Circuit forming substrate, and method for manufacturing a circuit forming substrate

Abstract

In an inkjet method, the impact position of an inkjet droplet is controlled to perform additional wiring miniaturization. A circuit forming substrate having a wiring pattern comprises an insulating substrate, a resin layer formed on the insulating substrate and containing an epoxy resin, an inkjet droplet impact layer formed by the impact of a plurality of inkjet droplets containing metal particles formed on the resin layer, and a plating layer formed on the inkjet droplet impact layer, wherein the storage modulus (Pa) of the resin layer at 25°C is 4.0711 x 10⁸ or less, and the loss modulus (Pa) is 6.4825 x 10⁸ or less.

Description

Technology Field

[0001] The present disclosure relates to a circuit forming substrate and a method for manufacturing a circuit forming substrate. Background Technology

[0002] A technique is known for the purpose of providing a method for manufacturing an electronic circuit board capable of rapidly and efficiently applying a uniform nano-ink composition layer at room temperature and pressure, and an electronic circuit board obtained thereby, wherein a nano-ink composition containing metal particles is maintained on a printing plate having an ink retention portion of a predetermined pattern formed on its surface, the surface of a substrate is adhered to the printing plate, the nano-ink composition maintained in the ink retention portion is transferred onto the substrate, and after transfer, the transferred nano-ink composition is dried and immobilized in an environment of 40°C or lower in the atmosphere to form an electronic circuit of a predetermined pattern (Patent Document 1 below).

[0003] In addition, from the perspective of the prior art mentioned above, the inkjet method is avoided because it is not efficient, and the flexographic printing method is adopted. Prior art literature

[0004] Patent Document 1: Japanese Patent Publication No. 2016-76538 The problem to be solved

[0005] However, the manufacturing of wiring boards using the inkjet method offers many advantages that are immeasurable according to conventional productivity evaluations, such as the ability to reduce environmental burden through production like material reduction, and is anticipated from the perspective of realizing a sustainable world. Recently, as the development of the inkjet method has progressed and line widths have narrowed, we have faced the challenge of difficulty in controlling the landing position of inkjet droplets. If the landing position of the inkjet droplets does not land at the desired location, it becomes difficult to miniaturize the circuit.

[0006] Accordingly, at least one aspect of the problem of the present disclosure is to control the impact position of an inkjet droplet in an inkjet method and to perform additional wiring miniaturization. Furthermore, problems that are obvious to a person skilled in the art, which can be read from the embodiments or descriptions characteristic of the present disclosure described in the specification, drawings, etc. of the present disclosure, may also be problems that the divided invention must solve when a divisional application based on the present disclosure is filed. means of solving the problem

[0007] To achieve the above-mentioned objective, the circuit forming substrate of the present disclosure is a circuit forming substrate having a wiring pattern on at least a portion thereof, comprising an insulating substrate, a resin layer formed on the insulating substrate and comprising an epoxy resin, an inkjet drop impact layer formed by impact of a plurality of inkjet droplets comprising metal particles formed on the resin layer, and a plating layer formed on the inkjet drop impact layer, wherein the storage modulus (Pa) of the resin layer at 25°C is 4.0711X10 8 It is less than or equal to, and the loss modulus of elasticity (Pa) is 6.4825X10 7 It is as follows.

[0008] In addition, to achieve the above-mentioned purpose, the method for manufacturing a circuit forming substrate of the present disclosure is a method for manufacturing a circuit forming substrate having a wiring pattern on at least a portion thereof, comprising the steps of: forming a resin layer comprising an epoxy resin on an insulating substrate; forming an inkjet droplet impact layer formed by impacting a plurality of inkjet droplets comprising metal particles and an alcohol-based solvent or a derivative thereof onto the resin layer; and forming a plating layer on the inkjet droplet impact layer, wherein the storage modulus (Pa) of the resin layer at 25°C is 4.0711X10 8 It is less than or equal to, and the loss modulus of elasticity (Pa) is 6.4825X10 7 It is as follows. Effects of the invention

[0009] According to the present disclosure, additional wiring can be miniaturized by controlling the impact position of an inkjet droplet in an inkjet method. Brief explanation of the drawing

[0010] [Fig. 1] This is a schematic diagram showing the layer structure of a circuit forming substrate according to the present disclosure. [Fig. 2] This is a flowchart showing the basic processing flow of the method for manufacturing a circuit forming substrate of the present disclosure. [Fig. 3] This is a micrograph showing an example where the drawing of fine lines was not properly performed. [Fig. 4] This is a schematic diagram showing the interference between droplets after the ink droplet impact. [Fig. 5] This is a photograph showing the state before and after plating treatment when a resin layer is formed using an ink-accepting layer forming material that has no plating resistance. [Fig. 6] This is a table showing the relationship between the success of pattern drawing with varying storage modulus and loss modulus. [Fig. 7] A plot including the success of pattern drawing with varying storage modulus and loss modulus. [Fig. 8] This is a table showing the relationship between swelling degree and the success of pattern drawing. [Fig. 9] Microscopic image showing the appearance of the wiring pattern formed after inkjet impact. [Fig. 10] This is a photograph showing the appearance of a circuit-forming substrate after plating treatment. [Fig. 11] This is a table showing the relationship between the evaluation of elastic modulus using an atomic force microscope and the success of pattern drawing. [Fig. 12] This is a table showing the relationship between the evaluation of dissipated energy using an atomic force microscope and the success of pattern drawing. Specific details for implementing the invention

[0011] Embodiments of the present disclosure will be described using drawings. FIG. 1 is a schematic diagram showing the layer structure of a circuit forming substrate according to the present disclosure. This diagram illustrates a single layer of the circuit forming substrate, and the circuit forming substrate may be composed of a plurality of wiring structures in which a layer of an insulator, such as resin, and a layer of a conductor, such as metal, are stacked. For example, a single-sided substrate (1-layer substrate), a double-sided substrate (2-layer substrate), a 4-layer substrate, a 6-layer substrate, an 8-layer substrate, or more stacked substrates may be included. FIG. 2 is a flowchart showing the basic processing flow of a method for manufacturing a circuit forming substrate according to the present disclosure.

[0012] A circuit forming substrate comprises an insulating substrate (1), a resin layer (2) formed on the insulating substrate (1), an inkjet droplet impact layer (3) formed by a plurality of nano metal particles impacted as a plurality of inkjet droplets on the resin layer (2), and a plating layer (4) formed on the inkjet droplet impact layer (3).

[0013] First, as step S100, an insulating substrate (1) is prepared. This insulating substrate (1) is an insulating substrate such as a flexible printed circuit board or a rigid printed circuit board, and may be supplied in various forms such as a film-like material, a sheet-like material, a roll-like material, or a rigid anclad material.

[0014] Flexible insulating substrates may include, for example, polyimide, polyamide, polyesters such as polyethylene terephthalate (PET) and polyethylene naphthalate (PEN), polyamide synthetic resins such as nylon (registered trademark) specified as nylon 6, 10, nylon 4, 6, etc., polyether ether ketone, resins such as acrylonitrile butadiene styrene (ABS), polymethyl methacrylate (PMMA), and polyvinyl chloride, epoxy resins, polystyrene, and polyphenylene sulfide (PPS).

[0015] In addition, as other flexible insulating substrates, inorganic substrates, for example, ceramics, etc. may be used. As other organic substrates, for example, polyvinylidene chloride, polyvinyl alcohol, styrene acrylonitrile copolymer, polyethylene, styrene vinyl acetate copolymer, polyacetal, cellulose acetate, polycarbonate, thermoplastic polyurethane, and polytetrafluoroethylene may be used.

[0016] The rigid insulating substrate may be, for example, a material having a hardness of 10 GPa or more and a tensile modulus. Since the tensile modulus is expressed using physical quantities such as Young's modulus, it may be defined by Young's modulus. Generally, for resins or their composite materials, even when the tensile modulus is relatively high and referred to as semi-flexible, it is only about a few GPa; therefore, a material having a hardness of 10 GPa or more and a tensile modulus is used as the rigid substrate. For example, an insulating rigid substrate containing glass epoxy resin has a tensile modulus of about 20 GPa.

[0017] Next, in step S101, a resin layer (2) is formed on an insulating substrate (1). A resin layer (2) may be formed on the surface of the insulating substrate (1) for various purposes, such as improving the applicability of an ink composition or modifying the surface of the insulating substrate (1). The resin layer (2) may generally be formed by applying a resin; or an adhesion enhancer containing a resin that improves the adhesion of the ink; but in the present disclosure, it may also be formed for the purpose of controlling the behavior of an inkjet droplet upon impact. This will be described later.

[0018] The resin layer (2) can be formed by diluting the material of the resin layer (2) in a diluent solvent, coating it onto an insulating substrate (1), and curing it by raising the temperature. For example, a 50% diluted solution may be prepared by diluting it in ethylene glycol monomethyl ether. Other diluent solvents may also be used. When using the ratio of curable resin to the total value of curable resin in the diluent solvent as one of the dilution rates, 1 to 90% is preferred, more preferably 10 to 70%, and even more preferably 20 to 60%. If the dilution rate is high, it may be difficult to achieve the desired primer properties because the specified film thickness cannot be reached. The desired properties mentioned here are mainly related to the control of the impact position of the inkjet droplet of the present disclosure. If the dilution rate is low, the liquid viscosity may increase, and there is a tendency for the uniform coating properties to be insufficient.

[0019] The thickness of the printed film of the coating may be, for example, 1 to 100 μm with respect to the insulating substrate (1). More preferably, it is 5 to 70 μm, and even more preferably, 10 to 50 μm. If the thickness of the printed film is low, it may not reach the specified film thickness, making it difficult to exhibit the desired physical properties mentioned above. If the thickness of the printed film is high, it is prone to high costs in terms of materials, and also, the ratio of the thickness of the resin layer (2) to the thickness of the insulating substrate (1) increases, which may result in failure to satisfy the substrate characteristics. For example, the bending resistance may decrease.

[0020] Regarding the effect after this printing process, the temperature may be raised to a temperature that meets the curing conditions and maintained for 1 to 120 minutes to cure. Although the curing temperature cannot be specified, it can be assumed that a curing temperature suitable for the material of the resin layer (2) can be determined through a number of trials and experiments that are common sense to those skilled in the art. As an example of a suitable curing temperature, it is preferable to obtain the exothermic peak of the TGDTA measurement and set it to ±30℃ of that exothermic peak. The primer curing time is preferably 1 to 120 minutes, more preferably 10 to 60 minutes, and even more preferably 30 to 60 minutes. If the curing time is short, there may be a failure in the curing of the primer, and if the curing time is long, there is a risk of reduced productivity.

[0021] The film thickness of the resin layer (2) after curing may be 0.5 to 50 μm. More preferably, it is 0.5 μm to 30 μm, and even more preferably, 1 μm to 20 μm. If the film thickness is low, it may be difficult to achieve the desired physical properties mentioned above. If the film thickness is high, it is easy to incur high costs in terms of materials, and also, the ratio of primer to substrate thickness increases, which may result in failure to satisfy substrate characteristics. For example, bending resistance may decrease.

[0022] Next, in step S102, an ink composition containing metal nanoparticles is applied by extruding it from an inkjet head onto a wiring pattern using an inkjet printing device. The application of the ink composition is achieved by the impact of an inkjet droplet of the ink composition containing metal nanoparticles. The metal nanoparticles include various types such as gold, silver, platinum, copper, or alloys thereof, and technically are not limited to a single metal; however, considering conductivity, ease of availability, cost, and worldwide supply, copper nanoparticles may be a suitable example. Therefore, metal nanoparticles and copper nanoparticles may be described together below. A copper nano ink composition containing copper nanoparticles, a coating material, a dispersant, and a solvent is described below as an example, but copper nano inks composed of other compositions may also be used.

[0023] The copper nanoparticles preferably have an average particle diameter of 1 nm to 200 nm, and more preferably 10 nm to 100 nm. If the particle diameter is too small, the reactivity of the particles increases, and there is a possibility that the preservation and stability of the ink may decrease. If the particle diameter is too large, there is a possibility that the uniformity of the thin film may decrease, and that sedimentation of the ink particles may occur easily.

[0024] The coating material is intended to prevent the copper nanoparticles from being easily oxidized, and may be a carboxylic acid, and more preferably a monocarboxylic acid with an integer number of 6 to 10, such as hexanoic acid, heptanoic acid, octanoic acid, nonanoic acid, or decanoic acid.

[0025] The dispersant is intended to disperse copper nanoparticles covered with a coating material to form an ink, and to uniformly disperse the dispersed copper nanoparticles in a solvent, which is a dispersion medium, so as to maintain a stable dispersed state without aggregation. The dispersant may be a carboxylic acid-based, thiol-based, phenol-based, phosphate-based, and amine-based compound. Preferably, it may be a carboxylic acid-based compound capable of forming a coordination bond with copper.

[0026] As a more desirable example, and not limited to, when octanoic acid is selected as a coating material, polycarboxylic acid may be cited as a preferred dispersant. As a more preferred polycarboxylic acid, polycarboxylic acid having a comb-like structure may be cited.

[0027] As for the solvent, it may be an aqueous solvent or an organic solvent. As for the organic solvent, it may be an alcohol-based solvent or a derivative thereof, and more specifically, glycol ethers, such as ethylene glycol monoethyl ether, diethylene glycol monobutyl ether, propylene glycol monomethyl ether, or a mixture thereof may be used, and also the solvent described below may be used.

[0028] In addition, stabilizers and other additives may be used.

[0029] Regarding the content ratio of copper nanoparticles in the ink composition, it may be 5% to 60% by weight or 10% to 30% by weight in mass ratio. The reason for selecting these ranges is that if the content ratio is too low, there is a lack of nanoparticles necessary to form a conductive layer with copper nanoparticles, which may result in the occurrence of pores such as pinholes, and if the content ratio is too high, the stability of the ink may be compromised, such as when particles tend to aggregate within the ink.

[0030] The viscosity of the ink composition is preferably 1 to 100 mPa·s at a measurement temperature of 25°C, as measured by an E-type viscometer or a rheometer. In addition, it is more preferable that the viscosity be 1 to 100 mPa·s or 1 to 50 mPa·s at a shear rate of 100 (1 / S) or higher. This is because the conditions are suitable for the environment in which ink is ejected by an inkjet head, and if the viscosity is too high, ejection from the inkjet head becomes difficult.

[0031] The diameter of a drop of ink ejected from an inkjet nozzle of an inkjet printing device is, for example, a value within the range of 1 μm to 100 μm.

[0032] As such, in the present disclosure, a pattern is formed in advance by inkjet printing, and there is no need to perform etching to form a pattern of a desired shape. That is, the basic wiring pattern is already formed on this circuit forming substrate at the time the inkjet droplet lands. This method of additionally forming a circuit is superior in terms of reducing environmental burden.

[0033] Next, in step S103, metal nanoparticles contained in the inkjet droplet attachment layer (3) are fixed onto the resin layer (2). The inkjet droplet attachment layer (3) of metal nanoparticles may be formed by applying an ink composition containing metal nanoparticles and, for example, by photo-sintering. There are various methods for fixing the metal nanoparticles contained in the inkjet droplets, and in addition to photo-sintering, a wet reduction process using a reducing agent such as formalin or hydrazine, various heating processes, or drying processes may be appropriately utilized. The drying process may be a heat treatment, or a hot air treatment using nitrogen or air streams. As a result, the metal nanoparticles remain on the resin layer (2).

[0034] Regarding the inkjet droplet impact layer (3), in addition to removing components other than metal nanoparticles in the ink composition, it is necessary to cause bonding, melting, and contact between the metal nanoparticles. The state in which metal nanoparticles approach and bond while maintaining their shape is called necking, and the phenomenon in which nanoparticles melt from the necking state and become one with a change in shape is called fusion. Also, the bonding between particles is simply referred to as necking. In this way, as the nanoparticles melt and bulk up through sintering, conductivity is improved and they adhere to the resin layer (2) on the insulating substrate (1).

[0035] For the sintering of metal nanoparticles, copper nanoparticles can be bonded by photo-sintering using, for example, flash lamp irradiation. Due to the instantaneous heating of the flash discharge lamp, heat is applied only to the surface of the substrate, and heating into the interior of the substrate can be suppressed, which is desirable in terms of shortening production time and reducing the load on the substrate. Regarding the irradiation conditions of the flash lamp, a person skilled in the art can appropriately adjust them using parameters such as input power, Joule heat according to input power, and charge voltage per shot.

[0036] Sintering is not limited to flash lamps; heating methods using infrared light, such as ovens or infrared furnaces, can also be adopted from the perspective that they do not apply a sudden thermal load, and a sintered layer of copper nanoparticles can be formed by these heating methods as well.

[0037] In addition, a metal layer identical to the above-mentioned sintered layer can also be formed by a method of reducing materials such as inkjet-dropped metal oxide nanoparticles using a reducing agent.

[0038] Next, in step S104, a plating layer (4) of a metal suitable for the type of metal nanoparticle is formed on the inkjet droplet impact layer (3). If the metal nanoparticle is copper, copper may be plated. The plating method is the same as a known plating treatment using a known plating solution, and specifically may include electroless copper plating, electrolytic copper plating, etc. By doing so, the plating metal is deposited on the surface and inside the inkjet droplet impact layer (3).

[0039] By going through the above process, a circuit forming substrate having a desired pattern of wiring formed on an insulating substrate (1) can be manufactured.

[0040] However, with the miniaturization of wiring, the droplets interfere with each other after the ink droplet impact, making it difficult to draw fine lines. Figure 3 is a micrograph showing an example where the drawing of fine lines was not properly performed, and Figure 4 is a schematic diagram showing the appearance of the droplets interfering with each other after the ink droplet impact.

[0041] In circuit boards, line width is known and used as an indicator of fineness, for example, L / S (line and space). For example, if L / S is 1000 μm, it indicates the ability and quality to form wiring patterns with a line width of 1000 μm or less. In the L / S area of ​​1000 μm or less, for example in FIG. 3, multiple inkjet droplets form lines (L), and there is a space (S) between the lines (L) where metal wires are not placed. However, if the behavior of the impact cannot be controlled and a difference in the impact position occurs, wiring with the desired position and pattern shape may not be drawn. As a result, the position of the inkjet droplets is misaligned and shifted, and the space (S) is narrowed in some parts.

[0042] The wiring pattern formed by the inkjet method is an aggregate of multiple inkjet droplets that have been impacted. As mentioned above, since the diameter of a single ink drop is, for example, within the range of 1 μm to 100 μm, even if droplets of 50 μm are used, at least 20 droplets are required to draw a line width of 1000 μm, and in reality, in order to ensure conductivity between metals contained in the ink droplets, it is necessary to impact a greater number of droplets in multiple stages.

[0043] FIG. 4 is a schematic diagram showing the appearance, but does not accurately represent actual dimensions, etc. In this drawing, when an inkjet droplet (31) newly lands on the resin layer (2), if it moves without converging to the intended landing position, it interferes with an inkjet droplet (32) that has already landed nearby and combines with it as if being sucked in, causing it to move away from its original position. Furthermore, the above description of the phenomenon is merely a simplified explanation of the situation for the purpose of understanding the problem. However, due to the accumulation of such interference, a situation may arise where a desired pattern cannot be obtained in fine wiring as shown in FIG. 3.

[0044] As a countermeasure to avoid such differences in the impact positions of inkjet droplets, one can consider methods such as increasing the time interval between drops or increasing the stage temperature. The former involves exchanging drops over time so that a second droplet is ejected nearby only after the impact position of the first droplet has stabilized, but this wastes time. Furthermore, the latter promotes the drying or volatilization of the solvent, but since the distance between the stage and the inkjet head is small, the head temperature may rise, potentially causing problems with ejection control.

[0045] Here, in order to control the impact of inkjet droplets, consideration was given to imparting the function of an ink receiving layer to the resin layer (2) to control the impact position of the ink. As for the function of the layer having the function of an ink receiving layer, there are porous and swelling types that both absorb ink solvents. However, regarding ink receiving layers that can be formed using readily available materials, it became a problem that they lack resistance to plating treatment performed after inkjet printing. Specifically, resistance to high alkaline environments such as electroless copper plating was required.

[0046] FIG. 5 is a photograph showing the state before and after plating treatment when a circuit forming board is manufactured using the above method when a resin layer (2) is formed using an ink receiving layer forming material that has no plating resistance. According to this figure, it is understood that even if fine inkjet droplet impact control becomes possible by forming an ink receiving layer, a circuit board cannot be formed if there is no plating resistance.

[0047] Here, as a result of verification through examination and experiment, the resin layer (2) contains epoxy resin and has a storage modulus of 4.0711X10 at 25℃. 8 It is less than or equal to, and the loss modulus is 6.4825X10 7 As described below, it has been revealed that additional wiring miniaturization can be performed by controlling the impact position of inkjet droplets in the inkjet method.

[0048] In addition, it was also revealed that such a resin layer (2) has a swelling degree of 128 or more for 2-ethoxyethanol.

[0049] To explain the circumstances leading to such results, first, attention was paid to an epoxy primer as a material for forming a resin layer (2) that is highly resistant to the electroless copper plating process, and an attempt was made to realize the ability to receive inkjet droplets by controlling the viscoelastic properties of the epoxy primer.

[0050] Epoxy resin is a thermosetting resin containing epoxy groups in its molecules, and the resin is chemically stable against alkali after curing. A typical example of manufacturing epoxy resin is by the condensation reaction of bisphenol A [2,2-bis(4-hydroxyphenyl-propane)] and epichlorohydrin. First, the raw material bisphenol A is synthesized from phenol and acetone, and epichlorohydrin is synthesized from propylene. By using these raw materials and condensing bisphenol A and epichlorohydrin, a resin having epoxy groups is produced. Such epoxy resin can be made into a material having desired viscoelastic properties and chemical stability depending on the composition of various components or reactions with various curing agents.

[0051] Focus was placed on storage modulus and loss modulus as viscoelastic properties for controlling the impact of inkjet droplets in epoxy resins. Storage modulus is an indicator of a material's elastic properties. Simply put, it represents the ability to store and recover deformation energy, expressing spring-like properties. The closer a material is to a perfect elastic body, the higher its storage modulus. On the other hand, loss modulus is an indicator of a material's viscous properties. Simply put, it represents the degree to which energy is dissipated as heat during deformation, expressing damper-like properties. The closer a material is to a perfect viscous body, the higher its loss modulus.

[0052] FIG. 6 is a table showing the results of verifying the success or failure of pattern drawing by controlling the impact of inkjet droplets, after forming a resin layer (2) containing an epoxy resin with varying storage modulus and loss modulus, and FIG. 7 is a plot thereof. In FIG. 7, the storage modulus (Pa) is plotted on the vertical axis and the loss modulus (Pa) on the horizontal axis on a logarithmic scale, and cases where the desired pattern drawing was properly achieved (Examples 1 to 8) are plotted as ○, and cases where it was not properly achieved (Comparative Examples 1 to 2) are plotted as Х. In addition, the success or failure of such pattern drawing is determined from the appearance of the pattern on the manufactured circuit forming substrate.

[0053] For Examples 1 to 8, an approximation formula by power approximation was calculated from the relationship between the measurement results of the storage modulus and the loss modulus of each example, resulting in y=0.0001x 1.6142 is derived, and R 2 The result was = 0.9484. However, since the positions of Comparative Examples 1 and 2 also generally follow this approximation formula, the following properties regarding this approximation formula can be inferred. That is, it can be inferred that even if the absolute values ​​of the material's loss modulus and storage modulus differ, they possess similar elastic and viscous properties. Comparative Examples 1 and 2 and Examples 1 to 8 are all resin layers containing epoxy resin. Therefore, the above approximation formula may represent the measurement of viscoelasticity of resin layers containing epoxy resin. As a result of calculating the residual band from the values ​​of the examples located above and below the approximation formula to predict future values ​​and set the confidence interval, for storage modulus (Pa) Y and loss modulus (Pa) X, 3.0×10 -5 X 1.6142 ≤Y≤4.0Х10 -4 X 1.6142 It was statistically estimated that 95% falls within the range. Therefore, the resin layer included in this range is highly likely to have the same viscoelastic properties as the embodiment of the present disclosure.

[0054] Furthermore, upon reviewing the boundary between the examples and comparative examples, it was determined that a vertical line corresponding to the upper limit of the 95% confidence interval of the loss modulus (Pa) values ​​of Examples 1 to 8 might be appropriate. As can be seen from FIG. 7, the vertical line is located between the examples and comparative examples with respect to the loss modulus (Pa). The loss modulus (Pa) X1 corresponding to this value is 6.4825X10 7 It is Pa. This vertical line represents the upper limit of the 95% confidence interval for the population mean of data assumed to follow a log-normal distribution. Although there are constraints on the sample size and the assumption that the data follows a log-normal distribution, it can be considered that there is certain validity in setting the upper limit of such loss modulus.

[0055] In addition, the intersection point between the vertical line of X1 above and the approximation formula of the example was calculated, and as shown in FIG. 7, the horizontal line passing through this intersection point is storage modulus (Pa) Y1: 4.0711X10 8 A horizontal line was obtained where (Pa) is obtained. By this horizontal line, the region of the example and the region of the comparative example could also be clearly separated. From the above results, in the manufacture of the circuit forming substrate of the present disclosure, the range in which a desired pattern formation can be achieved is such that the storage modulus (Pa) of the resin layer (2) at 25°C is 4.0711X10 8 It is less than or equal to, and the loss modulus of elasticity (Pa) is 6.4825X10 7 It was decided that it was less than or equal to.

[0056] In addition, this result was summarized for a measurement temperature of 25℃, and while the specific values ​​of storage modulus (Pa) and loss modulus (Pa) change with temperature, it was confirmed that the relationship between the storage modulus (Pa) and loss modulus (Pa) between the example and the comparative example remains the same when the temperature is varied from -50℃ to 300℃.

[0057] From the above results, the resin layer (2), containing epoxy resin, has a storage modulus (Pa) of 4.0711X10 at 25°C. 8 It is less than or equal to, and the loss modulus of elasticity (Pa) is 6.4825X10 7 It has been revealed that, as described below, the impact position of an inkjet droplet in the inkjet method can be controlled to perform further miniaturization of the wiring. The reason for this is speculated below. If the viscosity of the resin layer (2) is high, the shock absorption is improved, but excessively high viscosity slows down the transmission of impact energy. As a result, the inkjet droplet may remain in contact with the surface of the resin layer (2) for a long time, and there is a possibility that the movement in the lateral direction may increase. On the other hand, appropriate elasticity can temporarily store collision energy, making it easier to control the behavior of the inkjet droplet.

[0058] In addition, as a more desirable range of viscoelastic properties of the resin layer (2), with respect to the storage modulus (Pa) Y and loss modulus (Pa) X at 25°C of the resin layer, 3.0×10 -5 X 1.6142 ≤Y≤4.0Х10 -4 X 1.6142 It may be assumed that this is the range in which 95% is statistically estimated to be included based on the result of calculating the residual zone from the values ​​of the examples located above and below the above approximation formula. Therefore, the resin layer included in this range is more likely to have the same viscoelastic properties as the examples of the present disclosure.

[0059] Also, regarding the loss modulus (Pa), while it is clear that zero is excluded, if you want to establish a lower limit, X2: 2.3765X10 6It is acceptable to use the above. Since there are no failures on the lower end for the loss modulus (Pa), this value is taken slightly wider than the lower limit of the 95% confidence interval of X based on Examples 1 to 8, and is a robust estimate representing the lower end of the data distribution assuming a log-normal distribution based on the median of Examples 1 to 8. Specifically, the median absolute deviation (MAD) was used instead of the standard deviation. A scaled value was used by multiplying the MAD of the loss modulus (Pa) based on Examples 1 to 8 by a scale factor (1.4826: a statistically derived value widely used for adjusting MAD), and the median of the loss modulus (Pa) of Examples 1 to 8 minus 1.4826 χ MAD was set as the lower limit. This was used strictly to practically identify the downward trend of the data in a situation involving a small sample size and the possibility of potential deviations.

[0060] Additionally, as a more desirable range, there is a range defined by the values ​​of storage modulus (Pa) Y and loss modulus (Pa) X measured in Examples 1 to 8, specifically, as can be seen from the values ​​shown in the table of FIG. 6, it is a range where 4464500≤X≤32205200 and 9071680≤Y≤17109200. The above values ​​may be used as the most desirable upper and lower limits for XY, respectively.

[0061] The storage modulus and loss modulus of the resin layer (2) above can be evaluated by dynamic viscoelasticity measurement (DMA). In DMA, there may be a measurement with a fixed frequency and a mode for evaluating frequency dependency by sweeping the frequency, and evaluation is possible with a measurement with a fixed frequency. The measurement frequency in the case of fixing is, for example, 10 Hz.

[0062] Additionally, the relationship between storage modulus, loss modulus, and degree of swelling was also verified. The degree of swelling is,

[0063] Q(%) = 100X (W - Wa) / Wa

[0064] It is represented by W, which represents the weight of the sample after swelling, and Wa, which represents the weight of the sample before swelling.

[0065] Figure 8 is a table comparing the results of a penetration test of 2-ethoxyethanol, an alcohol-based solvent that can be simulated as an example of a solvent for an ink composition, with respect to materials constituting multiple types of resin layers, and the composition of the pattern formation.

[0066] From this table, it was confirmed that suitable requirements for the material constituting the resin layer (2) can be defined by the condition that the degree of swelling of the resin layer (2) with respect to 2-ethoxyethanol is 128 or higher. More preferably, it is more desirable to satisfy all requirements of storage modulus, loss modulus, and degree of swelling. Thus, the fact that the degree of swelling affects the reception of inkjet droplets may be related to the fact that the solvent of the ink composition can be absorbed at a suitable rate by means of a suitable degree of swelling.

[0067] <Examples >

[0068] Examples of circuit forming substrates manufactured using the above resin layer are described below.

[0069] <Example of Ink Composition>

[0070] Below, an example of an ink used for making a circuit board is described. 15 parts of copper nanoparticles, 1 part of a polycarboxylic acid-based dispersant, 10 parts of 2-ethoxyethanol (Tokyo Kasei Kogyo), 15 parts of 2-(2-n-butoxyethoxy)ethanol (Tokyo Kasei Kogyo) (diethylene glycol monobutyl ether), 10 parts of 3-methoxy-methylbutanol (Tokyo Kasei Kogyo), and 47 parts of 2-(2-methoxyethoxy)ethanol (Tokyo Kasei Kogyo) (diethylene glycol monomethyl ether) were mixed in a container, and a dispersion operation was performed using a self-rotating rotary mixer. Thereby, 0.2 to 1.0 parts of various additives were mixed, and a dispersion operation was performed using the same self-rotating rotary mixer to obtain a copper-brown copper ink composition containing additives. Then, a circuit board was fabricated using the obtained ink composition.

[0071] <Inkjet Droplet Example or L / S Example>

[0072] When a piezo-type inkjet device is used and droplets are ejected onto an epoxy resin in the elastic modulus range shown in this embodiment, the impact size was in the range of 40 to 80 μm. In an epoxy resin having an ink-accepting layer function, it was found that the behavior of the droplets after impact could be controlled, and a line width of 40 to 200 μm could be achieved.

[0073] <Examples of storage modulus and loss modulus of a resin layer containing epoxy resin>

[0074] For a resin mixed with a general-purpose epoxy resin and a curing agent, a mixed solution was prepared by diluting it with 2-ethoxyethanol to a solid content ratio of 40%. Using this mixed solution, after solvent removal, the resin was coated to a total thickness of approximately 2 mm, and a drying and curing treatment was performed at 180°C for 60 minutes. The obtained cured material was cut to a width of 3 mm and a length of 20 mm to prepare a DMA measurement sample. Using a DMA measuring device, the elastic modulus of the sample was measured from -50 to 300°C under conditions of a strain of 0.1% and a frequency of 1 Hz. Based on the obtained elastic modulus measurement results, an epoxy resin having an ink-accepting layer function was defined based on the loss modulus (Pa) and storage modulus (Pa) at 25°C.

[0075] Microscopic view of the inkjet impact after impact

[0076] Figure 9 is a microscopic photograph showing the appearance of a wiring pattern formed after inkjet impact. In this figure, it can be seen that fine lines with an L / S of 50 μm are clearly depicted.

[0077] <Appearance after plating>

[0078] Figure 10 is a photograph showing the appearance of the circuit forming substrate drawn in Figure 9 after applying a plating treatment. Even after undergoing the plating process, problems such as peeling due to the plating treatment basically did not occur. In addition, since it is a test pattern, some areas where the drawing was not properly done are shown, but there is no problem.

[0079] <Adhesion Strength>

[0080] As a peel test to verify the adhesion strength of the plating layer to the substrate, the peel test is performed at a 90-degree angle in accordance with the U.S. UL standard, more specifically, UL796F. The peel test was performed multiple times for each of the widths of the test specimens. By doing so, an adhesion strength of 0.8 N / mm was confirmed.

[0081] · Complementary evaluation methods

[0082] (Evaluation by dynamic viscoelasticity measurement using atomic force microscopy)

[0083] In addition, Comparative Examples 3 and 4 and Examples 9 to 16 were prepared using the same resin layers as Comparative Examples 1 and 2 and Examples 1 to 8, and were samples for evaluation using an Atomic Force Microscope (AFM), and were also evaluated by AFM-QNM (Quantitative Nanomechanical Mapping). The QNM mode is a method for non-destructively measuring surface shape and mechanical properties simultaneously by scanning while contacting a cantilever with a constant contact pressure on the sample surface and controlling it with high-speed feedback. The measurement principle considers the cantilever as a spring and calculates the force from the indentation amount based on Hooke's Law. From the obtained force, the elastic modulus of the sample is determined using contact mechanics models such as DMT theory. In addition, the measurement temperature is the same at 25℃.

[0084] FIG. 11 is a table showing the elastic modulus (Pa) of each sample measured by AFM-QNM and the pattern formation properties. In this table, Comparative Examples 3 and 4 are circuit forming substrates with a resin layer formed in the same way as Comparative Examples 1 and 2 shown in the table of FIG. 6, and Examples 10 to 16 are circuit forming substrates with a resin layer formed in the same way as Examples 1 to 8. Regarding the elastic modulus, since it can often be acquired as a two-dimensional map in AFM, it may be a single point, such as the center position of any measurement location, or a surface average value.

[0085] The elastic modulus (Pa) measured by AFM-QNM is not the same physical quantity as the storage modulus and loss modulus measured by the aforementioned DMA. In principle, due to the influence of the interaction between the cantilever and the sample, the measurement value may not necessarily have a high correlation with the storage modulus and loss modulus obtained by DMA, but a certain correlation exists. For example, while DMA is suitable for macro-scale evaluation of bulk samples, AFM is suitable for measuring local characteristics at the nano-scale. Therefore, depending on the form of the sample, evaluation using AFM may also be performed. According to the table in Fig. 11, the elastic modulus (Pa) measured using an atomic force microscope at 25°C on the surface of the resin layer is 4.60 x 10 8 The above, 2.18X10 9 It can be seen that in the case below, the pattern can be formed well.

[0086] In addition, when performing evaluations using AFM-QNM, dissipated energy (eV) (also referred to as energy dissipation) can also be measured. Dissipated energy is the value of energy that is lost due to fluid viscosity and converted into thermal energy. Generally, this dissipated energy represents the portion of energy that is converted into heat or other forms when a material is subjected to stress. It aids in understanding the viscous behavior and internal structure of materials and is important when evaluating the viscoelastic properties of thin films or micro-scale samples. Likewise, regarding dissipated energy, since it can often be acquired as a two-dimensional map in AFM, it can be a single point, such as the center of an arbitrary measurement location, or an area average value.

[0087] FIG. 12 is a table showing the dissipation energy (eV) and pattern formation capability obtained in conjunction with the measurement of the elastic modulus (Pa) of each sample measured by the above AFM-QNM. In this table, it can be seen that when the dissipation energy (eV) measured using an atomic force microscope at 25°C on the surface of the resin layer is 65 or higher and 307 or lower, the pattern can be formed well.

[0088] By the above, in the inkjet method of the present disclosure, the impact position of the inkjet droplet can be controlled to perform additional miniaturization of the wiring.

[0089] The description ends here, but the new technology according to the present disclosure may be realized in various other forms, and parts of the content may be omitted, modified, or changed within the scope of not departing from the common knowledge of the present disclosure. The embodiments or variations thereof shown in the present disclosure are also included in the subject matter or common knowledge of the present disclosure and are treated as equivalent or equivalent to the technology to be protected by the patent claims. Furthermore, the technical scope of the present disclosure may be defined by excluding parts thereof. For example, when physical quantities 1 to 100 are disclosed in the present disclosure, an expression such as 1 to 100 (excluding 20 to 40) may be used to indicate superiority over other technologies.

[0090] Several embodiments included in the present disclosure are noted below.

[0091] [1]

[0092] As a circuit forming substrate having a wiring pattern on at least a portion thereof,

[0093] Insulating substrate and,

[0094] A resin layer comprising epoxy resin formed on the above insulating substrate, and

[0095] An inkjet drop impact layer formed by the impact of a plurality of inkjet droplets containing metal particles formed on the resin layer, and

[0096] The plating layer formed on the above inkjet droplet impact layer, and

[0097] At 25°C of the above resin layer,

[0098] Storage modulus is 4.0711X10 8 The following,

[0099] The loss modulus is 6.4825X10 7 Lee Ha-in, circuit forming substrate.

[0100] [2]

[0101] With respect to the storage modulus (Pa) Y and loss modulus (Pa) X of the above resin layer at 25°C,

[0102] 3.0X10 -5 X 1.6142 ≤Y≤4.0Х10 -4 X 1.6142 A circuit forming substrate as described in [1].

[0103] [3]

[0104] A circuit forming substrate described in [2], wherein the swelling degree of the resin layer with respect to 2-ethoxyethanol is 128 or higher.

[0105] [4]

[0106] At 25°C of the above resin layer,

[0107] The loss modulus of elasticity (Pa) is 6.4825X10 7 The circuit forming substrate described in [2] below.

[0108] [5]

[0109] A circuit forming substrate having a wiring pattern having a line width of 1000 μm or less in at least a portion thereof,

[0110] The average particle diameter of the above metal particles is 1 nm to 200 nm, and

[0111] A circuit forming substrate described in any one of [1] to [4], wherein the diameter of the inkjet droplet is 1 μm to 100 μm.

[0112] [6]

[0113] A method for manufacturing a circuit forming substrate having a wiring pattern on at least a portion thereof,

[0114] A step of forming a resin layer containing epoxy resin on an insulating substrate, and

[0115] A step of forming an inkjet droplet impact layer formed by impacting a plurality of inkjet droplets containing metal particles and an alcohol solvent onto the resin layer, and

[0116] The method comprises a step of forming a plating layer on the above inkjet droplet impact layer, and

[0117] At 25°C of the above resin layer,

[0118] Storage modulus is 4.0711X10 8 The following,

[0119] The loss modulus is 6.4825X10 7 Method for manufacturing a circuit forming substrate, wherein the above

[0120] [7]

[0121] With respect to the storage modulus (Pa) Y and loss modulus (Pa) X of the above resin layer at 25°C,

[0122] 3.0×10 -5 X 1.6142 ≤Y≤4.0Х10 -4 X 1.6142 Method for manufacturing a circuit forming substrate as described in [6].

[0123] [8]

[0124] A method for manufacturing a circuit forming substrate as described in [7], wherein the swelling degree of the resin layer with respect to 2-ethoxyethanol is 128 or higher.

[0125] [9]

[0126] At 25°C of the above resin layer,

[0127] The loss modulus of elasticity (Pa) is 2.3765X10 6 The above method for manufacturing a circuit forming substrate as described in [8].

[0128]

[10]

[0129] A circuit forming substrate having a wiring pattern having a line width of 1000 μm or less in at least a portion thereof,

[0130] The average particle diameter of the above metal particles is 1 nm to 200 nm, and

[0131] A method for manufacturing a circuit forming substrate as described in any one of [6] to [9], wherein the diameter of the inkjet droplet is 1 μm to 100 μm.

[0132]

[11]

[0133] As a circuit forming substrate having a wiring pattern on at least a portion thereof,

[0134] Insulating substrate and,

[0135] A resin layer comprising epoxy resin formed on the above insulating substrate, and

[0136] An inkjet drop impact layer formed by the impact of a plurality of inkjet droplets containing metal particles formed on the resin layer, and

[0137] The plating layer formed on the above inkjet droplet impact layer, and

[0138] By measurement using an atomic force microscope at 25°C on the surface of the above resin layer,

[0139] The elastic modulus (Pa) is 4.60 x 10 8 The above, 2.18X10 9 Lee Ha-in, circuit forming substrate.

[0140]

[12]

[0141] By measurement using an atomic force microscope at 25°C on the surface of the above resin layer,

[0142] A circuit forming substrate as described in

[11] , having a dissipation energy (eV) of 65 or more and 307 or less.

[0143]

[13]

[0144] A method for manufacturing a circuit forming substrate having a wiring pattern on at least a portion thereof,

[0145] A step of forming a resin layer containing epoxy resin on an insulating substrate, and

[0146] A step of forming an inkjet droplet impact layer formed by impacting a plurality of inkjet droplets containing metal particles and an alcohol solvent onto the resin layer, and

[0147] The method comprises a step of forming a plating layer on the above inkjet droplet impact layer, and

[0148] By measurement using an atomic force microscope at 25°C on the surface of the above resin layer,

[0149] The elastic modulus (Pa) is 4.60 x 10 8 The above, 2.18X10 9 Method for manufacturing a circuit forming substrate, wherein the above

[0150]

[14]

[0151] By measurement using an atomic force microscope at 25°C on the surface of the above resin layer,

[0152] A method for manufacturing a circuit forming substrate as described in

[13] , having a dissipation energy (eV) of 65 or more and 307 or less. Explanation of the symbols

[0153] 1 Insulating material 2 resin layer 3 Inkjet droplet impact layer 4 plating layer 31 Inkjet droplets 32 Inkjet droplets

Claims

Claim 1 A circuit forming substrate having a wiring pattern on at least a portion, comprising an insulating substrate, a resin layer formed on the insulating substrate and comprising an epoxy resin, an inkjet drop impact layer formed by impact of a plurality of inkjet droplets comprising metal particles formed on the resin layer, and a plating layer formed on the inkjet drop impact layer, wherein the storage modulus (Pa) of the resin layer at 25°C is 4.0711X10 8 It is less than or equal to, and the loss modulus of elasticity (Pa) is 6.4825X10 7 Lee Ha-in, circuit forming substrate. Claim 2 In claim 1, with respect to the storage modulus (Pa) Y and loss modulus (Pa) X of the resin layer at 25°C, 3.0×10 -5 X 1.6142 ≤Y≤4.0Х10 -4 X 1.6142 Phosphate, circuit forming substrate. Claim 3 A circuit forming substrate according to claim 2, wherein the swelling degree of the resin layer with respect to 2-ethoxyethanol is 128 or higher. Claim 4 In claim 2, the loss modulus (Pa) of the resin layer at 25°C is 2.3765X10 6 Lee Sang-in, circuit forming substrate. Claim 5 A circuit forming substrate according to any one of claims 1 to 4, wherein the circuit forming substrate has a wiring pattern having a line width of 1000 μm or less in at least a portion thereof, wherein the average particle diameter of the metal particles is 1 nm to 200 nm and the diameter of the inkjet droplets is 1 μm to 100 μm. Claim 6 A method for manufacturing a circuit forming substrate having a wiring pattern on at least a portion thereof, comprising the steps of: forming a resin layer containing an epoxy resin on an insulating substrate; forming an inkjet droplet impact layer formed by impacting a plurality of inkjet droplets containing metal particles and an alcohol solvent on the resin layer; and forming a plating layer on the inkjet droplet impact layer, wherein the storage modulus (Pa) of the resin layer at 25°C is 4.0711X10 8 It is less than or equal to, and the loss modulus of elasticity (Pa) is 6.4825X10 7 Method for manufacturing a circuit forming substrate, wherein the above Claim 7 In claim 6, with respect to the storage modulus (Pa) Y and loss modulus (Pa) X of the resin layer at 25°C, 3.0×10 -5 X 1.6142 ≤Y≤4.0Х10 -4 X 1.6142 Method for manufacturing a circuit forming substrate. Claim 8 A method for manufacturing a circuit forming substrate according to claim 7, wherein the swelling degree of the resin layer with respect to 2-ethoxyethanol is 128 or higher. Claim 9 In claim 8, the loss modulus (Pa) of the resin layer at 25°C is 2.3765X10 6 A method for manufacturing a circuit forming substrate, according to the above. Claim 10 A method for manufacturing a circuit forming substrate according to any one of claims 6 to 9, wherein the circuit forming substrate has a wiring pattern having a line width of 1000 μm or less in at least a portion, wherein the average particle diameter of the metal particles is 1 nm to 200 nm and the diameter of the inkjet droplets is 1 μm to 100 μm.

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