts by weight and 40 parts by weight of methyl ethyl ketone.
Nitrogen was introduced from the nitrogen introduction tube to create a nitrogen atmosphere inside the flask. Next, 2% by weight of ethyl acrylate, 38% by weight of 2-ethylhexyl acrylate, 4.94% by weight of methyl methacrylate, and cyclohexyl methacrylate were added to the mixing monomer dropping funnel.
100 parts by weight of a mixed monomer consisting of 25% by weight, 30% by weight of lauryl methacrylate and 0.06% by weight of methacrylic acid were charged, and 0.4 parts by weight of azobisisobutyronitrile was charged into the polymerization initiator dropping funnel. 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, then at 60°C for 2 hours, then at 80°C for 2 hours.
After heating for a period of time, the mixture was cooled to prepare a binder a having a solid concentration of 45%, 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. Reference Example 2 Binder b shown in Table 1 was prepared in the same manner as Reference Example 1 except for changing the monomer composition ratio etc.
-h were prepared.

[Table] Reference example 3 Alumina (LS- manufactured by Nikkei Kako Co., Ltd.) was used as an inorganic powder.
23) Low-temperature sintering type powder () consisting of 45% by weight and 55% by weight of borosilicate glass, and a flux consisting of 96% by weight of alumina (AL-45 manufactured by Showa Denko K.K.) and MgO, CaO, and SiO ₂ A high temperature sintered powder () containing 4% by weight 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 for 5 minutes in a Baintoshaker 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 () obtained in Reference Example 3 was added with an acid value of 0.5 and a glass transition temperature of - obtained in Reference Example 1.
35℃, weight average molecular weight 75000, number average molecular weight 30000
Add 12 parts by weight of binder a as a solid content,
Further, 18 parts by weight of a mixed solvent of toluene/methyl ethyl ketone (weight ratio 2/1) was added as a solvent, and the mixture was kneaded in a ball mill for 24 hours to prepare a slurry. This slurry was casted onto a polymer film using the doctor blade method and heated to 80°C.
The green sheet A was dried to obtain a green sheet A having a thickness of 70 μm. In addition, the high temperature sintered powder obtained in Reference Example 3 ()
The thickness is the same except that the thickness is
A green sheet K of 70 μm was obtained. The binder content in each green sheet is 11
It was in weight%. As for the characteristics of the obtained green sheets A and K, the centerline average roughness (Ra) of the green sheet surface was measured using a stylus type and linear scanning method using a surface profile measuring device (Dektak 3030), and a ceramic strength tester (Shimadzu Manufacturer: Servo pulser EHF-ED3-10L)
The tensile stress and elongation of the green sheet until breakage were measured using the following method. In addition, it has flexibility by winding it into a 10mmφ glass rod and 40×40mm with a 0.15mmφ punch.
The punching performance was visually observed when the area was punched with a pitch of 2 mm, and the results are shown in Table 2. The surface shapes of green sheets A and K are shown in Figures 1 and 2.

[Table] *Visual observation ○: Good △: Slightly good ×: Bad Example 2 100 parts by weight of the low temperature sintered powder () obtained in Reference Example 3 had an acid value of 1.0 and a glass transition obtained in Reference Example 2. Temperature -
A green sheet B having a thickness of 50 μm was obtained in the same manner as in Example 1 at 18° C., using binder B having a weight average molecular weight of 80,000 and a number average molecular weight of 27,000. The binder content in this green sheet is 11
It was in weight%. The properties of the obtained green sheet B are shown in Table 2. Example 3 100 parts by weight of the low-temperature sintered powder () obtained in Reference Example 3 was added with an acid value of 1.7 and a glass transition temperature of - obtained in Reference Example 2.
9℃, conventional average molecular weight 60,000, number average molecular weight 25,000
Add 18 parts by weight of binder c as a solid content,
Furthermore, a mixed solvent of toluene/ethyl acetate/isopropanol (weight ratio 6/3/1) was added as a solvent.
1 part by weight of dioctyl phthalate was added as a plasticizer, and the mixture was kneaded in a ball mill for 16 hours to prepare a slurry. This slurry was used in Example 1.
Green sheet C with a thickness of 100 μm in the same manner as
I got it. Further, a green sheet L having a thickness of 90 μm was obtained in the same manner as above except that the high temperature sintered powder () obtained in Reference Example 3 was used. 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 binders d, e, f, g, and h obtained in Reference Example 2 were added to the low-temperature sintered powder () and the high-temperature sintered powder () obtained in Reference Example 3 as shown in Table 2. In the same manner as in Example 1, green sheets D, E, G, H and M having a thickness of 70 μm 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 green sheet H is shown in Figure 3. Comparative Example 2 To 100 parts by weight of the 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 and 6 parts by weight of the binder e were added, and Example 1 was prepared. A green sheet I having a thickness of 70 μm was obtained in the same manner as above. Further, a green sheet N having a thickness of 70 μm was obtained in the same manner as above except that the high-temperature sintered powder () obtained in Reference Example 3 was used. The binder content in each green sheet was 11% by weight. Table 2 shows the properties of the obtained green sheets I and K.
It was shown in Comparative Example 3 10 parts by weight of polyvinyl butyral (PVB) resin (3000-K manufactured by Denki Kagaku Co., Ltd.) was added to 100 parts by weight of the low-temperature sintered powder ( ) obtained in Reference Example 3, and toluene/ethyl acetate was added as a solvent. 36 parts by weight of a mixed solution of /n-butyl alcohol (weight ratio 6/3/1),
4 parts by weight of dioctyl phthalate was added as a plasticizer, and then kneaded in a ball mill for 36 hours to prepare a slurry. This slurry was treated in the same manner as in Example 1 to obtain a green sheet J having a thickness of 120 μm.
In addition, the thickness was reduced in the same manner except that the high temperature sintered powder () obtained in Reference Example 3 was used.
A green sheet O of 150 μm was obtained. The binder content in each green sheet was 9% by weight. The properties of the obtained green sheets J and O are shown in Table 2. Example 4 For green sheets A and K obtained in Example 1 and green sheet B obtained in Example 2, a 40×40 mm area was punched with a 2 mm pitch using a 0.15 mmφ punch.
I punched it out and got a through hole. These through holes were filled with conductive paste to create 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 deviation of green sheet A along the diagonal line of 40×40 mm was 0.054 mm, the deviation of green sheet K was 0.069 mm, and the deviation of green sheet B was 0.057 mm. Comparative Example 4 Green sheets D, E, obtained in Comparative Example 1
The amount of dimensional change was determined in the same manner as in Example 4 for Green Sheets G, B, and M, Green Sheets I and N obtained in Comparative Example 2, and Green Sheets J and O obtained in Comparative Example 3. As a result, the deviations along the diagonal lines of 40 x 40 mm were all 0.15 mm or more, which corresponded to the diameter of the via hole, and had the potential to cause poor conduction. [Effects of the Invention] The green sheets A, B, C, K and L of the present invention have excellent properties in surface smoothness, machinability, flexibility, tensile strength, dimensional stability and thermal decomposition, It is suitable as a material for ceramic substrates, especially ceramic multilayer wiring boards, because it has the characteristics of printability of fine wiring patterns and stability of printed patterns.

[Brief explanation of the drawing]

FIG. 1, FIG. 2, and FIG. 3 are diagrams showing the surface shapes of green sheets A, K, and H, respectively.

Claims (1)

[Scope of Claims] 1. A ceramic green sheet comprising an inorganic powder containing 40% by weight or more of alumina and a (meth)acrylic binder,
The acid value of the acrylic binder is in the range of 0.1 to 2.0,
Weight average molecular weight (Mw) ranges from 50000 to 90000,
The number average molecular weight (Mn) is in the range of 20000 to 40000,
The degree of heterogeneity (V) expressed by the formula (Mw/Mn)-1 is in the range of 1 to 2,
A ceramic green sheet characterized in that the content of the (meth)acrylic binder in the ceramic green sheet is in the range of 5 to 30% by weight. 2. The ceramic green sheet according to claim 1, wherein the center line average roughness (Ra) of the surface of the green sheet is 0.5 μm or less.