JP7152501B2 - Via-filled substrate manufacturing method and conductive paste kit - Google Patents

Description

The present invention relates to a method for manufacturing a front/back conductive board (via-filled board) used in various electronic devices, and a conductive paste kit for manufacturing the via-filled board.

Conventionally, electronic substrates have been used for arranging functional parts and forming wiring circuits. In recent years, in order to reduce the size, increase the functionality, and increase the integration of electronic devices or parts, through holes (holes or vias) are formed in an insulating substrate, and a conductive material is provided in the through holes to electrically connect both sides of the substrate. There is an increasing number of applications in which the As a method for electrically conducting both sides of a substrate, a method of plating a conductive material inside a through-hole is known. low.

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

Furthermore, a method is also known in which through-holes are filled with a conductive paste composed of metal powder, an inorganic binder, and a resin, and the metal powder is sintered by heating to a temperature higher than the sintering temperature of the metal to obtain a conductive filled via. This method is excellent in simplicity, and the resin component as the organic vehicle is evaporated and decomposed by baking. Therefore, the filled vias obtained by this method also have relatively high electrical conductivity, thermal conductivity and heat resistance.

However, a via-filled substrate obtained by firing a conductive paste after filling the vias may have gaps or voids between the filled conductor (conductive via portion) and the wall surface of the hole. Part of the cause of the formation of these gaps and voids is presumed to be 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.

If there is a gap between the filling conductor and the wall surface, at least the following three problems may occur.
(1) When a conductive film (electrode, wiring, etc.) is formed on the substrate surface across the filling portion, the conductive film may be cut due to the existence of the gap, leading to deterioration in conductive performance or disconnection.
(2) The gaps existing in the wall surface are connected to each other along the wall surface, and there is a possibility that impermeability such as airtightness and solder barrier property of the filling portion cannot be ensured.
(3) When the via-filled substrate undergoes a wet process such as plating as a post-process, there is a risk that chemicals or the like will enter the gaps, causing problems such as bursting of the vias, blistering of the surface film, and discoloration.

Therefore, in a method using a conductive paste, a conductive paste that can suppress sintering shrinkage during firing has been proposed. Disclosed is a method of forming an oxide layer of an active metal, further forming a conductor layer made of the active metal inside this oxide layer, and improving adhesion and adhesion between the inner via conductor and the wall surface of the via. It is

Patent Document 1 does not disclose the details of the conductive paste for forming the conductive via portion, and does not verify the airtightness and impermeability of the via-filled substrate.

Furthermore, Japanese Patent Application Laid-Open No. 2017-63109 (Patent Document 2) describes a metal film forming step of forming a metal film containing an active metal on the hole wall surface of an insulating substrate having a hole, volume change before and after firing Disclosed is a method for manufacturing a via-filled substrate, which includes a filling step of filling a hole formed with a metal film with a conductor paste having a ratio of −10 to 20%, and a firing step of firing an insulating substrate filled with the conductor paste. It is

Japanese Patent Application Laid-Open No. 2013-153051 (Patent Document 3) describes a metallized ceramic via substrate in which conductive vias are formed in a ceramic sintered body substrate, and a metal having a melting point of 600 ° C. or higher and 1100 ° C. or lower ( A), a metal (B) having a higher melting point than the metal (A), and a conductive metal containing an active metal are densely packed in the through hole of the ceramic sintered substrate. and having a surface conductive layer made of a conductive metal containing the metal (A), the metal (B), and an active metal on at least one of both surfaces of the ceramic sintered substrate It has a wiring pattern, the wiring pattern has a plating layer on the surface of the surface conductive layer, the interface between the conductive via and the ceramics sintered substrate and the surface conductive layer and the ceramics sintered substrate. A metallized ceramic via substrate is disclosed in which an active layer is formed at the interface with the metallized ceramic via substrate.

Japanese Patent Application Laid-Open No. 2009-59744 Japanese Patent Application Laid-Open No. 2017-63109 Japanese Patent Application Laid-Open No. 2013-153051

However, in the via-filled substrates of Patent Documents 1 and 2, although the airtightness and adhesion to the wall surface of the hole can be improved to some extent by forming the active metal layer, electrical conductivity and thermal conductivity cannot be sufficiently improved. There is fear. The reason for this is presumed to be that in these via-filled substrates, the density of the conductive via portion itself is low. Specifically, in the method of filling the through-holes with a conductive paste containing an organic vehicle, the organic vehicle disappears due to evaporation and decomposition, creating voids. It becomes porous and the denseness tends to decrease. That is, in the methods of Patent Documents 1 and 2, electrical conductivity and thermal conductivity are inevitably greatly reduced compared to bulk metals that do not have voids, making it difficult to improve compactness. Therefore, in the method of filling a through-hole with a conductive paste containing an organic vehicle, in addition to the airtightness and adhesion, denseness of the conductive via portion is also required. Furthermore, in the metallized ceramic via substrate of Patent Document 3, it is necessary to use a heat-resistant container under a non-reactive atmosphere such as a vacuum in order to prevent the reactive gas such as oxygen and nitrogen from reacting with the active metal. and cannot be manufactured by a simple method.

SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide a method for easily manufacturing a via-filled substrate having a highly dense conductive via portion and high airtightness and adhesion between the conductive via portion and the wall surface of the hole, and to manufacture the via-filled substrate. To provide a kit of conductive paste for

As a result of intensive studies to achieve the above object, the inventors of the present invention have found that after filling the holes of an insulating substrate having holes with a specific first conductive via portion precursor, By laminating a specific second conductive via precursor on the first conductive via precursor and baking it in a nitrogen atmosphere, the denseness of the conductive via is high, and the conductive via is highly dense. The inventors have found that a via-filled substrate having high airtightness and adhesion to the hole can be easily manufactured, and have completed the present invention.

That is, the method for manufacturing a via-filled substrate of the present invention includes:
filling a hole of an insulating substrate having a hole with a first conductive via precursor, filling the hole with the first conductive via precursor in the filling step; A method for producing a via-filled substrate, comprising a lamination step of laminating a second conductive via portion precursor thereon, and a baking step of baking the insulating substrate containing both precursors obtained in the lamination step in a nitrogen atmosphere. and
wherein the first conductive via part precursor contains a filling conductive paste containing a metal component A and a first organic vehicle;
The metal component A is a high melting point metal particle having a melting point exceeding the firing temperature,
The filling step includes a paste filling step of filling the hole with the filling conductive paste,
the second conductive via part precursor is a lamination conductive paste containing a metal component B and a second organic vehicle;
The metal component B is a difficult-to-melt metal particle having a melting point lower than the firing temperature,
at least one of the first conductive via precursor and the second conductive via precursor contains an active metal component containing an active metal;
At least one of the filling conductive paste and the second conductive via portion precursor contains a metal component C, which is easily meltable metal particles having a melting point lower than that of the hardly meltable metal particles.

The filling conductive paste may contain the active metal component and the metal component C. The first conductive via portion precursor contains the active metal component, and the filling step forms a metal film containing the active metal component on the hole wall surface of the hole as a pre-process of the paste filling step. It may further include a metal film forming step. The refractory metal particles of the metal component A contain at least one refractory metal selected from the group consisting of Cu, Ag, Ni, W, Mo, Au, Pt and Pd or an alloy containing this refractory metal. You can stay. The difficult-to-melt metal particles of the metal component B have a melting point exceeding 450° C. and contain at least one high-melting-point metal selected from the group consisting of Cu, Ag, Ni, Au, Pt and Pd. It may contain an alloy. The easily meltable metal particles of the metal component C have a melting point of 450° C. or less and are at least one easily meltable metal selected from the group consisting of Bi, Sn, In and Zn, or an alloy containing this easily meltable metal. may contain The active metal component is at least one selected from the group consisting of active metals, alloys containing active metals, and hydrides of active metals, and the active metal is selected from the group consisting of Ti, Zr and Nb. or at least one active metal.

The present invention provides a conductive paste kit for manufacturing a via-filled substrate by the manufacturing method,
A filling conductive paste containing a metal component A, which is a high melting point metal particle having a melting point higher than the firing temperature, a first organic vehicle, and a metal component B, which is a difficult-to-melt metal particle having a melting point lower than the firing temperature. , and a second organic vehicle in combination with a conductive lamination paste,
At least one of the conductive filling paste and the conductive lamination paste contains an active metal component that is an active metal-containing particle containing an active metal,
At least one of the conductive paste for filling and the conductive paste for lamination includes a metal component C, which is easily meltable metal particles having a melting point lower than that of the hardly meltable metal particles.

In the present application, the term "precursor for conductive via portion" means all unfired materials introduced into the holes of the insulating substrate in order to form the conductive via portion. Therefore, when a metal film is formed on the hole wall surface by sputtering or the like prior to the introduction of the filling conductive paste, the first conductive via portion precursor contains the filling material introduced into the hole. The metal film is included as well as the conductive paste.

In the present invention, after the hole of the insulating substrate having the hole is filled with a specific first conductive via precursor, on top of the filled first conductive via precursor, Since the specific second conductive via portion precursor is laminated and fired in a nitrogen atmosphere, the conductive via portion in the via-filled substrate is highly dense and the conductive via portion and the hole (through hole) are airtight. It is possible to easily manufacture a via-filled substrate with high strength and adhesion. In particular, the filling density of the conductive via portion can be increased, and the porosity due to gaps and voids can be reduced to 10% by volume or less, so that electrical conductivity and thermal conductivity can be improved. Furthermore, the adhesion between the wall surface of the hole and the conductive via can be enhanced, and a via-filled substrate having substantially no gap between the wall of the hole and the conductive via can be prepared.

FIG. 1 is a schematic process diagram showing an example of a method for manufacturing a via-filled substrate according to the present invention. FIG. 2 is a schematic process diagram showing another example of the method for manufacturing a via-filled substrate according to the present invention. 3 shows a cross-sectional scanning electron microscope (SEM) image of a hole (conductive via portion) in the via-filled substrate obtained in Example 1. FIG. FIG. 4 is an enlarged image of the interface between the conductive via portion and the wall surface of the hole in the SEM image of FIG. FIG. 5 is an elemental mapping image of the active metal Ti at the interface between the conductive via portion and the wall surface of the hole in the SEM image of FIG. FIG. 6 shows a cross-sectional SEM image of the conductive via portion in the via-filled substrate obtained in Example 3. FIG. FIG. 7 is an enlarged image of the interface between the conductive via portion and the wall surface of the hole in the SEM image of FIG. FIG. 8 is an elemental mapping image of the active metal Ti at the interface between the conductive via portion and the wall surface of the hole in the SEM image of FIG. FIG. 9 shows a cross-sectional SEM image of the conductive via portion in the via-filled substrate obtained in Example 4. FIG. FIG. 10 is an elemental mapping image of the active metal Ti at the interface between the conductive via portion and the wall surface of the hole in the SEM image of FIG. 11 shows a cross-sectional SEM image of the conductive via portion in the via-filled substrate obtained in Comparative Example 1. FIG. FIG. 12 shows a cross-sectional SEM image (enlarged image of the interface with the wall surface of the hole) of the conductive via portion in the via-filled substrate obtained in Comparative Example 2. As shown in FIG. FIG. 13 is an elemental mapping image of active metal Ti in the SEM image of FIG. 14 shows a cross-sectional SEM image of the conductive via portion in the via-filled substrate obtained in Comparative Example 7. FIG. FIG. 15 is an enlarged image of the interface between the conductive via portion and the wall surface of the hole in the SEM image of FIG.

[Manufacturing method of via-filled substrate]
A method for manufacturing a via-filled substrate according to the present invention includes a filling step of filling a hole of an insulating substrate having a hole with a first precursor for a conductive via portion; A lamination step of laminating a second conductive via precursor on the conductive via precursor, and a baking step of baking the insulating substrate containing both precursors obtained in the lamination step in a nitrogen atmosphere. include.

In the present invention, by combining the filling step and the laminating step, the airtightness and adhesion between the conductive via portion and the wall surface of the hole can be improved, and the denseness of the conductive via portion can be improved. The reason is as follows. can be estimated to

In the method of the present invention, since the metal component A does not melt at the firing temperature in the firing process, it forms the shape (skeleton) of the filling portion so as not to flow out from the hole as the main component responsible for the conductivity of the conductive via portion. have a role. As described above, when the conductive paste filled in the holes is fired, voids are generated as the organic vehicle disappears. In contrast, in the method of the present invention, after filling the hole with a first conductive via precursor containing a conductive paste containing a metal component A and an organic vehicle, the first conductive via precursor On top of this, a second conductive via portion precursor containing metal component B, which is a hard-to-melt metal particle, is layered and fired at a temperature higher than the melting point of metal component B, preferably in a dry state. As a result, the molten metal component B flows into voids generated by the disappearance of the organic vehicle and gaps between particles of the metal component A (in particular, voids caused by the disappearance of the large-volume organic vehicle), filling the voids and gaps. By sintering the metal, it can be assumed that the whole is densely sintered and the denseness of the conductive via portion is improved. Furthermore, it is presumed that the metal component B flows into the gap between the wall surface of the hole and the first conductive via portion precursor, and sinters the metal while filling the gap, thereby improving airtightness and adhesion. can.

Furthermore, in the method of the present invention, in the firing step, the metal component C (easily fusible metal particles) melts at a low temperature and covers the surface of the active metal component (active metal particles), so that the active metal component remains in the vicinity even at high temperatures. It is possible to prevent reaction with existing gases (nitrogen in the firing atmosphere gas, carbon and volatile organic compounds generated by decomposition of the organic vehicle, etc.). Due to this action, the active metal component can retain its activity even at high temperatures even in a nitrogen atmosphere. and the insulating substrate, so that the conductive via portion and the wall surface of the hole can be firmly bonded. Since the easily meltable metal (metal component C) literally liquefies and flows, it can be presumed that the easily meltable metal component also wets the surfaces of the high-melting metal particles, thereby preventing excessive flow. Depending on the type of easily meltable metal and high melting point metal, fluidization is suppressed by utilizing the fact that alloying progresses between the easily meltable metal and the high melting point metal during firing and the melting point of the easily meltable metal rises. is also possible. In particular, according to the method of the present invention, the activity of the active metal component is maintained by the action of the easily fusible metal component, so that the insulating substrate can be manufactured by firing in a nitrogen atmosphere. Filled substrates can be easily manufactured, and productivity is also high.

The metal component A, the metal component B, the active metal component and the metal component C improve the denseness of the conductive via portion and the airtightness and adhesion between the conductive via portion and the hole (hereinafter referred to as “denseness and airtightness”). It can be estimated that it is possible to improve the "strength and adhesion"). The active metal component and metal component C may be contained in the conductive filling paste and/or the conductive lamination paste, and the active metal component may be preliminarily laminated on the wall surface of the hole.

(Filling process)
In the filling step, the first conductive via part precursor contains a filling conductive paste containing a metal component A and a first organic vehicle, and the filling step includes a paste filling step of filling the filling conductive paste.

(a) Paste Filling Step In the paste filling step, the filling conductive paste contains a metal component A, which is a high melting point metal particle having a melting point exceeding the firing temperature.

(a1) metal component A
The metal forming the high-melting-point metal particles, which is the metal component A, is not particularly limited as long as it has a melting point (for example, 600° C. or higher) exceeding the firing temperature. The metal may be a refractory metal simple substance or an alloy containing the refractory metal. Specifically, examples of the refractory metal include Cu, Ag, Ni, W, Mo, Au, Pt, and Pd. The alloy containing the high-melting-point metal may be an alloy of the high-melting-point metals, or may be an alloy of the high-melting-point metal and another metal. The other metal is not particularly limited as long as the melting point of the alloy exceeds the firing temperature, and any metal that can be alloyed with the high-melting-point metal can be used. hard-to-melt metals, easy-to-melt metals exemplified in the section of metal component C described later, and active metals exemplified in the section of active metal components to be described later. Other metals can also be used singly or in combination of two or more.

The metal constituting the high melting point metal particles is preferably at least one high melting point metal selected from the group consisting of Cu, Ag, Ni, W, Mo, Au, Pt and Pd, or an alloy containing this high melting point metal. , Cu, Ag, Ni, W and Mo or at least one refractory metal or an alloy containing this refractory metal is particularly preferred.

These high melting point metal particles can be used alone or in combination of two or more. Furthermore, it is preferable to combine two or more kinds of high-melting-point metal particles in order to control the sinterability of the particles during firing and to facilitate the shape retention of the conductive via portions.

Among these metal particles, Cu particles (melting point 1085° C.), Ag particles (melting point 1085° C.), Ag particles (melting point 962° C.) is preferred, and Cu particles are particularly preferred from the viewpoint of economy.

Cu particles may be combined with other refractory metal particles, and a combination of Cu particles and at least one metal particle selected from the group consisting of Ni, W and Mo is preferred. When Cu particles and other high-melting-point metal particles are combined, the ratio of the other high-melting-point metal particles is, for example, 10 to 1000 parts by volume, preferably 30 to 500 parts by volume, more preferably 30 to 500 parts by volume, with respect to 100 parts by volume of the Cu particles. is 50 to 300 parts by volume, more preferably 80 to 200 parts by volume.

Furthermore, the high melting point metal particles preferably contain low thermal expansion metal particles (especially W particles and/or Mo particles) having a small thermal expansion coefficient, in order to further improve airtightness and adhesion. By including low thermal expansion metal particles with a small thermal expansion coefficient, it is possible to reduce the difference in thermal expansion coefficient from that of the insulating substrate. Separation from the wall surface can be suppressed.

The low thermal expansion metal particles may be combined with high thermal expansion metal particles having a large thermal expansion coefficient (high melting point metal particles other than low thermal expansion metal particles), and the combination with excellent sinterability Cu particles and/or Ag particles is preferable. . When low thermal expansion metal particles (particularly W particles and/or Mo particles) and high thermal expansion metal particles (particularly Cu particles and/or Ag particles) are combined, the proportion of the low thermal expansion metal particles is the same as that of the high thermal expansion metal particles. For example, it is 10 to 99% by volume, preferably 30 to 90% by volume, more preferably 50 to 80% by volume, more preferably 60 to 70% by volume, relative to the total volume.

In addition, in this application, a volume ratio is a volume ratio at 25 degreeC and atmospheric pressure.

The shape of the refractory metal particles includes, for example, a spherical (perfectly spherical or substantially spherical), an ellipsoidal (elliptical) shape, a polyhedral shape (polygonal prism shape such as a polygonal pyramid shape, a cubic shape, a rectangular parallelepiped shape, etc.), a plate shape (flat shape, scale-like, flake-like, etc.), rod-like or bar-like, fiber-like, dendrite-like, irregular shape, and the like. The shape of the high-melting-point metal particles is usually spherical, ellipsoidal, polyhedral, amorphous, or the like. A spherical shape is preferable from the viewpoint of high packing density and excellent fluidity as a paste.

The median particle size (D50) of the high melting point metal particles may be about 100 μm or less (especially 50 μm or less) from the viewpoint of improving fluidity as a paste, denseness after firing, and airtightness and adhesion. For example, it is 0.001 to 50 μm, preferably 0.01 to 20 μm, more preferably 0.1 to 10 μm, more preferably 0.2 to 10 μm. If the median particle size is too large, it may become difficult to fill small pores.

The high-melting-point metal particles can improve the metal content in the paste and improve the denseness and conductivity of the conductive via portion. A combination of high-melting-point metal large particles (hereinafter referred to as "large particles") having a particle size of 3 to 50 μm is preferred.

The median particle size of the small particles is, for example, 0.1 to 2.5 μm, preferably 0.2 to 2 μm, more preferably 0.25 to 1.5 μm, more preferably 0.3 to 1 μm. If the median particle size of the small particles is too small, the viscosity of the conductive paste may increase, making it difficult to handle.

The median particle size of the large particles is, for example, 3 to 30 μm, preferably 4 to 20 μm, more preferably 4.5 to 15 μm, more preferably 5 to 10 μm. If the central particle size of the large particles is too small, the sintering shrinkage of the conductor paste may increase, and if it is too large, the filling properties of the conductive via portion may deteriorate.

In addition, in this application, the median particle diameter means the average particle diameter (volume basis) measured using a laser diffraction scattering type particle size distribution analyzer.

When small particles and large particles are combined as the high-melting-point metal particles, the proportion of the small particles is, for example, 1 to 100 parts by volume, preferably 5 to 80 parts by volume, more preferably 10 parts by volume, with respect to 100 parts by volume of the large particles. ~50 parts by volume, more preferably 20 to 40 parts by volume. If the ratio of the small particles is too small, the fillability of the conductive via portion may deteriorate, and if it is too large, the handleability may deteriorate.

The melting point of the high-melting-point metal particles may be any melting point exceeding the sintering temperature, and may be, for example, 600° C. or higher. is 850 to 2000°C, more preferably 900 to 1500°C, more preferably 950 to 1200°C. If the melting point is too low, the electrical conductivity and heat resistance may deteriorate.

Since the metal component A, which is a high melting point metal particle, has such a melting point, it does not melt during the firing process, but it can be sintered between the particles of the metal component A, or the metal component A and the metal component B may be alloyed by sintering each other.

High-melting-point metal particles can be produced by conventional methods such as wet reduction, electrolysis, atomization, and water atomization.

The proportion of the metal component A (high-melting-point metal particles) in the filling conductive paste may be 30% by volume or more, for example 30 to 99% by volume, preferably 35 to 80% by volume, more preferably 40 to 60% by volume. %, more preferably 45-55% by volume. If the ratio of the metal component A is too low, the shape retention of the conductive via portion may deteriorate.

The volume ratio of the metal component A to the total volume of the metal component A, the metal component C and the active metal component contained in the first precursor for the conductive via portion (hereinafter referred to as the "total volume of the inorganic components") is It may be 50% by volume or more, for example 60 to 100% by volume, preferably 65 to 95% by volume, more preferably 70 to 92% by volume, more preferably 80 to 90% by volume. If the volume ratio of the metal component A is too small, the shape retention of the conductive via portion may deteriorate, and voids and gaps may occur. there is a risk of

(a2) First Organic Vehicle The filling conductive paste further contains an organic vehicle (first organic vehicle) in addition to the metal component A in order to make it pasty (fluid state).

The first organic vehicle may be a conventional organic vehicle such as an organic binder and/or an organic solvent that is utilized as an organic vehicle for conductive pastes containing metal particles. The organic vehicle may be either an organic binder or an organic solvent, but is usually a combination of an organic binder and an organic solvent (a solution of an organic binder in an organic solvent).

The organic binder is not particularly limited, and examples thereof include thermoplastic resins (olefin-based resins, vinyl-based resins, acrylic-based resins, styrene-based resins, polyether-based resins, polyester-based resins, polyamide-based resins, cellulose derivatives, etc.), Thermosetting resins (thermosetting acrylic resins, epoxy resins, phenol resins, unsaturated polyester resins, polyurethane resins, etc.) and the like are included. These organic binders can be used alone or in combination of two or more. Among these organic binders, resins that are easily burnt off during the firing process and have a low ash content, such as acrylic resins (polymethyl methacrylate, polybutyl methacrylate, etc.), cellulose derivatives (nitrocellulose, ethyl cellulose, butyl cellulose, cellulose acetate). etc.), polyethers (polyoxymethylene, etc.), and rubbers (polybutadiene, polyisoprene, etc.) are widely used. Poly(meth)acrylic acid C _1-10 alkyl esters such as are preferred.

The organic solvent is not particularly limited, and may be an organic compound that imparts an appropriate viscosity to the paste and can be easily volatilized by drying after the paste is applied to the substrate, even if it is an organic solvent with a high boiling point. good. Examples of such organic solvents include aromatic hydrocarbons (paraxylene, etc.), esters (ethyl lactate, etc.), ketones (isophorone, etc.), amides (dimethylformamide, etc.), aliphatic alcohols (octanol, decanol, etc.), , diacetone alcohol, etc.), 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), aliphatic polyhydric alcohols (ethylene glycol, diethylene glycol, dipropylene glycol, butanediol, triethylene glycol, glycerin, etc.), alicyclic alcohols [e.g., cyclo cycloalkanols such as hexanol; terpene alcohols such as terpineol and dihydroterpineol (monoterpene alcohols, etc.)], aromatic alcohols (methacresol, etc.), aromatic carboxylic acid esters (dibutyl phthalate, dioctyl phthalate, etc.), nitrogen-containing heterocyclic compounds (dimethylimidazole, dimethylimidazolidinone, etc.); These organic solvents can be used alone or in combination of two or more. Among these organic solvents, carbitols such as carbitol and alicyclic alcohols such as terpineol are preferable from the viewpoint of fluidity of the paste.

When an organic binder and an organic solvent are combined, the ratio of the organic binder is, for example, 1 to 200 parts by mass, preferably 10 to 100 parts by mass, and more preferably about 20 to 50 parts by mass with respect to 100 parts by mass of the organic solvent. 5 to 80% by mass, preferably 10 to 50% by mass, more preferably 20 to 30% by mass, based on the total organic vehicle.

The ratio of the first organic vehicle is, for example, 10 to 300 parts by volume, preferably 30 to 200 parts by volume, more preferably 50 to 150 parts by volume, more preferably 70 to 100 parts by volume, with respect to 100 parts by volume of the metal component A. is. If the ratio of the first organic vehicle is too small, the handleability may deteriorate, and if it is too large, the compactness, airtightness and adhesion may deteriorate.

(a3) Metal component C
In addition to the metal component A and the first organic vehicle, the filling conductive paste protects the active metal component and suppresses the reaction between nitrogen, oxygen, carbon, and the like and the active metal at high temperature, thereby preventing the above-described In order to improve airtightness and adhesion, metal component C (first metal component C) may be further included. The conductive filling paste may not contain the metal component C, but if the conductive filling paste does not contain the metal component C, the conductive paste for lamination described later (for the second conductive via portion precursor) must contain the metal component C. That is, at least one of the conductive paste for filling and the conductive paste for lamination should contain the metal component C, and at least the conductive paste for filling contains the metal component C from the viewpoint of improving denseness, airtightness, and adhesion. is preferred, and it is more preferred that only the filling conductive paste contains the metal component C.

The metal forming the easily fusible metal particles, which is the metal component C, is not particularly limited as long as it has a melting point lower than that of the hardly fusible metal particles. The metal forming the easily-meltable metal particles may be an easily-meltable metal alone or an alloy containing the easily-meltable metal. Specifically, examples of the easily meltable metal include Bi, Sn, In, and Zn. The alloy containing the easily meltable metal may be an alloy of the easily meltable metals, or may be an alloy of the easily meltable metal and another metal. The other metal is not particularly limited as long as the melting point of the alloy is lower than that of the difficult-to-melt metal particles. hard-to-melt metals exemplified in the section above, and active metals exemplified in the section on active metal components to be described later. Other metals can also be used singly or in combination of two or more.

As the metal constituting the easily meltable metal particles, at least one easily meltable metal selected from the group consisting of Bi, Sn, In and Zn or a metal containing an alloy containing this easily meltable metal is preferable.

These fusible metal particles can be used alone or in combination of two or more. Among these fusible metal particles, Bi particles, Sn particles, In particles and Zn particles are more preferred, and Sn particles are particularly preferred.

The shape of the easily fusible metal particles can be selected from the shapes exemplified as the shapes of the high-melting metal particles, which are the metal component A, including normal and preferred modes.

The median particle size (D50) of the easily fusible metal particles can be selected from the range of about 0.1 to 100 μm, and from the viewpoint of the handling of the filling conductive paste and the effect even with a smaller amount, it is, for example, 0.2 to 30 μm. , preferably 0.5 to 20 μm, more preferably 1 to 10 μm.

The melting point of the easily fusible metal particles is preferably 450° C. or less in order to cover the surface of the active metal component (active metal particles) and protect it from reaction with nitrogen or the like in the firing atmosphere gas. It can be selected from the range of about 100 to 450°C, for example 130 to 420°C, preferably 150 to 400°C, more preferably 180 to 300°C, more preferably 200 to 250°C. If the melting point of the easily meltable metal particles is too high, the function of covering and protecting the surface of the active metal component (active metal particles) by the melted easily meltable metal particles is reduced, and the bonding strength between the conductive via portion and the wall surface of the hole is reduced. is insufficient, and airtightness and adhesion may deteriorate.

Since the metal component C has lower conductivity than the metal component A, which is the main component responsible for conductivity, it is preferable to adjust the proportion necessary to protect the active metal. The ratio of the metal component C can be selected from a range of about 1 to 40 parts by volume with respect to 100 parts by volume of the metal component A, for example 2 to 30 parts by volume, preferably 3 to 25 parts by volume, more preferably 5 to 20 parts by volume. , more preferably 10 to 15 parts by volume. If the proportion of the metal component C is too low, the function of melting during firing will be reduced, and the bonding strength between the conductive via portion and the wall surface of the hole portion will be insufficient, and airtightness and adhesion may decrease. If the proportion of the metal component C is too high, the electrical conductivity and heat resistance of the conductive via portion are lowered, or the molten metal component C enters between the particles of the metal component A (high-melting-point metal particles), causing the metal to flow from the surface. There is a risk that the inflow path of component B will be obstructed and the pores (voids) will not be filled. Moreover, if the ratio of the metal component C is too high, there is a possibility that the metal component C may flow out from the filled portion during firing.

The total volume of the metal component C contained in the first conductive via portion precursor is, for example, 0.5 to 30% by volume, preferably 1 to 25% by volume, relative to the total volume of the inorganic components. , more preferably 3 to 20% by volume, more preferably 5 to 15% by volume.

(a4) Active metal component In addition to the metal component A and the first organic vehicle, the filling conductive paste contains an active metal component (first active metal component) may further be included. The conductive paste for filling may not contain an active metal component. must contain ingredients. That is, at least one of the conductive paste for filling, the metal film, and the conductive paste for lamination should contain an active metal component, and from the viewpoint of improving the denseness, airtightness, and adhesion, the conductive filling paste and / or the metal Preferably, the film comprises an active metal component, more preferably at least the conductive filling paste comprises an active metal component, more preferably only the conductive filling paste comprises an active metal component. Note that the metal film is not essential.

The active metal component contained in the conductive filling paste may be active metal-containing particles. Examples of active metals contained in the active metal-containing particles include Ti, Zr, Hf, and Nb. These active metals can be used alone or in combination of two or more. Among these active metals, at least one selected from the group consisting of Ti, Zr and Nb is preferable because it has excellent activity in the firing process and can improve the bonding strength between the insulating substrate and the conductive via portion. Ti and/or Zr are more preferred, and Ti is particularly preferred.

The active metal-containing particles need only contain an active metal, and may be formed of the active metal alone. However, from the viewpoint of excellent activity in the firing process, the active metal-containing particles are preferably formed of a compound containing an active metal. preferable.

Examples of compounds containing active metals include, but are not limited to, titanium hydride (TiH _{2 ), zirconium hydride (ZrH 2 )} , and niobium hydride (HNb). Among these, titanium hydride (TiH ₂ ) is preferable because of its excellent activity in the firing process.

Active metal-containing particles containing these active metals can be used alone or in combination of two or more. Titanium hydride particles and/or zirconium hydride particles are more preferred, and titanium hydride particles are particularly preferred.

The shape of the active metal-containing particles can be selected from the shapes exemplified as the shapes of the high-melting-point metal particles, which are the metal component A, including normal modes and preferred modes.

The median particle size (D50) of the active metal-containing particles can be selected from the range of about 0.1 to 100 μm, and from the viewpoint of handling of the conductive filling paste, for example, 0.2 to 50 μm, preferably 0.5 to 50 μm. 20 μm, more preferably 1 to 10 μm.

The ratio of the active metal component can be selected from a range of about 0.3 to 40 parts by volume with respect to 100 parts by volume of the metal component A, for example, 0.4 to 36 parts by volume, preferably 1 to 30 parts by volume, more preferably 2 parts by volume. ~30 parts by volume, more preferably 3-20 parts by volume, most preferably 5-10 parts by volume. If the proportion of the active metal component is too low, the bonding strength between the conductive via portion and the wall surface of the hole may be insufficient, and airtightness and adhesion may be reduced. there is a risk of

The total volume of the active metal components contained in the first conductive via portion precursor is, for example, 0.1 to 30% by volume, preferably 0.3 to 25% by volume, relative to the total volume of the inorganic components. % by volume, more preferably 0.5 to 20% by volume, more preferably 1 to 15% by volume, and most preferably 3 to 10% by volume.

(a5) Other Components In addition to the metal component A and the first organic vehicle, the filling conductive paste may further contain conventional additives within a range that does not impair the effects of the present invention. Usual additives include, for example, inorganic binders (glass frit, etc.), curing agents (curing agents for acrylic resins, etc.), thermal expansion coefficient modifiers (silica powder, etc.), colorants (dyes and pigments, etc.), and hue modifiers. agent, dye fixing agent, gloss imparting agent, metal corrosion inhibitor, stabilizer (antioxidant, UV absorber, etc.), surfactant or dispersant (anionic surfactant, cationic surfactant, nonionic surfactant active agents, amphoteric surfactants, etc.), dispersion stabilizers, viscosity modifiers or rheology modifiers, moisturizing agents, thixotropic agents, leveling agents, antifoaming agents, bactericides, fillers and the like. These additives can be used alone or in combination of two or more. The ratio of other components can be selected according to the type of component, and is usually about 10% by mass or less (eg, 0.01 to 10% by mass) with respect to the entire conductive paste for filling.

(a6) Insulating substrate The material of the insulating substrate in which the hole is filled with the conductive paste for filling is required to have heat resistance because it undergoes a firing process, and may be an organic material such as engineering plastic. , is an inorganic material (inorganic material).

Examples of inorganic materials include ceramics {metal oxides (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 nitrides (aluminum nitride, titanium nitride, etc.), silicon nitride, boron nitride, carbon nitride, metal carbides (titanium carbide, tungsten carbide, etc.), silicon carbide, boron carbide, metal borides (titanium boride, zirconium boride etc.), metal double oxides [metal titanates (barium titanate, strontium titanate, lead titanate, niobium titanate, calcium titanate, magnesium titanate, etc.), metal zirconates (barium zirconate, zirconate calcium, lead zirconate, etc.), etc.}, glasses (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.), silicons (semiconductor silicon, etc.), and the like. The inorganic material may be a composite material (for example, enamel) of these inorganic materials and metal.

The insulating substrate may be, for example, a heat-resistant substrate such as a ceramic substrate, a glass substrate, a silicon substrate, or an enamel substrate. Among these heat-resistant substrates, ceramic substrates such as alumina substrates, sapphire substrates, aluminum nitride substrates, silicon nitride substrates and silicon carbide substrates; and glass substrates such as quartz glass substrates are preferred.

The wall surface of the hole of the insulating substrate is subjected to oxidation treatment [surface oxidation treatment, such as discharge treatment (corona discharge treatment, glow discharge treatment, high temperature oxidation treatment, etc.), acid treatment (chromic acid treatment, etc.), ultraviolet irradiation treatment, flame treatment. etc.], surface treatment such as surface unevenness treatment (solvent treatment, sandblast treatment, etc.) may be performed.

The average thickness of the insulating substrate may be appropriately selected depending on the application. .8 mm.

The insulating substrate is formed with holes (usually a plurality of holes) for filling the conductive vias, and these holes are usually through holes, but may be non-through holes. . The cross-sectional shape of the hole parallel to the substrate surface direction is not particularly limited, and may be polygonal (triangular, quadrangular, hexagonal, etc.). Shape is preferred.

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

A method for forming the hole is not particularly limited, and known methods such as laser method, blasting method, ultrasonic method, grinding method, and drilling method can be used as appropriate.

(a7) Filling Method of Conductive Paste for Filling Methods for filling the hole with the conductive paste for filling include, for example, a screen printing method, an inkjet printing method, an intaglio printing method (e.g., gravure printing method), an offset printing method, and an intaglio printing method. Examples include printing methods such as offset printing and flexographic printing, and direct press-fitting methods such as roll press-fitting, squeegee press-fitting and press press-fitting. Among these methods, the screen printing method and the like are preferable.

After filling, it may be dried naturally or may be dried by heating. The heating temperature can be selected according to the type of organic solvent, and is, for example, about 50 to 200°C, preferably 60 to 180°C, more preferably about 100 to 150°C. The heating time is, for example, 1 to 60 minutes, preferably 3 to 40 minutes, more preferably 5 to 30 minutes.

(b) Metal film forming step The filling step is a metal film forming step of forming a metal film containing an active metal component (second active metal component) on the hole wall surface of the hole as a pre-process of the paste filling step. may further include The metal film forming step is effective when the conductive paste for filling in the paste filling step and/or the conductive paste for lamination in the lamination step described later does not contain an active metal component, and the conductive paste for filling does not contain an active metal component. It is especially effective when it is not included. Even if the conductive paste for filling and/or the conductive paste for lamination does not contain an active metal component, a metal film containing an active metal component is laminated on the wall surface of the hole as a precursor for the first conductive via part. Accordingly, it acts on the metal component A in the conductive paste to improve denseness, airtightness and adhesion.

The metal film should just contain an active metal. The average thickness of the metal film is, for example, 0.01 μm or more, for example, 0.05 to 1 μm, preferably 0.1 to 0.5 μm, more preferably 0.2 to 0.4 μm.

The metal film forming step may include an active metal layer forming step of forming an active metal layer made of an active metal, although the metal film may contain an active metal component.

Examples of the active metal include the active metals exemplified in the section of the filling conductive paste. The active metals can be used alone or in combination of two or more. Among the active metals, Ti and/or Zr are preferable, and Ti is particularly preferable, because they are excellent in activity in the firing process and can improve the bonding strength between the insulating substrate and the conductive via portion.

The average thickness of the active metal layer is, for example, 0.005 μm or more, for example, 0.005 to 1 μm, preferably 0.01 to 0.5 μm, more preferably 0.05 to 0.4 μm, more preferably 0.1 μm. ~0.3 μm. If the thickness of the active metal film is too thin, there is a risk that the adhesion will be reduced, and if it is too thick, there is a risk that the conductivity and sinterability will be reduced.

Preferably, the step of forming a metal film further includes a step of forming a protective layer made of a high-melting-point metal on the active metal film. In the present invention, by laminating a protective layer on the active metal layer, the active metal film formed on the wall surface of the pore is prevented from reacting with oxygen, nitrogen, carbon, etc. before or during firing. It can protect the active metal film and suppress deactivation of the active metal. In particular, by combining with the metal component C contained in the filling conductive paste, the function of protecting the active metal can be further improved.

Examples of refractory metals include Cu, Ni, Pd, and Pt. These high-melting-point metals can be used alone or in combination of two or more, and may be an alloy in which two or more are combined. Among these refractory metals, Pd and Pt are preferred, and Pd is particularly preferred.

The average thickness of the protective layer is, for example, 0.005 μm or more, for example, 0.005 to 1 μm, preferably 0.01 to 0.5 μm, more preferably 0.05 to 0.3 μm, more preferably 0.08 to 0.08 μm. 0.2 μm. If the thickness of the protective layer is too thin, the effect of improving adhesion may be reduced, and if it is too thick, the conductivity and sinterability may be reduced.

A physical vapor deposition method (PVD method), a chemical vapor deposition method (CVD method), or the like can be used as a method for forming a metal film, but the 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. Among these methods, the sputtering method and the ion plating method are preferable, and the sputtering method is particularly preferable, because they have high physical energy and can improve the adhesion between the formed metal film and the insulating substrate. Sputtering methods are available under conventional conditions.

(polishing process)
The insulating substrate whose holes are filled with the first conductive via precursor in the filling step may be directly subjected to the lamination step. The lamination step may be performed after the polishing step of polishing the surface of the substrate. When the surface of the first conductive via portion precursor is smoothed by the polishing step, the second conductive via portion precursor can be easily laminated uniformly, and denseness, airtightness, and adhesion can be improved.

The polishing method in the polishing step may be a physical polishing method or a chemical polishing method. Examples of physical polishing methods include buffing, lapping, and polishing. Examples of the chemical polishing method (surface treatment method) include a method of soft etching the outermost surface with an aqueous solution of sodium persulfate or the like. Among these, physical polishing methods such as buffing are preferred.

(Lamination process)
In the lamination step, the second conductive via portion precursor is a lamination conductive paste containing the metal component B and the second organic vehicle.

(c1) metal component B
The metal forming the hard-to-melt metal particles, which is the metal component B, is not particularly limited as long as it has a melting point (lower melting point than that of the metal component A) at the firing temperature. The metal may be a single substance of a difficult-to-melt metal, or may be a difficult-to-melt alloy. Specifically, examples of difficult-to-melt metals include Mg and Al. Examples of the difficult-to-melt alloys include alloys of the aforementioned difficult-to-melt metals, alloys of high-melting metals exemplified in the section of metal component A, alloys of difficult-to-melt metals and high-melting metals, and difficult-to-melt metals and metal component C. , alloys of high-melting metals and easily-melting metals, and alloys of high-melting-point metals, hardly-melting metals, and easily-melting metals.

As the metal constituting the hard-melting metal particles, a hard-melting metal alone, an alloy of high melting point metals, an alloy of a high melting point metal and an easily melting metal, and an alloy of high melting point metals is particularly preferred.

Cu, Ag, Ni, Au, Pt, and Pd (especially Cu and/or Ag) are preferable as the refractory metal that constitutes the difficult-to-melt alloy.

Bi, Sn, and Zn (especially Sn and/or Zn) are preferable as the easily meltable metal that constitutes the difficult-to-melt alloy. By combining a high-melting-point metal or a difficult-to-melt metal with an easily-melting metal as an alloy, it is possible to adjust the melting point of the metal component B in a wide range. It is preferable to keep the proportion of the easily meltable metal to the minimum necessary amount.

At least one selected from the group consisting of Cu, Ag, Ni, Au, Pt and Pd from the viewpoint that electrical conductivity can be improved in addition to denseness, airtightness and adhesion among these hardly-melting metal particles. refractory metal particles containing a refractory alloy containing a refractory metal (in particular, refractory alloy particles containing at least one refractory metal selected from the group consisting of Cu, Ag, Ni, Au, Pt and Pd) is preferred, alloy particles containing Ag and / or Cu are more preferred, and alloy particles containing Ag (e.g., Ag-Cu alloy particles, Ag-Sn alloy particles, Ag-Cu-Zn-Sn alloy particles, etc.) are more preferred. , Ag—Cu alloy particles are particularly preferred.

In addition, since the metal component B is prepared separately from the first conductive via portion precursor and laminated on the first conductive via portion precursor, a plurality of metal single particles that can be alloyed are combined and When mixed, in the firing process, the single metal particles are alloyed with each other and flow into the gaps and voids of the pores. Therefore, in the present application, the alloy in the metal component B is used in the sense of including a combination of a plurality of single metal particles that are alloyed as the metal component B in the firing process, even if it is a single metal particle in the raw material stage. Furthermore, in a mode in which metal single particles are combined as an alloy, the melting point of the metal component B is not the melting point of each metal single particle but the melting point of the alloy particles alloyed in the firing process. Therefore, even if some of the metal single particles before alloying in the raw material stage are easily meltable metal particles in the conductive paste for filling, the alloy corresponds to a difficult-to-melt metal. It is classified as a difficult-to-melt metal particle as a possible combination of single metal particles.

The shape of the difficult-to-melt metal particles can be selected from the shapes exemplified as the shapes of the high-melting-point metal particles, which are the metal component A, including normal and preferred modes.

The median particle diameter (D50) of the hard-to-melt metal particles can be selected from the range of about 0.01 to 100 μm, and from the viewpoint of handling of the conductive paste for lamination, for example, 0.1 to 30 μm, preferably 0.5 to 20 μm. , more preferably 1 to 15 μm, more preferably 3 to 15 μm, most preferably 4 to 10 μm.

When the metal component B contains particles made of a single substance of a difficult-to-melt metal, the median particle size (D50) of the particles may be 10 μm or less, for example 0.01 to 10 μm, preferably 0.05 to 5 μm, More preferably 0.1 to 3 μm, more preferably 0.3 to 1 μm. If the particle diameter of the particles formed from the single substance of the difficult-to-melt metal is too large, the alloying may not proceed sufficiently.

The melting point of the hard-to-melt metal particles should be lower than the firing temperature, but usually exceeds 450°C. ~960°C, more preferably 650 to 900°C, more preferably 700 to 830°C, most preferably 750 to 800°C. If the melting point of the difficult-to-melt metal particles is too high, the fluidity of the difficult-to-melt metal particles may decrease, and the compactness, airtightness, and adhesion may decrease. If the melting point of the hard-to-melt metal particles is too low, the heat resistance and conductivity of the conductor (conductive via portion) may be lowered.

The proportion of the metal component B in the conductive paste for lamination may be 30% by volume or more, for example 30 to 75% by volume, preferably 40 to 70% by volume, more preferably 45 to 60% by volume, more preferably 50% by volume. ~55% by volume. If the ratio of the metal component B is too small, the amount of the metal component B flowing into the filled via portion may be insufficient, resulting in a decrease in density. be. If the number of times of lamination is too large, the printability will deteriorate.

The ratio of the metal component B is, for example, 10 to 100 parts by volume, preferably 20 to 60 parts by volume, more preferably 30 to 50 parts by volume, with respect to 100 parts by volume of the metal component A contained in the conductive filling paste. Preferably 35 to 45 parts by volume. If the ratio of the metal component B to the metal component A is too small, the compactness, airtightness, and adhesion (especially compactness) may deteriorate. If the ratio of the metal component B to the metal component A is too high, the heat resistance of the conductor may deteriorate.

In the conductive paste for lamination (precursor for the second conductive via portion), the volume ratio of the metal component B is, for example, 60 to 100% by volume, preferably 70 to 100% by volume, with respect to the total volume of the inorganic components, More preferably 80 to 100% by volume, more preferably 85 to 100% by volume. If the volume ratio of the metal component B is too small, there is a risk that the fluidity will decrease and the compactness, airtightness and adhesion (especially compactness) will decrease. If the conductive paste for lamination does not need to contain the active metal component or the metal component C, the content is preferably 100% by volume.

When the proportion of the metal component B is substantially the same as the volume of the first organic vehicle, the voids generated by the disappearance of the first organic vehicle during firing are filled with the metal component B just enough to form the conductive via portion. The denseness of the conductive via portion can be improved without impairing the heat resistance of the metal component A, which is the main component of . Therefore, the volume of the second conductive via portion precursor can be selected from the relationship between the volumes of the metal component B and the first organic vehicle. Since B easily stays on the substrate surface around the hole or flows out from the hole, the proportion may be larger than the same volume.

Specifically, the ratio of the metal component B is, for example, 100 to 1000 volume parts, preferably 120 to 700 volume parts, more preferably 150 to 500 volume parts, more preferably 100 volume parts of the first organic vehicle. is 200-300 parts by volume. If the volume ratio of the metal component B is too small, the denseness may be lowered, and if it is too large, the heat resistance may be lowered.

(c2) Second Organic Vehicle The conductive paste for lamination further contains an organic vehicle (second organic vehicle) in addition to the metal component B in order to improve handleability.

The material of the second organic vehicle can be selected from the materials of the first organic vehicle exemplified in the section of the conductive paste for filling, including preferred embodiments.

The ratio of the second organic vehicle is, for example, 25 to 65% by volume, preferably 30 to 60% by volume, more preferably 40 to 55% by volume, more preferably 45 to 52%, relative to the total volume of the conductive paste for lamination. % by volume. If the ratio of the second organic vehicle is too small, the handling property may deteriorate. In order to do so, it is necessary to increase the number of times of lamination (printing).

(c3) metal component C
The lamination conductive paste may further contain a metal component C (second metal component C) in addition to the metal component B and the second organic vehicle.

The material of the metal component C can be selected from the materials of the metal component C (first metal component C) exemplified in the section of the conductive paste for filling, including preferred embodiments.

The proportion of the metal component C may be 40% by volume or less (for example, 0.1 to 40% by volume), preferably 30% by volume or less, more preferably 20% by volume, relative to the total volume of the conductive paste for lamination. below (for example, 1 to 20% by volume).

(c4) Active Metal Component The conductive paste for lamination may further contain an active metal component (third active metal component) in addition to the metal component B and the second organic vehicle.

The material of the active metal component can be selected from the materials of the active metal component (first active metal component) exemplified in the section of the conductive paste for filling, including preferred embodiments.

The proportion of the active metal component may be 40% by volume or less (for example, 0.1 to 40% by volume), preferably 30% by volume or less, more preferably 10% by volume, relative to the total volume of the conductive paste for lamination. or less (for example, 1 to 10% by volume).

(c5) Other Components In addition to the metal component B and the second organic vehicle, the lamination conductive paste may further contain conventional additives within a range that does not impair the effects of the present invention. Commonly used additives include the additives exemplified in the section of the filling conductive paste. The ratio of other components can be selected depending on the type of component, and is usually about 10% by volume or less (for example, 0.01 to 10% by volume) with respect to the total volume of the conductive paste for lamination.

(c6) Proportion of conductive paste for lamination It may be laminated on the insulating substrate so as to cover at least a portion of the first precursor for conductive via portion filled in the hole of the insulating substrate and exposed at the opening of the hole. Specifically, from the viewpoint of improving denseness, airtightness and adhesion, it is 50% or more (preferably 80% or more, more preferably 100% or more) of the second conductive via portion precursor is laminated. From the viewpoint of productivity, it is preferable to laminate the second conductive via precursor with a diameter larger than that of the opening. , preferably 1.2 to 3 times, more preferably about 1.3 to 2 times) may be laminated.

The ratio of the second conductive via portion precursor may be such that the volume ratio of the metal component B to the first organic vehicle falls within the above range. When adjusting the ratio of the second conductive via precursor (laminating conductive paste) based on the first organic vehicle of the first conductive via precursor, the following method can be used.

That is, the required amount of the second conductive via portion precursor (laminating conductive paste) can be calculated based on the following formula.

Necessary amount of conductive paste for lamination = [necessary amount of metal component B] ÷ [volume ratio of metal component B in conductive paste for lamination]

In addition, the required amount of the metal component B can be calculated based on the following formula.

Required amount (volume) of metal component B=[volume of hole (conductive via part)]×[volume ratio of first organic vehicle in filling conductive paste].

The thickness of the second conductive via precursor can be obtained from the amount of the conductive paste for lamination and the laminated coating area based on the above ratio. depth), for example, 5 to 120%, preferably 8 to 100%, more preferably 10 to 80%, more preferably 12 to 70%, and most preferably 15 to 50%.

(c7) Lamination method of conductive paste for lamination The method for laminating the conductive paste for lamination on the upper surface of the hole includes, for example, a screen printing method, an inkjet printing method, an intaglio printing method (e.g., gravure printing method), an offset printing method, Printing methods such as an intaglio offset printing method and a flexographic printing method can be used. Among these methods, the screen printing method and the like are preferable.

After lamination, it may be dried naturally, or it may be dried by heating. The heating temperature can be selected according to the type of organic solvent, and is, for example, about 50 to 200°C, preferably 60 to 180°C, more preferably about 100 to 150°C. The heating time is, for example, 1 to 60 minutes, preferably 3 to 40 minutes, more preferably 5 to 30 minutes.

Lamination may be performed by laminating a plurality of layers by repeating printing according to the required thickness. When printing is repeated, drying may be performed after each printing.

(Baking process)
In the firing step, the firing temperature should be lower than the melting point of the metal component A and higher than the melting point of the metal component B. The firing temperature (peak temperature) may be 600°C or higher, for example 600 to 1500°C, preferably 700 to 1200°C, more preferably 800 to 1000°C, more preferably 850 to 950°C. The firing time (peak retention time) is, for example, 5 minutes to 3 hours, preferably 8 minutes to 1 hour, more preferably 10 minutes to 20 minutes. The temperature rise from room temperature to the peak temperature and the temperature drop from the peak holding time to room temperature are respectively 10 minutes to 3 hours, preferably 20 minutes to 2 hours, more preferably 25 minutes to 60 minutes.

The firing atmosphere is a nitrogen gas atmosphere. In the present invention, even if nitrogen gas, which reacts with the active metal, is used as the atmosphere gas, the activity of the active metal can be maintained at high temperatures due to the action of the metal component C. A via-filled substrate with high density, airtightness, and adhesion can be manufactured by a simple method without using

(Description by drawing)
The manufacturing steps of the via-filled substrate manufacturing method of the present invention will be described below with reference to the drawings. FIG. 1 is a process diagram of a manufacturing method in which the filling process is only a paste filling process, and FIG. 2 is a process diagram of a manufacturing method in which the filling process consists of a metal film forming process and a paste filling process. Both FIGS. 1 and 2 are examples of the manufacturing method of the present invention.

In the manufacturing method in which the filling process is only the paste filling process, first, a hole 1a is formed in a heat-resistant substrate 1 as shown in FIG. 1(a). Next, as shown in FIG. 1(b), as a filling step, the holes 1a are filled with the conductive filling paste 3, and after drying, the surface of the filled conductive filling paste 3 is polished to be flattened. do. Further, as shown in FIG. 1(c), a lamination conductive paste 4 is laminated on the polished surface of the filling conductive paste 3 and dried. Finally, the insulating substrate 1 containing both conductive pastes is fired to form the conductive via portion 5 .

In the manufacturing method in which the filling step includes the metal film forming step and the paste filling step, holes 11a are first formed in the heat-resistant substrate 11 as shown in FIG. 2(a). Next, in this method, after a metal film 12 containing an active metal is formed on the wall surface (inner wall surface) of the formed hole 11a by sputtering or the like, a filling conductive material is applied to the hole 11a having the metal film 12 laminated on the wall surface. Fill with paste 13 . After filling with the filling conductive paste 13, the lamination conductive paste 14 is laminated to form the conductive via portion 15 in the same manner as in the method of FIG.

[Via-filled board]
The via-filled substrate of the present invention is a via-filled substrate that is obtained by the manufacturing method described above and that electrically connects both surfaces of an insulating substrate. and a conductive via portion formed of a conductive material. This via-filled substrate has a highly dense conductive via portion. The porosity of the conductive via portion is 10% by volume or less, preferably 8% by volume or less, more preferably 5% by volume or less. In addition, in the present application, the porosity of the conductive via portion can be measured using an SEM, and in detail, it can be measured by the method described in Examples described later.

In the via-filled substrate, the adhesion between the conductive via portion and the hole wall surface is high, and the gap between the conductive via portion and the hole wall surface is small. Specifically, if there is a gap between the conductive via portion and the wall surface of the hole, it is local, and the size of the gap is preferably 0.5 μm or less. It is more preferred that there are no gaps, and it is particularly preferred that there are no gaps. In addition, in the present application, the gap between the conductive via portion can be measured using an SEM, and in detail, it can be measured by the method described in Examples described later.

The via-filled substrate has high adhesion between the conductive via portion and the hole wall surface, and in a seal test using ink, ink leakage is 20% or less, preferably 10% or less, and more preferably 0%. . In addition, in this application, as the evaluation method of the seal test using ink, the measurement can be performed by the method described in Examples described later.

The conductive via portion of the via-filled substrate has a phase separation structure of an active metal-containing phase containing an active metal and an active metal-free phase that does not substantially contain an active metal. Since the stress in the via portion is relaxed, it is possible to improve denseness, airtightness, and adhesion.

The phase separation structure may be a sea-island structure, which is a combination of a continuous phase (matrix phase) and a dispersed phase, or a bicontinuous structure, in which both phases are continuous phases, but the sea-island structure is preferred. In the case of a sea-island structure, the active metal-containing phase may be a continuous phase, but is preferably a dispersed phase from the viewpoint of electrical conductivity.

The ratio of the active metal-containing phase and the active metal-free phase can be selected from the range of the former/latter = 1/99 to 90/10, for example, 3/97 to 60/40, It is preferably 5/95 to 50/50, more preferably 10/90 to 40/60, more preferably 10/90 to 30/70.

When the phase separation structure is a sea-island structure, the shape of the dispersed phase is not particularly limited. irregular shape, etc.).

The average diameter of the dispersed phase is, for example, 0.1-100 μm, preferably 1-80 μm, more preferably 3-50 μm, more preferably 5-30 μm.

In addition, in this application, the said ratio and average diameter can be measured based on a cross-sectional SEM image. When the dispersed phase has an anisotropic shape, the diameter of each dispersed phase is the average value of the major axis and the minor axis.

The active metal-containing phase exists at the interface with the wall surface of the pore, and the active metal-containing phase existing at the interface may exist as the dispersed phase. , the phase (continuous phase) extending continuously along the interface at the interface with the hole wall surface. When the active metal-containing phase present at the interface is a continuous phase extending to the interface with the wall surface of the hole, the conductive via preferably has the sea-island structure inside the conductive via.

(active metal-containing phase)
The active metal-containing phase preferably contains at least one active metal selected from the group consisting of Ti, Zr and Nb. These active metals can be used alone or in combination of two or more. Among these, Ti and/or Zr are preferred, and Ti is particularly preferred.

The active metal ratio (element ratio) in the active metal-containing phase may be 0.5% or more, for example 1% or more, preferably 2% or more, and more preferably 3% or more.

When the active metal-containing phase is a dispersed phase, the proportion (elemental ratio) of the active metal in the active metal-containing phase may be 30% or less, for example 0.5 to 30%, preferably 1 to 20%, More preferably 2 to 15%, more preferably 3 to 10%. If the proportion of active metal is too high, there is a risk that the electrical conductivity and heat resistance will decrease.

When the active metal-containing phase is a continuous phase extending along the interface with the pore wall surface, the ratio of the active metal (element ratio) in the active metal-containing phase may be 10% or more, preferably 30% or more. , preferably 50% or more, more preferably 80% or more, more preferably 90% or more, and the active metal alone may be used. If the proportion of the active metal is too low, there is a risk that adhesion and airtightness will deteriorate.

The active metal-containing phase further contains, in addition to the active metal, at least one low melting point metal (hardly melting metal and easily melting metal) selected from the group consisting of Mg, Al, Bi, Sn, In and Zn. You can These low melting point metals can be used alone or in combination of two or more. Among these, Bi, Sn, In and Zn are preferred, Bi, Sn and Zn are more preferred, and Sn and/or Zn are particularly preferred.

The proportion (element ratio) of the low melting point metal in the active metal-containing phase may be 50% or less, for example 1 to 50%, preferably 3 to 30%, more preferably 5 to 20%, more preferably 10%. ~15%. If the proportion of the low-melting metal is too low, voids may occur and the compactness may deteriorate.

The active metal-containing phase may further contain, in addition to the active metal, at least one refractory metal selected from the group consisting of Cu, Ag, Ni, W, Mo, Au, Pt and Pd. These high melting point metals can be used alone or in combination of two or more. Among these, Cu, Ag, Ni, W and Mo are preferred, and Cu and/or Ag are particularly preferred.

The proportion (element ratio) of the refractory metal in the active metal-containing phase may be 99.5% or less, for example 10 to 99%, preferably 30 to 95%, more preferably 50 to 93%, more preferably is 70-90%. If the proportion of the high-melting-point metal is too low, the electrical conductivity and heat resistance may be reduced, and if it is too high, the airtightness and adhesion may be reduced.

(active metal-free phase)
The active metal-free phase may contain at least one refractory metal selected from the group consisting of Cu, Ag, Ni, W, Mo, Au, Pt and Pd. These high melting point metals can be used alone or in combination of two or more. Among these, Cu, Ag, Ni, W and Mo are preferred, and Cu and/or Ag are particularly preferred.

The proportion (element ratio) of the refractory metal in the active metal-free phase may be 50% or more, for example 80% or more, preferably 90% or more, more preferably 95% or more, more preferably 98% or more. is. If the proportion of the high-melting-point metal is too low, the electrical conductivity and heat resistance may deteriorate.

In the present application, the metal composition of the active metal-containing phase and the active metal-free phase can be measured by SEM-EDS elemental analysis of each phase after confirming the phase separation structure with an SEM image, and the details will be described later. It can be measured by the method described in Examples.

EXAMPLES The present invention will be described in more detail below based on examples, but the present invention is not limited by these examples. In the following examples, the preparation method of the conductive paste and the measurement method of the evaluation test are shown below.

[Materials used]
(Metal component A)
Copper particles A: copper particles with a median particle size of 0.8 µm, melting point of 1085°C
Copper particles B: copper particles with a median particle size of 6.5 µm, melting point of 1085°C
Copper particles C: copper particles with a median particle size of 8 µm, melting point of 1085°C
Silver particles A: silver particles with a median particle size of 2.5 µm, melting point of 962°C
Nickel particles: Nickel particles with a median particle size of 0.7 µm, melting point of 1455°C
Molybdenum particles: Molybdenum particles with a median particle size of 3 µm, melting point of 2620°C
Tungsten particles: Tungsten particles with a median particle size of 5 µm, melting point of 3683°C
(Metal component B)
Copper particles D: copper particles with a median particle size of 0.5 µm, melting point of 1085°C
Silver particles B: silver particles with a median particle size of 0.5 µm, melting point of 962°C
AgCu particles: 72Ag-28Cu alloy particles with a median particle size of 5 µm, melting point of 780°C
AgCuZnSn particles: 56Ag-22Cu-17Zn-5Sn solder powder with a median particle size of 5 µm, melting point of 650°C
Tin particles: tin particles with a median particle size of 8 µm, melting point of 232°C
(Metal component C)
Tin particles: tin particles with a median particle size of 8 µm, melting point of 232°C
Bismuth particles: bismuth particles with a median particle size of 16 µm, melting point of 271°C
Indium particles: indium particles with a median particle size of 25 µm, melting point of 156°C
Zinc particles: Zinc particles with a median particle size of 7 µm, melting point of 419°C
(active metal)
Titanium hydride (TiH ₂ ) particles: central particle size 6 μm
Zirconium hydride (ZrH ₂ ) particles: median particle size 5 μm
(organic vehicle)
A mixture obtained by mixing an acrylic resin as an organic binder and a mixed solvent of carbitol and terpineol as organic solvents (mass ratio of 1:1) at a mass ratio of organic binder:organic solvent=1:3.

[Preparation of conductive paste]
Each raw material was weighed according to the composition shown in Tables 1 to 3, mixed with a mixer, and then uniformly kneaded with a triple roll to obtain conductive paste 1 (conductive paste for filling) and conductive paste 2 (conductive paste for lamination). was prepared.

In Tables 1 and 2, the ratio (volume ratio) of the metal component A, the active metal, and the metal component C is the ratio to the total volume of the inorganic components in the conductive paste 1.

[Porosity (void ratio) of conductive via part]
The vicinity of the central portion of the conductive via portion of the via-filled substrate after baking was cut with a diamond saw in a direction perpendicular to the substrate, and the cut surface was finished smooth by ion milling. The processed sample was observed with a scanning electron microscope (manufactured by JEOL Ltd.), the presence of two phases was confirmed in the composition image, and the porosity (void ratio) of the conductive via portion was calculated by image analysis.

(Determination method)
◎: porosity (void ratio) 5% or less (accepted)
○: porosity (void ratio) more than 5% and 10% or less (accepted)
x: Porosity (void ratio) exceeds 10% (failed).

[Adhesion between conductive via part and substrate]
Regarding the adhesion between the conductive via portion and the substrate (the wall surface of the hole), the sample that had been smoothed and finished by the above ion milling was observed with a scanning electron microscope at a magnification of 3000 times. It was confirmed whether there was a gap between the part and the wall surface of the hole. In addition, since the coefficient of thermal expansion of the conductor is higher than that of the ceramic substrate, when the conductor shrinks more than the substrate when it cools down to room temperature after firing at a high temperature, the adhesion between the conductor and the substrate is insufficient. , the conductor is peeled off from the wall of the hole, resulting in a minute gap.

(Determination method)
◎: no gap (pass)
○: A gap of 0.5 μm or less exists locally (accepted)
×: There is a gap exceeding 0.5 μm (failed)

[Sealability (airtightness) of conductive via part]
Red ink was applied to the surface of the hole, and after sealing, the ink-coated surface was pressurized with compressed air at a pressure of 0.5 MPa for 60 seconds. Check for leakage of red ink from the opposite side of the hole.

(Determination method)
◎: Out of 10 holes, 0 holes for ink leakage (accepted)
◯: Up to 2 holes with ink leakage out of 10 holes (accepted)
x: 3 holes or more out of 10 holes for ink leakage (failed).

[Composition analysis of phase constituent metals]
The sample finished smooth by ion milling was observed with a scanning electron microscope to confirm the presence of different phases, and the constituent metal composition (% by mass) of each phase was confirmed by SEM-EDS analysis. For the SEM-EDS analysis, an energy dispersive X-ray fluorescence spectrometer JED-2300 attached to a scanning electron microscope JSM-IT300LA manufactured by JEOL Ltd. was used.

[Comprehensive evaluation method (ranking)]
The results of porosity, adhesion and sealability were judged and ranked according to the following criteria as a comprehensive evaluation.

A: Porosity (void ratio), adhesion, and sealability are all ◎ (accepted)
B: Porosity (void ratio), adhesion, and sealability are ◎ or ○ (pass)
C: Any of the porosity (void ratio), adhesion, and sealability is x (failed).

[Example 1]
A substrate was produced by the method shown below.

(Preparation of substrate)
A plurality of through-holes having diameters of φ0.1 mm and φ0.3 mm were formed in an aluminum nitride substrate (“170W” manufactured by MARUWA Co., Ltd.) of 2 inches×2 inches×0.5 mm in thickness using a laser device.

(Manufacturing process of via-filled substrate)
A metal mask (with a plate thickness of 0 The through-holes were filled by screen printing through a metal mask having an opening diameter of 0.2 mm larger than the diameter of the through-holes) and dried in a blower dryer at 120°C for 10 minutes. Thereafter, the substrate was passed through a buffing machine once to remove the conductive paste protruding from the substrate surface above the holes originating from the metal mask, thereby flattening the substrate surface.

After that, using the same metal mask as above, the conductive paste 2-1 is printed on one surface of the hole filled with the conductive paste 1-1, and the conductive paste 2 having a diameter 0.2 mm larger than the hole diameter is printed on the hole surface. A circular pattern was formed. The substrate on which the conductive paste 2-1 was printed was dried for 10 minutes in a blower dryer at 100°C. Regarding the through-hole with a hole diameter of φ0.3 mm, the amount of paste 2 printed once (wet film thickness of 0.1 mm) may not be enough to completely fill the void inside the hole. After the paste 2-1 was printed and dried, it was further overlapped and printed twice (three times in total).

The surface printed with the conductive paste 2-1 was placed on top of the substrate, and fired in a belt-type continuous firing furnace in a nitrogen atmosphere at a peak temperature of 900° C. for a peak retention time of 10 minutes. The total time from putting the substrate into the firing furnace to discharging the substrate after firing was 60 minutes.

The conditions and evaluation results of Example 1 are shown in Tables 4-7. Copper mixed powder (84.0% by volume) with different particle diameters containing metal component A that does not melt at the firing temperature, titanium hydride (5.7% by volume) as the active metal component, and tin powder (10.0% by volume) as the metal component C. 4% by volume) of the conductive paste 1-1 is used to fill the through-holes of the aluminum nitride substrate, and silver-copper alloy powder of 72% silver and 28% copper is applied to the upper surface of the filled conductive via portion as the metal component B. (melting point 780° C.) was printed, layered, and fired, the porosity (void ratio) of the conductive via portion, the adhesion between the conductive via portion and the substrate, and the sealing performance were confirmed. .

FIG. 3 is a cross-sectional SEM image of the hole (conductive via) in Example 1, and FIG. 4 is an enlarged image of the interface between the conductive via and the wall surface of the hole. FIG. 5 is an elemental mapping image of the active metal Ti at the interface between the conductive via portion and the hole wall surface. 4 and 5, the right side is the conductive via portion side. From the overall image of the cross section in FIG. 3, no voids were observed in the conductive via portion [porosity (void ratio) of 1% or less]. Further, from the enlarged image of the joint portion between the conductive via portion and the hole wall surface in FIG. 4, there was no gap between the conductive via portion and the hole wall surface, and the adhesion was excellent. Furthermore, the sealing property was also excellent.

Further, from the enlarged image of FIG. 4, it can be seen that two phases of gray and white are present in the conductive via portion. According to the composition analysis of the constituent metals of the phases, the metal composition of the dark gray phase is Cu/Ag=91/9 (Cu-rich phase), and the metal composition of the light white phase is Ag/Cu/Sn/Ti= 76.7/7/12/4.3 (Ag-rich phase). The Ag-rich phase corresponds to a portion where voids such as voids are filled with the conductive paste 2-1, and it can be presumed that this phase would have been a void if the conductive paste 2-1 were not used.

Further, from the Ti mapping image in FIG. 5, it can be seen that the Ti component, which is an active metal, exists in the Ag-rich phase, and particularly in the interface between the conductive via portion and the wall surface of the hole portion. It can be inferred that the active metal component contained in the conductive paste 1-1 diffused and segregated at the interface, bonded to the wall surface of the hole, and formed a strong adhesive force. In addition, in FIG. 5, the white region is the Ti component.

[Examples 2 to 6]
Instead of the conductive paste 1-1, conductive pastes 1-2, 1-3, 1-4, 1-5, and 1-6 are used as the metal component A that does not melt at the firing temperature in the conductive paste 1. Via-filled substrates were produced in the same manner as in Example 1, except that copper mixed powder, silver powder, nickel/copper mixed powder, molybdenum/copper mixed powder, and tungsten/copper mixed powder with different particle sizes were used.

The conditions and evaluation results of Examples 2-6 are shown in Tables 4-7. As in Example 1, favorable results were obtained in terms of porosity (void ratio), adhesion, and sealability.

FIG. 6 is a cross-sectional SEM image of the hole in Example 3, and FIG. 7 is an enlarged image of the interface between the conductive via portion and the wall surface of the hole in the hole. FIG. 8 is an elemental mapping image of the active metal Ti at the interface between the conductive via portion and the hole wall surface in the hole. 7 and 8, the left side is the conductive via portion side. Since silver powder was used as the metal component A, which is the main component of the conductive via portion, the area of the silver-rich phase (white phase) is large, and copper is contained in the metal component B and fills the voids. , the gray phase and the white phase are reversed from those in Example 1. This also shows that the metal component B contained in the lamination paste fills the voids and contributes to the denseness.

From the elemental mapping image of Ti in FIG. 8, it can be seen that, as in Example 1, a large amount of the Ti component, which is an active metal, is present at the interface between the conductive via portion and the hole wall surface. It can be inferred that the active metal component contained in the conductive paste 1-3 diffused, segregated at the interface, joined with the wall surface of the hole, and formed a strong adhesive force.

FIG. 9 is a cross-sectional SEM image of the hole in Example 4, and FIG. 10 is an enlarged image of the interface between the conductive via portion and the wall surface of the hole in the hole. In addition, in FIG. 10, the right side is the conductive via part side. The cross-sectional shape is similar to that of Example 1, and it can be seen that there are no voids, gaps, voids, or the like.

[Comparative Example 1] (an example in which the conductive paste 2 is not used)
After the hole was filled with the same conductive paste 1-1 as in Example 1, the conductive paste 2 was not printed on the upper surface of the hole, and it was fired at 900° C. in a nitrogen atmosphere. FIG. 11 shows a cross section of the hole (conductive via portion).

Since there is no molten metal component flowing into the hole (conductive via) from above, there are many voids throughout the hole (conductive via), and there is a large gap between the conductive via and the wall surface of the hole. exists. Therefore, all of the porosity (void ratio), adhesion, and sealing properties were rejected. Also, the metal component did not have a two-phase structure as in Example 1.

[Examples 7-9]
Example 1 except that conductive pastes 1-7, 1-8, and 1-9 were used instead of conductive paste 1-1, and metal component C was changed to bismuth particles, indium particles, and zinc particles, respectively. A via-filled substrate was produced in the same manner as in . Similar good results as in Example 1 were obtained even when the type of metal component C was changed.

[Examples 10 to 15]
Active metal (titanium hydride ) and metal component C (low-melting-point metal particles) for protecting the active metal were changed in the same manner as in Example 1 to fabricate a via-filled substrate.

The proportion of the active metal (titanium hydride) was 8.5% (Example 10), 12.6% (Example 11), and 17.8% with respect to 5.7% in the conductive paste 1-1. (Example 12), 24.2% (Example 13), 2.1% (Example 14), and 0.4% (Example 15). Correspondingly, the ratio of the metal component C was also 15.6% (Example 10), 17.3% (Example 11), 16.3% (Example 12), and 8.3% (Example 13). , 3.9% (Example 14) and 2.7% (Example 15).

In Example 13, in which the proportion of active metal is 24.2%, the porosity (void ratio) of the conductive via part is slightly high. Although the adhesion to the wall surface of the part slightly decreased, both were at a practical level. In the other examples, as in Example 1, good results were obtained in terms of porosity (void ratio), adhesion, and sealability.

[Examples 16-17]
In the same manner as in Examples 1 and 3, except that the conductive pastes 1-16 and 1-17 were used instead of the conductive pastes 1-1 and 1-3, and the active metal was changed to zirconium hydride. A via-filled substrate was fabricated. Similar to Examples 1 and 3 in which titanium hydride was used as the active metal, good results were obtained in terms of porosity (void ratio), adhesion and sealability.

[Examples 18-19]
Instead of the conductive paste 1-1, conductive pastes 1-18 and 1-19 were used, and the proportion of the metal component C was changed to 24.3% (Example 18) and 1.3% (Example 19). A via-filled substrate was produced in the same manner as in Example 1, except that

In Example 18, in which the ratio of the metal component C was high, some voids were present in the conductive via portion, and some gaps were observed at the interface between the conductive via portion and the hole wall surface, but the sealing performance was good. , was at a practical level. This is probably because the metal component B contained in the conductive paste 2-1 was less likely to penetrate during firing due to the increase in the amount of the metal component C, and internal voids and interfacial gaps remained.

On the other hand, in Example 19, in which the ratio of the metal component C was as low as 1%, the porosity (void ratio) and sealing properties were good, but the adhesion between the conductive via portion and the wall surface of the hole portion was poor (the interface was some gaps were observed). As a result, the amount of the metal component C (low-melting-point metal particles) for protecting the active metal was insufficient, the active metal could not be sufficiently protected, and the active metal reacted with nitrogen, resulting in a decrease in reactivity with the substrate. presumably because Therefore, the proportion of metal component C (low melting point metal) is preferably 2 to 20%.

[Comparative Example 2] (Example containing no metal component C)
A via-filled substrate was produced in the same manner as in Example 1, except that conductive paste 1-20 containing no metal component C (low-melting-point metal particles) was used instead of conductive paste 1-1. As a result, a gap was partially found at the interface with respect to the adhesion between the conductive via portion and the wall surface of the hole. Moreover, the sealing property was insufficient. This is because the metal component C (low-melting-point metal particles) does not exist, so the active metal cannot be protected during firing, and the active metal particles react with nitrogen or carbon, deactivating the conductive vias and the wall surfaces of the holes. It is considered that a gap was generated at the interface due to shrinkage of the conductive via portion because sufficient adhesion was not obtained.

12 is a cross-sectional SEM image of the hole in Comparative Example 2, and FIG. 13 is an elemental mapping image of the active metal Ti in the SEM image of FIG. 12 and 13, the upper side is the conductive via portion side. From the enlarged image of the interface in FIG. 12, the filled via portion was dense and had no voids, but a gap of 1 μm or more existed at the interface between the conductive via portion and the hole wall surface. Therefore, the sealing performance between the conductive via portion and the wall surface of the hole was insufficient. From the elemental mapping image of the active metal Ti in FIG. 13, Ti accumulated in the conductive via portion in the form of particles, and diffusion of the active metal component and segregation to the interface between the conductive via portion and the wall surface of the hole were not observed. This is because the metal component C (low-melting-point metal particles) does not exist, so the active metal particles react with nitrogen, carbon, etc. during firing to change into insoluble and non-reactive substances such as titanium nitride and titanium carbide. It is presumed that diffusion to the wall surface of the hole became impossible, and even if it diffused, reactivity disappeared, and peeling occurred at the interface due to shrinkage of the conductive via part due to insufficient adhesion to the wall surface of the hole. be. From this result, it can be seen that the metal component C (low-melting-point metal particles) contributes to the protection of the active metal particles and their diffusion to the interface.

[Comparative Example 3] (Example containing no active metal)
A via-filled substrate was produced in the same manner as in Example 1, except that conductive paste 1-21 containing no active metal was used instead of conductive paste 1-1. As a result, the adhesion and sealing properties were even lower than in Comparative Example 2, and the sample was rejected. This is presumably because there is no active metal that reacts with the substrate, so that sufficient adhesion between the conductive via portion and the wall surface of the hole cannot be obtained, and a gap is generated at the interface due to contraction of the conductive via portion.

[Comparative Example 4] (Example not containing active metal and metal component C)
A via-filled substrate was produced in the same manner as in Example 1, except that conductive paste 1-22 containing no active metal and metal component C was used instead of conductive paste 1-1. As a result, similarly to Comparative Example 3, the sealability and adhesion were rejected.

[Comparative Example 5] (an example in which an active metal (Ti) sputtered film was formed on the hole wall surface without containing the active metal and the metal component C in the conductive paste)
A sputtering device (“E-200S” manufactured by Canon Anelva Co., Ltd.) was applied to the surface of the aluminum nitride substrate and the wall surface inside the through hole (hole wall surface), and the voltage was 200 W, the argon gas was 0.5 Pa, and the substrate was heated to 200. °C, titanium and palladium were sputtered in that order. A ceramic substrate on which a Ti/Pd thin film was formed was obtained, in which the titanium layer had a thickness of 0.2 μm and the palladium layer had a thickness of 0.1 μm after sputtering.

A via-filled substrate was produced in the same manner as in Comparative Example 4 except that this substrate was used. As a result, the sealing performance was improved as compared with Comparative Example 4 (judgment: ◯), but the adhesion between the conductive via portion and the wall surface of the hole portion (partial gap was observed at the interface) was insufficient.

[Example 20] (an example in which an active metal (Ti) sputtered film was formed on the hole wall surface without containing an active metal in the conductive paste)
When the conductive paste 1-21 containing the metal component C (low-melting-point metal particles) is used for Comparative Example 5, that is, for Example 1, a substrate on which a Ti/Pd thin film is formed by sputtering on the wall surface of the hole is used, and a conductive paste 1-21 containing no active metal is used.

In this example, as in Example 1, the porosity (void ratio), adhesion, and sealability were all good. Compared to Comparative Example 5, the presence of metal component C (low-melting-point metal particles) in the conductive paste causes the active metal (Ti) contained in the thin film formed on the wall surface to be reduced by the metal component C contained in the conductive paste. Adhesion and sealability are improved by being protected and not deactivated and effectively contributing to the reaction with the substrate.

[Comparative Example 6] (Example that does not contain metal particles A as a main component)
A via-filled substrate was produced in the same manner as in Example 1, except that instead of the conductive paste 1-1, a conductive paste 1-23 containing no metal particles A (high-melting-point metal particles) as a main component was used. did. As a result, the conductor flowed out from the through-hole during firing, and the conductor could not be formed.

[Examples 21-22]
In contrast to Example 4 using a mixed metal powder of copper and nickel as the main component (metal component A), silver particles / copper particles = 70/30, 50/50 (mass ratio A via-filled substrate was produced in the same manner as in Example 4, except that the conductive pastes 2-2 and 2-3 using the mixed powder of ) were used.

Example 21 using a mixed powder of silver particles/copper particles=70/30 gave results equivalent to those of Example 4, and the same results as AgCu alloy particles were obtained even when the mixed powder of silver particles/copper particles was used. We have shown that This is because alloying progresses while silver particles and copper particles are sintered during the heating process during sintering, and the melting point is lowered, causing melt flow similar to AgCu alloy powder, resulting in a densification effect. It is considered to be

On the other hand, in Example 22 using a mixed powder of silver particles/copper particles=50/50, the porosity (void ratio) was slightly higher than that of Example 21, but the adhesion and sealing properties were good. This is because when the ratio of silver particles/copper particles becomes 50/50, the melting point rises due to the change in the AgCu alloy ratio, and the flowability of the conductive paste 2-3 during firing decreases, resulting in a compactness effect. is considered to have decreased slightly.

[Example 23]
In contrast to Example 1, conductive paste 2-4 using AgCuZnSn solder powder as metal component C (low melting point metal particles) was used instead of conductive paste 2-1, and the firing temperature was set to 800 ° C. , a via-filled substrate was produced in the same manner as in Example 1. As a result, good results equivalent to those of Example 1 were obtained.

[Example 24]
Conductive paste 2-5 using a mixed powder of silver particles/tin particles=88/12 (mass ratio) as metal component C (low-melting-point metal particles) instead of conductive paste 2-1 in Example 1. A via-filled substrate was produced in the same manner as in Example 1, except that . As a result, good results equivalent to those of Example 1 were obtained.

[Comparative Example 7] (when the firing temperature is lower than the melting point of the metal component B; an example in which the metal component B does not melt during firing)
A via-filled substrate was produced in the same manner as in Example 1, except that the firing temperature was set to 750° C., which is lower than the melting point (780° C.) of the metal component B.

FIG. 14 is a cross-sectional SEM image of the obtained hole (conductive via), and FIG. 15 is an enlarged image of the interface between the conductive via and the wall surface of the hole. In addition, in FIG. 15, the right side is the conductive via part side. There are many voids inside the conductive vias, and there are gaps at the interfaces between the conductive vias and the wall surfaces of the holes. rice field. This indicates that since the firing temperature is lower than the melting point of the metal component B of 780° C., the metal component B melts during firing and cannot flow into the pores, filling the voids and densifying. ing.

[Comparative Example 8] (an example in which the hole is filled with a full mixed paste in which all components are mixed from the beginning, and the full mixed paste is further laminated in the hole after filling)
Example 1, except that the entire mixed paste obtained by mixing the conductive paste 1-1 and the conductive paste 2-1 at a mass ratio of 1:1 was used as the conductive paste for filling and the conductive paste for lamination. A via-filled substrate was produced in a similar manner.

As a result, the porosity (void ratio), adhesion and sealing properties were all unsatisfactory. This is because the metal component B of the conductive paste for filling is present in the conductive paste for filling. It is presumed that this hindered the conductive paste from flowing into the holes. From this result, it can be seen that it is preferable not to add the metal component B to the conductive paste for filling, but to add it to the conductive paste for lamination.

[Examples 25-28]
A via-filled substrate was fabricated in the same manner as in Example 1, except that the material of the ceramic substrate was changed from aluminum nitride to alumina, sapphire, silicon nitride, and quartz glass. In both cases, the porosity (void ratio), adhesion, and sealability were good as in Example 1.

Tables 4 to 7 show the conditions and evaluation results of Examples and Comparative Examples.

The via-filled substrate of the present invention can be used for circuit boards, electronic components, semiconductor package substrates, and the like.

DESCRIPTION OF SYMBOLS 1, 11... Insulating substrate 1a, 11a... Hole 12... Metal film 3, 13... Conductive paste for filling 4, 14... Conductive paste for lamination 5, 15... Conductive via part

Claims (5)

filling a hole of an insulating substrate having a hole with a first conductive via precursor, filling the hole with the first conductive via precursor in the filling step; A method for producing a via-filled substrate, comprising a lamination step of laminating a second conductive via portion precursor thereon, and a baking step of baking the insulating substrate containing both precursors obtained in the lamination step in a nitrogen atmosphere. and
wherein the first conductive via part precursor contains a filling conductive paste containing a metal component A and a first organic vehicle;
The metal component A is a high melting point metal particle having a melting point exceeding the firing temperature,
The filling step includes a paste filling step of filling the hole with the filling conductive paste,
the second conductive via part precursor is a lamination conductive paste containing a metal component B and a second organic vehicle;
The metal component B is a difficult-to-melt metal particle having a melting point lower than the firing temperature,
The ratio of the metal component B is 100 to 1000 parts by volume with respect to 100 parts by volume of the first organic vehicle,
at least one of the first conductive via precursor and the second conductive via precursor contains an active metal component containing an active metal;
At least one of the filling conductive paste and the second conductive via portion precursor contains a metal component C, which is a readily fusible metal particle having a melting point lower than that of the hardly fusible metal particle,
The ratio of the metal component C is 1 to 40 parts by volume with respect to 100 parts by volume of the metal component A, and 2 to 20% by volume with respect to the total of the metal component A, the active metal component and the metal component C. manufacturing method. 2. The manufacturing method according to claim 1, wherein the filling conductive paste contains the active metal component and the metal component C. The first conductive via portion precursor contains the active metal component, and the filling step forms a metal film containing the active metal component on the hole wall surface of the hole as a pre-process of the paste filling step. 2. The manufacturing method according to claim 1, further comprising a step of forming a metal film. The refractory metal particles of the metal component A contain at least one refractory metal selected from the group consisting of Cu, Ag, Ni, W, Mo, Au, Pt and Pd or an alloy containing this refractory metal. ,
The difficult-to-melt metal particles of the metal component B have a melting point exceeding 450° C. and contain at least one high-melting-point metal selected from the group consisting of Cu, Ag, Ni, Au, Pt and Pd. including alloys,
The easily meltable metal particles of the metal component C have a melting point of 450° C. or less and are at least one easily meltable metal selected from the group consisting of Bi, Sn, In and Zn, or an alloy containing this easily meltable metal. including
The active metal component is at least one selected from the group consisting of active metals, alloys containing active metals, and active metal hydrides, and the active metal is selected from the group consisting of Ti, Zr and Nb. The production method according to any one of claims 1 to 3, wherein at least one active metal is used. A kit of conductive pastes for manufacturing a via -filled substrate, comprising:
A filling conductive paste containing a metal component A, which is a high melting point metal particle having a melting point higher than the firing temperature, a first organic vehicle, and a metal component B, which is a difficult-to-melt metal particle having a melting point lower than the firing temperature. , and a second organic vehicle in combination with a conductive lamination paste,
The ratio of the metal component B is 100 to 1000 parts by volume with respect to 100 parts by volume of the first organic vehicle,
At least one of the conductive filling paste and the conductive lamination paste contains an active metal component that is an active metal-containing particle containing an active metal,
At least one of the conductive paste for filling and the conductive paste for lamination contains a metal component C that is easily meltable metal particles having a melting point lower than that of the hardly meltable metal particles,
The ratio of the metal component C is 1 to 40 parts by volume with respect to 100 parts by volume of the metal component A, and 2 to 20% by volume with respect to the total of the metal component A, the active metal component and the metal component C. A kit that is.

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