JP2008186908A - Manufacturing method for multilayer circuit board - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a manufacturing method for a multilayer circuit board capable of obtaining the multilayer circuit board largely projecting no via-hole conductor from the surface of an insulating base body and having an excellent mounting property and a high dimensional accuracy. <P>SOLUTION: The manufacturing method for the multilayer circuit board contains a process superposing burning-shrinkage suppressing sheets 5 for suppressing a burning shrinkage in the direction perpendicular to the laminating direction of a green-sheet laminate on the upper side and lower side of the green-sheet laminate 1, baking the burning-shrinkage suppressing sheets 5 and removing the burning-shrinkage suppressing sheets 5. In this manufacturing method, through-holes are formed on the green sheet 1a arranged on at least a surface layer; the through-holes are filled with paste for the via-hole conductor containing metallic powder having a mean grain size of 1 to 5 μm; paste 3 for a surface wiring layer comprising metallic power having the mean grain size of 1/10 or less of metallic powder contained in paste 2 for the via-hole conductor is coated and formed at places coating at least the through-holes of the top face of the green sheet arranged on the surface layer. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a method for producing a multilayer circuit board that suppresses firing shrinkage in the XY direction of a green sheet laminate by superimposing firing shrinkage suppression sheets on the upper and lower sides of the green sheet laminate.

  Conventionally, as a multilayer circuit board applied to a semiconductor element housing package for mounting semiconductor elements such as ICs and LSIs, which are becoming increasingly integrated, and a hybrid integrated circuit device on which various electronic components are mounted, an alumina sintered body is used. Insulating substrates have been used in many cases. 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 ceramics. Among them, crystallized glass is used as a glass to precipitate crystals having desired characteristics and various characteristics. In recent years, research has been focused on the fact that a glass-ceramic sintered body having the above can be obtained.

  As a specific method of forming such a multilayer circuit board, a slurry prepared by adding a solvent to a glass ceramic raw material powder and an organic binder is formed into a sheet shape by a doctor blade method or the like, and the obtained green sheet is passed through. Holes are punched, and the through holes are filled with a conductor 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 Crimp to. Thereafter, a plurality of these green sheets are pressure-laminated and fired at 800 to 1000 ° C. to produce a multilayer circuit board.

  On the other hand, in recent years, as the density of multilayer circuit boards has increased, the demand for higher dimensional accuracy has also increased. Improvement of substrate dimensional accuracy to cope with this is also an important technique. However, the multilayer circuit board manufactured by the above-described method shrinks in volume by about 40 to 50% by firing. At this time, the variation in the shrinkage rate (average of 15 to 20% in one direction) in the direction perpendicular to the stacking direction of the multilayer circuit board (XY direction) becomes the position 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.

Therefore, as a method for improving the dimensional accuracy of the substrate, a shrinkage suppression layer containing an inorganic material powder having a sintering temperature higher than that of the green sheet is formed on both upper and lower surfaces of the green sheet laminate in which green sheets containing glass and ceramics are laminated. After forming and firing at a temperature at which the shrinkage suppression layer does not sinter, the dimensional accuracy of the obtained substrate is suppressed by suppressing the shrinkage in the XY direction of the green sheet laminate by peeling and removing the shrinkage suppression layer It is known that can be increased (see Patent Document 1).
Japanese Patent No. 2554415

  In the method described in Patent Document 1, since the shrinkage of the green sheet laminate in the XY direction during firing is suppressed, the shrinkage of the green sheet laminate in the lamination direction (Z direction) increases.

  However, the conductor paste (via hole conductor paste) as a via-hole conductor filled in the through hole of the green sheet has a larger shrinkage in the XY direction than the green sheet in which the shrinkage in the XY direction is suppressed. This is because the via hole conductor paste and the surface wiring layer paste are solid phase sintered while the green sheet is liquid phase sintered.

  The green sheet is sintered by liquid phase sintering in which ceramics are rearranged when the glass softens and flows. At this time, since the glass sheet side glass moves to the shrinkage suppression layer side by a small amount, the adhesive force between the green sheet and the shrinkage suppression layer is strengthened, so the shrinkage suppression effect in the XY direction with respect to the green sheet is large.

  On the other hand, the via-hole conductor paste and the surface wiring layer paste are sintered by solid-phase sintering of the metal particles contained in the paste. Therefore, the adhesive force between the via-hole conductor paste and the surface wiring layer paste using the same metal particles is strong, but the adhesive force between the shrinkage suppression layer and the surface wiring layer paste is the same as that of the green sheet. It is weak compared with the adhesive force between the suppression layers. Also, the surface wiring layer paste has solid-phase sintering of the metal particles, thereby reducing the unevenness of the adhesion portion with the shrinkage suppression layer and reducing the frictional force between the surface wiring layer paste and the shrinkage suppression layer. Therefore, the shrinkage suppression effect of the shrinkage suppression layer on the surface wiring layer paste is weakened. Therefore, the shrinkage in the XY direction of the via-hole conductor paste is larger than that of the green sheet in which the shrinkage in the XY direction is suppressed.

  Therefore, if the via-hole conductor paste shrinks by the original volume shrinkage, the shrinkage in the Z direction does not become as large as the shrinkage of the green sheet, and the via-hole conductor formed by firing the via-hole conductor paste is a multilayer circuit board This has caused a problem that the mountability of the electronic components mounted on the surface of the surface of the substrate is greatly reduced.

  The present invention has been made in view of such circumstances, and a multilayer circuit capable of obtaining a multilayer circuit board having good mountability and high dimensional accuracy in which a via-hole conductor does not protrude greatly from the surface of an insulating substrate. An object is to provide a method for manufacturing a substrate.

  The present invention is a method of manufacturing a multilayer circuit board in which a surface wiring layer is formed on the surface of an insulating base composed of a plurality of insulating layers, and via-hole conductors connected to the surface wiring layer are formed inside the insulating base. Forming a plurality of green sheets to be a plurality of insulating layers after firing, and forming a through hole in at least the green sheet disposed on the surface layer, and a metal powder having an average particle diameter of 1 to 5 μm in the through hole The step of filling the paste for via-hole conductor, and at least 1/10 of the average particle diameter of the metal powder contained in the paste for via-hole conductor at a position covering at least the through hole on the upper surface of the green sheet disposed on the surface layer A step of depositing and forming a paste for a surface wiring layer containing a metal powder having the following average particle diameter; and the via-hole conductor paste is filled in the through-holes And forming a green sheet laminated body in which the plurality of green sheets are laminated using a green sheet having the surface wiring layer paste deposited on the upper surface as a surface layer, and upper and lower sides of the green sheet laminated body. And a step of superposing a firing shrinkage suppression sheet on the side to suppress firing shrinkage in a direction perpendicular to the lamination direction of the green sheet laminate and removing the firing shrinkage suppression sheet after firing. It is a manufacturing method of a circuit board.

  Here, it is preferable that the main components of the metal powder contained in the via-hole conductor paste and the metal powder contained in the surface wiring layer paste are the same.

  According to the present invention, when manufacturing a multilayer circuit board using a firing shrinkage suppression sheet, the firing shrinkage start temperature of the surface wiring layer paste can be lowered, and the via-hole conductor after the firing shrinkage of the surface wiring layer paste is completed. The baking shrinkage of the paste can be started. Therefore, it is possible to obtain a via-hole conductor whose shrinkage in the XY direction is suppressed to the same extent as that of the insulating layer and is mainly contracted in the Z direction. The multilayer circuit board obtained by this manufacturing method has good insulation and mountability without the via-hole conductor projecting greatly from the surface.

  In particular, when the main components of the metal powder contained in the via-hole conductor paste and the metal powder contained in the surface wiring layer paste are the same, the shrinkage of firing between the via-hole conductor paste and the surface wiring layer paste is reduced. It becomes easy to control the start temperature (shrinkage behavior) to be different.

Embodiments of the present invention will be described with reference to the drawings.
FIG. 1 is an explanatory view of a method for producing a multilayer circuit board according to the present invention, and shows a state where firing shrinkage suppression sheets are superimposed on the upper side and the lower side of a green sheet laminate.

  The present invention is a method of manufacturing a multilayer circuit board in which a surface wiring layer is formed on the surface of an insulating substrate composed of a plurality of insulating layers, and via-hole conductors connected to the surface wiring layer are formed inside the insulating substrate.

  First, a plurality of green sheets (1a, 1b, 1c, 1d) to be insulating layers after firing are formed. As raw materials for forming the green sheets (1a, 1b, 1c, 1d), it is preferable to use those prepared at a ratio of 30 to 80% by mass of glass powder and 20 to 70% by mass of ceramic powder, and these raw materials are used. For example, an insulating layer made of glass ceramics that can be fired at a low temperature can be formed.

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 a specific example, 25 to 45 wt% of Si in terms of SiO _2, 10 to 25 wt% of Al in terms _{of Al} 2 _{O 3,} 10 to 24 wt% in terms of MgO for Mg, and B in terms _{of B} 2 _{O 3} 5 A crystalline glass composed of ˜20 mass%, Zn of 5 to 20 mass% in terms of ZnO, and Ca of 0.5 to 4 mass% in terms of CaO is desirable.

By using such crystalline glass, crystal phases with a high thermal expansion coefficient such as garnite (ZnO.Al ₂ O ₃ ) and enstatite (MgO.SiO ₂ ) are precipitated after firing, and the ceramic wiring board is increased in thermal expansion. It becomes possible to do.

As the ceramic 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. Of these, it is preferable to use alumina from the viewpoint of increasing strength, reducing cost, and quartz from the viewpoint of increasing thermal expansion.

  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. To form a green sheet having a thickness of 10 to 500 μm.

  Next, a through-hole is formed in the green sheet 1a arranged on at least the surface layer of the plurality of green sheets (1a, 1b, 1c, 1d). The through hole is formed with a diameter of about 60 to 200 μm by laser, micro drill, punching or the like.

  Then, the via-hole conductor paste 2 that becomes the via-hole conductor after firing is filled in the through hole.

The via-hole conductor paste 2 is obtained by mixing an organic binder and an organic solvent with metal powder such as gold powder, silver powder, copper powder, and aluminum powder having an average particle diameter of 1 to 5 μm. Here, it is necessary to make the average particle diameter of the metal powder smaller than the diameter of the through hole. However, if it becomes smaller than 1 μm, the difference in firing shrinkage behavior between the via-hole conductor paste 2 and the green sheets 1a to 1d is greatly different, and there is a gap between the through-hole (through-hole) wall surface in the fired insulating layer and the via-hole conductor. As a result, the insulation of the multilayer circuit board is deteriorated due to airtight failure. Therefore, the metal powder used for the via-hole conductor paste 2 preferably has an average particle diameter in the range of 1 to 5 μm. Further, for the purpose of adjusting the sintering start temperature of the metal powder, a metal powder coated with an inorganic oxide such as alumina or silica may be used. Furthermore, in order to adjust the sintering behavior of the via-hole conductor, improve the adhesive strength with the glass ceramic, and reduce the difference in thermal expansion between the via-hole conductor and the glass ceramic, glass powder may be included. Examples include borosilicate glass, zinc borosilicate glass, and lead borosilicate glass. In particular, SiO ₂ —Al ₂ O ₃ —BaO—CaO— 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 an insulating substrate made of glass ceramics. B ₂ O ₃ glass is preferred. 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 viscosity of the via-hole conductor paste 2 is preferably 100 to 350 Pa · s in consideration of the filling property to the through holes.

  Examples of the filling method include screen printing, but are not particularly limited. In addition, formation of the said through-hole and filling with the paste for via-hole conductors is not limited to the green sheet 1a arrange | positioned at a surface layer.

  Subsequently, a wiring layer paste is formed on a plurality of green sheets by screen printing or the like. Here, the wiring layer paste (surface wiring layer paste 3) formed on the surface of the green sheet laminate is baked to have a function of a solder connection terminal with a silicon chip, a capacitor, a printed board, or the like. It becomes. Also, the wiring layer paste (internal wiring layer paste 4) formed inside the green sheet laminate is fired to form an internal wiring layer. The coating thickness of these wiring layer pastes is formed to be about 12 to 22 μm, and the wiring layer thickness after firing is 10 to 18 μm. Here, as the metal powder contained in the internal wiring layer paste, those having the same or smaller particle size as the metal powder as the raw material contained in the via-hole conductor paste can be adopted. On the other hand, as the metal powder contained in the surface wiring layer paste, an average particle of 1/10 or less of the average particle diameter of the metal powder contained in the via-hole conductor paste at a position covering at least the through hole (through hole). It is important to use a metal powder having a diameter.

  By setting the relationship of the average particle size of the metal powder contained in each conductor paste in this way, the firing shrinkage of the via-hole conductor paste 2 can be started after the firing shrinkage of the surface wiring layer paste 3 is completed. . At the time of firing shrinkage of the via-hole conductor paste 2, the shrinkage of the via-hole conductor paste 2 in the XY direction can be suppressed by the already sintered surface wiring layer paste 3 (surface wiring layer). By suppressing the firing shrinkage in the XY direction, the via-hole conductor paste 2 shrinks mainly in the Z direction. Also, the surface wiring layer paste 3 (surface wiring layer) that has already been sintered is covered. Therefore, the via-hole conductor after firing does not protrude greatly from the surface, and the mountability is good.

  A plurality of the green sheets obtained in this manner are stacked in accordance with a predetermined stacking order to form the green sheet stack 1. Specifically, the green sheet 1a on which the surface wiring layer paste is deposited is used as the surface layer. 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.

  Further, as shown in FIG. 1, firing shrinkage for suppressing firing shrinkage in the direction (XY direction) perpendicular to the laminating direction of the green sheet laminate 1 on the upper and lower sides of the green sheet laminate 1. The suppression sheet | seat 5 is arrange | positioned and these are piled up. Specifically, the green sheet laminate 1 and the firing shrinkage suppression sheet 5 are aligned by image recognition, and a rigid press method or an isostatic press method is applied.

  The firing shrinkage suppression sheet 5 is removed after firing the green sheet laminate 1, and examples thereof include a green sheet mainly composed of ceramic powder that does not sinter at the firing temperature of the green sheet laminate 1. . Specifically, alumina that is versatile and inexpensive is most suitable. Furthermore, in order to increase the affinity between the green sheet laminate 1 and the firing shrinkage suppression sheet 5 in the firing process of the multilayer circuit board, it contains the same glass powder as the glass powder contained in the green sheet in a range of 20% by mass or less. May be. Thereby, the shrinkage suppressing effect is further enhanced, and a multilayer circuit board with higher dimensional accuracy can be obtained. Using this firing shrinkage suppression sheet 5, the green sheet laminate 1 and the firing shrinkage suppression sheet 5 are fired at a firing temperature lower than the firing shrinkage start temperature of the firing shrinkage suppression sheet 5 and sintering the green sheet laminate 1. Thereby, the baking shrinkage | contraction of the XY direction of the green sheet laminated body 1 can be suppressed.

  In addition, as this baking shrinkage suppression sheet | seat 5, what does not shrink by baking (sintered body) can also be employ | adopted. “No firing shrinkage” means, for example, that it has already been sintered and no longer shrinks by firing. As this firing shrinkage suppression sheet 5, an alumina sintered body or a low-temperature sintering with a high degree of crystallinity of 99% or more and low residual glass. Examples thereof include a silicon nitride sintered body, a silicon nitride sintered body, carbon, and a tungsten sintered body having excellent thermal conductivity. By bonding the firing shrinkage suppression sheet 5 to the green sheet laminate 1 using a viscous member such as an acrylic resin having excellent thermal decomposability, the firing shrinkage in the XY direction of the green sheet laminate 1 is suppressed. Can do.

  And it transfers to the baking process which bakes the green sheet laminated body 1 and the baking shrinkage | contraction suppression sheet | seat 5 which were piled up. Specifically, after performing a degreasing treatment for decomposing and eliminating organic components, the main baking is performed. In this firing step, the green sheet laminate 1 and the firing shrinkage suppression sheet 5 are restrained from each other by maintaining separately at an intermediate temperature from the degreasing to the firing, in addition to the change in the heating rate and the maintenance of the firing temperature. It is also possible to increase the power and reduce warping and swell.

  The firing temperature at this time is the end temperature of firing shrinkage of the green sheet laminate 1 when the firing shrinkage suppression sheet 5 is a green sheet mainly composed of ceramic powder that is not sintered at the firing temperature of the green sheet laminate 1. It is above and it is preferable that it is less than the starting temperature of the baking shrinkage of the baking shrinkage suppression sheet 5. Further, even if the firing shrinkage suppression sheet 5 is a sintered body, there is no restriction as in the case of a green sheet, but it is not less than the end temperature of firing shrinkage of the green sheet laminate 1 and the firing shrinkage suppression sheet 5 It is preferable that the temperature be lower than the firing shrinkage start temperature. 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 press-molding each independently. At this time, each contracts isotropically and is converted from volumetric shrinkage of TMA to volume shrinkage.

  Prior to firing, the green sheet laminate 1 is preferably heat-treated at 100 to 800 ° C., particularly 400 to 750 ° C. to decompose and remove internal organic components as desired. Further, simultaneous firing at 800 to 1000 ° C., particularly 850 to 950 ° C. is preferable in terms of sufficient sintering and prevention of oversintering. At this time, when Cu is used as the metal powder in the via-hole conductor paste, firing is preferably performed in a nitrogen atmosphere from the viewpoint of preventing oxidation of Cu.

  After the firing step is completed in this manner, the firing shrinkage-suppressing sheet 5 remaining on the upper and lower surfaces of the multilayer circuit board after firing is usually subjected to ultrasonic cleaning, polishing, water jet, chemical blasting, sand blasting, wet blasting, etc. A multilayer circuit board can be obtained by removing by a technique.

  The shrinkage suppression effect in the XY direction of the via-hole conductor paste 2 by the firing shrinkage suppression sheet 5 is smaller than the shrinkage suppression effect in the XY direction of the green sheet laminate 1 by the firing shrinkage suppression sheet 5. However, the average particle diameter of the metal powder included in the position covering at least the through hole of the surface wiring layer paste 3 is considerably smaller than the average particle diameter of the metal powder included in the via-hole conductor paste 2, specifically 1 / 10 or less, the firing shrinkage of the via-hole conductor paste 2 can be started after the firing shrinkage of the surface wiring layer paste 3 at least at the position covering the through hole. Shrinkage in the Y direction can be suppressed. By suppressing the firing shrinkage in the XY direction, the via-hole conductor paste 2 shrinks mainly in the Z-direction, so that the via-hole conductor paste 2 does not greatly protrude from the surface, and the mountability is good. Become.

  The main components of the metal powder contained in the via-hole conductor paste 2 and the metal powder contained in the surface wiring layer paste 3 are preferably the same. Specifically, the main component is at least one of gold, silver, copper, and aluminum, and silver or copper is particularly preferable from the viewpoint of price and conduction resistance. In the case where the main component of the metal powder contained in the via-hole conductor paste is an alloy made of Cu, Ag, Au, or the like, the alloy is preferably used for the surface wiring layer paste 3 as well. In addition, inorganic components such as other metals, oxides, glasses, ceramics, and the like may be included within a range in which the electrical resistance is not deteriorated with respect to these main components.

  This is because, by using the same main component, it is easy to control the surface wiring layer paste 3 and the via-hole conductor paste 2 to have different firing shrinkage start temperatures (shrinkage behavior). Even if the main components are different, the same main component is not necessarily used as long as the firing shrinkage start temperature (shrinkage behavior) of the surface wiring layer paste 3 and the via-hole conductor paste 2 can be controlled to be different. It doesn't matter.

First, as a glass ceramic material for forming a green sheet that becomes an insulating layer after firing, 43.3 mass% SiO ₂ , 12.9 mass% Al ₂ O ₃ , 18.0 mass% MgO, 14. 1 wt% of BaO, 7.5 wt% of _B 2 _O 3, 1.0 wt% of _Y 2 _O 3, 1.7 wt% of CaO, 0.5 wt% of SrO, 1.0 weight% A glass ceramic material composed of 60% by mass of glass composed of ZrO ₂ and 40% by mass of Al ₂ O ₃ was prepared. An acrylic organic binder, a plasticizer, and an organic solvent were added to the glass ceramic material to prepare a slurry, which was then thinned by a doctor blade method to prepare a green sheet for an insulating substrate. At this time, the thickness of the green sheet was 74 μm.

In addition, silver powder having an average particle size of 0.5 μm, 3.5 μm, and 5.0 μm is prepared, and the SiO ₂ —Al ₂ O ₃ —BaO—CaO—B ₂ O ₃ system with respect to 100% by mass of the silver powder. 12% by mass of glass was added, an acrylic resin as an organic binder, and a mixed solution of terpineol and dibutyl phthalate (80:20 by mass) as a solvent were added and kneaded to prepare a via-hole conductor layer paste.

  Further, a through-hole having a diameter of 90 μm was formed in the green sheet with a laser, and the through-hole conductor layer paste was filled into the through-hole by a screen printing method.

Furthermore, silver powder having an average particle diameter of 2.5 μm is prepared, and 0.5 mass% of SiO ₂ —Al ₂ O ₃ —BaO—CaO—B ₂ O ₃ glass is added to 100 mass% of the silver powder. Then, an acrylic resin was added as the organic binder, and a mixed solution of terpineol and dibutyl phthalate (80:20 in mass ratio) was added and kneaded to prepare an internal wiring layer paste. The obtained internal wiring layer paste was printed by a screen printing method.

Furthermore, silver powder having an average particle size of 0.1 μm, 0.3 μm, 0.5 μm, 1.8 μm, 2.5 μm, and 5.0 μm was prepared, and SiO ₂ —Al with respect to 100% by mass of silver powder. 1% by mass of ₂ O ₃ —BaO—CaO—B ₂ O ₃ glass is added, an acrylic resin is added as an organic binder, and a mixed solution of terpineol and dibutyl phthalate (80:20 by mass) is added and kneaded. Thus, a surface wiring layer paste was prepared. Using the obtained surface wiring layer paste, it was formed by screen printing so as to have a thickness of 20 μm and a diameter of 200 μm immediately above the through hole.

  Five green sheets thus obtained were laminated to prepare a green sheet laminate.

Next, as a firing shrinkage suppression sheet, 90% by mass of Al ₂ O ₃ and 10% by mass of glass using Al ₂ O ₃ having an average particle diameter of 3 μm and the same glass component as the glass component in the green sheet. A green sheet having a thickness of 150 μm was prepared. The organic binder, plasticizer, solvent, and the like at the time of producing the fired shrinkage suppressing sheet were the same as those of the green sheet made of the glass ceramic material that becomes the insulating layer after firing. The green sheet laminate and the fired shrinkage suppression sheet were aligned by image recognition, and pressure laminated by a rigid press method (45 ° C., 5 MPa).

Subsequently, the green sheet laminate and the firing shrinkage suppression sheet that were superposed in a continuous furnace were fired. In firing, the stacked green sheet laminate and firing shrinkage suppression sheet are placed on an Al ₂ O ₃ base plate, and this is removed in the atmosphere at 400 ° C. in order to decompose and remove organic components such as an organic binder. Then, the binder was treated at 910 ° C. and fired at 910 ° C. in the atmosphere, and then the firing shrinkage-suppressing sheet was removed by blasting to produce a multilayer circuit board. The thickness of the surface wiring layer after firing was 15 μm.

In the fired multilayer circuit board, the surface irregularities near the edge of the board were measured with a three-dimensional laser displacement meter. At this time, among the obtained measurement data, the difference between the lowest point and the highest point on the surface of the surface wiring layer was defined as the protrusion height and measured. Table 1 shows the maximum protrusion height in the results of 8 substrates. The results are shown in Table 1.

  From Table 1, sample No. manufactured by the method for manufacturing a multilayer circuit board according to the present invention is shown. In 1-4, the maximum value of the protrusion height was 15 μm or less. In particular, sample no. When the average particle size of the metal powder contained in the surface wiring layer paste of 1 is 1/50 of the average particle size of the metal powder contained in the via-hole conductor paste, the maximum protrusion height is as extremely as 4 μm. It was very good.

  On the other hand, the sample No. manufactured by the manufacturing method of the multilayer circuit board which is outside the scope of the present invention. About 5-7, protrusion height rose remarkably. Sample No. When the metal powder contained in the via-hole conductor paste as small as 0.5 μm as in FIG. 8 was not able to suppress firing shrinkage in the XY direction of the via-hole conductor paste, the protrusion height was significantly increased.

It is explanatory drawing of the manufacturing method of the multilayer circuit board of this invention, Comprising: The state which accumulated the baking shrinkage | contraction suppression sheet | seat on the upper side and lower side of the green sheet laminated body is shown.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Green sheet laminated body 1a-1d ... Green sheet 2 ... Via-hole conductor paste 3 ... Surface wiring layer paste 4 ... Internal wiring layer paste 5 ... Baking shrinkage suppression sheet

Claims (2)

A surface wiring layer is formed on the surface of an insulating substrate composed of a plurality of insulating layers, and a manufacturing method of a multilayer circuit board in which a via-hole conductor connected to the surface wiring layer is formed inside the insulating substrate,
Forming a plurality of green sheets to be a plurality of insulating layers after firing;
Forming a through hole in the green sheet disposed at least on the surface layer, and filling the through hole with a via-hole conductor paste containing metal powder having an average particle diameter of 1 to 5 μm;
A metal powder having an average particle diameter of 1/10 or less of an average particle diameter of the metal powder contained in the via-hole conductor paste is included at least in a position covering the through hole on the upper surface of the green sheet disposed on the surface layer. A step of depositing a surface wiring layer paste;
A green sheet laminated body in which the plurality of green sheets are laminated is formed using a green sheet in which the through hole is filled with the via hole conductor paste and the surface wiring layer paste is deposited on the upper surface. Process,
A step of removing the firing shrinkage suppression sheet after firing by overlapping and firing firing shrinkage suppression sheets for restraining firing shrinkage in a direction perpendicular to the stacking direction of the green sheet laminate on the upper and lower sides of the green sheet laminate A method for manufacturing a multilayer circuit board. 2. The method for manufacturing a multilayer circuit board according to claim 1, wherein the main components of the metal powder contained in the via-hole conductor paste and the metal powder contained in the surface wiring layer paste are the same.

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