JP2008016572A - Wiring substrate, and method for manufacturing the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a wiring substrate and a method for manufacturing the same with which delamination and voids are never concentrated at the area near the junction area between wiring conductors and via conductors, and a higher conductivity can be attained in a high frequency region. <P>SOLUTION: In the wiring substrate 1, a wiring conductor 2 and a via conductor 3 are formed in insulating layers 1a to 1g formed of a glass ceramics obtained with the baking process. A wiring conductor 2 is formed with a copper foil, a conductive layer 4b is formed including a metallic element in the amount more than non-metallic element that is formed by baking a conductor powder layer on the surface perpendicular to the thickness direction of the copper foil, and this conductor layer 4b is joined with the via conductor 3 and insulating layers 1a to 1g. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a wiring board and a manufacturing method thereof, and more particularly to a wiring board that can be suitably used for a multilayer wiring board, a package for housing a semiconductor element, a hybrid integrated circuit device, and the like, and a manufacturing method thereof.

  As a wiring board applied to semiconductor element storage packages that mount semiconductor elements such as IC (Integrated Circuit) and LSI (Large Scale Integration), which are becoming increasingly integrated, and hybrid integrated circuit devices that are equipped with various electronic components In many cases, a wiring board using an alumina sintered body as an insulating material is used. In recent years, in order to mount ICs and LSIs that are becoming increasingly integrated, low wiring resistance is required, and metals with low conductor resistance such as copper, silver, and gold that melt at about 1050 ° C. Therefore, glass ceramics that can be sintered at a low temperature of 1050 ° C. or lower have been used as insulating materials for wiring boards.

  Glass ceramics can be obtained by firing glass, or by mixing and firing glass and filler. Among them, by using glass that crystallizes by firing, crystals having desired characteristics are precipitated. Since glass ceramics having various characteristics can be obtained, research has been conducted intensively in recent years.

  Such a conventional glass-ceramic wiring board has a structure in which a wiring conductor mainly composed of copper, silver, gold or the like is disposed on a through-hole portion or a surface of an insulating layer.

  Recently, for the purpose of reducing direct current resistance and reducing voids, a glass ceramic wiring board using a copper foil as a wiring conductor has attracted attention.

  For example, Patent Document 1 discloses a glass ceramic multilayer wiring circuit characterized in that after a copper foil having a surface roughness of 3 μm or more is formed into a pattern, the processed surface is laminated and pressure-bonded so as to be an adhesive surface with a green sheet. A method for manufacturing a substrate is disclosed.

  And in patent document 2, by electrodepositing the metal layer or particle | grains containing at least 1 sort (s) of Zn, Zr, Sn which has the effect which inhibits the crystal grain growth of copper on the surface of the copper foil to transfer, It is disclosed that the shape of the roughened surface of the copper foil can be maintained even after sintering.

  Patent Document 3 discloses adhesion between a wiring conductor layer and an insulating substrate by forming an adhesive layer in which metal particles are dispersed in glass at the interface between the wiring conductor layer made of a high-purity metal such as a metal foil and the insulating substrate. It is disclosed that the strength can be increased.

  As a specific method for producing these glass ceramic wiring boards, first, a raw material powder to become glass ceramics and a slurry prepared by adding a solvent to an organic binder are formed into a sheet shape by a doctor blade method or the like to produce a green sheet. To do. Next, a via hole is punched into the obtained green sheet.

  Next, the via hole is filled with a via conductor paste mainly composed of copper, silver, gold or the like. Subsequently, a conductor paste mainly composed of copper, silver, gold or the like is printed on the green sheet in a wiring pattern by a screen printing method or the like. Alternatively, an electrolytic copper foil or a rolled copper foil is formed into a desired pattern shape and then pressed onto a green sheet.

  Finally, a plurality of produced green sheets are pressure-laminated and fired at 800 ° C. to 1000 ° C., whereby a glass ceramic wiring substrate can be produced.

Japanese Patent Laid-Open No. 11-330697 Japanese Patent Laid-Open No. 2000-200909 Japanese Patent Laid-Open No. 2002-50865

  It is known that metal foil such as copper foil does not substantially shrink by firing. When such a metal foil is used as a wiring conductor, a mismatch in behavior occurs between the insulating layer that shrinks during firing and the metal foil during firing, causing problems such as peeling of the metal foil and deformation of the insulating layer. .

  Therefore, when using a metal foil for the wiring conductor, it is necessary to perform non-shrinkage firing that suppresses firing shrinkage. In non-shrinkage firing, the wiring board is not fired and shrunk in the direction perpendicular to the thickness direction of the wiring board, and is fired and shrunk only in the thickness direction.

  During this non-shrinkage firing, if a mismatch in sintering behavior occurs between the insulating layer and the via conductor, the surfaces perpendicular to the thickness direction of the insulating layer and the via conductor do not match, and the via conductor has a large protrusion, or It will sink.

  Specifically, the via conductor protrudes when the shrinkage amount of the via conductor is smaller than that of the insulating layer or when the firing end temperature of the via conductor is lower than the firing end temperature of the insulating layer.

  In addition, the via conductor is depressed when the amount of shrinkage of the via conductor is larger than that of the insulating layer, or when the firing shrinkage temperature of the via conductor is higher than the firing shrinkage temperature of the insulating layer.

  On the other hand, in the vicinity of the joint between the metal foil and the via conductor, the metal foil is not plastic and does not shrink by firing. Therefore, the deformation of the via conductor as described above causes concentration of delamination and voids. .

  In addition, the electrical conductivity of the wiring conductor in the high-frequency region is affected by the specific resistance of the wiring conductor and the shape of the interface between the wiring conductor and the insulating layer. become.

  This is because when the frequency of the electromagnetic wave flowing through the wiring conductor increases, the current density flowing near the interface between the wiring conductor and the insulating layer increases due to the skin effect. When the unevenness of the interface between the wiring conductor and the insulating layer is large, the movement distance of the charge becomes longer than when the interface is smooth, and the movement of the charge is delayed because the charge is concentrated near the tip of the unevenness, The conductivity decreases.

  Furthermore, recent research results have confirmed that the unevenness of the end surface, which is the surface in the thickness direction of the wiring conductor, has a large effect on the conductivity.

  In Patent Document 1 and Patent Document 2, a copper foil having a roughened surface is used as a wiring conductor. This is because it is difficult for a copper foil alone to maintain sufficient adhesive strength with the insulating layer, and by making the surface rough, the copper foil anchors to the insulating layer and maintains sufficient adhesive strength. be able to.

  However, in this method, the roughness of the interface increases due to the roughening treatment, and the conductivity of the copper foil is greatly reduced.

  In patent document 3, since there is much content of the glass and filler component in a contact bonding layer, the resistance value of a contact bonding layer will become high and electrical conductivity will fall.

  Moreover, in patent documents 1-3, since metal foil and a via conductor join directly, there exists a problem that concentration of a delamination and a void will generate | occur | produce in the vicinity of a junction part.

  The object of the present invention is to solve the above-mentioned problems, and to provide a wiring board having no delamination or void concentration near the junction between the wiring conductor and the via conductor and having high conductivity in the high frequency region, and a method for manufacturing the same. For the purpose.

  The present invention provides a wiring board in which a wiring conductor and a via conductor are formed by simultaneous firing on an insulating layer made of glass ceramics, wherein the wiring conductor is formed of a metal foil and has a surface perpendicular to the thickness direction of the metal foil. A first conductive layer obtained by firing a conductive powder layer on one of the surfaces and containing a metal component more than a non-metallic component is formed, and the first conductive layer includes the via conductor and the insulation. A wiring board characterized by being bonded to a layer.

  The wiring board of the present invention is characterized in that X is 20 or less when the ratio of the metal component to the non-metal component of the first conductor layer is 100: X.

  In the wiring board of the present invention, the conductor powder layer is fired on one of the surfaces perpendicular to the thickness direction of the metal foil and opposite to the surface on which the first conductor layer is formed. A second conductor layer containing a metal component more than a non-metal component is formed, and the second conductor layer is bonded to the insulating layer.

  The wiring board of the present invention is characterized in that Y is 20 or less when the ratio of the metal component and the non-metal component of the first conductor layer and the second conductor layer is 100: Y. To do.

  In the wiring board of the present invention, the metal foil and the first or second conductor layer have the same size when viewed in a plan view from a direction perpendicular to the main surface of the wiring board. The second conductor layer is formed in a range where the metal foil is formed.

The present invention also includes (a) a step of forming a through hole in a green sheet containing glass powder, and filling the through hole with a via conductor paste;
(B) applying a conductive paste to the green sheet to form a first conductive powder layer;
(C) transferring a metal foil onto the first conductor powder layer;
(D) a step of laminating a plurality of the green sheets including the green sheet on which the metal foil is formed to produce a laminate;
And (e) firing the laminated body at a temperature lower than the melting point of the metal forming the metal foil while suppressing shrinkage in a direction perpendicular to the thickness direction of the laminated body. It is a manufacturing method of a wiring board.

  Moreover, the manufacturing method of the wiring board of the present invention is characterized in that the average particle size of the metal powder contained in the conductor paste is 5 μm or less.

  According to the present invention, in a wiring board in which a wiring conductor and a via conductor are formed on an insulating layer made of glass ceramics, the wiring conductor is formed of a metal foil, and one of the surfaces perpendicular to the thickness direction of the metal foil. Obtained by firing a conductor powder layer on one surface, a first conductor layer containing a metal component more than a non-metal component is formed, and the first conductor layer is bonded to a via conductor Because the via conductor and the conductor layer are joined at the joint between the via conductor and the wiring conductor, the conductor powder layer absorbs the deformation of the via conductor during non-shrinkage firing, and delamination and void concentration occur. Generation can be reduced.

  Moreover, since the first conductor layer is bonded to the insulating layer, the adhesive strength between the metal foil and the insulating layer can be increased without roughening the metal foil.

  Furthermore, since the interface between the insulating layer and the wiring conductor can be smoothed by the conductor layer, high conductivity can be obtained in the high frequency region.

  Further, according to the present invention, when the ratio of the metal component to the non-metal component of the first conductor layer is 100: X, the resistance value of the first conductor layer is reduced by setting X to 20 or less. Therefore, higher electrical conductivity can be obtained in the high frequency region.

  Further, according to the present invention, the conductive powder layer is obtained by firing on one of the surfaces perpendicular to the thickness direction of the metal foil and on the surface opposite to the surface on which the first conductor layer is formed. The second conductor layer containing a metal component more than the non-metal component is formed, and the second conductor layer is bonded to the insulating layer without roughening the surface of the metal foil. The adhesive strength between the metal foil and the insulating layer can be further increased.

  Further, since the interface between the insulating layer and the wiring conductor can be smoothed by the conductor layer, higher conductivity can be obtained in the high frequency region.

  Further, according to the present invention, when the ratio of the metal component and the non-metal component of the first conductor layer and the second conductor layer is 100: Y, the first conductor is reduced by setting Y to 20 or less. Since the resistance values of the layer and the second conductor layer are low, higher conductivity can be obtained in the high frequency region.

  Further, according to the present invention, the metal foil and the first or second conductor layer have the same size when viewed in a plan view from a direction perpendicular to the main surface of the wiring board, and these first or second conductors Since the layer is formed within the range in which the metal foil is formed, the current in the high-frequency region flowing through the end surface flows only through the metal foil portion, so that an end surface having high conductivity can be obtained.

  In addition, the wiring board of the present invention has a laminate formed by laminating a plurality of green sheets including the first conductor powder layer and the green sheet on which the metal foil is formed, and then the melting point of the metal forming the metal foil. It is manufactured by firing at a low temperature while suppressing shrinkage in the direction perpendicular to the thickness direction of the laminate.

  In the manufacturing method described above, by firing while suppressing shrinkage in the direction perpendicular to the thickness direction of the laminate, there is no delamination or void concentration near the junction between the wiring conductor and the via conductor, and conduction in the high-frequency region. A wiring board having a high rate can be provided.

  According to the present invention, since the average particle size of the metal powder contained in the conductor paste is 5 μm or less, the influence of the unevenness at the interface between the insulating layer and the wiring conductor is reduced, so that higher conductivity in the high frequency region. It is possible to provide a wiring board capable of obtaining a rate.

  The wiring board of the present invention is a glass ceramic wiring board in which wiring conductors and via conductors are formed in an insulating layer.

  FIG. 1A is a partial cross-sectional view showing the structure of the wiring board of the present invention, and FIG. 1B shows the vicinity of the junction between the internal conductor 2b and the via conductor 3 of the wiring board of FIG. It is a fragmentary sectional view showing the structure.

  As shown in FIG. 1A, a wiring board 1 of the present invention is composed of seven insulating layers 1a to 1g, and a surface conductor 2a is formed on the insulating layers 1a and 1g located on the surface of the wiring board 1. ing. An internal conductor 2b is formed between the insulating layers 1a to 1g. The insulating layers 1a to 1g are formed with via conductors 3 for connecting the surface conductor 2a and the internal conductor 2b in the thickness direction or for connecting the internal conductors 2b.

In the wiring board 1 of the present invention, for example, as shown in FIG. 1B, the wiring conductor 2 composed of the surface conductor 2a and the internal conductor 2b is mainly formed of a metal foil 4a.
A conductive layer 4b obtained by firing a conductive powder layer on a surface perpendicular to the thickness direction of the metal foil 4a and containing a metal component more than a non-metallic component is formed. The conductive layer 4b is an insulating layer. 1c-1e and the via conductor 3 are joined.

  In the firing process, the conductor powder layer is softly deformed compared to the metal foil 4a, so that the conductor powder layer absorbs the deformation of the via conductor 3 that occurs at the time of non-shrink firing at the joint between the conductor layer 4b and the via conductor 3. It is possible to reduce the concentration of delamination and voids generated near the junction between the wiring conductor 2 and the via conductor 3.

  Moreover, by providing the conductor layer 4b between the metal foil 4a and the insulating layers 1c to 1e, the adhesive strength between the metal foil 4a and the insulating layers 1c to 1e can be increased without roughening the metal foil 4a. .

  Furthermore, since the interface between the insulating layers 1c to 1e and the wiring conductor 2 can be smoothed by the conductor layer 4b, the unevenness of the interface between the wiring conductor 2 and the insulating layers 1c to 1e compared to the roughened metal foil 4a. And high conductivity can be obtained in a high frequency region.

  Further, when the ratio of the metal component and the non-metal component of the conductor layer 4b is 100: X in terms of mass part ratio, X is preferably 20 or less. Thereby, since the resistance value of the conductor layer 4b becomes low, higher conductivity can be obtained in the high frequency region.

  In the present invention, the metal foil 4a may or may not be roughened. However, if the surface roughness of the surface perpendicular to the thickness direction of the metal foil 4a is increased, it is difficult to eliminate the surface roughness by the conductor layer 4b, and the conductivity near the interface of the wiring conductor 2 is decreased. It is preferable not to roughen the metal foil 4a.

  Further, when viewed in a plan view from a direction perpendicular to the main surface of the wiring board 1, the metal foil 4a and the conductor layer 4b are substantially the same size, and the conductor layer 4b is formed within the range where the metal foil 4a is formed. It is preferable that That is, it is preferable that the width 5 of the conductor layer 4b is not more than the width 6 of the metal foil 4a.

  When the wiring conductor 2 is formed with the metal foil 4a, the patterning is performed by etching the metal foil 4a, so that the shape of the end face is smooth.

  On the other hand, the conductor layer 4b has less irregularities at the interface than the roughened metal foil 4a. However, since the screen conductor is used when the wiring conductor 2 is formed, the conductor layer 4b is affected by the mesh of the screen. The unevenness of becomes large.

  Therefore, in order to obtain an end face having high conductivity in the high frequency region, it is necessary that the current flowing through the end face flows only through the metal foil 4a having a smooth end face shape, and therefore the width 6 of the metal foil 4a and the conductor By setting the difference from the width 5 of the layer 4b to be 30 μm or less, an end face having high conductivity can be obtained.

  As a result, the conductor layer 4b can smooth the interface of the wiring conductor 2 with the insulating layers 1a to 1g, and the difference between the width 6 of the metal foil 4a and the width 5 of the conductor layer 4b is 30 μm or less. Since the end surface of the wiring conductor 2 can be made smooth by making the above, a high conductivity of the wiring conductor 2 can be obtained.

  In the present invention, depending on the use of the wiring board 1 and the design of the wiring conductor 2, the portion of the wiring conductor 1 that requires particularly high conductivity is made a layer composed of the metal foil 4a and the conductor layer 4b, and other portions. It is good also as a layer comprised only by the metal foil 4a or the conductor layer 4b. In that case, the layer constituted by only one of them is preferably a layer constituted only by a conductor layer in order to suppress delamination and concentration of voids at the joint portion between the wiring conductor and the via conductor.

  Further, as another embodiment, as shown in FIG. 2, a configuration in which the conductor layer 4 b is not formed on the surface perpendicular to the thickness direction of the metal foil 4 a opposite to the surface bonded to the via conductor. It may be.

The manufacturing method of the wiring board 1 of the present invention includes a step of producing a green sheet, a step of producing a via hole and filling a via conductor paste, a step of forming a first conductor powder layer, a metal foil, as shown in FIG. And a step of forming a second conductor powder layer, a step of producing a laminate, and a firing step.
Below, the manufacturing method of the wiring board 1 of this invention is demonstrated in detail.

(Process for producing green sheets)
First, in order to prepare a slurry for producing a green sheet, a glass powder and a ceramic filler powder are prepared as raw material powders.

The glass powder contains SiO ₂ and at least one of B ₂ O ₃ , Al ₂ O ₃ , ZnO, PbO, alkaline earth metal oxide, and alkali metal oxide. For example, SiO ₂ —B ₂ O ₃ system, SiO ₂ —B ₂ O ₃ —Al ₂ O ₃ system, SiO ₂ —B ₂ O ₃ —Al ₂ O ₃ —MO system (M is Ca, Sr, Mg, Borosilicate glass, alkali silicate glass, Ba glass, Pb glass, Bi glass, and the like.

  Among these, after baking treatment, at least one kind of crystals of lithium silicate, quartz, cristobalite, cordierite, mullite, anorthite, serdian, spinel, garnite, willemite, dolomite, petalite, diopside and substituted derivatives thereof. The glass that precipitates the above is preferable, and glass in which diopside is precipitated is preferable in that the flexural strength of the wiring board is increased, and the cordage is provided in that the dielectric constant and the thermal expansion of the wiring board can be reduced. Glass from which light is deposited is preferred.

The ceramic filler powder is not particularly limited, and SiO ₂ such as quartz and cristobalite, Al ₂ O ₃ , ZrO ₂ , cordierite, mullite, forsterite, enstatite, spinel, magnesia and the like are suitable. is there.

  Among these, alumina is preferable in terms of excellent strength and low cost, and quartz is preferable in that the wiring board can be highly thermally expanded.

  A predetermined amount of the above raw material powder is weighed and a slurry is prepared by adding an organic binder, a solvent, and optionally a plasticizer, and then formed into a sheet by a known forming method such as a doctor blade method, a rolling method, or a pressing method. Then, a green sheet having a thickness of 20 μm to 500 μm is produced.

(Process for making via holes and filling via conductor paste)
Subsequently, via holes (through holes) with a diameter of 80 μm to 200 μm are formed in the produced green sheet by laser, micro drill, punching, or the like.

  Next, in order to prepare a via conductor paste for filling the via hole, a metal powder and a glass powder are prepared as raw material powders.

  Although it does not specifically limit as metal powder, Copper, silver, or gold | metal | money is preferable from the point which is excellent in low resistance.

The glass powder is not particularly limited, and examples thereof include borosilicate glass, zinc borosilicate glass, and lead borosilicate glass. In particular, SiO ₂ —B ₂ O ₃ —Al ₂ O ₃ —BaO—CaO-based glass is preferable because it is excellent in co-firing with metal powder at 800 ° C. to 1100 ° C. and improves the adhesive strength with glass ceramics. .

  However, since the glass powder is added for the purpose of adjusting the sintering behavior of the via conductor and improving the adhesive strength with the glass ceramic, it can be removed if these requirements are small.

  In addition to metal powder and glass powder, the sintering behavior can be adjusted by adding filler components such as alumina and silica and organic components such as resin beads.

  A predetermined amount of the above raw material powder is weighed, and an organic binder and a solvent, and further, a dispersant as required are added to prepare a via conductor paste.

  The viscosity of the via conductor paste is preferably 100 Pa · s to 350 Pa · s in consideration of the filling property to the via hole.

  Next, the via conductor paste is filled into the via hole by using a filling method such as screen printing.

(Step of forming the first conductor powder layer)
Subsequently, a conductor paste used for pattern printing for forming the first conductor powder layer is prepared.

The method for preparing the conductor paste is the same as the method for preparing the via conductor paste.
Here, the particle size of the metal powder used for the conductor paste is desirably small, and the average particle size is preferably 5 μm or less.

  When the particle size of the metal powder is large, the space surrounded by the metal particles in the conductor paste becomes large, and this space greatly affects the unevenness of the conductor layer after firing. Therefore, when the average particle diameter is 5 μm or less, the influence of the unevenness at the interface between the wiring conductor and the insulating layer is reduced, and higher conductivity can be obtained in the high frequency region.

  The first conductor powder layer is a layer mainly composed of metal powder, and may contain an organic binder or the like in order to maintain the shape. The first conductor powder layer can be produced by drying the conductor paste, but may be produced by molding metal powder by other methods.

  As an inorganic component in the first conductor powder layer, glass powder, ceramic filler, and the like may be included in addition to the metal powder. It is preferable that the metal component in the inorganic component in the first conductor powder layer is contained more than the nonmetal component, but when the ratio of the metal component and the nonmetal component is 100: X in terms of parts by mass, If X is 20 or less, the resistance value of the first conductor layer obtained by firing the first conductor powder layer will be low, and the interface conductivity will be higher. In order to further increase the interface conductivity, X is more preferably 15 or less, and further preferably 8 or less.

  The ratio of the metal component and the nonmetal component of the first conductor layer obtained by firing the first conductor powder layer is the ratio of the metal component and the nonmetal component in the inorganic component in the first conductor powder layer. The ratio is the same.

  In addition, the viscosity of the conductor paste is 10 Pa · s to 100 Pa · s, particularly 15 Pa · s to 80 Pa · s, more preferably 20 Pa · s to 60 Pa · s, from the viewpoint of printing properties, leveling properties, and thin application of the paste. Preferably there is.

Next, the conductor paste is applied to the surface of the green sheet by using an application method such as screen printing to form a first conductor powder layer.
The thickness of the first conductor powder layer is preferably 5 μm to 10 μm.

(Process of forming metal foil and second conductor powder layer)
Subsequently, a metal foil is formed on the first conductor powder layer.

  As a method for forming a metal foil, a method of forming a metal foil having a desired wiring pattern by a technique such as a photo etching method after bonding the metal foil to the surface of a green sheet is known. In the present invention, it is preferable to use a transfer method because the green sheet is altered by the etching solution.

  As a method for forming a metal foil by the transfer method, first, a metal foil is bonded onto a transfer film made of a polymer material, and then a mirror image resist is applied to the surface of the metal foil in the form of a wiring pattern, and etching treatment and resist removal are performed. To form a wiring pattern-like metal foil.

  Next, the transfer film on which the metal foil of the mirror image wiring pattern is formed is aligned with the surface of the green sheet on the side on which the first conductor powder layer is formed, laminated and pressed, and then the transfer film is peeled off to remove the metal foil. Form.

  At this time, the end surface of the wiring conductor 2 having high conductivity in the high frequency region can be obtained by increasing the range in which the metal foil is formed in comparison with the range in which the first conductor powder layer is formed.

  If a screen printing method or the like is used when forming the first conductor powder layer, the width of the first conductor powder layer varies by about 10 μm. Therefore, considering such variations, the width of the metal foil is the first conductor powder layer. It is preferable to make it 15 μm or more larger than the width of the powder layer.

  However, if the width of the metal foil becomes too large, the effect of improving the conductivity in the vicinity of the interface due to the provision of the conductor layer 4b is reduced. Therefore, the width of the metal foil is 30 μm or less than that of the first conductor powder layer. It is preferable that

  Therefore, the width of the metal foil is preferably 15 μm to 30 μm larger than the width of the first conductor powder layer.

  Although it does not specifically limit as metal foil, Copper, silver, or gold | metal | money is preferable from the point which is excellent in low resistance.

The thickness of the metal foil is preferably 8 μm to 20 μm.
Next, a second conductor powder layer is again formed on the metal foil with a conductor paste. The formation method is the same as the formation method of the first conductor powder layer.

  The second conductor powder layer is a layer mainly composed of metal powder, and may contain an organic binder or the like in order to maintain the shape. The second conductor powder layer can be produced by drying the conductor paste, but may be produced by molding metal powder by other methods.

  The inorganic component in the second conductor powder layer may include glass powder, ceramic filler, and the like in addition to the metal powder. The metal component in the inorganic component in the second conductor powder layer is preferably contained more than the non-metal component, but when the ratio of the metal component to the non-metal component is 100: Y by mass part ratio, If Y is 20 or less, the resistance value of the second conductor layer obtained by firing the second conductor powder layer becomes low, and the interface conductivity becomes higher. In order to further increase the interface conductivity, Y is more preferably 15 or less, and further preferably 8 or less.

  The ratio of the metal component and the nonmetal component of the second conductor layer obtained by firing the second conductor powder layer is the ratio of the metal component and the nonmetal component in the inorganic component in the second conductor powder layer. The ratio is the same.

(Process for producing a laminate)
Then, when producing a multilayer wiring board like the wiring board 1, the green sheet laminated body is produced by laminating and pressing a plurality of green sheets on which the conductor powder layer and the metal foil are formed as described above.

  The method for laminating the green sheets is not particularly limited. For example, a method of applying heat and pressure to the stacked green sheets and thermocompression bonding, or an adhesive composed of an organic binder, a plasticizer, a solvent, etc. The method of apply | coating between sheets and carrying out thermocompression bonding etc. is mentioned.

  When the laminate is fired, the metal foil itself does not shrink by firing, and therefore, in order to suppress the deformation of the wiring board caused by the difference in shrinkage between the shrinking green sheet and the metal foil, it is perpendicular to the thickness direction of the wiring board. It is necessary to suppress the shrinkage in the correct direction.

  As a method for suppressing the shrinkage, a method of laminating and firing a constraining sheet that does not shrink by firing on the laminate, or a laminate of green sheets mainly composed of raw materials having different firing shrinkage temperatures, Examples thereof include a method for preventing the other green sheet from contracting in a temperature range where one green sheet contracts, and a method for applying pressure to the entire main surface of the laminate during firing. However, contraction may be suppressed by other methods.

  Among these, a method using a constraining sheet and a method of laminating green sheets of different raw materials are more preferable because they do not require special firing equipment and the manufacturing cost is low.

  The method using a constraining sheet is more preferable because the constraining sheet hardly shrinks due to firing, and therefore shrinkage in the direction perpendicular to the thickness direction of the wiring board of the laminate is less.

  The method of laminating green sheets of different raw materials is that the cavities are formed in the laminate and the laminate is not a simple flat plate shape. Since shrinkage | contraction can be suppressed, it is more preferable.

  As a method for producing a laminate with a restraint sheet, after laminating green sheets, a restraint sheet mainly composed of a ceramic material that is hardly sinterable at the firing temperature of the laminate is pressure-laminated on both sides or one side of the laminate. To produce a laminate with a constraining sheet.

  As a method for producing the constraining sheet, a slurry obtained by adding an organic binder, a plasticizer, a solvent and the like to an inorganic component composed of a hardly sinterable ceramic material and glass powder is formed into a sheet shape.

Specifically, the hardly sinterable ceramic material is composed of a ceramic composition that does not become dense at a temperature of 1000 ° C. or less. For example, Al ₂ O ₃ , SiO ₂ , MgO, ZrO ₂ , BN, TiO ₂ Or powders of these compounds (forsterite, enstatite, etc.).

  In addition, the organic binder, plasticizer, and solvent are not particularly limited, and for example, the same materials as those used for producing the green sheet can be used.

  In this way, by suppressing shrinkage in the direction perpendicular to the thickness direction of the laminated body during firing, there is no delamination or void concentration near the junction between the wiring conductor 2 and the via conductor 3, and conduction in a high-frequency region. A wiring board having a high rate can be provided.

(Baking process)
Prior to firing, the laminate may be heat-treated at 100 ° C. to 800 ° C., preferably 400 ° C. to 750 ° C. to decompose and remove organic components in the laminate.

  Further, the firing is preferably performed at 800 ° C. to 1000 ° C., preferably 850 ° C. to 950 ° C., and firing under these conditions can sufficiently perform sintering and prevent oversintering.

  At this time, when copper is used as the metal in the conductor, firing is preferably performed in a nitrogen atmosphere from the viewpoint of preventing copper oxidation.

  By the manufacturing method as described above, it is possible to obtain a wiring substrate having no delamination or void concentration near the joint between the wiring conductor 2 and the conductor layer 4b and having high conductivity in the high frequency region.

  EXAMPLES The present invention will be specifically described below with reference to examples and comparative examples, but the present invention is not particularly limited as long as it does not exceed the gist thereof.

〔Evaluation methods〕
In the following manner, the cross section of the wiring board for evaluating the presence or absence of delamination and voids in the non-shrinkage firing of the wiring board of the present invention, the vicinity of the interface with the insulating layer of the wiring conductor and the conductivity of the end face and the conductor The transmission characteristics were measured.

(Section observation)
In order to confirm the presence of delamination and void concentration near the junction between the wiring conductor and the via conductor, a cross-sectional observation substrate was prepared.

  The cross-sectional observation substrate is formed of 25 via conductors having a diameter of 100 μm at an interval of 500 μm in an insulating layer having a width of 25 mm × 25 mm and a thickness of 100 μm, and a conductor layer having a land pattern shape of 10 mm square is disposed. Substrate.

For cross-sectional observation, the cross-sectional observation substrate was broken and the broken cross-section was observed with a 100 × optical microscope. As an evaluation standard for the presence or absence of delamination or void concentration, it was judged that delamination was present when peeling was observed between the copper foil and the insulating layer or between the insulating layers. Also, comparing the void ratio in the vicinity of the joint between the via conductor and the copper foil and the void ratio in the periphery of the via conductor other than the joint, and when the former void ratio is high, there is a concentration of voids It was judged. The void ratio was obtained by observing the cross section of the sample with a 500-fold electron microscope and calculating a void ratio in the range of 0.05 mm ² .

(Conductivity measurement near the interface with the insulation layer of the wiring conductor)
In order to measure the electrical conductivity in the vicinity of the interface with the insulating layer of the wiring conductor in the high-frequency region (hereinafter referred to as the interface conductivity), an interface conductivity evaluation board was produced.

  The interfacial conductivity evaluation board is provided with a conductor layer having a diameter of 40 mm, in which an insulating layer having a width of 52 mm × 52 mm and a thickness of 200 μm is laminated, and is made of copper between the layers.

The interface conductivity was measured using the method disclosed in Japanese Patent Application Laid-Open No. 2000-46756 under the condition of a measurement frequency of 2 GHz. Specifically, it was performed by a cylindrical resonator method using a network analyzer. The interface conductivity is standardized by copper conductivity 5.8 × 10 ⁷ / Ω · m.

  Evaluation criteria were good if the interface conductivity was 50% or more, acceptable if it was less than 50% and 42% or more, and poor if it was less than 42%.

(Measurement of end face conductivity)
In order to compare the conductivity of the end face of the wiring board in the high frequency region, an end face conductivity evaluation board was prepared.

  The end face conductivity measurement substrate includes a substrate in which a ring pattern conductor layer having a diameter of 10 mm and a ring width of 1 mm is formed on the surface of an insulating layer having a width of 30 mm × 30 mm and a thickness of 300 μm, and an insulating layer having a width of 30 mm × 30 mm and a thickness of 300 μm. And a second measurement substrate that is different from the first measurement substrate only in a ring width of 0.1 mm.

The end face conductivity was measured under the condition of a measurement frequency of 2 GHz using the method disclosed in Japanese Patent Application Laid-Open No. 2005-308716. Specifically, it was performed by a ring resonator method using a network analyzer. The standardization of the end face conductivity was performed using copper conductivity of 5.8 × 10 ⁷ / Ω · m, as in the case of the interface conductivity measurement.

  As an evaluation standard, if the end face conductivity is 32% or more, it is good, and if it is less than 32%, it is regarded as defective.

(Transmission characteristics measurement)
In order to measure the transmission characteristic (S parameter) of the wiring board in the high frequency region, a transmission characteristic evaluation board was prepared.

  The transmission characteristic evaluation board is composed of four insulating layers with a width of 60 mm × 60 mm and a thickness of 200 μm, a strip width of 0.1 mm and a length of 10 mm, 11 mm, 12 mm, 20 mm, and 30 mm on the inner layer, Is formed, and a total of six lines for measuring reflection are formed. A via was joined to the end of the line, and this was joined to the surface layer pad.

The transmission characteristics were measured using a network analyzer with a probe in contact with the surface layer pad and under a measurement frequency of 2 GHz.
As an evaluation standard, a value of −0.12 dB / cm or more was considered good.

〔Production method〕
Below, it shows about the manufacturing method of said board | substrate for cross-sectional observation, an interface conductivity evaluation board | substrate, an end surface conductivity evaluation board | substrate, and a transmission characteristic evaluation board | substrate.

(Process for producing green sheets)
First, a slurry for producing a green sheet was prepared.

First, a glass powder having a composition composed of SiO ₂ : 43% by mass, B ₂ O ₃ : 8% by mass, Al ₂ O ₃ : 6% by mass, CaO: 5% by mass, and BaO: 38% by mass was prepared. .

Next, 50% by mass of the prepared glass powder, 48% by mass of quartz and 2% by mass of ZrO ₂ as a ceramic filler powder were weighed and mixed to prepare a glass ceramic composition as a raw material powder.

  Next, 4 parts by mass of an acrylic resin as an organic binder, 4.5 parts by mass of dibutyl phthalate as a plasticizer, and 35 parts by mass of toluene as a solvent were added to 100 parts by mass of the raw material powder to prepare a slurry for producing a green sheet.

  Next, three types of green sheets having thicknesses of 170 μm, 330 μm, and 500 μm were produced by the doctor blade method using the prepared slurry for producing green sheets.

(Process for making via holes and filling via conductor paste)
Subsequently, 25 via holes having a diameter of 100 μm were formed by punching in a green sheet having a thickness of 170 μm in 5 rows × 5 columns at intervals of 500 μm.

Next, a via conductor paste for filling the via hole was prepared.
As a method for preparing the via conductor paste, 12 parts by mass of SiO ₂ —B ₂ O ₃ —Al ₂ O ₃ —CaO—BaO-based glass powder is added to 100 parts by mass of copper powder, and acrylic resin is used as an organic binder. 4 parts by mass, 6 parts by mass of a mixed solution of terpineol and dibutyl phthalate (80:20 by mass ratio) as a solvent was added and kneaded to prepare a via conductor paste having a viscosity of 180 Pa · s. The viscosity was measured at room temperature using a pisco tester.

  Next, the prepared via conductor paste was filled into a via hole provided in a green sheet having a thickness of 170 μm by a screen printing method.

(Step of forming the first conductor powder layer)
Subsequently, a conductor paste for forming the first conductor powder layer was prepared.

First, a copper powder having an average particle size shown in Table 1 and a SiO ₂ —B ₂ O ₃ —Al ₂ O ₃ —CaO—BaO-based glass powder were prepared. The powder was added in the amount shown in Table 1. Further, 5.3 parts by mass of an acrylic resin as an organic binder and 1 part by mass of a mixed solution of terpineol and dibutyl phthalate as a solvent (80:20 by weight) were added and kneaded to prepare a conductor paste having a viscosity of 60 Pa · s. .

  Next, a solid conductor-shaped first conductor powder layer having a thickness of 6 μm was printed on the green sheet by screen printing using the prepared conductor paste. That is, a 10 mm square solid pattern first conductive powder layer is formed on a 170 μm thick green sheet, and a solid pattern first conductive powder layer having a diameter of 40 mm is formed on a 330 μm thick green sheet. The sheet is provided with two types of ring pattern-shaped first conductor powder layers having a diameter of 10 mm and a ring width of 1 mm and 0.1 mm, and another green sheet having a thickness of 500 μm has a solid pattern-shaped first layer on the entire surface. A conductor powder layer was printed.

(Process of forming copper foil and second conductor powder layer)
First, a copper foil having a purity of 99.5% or more is bonded to a polymer film, a mirror image resist is applied to the surface of the copper foil in a wiring pattern, etching treatment and resist removal are performed, and the wiring pattern-shaped copper foil is applied. To form a transfer sheet.

  Next, the transfer sheet is laminated on the surface of the green sheet on the side where the first conductor powder layer is printed, while being aligned, and after thermocompression bonding at 60 ° C. and 3 MPa, the transfer sheet is peeled off, and a copper foil having a thickness of 15 μm Formed.

Next, the second conductor powder layer was printed on the copper foil in the same manner as the first conductor powder layer.
In addition, the presence or absence of the roughening process of the surface perpendicular to the thickness direction of the copper foil and the difference between the width of the copper foil and the width of the first and second conductor powder layers were adjusted as shown in Table 1.

(Process for producing a laminate)
A laminate was produced using the first and second conductor powder layers produced as described above and the green sheet on which the copper foil was formed.

  The cross-sectional observation substrate was prepared by laminating four layers of 170 μm thick green sheets on which a via conductor, a 10 mm square solid-pattern conductor powder layer, and a copper foil were formed. At this time, an adhesive was uniformly applied between the green sheets, and pressure lamination was performed under the conditions of 45 ° C. and 4 MPa.

  The interfacial conductivity evaluation substrate is obtained by laminating a 330 μm thick green sheet on which a conductive powder layer and copper foil are not formed on a solid powder having a solid pattern shape of 40 mm in diameter and a copper foil having a thickness of 330 μm. Made. The lamination conditions are the same as those for the cross-sectional observation substrate.

  The end face conductivity evaluation board is formed by laminating a 500 μm-thick green sheet having a ring pattern-shaped conductor powder layer and a copper foil on a 500 μm-thick green sheet having a solid pattern-shaped conductor powder layer and a copper foil formed on the entire surface. And produced. The lamination conditions are the same as those for the cross-sectional observation substrate.

Next, a restraint sheet was produced.
First, 95% by mass of alumina having a purity of 99.99% or more and 5% by mass of SiO ₂ —B ₂ O ₃ —Al ₂ O ₃ —CaO—BaO glass powder were weighed and mixed to prepare a raw material powder.

  A slurry is prepared by adding 9 parts by mass of an acrylic resin as an organic binder, 4.5 parts by mass of dibutyl phthalate as a plasticizer, and 15 parts by mass of toluene as a solvent to the raw material powder, and a restraint sheet having a thickness of 300 μm by a doctor blade method. Was made.

  Subsequently, the produced constraining sheet was subjected to pressure laminating on the upper and lower surfaces of each laminate under the conditions of 45 ° C. and 4 MPa to prepare a laminate with constraining sheets.

(Baking process)
Subsequently, after these laminates with constraining sheets were placed on an Al ₂ O ₃ base plate and subjected to heat treatment at 770 ° C. for 1 hour in a nitrogen atmosphere in order to decompose and remove organic components such as organic binders. And calcination at 900 ° C. for 1 hour.

  Since the restraint sheet hardly burns and shrinks when fired at 900 ° C., the shrinkage rate in the direction perpendicular to the thickness direction of the laminate is suppressed to 1% or less, and the shrinkage of the laminate occurs mainly in the thickness direction of the laminate.

  After firing, the constraining sheet was removed by blasting to produce the intended cross-sectional observation substrate, interface conductivity evaluation substrate, and end surface conductivity evaluation substrate.

  Cross-sectional observation results, interface conductivity measurement results, and end face conductivity measurements of the wiring boards of Examples 1 to 15 and the wiring boards of Comparative Examples 1 and 2 that are outside the scope of the present invention manufactured as described above. Table 1 shows the results and the measurement results of the S parameter (S21), which is the transmission characteristic.

  In Comparative Example 1, a wiring board in which the wiring conductor was formed only from a copper foil was used, and in Comparative Example 2, a wiring board formed from only a conductor layer was used. The thickness of the wiring conductor of Comparative Example 1 and Comparative Example 2 was set to 27 μm so as to be the same as the thickness of the wiring conductor of the example. Moreover, in Comparative Example 1, since the copper foil alone cannot provide sufficient adhesive strength with the substrate, a copper foil whose surface was roughened by blasting was used.

  In Comparative Examples 3 to 6, the ratio of the metal component and the glass component (non-metal component) to the portion corresponding to the conductor powder layer of the wiring board is 100: 150 or 100: 230 by mass part. The wiring board was produced by forming. However, in this case, the portion where the glass powder layer is sintered becomes a layer mainly made of glass, and the resistance value becomes high. Therefore, in Comparative Examples 4 and 6, the via conductor and the copper foil were directly joined without forming a glass powder layer at the portion where the via conductor and the copper foil were joined.

  Furthermore, as Comparative Example 7, a conductor layer obtained by firing the conductor powder layer on the fired wiring board was produced by copper plating with a thickness of 21 μm.

  Table 1 shows the method of forming the copper foil and the conductor powder layer and the presence or absence of the bonding between the via conductor and the metal foil.

  From the results shown in Table 1, the wiring board produced in each of Examples 1 to 15 according to the present invention has a device near the junction between the wiring conductor and the via conductor as compared with the wiring boards of Comparative Examples 1, 4 and 6. There is no concentration of lamination and voids, and the interface conductivity is 42% or more and the end surface conductivity is 38% or more in the high frequency region, and high conductivity can be obtained near the interface with the insulating layer of the wiring conductor and at the end surface. It was.

  For example, the wiring board according to Example 2 of the present invention has no delamination or void concentration near the joint between the wiring conductor and the via conductor, and has an interface conductivity of 69% and an end surface conductivity of 50% in the high frequency region. High conductivity was exhibited, and the transmission characteristics were -0.115 B / cm, and good performance was obtained.

  In Examples 3, 4, 5, and 7, good performance was obtained in all items as in Example 2.

  In Example 1, since the average particle diameter of the copper powder used for the conductor paste was as large as 10.2 μm, the unevenness at the interface with the insulating layer of the wiring conductor was increased, and the interface conductivity was slightly decreased, It was available performance.

  In Example 6, since the width of the metal foil is 40 μm larger than the width of the first and second conductor powder layers, there is an effect of improving the conductivity in the vicinity of the interface with the insulating layer of the wiring board by providing the conductor layer. Although the interfacial conductivity slightly decreased due to the reduction, the performance was sufficiently usable.

  In Example 8 and Example 9, since the width of the metal foil was 10 μm and 20 μm smaller than the width of the first and second conductor powder layers, the irregularities on the end face of the wiring conductor increased, and the end face conductivity was slightly Although it decreased, it was a fully usable performance.

  In Example 10, the surface perpendicular to the thickness direction of the metal foil was roughened, but the interface between the insulating layer and the wiring conductor could be smoothed by the conductor layer, so that good performance was obtained.

  In addition, in Example 11 and Example 12, the addition amount of the glass powder was increased to 25 parts by mass and 30 parts by mass, and although the interface conductivity was slightly reduced, the copper powder was more contained, so that It was available performance.

  In Examples 11 to 15, although the addition amount of the glass powder that is a non-metal component was increased, the copper powder that was a metal component was contained more than the glass powder, and thus good performance was obtained.

  In Examples 1 to 13 in which the amount of glass powder added was 20 parts by mass or less, the transmission characteristics were −0.12 dB / cm or more, and particularly good performance was obtained.

  On the other hand, in Comparative Example 1, which was outside the scope of the present invention and the wiring conductor was formed only of copper foil, delamination occurred near the junction between the wiring conductor and the via conductor.

  Further, in Comparative Example 2 in which the wiring conductor is formed only of the conductor layer, no copper foil is used, so that no delamination or void concentration is observed near the junction between the wiring conductor and the via conductor, and the interface conductivity is also low. Although it was as high as 83%, the end face conductivity was as low as 28%. The transmission characteristics were as low as -0.143 dB / cm. It can be seen that even if the interface conductivity is good, the transmission characteristics of the high-frequency signal deteriorate if the end-face conductivity is inferior.

  In Comparative Examples 3 and 5, there was no delamination or void concentration in the vicinity of the junction between the wiring conductor and the via conductor, but a layer mainly made of glass having a large amount of nonmetallic components between the copper foil and the via conductor. For this reason, the resistance between the copper foil and the via conductor is large, and interface conductivity, single-surface conductivity, and transmission characteristics cannot be measured.

  In Comparative Examples 4 and 6, since the copper foil and the via conductor were directly joined, delamination was generated in the vicinity of the junction between the wiring conductor and the via conductor as in Comparative Example 1.

  In Comparative Example 7, instead of using the copper foil, the wiring conductor obtained by firing the conductive powder layer on the surface of the wiring board is subjected to copper plating. In addition, since a copper foil wiring conductor cannot be formed inside the wiring board, the copper layer after firing was formed with a conductor layer exposed on the surface of the wiring board. The interfacial conductivity was as high as 83%, but the variation in the width of the copper plating formed on the fired wiring conductor was 10 μm, which is almost the same as that of the fired conductor layer of the conductor powder layer. The end face conductivity was as low as 30%. Transmission characteristics were as low as -0.142 dB / cm. In Comparative Example 7, as in Comparative Example 2, the interface conductivity was good, but the end surface conductivity was inferior, and the high-frequency signal transmission characteristics were deteriorated.

  As described above, as a general review of the results obtained by comparing the wiring boards of Examples 1 to 10 and Comparative Examples 1 and 2 according to the present invention, the wiring board of the present invention has a wiring conductor formed of a metal foil and is perpendicular to the thickness direction of the metal foil. By firing the conductor powder layer on the surface, a conductor layer containing more metal component than non-metal component is formed, and this conductor layer is joined to the via conductor and the insulating layer. There is no delamination or void concentration near the junction with the conductor, and high conductivity can be obtained in the high frequency region.

  Further, when the ratio of the metal component to the nonmetal component of the conductor layer is 100: X, when X is 20 or less, higher conductivity can be obtained in the high frequency region.

FIGS. 1A and 1B show a structure of a wiring board according to the present invention, and FIG. 1B is a partial cross-sectional view showing a structure in the vicinity of a junction between a wiring conductor and a via conductor. The structure of the wiring board of other embodiment of this invention is shown, and it is a fragmentary sectional view which shows the structure of the junction part vicinity of a wiring conductor and a via conductor. It is process drawing explaining the manufacturing method of the wiring board of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Wiring board 1a-1g Insulating layer 2 Wiring conductor 2a Surface conductor 2b Inner conductor 3 Via conductor 4a Metal foil 4b Conductor layer 5 Conductor layer width 6 Metal foil width

Claims (7)

  In a wiring board in which a wiring conductor and a via conductor are formed by simultaneous firing on an insulating layer made of glass ceramics, the wiring conductor is formed of a metal foil, and one of the surfaces perpendicular to the thickness direction of the metal foil A first conductive layer obtained by firing a conductive powder layer on a surface and containing a metal component more than a non-metallic component is formed, and the first conductive layer is bonded to the via conductor and the insulating layer. A wiring board characterized by the above.   The wiring board according to claim 1, wherein X is 20 or less when a ratio of a metal component and a non-metal component of the first conductor layer is 100: X.   It is obtained by firing a conductor powder layer on one of the surfaces perpendicular to the thickness direction of the metal foil and opposite to the surface on which the first conductor layer is formed. The wiring board according to claim 1, wherein a second conductor layer containing more than a nonmetallic component is formed, and the second conductor layer is bonded to the insulating layer.   4. The wiring according to claim 3, wherein Y is 20 or less when the ratio of the metal component and the non-metal component of the first conductor layer and the second conductor layer is 100: Y. 5. substrate.   When viewed in plan from a direction perpendicular to the main surface of the wiring board, the metal foil and the first or second conductor layer have the same size, and the first or second conductor layer is the metal The wiring board according to claim 1, wherein the wiring board is formed within a range where the foil is formed. (A) forming a through hole in a green sheet containing glass powder, and filling the through hole with a via conductor paste;
(B) applying a conductive paste to the green sheet to form a first conductive powder layer;
(C) transferring a metal foil onto the first conductor powder layer;
(D) a step of laminating a plurality of the green sheets including the green sheet on which the metal foil is formed to produce a laminate;
And (e) firing the laminated body at a temperature lower than the melting point of the metal forming the metal foil while suppressing shrinkage in a direction perpendicular to the thickness direction of the laminated body. A method for manufacturing a wiring board.   The method for manufacturing a wiring board according to claim 6, wherein an average particle diameter of the metal powder contained in the conductor paste is 5 μm or less.

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