JP5951970B2 - Wiring board manufacturing method - Google Patents

Description

The present invention, the wiring conductor is relates to the manufacture how the wiring board which is embedded in the insulating substrate.

  2. Description of the Related Art Conventionally, a wiring board for mounting electronic components such as a semiconductor element such as an image pickup element and a crystal resonator is made of tungsten or molybdenum on the surface of an insulating base using an electrically insulating material such as an aluminum oxide sintered body. It is produced by providing a wiring conductor using a metal material such as.

  Such a wiring board is produced by forming a conductor pattern on a ceramic green sheet and then firing it. The ceramic green sheet is prepared by molding a slurry prepared by adding an organic binder, a plasticizer, a solvent, and the like to ceramic powder by a doctor blade method or the like. The conductor pattern is formed by screen-printing a conductor paste containing metal powder on a ceramic green sheet (see, for example, Patent Document 1). When the wiring board has a plurality of layers, a plurality of ceramic green sheets on which wiring patterns are formed are stacked and pressed to obtain a stacked body, and then the stacked body can be fired.

JP 2007-36286

  In recent years, the wiring conductor of the wiring board has been increased in density, and it is required to make the wiring conductor thinner. However, in the method of manufacturing a wiring board as described above, if the conductor paste is formed by screen printing in the step of forming a conductor pattern to be a wiring conductor, it is difficult to further reduce the wiring conductor.

  The present invention has been devised in view of the above-described problems of the prior art, and an object thereof is to provide a method of manufacturing a wiring board capable of thinning a wiring conductor.

  According to one aspect of the present invention, there is provided a method of manufacturing a wiring board, comprising: a first step of providing a conductive pattern containing a second thermoplastic resin on a ceramic green sheet containing a first thermoplastic resin; An inner surface portion formed of the conductor pattern by heating the first thermoplastic resin and the second thermoplastic resin so as to have a temperature equal to or higher than the glass transition temperature and pressurizing the ceramic green sheet so as to be pushed into the ceramic green sheet. And a third step of firing the ceramic green sheet and the conductor pattern so that the recess is closed by shrinkage.

According to the method for manufacturing a wiring board according to one aspect of the present invention, the conductor pattern is heated to a temperature equal to or higher than the glass transition temperature of the first thermoplastic resin and the second thermoplastic resin, and the ceramic green sheet Since it has the process of pressing so that it may be pushed in, the width of the conductor pattern can be reduced after the conductor pattern is printed, so that the wiring conductor can be thinned.

(A)-(d) is sectional drawing which shows the manufacturing method of the wiring board in the 1st Embodiment of this invention. (A) is a top view which shows 1 process of the manufacturing method of the wiring board in the 1st Embodiment of this invention, (b) is sectional drawing in the AA of (a). (A) is a top view which shows 1 process of the manufacturing method of the wiring board in the 1st Embodiment of this invention, (b) is sectional drawing in the AA of (a). (A) is a top view which shows 1 process of the manufacturing method of the wiring board in the 1st Embodiment of this invention, (b) is sectional drawing in the AA of (a). (A) is a top view which shows 1 process of the manufacturing method of the wiring board in the 2nd Embodiment of this invention, (b) is sectional drawing in the AA of (a).

  Hereinafter, some exemplary embodiments of the present invention will be described with reference to the drawings.

(First embodiment)
The method for manufacturing a wiring board according to the first embodiment of the present invention includes a conductor containing a second thermoplastic resin on a ceramic green sheet 1 containing a first thermoplastic resin as in the example shown in FIG. The first step of providing the pattern 2 and the conductor pattern 2 as in the example shown in FIG. 1C so that the temperature is equal to or higher than the glass transition temperature of the first thermoplastic resin and the second thermoplastic resin. A second step of heating and pressurizing the ceramic green sheet 1 to form a recess 3 having an inner surface portion made of the conductor pattern 2 in the ceramic green sheet 1, and an example shown in FIG. And the third step of firing the ceramic green sheet 1 and the conductor pattern 2 so as to close the concave portion 3 by contraction.

  The ceramic green sheet 1 is produced by producing a slurry containing ceramic powder, an organic binder, a solvent, and a first thermoplastic resin, forming the slurry into a sheet shape, and drying the slurry. A predetermined amount of a plasticizer and a dispersant may be added to the slurry as necessary. The slurry is applied to a resin or paper support such as PET (polyethylene terephthalate) by a forming method such as a doctor blade method, a lip coater method or a die coater method, and formed into a sheet shape. As a drying method, warm air drying, vacuum drying, far-infrared drying, or the like can be used.

As the ceramic powder, for example, aluminum oxide (Al ₂ O ₃ ) powder, aluminum nitride (AlN) powder, glass ceramic powder, or the like can be used, and is appropriately selected according to the characteristics required for the wiring board.

When the ceramic powder is an aluminum oxide powder or an aluminum nitride powder, a powder of a component serving as a sintering aid such as silicon oxide (SiO ₂ ) or magnesium oxide (MgO) is added, and manganese oxide (MnO) is used as a colorant. ) Etc. may be added.

When the ceramic powder is a glass ceramic powder, the glass powder and filler powder are mixed at a mass ratio of 10:90 to 99: 1, preferably 40:60 to 80:20. As the glass powder of the glass ceramic powder, those conventionally used for glass ceramics may be used. 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 (where M is Ca, Sr, Mg) , Ba or Zn), SiO ₂ —Al ₂ O ₃ —M ₁ O—M ₂ O system (where M 1 and M 2 are the same or different and represent Ca, Sr, Mg, Ba or Zn), SiO _{2. -B 2 O 3 -Al 2 O 3} -M1O-M2O -based (where, M1 and M2 are as defined _{above.), SiO 2 -B 2 O} 3 -M3 2 O system (although, M3 is Li, Na Or K.), SiO ₂ —B ₂ O ₃ —Al ₂ O ₃ —M3 ₂ O-based (where M3 is the same as above), Pb-based, Bi-based, etc. .

Moreover, what is conventionally used for glass ceramics should just be used as filler powder of glass ceramic powder. For example, a composite oxide of Al ₂ O ₃ , SiO ₂ , ZrO ₂ and an alkaline earth metal oxide, a composite oxide of TiO ₂ and an alkaline earth metal oxide, Al ₂ O ₃ and SiO ₂ (cristobalite, quartz And ceramic powders such as composite oxides containing at least one of (for example, spinel, mullite, cordierite).

  As the organic binder, those conventionally used for ceramic green sheets can be used. For example, acrylic (acrylic acid, methacrylic acid or their ester aggregate or copolymer, specifically acrylic ester copolymer, methacrylic ester copolymer, acrylic ester-methacrylic ester copolymer Homopolymers or copolymers of polyvinyl butyral, polyvinyl alcohol, acrylic-styrene, polypropylene carbonate, cellulose, etc. In view of decomposability and volatility in the firing step, an acrylic binder is more preferable. Moreover, although the addition amount of an organic binder changes with ceramic powder, it should just be a quantity which is easy to be decomposed | disassembled and removed at the time of baking, the ceramic powder is disperse | distributed, and the handling property and workability of a green sheet are favorable. For example, about 10 to 20% by mass is desirable with respect to the ceramic powder.

The solvent contained in the slurry is made of organic materials such as hydrocarbons, ethers, esters, ketones, alcohols, etc. so that a slurry having a viscosity suitable for green sheet molding can be obtained by dispersing ceramic powder and organic binder. A solvent and water are mentioned. Among these, solvents having a high evaporation coefficient such as toluene, methyl ethyl ketone, and isopropyl alcohol are preferable because the drying process after slurry application can be completed in a short time. The solvent is added in an amount of 30 to 100% by mass with respect to the ceramic powder, so that the viscosity is such that the slurry can be satisfactorily coated on the support, specifically about 3 to 100 cps. It is desirable to make it.

The first thermoplastic resin is a thermoplastic resin whose molecular weight, crystallinity, etc. are adjusted so as to have a glass transition temperature in the range of 40 ° C. to 200 ° C., for example. As such a thermoplastic resin, for example, polyvinyl acetate, high-density polyethylene, acrylic resin, butyral resin, or wax can be used. These thermoplastic resins may be used alone or in combination of two or more.

  The conductor pattern 2 is formed, for example, by printing a conductor paste for the conductor pattern 2 on the main surface of the ceramic green sheet 1 in a predetermined pattern shape by a printing method such as a screen printing method or a gravure printing method. The conductor pattern 2 to be a through conductor is formed by forming a through hole for the conductor pattern 2 to be a through conductor in the ceramic green sheet 1 by punching, punching with a die or laser processing, and a conductor to be a through conductor in this through hole. The conductive paste for pattern 2 is formed by being embedded by screen printing or press filling.

  Conductor paste is added to a conductive powder such as metal with an appropriate organic binder, solvent and second thermoplastic resin, and uniformly dispersed and kneaded by a kneading means such as a ball mill or planetary mixer, and then the required amount of solvent is added. Then, it is produced by adjusting the viscosity to be suitable for printing and filling of the through holes.

  The conductor powder is, for example, a metal powder that is sintered by co-firing with a ceramic green sheet in a firing step, such as tungsten (W), molybdenum (Mo), manganese (Mn), gold (Au), silver (Ag), One type or two or more types of copper (Cu), palladium (Pd), platinum (Pt) and the like can be mentioned, and in the case of two or more types, any form such as mixing, alloy, coating and the like may be used.

  As the organic binder used for the conductive paste, those conventionally used for the conductive paste can be used. For example, the same organic binder used for the ceramic green sheet 1 described above can be used. In view of decomposability and volatility in the firing step, acrylic and alkyd organic binders are more preferable. Moreover, although the addition amount of an organic binder changes with metal powders, it should just be the quantity which is easy to be decomposed | disassembled and removed at the time of baking and can disperse | distribute metal powder. For example, it is desirable that the amount is about 5 to 20% by mass with external addition to the metal powder.

The solvent used for the conductor paste is not particularly limited as long as the metal powder and the organic binder can be well dispersed and mixed, and examples thereof include terpineol and butyl carbitol acetate. In view of formability after printing and drying properties, it is preferable to use a low boiling point solvent. The solvent is added in an amount of 4 to 15% by mass based on the metal powder, and the viscosity becomes such that these conductor pastes can be satisfactorily formed. Specifically, the conductor paste for the conductor pattern 2 is about 3000 to 40,000 cps, and the conductor paste for the through conductor pattern is 15000 to 40,000 cp.
It is adjusted to be about s.

  As the second thermoplastic resin, the same material as the first thermoplastic resin described above can be used. Such a material of the second thermoplastic resin may be the same as or different from the first thermoplastic resin depending on the purpose.

  Glass or ceramic powder may be added to the conductor paste in order to match the firing shrinkage behavior and shrinkage rate of the ceramic green sheet during firing, or to ensure the bonding strength of the wiring conductor 12 after firing.

  Next, the ceramic green sheet 1 and the conductor pattern 2 are heated and pressed to form a recess 3 having an inner surface portion made of the conductor pattern 2 in the ceramic green sheet 1.

  The conductor pattern 2 is heated at a temperature equal to or higher than the glass transition temperature of the first thermoplastic resin and the second thermoplastic resin. For example, if the first thermoplastic resin and the second thermoplastic resin are waxes, the ceramic green sheet 1 and the conductor pattern 2 are heated to a temperature of 40 ° C. or higher.

  Pressurization to the ceramic green sheet 1 and the conductor pattern 2 is performed by applying a force that pushes the conductor pattern 2 into the ceramic green sheet 1.

Such pressurization is performed using a pressing member 4 having a shape having a convex portion 5 for pressing the wiring pattern 2 as in the example shown in FIG. Such a pressing member 4 can be produced using metal or resin. Specifically, as in the example shown in FIG. 1B, the pressing member 4 and the ceramic green sheet 1 provided with the conductor pattern 2 are shown in plan view, and the convex portion 5 and the conductor pattern 2 of the pressing member 4 are in a plan view. Arrange them so that they overlap.

  Thereafter, as in the example shown in FIG. 1C, the pressing member 4 presses the conductor pattern 2 and the ceramic green sheet 1 so that the conductor pattern 2 is pushed into the ceramic green sheet 1. At this time, by heating the pressing member 4, the ceramic green sheet 1 and the conductor pattern 2 are heated via the pressing member 4 to soften and pressurize the ceramic green sheet 1 and the conductor pattern 2.

  At this time, in order to make the shrinkage ratio between the ceramic green sheet 1 and the conductor pattern 2 close when the ceramic green sheet 1 and the conductor pattern 2 are heated, the first thermoplastic resin and the second thermoplastic resin are: It is preferable to use the same material.

  By performing the heating and pressurization described above, the ceramic green sheet 1 provided with the concave portion 3 having the inner surface portion made of the conductor pattern 2 as in the example shown in FIG.

  In the recess 3, the conductor pattern 2 may be provided along the side surface and the bottom surface of the recess 3 as in the example shown in FIG. 3, or the conductor pattern 2 may be provided only on the side surface of the recess 3. .

The recess 3 may be provided in such a width that the inner surface portions are in contact with each other by firing shrinkage of the ceramic green sheet 1 during firing. Specifically, for example, the recess 3 is preferably formed in a groove shape having a width of 0.1 μm to 20 μm.

  Next, the ceramic green sheet 1 provided with the recesses 3 is debindered at a temperature of 300 to 600 ° C. and fired. The firing of the ceramic green sheet 1 is performed at a temperature of 1500 to 1800 ° C., for example, when the ceramic green sheet 1 contains alumina, silica, calcia, magnesia and the like as ceramic powder. Moreover, if the ceramic green sheet 1 is a glass ceramic, it will bake at a temperature of 800-1000 degreeC.

  The firing atmosphere is the atmosphere when the conductor powder contained in the conductor pattern 2 is a material that is difficult to oxidize such as Ag, and the conductor powder contained in the conductor pattern 2 is a material that easily oxidizes such as Cu. In this case, a nitrogen atmosphere is preferable. Note that it is preferable to use a humidified atmosphere so that the binder can be easily removed.

  The concave portion 3 is closed by contact with the inner surface portion made of the conductor pattern 2 as in the example shown in FIG. 4 due to shrinkage during firing of the ceramic green sheet 1. At the same time as the recess 3 is closed or after the recess 3 is closed, the conductor pattern 2 is sintered to become a wiring conductor.

  According to the method for manufacturing a wiring board in the first embodiment of the present invention, the conductor pattern 2 is heated to a temperature equal to or higher than the glass transition temperature of the first thermoplastic resin and the second thermoplastic resin. Since the step of applying pressure to push into the ceramic green sheet 1 is provided, the width of the conductor pattern 2 can be reduced after the conductor pattern 2 is printed, so that the wiring conductor 12 can be thinned.

  The wiring board according to the first embodiment includes the insulating base 11 and the wiring conductor 12 having a depth dimension larger than the width dimension and embedded in the insulating base 11. The wiring conductor 12 can be thinned without increasing the resistance value of the conductor 12.

Also, by increasing the depth at which the conductor pattern 2 is pushed into the ceramic green sheet 1, the conductor pattern 2 having a higher aspect ratio can be formed as compared with the case where the wiring pattern 2 is provided by screen printing. A wiring conductor 12 can be provided. Since the wiring conductor 12 having a high aspect ratio can increase the cross-sectional area of the wiring conductor 12 even if the width of the wiring conductor is reduced, the resistance value can be reduced when the wiring conductor is thinned.

(Second Embodiment)
Next, a method for manufacturing a wiring board according to a second embodiment of the present invention will be described with reference to FIG.

  The wiring board manufacturing method according to the second embodiment of the present invention differs from the wiring board manufacturing method according to the first embodiment described above in the second step as in the example shown in FIG. The point is that the conductor pattern 2 is pushed into the ceramic green sheet 1 so as to form a recess having a plurality of regions having different depths.

  The method for manufacturing a wiring board in the present embodiment is formed by pressing the conductor pattern 2 into the ceramic green sheet 1 so as to form a recess having a plurality of regions having different depths, and firing to close the recess. In the formed wiring conductor, the width of the portion corresponding to the region where the depth of the recess is deep is smaller than the width of the portion corresponding to the region where the depth of the recess is shallow. This is because the conductor pattern 2 is pushed more into the ceramic green sheet 1 in the region where the depth of the recess is deeper than in the region where the depth of the recess is shallow. Therefore, according to the method for manufacturing a wiring board in the present embodiment, a wiring conductor having a narrow width can be formed.

DESCRIPTION OF SYMBOLS 1 ... Ceramic green sheet 2 ... Conductor pattern 3 ... Concave part 4 ... Pressing member 5 ... Convex part
11 ... Insulating substrate
12 ... Wiring conductor

Claims (2)

A first step of providing a conductive pattern containing a second thermoplastic resin on a ceramic green sheet containing the first thermoplastic resin;
The conductor pattern is heated so as to have a temperature equal to or higher than the glass transition temperature of the first thermoplastic resin and the second thermoplastic resin, and is pressed so as to be pushed into the ceramic green sheet. A second step of forming, in the ceramic green sheet, a recess having an inner surface made of a pattern;
A method of manufacturing a wiring board, comprising: a third step of firing the ceramic green sheet and the conductor pattern so that the recess is closed by shrinkage.   2. The manufacturing of a wiring board according to claim 1, wherein, in the second step, the conductor pattern is pushed into the ceramic green sheet so as to form the concave portion having a plurality of regions having different depths. Method.

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