Method for production of ceramic circuit board

A method for producing a ceramic circuit board comprising the steps of (i) forming a conductor portion of the ceramic circuit board by printing a conductive paste composition on a ceramic base plate for the circuit board and then (ii) firing the ceramic base plate and the conductive paste composition together, wherein a copper-base composition comprising a copper powder and 0.5 to 5 parts by weight, based on 100 parts by weight of copper powder, of at least one organo metallic compound capable of forming an inorganic compound or compounds, respectively, when fired in an inert atmosphere, is used as the conductive paste composition. The combined use of isopropyl tridodecylbenzene sulfonyl titanate and isopropyl triisostearoyl titanate greatly improve the flowability of the copper-base conductive paste composition.

BACKGROUND OF THE INVENTION 
1. Field of the Invention 
The present invention relates to a method for producing a ceramic circuit 
board More specifically, it relates to a method for producing a multilayer 
glass ceramic copper circuit board having an improved printing property 
and adhesion property, without adversely affecting the conditions of 
through-holes therein, by using a copper-base conductive paste composition 
2. Description of the Related Art 
Glass ceramic composite multilayer circuit boards having superior 
electrical characteristics can include a copper conductive layer, since 
the boards can be fired or baked at a relatively low temperature (e.g., 
1000.degree. C. or less) to greatly improve the conductivity of the 
boards. However, known copper-base pastes used to form conductors have 
been developed mainly for use with alumina circuit boards and, therefore, 
have not been directly applied to multilayer glass-ceramic circuit boards. 
Nevertheless, the development of glass-ceramic circuit boards having good 
electric characteristics is progressing and, therefore, there is a need to 
develop conductive copper paste compositions suitable for use in 
glass-ceramic composite circuit boards in the form of a green sheet before 
firing, having good printing properties, excellent adhesion properties, 
and further, capable of entirely filling through holes in the boards. 
Various conductive paste compositions are known and used in the art. For 
example, paste compositions containing a conductor component of a noble 
metal such as gold, silver, and palladium dispersed in organic vehicles, 
paste compositions containing a conductor component of a high-melting 
point metal such as tungsten and molybdenum dispersed in organic vehicles, 
and paste compositions containing a conductor component of copper 
dispersed in organic vehicles 
Of the above-mentioned conductive paste compositions, the conventional 
copper paste compositions which can be fired at a relatively low 
temperature generally contain copper powder, glass powder, and an organic 
vehicle. Namely, generally 1% to 5% by weight, based on the weight of the 
copper powder (i.e., conductor component), of the glass powder is 
contained, to provide the required adhesion strength with the binder and 
the substrate, and the organic vehicle is contained so that the glass 
powder can be made into a paste by mixing therewith. 
For example, JP-A-59-155988 (Kokai) discloses a method for producing a 
conductive paste composition for coating a thicker film or layer 
containing gold, silver, copper, platinum, palladium, nickel, and/or 
aluminum powder and an organic vehicle by mixing in the presence of a 
titanate coupling agent However, this paste is used only for alumina 
substrates and the titanate coupling agent is used to prevent the 
formation of metal flakes. 
JP-A-58-74759 (Kokai) discloses a conductive copper paste composition 
containing copper powder, a thermosetting resin binder, an unsaturated 
fatty acid, and an organic titanium compound However, the organic titanium 
compound is used, together with the unsaturated fatty acid, to ensure a 
fine dispersion of the copper powder and to provide a stable and good 
conductivity. 
U.S. Pat. No. 4,503,090 discloses a thick film resistor circuit formed from 
a paste containing copper, silver and aluminum, a binder, ethyl cellulose, 
and a solvent. 
When the above known conductive paste compositions are used as a conductor 
component, however, the following disadvantages arise. 
(1) The paste compositions containing a noble metal as a conductor 
component are expensive and, therefore, are not preferable in practice 
(2) The paste compositions containing a metal having a high melting point 
cannot be fired at a relatively low temperature and, since the resistivity 
of the conductor component is high, the conductor has a poor quality. 
(3) Although the development of paste compositions having copper as the 
conductor component is very desirable, the properties when printed on a 
green sheet of glass-ceramic composite substrate are poor and the adhesion 
strength after the integral firing is low. Furthermore, although it has 
been proposed that a small amount of glass having a low melting point be 
added, to improve the adhesion strength, this is not substantially 
effective for glass-ceramic composite substrates. Furthermore, when a 
small amount of glass powder having a low melting point is added, the 
copper powder has little or no flowability, and during the printing, the 
copper-base paste composition is not easily filled into through-holes in a 
glass-ceramic green sheet. 
SUMMARY OF THE INVENTION 
Accordingly, an object of the present invention is to solve the 
above-mentioned problems of the prior art and to provide a method for 
producing a ceramic circuit board, by using a copper-base conductive paste 
composition, having improved printing and adhesion properties, and having 
other properties such that the copper-base conductive paste composition 
can be easily filled into through holes in a glass-ceramic green sheet 
before firing. 
Other objects and advantages of the present invention will be apparent from 
the following description. 
In accordance with the present invention, there is provided a method for 
producing a ceramic circuit board comprising the steps of (i), forming a 
conductor portion of the ceramic circuit board by printing a conductive 
paste composition on a ceramic base plate for the ceramic circuit boards 
and then (ii) firing the ceramic base plate and the conductive paste 
composition, wherein a copper-base composition comprising a copper powder 
as a main component, and 0.5 to 5 parts by weight, based on 100 parts by 
weight of copper powder, of at least one organo metallic compound capable 
of forming an inorganic compound or compounds, respectively, when fired in 
an inert atmosphere, is used as the conductive paste composition. 
In accordance with the present invention, there is also provided a method 
for producing a multilayer ceramic circuit board comprising the steps of 
(i), forming a conductor portion of the ceramic circuit board by printing 
a conductive paste composition on the circuit board and then (ii) firing 
the combined board and pastes, wherein a composition comprising a copper 
powder and a vehicle composed of a binder, an organic 
thixotropicity-providing agent, an alcoholic solvent, and 0.5 to 3.5 parts 
by weight of isopropyl tridodecylbenzene sulfonyl titanate and 0.5 to 3.5 
parts by weight of isopropyl triisostearoyl titanate, both based on 100 
parts by weight of the copper powder, is used as the conductive base board 
.

DESCRIPTION OF THE PREFERRED EMBODIMENTS 
As mentioned above, according to the present invention, a copper-base paste 
composition comprising 0.5 to 5 parts by weight, based on 100 parts by 
weight of copper powder, of an organo metallic compound, especially an 
organic titanate or aluminate compound capable of forming an inorganic 
compound, especially an inorganic titanium or aluminum compound (e.g., 
TiO.sub.2 or Al.sub.2 O.sub.3), respectively, when fired in an inert 
atmosphere (e.g., an inert gas or nitrogen) is used. 
The copper powder used in the paste composition may be any copper powder 
usually used in copper-base conductive paste compositions, such as copper 
powders having an average particle size of 0.1 to 10 .mu.m. 
The organic titanate compounds usable in the present invention include, for 
example, isopropyl tridodecylbenzene sulfonyl titanate, isopropyl 
triisostearoyl titanate, isopropyl tris(dioctyl pyrophosphate) titanate, 
bis(dioctyl pyrophosphate)oxyacetate titanate, isopropyl 
tri(N-aminoethyl-aminoethyl)titanate, tetraisopropyl bis(dioctyl 
phosphite)titanate, bis(dioctyl pyrophosphate) ethylene titanate, 
tetraoctyl bis(ditridecyl phosphite) titanate, and isopropyl tri(dioctyl 
phosphate) titanate. The preferable compounds are isopropyl 
tridodecylbenzene sulfonyl titanate and isopropyl tris(dioctyl 
pyrophosphate) titanate. 
The organic aluminate compounds usable in the present invention include, 
for example, acetoalkoxy aluminum diisopropylate having the following 
formula: 
##STR1## 
The organic titanate or aluminate compounds is used in an amount of 0.5 to 
5 parts by weight, preferably 0.5 to 1 part by weight, based on 100 parts 
by weight of the copper powder. When the amount of the organic titanate or 
aluminum compound is less than 0.5 parts by weight, the desired paste 
composition is not obtained. This is thought to be because the entire 
surfaces of the copper powder particles are not coated by the organic 
titanate or aluminate compound. Conversely, when the amount is more than 5 
parts by weight, the excess amount of the organic compound remains in the 
paste composition and will cause voids to appear in the conductor. 
The copper-base conductive paste composition according to the present 
invention can be prepared by first dissolving the organic titanate or 
aluminate compound in a solvent such as an alcoholic high boiling point 
solvent (e.g., terpineol, 2-butoxyethanol, 2-hexyloxyethanol, 
4-methylcyclohexanol, 3-methylcyclohexanol, and/or 2-hexyloxy ethanol) and 
then thoroughly mixing the resultant organic vehicle with the copper 
powder, while stirring, to produce the desired copper-base conductive 
paste composition in the form of a dispersion having a viscosity of 10,000 
to 200,000 c.p. 
The copper-base conductive paste composition according to the present 
invention can be applied to a glass-ceramic substrate such as ceramic 
composites of borosilicate glass and alumina, zirconia, or magnesia in any 
conventional manner. 
According to the present invention, since the entire surfaces of the copper 
powder particles in the copper-base paste composition are covered with, 
for example, the organic titanate having a monoalkoxy group, the 
flowability between the copper powder particles is good. Furthermore, a 
green sheet of a glass-ceramic composite substrate to be printed contains 
a large amount of a solvent, and thus the wetability of the conductive 
paste composition to the green sheet is increased. Furthermore, since the 
organic titanate typically represented by isopropyl tridodecylbenzene 
sulfonyl titanate is converted to rutile typetitanium dioxide (TiO.sub.2) 
when the copper-base paste composition is fired in an inert atmosphere 
such as nitrogen, the adhesion strength at the interface between the 
copper conductor and the glass-ceramic substrate is greatly improved. In 
the case of the organic aluminate compound, aluminum oxide(Al.sub.2 
O.sub.2) is formed. 
FIG. 1 shows a typical process block diagram illustrating the basic steps 
for forming a copper base paste of the present invention. An example of a 
process diagram illustrating the basic steps for manufacturing a 
multilayer ceramic circuit board with copper conductor of the present 
invention is shown in FIG. 2. 
It is feasible that the multilayered structure be formed such that the 
patterns of copper-based conductors and the glass-ceramic paste are 
alternately printed on a sintered ceramic substrate, the glass-ceramic 
paste layers having openings to form through-holes therethrough. 
It is advantageous that the multilayered structure be formed such that a 
plurality of composite layers is laminated, each layer being produced by 
printing patterns of copper-based conductors on a glass-ceramic green 
sheet, which contains the thermally depolymerizable resin and minute 
copper balls are filled in a row penetrating or by printing copper base 
paste to the opening as through-holes through the glass-ceramic green 
sheet. It is applicable that firing process comprises prefiring the 
multilayer structure in an inert atmosphere containing water vapor, the 
partial pressure of which is 0.005 to 0.3 atmosphere, at a temperature at 
which the thermally depolymerizable resin is eliminated; and firing the 
multilayer structure in an inert atmosphere containing no water vapor at a 
temperature below the melting point of copper so as to sinter the 
glassceramic. 
FIG. 3 is a graph of the adhesion strength of the copper conductor pattern 
to glass-ceramic substrate and the sheet resistivity of the copper 
conductor pattern, after sintering, as a function of concentration of the 
coupling agent in the copper base paste. Sintering was done prefiring 
870.degree. C..times.4 hr. in an inert atmosphere containing water vapor 
and then firing 1020.degree. C..times.4 hr. in an inert atmosphere not 
containing water vapor. The composition of the copper base paste used in 
FIG. 3 was as follows. 
______________________________________ 
Composition of Cu Paste 
Ingredient Maker Rate (phr) 
______________________________________ 
Cu Powder MITSUI KINZOKU 100.0 
(.phi.1.25) 
PMMA MITSUBISHI 1.5 
Caster oil NODA WAX 0.3 
Terpineol WAKOH JUNYAKU 10.5 
Coupling* AJINOMOTO 1.0 
Agent 
______________________________________ 
*(CH.sub.3).sub.2 CHOTi(OSO.sub.2 C.sub.6 H.sub.4 C.sub.12 H.sub.25).sub. 
Isopropyl tridodecylbenzene sulfonyl titanate 
According to the second aspect of the present invention, two types of 
organic titanate coupling agents, e.g., 0.5 to 3.5 parts by weight, 
preferably 0.5 to 1 part by weight, of isopropyl tridodecylbenzene 
sulfonyl titanate and 0.5 to 3.5 parts by weight, preferably 0.5 to 1 part 
by weight of isopropyl triisostearoyl titanate, both in relation to 100 
parts by weight of the copper powder, are contained in the copper-base 
conductive paste composition, without using a glass frit, which has an 
adverse affect on the hole filling properties thereof. The isopropyl 
triisostearoyl titanate contained in the composition improves the 
flowability of the copper powder during the hole filling, and the 
isopropyl tridodecylbenzene sulfonyl titanate improves the adhesion 
properties to the glass-ceramic substrate, as mentioned above. 
Thus, the flowability between the copper powder particles is improved by 
the inclusion of the above-mentioned two types of the titanate coupling 
agents and, therefore, when the conductive paste composition is made to 
flow into a through-hole in the green sheet during the printing, since the 
flowability of the copper-base paste composition is improved and, 
furthermore, the penetration of the organic vehicle into the green sheet 
is prevented, the copper-base paste composition can easily flow into the 
through-hole without causing voids. Furthermore, the adhesion strength is 
remarkably improved by the action of the two types of the titanate 
coupling agents, compared to such paste compositions not containing the 
titanate coupling agents. 
In the paste composition, according to the present invention, a vehicle 
containing any connectional ingredients such as binders, 
thiotropicity-providing agents, solvents, and other optional ingredients 
may be used. These ingredients may be used alone or in any mixtures 
thereof. The amounts of a vehicle in the composition is preferably 5 to 30 
parts by weight based on 100 parts by weight of the copper powder. 
As mentioned above, and as explained below, according to the present 
invention, the printing of the copper-base paste composition on the 
glass-ceramic substrate is remarkably improved and the adhesion between 
the substrate and the conductor is excellent. Furthermore, especially 
according to the second aspect of the present invention, a conductor 
without voids can be obtained, without causing a penetration of the 
solvent and without an adverse affect on the flowability of the powder 
particles during the filling of the holes in the board. 
EXAMPLES 
The present invention now will be further illustrated by, but is by no 
means limited to, the following Examples and Comparative Examples, wherein 
all parts and percentages are expressed on a weight basis unless otherwise 
noted. 
EXAMPLE 1 
The copper-base paste compositions having the following formulations listed 
in Table 1 according to the present invention were prepared. 
TABLE 1 
______________________________________ 
Formulation of Copper-Base Paste 
Copper Paste Sample No. 
Component 1 2 3 
______________________________________ 
Copper powder (1 .mu.m) 
100 parts 100 parts 
100 parts 
Organic vehicle*.sup.1 
13 parts 13 parts 
13 parts 
Organic titanate*.sup.2 
0.5 parts 1.0 parts 
1.5 parts 
Viscosity (poise) 
400-600 400-600 400-600 
______________________________________ 
*.sup.1 : Mixture of terpinol, poly(methyl methacrylate) resin, and casto 
oil 
*.sup.2 : Isopropyl tridodecylbenzene sulfonyl titanate 
The copper-base paste composition Sample Nos. 1 to 3 were prepared as 
follows. 
That is, the isopropyl tridodecylbenzene sulfonyl titanate was dissolved in 
a high boiling point alcoholic solvent (i.e., terpineol) at a temperature 
of 25.degree. C., followed by adding thereto a thixotropy providing agent 
(i.e., castor oil) and an organic depolymerizable binder (PMMA). Thus, the 
organic vehicle was prepared. The copper powder having a particle size of 
1.5 .mu.m was mixed into the organic vehicle and the resultant mixture was 
mixed by a wet ball mill mixing at room temperature for 48 hours, followed 
by drying and then mixing or kneading in a three-roll mill. 
The copper-base paste composition Sample Nos. 1 to 3 were evaluated with 
respect to their characteristics by using a glass-ceramic substrate 
composed of borosilicate glass and alumina as follows. 
That is, the above-prepared copper-base paste composition Sample Nos. 1 to 
3 were applied on the surfaces of green sheets of borosilicate 
glass-alumina composite ceramic having a thickness of 300 .mu.m in a 
conventional manner under the conditions of a size of a screen mask of 300 
mesh, a pattern width of 80 .mu.m, and a squeegee hardness of 80. 
The printed paste composition was then dried in a constant temperature bath 
at a temperature of 70.degree. C. for 30 min to evaporate the solvent 1 
the printed green sheet was then pressed in a mold under the conditions of 
10 MPa.times.100.degree. C..times.30 min. The resultant laminate having 30 
layers was heated from room temperature at a rate of 
80.degree.-100.degree. C./hr and allowed to stand for 5 hours at a maximum 
temperature of 850.degree. C in a nitrogen atmosphere containing water 
vapor, followed by allowing to cool to room temperature. Thereafter, the 
resultant laminate was heated from room temperature to a maximum 
temperature of 1000.degree. C. at a rate of 80.degree. C. to 100.degree. 
C./hr and allowed to stand at the maximum temperature for 4 hours in a 
nitrogen atmosphere not containing water vapor, followed by allowing to 
cool to room temperature. As mentioned above, a typical manufacturing 
process of the multilayer ceramic board with the copper conductor is shown 
in FIG. 2. 
The results are shown in Table 2. 
TABLE 2 
______________________________________ 
Printing Property of Copper-Base Paste 
Composition to Borosilicate Glass-Alumina 
Composite Ceramic Green Sheet 
Copper Minimum Pattern 
Paste Width to Be Printed 
Sample (.mu.m) Levelling Property*.sup.1 
______________________________________ 
1 80 Good 
2 80 Good 
3 80 Good 
.sup. 4*.sup.2 
100 Poor 
.sup. 5*.sup.3 
200 Poor 
.sup. 6*.sup.4 
100 Poor 
______________________________________ 
*.sup.1 : After printing, soft Xray was irradiated from the upper side of 
the print, conductive laminate and the transmission conditions of the Xra 
was taken in photographs to use, after enlargement, for the evaluation of 
the surface undulation conditions of the conductive laminate. This 
evaluation method is based on the that the transmission conditions of sof 
Xray depends upon the thickness of the electrically conductive laminate. 
*.sup.2 : The same paste as that of Sample No. 2, except that no isopropy 
tridodecylbenzene sulfonyl titanate was contained 
*.sup.3 : The same paste as that of Sample No. 4, except that 10 parts of 
glass frit (i.e., borosilicate glass having a softening point of about 
700.degree. C.) was contained 
*.sup.4 : Typical commercially available copper paste (i.e., Copper paste 
ESL#2310 available from ElectroScience Laboratories, Inc. 
The evaluation results of the conductor characteristics of Sample Nos. 1 to 
6 are shown in Table 3. 
TABLE 3 
______________________________________ 
Conductor Characteristics of Copper-Base Paste when 
Applied to Borosilicate Glass-Alumina Ceramic 
Composite Substrate 
Copper Sheet Resistivity 
Adhesion Strength between 
Paste of Conductor*.sup.1 
Substrate and Conductor*.sup.2 
Sample (m.OMEGA./.quadrature.) 
(kg/mm.sup.2) 
______________________________________ 
1 1.2 more than 3.2*.sup.4 
2 1.0 more than 3.2*.sup.4 
3 1.0 more than 3.2*.sup.4 
4*.sup.3 
1.2 0.5 
5*.sup.3 
1.5 2.0 
6*.sup.3 
1.2 0 
______________________________________ 
##STR2## 
The resistivity of sample conductor having pattern width W(100 .mu.m), a 
length l of 10 cm, and a thickness t was converted to those having a 
thickness of 25.4 .mu.m. 
*.sup.2 Adhesive strength under tension at stress rate of 5 mm/min 
*.sup.3 See Footnotes of Table 2 
*.sup.4 Glass-Ceramic substrate was broken. 
EXAMPLE 2 
Various copper-base paste compositions containing various coupling agents 
listed in Table 4 were prepared in the same manner as in Sample No. 2 of 
Example 1. 
TABLE 4 
______________________________________ 
Copper Adhesion Strength 
Sheet Resis- 
Paste between Substrate 
tivity of Pattern 
Sample and Conductor*.sup.2 
Conductor Printing 
No. (kg/mm.sup.2) (m.OMEGA./.quadrature.) 
Property 
______________________________________ 
1*.sup.1 
3.2 1.1 Good 
2*.sup.2 
1.0 1.1 Excellent 
3*.sup.3 
1.6 1.1 Good 
4*.sup.4 
1.0 1.1 Good 
5*.sup.5 
0.5 1.2 Good 
6*.sup.6 
0.5 1.0 Good 
7*.sup.7 
1.0 1.2 Good 
8*.sup.8 
0.2 1.3 Good 
9*.sup.9 
3.2 1.5 Poor 
10*.sup.10 
0.5-1.0 1.1 Good 
11*.sup.11 
0 1.1 Excellent 
______________________________________ 
*.sup.1 Isopropyl tridodecylbenzene sulfonyl titanate 
(CH.sub.3).sub.2 CHOTi(OSO.sub.2 C.sub.6 H.sub.4 C.sub.12 H.sub.25).sub.3 
(KR9S available from Ajinomoto Co., Inc.) 
*.sup.2 Isopropyl triisostearoyl titanate (CH.sub.3).sub.2 
CHOTi(OCOC.sub.17 H.sub.35).sub.3 (KRTTS available from Ajinomoto Co., 
Inc.) 
*.sup.3 Isopropyl tris(dioctyl pyrophosphate)titanate 
(CH.sub.3).sub.2 CHOTi[OPOOHOPOOPO(OC.sub.8 H.sub.17).sub.2 ].sub.3 (KR38 
available from Ajonomoto Co., Inc.) 
*.sup.4 Bis(dioctyl pyrophosphate)oxyacetate titanate 
##STR3## 
(KR138S available from Ajinomoto Co., Inc) 
*.sup.5 Isopropyl tri(Naminoethyl-aminoethyl)titanate 
(CH.sub.3).sub.2 CHOTi[OC.sub.2 H.sub.4 NHC.sub.2 H.sub.4 NH.sub.2 ].sub. 
(KR44 available from Ajinomoto Co., Inc.) 
*.sup.6 Tetraisopropyl bis(dioctyl phosphite)titanate 
[(CH.sub.3).sub.2 CHO].sub.4 Ti[P(OC.sub.8 H.sub.17).sub.2 OH].sub.2 
(KR41B available from Ajinomoto Co., Inc.) 
*.sup.7 Bis(dioctyl pyrophosphate)ethylene titanate 
##STR4## 
(KR238S available from Ajinomoto Co., Inc.) 
*.sup.8 5 phr glass (i.e., borosilicate glass having a softening point of 
700.degree. C.) was added instead of the titanate 
*.sup.9 Titanate coupling agent (i.e., isopropyltridodecyl henzene 
sulfonyl titanate) and 10 phr glass (i.e., borosilicate glass having a 
softening point of 700.degree. C.) 
*.sup.10 No titanate coupling agent and no glass were included 
*.sup.11 Commercially available copper paste ESL 2310 available from 
ElectroScience Laboratories, Inc. 
In the abovementioned copperbase paste composition samples, the following 
inorganic compounds were found to be found after firing the copperbase 
paste composition samples. 
In The above-mentioned copper-base paste composition samples, the following 
inorganic compounds were found to be found after firing the copper-base 
paste composition samples. 
______________________________________ 
Sample Nos. 2 and 5: 
Ti and TiO.sub.2 
Sample Nos. 3 and 6: 
TiN and TiO.sub.2 
Sample No. 4: Ti and P-compound 
Sample No. 1: TiO.sub.2 
______________________________________ 
As is clear from the above-mentioned Examples, the copper-base paste 
compositions according to the present invention can remarkably increase 
the adhesion property to the glass-ceramic composite substrates, when 
compared to the commercially available paste composition containing a 
small amount of low-melting point glass, and also remarkably improve the 
printing property, when compared to the commercially available paste 
composition and also the glass-containing paste composition. 
EXAMPLE 3 
The copper-base paste composition Sample Nos. 1 and 2 according to the 
present invention having the compositions, listed in Table 5 were 
prepared. 
TABLE 5 
______________________________________ 
Composition of Copper Paste 
Copper 
Paste 
Sample 
(parts) 
Ingredient 1 2 
______________________________________ 
Copper powder (1.5 .mu.m.phi.) 
100 100 
Organic vehicle 13 14 
Isopropyl tridodecylbenzene 
0.5 0.5 
sulfonyl titanate 
Isopropyl tristearoyl 
0.5 1 
titanate 
______________________________________ 
These copper paste compositions were prepared as follows. 
To the organic vehicle containing an organic solvent (i.e., 2-hexyloxy 
ethanol, and terpineol), an organic thixotropy providing agent (i.e., 
castor oil), and a binder (i.e., ethyl cellulose, and poly(methyl 
methacryl) resin the Ti coupling agent listed in Table 5 was added. The 
mixture was agitated at a temperature of 25.degree. C. and the copper 
powder having a size of 1.5 .mu.m was mixed thereinto. The mixture was 
mixed by a wet ball mill mixing and, after drying, the mixture was mixed 
or kneaded in a three roll mill to produce the desired copper-base 
composition in the form of a paste. 
The paste compositions thus prepared were applied, in the same manner as in 
Example 1, to borosilicate glass-alumina composite ceramic substrate. The 
evaluation was carried out in the same manner as in Example 1. The results 
of the sheet resistivity, the adhesion strength to the substrate, and hole 
filing property are shown in Tables 6 and 7. 
TABLE 6 
______________________________________ 
Characteristics of Copper Paste after Firing 
Paste Adhesion Strength 
Composition Sheet Resistivity 
to Substrate 
Sample No. (m.OMEGA..quadrature.) 
(kg/mm.sup.2) 
______________________________________ 
1 .sup. 1.0 1.6 
2 .sup. 1.0 1.6 
3*.sup.1 1.0 0.5 
4*.sup.2 1.5 2.0 
5*.sup.3 1.2 0 
6*.sup.4 1.0 0 
______________________________________ 
*.sup.1 : No coupling agent was contained in the paste listed in Table 5 
*.sup.2 : 10 phr glass frit (i.e., borosilicate glass having a softening 
point of 700.degree. C.) was contained in the paste listed in Table 5. 
*.sup.3 : Commercially available copperbase paste for alumina ESL 2310 
*.sup.4 : Commercially available copperbase paste for alumina Remex 53 
.times. 3(Remex Co.) 
TABLE 7 
______________________________________ 
Hole-Filling of Copper Paste to 
Glass-Ceramic Green Sheet 
Paste Hole-Filling Percentage*.sup.2 
Hole-Filling 
Sample No. (100 .mu.m.phi., v = 1000) 
Conditions*.sup.3 
______________________________________ 
1 .sup. 99.0% Good 
2 .sup. 99.0% Good 
3*.sup.1 90.0% Good 
4*.sup.1 60.0% Void in Via 
5*.sup.1 99.0% Void in Via 
6*.sup.1 90.0% Good 
______________________________________ 
*.sup.1 : See Footnote of Table 6 
*.sup.2 : Conditions of the upper and lower portions of throughholes were 
visually observed after filling the paste into the throughholes by a 
screen printing method. 
*.sup.3 : After the paste was 100% filled into throughholes of the green 
sheets, the green sheets were evaluated and fired. Thereafter, the 
throughhole portions were vertically cut and, after polishing, the fillin 
conditions were visually and microscopically evaluated, 
Furthermore, when isopropyl tridodecylbenzene sulfonyl titanate and 
isopropyl triisostearoyl titanate are used together, the improvement in 
the adhesion strength was obtained when 0.5 parts by weight or more of 
isopropyl tridodecylbenzene sulfonyl titanate was used and the improvement 
in the flowability was obtained when 0.5 parts by weight or more of 
isopropyl triisostearoyl titanate was used. On the other hand, the upper 
limit of the total amount of the isopropyl tridodecylbenzene sulfonyl 
titanate and isopropyl triisostearoyl titanate is preferably 4 parts by 
weight, because, when the total amount is more than 4 parts by weight, the 
organic content in the paste composition becomes large and the generation 
of voids around the via is liable to occur after firing the multilayer 
circuit board. 
EXAMPLE 4 
The copper-base paste compositions were prepared in the same manner as in 
Example 1, except that acetoalkoxy aluminum diisopropylate was used 
instead of the titanate. 
The sheet resistivities of the resultant conductors were 1.2 
m.OMEGA./.quadrature., the adhesion strength was more them 3.2 
kg/mm.sup.2, and the printing properties were better than those of the 
titanate. The leveling properties were good and the minimum pattern 
widthes were 80 .mu.m. The acetoalkoxy aluminum diisopropylate was 
converted to Al.sub.2 O.sub.3 after firing.