Resin plating material and method for producing resin plating material

Abstract

Provided is a resin plating material in which the adhesion strength between a base material and a plating layer is enhanced over the prior art, substantially without unevenness being provided on the surface of the base material.　This resin plating material comprises: a base material that contains an insulating resin material; a microporous layer that is formed over a prescribed depth region from the surface of the base material and contains voids having a nanometer-order size; an adhesion layer that is composed of an organic compound exhibiting a different composition from the base material formed in the region, within the base material, where the microporous layer is formed; and an electroless plating layer that is formed as the layer above the adhesion layer.

Description

Resin-plated material, and manufacturing method of resin-plated material

[0001] The present invention relates to a resin-plated product and a method for producing a resin-plated product.

[0002] A wiring board having a wiring pattern formed on the surface of an insulating resin material is known. Conventionally, this wiring board is obtained by forming an electroless plating layer called a seed layer on a resin base material, and then forming an electrolytic copper plating layer on top of that. Another known method for producing a wiring board is to bond or bond copper foil to one or both sides of an insulating resin material using an adhesive.

[0003] To obtain stable electrical properties, the resin and the electroless plating layer (seed layer) must be firmly adhered to each other. A conventional method for improving adhesion involves roughening the surface of the resin to create irregularities, and then forming a seed layer on the irregular surface of the resin. The anchor effect resulting from the presence of irregularities firmly fixes the resin and seed layer together.

[0004] Incidentally, a system known as 5G communication, which has been under development in recent years, utilizes extremely high-frequency electrical signals. Such high-frequency currents flow only through the surface layer of the conductor, with difficulty flowing through the center of the conductor due to a phenomenon known as the skin effect. If the surface of the conductor is uneven, the signal transmission path becomes longer, resulting in increased transmission loss. Therefore, it is preferable to minimize the unevenness of the conductor surface, especially for wiring boards intended to handle high-frequency signals.

[0005] In consideration of the above circumstances, the following technologies have been proposed.

[0006] JP 2023-080480 A JP 2023-080489 A

[0007] The present invention aims to provide a resin-plated product that enables the adhesive strength between a substrate and a plating layer to be improved compared to conventional methods without creating substantial irregularities on the surface of the substrate, and a method for producing the same.

[0008] The resin-plated product according to the present invention is characterized by comprising a substrate containing an insulating resin material, a microporous layer formed from the surface of the substrate to a predetermined depth region and containing voids of nanometer order size, an adhesion layer formed in the region where the microporous layer is formed inside the substrate and made of an organic compound having a composition different from that of the substrate, and an electroless plating layer formed on top of the adhesion layer.

[0009] In this specification, the term "microporous layer" refers to a layer containing voids generated by cleavage of some of the polymer chains of the resin material constituting the substrate. These voids are on the order of nanometers (1 nm to several nanometers) in size. The presence and thickness of the microporous layer can be confirmed by observing the cross section of the resin-plated product with a TEM (transmission electron microscope). The microporous layer is a layer formed by modifying the substrate, and can also be referred to as a "modified layer."

[0010] According to the above configuration, an adhesion layer made of an organic compound having a different composition from the substrate penetrates into the microporous layer formed on the surface region of the substrate. This allows the adhesion layer to exhibit a nano-level anchoring effect within the substrate, firmly fixing the two together. Furthermore, by forming an electroless plating layer on top of this adhesion layer, a portion of the electroless plating layer also penetrates into the substrate. This firmly fixes the substrate and the electroless plating layer together.

[0011] Examples of the material for the substrate include polyimide resin, liquid crystal polymer, polystyrene, polyphenylene sulfide, polyether ether ketone, polyethylene naphthalate, cycloolefin polymer, cyclic olefin copolymer, polytetrafluoroethylene, polyurethane, phenolic resin, and epoxy resin, and a mixture of these materials may be used.

[0012] The microporous layer can be formed by applying energy to the surface of the substrate from outside the substrate to modify a portion of the resin material that constitutes the substrate. More specifically, by irradiating the substrate with ultraviolet light of a predetermined wavelength, the microporous layer can be formed in a region extending from the surface of the substrate to a predetermined depth. The region where the microporous layer is formed contains voids, allowing liquid to penetrate into the interior.

[0013] Therefore, by immersing a substrate on which a microporous layer has been formed in a liquid containing a material that will be the precursor of the adhesion layer, an adhesion layer can be formed from the surface of the substrate to a predetermined depth, in other words, inside the microporous layer.

[0014] In this way, by supporting a catalyst in a state in which a microporous layer and an adhesion layer are formed near the surface side of the substrate, the catalyst can be applied not only to the surface of the substrate but also to the interior of the substrate near the surface where the microporous layer and adhesion layer are formed. Therefore, by subsequently growing electroless plating, an electroless plating layer is formed not only on the surface of the substrate but also inside the substrate. This creates a nano-level anchor effect between the electroless plating layer and the adhesion layer, firmly fixing the substrate and the electroless plating layer.

[0015] As the liquid containing the material that will be the precursor of the adhesion layer, it is preferable to use a liquid containing a compound that exhibits the property of exhibiting an auto-oxidation reaction and a compound that exhibits the property of exhibiting a self-polymerization reaction. Note that, when a single compound exhibits the property of exhibiting both an auto-oxidation reaction and a self-polymerization reaction, a liquid containing the single compound may be used.

[0016] For example, dopamine is known to exhibit the property of undergoing autoxidation and autopolymerization in air. Therefore, by immersing a substrate on which a microporous layer has been formed in a solution containing dopamine adjusted to a predetermined pH, the solution containing dopamine is incorporated into the microporous layer. Then, as the dopamine incorporated into the microporous layer undergoes autoxidation and autopolymerization, a layer (adhesion layer) exhibiting high adhesion to the microporous layer, in other words, to the substrate, is formed within the microporous layer. Subsequently, an electroless plating layer is formed via a catalyst, thereby exhibiting high adhesion between the electroless plating layer and the adhesion layer.

[0017] A typical example of a reactive group having a self-oxidizing function is a phenolic hydroxyl group, and a catechol group in particular is known as a reactive group having a self-oxidizing function. Furthermore, compounds having a nucleophilic reactive group tend to react with other compounds and polymerize. Known examples of such nucleophilic reactive groups include amino groups and thiol groups. In other words, by immersing a substrate having a microporous layer in a solution adjusted to a predetermined pH and containing a first compound having a catechol group and a second compound having an amino group, an adhesive layer exhibiting high adhesive strength to the microporous layer, in other words, to the substrate, is formed within the microporous layer for the same reason as described above.

[0018] The substrate may be made of a resin material that does not contain nitrogen atoms, and the adhesive layer may be made of one or more organic compounds that contain nitrogen atoms.

[0019] As described above, an amino group can be used as the nucleophilic reactive group exhibiting a self-polymerization reaction. In this case, a compound containing an amino group is used as a precursor of a material for forming the adhesion layer, and the adhesion layer is made of one or more organic compounds containing a nitrogen atom.

[0020] Here, by forming the substrate from a resin material that does not contain N atoms, it is possible to easily verify that the adhesion layer has penetrated into the substrate by analysis using, for example, a TOF-SIMS method, etc. Among the examples of materials for the substrate, examples of resin materials that do not contain N atoms include liquid crystal polymers, polystyrene, polyphenylene sulfide, polyether ether ketone, polyethylene naphthalate, cycloolefin polymers, cyclic olefin copolymers, polytetrafluoroethylene, phenolic resins, and epoxy resins.

[0021] The microporous layer may be formed to a depth of 30 nm or more from the surface of the substrate.

[0022] This allows an adhesive layer to be formed on the inner side of the substrate over a sufficient thickness, and also makes it easier to support the catalyst in the microporous layer during production.

[0023] As described above, the microporous layer is a layer containing voids generated by cleavage of some of the polymer chains of the resin material constituting the substrate. Therefore, if the thickness of the microporous layer is too large, the proportion of low-molecular-weight regions in the substrate increases, which may reduce the strength of the substrate itself.

[0024] From this viewpoint, the microporous layer may be formed in a region within a range between the surface of the substrate and a depth position of 200 nm or less from the surface of the substrate.

[0025] The method for manufacturing a resin-plated product according to the present invention comprises the steps of: (a) preparing a substrate containing an insulating resin material; (b) irradiating the surface of the substrate with ultraviolet light to modify a region from the surface of the substrate to a predetermined depth into a microporous layer containing voids of nanometer order size in the substrate; (c) after the step (b), impregnating at least the surface of the substrate on which the microporous layer is formed with a solution containing a reaction compound having a phenolic hydroxyl group and a nucleophilic reactive group to form an adhesion layer made of a derivative of the reaction compound in the region where the microporous layer is formed; (d) supporting a catalyst in the microporous layer; and (e) after the step (d), forming an electroless plating layer via the catalyst.

[0026] The phenolic hydroxyl group may be a catechol group, and the nucleophilic reactive group may be an amine group. In this case, the reactive compound may be dopamine.

[0027] The method for producing a resin-plated product according to the present invention is characterized in that it comprises the steps of: (a) preparing a substrate containing an insulating resin material; (b) irradiating the surface of the substrate with ultraviolet light to modify a region from the surface of the substrate to a predetermined depth into a microporous layer containing voids of nanometer order size in the substrate; (c) after the step (b), impregnating at least the surface of the substrate on which the microporous layer is formed with a solution containing a first compound having a phenolic hydroxyl group and a second compound having a nucleophilic reactive group to form an adhesion layer derived from the first compound and the second compound in the region where the microporous layer is formed; (d) supporting a catalyst in the microporous layer; and (e) after the step (d), forming an electroless plating layer via the catalyst.

[0028] In the above method, the phenolic hydroxyl group may be a catechol group, and the nucleophilic reactive group may be an amine group. In this case, the first compound may be a catechol, and the second compound may be a polyamine.

[0029] The ultraviolet light irradiated in the step (b) may have a light output at a wavelength of 200 nm or less, and more preferably, the ultraviolet light irradiated in the step (b) may have a main peak wavelength or a sub-peak wavelength of 200 nm or less.

[0030] Here, the term "main peak wavelength" refers to the wavelength with the highest light intensity in the spectrum of light emitted from a light source. Furthermore, the term "sub-peak wavelength" refers to a wavelength with a lower light intensity than the main peak wavelength, but with a higher light intensity than the wavelengths before and after the sub-peak wavelength. For example, a wavelength around 185 nm in the spectrum of ultraviolet light emitted from a low-pressure mercury lamp corresponds to the sub-peak wavelength. Meanwhile, a wavelength around 172 nm in the spectrum of ultraviolet light from a Xe excimer lamp corresponds to the main peak wavelength.

[0031] According to the present invention, a resin-plated product is realized in which the adhesive strength between the substrate and the plating layer is improved compared to conventional products, without providing the substrate surface with substantial irregularities.

[0032] FIG. 1 is a cross-sectional view schematically showing the structure of one embodiment of a resin-plated product of the present invention. FIG. 2 is a drawing schematically showing the structure of a microporous layer. FIG. 3 is a cross-sectional view schematically showing the structure of a resin-plated product including a patterned electrolytic plated layer. FIG. 4 is a drawing schematically showing the results of elemental analysis by EDS of a cross-sectional image of the surface vicinity of a substrate included in the resin-plated product, obtained using STEM-EDX. FIG. 5 is a flowchart showing an example of the procedure for a method for manufacturing a resin-plated product. FIG. 6 is a drawing schematically showing one procedure for a method for manufacturing a resin-plated product. FIG. 7 is a drawing schematically showing one procedure for a method for manufacturing a resin-plated product. FIG. 8 is a drawing schematically showing one procedure for a method for manufacturing a resin-plated product. FIG. 9 is a graph showing the results of mass spectrometry performed by TOF-SIMS on a sample of Comparative Example 1. FIG. 10 is a graph showing the results of mass spectrometry performed by TOF-SIMS on a sample of Example 1. 1 is a graph showing the results of mass spectrometry performed by TOF-SIMS on the sample of Comparative Example 1. FIG. 2 is a graph showing the results of mass spectrometry performed by TOF-SIMS on the sample of Example 1.

[0033] Embodiments of a resin-plated product and a method for manufacturing the same according to the present invention will be described below with reference to the accompanying drawings. The drawings are schematic illustrations, and the dimensional ratios in the drawings do not necessarily correspond to the actual dimensional ratios. Furthermore, the dimensional ratios between the drawings may not match each other.

[0034] [Resin Plated Product] Fig. 1 is a cross-sectional view showing the structure of a resin plated product 1. As shown in Fig. 1, the resin plated product 1 includes a substrate 3 and an electroless plating layer 9 formed on the +Z side surface of the substrate 3.

[0035] In the following drawings, the Z direction refers to the direction perpendicular to the main surface of the substrate 3. The main surface of the substrate 3 refers to a surface that is much larger in area than the other surfaces that make up the substrate 3. Of the main surfaces of the substrate 3, the surface on the +Z side, i.e., the surface on which the electroless plating layer 9 is formed, may be referred to as the "surface 3a" of the substrate 3 for convenience. Furthermore, the direction from the surface 3a of the substrate 3 toward the substrate 3 side (-Z direction) may be referred to as the "depth direction" for convenience.

[0036] In this embodiment, the substrate 3 is made of an insulating resin material. Specific examples of materials constituting the substrate 3 include polyimide resin, liquid crystal polymer, polystyrene, polyphenylene sulfide, polyether ether ketone, polyethylene naphthalate, cycloolefin polymer, cyclic olefin copolymer, polytetrafluoroethylene, polyurethane, phenolic resin, and epoxy resin, and a mixture of these materials may also be used. The substrate 3 may be a sheet-like film or a plate-like member.

[0037] The substrate 3 has a microporous layer 5 formed from the surface 3a of the substrate 3 to a depth D1. The microporous layer 5 is a layer formed by modifying the substrate 3, as described below. The depth D1 is 20 nm or more, more preferably 30 nm or more, and particularly preferably 70 nm or more. The depth D1 is preferably 200 nm or less.

[0038] FIG. 2 is a diagram schematically illustrating the structure of the microporous layer 5. The substrate 3 is formed of a polymeric resin material. As described below, the microporous layer 5 corresponds to a layer formed when the substrate 3 is irradiated with ultraviolet light, resulting in cleavage of some of the polymer chains of the resin material and oligomerization. Oligomerization of the polymeric material forms spaces (voids 4) between the oligomers. The microporous layer 5 corresponds to a layer containing voids 4 as a result of modifying a portion of the substrate 3 in this manner. The voids 4 are on the order of nanometers (1 nm to several nanometers) in size.

[0039] As shown in FIG. 1 , the resin-plated product 1 of this embodiment has an adhesion layer 2 within the region of the substrate 3 where the microporous layer 5 is formed. This adhesion layer 2 is a layer made of an organic compound having a different composition from that of the substrate 3. As described below, the adhesion layer 2 is formed by oxidation and polymerization reactions after a liquid containing a material that will be a precursor of the adhesion layer 2 penetrates into the microporous layer 5. According to the manufacturing method of the resin-plated product 1 described below, the substrate 3 is immersed in a liquid containing a material that will be a precursor of the adhesion layer 2, so that the adhesion layer 2 is formed over the entire outer surface of the substrate 3. The outer surface of the substrate 3 is then washed, removing most of the adhesion layer 2 formed on the outer surface of the substrate 3. Meanwhile, the adhesion layer 2 formed within the microporous layer 5 remains even after the washing process because, in addition to chemical bonding, physical bonding resulting from a nano-level anchoring effect occurs in the areas where the microporous layer 5 is formed.

[0040] However, depending on the strength of the cleaning treatment, a portion of the adhesion layer 2 may remain on the outer peripheral surface of the substrate 3, such as on the upper surface on the +Z side of the substrate 3. The present invention does not exclude an embodiment in which a portion of the adhesion layer 2 remains on the outer peripheral surface of the substrate 3 in the resin-plated product 1.

[0041] In FIG. 1, for ease of understanding, the region where the microporous layer 5 is formed is shown with hatching slanting downward to the right, and the region where the adhesive layer 2 is formed is shown with hatching slanting upward to the right with dashed lines.

[0042] As shown in Fig. 1, a catalyst 7 is supported within a microporous layer 5 provided on a substrate 3. The catalyst 7 may be any compound containing molecules or atoms that exhibit catalytic effects (hereinafter referred to as a "catalytic compound"), and typically a substance containing Pd is used, but Ni, Ag, etc. can also be used.

[0043] As described above, the adhesion layer 2 is formed inside the microporous layer 5, but the microporous layer 5 is a layer that includes voids 4, and not all of these voids 4 are filled with the adhesion layer 2. In other words, the catalyst 7 is supported not only on the upper surface of the substrate 3 but also inside the microporous layer 5. Since the adhesion layer 2 and the microporous layer 5 are mixed together, the region where the adhesion layer 2 is formed is also the region where the microporous layer 5 is formed, and it can be said that the catalyst 7 is supported inside the adhesion layer 2.

[0044] 1, the electroless plated layer 9 is formed on the +Z side surface of the substrate 3, and more specifically, is located on top of the microporous layer 5. As shown in FIG. 1, a portion of the electroless plated layer 9 penetrates into the microporous layer 5 in the depth direction. This is because the formation of the electroless plated layer 9 progresses from the catalyst 7 supported in the microporous layer 5.

[0045] The electroless plating layer 9 is typically a film made of a conductive material containing Cu, but may also be a film made of a conductive material containing other metal elements such as Ni.

[0046] As described above, the catalyst 7 is supported in the microporous layer 5 and the adhesion layer 2. Therefore, at positions within the microporous layer 5 and the adhesion layer 2, electrons released when the reducing agent is decomposed on the catalyst 7 can be received by metal ions containing elements that constitute the electroless plated layer 9. As a result, the electroless plated layer 9 is also formed at positions within the microporous layer 5 and the adhesion layer 2.

[0047] That is, according to the above configuration, the electroless plated layer 9 penetrates into the microporous layer 5 and the adhesion layer 2. This creates a nano-level anchoring effect between the substrate 3 and the electroless plated layer 9, firmly fixing them together. In particular, by forming not only the microporous layer 5 but also the adhesion layer 2, the electroless plated layer 9 exerts a nano-level anchoring effect on both the microporous layer 5 and the adhesion layer 2, resulting in strong adhesion between the substrate 3 and the electroless plated layer 9. Furthermore, the adhesion layer 2 has strong adhesion (the force between the adhesion layer 2 and the electroless plated layer 9) due to a chemical reaction. By having the adhesion layer 2 penetrate into the voids 4 formed in the microporous layer 5, in addition to the above-mentioned effect of the microporous layer 5, the adhesion layer 2 also provides the effect of firmly stabilizing the substrate 3 and the electroless plated layer 9. This point will be described later with reference to examples.

[0048] Fig. 3 is a cross-sectional view schematically showing a state in which a patterned electrolytic plated layer 11 has been formed on the resin-plated product 1 shown in Fig. 1. After the electrolytic plated layer 11 has been formed on the top surface of the electroless plated layer 9 of the resin-plated product 1 shown in Fig. 1, a patterning step according to the wiring pattern is performed. As a result, a predetermined region A1 is etched in the depth direction, exposing the substrate 3.

[0049] Here, near the +Z side surface (surface 3 a) of substrate 3, electroless plated layer 9 penetrates into substrate 3, more specifically, into microporous layer 5. Therefore, during etching, the proportion of electroless plated layer 9 that is etched increases, and the amount of etching of substrate 3 made of a resin material can be reduced. As a result, a decrease in adhesion between substrate 3 and electroless plated layer 9 can be prevented when forming a wiring pattern.

[0050] The thickness (i.e., depth D1) of the microporous layer 5 formed near the surface 3a of the substrate 3 and the depth to which the electroless plated layer 9 penetrates into the microporous layer 5 can both be confirmed by analyzing images of the resin-plated material 1 taken with a scanning transmission electron microscope (STEM). More specifically, these can be confirmed by photographing the resin-plated material 1 using an STEM equipped with an energy dispersive X-ray spectrometer (EDX) or an electron energy loss spectrometer (EELS) and understanding the change in elemental composition in the depth direction.

[0051] 4 is a diagram showing the results of elemental analysis using STEM-EDX on the surface 3a and the vicinity of the substrate 3 of the resin-plated product 1. The vertical axis represents signal intensity, and the horizontal axis represents the distance traveled in the depth direction (-Z direction) from the side of the resin-plated product 1. In the following description, it is assumed that a material containing Cu is used for the electroless plating layer 9 and a material containing Pd is used for the catalyst 7.

[0052] As will be described later, the catalyst 7 is applied to the substrate 3 before the electroless plating layer 9 is formed by immersing the substrate 3 in a solution containing the catalyst 7, in order to grow the electroless plating layer 9. Therefore, it is expected that the catalyst 7 will be supported at the highest rate on the surface 3a of the substrate 3. From this perspective, it can be determined from the results of the STEM-EDX analysis that the depth position corresponding to the peak value of the Pd signal intensity corresponds to the depth position on the surface 3a of the substrate 3. At this time, the electroless plating layer 9 is formed shallower than the surface 3a.

[0053] 4, the presence of a Pd signal is observed even deeper than the surface 3a of the substrate 3. This suggests that a microporous layer 5 containing voids 4 is formed near the surface 3a of the substrate 3, and Pd as a catalyst 7 is incorporated into the voids 4 within the microporous layer 5. The Pd signal intensity attenuates as the depth increases and eventually reaches the detection limit. The depth position at which the Pd signal reaches the detection limit can be inferred to be a position where the microporous layer 5 containing voids 4 for supporting Pd does not exist. From this perspective, the thickness D1 of the microporous layer 5 can be determined by the distance traveled in the depth direction from the depth position at which the Pd signal intensity peaks to the depth position at which the Pd signal intensity reaches the detection limit.

[0054] 4, the presence of Cu signals is observed even deeper than the surface 3a of the substrate 3. This suggests that an electroless plating layer 9 is formed in the microporous layer 5 via the catalyst 7 incorporated in the microporous layer 5. In other words, this indicates that the electroless plating layer 9 has penetrated into the substrate 3, more specifically, into the microporous layer 5 formed by modifying the substrate 3.

[0055] Within the microporous layer 5, the Cu signal intensity attenuates as the Cu signal advances in the depth direction, eventually reaching the detection limit. It can be inferred that the depth position at which the Cu signal reaches the detection limit is the position at which the formation of the electroless plated layer 9 has no longer been realized. From this perspective, the thickness D2 of the electroless plated layer 9 that penetrates into the substrate 3, in other words, the thickness D2 of the electroless plated layer 9 that penetrates into the microporous layer 5, can be confirmed by the distance traveled in the depth direction from the depth position at which the Pd signal intensity peaks to the depth position at which the Cu signal intensity reaches the detection limit.

[0056] [Method for Manufacturing Resin-Plated Product] Fig. 5 is a flowchart showing an example of the steps of a method for manufacturing the resin-plated product 1. In the following description, the step numbers in Fig. 5 will be referred to as appropriate.

[0057] (Step #1) As shown in Fig. 6, a base material 3 made of the above-mentioned resin material is prepared. This step #1 corresponds to the process (a).

[0058] In step #1, the substrate 3 may be heated at a predetermined temperature to remove the organic solvent residue adhering to the surface of the substrate 3. An example of the heating conditions is 100° C. for 30 minutes.

[0059] In addition to the above heating, the substrate 3 may be heated at a temperature higher than 100°C but lower than the glass transition temperature of the resin material constituting the substrate 3. The heating temperature is preferably lower than 160°C. A typical example of heating conditions is 140°C for 30 minutes. This heating step is carried out for the purpose of increasing the hardness of the resin constituting the substrate 3. However, if the heating temperature is too high, the substrate 3 becomes too hard, making it difficult to form the microporous layer 5 in the next step #2. Therefore, heating at a temperature lower than 160°C is preferable.

[0060] As a specific method for performing the heat treatment on the substrate 3, for example, a method of placing the substrate 3 in a chamber including a heater and heating the substrate 3 for a predetermined time can be employed. Another method of placing the substrate 3 on the upper surface of a stage equipped with a heating mechanism for a predetermined time can be employed. However, in this embodiment, it is optional whether or not to perform a heating step on the substrate 3 before step #2 described below.

[0061] (Step #2) Next, as shown in Fig. 7, ultraviolet light L1 is irradiated onto the substrate 3. The ultraviolet light L1 may be any light source that exhibits optical output at a wavelength of 200 nm or less. Preferably, the main peak wavelength or sub-peak wavelength of the ultraviolet light L1 is 200 nm or less.

[0062] The light source of the ultraviolet light L1 may be, for example, an Xe2 excimer lamp or a low-pressure mercury lamp. Alternatively, the light source of the ultraviolet light L1 may be a solid-state light source such as an LED or a laser diode.

[0063] Ultraviolet light with a wavelength of 200 nm or less, especially ultraviolet light with a wavelength of around 185 nm, is easily absorbed by oxygen (O2). Therefore, when ultraviolet light L1 is irradiated onto a resin substrate 3 in an atmospheric environment, part of the ultraviolet light L1 is absorbed by O2 in the atmosphere, and the ground state atomic oxygen O( 3P) is generated. The left side of equation (1) conveniently expresses the absorption of ultraviolet light of wavelength λ by O2, and μ indicates the frequency of wavelength λ. O2 + hν(λ) → O( 3 P) + O( 3 P) ... (1)

[0064] Atomic oxygen O( 3 P) reacts with O2 in the atmosphere to produce ozone (O3) according to the following formula (2): O( 3 P) + O2 → O3 (2)

[0065] O3 has the property of absorbing ultraviolet rays. When ultraviolet rays are absorbed by O3, excited atomic oxygen O( 1 D) is produced. O3 + hν(λ) → O2 + O( 1 D) ...(3)

[0066] When ultraviolet light L1 is irradiated onto the surface 3a of the substrate 3, part of the ultraviolet light L1 is absorbed by O2 in the atmosphere between the light source and the surface 3a, and the above-mentioned excited state atomic oxygen O( 1 D) is produced.

[0067] Atomic oxygen O( 1 D) has extremely high reactivity. m H n O k ) and cuts the molecular chain. In the following formula (4), m, m', n, n, k, and k' are all integers, with m>m', n>n', and k>k'. However, please note that formula (4) is a schematic representation of the reaction and is not an accurate chemical reaction formula. C m H n O k + O( 1 D) → H2O, CO, CO2 + C m' H n' O k' ...(4)

[0068] The reaction breaks the polymer bonds of the resin material near the surface 3 a of the substrate 3, modifying it into low-molecular-weight oligomers. As a result, the region near the surface 3 a of the substrate 3 is modified into a microporous layer 5 containing voids 4, as described above with reference to FIG.

[0069] The thickness of the microporous layer 5 obtained in step #2 is preferably set to 30 nm to 200 nm from the viewpoint of ensuring adhesion between the substrate 3 and the electroless plated layer 9 and the strength of the substrate itself. The thickness of the microporous layer 5 can be appropriately set by adjusting the exposure dose of ultraviolet light L1.

[0070] This step #2 corresponds to process (b).

[0071] Note that, when performing step #2, a heating process may be performed in parallel. For example, the substrate 3 may be placed on a stage including a heating mechanism, and ultraviolet light L1 from a light source may be irradiated onto the substrate 3. As another example, the substrate 3 may be placed in a chamber containing a heater and a light source, and heating of the substrate 3 and irradiation of ultraviolet light L1 may be performed in parallel within the chamber. In this case, the heating temperature is higher than 50°C and lower than the glass transition temperature of the resin material constituting the substrate 3. The heating temperature is preferably lower than 160°C. An example of a typical heating condition is 100°C for 30 minutes. Note that the heating time may be changed as appropriate depending on the type of resin material, and may be, for example, about 1 minute.

[0072] (Step #3) Next, as shown in Fig. 8, the substrate 3 on which the microporous layer 5 has been formed through step #2 is immersed in a predetermined solution 21. The following two types of solution 21 can be used.

[0073] The solution 21 may be a solution in which a reaction compound having a phenolic hydroxyl group and a nucleophilic reactive group is dissolved. The phenolic hydroxyl group may be one or more selected from the group consisting of a catechol group, a resorcinol group, a hydroquinone group, a hydroxyquinol group, a phloroglucinol group, a pyrogallol group, and a group in which two or more hydroxy groups are substituted for hydrogen atoms on a benzene ring, and is typically a catechol group. The nucleophilic reactive group may be one or more selected from the group consisting of an amino group, a thiol group, an amide group, a triazine group, and a silanol group, and is typically an amino group. An example of a typical reaction compound having a catechol group and an amino group is dopamine.

[0074] The pH of the solution 21 is adjusted to make it basic. As a typical example, powdered dopamine is dissolved in a basic solvent made of Tris-HCl buffer solution to obtain the solution 21. In this case, the dopamine corresponds to the reaction compound. By immersing the substrate 3 in this solution 21, the solution 21 adheres to the outer surface of the substrate 3 and penetrates into the microporous layer 5.

[0075] Dopamine undergoes a reaction represented by the following formula (5), resulting in self-oxidation and self-polymerization.

[0076]

[0077] According to this example, dopamine as a precursor contained in the solution 21 penetrates into the microporous layer 5, while undergoing self-oxidation and self-polymerization. As a result, an adhesion layer 2 made of an organic compound (here, polydopamine) having a composition different from that of the substrate 3 is formed within the substrate 3, more specifically, within the microporous layer 5. At this point, an adhesion layer 2 is also formed on the outer surface of the substrate 3. In this example, polydopamine corresponds to a dopamine derivative as a reaction compound.

[0078] In another embodiment, the solution 21 may be a solution containing a first compound having a phenolic hydroxyl group and a second compound having a nucleophilic reactive group. The phenolic hydroxyl group may be one or more selected from the group consisting of a catechol group, a resorcinol group, a hydroquinone group, a hydroxyquinol group, a phloroglucinol group, a pyrogallol group, and a group in which two or more hydroxy groups are substituted for hydrogen atoms on a benzene ring, and is typically a catechol group. The nucleophilic reactive group may be one or more selected from the group consisting of an amino group, a thiol group, an amide group, a triazine group, and a silanol group, and is typically an amino group. Typical examples of the first compound having a catechol group include benzenediol, benzenetriol, caffeic acid, and chlorogenic acid. Typical examples of the second compound having an amino group include polyamine, polyalanine, and polyaniline. Catechol belongs to the benzenediol group.

[0079] The pH of the solution 21 is adjusted to a basic state. In a typical example, powdered catechol and polyamine are dissolved in a basic Tris-HCl buffer solution to obtain the solution 21. In this case, by immersing the substrate 3 in this solution 21, in which catechol corresponds to the first compound and polyamine corresponds to the second compound, the solution 21 adheres to the outer surface of the substrate 3 and penetrates into the microporous layer 5. Note that tetraethylenepentamine can be used as an example of the polyamine. Another example is pentaethylenehexamine.

[0080] Catechol exhibits self-oxidation properties. Furthermore, by undergoing a Michael addition reaction or a Schiff base reaction with polyamine, the oxidation of catechol and the polymerization reaction by crosslinking proceed. The reaction is visualized in the following formula (6).

[0081]

[0082] In this case, the precursors catechol and polyamine contained in the solution 21 undergo self-oxidation and self-polymerization while penetrating into the microporous layer 5. As a result, similar to the case of dopamine, an adhesion layer 2 made of an organic compound having a composition different from that of the substrate 3 is formed in the substrate 3, more specifically, in the microporous layer 5. At this point, an adhesion layer 2 is also formed on the outer surface of the substrate 3.

[0083] The substrate 3 is left immersed in the solution 21 for a predetermined time. For example, it is left for about 3 to 4 hours in an atmospheric / room temperature environment. Note that, from the viewpoint of promoting the reaction, ultraviolet light may be irradiated onto the solution 21. However, the ultraviolet light used in this case has a longer wavelength than the ultraviolet light used in step #2, for example, ultraviolet light having a main peak wavelength or a sub-peak wavelength within the range of 200 nm to 400 nm.

[0084] After immersing the substrate 3 in the solution 21 for a predetermined time, the substrate 3 is removed from the solution 21 and subjected to a cleaning process. Examples of the cleaning process include a first cleaning process using pure water, a second cleaning process using ethanol, and a drying process using N2. By performing this cleaning process, the adhesion layer 2 attached to the surface of the substrate 3 is removed. On the other hand, with regard to the adhesion layer 2 formed inside the microporous layer 5, a portion of the adhesion layer 2 penetrates into the voids 4 formed in the microporous layer 5, forming an anchor effect and achieving high adhesion between the adhesion layer 2 and the substrate 3, so that the adhesion layer 2 remains inside the substrate 3 even after the above cleaning process. FIG. 9 is a cross-sectional view schematically showing the structure of the substrate 3 after the cleaning process has been performed.

[0085] This step #3 corresponds to the process (c). In the above, the entire substrate 3 is immersed in the liquid 21. However, the substrate 3 may be immersed in the liquid 21 to at least the depth region where the microporous layer 5 is formed.

[0086] (Step #4) Next, as shown in Fig. 10, the catalyst 7 is applied to the substrate 3. As a specific example, the substrate 3 is immersed in a solvent containing a catalyst contributing compound.

[0087] As described above, in step #2, the microporous layer 5 containing voids 4 is formed on the substrate 3 from the surface 3a to the thickness D1. Therefore, by applying the catalyst 7 to such a substrate 3, the catalyst 7 is supported not only on the surface 3a of the substrate 3 but also in the microporous layer 5.

[0088] In step #3, the adhesion layer 2 is formed inside the microporous layer 5, but the adhesion layer 2 does not completely fill the voids 4 in the microporous layer 5, and some of the voids 4 remain. That is, more specifically, the catalyst 7 is supported not only on the surface 3 a of the substrate 3 but also in the region where the microporous layer 5 and the adhesion layer 2 are mixed.

[0089] This step #4 corresponds to process (d).

[0090] (Step #5) Next, as shown in Fig. 1, an electroless plated layer 9 is formed on the upper surface of the base material 3. As a specific example, the base material 3 is immersed in a plating solution containing the constituent materials of the electroless plated layer 9.

[0091] Through this process, an electroless plating layer 9 is formed on the upper surface of the substrate 3 via the catalyst 7. The plating solution also penetrates into the microporous layer 5, and because the catalyst 7 is also supported in this microporous layer 5, the electroless plating layer 9 also grows within the microporous layer 5. As a result, part of the electroless plating layer 9 penetrates into the interior of the substrate 3, more specifically, into the microporous layer 5.

[0092] This step #5 corresponds to process (e).

[0093] (Post-Processing) Thereafter, post-processing is carried out, including a step of forming an electrolytic plated layer 11 on the electroless plated layer 9, thereby obtaining the resin-plated product 1.

[0094] According to the above-described method, in step #3, the adhesion layer 2 is formed inside the microporous layer 5. Then, because the catalyst 7 is supported inside the microporous layer 5 on which the adhesion layer 2 is formed, a portion of the electroless plating layer 9 penetrates into this region. As a result, the effect of firmly stabilizing the substrate 3 and the electroless plating layer 9 is obtained. Furthermore, the adhesion layer 2 has strong adhesion (the force between the adhesion layer 2 and the electroless plating layer 9) due to a chemical action. By having the adhesion layer 2 penetrate into the voids 4 formed in the microporous layer 5, in addition to the above-described effect of the microporous layer 5, the adhesion layer 2 also has the effect of firmly stabilizing the substrate 3 and the electroless plating layer 9.

[0095] Specific examples will be shown below to explain the present invention in more detail, but the present invention is not limited to these examples.

[0096] (Verification 1: Difference in formation of adhesion layer 2 depending on whether or not microporous layer 5 is present) Samples were prepared using PPS resin as the substrate 3, Comparative Example 1 in which a polydopamine film was directly deposited without performing step #2, and Example 1 in which a polydopamine film was introduced via step #2.

[0097] The deposition and introduction of the polydopamine film was carried out by immersing the substrate 3 in a solution of 2 mg / mL dopamine dissolved in 0.01 mol / L Tris-HCl buffer (pH 8.5) and leaving it for 3 hours.

[0098] In Example 1, a light irradiation device (Ushio Inc.: SVC 232 Series, peak wavelength 172 nm) was used, and the illuminance was 600 mJ / cm 2 Then, step #2 was performed by irradiating the surface of the substrate 3 with ultraviolet light L1 for 30 seconds. Thereafter, the introduction process of the polydopamine film was performed.

[0099] For each sample of Example 1 and Comparative Example 1, mass analysis was performed by TOF-SIMS while sputtering the surface of the substrate 3 on which the polydopamine film was formed using an Ar gas cluster ion beam (Ar-GCIB). The results are shown in Figures 11 and 12. In both graphs, the horizontal axis represents the depth position from the surface of the substrate 3, and the vertical axis represents the spectral intensity corresponding to a specific substance.

[0100] Since PPS resin does not contain N atoms, the signal derived from C5H9N2 can be assumed to be a signal derived from the polydopamine film. Figure 11 shows that in the sample of Comparative Example 1, the signal intensity derived from C5H9N2 is high at the surface and gradually decreases as the sample progresses in the depth direction. It was also confirmed that the signal intensity derived from C5H9N2 was at the detection limit level at a depth of 15 nm.

[0101] 12, it can be seen that the intensity of the signal derived from C5H9N2 is high at the surface position and gradually decreases as the signal progresses in the depth direction, also in the sample of Example 1. However, unlike Comparative Example 1, the intensity of the signal derived from C5H9N2 was confirmed down to a depth of 30 nm.

[0102] Considering that the signal intensity derived from CHN was confirmed deeper in the sample of Example 1 than in the sample of Comparative Example 1 despite the same polydopamine film formation conditions, it can be determined that the polydopamine film is introduced into the interior of the substrate 3 in the sample of Example 1. In the case of the sample of Comparative Example 1, the polydopamine film is only formed on the surface of the PPS resin, while the results in Figure 11 suggest that the polydopamine film is deposited from the surface of the PPS resin to a thickness of 15 nm. In other words, considering the results in Figures 11 and 12, it is suggested that in the sample of Example 1, the polydopamine film is deposited from the surface of the PPS resin to a thickness of 15 nm, and further penetrates into the depth direction of the PPS resin to a depth of 15 nm.

[0103] From these results, it is believed that irradiation with ultraviolet light L1 formed a microporous layer 5 near the surface of the substrate 3 made of PPS resin, and that when a dopamine solution was introduced into this microporous layer 5, the dopamine introduced into the microporous layer 5 progressed in a self-oxidation and self-polymerization reaction, resulting in the formation of a polydopamine film as an adhesion layer 2 within the microporous layer 5.

[0104] 13 and 14 are graphs showing the results of mass spectrometry performed by TOF-SIMS in the same manner as in FIGS. 11 and 12. The signal intensities derived from the substances shown in FIGS. 13 and 14 vary in order of magnitude depending on the substance, and therefore two vertical axes, a left vertical axis and a right vertical axis, are used to indicate intensity. In FIGS. 13 and 14, for substances with a right arrow next to their names, the signal intensity corresponds to the right vertical axis, and for substances without a right arrow next to their names, the signal intensity corresponds to the left vertical axis.

[0105] 13 and 14, the values ​​on the horizontal axis are doubled compared to those in FIGS. 11 and 12 for ease of illustration. Specifically, according to FIG. 13, the intensity of the signal derived from CHN in the sample of Comparative Example 1 drops to the detection limit near a depth of 30 au. This value of 30 au corresponds to 15 nm, which is consistent with the results in FIG. 11. Similarly, according to FIG. 14, the intensity of the signal derived from CHN in the sample of Example 1 drops to the detection limit near a depth of 60 au. This value of 60 au corresponds to 30 nm, which is consistent with the results in FIG. 12. In FIGS. 13 and 14, positive secondary ions are labeled "positive," and negative secondary ions are labeled "negative."

[0106] No signals derived from C6H4SO3 or C6H4SO4 were detected in the sample of Comparative Example 1 shown in Figure 13. In contrast, signals derived from C6H4SO3 and C6H4SO4 were detected in the sample of Example 1 shown in Figure 14. From this, it is presumed that the signals derived from C6H4SO3 and C6H4SO4 are both signals derived from substances produced by modifying a portion of the PPS resin when the substrate 3 made of PPS resin is irradiated with ultraviolet light L1. That is, from the results of Figure 14, it can be presumed that a microporous layer 5 is formed in the depth range where signals derived from C6H4SO3 and C6H4SO4 can be confirmed.

[0107] 14, the intensity of the signal derived from C5H9N2 derived from polydopamine decreases in accordance with the decreasing trend of the intensities of the signals derived from C6H4SO3 and C6H4SO. From this result, it can be inferred that the adhesive layer 2 corresponding to the polydopamine layer is formed inside the substrate 3 over the depth range of the microporous layer 5.

[0108] (Verification 2: Comparison of Adhesion Strength) After electroless plating layer 9 was grown on substrate 3 under different conditions, the adhesion strength between substrate 3 and electroless plating layer 9 was compared.

[0109] Example 2 A PPS resin was prepared as the substrate 3, and a light irradiation device (Ushio Inc.: SVC 232 Series, peak wavelength 172 nm) was used to irradiate the PPS resin with an illuminance of 600 mJ / cm. 2 Step #2 was performed by irradiating the surface of the substrate 3 with ultraviolet light for 30 seconds. Thereafter, a solution 21 was prepared by dissolving catechol at a concentration of 15 m·mol / L and tetraethylenepentamine at a concentration of 5 m·mol / L in a Tris-HCl buffer solution (pH 9.5) at a concentration of 0.01 mol / L (pure water was used as the dilution solvent), and the sample after step #2 was immersed in the solution. The immersion time was set to 3 hours. The immersion treatment was performed in an atmospheric environment at room temperature.

[0110] Thereafter, the substrate 3 was taken out of the solution 21, and the substrate 2 was washed with pure water, washed with ethanol, and dried with N2.

[0111] Thereafter, a catalyst was applied to the substrate 3, and then an electroless plating layer was formed. Specifically, the following procedure was carried out.

[0112] First, the substrate 3 was immersed in a conditioner liquid M1 for degreasing. Next, after a water rinse, the substrate was immersed in a pre-dip liquid M2 to adjust the surface potential of the substrate 3 to an anion. Next, after the water rinse, the substrate 3 was immersed in a catalyst imparting liquid M3 to impart a catalyst complex to the surface of the substrate 3. Next, after the water rinse, the substrate 3 was immersed in an activation treatment liquid M4 to reduce the catalyst complex to a metal. Next, after the water rinse, the substrate 3 was immersed in an electroless metal plating liquid M5 to reduce the metal ions via the catalyst, thereby forming an electroless plating layer 9 on the substrate 3. The substrate 3 was then baked in a drying oven at 100°C for 60 minutes.

[0113] The chemical solutions used were as follows: Conditioner solution M1: Top LECS Conditioner (manufactured by Okuno Pharmaceutical Industries Co., Ltd.) Pre-dip solution M2: Top LECS Pre-dip M (manufactured by Okuno Pharmaceutical Industries Co., Ltd.) Catalyst application solution M3: A mixture of Top LECS Catalyst A and Top LECS Catalyst C (both manufactured by Okuno Pharmaceutical Industries Co., Ltd.) Activation treatment solution M4: A mixture of Top LECS Accelerator (manufactured by Okuno Pharmaceutical Industries Co., Ltd.) and boric acid Electroless metal plating solution M5: A mixture of Top LECS Copper A, Top LECS Copper M, Top LECS Copper C and Electroless Copper RN (all manufactured by Okuno Pharmaceutical Industries Co., Ltd.)

[0114] Comparative Example 2 A sample was obtained by carrying out the same steps as in Example 2, except that the step of irradiating the substrate 3 with ultraviolet light L1 and the step of immersing it in the solution 21 were not carried out on the substrate 3, and the sample was designated as Comparative Example 2.

[0115] Comparative Example 3 A sample was obtained as Comparative Example 3 by carrying out the same steps as in Example 2, except that the step of irradiating the substrate 3 with ultraviolet light L1 was not carried out.

[0116] Comparative Example 4 A sample was obtained as Comparative Example 4 by carrying out the same steps as in Example 2, except that the step of immersing the substrate 3 in the solution 21 was not carried out.

[0117] The adhesion strength of the samples obtained by the methods of Example 2 and Comparative Examples 2 to 4 was compared using a method conforming to the "Tape Test Method" specified in JIS H 8504:1999 "Methods for Testing Plating Adhesion." The evaluation results are shown in Table 1.

[0118]

[0119] For the sample of Comparative Example 2, the electroless plated layer 9 could not be stably formed on the surface of the substrate 3, so the tape peel test was omitted. For the sample of Comparative Example 3, when the tape peel test was performed at the standard strength, the electroless plated layer 9 peeled along the tape. For the sample of Comparative Example 4, when the tape peel test was performed at the standard strength, the electroless plated layer 9 peeled off over an area of ​​about 10% of the tape adhesive area. For the sample of Example 2, when the tape peel test was performed at the standard strength, the electroless plated layer 9 did not peel off.

[0120] The above results suggest that by forming the electroless plating layer 9 so that it penetrates into the microporous layer 5 while the adhesion layer 2 is formed within the microporous layer 5, extremely high adhesion can be achieved between the electroless plating layer 9 and the substrate 3.

[0121] The present invention is not limited to the above-described embodiments and includes various modifications. For example, the above-described embodiments have been described in detail for a better understanding of the present invention, and are not necessarily limited to those having all of the configurations described. The scope of the present invention is defined by the claims, and it is intended to include all modifications within the meaning and scope of the claims.

[0122] REFERENCE SIGNS LIST 1: Resin plated material 2: Adhesion layer 3: Base material 3a: Surface of base material 4: Void 5: Microporous layer 7: Catalyst 9: Electroless plated layer 11: Electrolytic plated layer 21: Solution L1: Ultraviolet light

Claims

1. A resin-plated product comprising: a substrate containing an insulating resin material; a microporous layer formed from the surface of the substrate to a predetermined depth region and containing voids of nanometer order size; an adhesion layer formed in the region inside the substrate where the microporous layer is formed, the adhesion layer being made of an organic compound having a different composition from that of the substrate; and an electroless plating layer formed on top of the adhesion layer.

2. The resin-plated product according to claim 1, wherein the substrate is made of a resin material that does not contain nitrogen atoms, and the adhesion layer is made of one or more organic compounds that contain nitrogen atoms.

3. The resin-plated product according to claim 1, wherein the microporous layer is formed to a depth of 30 nm or more from the surface of the substrate.

4. A resin-plated product according to claim 1 or 2, characterized in that the microporous layer is formed in a region within a range between the surface of the substrate and a depth position of 200 nm or less from the surface of the substrate.

5. A method for producing a resin-plated product, comprising: (a) a step of preparing a substrate containing an insulating resin material; (b) a step of irradiating the surface of the substrate with ultraviolet light to modify a region from the surface of the substrate to a predetermined depth into a microporous layer containing voids of nanometer order size in the substrate; (c) a step of impregnating, after the step (b), at least the surface of the substrate on which the microporous layer is formed, with a solution containing a reaction compound having a phenolic hydroxyl group and a nucleophilic reactive group to form an adhesion layer consisting of a derivative of the reaction compound in the region where the microporous layer is formed; (d) a step of supporting a catalyst in the microporous layer; and (e) a step of forming an electroless plating layer via the catalyst after the step (d).

6. A method for producing a resin-plated product, comprising: (a) a step of preparing a substrate containing an insulating resin material; (b) a step of irradiating the surface of the substrate with ultraviolet light to modify a region from the surface of the substrate to a predetermined depth into a microporous layer containing voids of nanometer order size in the substrate; (c) a step of impregnating, after the step (b), at least the surface of the substrate on which the microporous layer is formed, with a solution containing a first compound having a phenolic hydroxyl group and a second compound having a nucleophilic reactive group to form an adhesion layer derived from the first compound and the second compound in the region where the microporous layer is formed; (d) a step of supporting a catalyst in the microporous layer; and (e) a step of forming an electroless plating layer via the catalyst after the step (d).

7. A method for producing a resin-plated product according to claim 5 or 6, characterized in that the phenolic hydroxyl group is a catechol group, and the nucleophilic reactive group is an amine group.

8. The method for producing a resin-plated product according to claim 5, wherein the reaction compound is dopamine.

9. The method for producing a resin-plated product according to claim 6, wherein the first compound is catechol, and the second compound is polyamine.

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