JPH0697657A - Method for manufacturing low temperature fired ceramic multilayer substrate - Google Patents

Abstract

(57) [Summary] (Modified) [Structure] An organic binder and a plasticizer are added to a low temperature fired ceramic raw material that can be fired at a temperature lower than the melting point of copper and a high temperature fired ceramic raw material that can be fired at a temperature higher than the melting point of copper. To form the low temperature fired green sheet 12 and the high temperature fired green sheet 11, form the through holes 15 in the low temperature fired green sheet 12, and print the conductor paste 14 containing copper oxide as a main component on the surface of the low temperature fired green sheet 12. To form a circuit pattern. Next, this green sheet 1
2 is laminated to form a laminate 13 of low temperature fired green sheets, and high temperature fired green sheets 11 are laminated on the upper and lower surfaces thereof to form a green sheet laminate 10. [Effect] The decomposition gas can be diffused and the oxygen and the reducing gas can be sufficiently permeated.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing a ceramic multilayer substrate, and more particularly to a low temperature fired ceramic multilayer using copper as a conductor material for mounting LSIs, chip parts and the like and interconnecting them. The present invention relates to a method for manufacturing a substrate.

[0002]

2. Description of the Related Art Conventionally, alumina, which has excellent insulating properties, thermal conductivity, stability and mechanical strength, has been widely used as a mounting substrate for LSIs, chip parts and the like. Also,
Since a high temperature of 1500 ° C. or higher is required to burn alumina to form a substrate, high melting point tungsten (W) or molybdenum (Mo) is used for the wiring conductor fired together with alumina. However, the alumina substrate has a high dielectric constant, poor matching of the thermal expansion coefficient with silicon, and W or Mo having high conduction resistance must be used for the wiring conductor. There are problems in high frequency of electric signals, high speed processing, reliability, etc.
Further, there is a problem in that there is a limit to high density and miniaturization. In recent years, to solve these problems, gold (Au),
Insulators made of silver (Ag), silver-palladium alloy (Ag-Pd), copper (Cu), and other conductive materials with low conduction resistance and capable of firing at temperatures below the melting point of these metals A low-temperature fired ceramic multilayer substrate has been developed which is used for firing.

However, among the above-mentioned conductor materials, noble metals such as Au have high reliability because they can be fired in an oxidizing atmosphere, but they are scarce in resources, expensive and subject to severe price fluctuations, so that they can be economically used. It is difficult, and Ag has a problem that a short circuit is likely to occur due to migration.

On the other hand, although copper needs to be fired in a non-oxidizing atmosphere in which oxidation does not occur, it is inexpensive, has low resistance, and is excellent in migration resistance, so that the distance between layers is reduced. Can be made narrower, higher density,
It is attracting attention as the most powerful conductor material for mounting boards that can handle higher speeds. However, it is difficult to decompose and dissipate the organic binder contained in the green sheet or the conductor paste by firing in a non-oxidizing atmosphere, and as a result, the organic binder is carbonized and remains in the substrate, and copper powder or ceramic powder There is a problem that not only the progress of sintering is hindered but also substrate characteristics such as insulation resistance and withstand voltage are deteriorated.

In order to solve such a problem, a method of decomposing / dissipating the organic binder in a nitrogen atmosphere containing water vapor (JP-A-60-254697 and JP-A-2).
However, this method has a problem that it requires calcination for a long time to decompose and diffuse the organic binder, which is not economical.

A method of decomposing / dissipating the organic binder in an air atmosphere (Japanese Patent Laid-Open No. 2-155294) has also been proposed. In this method, carbon in the burned material after the decomposing / dissipating step is also proposed. Remaining amount from 600 to 1
It is necessary to adjust within 500 ppm or within the range of 600 to 3000 ppm, and it is extremely difficult to set this condition. Moreover, when the Cu conductor and the ceramic material are fired at the same time, even if Cu is slightly oxidized, there is a problem that the volume expands and cracks (delamination) easily occur in the ceramic layer.

[0007] Further, a method of performing the decomposition / dissipation process of the organic binder in a weakly oxidizing atmosphere and then firing it in a reducing atmosphere (Japanese Patent Laid-Open No. 2-25094), containing a very small amount of water vapor and oxygen. A method of firing in a nitrogen atmosphere (JP-A-63-292692) and a method of using an easily decomposable resin for the organic binder (JP-A-2-1679).
No. 5) has been proposed. However, in any of these methods, it is necessary to adjust the firing atmosphere in order to achieve both decomposition / emission of the organic binder and oxidation prevention of the copper conductor, and it is extremely difficult to set this condition, and the size of the laminate,
When the number of laminated layers or the wiring pattern of the copper conductor changes frequently, it is difficult to readjust the atmosphere in response to this.

In order to solve the above problems, copper oxide powder is used as the conductor material, heat treatment is performed in air to decompose and diffuse the organic binder, and then copper oxide is reduced to copper. A method for manufacturing a ceramic multilayer substrate by sintering copper and a ceramic material to integrate them has been proposed (Japanese Patent Laid-Open No. 61-26293 and Japanese Patent Publication No. 3-21109).

[0009]

DISCLOSURE OF THE INVENTION Problems to be Solved by the Invention
In the method for manufacturing a ceramic multilayer substrate proposed in Japanese Patent Publication No. 293 and Japanese Patent Publication No. 3-21109, it is easy to completely remove the organic binder because it is heated and oxidized in air. However, in the reduction and sintering steps described above, the volumetric shrinkage rate when copper oxide is reduced to copper is about 44%, and in addition, the shrinkage rate of about 25% due to sintering is added, so that the volumetric shrinkage rate of the conductor portion is Although extremely large, ceramics only shrink due to sintering, which is generally about 44%, which is small. Since the difference in the volumetric shrinkage between the ceramic portion and the conductor portion is large as described above, there is a problem that internal stress is generated between them and the ceramic multilayer substrate is deformed. Also,
When the copper oxide is reduced, the ceramic part in the course of sintering is porous (porous), and since the strength is still low, there is a problem that cracks may occur in the ceramic part due to the internal stress. there were. Therefore, there has been a problem that small electronic components cannot be mounted on the substrate with high density.

As a firing method for suppressing the deformation of ceramics, there is a method in which a green sheet laminate is put in a mold and is fired while being pressed. In this case, the green sheet laminate is pressed into the mold, The paths (passages) necessary for the organic binder contained in the green sheet or the conductor paste to decompose and become a gas to be diffused to the outside of the green sheet laminate,
Alternatively, the path necessary for permeating the reducing gas for reducing the copper oxide in the conductor paste is blocked. Therefore, there is a problem that decomposition / emission of the organic binder or reduction of copper oxide is suppressed, and contamination such as carbon easily adheres to the ceramics.

As another method for suppressing the deformation of ceramics, there is a method in which the green sheet laminate is fired while being pressed by a porous ceramics body. Since the ceramic multi-layer substrate is burnt on the ceramics, there is a problem that it is necessary to remove the porous ceramics by polishing after firing.

The present invention has been made in view of the above problems, and can suppress the deformation and cracking of the substrate, can easily perform the treatment after firing, and can decompose and decompose the organic binder. By being able to diffuse enough,
Low-temperature firing that can improve the insulation resistance and withstand voltage characteristics of the substrate and reduce the conduction resistance of the copper conductor, thus obtaining a ceramic multilayer substrate with high density and high-speed signal processing. It is an object of the present invention to provide a method for manufacturing a ceramic multilayer substrate.

[0013]

In order to achieve the above object, the present inventor has conducted extensive research on a method for producing a ceramic multilayer substrate. As a result, a conductor paste containing copper oxide powder as a main component was applied to a low temperature firing ceramic material. Printing is performed on the surface of the low-temperature fired green sheet formed by using the low-temperature fired green sheets, and the low-temperature fired green sheets are laminated to form a low-temperature fired green sheet laminate. The high temperature fired green sheets thus formed are laminated and hot pressed, and then the green sheet laminate is subjected to heat treatment for binder removal and reduction / firing treatment at a temperature not higher than the firing temperature of the high temperature fired green sheets. When the high temperature fired green sheet comes into close contact with the low temperature fired green sheet, the rigidity of the high temperature fired green sheet Therefore, the deformation of the low temperature fired green sheet laminate is suppressed, and the decomposition gas is diffused and the oxygen and the reducing gas penetrate sufficiently from the air-permeable high temperature fired green sheet surface and the open side surface of the green sheet laminate. The present invention has been completed by discovering that the low temperature fired green sheet laminate is sintered after the firing, but the high temperature fired green sheet portion is not sintered, so that this can be easily removed. .

The gist of the present invention is to add at least an organic binder and a plasticizer to each of a low temperature fired ceramic raw material capable of firing at a temperature lower than the melting point of copper and a high temperature fired ceramic raw material capable of firing at a temperature higher than the melting point of copper. And forming a low temperature fired green sheet and a high temperature fired green sheet, forming a through hole in the low temperature fired green sheet, and printing a conductor paste containing copper oxide as a main component on the surface of the low temperature fired green sheet. A step of forming a circuit pattern, a step of laminating green sheets printed with the circuit to form a laminate of low temperature fired green sheets, and the high temperature fired green sheets on the upper and lower surfaces of the low temperature fired green sheet laminate. Stacking to form a green sheet laminate, and the organic vine in the green sheet laminate A heat treatment step to decompose and dissipate,
There is a step of reducing / burning the low temperature fired green sheet at the same time as reducing the copper oxide in a reducing atmosphere, and a step of removing the unfired high temperature fired green sheet portion.

Further, instead of the above-mentioned reduction / firing process,
It is to include a reduction step of reducing copper oxide in a reducing atmosphere, and a firing step of firing the low temperature firing green sheet in a neutral atmosphere after the reduction step.

Further, in the step of forming the above-mentioned high temperature fired green sheet, holes are formed at positions facing the through holes formed on the upper and lower surfaces of the low temperature fired green sheet laminate.

The copper oxide in the present invention may be either cuprous oxide or cupric oxide, but the particle size is preferably about 0.5 μm to 10 μm in order to facilitate paste formation. If the particle size is less than about 0.5 μm, the bulk density of the copper oxide powder is small, so the amount of copper oxide in the conductor paste will be small and the formation of a dense conductor will be hindered. It is not preferable because it becomes difficult to screen-print the paste for use with high accuracy.

The copper oxide paste in the present invention is prepared by adding the above-mentioned copper oxide powder to a vehicle in which a resin and a plasticizer are dissolved in a solvent and kneading with a three-roll mill. Ethyl cellulose or acrylic resin can be used as the resin, terpineol as the solvent, and dibutyl phthalate as the plasticizer. A glass frit may be added to the copper oxide paste in order to improve the adhesion between the copper conductor and the ceramic insulating layer during reduction firing.
In this case, a known glass frit can be used, but it is desirable that the softening point is in the range of about 500 ° C. to about 800 ° C. because it needs to be melted and fluidized in the reduction firing step, and for example, lead can be used. Borosilicate glass can be used. In this case, the amount of glass frit added is
If it exceeds 5% by weight with respect to copper, the conduction resistance of the conductor increases and the solder wettability also decreases, so 5% by weight or less is desirable.

Further, the low temperature fired ceramic raw material in the present invention is required to be able to be sintered at a melting point of copper or lower,
Examples thereof include glass composite ceramics in which glass and inorganic filler are mixed, crystallized glass-based ceramics, non-glass-based ceramics, and the like. For example, ceramics in which inorganic fillers such as alumina, mullite, and forsterite are combined with borosilicate glass. Is desirable.

Further, the high-temperature fired ceramic raw material in the present invention needs to be chemically stable in the heat treatment step of heating at a temperature at which the organic binder decomposes and the reduction / firing step of heating in a reducing atmosphere. Alumina, zirconia, magnesia, oxides such as silica, aluminum nitride, nitrides such as silicon nitride, glass having a softening point higher than the melting point of copper, or a mixture thereof can be used, but from the viewpoint of cost, alumina It is better to use. However, since low-purity alumina may slightly sinter when fired at a temperature lower than the melting point of copper, alumina having a purity of about 95% or more is desirable.

The slurry for forming the green sheet in the present invention is obtained by subjecting the ceramic material to wet pulverization / mixing in a solvent, and then adding an organic binder, a dispersant,
It is prepared by appropriately mixing and mixing a plasticizer and the like. As a solvent used for this slurrying, an organic solvent such as alcohol, toluene, acetone, methyl ethyl ketone, trichloroethylene or a mixture thereof, water, etc. can be used. As the organic binder, an easily binder organic binder such as a methacrylic acid ester polymer, an acrylic acid ester-methacrylic acid ester copolymer, an α-methylstyrene polymer, and a tetrafluoroethylene polymer can be used. However, polyvinyl butyral, vinyl acetate and the like, which have high thermal decomposition temperatures, are not preferable. As the dispersant, octadecylamine, glyceryl monooleate, sorbitan monooleate, etc. are used, and as the plasticizer, dioctyl phthalate (DOP), dibutyl phthalate (D).
BP), polyethylene glycol, glycerin and the like can be used.

Further, the low temperature fired green sheet of the present invention uses the slurry obtained by the above method and is formed into a uniform thickness by a known technique such as a doctor blade method, and then, until it becomes a state in which it can be handled. It is dried and then formed into a desired shape by a cutter or a punching die, and if necessary, a through hole is formed at a desired position by the punching die. Then, a copper oxide paste is screen-printed on the low-temperature fired green sheet to form a wiring pattern.

Further, the high temperature fired green sheet in the present invention is produced by using the slurry obtained by the above method and molding it into a desired shape in the same manner as in the case of the low temperature fired green sheet. When forming a hole in the high temperature fired green sheet, a hole having substantially the same diameter as the through hole is formed at a location facing the through hole formed on the upper and lower surfaces of the low temperature fired green sheet laminate.

Further, the lamination of the green sheets in the present invention is carried out by stacking a desired number of the low temperature fired green sheets on which the wiring pattern is formed to form a low temperature fired green sheet laminate, and The high temperature fired green sheet is laminated on the lower surface and heated and pressed to form a green sheet laminate. It should be noted that it is preferable to use, as the uppermost low temperature fired green sheet in the low temperature fired green sheet laminate, one having no wiring pattern. The number of the high temperature fired green sheets to be laminated may be one on each of the upper and lower surfaces, but it is preferable to laminate two or more layers in order to maintain the shape of the low temperature fired green sheet laminate. However, it is not preferable that the number of laminated layers is 5 layers or more, because the decomposition gas emission and the penetration of oxygen and reducing gas in the green sheet are hindered. When laminating the high temperature fired green sheets having holes further formed, the holes are laminated so that the holes are aligned with the through holes formed on the upper and lower surfaces of the low temperature fired green sheet laminate, and the heating / heating is performed in the same manner as above. A green sheet laminate is formed by applying pressure.

The heat treatment step in the present invention is a step of decomposing / dissipating the organic binder in the green sheet laminate, and is performed in the temperature range of about 550 ° C. to less than the sintering temperature of the low temperature firing green sheet. Is desirable. If the heating temperature is lower than 550 ° C, the decomposition / emission of the organic binder becomes insufficient, while if the heating temperature is higher than the above, the low-temperature fired green sheet starts to sinter, shrinks and becomes dense, and reduces the copper oxide conductor. It is not preferable because it inhibits the reaction and causes internal stress due to the volume difference between the low temperature fired green sheet portion and the copper oxide conductor to cause deformation.

The reduction / firing process in the present invention is
This is a step of reducing the copper oxide in the conductor paste to copper, and firing / integrating the low-temperature fired green sheet laminate to form a multi-layer substrate. Hydrogen and nitrogen are used to reduce the copper oxide. It is necessary to perform firing in a mixed reducing atmosphere, to sinter the low temperature firing green sheet laminate, and to perform firing in a temperature range of 800 to 1050 ° C. in order not to deform the conductor pattern. If the hydrogen concentration exceeds 3%, the risk of explosion is high, so it is desirable to keep the hydrogen concentration in the reducing atmosphere at 3% or less. Further, instead of the reduction / calcination step, it may be performed in two steps of a reduction step and a firing step. In this case, after reducing copper oxide to copper at about 400 ° C. in a reducing atmosphere, neutralization is performed. Baking at 800-1050 degreeC in an atmosphere.

Further, the step of removing the high temperature fired green sheet portion in the present invention is performed by a method such as lightly vibrating the multilayer substrate to complete the ceramic multilayer substrate. When alumina adheres to the holes of the high temperature fired green sheet arranged directly above the through holes, it is removed by light buffing.

[0028]

As described above, in the present invention, the organic binder is heated in the air to be oxidized, and the decomposed gas is diffused from the open side surface of the high temperature fired green sheet surface or the low temperature fired green sheet laminate having good air permeability. The adhesion of contamination such as carbon is suppressed.

Further, the reducing gas permeates from the high temperature fired green sheet surface having good air permeability and the open side surface of the low temperature fired green sheet laminate, and the copper oxide is sufficiently reduced.

Further, in the reduction / firing step, the ceramic particles of the high temperature fired green sheet and the ceramic particles of the low temperature fired green sheet laminate are intermeshed on the contact surface in particle order, and are not sintered but have rigidity. The high temperature fired green sheet sandwiches and constrains the low temperature fired green sheet laminate, so that the deformation of the low temperature fired green sheet laminate is suppressed.

Further, since the high temperature fired green sheet does not fire at the temperature at which the low temperature fired green sheet laminate is fired, the high temperature fired green sheet portion is easily removed in the removing step.

Further, it is possible to carry out the reducing step at about 400 ° C. in a reducing atmosphere containing hydrogen, and the risk of hydrogen explosion is mitigated as compared with the case where the reducing step is carried out at a higher temperature.

According to the method of manufacturing a low temperature fired ceramic multilayer substrate according to the present invention, at least an organic material is used as a low temperature fired ceramics raw material that can be fired at a temperature lower than the melting point of copper and a high temperature fired ceramics raw material that can be fired at a temperature higher than the melting point of copper. A step of forming a low temperature fired green sheet and a high temperature fired green sheet by adding a binder and a plasticizer; forming a through hole in the low temperature fired green sheet, and conducting a low temperature firing of a conductor paste containing copper oxide as a main component. A step of forming a circuit pattern by printing on the surface of the green sheet, a step of laminating the green sheets on which the circuit is printed to form a laminate of low temperature fired green sheets, and upper and lower surfaces of the low temperature fired green sheet laminate A step of laminating the high temperature fired green sheet to a green sheet laminate to form a green sheet laminate; A heat treatment step of decomposing / dissipating the organic binder in the sheet laminated body; a reduction / firing step of firing the low temperature firing green sheet at the same time as reducing the copper oxide in a reducing atmosphere; and an unfired high temperature firing green Since it includes the step of removing the sheet portion,
By allowing the decomposition of the decomposition gas and the permeation of oxygen and reducing gas through the air-permeable high-temperature-baked green sheet surface and the open side surface of the green sheet laminate to be sufficiently performed, and the rigid high-temperature-baked green sheet to be in close contact. Deformation of the low temperature fired green sheet laminate is suppressed, and after firing, the low temperature fired green sheet laminate is sintered, but the high temperature fired green sheet portion is not sintered.
This unsintered portion is easily removed.

Further, in the above-mentioned method for manufacturing a ceramic multilayer substrate, instead of the reducing / firing step, a reducing step of reducing copper oxide in a reducing atmosphere, and a low temperature firing green sheet in a neutral atmosphere after the reducing step Since it includes a firing step of firing, the reduction rate of copper oxide is slowed by a low reduction temperature, internal stress is dispersed and relaxed during this time, and deformation of the low temperature firing green sheet laminate is suppressed, The risk of hydrogen explosion will be reduced.

Further, in the step of forming the above-mentioned high temperature fired green sheet, holes are formed at the positions facing the through holes formed on the upper and lower surfaces of the low temperature fired green sheet laminate. The copper oxide in the through-holes that come into contact with each other easily come into contact with the reducing gas, and when the glass frit is added to the conductor paste, the adhesion of the glass frit to the high temperature fired green sheet part is suppressed. . Therefore, the conduction resistance of the copper conductor in the through hole portion is further improved, and the high temperature fired green sheet portion can be easily removed.

[0036]

EXAMPLES AND COMPARATIVE EXAMPLES Examples and comparative examples of the method for manufacturing a ceramic multilayer substrate according to the present invention will be described below. The manufacturing method of the ceramic multilayer substrates according to Examples 1 to 12 shown in Table 1 below are different in the sample shape, the number of laminated low-temperature fired green sheets, and the number of laminated high-temperature fired green sheets. The manufacturing methods are the same as shown below.

[0037]

[Table 1]

That is, first, 50 wt% of alumina powder and 50 wt% of borosilicate glass powder were mixed and pulverized.
The mixture was mixed to obtain a low temperature fired ceramic raw material. Next, a very small amount of the octadecylamine dispersant was added to 69 wt% of the low temperature fired ceramic raw material, 9 wt% of methacrylic acid ester resin, 3 wt% of DOP, 9 wt% of toluene and 10 wt% of isopropyl alcohol, and mixed by a ball mill to prepare a slurry. After defoaming the slurry with a vacuum defoaming machine, the thickness of the slurry is about 25 using the doctor blade method.
A low-temperature fired green sheet of 0 μm was prepared. After cutting the low-temperature fired green sheet to a predetermined size, through holes having a diameter of about 200 μm were formed at required positions.

Further, the high temperature fired green sheet was made to have a predetermined size in the same manner as above using alumina powder having an average particle size of about 2 μm.

On the other hand, copper oxide powder having an average particle size of about 3 μm was dispersed in a vehicle composed of 5% by weight of ethyl cellulose, 55% by weight of terpineol and 40% by weight of dibutyl phthalate and kneaded with a three roll mill to prepare a conductor paste. This conductor paste was applied by screen printing to form a wiring pattern of the conductor paste 14 shown in FIG. 1 on the low temperature fired green sheet. The printing area ratio of the conductor paste 14 at this time was set to about 60% in any of the examples and the comparative examples. Further, the inside of the through hole 15 shown in FIG. 1 was also filled with the conductor paste 14 by the printing.

Next, a desired number of the low-temperature fired green sheets on which a predetermined wiring pattern is formed are overlapped, and only the through holes are formed on the uppermost of them, and the low-temperature firing green sheet is not formed with the wiring pattern. To form a low temperature fired green sheet laminate, and further stacking a predetermined number of the high temperature fired green sheets on the upper and lower surfaces of this low temperature fired green sheet laminate, and the pressure is about 30MP.
a. A laminated body of green sheets was formed by heating and pressurizing at a temperature of about 100 ° C. FIG. 1 is a cross-sectional view schematically showing a laminated state of green sheets in the method for manufacturing a ceramic multilayer substrate according to Examples 1 to 12.
0 is a green sheet laminate, 11 is a high temperature fired green sheet, 12a is a low temperature fired green sheet without a wiring pattern, 12b is a low temperature fired green sheet with a wiring pattern formed, and 13 is a low temperature fired green sheet laminate. , 14 are conductor pastes, and 15 are through holes.

Next, the green sheet laminate 10 is loaded into a heat treatment furnace filled with air, and the peak temperature is 600.degree.
The peak temperature was maintained for about 90 minutes, and heat treatment was performed according to a heating profile for a total of 3 hours including the peak retention time to decompose and diffuse the organic binder in the green sheet laminate 10. The amount of residual carbon in the green sheet laminate 10 after the heat treatment was 50 ppm or less.

Next, the green sheet laminate 10 was subjected to a heating profile for a total of 1.5 hours including a peak temperature of 900 ° C. and a peak holding time of 30 minutes in a mixed gas of 1% hydrogen and 99% nitrogen. A reduction / firing treatment was performed to reduce the copper oxide in the conductor paste to copper, and the low temperature firing green sheet laminate 13 was fired / integrated. Then, a ceramic multilayer substrate is produced by shaking off 11 parts of the high temperature fired green sheet, and a wiring pattern is printed on the surface of the uppermost ceramic substrate 12a with a copper conductor paste, and the peak temperature is 900 ° C. in a nitrogen atmosphere. Total 1 including peak retention time of 10 minutes
The ceramic multilayer substrate was finally completed by baking with a heating profile of time.

The manufacturing methods of the ceramic multilayer substrates according to Examples 13 to 24 shown in Table 1 are different in the sample shape, the number of low temperature fired green sheets laminated, and the number of high temperature fired green sheets laminated. The manufacturing methods are the same, and the points different from the manufacturing methods of the ceramic multilayer substrates according to Examples 1 to 12 will be described with reference to FIG.

FIG. 2 is a cross-sectional view schematically showing a laminated state of green sheets in the method for manufacturing a ceramic multilayer substrate according to Examples 13 to 24.
b shows a low temperature firing green sheet formed and laminated in the same manner as in Examples 1 to 12 above. The low temperature fired green sheet 12b has a wiring pattern formed by using a conductor paste 17 to which 3 wt% of lead borosilicate glass frit is added, and the through hole 15 is filled with the low temperature fired green sheet 12a. Only the hole 15 is filled. Further, holes 16 are formed at predetermined locations on the high temperature fired green sheet 11, and the high temperature fired green sheet 1 is formed so that the holes 16 come into contact with the through holes 15 formed on the upper and lower surfaces of the low temperature fired green sheet laminate 13.
1 is laminated to form a green sheet laminate 10.

As a comparative example, in Example 12, a method of not laminating the high temperature fired green sheets 11 of three layers each on the upper and lower sides (Comparative Example 1) and a method of not laminating the three layers of high temperature fired green sheets 11 of the upper surface in Example 12 were used. (Comparative example 2)
Ceramic multi-layered substrates were produced by the respective methods.

Below, Examples 1 to 24 and Comparative Examples 1 and 2
The measurement results of the degree of unevenness on the substrate surface and the conduction resistance of the conductive wiring will be described with reference to Table 1. The unevenness of the substrate surface is obtained by measuring the surface roughness on two diagonal lines on the upper and lower surfaces of the substrate using a surface roughness meter, and averaging the difference between the highest value and the lowest value.

As is clear from Table 1, Examples 1-24
In each of the ceramic multilayer substrates manufactured by the method (1), the degree of unevenness of the substrate is 10 μm or less, and the deformation is small and smooth, so that small electronic components can be mounted on the surface of the substrate with high density. Further, the conductivity (sheet resistance value) of the conductor is also good, so that it is possible to sufficiently cope with the high frequency.

On the other hand, in the case of Comparative Example 1, the degree of unevenness is 20 μm or more, and in the case of Comparative Example 2, the concave shape is curved. Therefore, by laminating the high temperature fired green sheets 11, a very large restraining effect can be obtained. You can see that

It should be noted that, instead of the high temperature fired green sheet 11, a method of printing / applying a high temperature fired ceramics paste on the low temperature fired green sheet 12a or a method of spraying the same has substantially the same effect.

[0051]

As described above in detail, in the method for manufacturing a ceramic multilayer substrate according to the present invention, the low temperature firing ceramic raw material capable of firing at a temperature lower than the melting point of copper and the high temperature capable of firing at a temperature higher than the melting point of copper. A step of forming a low temperature fired green sheet and a high temperature fired green sheet by adding at least an organic binder and a plasticizer to each of the fired ceramics raw materials, and forming a through hole in the low temperature fired green sheet and containing copper oxide as a main component A step of printing a conductor paste on the surface of the low-temperature fired green sheet to form a circuit pattern; a step of laminating the green sheets on which the circuit is printed to form a laminate of low-temperature fired green sheets; A process for forming the green sheet laminate by laminating the high temperature fired green sheets on the upper and lower surfaces of the green sheet laminate. A heat treatment step of decomposing / dissipating the organic binder in the green sheet laminate, a reduction / firing step of reducing the copper oxide in a reducing atmosphere and simultaneously firing the low temperature firing green sheet, and Since the step of removing the high temperature fired green sheet portion is included, the emission of decomposition gas and the penetration of oxygen and reducing gas through the high temperature fired green sheet surface having air permeability and the open side surface of the green sheet laminate are sufficiently performed. It is possible to suppress deformation of the low temperature fired green sheet laminate by closely adhering the high temperature fired green sheet having rigidity, and further, the low temperature fired green sheet laminate is sintered after firing. Since the high temperature fired green sheet portion is not sintered, this unsintered portion can be easily removed.

Further, in the above-mentioned method for manufacturing a ceramic multilayer substrate, instead of the reduction / firing step, a reduction step of reducing copper oxide in a reducing atmosphere, and a low temperature firing green sheet in a neutral atmosphere after the reduction step As a result, the reduction rate of copper oxide can be slowed down by a low reduction temperature, and internal stress is dispersed / relaxed during this period to suppress deformation of the low temperature firing green sheet laminate. In addition, the risk of hydrogen explosion can be reduced.

Further, in the step of forming the above-mentioned high temperature fired green sheet, holes are formed in the portions facing the through holes formed on the upper and lower surfaces of the low temperature fired green sheet laminate, so that the holes are contacted. It is possible to make it easier for copper oxide in the through-holes that come into contact with the reducing gas to come into contact,
When glass frit is added to the conductor paste, it is possible to prevent the glass frit from adhering to the high temperature fired green sheet portion. Therefore, the conduction resistance of the copper conductor in the through hole portion can be further improved, and the high temperature fired green sheet portion can be easily removed.

Therefore, small electronic components can be mounted on the surface of the substrate with high density, and high frequency can be dealt with.

[Brief description of drawings]

FIG. 1 is a cross-sectional view schematically showing a laminated state of green sheets in a method for manufacturing a ceramic multilayer substrate according to Examples 1 to 12 of the present invention.

FIG. 2 is a cross-sectional view schematically showing a laminated state of green sheets in the method for manufacturing a ceramic multilayer substrate according to Examples 13 to 24 of the present invention.

[Explanation of symbols]

 10 Green Sheet Laminate 11 High Temperature Firing Green Sheet 12a Low Temperature Firing Green Sheet 12b Low Temperature Firing Green Sheet 13 Low Temperature Firing Green Sheet Lamination 14 Conductor Paste 15 Through Hole 16 Hole 17 Conductor Paste

Claims (3)

[Claims] 1. A low temperature fired green sheet obtained by adding at least an organic binder and a plasticizer to a low temperature fired ceramic raw material capable of firing at a temperature lower than the melting point of copper and a high temperature fired ceramic raw material capable of firing at a temperature higher than the melting point of copper, respectively. Forming a high temperature fired green sheet, and forming a through hole in the low temperature fired green sheet,
A step of forming a circuit pattern by printing a conductor paste containing copper oxide as a main component on the surface of the low temperature fired green sheet, and stacking the green sheets on which the circuit is printed to form a laminate of low temperature fired green sheets. And a step of stacking the high temperature fired green sheets on the upper and lower surfaces of the low temperature fired green sheet laminate to form a green sheet laminate, and decomposing the organic binder in the green sheet laminate.
It includes a heat treatment step of dissipating, a reduction / firing step of reducing the copper oxide in a reducing atmosphere and at the same time firing the low temperature fired green sheet, and a step of removing the unfired high temperature fired green sheet portion. A method of manufacturing a low temperature fired ceramic multilayer substrate, comprising: 2. A reducing step of reducing copper oxide in a reducing atmosphere in place of the reducing / firing step of claim 1, and a firing step of firing the low temperature fired green sheet in a neutral atmosphere after the reducing step. A method of manufacturing a low-temperature fired ceramic multilayer substrate, comprising: 3. The step of forming a high temperature fired green sheet, wherein holes are formed at positions facing the through holes formed on the upper and lower surfaces of the low temperature fired green sheet laminate. A method for producing the low-temperature-fired ceramic multilayer substrate described.