JP2007324362A - Ceramic circuit substrate and method for manufacturing therefor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a ceramic circuit substrate and its method for manufacturing which has low transmission loss for high-frequency signals by lowering the loss of a conductor. <P>SOLUTION: A through-conductor 11 includes a sintered conductor 12 which is made by sintering a conductor, an air gap 13 is formed in the interface of a part of the sintered conductor 12 and an insulating layer 3, and a part of the sintered conductor portion 12 is arranged along the direction in which the current of the through conductor 11 flows. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a ceramic circuit board and a manufacturing method thereof, and more particularly, to a ceramic circuit board suitably applied to a multilayer wiring board using a high-frequency signal, a package for housing semiconductor elements, a module board, a high-frequency component, and the like, and a manufacturing method thereof. Is.

  Along with the development and popularization of mobile communications such as mobile phones, miniaturization, high functionality, low power, etc. of communication devices and electronic devices have been promoted, such as Au, Ag, Cu, Pd, Pt, etc. Ceramic circuit boards have been used as wiring boards for modules in which elements such as resonators, capacitors, coils and filters are formed by low melting point, low resistance conductive materials and low-temperature fired ceramics such as glass ceramics. Yes.

In such circuit boards, the use of high-frequency signals is increasing, so there is a strong demand for lower loss as well as lower resistance of conductors. A glass ceramic circuit board that can be fired at about 1050 ° C. or less has a relatively low loss because a wiring conductor mainly composed of a low melting point metal such as Au, Ag, and Cu can be used, but in order to further reduce the loss, There is a need for improved wiring conductors. In other words, the current of the high-frequency signal passing through the substrate is concentrated near the interface between the conductor and the insulator due to the skin effect, and the conductivity near the conductor interface affects the loss, so it is necessary to suppress the loss near the conductor interface. was there. Here, the skin depth δ of the high-frequency signal is expressed as follows using the frequency f, the magnetic permeability μ, and the conductivity σ.
δ = (π · fμσ) ^−1/2

  Conventionally, by making the cross-sectional shape of the stripline resonant line formed of the wiring conductor H-shaped, the concentration of the magnetic field due to the skin effect at the edge portions of both ends of the stripline resonant line is alleviated and the loss of the wiring conductor is reduced. A technique has been proposed (see, for example, Patent Document 1).

  A technique has been proposed for improving the electrical characteristics in the high-frequency region by providing thick portions at both ends of the conductor pattern, thereby making it difficult for magnetic field and electric field to concentrate on the edge of the conductor pattern ( For example, see Patent Document 2). Also, the electric field concentrates on the corners of the cross-sectional shape of the wiring conductor, causing transmission loss and lowering the conductivity. Therefore, the cross-sectional shape of the wiring conductor is changed to an inverted trapezoidal shape, with sharp corners at the upper ends of the inverted trapezoid. It has been proposed to reduce the surface resistance when a high frequency signal is transmitted by rounding (see, for example, Patent Document 3).

  The line-shaped conductor as described above is bent and arranged over a plurality of insulating layers. The line-shaped conductors formed on the respective insulating layers are connected by through conductors penetrating the insulating layers, thereby reducing the size of the ceramic circuit board.

JP-A-10-126121, paragraphs [0034] to [0039], FIG. Japanese Patent Laid-Open No. 2001-60516, paragraphs [0013] and [0018], FIG. 2 and FIG. Japanese Patent Laid-Open No. 2003-174261, FIG. 1 (b)

  However, all of the prior art described in the above-mentioned publications change the shape of the outer periphery of the cross section perpendicular to the direction of current flow to reduce the loss of current flowing near the outer periphery. As a result, there is a problem that the conductor cannot be reduced in loss.

  An object of the present invention is to provide a ceramic circuit board with a small transmission loss of a high-frequency signal by reducing the loss of a conductor and a method for manufacturing the same.

The present invention is a ceramic circuit board comprising an insulating layer made of ceramics, and a through conductor disposed in the insulating layer,
The through conductor includes a sintered conductor portion formed by sintering a conductor portion,
The ceramic circuit board is characterized in that a gap is formed at an interface between a part of the sintered conductor portion and the insulating layer.

Further, the present invention is a ceramic circuit board comprising an insulating layer made of ceramics and a through conductor disposed in the insulating layer,
The through conductor includes a sintered conductor part formed by sintering a conductor part, and a non-conductor part,
A part of the non-conductor portion faces the interface of the insulating layer.

  Further, the invention is characterized in that a part of the non-conductor portion is disposed along a current flowing direction of the through conductor.

  Further, the present invention is characterized in that the sintered conductor portion and the non-conductor portion are realized by a three-dimensional network structure that is coupled to each other.

  In the invention, it is preferable that the non-conductor portion is defined as 10% by volume or more and 80% by volume or less of the entire through conductor.

  According to the present invention, the sintered conductor portion has an average thickness obtained by cutting the sintered conductor portion along a virtual plane perpendicular to the substrate thickness direction, which is six times the skin depth of the high-frequency signal flowing through the through conductor. It is characterized by being defined above.

The present invention is also a method for manufacturing a ceramic circuit board comprising an insulating layer made of ceramics and a through conductor disposed in the insulating layer,
Producing a ceramic green sheet;
Producing a conductor paste including a precursor of the through conductor and a resin piece made of a resin to be bonded by a crosslinking reaction;
Filling the conductive paste into a through-hole formed in the ceramic green sheet;
Firing the ceramic green sheet and the conductor paste;
A method for producing a ceramic circuit board, comprising:

  According to the present invention, the through conductor includes a sintered conductor portion formed by sintering the conductor portion, and a gap is formed at the interface between a part of the sintered conductor portion and the insulating layer. There are effects like this. The surface area of the through conductor is increased, and the concentration of the magnetic field at the interface between the through conductor and the insulating layer is reduced. In other words, it is possible to flow current as much as possible inside the through conductor. Therefore, it is possible to reduce the loss of the through conductor and to minimize the transmission loss of a high-frequency signal or the like.

  According to the present invention, since a part of the non-conductor portion faces the interface of the insulating layer, the surface area of the through conductor is increased, and the concentration of the magnetic field at the interface between the through conductor and the insulating layer is reduced. Other effects similar to those of the first aspect of the invention are achieved.

  In addition, according to the present invention, a part of the non-conductor portion is disposed along the direction in which the current flows through the through conductor. Therefore, it is possible to suppress transmission loss due to particularly a long line length. Therefore, the transmission loss of the high frequency signal of the conductor can be further reduced.

  Moreover, according to this invention, a sintered conductor part and a nonconductor part are realizable by a three-dimensional network structure.

  In addition, according to the present invention, the non-conductor portion is defined to be 10% by volume or more and 80% by volume or less of the entire through conductor, thereby suppressing transmission loss of high-frequency signals and reducing the resistance of DC signals. Can do. When the volume ratio of the non-conductor portion is less than 10% by volume of the entire through conductor, the surface area of the through conductor becomes too small, and the effect of reducing the transmission loss of high-frequency signals cannot be obtained. If the volume ratio of the non-conductor portion exceeds 80% by volume of the entire through conductor, the volume of the sintered conductor portion becomes relatively small and the direct current resistance increases.

  Further, according to the present invention, since the average thickness of the sintered conductor portion is defined to be six times or more the skin depth of the high-frequency signal flowing through the through conductor, the following effects can be obtained. A sufficient cross-sectional area can be ensured with respect to the electromagnetic wave, and local concentration of the electromagnetic wave can be avoided.

  Further, according to the present invention, it is possible to obtain a through conductor having a three-dimensional network structure by suppressing the aggregation of the resins by producing a conductor paste including a resin piece made of a resin to be bonded by a crosslinking reaction. It becomes. Therefore, the surface area of the through conductor is increased, and the concentration of the magnetic field at the interface between the through conductor and the insulating layer is reduced. Therefore, it is possible to reduce the loss of the through conductor and to minimize the transmission loss of a high-frequency signal or the like.

  FIG. 1 is a cross-sectional view of a ceramic circuit board 1 according to an embodiment of the present invention, cut along a virtual plane in the board thickness direction. The ceramic circuit board 1 according to the present embodiment is applied to at least one of a multilayer wiring board using a high-frequency signal, a package for housing a semiconductor element, a module board, a high-frequency component, and the like. However, the ceramic circuit board according to the present embodiment can be applied in addition to these. The following description also includes a description of a method for manufacturing a ceramic circuit board.

  The ceramic circuit board 1 is configured by, for example, seven insulating layers 2 to 8 stacked in the thickness direction of the board. Surface conductors 9 are formed on the surface portions 2a and 8a of the uppermost and lowermost insulating layers 2 and 8, respectively. An internal conductor 10 is formed between insulating layers adjacent to each other in the substrate thickness direction. These insulating layers 2 to 8 are electrically and mechanically connected to the inner conductor 10 and the inner conductor 10 in the substrate thickness direction, and electrically and mechanically to the surface conductor 9 and the inner conductor 10. A through conductor 11 for connection is formed.

  FIG. 2 is a view showing the through conductor 11, FIG. 2A is an enlarged view of a main part of the through conductor 11, and FIG. 2B is a cross-sectional view taken along line AA in FIG. 2A. It is sectional drawing. The through conductor 11 includes a sintered conductor portion 12 in which the conductor portion is sintered, and a plurality of interfaces are formed at the interface between the insulating layer 3 on which the through conductor 11 is provided and a part of the sintered conductor portion 12. A gap 13 is formed. The gaps 13 at the interface are formed at appropriate intervals in the circumferential direction, and the gaps 13 are formed along the direction in which the current flows through the through conductor 11 (the so-called axial direction of the through conductor 11). A plurality of voids 13 are also formed inside the sintered conductor portion 12. Through the plurality of gaps 13, the through conductors 11 have a three-dimensional network structure coupled to each other.

  By the way, sufficient conductivity could not be obtained with the conventional ceramic circuit board because the interface between the through conductor and the insulating layer was rough despite the large cross-sectional area of the through conductor, and the isolated void inside the through conductor. It was because it included. That is, the conventional through conductor has to increase the adhesive strength with the insulating layer in order to suppress the peeling of the interface in the firing process due to the difference in thermal expansion coefficient with the insulating layer. As a result, an anchor-like adhesive portion was formed at the interface between the through conductor and the insulating layer, and the roughness of the interface was rough.

  Moreover, in order to relieve the distortion due to the difference in shrinkage behavior and the difference in firing shrinkage rate between the through conductor and the insulating layer, an isolated void was generated inside the through conductor. In this way, if the interface, that is, the surface of the through conductor is rough and there are isolated voids inside the through conductor, high-frequency signal current is concentrated near the conductor surface or near the interface between the conductor and the insulating layer due to the skin effect. As a result, the line length becomes longer and the thickness of the conductor near the surface becomes thinner due to voids, which increases the loss in high-frequency signal transmission.

  In the present embodiment, a gap 13 is formed at the interface between the insulating layers 2 to 8 and a part of the sintered conductor portion 12, and the gap 13 extends along the axial direction of the through conductor 11 (indicated by an arrow L1). Is formed. In other words, among the through conductors 11 provided in the through holes formed in the insulating layers 2 to 8, the portion other than the air gap 13 is the sintered conductor portion 12, and the surface 12 a is smooth. The conductor loss in can be kept low. The gap 13 formed at the interface only needs to extend a predetermined small distance in the axial direction, and may have any structure such as a columnar shape or a three-dimensional mesh shape.

  In order for the surface 12a of the sintered conductor portion to be smooth, the sintered conductor portion 12 is preferably in a state where the sintering has proceeded. Since the air gap 13 is formed at the interface between each insulating layer and a part of the sintered conductor portion 12 including the sintered conductor portion 12 on which such a smooth surface 12a is formed, an anchor as in the prior art It is possible to suppress the peeling of the interface while eliminating the need for an adhesive portion. In other words, since the surface 12a of the sintered conductor portion 12 can be smoothed as much as possible, when a high-frequency signal current flows in the vicinity of the interface between the sintered conductor portion 12 and each insulating layer, The line length can be shortened as much as possible, and the loss in the transmission of high-frequency signals can be reduced.

As shown in FIG. 2 (b), the thickness of the sintered conductor portion 12 separating the gaps 13 and 13 adjacent to each other in the direction perpendicular to the axial direction is 6 times or more the skin depth of the high-frequency signal passing through the through conductor 11. It is preferable that The skin depth δ is expressed by the following equation using the frequency f, the magnetic permeability μ, and the conductivity σ.
δ = (π · fμσ) ^−1/2

  By setting the thickness of the sintered conductor portion 12 to three times or more of the skin depth δ of the high-frequency signal passing through the through conductor 11, a sufficient cross-sectional area for the electromagnetic wave can be secured, and the local area of the electromagnetic wave can be secured. Can avoid general concentration. Even when the sintered conductor portion 12 is thick, the current substantially flows in a portion within 3δ from the surface of the conductor, and 95% or more of the current flows in this portion. If the conductor is pure silver, 3δ is about 90 μm at 5 MHz, about 9 μm at 500 MHz, and about 4.5 μm at 2 GHz. On the other hand, the dimensions of the surface conductor 9 and the internal conductor 10 are about 50 μm to 1 mm in width and about 5 μm to 30 μm in thickness, and the dimension of the through conductor 11 is about 50 μm to 300 μm in diameter.

  The volume ratio of the gap 13 in the through conductor 11 is preferably 10% by volume to 80% by volume. Thereby, the loss of the high-frequency signal can be suppressed and the resistance of the DC signal can be reduced. When the volume ratio of the gap 13 is less than 10% by volume of the entire through conductor, the surface area of the through conductor 11 becomes too small, and the effect of reducing the loss of high frequency signals cannot be obtained. On the other hand, when the volume ratio of the gap 13 exceeds 80% by volume of the entire through conductor, the volume of the sintered conductor portion 12 in the entire through conductor becomes too small, and the direct current resistance increases. Air or other gas is present in the gap 13, but it may be vacuum. Such a gap 13 is preferable because the through conductor 11 can have a fine structure.

  In the present embodiment, the gap 13 is formed in the through conductor 11, but a through conductor including the sintered conductor portion 12 and the nonconductor portion 13 </ b> A may be used. If the non-conductor portion 13A has a dielectric constant comparable to that of the insulating layers 2 to 8 around the conductor, the current flows in a distributed manner, so that the transmission loss of high-frequency signals is smaller than that of the prior art. Furthermore, when a conductor serving as a ground is formed near the conductor, the current concentrates on a portion facing the ground around the conductor, so that the dielectric constant of the non-conductor portion 13A is set so as to cancel out the current. The dielectric constant of the insulating layers 2 to 8 may be higher.

  3 to 5 are cross-sectional views of the ceramic circuit board according to the present embodiment. FIG. 6 is a flowchart showing stepwise the method for manufacturing the ceramic circuit board 1 according to the embodiment of the present invention.

  A method for manufacturing the ceramic circuit board 1 will be specifically described. As shown in FIG. 6, the manufacturing method of the ceramic circuit board 1 according to the present embodiment mainly includes a ceramic green sheet manufacturing process (step a1), a resin piece adding process (step a2), and a conductor paste filling process ( Step a3) and a firing step (Step a4). First, in step a1, a ceramic green sheet (simply referred to as “green sheet”) made of glass and a ceramic filler is prepared. The green sheet is made into a slurry by mixing a predetermined glass and ceramic powder composition, a volatile organic binder that easily volatilizes during firing, an organic solvent and, if necessary, a plasticizer. Using this slurry, a tape is formed by a lip coater method, a doctor blade method, or the like, and cut into a predetermined size to produce a green sheet.

Next, it transfers to step a2 and the conductor paste used as a penetration conductor is produced. As a conductive paste, add an organic binder, an organic solvent, and, if necessary, an organic or inorganic additive to any one of gold powder, silver powder, copper powder, and aluminum powder. A kneaded product is used. The shape of the conductor powder is not limited, but in order to form voids or non-conductor portions inside the through conductor, those having a relatively low Tap density are suitable, for example, 3 g / cm ³ or less.

  In order to form the gap 13 in the through conductor 11, resin beads (corresponding to a resin piece) made of a resin such as acrylic are added to the conductor paste. The shape of the resin beads is not limited to a spherical shape, and may be an elliptical shape or a rod shape. By changing the addition amount, size, and shape of the resin beads, the volume ratio of the gap 13 in the through conductor 11 can be changed. In other words, by controlling the volume ratio of the air gap 13 based on the addition amount, size, and shape of the resin beads, it is possible to suppress the loss of the high frequency signal and to reduce the resistance of the DC signal as much as possible. Can do. As described above, the loss of the high-frequency signal can be easily and reliably suppressed, and the resistance of the DC signal can be easily and reliably reduced.

  As an example of the resin beads, a cross-linked acrylic resin in which the main chain of the acrylic resin is bonded by a cross-linking reaction, which is spherical and has an average particle diameter of about 1 μm is preferable. By applying a cross-linked acrylic resin, the shape of the conductor paste is prevented from losing its shape and the resin is dispersed better. Therefore, problems such as the gap 13 of the through conductor 11 being lost due to the aggregation of the resins can be solved in advance. The particle diameter of the resin beads is preferably equal to or less than that of the conductor powder from the viewpoint of dispersion, and for example, about 1 μm to 3 μm is preferable. By changing at least one of the shape, size, and combination of resin beads made of acrylic resin, a void such as a three-dimensional network structure can be produced.

  In order to form a dielectric as the non-conductor portion 13A in the through conductor 11, a glass piece that softens and flows in a firing step described later is added instead of the resin beads.

  By changing the addition amount, size, and shape of the glass piece, the volume ratio of the non-conductor portion in the through conductor can be changed. By changing the volume ratio of the non-conductor portion, it is possible to easily and surely suppress the loss of the high-frequency signal and to reduce the resistance of the DC signal as much as possible.

  The softening and flowing temperature is preferably after the start of the sintering of the conductor powder. Thereby, it is possible to prevent the glass piece from undesirably coming out of the through conductor 11. On the contrary, the glass piece may come out of the through conductor 11 before the sintering of the conductor powder is started. The glass piece according to the present embodiment preferably has a low affinity with the conductor in order to reduce the roughness of the surface of the sintered conductor portion of the through conductor 11. For example, chemically wet glass with a conductor is glass with poor affinity for the conductor. In addition, the glass transition point is a glass lower than the sintering start temperature of the conductor powder, and is an amorphous glass or a crystalline glass having a high crystallization temperature from the sintering end temperature of the conductor powder, Or the crystal | crystallization which precipitates by the completion | finish temperature of sintering of conductor powder, or the crystalline glass which is 70 volume% or less is also glass with a bad affinity with a conductor. By applying such a glass piece having a low affinity with the conductor, the roughness of the surface of the sintered conductor portion of the through conductor 11 can be reduced, and therefore the conductor loss in high-frequency transmission can be kept low. Can do.

  Next, the process proceeds to the conductor paste filling step of step a3. First, a through hole is formed in the green sheet by punching or laser. In the formation stage of one through hole, the perimeter of the through hole is not only circular but also the shape of the through hole, such as gear shape and petal shape, by punching multiple times or scanning the laser May be longer than a circular one. The “plan view” is synonymous with viewing the through hole in the axial direction.

  The through-hole formed in this way is filled with the conductor paste. For the filling of the conductor paste, a screen printing method using a metal mask or an emulsion mesh screen mask drilled at a position corresponding to the through conductor forming position is used. At this time, as a method of extruding the paste through the mask, a method using a plate-like (or sword-like) squeegee made of polyurethane, a method of pressurizing and injecting the paste into the through-hole using a paste extruding squeegee head, etc. Use. If necessary, the conductor paste protruding from the surface of the green sheet is pressed and pushed into the through hole. Furthermore, the surface conductor layer and the inner conductor layer are deposited by screen printing using a conductor paste. Each green sheet or insulator paste thus obtained is laminated in the substrate thickness direction in accordance with a predetermined lamination order to form a laminated molded body. Thereafter, the process proceeds to the firing step of step a4. In the firing step, in addition to firing the laminated body alone, the laminated molded body may be fired while being constrained in the surface direction by pressure or the like.

  According to the ceramic circuit board and the manufacturing method thereof described above, since the gap 13 is formed at the interface between a part of the sintered conductor portion 12 and the insulating layers 2 to 8, the following effects can be obtained. The surface area of the through conductor 11 is increased, and the concentration of the magnetic field at the interface between the through conductor 11 and the insulating layers 2 to 8 is alleviated. In other words, a current can flow as much as possible inside the through conductor 11. Accordingly, the loss of the through conductor 11 can be reduced, and the transmission loss of a high frequency signal or the like can be minimized.

  When a dielectric is formed on the through conductor 11 as the non-conductor portion 13A, a part of the non-conductor portion 13A faces the interface between the insulating layers 2 to 8, so that the surface area of the through conductor 11 increases, and the through conductor 11 And the concentration of the magnetic field at the interface between the insulating layers 2 to 8 is alleviated. Other effects similar to those in the case of the gap 13 are obtained. Since a part of the gap 13 or the non-conductor portion 13A is arranged along the direction in which the current flows through the through conductor 11, it is possible to suppress transmission loss particularly due to an increase in the line length. Therefore, the transmission loss of the high frequency signal of the conductor can be further reduced.

FIG. 3 is a cross-sectional view of the ceramic circuit board 31 according to the present embodiment.
The ceramic circuit board 31 is configured, for example, by laminating 15 insulating layers 31a to 31o in the thickness direction of the board. Surface conductors 32 are formed on the surface portions of the uppermost and lowermost insulating layers 31a and 31h, respectively. An internal conductor 33 is formed between insulating layers adjacent to each other in the substrate thickness direction. The insulating layers 31a to 31o are electrically and mechanically connected to the inner conductor 33 and the inner conductor 33 in the substrate thickness direction, and are electrically and mechanically connected to the surface conductor 32 and the inner conductor 33. A through conductor 34 for connection is formed. In addition, a cavity 35 is formed in the ceramic circuit board 31.

  The insulating layers 31a to 31h are first insulating layers, and the insulating layers 31i to 31o are second insulating layers having a composition different from that of the first insulating layers 31a to 31h. The first insulating layer and the second insulating layer have different shrinkage temperatures during firing, and any one of the first insulating layers 31a to 31h and the second insulating layers 31i to 31o is fired. The composition is such that the firing shrinkage of the other insulating layer is almost completed by the temperature at which the shrinkage starts. The term “shrinkage shrinkage almost completed” means that the shrinkage of 97% or more, particularly 98% or more, further 99% or more of the final firing volume shrinkage is finished.

  As described above, the temperature range in which the first insulating layers 31a to 31h are baked and contracted is different from the temperature range in which the second insulating layers 31i to 31o are baked and contracted. Accordingly, when the first insulating layers 31a to 31h contract, the second insulating layers 31i to 31o do not contract. Therefore, the first insulating layers 31a to 31h are in the XY direction (parallel to the main surface of the substrate). ) In the Z direction (the thickness direction of the substrate). In addition, when the second insulating layers 31i to 31o contract, the first insulating layers 31a to 31h do not contract. Therefore, the second insulating layers 31i to 31o are prevented from contracting in the XY direction. Contracts in the Z direction. That is, the first insulating layers 31a to 31h and the second insulating layers 31i to 31o can suppress the contraction in the XY direction, and the ceramic circuit board 31 contracts in the XY direction. The variation in the amount can be suppressed, and the amount of contraction in the XY direction can be made close to zero.

  Although the ceramic circuit board that suppresses the shrinkage in the XY direction as described above improves the dimensional accuracy in the XY direction, the shrinkage of the through conductor is difficult to be restrained in the XY direction. The through conductors protruded from the surface of the ceramic circuit board or were depressed.

  In the ceramic circuit board 31 according to the embodiment of the present invention, a gap is formed in the through conductor 34 even after the through conductor 34 is sintered in the firing step of the ceramic circuit board 31. Following the firing shrinkage of the insulating layer shrinking in the Z direction, the penetrating conductor 34 is easily deformed, and the penetrating conductor 34 can be prevented from protruding or sinking. In order to further suppress protrusions or depressions, it is preferable that the through conductors 34 are not baked and shrunk at a temperature higher than the end of sintering shrinkage of the first insulating layers 31a to 31h and the second insulating layers 31i to 31o. It is more preferable that the temperature at which the firing shrinkage of the through conductor 34 is completed is lower than the firing shrinkage start temperature of the insulating layer having the higher shrinkage temperature, and the firing shrinkage start temperature of the insulating layer having the lower firing shrinkage temperature is lower. It is more preferable that the temperature at which the firing shrinkage of the through conductor 34 is completed is lower.

  Each of the first insulating layers 31a to 31h and the second insulating layers 31i to 31o is a surface conductor 32, an inner conductor 33, and a through conductor 34 made of a conductor mainly composed of a low melting point metal such as Au, Ag and Cu. In order to use it, it is preferable that it is a glass ceramic which can be baked at about 1050 degreeC or less. The first insulating layer is made of glass ceramics because the raw material of the first insulating layer is made of the first glass and the first ceramic, or made of the first glass. is there. The second insulating layer is made of glass ceramics because the raw material of the second insulating layer is made of the second glass and the second ceramic, or made of the second glass. is there.

  In order to suppress shrinkage in the XY direction more effectively, the softening temperature of the first glass is 10 ° C. or more, more preferably 40 ° C. or more, and preferably 90 ° C. than the softening temperature of the second glass. It is preferable that the value is lower. In addition, the material glass of the insulating layer having a lower firing shrinkage temperature is a crystalline glass having a crystallization temperature lower than the softening point of the glass of the insulating layer material having a higher firing shrinkage temperature. Since the glass of the insulating layer having a low shrinkage temperature is crystallized, and the insulating layer having a higher temperature at which the baking shrinks after the insulating layer becomes strong, the shrinkage in the XY direction is more effectively suppressed. it can.

  In order to suppress the deformation of the cavity 35, it is preferable that the insulating layer 31 a is an insulating layer having a low temperature at which the insulating layer 31 a is baked and shrunk on the outermost layer on the surface of the ceramic circuit board 31, and the insulating layer 31 a It is preferable that the thickness is thinner than the second insulating layer 31i stacked on the layer.

  FIG. 3 shows an example in which both the first insulating layer and the second insulating layer are provided between the inner conductor 33 and the inner conductor 33 or between the surface conductor 32 and the inner conductor 33. The configuration of the first insulating layer and the second insulating layer is not limited to this. For example, a part of the insulating layer between the inner conductor 33 and the inner conductor 33 in FIG. 3 or between the surface conductor 32 and the inner conductor 33 is one of the first insulating layer and the second insulating layer. 1 may be used as the first insulating layer, and the insulating layers 3 to 7 may be used as the second insulating layer.

First, an average composition comprising 24.9% by mass of MgO, 2.7% by mass of _{Al 2} O ₃ , 45.0% by mass of SiO ₂ , 0.1% by mass of CuO, and 27.3% by mass of CaO. A ceramic material consisting of 60% by mass of glass powder having a particle size of 2 μm and 40% by mass of _{Al 2} O ₃ powder having an average particle size of about 1 μm was prepared. A slurry obtained by adding an acrylic organic binder, a plasticizer, and an organic solvent to this ceramic material was thinned by a doctor blade method to produce a green sheet for a substrate.

Next, a small amount of ruthenium oxide and rhodium are added to the silver powder, and 5 parts by mass of acrylic beads having a diameter of 3 μm and 15 parts by mass of the organic vehicle are added to 100 parts by mass of the silver powder, and these are stirred. Then, the mixture was mixed with a three-roll mill until the aggregates of silver powder and organic binder disappeared to produce a conductor paste. Here, as an organic vehicle, what comprised 5 mass parts of ethyl cellulose as an organic binder, and 95 mass parts of (alpha)-terpineol as an organic solvent was used. The Ag powder used here has a specific surface area of 0.3 m ² / g or less, a number of primary particles necked by heat treatment, and a Tap density of 2 g / cm ³ or less.

  Next, a through hole having a diameter of 200 μm for filling the through conductor was formed in the green sheet by a laser, and the through hole was filled with the conductive paste. Next, the green sheet in which the through hole was filled with the conductive paste was pressed with a flat plate mold, and the portion of the conductive paste protruding from the green sheet was pushed into the through hole.

  A conductor pattern to be a signal conductor of the λ / 4 resonator was formed on the surface of the green sheet by screen printing. In a specific structure of the λ / 4 resonator, a signal conductor having a length of λ / 4 is formed by the internal conductor 42 and the through conductor 43, and one end of the through conductor 43 is connected to the ground conductor 44 (see FIG. 4). ). Similarly, as shown in FIG. 5, a conductor pattern was separately printed to produce a λ / 2 resonator composed of one end of a line conductor 52 having a length of λ / 2 and a ground conductor 53. Then, after aligning these green sheets, they are laminated and pressed to produce a laminate, which is debindered at 400 ° C. in the atmosphere, and further baked at 910 ° C. in the atmosphere to produce a wiring board. did. As described above, samples in which the lengths of the through conductors forming the resonator were changed were produced.

By changing the addition amount of the acrylic beads, samples having different void volume% were prepared. Further, instead of acrylic beads, the composition is 18.3% by mass of BaO, 37.1% by mass of B ₂ O ₃ , 32.6% by mass of SiO ₂ , 2.5% by mass of SnO ₂ , , 9.5 mass% CaO glass was added to prepare a sample in which a dielectric was formed as a non-conductor portion.

  The resonance characteristics at 2 GHz of each circuit board after firing were measured, and the transmission loss of Via was calculated from them. Specifically, the electrical conductivity is calculated from the unloaded Q (Qu) of the λ / 4 resonator, and is used as the combined conductivity of the line conductor and the Via conductor. Similarly, from the λ / 2 resonator to the line The conductivity of the conductor alone was obtained, and the loss of the through conductor was calculated from the difference between the conductivity obtained from the λ / 4 resonator and the conductivity obtained from the λ / 2 resonator.

  FIG. 7 is a scanning electron microscope image of a fractured surface near the interface between the through conductor 11 and the insulating layer 3. In addition, the through conductor was cut with a microtome, and the area% of the void or non-conductor portion in the longitudinal section was measured with an image analysis apparatus (Luzex) in a 50 × 50 μm range of a 500 × scanning electron microscope image. Was the volume% of the non-conductor portion of the through conductor. Further, similarly to the above, the through conductor was cut at three places with a microtome, and the longitudinal section was observed with a scanning electron microscope, thereby confirming that the gap or the non-conductor portion was connected in the axial direction. When it was difficult to judge from the longitudinal cross section, the conductor sintered portion was scraped off and confirmed by a secondary ion mass spectrometer. In addition, the through conductor was cut at 10 locations with a microtome, and the thickness of the sintered conductor portion in the cross section was measured from a scanning electron microscope image at a magnification of 1000 times. Specifically, on one cut surface, the minimum thickness of the conductor part is measured with a ruler, and the actual dimension calculated from the magnification of the photograph is taken as the thickness of the sintered conductor part in the cross section, and measurement of 10 cross sections The average of the values was defined as the thickness of the sintered conductor portion of the through conductor.

  Further, the direct current resistance of the through conductor was measured with an mΩ meter, and the volume resistivity was calculated from the diameter and length obtained from the cross section. Table 1 shows the result of characteristic evaluation under each condition.

  In the sample of the present invention, when the volume ratio of the gap or non-conductor portion connected to the interface between the through conductor and the insulating layer is 10% by volume or more and 80% by volume or less, 0.1 dB / cm or more as compared with the conventional through conductor It was found that the transmission loss was less than 0.4 dB / cm. Sample No. in which the nonconductor portion is a dielectric. Sample No. 7 in which a gap is formed in the through conductor. Compared to 4, it was found that transmission loss was reduced.

It is sectional drawing which cut | disconnected and saw the ceramic circuit board 1 which concerns on embodiment of this invention with the virtual plane of the board | substrate thickness direction. FIGS. 2A and 2B are diagrams illustrating the through conductor 11, FIG. 2A is an enlarged view of a main part of the through conductor 11, and FIG. 2B is a cross-sectional view of FIG. 2A taken along line AA. . It is sectional drawing of the ceramic circuit board 31 which concerns on this embodiment. It is sectional drawing of the ceramic circuit board which concerns on this embodiment. It is sectional drawing of the ceramic circuit board which concerns on this embodiment. It is a flowchart showing the manufacturing method of the ceramic circuit board 1 which concerns on embodiment of this invention in steps. 3 is a scanning electron microscope image of a fracture surface near the interface between a through conductor 11 and an insulating layer 3.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Ceramic circuit board 2-8 Insulation layer 9 Surface conductor 10 Inner conductor 11 Through conductor 13 Space | gap 13A Nonconductor part 41 Ceramic circuit board ((lambda) / 4 resonator)
41a-f Insulating layer 42 Inner conductor (λ / 4 length signal conductor)
42 Through conductor (λ / 4 length signal conductor)
44 Internal conductor (grounding conductor)
51 Ceramic circuit board (λ / 2 resonator)
51a-f Insulating layer 52 Inner conductor (λ / 2 length signal conductor)
53 Internal conductor (grounding conductor)

Claims (7)

A ceramic circuit board comprising an insulating layer made of ceramics and a through conductor disposed in the insulating layer,
The through conductor includes a sintered conductor portion formed by sintering a conductor portion,
A ceramic circuit board, wherein a gap is formed at an interface between a part of the sintered conductor portion and the insulating layer. A ceramic circuit board comprising an insulating layer made of ceramics and a through conductor disposed in the insulating layer,
The through conductor includes a sintered conductor part formed by sintering a conductor part, and a non-conductor part,
A ceramic circuit board, wherein a part of the non-conductor portion faces the interface of the insulating layer.   The ceramic circuit board according to claim 2, wherein a part of the non-conductor portion is disposed along a direction in which a current flows through the through conductor.   4. The ceramic circuit board according to claim 2, wherein the sintered conductor portion and the non-conductor portion are realized by a three-dimensional network structure coupled to each other.   5. The ceramic circuit board according to claim 2, wherein the non-conductor portion is defined to be 10 volume% or more and 80 volume% or less of the entire through conductor.   The sintered conductor portion is defined to have an average thickness obtained by cutting the sintered conductor portion along a virtual plane perpendicular to the substrate thickness direction to be not less than 6 times the skin depth of the high-frequency signal flowing through the through conductor. The ceramic circuit board according to claim 1, wherein the ceramic circuit board is provided. A method of manufacturing a ceramic circuit board comprising an insulating layer made of ceramics and a through conductor disposed in the insulating layer,
Producing a ceramic green sheet;
Producing a conductor paste including a precursor of the through conductor and a resin piece made of a resin to be bonded by a crosslinking reaction;
Filling the conductive paste into a through-hole formed in the ceramic green sheet;
Firing the ceramic green sheet and the conductor paste;
A method for producing a ceramic circuit board, comprising: