JP5285016B2 - Wiring board - Google Patents

Description

  The present invention relates to a wiring board using a copper paste that is filled in via hole holes formed in a ceramic green sheet and simultaneously fired to connect between conductor layers (wiring patterns) laminated via an insulating layer. It is.

  2. Description of the Related Art In recent years, wiring boards have been used in a high-frequency region of the GHz band or higher with the increase in information communication speed, and reduction of transmission loss is required. For this reason, the wiring board is produced by forming a conductor layer made of silver, copper or the like, which is a metal having a low conductor resistance and a low melting point, on a ceramic substrate having a relatively low dielectric constant. Further, as the circuit density is increased and the number of layers is increased, there is a demand for a wiring board using copper, which has better migration resistance than silver, as a conductor layer and a via conductor.

  When the wiring board is multilayered, the ceramic layers and the conductor layers are alternately laminated, and the conductor layers overlapping via the ceramic layers are connected by via conductors formed through the ceramic layers.

  In order to produce a wiring board using copper as a conductor layer or via conductor, it is necessary to efficiently remove organic components while suppressing copper oxidation. As this method, for example, a method of firing in a wet nitrogen atmosphere (in a mixed atmosphere of water vapor and nitrogen) is known.

  That is, in this method, first, a slurry prepared using a ceramic raw material powder, an organic binder, a solvent and the like is prepared, and a ceramic green sheet is formed by a sheet forming method such as a doctor blade method. Next, via hole holes are formed in the ceramic green sheet, and the via hole holes are filled with a copper paste and dried to form a via conductor before firing. Further, a conductor layer serving as a wiring pattern is printed on the surface of the ceramic glue sheet using copper paste and dried to form a ceramic green sheet in which the via conductor and the conductor layer are connected. Next, a plurality of ceramic green sheets are laminated to form a laminated body, and this laminated body is debindered at a temperature of several hundred degrees Celsius in a mixed atmosphere of water vapor and nitrogen gas and contained in the copper paste and the ceramic green sheet. The organic component is removed and the temperature is raised to about 1000 ° C. or higher and firing is performed. Thereby, the conductor layers laminated via the ceramic layers are connected by the via conductors, and a multilayered wiring board is manufactured.

  The wiring board thus fabricated has different sintering temperatures and firing shrinkage timings between the copper serving as the via conductor and the ceramic layer serving as the insulating layer in the firing process, so that the via conductor protrudes from the surface of the wiring board by firing. The problem of pushing up is likely to occur. Then, the copper metallized composition for improving this problem and the glass ceramic wiring board using the same are known.

For example, in order to reduce firing of the via conductor from the surface of the glass ceramic wiring board by matching the firing shrinkage behavior of the glass ceramic porcelain and the copper metallized composition, the glass transition point is 700 with respect to 100 parts by weight of the main component copper powder. to 750 ° C. of _{SiO 2 -Al 2 O 3 -RO (} R: alkaline earth metal) -B ₂ O ₃ based copper metallization composition for via holes and the glass frit contains 2-20 parts by weight and the copper metallization composition There is a glass-ceramic wiring board that is co-fired with a glass-ceramic porcelain at a temperature of 700 to 1000 ° C. (for example, see Patent Document 1).

JP 11-53940 A (page 3-5)

  As the size of the wiring board is reduced and the transmission signal speed increases, plating is performed on the via conductor exposed on the wiring board to form a circuit terminal, and a semiconductor terminal is superimposed on the upper surface of the circuit terminal and directly soldered. There is a demand for a free chip structure for bonding.

  However, according to the copper metallized composition disclosed in Patent Document 1 and the glass-ceramic wiring board using the copper metallized composition, glass frit is added to the copper metallized composition, so that the glass floats on the surface of the via conductor and remains. When the wiring circuit is formed by plating the via hole electrode surface, the plating process becomes difficult.

  The present invention solves the above-mentioned problems, and in a wiring board using copper as a via conductor, the push-up of the via conductor due to firing can be reduced, and there is no protrusion of glass on the via conductor surface, and the copper can be easily plated. An object of the present invention is to provide a wiring board using a paste.

The invention according to claim 1, which has been made to achieve such an object, is a ceramic wiring board, wherein a via conductor is formed in a cross section in the thickness direction of the wiring board inside a via conductor containing copper formed after firing. above particle size 2μm being dispersed, and ceramic particles contained in the pre-copper paste, there are inorganic materials inorganic component diffused in the via conductor is contained is Deki gathered ceramic green sheet, the particle size 2μm or more The total area of the inorganic substance is 10% or less of the cross-sectional area of the via conductor, the total area of the inorganic substance having a particle diameter of 5 μm or more is 5% or less of the cross-sectional area of the via conductor, and the inorganic substance has a particle diameter of 10 μm or more. The total area of the wiring board is 2% or less of the cross-sectional area of the via conductor.

According to the wiring board according to claim 1, in the cross-section in the thickness direction of the wiring board, the particle diameter of 2 μm or more dispersed in the via conductor is previously contained in the ceramic paste or in the ceramic green sheet. The total area of the inorganic substance formed by collecting the inorganic components diffused in the via conductor is 10% or less of the cross-sectional area of the via conductor and the total area of the inorganic substance having a particle diameter of 5 μm or more is the cross-sectional area of the via conductor. 5% or less, and furthermore, the total area of the inorganic substance having a particle diameter of 10 μm or more is 2% or less of the cross-sectional area of the via conductor. Therefore, even if a part of the inorganic substance is exposed on the via conductor surface, this via There is obtained an effect that the plating process can be easily performed without impairing the plating property of the conductor surface.
In addition, since this inorganic substance exists in the via conductor in a spherical shape, a substantially spherical shape, or an indefinite shape, and its shape is often a substantially circular diameter, the major axis may be the size of the inorganic substance. However, when the cross section of the inorganic substance does not appear circular, the diameter (d) obtained by converting the area into a circle, that is, the cross section area of the inorganic substance = π (d / 2) ² , d = 2 X (Cross sectional area of inorganic substance / π) ^0.5 is the size of the inorganic substance.

  According to a second aspect of the present invention, in the wiring board according to the first aspect, when the via conductor is exposed on at least one surface of the wiring board and the shape of the via conductor is spherical or substantially spherical. When the major axis is irregular, the diameter obtained by converting the cross section into a circle is 10 μm or less, the ceramic particles previously contained in the copper paste, and the via contained in the ceramic green sheet. An inorganic substance formed by collecting inorganic components diffused in the conductor is exposed.

  In the wiring board according to claim 2, since the size of the inorganic material exposed on the surface of the via conductor is 10 μm or less, the plating film on the surface of the via conductor is not impaired and the plating film with few defects such as pinholes is provided. The effect that can be formed easily is obtained.

  In the present invention, the via conductor may be used as a mounting terminal as it is, but a mounting pad may be further formed thereon by a simultaneous firing method or a thick film method. Since the inorganic substance hardly diffuses on the surface of the mounting pad, a good plating film can be formed.

The invention according to claim 3 is the wiring board according to claim 1 or 2, wherein the via conductor is exposed on at least one surface of the wiring board, and a plating layer is formed on the exposed upper surface. It is characterized by.

According to the wiring substrate of claim 3 , since there is little inorganic residue on the surface of the via conductor, the plating process can be easily performed, and a good plating layer is formed without defects such as plating unevenness, pinhole defects, and peeling. Therefore, it is possible to obtain an effect that a mounting board having excellent durability such as temperature load, humidity load, and heat load can be configured.

  In the present invention, the via conductor on which the plated layer is formed may be used as a mounting terminal as it is, but the plated layer may be formed after the mounting pad is formed on the via hole. Since the inorganic substance hardly diffuses on the surface of the mounting pad, a good plating film can be formed.

According to a fourth aspect of the present invention, in the wiring board according to the third aspect , a semiconductor element is mounted, and a terminal of the semiconductor element and the via conductor are connected via a bonding material. According to the wiring board described in Item 4 , since the conductor resistance of the via conductor is low and the via conductor is connected to the terminal of the semiconductor element via a joining member such as solder or brazing material, the electrical characteristics of the semiconductor In addition, there can be obtained an operational effect that a highly reliable wiring board can be configured without causing variation and deterioration.

According to a fifth aspect of the present invention, in the wiring board according to any one of the first to fourth aspects, the via conductor is configured as a thermal via serving as a heat conduction path.
According to the wiring board according to claim 5 , since the via conductor is densely baked to increase the thermal conductivity, the wiring board is excellent in the heat dissipation effect when configured as a thermal via in the high-density mounting type wiring board. Is obtained.

It is sectional drawing showing the cut surface of the baking sample in one Example with which this invention was applied. It is sectional drawing showing the cut surface of the baking sample of the comparative example. It is sectional drawing showing the structure of the wiring board of one Example to which this invention was applied.

Hereinafter, the present invention will be described with reference to one embodiment.
"Production of ceramic green sheets"
First, 50 parts by mass of glass powder having a composition of 63.3 parts by mass of SiO ₂ , 24.1 parts by mass of B ₂ O ₃ , 5.7 parts by mass of Al ₂ O ₃ , and 6.9 parts by mass of CaO; Then, 50 parts by mass of an alumina filler was mixed to prepare a mixed powder of alumina and glass having a particle size of 2.5 μm and an alkali metal impurity content of 0.2 mol% or less.

  Next, 20 parts by mass of an acrylic resin binder, 10 parts by mass of a plasticizer consisting of dibutyl phthalate, and an appropriate amount of a toluene / MEK mixed solvent were added to 100 parts by mass of the mixed powder of alumina and glass to prepare a slurry. .

  Next, a ceramic green sheet having a thickness of 250 μm was formed by sheet forming such as a doctor blade method using the slurry. This ceramic green sheet is a green sheet for low-temperature firing that can be fired at a relatively low temperature (here, 1000 ° C.).

"Preparation of copper paste"
Next, 12 parts by mass of the vehicle and the additives shown in (Table 1) were added to 100 parts by mass of the spherical copper powder having an average particle size of 5 μm, and mixed with a three roll mill to prepare a copper paste. The vehicle was prepared by dissolving 30 parts by mass of polyisobutyl methacrylate in 70 parts by mass of terpineol. Moreover, the addition amount of the vehicle with respect to 100 mass parts of copper powder was set so that a predetermined | prescribed viscosity (5000 poise-1 million poise) might be obtained. When the addition amount of the vehicle was 12 parts by weight, 14 parts by weight, and 16 parts by weight, the viscosity of the copper paste was 800,000 poise, 60,000 poise, and 5000 poise, respectively.

As shown in Table 1, copper having the compositions of Examples A to F as examples of the present invention and copper having the compositions of Comparative Examples A to D were compared with the effects of the present invention. A paste was prepared.

Example A is a copper paste to which 1.0 part by mass of Al ₂ O ₃ having an average particle diameter of 13 nm is added as ceramic particles.
Example B is a copper paste to which 1.0 part by mass of TiO ₂ having an average particle diameter of 21 nm is added as ceramic particles.

In Examples C to F, SiO ₂ having an average particle diameter of 12 nm was added as ceramic particles, and at this time, the amount of SiO ₂ added was changed in the range of 0.2 to 2.0 parts by mass. It is a paste.

Comparative Example A is a copper paste to which no additive is added.
Comparative Example B is a copper paste to which 1.0 part by mass of Al ₂ O ₃ having an average particle size of 300 nm is added as ceramic particles.

  Comparative Examples C and D have the same composition as the glass powder added in the production of the ceramic green sheet, and the glass frit having a particle size of 800 nm is changed in addition amount to 1.0 part by mass and 5.0 parts by mass. This is a copper paste added.

"Production of fired samples"
Next, a fired sample serving as a sample for evaluation was produced using the green sheet and the copper paste.

  First, a ceramic green sheet is cut into a size of 50 mm in length and 60 mm in width to produce two ceramic green sheet pieces, and a through hole having an inner diameter of 250 μm is formed in a substantially central portion of the ceramic green sheet piece to form a via hole. Formed.

  Next, in accordance with the arrangement of the via holes, it is covered with a thin-film metal screen in which a through hole having the same diameter as the via hole is formed, and copper paste is printed from above the metal screen with a squeegee, and the copper paste is placed in the via hole of the ceramic green sheet. Filled.

Next, the two ceramic green sheets were laminated and pressed together so that the centers of the via hole holes were not displaced, and a laminate was formed.
Next, the laminate is exposed to a furnace in which a mixed atmosphere of water vapor and nitrogen gas (a mixed atmosphere having a dew point of water vapor and nitrogen gas of 70 ° C.) is prepared and left at a temperature of 850 ° C. And the organic component contained in the ceramic green sheet was degreased and subsequently replaced with dry nitrogen gas, then heated to 1000 ° C. and allowed to stand for 2 hours, and fired to prepare a fired sample.

"Measurement of push-up amount"
Next, using the fired sample, the push-up dimension of the via conductor exposed and projected on the surface of the fired sample was measured.

  The via conductor push-up dimension is based on the upper surface of the ceramic layer that is 400 μm away from the center of the via conductor, and the maximum height of the via conductor protruding from this reference value is measured with a microscope. )Pointing out toungue.

"Check for vias on the surface of the via conductor"
Next, using the fired sample, the surface of the via conductor exposed on the surface of the fired sample was observed by magnifying it 500 times with a microscope, and the presence or absence of glass protrusion on the via conductor surface was confirmed. Table 1).

  As shown in Table 1, in Examples A to F of the present invention, the amount of the via conductor protruding from the surface of the fired sample is in the range of 1 to 27 μm, the glass on the surface of the via conductor is not raised, and plating is performed. It can be seen that a via conductor can be obtained which can be easily processed and can mount circuit components with high accuracy.

When comparing Comparative Examples A with Examples A to F of the present invention, it can be seen that no additive was added to the copper paste, and as a result, the push-up amount of the via conductor was as large as 54 μm.
In addition, when Comparative Example B is compared with Example A of the present invention, 1.0 part by mass of Al ₂ O ₃ is added as an additive, and the type and amount of additive are the same as Example A. It can be seen that the particle diameter is 300 nm, which is larger than the particle diameter of 13 nm in Example A of the present invention, and as a result, the push-up amount of the via conductor is as large as 52 μm.

  Further, in Comparative Examples C and D, when the glass frit is added, the amount of push-up of the via conductor reaches a level equivalent to that of Examples C, E, and F of the present invention as compared with Examples A to F of the present invention. Although it can be reduced, it can be seen that glass is raised on the surface of the via conductor, making the plating process difficult. In Comparative Examples C and D, the surface of the via conductor was magnified and observed with a microscope, and as a result, a large number of inorganic substances made of glass having a size of about 15 μm appeared on the surface.

Further, among the examples of the present invention, compared to Examples A and B, Example C has a via conductor push-up amount of Example A and B of 27 μm and 22 μm, whereas the via conductor push-up amount of Example C It can be seen that it is particularly preferable to add SiO ₂ as ceramic particles because the glass is as small as 5 μm and the glass is not raised.

Furthermore, in Examples C to F, the same SiO ₂ particles are added as additives.
It can be seen that the amount of addition of the SiO ₂ particles is preferably in the range of 0.5 parts by mass to 2.0 parts by mass because the amount of protrusion of the via conductors of Examples C, E, and F is much smaller than that of Example ₂ .

"Section observation of via conductor"
Next, the cross section of the via conductor of the fired samples of Example E and Comparative Example D of the present invention was observed with a microscope, and the dispersion state of the inorganic substance inside the via conductor was confirmed.

1 is a cross-sectional view showing a cross section of a fired sample of Example E in the present invention, and FIG. 2 is a cross-sectional view showing a cross section of a fired sample of Comparative Example D.
1 and 2, reference numerals 1 and 2 are ceramic porcelain, 3 and 4 are via conductors, 5 and 6 are baked copper, and 7 and 8 are inorganic materials.

  1 and 2, the cross sections of the via conductors of Example E and Comparative Example D of the present invention are compared. In Example E of the present invention shown in FIG. 1, the inorganic material 7 contained in the via conductor 3 is finely and uniformly dispersed with a thickness of about 5 μm or less, and the copper 5 is fired into a dense sintered crystal. On the other hand, in Comparative Example D shown in FIG. 2, the inorganic material 8 of about 15 μm is dispersed in the via conductor 4, and the sintered structure of the copper 6 is also rough. Therefore, according to Example E of this invention, it turns out that the inorganic substance 7 is disperse | distributed finely in the via conductor 3, and the via conductor 3 baked densely can be obtained.

Next, using the ceramic green sheet, a through hole having a diameter of 250 μm was formed in the ceramic green sheet.
Next, using the copper paste of Example E of the present invention and the copper paste of Comparative Example D, respectively, after filling the via hole hole of the ceramic green sheet and drying, a wiring pattern is formed on the surface of the ceramic green sheet In order to do so, a copper paste was printed.

  Next, a plurality of ceramic green sheets are laminated and pressed to produce a green sheet laminate, and this green sheet laminate is mixed with water vapor and nitrogen gas (a mixed atmosphere with a dew point of water vapor and nitrogen gas of 70 ° C.). .) Was left in the furnace prepared and degreased by leaving it at a temperature of 850 ° C. to degrease the organic components contained in the copper paste and the ceramic green sheet, followed by replacement with dry nitrogen gas at 1000 ° C. The mixture was allowed to stand for 2 hours at the temperature of

Next, Ni was plated on the surface of the via conductor exposed on the surface of the wiring board, and Au was further plated on the upper surface of Ni so as to form a circle with a diameter of 80 μm to produce a wiring board.
As a result of observing the surface of the obtained wiring board, the wiring board formed using the copper paste of Example E of the present invention has a circular Au plating layer with a diameter of 80 μm formed on the surface of the via conductor with high precision, and adheres to the plating. It was good with no unevenness. On the other hand, the wiring board using the copper paste of Comparative Example D was not able to be plated because the glass was raised on the via conductor surface.

Next, the wiring board produced using the copper paste of Example E and Comparative Example D was cut, the cut surface was polished, and the cross section of the via conductor was observed with an SEM (scanning electron microscope), and the reflected electron composition image Got. Further, the particle diameter of 2 μm or more existing in an arbitrary cross-sectional area of 4000 μm ² of the via conductor is 5 μm.
An inorganic substance having a particle size of 10 μm or more was detected based on the reflected electron composition image. In such reflected electron composition image, heavy elements such as Cu are represented by bright portions (white portions), and inorganic substances are represented by dark portions (black portions). As a result of calculating the ratio of the total area of the inorganic substance (dark part) to the via conductor cross-sectional area by image processing, Example E had a particle size of 2 μm or more, 1.9%, and a particle size of 5 μm or more, 0%. D was 29.5% when the particle size was 2 μm or more, 26.6% when the particle size was 5 μm or more, and 15.0% when the particle size was 10 μm or more.

  Therefore, as a result of calculating the total area of the inorganic substances having a particle size or more in the cross-sectional area of the via conductor and evaluating the plating property on the via conductor surface, the total of the inorganic substances having the particle diameters or more with respect to the cross-sectional area of the via conductor. If the area is 10% or less with a particle size of 2 μm or more, 5% or less with a particle size of 5 μm or more, and 2% or less with a particle size of 10 μm or more, even if a part of the inorganic material is exposed on the via conductor surface, this via conductor The plating process could be easily performed without impairing the plating properties of the surface.

Next, using the ceramic green sheet and the copper paste having the composition shown in Example E, a wiring board on which a semiconductor element was mounted was produced.
FIG. 3 is a cross-sectional view showing a configuration of a wiring board according to an embodiment to which the present invention is applied.

  In FIG. 3, reference numeral 10 denotes a wiring board. The wiring board 10 is formed by laminating and firing a plurality of ceramic green sheets, and a semiconductor installed on the upper surface of the ceramic layers 11-14. The element 15 and the semiconductor element 15 are accommodated in the hole 17 and the peripheral surface is constituted by a ceramic layer 14 and a lid body 16 joined by a brazing material (not shown).

  The ceramic layers 11 to 14 have internal conductor layers 24 to 29 formed on the overlapping surfaces. The internal conductor layers 24 to 29 are connected to via conductors 36 to 47 formed so as to penetrate the ceramic layers 11 to 14.

  Circuit terminals 18 to 23 are formed on the lower surface of the ceramic layer 11 so as to be connected to the via conductors 36 to 41, respectively. The circuit terminals 18 to 23 are formed by printing copper paste on the exposed surfaces of the via conductors 36 to 41 and co-firing, Ni plating on the surface of the conductor, and then Au plating on the surface of the Ni plating. Is formed. On the upper surface of the ceramic layer 14, plating layers 30 to 35 are formed so as to be connected to the via conductors 42 to 47, respectively. The plated layers 30 to 35 are formed by performing Ni plating on the exposed surfaces of the via conductors 42 to 47 and performing Au plating on the Ni plating surface. The terminals (not shown) of the semiconductor element 15 are connected by soldering so as to overlap the plated layers 30 to 35.

  As described above, the circuit board 18 to 23 of the lower ceramic layer 11 of the wiring board 10 has the plating layers 30 to 30 of the upper ceramic layer 14 via the via conductors 36 to 47, the internal conductor layers 24 to 29, and the like. 35 and is connected to the terminal of the semiconductor element 15 through the plated layers 30 to 35 to constitute an electric circuit.

  In the wiring substrate 10 obtained by the above configuration, the via conductors 36 to 47 are densely fired, the electric resistance is low, and the variation and deterioration of the electric characteristics of the semiconductor element 15 are small. In addition, the via conductors 36 to 47 were not pushed up from the wiring substrate 10 and could be easily plated and a good plating layer could be obtained.

Further, the via conductors 36 to 47 have good thermal conductivity, and the temperature rise of the semiconductor element 15 can be reduced.
The effects of the copper paste and the wiring board of the embodiment of the present invention having the above-described configuration will be described below.

  When the copper paste according to the embodiment of the present invention is filled in the via hole hole of the ceramic green sheet, and once fired after being exposed in a wet nitrogen atmosphere, the via conductor is hardly pushed up, and the glass on the surface of the via conductor is raised. Therefore, a plating process can be easily performed, and a via conductor capable of mounting circuit components with high accuracy can be obtained.

  In addition, the copper paste according to the embodiment of the present invention is filled in the via hole hole of the ceramic green sheet, and once exposed in a wet nitrogen atmosphere and baked, a dense and low resistance via conductor is obtained, and a high frequency signal is obtained. A wiring board with low transmission loss can be obtained.

  In addition, the wiring board according to the embodiment of the present invention is excellent in durability such as temperature load, humidity load, and heat load because a good plating layer free from plating unevenness, chipping and peeling is formed on the surface of the via conductor. An electric circuit can be formed.

  In addition, the wiring board according to the embodiment of the present invention has a low electrical resistance of the via conductor, and if the terminals of the semiconductor element are connected through the surface plating layer of the via conductor, the electrical characteristics of the semiconductor may vary or deteriorate. No electrical circuit can be formed.

  In addition, since the wiring board according to the embodiment of the present invention has a high thermal conductivity because the via conductors are densely fired, if the wiring board is laminated as a high density, it is excellent in heat dissipation effect.

  In the embodiment of the present invention, Ni is plated on the upper surface of copper as the conductor layer, and Au is further plated on the upper surface. However, other metal having low resistance may be plated on the upper surface of the copper. Good.

  Further, in the embodiment of the present invention, the via hole that penetrates the ceramic green sheet was filled with the conductive paste to form the via conductor, but instead of this via hole, a groove was formed on the end face of the wiring board. When the conductive paste of the present invention is filled in the groove to form the connection conductor of the wiring pattern, the connection conductor is less pushed up from the wiring board, and a dense and low resistance connection conductor can be obtained, so that various electrical circuits can be formed. Is preferred.

  Further, the copper paste of the present invention preferably contains no glass frit because it contains glass frit, which deteriorates the plating properties of the via conductors. However, according to the pattern design of the wiring board, solderability and plating properties are preferred. A trace amount of glass may be contained to such an extent that is not impaired.

  When manufacturing the wiring board by filling the via hole with the copper paste of the present invention, the ceramic green sheet coated with the copper paste is placed in wet nitrogen at 650 to 900 ° C. (dew point of water vapor and nitrogen gas is 70 ° C.). The organic component is removed (debinding step) in a mixed atmosphere at 0 ° C., and then fired at 850 to 1050 ° C. Here, the binder removal step is set in a range not exceeding the subsequent firing temperature.

  First, the organic components contained in the ceramic green sheet and the copper paste are removed (debindering step) in wet nitrogen at 650 to 900 ° C. Here, the binder removal step is set in a range not exceeding the subsequent firing temperature. Since the binder is removed in a state where the ceramic particles are dispersed around the copper powder in the copper paste, the sintering start of the copper powder is suppressed during the binder removal, but in the subsequent firing process at high temperature Since the sintering of the copper powder is promoted by exposure to wet nitrogen during debinding, a dense conductor layer can be obtained.

  In the firing process performed after the binder removal step, copper and the ceramic green sheet are fired simultaneously in nitrogen at 850 to 1050 ° C. or wet nitrogen. Since each sintering start temperature and firing shrinkage timing are controlled to be close to each other, it is possible to obtain a wiring board with less via conductor push-up, dense, low resistance, and low transmission loss of high-frequency signals. it can.

  DESCRIPTION OF SYMBOLS 1, 2 ... Ceramic porcelain, 3, 4 ... Via conductor, 5, 6 ... Copper, 7, 8 ... Inorganic substance, 10 ... Wiring board, 11-14 ... Ceramic layer (insulating layer), 15 ... Semiconductor element, 16 ... Cover Body, 17 ... hole, 18-23 ... circuit terminal, 24-29 ... inner conductor layer, 30-35 ... plated layer, 36-47 ... via conductor.

Claims (5)

A ceramic wiring board,
Inside the via conductor containing copper formed after firing, in the cross-section in the thickness direction of the wiring board, ceramic particles dispersed in the via conductor and having a particle diameter of 2 μm or more and previously contained in the copper paste, or ceramic green There is an inorganic substance that is formed by collecting inorganic components contained in the sheet and diffused into the via conductor ,
The total area of inorganic substances having a particle size of 2 μm or more is 10% or less of the cross-sectional area of the via conductor,
The total area of the inorganic substance having a particle size of 5 μm or more is 5% or less of the cross-sectional area of the via conductor, and
A wiring board, wherein a total area of inorganic substances having a particle diameter of 10 μm or more is 2% or less of a cross-sectional area of the via conductor.   The via conductor is exposed on at least one surface of the wiring board, and when the shape is spherical or substantially spherical on the exposed surface, the major axis is used. The inorganic substance formed by collecting ceramic particles previously contained in the copper paste having a diameter of 10 μm or less converted into a circle and the inorganic components contained in the ceramic green sheet and diffused into the via conductor is exposed. The wiring board according to claim 1.   3. The wiring board according to claim 1, wherein the via conductor is exposed on at least one surface of the wiring board, and a plating layer is formed on the exposed upper surface.   4. The wiring board according to claim 3, wherein a semiconductor element is mounted on the wiring board, and a terminal of the semiconductor element and the via conductor are connected via a bonding member.   The wiring board according to claim 1, wherein the via conductor is configured as a thermal via serving as a heat conduction path.