Circuit board and method for selecting insulating rigid base material for circuit board

Abstract

In order to improve adhesion between a sintered layer of metal nanoparticles and an insulating rigid substrate in a circuit board that uses a rigid insulating substrate, the present invention provides a circuit board that is provided with an insulating rigid base material containing a glass epoxy resin, a primer resin layer formed on the insulating rigid base material and containing an epoxy resin, a sintered layer of metal nanoparticles formed on the primer resin layer, and a plating layer formed on the sintered layer. The insulating rigid base material satisfies 147 ≤ X and 0.34 ≤ Y, where X is the glass transition temperature (°C) of the insulating rigid base material and Y is the thermal conductivity (W / mk) of the insulating rigid base material.

Description

Circuit board and method for selecting insulating rigid substrate for circuit board

[0001] The present disclosure relates to a circuit board and a method for selecting an insulating rigid substrate for a circuit board.

[0002] To form a conductive film, a method is known in which a plurality of copper nanoparticles are deposited on a substrate surface and at least a portion of the film is exposed to light to photosinter or fuse the copper nanoparticles, making the exposed portion conductive (see Patent Document 1 below).

[0003] Japanese Patent Application Laid-Open No. 2014-116315

[0004] However, although it is effective to form a primer layer containing resin on the substrate to improve adhesion of the metal nanoink sintered layer to the substrate, it has become clear that when the substrate is changed from a flexible substrate such as a film to a rigid substrate, peeling and deformation occur between the primer layer and the substrate.

[0005] Therefore, at least one aspect of the problem to be solved by the present disclosure is to improve the adhesion between a photosintered layer of metal nanoparticles and an insulating rigid substrate in a circuit board using a rigid insulating substrate. Note that problems that are obvious to a person skilled in the art and can be read from the embodiments and their descriptions that are characteristic of the present disclosure and are described in the specification, drawings, etc. of the present disclosure may also be problems to be solved by a divided invention if a divisional application based on the present disclosure is filed.

[0006] In order to achieve the above-mentioned object, the circuit board of the present disclosure is a circuit board comprising an insulating rigid substrate containing a glass epoxy resin, a primer resin layer formed on the insulating rigid substrate and containing an epoxy resin, a sintered layer of metal nanoparticles formed on the primer resin layer, and a plating layer formed on the sintered layer, wherein, when the glass transition temperature (°C) of the insulating rigid substrate is X and the thermal conductivity (W / mk) is Y, 147≦X and 0.34≦Y are satisfied.

[0007] According to the present disclosure, in a circuit board using a rigid insulating substrate, it is possible to improve the adhesion between a sintered layer of metal nanoparticles and the insulating rigid substrate.

[0008] Fig. 1 is a diagram schematically showing a layer structure of a circuit board according to the present disclosure; Fig. 2 is a flowchart showing the process flow of a method for manufacturing a circuit board according to the present disclosure; Fig. 3 is a diagram schematically showing a method for manufacturing a circuit board according to the present disclosure; Fig. 4 is a flowchart showing the process flow of a method for selecting an insulating rigid substrate for a circuit board according to the present disclosure; Fig. 5 is a diagram showing an example of the present disclosure.

[0009]

[0023] The embodiments of the present disclosure will be described with reference to the drawings. Fig. 1 is a diagram schematically illustrating the layer structure of a circuit board according to the present disclosure. This diagram illustrates a single layer of the circuit board, and the circuit board may be composed of multiple wiring structures.

[0010] The circuit board of the present disclosure is a circuit board including an insulating rigid substrate 1 containing a glass epoxy resin, a primer layer 2 formed on the insulating rigid substrate 1 and containing an epoxy resin, a photosintered layer 3 of metal nanoparticles formed on the primer layer 2, and a plating layer 4 formed on the photosintered layer 3, wherein the glass transition temperature (°C) and thermal conductivity (W / mk) of the insulating rigid substrate 1 satisfy predetermined conditions. The conditions will be described later.

[0011] The photosintered layer 3 of metal nanoparticles may be formed by applying an ink composition containing metal nanoparticles and then photosintering the applied ink composition. The metal nanoparticles may be copper nanoparticles. Below, a copper nanoink composition containing copper nanoparticles, a coating material, a dispersant, and a solvent will be described as an example, but copper nanoinks with other compositions may also be used.

[0012] The copper nanoparticles preferably have an average particle size of 1 nm to 200 nm, more preferably 10 nm to 100 nm. If the particle size is too small, the reactivity of the particles may increase, which may reduce the storage stability and stability of the ink. If the particle size is too large, the uniformity of the thin film may decrease, and the ink particles may be more likely to precipitate.

[0013] The coating material is intended to prevent the copper nanoparticles from being easily oxidized, and may be a carboxylic acid, more preferably a monocarboxylic acid having an integer of 6 to 10 carbon atoms, such as hexanoic acid, heptanoic acid, octanoic acid, nonanoic acid, or decanoic acid.

[0014] The surface of the copper nanoparticles may be coated with an oxide film. As will be described later, when a reduction reaction is caused using a chemical reduction reaction reagent such as formaldehyde, the reduction reaction from copper oxide to zero-valent metallic copper proceeds, and active metallic copper can be produced.

[0015] The dispersant is used to disperse the copper nanoparticles covered with a coating material to form an ink, and to uniformly disperse the copper nanoparticles (dispersoid) in the solvent (dispersion medium) and maintain a stable dispersion state without aggregation. The dispersant may be a carboxylic acid-based, thiol-based, phenol-based, phosphoric acid-based, or amine-based compound. Preferably, it may be a carboxylic acid-based compound capable of forming a coordinate bond with copper.

[0016] A more preferred example of a dispersant when octanoic acid is selected as the coating material is, but is not limited to, a polycarboxylic acid. A more preferred polycarboxylic acid is a polycarboxylic acid having a comb structure.

[0017] The solvent may be an aqueous solvent or an organic solvent, more specifically, glycol ethers such as ethylene glycol monoethyl ether, diethylene glycol monobutyl ether, propylene glycol monomethyl ether, ethylene glycol monoethyl ether, or mixtures thereof, and the solvents described below may also be used.

[0018] In addition, stabilizers and other additives may be used.

[0019] The content of copper nanoparticles in the ink composition may be 5 to 60% by weight, or 10 to 30% by weight, by mass. The reason for selecting these ranges is that if the content is too low, there may be a shortage of nanoparticles necessary to form a conductive layer of copper nanoparticles, which may result in the generation of voids such as pinholes, whereas if the content is too high, the particles may be more likely to aggregate in the ink, which may impair the stability of the ink.

[0020] The viscosity of the ink composition is preferably 1 to 100 mPa·s at a measurement temperature of 25°C, as measured using an E-type viscometer or a rheometer. Furthermore, the viscosity is preferably 1 to 100 mPa·s at a shear rate of 100 (1 / S) or more, and more preferably 1 to 50 mPa·s. This is because the viscosity is suitable for the environment in which the ink is ejected by an inkjet head, and if the viscosity is too high, it will be difficult for the ink to be ejected from the inkjet head.

[0021] <Circuit Board Manufacturing Method> Next, a basic process flow of the circuit board manufacturing method of the present disclosure will be described with reference to the flowchart shown in FIG.

[0022] First, in step S100, an insulating substrate is prepared. This insulating substrate is a rigid plate containing an organic-inorganic composite material, including a glass epoxy resin. The insulating substrate may be a prepreg made by impregnating an unclad substrate with a resin such as an epoxy resin.

[0023] Here, "rigid" may refer to a material having a hardness of, for example, a tensile modulus of elasticity of 10 GPa or more. Since the tensile modulus is expressed using the same physical quantity as Young's modulus, it may be defined by Young's modulus. Generally, for resins and composite materials, even those with a relatively high tensile modulus called semi-flexible are only a few GPa, so a material having a hardness of a tensile modulus of elasticity of 10 GPa or more is considered to be a rigid substrate. For example, the insulating rigid substrate containing glass epoxy resin used in the present disclosure has a tensile modulus of elasticity of about 20 GPa.

[0024] In existing circuit boards such as printed circuit boards, copper foil is laminated onto the surface of a prepreg. In the present disclosure, however, a metal nanoink composition is applied and then photosintered to form a photosintered layer. A plating layer is then formed on the photosintered layer, and the photosintered layer and plating layer form a conductive layer. The conductive layer is pre-patterned, for example, by inkjet printing, and no etching is required. In other words, when the conductive layer consisting of the photosintered layer and plating layer is formed, the circuit pattern forming the electric circuit, electronic circuit, and conductive circuit is already formed on this circuit board. In other words, this substrate is a circuit pattern-formed substrate.

[0025] A primer layer may be formed on the surface of the insulating rigid substrate for various purposes, such as improving the coatability of the ink composition, modifying the surface of the insulating rigid substrate, etc. The primer may contain, for example, any of polyimide, polyamide, polyamideimide, polyethylene terephthalate, polyethylene naphthalate, polyether ether ketone, acrylonitrile butadiene styrene, polymethyl methacrylate, polystyrene, polyphenylene sulfide, polyvinyl chloride, epoxy resin, and glass epoxy resin.

[0026] Next, in step S101, an ink composition containing copper nanoparticles is applied in a wiring pattern using an inkjet printing device (ink application step), thereby forming an ink coating layer on the insulating substrate.

[0027] The diameter of a single ink droplet ejected from an inkjet nozzle of an inkjet printing device is, for example, within a range of 1 μm to 100 μm.

[0028] After the ink coating layer is formed, a drying step may be performed to remove the solvent, etc. The drying step may be a heat treatment or a hot air treatment using a nitrogen or air flow. This leaves the copper nanoparticles on the primer layer and the insulating rigid substrate.

[0029] Next, in step S102, the ink composition is sintered to form a sintered layer (photo-sintering process). Regarding the ink coating layer, in addition to removing components other than the copper nanoparticles, it is necessary to cause bonding, melting, and contact between the copper nanoparticles. The state in which metal nanoparticles are close to each other and bonded while maintaining their shape is called "necking," and the phenomenon in which the nanoparticles melt from the necked state and become integrated with a change in shape is also called "fusion." The interparticle bonding is sometimes simply called "necking." In this way, sintering causes the nanoparticles to melt together and bulk, improving conductivity and adhering to the insulating rigid substrate.

[0030] As mentioned above, copper nanoparticles may also be reduced by chemical reduction. For example, the oxide film on the surface of copper nanoparticles can be reduced to metallic copper by using a chemical such as formaldehyde, which can induce the fusion phenomenon of metal nanoparticles in the same way as described above. Sintering processes involving chemical reactions and liquid phases, such as liquid phase sintering and reaction sintering, are already known, and because they ultimately achieve the same effect as sintering, namely, the melting and bonding of particles, this disclosure broadly considers the reduction approach to be a type of sintering process. This can increase conductivity.

[0031] For example, copper nanoparticles can be sintered and bonded together by using photosintering with a flash lamp. Instantaneous heating from a flash discharge lamp is advantageous because heat is applied only to the surface of the substrate, preventing heating inside the substrate. In addition to flash lamp sintering, heating methods using infrared light, such as ovens and infrared furnaces, can also be used, and these heating methods can also form a sintered layer of copper nanoparticles. Furthermore, as described above, reduction treatment using a reducing agent, wet reduction treatment, and dry reduction treatment can also be used. Heating to the extent necessary for such reduction treatment may be performed.

[0032] The irradiation conditions of the flash lamp can be adjusted as appropriate by those skilled in the art using parameters such as input power, Joule heat according to the input power, and charge voltage per shot.

[0033] Next, in step S103, a copper plating layer is formed on the photosintered layer (plating step).

[0034] After the ink application process and drying process, a photosintering process is performed, and the formed photosintered layer is plated (electrolytic plating or electroless plating). This causes a plating metal (plating layer) to be deposited on the surface and inside of the photosintered layer. The plating method is similar to a known plating process using a known plating solution, and specifically may include electroless copper plating, electrolytic copper plating, etc.

[0035] Through the above steps, a circuit board can be manufactured in which copper wiring of a desired pattern is formed on an insulating rigid substrate.

[0036] <Regarding Adhesion Strength with Substrate> Incidentally, a manufactured circuit board requires a considerable degree of adhesion strength between the photosintered layer and plating layer, which are conductor layers, and the insulating rigid substrate. For example, it is preferable that the adhesion strength be 0.2 N / mm or more. However, when multiple insulating substrates were evaluated, some circuit boards manufactured by the same process had low adhesion strength. Regarding this issue, the present inventors conducted extensive research as follows.

[0037] 3 is a diagram schematically illustrating the method for manufacturing a circuit board according to the present disclosure. In this diagram, a primer layer 2 and a photosintered layer 3 are shown from the bottom in the order in which they are formed on an insulating rigid substrate 1. A plating layer 4 is formed on the photosintered layer 3 as shown in FIG. 1. In a peel test for measuring adhesion strength, it was confirmed that the primer layer 2 peeled off together with the photosintered layer 3 and the plating layer 4 in the circuit boards with reduced adhesion strength. From this, it was inferred that the adhesion between the primer layer 2 and the insulating rigid substrate 1 was an issue.

[0038] In the circuit board of the present disclosure, instantaneous heating using a light source such as a flash lamp 8 during manufacturing causes rapid temperature increases and decreases in the primer layer 2 and the insulating rigid substrate 1. This is thermal stress that is significantly different from the heating and cooling caused by a typical baking device such as an oven, and occurs in just a few milliseconds. Xenon flash lamps have a broad wavelength distribution similar to sunlight, and heat is generated in layers that absorb that wavelength band, particularly those shallow from the surface. Therefore, if the heat cannot be effectively dissipated in the depth direction of the insulating rigid substrate, deformation occurs due to thermal expansion, and it is presumed that the adhesion strength between the primer layer 2 and the insulating rigid substrate 1 will decrease.

[0039] Here, the primer layer 2 is a thin layer formed by applying a resin or the like, and therefore does not exceed 500 μm in thickness at most. The insulating rigid substrate 1 typically exceeds 500 μm in thickness even for a single layer, even if a multilayer substrate is formed by stacking single layers. Therefore, the thermal properties of the insulating rigid substrate 1 are more important. The insulating rigid substrate 1 containing glass epoxy resin is prone to thermal expansion if the glass transition temperature of the material is low. Furthermore, if the thermal conductivity of the material is low, the ability to dissipate heat in the depth direction is reduced.

[0040] In view of these circumstances, in order to suppress the occurrence of the phenomenon of a decrease in adhesion strength as described above, the present inventors focused on the glass transition temperature and thermal conductivity of the insulating rigid substrate and clarified the relationship between the glass transition temperature and the adhesion strength.

[0041] <Insulating Rigid Base Material Selection Method> Next, the basic processing flow of the insulating rigid base material selection method for a circuit board according to the present disclosure will be described with reference to the flowchart shown in FIG.

[0042] First, in step S200, an insulating rigid substrate for a circuit board is prepared, which includes an insulating rigid substrate containing a glass epoxy resin, a primer resin layer formed on the insulating rigid substrate and containing an epoxy resin, a photosintered layer of metal nanoparticles formed on the primer resin layer, and a plating layer formed on the photosintered layer.

[0043] Next, in step S201, the glass transition temperature (°C) X of the insulating rigid substrate is obtained. For example, the glass transition temperature (°C) may be measured using the TMA method, or a catalog value such as a data sheet may be used.

[0044] Next, in step S202, the thermal conductivity (W / mk) of the insulating rigid substrate is obtained. For example, the thermal conductivity (W / mk) may be measured using a pulse heating method (flash method), or a catalog value such as a data sheet may be used.

[0045] Next, in step S203, an insulating rigid substrate is selected that satisfies predetermined conditions for glass transition temperature (° C.) and thermal conductivity (W / mk). Details of the predetermined conditions will be described later.

[0046] <Examples> (Regarding circuit board peeling test) Circuit boards according to the above-described embodiments were fabricated using a plurality of insulating rigid substrates with different glass transition temperatures and thermal conductivities, and heat resistance reliability tests and peeling tests were conducted to evaluate changes in adhesion strength. Circuit board samples were prepared by forming a copper sintered layer and a copper plating layer on the entire surface of the insulating substrate or on an area large enough to allow for a peeling test.

[0047] <Ink Composition Example> An example of an ink used to prepare a circuit board is described below. 15 parts of copper nanoparticles, 1 part of a polycarboxylic acid-based dispersant, 10 parts of 2-ethoxyethanol (manufactured by Tokyo Chemical Industry Co., Ltd.), 15 parts of 2-(2-n-butoxyethoxy)ethanol (manufactured by Tokyo Chemical Industry Co., Ltd.) (diethylene glycol monobutyl ether), 10 parts of 3-methoxy-methylbutanol (manufactured by Tokyo Chemical Industry Co., Ltd.), and 47 parts of 2-(2-methoxyethoxy)ethanol (manufactured by Tokyo Chemical Industry Co., Ltd.) (diethylene glycol monomethyl ether) were blended in a container and dispersed using a planetary rotary mixer. 0.2 to 1.0 parts of various additives were blended therein, and the mixture was dispersed using the planetary rotary mixer to obtain a copper-brown additive-containing copper ink composition. A circuit board was then fabricated using the resulting ink composition.

[0048] <Peel Test> A peel test to confirm the adhesive strength of the plating layer to the substrate was performed at a 90-degree angle in accordance with the US UL standard, more specifically, UL 796. In the peel test, peeling was performed multiple times for each of multiple test piece widths.

[0049] Figure 5 shows the relationship between glass transition temperature and thermal conductivity and the results of adhesion strength measurements performed on examples of the present disclosure using a peel test. The bottom of the figure shows the results of measurements of glass transition temperature, thermal conductivity, and adhesion strength for each test piece (sample). The conditions and manufacturing method for each sample were essentially the same. The top of the figure shows a plot of each sample, with the glass transition temperature (°C) on the X axis and the thermal conductivity (W / mk) on the Y axis. As a result of the adhesion strength measurements performed using the peel test, samples with an adhesion strength of 0.35 N / mm or more were selected as examples (plot legend: ◯), and samples with an adhesion strength of less than 0.35 N / mm were selected as comparative examples (plot legend: ×). An adhesion strength of approximately 0.20 N / mm can be considered to have a certain level of strength, but the examples showed even greater improvement in adhesion strength.

[0050] Next, we investigated a method for appropriately determining the range defined by the plots of Examples 1 to 6, which showed improved adhesion strength. Various methods were considered, but the definition using a minimum encompassing ellipse was found to be relatively robust against outliers, often formulated as a convex optimization problem, and less likely to lead to erroneous results. Furthermore, the plots in this study did not have any significant outliers in the XY coordinates, and the point cloud clusters were grouped together, so they were not inappropriate data for defining a minimum encompassing ellipse. As a result, defining a minimum encompassing ellipse that encompasses these plots was a reasonable and realistic option. Therefore, we calculated a minimum encompassing ellipse that includes all of these points. By calculating such a circle, we could appropriately define a range in which it is estimated that the same effects as those of the Examples can be obtained. As a result of the calculation, the center of gravity of these point groups is located at (171.67, 0.60) on the XY plane, with X representing the glass transition temperature (°C) and Y representing the thermal conductivity (W / mk), and the minimum encompassing ellipse is calculated with the center of gravity as its center, with a major axis radius a of 24.32, a minor axis radius b of 0.24, and a rotation angle (°): -0.17 (≒ -0.0030 (rad)). Note that, due to the relationship between fractions and the number of significant digits, the theoretically calculated values ​​for the major axis radius a and the minor axis radius b are multiplied by 1.1 to ensure that the examples do not fall outside the range of the ellipse.

[0051] The equation of an ellipse whose center is (h, k) and whose rotation angle is θ (rad) is ((X−h) cos θ + (Y−k) sin θ) ２ / a ２ +(-(X-h) sin θ+(Y-k) cos θ) ２ / b ２ Therefore, in order to be included in the range of the ellipse, the following formula ((X-171.67) + (-0.003 x (Y-0.60)) is used, substituting the above real values ​​as much as possible. ２ / 591.56 + (0.003 × (X − 171.67) + (Y − 0.60)) ２ It is sufficient to satisfy the condition: / 0.06≦1. If this condition is satisfied, it will be included in the range of the ellipse shown in FIG.

[0052] Furthermore, the inventors have defined a range where 147≦X and 0.34≦Y, where X is the glass transition temperature (°C) of the insulating rigid substrate and Y is the thermal conductivity (W / mk), as an effective range, since the same effect can be achieved as long as the glass transition temperature (°C) and the thermal conductivity (W / mk) are higher than the minimum value within the above-mentioned ellipse range.

[0053] With regard to this range, taking into consideration the upper limit as well as the maximum value of the glass transition temperature (°C) and the maximum value of the thermal conductivity (W / mk) within the range of the ellipse, when the glass transition temperature (°C) of the insulating rigid base material is X and the thermal conductivity (W / mk) is Y, the range may be 147≦X≦196 and 0.34≦Y≦0.86.

[0054] Just to be sure, a more limited range than the minimum encompassing ellipse is defined by a convex hull. A convex hull is the smallest convex polygon that encloses a set of points on a plane or in space. The convex hull inside the above ellipse is essentially represented by a rectangle formed by linearly connecting the plots on the XY plane shown in Example 1 (180, 0.79), Example 3 (155, 0.62), Example 2 (180, 0.43), and Example 5 (185, 0.49). An example of a method for determining whether a point is within the range is shown below. (Example of a judgment formula) Four vectors are calculated counterclockwise around the four vertices, and the vectors from a point (x, y) to each vertex of the rectangle are calculated. Then, the cross product of the vectors of each side and the vector from the point to the vertex is calculated. Specifically, the following inequalities regarding the cross product must be satisfied: c1: 25y - 17x + 3235 ≧ 0, and c2: -25y - 19x - 2870 ≧ 0, and c3: -5y + 6x - 1050 ≧ 0, and c4: 5y + 30x - 5535 ≧ 0, or c1: 25y - 17x + 3235 ≦ 0, and c2: -25y - 19x - 2870 ≦ 0, and c3: -5y + 6x - 1050 ≦ 0, and c4: 5y + 30x - 5535 ≦ 0. For example, the plot for Example 5 is c1 = 0.10, c2 = 1.70, c3 = 2.30, c4 = 6.70, and since all the cross product results are positive, it can be said that this point is located within the convex hull. It is also possible to determine whether a point is inside the convex hull using other methods.

[0055] As described above, according to the circuit board and the method for selecting an insulating rigid substrate for a circuit board of the present disclosure, it is possible to improve the adhesion between the sintered layer of metal nanoparticles and the insulating rigid substrate.

[0056] The new technology of this disclosure can be realized in various other forms, and part of the content can be omitted, modified, or replaced within the scope of the gist of this disclosure. The embodiments and modifications shown in this disclosure are also within the scope and gist of this disclosure, and are treated as technologies that should be protected by the claims, and are equivalent or similar to them.

[0057] The following additional notes are provided regarding embodiments included in the present disclosure. [1] A circuit board including an insulating rigid substrate containing a glass epoxy resin, a primer resin layer formed on the insulating rigid substrate and containing an epoxy resin, a sintered layer of metal nanoparticles formed on the primer resin layer, and a plating layer formed on the sintered layer, wherein, when X is the glass transition temperature (°C) of the insulating rigid substrate and Y is the thermal conductivity (W / mk), the relationships satisfy 147≦X≦196 and 0.34≦Y. [2] The circuit board according to claim 1, wherein, when X is the glass transition temperature (°C) of the insulating rigid substrate and Y is the thermal conductivity (W / mk), the relationships satisfy 147≦X≦196 and 0.34≦Y≦0.86. [3] When the glass transition temperature (°C) of the insulating rigid base material is X and the thermal conductivity (W / mk) is Y, ((X-171.67) + (-0.003 × (Y-0.60)) ２ / 591.56 + (0.003 × (X − 171.67) + (Y − 0.60)) ２ 1. The circuit board according to claim 2, wherein the temperature coefficient of thermal conductivity (W / mk) of the insulating rigid substrate is 147≦X and 0.06≦Y. [4] A method for selecting an insulating rigid substrate for a circuit board including an insulating rigid substrate containing a glass epoxy resin, a primer resin layer containing an epoxy resin formed on the insulating rigid substrate, a sintered layer of metal nanoparticles formed on the primer resin layer, and a plating layer formed on the sintered layer, the method comprising the steps of: preparing the insulating rigid substrate; obtaining a glass transition temperature (°C) X of the insulating rigid substrate; obtaining a thermal conductivity (W / mk)Y of the insulating rigid substrate; and selecting the insulating rigid substrate such that X and Y satisfy the conditions 147≦X and 0.34≦Y.

[0058] REFERENCE SIGNS LIST 1 insulating rigid substrate 2 primer layer 3 photosintered layer 4 plating layer 8 flash lamp

Claims

1. A circuit board comprising an insulating rigid substrate containing a glass epoxy resin, a primer resin layer formed on the insulating rigid substrate and containing an epoxy resin, a sintered layer of metal nanoparticles formed on the primer resin layer, and a plating layer formed on the sintered layer, wherein, when the glass transition temperature (°C) of the insulating rigid substrate is X and the thermal conductivity (W / mk) of the insulating rigid substrate is Y, the relationship between X and Y is 147≦X and 0.34≦Y.

2. The circuit board according to claim 1, wherein, when X is the glass transition temperature (°C) of the insulating rigid base material and Y is the thermal conductivity (W / mk), the relationships 147≦X≦196 and 0.34≦Y≦0.86 are satisfied.

3. When the glass transition temperature (°C) of the insulating rigid base material is X and the thermal conductivity (W / mk) is Y, ((X-171.67) + (-0.003 x (Y-0.60)) ２ / 591.56 + (0.003 × (X − 171.67) + (Y − 0.60)) ２ 3. The circuit board according to claim 2, wherein 0.06≦1.

4. A method for selecting an insulating rigid substrate for a circuit board comprising: an insulating rigid substrate containing a glass epoxy resin; a primer resin layer containing an epoxy resin formed on the insulating rigid substrate; a sintered layer of metal nanoparticles formed on the primer resin layer; and a plating layer formed on the sintered layer, the method comprising the steps of: preparing the insulating rigid substrate; obtaining the glass transition temperature (°C) X of the insulating rigid substrate; obtaining the thermal conductivity (W / mk)Y of the insulating rigid substrate; and selecting the insulating rigid substrate such that X and Y satisfy 147≦X and 0.34≦Y.

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