JP2017183715A - Double-sided wiring board having through electrode and method of producing the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a double-sided wiring board in which a high performance conductor pattern is formed with a high adhesion force to a via filling substrate.SOLUTION: A double-sided wiring board is prepared by combining: an insulating substrate having a pore; a conductive via existing in the pore and including a conductor; a junction layer laminated to a region of at least a part of surfaces of the insulating substrate and the conductive via and including an active metal layer; and a surface conductor layer laminated on the junction layer, including a conductor, and having a porous structure. The active metal layer may include at least one active metal selected from the group consisting of Ti, Zr, Hf, Nb, Ta, Cr, Mn, and Al, or an alloy including the active metal. The junction layer further may include a non-transmission layer. The non-transmission layer may include at least one barrier metal selected from the group consisting of Mo, W, Ni, Pd, and Pt, or an alloy including the barrier metal.SELECTED DRAWING: None

Description

  The present invention relates to a heat-resistant substrate used in various electronic devices and a method for manufacturing the same, and more particularly, to a double-sided wiring substrate having a through electrode for use in high-performance applications such as high heat dissipation, large current, and high-density mounting ( And a manufacturing method thereof.

  Conventionally, electronic boards have been used for the placement of functional components and the formation of wiring circuits. In recent years, through holes (vias) are formed in an insulating substrate and a conductive material is provided in the through holes to electrically connect both surfaces of the substrate in order to reduce the size, functionality, and integration of electronic devices or components. Applications are increasing. As a method for electrically conducting both surfaces of a substrate, Japanese Patent Laid-Open No. 5-308182 (Patent Document 1) discloses a method of forming an Au plating layer as a metal layer on the inner wall portion of a through hole of an insulating substrate. Japanese Patent Laid-Open No. 2006-203112 (Patent Document 2) discloses a method of completely filling a substantially drum-shaped through hole formed at a predetermined position of an insulating substrate with a plated metal.

  However, these methods require a plating process with a large environmental load as a manufacturing process of the substrate itself, so that the process is complicated and economical.

  There is also known a method of filling a through-hole with a conductive paste (conductive paste) composed of metal powder and a curable resin and curing to obtain a filled via. However, since this filled via also contains a resin in the conductive material, its conductivity is low, its use is limited by the heat resistance of the resin, and the heat resistance of the substrate is also low.

  Also known is a method of filling a through hole with a conductive paste composed of metal powder, an inorganic binder and a resin, and heating the metal paste to a temperature higher than the sintering temperature of the metal to sinter the metal powder to obtain a conductive filled via. This method is excellent in convenience and the resin component is evaporated and decomposed by firing. Therefore, the filled via obtained by this method has high conductivity, thermal conductivity, and heat resistance. However, in a via-filled substrate obtained by firing after filling a via with a conductive paste, a gap or a void may exist between the filled conductor (conductive via part) and the wall surface of the hole. The cause of the generation of these gaps and voids can be presumed to be partly due to shrinkage due to solvent removal (drying) of the conductive paste filled in the holes and shrinkage due to sintering of the metal powder during high-temperature firing.

  After the filling via is formed in the through hole, the double-sided wiring board is usually manufactured through a process of forming a conductor film having a predetermined pattern shape on both surfaces of the substrate as a post process. As a method for forming a conductor film, a thin film method, a plating method, and a thick film method are generally used. However, if a gap exists between a filled conductor and a wall surface, the following problems occur in the thin film method and the plating method. There is a fear.

  That is, in the case of the thin film method, since the film is formed by sputtering or the like, the film thickness of the conductor film is usually less than 2 to 3 μm. For this reason, when there is a gap between the filled conductor and the substrate, the conductive film may be cut and the conductive performance may be deteriorated or disconnected. Note that the thin film wiring method is applicable only to applications that do not require a large driving force because the film thickness is thin.

  In the case of the plating method, the substrate filled with vias is put into a plating bath to perform plating. However, the chemical solution enters the voids and gaps in the via filling portion, and after the plating film is formed, the solution penetrates into the gaps. There is a risk of chemicals being trapped. Further, when the confined chemical solution is heated in a subsequent process or mounting, it may expand and cause problems such as blistering, bursting, peeling, or discoloration.

  On the other hand, in the case of the thick film method, the conductor paste is applied by the screen printing method and thick film printing is performed, so even if there are voids or gaps on the surface of the via filling portion, it is repaired to some extent when the conductor paste is printed. Since the film thickness is 10 μm or more, there is no problem in conduction even if there are some voids or gaps in the via filling portion. However, in the case of thick film conductor paste, the adhesion strength to the substrate is ensured mainly by the glass component blended in the paste. I can't get it. As a result, long-term reliability such as thermal shock resistance may be insufficient. In addition, thick film screen printing has a limit of about 100 μm in pattern resolution, and it is difficult to form a fine pattern of 100 μm or less. Furthermore, since the cross-sectional shape of the pattern is a semi-cylindrical shape and does not have a rectangular shape, it cannot be used for a high-density mounting substrate that requires a high pattern shape and high accuracy.

  In JP-A-6-204645 (Patent Document 3), in order to obtain a good pattern shape, a thick film conductor paste is not printed on a pattern, but is printed on a larger area than the pattern or on the entire surface of the substrate (solid printing). Then, after baking the conductor film, a resist pattern is formed on the surface of the conductor film, and an unnecessary conductor portion is removed by etching to obtain a required pattern.

  However, even with this method, the etching resistance of the glass component compounded in the conductor paste is strong, and some glass components remain even after normal etching. Is unsuitable. Under such circumstances, the “thick film method” cannot be realized in the “double-sided wiring board having a through electrode” for application to high performance.

  Therefore, although the double-sided wiring board having a through electrode is originally a wiring board that is applied to high-performance applications such as high heat dissipation, large current, and high-density mounting, the above-described problems cannot be overcome by the conventional technology. , It was not fully realized.

JP-A-5-308182 (Claim 1, FIG. 2) JP 2006-203112 A (Claim 1, FIG. 3) JP-A-6-204645 (Claims, paragraph [0010])

  Accordingly, it is an object of the present invention to provide a double-sided wiring board in which a high-performance conductor pattern is formed on a via-filled board with high adhesion and a method for manufacturing the same.

  Another object of the present invention is to provide a double-sided wiring board having high heat resistance, thermal shock resistance and reliability, and a method for manufacturing the same.

  Still another object of the present invention is to provide a double-sided wiring board and a method for manufacturing the same, which can suppress swelling, peeling, and discoloration in a conductive via portion even when subjected to a wet process such as plating.

  Another object of the present invention is to provide a double-sided wiring board excellent in etching suitability and capable of forming a fine pattern and a method for manufacturing the same.

  As a result of intensive studies in order to achieve the above-mentioned problems, the present inventors have found that an insulating substrate having a hole, a conductive via part that exists in the hole and includes a conductor, and the insulating substrate and the conductive via part. A via-filled substrate by combining a bonding layer including an active metal layer laminated on at least a partial region of the surface of the substrate and a surface conductor layer including a conductor having a porous structure and laminated on the bonding layer. In addition, the inventors have found that a high-performance conductor pattern can be formed with a high adhesion force and completed the present invention.

  That is, the double-sided wiring board of the present invention includes an insulating substrate having a hole, a conductive via part that exists in the hole and includes a conductor, and at least a part of the surfaces of the insulating substrate and the conductive via part. A bonding layer that is laminated in a region and includes an active metal layer, and a surface conductor layer that is laminated on the bonding layer, includes a conductor, and has a porous structure. The active metal layer may include at least one active metal selected from the group consisting of Ti, Zr, Hf, Nb, Ta, Cr, Mn, and Al or an alloy containing the active metal. The bonding layer may further include a non-transmissive layer. The non-permeable layer may include at least one barrier metal selected from the group consisting of Mo, W, Ni, Pd, and Pt or an alloy including the barrier metal. The non-permeable layer may be interposed between the active metal layer and the surface conductor layer. The bonding layer may further include an affinity layer. This affinity layer may contain the same metal as that contained in the surface conductor layer or an alloyable metal. The affinity layer may be in contact with the surface conductor layer. The conductor included in the surface conductor layer may include at least one conductive metal selected from the group consisting of Ni, Pt, Cu, Ag, Au, and Al, or an alloy including this conductive metal. The porosity of the surface conductor layer is about 5 to 30% by volume. The surface conductor layer may not contain a glass component. The average thickness of the surface conductor layer is about 5 to 1000 times the average thickness of the bonding layer. The conductor included in the conductive via portion may have a porous structure. The porosity of the conductive via part including the conductor having a porous structure is about 15 to 45% by volume. A via bonding layer including an active metal layer may be interposed between the hole wall surface of the insulating substrate and the conductive via portion. The insulating substrate may be a ceramic substrate, a glass substrate, a silicon substrate, or an enamel substrate. In the double-sided wiring board of the present invention, a plating layer (particularly a wet plating layer) may be further laminated on the surface conductor layer.

  The present invention includes a via filling step of filling a hole in an insulating substrate having a hole with a conductive paste for a conductive via portion including metal particles and an organic vehicle, and a temperature equal to or higher than a sintering temperature of the metal particles included in the conductive paste. A via firing step in which conductive paste is fired by heating to form a conductive via portion; a bonding layer forming step in which a bonding layer including an active metal layer is laminated on the surface of the insulating substrate having the conductive via portion; A conductor coating step of applying a conductive paste for a surface conductor layer containing metal particles and an organic vehicle, heating the conductor paste to a temperature higher than the sintering temperature of the metal particles contained in the applied conductor paste, The manufacturing method of the said double-sided wiring board including the conductor baking process which forms the surface conductor layer containing the conductor which has a quality structure is also included.

  In the present invention, a bonding layer is formed by laminating a bonding layer containing an active metal layer on the surface of an insulating substrate having a hole, and laminating a via bonding layer containing an active metal on the wall of the hole. Process, via filling step of filling conductive hole for conductive via part including metal particles and organic vehicle into hole part of insulating substrate on which via bonding layer is formed, heating above the sintering temperature of metal particles contained in said conductive paste A via firing step of firing a conductive paste to form a conductive via portion, and applying a conductor paste for a surface conductor layer containing metal particles and an organic vehicle on the bonding layer and the conductive via portion on the surface of the insulating substrate. A step of firing a conductor to form a surface conductor layer containing a conductor and having a porous structure by firing the conductor paste by heating to a temperature higher than the sintering temperature of the metal particles contained in the applied conductor paste Method for producing a double-sided wiring board including also included.

  Furthermore, in the present invention, a bonding layer is formed by laminating a bonding layer including an active metal layer on the surface of an insulating substrate having a hole and laminating a via bonding layer including an active metal on the wall surface of the hole. A step of filling a hole in the insulating substrate on which the via bonding layer is formed with a conductive paste for a conductive via including metal particles and an organic vehicle; a conductor filling the bonding layer and the hole on the surface of the insulating substrate; Conductor coating step of applying a conductor paste for a surface conductor layer containing metal particles and an organic vehicle on the paste, a sintering temperature of metal particles contained in the applied conductor paste for a surface conductor layer and a conductor paste for a conductive via portion The conductor paste for the surface conductor layer and the conductor paste for the conductive via part are simultaneously fired to form a surface conductor layer and a conductive via part including the conductor and having a porous structure. Method for producing a double-sided wiring board including a degree also included.

  In the manufacturing method, the surface of the insulating substrate may be smoothed before or after the conductive via portion conductive paste is fired. In the bonding layer forming step, after forming the active metal layer, a non-permeable layer and / or an affinity layer may be further laminated on the active metal layer. In the bonding layer forming step, the bonding layer may be formed by physical vapor deposition. In the conductor applying step, before applying the conductor paste, the melting point of the metal having the lowest melting point among all the metal species that are 400 ° C. or higher in an inert gas atmosphere and that constitute the bonding layer, and the bonding layer The bonding layer may be heated and annealed at a temperature equal to or lower than the lower melting point of the alloy constituting the alloy. In the manufacturing method of the present invention, after forming a resist pattern in a partial region of the surface conductor layer obtained in the conductor firing step, the surface conductor layer and the bonding layer in the exposed region where the resist pattern is not formed are removed, Furthermore, a first etching step for removing the resist pattern may be further included. Furthermore, the manufacturing method of the present invention is a bonding layer for pattern printing the conductor paste for the surface conductor layer in the conductor coating step and removing the bonding layer exposed from the surface conductor layer (pattern) as a subsequent step of the conductor baking step. A removal step may be further included. In the bonding layer forming step, a bonding layer including an active metal layer may be formed in a pattern shape (target pattern shape in the surface conductor layer) on the surface of the insulating substrate. The production method of the present invention may further include a plating step of forming a plating layer on the surface of the surface conductor layer obtained in the conductor firing step. In the manufacturing method of the present invention, after forming a resist pattern in a partial region of the surface conductor layer obtained in the conductor firing step, a noble metal is applied to the surface of the surface conductor layer in the exposed region where the resist pattern is not formed. It may further include a second etching step of forming a plating layer including the resist pattern and removing the surface conductor layer and the bonding layer in the exposed region where the plating layer is not formed. The volume change rate before and after firing in the conductive via portion conductive paste may be -10% to 20%.

  In the present invention, an insulating substrate having a hole, a conductive via part that exists in the hole and includes a conductor, and is laminated on at least a part of the surface of the insulating substrate and the conductive via part, and A high-performance conductor pattern is formed on the via-filled substrate with high adhesion because the bonding layer including the active metal layer is combined with the surface conductor layer including a conductor that has a porous structure and is laminated on the bonding layer. it can. Moreover, when a joining layer contains a specific active metal, heat resistance and reliability can also be improved highly. Furthermore, since the surface conductor layer is a porous body, the thermal stress caused by the difference in coefficient of thermal expansion between the surface conductor layer and the insulating substrate is relieved, and the thermal shock resistance can be improved. In particular, since the conductive via portion is covered with the surface conductor layer, even if it is subjected to a wet process such as plating, swelling, peeling, discoloration, and the like in the conductive via portion can be suppressed. Furthermore, it is excellent in etching suitability, and when a pattern is formed by etching the surface conductive layer, a fine pattern can be formed.

FIG. 1 is a schematic view showing a manufacturing process of the double-sided wiring board obtained in Example 1. FIG. FIG. 2 is a schematic view showing a manufacturing process of the double-sided wiring board obtained in Comparative Example 1. FIG. 3 is a schematic view showing a manufacturing process of the double-sided wiring board obtained in Example 25.

[Double-sided wiring board]
The double-sided wiring board of the present invention includes an insulating substrate having a hole, a conductive via portion that is present in the hole and includes a conductor, and at least a part of the surface of the insulating substrate and the conductive via portion. A bonding layer that is stacked and includes an active metal layer, and a surface conductor layer that is stacked on the bonding layer and includes a conductor having a porous structure.

(Insulating substrate)
The material constituting the insulating substrate having the hole is required to have heat resistance because it undergoes a firing process, and may be an organic material such as engineering plastic, but is usually an inorganic material (inorganic material).

  Examples of inorganic materials include ceramics {metal oxide (quartz, alumina or aluminum oxide, zirconia, sapphire, ferrite, titania or titanium oxide, zinc oxide, niobium oxide, mullite, beryllia, etc.), silicon oxide (silicon dioxide, etc.). , Metal nitride (aluminum nitride, titanium nitride, etc.), silicon nitride, boron nitride, carbon nitride, metal carbide (titanium carbide, tungsten carbide, etc.), silicon carbide, boron carbide, metal boride (titanium boride, zirconium boride) Etc.), metal composite oxide [metal titanate (barium titanate, strontium titanate, lead titanate, niobium titanate, calcium titanate, magnesium titanate, etc.), zirconate metal salt (barium zirconate, zirconate Calcium, lead zirconate, etc.) Etc.}, glass (soda glass, borosilicate glass, crown glass, barium-containing glass, strontium-containing glass, boron-containing glass, low alkali glass, alkali-free glass, crystallized transparent glass, silica glass, quartz glass, heat-resistant glass Etc.) and silicon (semiconductor silicon etc.). The inorganic material may be a composite material of these inorganic material and metal (for example, enamel).

  The insulating substrate may be a heat resistant substrate such as a ceramic substrate, a glass substrate, a silicon substrate, or an enamel substrate. Of these heat-resistant substrates, ceramic substrates such as alumina substrates, aluminum nitride substrates, and silicon nitride substrates are preferable.

  The hole wall surface of the insulating substrate is oxidized (surface oxidation treatment, for example, discharge treatment (corona discharge treatment, glow discharge, etc.), acid treatment (chromic acid treatment, etc.), ultraviolet irradiation treatment, wrinkle treatment, etc.) Surface treatment such as treatment (solvent treatment, sandblast treatment, etc.) may be performed. Furthermore, the hole wall surface may have a via bonding layer formed with the same composition as the bonding layer described later in order to improve the adhesion with the conductive via portion. The average thickness of the via bonding layer can also be selected from the range of the average thickness of the bonding layer described later, and is usually the same thickness as the bonding layer.

  What is necessary is just to select the average thickness of an insulating board | substrate suitably according to a use, for example, 0.01-10 mm, Preferably it is 0.05-5 mm, More preferably, it is 0.1-1 mm (especially 0.2-0.8 mm). ) Degree.

  The insulating substrate has holes (usually a plurality of holes) for forming conductive vias, and the holes include through holes for forming a double-sided wiring board. The non-through hole may be included, but usually only the through hole. The cross-sectional shape parallel to the substrate surface direction of the hole is not particularly limited, and may be a polygonal shape (triangular shape, quadrangular shape, hexagonal shape, etc.), etc., but is usually circular or elliptical, Shape is preferred.

  The average hole diameter of the holes is, for example, 0.05 to 10 mm, preferably 0.08 to 5 mm, and more preferably about 0.1 to 1 mm.

  The method for forming the hole is not particularly limited, and a known method such as a laser method, a blast method, an ultrasonic method, a water jet method, a punching method, a grinding method, or a drill method can be appropriately used.

(Conductive via part)
The conductive via part is formed (or filled) in the hole of the insulating substrate, and the double-sided wiring board only needs to include a conductor (particularly a sintered conductor) for forming the double-sided electrode. The double-sided wiring board of the present invention is provided with a conductive via part so that a through electrode that electrically conducts both the front and back surfaces of the board is formed and functions as a front and back conductive type wiring board.

  The conductor contained in the conductive via portion is not particularly limited as long as it has conductivity, but is usually a conductive metal or an alloy containing this conductive metal. Examples of the conductive metal include Ni, Pt, Cu, Ag, Au, and Al. These metals can be used alone or in combination of two or more kinds, and may be an alloy in which two or more kinds are combined. Among these, Cu or Ag is preferable from the viewpoint of conductivity, reliability, economy, and the like.

  The conductive via portion includes a non-conductor such as a semiconductor or an insulator (for example, an organic vehicle remaining after firing, an inorganic binder such as a glass component) as long as it has conductivity capable of forming a double-sided wiring board. Also good. The proportion of the conductor in the conductive via portion may be 50% by mass or more, for example, 80% by mass or more, preferably 90% by mass or more, more preferably 95% by mass or more, and particularly 100% by mass (conductor alone) Formation).

  The conductive via portion only needs to be formed in the hole portion of the insulating substrate, and may be a solid body (non-porous body) or a porous body having a porous structure. When the conductive via part is a porous body, the thermal stress generated by the difference in thermal expansion coefficient between the conductive via part and the insulating substrate is relieved, and the thermal shock resistance can be improved. In particular, the conductive via portion obtained using the conductive paste (metal paste or conductive paste) may be a porous body generated by firing. The average pore diameter of the porous body is, for example, about 0.01 to 10 μm, preferably about 0.05 to 5 μm, and more preferably about 0.1 to 2 μm. The porosity of the porous body (average value when the double-sided wiring board has a plurality of conductive via portions) is, for example, about 5 to 60% by volume, preferably about 10 to 50% by volume, and more preferably about 15 to 40% by volume. is there. If the porosity is too large, the electrical conductivity may decrease, and if it is too small, the thermal shock resistance may decrease. The porous structure of the porous body is not particularly limited, and may be any of a continuous pore structure, an independent pore structure, or a mixed structure of both. An independent pore structure is preferred because of the airtightness of the filled via portion.

  The average pore diameter of the porous body can be measured based on observation with a scanning electron microscope (SEM) or a transmission electron microscope (TEM). Moreover, the porosity of a porous body can be measured based on the organic component volume ratio and baking shrinkage rate which are contained in a conductor paste, and can be measured by the method as described in the Example mentioned later in detail.

(Active metal layer)
The bonding layer is a thin film laminated on at least a part of the surface of the insulating substrate and the conductive via part, and usually has a shape corresponding to the pattern shape of the surface conductor layer. In particular, the bonding layer can improve the adhesion between the insulating substrate and the surface conductor layer, and in the region covering the conductive via portion (excluding the conductive via portion) (between the insulating substrate and the surface conductor layer). The conductive via portion is usually formed in a region covering the conductive via portion (a region including the conductive via portion), and the conductive via portion is covered with a bonding layer so that the conductive via portion is surface-conductive. Covered with layers. Further, the bonding layer includes an active metal layer (reaction layer with the insulating substrate) as an essential layer, so that the active metal layer reacts with a component of the insulating substrate or forms a compound, and the insulating group The adhesion between the material and the surface conductor layer is improved.

  The active metal layer includes an active metal or an alloy containing the active metal. The active metal may be a metal that reacts with a component of the insulating substrate or a metal that can form a compound with the component and is different from the metal that constitutes the surface conductor layer or the conductive via portion. For example, Ti, Zr, Hf, Nb, Ta, Cr, Mn, Al, etc. are mentioned. These active metals can be used alone or in combination of two or more kinds, and may be an alloy in which two or more kinds are combined.

  Of these active metals, active metals including Ti, Zr, and Cr are preferable, and these active metal simple substances are generally used.

  Furthermore, even if the active metal has a simple film structure (especially without forming a non-permeable layer), the electrical characteristics of the surface conductor layer and the adhesion between the surface conductor layer and the insulating substrate are compatible. From the point which can do, the alloy with the barrier metal (especially Mo or W) which comprises the non-permeable layer mentioned later may be sufficient. In the alloy of the active metal and the barrier metal, the ratio of the barrier metal is 200 parts by mass or less with respect to 100 parts by mass of the active metal, for example, 1 to 150 parts by mass, preferably 5 to 150 parts by mass, and more preferably. Is about 10 to 100 parts by mass. If the ratio of the barrier metal is too large, the adhesion between the hole wall surface of the insulating substrate and the metal film may be lowered.

The active metal layer only needs to contain an active metal, and may be, for example, an active metal compound, but is usually an active metal simple substance, an alloy of active metals, or an alloy of an active metal and a barrier metal. As the active metal compound, a compound (for example, TiH ₂ , ZrH _2, etc.) from which an active metal is easily generated by heating is preferable.

  The average thickness of the active metal layer may be 0.005 μm or more, for example, 0.005 to 1.0 μm, preferably 0.01 to 0.5 μm, more preferably 0.05 to 0.3 μm (especially 0.00. 08-0.2 μm). If the thickness of the active metal layer is too thin, the adhesion between the surface conductor layer and the insulating substrate may be reduced. On the other hand, if the thickness of the active metal layer is too thick, the conductivity of the surface conductor layer may be impaired, and it is disadvantageous in terms of cost.

(Non-transparent layer)
The bonding layer may be formed of the active metal layer alone, but the active metal layer is capable of highly improving the electrical properties of the surface conductor layer and the adhesion between the surface conductor layer and the insulating substrate. Further, a non-transmissive layer may be interposed between the surface conductor layer and the surface conductor layer. Phenomenon that occurs between the active metal layer and the surface conductor layer, although the bonding layer is formed of the active metal layer alone, has higher electrical characteristics and adhesion than conventional via-filled substrates If the active metal layer diffuses into the surface conductor layer, the electrical characteristics of the surface conductor layer may be slightly reduced. On the other hand, when the metal constituting the surface conductor layer diffuses into the active metal layer and further alloyed, the adhesion to the insulating substrate is slightly reduced (the active metal film is peeled off from the insulating substrate due to diffusion and alloying). There is also a fear. Therefore, in order to further improve the effect of the present invention, when a non-permeable layer is interposed between the active metal layer and the surface conductor layer, the non-permeable layer serves as a barrier, and the active metal layer and the surface conductor layer are removed during high-temperature firing. It is possible to prevent the constituent metals from diffusing each other. Furthermore, when the active metal layer is formed and exposed to air, the active metal is likely to be oxidized, and the function as a bonding layer may be reduced. On the other hand, the oxidation of the active metal can be suppressed by coating a metal that is relatively difficult to oxidize as a non-permeable layer (barrier layer).

  The non-permeable layer includes a barrier metal or an alloy containing the barrier metal. The barrier metal is not particularly limited as long as it has the above-described barrier property and is different from the metal constituting the surface conductor layer or the conductive via portion. For example, Mo, W, Ni, Pd, Pt, etc. Can be mentioned. These barrier metals can be used alone or in combination of two or more kinds, and may be an alloy in which two or more kinds are combined.

  Among these barrier metals, Pd, Pt, and Ni are preferable from the viewpoints of conductivity, stability, adhesion to the surface conductor layer, and barrier properties. Usually, these barrier metals are generally used.

  The non-permeable layer only needs to contain a barrier metal, and may be, for example, a barrier metal compound, but is usually a single barrier metal or an alloy of barrier metals.

  The average thickness of the non-transmissive layer may be 0.01 μm or more, for example, 0.01 to 1.0 μm, preferably 0.05 to 0.5 μm, and more preferably about 0.1 to 0.3 μm. If the thickness of the non-transmissive layer is too thin, the effect of the active metal layer may be reduced, or the adhesion between the surface conductor layer and the insulating substrate may be reduced. If the thickness of the non-permeable layer is too thick, it is disadvantageous in terms of cost.

(Affinity layer)
The bonding layer may include an affinity layer (a layer that increases the affinity with the surface conductor layer) on the outermost surface in contact with the surface conductor layer in order to further improve the adhesion between the surface conductor layer and the insulating substrate. . The affinity layer may be in contact with the surface conductor layer, may be laminated on the active metal layer, or may be formed on the non-permeable layer. By bringing the affinity layer into contact with the surface conductor layer, the affinity (wetting property) with the surface conductor layer is increased, and the surface conductor layer and the insulating substrate (specifically, the active metal layer or the non-transparent layer) are bonded satisfactorily. it can. In addition, when the metal of the non-transmissive layer is a metal having the property of the bonding layer, the non-transmissive layer can also serve as the bonding layer.

  The affinity layer is a metal that is different from the metal that forms the layer (non-permeable layer or active metal layer) in contact with the bonding layer, and can be the same as or alloyed with the metal contained in the surface conductor layer (affinity metal). including. Examples of the affinity metal include Ni, Pd, Pt, Cu, Ag, Au, and Al. These metal for affinity can be used individually or in combination of 2 or more types, The alloy which combined 2 or more types may be sufficient.

  Of these metals for affinity, the same metal as that contained in the surface conductor layer is preferred. A preferable metal for affinity may be, for example, a metal containing Ni, Cu, Ag, Au, or Al, and these simple metals are generally used. These affinity metals are highly conductive metals that are usually used as conductive via portions and surface conductor layers, and in particular, when they are the same as the metals contained in the surface conductor layers, they can improve wettability and adhesion. It is possible to adhere more firmly to the insulating substrate.

  The affinity layer only needs to contain an affinity metal. For example, the affinity layer may be an affinity metal compound, but is usually an affinity metal simple substance or an alloy of affinity metals.

  The average thickness of the affinity layer may be 0.01 μm or more, for example, 0.01 to 0.5 μm, preferably 0.1 to 0.3 μm, and more preferably about 0.15 to 0.25 μm. If the affinity layer is too thin, the effect of forming the affinity layer may be reduced.

  The average thickness of the bonding layer may be 0.05 μm or more, for example, 0.1 to 1 μm, preferably 0.2 to 0.8 μm, and more preferably about 0.3 to 0.5 μm.

(Surface conductor layer)
The surface conductor layer (or surface conductor film) is laminated on the bonding layer, includes a conductor (especially a sintered conductor), and has a porous structure. Can be realized. The surface conductor layer only needs to be laminated on the insulating substrate with a bonding layer interposed in at least a part of the region, and there is a region where the surface conductor layer is directly laminated on the insulating substrate without the bonding layer. May be. For example, in order to improve economy, a bonding layer is interposed in a region (usually the front surface) where a high degree of adhesion or pattern accuracy is required, and a bonding layer is interposed in a region where it is not highly required (usually the back surface). You don't have to. From the viewpoint of the performance of the double-sided wiring board, it is preferable that all the surface conductive layers are laminated on the insulating substrate with a bonding layer interposed.

  The conductor contained in the surface conductor layer is the same as the conductor contained in the conductive via part, including preferred embodiments. The conductor may be a sintered conductor. As long as the surface conductor layer does not impair the effects of the present invention, a non-conductor such as a semiconductor or an insulator (for example, a filler such as ceramic, an organic vehicle remaining after firing, an inorganic binder such as a glass component) is used. May be included. The proportion of the conductor in the surface conductor layer may be 50% by mass or more, for example, 90% by mass, preferably 95% by mass or more, more preferably 99% by mass or more, and particularly 100% by mass (formed by the conductor alone). ). As described above, the surface conductor layer can improve the adhesion to the insulating substrate even if it does not contain an inorganic binder such as a glass component by interposing a bonding layer. Therefore, the surface conductor layer may not substantially contain an inorganic binder (particularly a glass component) and preferably does not contain a glass component. The ratio of the inorganic binder (particularly the glass component) is 1 part by mass or less (particularly 0.1 part by mass or less) with respect to 100 parts by mass of the conductor. There is a risk of doing.

  Moreover, since the surface conductor layer is a porous body having a porous structure, the elastic modulus of the surface conductor layer is low, the thermal stress caused by the difference in thermal expansion coefficient between the surface conductor layer and the insulating substrate is relaxed, Thermal shock resistance can be improved. The porous structure of the porous body is not particularly limited, and may be any of a continuous pore structure, an independent pore structure, or a mixed structure of both. An independent pore structure is preferred from the airtightness of the surface conductor layer and the barrier property against the plating solution. In particular, the surface conductor layer obtained using a conductor paste (metal paste or conductive paste) may be a porous body (sintered body) generated by firing. The average pore diameter of the porous body is, for example, about 0.01 to 5 μm, preferably about 0.05 to 3 μm, and more preferably about 0.1 to 2 μm. The porosity of the porous body is, for example, about 1 to 40% by volume, preferably about 5 to 30% by volume, and more preferably about 10 to 20% by volume. If the porosity is too large, the electrical conductivity may decrease, and if it is too small, the thermal shock resistance may decrease.

  Moreover, the surface conductor layer can also realize a double-sided conductive wiring board suitable for high plating by covering the conductive via portion. That is, in a front and back conductive type double-sided wiring board having a conductive via portion filled with a metal sintered body in a hole (through hole), when wet processing such as plating is performed directly, the chemical solution enters the conductive via portion. , Blistering, peeling, and discoloration are likely to occur. On the other hand, by covering the conductive via portion with the surface conductor layer, the swelling, peeling, discoloration and the like can be suppressed, and the plating resistance can be improved. The surface conductor layer is usually formed in a pattern shape, but the pattern shape preferably covers the conductive via portion.

  Furthermore, the surface conductor layer is thicker than the bonding layer which is a thin film, and in forming the surface conductor layer, the formation of the bonding layer by the thin film method and the formation of the surface conductor layer by the thick film method are combined, Wiring formation that can connect the front and back surfaces and the through hole can be realized. Therefore, the surface conductor layer can realize high adhesion to the insulating substrate without using a glass component due to the bonding layer. In the present invention, in addition to the above characteristics, the present invention can exhibit characteristics in all aspects such as adhesion, reliability, conductivity (corresponding to a large current), pattern accuracy, and cost.

  The film thickness of the surface conductor layer may be set according to the required amount of current, and since the surface conductor layer is a porous body in the present invention, it is difficult to form with a conventional method, for example, 200 μm. Even with the above, it is possible to form an ultra-thick film having high reliability. The average thickness of the surface conductor layer may be 0.5 μm or more, for example, 1 to 1000 μm, preferably 2 to 600 μm (for example, 3 to 500 μm), and more preferably about 4 to 300 μm (particularly 5 to 200 μm). If the thickness of the surface conductor layer is too thin, the electrical characteristics and plating resistance may be reduced. If the thickness of the surface conductor layer is too thick, it is disadvantageous in terms of cost.

  The surface conductor layer is thicker than the bonding layer, and the average thickness of the surface conductor layer can be selected from a range of about 3 to 5000 times the average thickness of the bonding layer, for example, 5 to 3000 times (for example, 5 to 5 times). 1000 times), preferably 8 to 2000 times (for example, 10 to 1500 times), more preferably about 10 to 1000 times (especially 15 to 500 times). If the thickness ratio of the surface conductor layer is too small, the electrical characteristics may be deteriorated. Conversely, if it is too thick, it is disadvantageous in terms of cost.

(Plating layer)
In the double-sided wiring board of the present invention, a plating layer may be further laminated on the surface conductor layer. The metal type of the plating layer is not particularly limited, and examples thereof include copper plating, nickel plating, silver plating, nickel gold plating, nickel palladium gold plating, tin plating, and solder plating. Among these, a plating layer containing a noble metal such as gold, silver, palladium, or platinum is preferable, and is particularly effective when a pattern is formed by a lift-off method as the second etching step.

  The plating layer may be a dry plating layer, but a wet plating layer is preferable from the standpoint that the effects of the present invention are remarkably exhibited. This is because wet plating requires a wet process at the time of forming the plating layer, and the plating solution is likely to be mixed into the via filling portion at the time of forming the plating layer, so that swelling and peeling are likely to occur. Examples of wet plating include electroplating and electroless plating. Furthermore, as a plating method, electroplating is particularly preferable because a wide variety of plating metal types and plating film thicknesses can be selected.

  The average thickness of the plating layer (the total thickness when a plurality of plating layers are laminated) is, for example, about 0.5 to 30 μm, preferably 1 to 10 μm, and more preferably 1.5 to 5 μm (particularly 2 to 4 μm). .

[Manufacturing method of double-sided wiring board]
The double-sided wiring board according to the present invention includes, for example, a via filling step of filling a hole of an insulating substrate having a hole with a conductive paste for a conductive via part including metal particles and an organic vehicle, and the metal particles contained in the conductor paste A conductive paste is fired by heating to a temperature equal to or higher than the sintering temperature, a via firing step for forming a conductive via portion, and a bonding layer including an active metal layer is formed on the surface of the insulating substrate having the conductive via portion. A layer forming step, a conductor coating step of applying a conductive paste for a surface conductor layer containing metal particles and an organic vehicle on the bonding layer, a conductor heated to a temperature higher than the sintering temperature of the metal particles contained in the applied conductor paste You may obtain through the conductor baking process which bakes a paste and forms the surface conductor layer which contains a conductor and has a porous structure.

(Via filling process)
In the filling step, the conductive via portion conductive paste (metal paste or conductive paste) includes metal particles formed of the conductive metal.

  The average particle diameter (center particle diameter) of the metal particles is about 100 μm or less (particularly 50 μm or less), for example, 0.001 to 50 μm, preferably 0.01 to 20 μm, and more preferably about 0.1 to 10 μm. . If the average particle size is too large, close filling of the holes may be difficult.

  The metal particles can improve the metal content in the paste and can improve the density and conductivity of the conductive via part, so that the metal small particles having a particle size of less than 1 μm (for example, 1 nm or more and less than 1 μm) and a particle size of 1 to 50 μm. It is preferable to contain large metal particles.

  The average particle size (center particle size) of the small metal particles can be selected from a range of about 0.01 to 0.9 μm (particularly 0.1 to 0.8 μm). In particular, when the small metal particles are Cu particles, the average particle size of the small metal particles is, for example, 0.1 to 0.95 μm, preferably 0.3 to 0.9 μm, and more preferably 0.4 to 0.85 μm. Degree. When the metal small particles are Ag particles, the average particle diameter of the metal small particles is, for example, 0.1 to 0.8 μm, preferably 0.1 to 0.5 μm, and more preferably about 0.1 to 0.3 μm. is there. If the average particle size of the small metal particles is too small, the viscosity of the conductor paste may increase and handling may be difficult, and if it is too large, the effect of improving the denseness may be reduced.

  The metal small particles preferably contain metal nanoparticles having a particle size of 100 nm or less from the viewpoint that the metal content in the paste can be further improved and a conductive via portion having higher density can be formed. The average particle diameter (center particle diameter) of the metal nanoparticles is, for example, about 5 to 80 nm, preferably 10 to 60 nm, and more preferably about 15 to 45 nm (particularly 20 to 40 nm). If the average particle size of the metal nanoparticles is too small, the handleability may be difficult, and if it is too large, the effect of improving the density of the conductive via portion may be reduced.

  The metal nanoparticles may be metal colloid particles containing a protective colloid (such as a carboxylic acid such as acetic acid or a polymer dispersant). Examples of the metal colloid particles are described in JP 2010-202943 A, JP 2010-229544 A, JP 2011-77177 A, JP 2011-93297 A, JP 2011-94233 A, and the like. Metal colloidal particles can be used.

  The proportion of the metal nanoparticles may be 0 to 90 mass% with respect to the whole metal small particles, for example, 5 to 90 mass%, preferably 10 to 80 mass%, more preferably 20 to 70 mass% (particularly 30 to 60% by mass). If the proportion of metal nanoparticles is too large, the amount of organic matter such as protective colloids incidentally increases, which may increase the sintering shrinkage of the conductor paste.

  The average particle size (center particle size) of the large metal particles can be selected from a range of about 1.5 to 30 μm (particularly 2 to 10 μm). In particular, when the large metal particles are Cu particles, the average particle size of the large metal particles is, for example, 2 to 30 μm, preferably 3 to 20 μm, and more preferably about 5 to 10 μm. When the metal large particles are Ag particles, the average particle diameter of the metal large particles is, for example, 1.2 to 20 μm, preferably 1.5 to 10 μm, and more preferably about 2 to 5 μm. If the average particle size of the large metal particles is too small, the sintering shrinkage of the conductor paste may increase, and if it is too large, the filling property of the conductive via portion may decrease.

  The mixing ratio of the small metal particles to the large metal particles can be selected from the range of the small metal particles / large metal particles = 10/90 to 50/50 as the volume ratio, for example, 15/85 to 45/55, preferably 20/80 to 40/60, more preferably about 25/75 to 35/65. When the metal small particles include metal nanoparticles, the mixing ratio of the two is, for example, as a volume ratio, for example, metal small particles / metal large particles = 20/80 to 70/30, preferably 30/70 to 60/40, Preferably it is about 40 / 60-60 / 40. In addition, when the material of the metal particles used for the conductor paste is one kind, the volume ratio is the same as the mass ratio, so it may be blended on a mass basis, but when two or more kinds of metal particles having different specific gravities are used. May be blended by converting each blending volume into mass.

  As a measuring method of the particle size of a metal particle, it can measure with a laser diffraction scattering type particle size distribution measuring apparatus and a transmission electron microscope (TEM), and can measure in detail by the method as described in the Example mentioned later.

  The conductor paste further includes an organic vehicle. The organic vehicle includes an organic binder, a dispersion medium (organic solvent), and the like. Note that protective colloids (such as carboxylic acids and polymer dispersants) contained in the above-described metal colloid particles are also included in the organic vehicle. The organic vehicle may be a combination of an organic binder and a dispersion medium.

Examples of organic binders include thermoplastic resins (olefin resins, vinyl resins, acrylic resins, styrene resins, polyether resins, polyester resins, polyamide resins, cellulose derivatives, etc.), thermosetting resins ( Thermosetting acrylic resin, epoxy resin, phenol resin, unsaturated polyester resin, polyurethane resin, etc.). These organic binders can be used alone or in combination of two or more. Among these organic binders, acrylic resins (polymethyl methacrylate, polybutyl methacrylate, etc.), cellulose derivatives (nitrocellulose, ethyl cellulose, butyl cellulose, cellulose acetate, etc.), polyethers (polyoxymethylene, etc.), polyvinyls ( Polybutadiene, polyisoprene, etc.) are widely used, and poly (meth) acrylic acid C _1-10 alkyl esters such as poly (meth) methyl acrylate and poly (meth) butyl butyl are preferred from the viewpoint of thermal decomposability and the like. .

  Examples of the dispersion medium include aromatic hydrocarbons (such as paraxylene), esters (such as ethyl lactate), ketones (such as isophorone), amides (such as dimethylformamide), and aliphatic alcohols (octanol, decanol, diacetone). Alcohol), cellosolves (methyl cellosolve, ethyl cellosolve, etc.), cellosolve acetates (ethyl cellosolve acetate, butyl cellosolve acetate, etc.), carbitols (carbitol, methyl carbitol, ethyl carbitol, etc.), carbitol acetates ( Ethyl carbitol acetate, butyl carbitol acetate, etc.), aliphatic polyhydric alcohols (ethylene glycol, diethylene glycol, dipropylene glycol, butanediol, pentanediol, Tylene glycol, glycerin, etc.), alicyclic alcohols [for example, cycloalkanols such as cyclohexanol; terpene alcohols such as terpineol and dihydroterpineol (monoterpene alcohols, etc.)], aromatic alcohols (such as metacresol) And aromatic carboxylic acid esters (dibutyl phthalate, dioctyl phthalate, etc.), nitrogen-containing heterocyclic compounds (dimethyl imidazole, dimethyl imidazolidinone, etc.) and the like. These dispersion media can be used alone or in combination of two or more. Of these dispersion media, aliphatic polyhydric alcohols such as pentanediol and alicyclic alcohols such as terpineol are preferred from the viewpoint of paste fluidity and filling properties.

  When combining an organic binder and a dispersion medium, the ratio of the organic binder is, for example, about 1 to 200 parts by weight, preferably about 5 to 100 parts by weight, and more preferably about 10 to 50 parts by weight with respect to 100 parts by weight of the dispersion medium. is there.

  The proportion of the organic vehicle may be 30 parts by mass or less with respect to 100 parts by mass of the metal particles, for example, 1 to 30 parts by mass, preferably 3 to 20 parts by mass, more preferably 4 to 15 parts by mass (particularly 5 10 mass parts). If the volume ratio of the organic vehicle is too large, the shrinkage rate of the conductor paste due to drying or baking after filling increases, and voids or gaps may be generated.

  The conductor paste may further contain an inorganic binder. Examples of the inorganic binder include low-melting glass such as borosilicate glass, zinc borosilicate glass, bismuth glass, and lead glass. These inorganic binders can be used alone or in combination of two or more. Among these inorganic binders, borosilicate glass or zinc borosilicate glass is preferable from the viewpoint of durability against plating.

  The mass ratio of the inorganic binder is 10% by mass or less with respect to the whole paste, for example, 0.1 to 10% by mass, preferably 0.2 to 5% by mass, and more preferably about 0.3 to 1% by mass. is there. Note that when the same layer as the bonding layer is laminated on the hole wall surface, the conductive paste can improve the adhesion between the conductive via portion and the hole wall surface of the insulating substrate even if it does not contain an inorganic binder. The conductive paste preferably does not contain an inorganic binder (particularly a glass component) from the viewpoint of improving the conductivity of the conductive via part.

  The conductor paste has a small volume change rate before and after firing, and the sintered conductor is firmly bonded to the hole wall surface without a gap. Therefore, the entire conductive via portion obtained by firing this paste is uniform and airtight. The volume change rate before and after firing is, for example, about -10% to 20%, preferably -5% to 15%, and more preferably about 0% to 10%. If the volume change rate is too large in the negative (minus) direction (minus and the absolute value is too large), voids or gaps may be generated due to shrinkage during firing. On the other hand, if the volume change rate is too large in the positive (plus) direction, a large void may be formed after firing, or the denseness of the filled via portion may be lowered, and the barrier property may be lowered. In addition, a large volume shrinkage (volume change rate is negative) occurs in the general-purpose conductor paste, whereas the conductor paste in the present invention is 10% or less even if shrinkage, rather it is expanded (a volume change rate is positive). It is characterized by being a compounding formula that works well. As a method for measuring the volume change rate, the pattern film thickness before and after firing can be calculated by measuring with a stylus-type film thickness meter, and can be measured in detail by the method described in the examples described later.

  Examples of the method of filling the conductor paste into the hole include printing methods such as screen printing, inkjet printing, intaglio printing (eg, gravure printing), offset printing, intaglio offset printing, flexographic printing, and the like. And direct press-fitting methods such as a roll press-fitting method, a squeegee press-fitting method, and a press-fitting method. Of these methods, the screen printing method and the like are preferable.

  After filling, it may be naturally dried, but may be dried by heating. The heating temperature can be selected according to the type of the dispersion medium, and is, for example, about 80 to 300 ° C, preferably about 100 to 250 ° C, and more preferably about 120 to 200 ° C. The heating time is, for example, about 1 to 60 minutes, preferably about 5 to 40 minutes, and more preferably about 10 to 30 minutes.

(Via firing process)
In the via firing step, the firing temperature may be equal to or higher than the sintering temperature of the metal particles in the conductive via portion conductive paste. The baking temperature may be, for example, 500 ° C. or more, and is, for example, 500 to 1500 ° C., preferably 550 to 1200 ° C., and more preferably about 600 to 1000 ° C. The firing time is, for example, about 10 minutes to 3 hours, preferably about 20 minutes to 3 hours, and more preferably about 30 minutes to 2 hours.

  The firing atmosphere can be selected according to the type of metal particles, and the noble metal particles such as Ag are not particularly limited and may be in the air, but the metal particles such as Cu are usually inert gas. In the atmosphere (for example, nitrogen gas, argon gas, helium gas, etc.) is preferable.

  In the via firing step, after the conductive via portion conductive paste is fired, a surface treatment for smoothing (planarizing or planarizing) the surface of the insulating substrate may be performed. The substrate surface after firing usually has a conductive via portion protruding from the surface of the insulating substrate due to the use of a mask, and in the surface treatment, the protruding portion of the conductive via portion is scraped to obtain the insulating substrate and the conductive via portion. Can be reduced. Further, in the leveling treatment, in addition to reducing the level difference, the surface of the insulating substrate itself may be smoothed. The surface treatment may be performed on the insulating substrate filled with the conductive paste before firing. In that case, since the filled conductive paste is not baked, the protruding portion can be more easily removed.

  As a method of leveling treatment (smoothing), for example, a method of physically or chemically polishing the substrate surface may be used. Examples of the physical polishing method include buff polishing, lapping polishing, polishing polishing (mirror polishing), cylindrical polishing, planar polishing, CMP polishing, and grinder polishing. Examples of the chemical polishing method (surface treatment method) include a method of soft-etching the outermost surface with an aqueous sodium persulfate solution. Of these methods, physical polishing is preferable, and lapping and mirror polishing are particularly preferable from the viewpoint that precise polishing is possible.

  The surface roughness Ra of the substrate surface (surface of the insulating substrate on which the conductive via portion is formed) after the surface-conditioning treatment is not particularly limited, but is generally known by those skilled in the art depending on the required wiring dimensions and wiring accuracy. Select based on common technical common sense. The surface roughness Ra is, for example, 0.5 μm or less (for example, 0.01 to 0.5 μm), preferably 0.015 to 0.3 μm, and more preferably about 0.02 to 0.2 μm. The surface roughness Ra can be measured according to JIS B0651-1976.

  The step between the surface of the insulating substrate and the surface of the conductive via portion is, for example, 15 μm or less, preferably 10 μm or less, and more preferably 5 μm or less.

(Junction layer forming process)
In the bonding layer forming step, a bonding layer including an active metal layer may be laminated on the surface of the insulating substrate having the conductive via portion. After the active metal layer is formed, the non-bonding layer is further formed on the active metal layer. A transmission layer and / or an affinity layer may be laminated.

  The bonding layer may be formed on the entire surface of the insulating substrate, or may be formed in a pattern shape on the surface of the insulating substrate. As a method for forming the pattern, a conventional method can be used. For example, a method using a mask, a method in which a photoresist pattern is formed on the substrate surface, and then a bonding layer is formed on the exposed portion. A bonding layer is formed on the entire surface of the substrate. And a method of forming a pattern by photolithography and etching.

  As a method for forming the bonding layer, a physical vapor deposition method (PVD method), a chemical vapor deposition method (CVD method), or the like can be used, but a physical vapor deposition method is preferable because a metal film can be easily formed. Examples of physical vapor deposition include vacuum vapor deposition, flash vapor deposition, electron beam vapor deposition, ion beam vapor deposition, sputtering, ion plating, molecular beam epitaxy, and laser ablation. Of these, sputtering, vacuum deposition, and ion plating are preferred because they can be processed stably in large quantities. Moreover, the sputtering method is particularly preferable because it has high physical energy and can improve the adhesion between the formed metal film and the insulating substrate. The sputtering method can be used under conventional conditions.

(Conductor application process)
In the conductor application step, a conductor paste for a surface conductor layer containing metal particles and an organic vehicle is applied on the bonding layer.

  The conductor paste includes metal particles formed of the conductive metal. The average particle diameter (center particle diameter) of the metal particles is about 100 μm or less (particularly 50 μm or less), for example, 0.001 to 50 μm, preferably 0.01 to 20 μm, and more preferably about 0.1 to 10 μm. . In particular, when the metal particles are Cu particles, the average particle size of the metal particles is, for example, about 0.1 to 3 μm, preferably about 0.2 to 2 μm, and more preferably about 0.3 to 1 μm. When the metal particles are Ag particles, the average particle size of the metal particles is, for example, 0.1 to 2 μm, preferably 0.1 to 1.5 μm, and more preferably about 0.1 to 1 μm. If the average particle size of the small metal particles is too small, the viscosity of the conductor paste may increase and handling may be difficult, and if it is too large, the effect of improving the denseness may be reduced.

  The organic vehicle contained in the conductive paste is the same as the organic vehicle contained in the conductive via part conductive paste, including preferred embodiments. The proportion of the organic vehicle may be 50 parts by mass or less with respect to 100 parts by mass of the metal particles, for example, 1 to 50 parts by mass, preferably 3 to 40 parts by mass, more preferably 5 to 30 parts by mass (particularly 10 (About 20 parts by mass).

  As a method for applying the conductive paste, for example, screen printing, offset printing, ink jet printing, dispenser coating, roller coater coating, spin coating coating, spray coating, dip coating (dip) or the like can be used. The printing (coating) shape may be full-surface coating (solid printing) or direct pattern printing. Although direct pattern printing may reduce the accuracy of the pattern shape, the process is simple and the cost is low. When the bonding layer is formed in a pattern shape, the same shape as the pattern of the bonding layer may be printed on the pattern of the bonding layer by screen printing or the like.

  In the conductor coating step, the insulating substrate provided with the bonding layer may be annealed by heating in an inert gas atmosphere before the conductor paste is coated. Annealing treatment is not essential, but depending on the type of bonding layer, if the insulating substrate is fired at a high temperature without being annealed, the metal of the conductor paste and the bonding layer are alloyed during firing. When the bonding layer is taken into the surface conductor layer and disappears, the adhesion between the surface conductor layer portion and the insulating substrate may be reduced. On the other hand, by subjecting it to annealing treatment, the active metal of the bonding layer reacts preferentially with the surface of the insulating substrate rather than alloying with the metal of the conductor paste, forming a strong bonding layer on the surface and forming an adhesive force. As well as alloying of different metals in the bonding layer. As a result, alloying of the metal component of the bonding layer and the metal of the conductor paste during the firing of the conductor paste can be suppressed, and the adhesion can be improved.

  The heating temperature in the annealing treatment is 400 ° C. or higher, and the melting point of the lower of the melting point of the metal having the lowest melting point and the melting point of the alloy constituting the joining layer among all the metal species constituting the joining layer. The temperature may be any of the following, and can be selected according to the metal species. The specific heating temperature is, for example, about 400 to 1500 ° C., preferably 500 to 1200 ° C., and more preferably about 600 to 1100 ° C. (particularly 700 to 1000 ° C.). If the heating temperature is too low, the effect of improving the adhesion between the bonding layer and the insulating substrate may be reduced. If the heating temperature is too high, the metal component melts and moves, and the uniformity of the bonding layer decreases. Part of the substrate may be exposed.

  The heating time may be, for example, 1 minute or longer, for example, 1 minute to 1 hour, preferably 3 to 30 minutes, and more preferably about 5 to 20 minutes. If the heating time is too short, the effect of improving the adhesion between the bonding layer and the substrate may be reduced.

  Annealing treatment may be performed in an active gas atmosphere such as in the air, but the active metal is not oxidized and the bonding layer can be efficiently formed to improve the adhesion to the substrate. It is preferably performed in an atmosphere (for example, nitrogen gas, argon gas, helium gas).

(Conductor firing process)
In the conductor firing step, the conductor paste is fired by heating to a temperature higher than the sintering temperature of the metal particles contained in the applied conductor paste to form a surface conductor layer. The firing method is the same as the firing method in the via firing step, including preferred embodiments.

(Etching process)
When a pattern is not formed in the bonding layer forming step or the conductor coating step, the surface conductor layer obtained by firing is usually subjected to an etching step. In the etching process, a pattern is formed on the surface conductor layer and the bonding layer using a resist pattern. The etching process includes a first etching process for forming a resist pattern as a pattern of the surface conductor layer and the bonding layer, and a second etching process for forming a region excluding the resist pattern as a pattern of the surface conductor layer and the bonding layer (lift-off). Law).

  Specifically, in the first etching step, after forming a resist pattern in a partial region of the surface conductor layer obtained in the conductor firing step, the surface conductor layer and the bonding layer in the exposed region where the resist pattern is not formed are formed. Then, the resist pattern is removed. On the other hand, in the second etching step (lift-off method), after forming a resist pattern in a partial region of the surface conductor layer obtained in the conductor baking step, the surface conductor layer in the exposed region where the resist pattern is not formed is formed. After the plating layer containing the noble metal is formed on the surface, the resist film is peeled off, and the surface conductor layer and the bonding layer in the exposed region where the plating layer is not formed are removed. By forming a resist pattern and performing an etching process, it becomes possible to form a fine pattern or a highly accurate pattern that cannot be handled by the direct printing method.

  A method for forming a resist pattern is not particularly limited, and a conventional method can be used. For example, a direct pattern printing of a resist or a lithography method can be used.

  A method for removing the surface conductor layer and the bonding layer is not particularly limited, and a conventional method can be used. Examples thereof include wet etching, dry etching, blasting, and laser.

  The method for removing the resist pattern is not particularly limited, and a conventional method can be used, and examples thereof include peeling and removing.

  In the second etching step, a method similar to the plating step described later can be used as a method for forming the plating layer containing the noble metal.

  In addition, an etching process is unnecessary when a surface conductor layer and a joining layer are formed by direct pattern printing instead of whole surface application (solid printing).

(Bonding layer removal process)
When the conductor paste for the surface conductor layer is printed in the pattern in the conductor coating step, the bonding layer existing between the adjacent surface conductor layer and the surface conductor layer in the formed pattern is removed and the pattern is formed in the bonding layer removing step. Insulating between.

  The method for removing the bonding layer is not particularly limited, and a conventional method can be used. Examples thereof include wet etching, dry etching, blasting, and laser.

(Plating process)
The obtained surface conductor layer is usually subjected to a plating treatment in accordance with demands for preventing oxidation and improving solder wettability, except when a plating layer is formed on the surface conductor layer by a lift-off method. The plating method is not particularly limited, and a conventional method can be used. For example, a chemical plating method such as an electroplating method or an electroless plating method can be used. The electroplating method is not particularly limited, and may be performed under the conditions recommended by the plating chemical manufacturer according to the plating type. The method of electroless plating is not particularly limited, and may be performed under conventional conditions depending on the type of plating.

(Other manufacturing methods)
The double-sided wiring board of the present invention is not limited to the above manufacturing method, and a bonding layer including an active metal layer is laminated on the surface of an insulating substrate having a hole, and an active metal is formed on the wall of the hole. A bonding layer forming step of laminating a via bonding layer containing metal, a via filling step of filling a conductive paste for a conductive via portion containing metal particles and an organic vehicle into a hole of an insulating substrate on which the via bonding layer is formed, and the conductive paste A via firing step in which the conductive paste is fired by heating to a temperature higher than the sintering temperature of the contained metal particles to form a conductive via portion, and the metal particles and the organic vehicle are included on the bonding layer and the conductive via portion on the surface of the insulating substrate. Conductor coating step for applying a conductor paste for a surface conductor layer, heating the conductor paste to a temperature higher than the sintering temperature of the metal particles contained in the applied conductor paste, firing the conductor paste, including a conductor, and having a porous structure Conductor firing step of forming the surface conductor layer may be obtained through. This manufacturing method is the same as the above manufacturing method except that the bonding layer forming step is a pre-process of the via filling step and the via bonding layer is also formed on the wall surface of the hole.

  Furthermore, in the double-sided wiring board of the present invention, a bonding layer including an active metal layer is stacked on the surface of an insulating substrate having a hole, and a via bonding layer including an active metal is stacked on the wall surface of the hole. Bonding layer forming step, via filling step of filling conductive hole for conductive via part containing metal particles and organic vehicle into hole part of insulating substrate on which via bonding layer is formed, filling bonding layer and hole part on said insulating substrate surface A conductor coating step of applying a conductor paste for a surface conductor layer containing metal particles and an organic vehicle on the applied conductor paste, firing of the metal particles contained in the applied conductor paste for a surface conductor layer and a conductor paste for a conductive via portion The conductor paste for the surface conductor layer and the conductor paste for the conductive via part are simultaneously fired by heating above the bonding temperature to form the surface conductor layer and the conductive via part including the conductor and having a porous structure. Conductor baking process may be obtained through that. In this manufacturing method, after filling the conductive paste for the conductive via portion into the hole portion of the insulating substrate on which the via bonding layer is formed, the conductive via portion is provided in the conductor coating step without going through the via firing step. The manufacturing method is the same as that described above except that the conductive paste for the surface conductor and the conductive paste for the surface conductor layer are fired simultaneously.

  In the bonding layer forming step in these other manufacturing methods, the bonding layer and the via bonding layer may be formed separately, but are usually formed simultaneously by a batch process for an insulating substrate having a hole.

  Also in these other manufacturing methods, the surface of the insulating substrate is smoothed (planarized or flattened) before or after the conductive via portion conductive paste is fired in the via firing step or conductor firing step. For this purpose, surface treatment may be performed.

  Hereinafter, the present invention will be described in more detail based on examples, but the present invention is not limited to these examples. In addition, the preparation method of the conductor paste used by the Example and the comparative example and the measuring method of the evaluation test of the double-sided board obtained by the Example and the comparative example are shown below.

[Method for preparing conductor paste]
(material)
Cu particle with a center particle size (D50) of 7 μm: manufactured by Mitsui Kinzoku Mining Co., Ltd. Cu particle with a center particle size (D50) of 0.8 μm: Ag particles with a center particle size (D50) of 2.5 μm : Ag particle having a center particle size (D50) of 0.25 μm manufactured by Mitsui Mining & Smelting Co., Ltd .: Ag nanoparticle having a center particle size (D50) of 100 nm or less manufactured by Mitsui Metal Mining Co., Ltd .: “MDot CF107 manufactured by Mitsuboshi Belting Co., Ltd. "
Glass particles: Zinc borosilicate glass powder having an average particle size of 3 μm, softening point 565 ° C.
Organic vehicle: A mixture of an acrylic resin as an organic binder and a mixed solvent of carbitol and terpineol (mass ratio 1: 1) as an organic solvent in a mass ratio of organic binder: organic solvent = 1: 3.

(Example of conductor paste preparation)
Each raw material is weighed with the composition shown in Tables 1 and 2 and mixed with a mixer, and then uniformly kneaded with three rolls to form a via filling Cu paste, a surface conductor layer Cu paste, a via filling Ag paste, An Ag paste for the surface conductor layer was prepared.

[Volume change rate of conductor paste]
The volume change rate before and after firing of the conductor paste was calculated by measuring the thickness of the conductor film screen-printed on the substrate surface before and after firing with a stylus-type film thickness meter ("Dektak 6m" manufactured by Beco). Specifically, using a 250-mesh screen plate on the surface of a 96% alumina substrate (Nikko Corporation), the conductor paste was screen printed in a 5 mm x 5 mm pattern, and the printed film thickness was determined as a non-contact film. The thickness was measured with a thickness gauge, and the film thickness was determined after printing. Furthermore, the organic solvent in a conductor paste was removed by heating at 120 degreeC for 20 minutes, and the dry film was obtained. The film thickness of this dry film was measured with a stylus type film thickness meter, and was defined as the film thickness before firing. Next, after baking the substrate under the baking conditions shown in Tables 1 and 2, respectively, the thickness of the pattern after baking was measured with a stylus type film thickness meter, and the film thickness values before and after baking were compared by the following formula, The volume change rate (%) was determined. The results are shown in Tables 1 and 2. If the volume change rate (%) is a negative value, the volume decreases (shrinks). Conversely, if the volume change rate (%) is a positive value, the volume increases.

    Volume change rate (%) = [(film thickness after firing−film thickness before firing) / film thickness before firing] × 100.

[Porosity of conductor]
Based on the ratio (volume ratio) of the organic component contained in the conductor paste and the shrinkage ratio due to firing, the calculation was performed according to the following formula.

Porosity (v / v%) = (Volume ratio of organic component in conductor paste−firing shrinkage ratio) / (1−firing shrinkage ratio) × 100
(In the formula, firing shrinkage ratio (v / v%) = [(film thickness after printing−film thickness after firing) / film thickness after printing] × 100).

  As is clear from the results of Tables 1 and 2, the firing volume change rate of the via filling Cu paste is -3.2% (3.2% volume shrinkage), but the firing volume change of the via filling Ag paste. The rate is + 3.1% (3.1% expansion).

  In the present invention, since the surface conductor layer paste is formed on the active metal bonding layer, it is not necessary to add a glass component for adhering to the ceramic substrate. On the other hand, the surface conductor layer Cu paste B was blended with a glass component so as to be in close contact with the substrate as a paste used in a comparative example in which an active metal bonding layer was not formed on the substrate surface.

[Average particle diameter of metal particles]
The average particle size of Cu particles and Ag particles was measured with a laser diffraction / scattering particle size distribution measuring device, and the average particle size of Ag nanoparticles was measured with a transmission electron microscope (TEM).

[Metal film thickness]
About the active metal layer and the barrier layer, the average thickness of five points was measured with a fluorescent X-ray film thickness meter.

[Heat resistance test (heat resistance)]
The evaluation substrate is heated on a hot plate at 350 ° C. for 10 minutes, and the heated substrate is observed visually and under a microscope to check for swelling, peeling, discoloration, ejection of foreign matter, and evaluated according to the following criteria. did.

○ (Pass): All items were normal. × (Fail): There was a problem with one or more items.

[Adhesion test (adhesion)]
A stud pin having a tip area of 1 mm ² was joined to a 2 × 2 mm square conductor pattern formed on the substrate surface vertically by solder (63Sn / 37Pb) to obtain a test piece. When the test piece (fired substrate) is fixed, the stud pin is gripped by the chuck portion of the tensile tester, and pulled vertically upward at a rising speed of 33 mm / min. When the conductor film (surface conductor layer) peels from the insulating substrate The breaking load was measured. And the adhesive strength was computed using the following formula from the measured value of the obtained destruction load, and the destruction area of a conductor film.

Adhesive strength (MPa) = Fracture load (kgf) / Fracture area (mm ² ) × 9.8 (N / kgf).

  The measured value was an average of 6 points. The adhesion strength was evaluated according to the following criteria for the average value of the calculated adhesion strength.

○: 50 MPa or more Δ: 30 MPa or more and less than 50 MPa ×: less than 30 MPa

[Etching aptitude test (etching property)]
The etched pattern was observed with a 60 × microscope, and the pattern shape and conductor removal status were confirmed and evaluated according to the following criteria.

○ (Pass): The pattern shape was rectangular, and the conductor film and the bonding layer were neatly removed to the skirt of the pattern. X (Fail): Residue of the conductor film or the bonding layer was present on the substrate surface and the skirt.

  Hereinafter, the result of having verified the effect by changing various conditions is demonstrated as Examples 1-30 and Comparative Examples 1-5. In addition, Tables 3 to 5 show the results of the obtained heat resistance test, adhesion strength test, and etching suitability test.

Example 1
As shown below, a double-sided wiring board having a through electrode was manufactured by the method shown in FIG. 1 in which schematic sectional views of the respective steps were described.

(Process for producing via-filled substrate)
Metal mask using a via-filling Cu conductor paste shown in Table 1 on an AlN substrate (“170W” manufactured by MARUWA Co., Ltd.) having a thickness of 2 inches × 2 inches × 0.635 mm having a large number of through-holes having a diameter of 0.1 mm. Through-holes were filled by screen printing, and dried for 20 minutes in a 120 ° C. blow dryer). The filled substrate was baked in a nitrogen atmosphere at 900 ° C. for 60 minutes to produce a Cu conductor via-filled substrate 1 (FIG. 1A). Since the manufactured via-filled substrate 1 uses a mask, the filling portion 2 is slightly protruded from the substrate surface. The fired substrate was adjusted to a thickness of 0.5 mm and a surface roughness Ra <0.1 μm by lapping (FIG. 1B). As a result of polishing, the level difference (unevenness) between the surface of the filling portion 2a and the insulating substrate surface was ± 3 μm or less.

(Junction layer formation process)
A Ti film 3a having a thickness of 100 nm as an active metal layer and a Pd film 3b having a thickness of 150 nm as a barrier layer were laminated in this order on both surfaces of the polished substrate by a sputtering method to form a bonding layer 3 (FIG. 3C). ). The sputtering conditions were: introduced gas: argon, sputtering pressure: 0.5 Pa, and substrate heating temperature: 300 ° C.

(Formation process of surface conductor layer (Cu))
After printing the surface conductor layer Cu paste A (Cu-A) shown in Table 1 on both surfaces of the substrate on which the bonding layer 3 was formed using a 400 mesh, stainless steel plate with a wire diameter of 18 μm, Dry for 20 minutes. The substrate was baked in a nitrogen atmosphere at a peak temperature of 700 ° C. and a peak holding time of 10 minutes to obtain a metallized substrate having a surface conductor layer (Cu film) 4 having a film thickness of about 8 μm baked on both surfaces (FIG. 1D).

(Formation of etching resist pattern)
In order to remove the unnecessary portion of the conductive film on the surface of the substrate and form a required pattern, an etching resist is pattern printed so that the unnecessary portions are exposed on the surface of the Cu film 4 on both sides of the substrate. The resist film 5 for etching was formed by partial drying. The resist film is formed so as to hide necessary portions such as a portion where a filled via exists and a 2 mm × 2 mm pattern for evaluating the adhesion of the conductive film on the substrate surface (FIG. 1E).

(etching)
The exposed Cu film of the substrate on which the etching resist film is formed and the Ti / Pd film that is the underlying bonding layer of the etching solution capable of dissolving Cu / Pd / Ti (“TCL-2 series” manufactured by Wako Pure Chemical Industries, Ltd.) )) And removed (FIG. 1 (f)). Thereafter, the etching resist film was peeled and removed to obtain a wiring board having a required conductor pattern 6 remaining on the surface (FIG. 1 (g)).

  Although the formation of the double-sided wiring board with the through electrode in the form of FIG. 1 (g) has been completed, it is formed on the outermost surface of the conductor pattern for the purpose of preventing the oxidation of the Cu film surface, improving the solder wettability and the wire bonding property. A plating film was formed.

(Ni / Au plating on Cu film surface)
A nickel plating film 7 and a gold plating film 8 were formed in this order on the Cu film on the substrate surface by electroplating. The nickel plating film 7 was electroplated using a watt bath at a current density of 2.0 A / dm ² and a temperature of 65 ° C. to form a nickel film having a thickness of 2 μm. The gold plating film 8 was formed using a pure gold bath at a current density of 0.5 A / dm ² and a temperature of 70 ° C. to form a 1 μm gold film. (FIG. 1 (h)). FIG. 1 does not show the wiring for the electroplating, but all the patterns are connected by the wiring for the electroplating.

(Evaluation)
When forming a pattern on the double-sided wiring board obtained in the above process by a heat resistance test for evaluating the presence or absence of liquid intrusion into the filling portion, an adhesion test for evaluating the adhesion between the surface conductor and the substrate, and etching. The etching property was evaluated for whether the conductor film was etched well. As a result, good results were obtained for all evaluation items.

Examples 2-3
A double-sided wiring board was produced by the same method as in Example 1 except that the printing of the Cu film for the surface conductor layer was changed to change the fired Cu film thickness to 5 μm and 12 μm, respectively. In both Cu thick films, there was no significant difference in heat resistance, adhesion, and etching properties, and all were good. Therefore, in the present invention, the Cu film thickness can be adjusted inexpensively and easily as required.

Comparative Example 1
As shown in FIG. 2, in the bonding layer forming step of Example 1, after forming the bonding layer 3 by the sputtering method (FIG. 2A), the surface conductor layer forming step by printing Cu paste is performed. First, an etching resist pattern (etching resist film) 5 was formed as it was (FIG. 2B). After the exposed bonding layer was removed by etching (FIG. 2C), the etching resist was peeled and removed to obtain a conductor pattern made of the bonding layer (FIG. 2D). A 2 μm Cu film 9 was formed on this conductor pattern by electroplating (copper sulfate plating), and then a Ni / Au plating film was formed by the same method as in Example 1 (FIG. 2E). As a result, there was no problem with the adhesion and etching property of the surface conductor layer, but swelling (dislocation), discoloration, and ejection of foreign matter were observed on the surface of the via filling portion due to heating.

Comparative Example 2
A double-sided wiring board was produced by the same method as in Comparative Example 1 except that the thickness of the electroplated Cu film was increased to 5 μm. The evaluation result was the same as Comparative Example 1.

  The results of Comparative Examples 1 and 2 show that the plating solution is almost exposed to the plating solution just by being covered with the thin Ti film and Pd film at the time of electroplating. It is thought that this is because it entered the gap (size of several μm) and was confined by the plating film after plating. The confined residual liquid expands when heated and breaks the plating film, causing defects such as blistering and discoloration.

  On the other hand, in the embodiment, since the Cu paste is printed and baked on the surface of the filling portion, the Cu paste fills the voids and gaps of the filling portion, and the surface of the filling portion is covered with a film of several μm, so subsequent plating Also in the process, the infiltration of liquid can be prevented.

Comparative Example 3
In the bonding layer forming step, a double-sided wiring board was produced by the same method as in Example 1 except that the active metal layer (Ti film) was not formed.

Comparative Example 4
In the bonding layer forming step, a double-sided wiring board was produced by the same method as in Example 1 except that the Ti film and the Pd film were not formed at all.

  In Comparative Example 3, there was no active metal layer that contributed to the adhesion to the substrate, so the adhesion of the surface conductor layer was very low at 12 MPa, and some peeling occurred during etching. In Comparative Example 4, since neither the Ti film nor the Pd film was present, the Cu paste film hardly adhered and was easily peeled off.

  From these results, it was found that the Cu paste A for the surface conductor layer cannot obtain the adhesion of the surface Cu film in Comparative Examples 3 and 4 where there is no active metal layer that can be bonded by reacting with the substrate.

Comparative Example 5
A double-sided wiring board was produced in the same manner as in Comparative Example 4 except that the surface conductor layer Cu paste B was used instead of the surface conductor layer Cu paste A. Since the glass component is mix | blended with Cu paste B, it can adhere | attach with a board | substrate, even if an active metal layer does not exist. In order to improve the adhesion of Cu paste B, the firing temperature was set to 900 ° C. As a result, the adhesion of the surface conductor layer to the substrate was 38 MPa, which was clearly lower than that of the example having the active metal bonding layer. Further, a copper film residue was present on the substrate surface after etching. The SEM-EDS analysis revealed that the etching residue was mainly a glass component in the copper paste, and the Cu component remained in the residue. These residues may adversely affect the insulation reliability of the substrate.

Examples 4 and 5
A double-sided wiring board was produced in the same manner as in Example 1 except that the hole diameter of the board was changed to 0.3 mm and 0.5 mm, respectively. The same good results as in Example 1 were obtained.

Examples 6 and 7
A double-sided wiring board was produced in the same manner as in Example 1 except that Cr and Zr were used instead of Ti as the active metal species. The adhesion was sufficiently good, although it tends to be slightly lower.

Examples 8 and 9
A double-sided wiring board was fabricated in the same manner as in Example 1 except that Pt and Ni were used instead of Pd as the barrier metal in the bonding layer forming step. Good results were obtained for all items.

Example 10
Double-sided wiring in the same manner as in Example 1 except that in the bonding layer forming step, a film was formed in the order of Ti and Pd, and subsequently Cu was formed as an affinity layer on the surface of the Pd film by sputtering to a thickness of 0.2 μm. A substrate was produced. As a result, the heat resistance and the etching property were almost the same as those of other examples, but the adhesion was high. It can be presumed that the reason why the adhesion is improved is that the Cu film (surface layer) obtained by the sputtering method and the Cu paste that becomes the surface conductor layer are integrated during firing.

Example 11
After forming the bonding layer and before printing the Cu paste for the surface conductor layer, the substrate having the bonding layer was annealed in a nitrogen atmosphere at a peak temperature of 700 ° C. and a peak temperature holding time of 10 minutes. A double-sided wiring board was produced by the same method as in FIG.

Example 12
After forming the bonding layer and before printing the Cu paste for the surface conductor layer, the substrate having the bonding layer was annealed in a nitrogen atmosphere at a peak temperature of 700 ° C. and a peak temperature holding time of 10 minutes. A double-sided wiring board was produced by the same method as in FIG.

  As a result, the adhesion strength of the conductor film was further improved to 82 MPa and 85 MPa in Examples 11 and 12, respectively, by annealing the bonding layer. It can be presumed that the reason why the adhesion is improved is that the active metal preferentially reacted with the substrate by the annealing treatment. On the other hand, when the Cu paste for the surface conductor layer is printed and fired at the same time without annealing treatment, a part of the metal component of the bonding layer containing the active metal diffuses and alloys into the Cu paste layer, and the active metal that reacts with the substrate becomes It can be estimated to decrease.

Example 13
In the manufacturing process of the via-filled substrate, the via-filled substrate was lapped (FIG. 1 (b)), and further double-sided in the same manner as in Example 1 except that the surface roughness Ra of the substrate was 0.05 μm by mirror polishing. A wiring board was produced. Although the surface of the substrate became smoother by mirror polishing, almost no difference from Example 1 was found in heat resistance, surface conductor adhesion, and etching properties.

Example 14
A double-sided wiring board was produced in the same manner as in Example 1 except that in the step of producing the via-filled substrate, the protruding portion of the filling portion was flattened by buffing instead of lapping. The amount of unevenness with respect to the substrate surface of the filled portion after buffing was about ± 10 μm. Also, since the buffing has a low grinding force and the substrate portion is hardly polished, the surface roughness of the substrate was about 0.2 μm Ra, which is the same as that of the input substrate. In this example, the unevenness of the filling portion and the surface roughness of the substrate were increased, but the heat resistance, surface conductor adhesion, and etching were good.

Examples 15 and 16
Double-sided in the same manner as in Example 1 except that the heat-resistant substrate was changed to an alumina substrate (Kyocera Corporation, purity 96%) and a silicon nitride substrate (Toshiba Materials Co., Ltd.) instead of the AlN substrate. A wiring board was produced. Both types of substrates were good in all evaluation items.

Example 17
A double-sided wiring board was produced in the same manner as in Example 1 except that the Pd metal film (barrier layer) was not formed in the bonding layer forming step. As a result, the conductor film adhesion decreased to 53 MPa as compared with Example 1, but the heat resistance and etching properties were good. Adhesion is also sufficient as a normal metallized film.

Example 18
In the bonding layer forming step, the same method as in Example 1 except that after the Ti film (active metal layer) was formed, the Pd film (barrier layer) was not formed, and the Cu film (surface layer) was formed by sputtering. A double-sided wiring board was prepared. As a result, all the evaluation items were good, but the adhesion was improved as compared with Example 17 in which no Cu film was formed by the sputtering method. The Cu thin film formed by sputtering on the Ti film has the effect of preventing the oxidation of the Ti film when exposed to the air after forming the bonding layer and improving the wettability of the Cu paste for the surface conductor layer to the Ti film. It can be estimated that the adhesion is improved.

Examples 19-22
A double-sided wiring board was fabricated in the same manner as in Example 1, except that the thickness of the Ti film (active metal layer) was 0.2 μm, 0.15 μm, 0.05 μm, and 0.02 μm, respectively, in the bonding layer forming step. did. As a result, the film thicknesses of 0.15 μm and 0.2 μm were almost the same as the film thickness of 0.1 μm of Example 1, but the adhesion decreased as the film thickness decreased to 0.05 μm and 0.02 μm. The tendency to do was seen. However, even in the case of a film thickness of 0.02 μm, the adhesion is markedly higher than that of Comparative Example 3 in which there is no active metal film.

Example 23
Example 1 except that the via filling Ag paste shown in Table 2 was used in place of the via filling Cu conductor paste and the filled substrate was baked for 60 minutes in the atmosphere of 600 ° C. A double-sided wiring board was produced by the same method as that described above. Even when the metal type of the via filling portion was changed from Cu to Ag, all the characteristics were not different from those in Example 1.

Example 24
In the step of forming the surface conductor layer, the same method as in Example 23, except that the surface conductor layer Ag paste shown in Table 2 was used instead of the surface conductor layer Cu paste A and baked in the atmosphere at 600 ° C. for 60 minutes. A double-sided wiring board was prepared. Even when the filling portion and the paste for the surface conductor layer were all changed from Cu to Ag, all the characteristics were good.

Example 25
As shown in FIG. 3, in the bonding layer forming step of Example 1, after forming the bonding layer 3 by the sputtering method (FIG. 3A), in the surface conductor layer forming step, the surface to the bonding layer surface is formed. In the printing of the conductor layer Cu paste A, a pattern having a designated shape was directly printed on both sides of the substrate using a screen plate instead of printing on the entire surface. Then, it dried at 120 degreeC for 20 minutes. The substrate was baked in a nitrogen atmosphere at a peak temperature of 700 ° C. and a peak holding time of 10 minutes to obtain a metallized substrate having a surface conductor layer (Cu film) 4a having a film thickness of about 9 μm on both sides (FIG. 3B). Thereafter, the substrate was immersed in an etching solution, and the bonding layer existing between the Cu patterns was dissolved and removed (FIG. 3C). Since the etching resist was not applied, the Cu pattern film is also slightly dissolved, but the etching rate for Ti and Pd is higher than that of Cu, and the bonding layer is thin, so the change in the Cu film is small. It was.

  The subsequent plating process was performed in the same manner as in Example 1 to obtain a double-sided wiring board (FIG. 3D). Even this method was good in all properties. The pattern shape was kamaboko, and the pattern shape of Example 1 was superior to the pattern shape of Example 25.

Example 26
A double-sided wiring board was obtained by the same method as in Example 1 except that a vacuum deposition method was used instead of the sputtering method as a method for forming the bonding layer. The vacuum deposition was performed at a degree of vacuum of 2 × 10 ⁻³ Pa and a substrate heating temperature of 300 ° C. The heat resistance, adhesion and etching were almost the same as the sputtering method, and all were good.

Example 27
In the same manner as in Example 1, a surface conductor layer (Cu film) having a film thickness of about 8 μm was baked on both surfaces through a via filling substrate manufacturing process, a bonding layer forming process, and a surface conductor layer (Cu) forming process. A metallized substrate was obtained. A plating resist pattern was formed on the surface of the Cu film of the obtained metallized substrate. Contrary to the etching resist pattern, the plating resist pattern exposed the Cu film retained as wiring and covered the Cu film in the region to be removed with the resist. The exposed Cu film was subjected to Ni / Au plating by the same method as in Example 1. The resist film was peeled off from the substrate on which the Cu film was plated, and the Cu / Pd / Ti copper film in the region not plated was removed by etching. That is, at the time of etching, the Ni / Au film on the surface was made to function as a resist. The performance evaluation result of the obtained substrate was the same as that of Example 1.

Example 28
As shown in FIG. 2, in the bonding layer forming step of Example 1, after forming the bonding layer 3 by the sputtering method (FIG. 2A), the surface conductor layer forming step by printing Cu paste is performed. First, an etching resist pattern 5 was formed as it was (FIG. 2B). After the exposed bonding layer was removed by etching (FIG. 2C), the etching resist was peeled and removed to obtain a conductor pattern made of the bonding layer (FIG. 2D). A Cu film having the same shape as the bonding layer pattern was printed on the surface conductor layer Cu paste A using a screen plate so as to be laminated on the conductor pattern. A substrate having a Cu film printed on the bonding layer is dried at 120 ° C. for 20 minutes and then baked in a nitrogen atmosphere at a peak temperature of 700 ° C. for a peak holding time of 10 minutes to have a surface conductor (Cu film) pattern with a film thickness of about 9 μm. A metallized substrate was obtained. The obtained metallized substrate was subjected to a plating step by the same method as in Example 1 to obtain a double-sided wiring substrate. Even this method was good in all properties. The pattern shape was kamaboko.

Example 29
A double-sided wiring board was produced in the same manner as in Example 1 except that the bonding layer was formed before the via-filled board production process and the polishing method was changed. That is, first, a bonding layer was formed on both sides of the substrate and the inner wall surface of the through hole with respect to the substrate having many through holes. The through hole was filled in the substrate on which the bonding layer had been formed by screen printing using a via filling Cu paste through a metal mask, and dried for 20 minutes with a 120 ° C. blower dryer. The Cu paste protruding on the filling via surface of the substrate filled with the Cu paste was removed by buffing. Since the protruding Cu paste was soft and unfired, it could be easily removed by buffing, but the bonding layer on the substrate surface was not affected by buffing. The polished substrate was baked in a nitrogen atmosphere at 900 ° C. for 60 minutes to prepare a Cu conductor via-filled substrate. Subsequently, the via-filled substrate was subjected to a surface conductor layer (Cu) forming step, and a double-sided wiring substrate was produced by the same method as in Example 1. The evaluation results of the obtained substrate were all good as in Example 1.

Example 30
The baking of the via-filled substrate after buffing is omitted, and the unfired via-filled substrate is subjected to the surface conductor layer (Cu) forming step, and then the via-filling Cu paste and the surface conductor layer Cu paste are simultaneously heated to 700 ° C. A double-sided wiring board was produced in the same manner as in Example 29 except that firing was performed. The evaluation results of the manufactured substrate were all good as in Example 1.

  The double-sided wiring board of the present invention can be used as a circuit board, an electronic component, a semiconductor package board, and the like.

DESCRIPTION OF SYMBOLS 1 ... Cu conductor via filling board | substrate 2 ... Filling part 3 ... Bonding layer 4 ... Surface conductor layer 5 ... Resist film for etching 6 ... Conductor pattern 7 ... Nickel plating film 8 ... Gold plating film

Claims (27)

  An insulating substrate having a hole portion, a conductive via portion that is present in the hole portion and includes a conductor, and is laminated on at least a part of a surface of the insulating substrate and the conductive via portion, and an active metal layer is provided. A double-sided wiring board comprising: a bonding layer including: a surface conductor layer laminated on the bonding layer, including a conductor, and having a porous structure.   2. The double-sided wiring board according to claim 1, wherein the active metal layer includes at least one active metal selected from the group consisting of Ti, Zr, Hf, Nb, Ta, Cr, Mn, and Al or an alloy containing the active metal. .   The bonding layer further includes a non-permeable layer, and the non-permeable layer includes at least one barrier metal selected from the group consisting of Mo, W, Ni, Pd, and Pt or an alloy including the barrier metal. The double-sided wiring board according to claim 1, wherein the non-transmissive layer is interposed between the active metal layer and the surface conductor layer.   The bonding layer further includes an affinity layer, the affinity layer includes a metal that is the same as or alloyable with the metal included in the surface conductor layer, and the affinity layer is in contact with the surface conductor layer. The double-sided wiring board according to any one of the above.   The conductor included in the surface conductor layer includes at least one conductive metal selected from the group consisting of Ni, Pt, Cu, Ag, Au, and Al, or an alloy including the conductive metal. The double-sided wiring board according to any one of the above.   The double-sided wiring board according to claim 1, wherein the porosity of the surface conductor layer is 5 to 30% by volume.   The double-sided wiring board according to claim 1, wherein the surface conductor layer does not contain a glass component.   The double-sided wiring board according to any one of claims 1 to 7, wherein the average thickness of the surface conductor layer is 5 to 1000 times the average thickness of the bonding layer.   The double-sided wiring board according to claim 1, wherein the conductor included in the conductive via portion has a porous structure.   The double-sided wiring board according to claim 9, wherein the porosity of the conductive via portion is 15 to 45% by volume.   The double-sided wiring board according to claim 1, wherein a via bonding layer including an active metal layer is interposed between the hole wall surface of the insulating substrate and the conductive via part.   The double-sided wiring board according to claim 1, wherein the insulating substrate is a ceramic substrate, a glass substrate, a silicon substrate, or an enamel substrate.   The double-sided wiring board according to any one of claims 1 to 12, wherein a plating layer is further laminated on the surface conductor layer.   The double-sided wiring board according to claim 13, wherein the plating layer is a wet plating layer.   A via filling step of filling a hole of an insulating substrate having a hole with a conductive paste for a conductive via part including metal particles and an organic vehicle, and heating the conductor to a temperature higher than the sintering temperature of the metal particles contained in the conductive paste. A via firing step of firing a paste to form a conductive via portion; a bonding layer forming step of laminating a bonding layer including an active metal layer on a surface of an insulating substrate provided with the conductive via portion; a metal on the bonding layer; A conductor coating step of applying a conductor paste for a surface conductor layer containing particles and an organic vehicle; heating the conductor paste to a temperature higher than a sintering temperature of the metal particles contained in the applied conductor paste; The manufacturing method of the double-sided wiring board in any one of Claims 1-14 including the conductor baking process which forms the surface conductor layer which has a quality structure.   A bonding layer forming step of laminating a bonding layer including an active metal layer on a surface of an insulating substrate having a hole and laminating a via bonding layer including an active metal on a wall surface of the hole, and forming a via bonding layer A via filling step of filling a conductive paste for a conductive via part containing metal particles and an organic vehicle into the holes of the insulated substrate, heating the conductive paste above the sintering temperature of the metal particles contained in the conductive paste, and firing the conductive paste A via firing step for forming a conductive via portion, a conductor coating step for applying a conductive paste for a surface conductor layer containing metal particles and an organic vehicle on the bonding layer and the conductive via portion on the surface of the insulating substrate, and the applied conductive paste The conductor paste is fired by heating to a temperature equal to or higher than the sintering temperature of the metal particles contained in the conductor, and includes a conductor firing step of forming a surface conductor layer containing a conductor and having a porous structure. Method for manufacturing a double-sided wiring board according to any one of the.   A bonding layer forming step of laminating a bonding layer including an active metal layer on a surface of an insulating substrate having a hole and laminating a via bonding layer including an active metal on a wall surface of the hole, and forming a via bonding layer A via filling step of filling the hole of the insulating substrate with a conductive paste for a conductive via portion containing metal particles and an organic vehicle, the metal particles on the bonding layer and the conductor paste filled in the hole of the insulating substrate surface; And a conductor coating step of applying a conductor paste for a surface conductor layer containing an organic vehicle, heating the surface conductor layer to a temperature higher than the sintering temperature of the metal particles contained in the applied conductor paste for the surface conductor layer and the conductor paste for a conductive via portion The conductor paste and the conductive via part conductive paste are fired at the same time, including a conductor and a conductor firing step of forming a surface conductor layer and a conductive via part having a porous structure. Method for manufacturing a double-sided wiring board according to any one of the 4.   The manufacturing method according to any one of claims 15 to 17, wherein the surface of the insulating substrate is smoothed before or after the conductive via portion conductive paste is fired.   The method according to any one of claims 15 to 18, wherein in the bonding layer forming step, after forming the active metal layer, a non-permeable layer and / or an affinity layer is further laminated on the active metal layer.   The manufacturing method according to claim 15, wherein the bonding layer is formed by a physical vapor deposition method.   In the conductor application process, before applying the conductor paste, the melting point of the metal having the lowest melting point among all the metal species that are 400 ° C. or higher in an inert gas atmosphere and that constitute the bonding layer, and the bonding layer The manufacturing method according to any one of claims 15 to 20, wherein the bonding layer is annealed by heating at a temperature equal to or lower than the lower melting point of the constituent alloy.   After forming a resist pattern in a partial region of the surface conductor layer obtained in the conductor firing step, the surface conductor layer and the bonding layer in the exposed region where the resist pattern is not formed are removed, and the resist pattern is further removed. The manufacturing method according to claim 15, further comprising one etching step.   The conductor coating step further includes a bonding layer removing step of pattern printing the conductor paste for the surface conductor layer and further removing the bonding layer exposed from the surface conductor layer as a subsequent step of the conductor baking step. The manufacturing method of crab.   The manufacturing method according to any one of claims 15 to 21, wherein a bonding layer including an active metal layer is formed in a pattern on the surface of the insulating substrate.   The manufacturing method according to any one of claims 15 to 24, further comprising a plating step of forming a plating layer on the surface of the surface conductor layer obtained in the conductor firing step.   After forming a resist pattern in a partial area of the surface conductor layer obtained in the conductor firing step, a plating layer containing a noble metal is formed on the surface of the surface conductor layer in the exposed area where the resist pattern is not formed. The manufacturing method according to claim 15, further comprising a second etching step of removing the surface conductor layer and the bonding layer in the exposed region where the plating layer is not formed.   27. The manufacturing method according to any one of claims 15 to 26, wherein the volume change rate before and after firing in the conductive via portion conductive paste is -10% to 20%.

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