JPH10182240A - Production of green sheet for ceramic substrate - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent gelation of slurry and deformation of a green sheet in the manufacture of the sheet containing a glass containing >=5wt.% alkali metal oxide. SOLUTION: The slurry is prepared by adding an acrylic resin having carboxyl group, a solvent and further a silane coupling agent such as a vinyl silane, and epoxy silane, an acryl silane and an amino silane to the glass powder containing >=5wt.% alkali metal oxide such as an alkali silica glass, a soda aluminum silicate glass or a powdery mixture of the glass powder and a ceramic powder. After that, the green sheet for ceramic substrate is manufactured by forming the slurry into a sheet shape and is stably manufactured by allowing the alkali component in the glass to selectively react with the silane coupling agent to suppress the reaction with the acrylic resin.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an improvement of a green sheet for a ceramic substrate which is mainly composed of a mixture of a glass powder and a ceramic powder and is used as an insulating substrate of a multilayer wiring substrate or a package for housing semiconductor elements.

[0002]

2. Description of the Related Art Conventionally, ceramic materials such as alumina have been used as wiring substrates for mounting semiconductor elements and the like, but recently, the dielectric constant and firing temperature are lower than those of alumina. Low resistance Cu, Au, Ag
Glass ceramic sinters have attracted attention as a substrate material that can be applied particularly to the demand for high integration of circuits, because it is excellent in that wiring can be formed with such conductors.

Conventionally, as a method of manufacturing a wiring board using a glass ceramic sintered body as an insulating substrate, a slurry is prepared by adding a forming organic binder and a solvent to a mixed powder composed of a glass powder and a ceramic filler. Thereafter, the slurry is formed by a doctor blade method or the like to produce a green sheet. Then, a conductor paste is printed on the surface of the green sheet to form a conductor pattern,
If desired, after laminating those sheets, the organic binder is decomposed and removed by heating, followed by baking.

[0004] As an organic binder for molding used in producing such a green sheet for a ceramic substrate, an acrylic resin is used in the case of an alumina-based resin, and an acrylic resin is used in the case of a non-oxide-based ceramic such as aluminum nitride. And polyvinyl butyral (PVB) are generally used. However, since PVB has low thermal decomposability when debinding in a non-oxidizing atmosphere, in recent years, it has been shifting to an acrylic resin having excellent thermal decomposability.

On the other hand, glass powder used is Si
Borosilicate glass containing O ₂ or B ₂ O ₃ , SiO
Glass having a main component such as _2- Al ₂ O ₃ -alkaline earth oxide is often used.
In addition to the above main components, there are many cases where an alkali metal oxide is contained for lowering the softening point or yield point of the glass or for controlling other properties of the glass. Recently, it has been proposed to use glass containing a large amount of an alkali metal oxide in order to precipitate a high thermal expansion crystal phase such as lithium silicate as a crystal phase.

[0006]

However, among allyl resins having excellent thermal decomposability, they have a carboxyl group as a functional group, and the resin having such a carboxyl group is used as an organic binder. When a glass containing a large amount of an alkali metal oxide is used as a powder, an interaction occurs between a carboxyl group in the acrylic resin and a cation of an alkali metal in the glass, and as a result, the slurry is easily gelled. And the dispersibility of the slurry is greatly reduced. For this reason, there are problems such as cracks occurring in the produced green sheet, a reduction in the filling rate of the green sheet, and a reduction in product yield due to variation in firing shrinkage.

[0007]

Means for Solving the Problems As a result of repeated studies on the above problems, the present inventors have found that glass-ceramic powder using glass containing a large amount of alkali metal oxide is
When a silane coupling agent is added to a system using an acrylic resin containing a carboxyl group as a functional group as an organic binder, the surface of the glass powder is coated with the silane coupling agent, so that the alkali metal component in the glass is reduced. It was found that it can selectively react with the silane coupling agent, suppress the reactivity with the allyl resin, and produce a green sheet with high yield even in firing without impairing the dispersibility of the slurry. Invented the invention.

That is, according to the method for producing a green sheet for a ceramic substrate of the present invention, an acrylic-based glass powder containing 5% by weight or more of an alkali metal oxide or a mixed powder of the glass powder and the ceramic powder is used. A slurry is prepared by adding and mixing a resin, a solvent and a silane coupling agent, and then formed into a sheet using the slurry. Particularly, as the silane coupling agent, vinyl silane, epoxy silane And at least one of acrylic silane and aminosilane.

[0009]

According to the method for producing a green sheet for a ceramic substrate of the present invention, first, a glass powder containing 5% by weight or more, particularly 7% by weight or more of an alkali metal oxide, or a mixture of this glass powder and a ceramic A mixed powder with the powder is prepared.

As the glass powder to be used, a known glass such as borosilicate glass, SiO ₂ —Al ₂ O ₃ —alkaline earth oxide glass, and an oxide of an alkali metal such as Li, Na, and K may be used. Glass or the like containing not less than% by weight is also used. Also, for those glass powders,
Various ceramic powders can be added to increase the strength of the obtained substrate. Known ceramic powders include Al ₂ O ₃ , SiO ₂ , MgO, mullite, cordierite, wollastonite, forsterite, and zirconia.

According to the present invention, the preferred form is
As the finally manufactured ceramic substrate, for example, a linear thermal expansion coefficient at 40 to 400 ° C. for the purpose of increasing the reliability against thermal cycling when mounted on an external electric circuit board having a high thermal expansion coefficient such as an organic resin 8 to 1
It is desirable to control it within the range of 8 ppm / ° C.

In producing such a high thermal expansion ceramic substrate, alkali silicate glass such as lithium silicate glass and soda aluminum silicate glass is preferably used as the glass powder to be used. The reason is that these glasses can precipitate a lithium silicate crystal or a soda aluminum silicate crystal having a high coefficient of linear thermal expansion of about 13 ppm / ° C. The ceramic powder to be mixed with the above glass powder has a linear thermal expansion coefficient of 6p at 40 to 400 ° C.
By using a ceramic powder composed of a metal oxide of not less than pm / ° C., the coefficient of linear thermal expansion of
It can be easily controlled in the range of 範 囲 18 ppm / ° C.

In addition, in the above-mentioned combination of the glass powder and the ceramic powder, the glass powder before crystallization is 4 times.
The linear thermal expansion coefficient at 0 to 400 ° C is 6 to 18 ppm /
C., particularly preferably 7 to 13 ppm / C. This is because if the coefficient of linear thermal expansion of glass deviates from the above range, a difference in thermal expansion from the ceramic powder occurs, which causes a reduction in the strength of the sintered body.

As the ceramic powder satisfying the above characteristics, for example, forsterite (2MgO.SiO ₂ ,
Linear thermal expansion coefficient 10 ppm / ° C), quartz (SiO ₂ ,
Linear thermal expansion coefficient 15 ppm / ° C), cristobalite (S
iO ₂ , linear thermal expansion coefficient 20 ppm / ° C.), wollastonite (CaO.SiO ₂ , linear thermal expansion coefficient 9 ppm /
° C), petalite (LiAlSi ₄ O ₁₀ , coefficient of linear thermal expansion 8 ppm / ° C), magnesia (MgO, coefficient of linear thermal expansion 9)
ppm / ° C), nepheline (Na ₂ O ₃ .Al ₂ O _3.
SiO ₂ , coefficient of linear thermal expansion 9 ppm / ° C) alumina (Al
₂ O ₃ , linear thermal expansion coefficient 7 ppm / ° C.) and the like.

The yield point of the glass used is 400-8.
The temperature is desirably 00 ° C, particularly 400 to 650 ° C.
This is necessary in order to efficiently remove the organic binder for molding described later in the firing step and to match the firing conditions with the metallization fired simultaneously with the insulating substrate, and if the yield point is lower than 400 ° C. This is because the sintering of the glass is started at a low temperature, so that the binder cannot be decomposed and volatilized, and the binder component remains to affect the properties. On the other hand, if the yield point is higher than 800 ° C., sintering becomes difficult unless the amount of glass is increased, and a large amount of expensive glass is required, which increases the cost of the sintered body.

The mixing ratio of the glass powder and the ceramic powder is desirably 20 to 80% by volume of the glass powder and 80 to 20% by volume of the ceramic powder. The reason why the amounts of the glass and the filler component are limited to the above range is that when the amount of the glass is less than 20% by volume, in other words, when the content of the filler is more than 80% by volume, a sufficient liquid phase is formed even when the glass is used. It is necessary to bake at high temperature because it is not
In that case, the metallization is melted in the simultaneous firing with the metallization of copper or the like. The glass is 80% by volume
If the content is larger, in other words, if the content of the filler 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. In addition, there arises a problem that it cannot be co-fired with the wiring conductor, and the cost of the raw material increases.

It is desirable that the amount of the ceramic powder is appropriately adjusted according to the yield point of the glass used. That is, when the yield point of the glass is as low as 400 to 650 ° C., the sinterability at low temperatures is increased, so that the ceramic powder content is 5%.
A relatively large amount of 0 to 80% by volume can be blended. On the other hand, when the yield point of the glass is as high as 650 to 800 ° C., the sinterability is reduced, so that the content of the glass is 20 to 50% by volume.
It is desirable that the amount is relatively small.

As a component of the alkali silicate glass and the soda aluminum silicate glass, SiO ₂ is an essential component for forming a silicate, and SiO ₂ accounts for 60% of the total amount of the glass.
Alkali metal oxides such as Li ₂ O and Na ₂ O are present in an amount of 5 to 30% by weight, in particular 5 to 2% by weight.
It is desirable to contain it at a ratio of 0% by weight, and that the total amount of SiO ₂ and alkali metal oxide be 65 to 95% by weight based on the total amount of the glass in order to precipitate alkali silicate crystals and soda aluminum silicate crystals. In these glasses, in addition to the above components, alkaline earth oxides such as CaO, SrO, and MgO, Al ₂ O ₃ , TiO ₂ , P
_It suitably contains ₂ O ₅ , ZnO, B ₂ O ₃ , PbO and the like.

According to the present invention, in order to prepare a green sheet for manufacturing a wiring board using the above-mentioned glass powder or a mixed powder of the glass powder and the ceramic powder, the above-mentioned powder or mixed powder is used. An organic resin binder for molding, a plasticizer, and a solvent are added and mixed to prepare a slurry.

In the present invention, an acrylic resin is used as the organic resin binder. This is because acrylic resin
This is because, when the binder is removed in a non-oxidizing atmosphere at the time of simultaneous sintering with Cu or the like as compared with other organic resins, the binder has a good decomposability and a small amount of carbon remains. Further, by having a carboxyl group as a functional group, the dispersibility of the ceramic powder can be improved.

Specific acrylic resins include acrylic resins, acrylate copolymers, methacrylate copolymers, acrylate-methacrylate copolymers, and the like. Are acrylic acid, methyl acrylate, ethyl acrylate, butyl acrylate, cyclohexyl acrylate, 2-ethylhexyl acrylate, methacrylic acid, methyl methacrylate, ethyl methacrylate, butyl methacrylate, cyclohexyl methacrylate, methacrylic acid 2
-Ethylhexyl and the like. By polymerizing a monomer having a carboxyl group on 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 capable of exhibiting 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.

As the solvent, one or more aromatic solvents such as benzene, toluene and xylene can be mentioned. These additives are 5 to 30% by weight of an organic resin binder, 30 to 80 parts by weight of a solvent, and 3 to 20 parts by weight of a plasticizer based on 100 parts by weight of glass powder or a mixed powder of glass powder and ceramic powder. A slurry can be prepared by blending it in a ratio of parts by weight and thoroughly mixing the mixture with a ball mill or the like. The slurry viscosity at this time is suitably from 10 to 50 poise.

In the present invention, it is important that the slurry further contains a silane coupling agent. This silane coupling agent is for coating the surface of the glass powder.
After coating the glass powder with the silane coupling agent in advance, it can be mixed with the ceramic powder or other additives, or added to the prepared slurry. Suitable silane coupling agents include at least one of vinyl silane, epoxy silane, acrylic silane, amino silane, chloro silane and alkoxy silane.

The following effects can be obtained by blending the silane coupling agent. 5% by weight of alkali metal component
The glass contained above has the property of absorbing moisture in the air and adsorbing moisture to the surface. This water does not disappear even after being dried at about 100 ° C., so that the compatibility with an organic solvent such as toluene is reduced, and the carboxyl group of the functional group in the acrylic resin and the cation of the alkali component in the glass are reduced. The interaction between the particles causes the slurry to gel,
The sheet is deformed due to water absorption of the green sheet.
Therefore, by coating the surface of the glass powder with a silane coupling agent, the water absorption of the above-mentioned glass powder is suppressed, and the gelling phenomenon due to the interaction between the carboxyl group of the functional group in the acrylic resin and the alkali metal. As a result, the uniformity of the green sheet can be increased, and the deformation and the like of the sheet can be prevented.

The addition amount of the silane coupling agent is an amount sufficient to coat the surface of the glass powder to be added, and the addition amount W (g) of the silane coupling agent is calculated by the following equation (1).

[0027]

(Equation 1)

Next, using the slurry obtained as described above, the green sheet of the present invention is formed by a known method such as a doctor blade method, a press forming method, a rolling method and a calender roll method. Can be produced. According to the present invention, it is desirable that the filling rate of the green sheet thus obtained, that is, the powder density of the green sheet with respect to the theoretical density of the powder is 50% or more, and cracks, cracks, etc. Must not occur. This means that this filling rate is 50%
If the temperature is lower, the firing shrinkage increases, so that the deformation during firing increases, and the defective rate increases.

In order to specifically manufacture a wiring board using this green sheet, an organic binder, a plasticizer, and a solvent are added to a metal powder suitable for forming a wiring layer on the surface of the green sheet, for example, copper powder. The metallized paste obtained by addition and mixing 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 the firing, the organic resin binder is first 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 and simultaneous baking of Cu or the like in manufacturing a wiring board, the sag point of the glass to be compounded is 400 to 650.
C. and the amount of the ceramic powder is preferably 50 to 80% by volume.

[0031]

Embodiments of the present invention will be described in detail below. 74% SiO ₂ -14% Li ₂ O-4% A by weight as lithium silicate glass
l ₂ O ₃ -2% P ₂ O ₅ -2% K ₂ O-2% ZnO-2
% Na ₂ O (bending point 480 ° C, BET specific surface area 1.5m
_{^{2 / g) 78% SiO 2}} -10% by weight ratio Li ₂ O-4% A
l ₂ O ₃ -2% P ₂ O ₅ -4% K ₂ O-1% B ₂ O _3-
1% Na ₂ O (yield point 650 ° C., BET specific surface area 1.5
m ² / g) were prepared.

As a soda aluminum silicate glass, 34% by weight of SiO ₂ -16% by weight of Na ₂ O-14% by weight
Al ₂ O ₃ -17% P ₂ O ₅ -8% K ₂ O-11% Zn
O (Yield point: 550 ° C., BET specific surface area: 1.5 m ² / g) 57% SiO ₂ -14% Na ₂ O-9% A by weight ratio
l ₂ O ₃ 7% B ₂ O ₃ -3% K ₂ O-6% TiO ₂ -4
% ZrO ₂ (bending point 630 ° C., BET specific surface area 1.5 m
² / g) were prepared. Ceramic powders shown in Table 1 were added to these glasses and mixed.

To 100 g of the mixed powder, 12 g of an acrylic binder (isobutyl methacrylate) containing a carboxyl group as a functional group, 10 g of dibutyl phthalate (DBP) as a plasticizer, and 50 g of toluene as a solvent were added to a ball mill. And mixed for 24 hours to obtain a slurry.
It was molded to a thickness of 0.3 mm.

As a method of treating the silane coupling agent, a method of adding 0.5% by weight of the coupling agent to glass powder and dry-mixing (dry mixing), and a method of adding the coupling agent to the slurry. The method was carried out by two methods of adding and mixing 0.5% by weight (slurry mixing). Samples Nos. 6, 9, 16, and 19 used these together.

The following items were evaluated in the above sheet production process. (Slurry property) The state of the slurry was observed, and a homogeneous slurry was evaluated as ○, and a gel was evaluated as ×. The results are shown in Table 1.

(Water Absorbency of Sheet) The weight increase (mg / cm ² ) after the prepared sheet was held in an atmosphere of 55% to 65% humidity for 48 hours was measured. The results are shown in Table 1.

(Sheet Deformability) The flatness of the prepared sheet was measured by using a three-dimensional measuring machine after being left in an atmosphere of 55% humidity and 65% wave for 48 hours. The results are shown in Table 1.

[0038]

[Table 1]

As is evident from the results in Table 1, the sample No.
As shown in 7, 10, 17, and 20, the slurry gelled, the water absorption was large, and the sheet was deformed.

On the other hand, in the method of the present invention, gelation of the slurry does not occur, and the water absorption is 0.05 mg / mg.
cm ² or less, and good results were obtained with no deformation of the sheet. Further, as a result of removing the binder from the green sheet of the present invention in a nitrogen atmosphere at 730 ° C., no residual carbon was detected in any case, and the binder was excellent in decomposability and removal of the binder.

[0041]

As described in detail above, according to the method of the present invention, when a green sheet is prepared using a powder containing glass containing a large amount of alkali metal, the reactivity of the alkali metal with the allylic resin is reduced. This makes it possible to manufacture a green sheet that does not cause gelation, deformation, or the like of the slurry, and to manufacture a highly reliable wiring board with high yield.

 ──────────────────────────────────────────────────続 き Continuing from the front page (72) Inventor Koichi Yamaguchi 1-4-4 Yamashita-cho, Kokubu-shi, Kagoshima

Claims (3)

[Claims] 1. An acrylic resin having a carboxyl group, a solvent and a silane coupling agent are added to a glass powder containing 5% by weight or more of an alkali metal oxide or a mixed powder of the glass powder and a ceramic powder. A method for producing a green sheet for a ceramic substrate, comprising: preparing a slurry by mixing, and then forming a sheet using the slurry. 2. The method according to claim 1, wherein the silane coupling agent comprises at least one of vinyl silane, epoxy silane, acryl silane and amino silane. 3. The method according to claim 1, wherein the glass powder is an alkali silicate glass,
The method for producing a green sheet for a ceramic substrate according to claim 1, wherein the method comprises one of soda aluminum silicate glass.