Primer resin solution for electroless plating, method for plating a glass substrate with through holes using the primer resin solution, and glass interposer substrate

Abstract

This invention provides a primer resin liquid capable of forming a primer resin layer on a glass substrate such as a TGV, while ensuring adhesion to form a metal film. [Solution] The present invention relates to a primer resin liquid for electroless plating, comprising a resin component and a solvent component. In the present invention, the resin component includes resin I, which is a main component, resin II, which is a crosslinking agent component, and resin III, which is an adhesion agent 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 according to the present invention has optimized viscosity and surface tension in order to form a primer resin layer on a substrate with through holes. Specifically, the primer resin liquid according to 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 by the Young-Laplace method at 22°C.

Description

Technical Field

[0001] The present invention relates to a primer resin liquid for forming a primer resin layer for ensuring adhesion to the substrate surface when forming a plating film by electroless plating. In particular, it relates to a primer resin liquid useful for a glass substrate with through-holes. The present invention also relates to a plating method optimized for forming a metal plating film in the through-holes of a glass substrate with through-holes using the above primer resin liquid.

Background Art

[0002] In order to meet the requirements for miniaturization and high integration of semiconductor devices, advanced two-dimensional mounting and 2.5-dimensional mounting using an interposer substrate as a semiconductor chip mounting technology have been put into practical use. This mounting method can achieve high integration of semiconductor chips and high-speed transmission of signals between chips by connecting semiconductor chips and circuit boards in the thickness direction through the interposer substrate, and thus is expected to be widely applied in the future. The interposer substrate used in this mounting method is an intermediate substrate in which through electrodes are formed on a base material at positions corresponding to connection parts such as bumps of semiconductor chips. The through electrodes are manufactured by forming a conductor inside through-holes formed in the base material. As such through electrodes, those in which a conductive metal such as copper (Cu) is filled in through-holes by plating (via filling) or those in which the inner surface of the hole is coated with a conductive metal film without filling the whole hole are known.

[0003] Many of the conventional interposer substrates have a resin substrate such as glass epoxy as a base material (core substrate). However, resin substrates have a large coefficient of thermal expansion and have problems with shape stability. An interposer substrate is a substrate having minute through-holes, and deformation of the substrate due to thermal expansion can lead to deformation and disconnection of the electrodes in the through-holes. Therefore, when applying a resin substrate to an interposer substrate, although a material change for reducing the coefficient of thermal expansion has been made and certain results have been obtained, there are still limitations. In particular, in order to cope with the recent miniaturization and high integration of wiring circuits, further miniaturization is required for the through-holes of the interposer substrate, and it is difficult to say that a resin substrate can sufficiently cope with this situation.

[0004] Therefore, silicon substrates and glass substrates are being considered as base materials 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 have excellent heat dissipation. However, since silicon is a semiconductor, transmission loss is large, making it difficult to apply to devices for high-frequency applications. Also, because silicon is a relatively expensive material, the range of devices that can be targeted is limited.

[0005] Therefore, there has been a rapid increase in the number of studies on interposer substrates using glass substrates (glass interposers). Glass has a low coefficient of thermal expansion and is an insulator, so it can address the problems of the aforementioned resin substrates and silicon substrates. In addition, glass substrates have the advantage of excellent smoothness. The surface roughness of metal wiring and metal electrodes formed on the interposer substrate is affected by the smoothness of the underlying substrate surface. If the surface roughness of the metal wiring and metal electrodes increases, the transmission loss (scattering loss) increases, making it difficult to apply to high-frequency applications. Therefore, the application of glass substrates with excellent surface smoothness is expected. Furthermore, due to improvements in manufacturing technology, glass substrates can be easily made thinner in addition to having the aforementioned smoothness, and are more useful than silicon substrates in terms of cost. Glass substrates with fine through holes that can be applied to such glass interposers have also been developed, called through glass vias (TGV), and research on the formation of fine through holes is also active.

[0006] To commercialize glass substrates with fine through-holes, such as those used in TGVs, key technologies include not only microfabrication techniques for through-hole formation, but also the establishment of techniques for depositing metal films onto the inner surface of the glass through-holes. In this regard, glass is a material that is more difficult to deposit metal films onto with good adhesion compared to the resins and silicon mentioned above. This is because glass, which is composed of covalent bonds of oxides such as silicon dioxide, aluminum oxide, and boron oxide, and metals, which are composed of metallic bonds of metal atoms, differ fundamentally in their bonding structure.

[0007] Furthermore, as mentioned above, glass is a material with excellent surface smoothness, but this is also a factor that reduces the adhesion of metal films. In conventional resin substrates, adhesion of metal films is ensured by the anchoring effect of surface roughening treatment, and it is not impossible to apply a similar treatment to glass substrates. However, since the surface smoothness of the substrate can contribute to reducing transmission loss in the metal film, it is not a good idea to deliberately eliminate this advantage.

[0008] Looking at prior art for depositing metal films on glass substrates, particularly on glass substrates with micro-through holes, Patent Documents 1 and 2 describe a method for forming a metal oxide layer at the glass / metal film interface. In this prior art, heating mixes the glass surface and the adhesion layer to form a metal oxide layer, and this intermediate layer ensures adhesion. Furthermore, Patent Document 3 improves adhesion by forming a porous film using the sol-gel method.

[0009] Furthermore, the applicant has proposed an electroless plating process that is applicable to glass substrates, which involves forming a predetermined resin layer called a primer resin layer on the substrate surface in advance before the plating process, and using a pretreatment solution containing nano-order noble metal nanoparticles as a catalytic nucleus to promote the growth of the plating film (Patent Documents 4-6).

[0010] In the electroless plating process described in Patent Document 4 by the present applicant, a primer resin liquid containing a resin with a glass transition temperature (Tg) of 40°C to 430°C is applied to a substrate to form a primer resin layer. Then, noble metal nanoparticles are adsorbed and fixed onto the primer resin layer, and the primer resin layer is fluidized by heat treatment within a range of ±50°C of the glass transition temperature of the resin, causing the noble metal nanoparticles to sink into the primer resin layer. By applying this primer resin layer and controlling the state of the noble metal nanoparticles, the adhesion of the plating film formed on the primer resin layer is ensured. Furthermore, in the electroless plating process by the present applicant, by compounding a specific resin with the resin constituting the primer resin layer, it can also be applied to the formation of fine circuits (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 Publication No. 2019-036607 [Patent Document 4] Patent No. 6312766 specification [Patent Document 5] Japanese Patent Publication No. 2019-123909 [Patent Document 6] Japanese Patent Publication No. 2019-123910 [Overview of the Initiative] [Problems that the invention aims to solve]

[0012] As described above, there are many studies on methods for forming metal films on glass interposers and ensuring their adhesion. However, there are areas that need improvement. For example, in the methods described in Patent Documents 1 and 2, a metal oxide layer is formed between the glass substrate and the metal film, but high-temperature heating is required for oxide layer formation, raising concerns about deformation and bending of the glass substrate. Furthermore, performing heat treatment after the formation of the metal film complicates the interposer manufacturing process. In addition, Patent Document 3 improves adhesion by forming a porous film and creating an uneven surface, but this method is not a desirable method for improving adhesion because it raises concerns about transmission loss when considering high-speed transmission.

[0013] Furthermore, while the electroless plating process developed by the applicant using a primer resin layer, as described in Patent Document 4, has been confirmed to be useful for flat glass substrates, its applicability to glass substrates with through holes remains unclear. In this regard, the formation of a primer resin layer using a primer resin liquid and the electroless plating process are wet processes. Since the liquid applied to wet processes can penetrate even narrow areas such as through holes, wet processes are inherently suitable for glass substrates with through holes. However, the ability to form a metal film on the inner surface of a through hole is greatly influenced by the aspect ratio of the through hole. Therefore, it may not be effective in the future when the diameter of the through hole becomes smaller or the aspect ratio of the through hole increases. Moreover, sufficient studies have not been conducted regarding the adhesion of the metal film to the inner surface of the through hole.

[0014] The present invention was made against the above background 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 addressing this issue, the present invention clarifies an optimized configuration of the primer resin liquid (primer resin layer) developed by the applicant for application to fine through-holes such as those in a TGV, and provides a suitable electroless plating process for glass substrates with fine through-holes that utilizes this configuration. [Means for solving the problem]

[0015] The present inventors confirmed whether it is possible to form a primer resin layer on the inner surface of through-holes in a glass substrate with micro-through-holes using the primer resin solution described above by the applicant, and to deposit a metal film (copper plating film) by electroless plating. As a result, they confirmed that when the existing primer resin solution is applied to a glass substrate with micro-through-holes, the primer resin layer may not be formed up to the center of the through-hole, or even if the primer resin layer is formed throughout the inside of the through-hole, blockage may occur, potentially hindering subsequent film formation by electroless plating.

[0016] Considering the factors contributing to the problems in the formation of the primer resin layer using conventional primer resin liquids, it is thought that the penetration of the primer resin liquid into the through-holes is insufficient, or that the fluidity of the primer resin liquid inside the through-holes is insufficient or excessive. Therefore, the inventors decided to improve the permeability 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 mixing ratio of the resin component and the solvent.

[0017] However, adjusting the proportion of solvent in the primer resin solution to ensure penetration and fluidity into through holes naturally changes the proportion of resin components. Changes in the proportion of resin components in the primer resin solution can affect the properties of the primer resin layer, and may therefore affect the adhesion of the metal film formed by electroless plating afterward.

[0018] Therefore, the inventors conducted a detailed study on the composition of the resin components in order to find a primer resin liquid that can achieve higher adhesion than the conventional technology while adjusting the properties of the primer resin liquid to optimize the penetration and flowability into through holes. As a result, they conceived of applying a mixed resin of three types as the resin component of the primer resin liquid: a main component resin, a crosslinking agent component resin, and an adhesion agent component resin. Of these resin components, the main component resin and the crosslinking agent component resin are also contained in conventional primer resin liquids (primer resin layers). The inventors decided to add a predetermined thermosetting resin in appropriate amounts as a resin component that can improve adhesion without impairing the function of the conventional primer resin layer. This thermosetting resin acting as an adhesion agent imparts rigidity (hardness) and toughness (flexibility) to the primer resin layer, thereby improving adhesion with the plating film formed thereafter. The inventors have optimized the composition of the resin components in the primer resin liquid as described above, and then, by adjusting the blending of the resin components and the solvent, have discovered a primer resin liquid having optimized viscosity and surface tension for glass substrates with through holes, leading to the present invention.

[0019] That is, the present invention is a primer resin liquid for electroless plating, which is composed of a resin component and a solvent component. The resin component includes resin I as the main component, resin II as the crosslinking agent component, and resin III as the adhesion promoter component. The resin III as the adhesion promoter 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, and the surface tension by the Young-Laplace method at 22°C is 40 mN / m or less. It is a primer resin liquid for electroless plating.

[0020] Hereinafter, the detailed configuration of the primer resin liquid for electroless plating according to the present invention will be described. Furthermore, the electroless plating process of the glass substrate with through holes to which the primer resin liquid for electroless plating according to the present invention is applied will be described.

[0021] A Configuration 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 has a resin component and a solvent as main components. Hereinafter, each configuration will be described.

[0022] A-1 Resin component The resin component is a mixed resin that essentially includes three types of resins: resin I, resin II, and resin III described below.

[0023] A-1-1 Resin I (main component) Resin I as the main component is the main component that forms the skeleton for establishing the primer resin layer as a structure. Also, resin I is an effective component for obtaining adhesion to the glass substrate. It is known that hydroxy groups are formed on the glass surface due to the deviation adsorption of moisture in the atmosphere. The resin constituting the primer resin layer includes hydrogen bonds as intermolecular bonds by oxygen-containing functional groups and the like. Due to these, hydrogen bonds are formed at the interface between the glass surface and the resin, and high adhesion is exhibited.

[0024] The main component, resin I, is a thermoplastic resin, and specifically, polyester resin, polyimide resin, LCP resin, polyethylene terephthalate resin, etc., are applicable.

[0025] A-1-2 Resin II (Crosslinking agent component) Resin II, which is a crosslinking agent component, is a component that promotes the crosslinking reaction of the resin constituting the primer resin layer, crosslinking the resin molecules both intramolecularly and intermolecularly to make them insoluble. Furthermore, in the electroless plating process of the present invention, it also acts 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 later, and have the function of promoting the formation of an electroless plating thin film. Therefore, the crosslinking agent component is also an essential resin for the present invention.

[0026] The type of resin used for resin II is not particularly limited as long as it has the two effects of promoting the crosslinking reaction and generating functional groups as described above. For example, melamine-based crosslinking agents, amine-based crosslinking agents, guanamine-based crosslinking agents, glycoluryl-based crosslinking agents, etc., can be used. Melamine-based crosslinking agents are particularly preferred. Examples of melamine-based crosslinking agents include methoxyalkyl melamines such as hexamethoxymethylmelamine / hexamethoxyethylmelamine (HMM), dimethoxymethylmelamine, trimethoxymethylmelamine, tetramethoxymethylmelamine, pentamethoxymethylmelamine, and hexamethoxymethylmelamine. There are also alkoxymethyl glycoluryls such as tetramethoxymethyl glycoluryl, 1,3-bismethoxymethyl-4,5-bismethoxyethyleneurea, and bismethoxymethylurea.

[0027] A-1-3 Resin III (adhesive component) The resins I (main component) and II (crosslinking agent component) described above have been used in the past as resin components of primer resin liquids applied in the electroless plating process (Patent Document 4, etc.) by the present applicant. The resin components of the primer resin liquid in the present invention are a three-component resin system that includes these, plus resin III, which acts as an adhesion agent component. The adhesion agent component does not itself have the function of an adhesion agent. The adhesion agent component is a component that imparts appropriate rigidity and toughness to the primer resin layer, which has previously consisted of resins I and II, thereby improving the adhesion strength with the plated film.

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

[0029] [ka]

[0030] In the present invention, resin III is preferably a resin having a bisphenol skeleton, and resin having a bisphenol A skeleton or a bisphenol F skeleton is particularly preferred. Specifically, resin III is preferably a bisphenol A type epoxy resin or a bisphenol F type epoxy resin having epoxy groups. Although thermosetting resins having epoxy groups include biphenyl type epoxy resins, glycidyl ester type epoxy resins, and alicyclic epoxy resins, these resins without a bisphenol skeleton are ineffective. Furthermore, the epoxy equivalent is preferably 150 to 3000, and particularly preferably 170 to 500.

[0031] A-1-4 Content of resin I, resin II, and resin III in the resin components Furthermore, in order 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 thermosetting resin is effective in increasing the rigidity of the primer resin layer, but if the content is excessively high and the rigidity is too high, the adhesion will decrease. By appropriately adjusting the content of thermosetting resin, the toughness of the primer resin layer can be ensured and optimal adhesion can be achieved. 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] Furthermore, the content of resin I and resin II in the resin component is not particularly limited within the range of the content of resin III described above. The content of resin I and resin II can be set within the range in which the effects and functions of each resin are exhibited. However, preferably, resin I is 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. Also, resin II is 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 types of resins, resins I, II, and III, it is preferable that the ratio of the content of resin I to the content of resin III (resin I / resin III) be between 1 and 4. Resin I, which is the main component, is the resin that forms the framework of the primer resin layer. The main component in the primer resin layer exhibits basic adhesion as an intermediate layer between the plated film and the substrate. In addition, the main component in the primer resin layer also has the effect of capturing and fixing noble metal nanoparticles, which are catalyst nuclei. Therefore, if the amount of resin I is less than the amount of resin III, these basic functions of the primer resin layer may be reduced, which may result in a decrease in the adhesion strength of the plated film. For this reason, it is preferable that the ratio of the content of resin I to the content of resin III be 1 or more. On the other hand, in order for resin III, which is the adhesion agent component, to exert its effect fully, it may be undesirable if the amount of resin I, which is the main component, is too much compared to resin III. For this reason, it is preferable that the ratio be 4 or less.

[0034] As described above, the primer resin liquid according to the present invention contains resin III, which is an adhesion agent component, thereby providing suitable adhesion to the primer resin layer formed after firing. Furthermore, by setting the ratio of resin I, resin II, and resin III within the preferred range described above, the primer resin layer can be given an appropriate coefficient of thermal expansion. In this case, the coefficient of thermal expansion of the primer resin layer is appropriately higher than the coefficient of thermal expansion of the glass substrate. As a result, the primer resin layer formed on the substrate can maintain its adhesion to the substrate even when subjected to thermal cycling.

[0035] A-2 Solvent The primer resin liquid according to the present invention is produced by dissolving the resin components, consisting of the above-mentioned resins I, II, and III, in a solvent. The solvent imparts fluidity to the resin components by dissolving them. Furthermore, when the primer resin liquid is applied to a substrate, the solvent acts to form a uniform resin layer (primer resin layer) of homogeneous and uniform thickness on the substrate.

[0036] In the present invention, suitable solvents for the primer resin liquid include ketone solvents, ether solvents, ester solvents, and aromatic hydrocarbon solvents. 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 solution is manufactured by mixing and dissolving the resin components in the solvent described above. There is no specific order in which the resin components (Resins I to III) and the solvent are mixed. Alternatively, the stock solutions of each resin dissolved in the solvent may be mixed. Furthermore, a high-concentration primer resin solution may be prepared in advance and then diluted with the solvent.

[0038] Furthermore, the solvent in the primer resin liquid volatilizes or decomposes and disappears during the pre-bake process described later for forming the primer resin layer. During this process, resins I, II, and III, which are resin components, form the primer resin layer without their content changing significantly. Considering the preferred mixing ratio of the resin components and solvent as described above, the concentrations of resins I, II, and III in the primer resin liquid are preferably 0.06% to 17% by mass for resin I, and more preferably 2.0% to 10% by mass. For resin II, it is preferably 0.03% to 5% by mass, and more preferably 0.1% to 3% by mass. For resin III, it is preferably 0.2% to 12% by mass, and more preferably 0.7% to 6% by mass. In addition, the concentration of additives such as reaction initiators in the primer resin liquid is preferably 0.007% to 2% by mass, and more preferably 0.02% to 0.1% by mass.

[0039] A-3 Additives for Primer Resin Liquid The primer resin liquid for electroless plating substrates of the present invention has the above-mentioned resin component and solvent as essential components, but may also contain other components (resins / compounds) as additives. For example, it may contain photoacid generators (PAGs) or sensitizers as reaction initiators. The photoacid generator may also act as a curing accelerator for the above-mentioned resin III. Examples of photoacid generators include compounds such as onium salts (sulfonium salts, iodonium salts, diazonium salts, etc.), nitrobenzyl esters, diazomethane, and triazine, which can be used alone or in combination. Examples of sensitizers include 9-methylanthracene, anthracene methanol, acenaphthylene, thioxanthone, methyl-2-naphthylketone, 4-acetylbiphenyl, and 1,2-benzofluorene. These additives / reaction initiators are preferably included in an amount of 0.4% to 10% by mass relative to the resin component. Furthermore, even when these additives and reaction initiators are added, it is preferable that the proportion of solvent in the primer resin liquid be 90% by mass or more and 97% by mass or less, with the remainder being resin components and additives.

[0040] Furthermore, the resin content of the primer resin solution, the content of resins I, II, and III relative to the total resin components, and the concentration of additives in the primer resin solution can be measured by Fourier transform infrared spectroscopy (FT-IR), near-infrared spectroscopy (NIR), gas chromatography-mass spectroscopy (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 solution for electroless plating according to the present invention has specified viscosity and surface tension. By optimizing the viscosity and surface tension of the primer resin solution, the permeability and fluidity are provided when considering application to glass substrates 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. Primer resin liquids with a viscosity exceeding 10 mPa·s have poor fluidity and have difficulty penetrating through holes. Furthermore, a decrease in the viscosity of the primer resin liquid tends to result in a thinner primer resin layer. From the viewpoint of forming a primer resin layer with sufficient thickness to exhibit adequate adhesion, the viscosity of the primer resin liquid should preferably be 0.4 mPa·s or higher at 25°C, and more preferably 2 mPa·s or higher. Viscosity of the primer resin liquid can be measured using various devices, including rotational viscometers, vibratory viscometers, capillary viscometers, and falling ball viscometers, with vibratory viscometers 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, 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 penetration, and there is a risk that the primer resin layer will not adequately cover the inner surface of the through-holes. Also, if the surface tension of the primer resin liquid is low, it becomes difficult to handle in the coating process. For this reason, it is preferable that the lower limit of the surface tension of the primer resin liquid be 20 mN / m or more, calculated by the Young-Laplace method at 22°C. Furthermore, 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 applying the Young-Laplace formula to the shape of droplets obtained by the pendant drop method.

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

[0045] The viscosity of the primer resin liquid according to the present invention is mainly controlled 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, it is preferable that the proportion of the solvent to the total primer resin liquid be 90% by mass or more and 97% by mass or less. If the proportion of the solvent is less than 90%, the viscosity of the primer resin liquid will deviate from the above-mentioned appropriate range, making it difficult to obtain the permeability and fluidity necessary to form a primer resin layer in the through-holes. If the proportion of the solvent exceeds 97% by mass, the resin component will become dilute, making it impossible to form a primer resin layer of effective thickness. More preferably, the proportion of the solvent to the total 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 set to the appropriate range described above.

[0047] The solvent for the primer resin liquid can be a single solvent consisting of one type of solvent, or a mixed solvent consisting of two or more types of solvents. The solvent does not affect the reaction in which the resin components change into the primer resin layer. The requirement for the solvent is whether or not it can keep the viscosity and surface tension of the primer resin liquid within the specified range, and whether it is a single solvent or a mixed solvent is not important. Examples of single solvents include those listed as suitable examples above, with cyclohexanone, N-methyl-2-pyrrolidone, toluene, and methyl ethyl ketone being particularly suitable. As for mixed solvents, it is preferable to include one or more of the solvents listed as suitable examples above. When using a mixed solvent, solvents not listed as suitable examples above may also be included. For example, dimethyl sulfoxide, aniline, morpholine, and nitrobenzene are not listed as suitable examples above. These solvents alone make it difficult to keep the surface tension of the primer resin liquid within the specified range, but they can be used when mixed with suitable solvents.

[0048] As described above, the viscosity and surface tension of the primer resin liquid are mainly adjusted by the proportion and type of solvent. However, the viscosity and surface tension of the primer resin liquid may also be affected by the composition of the resin components (content 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 combined formulation of the elements described above.

[0049] B Electroless plating process for glass substrates to which the primer resin solution according to the present invention is applied. The primer resin solution according to the present invention, as described above, is effectively applicable to electroless plating processes on various substrates. The electroless plating process using the primer resin solution according to the present invention is basically the same as the prior art by the applicant (Patent Document 4, etc.). In this electroless plating process, after the steps of forming a primer resin layer by applying the primer resin solution to the substrate and firing it, and the steps of adsorption and fixation of noble metal nanoparticles that serve as catalyst nuclei to the primer resin layer, the electroless plating process is performed. The steps of the electroless plating process of the present invention will be described below.

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

[0051] Regarding the application of the present invention, the glass composition and dimensions of the glass substrate are not particularly limited. Glass is a composite material of inorganic oxides (silicon oxide, aluminum oxide, boron oxide, etc.), and its composition is not particularly limited; generally, anything referred to as a glass substrate can be used. Furthermore, recent advances in manufacturing technology have made it possible to manufacture glass substrates of various thicknesses. The present invention can be applied without limitation on the thickness of the glass substrate. There are also no limitations on the through-holes formed in the glass substrate, and the invention can accommodate fine through-holes with a diameter of 30 μm or less. In addition, the aspect ratio (hole depth / hole diameter) is often used as a criterion when evaluating the film deposition capability in through-holes. The present invention can accommodate through-holes with a high aspect ratio of 30 or more.

[0052] Furthermore, while the primer resin solution and electroless plating process of the present invention are particularly effective for glass substrates with through holes, they can also be used for other types of substrates. The present invention is also effective for flat glass substrates without through holes. As mentioned above, the primer resin layer formed by the present invention has good adhesion to glass. In addition, the present invention can be applied to substrates made of materials other than glass (resins, plastics, ceramics, 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 solution to a substrate and firing it. Various methods can be applied to the substrate for applying the primer resin solution, including spraying, dipping, spin coating, roll coating, and various printing methods (screen printing, gravure printing, flexographic printing, inkjet printing, etc.).

[0054] In the firing process for forming the primer resin layer, the firing temperature should be between 150°C and 260°C. Below 150°C, it is difficult to form a good primer resin layer with sufficient adhesion. Above 260°C, the adsorption of the catalyst nuclei, described later, decreases. A firing temperature of 180°C to 240°C is preferable. The firing process can be carried out in an atmospheric environment, under reduced pressure, or in a non-oxidizing atmosphere. This firing process causes the solvent in the primer resin liquid to evaporate and the resins to harden. In addition, the action of 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 primarily by controlling the amount of primer resin solution applied. For example, in dipping-type coating, the substrate is immersed in the primer resin solution and then lifted out for coating. By controlling the lifting speed of the substrate, the amount of primer resin solution applied can be adjusted, thereby controlling the thickness of the primer resin layer.

[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 results in poor retention of catalyst nuclei and poor adhesion of the plating film. On the other hand, there is no significant difference in the adhesion of the plating film with a primer resin layer with a thickness of more than 2 μm. Furthermore, considering the formation of a plating film in fine through-holes, an excessively thick primer resin layer can cause blockage of the through-holes and hinder the formation of a plating film of appropriate thickness. In the primer resin solution application step described above, it is preferable to adjust the application conditions so that the primer resin layer has the aforementioned thickness.

[0057] B-3 Pretreatment steps for the primer resin layer (optional steps) The primer resin layer formed from the primer resin solution of the present invention has functional groups (amino groups) on its surface that act as acceptors for catalyst nuclei due to the action of resin II, which is a crosslinking agent component. The functional groups generated by coating and firing the primer resin solution are active, and in this state, noble metal nanoparticles can be adsorbed.

[0058] The functional groups on this primer resin layer are inactivated by irradiation with deep ultraviolet light with a wavelength of 300 nm or less. This inactivation of functional groups by light irradiation contributes to the selective immobilization of precious metal nanoparticles. In other words, by performing patterning with a photomask and selective inactivation of 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 above patterning and light irradiation before the adsorption of precious metal nanoparticles, a desired wiring pattern can be formed by an electroless plating film.

[0059] The present invention is effective for forming a plating film inside through-holes in a glass substrate with through-holes. However, on substrates such as interposers, wiring and electrodes may be formed on surfaces other than the through-holes. The formation of functional group patterns by deep ultraviolet light irradiation 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 described above, optional steps include surface modification treatments for the primer resin layer. Examples of modification treatments include hydrophilization treatments such as plasma surface modification and UV ozone surface modification, application of monomolecular dispersion films, and coating of hydrophilic films. However, these modification treatments are also optional steps and not mandatory.

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

[0062] As a method for adsorbing and immobilizing precious metal nanoparticles onto a primer resin layer, it is preferable to apply a dispersion of precious metal nanoparticles to the surface of the primer resin layer. In this case, an aqueous solution containing a sugar alcohol is preferred as the dispersion medium for the dispersion of precious metal nanoparticles. The sugar alcohol acts as a protective agent (dispersant) surrounding the precious metal nanoparticles, suppressing aggregation of the precious metal nanoparticles in the dispersion. Furthermore, the sugar alcohol bound to the precious metal nanoparticles in the dispersion replaces the functional groups on the surface of the primer resin layer, promoting the binding between the precious metal nanoparticles and the primer resin layer (and its functional groups). Suitable sugar alcohols for this protective agent include glycerin, erythritol, xylitol, sorbitol, mannitol, etc. The dispersion medium is preferably an aqueous solution containing 0.1 g / L to 20 g / L of sugar alcohol.

[0063] Methods for applying the dispersion of precious metal nanoparticles include spraying, dipping, spin coating, and roll coating. After application of the dispersion, drying and washing may be performed as needed.

[0064] B-5 Electroless Plating Process A plating film is formed by electroless plating a substrate on which precious metal nanoparticles are adsorbed. This invention can be applied to electroless plating of various metals. Metals that can be plated by electroless plating include precious metals such as Au, Ag, Pt, and Pd, as well as base metals such as Cu, Ni, and Co. Known methods and conditions can be applied to the composition of the electroless plating solution and the electroless plating method for these metals.

[0065] The electroless plating process according to the present invention is particularly suitable for the manufacture of interposers (glass interposers), and Cu is most commonly used as the conductive material constituting the through-electrode of the interposer. The present invention is effective in 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 these can also be applied in the present invention. The electroless Cu plating solution essentially contains a Cu salt and a reducing agent, and optionally contains additives such as complexing agents and pH adjusters.

[0066] Examples of Cu salts used in 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. Regarding reducing agents, formaldehyde, hydrazine, ascorbic acid, thiourea, hydroquinone, dimethylamine borane, hypophosphate, hydrogen peroxide, formic acid, hypophosphate, boron hydride, thiosulfate, hydroxylamine, and sodium erythorbate are known, including 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 bath) or plating solutions using hypophosphorous acid as a reducing agent (hypophosphorous acid bath) are preferably used. For Cu salts, copper sulfate and Cu chloride are preferred. Furthermore, hypophosphorous acid baths may contain metal ions other than Cu, such as Ni, Co, and Sn, to assist in Cu deposition. The electroless plating process according to the present invention makes it possible to form an electroless Cu plating film as a seed layer on the inner surface of through holes using these electroless Cu plating solutions, and it is also possible to directly form a Cu film as a through electrode.

[0067] B-6 Post-heat treatment process (curing process) In the electroless plating process, a plating film is formed on the primer resin layer, and the electroless plating process of the present invention is essentially completed at this point. However, it is preferable to add a post-heat treatment process called a curing process in order to ensure the adhesion strength between the plating film and the substrate. The curing process is a process in which the primer resin layer is heated to a temperature above the glass transition temperature of the composite resin constituting the primer resin layer, thereby fluidizing the primer resin layer and embedding the precious metal nanoparticles in the primer resin layer. By embedding the precious metal nanoparticles in the primer resin layer, the adhesion of the plating film can be improved.

[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 between 150°C and 300°C. Specifically, the temperature range is between 150°C and 260°C. Heating within this temperature range causes fluidization of the primer resin layer, and the noble metal nanoparticles are incorporated into the primer resin layer, increasing the adhesion strength. The curing process can be carried out in an air atmosphere, but it is also possible in a reduced pressure atmosphere or a non-oxidizing atmosphere. The heating time is preferably between 0.1 hours and 2 hours.

[0069] The curing process described above improves the adhesion between the plated film and the substrate (primer resin layer). After the curing process, post-treatment such as plasma ashing may be performed as needed.

[0070] Through the above series of steps, a primer resin layer and an electroless plating film are formed on the glass substrate. Subsequently, electroplating can be performed as needed to form wiring made of Cu or other materials. Alternatively, through holes can be filled and wiring can be formed using only the electroless plating process described above.

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

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

[0073] The primer resin solution for electroless plating according to the present invention has good penetration into through-holes in 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 also be favorably improved. [Brief explanation of the drawing]

[0074] [Figure 1] Cross-sectional photograph of a through-hole after electroless plating treatment using the primer resin solution of Example 2 of the second embodiment. [Figure 2]Cross-sectional photograph of a through-hole after electroless plating treatment using the primer resin solution of Comparative Example 1 of the second embodiment. [Figure 3] Photographs of the through-hole openings after electroless plating treatment using the primer resin solutions of Example 2 and Comparative Example 3 of the second embodiment. [Figure 4] A photograph for evaluating patternability when plating is performed under the conditions of Example a of the third embodiment. [Figure 5] Cross-sectional photographs of the through-holes after plating (electroless plating and electrolytic copper plating) in each embodiment of the fourth embodiment. [Modes for carrying out the invention]

[0075] First Embodiment (Preliminary Study) The embodiments of the present invention will now be described. In this embodiment, the primer resin liquid applied in the prior art (Patent Document 4, etc.) by the present applicant is used as a reference, and the composition of a primer resin liquid with higher adhesion is investigated. Specifically, the adhesion of the primer resin layer to the plating film when a thermosetting resin, which is an adhesion agent component, is added to the primer resin liquid of the prior art was evaluated.

[0076] In this embodiment, a primer resin solution was prepared by dissolving a polyester resin (Yupika Coat GV-110, manufactured by Nippon Yupika Co., Ltd.) as resin I (main component), a melamine resin (CYMEL® 303LF, manufactured by Allnex) as resin II (crosslinking agent component), a bisphenol A type 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 solutions (primer resin solutions A to G) evaluated in this embodiment are shown in Table 1. In Table 1, the conventional primer resin solution is primer resin solution H, which does not contain bisphenol A type epoxy resin.

[0077] In the preliminary studies of this embodiment, no conscious adjustments were made to the viscosity and surface tension of the primer resin liquid. That is, the preliminary studies of this embodiment prioritized defining the composition of resin components that can improve the adhesion of the plating film. For this purpose, we decided to investigate primer resin liquids in which the proportion of resin components was increased without considering viscosity and surface tension. Specifically, the proportion of resin components to the primer resin liquid was set to more than 10% by mass (the proportion of solvent was less than 90% by mass). As a result, the 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] For the formation of the primer resin layer, 4 mL of primer resin solution was applied to a glass substrate (10 cm x 10 cm) using the spin-coating method. The substrate was then pre-baked (fired) to remove the solvent and cure the resin, forming the primer resin layer. Pre-baking was performed in a forced-circulation oven under an air atmosphere 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 acceptors (amino groups) were partially deactivated by exposing the surface of the primer resin layer in a predetermined pattern. For the exposure treatment, a photomask was used to form a linear pattern (L / S=5μm) with a width of 5μm and spacing of 5μm, and a deep ultraviolet (DUV) light exposure machine was used. Multilight (manufactured by Ushio Inc.) emits deep ultraviolet light with a wavelength of 254 nm at a rate of 800 mJ / cm². 2 It was irradiated with it.

[0081] Then, an Au nanoparticle dispersion (SEADCAT® CAT Au-10, manufactured by EEJA Corporation) was applied to the surface of the substrate (primer resin layer) after exposure treatment, serving as a catalyst nucleus. This Au nanoparticle dispersion is 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 for 15 minutes at room temperature and then dried in the atmosphere.

[0082] After immobilizing Au nanoparticles on a primer resin layer, an Au plating film was formed by electroless plating. An Au electroless plating solution (AC FAB® AU-ACG3000GX, manufactured by EEJA Corporation) was used, and the Au plating film was formed at a plating temperature of 65°C for a plating time of 5 minutes. These plating conditions assume a thickness of 50 nm for the Au plating film.

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

[0084] Finally, an electrolytic Cu plating film was deposited on the Au plating film prepared above. Electrolytic Cu plating was performed using a commercially available electrolytic Cu plating solution (MICROFAB® Cu250, manufactured by EEJA Corporation) at a current density of 3 A / dm². 2 The material was then subjected to electroplating for 20 minutes to form a Cu plating film of approximately 15 μm thickness.

[0085] After depositing the Cu plating film, the adhesion (adhesion strength) of the plating film was evaluated. The adhesion strength was evaluated 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 higher were judged to be acceptable. This criterion was set to determine acceptance based on values ​​exceeding the value obtained when the acceptance value in the cross-cut test evaluation described in the prior art (Patent Document 4) was converted to the peel strength (0.2~0.3 N / mm) obtained by the peel test. The evaluation results, along with the composition of each primer resin layer, are shown in Table 2.

[0086] [Table 2]

[0087] Table 2 shows that, regarding the effect of the adhesion agent component (resin III), which is a thermosetting resin (resin having a bisphenol skeleton), the primer resin layers formed from primer resin solutions A to D all showed improved adhesion strength of the plated film compared to the primer resin layer formed from the conventional example primer resin solution H. Furthermore, primer resin solutions E to F, which had an excess of resin III added, resulted in lower adhesion strength of the plated film than the conventional example which did not contain resin III. From these results, it can be said that it is preferable to use a primer resin solution containing a three-component resin system with an appropriate amount of thermosetting resin having a bisphenol skeleton, which acts as the adhesion agent component. In addition, from the results for primer resin solution G, it can be seen that the main component (resin I) is also an essential component of the primer resin solution.

[0088] Second Embodiment In this embodiment, multiple types of primer resin solutions with different viscosities and surface tensions were produced by adjusting the type and proportion of solvents while keeping the resin component composition the same. Then, the feasibility of forming a primer resin layer on a glass substrate with through holes and the feasibility of forming an electroless Cu plating film were investigated using the various primer resin solutions produced.

[0089] In this embodiment, resin A, a three-component resin component investigated in the first embodiment and for which suitable adhesion was confirmed, was used. In this embodiment, the solvent 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, primer resin solutions were prepared using cyclohexanone as the solvent, with the viscosity adjusted by reducing the solvent ratio to less than 90% by mass (Comparative Examples 1 and 2), and a primer resin solution using dimethyl sulfoxide as the solvent (Comparative Example 3) was also prepared.

[0090] The viscosity and surface tension of the various primer resin liquids manufactured were measured before use. Viscosity was measured using a vibrating 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 droplets obtained by the pendant drop method was calculated by image analysis applying the Young-Laplace formula. The composition, viscosity, and surface tension of the various primer resin liquids manufactured in this embodiment are as follows.

[0091] [Table 3]

[0092] Then, a primer resin layer was formed on the glass substrate using the various primer resin solutions 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 in thickness and having 1300 through holes with a pore diameter of 100 μm (aspect ratio 4), was used as the substrate. To apply the primer resin layer, the glass substrate was dipped in 100 mL of primer resin solution, immersed for 1 minute, and then pulled out at a pulling speed of 0.5 mm / s. After applying the primer resin solution, the substrate was pre-baked at 200°C for 10 minutes in an air atmosphere to form the primer resin layer.

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

[0094] Subsequently, a Cu plating film was 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, and the Cu plating film was formed at a plating temperature of 38°C for a plating time of 3 minutes. After the Cu plating film was formed, the curing process was performed by heating in a stationary oven at 250°C in air for 30 minutes.

[0095] Using the above process, electroless Cu plating films were formed on glass substrates using various primer resin solutions. The cross-section of these substrates was observed to evaluate the condition inside the through-holes and the feasibility of Cu plating film formation. In this evaluation, a through-hole was deemed acceptable if the primer resin layer was formed over the entire inner wall. Similarly, a through-hole was deemed acceptable if the Cu plating film was formed over the entire inner wall. The number of through-holes that passed the evaluation for both the primer resin layer and the Cu plating film was measured, and the ratio of the number of passing holes to the total number of through-holes (1300) formed in the glass substrate was calculated. A ratio of 90% or more was evaluated as a pass (○), while a ratio of 30% or less was evaluated as a fail (×). Table 4 shows the evaluation results for primer resin layer and Cu plating film formation in through-holes in this embodiment.

[0096] [Table 4]

[0097] Table 4 shows that in substrates treated with the primer resin solutions of Examples 1 to 4, which had viscosity and surface tension within a predetermined range, a uniform primer resin layer was formed throughout the interior, and the Cu plating film was also formed in good condition. Figure 1 is a cross-sectional photograph of the inside 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 Figure 1 was confirmed in most 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 the primer resin layer and copper plating film inside the through-holes was insufficient or impossible. In the case of the high-viscosity 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 thought that the primer resin solutions of Comparative Examples 1 and 2 had excessive viscosity and hardened without penetrating to the center of the through-hole. As a result, in almost all of the through-holes formed in the substrate, the primer resin layer and Cu plating film were not formed on the entire inner wall (evaluation failed).

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

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

[0101] Third Embodiment In this embodiment, after forming a primer resin layer using the primer resin solution of Example 1 or Example 2, the feasibility of film formation and adhesion were evaluated when electroless Cu plating was performed by adjusting the composition of the noble metal nanoparticles and the electroless Cu plating solution.

[0102] In this embodiment, the same flat glass substrate as in the first embodiment was used. As described above, in this embodiment, the electroless plating process using the primer resin solution according to the present invention is to be examined for the influence of the type of noble metal nanoparticles that serve as catalyst nuclei for the plating film and the type of Cu plating solution. In such studies, 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, the primer resin solution was applied to the glass substrate by dipping, as in the first embodiment, and then pre-baked at 200°C for 10 minutes to form a primer resin layer. The primer resin solutions used in this embodiment were the primer resin solution of Example 1 (viscosity 8.4 Pa·s, surface tension 34.6 mN / m) and the primer resin solution of Example 2 (viscosity 4.2 Pa·s, surface tension 34.1 mN / m) that were investigated in the second embodiment.

[0104] After the primer resin layer was formed, precious metal nanoparticles were adsorbed. In this embodiment, dispersions of the following three types of precious metal nanoparticles were used. To adsorb the precious metal nanoparticles onto the primer resin layer, the glass substrate was immersed in each dispersion for 15 minutes at room temperature, and then dried in the atmosphere. • Au nanoparticles: Dispersion of Au particles as in the first embodiment (product name: SEADCAT® CAT Au-10, manufactured by EEJA Corporation) • Pd nanoparticles: Dispersion of 5nm Pd particles (manufactured by EEJA Corporation) • SnPd nanoparticles: Commercially available SnPd particle dispersion (product name: Mactivate10, 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, three commercially available electroless Cu plating solutions, α to γ, were used (Cu plating solution α is the same as the one used in the second embodiment). The composition of each Cu plating solution and the conditions (temperature) during the electroless plating process are as follows.

[0106] [Table 5]

[0107] After forming the Cu plating film by electroless plating, the curing process was performed by heating in a stationary oven at 250°C in air for 30 minutes.

[0108] Then, after electroless plating treatment with the various Cu plating solutions described above, the feasibility of forming a Cu plating film on the substrate surface was confirmed. The adhesion strength of the Cu plating film was then measured. The adhesion strength was measured using the same peel test method as in the first embodiment. Samples with a peel strength of 0.4 N / mm or higher were judged to be acceptable. The evaluation results of the electroless plating process examined in this embodiment are shown in Table 5.

[0109] [Table 6]

[0110] It was confirmed that the primer resin layer formed using the primer resin solution of this embodiment (primer resin solutions of Example 1 and Example 2) can form suitable plating films with all of the noble metal nanoparticles (catalyst nuclei) and electroless Cu plating solutions of Examples a to l. The Cu plating films formed in Examples a to l also showed good adhesion.

[0111] Furthermore, in this embodiment, the patternability of the plated films formed under the conditions of Examples a to f was also evaluated. In evaluating the patternability, a primer resin layer was formed on the substrate in the same manner as described above, and then the acceptors were partially deactivated by exposure treatment. For the exposure treatment, a photomask was used to form a linear pattern (L / S=5μm) with a width of 5μm and spacing of 5μm, and deep ultraviolet light with a wavelength of 254nm was applied at a rate of 800mJ / cm² using a deep ultraviolet exposure machine. 2 It was irradiated with it.

[0112] Then, noble metal nanoparticles (Au nanoparticles or Pd nanoparticles) were adsorbed onto a primer resin layer in which the acceptors had been partially deactivated. Subsequently, Cu plating was performed using electroless Cu plating solution (α~γ) in the same manner as above, followed by electrolytic Cu plating. The pass / fail criteria were determined visually based on the presence or absence of pinholes on the surface of the Cu plating film, 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 patternability was good and that fine Cu wiring could be formed on the surface of the glass substrate. Figure 4 shows the appearance of the plated 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 for plated film formation by patterning.

[0114] Fourth Embodiment In this embodiment, various glass substrates with through holes differing in thickness and hole diameter were prepared. A primer resin layer was formed on these substrates using a primer resin solution, 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, differing in substrate thickness and hole diameter, were treated with a primer resin solution. Using the primer resin solution examined in Example 1 or Example 2 of the second embodiment, a primer resin layer was formed by applying it to each glass substrate with through holes. The application conditions and pre-bake conditions for the primer resin solution were the same as in the second embodiment.

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

[0117] After electroless plating, the electrolytic Cu plating solution was used with a current density of 3 A / dm², as in the first embodiment. 2 The material was then subjected to electroplating for 10 to 20 minutes to form an electrolytic copper plating film of 10 μm to 25 μm thickness.

[0118] Cross-sectional observations were performed on each glass substrate with through holes after electrolytic plating. Cross-sectional observations determined that metallization within the through holes was possible when the electroless Cu plating and electrolytic plating film filled the interior of the through holes without interruption. Furthermore, a peel test similar to that of the first embodiment was performed on the Cu plating film deposited on the flat surface of each glass substrate with through holes, and adhesion was deemed satisfactory if the peel strength was 0.4 N / mm or higher. These evaluation results are shown in Table 7.

[0119] [Table 7]

[0120] Table 7 shows that by applying the primer resin layer formed with the primer resin solution of this embodiment, an Au or Cu plating film can be formed in the through-holes under all conditions (Examples m to u), and electrical conductivity can be achieved between the front and back surfaces of the substrate. Figure 5 shows cross-sectional photographs of the through-holes in each embodiment. Furthermore, examining the aspect ratio of the through-holes in each substrate, it was confirmed that the plating film can be filled even in through-holes with an aspect ratio of 20 or more. [Industrial applicability]

[0121] This invention applies a primer resin layer and noble metal nanoparticles acting as catalyst nuclei to a glass substrate as an electroless plating process. The primer resin solution according to this 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 according to this 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 aforementioned resin component includes resin I, which is the main component, resin II, which is the crosslinking agent component, and resin III, which is the adhesion agent component. The resin III, which is the adhesive component, is a thermosetting resin having a bisphenol skeleton. The content of 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 using the Young-Laplace method.

2. The primer resin solution for electroless plating according to claim 1, wherein resin I is a polyester resin, polyimide resin, LCP resin, or polyethylene terephthalate resin, and resin II is a resin containing amino groups.

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

4. A primer resin solution for electroless plating according to claim 1 or claim 2, wherein the ratio of the content of resin I to the content of resin III is 1 or more and 4 or less.

5. In a method for plating a glass substrate with through holes, in which one or more through holes are formed in the core substrate, an electroless plating film is formed on the surface of the glass substrate, The steps include applying the electroless plating primer resin solution described in claim 1 or claim 2 to the glass substrate and allowing the primer resin solution to penetrate the through-holes, The process involves firing the primer resin liquid at a temperature of 150°C to 260°C to form a primer resin layer. A step of dispersing a noble metal nanoparticle catalyst containing a noble metal with a particle size of 1 nm to 100 nm on the surface of the primer resin layer, A method for plating a glass substrate with through holes, comprising the step of forming a plating film on the surface of the primer resin layer using an electroless plating solution.

6. A method for plating a glass substrate with through holes according to claim 5, comprising a curing step of forming a plating film with an electroless plating solution and then heating a primer resin layer at a temperature within a range of 150°C to 300°C, within a range of ±50°C of its glass transition temperature (Tg).

7. In a glass interposer substrate made of a glass substrate having one or more through holes, A metal plating film 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 comprises a thermoplastic resin I as the main component, a resin II as the crosslinking agent component, and a thermosetting resin III having a bisphenol skeleton as the adhesion agent component. A glass interposer substrate characterized in that the content of 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.

Images