Method for manufacturing glass substrate with conductive via, metal paste for forming through-glass electrode, and glass substrate with conductive via

Abstract

This method for manufacturing a glass substrate with a conductive via comprises: a step a of preparing a glass substrate provided with a hole and providing a metal paste part containing metal particles and a volatile solvent so as to cover the surface of the glass substrate, at least at the periphery of the hole, while filling the inside of the hole; a step b of heating the metal paste part to remove a part of the volatile solvent; a step c of removing a part of the heated metal paste part so that the surface is exposed, to form, inside the hole, a conductive via precursor that has a flattened exposed surface and that includes the metal particles and the balance of the volatile solvent; and a step d of firing the conductive via precursor. The metal particles include first metal particles having a volume average particle diameter of 0.8 μm or more and second metal particles having a volume average particle diameter of 0.5 μm or less. The metal particle concentration of the metal paste part provided in step a is 95.0 mass % or more, and the content of the second metal particles in the metal paste part provided in step a is 50 mass % or less based on the total amount of metal particles.

Description

Manufacturing method of glass substrate with conductive via, metal paste for forming glass through-electrode, and glass substrate with conductive via

[0001] The present invention relates to a method for manufacturing a glass substrate with conductive vias, a metal paste, and a glass substrate with conductive vias.

[0002] In recent years, in order to reduce the size, improve functionality, and integrate electronic devices or components, attention has been focused on three-dimensional packaging technology in which glass substrates arranged above and below are electrically connected via electrodes called through-glass vias (TGVs) on the glass substrates, and semiconductor chips are densely stacked in the vertical direction (height direction).

[0003] As a method for forming a through electrode, for example, Patent Document 1 below discloses a method for manufacturing a semiconductor device having a glass through electrode, which includes a step of electroplating a non-through via formed in a glass substrate with copper using a specific copper plating solution. Also, Patent Document 2 below proposes a method for manufacturing a semiconductor device, which includes a step of forming a hollow through electrode in a glass substrate by electrolytic copper plating and further filling the electrode with a mixture of metal powder and a resin material.

[0004] JP 2019-134016 A JP 2016-96262 A

[0005] Recently, as glass substrates have been reduced in size to accommodate the miniaturization of electronic devices and components, the inner diameters of through holes have also been reduced to a minimum, making it necessary to form conductive vias with sufficient conductivity even within such through holes. Furthermore, wiring may be further provided on the surface of the substrate on which the conductive vias are formed by plating or the like, and in this case too, a sufficiently low connection resistance value is required.

[0006] Furthermore, in recent years, progress has been made in reducing power consumption by increasing signal speeds, miniaturizing substrates, and shortening transmission distances, and this has resulted in a demand for even greater improvements in connection reliability than before. Under these circumstances, a substrate with conductive vias (wiring substrate) on which the above-mentioned wiring is formed is required to have not only excellent conductivity but also excellent properties such as being less likely to increase connection resistance even when subjected to temperature changes (hereinafter also referred to as "connection reliability").

[0007] However, the inventors' investigations have revealed that in glass substrates equipped with copper-plated through-glass electrodes, cracks may occur around the periphery of the through-glass electrodes due to the thermal history of temperature cycles, resulting in an increase in connection resistance. While methods for preventing cracks in glass substrates include changing the material of the glass substrate or reinforcing it with resin, these methods are not sufficient to achieve both low connection resistance and excellent connection reliability.

[0008] Therefore, the present invention aims to provide a method for manufacturing a glass substrate with conductive vias that has glass through electrodes (TGVs) and can exhibit a sufficiently low connection resistance even after wiring formation, and that allows the resulting wiring substrate to have excellent connection reliability, a metal paste that can be used to form glass through electrodes, and a glass substrate with conductive vias.

[0009] As a result of intensive research to achieve the above object, the present inventors have found that the cause of high connection resistance after wiring formation is low flatness (or smoothness) of the conductive vias on the surface of the conductive via-equipped substrate (in other words, a large step between the conductive via portion and the substrate surface). Based on this finding, the present inventors have investigated methods for reducing the step, and have found that by forming conductive vias through a specific process using a metal paste containing specific metal particles and a volatile solvent, a sufficiently low connection resistance can be obtained even when wiring connected to the conductive vias is further formed, and that the obtained wiring substrate does not develop cracks in the glass substrate even after a temperature cycle reliability test, exhibiting excellent connection reliability, thereby completing the present invention.

[0010] That is, one aspect of the present invention relates to the following method for manufacturing a substrate with conductive vias: [1] A method for manufacturing a glass substrate with conductive vias, comprising: Step (a) of preparing a glass substrate having holes formed therein, and providing a metal paste portion containing metal particles and a volatile solvent so as to fill the holes and cover at least the surface of the glass substrate around the holes; Step (b) of heating the metal paste portion to remove a portion of the volatile solvent; Step (c) of removing a portion of the metal paste portion after heating to expose the surface, thereby forming a conductive via precursor containing the metal particles and the remainder of the volatile solvent and having a flattened exposed surface inside the holes; and Step (d) of firing the conductive via precursor, wherein the metal particles include first metal particles having a volume average particle size of 0.8 μm or more and second metal particles having a volume average particle size of 0.5 μm or less, the metal paste portion provided in Step (a) has a metal particle concentration of 95.0 mass % or more, and the content of the second metal particles in the metal paste portion provided in Step (a) is 50 mass % or less based on the total amount of the metal particles.

[0011] According to the above manufacturing method, in step a, a metal paste portion containing a volatile solvent and having the above-mentioned specific metal particle configuration is provided, and then steps b and c are carried out, thereby achieving both good filling of the interior of the hole and the formation of a conductive via precursor that is resistant to volumetric shrinkage upon firing, and step d makes it possible to form a conductive via with excellent conductivity and with sufficient suppression of cracks and voids, while sufficiently reducing the step with the substrate surface. This makes it possible to obtain a substrate with conductive vias that exhibits sufficiently low connection resistance even after wiring formation, and furthermore, the substrate with conductive vias (wiring substrate) on which wiring has been formed suppresses the occurrence of cracks in the glass substrate even after a temperature cycle reliability test, thereby providing excellent connection reliability.

[0012] The inventors speculate as follows about the reason why cracking of the glass substrate can be suppressed. First, stress due to the through-glass electrodes is considered to be the main cause of cracking. For example, as described in the following reference, the stress of a copper-plated film is known to exhibit a high Young's modulus of approximately 100 GPa. Reference: Measurement of Young's Modulus of Thin Films for Electronic Devices by Precision Three-Point Bending Method, Transactions of the Japan Society of Mechanical Engineers (Part A), Vol. 77, No. 773 (2011-1), p. 190. According to the manufacturing method [1] above, by firing the specific conductive via precursor, a sintered body having a Young's modulus of less than half that of a copper-plated film can be formed, and it is believed that the stress due to the through-glass electrodes is alleviated. The inventors speculate that this suppresses cracking of the glass substrate around the through-glass electrodes, enabling both low connection resistance and excellent connection reliability.

[0013] [2] The method for manufacturing a substrate with conductive vias according to [1], wherein the first metal particles and the second metal particles are copper particles. [3] The method for manufacturing a substrate with conductive vias according to [1] or [2], wherein the first metal particles include flaky copper particles.

[0014] Another aspect of the present invention relates to the following metal pastes: [4] A metal paste used to form a through-glass electrode, the metal paste containing metal particles and a volatile solvent, wherein the content of the metal particles is 95.0 mass% or more based on the total amount of the metal paste, the metal particles include first metal particles having a volume average particle size of 0.8 μm or more and second metal particles having a volume average particle size of 0.5 μm or less, and the content of the second metal particles is 50 mass% or less based on the total amount of the metal particles. [5] The metal paste for forming a through-glass electrode according to [4], wherein the first metal particles and the second metal particles are copper particles. [6] The metal paste for forming a through-glass electrode according to [4] or [5], wherein the first metal particles include flaky copper particles.

[0015] The above metal paste has sufficient printability, and the metal paste portion can be efficiently formed in the above method for manufacturing a glass substrate with conductive vias.

[0016] Another aspect of the present invention relates to the following glass substrate with conductive vias: [7] A glass substrate with conductive vias, comprising: a glass substrate having a through hole; and a conductive via provided in the through hole, wherein the conductive via contains a sintered body of the metal paste according to any one of [4] to [6].

[0017] According to the present invention, it is possible to provide a method for manufacturing a glass substrate with conductive vias that has glass through electrodes (TGVs) and can exhibit a sufficiently low connection resistance value even after wiring formation, and that allows the resulting wiring substrate to have excellent connection reliability, a metal paste that can be used to form glass through electrodes, and a glass substrate with conductive vias.

[0018] FIG. 1 is a schematic diagram showing an example of a method for manufacturing a glass substrate with conductive vias according to this embodiment; FIG. 2 is a schematic diagram showing an example of a method for manufacturing a glass substrate with conductive vias according to this embodiment; FIG. 3 is a schematic diagram showing an example of a method for manufacturing a glass substrate with conductive vias according to this embodiment; FIG. 4 is a schematic diagram showing an example of a method for forming wiring; FIG. 5 is a schematic diagram showing a test piece; FIG. 6 is a diagram showing a cross-sectional image of a conductive via in a glass substrate with conductive vias produced in Example 1; FIG. 7 is a diagram showing the appearance and cross-section of a wiring substrate produced in Example 1; FIG. 8 is a diagram showing the surface of a wiring substrate produced in Example 12 after a temperature cycle reliability test; FIG. 9 is a diagram showing the surface of a wiring substrate produced in Comparative Example 7 after a temperature cycle reliability test.

[0019] Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. The present invention is not limited to the following embodiments. In the drawings, the same or corresponding parts are designated by the same reference numerals, and duplicated explanations will be omitted.

[0020] The metal paste of this embodiment contains metal particles and a volatile solvent, and the metal particle content is 95.0 mass % or more based on the total amount of the metal paste. The metal paste of this embodiment can be used to form a metal paste portion in a method for manufacturing a glass substrate with conductive vias, which will be described later, and can form a glass through-electrode.

[0021] The content of metal particles in the metal paste of this embodiment may be 95.2% by mass or more, 95.5% by mass or more, 95.7% by mass or more, or 96% by mass or more, based on the total amount of the metal paste, and may be 98% by mass or less, 97% by mass or less, or 96.5% by mass or less, or may be 95.0 to 98% by mass, 95.2 to 97% by mass, or 95.7 to 96.5% by mass.

[0022] [Metal Particles] Examples of metal particles include nickel, silver, copper, gold, palladium, platinum, solder, etc. When the metal paste contains copper particles, it is easy to obtain a conductor that has sufficient conductivity and is resistant to increases in resistance even when subjected to temperature changes, and a substrate that has sufficient conductivity and a through electrode with excellent connection reliability. In this embodiment, the metal particles include first metal particles having a volume average particle size of 0.8 μm or more and second metal particles having a volume average particle size of 0.5 μm or less.

[0023] In this specification, the volume average particle size of particles (hereinafter sometimes referred to as "average particle size") means the 50% volume average particle size (D50). The volume average particle size of metal particles can be determined by, for example, dispersing raw material metal particles in a dispersion medium such as water or alcohol and measuring the dispersion using a laser diffraction / scattering particle size distribution analyzer.

[0024] The first metal particles and the second metal particles may be copper particles from the viewpoints of reducing resistance, ensuring ion migration resistance, and facilitating wiring formation. This embodiment will be described in detail using as an example a case in which the first metal particles are copper particles (hereinafter referred to as "first copper particles") and the second metal particles are copper particles (hereinafter referred to as "second copper particles").

[0025] (First Copper Particles) The average particle size of the first copper particles may be 0.8 μm or more, 1.0 μm or more, 2.0 μm or more, or 3.0 μm or more from the viewpoint of improving the sintering density in holes (e.g., through holes or blind holes) of the substrate and suppressing voids and cracks occurring in the holes; for example, from the viewpoint of suppressing particle clogging in microvias with an inner diameter of 100 μm or less and improving filling properties, it may be 10 μm or less, 8.0 μm or less, 5.0 μm or less, or 4.0 μm or less; and from the viewpoint of suppressing voids and cracks and suppressing particle clogging in microvias, it may be 0.8 μm to 4.0 μm, 1.0 μm to 3.5 μm, or 1.2 μm to 3.0 μm. The ratio (DC1 / DH) of the average particle diameter DC1 of the first copper particles to the inner diameter DH of the hole may be 0.01 or more, 0.03 or more, or 0.04 or more from the viewpoint of suppressing particle clogging in the microvias and improving filling properties, and may be 0.15 or less, 0.1 or less, or 0.05 or less from the viewpoint of suppressing voids and cracks by reducing shrinkage due to firing. Furthermore, from the above viewpoint, the ratio (DC1 / DH) may be 0.01 to 0.15, or 0.03 to 0.1.

[0026] The shape of the first copper particles may be, for example, spherical, blocky, needle-like, flat (flake-like), or approximately spherical. The first metal particles may be aggregates of copper particles having these shapes. The metal paste of this embodiment may contain spherical copper particles as the first copper particles, from the viewpoint of reducing the step between the conductive via portion to be formed and the substrate surface and suppressing fluctuations in connection resistance even after a reliability test (e.g., a temperature cycle test).

[0027] From the viewpoint of improving the printability of the metal paste, the first copper particles may contain particles, such as spherical particles, having an aspect ratio of 2 or less in an amount of 60% by mass or more, 80% by mass or more, or 100% by mass. The aspect ratio (major axis / minor axis) of the particles can be determined, for example, by observing an SEM image of the particles and measuring the major axis and minor axis (e.g., thickness).

[0028] The metal paste of this embodiment may contain flaky copper particles as the first copper particles in order to reduce shrinkage due to firing and thereby suppress voids and cracks, or may contain spherical copper particles and flaky copper particles in order to reduce the viscosity of the metal paste, improve filling of microvias, and reduce shrinkage due to firing and thereby suppress voids and cracks. When spherical copper particles and flaky copper particles are used in combination, the mass ratio thereof (spherical copper particles) / (flaky copper particles) may be 1 to 9, 1.2 to 2.5, or 1.4 to 4.

[0029] The flaky copper particles may have an aspect ratio of 1.5 or more, 2 or more, or 3 or more.

[0030] The first copper particles may be produced by a chemical reduction method, an atomization method, an electrolysis method, a pulverization method, a plasma rotating electrode method, a uniform liquid spray method, a heat treatment method, or the like, and may be wet copper powder or atomized copper powder from the viewpoint of easily obtaining a uniform diameter and improving the dispersibility of the metal paste.

[0031] The first copper particles may contain wet-processed copper powder. In this case, conductive vias with excellent conductivity are easily obtained. This effect is thought to be achieved by the wet-processed copper powder's ability to easily bond with the copper particles blended as the second metal. The wet-processed copper powder may have a D90 / D50 ratio of 1.5 or less.

[0032] The copper particles may also contain wet-processed copper powder and atomized copper powder. In this case, the printability of the metal paste is improved, the step between the formed conductive via and the substrate surface is reduced, and fluctuations in connection resistance are easily suppressed even after reliability tests (e.g., temperature cycle tests). The reason for this effect is presumed to be the following: The coexistence of wet-processed copper powder, which is easily bonded to the second copper particles and has a uniform particle size, and atomized copper powder, which has a wide particle size distribution, allows the wet-processed copper powder to bond between the atomized copper powder particles while also bonding to the second copper particles, thereby forming a strong sintered body with a close-packed structure and suppressing shrinkage during sintering, thereby suppressing the occurrence of voids and cracks and depressions. The atomized copper powder may have a D90 / D50 ratio of 1.6 or more, 1.7 or more, or 1.8 or more.

[0033] When the first copper particles contain a wet copper powder and an atomized copper powder, the content of the wet copper powder may be more than 0 parts by mass and less than 100 parts by mass, or may be 20 to 80 parts by mass, relative to 100 parts by mass of the total amount of the wet copper powder and the atomized copper powder.

[0034] Commercially available first copper particles can be used. Examples of commercially available first copper particles include 1050Y (manufactured by Mitsui Kinzoku Co., Ltd., trade name, average particle size (D50): 0.81 μm, D90: 1.1 μm, spherical, wet-process copper powder), 1100Y (manufactured by Mitsui Kinzoku Co., Ltd., trade name, average particle size (D50): 1.1 μm, D90: 1.6 μm, spherical, wet-process copper powder), 1200Y (manufactured by Mitsui Kinzoku Co., Ltd., trade name, average particle size (D50): 2.1 μm, D90: 3.1 μm, spherical, wet-process copper powder), 1300Y (manufactured by Mitsui Kinzoku Co., Ltd., trade name, average particle size (D50): 3.5 μm, D90: 5 μm, spherical, wet-process copper powder), and 1100YP (manufactured by Mitsui Kinzoku Co., Ltd., trade name, average particle size (D50): 1.4 μm, D90: 2.3 μm, flat, wet-process copper powder), 1200YP (manufactured by Mitsui Kinzoku Co., Ltd., trade name, average particle size (D50): 3.1 μm, D90: 5.3 μm, flat, wet-process copper powder), MA-C02K (manufactured by Mitsui Kinzoku Co., Ltd., trade name, average particle size (D50): 1.8 μm, D90: 3.6 μm, spherical, atomized copper powder), MA-C025K (manufactured by Mitsui Kinzoku Co., Ltd., trade name, average particle size (D50): 2.4 μm, D90: 5.2 μm, spherical, atomized copper powder), and MA-C03K (manufactured by Mitsui Kinzoku Co., Ltd., trade name, average particle size (D50): 3.4 μm, D90: 6.3 μm, spherical, atomized copper powder).

[0035] The first copper particles may be treated with a surface treatment agent from the viewpoint of dispersion stability and oxidation resistance. The surface treatment agent may be one that is removed during wiring formation (sintering of the copper particles). Examples of such surface treatment agents include aliphatic carboxylic acids such as palmitic acid, stearic acid, arachidic acid, and oleic acid; aromatic carboxylic acids such as terephthalic acid, pyromellitic acid, and o-phenoxybenzoic acid; aliphatic alcohols such as cetyl alcohol, stearyl alcohol, isobornylcyclohexanol, and tetraethylene glycol; aromatic alcohols such as p-phenylphenol; alkylamines such as octylamine, dodecylamine, and stearylamine; aliphatic nitriles such as stearonitrile and decanenitrile; silane coupling agents such as alkylalkoxysilanes; and polymer treatment agents such as polyethylene glycol, polyvinyl alcohol, polyvinylpyrrolidone, and silicone oligomers. One type of surface treatment agent may be used alone, or two or more types may be used in combination.

[0036] The amount of the surface treatment agent may be an amount equivalent to one molecular layer or more on the particle surface. The amount of the surface treatment agent varies depending on the specific surface area of ​​the first copper particles, the molecular weight of the surface treatment agent, and the minimum coverage area of ​​the surface treatment agent. The amount of the surface treatment agent is usually 0.001% by mass or more.

[0037] The amount of the surface treatment agent is determined based on the number of molecular layers (n) attached to the surface of the first copper particles and the specific surface area (A ｐ ) (unit m ２ / g) and the molecular weight of the surface treatment agent (M ｓ ) (unit: g / mol) and the minimum coverage area of ​​the surface treatment agent (S Ｓ ) (unit m ２ / piece) and Avogadro's number (N Ａ ) (6.02 x 10 ２３ Specifically, the amount of surface treatment agent can be calculated from the following formula: Treatment amount of surface treatment agent (mass%) = {(n × A ｐ ×M ｓ ) / (S Ｓ ×N Ａ + n × A ｐ ×M ｓ )} × 100%.

[0038] The specific surface area of ​​the first copper particles can be calculated by measuring the dried copper particles using a BET specific surface area measurement method. When the surface treatment agent is a linear saturated fatty acid, the minimum coverage area of ​​the surface treatment agent is 2.05 × 10 －１９ m ２ / 1 molecule. In the case of other surface treatment agents, it can be measured, for example, by calculation from a molecular model or by the method described in "Chemistry and Education" (Kamieda Katsuhiro, Inafuku Sumio, Mori Iwao, 40(2), 1992, pp. 114-117). An example of a method for quantifying the surface treatment agent is shown below. The surface treatment agent can be identified by a thermal desorption gas / gas chromatograph mass spectrometer for the dried powder obtained by removing the dispersant from the metal paste, thereby determining the carbon number and molecular weight of the surface treatment agent. The carbon content of the surface treatment agent can be analyzed by carbon content analysis. Examples of carbon content analysis methods include high-frequency induction heating furnace combustion / infrared absorption method. The amount of the surface treatment agent can be calculated using the above formula from the carbon number, molecular weight, and carbon content of the identified surface treatment agent.

[0039] (Second Copper Particles) The average particle size of the second copper particles may be 0.5 μm or less, 0.4 μm or less, 0.3 μm or less, or 0.2 μm or less from the viewpoint of sinterability, and may be 0.01 μm or more, 0.03 μm or more, 0.05 μm or more, 0.08 μm or more, or 0.1 μm or more from the viewpoint of suppressing synthesis costs, good dispersibility, and suppressing the amount of surface treatment agent used. From the viewpoint of obtaining low-temperature sinterability and good dispersibility in the paste, it may be 0.1 μm to 0.3 μm, 0.12 μm to 0.28 μm, or 0.15 μm to 0.25 μm.

[0040] The second copper particles can act as copper particles that suitably bond the first copper particles together. Furthermore, the second copper particles have superior sinterability to the first copper particles and can promote sintering of the copper particles. For example, the copper particles can be sintered at a lower temperature than when the first copper particles are used alone.

[0041] The second copper particles may be wet copper powder produced by a chemical reduction method.

[0042] The shape of the second copper particles may be, for example, spherical, blocky, needle-like, flat (flake-like), or approximately spherical. The second copper particles may also be an aggregate of copper particles having these shapes. From the viewpoint of dispersibility and packing ability, the shape of the second copper particles may be spherical, approximately spherical, or flat (flake-like). From the viewpoint of combustibility and mixability with the first copper particles, the shape may be spherical or approximately spherical.

[0043] The aspect ratio of the second copper particles may be 5 or less, 4 or less, or 3 or less, from the viewpoints of dispersibility, packing ability, and mixability with the first copper particles.

[0044] The second copper particles may be synthesized or commercially available. Examples of commercially available second copper particles include CH0200L1 (manufactured by Mitsui Mining & Smelting Co., Ltd., average particle size (D50): 200 nm, spherical) and Tn-Cu100 (manufactured by Taiyo Nippon Sanso Co., Ltd., average particle size (D50): 120 nm, spherical).

[0045] The second copper particles may be treated with a specific surface treatment agent. Examples of the specific surface treatment agent include organic acids having 8 to 16 carbon atoms. Examples of organic acids having 8 to 16 carbon atoms include caprylic acid, methylheptanoic acid, ethylhexanoic acid, propylpentanoic acid, pelargonic acid, methyloctanoic acid, ethylheptanoic acid, propylhexanoic acid, capric acid, methylnonanoic acid, ethyloctanoic acid, propylheptanoic acid, butylhexanoic acid, undecanoic acid, methyldecanoic acid, ethylnonanoic acid, propyloctanoic acid, butylheptanoic acid, lauric acid, methylundecanoic acid, ethyldecanoic acid, propylnonanoic acid, butyloctanoic acid, Saturated fatty acids such as pentylheptanoic acid, tridecanoic acid, methyl dodecanoic acid, ethyl undecanoic acid, propyl decanoic acid, butyl nonanoic acid, pentyl octanoic acid, myristic acid, methyl tridecanoic acid, ethyl dodecanoic acid, propyl undecanoic acid, butyl decanoic acid, pentyl nonanoic acid, hexyl octanoic acid, pentadecanoic acid, methyl tetradecanoic acid, ethyl tridecanoic acid, propyl dodecanoic acid, butyl undecanoic acid, pentyl decanoic acid, hexyl nonanoic acid, palmitic acid, methyl pentadecanoic acid, ethyl tetradecanoic acid, propyl tridecanoic acid, butyl dodecanoic acid, pentyl undecanoic acid, hexyl decanoic acid, heptyl nonanoic acid, methyl cyclohexane carboxylic acid, ethyl cyclohexane carboxylic acid, propyl cyclohexane carboxylic acid, butyl cyclohexane carboxylic acid, pentyl cyclohexane carboxylic acid, hexyl cyclohexane carboxylic acid, heptyl cyclohexane carboxylic acid, octyl cyclohexane carboxylic acid, and nonyl cyclohexane carboxylic acid; octene Examples of the organic acid include unsaturated fatty acids such as nonenoic acid, methylnonenoic acid, decenoic acid, undecenoic acid, dodecenoic acid, tridecenoic acid, tetradecenoic acid, myristoleic acid, pentadecenoic acid, hexadecenoic acid, palmitoleic acid, and sapienic acid; and aromatic carboxylic acids such as terephthalic acid, pyromellitic acid, o-phenoxybenzoic acid, methylbenzoic acid, ethylbenzoic acid, propylbenzoic acid, butylbenzoic acid, pentylbenzoic acid, hexylbenzoic acid, heptylbenzoic acid, octylbenzoic acid, and nonylbenzoic acid. One organic acid may be used alone, or two or more organic acids may be used in combination.By combining such an organic acid with the second copper particles, it tends to be possible to achieve both the dispersibility of the second copper particles and the elimination of the organic acid during sintering.

[0046] The amount of the surface treatment agent to be applied may be an amount sufficient to adhere to the surface of the second copper particles in a monolayer to trilayer form. The amount of the surface treatment agent to be applied may be 0.07% by mass or more, 0.10% by mass or more, or 0.2% by mass or more, and may be 2.1% by mass or less, 1.6% by mass or less, or 1.1% by mass or less. The amount of the surface treatment agent to be applied to the second copper particles can be calculated by the method described above for the first copper particles. The same applies to the specific surface area, the molecular weight of the surface treatment agent, and the minimum coverage area of ​​the surface treatment agent.

[0047] The content of the second metal particles in the metal paste is 50 mass % or less based on the total amount of metal particles from the viewpoint of connection reliability, and may be 10 to 50 mass % or 20 to 40 mass % from the viewpoints of lowering the sintering temperature to improve adhesion to the base metal layer, reducing the porosity of the sintered body, suppressing shrinkage during sintering, and suppressing the occurrence of cracks.

[0048] The total content of the first copper particles and the second copper particles in the metal paste may be 100 parts by mass, 85 to 99.5 parts by mass, 90 to 99 parts by mass, or 95 to 98 parts by mass, when the total mass of the metal particles is 100 parts by mass.

[0049] The contents of the first copper particles and the second copper particles may be 50 to 90 parts by mass and 50 to 10 parts by mass, 55 to 85 parts by mass and 45 to 15 parts by mass, or 60 to 80 parts by mass and 40 to 20 parts by mass, respectively, relative to 100 parts by mass of the total of the first copper particles and the second copper particles.

[0050] The metal paste of this embodiment may contain copper particles and metal particles other than copper particles (hereinafter also referred to as "other metal particles"). In this case, the other metal particles may be nickel particles, silver particles, gold particles, palladium particles, platinum particles, or solder particles. One or more of these may be contained. The average particle size of the other metal particles may be 0.01 μm or more, 0.03 μm or more, or 0.05 μm or more, and may be 5 μm or less, 3.0 μm or less, or 2.0 μm or less. The average particle size of the solder particles may be 1.0 μm or more, 1.5 μm or more, 2.0 μm or more, 3.0 μm or more, or 4.0 μm or more, and may be 15 μm or less, 10 μm or less, 8.0 μm or less, or 5.0 μm or less.

[0051] The content of the other metal particles may be 5 parts by mass or less, 3 parts by mass or less, 1 part by mass or less, or 0.8 parts by mass or less, when the total mass of the copper particles is 100 parts by mass. The metal paste of this embodiment may not include solder particles as the other metal particles.

[0052] [Volatile Solvent] Examples of the volatile solvent include monohydric and polyhydric alcohols such as pentanol, hexanol, heptanol, octanol, decanol, ethylene glycol, diethylene glycol, propylene glycol, butylene glycol (e.g., 1,3-butanediol), α-terpineol, and isobornylcyclohexanol (MTPH); ethylene glycol butyl ether, ethylene glycol phenyl ether, diethylene glycol methyl ether, diethylene glycol ethyl ether (ethyl carbitol), diethylene glycol butyl ether (e.g., diethylene glycol mono-n-butyl ether), diethylene glycol isobutyl ether, diethylene glycol hexyl ether, triethylene glycol methyl ether, diethylene glycol dimethyl ether, diethylene glycol diethyl ether, diethylene glycol dibutyl ether, diethylene glycol butyl methyl ether, diethylene glycol isopropyl methyl ether, triethylene glycol dimethyl ether, triethylene glycol butyl methyl ether, and propanediol. ethers such as propylene glycol propyl ether, dipropylene glycol methyl ether, dipropylene glycol ethyl ether, dipropylene glycol propyl ether, dipropylene glycol butyl ether, dipropylene glycol dimethyl ether, tripropylene glycol methyl ether, and tripropylene glycol dimethyl ether; esters such as dimethyl phthalate, ethylene glycol ethyl ether acetate, ethylene glycol butyl ether acetate, propylene glycol diacetate, diethylene glycol ethyl ether acetate, diethylene glycol butyl ether acetate, dipropylene glycol methyl ether acetate (DPMA), ethyl lactate, butyl lactate, γ-butyrolactone, and propylene carbonate; acid amides such as N-methyl-2-pyrrolidone, N,N-dimethylacetamide, and N,N-dimethylformamide; aliphatic hydrocarbons such as cyclohexane, octane, nonane, decane, and undecane; aromatic hydrocarbons such as benzene, toluene, and xylene; mercaptans having an alkyl group having 1 to 18 carbon atoms;Examples of mercaptans having a cycloalkyl group having 5 to 7 carbon atoms include mercaptans having an alkyl group having 1 to 18 carbon atoms include ethyl mercaptan, n-propyl mercaptan, i-propyl mercaptan, n-butyl mercaptan, i-butyl mercaptan, t-butyl mercaptan, pentyl mercaptan, hexyl mercaptan, and dodecyl mercaptan. Examples of mercaptans having a cycloalkyl group having 5 to 7 carbon atoms include cyclopentyl mercaptan, cyclohexyl mercaptan, and cycloheptyl mercaptan. The volatile solvents may be used alone or in combination of two or more.

[0053] The metal paste of this embodiment may contain, as a volatile solvent, a solvent having a vapor pressure of 4 Pa ​​or more and 30 Pa or less at 20° C. (hereinafter also referred to as a “high vapor pressure solvent”) from the viewpoint of printability and suppressing volumetric shrinkage before and after firing the conductive via precursor (for example, between step c of forming the conductive via precursor and step d of firing the conductive via precursor) to suppress voids and cracks. One type of high vapor pressure solvent may be used alone, or two or more types may be used in combination.

[0054] Examples of high vapor pressure solvents include α-terpineol, 1,3-butanediol, ethyl carbitol, and propylene glycol diacetate.

[0055] The metal paste of this embodiment may contain, as a volatile solvent, a solvent having a vapor pressure of less than 4 Pa ​​at 20° C. (hereinafter also referred to as a “low vapor pressure solvent”), from the viewpoint of suppressing powdering due to drying accompanying solvent volatilization during printing or paste preparation. One type of low vapor pressure solvent may be used alone, or two or more types may be used in combination.

[0056] Examples of low vapor pressure solvents include isobornylcyclohexanol (MTPH), dimethyl phthalate, and diethylene glycol mono-n-butyl ether.

[0057] From the viewpoint of achieving both printability and suppressing volume shrinkage before and after firing the conductive via precursor (for example, between step c of forming the conductive via precursor and step d of firing the conductive via precursor) to suppress voids and cracks, the metal paste of this embodiment may contain a high vapor pressure solvent and a low vapor pressure solvent. In this case, the high vapor pressure solvent and the low vapor pressure solvent may each be used alone or in combination of two or more. The content ratio of the high vapor pressure solvent and the low vapor pressure solvent may be 20 / 80 to 80 / 20, or 30 / 70 to 70 / 30, in terms of the mass ratio [high vapor pressure solvent / low vapor pressure solvent].

[0058] The content of the volatile solvent in the metal paste of this embodiment may be 2 mass% or more, 3 mass% or more, or 3.5 mass% or more, based on the total mass of the metal paste, and may be 5 mass% or less, 4.8 mass% or less, 4.5 mass% or less, 4.3 mass% or less, or 4 mass% or less, or may be 2 to 5 mass%, 3 to 4.8 mass%, or 3.5 to 4.5 mass%.

[0059] The metal paste of the present embodiment may contain a resin component such as an epoxy resin. The metal paste of the present embodiment may have a resin component content of 10% by mass or less, or 5% by mass or less, or may not contain a resin component.

[0060] The metal paste can be prepared by mixing metal particles such as the copper particles and optional components (additives, etc.) with the volatile solvent. After mixing the components, stirring may be performed. The maximum particle size of the dispersion may be adjusted by classification. Furthermore, the components can be mixed using a three-roll mill, kneader, planetary mixer, or other means.

[0061] When the metal paste contains the first copper particles and the second copper particles, the second copper particles, the surface treatment agent, and the dispersion medium may be mixed in advance, followed by a dispersion treatment to prepare a dispersion of the second copper particles, and then the first copper particles, and optionally other metal particles and optional additives may be mixed therewith. This procedure improves the dispersibility of the second copper particles, improving their mixability with the first copper particles and further improving the performance of the metal paste. The dispersion of the second copper particles may be subjected to a classification operation to remove aggregates.

[0062] From the viewpoint of printability, the metal paste of this embodiment may have a viscosity of 100 to 600 Pa·s, or 150 to 400 Pa·s at 25° C. The viscosity of the metal paste is measured using a micro spiral viscometer PCU-02V (manufactured by Malcom Co., Ltd., product name) at a rotation speed of 10 rpm and a temperature of 25° C.

[0063] The Young's modulus of the sintered body of the metal paste of this embodiment, measured by the following method, may be 15 to 75 GPa, 20 to 60 GPa, or 25 to 50 GPa. In this case, cracks are less likely to occur around the through-glass electrodes formed on the glass substrate. [Young's Modulus Measurement] The metal paste was applied to a glass substrate so that the dried dimensions were 40 mm x 10 mm x 0.22 mm. Next, the metal paste coating was fired using the following procedure: (a) The glass substrate with the metal paste coating was placed in a tube furnace (manufactured by AVC Corporation), and argon gas was flowed at 1 L / min to replace the air in the tube furnace with argon gas. (b) Next, while flowing hydrogen gas at 300 mL / min, the temperature was raised to 300°C over 10 minutes, and sintering treatment was performed at 300°C for 60 minutes. (c) Thereafter, the glass substrate on which the sintered body was formed was cooled by flowing argon gas at a flow rate of 0.3 L / min, and then taken out into the air at a temperature of 50° C. or less. (d) The Young's modulus of the obtained sintered body was measured by a resonance method using a JE2-RT model manufactured by Nippon Technoplus Co., Ltd., under the conditions of a temperature of 23° C. and a resonance frequency of 278.4 Hz.

[0064] In the metal paste of this embodiment, for example, if the firing temperature is lowered to reduce the degree of sintering of the metal particles, or if the porosity is increased by blending or combining the metal particles, the Young's modulus of the sintered body tends to decrease, whereas if the firing temperature is increased to increase the degree of sintering of the metal particles, or if the porosity is decreased by blending or combining the metal particles, the Young's modulus of the sintered body tends to increase.Therefore, by appropriately setting the firing temperature and the blending composition of the metal particles, the Young's modulus of the sintered body can be set within the above-mentioned range.

[0065] <Method for manufacturing glass substrate with conductive vias> A method for manufacturing a glass substrate with conductive vias according to the present embodiment includes the steps of: preparing a glass substrate having holes formed therein; and providing a metal paste portion containing metal particles and a volatile solvent so as to fill the holes and cover at least the surface of the glass substrate around the holes; heating the metal paste portion to remove a portion of the volatile solvent; removing a portion of the heated metal paste portion to expose the surface, thereby forming a conductive via precursor containing the metal particles and the remainder of the volatile solvent and having a flattened exposed surface inside the hole; and firing the conductive via precursor to form a conductive via, wherein the metal particles include first metal particles having a volume average particle size of 0.8 μm or more and second metal particles having a volume average particle size of 0.5 μm or less; the metal particle concentration of the metal paste portion provided in the step a is 95.0 mass % or more; and the content of the second metal particles in the metal paste portion provided in the step a is 50 mass % or less based on the total amount of the metal particles.

[0066] 1 to 3 are schematic diagrams showing an example of a method for manufacturing a glass substrate with conductive vias according to this embodiment. Fig. 1 shows an example of a glass substrate used in the method for manufacturing a glass substrate with conductive vias. Hereinafter, the method for manufacturing a glass substrate with conductive vias according to this embodiment will be described with reference to these figures. Note that this embodiment illustrates a case in which the metal paste contains the above-mentioned copper particles as metal particles, and therefore the copper particles, copper layer, and copper sintered body can be read as metal particles, metal layer, and metal sintered body, respectively.

[0067] [Step a] Examples of the material of the glass substrate provided with holes in this step include alkali-free glass, borosilicate glass, quartz glass, etc. The material of the glass substrate may be borosilicate glass or alkali-free glass from the viewpoint of suppressing the occurrence of cracks around the conductive vias and further improving the connection reliability of the wiring substrate.

[0068] The holes may be through holes or blind holes. In this embodiment, for example, as shown in (a) of Fig. 1, a glass substrate 40 can be prepared, which has a glass substrate 1 with through holes 30 formed therein and a metal coating 2 formed on the wall surfaces of the through holes and on the surface of the glass substrate 1. The through holes 30 communicate with both main surfaces of the glass substrate 40. An example will be described in which conductive vias are provided in this glass substrate 40.

[0069] The thickness of the glass substrate 1 may be 100 μm or more, 200 μm or more, or 300 μm or more from the viewpoint of suppressing warping of the substrate after sintering, and may be 800 μm or less, 300 μm or less, 200 μm or less, or 100 μm or less from the viewpoint of reducing the weight and increasing the density of the substrate.

[0070] The average linear thermal expansion coefficient α of the glass substrate 1 is 0.3×10 －６ ~10 x 10 －６ K －１ 2×10 －６ ~8 x 10 －６ K －１ may be.

[0071] The upper limit of the diameter of the through hole 30 may be 200 μm or less, 100 μm or less, or 60 μm or less, from the viewpoint of increasing the density of the resulting semiconductor device, and the lower limit of the diameter of the through hole 30 is not particularly limited, but may be 20 μm or more, 30 μm or more, or 50 μm or more.

[0072] The number of through holes 30 provided in the glass substrate 40 is set per 1 cm of the main surface of the substrate from the viewpoint of increasing the density of the semiconductor device to be obtained. ２ There may be 100 or more, 200 or more, or 300 or more per unit area.

[0073] The metal coating 2 may be provided on both main surfaces of the glass substrate 1 and on the wall surfaces of the through holes 30, or on at least one main surface of the glass substrate 1 and on the wall surfaces of the through holes 30, or may be provided only on the wall surfaces of the through holes 30, or may not be provided at all. In the embodiment shown in (a) of Figure 1, a glass substrate 40 is provided with a metal coating 2 on both main surfaces of the glass substrate 1 and on the wall surfaces of the through holes 30. Note that a primer layer of epoxy resin or the like may be formed on both main surfaces of the glass substrate 1 and on the wall surfaces of the through holes 30, and the metal coating 2 may be provided on the surface of the primer layer.

[0074] Examples of the metal coating 2 include titanium, nickel, chromium, copper, aluminum, palladium, platinum, and gold. From the viewpoint of adhesion, the metal coating 2 is preferably a coating in which titanium, nickel, and copper are layered in this order. Adhesion is improved by oxidizing the surface of the glass substrate 1 to form silicon oxide and then forming a titanium layer on the silicon oxide. Furthermore, by providing a nickel layer on the titanium layer and then providing a copper layer on that, diffusion of copper into the glass substrate 1 can be suppressed compared to when a copper layer is provided directly on the titanium layer. Furthermore, providing a copper layer on the surface improves adhesion between the copper layer and copper particles in the metal paste, thereby improving reliability.

[0075] 1B, when preparing a glass substrate 41 having non-through holes 31 as holes, conductive vias serving as through electrodes can be formed by grinding the side of the glass substrate opposite to the side on which the non-through holes 31 are formed after step a, step b, step c, or step d. Grinding methods include, for example, mechanical polishing and chemical mechanical polishing.

[0076] As shown in (a) to (c) of Figure 2, the metal paste portion 3 can be provided, for example, by preparing a metal particle film on a support film 7, in which a metal particle-containing layer 3p made of the metal paste of the present embodiment described above is provided, and then pressing this metal particle film against a substrate.

[0077] Examples of the support film 7 include a polyimide film, a polyethylene naphthalate film, and a polyethylene terephthalate film. From the viewpoint of workability in forming the metal particle-containing layer by coating, the thickness of the support film may be 20 to 200 μm, 25 to 175 μm, or 30 to 150 μm.

[0078] The composition of the metal particles and volatile solvent in the metal particle-containing layer can be appropriately set so as to satisfy the conditions for the metal paste of this embodiment described above. The thickness of the metal particle-containing layer may be 100 μm or less. From the viewpoint of easily ensuring sufficient filling of the through holes or non-through holes, the thickness of the metal particle-containing layer may be 30 μm or more, 40 μm or more, or 50 μm or more.

[0079] From the viewpoint of suppressing the generation of voids in the through holes or non-through holes, the metal particle-containing layer may have a waviness (height difference) of 20 μm or less on the surface opposite to the support film, or may have a waviness (height difference) of 10 μm or less. By reducing the waviness (height difference), when the metal particle film is pressed to fill the holes in the substrate with the metal particle composition, it becomes easier to simultaneously fill the numerous through holes or non-through holes present in the substrate, and it becomes easier to reduce the number of through holes or non-through holes that are completely unfilled or through holes or non-through holes where voids are partially generated. The waviness (height difference) can be evaluated by a non-contact method using a laser displacement meter or the like.

[0080] The above-mentioned metal particle film can be produced by applying the metal paste of the present embodiment described above onto a support film to form a metal particle-containing layer having a metal particle concentration of 95.0 mass % or more, or by applying a metal paste in which the content of a volatile solvent has been increased (for example, increased to an amount such that the metal particle concentration is less than 94.0 mass %) and drying the applied film to form a metal particle-containing layer having a metal particle concentration of 95.0 mass % or more.

[0081] Examples of methods for applying the metal paste include screen printing, transfer printing, offset printing, jet printing, and methods using a dispenser, jet dispenser, needle dispenser, comma coater, slit coater, die coater, gravure coater, slit coat, letterpress printing, intaglio printing, gravure printing, stencil printing, soft lithography, bar coating, applicator, particle deposition method, spray coater, spin coater, dip coater, etc.

[0082] From the viewpoint of ease of application and uniformity of the applied film thickness, the metal paste can be applied onto the support film by screen printing.

[0083] The thickness of the coating film may be 1 μm or more, 2 μm or more, 3 μm or more, 5 μm or more, 10 μm or more, 15 μm or more, or 20 μm or more, and may be 300 μm or less, 250 μm or less, 200 μm or less, 150 μm or less, 120 μm or less, 100 μm or less, 80 μm or less, or 50 μm or less.

[0084] The step of drying the coating film to form the metal particle-containing layer can be carried out at room temperature or at a temperature of room temperature to 100° C. or less, and the atmosphere may be air or nitrogen.

[0085] In step a, the metal particle film described above is pressed against the glass substrate 40 so that the metal particle-containing layer 3p of the metal particle film contacts the glass substrate 40, and the through-holes 30 in the glass substrate 40 are filled with a metal paste. In this case, for example, as shown in FIG. 2(b), the metal particle film and the glass substrate 40 can be sandwiched and pressed from above and below by a pressing jig A. The pressing jig A is not particularly limited, but may be a commercially available one, or may be fabricated using a metal member having a flat portion. For example, a pressing jig having two or more of the above-mentioned metal members can press the metal particle film against the glass substrate by sandwiching the metal particle film and the glass substrate between the metal members arranged so that their flat portions face each other. The pressing jig A may have a mechanism for adjusting the pressure applied to the metal particle film and the glass substrate. A spring or the like can be used as the pressure adjustment means.

[0086] The pressing can be performed, for example, at a temperature of room temperature to 50°C or lower, and the atmosphere may be a vacuum, air, or nitrogen. To reduce voids, the metal particle film may be pressed onto the glass substrate after being maintained at a vacuum of 1000 Pa or lower, or a vacuum of 200 Pa or lower. The pressure of the pressing tool used to press the metal particle film onto the glass substrate may be any pressure within a range that does not crack the glass substrate, and may be, for example, 0.01 MPa or higher, 0.1 MPa or higher, or 1 MPa or higher.

[0087] The metal paste portion 3 may be formed to fill the inside of the hole and cover at least the surface of the substrate around the hole. However, as shown in FIGS. 2(b) and 2(c), the metal paste portion 3 may be formed to cover the opening of the through-hole (VP in FIG. 2(a)) located on the opposite side of the substrate from the side where the metal particle film is pressed. ０ The metal paste portion may protrude from the hole and cover the surface around the hole.

[0088] [Step b] In this step, the metal paste portion is heated to remove a portion of the volatile solvent, i.e., the metal paste portion is heated so that a portion of the volatile solvent remains. Note that, when using the above-mentioned metal particle film, the metal paste portion can be heated after peeling off the support film.

[0089] For heating, for example, a hot plate, a hot air dryer, a hot air heating furnace, a nitrogen dryer, an infrared dryer, an infrared heating furnace, a far-infrared heating furnace, a microwave heating device, a laser heating device, an electromagnetic heating device, a heater heating device, a steam heating furnace, a hot plate press device, etc. can be used.

[0090] The heating atmosphere may be air, an oxygen-free atmosphere such as nitrogen and rare gas, or a reducing atmosphere such as hydrogen and formic acid. In the air, copper particles are prone to oxidation when the heating temperature exceeds 100 ° C. However, if the metal paste portion contains the high vapor pressure solvent described above as a volatile solvent, part of the volatile solvent can be removed at a temperature below 100 ° C., 95 ° C. or less, or 90 ° C. or less. In addition, if the metal paste portion does not contain a high vapor pressure solvent as a volatile solvent, for example, if it contains only the low vapor pressure solvent described above, by heating in an oxygen-free atmosphere or a reducing atmosphere at 110 ° C. or more, 130 ° C. or more, or 150 ° C. or more, oxidation of the copper particles can be suppressed while part of the volatile solvent is removed.

[0091] When the metal paste portion contains a high vapor pressure solvent, the heating temperature may be 70°C or higher but lower than 100°C, or 80°C or higher but lower than 95°C, from the viewpoint of suppressing oxidation of the copper particles, and the heating time may be 5 to 60 minutes, or 10 to 30 minutes, from the viewpoint of suppressing oxidation of the copper particles.

[0092] In addition, in order to suppress volumetric shrinkage before and after firing the conductive via precursor (for example, between step c of forming the conductive via precursor and step d of firing the conductive via precursor) and thereby suppress voids and cracks, the conductive via precursor may be heated so that the concentration of metal particles in the metal paste portion becomes 96 mass% or more, 97.5 mass% or more, or 98 mass% or more.

[0093] [Step c] In this step, as shown in (a) to (d) of Figure 3, the metal paste portion 3a obtained in step b after heating is subjected to planarization (or smoothing) of the metal paste filled in the hole while removing the metal paste covering the surface of the substrate. As a result, the planarized exposed surface VP １ A conductive via precursor 3b containing metal particles and the remainder of the volatile solvent can be formed inside the hole (through hole 30) ((d) of FIG. 3).

[0094] The metal paste portion can be removed using, for example, a rubber squeegee 42 as shown in (b) and (d) of Figure 3. This allows the surface SP of the glass substrate 40 to be removed. ０and the exposed surface VP of the conductive via precursor 3b １ A portion of the metal paste portion (the metal paste covering the surface of the substrate and the metal paste protruding from the holes) can be removed so that the surface is flush with the metal paste. Another method is to remove the metal paste using a metal squeegee such as SUS.

[0095] Surface SP of glass substrate 40 ０ and the exposed surface VP of the conductive via precursor 3b １ The step between the hole (via) and the exposed surface of the conductive via precursor and the opening of the hole (via) may be 5 μm or less, or 3 μm or less, in the direction perpendicular to the substrate surface. The average step calculated by the following method may be within the above range. (Average Step) An image of a cross section passing through the center of the hole (via) is acquired and binarized to determine the cross-sectional area Sa enclosed by the inner wall of the hole (via), the exposed surface of the conductive via precursor, and the opening of the hole (via), and this is divided by the spacing Wa between the inner walls of the hole to calculate the average step.

[0096] [Step d] In this step, the conductive via precursor 3b formed in step c is fired. This allows the formation of a conductive via 3c made of a metal body. The metal body may include a copper sintered body having a porous structure. The porosity of the conductive via may be 7% or less, 1.0 to 6.5%, or 1.5 to 5.0%, from the viewpoint of suppressing penetration of chemicals into the copper sintered body when immersed in a chemical solution such as a resist stripper or plating pretreatment solution in a subsequent step and improving reliability. When the conductive via is made of a copper sintered body, the porosity of the copper sintered body may be within the above range. The porosity can be determined by the method described in the Examples.

[0097] The firing can be carried out by a heating treatment, which can be performed using a heating means such as a hot plate, a hot air dryer, a hot air heating furnace, a nitrogen dryer, an infrared dryer, an infrared heating furnace, a far-infrared heating furnace, a microwave heating device, a laser heating device, an electromagnetic heating device, a heater heating device, or a steam heating furnace.

[0098] The firing atmosphere may be an oxygen-free atmosphere from the viewpoint of suppressing oxidation of the copper sintered body, or a reducing atmosphere from the viewpoint of removing surface oxides of the copper particles in the conductive via precursor. Examples of oxygen-free atmospheres include the introduction of oxygen-free gases such as nitrogen or rare gases, or under vacuum. Examples of reducing atmospheres include pure hydrogen gas, a mixed gas of hydrogen and nitrogen such as forming gas, nitrogen containing formic acid gas, a mixed gas of hydrogen and rare gas, and a rare gas containing formic acid gas. When the conductive via precursor is sintered by heating without pressure, pure hydrogen gas or a mixed gas of hydrogen and nitrogen such as forming gas is preferred, and pure hydrogen gas is preferable. Heating in pure hydrogen gas makes it possible to lower the sintering temperature of the copper particles. When pure hydrogen gas is used, even if the substrate is as thick as 600 μm and the through hole 30 has a small diameter of 10 μm, the gas reaches the center of the through hole 30, making it easy to obtain a metal body containing a copper sintered body.

[0099] The maximum temperature reached during the heat treatment may be 150°C or higher, and may be 350°C or lower, 300°C or lower, or 260°C or lower, from the viewpoint of reducing thermal damage to each component and improving yield. If the maximum temperature reached is 150°C or higher, sintering tends to proceed sufficiently when the maximum temperature is held for 60 minutes or less. From the viewpoint of volatilizing all the volatile solvent and improving yield, the maximum temperature holding time may be 1 minute or higher, and may be 60 minutes or lower, 40 minutes or lower, or 30 minutes or lower.

[0100] In this embodiment, by using the metal paste of this embodiment, sintering can be performed in an atmosphere containing formic acid gas at a low temperature of 300° C. or less, 200° C. or less, or 150° C. or less, and firing may be performed at 100 to 300° C., 100 to 200° C., or 100 to 150° C. In this case as well, a conductive via with excellent conductivity and connection reliability can be formed.

[0101] The conductive via precursor may be fired without pressure or under pressure. In the latter case, in an atmosphere containing pure hydrogen gas, the pressure may be 0.05 MPa or more, 0.1 MPa or more, or 0.3 MPa or more, and 20 MPa or less, 15 MPa or less, or 10 MPa or less. In addition, in an atmosphere containing nitrogen gas, the pressure may be 1 MPa or more, or 3 MPa or more, and 20 MPa or less, 15 MPa or less, or 10 MPa or less.

[0102] By setting the pressure to 0.05 MPa or more when pure hydrogen gas is used, or 1 MPa or more when nitrogen gas is used, it becomes easier to suppress the generation of voids in the conductive via formed in the center of the through hole 30, and it becomes easier to obtain a conductive via with good conductivity. Furthermore, by setting the pressure to the above-mentioned lower limit or more, when the glass substrate 40 has a metal coating 2, it becomes easier to improve the bonding strength between the metal coating 2 and the conductive via.

[0103] Furthermore, as long as the pressure applied during firing is within the above range, no special pressure device is required, and voids can be reduced and the bonding strength and connection reliability can be further improved without impairing yield. Methods for applying pressure to the glass substrate having the conductive via precursor formed in the through hole include, for example, a method of placing a weight, a method of applying pressure using a pressure device, and a method of applying pressure using a fixing jig for applying pressure.

[0104] The copper sintered body contained in the metal body may have a copper element ratio of 95% by mass or more, 97% by mass or more, 98% by mass or more, or even 100% by mass, excluding light elements, among the constituent elements. If the copper element ratio in the copper sintered body is within the above range, the formation of intermetallic compounds or the precipitation of different elements at the metallic copper crystal grain boundaries can be suppressed, the properties of the metallic copper constituting the copper sintered body are likely to be strengthened, and even better connection reliability is likely to be obtained.

[0105] In step d, the conductive via precursor is formed on an exposed surface VP that is flat and has a sufficiently small step with the substrate surface. １ and has a composition that is resistant to volume shrinkage due to firing. ０and the exposed surface VP of the conductive via 3c ２ The difference in level between the two can be made sufficiently small.

[0106] Surface SP of glass substrate 40 ０ and the exposed surface VP of the conductive via 3c ２ The step (or the depression of the conductive via 3c) between the hole (via) and the exposed surface of the conductive via 3c may be 5 μm or less, or may be 3 μm or less, in the direction perpendicular to the substrate surface. The average step calculated by the following method may be within the above range. (Average Step) An image of a cross section passing through the center of the hole (via) is acquired and binarized to determine the cross-sectional area Sb enclosed by the inner wall of the hole (via), the exposed surface of the conductive via, and the opening surface of the hole (via), and this is divided by the spacing Wb of the inner walls of the hole to calculate the average step.

[0107] Through the above-described steps a to d, the glass substrate 50 with conductive vias can be obtained. In the glass substrate 50 with conductive vias, the exposed surfaces of the conductive vias are flat (smooth), and the surface SP of the glass substrate 40 ０ Since the step between the wiring and the substrate is sufficiently small, the wiring can be easily formed and a sufficiently low connection resistance can be exhibited even after the wiring is formed.

[0108] The method for manufacturing a glass substrate with conductive vias of this embodiment may further include a step e of forming wiring. In this case, the method may be used as a method for manufacturing a wiring substrate with conductive vias.

[0109] [Step e] This step may include a resist forming step, a plating step, a resist removing step, and an etching step, which will be described below.

[0110] <Resist Forming Process> In the resist forming process, for example, as shown in (a) and (b) of FIG. 4, a negative photosensitive dry film 8 for etching resist is laminated on the main surface of the glass substrate 40 and the conductive via 3c, and then a light-transmitting photomask is placed over the wiring shape, exposed to ultraviolet light, and the unexposed areas are removed with a developer, thereby forming an etching resist 8a.

[0111] Other methods for forming the etching resist 8a include, for example, a method of silk-screen printing resist ink and a method of laminating a dry film resist using a laminator.

[0112] <Plating Step> In the plating step, for example, as shown in FIG. 4C, the wiring 9 can be formed in the opening of the etching resist 8a by a method such as electrolytic plating or electroless plating.

[0113] <Resist Removal Step> In the resist removal step, for example, as shown in FIG. 4D , the etching resist 8 a can be removed by a method such as stripping by a wet process using an alkaline aqueous solution or an organic solvent-based chemical liquid such as an organic amine-based liquid such as TMAH or a ketone-based liquid such as acetone, or stripping by a dry process using plasma, ozone, or the like.

[0114] <Etching Step> In the etching step, the metal coating 2 in the portion not covered by the wiring 9 can be removed by etching. In this embodiment, a portion of the metal coating 2 provided on each main surface of the glass substrate 1 is removed by etching.

[0115] Examples of etching methods include methods using chemical etching solutions typically used for wiring boards, such as a solution of cupric chloride and hydrochloric acid, a ferric chloride solution, a solution of sulfuric acid and hydrogen peroxide, or an ammonium persulfate solution.

[0116] By the above step e, a wiring substrate 52 with conductive vias as shown in FIG. 4(e) can be obtained.

[0117] In the above-described method, a step of removing at least a part of the conductor such as the sintered body of metal base or the metal coating 2 remaining on the main surface of the glass substrate 40 may be performed before the step e.

[0118] The means for removing the conductor include chemical polishing, mechanical polishing, chemical mechanical polishing, fly-cutting, plasma treatment, etc. Fly-cutting refers to cutting and flattening with a surface planer.

[0119] According to the manufacturing method of the glass substrate with conductive vias of this embodiment, it is possible to obtain a substrate with conductive vias in which the main surface of the substrate (e.g., the metal coating 2, etc.) is fully exposed and the step between the main surface of the substrate and the conductive vias is sufficiently small, so that it is possible to omit processes for smoothing the main surface of the substrate, such as the process of removing the conductor described above.

[0120] In step e of this embodiment, a resin layer forming step may be further provided in which a resin layer is formed on the wiring substrate with conductive vias. This allows a resin layer to be formed that covers the wiring 9, more effectively preventing cracks from occurring around the conductive vias and a decrease in adhesion between the glass and the wiring in a reliability test, and further improving the connection reliability of the wiring substrate.

[0121] The resin layer may be formed by coating a resin composition or by attaching a resin film. The resin composition and resin film may be used as an interlayer insulating material. The resin layer may be cured by heating.

[0122] The present invention will be explained in more detail below with reference to examples and comparative examples, but the present invention is not limited to the following examples.

[0123] [Preparation of Metal Paste] (Preparation Examples A to J and Comparative Preparation Example A) The raw materials shown below were mixed using a triple roll mill in the proportions (parts by mass) shown in Tables 1 and 2 to prepare metal pastes.

[0124] <First Copper Particles> (Wet Copper Powder) Spherical copper particles W1: 1050Y (manufactured by Mitsui Kinzoku, Co., Ltd., average particle size (D50): 0.81 μm, spherical) Spherical copper particles W2: 1100Y (manufactured by Mitsui Kinzoku, Co., Ltd., average particle size (D50): 1.1 μm, spherical) Spherical copper particles W3: 1200Y (manufactured by Mitsui Kinzoku, Co., Ltd., average particle size (D50): 2.1 μm, spherical) Spherical copper particles W4: 1300Y (manufactured by Mitsui Kinzoku, Co., Ltd., average particle size (D50): 3.5 μm, spherical) Flat copper particles W1: 1100YP (manufactured by Mitsui Kinzoku, Co., Ltd., average particle size (D50): 1.4 μm, flat) Flat copper particles W2: 1200YP (manufactured by Mitsui Kinzoku, Co., Ltd., average particle size (D50): 3.1 μm, flat) (Atomized Copper Powder) Spherical copper particles A1: MA-C02K (manufactured by Mitsui Kinzoku Co., Ltd., average particle size (D50): 1.8 μm, spherical) Spherical copper particles A2: MA-C025K (manufactured by Mitsui Kinzoku Co., Ltd., average particle size (D50): 2.4 μm, spherical) Spherical copper particles A3: MA-C03K (manufactured by Mitsui Kinzoku Co., Ltd., average particle size (D50): 3.4 μm, spherical)

[0125] <Second copper particles> Spherical copper particles W5: CH0200L1 (manufactured by Mitsui Kinzoku Co., Ltd., average particle size (D50): 200 nm, spherical)

[0126] <Resin Components> Resin R1: A mixture of "KFA-2000" (acrylic binder manufactured by GOO Chemical Industry Co., Ltd.) as an organic binder and a mixture of carbitol and terpineol as an organic solvent (the mass ratio of carbitol to terpineol in the mixture [carbitol:terpineol] = 1:1) in a mass ratio of 1:2.

[0127] <Volatile solvents> (High vapor pressure solvent: vapor pressure of 4 Pa ​​or more and 30 Pa or less at 20°C) α-Terpineol: manufactured by Fujifilm Wako Pure Chemical Industries, Ltd., vapor pressure of 6.5 Pa at 20°C (Low vapor pressure solvent: vapor pressure of less than 4 Pa ​​at 20°C) Diethylene glycol mono-n-butyl ether: manufactured by Showa Chemical Co., Ltd., vapor pressure of 1.3 Pa at 20°C

[0128] The metal pastes obtained in Preparation Examples A to J and Comparative Preparation Example A were evaluated for viscosity, printability, bondability, and volume resistivity of the sintered body according to the following methods.

[0129] <Viscosity> The viscosity of the metal paste was measured using a micro spiral viscometer PCU-02V (product name, manufactured by Malcom Co., Ltd.) The measurement conditions were a rotation speed of 10 rpm and a temperature of 25°C.

[0130] <Printability> In the <Preparation of Metal Particle Film> described below, when printing was performed on a 100 μm-thick PET film using a screen printer, the number of pinholes that had formed due to the failure to coat the PET film side was measured. Based on the number of pinholes, printability was evaluated according to the following criteria. Evaluations A to D can be considered as good. (Evaluation Criteria) A: Number of pinholes: 0 B: Number of pinholes: 1 or more but less than 3 C: Number of pinholes: 3 or more but less than 5 D: Number of pinholes: 5 or more but less than 10 E: Number of pinholes: 10 or more but less than 20 F: Number of pinholes: 20 or more

[0131] In the <Preparation of Metal Particle Film> described later, the coating amount (g) of an 8-inch diameter film was measured after printing on a 100 μm thick PET film using a screen printer.

[0132] <Bondability> Bonded samples for shear strength tests were prepared and die shear strength was measured according to the following method, and the bondability was evaluated according to the following criteria. Note that samples with ratings A to C can be considered as good.

[0133] (Preparation of joint sample for shear strength test) 3 x 3 mm ２Using a 100 μm thick stainless steel mask with square openings and a squeegee, the metal paste was stencil printed on a copper plate measuring 25 × 20 × 3 mm thick. After drying at 90 ° C for 10 minutes using a hot plate, it was placed in a tube furnace (manufactured by AVC Corporation), and argon gas was flowed at a flow rate of 1 L / min to replace the air in the tube furnace with argon gas. The temperature was then raised to 225 ° C over 10 minutes while hydrogen gas was flowed at 300 mL / min, and the metal paste was sintered by sintering at 225 ° C for 60 minutes. The metal paste was then cooled by flowing argon gas at a flow rate of 0.3 L / min, and removed into air at 50 ° C or below. A substrate with a metal body formed on the copper plate was obtained as a bonded sample for shear strength testing.

[0134] (Measurement of die shear strength) For the bonded samples for shear strength testing, a universal bond tester (4000 series, manufactured by Daisi Japan Co., Ltd.) equipped with a DS-100 load cell was used to press the metal body or Cu plate horizontally under measurement conditions of a measurement speed of 5 mm / min and a measurement height of 50 μm, and the die shear strength was measured. The average value of 10 locations was calculated and used as the average bond strength. (Evaluation criteria) A: Average bond strength of 50 N or more B: Average bond strength of 40 N or more but less than 50 N C: Average bond strength of 20 N or more but less than 40 N D: Average bond strength of 10 N or more but less than 20 N E: Average bond strength of less than 10 N

[0135] <Volume Resistivity Measurement> The metal paste prepared above was applied to a 1 mm thick glass wafer using an automatic film applicator (manufactured by Allgood Co., Ltd.) to a coating thickness of approximately 150 μm. The coating area was approximately 5 cm x 10 cm. Next, the wafer with the coating film was dried at 90 ° C for 10 minutes using a hot plate, then placed in a tube furnace (manufactured by AVC Corporation). Argon gas was flowed at 1 L / min to replace the air in the tube furnace with argon gas. The temperature was then raised to 225 ° C over 10 minutes while hydrogen gas was flowed at 300 mL / min, and the metal paste was sintered by sintering at 225 ° C for 60 minutes. The wafer was then cooled by flowing argon gas at a flow rate of 0.3 L / min and removed into air at 50 ° C or below to obtain a sample with a metal body formed on the wafer.

[0136] The volume resistivity of the metal body in the above sample was calculated from the sheet resistance value measured with a four-point needle sheet resistance meter (Loresta GP, manufactured by Mitsubishi Analytech Co., Ltd.) and the film thickness determined with a non-contact surface / layer cross-sectional shape measurement system (VertScan, manufactured by Ryoka Systems Co., Ltd.).

[0137]

[0138]

[0139] [Preparation of Glass Substrates with Conductive Vias] (Examples 1 to 13 and Comparative Examples 1 to 4) Glass substrates with conductive vias were prepared in the following manner.

[0140] <Preparation of Glass Substrate> Glass substrate A: A glass substrate "D263Teco" (trade name, manufactured by SCHOTT GmbH, material: borosilicate glass, average linear thermal expansion coefficient α: 7.2 × 10) having through holes and on both main surfaces and wall surfaces of the through holes, a titanium layer (thickness: 100 nm) and a copper layer (thickness: 300 nm) formed in this order. －６ K －１) was prepared. The glass substrate had a diameter of 6 inches and a thickness of 300 μm, and the titanium layer and copper layer were formed in this order by sputtering, with through-holes having a hole diameter (via diameter) of 90 μm. Glass substrate B: A glass substrate "OA-10G" (manufactured by Nippon Electric Glass Co., Ltd., material: alkali-free glass, average linear thermal expansion coefficient α: 3.8 × 10) having through-holes, on both main surfaces and on the wall surfaces of the through-holes, a titanium layer (thickness 100 nm) and a copper layer (thickness 300 nm) formed in this order. －６ K －１ The glass substrate had a diameter of 6 inches and a thickness of 300 μm, and the titanium layer and copper layer were formed in this order by sputtering, with through holes having a hole diameter (via diameter) of 90 μm.

[0141] <Preparation of Metal Particle Film> The metal paste prepared above was printed onto a 100 μm thick PET film in an 8-inch diameter (circular shape with a diameter of 20 cm) using a screen printing plate (line diameter: 23 μm, mesh number: 400, mesh size: 41 μm, void ratio: 41 μm) using a screen printer, to obtain a metal particle film provided with a metal particle-containing layer.

[0142] <Formation of Conductive Vias> Using a bonding device VJ-35 (manufactured by Ayumi Industries Co., Ltd.), the metal particle film was bonded to the glass substrate from the metal particle-containing layer side, and the laminate was then vacuum-pressed at room temperature under a pressure of 3 MPa to fill the through holes with the metal paste. At this time, the metal paste was caused to protrude from the side of the glass substrate opposite to the side to which the metal particle film was bonded. Note that glass substrate A was used in Examples 1 to 11 and Comparative Examples 1 and 2, and glass substrate B was used in Examples 12 and 13 and Comparative Examples 3 and 4.

[0143] Next, the PET film was peeled off from the laminate, and the laminate was dried in the air for 10 minutes at 90° C. The concentrations (mass%) of metal particles in the metal paste portion before and after drying are shown in the table.

[0144] For the dried laminate, as shown in Figures 3(a) to 3(d), the metal paste on the main surface of the glass substrate on which the metal particle film was bonded was removed using a rubber squeegee, and then the metal paste protruding from the side of the glass substrate opposite to the side on which the metal particle film was bonded was removed using a rubber squeegee.

[0145] Next, the glass substrate with the conductive via precursor formed in the through-hole by the above-mentioned process was placed in a tube furnace (manufactured by AVC Corporation), and argon gas was flowed at 1 L / min to replace the air in the tube furnace with argon gas. Thereafter, while flowing hydrogen gas at 300 mL / min, the temperature was raised to 300 ° C over 10 minutes, and a sintering treatment was performed at 300 ° C for 60 minutes to sinter the conductive via precursor. Thereafter, argon gas was flowed at a flow rate of 0.3 L / min to cool the substrate, and the substrate was removed into air at 50 ° C or below to obtain a glass substrate with conductive vias.

[0146] <Evaluation of Glass Substrates with Conductive Vias> The glass substrates with conductive vias obtained above were evaluated for the presence or absence of cracks and voids in the conductive vias, the porosity of the conductive vias, and depressions after sintering according to the following methods.

[0147] (Presence or absence of cracks in conductive vias) The cross sections of the conductive vias of the glass substrate with conductive vias were exposed by cross-section polishing, and 30 conductive vias were observed using a digital microscope (VHX-6000, manufactured by Keyence Corporation) to check for the presence or absence of cracks (length 10 μm or more).

[0148] (Presence or absence of voids in conductive vias) The cross sections of the conductive vias of the glass substrate with conductive vias were exposed by cross-section polishing, and 30 conductive vias were observed using a digital microscope (VHX-6000, manufactured by Keyence Corporation) to confirm the presence or absence of voids (diameter 5 μm or more).

[0149] (Dentation after sintering) The cross section of the conductive via of the glass substrate with conductive vias was exposed by cross-section polishing, and 30 conductive vias were observed using a digital microscope (VHX-6000, manufactured by Keyence Corporation), and the average step height was calculated using the following method. [Average step height] An image of the cross section passing through the center of the via was acquired and binarized to determine the cross-sectional area Sb surrounded by the inner wall of the via, the exposed surface of the conductive via, and the opening surface of the via, and this was divided by the spacing Wb between the inner walls of the hole to calculate the average step height (= Sb / Wb). The average value of the average step heights at 30 locations was calculated, and the dent height after sintering was evaluated according to the following evaluation criteria. Note that a rating of C or higher can be considered good. (Evaluation Criteria) A: The average value of the average step height is less than 1 μm. B: The average value of the average step height is 1 μm or more and less than 3 μm. C: The average value of the average step height is 3 μm or more and less than 5 μm. D: The average value of the average step height is 5 μm or more and less than 10 μm. E: The average value of the average step height is 10 μm or more.

[0150] (Porosity of Conductive Vias) A glass substrate with conductive vias that had been mechanically polished was cut in the thickness direction, and the cross section of the center of the conductive via in the glass substrate was exposed using a focused ion beam, and this cross section was observed. When observing the cross section of the center of the through hole in the glass substrate, a range of ±5 μm from the center of the through hole in the thickness direction of the glass substrate and ±5 μm in the direction perpendicular to the thickness direction of the glass substrate was observed. A focused ion beam processing observation device MI4050 (manufactured by Hitachi High-Technologies Corporation) was used. For observation, a scanning electron microscope S-3700N (manufactured by Hitachi High-Technologies Corporation) was used at a magnification of 5000x, and cross-sectional images (approximately 10 μm square) of the conductor were taken. Five observation locations were used. The obtained cross-sectional images were binarized using image analysis software (Adobe Photoshop (registered trademark) Elements) to separate the sintered copper portion and the porous (void) portion. For each of the five observation points, the ratio of the area of ​​the porous portion to the total area of ​​the cross section of the conductive via was calculated, and this was taken as the porosity. The average value of the porosities at the five observation points was taken as the porosity of the conductive via.

[0151] [Fabrication and Evaluation of Wiring Boards] (Examples 1 to 13 and Comparative Examples 1 to 4) Wiring was formed on a glass substrate with conductive vias fabricated in the same manner as above, in the following manner to obtain wiring boards, which were then evaluated.

[0152] A UV-curable etching resist dry film H-W425 (trade name, manufactured by Resonac Corporation) was pressure-bonded to the surface of the glass substrate with conductive vias obtained above using a laminator. A photomask was then aligned, the wiring pattern was exposed, and the resist was developed. Next, electrolytic plating was performed on the resist openings, followed by resist peeling and seed layer etching to form wiring with a 300 μm x 600 μm wiring pattern, thereby obtaining test piece 55 (wiring substrate) as shown in FIG. 5. The wiring pattern was finished so that its thickness was approximately 10 μm after etching the seed layer. In test piece 55, the conductive vias formed in the through holes were electrically connected by wiring provided on the substrate surface.

[0153] In Examples 11 and 13 and Comparative Examples 2 and 4, ABF films "ABF GX92" (manufactured by Ajinomoto Fine-Techno Co., Ltd.) were attached by heat pressing to both sides of test piece 55 on which a wiring pattern was formed, to prepare test pieces with a resin layer. The thickness of the resin layer was approximately 30 μm.

[0154] The test pieces obtained above were evaluated for initial resistance, connection reliability, the presence or absence of cracks in the substrate, and depressions in the conductive vias after resist peeling, according to the following methods.

[0155] (Initial Resistance Value) The initial resistance value of the test piece 55 (or the test piece with the resin layer) was measured as the resistance value of 1,000 connected 90 μmφ vias. Based on this connected connection resistance value, the initial resistance value was evaluated according to the following criteria. A rating of B or higher can be judged as good. (Number of Vias) 90 μmφ: 1,000 pieces (Evaluation Criteria) A: Resistance value less than 6 Ω B: Resistance value 6 Ω or more and less than 10 Ω C: Resistance value 10 Ω or more and less than 20 Ω D: Resistance value 20 Ω or more and less than 50 Ω E: Resistance value 50 Ω or more

[0156] (Connection Reliability) Test piece 55 (or test piece with resin layer) was set in a temperature cycle tester (TSA-72SE-W, manufactured by Espec Corporation), and a temperature cycle connection reliability test was performed under the following conditions: low temperature side: -55°C, 15 minutes; room temperature: 2 minutes; high temperature side: 125°C, 15 minutes; defrosting cycle: automatic; number of cycles: 50, 100, 300, 500, 1000 cycles. For the test piece that had undergone each number of cycles, the resistance value of the connection of the above number of vias was measured. Based on this connected connection resistance value, the connection reliability was evaluated according to the following criteria. (Evaluation criteria) A: Resistance change rate is less than 1% of the initial resistance value. B: Resistance change rate is 1% or more and less than 3% of the initial resistance value. C: Resistance change rate is 3% or more and less than 5% of the initial resistance value. D: Resistance change rate is 5% or more and less than 10% of the initial resistance value. E: Resistance change rate is 10% or more and less than 20% of the initial resistance value. F: Resistance change rate is 20% or more of the initial resistance value. G: Poor continuity occurs.

[0157] (Cracks in the Substrate) The test piece 55 (or the test piece with the resin layer) was visually inspected to check for cracks in the glass substrate.

[0158] (Dent after resist removal) In producing test piece 55 (or test piece with resin layer), after removing the resist, the cross section of the conductive via was exposed by cross-section polishing, and 30 conductive vias were observed using a digital microscope (VHX-6000, manufactured by Keyence Corporation), and the average value of the average step height was calculated in the same manner as in the evaluation of the dents after sintering described above. Then, the dents after resist removal were evaluated according to the following evaluation criteria. Note that dents with an evaluation of C or higher can be judged as good. (Evaluation criteria) A: The average value of the average step height is less than 1 μm B: The average value of the average step height is 1 μm or more and less than 3 μm C: The average value of the average step height is 3 μm or more and less than 5 μm D: The average value of the average step height is 5 μm or more and less than 10 μm E: The average value of the average step height is 10 μm or more

[0159]

[0160]

[0161] [Observation and Consideration of Conductive Vias] (Observation 1) For the glass substrate with conductive vias produced in Example 1, a focused ion beam processing and observation device (manufactured by Hitachi High-Technologies Corporation, product name: MI4050) was used to expose the cross section of the center of the conductive via of the glass substrate with conductive vias using a focused ion beam, and the cross section was observed. For the observation, a scanning electron microscope (manufactured by Hitachi High-Technologies Corporation, product name: S-3700N) was used, and images of the cross section of the copper sintered body were taken at magnifications of 5,000 and 20,000 (see FIG. 6). The images shown in FIG. 6 are (a) an image at a magnification of 5,000 times, and (b) an image at a magnification of 20,000 times. As shown in FIG. 6(b), the copper sintered body has a structure in which first copper particles are filled between second copper particles, and the particles are bonded to each other. It is believed that the formation of such a dense copper sintered body and the suppression of voids and cracks as well as depressions due to the suppression of shrinkage during sintering enable a sufficiently low connection resistance to be exhibited even after wiring formation, and that the resulting wiring board has excellent connection reliability.

[0162] [Observation and Consideration of Wiring Board] The appearance and cross section of the wiring board produced in Example 1 were observed using an optical microscope. The images shown in Figure 7 are (a) the appearance of the wiring board, (b) an enlarged view of a portion of (a), and (c) a cross section of the wiring board. As shown in Figure 7, the via portion of the glass substrate is filled with the copper sintered body without voids, and copper wiring is well formed in the conductive via portion filled with the copper sintered body.

[0163] [Preparation of Glass Substrates with Conductive Vias] (Comparative Examples 5 to 8) Glass substrates with conductive vias were prepared by the following procedure.

[0164] <Preparation of Glass Substrate> The same glass substrate A and glass substrate B as above were prepared.

[0165] <Formation of Conductive Vias> The glass substrate was immersed in a copper sulfate plating solution to perform electrolytic copper plating, thereby filling the vias with a diameter of 90 μm. Next, the copper plating films deposited on both sides of the glass substrate were polished using a CMP slurry, so that the copper thickness on the glass substrate was approximately 1 μm.

[0166]

[0167] [Observation and Consideration of Wiring Boards After Temperature Cycle Test] The surfaces of the wiring boards produced in Example 12 and Comparative Example 7 after the temperature cycle test (50 times) were observed with an optical microscope. As shown in FIG. 8A, the wiring board produced in Example 12 suppressed the occurrence of cracks even after the temperature cycle test. FIG. 8B is an enlarged view of a portion of FIG. 8A. On the other hand, as shown in FIG. 9A, the wiring board produced in Comparative Example 7 had cracks occurring in the glass substrate around the conductive vias. FIG. 9B is an enlarged view of a portion of FIG. 9A.

[0168] [Young's Modulus of Sintered Body of Metal Paste] The Young's modulus of the sintered body of the metal paste of Preparation Example A was measured using the following method. (Young's Modulus Measurement) The metal paste was coated onto a glass substrate so that the dried dimensions were 40 mm x 10 mm x 0.22 mm. Next, the metal paste coating was fired using the following procedure. (a) The glass substrate with the metal paste coating was placed in a tube furnace (manufactured by AVC Corporation), and argon gas was flowed at 1 L / min to replace the air in the tube furnace with argon gas. (b) Next, while flowing hydrogen gas at 300 mL / min, the temperature was raised to 300°C over 10 minutes, and sintering treatment was performed at 300°C for 60 minutes. (c) Thereafter, argon gas was flowed at a flow rate of 0.3 L / min to cool the glass substrate with the sintered body, and the glass substrate with the sintered body formed thereon was removed into air at 50°C or below. (d) The Young's modulus of the obtained sintered body is measured by a resonance method using a JE2-RT model manufactured by Nippon Technoplus Co., Ltd., under the conditions of a temperature of 23° C. and a resonance frequency of 278.4 Hz.

[0169] The metal paste of Preparation Example A had a Young's modulus of 27.4 GPa for the sintered body. This value is approximately one-third of the Young's modulus of a typical electrolytic copper plating film, which is approximately 100 GPa. It is believed that filling the via with a copper sintered body with such a low Young's modulus reduced stress around the via and prevented cracks from occurring around the via after the temperature cycle test.

[0170] DESCRIPTION OF SYMBOLS 1...glass substrate, 2...metal coating, 3...metal paste portion, 3b...conductive via precursor, 3c...conductive via, 3p...metal particle-containing layer, 7...support film, 8a...etching resist, 9...wiring, 30...through hole, 31...blind hole, 40, 41...glass substrate, 42...rubber squeegee, 50...glass substrate with conductive via, 52...wiring board with conductive via, 55...test piece, A...pressure jig

Claims

1. A method for manufacturing a glass substrate with conductive vias, comprising: step a) of preparing a glass substrate having holes formed therein; and providing a metal paste portion containing metal particles and a volatile solvent so as to fill the holes and cover at least the surface of the glass substrate around the holes; step b) of heating the metal paste portion to remove a portion of the volatile solvent; step c) of removing a portion of the metal paste portion after heating to expose the surface, thereby forming a conductive via precursor containing the metal particles and the remainder of the volatile solvent and having a flattened exposed surface inside the hole; and step d) of firing the conductive via precursor, wherein the metal particles include first metal particles having a volume average particle size of 0.8 μm or more and second metal particles having a volume average particle size of 0.5 μm or less, the metal paste portion provided in step a has a metal particle concentration of 95.0 mass % or more, and the content of the second metal particles in the metal paste portion provided in step a is 50 mass % or less based on the total amount of the metal particles.

2. The method for manufacturing a glass substrate with conductive vias according to claim 1, wherein the first metal particles and the second metal particles are copper particles.

3. The method for manufacturing a glass substrate with conductive vias according to claim 1 or 2, wherein the first metal particles include flaky copper particles.

4. A metal paste used to form a glass through electrode, comprising metal particles and a volatile solvent, the content of the metal particles being 95.0 mass% or more based on the total amount of the metal paste, the metal particles including first metal particles having a volume average particle size of 0.8 μm or more and second metal particles having a volume average particle size of 0.5 μm or less, and the content of the second metal particles being 50 mass% or less based on the total amount of the metal particles.

5. The metal paste for forming a glass through electrode according to claim 4, wherein the first metal particles and the second metal particles are copper particles.

6. The metal paste for forming a glass through electrode according to claim 4 or 5, wherein the first metal particles include flaky copper particles.

7. A glass substrate with conductive vias, comprising a glass substrate having a through hole and a conductive via provided in the through hole, wherein the conductive via contains a sintered body of the metal paste according to claim 4 or 5.

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