JP2008159726A - Multilayer wiring substrate - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a multilayer wiring substrate which has a high dimensional accuracy, ensures an air tightness by suppressing a gap to be produced between the through hole wall surface of an insulating layer and a via hole conductor, and also has a high conductivity in high-frequency band. <P>SOLUTION: The multilayer wiring substrate is formed of a first insulating layer and a second insulating layer having a calcination contract starting temperature higher than the calcination contract finishing temperature of the first insulating layer, which are laminated alternately, and a via hole conductor 4 is formed so as to penetrate the laminate consisting of a set of the first insulating layer and the second insulating layer while a wiring layer 5, connected to the via hole conductor, is formed on the surface of the first insulating layer side of the laminate. In the wiring layer 5, a connecting unit 51 to the via hole conductor 4 is formed of a metal foil consisting of the principal metal constituent of the via hole conductor 4, and the other region 52 is formed of a conductor paste. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a multilayer wiring board that can be suitably used for a package for housing semiconductor elements, a hybrid integrated circuit device, and the like.

  Conventionally, as a wiring substrate applied to a package for housing a semiconductor element in which semiconductor elements such as IC and LSI, which have been highly integrated, and various electronic parts are mounted, an alumina sintered body is used. Many insulating substrates have been used. In recent years, the resistance of the wiring layer has been required to be reduced, so that the wiring layer mainly composed of a low resistance conductor such as Cu, Ag, or Au that melts at about 1050 ° C. can be simultaneously fired with the insulating substrate. A glass-ceramic sintered body that can be sintered at a low temperature of 1050 ° C. or lower has been used as an insulating substrate.

  A glass-ceramic sintered body is generally obtained by combining glass and a ceramic filler. Among them, by using crystallized glass as a glass, crystals having desired characteristics are precipitated, Since a glass-ceramic sintered body having characteristics can be obtained, research has been conducted intensively in recent years.

  By the way, a wiring board using a glass ceramic sintered body as an insulating base is provided with a wiring layer on the surface or inside of the insulating base, and the wiring layers are filled in through holes (through holes) formed in the insulating base. It is connected via via-hole conductors. Further, in order to prevent a connection failure due to a shift in the laminated position in the connection portion between the via hole conductors, a wiring layer called a land is provided only in the connection portion with the via hole conductor.

  As a specific method for forming the via-hole conductor and the wiring layer, a glass ceramic raw material powder, a slurry prepared by adding a solvent to an organic binder is formed into a sheet shape by a doctor blade method or the like, and a through hole is formed in the obtained green sheet. The via hole conductor is formed by filling the through hole with a conductive paste mainly composed of Cu, Ag, Au or the like. At the same time, a conductive paste mainly composed of Cu, Ag, Au or the like is formed on the green sheet by printing it into a wiring pattern by a screen printing method or the like, or after forming electrolytic copper foil or rolled copper foil into a desired pattern, the green sheet To form a wiring layer. A plurality of green sheets on which via-hole conductors and wiring layers are formed are pressure-laminated and fired at 800 to 1000 ° C. to produce a multilayer wiring board.

  On the other hand, in recent years, as the density of multilayer wiring boards increases, the demand for higher dimensional accuracy has also increased. Improving the substrate dimensional accuracy to cope with this is also an important technique. The multilayer wiring board shrinks in volume by about 40 to 50% by firing. At this time, the variation in shrinkage rate (average of 15 to 20% in one direction) in the direction parallel to the main surface of the multilayer wiring board (XY direction) is the positional variation of the wiring layer, resulting in poor substrate dimensional accuracy. It was. Here, the shrinkage rate is defined as a value obtained by dividing a value obtained by subtracting a dimension after firing from a dimension before firing by a dimension before firing.

  As a method for improving the substrate dimensional accuracy, two types of green sheets having different firing shrinkage start temperatures or firing shrinkage end temperatures are laminated and fired to suppress shrinkage in the XY direction, mainly in the lamination direction (Z (For example, refer to Patent Document 1).

  According to this method, when one of the green sheets starts firing shrinkage, it is restrained by the other green sheet that has not started firing shrinkage, and when the other green sheet starts firing shrinkage, Since it is restrained by one of the green sheets that has finished (sintered), the shrinkage in the XY direction due to firing is suppressed as a result.

  However, a via-hole conductor formed on the same axis that penetrates two different types of insulating layers (green sheets) is usually fired and shrunk simultaneously with the insulating layer having a lower firing shrinkage temperature, and therefore faces this insulating layer. If the end portion of the via-hole conductor is formed at such a position, the end portion is not suppressed from contracting in the XY direction by the insulating layer. Further, when two or more types of insulating layers having different via-hole conductors pass through a plurality of layers, for example, four layers, the via-hole conductors penetrating at least two inner layers are not suppressed in the XY direction. Therefore, the shrinkage in the XY direction of the via-hole conductor is larger than that of the insulating layer in which the shrinkage in the XY direction is suppressed.

For this reason, a via-hole conductor will peel from the wall surface of the through hole formed in the insulating layer, and a clearance gap will arise between the through-hole wall surface of an insulating layer and a via-hole conductor. Due to the gap, the airtightness of the multilayer wiring board is deteriorated, and there is a problem that the insulating property of the multilayer wiring board is deteriorated when moisture or the like enters.
JP-A-10-308584

  Here, when a wiring layer formed of a conductive paste is connected to the via-hole conductor and the end portion of the via-hole conductor is covered by this wiring layer, the wiring layer also burns and shrinks at the same time as the via-hole conductor. The layer does not suppress the shrinkage of the via-hole conductor in the XY direction, and the problem that a gap is generated between the through-hole wall surface of the insulating layer and the via-hole conductor cannot be solved.

  On the other hand, when a wiring layer formed of a metal foil is connected to the via-hole conductor and the end of the via-hole conductor is covered with this wiring layer, the metal foil does not shrink by firing, so the wiring layer is X of the via-hole conductor. Shrinkage in the -Y direction can be suppressed. However, when the wiring layer is formed of a metal foil, it is necessary to expose the surface in order to provide adhesion strength with the insulating layer, and thereby the conductivity in the vicinity of the interface between the wiring layer and the insulating layer (interface conductivity). There is a problem that the multi-layer wiring board has a low conductivity in the high frequency band.

  The present invention has been made in view of such circumstances, and the airtightness in which the formation of a gap between the through-hole wall surface of the insulating layer and the via-hole conductor is suppressed without reducing the interfacial conductivity of the wiring layer. An object of the present invention is to provide a highly reliable multilayer wiring board.

  In the present invention, the first insulating layer and the second insulating layer whose firing shrinkage start temperature is higher than the end temperature of firing shrinkage of the first insulating layer are alternately stacked, A via-hole conductor is formed so as to penetrate through the laminated body made of the insulating layer and the second insulating layer, and a wiring layer connected to the via-hole conductor is formed on the surface of the laminated body on the first insulating layer side. A multilayer wiring board formed, wherein the wiring layer is formed by forming a connection portion with the via-hole conductor with a metal foil made of a main metal component of the via-hole conductor and forming other regions with a conductor paste. It is characterized by being.

  According to the present invention, since the connection portion of the wiring layer with the via hole conductor is formed of the metal foil made of the main metal component of the via hole conductor, the wiring layer can suppress the shrinkage of the via hole conductor in the XY direction. it can. As a result, a multilayer wiring board having high dimensional accuracy and airtightness can be obtained without generating a gap between the through-hole wall surface of the insulating layer and the via-hole conductor. In addition, since the region other than the region near the connection portion with the via-hole conductor in the wiring layer is formed of the conductive paste, the multilayer wiring board does not decrease the interface conductivity of the wiring layer and does not decrease the conductivity in the high frequency band. Can be obtained.

  Hereinafter, an embodiment of the present invention will be described with reference to the drawings.

  FIG. 1 is a partial cross-sectional view showing the structure of a multilayer wiring board according to the present invention, and FIG. 2 is an enlarged explanatory view of the wiring layer shown in FIG. 1. As shown in FIGS. The first insulating layer and the second insulating layer whose firing shrinkage starting temperature is higher than the end temperature of firing shrinkage of the first insulating layer are alternately stacked, and a set of the first insulating layers And a via hole conductor 4 is formed so as to penetrate the multilayer body composed of the second insulating layer, and a wiring layer 5 connected to the via hole conductor is formed on the first insulating layer side surface of the multilayer body. Thus, the wiring layer 5 is characterized in that the connection portion 51 with the via-hole conductor 4 is formed of a metal foil made of the main metal component of the via-hole conductor 4 and the other region 52 is formed of a conductor paste.

  The first insulating layer shown in FIG. 1 has seven layers (1a, 1b, 1c, 1d, 1e, 1f, 1g), and the second insulating layer has six layers (2a, 2b, 2c, 2d, 2e, 2f). ) And are alternately stacked.

  Ceramic sintered bodies are used as the first insulating layer and the second insulating layer. Examples of the ceramic sintered body include glass ceramics, alumina, mullite, and the like, but glass ceramics are preferable in that a low resistance conductor such as gold, silver, or copper can be used. Hereinafter, the case where the first insulating layers 1a, 1b, 1c, 1d, 1e, 1f, and 1g and the second insulating layers 2a, 2b, 2c, 2d, 2e, and 2f are formed of a glass ceramic sintered body will be described. To do.

  Glass ceramic sintered body constituting the first insulating layer 1a, 1b, 1c, 1d, 1e, 1f, 1g and glass ceramic sintered body constituting the second insulating layer 2a, 2b, 2c, 2d, 2e, 2f The body has a different firing shrinkage starting temperature during firing. Specifically, the firing shrinkage end temperatures of the green sheets for forming the second insulating layers 2a, 2b, 2c, 2d, 2e, and 2f are the first insulating layers 1a, 1b, 1c, 1d, 1e, The green sheet for forming the first insulating layer after completion of the firing shrinkage of the green sheet for forming the second insulating layer because it is lower than the firing shrinkage starting temperature of the green sheet for forming 1f and 1g Starts firing shrinkage.

  Here, the firing shrinkage start temperature is defined as the temperature at which the volume shrinks by 0.3% when the target material is fired alone. The term “firing shrinkage end temperature” as used herein refers to a temperature at which the shrinkage amount is 90% or more with respect to the shrinkage amount from the state before firing to the state after firing. The volume shrinkage is determined by TMA (thermomechanical analysis) by individually press-molding the inner restraint portion and the outer conductor portion. At this time, each contracts isotropically and is converted from volumetric shrinkage of TMA to volume shrinkage.

  As a result, when the green sheet for forming the first insulating layer starts firing shrinkage, it is restrained by the green sheet for forming the second insulating layer that has not yet started firing shrinkage, When the green sheet for forming the insulating layer 2 starts firing shrinkage, it is constrained by the first insulating layer that has already finished firing shrinkage, and as a result, shrinkage in the XY direction due to firing. Is suppressed.

  A set of first insulating layer and second insulating layer, specifically, first insulating layer 1a and second insulating layer 2a, first insulating layer 1b and second insulating layer 2b, first Via hole conductors are formed so as to penetrate through the laminated body composed of the first insulating layer 1d and the second insulating layer 2d, and the first insulating layer 1e and the second insulating layer 2e. Usually, a through-hole is made in a composite green sheet that is a laminate after firing, in which one green sheet that becomes the first insulating layer after firing and one green sheet that becomes the second insulating layer after firing. By forming via-hole conductors.

  A wiring layer 5 connected to the via-hole conductor 4 is formed on the surface of the multilayer body on the first insulating layer side. When the wiring layer 5 is provided on the surface of the multilayer wiring board, it mainly functions as a connection pad serving as an electronic component element mounting portion. When the wiring layer 5 is provided inside the multilayer wiring board, each circuit element is mainly electrically connected. Function as circuit elements such as wiring and inductors / capacitors to be connected to each other.

  In the wiring layer 5, it is important that the connection portion 51 with the via-hole conductor 4 is formed of a metal foil made of the main metal component of the via-hole conductor 4, and the other region 52 is formed of a conductor paste. The wiring layer 5 includes a so-called land 53 formed only in the connection portion 51 with the via-hole conductor 4 in order to suppress the occurrence of poor connection between the via-hole conductors 3 due to the misalignment. It is important that 53 is formed of a metal foil made of the main metal component of the via-hole conductor 4.

  Here, the connection layer is preferably formed up to a region that can also function as a land provided in order to prevent poor connection between via-hole conductors due to misalignment of the laminated positions. This refers to a region up to twice the diameter of the via-hole conductor 4 to be formed.

  When the wiring layer 5 is formed of a conductor paste made of the main metal component of the via-hole conductor, the firing temperature is close to the firing temperature of the second insulating layer, and the wiring layer 5 is fired and contracted together with the second insulating layer. . Therefore, the connection portion 51 or the land 53 with the via-hole conductor 4 in the wiring layer 5 is between the surface not connected to the via-hole conductor 4 and the second insulating layer or on the side connected to the via-hole conductor 4. When a via-hole conductor is connected to the surface opposite to the surface, the shrinkage suppressing force in the XY direction does not act between the surface and the via-hole conductor. Therefore, the connection part 51 with the via-hole conductor 4 in the wiring layer 5 or the via-hole conductor near the land 53 shrinks in the radial direction, and a gap is generated between the through-hole wall surface.

  On the other hand, when the wiring layer 5 is formed of a metal foil made of the main metal component of the via-hole conductor, a technique for roughening the metal foil is used. This is because the metal foil cannot maintain sufficient adhesive strength with the insulating layer as it is, and by roughening, the metal foil and the insulating layer can be anchor-bonded to maintain the adhesive strength. However, since the irregularities at the interface between the metal foil and the insulating layer are increased, the interface conductivity is greatly reduced, and the conductivity in the high frequency band of the wiring board is decreased.

  Therefore, it is important that the connection portion 51 (land 53) with the via-hole conductor 4 is formed of a metal foil made of the main metal component of the via-hole conductor 4, and the other region 52 is formed of a conductor paste.

  Since the connection part 51 (land 53) with the via-hole conductor 4 in the wiring layer 5 is formed of a metal foil made of the main metal component of the via-hole conductor, the metal molecules in the via-hole conductor and the metal in the metal foil during firing The molecule is necked. Since the metal foil does not shrink by firing, the metal molecules in the via hole conductor that are necked with the metal molecules of the metal foil cannot move in the XY direction, and as a result, the via hole conductor is prevented from shrinking in the XY direction. The Moreover, in the connection part with the via-hole conductor 4, the contact area with the metal molecule in the via-hole conductor is increased by roughening, and the shrinkage of the via-hole conductor in the XY direction can be more effectively suppressed. it can.

  Since the other region 52 in the wiring layer 5 is formed of a conductor paste, the unevenness at the interface between the other region 52 and the insulating layer is determined by the size of the metal particles in the paste and the crystal phase of the insulating layer. Compared with the unevenness in the case of using a roughened metal foil, it is sufficiently small and the interface conductivity is not greatly reduced.

  Here, the main metal component of the via hole conductor 4, the metal foil that forms the connection portion 51 (land 53) with the via hole conductor 4 in the wiring layer 5, and the main metal component of the conductor paste that forms the other region 52 in the wiring layer are low resistance. In this respect, Cu, Ag, Au and the like are preferable. Further, when the main metal component of the via-hole conductor is an alloy mainly composed of Cu, Ag, Au, etc., as the metal foil that forms the connection portion 51 (land 53) with the via-hole conductor 4 in the wiring layer 5, It is preferable to use a foil using a metal having a higher composition ratio in the alloy.

  In addition, when the firing shrinkage amount of the insulating layer and the via-hole conductor is compared, there is a large divergence, and when the firing shrinkage amount of the via-hole conductor is small, the via-hole conductor is connected to the via-hole conductor in the wiring layer (land) When the amount of firing shrinkage of the via-hole conductor is large, the via-hole conductor portion is depressed. At this time, if a metal foil is used for the land, delamination and void concentration may occur near the joint between the metal foil and the via-hole conductor because the metal foil is not plastic. Therefore, by providing a conductor paste layer between the metal foil and the via-hole conductor, the plastic conductor paste absorbs the deformation of the via-hole conductor, so delamination is near the joint between the metal foil and the via-hole conductor. Concentration of voids does not occur. Therefore, you may provide a conductor paste layer between metal foil and a via-hole conductor.

  Next, a method for manufacturing the multilayer wiring board of FIG. 1 will be described as a method for manufacturing the multilayer wiring board of the present invention. First, two types of green sheets each containing a glass ceramic material for forming the first insulating layer and the second insulating layer are prepared.

  Specifically, first, a glass powder and a ceramic filler powder are prepared as raw material powders in order to produce a green sheet.

The glass powder contains at least SiO ₂ and contains at least one of Al ₂ O ₃ , B ₂ O ₃ , ZnO, PbO, alkaline earth metal oxide, and alkali metal oxide. For example, borosilicate glass such as SiO ₂ —B ₂ O ₃ system, SiO ₂ —B ₂ O ₃ —Al ₂ O ₃ system—MO system (where M represents Ca, Sr, Mg, Ba or Zn) , Alkali silicate glass, Ba glass, Pb glass, Bi glass and the like. These glasses can be amorphous glass even when fired, and lithium silicate, quartz, cristobalite, enstatite, cordierite, mullite, ananosite, serdian, spinel, gallium by firing. -Any one of depositing at least one kind of crystals of knight, willemite, dolomite, petalite, diopside and substituted derivatives thereof can be used.

As the glass for the first insulating layer, glass from which crystals are precipitated by baking treatment is preferable. In glass ceramics, when crystals begin to precipitate from glass, the amount of liquid phase that serves as a driving force for sintering of glass ceramics decreases, so that the amount of firing shrinkage is extremely reduced. If precipitation of crystals in the first insulating layer starts at a temperature at which the second insulating layer starts firing shrinkage, the effect of suppressing firing shrinkage in the XY direction of the second insulating layer becomes high. Therefore, the glass used for the first insulating layer is preferably glass from which crystals are deposited. Among them, 1 to 30 wt% of Si in terms of SiO _2, 5 to 25 wt% of Al in terms _{of Al} 2 _{O 3,} 25 to 60 wt% of Mg in terms of MgO, 0 to 10 mass% of Ca in terms of CaO 0-20 wt% of Ba in terms of BaO, 5 to 25 wt% of B in terms _{of B} 2 _{O 3,} 0-10 wt% of P in terms _{of P} 2 _{O 5,} 0 to 10 mass of Sn in terms of SnO ₂ %, include those containing 0-3 wt% of Na in terms of Na ₂ O. By using the glass, the firing shrinkage start temperature of the first insulating layer can be lowered, and further, the crystal is precipitated from the glass before the second insulating layer starts firing shrinkage, whereby the insulating base 1 It becomes possible to effectively suppress firing shrinkage in the XY direction.

As the glass for the second insulating layer, 10 to 24 wt% of Si 25 to 45 mass% in terms of SiO _2, 10 to 25 wt% of Al in terms _{of Al} 2 _{O 3,} the Mg in terms of MgO, A crystalline glass comprising 5 to 20% by mass in terms of B ₂ O ₃ , 5 to 20% by mass in terms of ZnO, and Ca to 0.5 to 4% by mass in terms of CaO is desirable. By using the above glass, a crystal phase with a high thermal expansion coefficient such as garnite (ZnO.Al ₂ O ₃ ) and enstatite (MgO.SiO ₂ ) is precipitated after firing, and the ceramic wiring board can be made high in thermal expansion. become.

As the ceramic filler powder, SiO ₂ such as quartz and cristobalite, Al ₂ O ₃ , ZrO ₂ , cordierite, mullite, forsterite, enstatite, spinel, magnesia and the like are preferably used. Among these, alumina is preferable from the viewpoint of increasing strength and cost, and quartz is preferable from the viewpoint of increasing thermal expansion.

  At this time, it is desirable that the glass ceramic material for the first insulating layer and the second insulating layer is composed of 30 to 100% by mass of glass powder and 0 to 70% by mass of ceramic filler powder.

  A predetermined amount of the above raw material powder is weighed, and further, an organic binder, an organic solvent, and optionally a plasticizer are added to prepare a slurry, which is then formed into a sheet by a known forming method such as a doctor blade method, a rolling method, or a pressing method. A green sheet forming a ceramic wiring board having a thickness of 10 to 500 μm is formed. In some cases, the green sheet forming the first insulating layer and the second insulating layer is pressure-bonded, or the green sheet to be the first insulating layer is molded and then the second insulating layer is directly formed on the surface. It is also possible to form a green sheet to be a green sheet composite (the order may be changed), and to supply this composite as a layer unit to the subsequent processes.

  Then, a through hole having a diameter of 60 to 200 μm for filling the via paste is formed in the green sheet composite by laser, micro drill, punching or the like.

  Subsequently, a via paste is produced. Metal powder and glass powder are prepared as raw material powder. As the metal powder, Cu, Ag, and Au are preferable in terms of low resistance. For the purpose of adjusting the sintering start temperature of the metal powder, a powder obtained by coating the metal powder with an inorganic oxide such as alumina or silica may be used. Examples of the glass powder include borosilicate glass, zinc borosilicate glass, and lead borosilicate glass.

In particular, SiO ₂ —Al ₂ O ₃ —BaO—CaO—B ₂ O ₃ is superior in that it is excellent in co-firing with metal powder at 800 to 1100 ° C. and can improve the adhesive strength with glass ceramics. Based glass is preferred. However, the glass powder is added for the purpose of adjusting the sintering behavior of the via-hole conductor, improving the adhesive strength with the glass ceramic, and reducing the difference in thermal expansion between the via-hole conductor and the glass ceramic.

  In addition to the 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. The via paste is prepared by adding the above metal powder, glass powder, organic binder, organic solvent, and, if desired, a dispersant. The viscosity of the via paste is preferably 100 to 350 Pa · s in consideration of the filling property to the through hole.

  Then, the via paste is filled into the through hole. As the filling method, screen printing or the like is used.

  Subsequently, a conductor paste used for pattern printing (formation of other regions 52 in the wiring layer 5) is prepared. The manufacturing method is the same as that of the via paste. Even if it produces only with metal powder, you may add glass powder, a filler component, etc. in order to adjust shrinkage | contraction behavior and to improve adhesive strength with glass ceramic. Here, it is preferable that the particle size of the metal powder used for the conductor paste for patterns is small. When the particle size of the metal powder is large, the space between the metal particles in the paste becomes large, and this space greatly affects the unevenness caused by the conductor after firing. Therefore, 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. The viscosity of the conductor paste is preferably 10 to 120 Pa · s, particularly 20 to 80 Pa · s, from the viewpoint of paste printability, paste leveling properties, and thin coating of the paste.

  Then, the conductor paste is applied to the surface of the green sheet using a coating method such as screen printing to form a wiring pattern.

  Subsequently, a connection portion between the wiring layer and the via-hole conductor is formed with a metal foil. For the wiring layer made of metal foil, a method of forming a desired circuit by a well-known photo-etching method after bonding the metal foil to the surface of the green sheet is known. Therefore, it is preferable to form by a transfer method. As a formation method 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 a circuit pattern, and etching treatment and resist removal are performed. To form a wiring layer. Next, after aligning the transfer film on which the wiring pattern of the mirror image is formed on the surface of the green sheet on which the via-hole conductor is formed and laminating and press-bonding, a wiring layer made of a metal foil is formed by peeling off the transfer film.

  The green sheets or green sheet composites thus obtained are laminated according to a predetermined lamination order to form a laminated molded body, and then fired. For the lamination of green sheets, a method of applying heat and pressure to the stacked green sheets and thermocompression bonding, a method of applying an adhesive composed of organic binder, plasticizer, solvent, etc. between the sheets, and thermocompression bonding are adopted. Is possible.

  Prior to firing, if necessary, the green sheet or laminate thereof can be heat-treated at 100 to 800 ° C., particularly 400 to 750 ° C. to decompose and remove organic components in the laminate. Further, it is preferable that the firing is performed at 800 to 1000 ° C., particularly 850 to 950 ° C., from the viewpoint of sufficient sintering and prevention of oversintering. At this time, when Cu is used as the metal in the conductor, firing is preferably performed in a nitrogen atmosphere from the viewpoint of preventing oxidation of Cu.

  In firing, the following firing may be performed to improve the dimensional accuracy. After the temperature rises and reaches the firing shrinkage start temperature of the first insulating layer, the temperature is gradually raised, or the firing shrinkage start temperature, or the firing shrinkage start temperature or more and the firing shrinkage start temperature of the second insulating layer At the lower temperature, the in-furnace temperature is temporarily maintained, and the first insulating layer is maintained until the firing shrinkage of 90% or more of the final firing volume shrinkage proceeds. At this time, the shrinkage in the XY direction is suppressed and the first insulating layer is fired and shrunk in the Z direction by the second insulating layer that is not fired and shrunk at that temperature. Thereafter, after the first insulating layer shrinks 90% or more of the final firing volume shrinkage, the temperature is raised to the shrinkage start temperature of the second insulating layer or more and fired. By this firing, the second insulating layer is baked and shrunk in the Z direction while the firing shrinkage in the XY direction is suppressed by the first insulating layer that has been almost sintered. As a result, it is possible to manufacture a substrate with high dimensional accuracy in which both the first insulating layer and the second insulating layer are suppressed from firing shrinkage in the XY direction and fired and shrunk in the Z direction.

  The glass ceramic wiring board produced in this manner is a glass ceramic excellent in dimensional accuracy that suppresses firing shrinkage in the XY directions by integrally firing insulating layers having different shrinkage behaviors in firing. Wiring shrinkage in the XY direction is also suppressed for the via-hole conductor, so there is no gap between the through-hole wall surface of the insulating layer and the via-hole conductor, and the conductivity in the high frequency band It becomes a multi-layered wiring board with high.

  A separation evaluation board for evaluating the presence or absence of a gap between the through-hole wall surface and the via-hole conductor and an interface conductivity evaluation board were produced as follows. The separation evaluation board has an insulating layer having a width of 30 mm × 30 mm and a thickness of 330 μm, and a total of 25 via-hole conductors with a diameter of 90 μm are arranged in the center of the board in 5 rows × 5 columns at intervals of 500 μm. Is a land having a diameter of 125 μm. The interfacial conductivity evaluation substrate is a laminate in which an insulating substrate having a width of 50 mm × 50 mm and a thickness of 200 μm is laminated and a wiring layer having a diameter of 40 mm is provided between the layers. A manufacturing method will be described below.

First, a green sheet to be a first insulating layer was produced. SiO ₂ is 9% by mass, B ₂ O ₃ is 17% by mass, P ₂ O ₅ is 1.7% by mass, Al ₂ O ₃ is 17% by mass, MgO is 44% by mass, BaO is 8% by mass, SnO ₂ Of 1.7% by mass, CaO 0.5% by mass, and NaO 0.1% by mass of glass powder and quartz powder were prepared. These were 85.6% by mass of glass and 14.4% of quartz powder. %, And an organic binder was added to prepare a glass ceramic composition. Using the slurry prepared by adding an acrylic resin as an organic binder, dioctyl phthalate as a plasticizer, and toluene as a solvent to the raw material powder, a green sheet having a thickness of 200 mmSQ and a thickness of 10 μm was formed by a doctor blade method.

Then, the green sheet used as the 2nd insulating layer was produced. SiO ₂ is 35.9 mass%, B ₂ O ₃ is 12 mass%, Al ₂ O ₃ is 6.6 mass%, MgO is 17.5 mass%, CaO is 2.5 mass%, ZnO is 14.4 mass%. A glass powder containing 5% by mass, a quartz powder, and a CaZrO ₃ powder were prepared. These were weighed 58.7% by mass of glass, 36.5% by mass of quartz powder, and 4.8% by mass of CaZrO ₂ powder. A glass ceramic composition was prepared by adding a binder. Using the slurry prepared by adding acrylic resin as organic binder, dioctyl phthalate as plasticizer, and toluene as solvent to the above raw material powder, it is molded by the doctor blade method to produce green sheets with 200mmSQ and thickness of 125μm and 300μm did.

  Then, the green sheet for the first insulating layer and the green sheet for the second insulating layer were prepared one by one, and these were thermocompression bonded to produce a composite green sheet. Also, two green sheets for the first insulating layer and one green sheet for the second insulating layer are prepared for the lowermost layer, and the first insulating layer green sheet is sandwiched between the first insulating layer green sheet and the first insulating layer green sheet. The green sheet for insulating layer was heat-pressed.

  Here, a through hole having a diameter of 90 μm was formed by punching in the composite green sheet using the second insulating layer having a thickness of 125 μm.

Next, a via paste was produced. 18% by mass of SiO ₂ —Al ₂ O ₃ —BaO—CaO—B ₂ O ₃ glass is added to 100% by mass of copper powder, acrylic resin is used as an organic binder, and terpineol and dibutyl phthalate are mixed as a solvent. A solution (80:20 by mass) was added and kneaded to prepare a via paste. The prepared via paste was filled into the through-hole provided earlier by a screen printing method.

  Subsequently, a copper foil having a purity of 99.5% or more was adhered to the polymer film, and after etching, a wiring pattern was formed to prepare a transfer sheet. Two types of wiring patterns were prepared, one with a land pattern with a diameter of 125 μm and the other with a solid pattern with a diameter of 40 mm.

  Next, while aligning the composite green sheet, the transfer sheet was laminated and thermocompression bonded at 60 ° C. and 3 MPa. Subsequently, the transfer sheet was peeled off.

Subsequently, a wiring conductor paste to be the other region 52 in the wiring layer 5 was produced. 4% by mass of SiO ₂ —Al ₂ O ₃ —BaO—CaO—B ₂ O ₃ glass is added to 100% by mass of copper powder, acrylic resin is used as an organic binder, and terpineol and dibutyl phthalate are mixed as a solvent. A solution (80:20 by mass ratio) was added and kneaded to prepare a wiring conductor paste. The obtained wiring conductor paste was printed by a screen printing method. A pattern having a diameter of 125 μm was printed as a land pattern directly on the via-hole conductor. A solid pattern having a diameter of 40 mm was printed on the composite green sheet using the second insulating layer having a thickness of 300 μm.

  A laminate was prepared using the composite green sheet thus obtained. For the separation evaluation board, three composite green sheets and one composite green sheet prepared for the lowermost layer are prepared, and an adhesive is uniformly applied between the green sheets, and pressure lamination is performed at 45 ° C. and 4 MPa. Went. As the interfacial conductivity evaluation substrate, a composite green sheet having a solid pattern with a diameter of 40 mm and a composite green sheet having no pattern were prepared and laminated so that the pattern was sandwiched between the green sheets. The lamination conditions were the same as those for the separation evaluation substrate.

Subsequently, these laminates are placed on an Al ₂ O ₃ base plate and subjected to heat treatment at 750 ° C. in a nitrogen atmosphere in order to decompose and remove organic components such as an organic binder, and then in a nitrogen atmosphere. And calcination at 900 ° C. for 1 hour.

The obtained separation evaluation substrate was immersed in a fluorescent penetrant flaw detection liquid, kept in a desiccator for 2 hours in a vacuumed state until reaching a pressure of 1 × 10 ⁻² Pa, and then washed with tap water. The via-hole conductor portion was polished by about 50 μm from the substrate surface in the substrate stacking direction, and the presence / absence of penetration of the fluorescent penetrating flaw detection liquid into the through-hole (presence / absence of light emission) was evaluated. Evaluation is made by observing the polished substrate with a fluorescence microscope. Samples with through holes where one or more fluorescent parts are recognized in 25 via holes (present in the table) are defective, and samples at 0 locations (none in the table) are It was a good product.

The interface conductivity was measured under the condition of a measurement frequency of 10 GHz using the method disclosed in Japanese Patent Application Laid-Open No. 2000-46756. Specifically, it was performed by a cylindrical resonator method using a network analyzer. Here, a non-defective product having an interface conductivity of 50% or more was determined. The interface conductivity is standardized by copper conductivity 5.8 × 10 ⁷ / Ω · m.

  Sample No. 3, since copper foil is used for the connection portion 51 (land 53) of the wiring layer 5 with the via-hole conductor 4, it is possible to suppress the shrinkage of the via-hole conductor in the X-Y direction. It was confirmed that no separation occurred between the wall surface of the through hole and the via hole conductor. Further, since the conductor paste was used for the other region 52 in the wiring layer 5, the interface conductivity was as high as 84%.

  On the other hand, the connection part 51 (land 53) with the via-hole conductor 4 in the wiring layer 5 and the other region 52 in the wiring layer are both sample No. In No. 1, the interface conductivity was as high as 83%, but the fluorescence flaw detection liquid emitted light. Separation occurred between the through-hole wall surface and the via-hole conductor because the via-hole conductor did not have a shrinkage suppression effect.

  Further, the sample No. 1 in which the connection portion 51 (land 53) with the via-hole conductor 4 in the wiring layer 5 is formed of a conductor paste and the other region 52 in the wiring layer is formed of copper foil. In No. 2, light emission from the fluorescent flaw detection liquid was observed and separation occurred. Further, the interface conductivity was as low as 42% due to the effect of roughening the copper foil.

  In addition, the connection part 51 (land 53) with the via-hole conductor 4 in the wiring layer 5 and the other region 52 in the wiring layer are both sample Nos. Formed with copper foil. In No. 4, no light was emitted from the fluorescent flaw detection liquid and no separation occurred, but the interface conductivity was as low as 41%.

It is a fragmentary sectional view which shows the structure of the multilayer wiring board of this invention. FIG. 2 is an enlarged explanatory view of a wiring layer shown in FIG. 1.

Explanation of symbols

1a-1g ... 1st insulating layer 2a-2g ... 2nd insulating layer 4 ... Via-hole conductor 5 ... Wiring layer 51 ... Connection part 52 ... Other area | region 53 ... ·land

Claims (1)

The first insulating layer and the second insulating layer whose firing shrinkage start temperature is higher than the end temperature of firing shrinkage of the first insulating layer are alternately stacked, and the set of the first insulating layer and the first insulating layer A via-hole conductor is formed so as to penetrate the multilayer body made of the second insulating layer, and a wiring layer connected to the via-hole conductor is formed on the surface of the multilayer body on the first insulating layer side. A multilayer wiring board,
The multilayer wiring board, wherein the wiring layer is formed by forming a connection portion with the via-hole conductor from a metal foil made of a main metal component of the via-hole conductor and forming other regions with a conductor paste.

Images