JP3510945B2 - Manufacturing method of green sheet for ceramic substrate - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing a green sheet for a ceramic substrate made of glass ceramic which is useful as an insulating substrate for a multilayer wiring substrate or a package for housing semiconductor elements. It is. [0002] Generally, a green sheet for a ceramic substrate can be obtained by uniformly placing a slurry containing ceramic powder on a film by a doctor blade method and drying the slurry. To this slurry, an organic binder, a plasticizer, a solvent, and the like are added in addition to the ceramic powder. [0003] PVB (polyvinyl butyral) has been generally used as an organic binder to be added to ceramic powder. However, when degreasing is performed in a non-oxidizing atmosphere, PVB has poor thermal decomposition properties. In recent years, the use of acrylic resins having excellent thermal decomposability has been shifting to the use of acrylic resins having excellent thermal decomposability, especially acrylic resins having a carboxyl group as a functional group due to problems such as poor appearance and deterioration of electrical characteristics due to residual carbon. Are known as having excellent dispersibility. Recently, as a low-temperature fired substrate material which can be fired simultaneously with a wiring layer made of Cu having good electric conductivity,
A so-called glass-ceramic substrate has been developed in which a mixture of glass powder and ceramic filler powder is molded to produce a green sheet, which is fired. Also in the case of producing a green sheet for a glass ceramic substrate, an acrylic resin is generally used as an organic binder. However, conventional glass ceramics are:
Strength is low, if it is mounted on an external electric circuit board of the organic resin, there is such an electrical connection failure is caused by stress due to difference in thermal expansion coefficient in question, whereas, the applicant, Li ₂ An alkali silicate glass containing an alkali metal such as O and a filler powder such as forsterite were added and fired to precipitate an alkali metal silicate, and a glass ceramic material with high strength was proposed. However, when a green sheet of a glass ceramic substrate is produced, an acrylic resin having excellent thermal decomposability, for example, having a carboxyl group as a functional group, is used as an organic binder, and a glass raw material powder is used. When an alkali silicate glass as described above is employed, an interaction occurs between a carboxyl group of a functional group in the acrylic resin and a cation of an alkali component in the glass,
As a result, the slurry is easily gelled, and the dispersibility of the slurry is reduced, so that cracks are generated in the sheet, the filling rate of the green sheet is reduced, and the product yield is reduced due to variation in shrinkage during firing. There was a problem. The inventors of the present invention have studied the above problems and found that alkali silicate glass is more likely to dissolve water vapor during the manufacturing process than alumina. The water content is high, the water content is found to tend to increase as the specific surface area of the glass increases, the specific surface area of the alkali silicate glass powder used is controlled, and the water content in the powder is controlled to be small, The present inventors have found that gelation of the slurry can be prevented, and have reached the present invention. That is, in the present invention, a slurry is prepared by adding a binder and a solvent comprising an acrylic resin containing a carboxyl group as a functional group to a mixed powder of an alkali silicate glass powder and a ceramic powder, and forming the slurry into a sheet. And producing a green sheet, wherein the alkali silicate glass has a BET specific surface area of 0.5 to 3 m.
² / g and a water content of 15000 ppm or less, and the alkali silicate glass powder has a yield point of 400 ° C. to 800 ° C. According to the present invention, in producing a green sheet using a mixture of an alkali silicate glass powder and a filler powder, the BET specific surface area of the alkali silicate glass powder is set to 0.5 to 3 m ² / g. , Its water content is 15000p
pm or less, ionization of the carboxyl group by water of the acrylic resin containing a carboxyl group can be suppressed, the slurry can be prevented from gelling, the sheet filling rate can be increased, and cracks in the sheet can be reduced. This can significantly improve the yield during green sheet production. Thus, the glass ceramic substrate can be manufactured at low cost. [0010] According to the method for producing a glass ceramic sintered body of the present invention, a glass powder and a filler powder are used as raw materials. According to the present invention, the glass powder is made of lithium. An alkali silicate glass such as a silicate glass or a soda aluminum silicate glass is used. The reason for using such an alkali silicate glass is that the coefficient of thermal expansion is about 13 in order to reduce the difference in thermal expansion when mounted on an organic resin-based external electric circuit board.
This is for increasing the thermal expansion of the glass ceramic sintered body itself by precipitating lithium silicic acid or soda aluminum silicic acid having a high thermal expansion coefficient of ppm / ° C. According to the present invention, it is important that the alkali silicate glass has a BET specific surface area of 0.5 to ³ m ² / g. This means that the water content in the glass is 1500
When the specific surface area is less than 0.5 m ² / g, it is not possible to obtain a dense sintered body after firing, and when the specific surface area exceeds 3 m ² / g, the glass is required. Has a water content of more than 15000 ppm, the slurry is apt to gel, and the yield during the production of green sheets is reduced. In particular, it is desirable that the glass has a BET specific surface area of 1 to 2.5 m ² / g and a water content of 10,000 ppm or less. Since the water content tends to increase as the BET specific surface area increases, the water content is controlled to 15000 ppm or less by adjusting the BET specific surface area to 3 m ² / g or less by grinding glass. it can. The glass powder has a yield point of 400.
C. to 770.degree. C. is desirable. This is because when molding a mixture consisting of glass and filler, a molding binder such as an organic resin is added. This binder is efficiently removed, and the firing conditions are matched with the metallization fired simultaneously with the insulating substrate. If the yield point is lower than 400 ° C., the glass starts sintering at a low temperature. For example, the sintering start temperature of Ag, Cu, etc. is about 600 to 800 ° C. This is because simultaneous firing cannot be performed, and densification of the molded body starts at a low temperature, so that the binder cannot be decomposed and volatilized, resulting in a binder component remaining and affecting properties. On the other hand, if the yield point is higher than 770 ° C., sintering becomes difficult unless the compounding amount of the glass is increased to 50% by volume or more, so that a large amount of expensive crystalline glass is required, and the cost of the sintered body is increased. Will be. Preferably the yield point is 4
00-650 ° C. As the glass used in the present invention, specifically, an alkali metal oxide such as Li ₂
Alkali silicate glass containing O or Na ₂ O in an amount of 5 to 30% by weight, particularly 5 to 20% by weight is used. In order to increase the strength, alkali silicate or alkali aluminum silicate is preferably formed. in order to, SiO ₂
Is present in a proportion of 60 to 85% by weight in the total amount of glass, and Si
65 to 95% by weight of O ₂ and alkali metal oxide in total
Al ₂ O ₃ , MgO, TiO ₂ , Na
_Use alkali silicate glass containing at least one of ₂ O, K ₂ O, ZnO, P ₂ O ₅ , F, CaO, etc., particularly crystallized glass from which alkali silicate or alkali aluminum silicate can be precipitated in the sintering process. It is desirable. In these glasses, B ₂ O ₃ is desirably 1% by weight or less. The glass powder used has a coefficient of linear thermal expansion at 40 ° C. to 400 ° C. of 6 to 18 ppm / ° C., especially 7 to 13 p.
pm / ° C. The reason why the content of the alkali metal oxide in the glass is limited to the above range is that if the content is less than 5% by weight, the amount of crystals of alkali silicic acid generated during sintering decreases, resulting in high strength and high thermal expansion. This is because good properties as a substrate cannot be expected, such as a dielectric loss exceeding 100 × 10 ^{−4 if the} content is more than 30% by weight. On the other hand, the filler powder mixed with the above-mentioned glass powder includes alumina, silica, quartz, quartz, cristobalite, forsterite, mullite, magnesia, petalite, spinel, wollastonite, nepheline, enstatite, garnite and the like. Among these, as a metal oxide having a linear thermal expansion coefficient of 6 ppm / ° C. or more at 40 ° C. to 400 ° C., forsterite (2MgO · SiO ₂ , linear thermal expansion coefficient 1)
0 ppm / ° C), quartz (SiO ₂ , linear thermal expansion coefficient 1)
5 ppm / ° C.), cristobalite (SiO ₂ , coefficient of linear thermal expansion 20 ppm / ° C.), wollastonite (CaO ·
SiO ₂ , linear thermal expansion coefficient 9 ppm / ° C.), petalite (LiAlSi ₄ O ₁₀ , linear thermal expansion coefficient 8 ppm / ° C.),
Magnesia (MgO, linear thermal expansion coefficient 9 ppm / ° C), nepheline (Na ₂ O · Al ₂ O ₃ · SiO ₂ , linear thermal expansion coefficient 9 ppm / ° C), alumina (Al ₂ O ₃ , linear thermal expansion coefficient 7 ppm / ° C) ) Etc., so that the coefficient of linear thermal expansion of the entire sintered body is 8 to 18 ppm / ° C.
Can be easily controlled within the range. If the coefficient of thermal expansion of each powder deviates from the above range as described above, a difference in thermal expansion between the glass powder and the ceramic powder occurs, which causes a reduction in the strength of the sintered body. If the coefficient of linear thermal expansion of the ceramic powder is less than 6 ppm / ° C., it may be difficult to make the coefficient of linear thermal expansion of the sintered body 8 to 18 ppm / ° C. The above-mentioned alkali silicate glass powder and filler powder are mixed at a ratio of 20 to 80% by volume of glass powder and 80 to 20% by volume of filler powder. This is because the glass used in the present invention has a shrinkage onset temperature of 700 ° C. or lower when no filler is added, and a part of the glass is melted at 800 ° C. or higher, so that it is difficult to simultaneously form a metallized wiring layer. It is. However, by mixing the glass powder at a ratio of 20 to 80% by volume and the filler powder at a ratio of 80 to 20% by volume, a liquid phase is formed at the firing temperature for crystal precipitation and liquid phase sintering of the filler component. Can be. In addition, since the shrinkage start temperature of the entire molded body can be increased, the co-firing condition with the metallized wiring layer can be matched by the type of metallization used by adjusting the content of the filler. The reason why the amounts of the glass and the filler component are limited to the above ranges is that the glass amount is less than 20% by volume,
In other words, if the filler component is more than 80% by volume, a sufficient liquid phase is not generated even if the glass is used, so that it is necessary to fire at a high temperature. In that case, the metallization is melted in the simultaneous firing of the metallization. Also, if the glass is 8
If the content is more than 0% by volume, in other words, if the filler component is less than 20% by volume, the properties of the sintered body greatly depend on the properties of the glass, making it difficult to control the material properties and lowering the sintering start temperature. Therefore, there arises a problem that it cannot be fired simultaneously with the wiring conductor, and the cost of the raw material also increases. In order to reduce the raw material cost, it is preferable to reduce the content of expensive glass, particularly, 20 to 50% by volume of glass powder, 50 to 80% by volume of filler powder, and 20 to 40% by volume of glass powder. And 60 to 80% by volume of the filler powder. In the above composition, the amount of the filler component is desirably adjusted appropriately according to the yield point of the glass. That is, the yield point of glass is 400 ° C. to 65 ° C.
When the temperature is as low as 0 ° C., the sinterability at a low temperature is increased, so that the content of the filler can be relatively large as 50 to 80% by volume.
On the other hand, the yield point of crystalline glass is 650 ° C. to 77 ° C.
If the temperature is as high as 0 ° C., the sinterability is reduced. Therefore, the content of the filler is desirably relatively low, ie, 20 to 50% by volume. In order to produce a green sheet for producing a wiring board using the above glass powder and filler powder, an appropriate organic resin binder, a plasticizer and a solvent are added to the mixed powder mixed in the above ratio. Add and mix to prepare a slurry. An acrylic resin is used as an organic resin binder to be used. This is because the acrylic resin has good decomposability and removal of carbon in the case of removing the binder in a non-oxidizing atmosphere at the same time as co-firing with Cu or the like compared to other organic resins, and there is almost no carbon residue. It is.
Further, by having a carboxyl group as a functional group, dispersibility of the ceramic powder can be improved. Specific examples of the acrylic resin include an acrylic resin, an acrylate copolymer, a methacrylate copolymer, an acrylate-methacrylate copolymer, and the like. Acrylic acid, methyl acrylate, ethyl acrylate, butyl acrylate, cyclohexyl acrylate,
2-ethylhexyl acrylate, methacrylic acid, methyl methacrylate, ethyl methacrylate, butyl methacrylate, cyclohexyl methacrylate, 2-methacrylic acid
Ethylhexyl and the like. By polymerizing a monomer having a carboxyl group with these monomers, an acrylic resin having a carboxyl group as a functional group can be obtained. As the plasticizer, it is desirable to select a plasticizer having a high plasticizing efficiency, that is, a plasticizer which can exhibit plasticity by adding a small amount thereof, in order to avoid deterioration of the flexibility of the green sheet. As a plasticizer satisfying this condition, adipates or phthalates may be used. Examples of the solvent include aromatic solvents such as benzene, toluene and xylene; alcohol solvents such as methanol, ethanol, isopropyl alcohol (IPA) and butanol; acetone, methyl ethyl ketone;
It can be used alone or in a mixture of ketone solvents such as methyl isobutyl ketone. These include 5 to 30% by weight of the binder and 3% of the plasticizer based on the glass-ceramic mixed powder.
A slurry can be prepared by mixing the solvent at a ratio of 20 to 20% by weight and a solvent at a ratio of 30 to 80% by weight, and sufficiently mixing the mixture with a ball mill or the like. At this time, the viscosity of the slurry is 10
~ 50 poise is appropriate. Next, a sheet-like molded body (green sheet) can be produced from the obtained slurry by a known method such as a doctor blade method, a press molding method, a rolling method, and a calender roll method. . According to the present invention, the filling rate of the green sheet obtained as described above, that is, the powder density of the green sheet with respect to the theoretical density of the powder is 50% or more, and the sheet has cracks and appearances in appearance. It is necessary that cracks and the like do not occur. If this filling ratio is lower than 50%, firing shrinkage becomes large. Therefore, non-defective sheets are selected by this filling ratio and appearance inspection. In order to specifically manufacture a wiring board using this green sheet, a metal powder suitable for forming a wiring layer on the surface of the green sheet, for example, copper powder, an organic binder, a plasticizer, A metallized paste obtained by adding and mixing a solvent is applied by a screen printing method, an offset printing method, or the like. Further, if necessary, after forming a through hole and filling with a metallizing paste, a plurality of green sheets are laminated, pressed and fired. In firing, first, the organic resin binder is removed. When Cu is used as the wiring conductor, the firing is performed in a nitrogen atmosphere at 100 to 800 ° C. containing water vapor. Subsequent firing is performed at 850 to 1050 ° C.
_2. Performed in a non-oxidizing atmosphere such as Ar. In particular, when performing metallization of Cu or the like and simultaneous baking in the production of a wiring board, the sag point of the compounded glass is 400 ° C. to 65 ° C.
At 0 ° C., the content of the filler is desirably 50 to 80% by volume. Example 1 As alkali silicate glass, lithium silicate glass 74% SiO ₂ -14% Li ₂ O-4% Al ₂ O ₃ -2 by weight ratio
% P ₂ O ₅ -2% K ₂ O-2% ZnO-2% Na ₂ O
(Yield point 480 ° C) Soda aluminum silicate glass 34% SiO ₂ -15% Na ₂ O -15% Al ₂ O ₃ −
17% P ₂ O ₅ -8% K ₂ O-11% ZnO (Yield point 6
(00 ° C.), a plurality of glasses having different BET specific surface areas and different water contents were prepared. The BET specific surface area of these glasses was measured by a gas adsorption method, and the water content was measured by a thermal desorption gas analysis method. Various filler powders were weighed and mixed with this glass so as to have the composition shown in Table 1. Further, for 100 g of the mixed powder, 12 g of an organic resin of isobutyl methacrylate (i-BMA) or normal butyl methacrylate (n-BMA) containing a carboxyl group as a functional group, and dibutyl phthalate (DBP) as a plasticizer were used. Was added as a solvent, 55 g of toluene as a solvent, and 5 g of isopropyl alcohol were added and mixed with a ball mill for 24 hours to form a slurry. The viscosity of the obtained slurry was measured at a shear rate of 10S ^-1 . This slurry was prepared by the doctor blade method for 0.2
A green sheet was formed by molding to a thickness of mm. In addition, as an organic resin, the samples No. 1 to 14
MA was used, and the above n-BMA was used for Sample Nos. 15 to 19, respectively. The obtained green sheet was evaluated for sheet filling rate. The filling rate was determined by cutting a green sheet into a square of 35 mm × 30 mm, measuring the thickness and weight to determine the green sheet density, and determining the filling rate from the specific gravity of the raw material powder. In addition, 20 sheets were prepared for each sample, and as a result of the appearance inspection of the sheets, the number of the cracks observed was examined. The results are shown in Table 1. [Table 1] As is clear from the results in Table 1, the samples No. 3, 6, 10, 1 having a BET specific surface area of more than 3 m ² / g.
Each of 3, 14, 18, and 19 has a water content of 15000.
ppm, and as a result, the viscosity of the slurry was as high as 50 poise or more, the filling rate was low, and many cracks were observed in the appearance inspection. On the other hand, all of the samples of the present invention have a slurry viscosity of 50 poise or less and a filling rate of 50% or more, almost no occurrence of cracks is observed, and a sheet with a high yield can be produced. there were. Further, with respect to the green sheet of the present invention,
As a result of removing the binder in a nitrogen atmosphere at 730 ° C., no residual carbon was detected in any case, and the binder was excellent in decomposing and removing properties. As described in detail above, according to the present invention, in the production of a glass ceramic substrate comprising an alkali silicate glass and a filler, the specific surface area and the water content of the alkali silicate glass are controlled. A green sheet having a good filling rate and free from cracks or the like can be obtained. Thereby, the yield at the time of manufacturing the green sheet can be improved, and an inexpensive substrate can be manufactured.

(56) References JP-A-64-51346 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) C04B 35/00-35/22

Claims (1)

(57) [Claim 1] A slurry obtained by adding a binder and a solvent comprising an acryl-based resin having a carboxyl group as a functional group to a mixed powder of an alkali silicate glass powder and a ceramic powder. prepared, a method of manufacturing a green sheet by molding the slurry into a sheet, BET specific surface area of the alkali silicate glass 0.5-3 m ² / g, moisture content 1
A method for producing a green sheet for a ceramic substrate, wherein the content is 5000 ppm or less.