Method for manufacturing a via-filled substrate and a set of conductive pastes

Abstract

A through-hole filled substrate in which a conductive via portion is easily manufactured, and which has high density, and high airtightness and adhesion between the conductive via portion and a hole portion. The through-hole filled substrate is manufactured by: a filling step of filling a first conductive via portion precursor including a filling conductive paste containing a high-melting-point metal particle, i.e., a metal component A, and a first organic vehicle, into a hole portion of an insulating substrate having the hole portion; a lamination step of laminating a laminating conductive paste containing a refractory metal particle, i.e., a metal component B, and a second organic vehicle, on the first conductive via portion precursor filled into the hole portion by the filling step; and a firing step of firing the insulating substrate including the two precursors obtained by the lamination step in a nitrogen atmosphere. The filling step includes a paste filling step of filling the filling conductive paste. At least one of the first conductive via portion precursor and the second conductive via portion precursor includes 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 having a lower melting point than the refractory metal particle.

Description

Technical Field

[0001] The present invention relates to a method for manufacturing a through-hole filled substrate (through-hole filled substrate) used in various electronic devices, and a kit for manufacturing the conductive paste for the through-hole filled substrate. Background Technology

[0002] Electronic substrates have long been used for configuring functional components and forming wiring circuits. In recent years, in order to miniaturize, increase the performance of electronic devices or components, the use of forming through-holes (holes or vias) in insulating substrates and placing conductive material within the through-holes to make the substrate electrically conductive on both sides is increasing. As a method to make the substrate electrically conductive on both sides, a method of plating conductive material within the through-holes is known, but this requires a plating process with high environmental impact, and therefore the process is complex and uneconomical.

[0003] In addition, there is a known method of obtaining a filled through-hole by filling it with a conductive paste (conductor paste) composed of metal powder and curable resin and then curing it. However, this filled through-hole also contains resin in a conductive material, so the conductivity is low, and the heat resistance is limited by the heat resistance of the resin, resulting in low heat resistance of the substrate.

[0004] Furthermore, a method is known to fill through-holes with a conductive paste composed of metal powder, inorganic binder, and resin, and then heat it to above the sintering temperature of the metal to sinter the metal powder, thereby obtaining conductive filled through-holes. This method is simple and efficient, and the resin component, acting as an organic carrier, evaporates and decomposes during sintering. Therefore, the filled through-holes obtained by this method also exhibit high conductivity, thermal conductivity, and heat resistance.

[0005] However, for through-hole filled substrates obtained by filling conductive paste into through-holes and then firing them, gaps and pores sometimes exist between the filled conductor (conductive through-hole portion) and the wall of the hole portion. As for the causes of these gaps and pores, it can be speculated that they are partly caused by shrinkage due to the removal (drying) of the solvent from the conductive paste filled into the hole portion, and shrinkage caused by the sintering of metal powder during high-temperature firing.

[0006] If there is a gap between the filling conductor and the wall, at least the following three problems may occur.

[0007] (1) When a conductive film (electrode, wiring, etc.) is formed across the filling portion on the substrate surface, the conductive film may break due to the presence of gaps, resulting in a decrease in conductivity or wire breakage.

[0008] (2) There may be gaps in the wall that are connected to each other along the wall, which may make it impossible to ensure the airtightness, weld resistance and other impermeability of the filling part.

[0009] (3) When the through-hole filled substrate is subjected to wet processes such as plating as a subsequent process, reagents may seep into the gap, causing defects such as cracking of the through-hole, blistering of the surface film, and discoloration.

[0010] Therefore, in the method of using conductive paste, a conductive paste that can suppress sintering shrinkage during firing has been proposed. Japanese Patent Application Publication No. 2009-59744 (Patent Document 1) discloses the following method: an oxide layer of an active metal is formed on the inner wall of a through hole, and then a conductor layer composed of the active metal is formed on the inner side of the oxide layer, thereby improving the adhesive force and adhesion between the inner through hole conductor and the through hole wall.

[0011] Patent document 1 does not disclose detailed information about the conductive paste used to form the conductive via, nor does it verify the airtightness and impermeability of the via-filled substrate.

[0012] Furthermore, Japanese Patent Application Publication No. 2017-63109 (Patent Document 2) discloses a method for manufacturing a via-filled substrate, which includes: a metal film forming step of forming a metal film containing an active metal on the wall surface of a via of an insulating substrate having vias; a filling step of filling a conductor paste with a volume change rate of -10% to 20% before and after firing into the vias in which the metal film is formed; and a firing step of firing the insulating substrate filled with conductor paste.

[0013] Japanese Patent Application Publication No. 2013-153051 (Patent Document 3) discloses a metallized ceramic through-hole substrate, which is a metallized ceramic through-hole substrate on which conductive through-holes are formed. The conductive through-holes are formed by tightly filling the through-holes of the ceramic sintered substrate with a conductive metal containing a metal (A) with a melting point of 600°C or higher and 1100°C or lower, a metal (B) with a melting point higher than that metal (A), and an active metal. At least one of the two sides of the ceramic sintered substrate has a wiring pattern. The wiring pattern has a surface conductive layer composed of a conductive metal containing the aforementioned metal (A), the aforementioned metal (B), and the active metal. The wiring pattern has a plating layer on the surface of the surface conductive layer. An active layer is formed at the interface between the conductive through-holes and the ceramic sintered substrate, and at the interface between the surface conductive layer and the ceramic sintered substrate.

[0014] Existing technical documents

[0015] Patent documents

[0016] Patent Document 1: Japanese Patent Application Publication No. 2009-59744

[0017] Patent Document 2: Japanese Patent Application Publication No. 2017-63109

[0018] Patent Document 3: Japanese Patent Application Publication No. 2013-153051 Summary of the Invention

[0019] The problem that the invention aims to solve

[0020] However, for the via-filled substrates of Patent Documents 1 and 2, although the airtightness and sealing with the via wall can be improved to some extent by forming an active metal layer, it may not be sufficient to improve conductivity and thermal conductivity. The reason for this is presumably that the density of the conductive via portion itself in these via-filled substrates is low. Specifically, in the method of filling the via with a conductive paste containing an organic carrier, the organic carrier disappears due to evaporation and decomposition, creating voids (pores). Therefore, the interior of the conductive via portion (filled conductor) becomes porous, and its density is easily reduced. That is, in the methods of Patent Documents 1 and 2, compared to a bulk metal without pores, conductivity and thermal conductivity are inevitably significantly reduced, making it difficult to improve density. Therefore, in the method of filling the via with a conductive paste containing an organic carrier, in addition to the aforementioned airtightness and sealing, the density of the conductive via portion is also required. Furthermore, for the metallized ceramic through-hole substrate of Patent Document 3, in order to prevent reactive gases such as oxygen and nitrogen from reacting with the active metal, a heat-resistant container must be used in a non-reactive atmosphere such as a vacuum, and it cannot be manufactured by a simple method.

[0021] Therefore, the object of the present invention is to provide a method for easily manufacturing a through-hole filled substrate with high density of conductive via portions and high airtightness and tightness between the conductive via portions and the via walls, as well as a kit for manufacturing the aforementioned through-hole filled substrate with conductive paste.

[0022] Methods for solving problems

[0023] In order to solve the above-mentioned problems, the inventors conducted in-depth research and found that by filling the holes of an insulating substrate with holes with a specific first conductive via precursor, stacking a specific second conductive via precursor on the filled first conductive via precursor, and firing it in a nitrogen atmosphere, it is possible to easily manufacture a via-hole filled substrate with high density of conductive vias and high airtightness and sealing between conductive vias and holes, thus completing the present invention.

[0024] That is, the manufacturing method of the via-filled substrate of the present invention includes: a filling step of filling the hole portion of an insulating substrate having a hole portion with a first conductive via portion precursor; a lamination step of laminating a second conductive via portion precursor onto the first conductive via portion precursor filled into the hole portion by the filling step; and a firing step of firing the insulating substrate containing the two precursors obtained by the lamination step under a nitrogen atmosphere, wherein the first conductive via portion precursor includes a conductive paste for filling containing a metal component A and a first organic carrier, wherein the metal component A is a high melting point metal particle having a melting point higher than the firing temperature. The filling process includes a paste filling process of filling the above-mentioned conductive paste into the above-mentioned hole portion. The above-mentioned second conductive through-hole portion precursor is a laminated conductive paste containing metal component B and a second organic carrier. The above-mentioned metal component B is refractory metal particles with a melting point lower than the firing temperature. At least one of the above-mentioned first conductive through-hole portion precursor and the above-mentioned second conductive through-hole portion precursor contains an active metal component containing an active metal. At least one of the above-mentioned filling conductive paste and the above-mentioned second conductive through-hole portion precursor contains a metal component C. The metal component C is fusible metal particles with a melting point lower than the above-mentioned refractory metal particles.

[0025] The conductive paste for filling may contain the aforementioned active metal component and the aforementioned metal component C. The precursor for the first conductive via may contain the aforementioned active metal component, and the filling process may further include a metal film forming process, which forms a metal film containing the aforementioned active metal component on the wall surface of the via, as a pre-process for the paste filling process. The high-melting-point metal particles of the aforementioned metal component A may contain 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 such a high-melting-point metal. The refractory metal particles of the aforementioned metal component B may have a melting point higher than 450°C and contain a refractory alloy containing at least one high-melting-point metal selected from the group consisting of Cu, Ag, Ni, Au, Pt, and Pd. The fusible metal particles of the aforementioned metal component C may have a melting point lower than 450°C and contain at least one fusible metal selected from the group consisting of Bi, Sn, In, and Zn, or an alloy containing such a fusible metal. The aforementioned active metal component may be at least one selected from the group consisting of active metals, alloys containing active metals, and hydrides of active metals, and the aforementioned active metal may be at least one selected from the group consisting of Ti, Zr, and Nb.

[0026] The present invention also includes a kit for manufacturing a through-hole filled substrate by the above-described manufacturing method, wherein the kit is a combination of a filling conductive paste and a laminating conductive paste. The filling conductive paste contains a metal component A and a first organic carrier. The metal component A is a high-melting-point metal particle having a melting point higher than the firing temperature. The laminating conductive paste contains a metal component B and a second organic carrier. The metal component B is a refractory metal particle having a melting point lower than the firing temperature. At least one of the filling conductive paste and the laminating conductive paste contains an active metal component. The active metal component is an active metal particle containing an active metal. At least one of the filling conductive paste and the laminating conductive paste contains a metal component C. The metal component C is a fusible metal particle having a melting point lower than the refractory metal particle.

[0027] It should be noted that, in this application, "precursor for conductive via" refers to all unburned material introduced into the hole of the insulating substrate for forming a conductive via. Therefore, when a metal film is formed on the wall of the hole by sputtering or the like before introducing the conductive paste for filling, the first precursor for conductive via includes not only the conductive paste for filling introduced into the hole, but also the metal film.

[0028] Invention Effects

[0029] In this invention, by filling the holes of an insulating substrate with pores with a specific first conductive via precursor, then stacking a specific second conductive via precursor on the filled first conductive via precursor and sintering under a nitrogen atmosphere, it is possible to easily manufacture a via-filled substrate with high density of conductive vias and high airtightness and sealing between the conductive vias and the holes (through holes). In particular, the filling density of the conductive vias can be increased, reducing the porosity caused by gaps and pores to below 10% by volume, thereby improving electrical and thermal conductivity. Furthermore, the sealing force between the hole wall and the conductive vias can be increased, enabling the fabrication of a via-filled substrate with substantially no gap between the hole wall and the conductive vias. Attached Figure Description

[0030] Figure 1 This is a schematic process diagram illustrating an example of a method for manufacturing a through-hole filled substrate according to the present invention.

[0031] Figure 2 This is a schematic process diagram illustrating another example of a method for manufacturing a through-hole filled substrate according to the present invention.

[0032] Figure 3 This is a cross-sectional scanning electron microscope (SEM) image of the hole portion (conductive through-hole portion) in the through-hole filled substrate obtained in Example 1.

[0033] Figure 4 yes Figure 3 A magnified image of the interface between the conductive via and the via wall in the SEM image.

[0034] Figure 5 yes Figure 3 The elemental distribution of active metal Ti at the interface between the conductive via and the via wall in the SEM image.

[0035] Figure 6 This is a cross-sectional SEM image of the conductive via portion in the via-filled substrate obtained in Example 3.

[0036] Figure 7 yes Figure 6 A magnified image of the interface between the conductive via and the via wall in the SEM image.

[0037] Figure 8 yes Figure 6 The elemental distribution of active metal Ti at the interface between the conductive via and the via wall in the SEM image.

[0038] Figure 9 This is a cross-sectional SEM image of the conductive via portion in the via-filled substrate obtained in Example 4.

[0039] Figure 10 yes Figure 9 The elemental distribution of active metal Ti at the interface between the conductive via and the via wall in the SEM image.

[0040] Figure 11 This shows a cross-sectional SEM image of the conductive via portion in the via-filled substrate obtained in Comparative Example 1.

[0041] Figure 12 This shows a cross-sectional SEM image (enlarged image of the interface between the conductive via portion and the via wall) of the via-filled substrate obtained in Comparative Example 2.

[0042] Figure 13 yes Figure 12 The elemental distribution of active metal Ti in the SEM image.

[0043] Figure 14 This shows a cross-sectional SEM image of the conductive via portion in the via-filled substrate obtained in Comparative Example 7.

[0044] Figure 15 yes Figure 14 A magnified image of the interface between the conductive via and the via wall in the SEM image. Detailed Implementation

[0045] [Manufacturing method of through-hole filled substrate]

[0046] The method for manufacturing a via-filled substrate of the present invention includes: a filling step of filling a first conductive via precursor into the hole of an insulating substrate having a hole; a stacking step of stacking a second conductive via precursor onto the first conductive via precursor filled in the filling step; and a firing step of firing the insulating substrate containing the two precursors obtained by the stacking step under a nitrogen atmosphere.

[0047] In this invention, by combining the above-mentioned filling process and the above-mentioned lamination process, the airtightness and tightness of the conductive through-hole portion and the hole wall can be improved, and the density of the conductive through-hole portion can also be improved. The reason for this can be inferred as follows.

[0048] In the method of the present invention, during the firing process, metal component A does not melt at the firing temperature, thus having the shape (skeleton) to form the filling portion, and therefore the main component responsible for the conductivity of the conductive via portion does not flow out of the via portion. As described above, when the conductive paste filling the via portion is fired, voids (pores) are generated as the organic carrier disappears. In contrast, in the method of the present invention, after filling the via portion with a first conductive via portion precursor containing conductive paste containing metal component A and organic carrier, a second conductive via portion precursor containing metal component B as refractory metal particles is stacked on the first conductive via portion precursor, preferably firing in a dry state at a temperature higher than the melting point of metal component B. It can be inferred that as a result, molten metal component B flows into the voids generated by the disappearance of the organic carrier and the gaps between the particles of metal component A (especially the pores generated by the disappearance of the large organic carrier), filling the voids and gaps while sintering the metal, thereby achieving overall dense sintering and improving the density of the conductive via portion. Furthermore, it can be inferred that the metal component B also flows into the gap between the hole wall and the first conductive through hole, and sinters the metal while filling the gap, thereby improving the airtightness and tightness.

[0049] Furthermore, in the method of the present invention, during the firing process, the metal component C (fusible metal particles) melts at a low temperature and covers the surface of the active metal component (active metal particles). This prevents the active metal component from reacting with surrounding gases (nitrogen in the firing atmosphere, carbon produced by the decomposition of organic carriers, volatile organic compounds, etc.) even at high temperatures. Through this effect, the active metal component can maintain its activity up to high temperatures even in a nitrogen atmosphere. By containing an active metal that has retained its activity in the fusible metal component, the molten metal wets the insulating substrate, allowing a reaction to occur between the active metal and the insulating substrate, thus enabling a firm bond between the conductive via and the via wall. It should be noted that the fusible metal (metal component C) liquefies and flows as described in the text; therefore, it can be inferred that the fusible metal component also wets the surface of the high-melting-point metal particles, thereby preventing excessive flow. Depending on the type of fusible metal and the high-melting-point metal, alloying occurs between the fusible metal and the high-melting-point metal during firing, increasing the melting point of the fusible metal; this also helps to suppress flow. In particular, in the method of the present invention, by utilizing the effect of the fusible metal component to maintain the activity of the active metal component, an insulating substrate can be manufactured by firing under a nitrogen atmosphere. Therefore, it is possible to easily manufacture such through-hole filled substrates with excellent properties, and the productivity is also high.

[0050] It can be inferred that metal components A, B, active metal components, and C can improve the density of the conductive via and the airtightness and sealing between the conductive via and the hole (hereinafter referred to as "density, airtightness, and sealing") through such an action. Active metal components and metal component C can be contained in the conductive paste for filling and / or the conductive paste for lamination, and the active metal components can be pre-laminated on the wall surface of the hole.

[0051] (Filling process)

[0052] In the filling process, the first conductive via portion uses a precursor containing a conductive paste for filling containing a metal component A and a first organic carrier, and the filling process includes a paste filling process for filling the conductive paste for filling.

[0053] (a) Paste filling process

[0054] In the above-mentioned paste filling process, the conductive paste for filling contains a metal component A, which is a high-melting-point metal particle with a melting point higher than the firing temperature.

[0055] (a1) Metal composition A

[0056] The metal that forms the high-melting-point metal particles, which is metal component A, is not particularly limited as long as it has a melting point higher than the firing temperature (e.g., 600°C or higher). The aforementioned metal can be a high-melting-point elemental metal or an alloy containing the aforementioned high-melting-point metal. Specifically, examples of the aforementioned high-melting-point metals include Cu, Ag, Ni, W, Mo, Au, Pt, and Pd. The alloy containing the aforementioned high-melting-point metal can be an alloy of the aforementioned high-melting-point metals with each other, or an alloy of the aforementioned high-melting-point metal with other metals. For other metals, there is no particular limitation as long as the alloy's melting point is higher than the firing temperature; any metal capable of forming an alloy with the aforementioned high-melting-point metal is acceptable. Examples of other metals include: refractory metals listed in the section on metal component B (described later), fusible metals listed in the section on metal component C (described later), and active metals listed in the section on active metal components (described later). Other metals can also be used alone or in combination of two or more.

[0057] 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 such high-melting-point metal. It is particularly preferred to select at least one high-melting-point metal selected from the group consisting of Cu, Ag, Ni, W and Mo, or an alloy containing such high-melting-point metal.

[0058] These high-melting-point metal particles can be used alone or in combination of two or more. Furthermore, from the viewpoint of facilitating the control of the sinterability of the particles during firing and making it easier to maintain the shape of the conductive through-holes, it is preferable to combine two or more high-melting-point metal particles.

[0059] Among these metal particles, Cu particles (melting point 1085°C) and Ag particles (melting point 962°C) are preferred from the viewpoint that they have excellent electrical conductivity, low melting point, and are easy to sinter together at a firing temperature of 800–950°C. From the viewpoint of economy, Cu particles are particularly preferred.

[0060] Cu particles can be combined with other high-melting-point metal particles, preferably a combination of Cu particles with at least one metal particle selected from the group consisting of Ni, W, and Mo. When Cu particles are combined with other high-melting-point metal particles, the proportion of the other high-melting-point metal particles is, for example, 10 to 1000 parts by volume relative to 100 parts by volume of Cu particles, preferably 30 to 500 parts by volume, more preferably 50 to 300 parts by volume, and more preferably 80 to 200 parts by volume.

[0061] Furthermore, from the viewpoint of further improving airtightness and sealing, the high-melting-point metal particles preferably contain low-thermal-expansion metal particles (especially W particles and / or Mo particles) with a small coefficient of thermal expansion. By containing low-thermal-expansion metal particles with a small coefficient of thermal expansion, the difference in thermal expansion coefficient with the insulating substrate can be reduced. Therefore, shrinkage of the conductive vias caused by cooling after firing can be suppressed, and peeling from the via walls of the insulating substrate can be suppressed.

[0062] Low thermal expansion metal particles can be combined with high thermal expansion metal particles (high melting point metal particles other than low thermal expansion metal particles), preferably with Cu particles and / or Ag particles with excellent sinterability. When combining low thermal expansion metal particles (especially W particles and / or Mo particles) with high thermal expansion metal particles (especially Cu particles and / or Ag particles), the proportion of low thermal expansion metal particles relative to the total volume of high thermal expansion metal particles is, for example, 10-99 vol%, preferably 30-90 vol%, more preferably 50-80 vol%, and more preferably 60-70 vol%.

[0063] It should be noted that in this application, the volume ratio is the volume ratio at 25°C and atmospheric pressure.

[0064] Examples of shapes for high-melting-point metal particles include: spherical (perfectly spherical or nearly spherical), ellipsoidal (ellipsoidal sphere), polyhedral (pyramidal, cubic, cuboid, or other polygonal prism shapes), plate-like (flat, scaly, or sheet-like), rod-like, fibrous, spur-like, and amorphous. High-melting-point metal particles are typically spherical, ellipsoidal, polyhedral, or amorphous. From the perspective of increasing filling density and improving paste flowability, spherical shapes are preferred.

[0065] From the viewpoint of improving the fluidity of the paste, the density after firing, and the airtightness and tightness, the median particle size (D50) of the high-melting-point metal particles can be about 100 μm or less (especially about 50 μm or less), for example, 0.001 to 50 μm, preferably 0.01 to 20 μm, more preferably 0.1 to 10 μm, and more preferably 0.2 to 10 μm. If the median particle size is too large, it may be difficult to fill small pores.

[0066] From the viewpoint of being able to increase the metal content in the paste and improve the density and conductivity of the conductive via, the high melting point metal particles are preferably a combination of high melting point metal small particles (hereinafter referred to as "small particles") with a particle size of less than 3 μm (for example, 1 nm or more and less than 3 μm) and high melting point metal large particles (hereinafter referred to as "large particles") with a particle size of 3 to 50 μm.

[0067] The median particle size of the small particles is, for example, 0.1–2.5 μm, preferably 0.2–2 μm, more preferably 0.25–1.5 μm, and even more preferably 0.3–1 μm. If the median particle size of the small particles is too small, the viscosity of the conductor paste may increase, making it difficult to work with; if it is too large, the effect of improving density may be reduced.

[0068] The median particle size of the large particles is, for example, 3–30 μm, preferably 4–20 μm, more preferably 4.5–15 μm, and even more preferably 5–10 μm. If the median particle size of the large particles is too small, the sintering shrinkage of the conductor paste may increase; if it is too large, the filling performance of the conductive vias may decrease.

[0069] It should be noted that, in this application, the median particle size refers to the average particle size (volume standard) measured using a laser diffraction scattering particle size distribution measuring device.

[0070] When combining small and large particles as high-melting-point metal particles, the proportion of small particles relative to 100 volume parts of large particles is, for example, 1 to 100 volume parts, preferably 5 to 80 volume parts, more preferably 10 to 50 volume parts, and even more preferably 20 to 40 volume parts. If the proportion of small particles is too small, the filling performance of the conductive via may be reduced; if it is too large, the operability may be reduced.

[0071] The melting point of the high-melting-point metal particles can be higher than the firing temperature, for example, above 600°C. Specifically, it can be selected from the range of about 600°C to about 4000°C, for example, 800 to 2500°C, preferably 850 to 2000°C, more preferably 900 to 1500°C, and even more preferably 950 to 1200°C. If the melting point is too low, the electrical conductivity and heat resistance may decrease.

[0072] Metal component A, being a high-melting-point metal particle, has such a melting point that it does not melt during the firing process, but can undergo sintering between the particles of metal component A, or alloying with metal component B through sintering.

[0073] High-melting-point metal particles can be manufactured using conventional methods, such as wet reduction, electrolysis, atomization, and water atomization.

[0074] The proportion of metal component A (high melting point metal particles) in the conductive paste for filling can 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, and even more preferably 45 to 55% by volume. If the proportion of metal component A is too low, the shape retention of the conductive via may be reduced.

[0075] The volume percentage of metal component A, relative to the total volume of metal component A, metal component C, and active metal component contained in the precursor of the first conductive via (hereinafter referred to as the "total volume of inorganic components"), can 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, and more preferably 80 to 90% by volume. If the volume percentage of metal component A is too small, the conformability of the conductive via may be reduced, or pores or gaps may be generated; if it is too large, the adhesion between the conductive via and the wall of the via may be reduced.

[0076] (a2) First organic carrier

[0077] In order to make it into a paste (a fluid state), the above-mentioned conductive paste for filling contains an organic carrier (first organic carrier) in addition to the above-mentioned metal component A.

[0078] The first organic carrier can be a conventional organic carrier used as an organic carrier for conductive pastes containing metal particles, for example, it can be an organic binder and / or an organic solvent. The organic carrier can be either an organic binder or an organic solvent, typically a combination of an organic binder and an organic solvent (an organic solvent-based solution of an organic binder).

[0079] As organic binders, there are no particular limitations, but examples include: thermoplastic resins (olefin resins, vinyl resins, acrylic resins, styrene resins, polyether resins, polyester resins, polyamide resins, cellulose derivatives, etc.), thermosetting resins (thermosetting acrylic resins, epoxy resins, phenolic resins, unsaturated polyester resins, polyurethane resins, etc.). These organic binders can be used alone or in combination of two or more. Among these organic binders, resins that are easy to burn off during firing and have low ash content are widely used, 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.). From the viewpoint of thermal decomposition, poly(methyl methacrylate) and poly(butyl methacrylate) are preferred. 1-10 Alkyl esters.

[0080] There are no particular limitations on the organic solvent used; any organic compound that can impart appropriate viscosity to the paste and is easily volatile after drying when the paste is applied to the substrate is acceptable. High-boiling-point organic solvents are also acceptable. Examples of such organic solvents include: aromatic hydrocarbons (e.g., p-xylene), esters (e.g., ethyl lactate), ketones (e.g., isophorone), amides (e.g., dimethylformamide), aliphatic alcohols (e.g., octanol, decanol, diacetone alcohol), cellosolves (e.g., methyl cellosolve, ethyl cellosolve), cellosolve acetates (e.g., ethyl cellosolve acetate, butyl cellosolve acetate), carbitols (e.g., carbitol, methyl carbitol, ethyl carbitol), and carbitol acetates (e.g., ethyl carbitol). Organic solvents include butyl carbitol acetate, aliphatic polyols (ethylene glycol, diethylene glycol, dipropylene glycol, butanediol, triethylene glycol, glycerol, etc.), alicyclic alcohols [e.g., cyclohexanols such as cyclohexanol; terpenols such as dihydroterpenol (monoterpenols, etc.)], aromatic alcohols (m-cresol, etc.), aromatic carboxylic acid esters (dibutyl phthalate, dioctyl phthalate, etc.), and nitrogen-containing heterocyclic compounds (dimethylimidazol, dimethylimidazolinone, etc.). These organic solvents can be used alone or in combination of two or more. From the viewpoint of paste flowability, carbitols such as carbitol and alicyclic alcohols such as terpenol are preferred among these organic solvents.

[0081] When an organic binder is combined with an organic solvent, the proportion of the organic binder is, for example, about 1 to about 200 parts by mass, preferably about 10 to about 100 parts by mass, and more preferably about 20 to about 50 parts by mass, relative to 100 parts by mass of the organic solvent, and 5 to 80% by mass, preferably 10 to 50% by mass, and more preferably 20 to 30% by mass, relative to the total organic carrier.

[0082] The proportion of the first organic carrier is, for example, 10 to 300 parts by volume, preferably 30 to 200 parts by volume, more preferably 50 to 150 parts by volume, and more preferably 70 to 100 parts by volume relative to 100 parts by volume of metal component A. If the proportion of the first organic carrier is too small, the operability may be reduced; if it is too large, the tightness, airtightness, and sealing properties may be reduced.

[0083] (a3) Metallic composition C

[0084] In addition to metal component A and the first organic carrier, the aforementioned conductive paste for filling may also contain metal component C (first metal component C), which is a fusible metal particle with a lower melting point (preferably below 450°C) than the refractory metal particles described later as metal component B, in order to improve the aforementioned airtightness and adhesion by protecting the active metal component and suppressing the reaction between nitrogen, oxygen, carbon, etc., and the active metal at high temperatures. It should be noted that the conductive paste for filling may not contain metal component C, but if the conductive paste for filling does not contain metal component C, the conductive paste for lamination (precursor for the second conductive via portion) described later must contain metal component C. That is, it is sufficient for at least one of the conductive paste for filling and the conductive paste for lamination to contain metal component C. From the viewpoint of improving density, airtightness, and adhesion, it is preferable that at least the conductive paste for filling contains metal component C, and more preferably, only the conductive paste for filling contains metal component C.

[0085] The metal that forms the fusible metal particles, which is metal component C, is not particularly limited as long as it has a lower melting point than the refractory metal particles. The metal forming the fusible metal particles can be a fusible element or an alloy containing the aforementioned fusible metal. Specifically, examples of the aforementioned fusible metals include Bi, Sn, In, and Zn. The alloy containing the aforementioned fusible metal can be an alloy of the aforementioned fusible metals themselves or an alloy of the aforementioned fusible metal with other metals. Regarding the other metals, there is no particular limitation as long as the melting point of the alloy is lower than that of the refractory metal particles; any metal capable of forming an alloy with the aforementioned fusible metal is acceptable. Examples of other metals include refractory metals listed in the section on metal component B (described later) and active metals listed in the section on active metal components (described later). Other metals can be used alone or in combination of two or more.

[0086] The metal constituting the fusible metal particles is preferably a metal that contains at least one fusible metal selected from the group consisting of Bi, Sn, In and Zn, or an alloy containing such fusible metal.

[0087] 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 further preferred, with Sn particles being particularly preferred.

[0088] Regarding the shape of the fusible metal particles, including both the usual and preferred methods, the shapes can be selected from those exemplified above as the shapes of the high-melting-point metal particles of metal component A.

[0089] The median particle size (D50) of the fusible metal particles can be selected from the range of about 0.1 μm to about 100 μm. From the viewpoint of operability of the conductive paste for filling and effectiveness even with smaller quantities, for example, it is 0.2 to 30 μm, preferably 0.5 to 20 μm, and more preferably 1 to 10 μm.

[0090] To protect the surface of the active metal component (active metal particles) from reaction with nitrogen or other gases in the firing atmosphere, the melting point of the fusible metal particles is preferably below 450°C. Specifically, it can be selected from a range of about 100°C to about 450°C, for example, 130–420°C, preferably 150–400°C, more preferably 180–300°C, and even more preferably 200–250°C. If the melting point of the fusible metal particles is too high, the function of the molten fusible metal particles in protecting the surface of the active metal component (active metal particles) may be reduced, resulting in insufficient adhesion between the conductive via and the via wall, and reduced airtightness and sealing.

[0091] Compared to metal component A, which is the main component responsible for conductivity, metal component C has lower conductivity. Therefore, it is preferable to adjust it to the proportion required to protect the active metal. The proportion of metal component C can be selected from about 1 to about 40 parts by volume relative to 100 parts by volume of 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, and more preferably 10 to 15 parts by volume. If the proportion of metal component C is too low, the function that emerges during firing may be reduced, the bonding force between the conductive through-hole and the hole wall may be insufficient, and the airtightness and sealing may be reduced. If the proportion of metal component C is too high, the conductivity and heat resistance of the conductive through-hole may be reduced, or the molten metal component C may enter the interparticles of metal component A (high melting point metal particles), obstructing the flow path of metal component B flowing in from the surface and failing to fill the holes (voids). In addition, if the proportion of metal component C is too high, metal component C may also flow out from the filling part during firing.

[0092] The metal component C can be formulated in a volume ratio such that the total volume of the metal component C contained in the precursor for the first conductive via portion is, for example, 0.5 to 30 vol%, preferably 1 to 25 vol%, more preferably 3 to 20 vol%, and more preferably 5 to 15 vol%.

[0093] (a4) Active metal components

[0094] In the aforementioned conductive paste for filling, in addition to metal component A and the first organic carrier, an active metal component (first active metal component) may also be included to improve the adhesion between metal component A and the insulating substrate. It should be noted that the conductive paste for filling may also be free of the active metal component, but if the conductive paste for filling is free of the active metal component, the metal film and / or the conductive paste for lamination (described later) must contain the active metal component. That is, at least one of the conductive paste for filling, the metal film, and the conductive paste for lamination needs to contain the active metal component. From the viewpoint of improving density, airtightness, and adhesion, it is preferable that the conductive paste for filling and / or the metal film contains the active metal component; more preferably, at least the conductive paste for filling contains the active metal component; and even more preferably, only the conductive paste for filling contains the active metal component. It should be noted that the metal film is not mandatory.

[0095] The active metal component contained in the conductive paste for filling can be active metal particles. Examples of active metals included in the active metal particles include Ti, Zr, Hf, and Nb. These active metals can be used alone or in combination of two or more. From the viewpoint of having excellent activity during the firing process and being able to improve the bonding force between the insulating substrate and the conductive via, at least one of the group consisting of Ti, Zr, and Nb is preferred, more preferably Ti and / or Zr, and particularly preferably Ti.

[0096] The active metal particles can be formed from active metal elements, but from the viewpoint of excellent activity in the firing process, it is preferable to form them from compounds containing active metals.

[0097] The compound containing an active metal is not particularly limited, and examples include titanium hydride (TiH2), zirconium hydride (ZrH2), and niobium hydride (HNb). Among these, titanium hydride (TiH2) is preferred from the viewpoint of excellent activity during the sintering process.

[0098] These active metal particles can be used alone or in combination of two or more, with titanium hydride particles and / or zirconium hydride particles being more preferred, and titanium hydride particles being particularly preferred.

[0099] The shapes of the active metal particles described above include both common and preferred forms, and can be selected from the shapes exemplified above as the shapes of the high-melting-point metal particles that constitute metal component A.

[0100] The median particle size (D50) of the above-mentioned active metal particles can be selected from the range of about 0.1 μm to about 100 μm. From the viewpoint of operability of the conductive paste for filling, for example, it is 0.2 to 50 μm, preferably 0.5 to 20 μm, and more preferably 1 to 10 μm.

[0101] The proportion of the active metal component can be selected from about 0.3 to about 40 parts by volume relative to 100 parts by volume of metal component A, for example, 0.4 to 36 parts by volume, preferably 1 to 30 parts by volume, more preferably 2 to 30 parts by volume, more preferably 3 to 20 parts by volume, and most preferably 5 to 10 parts by volume. If the proportion of the active metal component is too small, the bonding force between the conductive via and the via wall may be insufficient, resulting in reduced airtightness and sealing. If the proportion is too large, conductivity and sinterability may be reduced.

[0102] The active metal component can be formulated in a ratio of the total volume of the active metal component contained in the precursor of the first conductive via to the total volume of the inorganic component, for example, 0.1 to 30 vol%, preferably 0.3 to 25 vol%, more preferably 0.5 to 20 vol%, more preferably 1 to 15 vol%, and most preferably 3 to 10 vol%.

[0103] (a5) Other components

[0104] In addition to the metal component A and the first organic carrier, the conductive paste for filling described above may contain conventional additives without impairing the effects of the present invention. Examples of conventional additives include: inorganic binders (glass frit, etc.), curing agents (curing agents for acrylic resins, etc.), coefficient of thermal expansion modifiers (silica powder, etc.), colorants (dyes, pigments, etc.), color improvers, dye fixatives, brighteners, metal corrosion inhibitors, stabilizers (antioxidants, UV absorbers, etc.), surfactants or dispersants (anionic surfactants, cationic surfactants, nonionic surfactants, amphoteric surfactants, etc.), dispersion stabilizers, viscosity modifiers or rheology modifiers, humectants, thixotropic agents, leveling agents, defoamers, bactericides, fillers, etc. These additives may be used alone or in combination of two or more. The proportions of other components can be selected according to the type of component, and are generally about 10% by mass or less (e.g., about 0.01% by mass to about 10% by mass) relative to the overall conductive paste for filling.

[0105] (a6) Insulating substrate

[0106] Regarding the material of the insulating substrate in which the holes are filled with the aforementioned conductive paste, heat resistance is required due to the firing process. It can be an organic material such as engineering plastics, but it is usually an inorganic material (inorganic raw material).

[0107] As inorganic materials, examples include: ceramics {metal oxides (quartz, alumina or aluminum oxide, zirconium oxide, sapphire, ferrite, titanium dioxide or titanium oxide, zinc oxide, niobium oxide, mullite, beryllium oxide, 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, boron bromide, etc.)} Inorganic materials include zirconium (e.g., zirconium), metal composite oxides [metal titanate salts (barium titanate, strontium titanate, lead titanate, niobium titanate, calcium titanate, magnesium titanate, etc.), metal zirconate salts (barium zirconate, calcium zirconate, lead zirconate, etc.)], glass (soda-lime glass, borosilicate glass, crown glass, barium-containing glass, strontium-containing glass, borosilicate glass, low-alkali glass, alkali-free glass, crystallized transparent glass, silica glass, quartz glass, heat-resistant glass, etc.), and silicon (semiconductor silicon, etc.). Inorganic materials can also be composite materials of these inorganic materials and metals (e.g., enamel).

[0108] The insulating substrate can be 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 are preferred; as are glass substrates such as quartz glass substrates.

[0109] The hole walls of the insulating substrate can be subjected to surface treatments such as oxidation treatment [surface oxidation treatment, for example, 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.] and surface roughening treatment (solvent treatment, sandblasting treatment, etc.).

[0110] The average thickness of the insulating substrate can be appropriately selected according to the application, for example, 0.01 to 10 mm, preferably 0.05 to 5 mm, more preferably 0.1 to 1 mm, and more preferably 0.2 to 0.8 mm.

[0111] An insulating substrate has holes (usually two or more) formed to fill conductive vias. These holes are typically through-holes, but can also be non-through-holes. The cross-sectional shape of the holes, parallel to the substrate surface, is not particularly limited and can be polygonal (triangle, quadrilateral, hexagon, etc.), but is usually circular or elliptical, preferably circular.

[0112] The average diameter of the hole is, for example, about 0.05 mm to about 10 mm, preferably about 0.08 mm to about 5 mm, and more preferably about 0.1 mm to about 1 mm.

[0113] There are no particular limitations on the method of forming the hole; known methods such as laser method, jetting method, ultrasonic method, grinding method, and drilling method can be used appropriately.

[0114] (a7) Filling method for conductive paste

[0115] Methods for filling the holes with conductive paste include, for example, screen printing, inkjet printing, gravure printing (e.g., photogravure printing), offset printing, gravure offset printing, flexographic printing, and other printing methods, as well as direct pressing methods such as roller pressing, squeegee pressing, and press pressing. Among these methods, screen printing is preferred.

[0116] After filling, it can be air-dried or dried by heating. The heating temperature can be selected according to the type of organic solvent, for example, about 50°C to about 200°C, preferably about 60°C to about 180°C, and more preferably about 100°C to about 150°C. The heating time is, for example, 1 to 60 minutes, preferably 3 to 40 minutes, and more preferably 5 to 30 minutes.

[0117] (b) Metal film formation process

[0118] The aforementioned filling process may further include a metal film forming process, which forms a metal film containing an active metal component (a second active metal component) on the wall surface of the hole as a pre-process of the aforementioned paste filling process. The metal film forming process is effective when the conductive paste for filling in the aforementioned paste filling process and / or the conductive paste for lamination in the later-described lamination process does not contain an active metal component, and is particularly effective when the conductive paste for filling does not contain an active metal component. Even when the conductive paste for filling and / or the conductive paste for lamination does not contain an active metal component, by laminating a metal film containing an active metal component on the wall surface of the hole as a precursor for the first conductive through-hole, the metal component A in the conductive paste can be acted upon, thereby improving density, airtightness, and sealing.

[0119] The metal film only needs to 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, and more preferably 0.2 to 0.4 μm.

[0120] In the metal film formation process, as long as the metal film contains an active metal component, it is acceptable. Preferably, it includes an active metal layer formation process that forms an active metal layer from an active metal.

[0121] Examples of active metals include those exemplified in the section on conductive pastes for filling. These active metals can be used alone or in combination of two or more. From the viewpoint of excellent activity during the firing process and the ability to improve the bonding force between the insulating substrate and the conductive via, Ti and / or Zr are preferred, with Ti being particularly preferred.

[0122] 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, and even more preferably 0.1 to 0.3 μm. If the thickness of the active metal film is too thin, the adhesion may be reduced; if it is too thick, the conductivity and sinterability may be reduced.

[0123] The metal film formation process preferably further includes a protective layer formation process in which a protective layer of high-melting-point metal is formed on the aforementioned active metal film. In this invention, by stacking a protective layer on the aforementioned active metal layer, the active metal film formed on the hole wall surface protects the active metal film from reacting with oxygen, nitrogen, carbon, etc., before and during firing, thereby inhibiting the deactivation of the active metal. In particular, by combining it with the metal component C contained in the conductive paste for filling, the protective function of the active metal can be further improved.

[0124] Examples of high-melting-point metals include Cu, Ni, Pd, and Pt. These high-melting-point metals can be used alone or in combination of two or more, or in alloys of two or more. Among these high-melting-point metals, Pd and Pt are preferred, with Pd being particularly preferred.

[0125] The average thickness of the protective layer is, for example, 0.005 μm or more, such as 0.005 to 1 μm, preferably 0.01 to 0.5 μm, more preferably 0.05 to 0.3 μm, and even more preferably 0.08 to 0.2 μm. If the thickness of the protective layer is too thin, the effect of improving the sealing may be reduced; if it is too thick, the conductivity and sinterability may be reduced.

[0126] As a method for forming metal films, physical vapor deposition (PVD) and chemical vapor deposition (CVD) can be used. From the viewpoint of easily forming metal films, physical vapor deposition is preferred. Examples of physical vapor deposition methods include vacuum evaporation, flash evaporation, electron beam evaporation, ion beam evaporation, sputtering, ion plating, molecular beam epitaxy, and laser ablation. Among these, sputtering and ion plating are preferred from the viewpoint of high physical energy and improved adhesion between the formed metal film and the insulating substrate, with sputtering being particularly preferred. Sputtering can be used under conventional conditions.

[0127] (Grinding process)

[0128] The insulating substrate for which the first conductive via portion precursor has been filled in the holes through the above-described filling process can be directly supplied to the lamination process, or it can be supplied to the lamination process after a grinding process in which the surface of the first conductive via portion precursor filled in the holes is ground. If the surface of the first conductive via portion precursor is made smooth through the grinding process, the second conductive via portion precursor can be stacked uniformly, thereby improving the compactness, airtightness, and sealing performance.

[0129] The grinding method used in the grinding process can be either a physical grinding method or a chemical grinding method. Examples of physical grinding methods include: buffing, polishing, and polishing. Examples of chemical grinding methods (surface treatment methods) include: soft etching of the outermost surface using an aqueous solution of sodium persulfate. Among these, physical grinding methods such as buffing are preferred.

[0130] (Layering process)

[0131] In the lamination process, the precursor for the second conductive via is a lamination conductive paste containing metal component B and a second organic carrier.

[0132] (c1) Metallic component B

[0133] The metal that forms the refractory metal particles that constitute metal component B is not particularly limited as long as it has a melting point at the firing temperature (lower than the melting point of metal component A). The metal can be a refractory metal element or a refractory alloy. Specifically, examples of refractory metals include Mg and Al. Examples of refractory alloys include alloys of the aforementioned refractory metals, alloys of high-melting-point metals listed in metal component A, alloys of refractory metals and high-melting-point metals, alloys of refractory metals and fusible metals listed in metal component C, alloys of high-melting-point metals and fusible metals, and alloys of high-melting-point metals and refractory metals and fusible metals.

[0134] The metals constituting the refractory metal particles are preferably refractory metal elements, alloys of high-melting-point metals, alloys of high-melting-point metals and fusible metals, and especially preferably alloys of high-melting-point metals.

[0135] Cu, Ag, Ni, Au, Pt, and Pd (especially Cu and / or Ag) are preferred as high-melting-point metals constituting refractory alloys.

[0136] Bi, Sn, and Zn (especially Sn and / or Zn) are preferred as fusible metals constituting refractory alloys. By combining high-melting-point metals or refractory metals with fusible metals as alloys, the melting point of metal component B can be adjusted over a wider range. However, since the electrical conductivity of metal component B containing fusible metals is reduced, the proportion of fusible metals is preferably at the necessary minimum.

[0137] From the viewpoint that these refractory metal particles can improve electrical conductivity in addition to density, airtightness, and tightness, it is preferable to include refractory metal particles containing at least one high-melting-point metal selected from the group consisting of Cu, Ag, Ni, Au, Pt, and Pd (especially refractory alloy particles containing at least one high-melting-point metal selected from the group consisting of Cu, Ag, Ni, Au, Pt, and Pd), more preferably alloy particles containing Ag and / or Cu, even more preferably alloy particles containing Ag (e.g., Ag-Cu alloy particles, Ag-Sn alloy particles, Ag-Cu-Zn-Sn alloy particles, etc.), and particularly preferably Ag-Cu alloy particles.

[0138] It should be noted that metal component B is prepared separately from the precursor for the first conductive via and laminated onto the precursor for the first conductive via. Therefore, if multiple alloyable elemental metal particles are combined, they flow into the gaps and pores of the via in a state of alloying with each other during the firing process. Therefore, in this application, the alloy in metal component B is used to mean that even if they are elemental metal particles in the raw material stage, they are alloyed as metal component B in the firing process. Furthermore, in the method of combining elemental metal particles as an alloy, the melting point of metal component B is not the melting point of each elemental metal particle, but the melting point of the alloy particles alloyed in the firing process. Therefore, even if some of the elemental metal particles before alloying in the raw material stage are fusible metal particles in the conductive paste for filling, the alloy is equivalent to a refractory metal. Therefore, for metal component B, it is classified as a refractory metal particle as a combination of elemental metal particles that can be alloyed with each other.

[0139] The shape of the refractory metal particles also includes both common and preferred forms, and can be selected from the shapes exemplified above for the shapes of high-melting-point metal particles as metal component A.

[0140] The median particle size (D50) of the refractory metal particles can be selected from about 0.01 μm to about 100 μm. From the viewpoint of operability of the conductive paste for lamination, for example, it is 0.1 to 30 μm, preferably 0.5 to 20 μm, further preferably 1 to 15 μm, more preferably 3 to 15 μm, and most preferably 4 to 10 μm.

[0141] When metal component B contains particles formed from refractory metal elements, the median particle size (D50) of these particles can be 10 μm or less, for example, 0.01–10 μm, preferably 0.05–5 μm, more preferably 0.1–3 μm, and even more preferably 0.3–1 μm. If the particle size of the particles formed from refractory metal elements is too large, alloying may not be sufficiently achieved.

[0142] The melting point of the refractory metal particles should be lower than the firing temperature, typically above 450°C. Specifically, it can be selected from a range above approximately 450°C and approximately 1100°C, for example, 500–1000°C, preferably 600–960°C, further preferably 650–900°C, more preferably 700–830°C, and most preferably 750–800°C. If the melting point of the refractory metal particles is too high, the fluidity, density, airtightness, and sealing properties of the refractory metal particles may decrease. If the melting point of the refractory metal particles is too low, the heat resistance and conductivity of the conductor (conductive through-hole portion) may decrease.

[0143] The proportion of metal component B in the conductive paste for lamination should be 30% by volume or more, for example, 30-75% by volume, preferably 40-70% by volume, more preferably 45-60% by volume, and even more preferably 50-55% by volume. If the proportion of metal component B is too low, the amount of metal component B flowing into the filling via may be insufficient, resulting in reduced density. To ensure sufficient flow, it is necessary to increase the number of laminations (printing). If the number of laminations is too high, the printability will decrease.

[0144] The proportion of 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, and more preferably 35 to 45 parts by volume, relative to 100 parts by volume of metal component A contained in the conductive paste for filling. If the proportion of metal component B relative to metal component A is too low, the density, airtightness, and sealing properties (especially density) may decrease. If the proportion of metal component B relative to metal component A is too high, the heat resistance of the conductor may decrease.

[0145] In the conductive paste for lamination (precursor for the second conductive via), the volume proportion of metal component B relative to the total volume of inorganic components is, for example, 60-100% by volume, preferably 70-100% by volume, more preferably 80-100% by volume, and even more preferably 85-100% by volume. If the volume proportion of metal component B is too small, the flowability may decrease, and the density, airtightness, and sealing (especially density) may decrease. If it is not necessary to incorporate active metal components or metal component C into the conductive paste for lamination, it is preferable to set it to 100% by volume.

[0146] If the proportion of metal component B is approximately the same as the volume of the first organic carrier, then metal component B will not fill the pores created by the disappearance of the first organic carrier during firing, either excessively or insufficiently. This allows for improved density of the conductive via without compromising the heat resistance of metal component A, which is the main component of the conductive via. Therefore, the volume of the precursor for the second conductive via can be selected based on the relationship between the volumes of metal component B and the first organic carrier. Theoretically, a ratio of equal volumes is preferred, but since metal component B tends to remain on the substrate surface around the via or easily flows out of the via, a ratio larger than equal volumes is also possible.

[0147] Specifically, the proportion of metal component B relative to 100 parts by volume of the first organic carrier is, for example, 100 to 1000 parts by volume, preferably 120 to 700 parts by volume, more preferably 150 to 500 parts by volume, and even more preferably 200 to 300 parts by volume. If the volume ratio of metal component B is too low, the density may decrease; if it is too high, the heat resistance may decrease.

[0148] (c2) Second organic carrier

[0149] To improve operability, the conductive paste for lamination described above may contain an organic carrier (second organic carrier) in addition to the metal component B.

[0150] Regarding the material of the second organic carrier, a preferred method is to select from the material of the first organic carrier exemplified in the above-mentioned section on conductive paste for filling.

[0151] The proportion of the second organic carrier is, for example, 25-65% by volume, preferably 30-60% by volume, more preferably 40-55% by volume, and even more preferably 45-52% by volume relative to the total volume of the conductive paste used for lamination. If the proportion of the second organic carrier is too low, the operability may be reduced; if it is too high, the metal component B flowing into the through-hole may be insufficient, resulting in reduced density. In order to ensure the inflow, it is necessary to increase the number of laminations (printing).

[0152] (c3) Metallic composition C

[0153] In addition to metal component B and the second organic carrier, the above-mentioned conductive paste for lamination may also contain metal component C (second metal component C).

[0154] Regarding the material of metal component C, a preferred method is to select from the materials of metal component C (first metal component C) exemplified in the above-mentioned section on conductive paste for filling.

[0155] The proportion of metal component C relative to the total volume of the conductive paste for lamination can be 40% by volume or less (e.g., 0.1 to 40% by volume), preferably 30% by volume or less, and more preferably 20% by volume or less (e.g., 1 to 20% by volume).

[0156] (c4) Active metal components

[0157] In addition to the metal component B and the second organic carrier, the above-mentioned conductive paste for lamination may also contain an active metal component (a third active metal component).

[0158] Regarding the material of the active metal component, a preferred method is to select from the materials of the active metal component (first active metal component) exemplified in the above-mentioned section on conductive paste for filling.

[0159] The proportion of the active metal component is 40% or less (e.g., 0.1 to 40% by volume) relative to the total volume of the conductive paste for lamination, preferably 30% or less, and more preferably 10% or less (e.g., 1 to 10% by volume).

[0160] (c5) Other ingredients

[0161] In addition to the metal component B and the second organic carrier, the above-described conductive paste for lamination may contain conventional additives without impairing the effects of the present invention. Examples of conventional additives include those exemplified in the section on conductive pastes for filling. The proportions of other components can be selected based on the type of component, and are typically about 10% by volume or less (e.g., about 0.01% to about 10% by volume) relative to the total volume of the conductive paste for lamination.

[0162] (c6) Proportion of conductive paste for lamination

[0163] The conductive paste is laminated onto the first conductive via precursor (one side of the first conductive via precursor) filling the holes in the insulating substrate, and the lamination is performed in such a way that at least a portion of the first conductive via precursor exposed at the opening of the hole is covered in the holes in the insulating substrate. Specifically, from the viewpoint of improving density, airtightness, and sealing, it is preferable to laminate the second conductive via precursor with an area ratio of 50% or more (preferably 80% or more, more preferably 100% or more) relative to the area of ​​the opening of the hole (the area of ​​the surface of the first conductive via precursor). From the viewpoint of productivity, it is preferable to laminate the second conductive via precursor with a diameter larger than the opening, and it is possible to laminate a second conductive via precursor having a diameter of 1.1 times or more (for example, about 1.1 times to about 5 times, preferably about 1.2 times to about 3 times, more preferably about 1.3 times to about 2 times) relative to the opening diameter of the opening.

[0164] The proportion of the precursor for the second conductive via portion can be a proportion in which the volume ratio of metal component B to the first organic carrier is within the range described above. When adjusting the proportion of the precursor for the second conductive via portion (conductive paste for lamination) based on the first organic carrier of the precursor for the first conductive via portion, it can be adjusted by the following method.

[0165] That is, the necessary amount of precursor (conductive paste for lamination) for the second conductive via portion can be calculated based on the following formula.

[0166] Required amount of conductive paste for lamination = [Required amount of metal component B] ÷ [Volume fraction of metal component B in the conductive paste for lamination]

[0167] It should be noted that the required amount of metallic component B can be calculated based on the following formula.

[0168] The required amount (volume) of metal component B = [volume of the hole (conductive through hole)] × [volume percentage of the first organic carrier in the conductive paste for filling].

[0169] The thickness of the precursor for the second conductive via portion can be determined based on the above ratio from the amount of conductive paste for lamination and the above-mentioned lamination coating area. It is approximately 5 to 120% of the thickness (hole depth) of the precursor for the first conductive via portion, preferably 8 to 100%, further preferably 10 to 80%, more preferably 12 to 70%, and most preferably 15 to 50%.

[0170] (c7) Lamination method for conductive paste

[0171] Methods for laminating conductive paste onto the holes include, for example, screen printing, inkjet printing, gravure printing (e.g., photogravure printing), offset printing, gravure offset printing, flexographic printing, etc. Among these methods, screen printing is preferred.

[0172] After lamination, the materials can be dried naturally or by heating. The heating temperature can be selected according to the type of organic solvent, for example, about 50°C to about 200°C, preferably about 60°C to about 180°C, and more preferably about 100°C to about 150°C. The heating time is, for example, 1 to 60 minutes, preferably 3 to 40 minutes, and more preferably 5 to 30 minutes.

[0173] Regarding layering, two or more layers can be layered through repeated printing to achieve the required thickness. In the case of repeated printing, drying can also be performed at each printing stage.

[0174] (Firing process)

[0175] In the firing process, the firing temperature only needs to be lower than the melting point of metal component A and higher than the melting point of metal component B. The firing temperature (peak temperature) can be 600°C or higher, for example, 600–1500°C, preferably 700–1200°C, more preferably 800–1000°C, and even more preferably 850–950°C. The firing time (peak holding time) is, for example, about 5 minutes to about 3 hours, preferably about 8 minutes to about 1 hour, and more preferably about 10 minutes to about 20 minutes. The temperature rise from room temperature to the peak temperature and the temperature drop to room temperature after the peak holding time are respectively 10 minutes to 3 hours, preferably 20 minutes to 2 hours, and more preferably 25 minutes to 60 minutes.

[0176] It should be noted that the firing atmosphere is a nitrogen atmosphere. In this invention, even when nitrogen, which reacts with the active metal, is used as the atmosphere gas, the activity of the active metal can be maintained at high temperatures through the action of the metal component C. Therefore, a dense, airtight, and well-sealed through-hole filled substrate can be manufactured by a simple method without the use of special manufacturing equipment such as vacuum devices or heat-resistant containers.

[0177] (Based on the accompanying drawings)

[0178] Hereinafter, the manufacturing process of the method for manufacturing the via-filled substrate of the present invention will be described with reference to the accompanying drawings. Figure 1 This is a process diagram of a manufacturing method where the filling process is only a paste filling process. Figure 2 It is a process diagram of a manufacturing method that includes a metal film formation process and a paste filling process. Figure 1 and Figure 2 Any of the figures in the diagram is an example of the manufacturing method of the present invention.

[0179] In manufacturing methods where the filling process is solely a paste filling process, firstly, as... Figure 1 As shown in (a), a hole 1a is formed on the heat-resistant substrate 1. Next, as... Figure 1 As shown in (b), as a filling process, conductive paste 3 is filled into the aforementioned hole 1a. After drying, the surface of the filled conductive paste 3 is ground to flatten it. Furthermore, as... Figure 1 As shown in (c), conductive paste 4 is layered on the surface of the ground conductive paste 3 and then dried. Finally, the insulating substrate 1 containing the two conductive pastes is fired to form the conductive through-hole portion 5.

[0180] In manufacturing methods that include a metal film formation process and a paste filling process in the filling process, it is also the first step... Figure 2(a) shows a hole 11a formed on a heat-resistant substrate 11. Next, in this method, after forming a metal film 12 containing an active metal on the wall surface (inner wall surface) of the formed hole 11a by sputtering or the like, a conductive paste 13 for filling is filled into the hole 11a on which the metal film 12 is deposited. After filling with the conductive paste 13, [the process is repeated]. Figure 1 The same method is used to layer conductive paste 14 to form conductive through-hole portions 15.

[0181] [Through-hole filled substrate]

[0182] The via-filled substrate of the present invention is a via-filled substrate that makes both sides of an insulating substrate electrically conductive, obtained by the above-described manufacturing method. Specifically, it comprises an insulating substrate having holes and conductive vias formed by conductors filling the holes. The conductive vias of this via-filled substrate have high density. The porosity of the conductive vias is 10% by volume or less, preferably 8% by volume or less, and more preferably 5% by volume or less. It should be noted that in this application, the porosity of the conductive vias can be measured using SEM; specifically, it can be measured using the method described in the embodiments described later.

[0183] For the aforementioned via-filled substrate, the adhesion between the conductive via portion and the via wall is high, and the gap between the conductive via portion and the via wall is small. Specifically, even if a gap exists between the conductive via portion and the via wall, it is preferably localized and the size of the gap is less than 0.5 μm; more preferably, there is no gap at all; and particularly preferably, there is no gap. It should be noted that in this application, the gap between the conductive via portion and the via portion can be measured using SEM; specifically, it can be measured using the method described in the embodiments described later.

[0184] For the aforementioned via-filled substrate, the sealing performance between the conductive via portion and the via wall is also high. In the ink sealing test, ink leakage is less than 20%, preferably less than 10%, and more preferably 0%. It should be noted that, in this application, the method for evaluating the ink sealing test can be measured by the method described in the embodiments described later.

[0185] The conductive via portion of the aforementioned via-filled substrate has a phase separation structure consisting of an active metal containing an active metal phase and an active metal non-containing phase that does not actually contain an active metal phase. This phase separation structure alleviates the stress in the conductive via portion, thereby improving compactness, airtightness, and sealing.

[0186] The phase-separated structure can be an 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, with an island structure being preferred. In the case of an island structure, the active metal-containing phase can be a continuous phase, but from the viewpoint of conductivity, a dispersed phase is preferred.

[0187] The ratio of the active metal containing phase to the active metal non-containing phase in the area ratio of the cross-sectional photograph can be selected from the range of about 1 / 99 to about 90 / 10, for example, 3 / 97 to 60 / 40, preferably 5 / 95 to 50 / 50, more preferably 10 / 90 to 40 / 60, and more preferably 10 / 90 to 30 / 70.

[0188] When the phase separation structure is an island structure, the shape of the dispersed phase is not particularly limited. It can be an isotropic shape (spherical, cubic, etc.) or an anisotropic shape (ellipsoidal, rod-shaped, fibrous, amorphous, etc.).

[0189] The average diameter of the dispersed phase is, for example, 0.1 to 100 μm, preferably 1 to 80 μm, more preferably 3 to 50 μm, and even more preferably 5 to 30 μm.

[0190] It should be noted that, in this application, the aforementioned ratios and average diameters can be determined based on cross-sectional SEM images. Furthermore, when the dispersed phase has an anisotropic shape, the diameter of each dispersed phase is set as the average of its major and minor axes.

[0191] The active metal-containing phase exists at the interface with the hole wall. This active metal-containing phase can exist in the form of the dispersed phase described above, but from the viewpoint of improving sealing and airtightness, it is preferable to have a phase that continuously extends along the interface with the hole wall (a continuous phase). When the active metal-containing phase at the interface is a continuous phase extending along the interface with the hole wall, the interior of the conductive via preferably has the aforementioned island structure.

[0192] (Active metals contain phases)

[0193] The active metal 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. Preferably, Ti and / or Zr are preferred, with Ti being particularly preferred.

[0194] The proportion (elemental ratio) of active metal in the active metal-containing phase can be 0.5% or more, for example, 1% or more, preferably 2% or more, and even more preferably 3% or more.

[0195] When the active metal-containing phase is a dispersed phase, the proportion (elemental ratio) of the active metal in the active metal-containing phase can be less than 30%, for example, 0.5% to 30%, preferably 1% to 20%, more preferably 2% to 15%, and more preferably 3% to 10%. If the proportion of active metal is too high, the conductivity and heat resistance may decrease.

[0196] When the active metal containing phase is a continuous phase extending along the interface with the pore wall, the proportion (elemental ratio) of the active metal in the active metal containing phase can be 10% or more, preferably 30% or more, more preferably 50% or more, further preferably 80% or more, more preferably 90% or more, or it can be only active metal. If the proportion of active metal is too low, the sealing and airtightness may decrease.

[0197] In addition to the active metal, the phase may also contain at least one low-melting-point metal (refractory or fusible metal) selected from the group consisting of Mg, Al, Bi, Sn, In, and Zn. These low-melting-point metals may be used alone or in combination of two or more. Bi, Sn, In, and Zn are preferred, more preferably Bi, Sn, and Zn, and particularly preferably Sn and / or Zn.

[0198] The proportion (elemental ratio) of low-melting-point metal in the active metal-containing phase can be less than 50%, for example, 1 to 50%, preferably 3 to 30%, more preferably 5 to 20%, and more preferably 10 to 15%. If the proportion of low-melting-point metal is too small, porosity may be generated and the density may be reduced; if it is too large, electrical conductivity and heat resistance may be reduced.

[0199] In addition to the active metal, the phase may also contain at least one high-melting-point metal selected from the group consisting of Cu, Ag, Ni, W, Mo, Au, Pt, and Pd. These high-melting-point metals may be used alone or in combination of two or more. Cu, Ag, Ni, W, and Mo are preferred, with Cu and / or Ag being particularly preferred.

[0200] The proportion (elemental ratio) of high-melting-point metal in the active metal-containing phase can be less than 99.5%, for example, 10-99%, preferably 30-95%, more preferably 50-93%, and more preferably 70-90%. If the proportion of high-melting-point metal is too low, the conductivity and heat resistance may decrease; if it is too high, the airtightness and sealing performance may decrease.

[0201] (Active metals do not contain phase)

[0202] The active metal-free phase may contain at least one high-melting-point metal selected from the group consisting of Cu, Ag, Ni, W, Mo, Au, Pt, and Pd. These high-melting-point metals may be used alone or in combination of two or more. Among them, Cu, Ag, Ni, W, and Mo are preferred, and Cu and / or Ag are particularly preferred.

[0203] The proportion (elemental ratio) of high-melting-point metal in the phase not containing active metal can be 50% or more, for example, 80% or more, preferably 90% or more, further preferably 95% or more, and more preferably 98% or more. If the proportion of high-melting-point metal is too low, the electrical conductivity and heat resistance may decrease.

[0204] It should be noted that, in this application, the metal composition of the active metal containing phase and the active metal not containing phase can be determined by elemental analysis of SEM-EDS after the phase separation structure is confirmed by SEM images. In detail, it can be determined by the method described in the embodiments below.

[0205] Example

[0206] The present invention will now be described in more detail based on embodiments, but the invention is not limited to these embodiments. In the following examples, the preparation method of the conductive paste and the determination method of the evaluation test are shown below.

[0207] [Materials used]

[0208] (Metallic component A)

[0209] Copper Particle A: Copper particles with a median particle size of 0.8 μm and a melting point of 1085℃.

[0210] Copper Particle B: Copper particles with a median particle size of 6.5 μm and a melting point of 1085℃.

[0211] Copper particles C: Copper particles with a median particle size of 8 μm and a melting point of 1085℃.

[0212] Silver Particle A: Silver particles with a median particle size of 2.5 μm and a melting point of 962℃.

[0213] Nickel particles: Nickel particles with a median particle size of 0.7 μm and a melting point of 1455℃.

[0214] Molybdenum particles: Molybdenum particles with a median particle size of 3 μm and a melting point of 2620℃

[0215] Tungsten particles: Tungsten particles with a median particle size of 5 μm and a melting point of 3683℃

[0216] (Metallic component B)

[0217] Copper particles D: Copper particles with a median particle size of 0.5 μm and a melting point of 1085℃.

[0218] Silver Particles B: Silver particles with a median particle size of 0.5 μm and a melting point of 962℃.

[0219] AgCu particles: 72Ag-28Cu alloy particles with a median particle size of 5μm and a melting point of 780℃.

[0220] AgCuZnSn particles: 56Ag-22Cu-17Zn-5Sn solder powder with a median particle size of 5μm and a melting point of 650℃.

[0221] Tin particles: Tin particles with a median particle size of 8 μm and a melting point of 232℃

[0222] (Metallic component C)

[0223] Tin particles: Tin particles with a median particle size of 8 μm and a melting point of 232℃

[0224] Bismuth particles: Bismuth particles with a median particle size of 16 μm and a melting point of 271℃.

[0225] Indium particles: Indium particles with a median particle size of 25 μm and a melting point of 156℃

[0226] Zinc particles: Zinc particles with a median particle size of 7 μm and a melting point of 419℃.

[0227] (Active metals)

[0228] Titanium hydride (TiH2) particles: median particle size 6 μm

[0229] Zirconium hydride (ZrH2) particles: median particle size 5 μm

[0230] (Organic carrier)

[0231] The mixture is prepared by mixing acrylic resin as an organic binder with a mixed solvent of carbitol and terpineol (mass ratio 1:1) as an organic solvent at a mass ratio of organic binder: organic solvent = 1:3.

[0232] [Preparation of Conductive Paste]

[0233] Weigh each raw material according to the composition shown in Tables 1 to 3, mix them using a mixer, and then knead them evenly using a three-roll mill to prepare conductive paste 1 (conductive paste for filling) and conductive paste 2 (conductive paste for layering).

[0234] It should be noted that in Tables 1 and 2, the ratio (volume ratio) of metal component A, active metal and metal component C is the ratio relative to the total volume of inorganic components in conductive paste 1.

[0235]

[0236]

[0237] [Table 3]

[0238] Table 3 (Composition of Conductive Paste 2)

[0239]

[0240] [Porosity of the conductive via]

[0241] The conductive via portion of the sintered via-filled substrate was cut near the center using a diamond saw in a direction perpendicular to the substrate, and then the cut surface was finished smooth by ion milling. The processed sample was observed using a scanning electron microscope (manufactured by Nippon Electron Ltd.), and the presence of two phases was confirmed in the composition image. The porosity of the conductive via portion was calculated by image analysis.

[0242] (Judgment Method)

[0243] ◎: Porosity (void ratio) is below 5% (qualified)

[0244] ○: Porosity greater than 5% and less than 10% (qualified)

[0245] ×: Porosity greater than 10% (unacceptable).

[0246] [Seamlessness between conductive via and substrate]

[0247] Regarding the adhesion between the conductive via and the substrate (the wall of the via), the samples that were finished smooth by ion milling were observed using a scanning electron microscope at 3000x magnification to confirm whether there was a gap between the conductive via and the wall of the via. It should be noted that the thermal expansion coefficient of the conductor is higher than that of the ceramic substrate. Therefore, when cooled to room temperature after high-temperature firing, the shrinkage of the conductor is greater than that of the substrate. Consequently, if the adhesion between the conductor and the substrate is insufficient, the conductor may peel off from the wall of the via, resulting in a small gap.

[0248] (Judgment Method)

[0249] ◎: No gaps (qualified)

[0250] ○: Gaps smaller than 0.5μm exist in some areas (acceptable)

[0251] ×: Gaps larger than 0.5μm exist (unacceptable)

[0252] [Sealing (airtightness) of the conductive through-hole]

[0253] Apply red ink to the surface of the hole, and then pressurize the ink-coated surface with compressed air at 0.5 MPa for 60 seconds while maintaining a sealed environment. Check for any red ink leakage from the opposite side of the hole.

[0254] (Judgment Method)

[0255] ◎: Out of 10 holes, 0 holes leaked ink (qualified).

[0256] ○: Of 10 holes, 2 or fewer leak ink (acceptable)

[0257] ×: Of the 10 holes, more than 3 holes leak ink (unacceptable).

[0258] [Phase Composition and Compositional Analysis of Metals]

[0259] For the samples that were finished smooth by ion milling, the presence of different phases was confirmed by observation using a scanning electron microscope. The composition (mass %) of each phase was then confirmed by SEM-EDS analysis. The SEM-EDS analysis was performed using the energy-dispersive fluorescence X-ray analyzer JED-2300, which is included with the JSM-IT300LA scanning electron microscope manufactured by Nippon Electron Ltd.

[0260] [Comprehensive Evaluation Judgment Method (Graded)]

[0261] The results of porosity, tightness, and sealing are judged and graded as a comprehensive evaluation according to the following criteria.

[0262] A: Porosity, tightness, and sealing are all rated ◎ (qualified).

[0263] B: Porosity, tightness, and sealing performance are marked with ◎ or ○ (qualified).

[0264] C: One of the following is present: porosity, tightness, or sealing (×) (unacceptable).

[0265] [Example 1]

[0266] The substrate is fabricated using the method shown below.

[0267] (Preparation of the substrate)

[0268] Two or more through holes with diameters of φ0.1mm and 0.3mm are formed in an aluminum nitride substrate (manufactured by MARUWA Corporation, "170W") with a thickness of 2 inches × 2 inches × 0.5mm using a laser device.

[0269] (Fabrication process of through-hole filled substrate)

[0270] On a 2-inch × 2-inch × 0.5-mm thick aluminum nitride substrate with two or more through holes of φ0.1mm and 0.3mm respectively, conductive paste 1-1 as shown in Table 1 is used to fill the through holes via screen printing through a metal mask (0.1mm thick, with an opening diameter 0.2mm larger than the diameter of the through hole). The through holes are then dried in a blower dryer at 120°C for 10 minutes. Then, the substrate surface is smoothed by passing the substrate through a polishing machine once to remove any protruding conductive paste from the holes in the metal mask.

[0271] Then, using the same metal mask as described above, conductive paste 2-1 is printed on one surface of the hole filled with conductive paste 1-1, forming a circular pattern of conductive paste 2 with a diameter 0.2 mm larger than the hole diameter on the hole surface. The substrate printed with conductive paste 2-1 is dried in a blower dryer at 100°C for 10 minutes. It should be noted that, for through holes with a diameter of φ0.3 mm, with a single printing amount of paste 2 (wet film thickness of 0.1 mm), it is possible that the internal voids of the hole may not be fully filled. Therefore, after printing and drying the conductive paste 2-1, it is repeated twice more (a total of three times).

[0272] The side printed with conductive paste 2-1 is positioned on top of the substrate, and the substrate is fired in a continuous belt furnace under a nitrogen atmosphere at a peak temperature of 900°C for a peak holding time of 10 minutes. The total time from the time the substrate is placed in the furnace to the time it is removed after firing is 60 minutes.

[0273] The conditions and evaluation results of Example 1 are shown in Tables 4-7. Through-holes in an aluminum nitride substrate were filled with conductive paste 1-1 containing copper mixed powder (84.0 vol%) of different particle sizes (a non-melting metal component A at firing temperature), titanium hydride (5.7 vol%) as an active metal component, and tin powder (10.4 vol%) as a metal component C. Conductive paste 2-1, containing silver-copper alloy powder (melting point 780°C) of 72% silver and 28% copper as metal component B, was printed and laminated on the upper surface of the filled conductive through-holes and fired. For the resulting substrate, the porosity of the conductive through-holes, the adhesion between the conductive through-holes and the substrate, and the sealing performance were confirmed.

[0274] Figure 3 This is a cross-sectional SEM image of the hole (conductive through-hole) in Example 1. Figure 4 This is an enlarged image of the interface between the conductive through-hole and the hole wall in the aforementioned hole. Figure 5 This is an image of the elemental distribution of the active metal Ti at the interface between the conductive via and the via wall. It should be noted that... Figure 4 and 5 In the middle, the right side is the conductive via section. Figure 3The overall cross-sectional image shows that no voids (pores) were found in the conductive via [porosity is less than 1%]. Furthermore, from... Figure 4 The magnified image of the junction between the conductive through-hole and the hole wall shows that there is no gap between the conductive through-hole and the hole wall, indicating excellent sealing performance. Furthermore, the sealing performance is also excellent.

[0275] Furthermore, by Figure 4 The magnified image revealed the presence of gray and white phases within the conductive via. Metal composition analysis showed that the dark gray phase had a Cu / Ag ratio of 91 / 9 (Cu-rich phase), while the light white phase had a Ag / Cu / Sn / Ti ratio of 76.7 / 7 / 12 / 4.3 (Ag-rich phase). The Ag-rich phase essentially filled the pores and voids with conductive paste 2-1. Without conductive paste 2-1, this phase would be considered a void.

[0276] In addition, by Figure 5 As can be seen from the Ti distribution image, the Ti component, as an active metal, exists in the Ag-rich phase, especially in large quantities at the interface between the conductive via and the via wall. It can be inferred that the active metal component contained in conductive paste 1-1 diffuses and segregates at the interface, bonding with the via wall to form a strong adhesion. It should be noted that... Figure 5 In the image, the white area represents the Ti component.

[0277] [Examples 2-6]

[0278] Conductive pastes 1-2, 1-3, 1-4, 1-5, and 1-6 were used instead of conductive paste 1-1 as metal component A that does not melt at the firing temperature in conductive paste 1. Copper mixed powder, silver powder, nickel / copper mixed powder, molybdenum / copper mixed powder, and tungsten / copper mixed powder of different particle sizes were used respectively. Otherwise, through-hole filled substrates were made by the same method as in Example 1.

[0279] The conditions and evaluation results of Examples 2-6 are shown in Tables 4-7. Similar to Example 1, good results were obtained in terms of porosity, tightness, and sealing performance.

[0280] Figure 6 This is a cross-sectional SEM image of the hole in Example 3. Figure 7 This is an enlarged image of the interface between the conductive through-hole and the hole wall in the aforementioned hole. Figure 8 This is an image showing the elemental distribution of the active metal Ti at the interface between the conductive via and the via wall in the aforementioned hole. It should be noted that... Figure 7 and 8In the image, the left side represents the conductive via portion. Because silver powder is used as the main component of the conductive via portion (metal component A), the area of ​​the silver-rich phase (white phase) is increased. Conversely, copper, contained in metal component B, becomes part of the void-filling component, resulting in the opposite gray and white phases compared to Example 1. This demonstrates that metal component B contained in the laminating paste fills the voids and contributes to density.

[0281] Depend on Figure 8 As can be seen from the elemental distribution of Ti in Example 1, similar to Example 1, a large amount of Ti, as an active metal, is present at the interface between the conductive via and the via wall. It can be inferred that the active metal component contained in conductive pastes 1-3 diffuses and segregates at the interface, bonding with the via wall to form a strong adhesion.

[0282] Figure 9 This is a cross-sectional SEM image of the hole in Example 4. Figure 10 This is a magnified image of the interface between the conductive through-hole and the hole wall in the aforementioned hole section. It should be noted that... Figure 10 In the middle, the right side is the conductive through-hole side. The cross-sectional shape is similar to that of Example 1, indicating that there are no pores, gaps, voids, etc.

[0283] [Comparative Example 1] (Example without using conductive paste 2)

[0284] After filling the holes with the same conductive paste 1-1 as in Example 1, conductive paste 2 was not printed on the upper surface of the holes, and the holes were directly fired at 900°C in a nitrogen atmosphere. A cross-section of the hole (conductive through-hole) is shown below. Figure 11 middle.

[0285] Because there is no molten metal flowing into the hole (conductive through-hole) from the top, a large number of pores exist throughout the hole (conductive through-hole), resulting in a large gap between the conductive through-hole and the hole wall. Therefore, the porosity, tightness, and sealing performance are all substandard. In addition, the metal composition is not a two-phase structure as in Example 1.

[0286] [Examples 7-9]

[0287] Conductive paste 1-1 was replaced with conductive pastes 1-7, 1-8, and 1-9, and the metal component C was changed to bismuth particles, indium particles, and zinc particles, respectively. Otherwise, the via-filled substrate was fabricated using the same method as in Example 1. Even with the change in the type of metal component C, good results were obtained as in Example 1.

[0288] [Examples 10-15]

[0289] The conductive paste 1-1 is replaced with pastes 1-10, 1-11, 1-12, 1-13, 1-14, and 1-15. The ratio of the active metal (titanium hydride) that is reactive with the ceramic substrate and the metal component C (low melting point metal particles) that protects the active metal is changed. Otherwise, the through-hole filling substrate is made by the same method as in Example 1.

[0290] The proportion of the active metal (titanium hydride) was changed from 5.7% in conductive paste 1-1 to 8.5% (Example 10), 12.6% (Example 11), 17.8% (Example 12), 24.2% (Example 13), 2.1% (Example 14), and 0.4% (Example 15). Correspondingly, the proportion of metal component C was also changed to 15.6% (Example 10), 17.3% (Example 11), 16.3% (Example 12), 8.3% (Example 13), 3.9% (Example 14), and 2.7% (Example 15).

[0291] In Example 13, where the proportion of active metal was 24.2%, the porosity of the conductive via was slightly higher. In Example 15, where the proportion of active metal was 0.4%, the seal between the conductive via and the via wall was slightly lower, but both were at practical levels. In other examples, similar to Example 1, good results were achieved in terms of porosity, seal, and tightness.

[0292] [Examples 16-17]

[0293] Conductive pastes 1-16 and 1-17 were used instead of conductive pastes 1-1 and 1-3, and the active metal was changed to zirconium hydride. Otherwise, the through-hole filled substrate was fabricated using the same method as in Examples 1 and 3. Similar to Examples 1 and 3 where titanium hydride was used as the active metal, good results were obtained in terms of porosity, tightness, and sealing.

[0294] [Examples 18-19]

[0295] Conductive paste 1-1 was replaced with conductive paste 1-1 by using conductive paste 1-18 and 1-19, and the proportion of metal component C was changed to 24.3% (Example 18) and 1.3% (Example 19), respectively. Otherwise, the through-hole filling substrate was made by the same method as in Example 1.

[0296] In Example 18, where the proportion of metal component C is high, some pores exist in the conductive through-hole portion, and some gaps are also observed at the interface between the conductive through-hole portion and the hole wall. However, the sealing performance is good and at a practical level. This is believed to be because, due to the increased proportion of metal component C, the metal component B contained in the conductive paste 2-1 is difficult to penetrate during firing, leaving internal pores and interfacial gaps.

[0297] On the other hand, in Example 19, where the proportion of metal component C was as low as 1%, the porosity and sealing performance were good, but the adhesion between the conductive via and the via wall was poor (some gaps were observed at the interface). This is believed to be because the amount of metal component C (low-melting-point metal particles) used to protect the active metal was insufficient, failing to adequately protect the active metal, causing it to react with nitrogen gas and thus reducing its reactivity with the substrate. Therefore, the proportion of metal component C (low-melting-point metal) is preferably 2% to 20%.

[0298] [Comparative Example 2] (An example that does not contain the metal component C)

[0299] Conductive paste 1-20, which does not contain metal component C (low-melting-point metal particles), was used instead of conductive paste 1-1, and the via-filled substrate was fabricated using the same method as in Example 1. As a result, regarding the adhesion between the conductive via portion and the via wall, some gaps were found at the interface. Furthermore, the sealing was insufficient. This is believed to be because, due to the absence of metal component C (low-melting-point metal particles), the active metal cannot be protected during firing. The active metal particles are deactivated by reacting with nitrogen and carbon, resulting in insufficient adhesion between the conductive via portion and the via wall. Gaps are generated at the interface due to the shrinkage of the conductive via portion.

[0300] Figure 12 This is a cross-sectional SEM image of the hole in Comparative Example 2. Figure 13 yes Figure 12 The elemental distribution of the active metal Ti in the SEM image. It should be noted that... Figure 12 and 13 In the middle, the upper side is the conductive via side. (From...) Figure 12 The magnified image of the interface shows that the filled via is dense and without voids, but there is a gap of more than 1 μm at the interface between the conductive via and the via wall. Therefore, the sealing between the conductive via and the via wall is insufficient. Figure 13 The elemental distribution of the active metal Ti shows that Ti accumulates in the conductive via as particles, with no diffusion of the active metal component or segregation at the interface between the conductive via and the via wall. This is presumably because, due to the absence of metal component C (low-melting-point metal particles), the active metal particles react with nitrogen, carbon, etc., during firing to become insoluble, non-reactive substances such as titanium nitride and titanium carbide, which cannot diffuse to the via wall. Furthermore, even if diffusion occurs, the reactivity disappears, and due to insufficient adhesion to the via wall, delamination occurs at the interface due to the shrinkage of the conductive via. Based on this result, it can be concluded that metal component C (low-melting-point metal particles) helps protect the active metal particles and diffuse towards the interface.

[0301] [Comparative Example 3] (An example without active metals)

[0302] The conductive paste 1-1 was replaced with conductive paste 1-21, which does not contain active metal, and the via-filled substrate was fabricated using the same method as in Example 1. As a result, the adhesion and sealing performance were further reduced compared to Comparative Example 2, rendering it unacceptable. This is believed to be because, due to the absence of an active metal that reacts with the substrate, sufficient adhesion between the conductive via portion and the via wall cannot be obtained, resulting in gaps at the interface due to the shrinkage of the conductive via portion.

[0303] [Comparative Example 4] (An example without active metals, containing metal component C)

[0304] Conductive paste 1-1 was replaced with conductive paste 1-22, which does not contain active metals or metal component C, and the via-filled substrate was otherwise fabricated using the same method as in Example 1. As a result, similar to Comparative Example 3, the sealing and adhesion were unsatisfactory.

[0305] [Comparative Example 5] (An example where the conductive paste does not contain active metal or metal component C, and an active metal (Ti) sputtered film is formed on the wall surface of the hole)

[0306] Titanium and palladium were sequentially sputtered on the surface of an aluminum nitride substrate and the walls inside the through-holes (hole walls) using a sputtering apparatus (CANONANELVA Co., Ltd. "E-200S") under conditions of 200W voltage, 0.5Pa argon gas, and substrate heating to 200°C. A ceramic substrate with a sputtered titanium layer thickness of 0.2μm and a palladium layer thickness of 0.1μm, forming a Ti / Pd thin film, was obtained.

[0307] Furthermore, in addition to using this substrate, a through-hole filled substrate was fabricated using the same method as Comparative Example 4. As a result, compared to Comparative Example 4, the sealing performance was improved (judgment ○), but the adhesion between the conductive through-hole portion and the hole wall (a gap was found at the interface) was insufficient.

[0308] [Example 20] (An example where the conductive paste does not contain active metal and an active metal (Ti) sputtered film is formed on the wall surface of the hole)

[0309] Compared to Comparative Example 5, the case of using conductive paste 1-21 containing metal component C (low melting point metal particles), that is, compared to Example 1, the case of using conductive paste 1-21 without active metal on a substrate on which a Ti / Pd thin film is formed by sputtering on the wall of the hole.

[0310] In this example, similar to Example 1, the porosity, adhesion, and sealing performance are all good. Compared to Comparative Example 5, due to the presence of metal component C (low-melting-point metal particles) in the conductive paste, the active metal (Ti) contained in the film formed on the wall surface is protected from deactivation by the metal component C contained in the conductive paste, which effectively facilitates the reaction with the substrate, thereby improving the adhesion and sealing performance.

[0311] [Comparative Example 6] (An example that does not include metal particles A, which are the main component)

[0312] Conductive paste 1-1 was replaced with conductive paste 1-23, which did not contain metal particles A (high melting point metal particles) that were the main component. Otherwise, the through-hole filled substrate was fabricated using the same method as in Example 1. As a result, during firing, the conductor flowed out of the through-hole and could not form a conductor.

[0313] [Examples 21-22]

[0314] Compared to Example 4, which uses a mixed metal powder of copper and nickel as the main component (metal component A), conductive paste 2-1 is replaced with conductive paste 2-2 and 2-3, which use a mixed powder of silver particles / copper particles = 70 / 30 and 50 / 50 (mass ratio). Otherwise, the through-hole filling substrate is made by the same method as in Example 4.

[0315] The results of Example 21, which used a mixed powder of silver particles / copper particles = 70 / 30, were identical to those of Example 4, demonstrating that even when using a mixed powder of silver particles / copper particles, the same results as with AgCu alloy particles were obtained. This is believed to be because, during the heating process at which the silver particles and copper particles sinter, alloying occurs simultaneously, lowering the melting point and resulting in a melt flow similar to that of AgCu alloy powder, thereby achieving a densification effect.

[0316] On the other hand, in Example 22, which used a mixed powder with a silver particle / copper particle ratio of 50 / 50, the porosity increased slightly compared to Example 21, but the compactness and sealing performance remained good. This is believed to be because, due to the change in the silver particle / copper particle ratio to 50 / 50, the melting point increased due to the change in the AgCu alloy ratio, and the fluidity of the conductive paste 2-3 during firing decreased, thereby slightly reducing the compaction effect.

[0317] [Example 23]

[0318] Compared to Example 1, conductive paste 2-4, which uses 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. Otherwise, the via-filled substrate was fabricated using the same method as in Example 1. The results were as good as those in Example 1.

[0319] [Example 24]

[0320] Compared to Example 1, conductive paste 2-5, which uses a mixed powder of silver particles / tin particles in a mass ratio of 88 / 12 as metal component C (low-melting-point metal particles), was used instead of conductive paste 2-1. Otherwise, the via-filled substrate was fabricated using the same method as in Example 1. The results were as good as those in Example 1.

[0321] [Comparative Example 7] (The case where the firing temperature is lower than the melting point of metal component B; an example where metal component B does not melt during firing)

[0322] In Example 1, the firing temperature was set to 750°C, which is lower than the melting point of metal component B (780°C), and otherwise the through-hole filled substrate was fabricated using the same method as in Example 1.

[0323] Figure 14 This is a cross-sectional SEM image of the obtained hole (conductive through-hole). Figure 15 This is a magnified image of the interface between the conductive through-hole and the hole wall in the aforementioned hole section. It should be noted that... Figure 15 In the image, the right side shows the conductive through-hole section. Inside the conductive through-hole section, there are many voids (pores), and gaps exist at the interface between the conductive through-hole section and the hole wall. The porosity, tightness, and sealing performance are all substandard. This indicates that because the firing temperature is below the melting point of metal component B (780°C), metal component B cannot melt and flow into the holes during firing, thus failing to fill the voids and achieve densification.

[0324] [Comparative Example 8] (An example in which the total mixture of all the ingredients was initially used to fill the holes, and then the total mixture was further layered on the holes after filling)

[0325] The total mixed paste obtained by mixing conductive paste 1-1 and conductive paste 2-1 at a mass ratio of 1:1 is used as the conductive paste for filling and the conductive paste for lamination. Otherwise, the through-hole filling substrate is made by the same method as in Example 1.

[0326] The result was that the porosity, tightness, and sealing performance all failed to meet the requirements. It is speculated that this is because the presence of metal component B in the conductive paste used for filling causes the molten metal component B to integrate with the surrounding metal component A during firing, eliminating air permeability within the pores and hindering the flow of the conductive paste used for lamination into the pores. Based on this result, it is preferable that metal component B is incorporated into the conductive paste used for lamination, rather than being incorporated into the conductive paste used for filling.

[0327] [Examples 25-28]

[0328] Compared to Example 1, the material of the ceramic substrate was changed from aluminum nitride to aluminum oxide, sapphire, silicon nitride, or quartz glass. Otherwise, the through-hole filled substrate was fabricated using the same method as in Example 1. In either case, the porosity, sealing, and overall performance were good, just as in Example 1.

[0329] The conditions and evaluation results of the examples and comparative examples are shown in Tables 4 to 7.

[0330] [Table 4]

[0331] Table 4 (Metallic film on substrate and hole walls)

[0332] 1 AIN none 2 AIN none 3 AIN none 4 AIN none 5 AIN none 6 AIN none 1 AIN none 7 AIN none 8 AIN none 9 AIN none 10 AIN none 11 AIN none 12 AIN none 13 AIN none 14 AIN none 15 AIN none 16 AIN none 17 AIN none 18 AIN none 19 AIN none 2 AIN none 3 AIN none 4 AIN none 5 AIN Ti / Pd 20 AIN Ti / Pd 6 AIN none 21 AIN none 22 AIN none 23 AIN none 24 AIN none 7 AIN none 8 AIN none 25 Alumina none 26 sapphire none 27 silicon nitride none 28 Quartz glass none

[0333] [Table 5]

[0334] Table 5 (Conductive Paste 1)

[0335]

[0336] [Table 6]

[0337] Table 6 (Conductive Paste 2)

[0338] 1 2-1 AgCu particles 780 2 2-1 AgCu particles 780 3 2-1 AgCu particles 780 4 2-1 AgCu particles 780 5 2-1 AgCu particles 780 6 2-1 AgCu particles 780 1 - - - 7 2-1 AgCu particles 780 8 2-1 AgCu particles 780 9 2-1 AgCu particles 780 10 2-1 AgCu particles 780 11 2-1 AgCu particles 780 12 2-1 AgCu particles 780 13 2-1 AgCu particles 780 14 2-1 AgCu particles 780 15 2-1 AgCu particles 780 16 2-1 AgCu particles 780 17 2-1 AgCu particles 780 18 2-1 AgCu particles 780 19 2-1 AgCu particles 780 2 2-1 AgCu particles 780 3 2-1 AgCu particles 780 4 2-1 AgCu particles 780 5 2-1 AgCu particles 780 20 2-1 AgCu particles 780 6 2-1 AgCu particles 780 21 2-2 Ag particles / Cu particles = 70 / 30 780 22 2-3 Ag particles / Cu particles = 50 / 50 860 23 2-4 AgCuZnSn particles 650 24 2-5 Ag particles / Sn particles = 88 / 12 830 7 2-1 AgCu particles 780 25 2-1 AgCu particles 780 26 2-1 AgCu particles 780 27 2-1 AgCu particles 780 28 2-1 AgCu particles 780

[0339] [Table 7]

[0340] Table 7 (Firing conditions and evaluation results)

[0341]

[0342] Industrial availability

[0343] The via-filled substrate of the present invention can be used as a circuit board, electronic component, semiconductor packaging substrate, etc.

[0344] Symbol Explanation

[0345] 1, 11… Insulating substrate

[0346] Holes 1a, 11a...

[0347] 12...metal film

[0348] 3, 13… Conductive paste for filling

[0349] 4, 14… Conductive paste for layering

[0350] 5, 15… Conductive through-hole section

Claims

1. A method for manufacturing a through-hole filled substrate, comprising: A filling process for filling a first conductive via precursor into the holes of an insulating substrate having holes; a lamination process for laminating a second conductive via precursor onto the first conductive via precursor filled into the holes by the filling process; and a firing process for firing the insulating substrate containing the two precursors obtained by the lamination process under a nitrogen atmosphere. In the manufacturing method described above The first conductive via portion uses a precursor comprising a conductive paste for filling containing a metal component A and a first organic carrier. The metal component A is a high-melting-point metal particle with a melting point higher than the firing temperature. The filling process includes a paste filling process in which conductive paste is used to fill the pores. The precursor for the second conductive via is a laminated conductive paste containing metal component B and a second organic carrier. The metal component B is refractory metal particles with a melting point below the firing temperature. The proportion of the metal component B is 100 to 1000 parts by volume relative to 100 parts by volume of the first organic carrier. At least one of the first conductive via precursor and the second conductive via precursor contains an active metal component. At least one of the conductive paste for filling and the precursor for the second conductive through-hole contains a metallic component C, wherein the metallic component C is a fusible metal particle having a melting point lower than that of the refractory metal particle. The proportion of metal component C is 1 to 40 parts by volume relative to 100 parts by volume of metal component A, and the total of metal component A, active metal component, and metal component C is 2 to 20 parts by volume relative to metal component A.

2. The manufacturing method as described in claim 1, wherein, The conductive paste for filling contains the active metal component and the metal component C.

3. The manufacturing method as described in claim 1, wherein, The first conductive via portion contains the active metal component in the precursor, and the filling process further includes a metal film forming process, which forms a metal film containing the active metal component on the wall surface of the via portion, as a pre-process of the paste filling process.

4. The manufacturing method according to any one of claims 1 to 3, wherein, The high-melting-point metal particles of metal component A comprise 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 that high-melting-point metal. The refractory metal particles of metal component B have a melting point higher than 450°C and comprise a refractory alloy containing at least one high-melting-point metal selected from the group consisting of Cu, Ag, Ni, Au, Pt, and Pd. The fusible metal particles of the metal component C have a melting point below 450°C and contain at least one fusible metal selected from the group consisting of Bi, Sn, In, and Zn, or an alloy containing such fusible metal. 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 at least one selected from the group consisting of Ti, Zr, and Nb.

5. A kit for manufacturing conductive paste for through-hole filling substrates, wherein, The kit is a combination of a conductive paste for filling and a conductive paste for lamination. The conductive paste for filling contains a metal component A and a first organic carrier. The metal component A is a high-melting-point metal particle with a melting point higher than the firing temperature. The conductive paste for lamination contains a metal component B and a second organic carrier. The metal component B is a refractory metal particle with a melting point lower than the firing temperature. The proportion of the metal component B is 100 to 1000 parts by volume relative to 100 parts by volume of the first organic carrier. At least one of the conductive paste for filling and the conductive paste for lamination contains an active metal component, wherein the active metal component is active metal particles containing active metal. At least one of the conductive paste for filling and the conductive paste for lamination contains a metallic component C, wherein the metallic component C is a fusible metal particle having a melting point lower than that of the refractory metal particles. The proportion of metal component C is 1 to 40 parts by volume relative to 100 parts by volume of metal component A, and the total of metal component A, active metal component, and metal component C is 2 to 20 parts by volume relative to metal component A.

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