Primer resin liquid for electroless plating, plating method for glass substrate with through holes using said primer resin liquid, and glass interposer substrate

Abstract

A primer resin liquid is provided that can form a primer resin layer for forming a metal film on a glass substrate such as a TGV while ensuring adhesion. [Solution] The present invention relates to a primer resin liquid for electroless plating, which comprises a resin component and a solvent component. In the present invention, the resin component includes resin I, which is a base component, resin II, which is a crosslinker component, and resin III, which is an adhesive component. Resin III is a thermosetting resin having a bisphenol skeleton, and the content of III in the resin component is 10% by mass or more and 48% by mass or less. The primer resin liquid of the present invention has an optimized viscosity and surface tension for forming a primer resin layer on a substrate with through holes. Specifically, the primer resin liquid of the present invention has a viscosity of 10 mPa·s or less at 25°C and a surface tension of 40 mN / m or less at 22°C, as measured by the Young-Laplace method.

Description

[Technical Field]

[0001] The present invention relates to a primer resin liquid for forming a primer resin layer on a substrate surface to ensure adhesion when forming a plating film by electroless plating. In particular, the present invention relates to a primer resin liquid useful for glass substrates with through holes. The present invention also relates to a plating method optimized for forming a metal plating film inside the through holes of a glass substrate with through holes, using the primer resin liquid. [Background technology]

[0002] To meet the demand for miniaturization and high integration of semiconductor devices, advanced 2D and 2.5D packaging technologies using interposer substrates have been put into practical use as semiconductor chip packaging technologies. This packaging method, which connects semiconductor chips and circuit boards through the interposer substrate in the thickness direction, enables high integration of semiconductor chips and high-speed signal transmission between chips, and is expected to be widely adopted in the future. The interposer substrate used in this packaging method is an intermediate substrate with through-holes formed in the substrate at locations corresponding to the bumps and other connection points of the semiconductor chip. These through-holes are fabricated by forming conductors inside through-holes formed in the substrate. Known through-holes include via-filling, in which the through-holes are filled with conductive metals such as copper (Cu) by plating (via filling), and vias in which the inner surface of the through-holes is coated with a conductive metal film without filling the entire hole.

[0003] Until now, most interposer substrates have used resin substrates such as glass epoxy as the base material (core substrate). However, resin substrates have a large thermal expansion coefficient, which poses challenges in terms of shape stability. Interposer substrates are substrates with minute through-holes, and deformation of the substrate due to thermal expansion can lead to deformation and disconnection of the electrodes inside the through-holes. Therefore, when applying resin substrates to interposer substrates, materials have been changed to lower the thermal expansion coefficient, and although this has had some success, there are limitations. In particular, in order to accommodate the miniaturization and high integration of wiring circuits in recent years, the through-holes in interposer substrates must be further miniaturized, and it has been difficult to say that resin substrates can adequately meet this demand.

[0004] Therefore, silicon substrates and glass substrates are being considered as the base material for interposer substrates. Silicon substrates (silicon interposers) do not have the problem of thermal expansion coefficient that is an issue with resin substrates, and they also have excellent heat dissipation properties. However, because silicon is a semiconductor, transmission loss is large, making it difficult to apply to high-frequency devices. In addition, because silicon is a relatively expensive material, the range of devices that can be used is limited.

[0005] For this reason, there has been a rapid increase in the number of studies into interposer substrates (glass interposers) using glass substrates. Glass, with its low thermal expansion coefficient and insulating properties, addresses the challenges posed by resin and silicon substrates. Glass substrates also offer the advantage of excellent smoothness. The surface roughness of the metal wiring and metal electrodes formed on interposer substrates is affected by the smoothness of the underlying substrate surface. Increased surface roughness of the metal wiring and metal electrodes increases transmission loss (scattering loss), making them unsuitable for high-frequency applications. Therefore, the application of glass substrates, with their excellent surface smoothness, is promising. Furthermore, advances in manufacturing technology have made glass substrates easier to thin and more cost-effective than silicon substrates. Glass substrates with fine through-holes for use in glass interposers, known as Through Glass Via (TGV), have also been developed, and research into the formation of fine through-holes is also active.

[0006] Important technologies for practical application of glass substrates with micro through-holes such as TGVs include microfabrication technology for forming the through-holes, as well as the establishment of technology for forming metal films on the inner glass surfaces of the through-holes. In this regard, glass is a material on which it is difficult to form metal films with good adhesion, compared to the resins and silicon mentioned above. This is because glass, which is formed by covalent bonds between oxides such as silicon dioxide, aluminum oxide, and boron oxide, is fundamentally different in bonding structure from metals, which are formed by metallic bonds between metal atoms.

[0007] Furthermore, as mentioned above, glass is a material with excellent surface smoothness, but this also reduces the adhesion of metal films. Conventional resin substrates ensure the adhesion of metal films through the anchoring effect of surface roughening treatment, and similar treatments can be applied to glass substrates. However, because the surface smoothness of the substrate can contribute to reducing transmission loss in metal films, it is not a good idea to intentionally eliminate this benefit.

[0008] Regarding conventional techniques for forming metal films on glass substrates, particularly on glass substrates with micro-throughholes, Patent Documents 1 and 2 describe methods for forming a metal oxide layer at the interface between glass and the metal film. In these techniques, the glass surface and the adhesive layer are mixed by heating to form a metal oxide layer, and this intermediate layer ensures adhesion. In Patent Document 3, adhesion is improved by forming a porous film using a sol-gel method.

[0009] The applicant of the present application has proposed an electroless plating process that can be applied to glass substrates, in which a specific resin layer called a primer resin layer is formed on the surface of the substrate before plating, and a pretreatment solution containing nano-order noble metal nanoparticles is used as catalytic nuclei to promote the growth of the plating film (Patent Documents 4 to 6).

[0010] In the electroless plating process disclosed in Patent Document 4 by the applicant, a primer resin liquid containing a resin with a glass transition temperature (Tg) of 40°C or higher and 430°C or lower is applied to a substrate to form a primer resin layer. After adsorbing and fixing precious metal nanoparticles onto the primer resin layer, the primer resin layer is fluidized by heat treatment within a range of ±50°C of the resin's glass transition temperature, causing the precious metal nanoparticles to sink into the primer resin layer. The application of this primer resin layer and control of the state of the precious metal nanoparticles ensures the adhesion of the plating film formed on the primer resin layer. Furthermore, the applicant's electroless plating process can also be applied to the formation of fine circuits by compounding specific resins with the resin that constitutes the primer resin layer (Patent Documents 5 and 6). [Prior art documents] [Patent documents]

[0011] [Patent Document 1] Japanese Patent Publication No. 2023-521835 [Patent Document 2] Japanese Patent Publication No. 2022-507156 [Patent Document 3] Japanese Patent Application Publication No. 2019-036607 [Patent Document 4] Patent No. 6312766 specification [Patent Document 5] Japanese Patent Application Publication No. 2019-123909 [Patent Document 6] Japanese Patent Application Publication No. 2019-123910 Summary of the Invention [Problem to be solved by the invention]

[0012] As described above, there have been many studies on methods for forming metal films on glass interposers and ensuring adhesion. However, these methods still have some room for improvement. For example, the methods described in Patent Documents 1 and 2, which form a metal oxide layer between a glass substrate and a metal film, require high-temperature heating to form the oxide layer, which can cause deformation or warping of the glass substrate. Furthermore, performing a heat treatment after forming the metal film complicates the interposer manufacturing process. Furthermore, Patent Document 3 improves adhesion by forming a porous film and creating an uneven surface. However, this method is not considered a desirable method for improving adhesion when high-speed transmission is considered, as it raises concerns about transmission loss.

[0013] Furthermore, while the electroless plating process developed by the present applicant using a primer resin layer, as disclosed in Patent Document 4, has been confirmed to be useful for planar glass substrates, its applicability to glass substrates with through holes is unclear. In this regard, the formation of a primer resin layer using a primer resin liquid and the electroless plating process are wet processes. Because the liquid used in wet processes can penetrate narrow areas such as through holes, wet processes are inherently suitable for glass substrates with through holes. However, the aspect ratio of the through holes significantly affects whether a metal film can be formed on the inner surface of the through holes. Therefore, this process may not be effective in cases where the diameter of the through holes is reduced or the aspect ratio of the through holes is increased. Furthermore, the adhesion of the metal film to the inner surface of the through holes has not been fully investigated.

[0014] The present invention has been made under the above-mentioned circumstances, and aims to clarify an electroless plating process for forming a metal film on a glass substrate such as a TGV while ensuring adhesion. In order to achieve this object, the present invention clarifies the configuration of a primer resin liquid (primer resin layer) developed by the applicant of the present application that is optimized for application to micro through holes in a TGV or the like, and provides an electroless plating process suitable for glass substrates with micro through holes that utilizes this. [Means for solving the problem]

[0015] The present inventors have confirmed whether it is possible to form a primer resin layer on the inner surface of a glass substrate with fine through holes using the primer resin liquid developed by the present applicant and to form a metal film (copper plating film) by electroless plating. As a result, it has been confirmed that when an existing primer resin liquid is applied to a glass substrate with fine through holes, the primer resin layer is not formed all the way to the center of the through holes, or even if the primer resin layer is formed all over the inside of the through holes, clogging occurs, which can interfere with subsequent film formation by electroless plating.

[0016] When considering the causes of the problems with primer resin layer formation using conventional primer resin liquids, it is believed that the primer resin liquid does not penetrate sufficiently into the through-holes, and that the fluidity of the primer resin liquid inside the through-holes is either excessive or insufficient. Therefore, the present inventors decided to improve the penetration and fluidity of the primer resin liquid. Specifically, they decided to change the viscosity and surface tension of the primer resin liquid by adjusting the compounding ratio of the resin component and the solvent.

[0017] However, adjusting the solvent ratio in the primer resin liquid to ensure permeability and fluidity into the through-holes naturally changes the ratio of the resin component. Changes in the ratio of the resin component in the primer resin liquid can affect the properties of the primer resin layer, which may affect the adhesion of the metal film formed later by electroless plating.

[0018] Therefore, the inventors conducted detailed studies on the composition of the resin components to find a primer liquid that can achieve higher adhesion than conventional techniques while adjusting the properties of the primer liquid to optimize the permeability and fluidity into through holes. As a result, they came up with the idea of ​​using a three-type mixed resin as the resin component of the primer liquid: a base resin, a crosslinker resin, and an adhesion agent resin. Of these resin components, the base resin and crosslinker resin are also contained in conventional primer liquids (primer resin layers). The inventors decided to add a specific thermosetting resin in an appropriate amount as a resin component that can improve adhesion without impairing the functionality of the conventional primer resin layer. This thermosetting resin as the adhesion agent component imparts rigidity (hardness) and toughness (flexibility) to the primer resin layer, thereby improving adhesion to the subsequently formed plating film. The inventors optimized the composition of the resin components in the primer resin liquid as described above, and then adjusted the blending ratio of the resin components and the solvent to discover a primer resin liquid having viscosity and surface tension optimized for glass substrates with through holes, and arrived at the present invention.

[0019] That is, the present invention provides a primer resin liquid for electroless plating comprising a resin component and a solvent component, the resin component including Resin I as a main component, Resin II as a crosslinker component, and Resin III as an adhesion agent component, the adhesion agent component Resin III being a thermosetting resin having a bisphenol skeleton, the content of Resin III in the resin component being 10% by mass or more and 48% by mass or less, the viscosity at 25°C being 10 mPa s or less, and the surface tension at 22°C measured by the Young-Laplace method being 40 mN / m or less.

[0020] The following describes in detail the constitution of the primer resin liquid for electroless plating according to the present invention, and further describes the electroless plating process for a glass substrate with through holes to which the primer resin liquid for electroless plating according to the present invention is applied.

[0021] A. Constitution of the primer resin liquid for electroless plating according to the present invention As described above, the primer resin liquid for electroless plating of the present invention mainly comprises a resin component and a solvent. The components of each component will be described below.

[0022] A-1 Resin component The resin component is a mixed resin containing the following three essential resins: Resin I, Resin II, and Resin III.

[0023] A-1-1 Resin I (main component) Resin I, the main component, is the main component that forms the framework for the primer resin layer to function as a structure. Resin I is also an effective component for achieving adhesion to glass substrates. It is known that hydroxyl groups are formed on the glass surface due to the dissociation and adsorption of moisture in the air. The resin that makes up the primer resin layer contains hydrogen bonds as intermolecular bonds due to oxygen-containing functional groups, etc. These form hydrogen bonds at the interface between the glass surface and the resin, providing high adhesion.

[0024] Resin I, which is the main component, is a thermoplastic resin, and specifically, polyester resin, polyimide resin, LCP resin, polyethylene terephthalate resin, etc. are used.

[0025] A-1-2 Resin II (crosslinking agent component) Resin II, the crosslinking agent component, promotes the crosslinking reaction of the resin constituting the primer resin layer, crosslinking the resin molecules both intramolecularly and intermolecularly to insolubilize them. Furthermore, in the electroless plating process of the present invention, it also functions as a component for generating functional groups (amino groups) during the crosslinking reaction. The generated functional groups act as acceptors that capture noble metal nanoparticles in the electroless plating process described below, and thus promote the formation of an electroless plated thin film. Therefore, the crosslinking agent component is also an essential resin for the present invention.

[0026] The type of resin that can be used as Resin II is not particularly limited as long as it has the dual functions of promoting the crosslinking reaction and generating functional groups. Examples of suitable crosslinking agents include melamine-based crosslinking agents, amine-based crosslinking agents, guanamine-based crosslinking agents, and glycoluril-based crosslinking agents. Melamine-based crosslinking agents are particularly suitable. Examples of melamine-based crosslinking agents include methoxyalkyl melamines such as hexamethoxymethylmelamine, hexamethoxyethylmelamine (HMM), dimethoxymethylmelamine, trimethoxymethylmelamine, tetramethoxymethylmelamine, pentamethoxymethylmelamine, and hexamethoxymethylmelamine. Other examples include alkoxymethylglycolurils such as tetramethoxymethylglycoluril, 1,3-bismethoxymethyl-4,5-bismethoxyethyleneurea, and bismethoxymethylurea.

[0027] A-1-3 Resin III (adhesion agent component) The above-mentioned resin I (main component) and resin II (crosslinker component) have been used as resin components of the primer resin liquid applied in the electroless plating process (Patent Document 4, etc.) by the applicant of the present application. The resin component of the primer resin liquid in the present invention is a three-component resin that also contains resin III, which serves as an adhesion agent component. The adhesion agent component does not itself function as an adhesion agent. The adhesion agent component is a component that imparts appropriate rigidity and toughness to the primer resin layer, which has previously been composed of resin I and resin II, thereby improving the adhesion strength with the plating film.

[0028] As described above, resin III, which is an adhesive component, is a resin that imparts rigidity and toughness to the primer resin layer formed by the present invention. Resin III is made of a thermosetting resin having a bisphenol skeleton. The bisphenol skeleton is a skeleton composed of two phenol groups, as shown in the following formula (1), and known examples of bisphenol skeletons, depending on the substituent R, include bisphenol A, bisphenol B, bisphenol C, bisphenol E, bisphenol F, bisphenol M, bisphenol P, bisphenol S, bisphenol Z, and phenoxy resin. The bisphenol skeleton is a structure that is effective in imparting rigidity and toughness to the resin.

[0029] [ka]

[0030] Resin III in the present invention is preferably a resin having a bisphenol skeleton, and particularly preferably a resin having a bisphenol A skeleton or a bisphenol F skeleton. Specifically, resin III is preferably a bisphenol A type epoxy resin or a bisphenol F type epoxy resin having an epoxy group. While biphenyl type epoxy resins, glycidyl ester type epoxy resins, and alicyclic epoxy resins are known as thermosetting resins having epoxy groups, these resins without a bisphenol skeleton are ineffective. Preferably, the epoxy equivalent is 150 or more and 3000 or less, and particularly preferably 170 or more and 500 or less.

[0031] A-1-4 Contents of Resin I, Resin II, and Resin III in Resin Components To improve the adhesion of the plating film, the resin component of the primer resin liquid of the present invention has a limited content of Resin III. Adding a thermosetting resin is effective in increasing the rigidity of the primer resin layer, but an excessively high content leads to a decrease in adhesion. By appropriately adjusting the content of the thermosetting resin, the toughness of the primer resin layer can be ensured, resulting in optimal adhesion. The content of Resin III in the resin component is 10% by mass or more and 48% by mass or less. Preferably, it is 15% by mass or more and 40% by mass or less.

[0032] The contents of Resin I and Resin II in the resin components are not particularly limited as long as they fall within the range of the above-mentioned Resin III content. The contents of Resin I and Resin II can be set within a range in which the respective resins exert their respective functions. However, the content of Resin I is preferably 30% by mass or more and 80% by mass or less, and more preferably 45% by mass or more and 75% by mass or less. The content of Resin II is preferably 2% by mass or more and 25% by mass or less, and more preferably 3% by mass or more and 20% by mass or less.

[0033] Furthermore, in a resin component consisting of three resins, Resin I, II, and III, the ratio of the content of Resin I to the content of Resin III (Resin I / Resin III) is preferably 1 or more and 4 or less. Resin I, the main component, is the resin that forms the backbone of the primer resin layer. The main component in the primer resin layer exerts basic adhesion as an intermediate layer between the plating film and the substrate. In addition, the main component in the primer resin layer also functions to capture and fix precious metal nanoparticles, which serve as catalyst nuclei. Therefore, if the content of Resin I is low relative to Resin III, this basic function of the primer resin layer may be reduced, resulting in a decrease in the adhesion strength of the plating film. Therefore, the ratio of the content of Resin I to the content of Resin III is preferably 1 or more. On the other hand, in order for Resin III, the adhesion component, Resin I, to fully exert its function, may not be desirable if the content of Resin I, the main component, is too high relative to Resin III. Therefore, the ratio is preferably 4 or less.

[0034] As described above, the primer resin liquid according to the present invention contains Resin III, an adhesive component, which imparts suitable adhesion to the primer resin layer formed after baking. Furthermore, by setting the ratio of Resin I, Resin II, and Resin III within the above-described suitable range, the primer resin layer can have a suitable thermal expansion coefficient. The thermal expansion coefficient of the primer resin layer at this time is suitably higher than the thermal expansion coefficient of the glass substrate, which is the substrate. This allows the primer resin layer formed on the substrate to maintain its adhesion to the substrate even when subjected to thermal cycles.

[0035] A-2 Solvent The primer resin liquid according to the present invention is produced by dissolving the resin components, which are the aforementioned Resin I, Resin II, and Resin III, in a solvent. The solvent dissolves the resin components, thereby imparting fluidity to the resin components. Furthermore, when the primer resin liquid is applied to a substrate, the solvent acts to form a homogeneous resin layer (primer resin layer) of uniform thickness on the substrate.

[0036] The solvent for the primer resin liquid in the present invention may be a ketone solvent, an ether solvent, an ester solvent, an aromatic hydrocarbon solvent, etc. Specific examples of suitable solvents include methyl ethyl ketone, methyl isobutyl ketone, 2-heptanone, cyclopentanone, cyclohexanone, 2-methoxy-1-propylene acetate, 2-methoxyethanol, 2-ethoxyethanol, 2-ethoxyethyl acetate, 1-methoxy-2-propyl acetate, 1,2-dimethoxyethaneethyl acetate, cellosolve acetate, propylene glycol monoethyl ether acetate, propylene glycol methyl ether acetate, methyl lactate, ethyl lactate, methyl pyruvate, ethyl pyruvate, ethyl 3-methoxypropionate, N-methyl-2-pyrrolidone, 1,4-dioxane, ethylene glycol monoisopropyl ether, diethylene glycol monoethyl ether, diethylene glycol monomethyl ether, diethylene glycol dimethyl ether, toluene, and benzyl benzoate.

[0037] The primer resin liquid is produced by mixing and dissolving the resin components in the above-mentioned solvent. There is no particular order for mixing the resins I to III that make up the resin components with the solvent. Alternatively, stock solutions of each resin dissolved in a solvent may be mixed. Furthermore, a highly concentrated primer resin liquid may be prepared in advance and then diluted with a solvent.

[0038] The solvent in the primer resin liquid volatilizes or decomposes during the pre-baking process described below to form the primer resin layer. During this process, the resin components, Resins I, II, and III, form the primer resin layer without substantially changing their content. Therefore, considering the preferred mixing ratios of the resin components and solvent described above, the concentrations of Resins I, II, and III in the primer resin liquid are as follows: Resin I is preferably 0.06% by mass to 17% by mass, and more preferably 2.0% by mass to 10% by mass; Resin II is preferably 0.03% by mass to 5% by mass, and more preferably 0.1% by mass to 3% by mass; Resin III is preferably 0.2% by mass to 12% by mass, and more preferably 0.7% by mass to 6% by mass. Furthermore, the concentrations of additives, such as reaction initiators, in the primer resin liquid are preferably 0.007% by mass to 2% by mass, and more preferably 0.02% by mass to 0.1% by mass.

[0039] A-3 Primer resin additives The primer resin solution for electroless plating substrates of the present invention essentially comprises the resin components and solvent described above, but may also contain other components (resins and compounds) as additives. For example, it may contain a photoacid generator (PAG) or a sensitizer as a reaction initiator. The photoacid generator may also function as a curing accelerator for the resin III described above. Examples of photoacid generators include onium salts (sulfonium salts, iodonium salts, diazonium salts, etc.), nitrobenzyl esters, diazomethane, triazines, and the like, used alone or in combination. Examples of sensitizers include 9-methylanthracene, anthracenemethanol, acenaphthylene, thioxanthone, methyl-2-naphthyl ketone, 4-acetylbiphenyl, and 1,2-benzofluorene. These additives and reaction initiators are preferably contained in an amount of 0.4% by mass to 10% by mass of the resin components. Even when these additives and reaction initiators are added, it is preferable that the ratio of the solvent in the primer resin liquid is 90% by mass or more and 97% by mass or less, with the remainder being the resin component, additives, etc.

[0040] The resin component content in the primer resin liquid, the content of resins I, II, and III relative to the total resin components, and the concentration of additives in the primer resin liquid described above can be measured by Fourier transform infrared spectroscopy (FT-IR), near-infrared spectroscopy (NIR), gas chromatography mass spectrometry (GC-MS), time-of-flight secondary ion mass spectrometry (TOF-SIMS), nuclear magnetic resonance spectroscopy (NMR), etc.

[0041] A-4 Viscosity and surface tension of primer resin liquid The primer resin liquid for electroless plating according to the present invention has a specified viscosity and surface tension. By optimizing the viscosity and surface tension of the primer resin liquid, the primer resin liquid is endowed with permeability and fluidity suitable for application to a glass substrate with through holes.

[0042] A-4-1 Viscosity of primer resin liquid The viscosity of the primer resin liquid should be 10 mPa·s or less at 25°C. A primer resin liquid with a viscosity exceeding 10 mPa·s has poor fluidity and is difficult to penetrate into the through-holes. Furthermore, as the viscosity of the primer resin liquid decreases, the thickness of the primer resin layer tends to become thinner. From the viewpoint of forming a primer resin layer with a thickness that can provide sufficient adhesion, the viscosity of the primer resin liquid should preferably be 0.4 mPa·s or more at 25°C, and more preferably 2 mPa·s or more. The viscosity of the primer resin liquid can be measured using devices such as a rotational viscometer, vibration viscometer, capillary viscometer, and falling-ball viscometer, with the use of a vibration viscometer being particularly preferred.

[0043] A-4-2 Surface tension of primer resin liquid The surface tension of the primer resin liquid is 40 mN / m or less as calculated by the Young-Laplace method at 22°C. If the surface tension of the primer resin liquid exceeds 40 mN / m, penetration into the through-holes of the glass substrate becomes difficult due to insufficient permeability, which may result in insufficient coating of the primer resin layer on the inner surface of the through-holes. Furthermore, a low surface tension of the primer resin liquid makes it difficult to handle during the application process. Therefore, the lower limit of the surface tension of the primer resin liquid is preferably 20 mN / m or more as calculated by the Young-Laplace method at 22°C. The surface tension of the primer resin liquid is preferably 25 mN / m or more and 40 mN / m or less, and more preferably 33 mN / m or more and 40 mN / m or less. The surface tension of the primer resin liquid of the present invention can be calculated by image analysis using the Young-Laplace equation to fit the shape of a drop obtained by the pendant drop method.

[0044] A-4-3 Adjustment of viscosity and surface tension of primer resin liquid The viscosity and surface tension of the primer resin liquid according to the present invention can be adjusted mainly by the proportion of the solvent in the primer resin liquid and the type of solvent selected.

[0045] The viscosity of the primer resin liquid according to the present invention is controlled primarily by the mixing ratio of the resin component and the solvent. Regarding the mixing ratio of the resin component and the solvent in the primer resin liquid according to the present invention, the ratio of the solvent to the entire primer resin liquid is preferably 90% by mass or more and 97% by mass or less. If the solvent ratio is less than 90%, the viscosity of the primer resin liquid deviates from the above-mentioned appropriate range, making it difficult to obtain the permeability and fluidity required to form a primer resin layer in the through-hole. Furthermore, if the solvent ratio exceeds 97% by mass, the resin component becomes diluted, making it impossible to form a primer resin layer of sufficient thickness. More preferably, the ratio of the solvent to the entire primer resin liquid is 93% by mass or more and 96% by mass or less.

[0046] The surface tension of the primer resin liquid can be adjusted by selecting the type of solvent. The range and specific examples of solvents suitable for the primer resin liquid of the present invention are as described above, and by using these solvents, the surface tension can be adjusted to the appropriate range described above.

[0047] The solvent for the primer resin liquid can be a single solvent consisting of one solvent, or a mixed solvent consisting of two or more solvents. The solvent does not affect the reaction that converts the resin component into a primer resin layer. The solvent must be able to maintain the viscosity and surface tension of the primer resin liquid within the above-mentioned ranges; whether it is a single solvent or a mixed solvent is not important. Examples of single solvents include those listed above as preferred examples, with particularly preferred solvents being cyclohexanone, N-methyl-2-pyrrolidone, toluene, and methyl ethyl ketone. Furthermore, mixed solvents containing one or more of the above-listed preferred solvents are preferred. When using mixed solvents, solvents not listed above as preferred solvents may be mixed. For example, dimethyl sulfoxide, aniline, morpholine, and nitrobenzene are not listed above as preferred solvents. While these solvents alone have difficulty maintaining the surface tension of the primer resin liquid within the specified range, they may be used in combination with a suitable solvent to form a mixed solvent.

[0048] As described above, the viscosity and surface tension of the primer resin liquid are adjusted mainly by the solvent ratio and type. However, the viscosity and surface tension of the primer resin liquid may also be affected by the composition of the resin components (contents of Resin I, Resin II, and Resin III). The preferred content of each resin constituting the resin components is as described above, and it is preferable to follow this. The viscosity and surface tension of the primer resin liquid according to the present invention are preferably set within a predetermined range by a complex blend of the various elements described above.

[0049] B. Electroless plating process for glass substrates using the primer resin liquid according to the present invention The primer resin liquid according to the present invention, as described above, is effectively applied to electroless plating processes for various substrates. The electroless plating process using the primer resin liquid according to the present invention basically conforms to the prior art (Patent Document 4, etc.) of the applicant of the present application. This electroless plating process involves a step of forming a primer resin layer by applying and baking the primer resin liquid to the substrate, and a step of adsorbing and fixing precious metal nanoparticles that serve as catalyst nuclei to the primer resin layer, followed by electroless plating treatment. Each step of the electroless plating process according to the present invention will be described below.

[0050] B-1 Base material The electroless plating process of the present invention is particularly effective for forming a plating film on a glass substrate. The primer resin layer formed by the present invention has improved adhesion to the plating film, and also has good adhesion between the resin and the glass. Furthermore, as described above, the primer resin liquid of the present invention has improved penetration into through holes, allowing a uniform primer resin layer to be formed on the inner surface of the through holes. Therefore, the present invention is particularly useful for glass substrates with through holes.

[0051] The glass composition and dimensions of the glass substrate are not particularly limited when applying the present invention. Glass is a composite material of inorganic oxides (silicon oxide, aluminum oxide, boron oxide, etc.), and its composition is not particularly limited; what is generally referred to as a glass substrate can be applied. Furthermore, recent advances in manufacturing technology have made it possible to manufacture glass substrates of various thicknesses. The present invention is applicable to any thickness of glass substrate. Furthermore, there are no limitations on the through holes formed in the glass substrate, and fine through holes with a hole diameter of 30 μm or less can be used. Furthermore, the aspect ratio (hole depth / hole diameter) is often used as a criterion for evaluating the film formation ability of through holes. The present invention can also be used to handle through holes with a high aspect ratio of 30 or more.

[0052] The primer resin liquid and electroless plating process of the present invention are particularly effective for glass substrates with through holes, but can also be used for other types of substrates. The present invention is also effective for flat glass substrates without through holes. This is because, as described above, the primer resin layer formed by the present invention has good adhesion to glass. The present invention can also be applied to substrates made of materials other than glass (resin, plastic, ceramic, etc.).

[0053] B-2 Application of primer resin liquid and formation of primer resin layer In the electroless plating process according to the present invention, a primer resin layer is formed by applying a primer resin liquid to a substrate and baking the applied liquid. The primer resin liquid can be applied to the substrate by various methods, such as spraying, dipping, a spin coater, a roll coater, or various printing methods (screen printing, gravure printing, flexographic printing, inkjet printing, etc.).

[0054] The baking temperature for the primer resin layer formation is set to 150°C or higher and 260°C or lower. At temperatures below 150°C, it is difficult to form a good primer resin layer with sufficient adhesion. At temperatures above 260°C, the adsorption of the catalyst nuclei, as described below, decreases. The baking temperature is preferably 180°C or higher and 240°C or lower. The baking process can be carried out in the air, or under reduced pressure or in a non-oxidizing atmosphere. This baking process volatilizes the solvent in the primer resin liquid and hardens each resin. Furthermore, the crosslinking agent generates active functional groups (amino groups) on the surface of the primer resin layer, forming acceptors for the catalyst nuclei.

[0055] The thickness of the primer resin layer can be adjusted mainly by the amount of primer resin liquid applied. For example, in application by dipping, the substrate is immersed in the primer resin liquid and then pulled up to apply the primer resin. In this case, the amount of primer resin liquid applied can be adjusted by controlling the speed at which the substrate is pulled up, and therefore the thickness of the primer resin layer can be adjusted.

[0056] In the electroless plating process of the present invention, the thickness of the primer resin layer is preferably 0.1 μm or more and 2 μm or less. A primer resin layer with a thickness of less than 0.1 μm will have poor catalyst nuclei retention and poor plating film adhesion. On the other hand, a primer resin layer with a thickness of more than 2 μm will not significantly affect plating film adhesion. Furthermore, considering the formation of a plating film in a fine through-hole, an excessively thick primer resin layer can cause the through-hole to become clogged or hinder the formation of a plating film with an appropriate thickness. In the above-mentioned primer resin liquid application process, it is preferable to adjust the application conditions so that the primer resin layer has the above thickness.

[0057] B-3 Pretreatment process for primer resin layer (optional process) The primer resin layer formed from the primer resin liquid of the present invention has functional groups (amino groups) that act as acceptors for catalyst nuclei generated on the surface by the action of Resin II, which is a crosslinking agent component. The functional groups generated by coating and baking the primer resin liquid are active, and in this state can adsorb precious metal nanoparticles.

[0058] The functional groups on this primer resin layer are inactivated by irradiation with deep ultraviolet light of wavelengths of 300 nm or less. This inactivation of functional groups by light irradiation contributes to the selective immobilization of precious metal nanoparticles. Specifically, by performing patterning using a photomask or the like and selectively inactivating the functional groups by irradiation with deep ultraviolet light, it becomes possible to form a pattern of active functional groups on the substrate. Therefore, by performing the patterning and light irradiation before adsorption of precious metal nanoparticles, the desired wiring pattern can be formed using an electroless plating film.

[0059] The present invention is effective for forming a plating film inside the through-holes of a glass substrate with through-holes, but in substrates such as interposers, wiring and electrodes may also be formed on surfaces other than the through-holes. The pattern formation of functional groups by irradiation with deep ultraviolet light described above is effective for forming such wiring and electrodes. However, this light irradiation step is optional and not a required step.

[0060] In addition to the light irradiation step, an optional step may be a surface modification treatment of the primer resin layer. Examples of such a modification treatment include hydrophilization treatments such as plasma surface modification and UV ozone surface modification, application of a monomolecular dispersion film, and application of a hydrophilic film. However, these modification treatments are also optional and not essential.

[0061] B-4 Precious metal nanoparticle adsorption process After forming the primer resin layer as described above, precious metal nanoparticles that serve as catalytic nuclei for plating film deposition are adsorbed onto the surface of the primer resin layer. The precious metal nanoparticles are fine particles made of a precious metal or a precious metal alloy, with an average particle size of 1 nm to 100 nm. The precious metal nanoparticles are preferably in a monodispersed state; if the particle size is too small, they tend to aggregate, so the particle size should be 1 nm or more. Furthermore, precious metal nanoparticles with excessively large particle sizes have a reduced ability to bond with the functional groups of the primer resin layer. The average particle size of the precious metal nanoparticles is more preferably 3 nm to 30 nm. Preferable precious metals are Au, Pt, and Pd, which have suitable catalytic properties. Furthermore, preferable precious metal alloys are alloys containing the above-mentioned precious metals Au, Pt, and Pd. Examples of precious metal alloys include SnPd.

[0062] A preferred method for adsorbing and fixing precious metal nanoparticles to the primer resin layer is to apply a dispersion of precious metal nanoparticles to the surface of the primer resin layer. In this case, the dispersion medium for the dispersion of precious metal nanoparticles is preferably an aqueous solution containing a sugar alcohol. The sugar alcohol acts as a protective agent (dispersant) surrounding the precious metal nanoparticles and suppresses aggregation of the precious metal nanoparticles in the dispersion. Furthermore, the sugar alcohol bonded to the precious metal nanoparticles in the dispersion is substituted with functional groups on the surface of the primer resin layer, promoting bonding between the precious metal nanoparticles and the functional groups of the primer resin layer. Examples of sugar alcohols that can be used as such protective agents include glycerin, erythritol, xylitol, sorbitol, and mannitol. The dispersion medium is preferably an aqueous solution containing 0.1 g / L to 20 g / L of a sugar alcohol.

[0063] The dispersion of noble metal nanoparticles can be applied by spraying, dipping, using a spin coater, a roll coater, etc. After application of the dispersion, drying and washing may be carried out as necessary.

[0064] B-5 Electroless plating process A plating film is formed by electroless plating a substrate onto which noble metal nanoparticles are adsorbed. The present invention can be applied to electroless plating of various metals. Metals that can be used to form films by electroless plating include noble metals such as Au, Ag, Pt, and Pd, as well as base metals such as Cu, Ni, and Co. Known electroless plating solution compositions and electroless plating methods and conditions can be used for electroless plating of these metals.

[0065] The electroless plating process according to the present invention is particularly suitable for manufacturing interposers (glass interposers), and Cu is the most commonly used conductive material for the through electrodes of interposers. The present invention is also effective for forming through electrodes made of Cu by electroless plating. Various electroless Cu plating solutions are known for forming Cu plating films by electroless plating, and can be applied to the present invention. The electroless Cu plating solution essentially contains a Cu salt and a reducing agent, and optionally contains additives such as a complexing agent and a pH adjuster.

[0066] Examples of Cu salts for electroless Cu plating solutions include copper sulfate, copper chloride, copper acetate, copper nitrate, copper fluoroborate, copper methanesulfonate, copper phenylsulfonate, copper p-toluenesulfonate, copper hydroxide, and copper oxide. Known reducing agents include formaldehyde, hydrazine, ascorbic acid, thiourea, hydroquinone, dimethylamine borane, hypophosphite, hydrogen peroxide, formic acid, hypophosphite, boron hydride, thiosulfuric acid, hydroxylamine, and sodium erythorbate, and include ascorbic acid, boron hydride, hydroquinone, and formaldehyde. In the electroless plating process according to the present invention, plating solutions using formaldehyde as a reducing agent (formalin baths) and plating solutions using hypophosphorous acid as a reducing agent (hypophosphorous acid baths) are preferably used. Copper sulfate and Cu chloride are preferred Cu salts. The hypophosphorous acid bath may contain metal ions other than Cu, such as Ni, Co, and Sn, to assist Cu deposition. By using these electroless Cu plating solutions, the electroless plating process according to the present invention can form an electroless Cu plating film as a seed layer on the inner surface of a through hole, and can also directly form a Cu film as a through electrode.

[0067] B-6 Post-heat treatment process (curing process) The electroless plating process forms a plating film on the primer resin layer, and the electroless plating process of the present invention is essentially completed at this point. However, to ensure the adhesive strength between the plating film and the substrate, it is preferable to add a post-heat treatment step called a curing step. The curing step involves heating the primer resin layer at a temperature above the glass transition temperature of the composite resin that makes up the primer resin layer, fluidizing the primer resin layer and embedding the precious metal nanoparticles in the primer resin layer. Embedding the precious metal nanoparticles in the primer resin layer can improve the adhesiveness of the plating film.

[0068] The heating temperature in the curing process is preferably within ±50°C of the glass transition temperature (Tg) of the primer resin layer, and is preferably 150°C or higher and 300°C or lower. A specific temperature range is 150°C or higher and 260°C or lower. Heat treatment within this temperature range fluidizes the primer resin layer, and the precious metal nanoparticles are incorporated into the primer resin layer, increasing adhesion strength. The curing process can be carried out in an air atmosphere, but can also be carried out in a reduced pressure atmosphere or a non-oxidizing atmosphere. The heating time is preferably 0.1 hour or higher and 2 hours or lower.

[0069] The curing step improves the adhesion between the plating film and the substrate (primer resin layer). After the curing step, post-treatment such as plasma ashing may be carried out as necessary.

[0070] The above series of steps form a primer resin layer and an electroless plating film on the glass substrate. Then, electrolytic plating can be performed as needed to form wiring such as Cu. Alternatively, the through-holes can be filled with the electroless plating process alone to form wiring.

[0071] C. Glass interposer using the primer resin liquid according to the present invention As described above, the primer resin liquid according to the present invention and the electroless plating process using the same are useful for forming a plating film on a glass substrate, particularly a glass substrate with one or more through holes. The glass interposer substrate according to the present invention has a metal plating film formed inside the through holes of the glass substrate with through holes, and a primer resin layer made of a resin is formed between the inner wall surface of the through hole and the plating film. The primer resin layer contains a thermoplastic resin I as a main component, a crosslinking agent resin II, and a thermosetting resin III having a bisphenol skeleton as an adhesive agent component, and the content of the resin III in the primer resin layer is 10% by mass or more and 48% by mass or less relative to all the resins constituting the primer resin layer. The blending ratio of each resin in the primer resin layer is the same as the blending ratio in the primer resin liquid. This is because, during the baking process to form the primer resin layer, the solvent is volatilized and removed, but the resin remains and forms the primer resin layer.

[0072] There are no particular limitations on the material or dimensions of the glass substrate in this glass interposer substrate. There are also no limitations on the dimensions or aspect ratio of the through holes, and it is possible to accommodate aspect ratios of 1 or more, and even through holes with high aspect ratios of 20 or more are applicable. Furthermore, an interposer substrate may be formed by stacking multiple glass interposer substrates according to the present invention. [Effects of the Invention]

[0073] The primer resin liquid for electroless plating according to the present invention has good permeability into the through holes of a glass substrate with through holes, and can form a suitable primer resin layer on the inner surface of the holes. Furthermore, according to the present invention, the adhesion strength of the metal plating film formed on the primer resin layer can be made suitable. [Brief explanation of the drawings]

[0074] [Figure 1] 10 is a cross-sectional photograph of a through hole when electroless plating is performed using the primer resin liquid of Example 2 of the second embodiment. [Figure 2]10 is a cross-sectional photograph of a through hole when electroless plating is performed using the primer resin liquid of Comparative Example 1 of the second embodiment. [Figure 3] 10 is a photograph of the opening of a through hole when the primer resin liquids of Example 2 of the second embodiment and Comparative Example 3 are applied and subjected to electroless plating. [Figure 4] 10 is a photograph for evaluating patterning properties when plating is performed under the conditions of Example a of the third embodiment. [Figure 5] 10A to 10C are cross-sectional photographs of through holes after plating treatment (electroless plating and electrolytic Cu plating) in each example of the fourth embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0075] First embodiment (preliminary study) Hereinafter, an embodiment of the present invention will be described. In this embodiment, a primer resin liquid applied in the prior art (Patent Document 4, etc.) by the applicant of the present application is used as a standard, and a primer resin liquid configuration with higher adhesion than this is investigated. Specifically, the adhesion of the primer resin layer to the plating film was evaluated when a thermosetting resin, which is an adhesion agent component, was added to the primer resin liquid of the prior art.

[0076] In this embodiment, a primer resin liquid was produced by dissolving polyester resin (UPICACOAT GV-110, manufactured by Japan U-Pica Corporation) as resin I (main component), melamine resin (CYMEL® 303LF, manufactured by Allnex) as resin II (crosslinker component), bisphenol A epoxy resin (jER828, manufactured by Mitsubishi Chemical Corporation) as resin III (adhesion agent component), and a photoacid generator (CYCAT® 4040, manufactured by Allnex) in cyclohexanone as a solvent. The compositions of the primer resin liquids evaluated in this embodiment (primer resin liquids A to G) are as shown in Table 1. In Table 1, the conventional primer resin liquid is primer resin liquid H, which does not contain bisphenol A epoxy resin.

[0077] In the preliminary study of this embodiment, no deliberate adjustments were made to the viscosity and surface tension of the primer resin liquid. In other words, the preliminary study of this embodiment prioritized determining the composition of the resin component that could improve the adhesion of the plating film. To this end, we decided to study a primer resin liquid that increased the proportion of the resin component without considering viscosity and surface tension. Specifically, we set the proportion of the resin component to the primer resin liquid to more than 10 mass% (the proportion of solvent was less than 90 mass%). As a result, the following primer resin liquids A to H in this embodiment had a surface tension of 40 mN / m or less and a viscosity of 12 mPa·s to 20 mPa·s.

[0078] [Table 1]

[0079] To form the primer resin layer, 4 mL of primer resin liquid was applied to a glass substrate (10 cm x 10 cm) by spin coating. The substrate after the primer resin liquid application was then prebaked to remove the solvent and harden the resin to form the primer resin layer. The prebaking was performed in an air atmosphere in a forced circulation oven at 260°C for 30 minutes.

[0080] Next, an Au plating film was formed on the primer resin layer by electroless plating. In this embodiment, the surface of the primer resin layer was exposed to light in a predetermined pattern to partially deactivate the acceptors (amino groups). The exposure process was carried out using a photomask to form a linear pattern (L / S=5 μm) with a width of 5 μm and an interval of 5 μm. Multilight (manufactured by Ushio Inc.) emits deep ultraviolet light with a wavelength of 254 nm at 800 mJ / cm 2 Irradiated with.

[0081] Then, an Au nanoparticle dispersion (SEADCAT (registered trademark) CAT Au-10, manufactured by EEJA Co., Ltd.) was applied to the surface of the substrate (primer resin layer) after the exposure treatment as precious metal nanoparticles that would become catalytic nuclei. This Au nanoparticle dispersion was a dispersion of Au nanoparticles with a particle size of 16 nm. In the Au nanoparticle dispersion application process, the substrate was immersed in the dispersion at room temperature for 15 minutes and then dried in the air.

[0082] After the Au nanoparticles were fixed to the primer resin layer, an Au plating film was formed by electroless plating. The Au plating film was formed using an Au electroless plating solution (AC FAB® AU-ACG3000GX, manufactured by EEJA Corporation) at a plating temperature of 65°C for 5 minutes. Note that these plating conditions were intended to produce an Au plating film with a thickness of 50 nm.

[0083] After the Au plating film was formed, a heat treatment (curing process) was performed to sink the Au nanoparticles into the primer resin layer. The curing process involved heating in a static oven at 260°C in air for 30 minutes. Through these processes, an Au plating film was formed on the electroless plating substrates of each example, conventional example, and comparative example.

[0084] Finally, an electrolytic Cu plating film was formed on the Au plating film formed above. The electrolytic Cu plating was performed using a commercially available electrolytic Cu plating solution (MICROFAB (registered trademark) Cu250, manufactured by EEJA Co., Ltd.) at a current density of 3 A / dm 2 The copper plated film was then subjected to electrolytic plating treatment at 4000 kJ / min for 20 minutes to form a Cu plating film having a thickness of about 15 μm.

[0085] After the Cu plating film was formed, the adhesion (adhesion strength) of the plating film was evaluated. The evaluation of adhesion strength was based on the peel strength obtained by a peel test (test conditions: 90° tensile test according to JIS K 6854-1). In this embodiment, samples with a peel strength of 0.4 N / mm or more were judged to pass. This criterion was set so that a value exceeding the value (0.2 to 0.3 N / mm) obtained by converting the pass value in the cross-cut test described in the prior art (Patent Document 4) into a peel strength in the peel test was considered to pass. The evaluation results are shown in Table 2, along with the composition of each primer resin layer.

[0086] [Table 2]

[0087] Table 2 shows the effectiveness of the thermosetting resin (resin with a bisphenol skeleton) used as the adhesive agent (Resin III). It was confirmed that the primer resin layers formed from Primer Resin Solutions A to D all had improved plating film adhesion strength compared to the primer resin layer formed from the conventional Primer Resin Solution H. Furthermore, Primer Resin Solutions E to F, which contain excessive amounts of Resin III, lowered plating film adhesion strength compared to the conventional primer resin layer without Resin III. These results suggest that a three-component primer resin solution containing an appropriate amount of a thermosetting resin with a bisphenol skeleton, which acts as an adhesive agent, is preferable. Furthermore, the results for Primer Resin Solution G indicate that the main component (Resin I) is also an essential component of the primer resin solution.

[0088] Second embodiment In this embodiment, several types of primer resin liquids with different viscosities and surface tensions were manufactured by adjusting the types and proportions of solvents while using a common resin component. Using the various primer resin liquids manufactured, we investigated whether a primer resin layer could be formed on a glass substrate with through holes and whether an electroless Cu plating film could be formed.

[0089] In this embodiment, Resin A, which is one of the three-component resin components investigated in the first embodiment and has been confirmed to have suitable adhesion, was used. The solvent used in this embodiment was cyclohexanone, the same as in the first embodiment (Examples 1 and 2), as well as toluene (Example 3). Furthermore, a mixed solvent of cyclohexanone and N-methyl-2-pyrrolidone (mixing ratio 1:1 (mass ratio)) was also used (Example 4). For comparison, a primer resin liquid (Comparative Examples 1 and 2) was produced using cyclohexanone as the solvent, with the viscosity adjusted to a solvent ratio of less than 90 mass%, and a primer resin liquid (Comparative Example 3) was produced using dimethyl sulfoxide as the solvent.

[0090] The viscosity and surface tension of each of the prepared primer resin liquids were measured before use. Viscosity was measured using a vibration viscometer (Vm-10, manufactured by Sekonic Corporation) at 25°C. Surface tension was measured using a contact angle meter (DMo-501, manufactured by Kyowa Interface Science Co., Ltd.) and the shape of a drop obtained by the pendant drop method was calculated using image analysis with fitting by the Young-Laplace equation. The composition, viscosity, and surface tension of each of the prepared primer resin liquids are as follows:

[0091] [Table 3]

[0092] Then, a primer resin layer was formed on a glass substrate using each of the primer resin liquids of Examples 1 to 4 and Comparative Examples 1 to 3. In this embodiment, a glass substrate with through holes measuring 10 cm × 10 cm × 400 μm thick and having 1,300 through holes with a hole diameter of 100 μm (aspect ratio of 4) formed therein was used as the substrate. To apply the primer resin layer, the glass substrate was dipped in 100 mL of primer resin liquid, immersed for 1 minute, and then pulled up at a pull-up speed of 0.5 mm / s. The substrate after application of the primer resin liquid was then pre-baked in an air atmosphere at 200°C for 10 minutes to form a primer resin layer.

[0093] After the primer resin layer was formed, the same Au nanoparticle dispersion liquid as in the first embodiment was applied as noble metal nanoparticles and dried.

[0094] A Cu plating film was then formed on the primer resin layer by electroless plating. A commercially available Cu plating solution (Cu concentration: 2.5 g / L) using formaldehyde as a reducing agent was used as the electroless Cu plating solution. The Cu plating film was formed at a plating temperature of 38°C for 3 minutes. After the Cu plating film was formed, it was cured by heating in air at 250°C for 30 minutes in a static oven.

[0095] The cross sections of glass substrates on which electroless Cu plating films were formed using various primer resin solutions according to the above process were observed to evaluate the state of the interior of the through holes and the success or failure of Cu plating film formation. In this evaluation method, a case in which a primer resin layer was formed on the entire inner wall of the through hole was judged as pass. Furthermore, a case in which a Cu plating film was formed on the entire inner wall of the through hole was judged as pass. The number of through holes judged as pass for each primer resin layer and Cu plating film was then counted, and the percentage of pass holes out of all through holes (1,300) formed on the glass substrate was calculated. A percentage of 90% or more was rated as pass (◯), while a percentage of 30% or less was rated as fail (×). Table 4 shows the evaluation results of the primer resin layer and Cu plating film formation on the through holes of this embodiment.

[0096] [Table 4]

[0097] As can be seen from Table 4, in the substrates treated with the primer resin solutions of Examples 1 to 4, which had viscosities and surface tensions set within a predetermined range, a uniform primer resin layer was formed throughout the entire interior, and a Cu plating film was also formed in a good condition. Fig. 1 is a cross-sectional photograph of the interior of a through-hole after electroless Cu plating using the primer resin solution of Example 2. In the substrates of Examples 1 to 4, the formation of a suitable primer resin layer and Cu plating film, as shown in Fig. 1, was confirmed in most of the through-holes.

[0098] On the other hand, in the substrates treated with the primer resin solutions of Comparative Examples 1 to 3, the formation of a primer resin layer and a copper plating film inside the through-hole was insufficient or impossible. In the case of the highly viscous primer resin solutions of Comparative Examples 1 and 2, the primer resin layer was formed only up to the vicinity of the opening of the through-hole, and the copper plating film followed suit. Figure 2 is a photograph of the cross section of the through-hole in Comparative Example 1. It is believed that the primer resin solutions of Comparative Examples 1 and 2 had too high a viscosity and were unable to penetrate to the center of the through-hole, causing it to harden. As a result, in almost all of the through-holes formed in the substrates, a primer resin layer and a Cu plating film were not formed on the entire inner wall (failed evaluation).

[0099] Furthermore, the primer resin liquid of Comparative Example 3 had a high surface tension and was prevented from penetrating at the edges of the through-hole openings. Figure 3 shows photographs of the through-hole openings of Example 2 and Comparative Example 3 viewed from above. As shown in Figure 3, in Comparative Example 3, the primer resin liquid remained near the edges of the openings of all of the through-holes, and no primer resin layer was formed inside the through-holes (failed evaluation).

[0100] The results of the study in this embodiment confirmed that by using a primer resin liquid in which both the viscosity and surface tension are adjusted to be within a certain range, it is possible to form a primer resin layer in the through hole and ensure conductivity, thereby forming an electroless Cu plating film in the through hole.

[0101] Third embodiment In this embodiment, a primer resin layer was formed using the primer resin solution of Example 1 or Example 2, and then the composition of the precious metal nanoparticles and electroless Cu plating solution was adjusted to perform electroless Cu plating, and the film formation possibility and adhesion, etc. were evaluated.

[0102] In this embodiment, a flat glass substrate was used, as in the first embodiment. As described above, in this embodiment, the electroless plating process using the primer resin liquid according to the present invention is examined to confirm the influence of the type of precious metal nanoparticles that serve as catalytic nuclei for the plating film and the type of Cu plating solution. In such an examination, it is necessary to evaluate the adhesion strength and patternability of the plating film, and a flat substrate is convenient for this purpose.

[0103] In the electroless plating process of this embodiment, a primer resin layer was formed by applying a primer resin liquid to a glass substrate by dipping, as in the first embodiment, and then pre-baking at 200°C for 10 minutes. The primer resin liquids used in this embodiment were the primer resin liquid of Example 1 (viscosity 8.4 Pa s, surface tension 34.6 mN / m) and the primer resin liquid of Example 2 (viscosity 4.2 Pa s, surface tension 34.1 mN / m) investigated in the second embodiment.

[0104] After the primer resin layer was formed, precious metal nanoparticles were adsorbed. In this embodiment, the following three types of dispersion liquids of precious metal nanoparticles were used. To adsorb the precious metal nanoparticles to the primer resin layer, the glass substrate was immersed in each dispersion liquid at room temperature for 15 minutes and then dried in the air. Au nanoparticles: the same dispersion of Au particles as in the first embodiment (product name: SEADCAT (registered trademark) CAT Au-10, manufactured by EEJA Co., Ltd.) Pd nanoparticles: Dispersion of Pd particles with a particle size of 5 nm (manufactured by EEJA Co., Ltd.) SnPd nanoparticles: commercially available SnPd particle dispersion (trade name: Mactivate 10, manufactured by MacDermid Enthone Industrial Solutions)

[0105] Then, a Cu plating film was formed on the primer resin layer by electroless plating. In this embodiment, the following three types of commercially available electroless Cu plating solutions, α to γ, were used (Cu plating solution α was the same as that used in the second embodiment). The composition of each Cu plating solution and the conditions (temperature) for the electroless plating process were as follows:

[0106] [Table 5]

[0107] After the Cu plating film was formed by electroless plating, a curing step was carried out by heating in the atmosphere at 250°C for 30 minutes in a static oven.

[0108] After electroless plating using the various Cu plating solutions described above, it was confirmed whether or not a Cu plating film was formed on the substrate surface. The adhesion strength of the Cu plating film was then measured. The adhesion strength was measured using the same peel test as in the first embodiment. Regarding adhesion strength, samples with a peel strength of 0.4 N / mm or more were judged to pass. Table 5 shows the evaluation results for the electroless plating process investigated in this embodiment.

[0109] [Table 6]

[0110] It was confirmed that the primer resin layer formed using the primer resin liquid of this embodiment (the primer resin liquids of Examples 1 and 2) was capable of forming a suitable plating film with all of the precious metal nanoparticles (catalytic nuclei) and electroless Cu plating solutions of Examples a to 1. The Cu plating films formed in Examples a to 1 also had good adhesion.

[0111] In this embodiment, the patterning properties of the plating films formed under the conditions of Examples a to f were also evaluated. In the evaluation of patterning properties, a primer resin layer was formed on the substrate in the same manner as above, and then an exposure treatment was performed to partially deactivate the acceptor. The exposure treatment used a photomask to form a linear pattern (L / S=5 μm) with a width of 5 μm and an interval of 5 μm, and deep ultraviolet light with a wavelength of 254 nm was applied at 800 mJ / cm using a deep ultraviolet light exposure machine. 2 Irradiated with.

[0112] Then, precious metal nanoparticles (Au nanoparticles or Pd nanoparticles) were adsorbed onto the primer resin layer with the acceptor partially deactivated. Subsequently, Cu plating was performed using electroless Cu plating solutions (α to γ) in the same manner as above, followed by electrolytic Cu plating. The pass / fail judgment was visually determined based on the presence or absence of pinholes on the Cu plating film surface, the presence or absence of metal deposition outside the set pattern, and whether the color of the plating film was standard.

[0113] As a result, it was confirmed that in all of Examples a to f, the patterning properties were good and fine Cu wiring could be formed on the surface of the glass substrate. Figure 4 shows the appearance of the plating film formed by patterning under the conditions of Example a. From these evaluation results, it was confirmed that the primer resin liquid investigated in this embodiment can also be used to form plating films by patterning.

[0114] Fourth embodiment In this embodiment, various glass substrates with through holes having different thicknesses and through hole diameters were prepared, a primer resin layer was formed on each of the substrates using a primer resin liquid, and an Au plating film or a Cu plating film was formed by electroless plating.

[0115] In this embodiment, various glass substrates with through holes having different substrate thicknesses and hole diameters were treated with a primer resin liquid. The primer resin liquid examined in Example 1 or Example 2 of the second embodiment was used and applied to each glass substrate with through holes to form a primer resin layer. The application conditions for the primer resin liquid and the pre-baking conditions were the same as those of the second embodiment.

[0116] After forming the primer resin layer, a dispersion of the three types of precious metal nanoparticles (Au nanoparticles, Pd nanoparticles, and SnPd nanoparticles) studied in the third embodiment was applied. Then, an Au plating film or a Cu plating film was formed by electroless plating. The electroless plating solution used was the same as in the first embodiment, and the same electroless Cu plating solution (Cu concentration: 2.5 g / L) as in the second embodiment.

[0117] After the electroless plating process, the same as in the first embodiment, the copper electroplating solution was used at a current density of 3 A / dm 2 The copper foil was subjected to electrolytic plating treatment for 10 to 20 minutes, and an electrolytic Cu plating film having a thickness of 10 μm to 25 μm was formed.

[0118] A cross-section of each glass substrate with through holes was observed after the electrolytic plating process. When the cross-sectional observation revealed that the inside of the through holes was filled with the electroless Cu plating and the electrolytic plating film without interruption, it was determined that metallization within the through holes was possible. Furthermore, a peel test similar to that in the first embodiment was performed on the Cu plating film formed on the flat surface of each glass substrate with through holes, and a peel strength of 0.4 N / mm or more was determined to be acceptable for adhesion. These evaluation results are shown in Table 7.

[0119] [Table 7]

[0120] Table 7 confirms that by applying a primer resin layer formed with the primer resin liquid of this embodiment, an Au plating film or a Cu plating film can be formed in the through-hole under all conditions (Examples m to u), and electrical continuity can be achieved between the front and back of the substrate. Cross-sectional photographs of the through-holes in each example are shown in Figure 5. Furthermore, when the aspect ratio of the through-holes in each substrate was examined, it was confirmed that the plating film could be filled even in through-holes with an aspect ratio of 20 or more. [Industrial Applicability]

[0121] The present invention applies a primer resin layer made from a newly formulated primer resin liquid and precious metal nanoparticles that serve as catalyst nuclei to a glass substrate as an electroless plating process. The primer resin liquid of the present invention has properties optimized for glass substrates with through holes, and can form a plating film with good adhesion within the through holes. The primer resin layer of the present invention and the electroless plating process using it are particularly expected to be applicable to glass interposer substrates.

Claims

1. A primer resin liquid for electroless plating, comprising a resin component and a solvent component, The resin component includes: resin I, which is a main component and is made of any one of polyester resin, polyimide resin, LCP resin, and polyethylene terephthalate resin; resin II, which is a crosslinking agent component and contains an amino group; and resin III, which is an adhesive agent component. The resin III, which is the adhesive component, is a thermosetting resin having a bisphenol skeleton, the content of the resin III in the resin component is 10% by mass or more and 48% by mass or less, The viscosity at 25°C is 10 mPa s or less, A primer resin liquid for electroless plating having a surface tension of 40 mN / m or less at 22°C as measured by the Young-Laplace method.

2. 2. The primer resin liquid for electroless plating according to claim 1, wherein the ratio of the solvent to the entire primer resin liquid is 90% by mass or more and 97% by mass or less.

3. 3. The primer resin liquid for electroless plating according to claim 1, wherein the ratio of the content of resin I to the content of resin III is 1 or more and 4 or less.

4. 1. A plating method for a glass substrate with through holes, comprising forming an electroless plating film on a surface of a glass substrate having one or more through holes formed in a core substrate, the method comprising: a step of applying the primer resin liquid for electroless plating according to claim 1 or 2 to the glass substrate and allowing the primer resin liquid to penetrate into the through holes; a step of baking the primer resin liquid at 150°C or higher and 260°C or lower to form a primer resin layer; a step of dispersing a noble metal nanoparticle catalyst containing a noble metal with a particle diameter of 1 nm or more and 100 nm or less on a surface of the primer resin layer; and forming a plating film on the surface of the primer resin layer using an electroless plating solution.

5. 5. The method for plating a glass substrate with through holes according to claim 4, further comprising a curing step of heating the primer resin layer to a temperature within a range of 150°C or higher and 300°C or lower, within a range of ±50°C of its glass transition temperature (Tg), after forming a plating film using the electroless plating solution.

6. A glass interposer substrate made of a glass substrate having one or more through holes, a plating film made of a metal is formed inside the through hole, a primer resin layer made of resin is formed between the inner wall surface of the through hole and the plating film; The primer resin layer includes a thermoplastic resin I, which is a main component and is made of any one of a polyester resin, a polyimide resin, an LCP resin, and a polyethylene terephthalate resin, a resin II containing an amino group, which is a crosslinking agent component, and a thermosetting resin III having a bisphenol skeleton, which is an adhesive agent component; A glass interposer substrate, characterized in that the content of the resin III in the primer resin layer is 10% by mass or more and 48% by mass or less with respect to all resins constituting the primer resin layer.

Images