Resin film with conductor layer, laminated substrate, and method for manufacturing resin film with conductor layer

Abstract

A conductor-layer-coated resin film (10) comprises, along a stacking direction, a resin film 1 comprising a thermoplastic resin and having voids 1h formed therein and a conductor layer 2 adjoining at least one main surface of the resin film 1, wherein in the resin film 1, when the position of the edge surface on the conductor layer 2 side is taken as a first position E1, a position apart from the first position E1 along the stacking direction at a distance corresponding to 1 / 3 the thickness of the resin film 1 is taken as a second position E2, and a position apart from the second position E2 along the stacking direction opposite from the first position E1 at a distance corresponding to 1 / 3 the thickness of the resin film 1 is taken as a third position E3, then the voids 1h localize between the first position E1 and the second position E2 so that the number of voids present between the first position E1 and the second position E2 is larger than the number of voids present between the second position E2 and the third position E3.

Description

[Technical Field]

[0001] The present invention relates to a resin film with a conductor layer, a laminated substrate, and a method for producing a resin film with a conductor layer. [Background technology]

[0002] As a laminated substrate used in various electronic devices, Patent Document 1 discloses a multilayer wiring board having a structure in which a ground layer or a power supply layer and a signal layer are arranged via an insulating layer, characterized in that the insulating layer is made of a porous film whose porosity varies in the thickness direction, and the surface of the porous film with the higher porosity is arranged on the signal layer side. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2003-8233 Summary of the Invention [Problem to be solved by the invention]

[0004] In laminated substrates such as the multilayer wiring board described in Patent Document 1, a technique is sometimes used in which a porous film is used as an insulating layer to reduce the dielectric constant of the insulating layer by the amount of pores present, in order to improve dielectric properties in the high frequency range. For example, in the multilayer wiring board described in Patent Document 1, as described in the examples of Patent Document 1, a porous film is used as the insulating layer, which is formed by a wet coagulation method using a film-forming solution containing a polyimide precursor, and then subjected to heat treatment to heat-close the polyimide precursor.

[0005] The present inventors investigated the use of a thermoplastic resin such as a liquid crystal polymer as a constituent material for the porous film in order to further improve the dielectric properties in the high-frequency range of the multilayer wiring board described in Patent Document 1. However, when attempting to form a porous film using a thermoplastic resin by the method described in the examples of Patent Document 1, it was found that the thermoplastic resin was prone to decomposition and that the viscoelasticity of the thermoplastic resin made it difficult to maintain the shape of the pores. As such, in the multilayer wiring board described in Patent Document 1, it was difficult to achieve a porous film containing a thermoplastic resin, so there was room for improvement in terms of further improving the dielectric properties in the high-frequency range.

[0006] The present invention has been made to solve the above problems, and aims to provide a resin film with a conductor layer that contains a thermoplastic resin and can improve dielectric properties in the high-frequency range. Another object of the present invention is to provide a laminated substrate having the above resin film with a conductor layer. A further object of the present invention is to provide a method for producing the above resin film with a conductor layer. [Means for solving the problem]

[0007] The resin film with a conductor layer of the present invention comprises a resin film containing a thermoplastic resin and having voids formed therein, and a conductor layer adjacent to at least one main surface of the resin film in a stacking direction, wherein the position of the end face of the resin film on the conductor layer side is defined as a first position, a position away from the first position in the stacking direction by a distance of 1 / 3 of the thickness of the resin film is defined as a second position, and a position away from the second position in the stacking direction toward the opposite side of the first position by a distance of 1 / 3 of the thickness of the resin film is defined as a third position, and the voids are unevenly distributed between the first position and the second position such that the number of voids between the first position and the second position is greater than the number of voids between the second position and the third position.

[0008] The laminated substrate of the present invention is characterized by comprising the conductor layer-provided resin film of the present invention.

[0009] The method for producing a resin film with a conductor layer of the present invention comprises the steps of: preparing a laminate having the resin film and the conductor layer in a stacking direction by providing a conductor layer adjacent to at least one main surface of a resin film containing a thermoplastic resin; and providing voids inside the resin film by heat-treating the laminate, wherein in the step of providing voids, when the position of the end face of the resin film on the conductor layer side is defined as a first position, a position spaced 1 / 3 of the thickness of the resin film from the first position in the stacking direction is defined as a second position, and a position spaced 1 / 3 of the thickness of the resin film from the second position in the stacking direction toward the opposite side of the first position is defined as a third position, the voids are provided so as to be unevenly distributed between the first position and the second position such that the number of voids between the first position and the second position is greater than the number of voids between the second position and the third position. [Effects of the Invention]

[0010] According to the present invention, a resin film with a conductor layer, which contains a thermoplastic resin and can improve dielectric properties in the high frequency range, can be provided. Also, according to the present invention, a laminated substrate having the resin film with a conductor layer can be provided. Furthermore, according to the present invention, a method for producing the resin film with a conductor layer can be provided. [Brief explanation of the drawings]

[0011] [Figure 1] FIG. 1 is a cross-sectional view showing an example of a resin film with a conductor layer according to the present invention. [Figure 2] FIG. 2 is a cross-sectional view showing a process for producing a laminate in one example of the method for producing a resin film with a conductor layer of the present invention. [Figure 3] FIG. 3 is a cross-sectional view showing a process for producing a laminate in one example of the method for producing a resin film with a conductor layer of the present invention. [Figure 4] FIG. 4 is a cross-sectional view showing a process for producing a laminate in an example of the method for producing a resin film with a conductor layer of the present invention. [Figure 5] FIG. 5 is a cross-sectional view showing an example of a resin film with a conductor layer according to the present invention, which is different from that shown in FIG. [Figure 6] FIG. 6 is a cross-sectional view showing an example of a resin film with a conductor layer according to the present invention, which is different from the examples shown in FIGS. [Figure 7] FIG. 7 is a cross-sectional view showing an example of the laminated substrate of the present invention. [Figure 8] FIG. 8 is a cross-sectional view showing a process for producing a resin film with a conductor layer in an example of the method for producing a laminated substrate of the present invention. [Figure 9] FIG. 9 is a cross-sectional view showing a process for producing a resin film with a conductor layer in an example of the method for producing a laminated substrate of the present invention. [Figure 10] FIG. 10 is a cross-sectional view showing a process for producing a resin film with a conductor layer in an example of the method for producing a laminated substrate of the present invention. [Figure 11] FIG. 11 is a cross-sectional view showing a process of forming a via hole in an example of the method for producing a laminated substrate of the present invention. [Figure 12] FIG. 12 is a cross-sectional view showing a process of forming a via hole in an example of the method for producing a laminated substrate of the present invention. [Figure 13] FIG. 13 is a cross-sectional view showing a step of filling a conductive paste in an example of a method for producing a laminated substrate of the present invention. [Figure 14] FIG. 14 is a cross-sectional view showing a step of filling a conductive paste in an example of a method for producing a laminated substrate of the present invention. [Figure 15] FIG. 15 is a cross-sectional view showing a step of forming an interlayer connection conductor in an example of a method for producing a laminated substrate of the present invention. [Figure 16] FIG. 16 is a cross-sectional view showing an example of the laminated substrate of the present invention, which is different from that shown in FIG. [Figure 17] FIG. 17 is a cross-sectional view showing an example of the laminated substrate of the present invention, which is different from the examples shown in FIGS. [Figure 18]FIG. 18 is a cross-sectional view showing an example of the laminated substrate of the present invention, which is different from the examples shown in FIGS. 7, 16, and 17. In FIG. [Figure 19] FIG. 19 is a cross-sectional view showing an example of the laminated substrate of the present invention, which is different from the examples shown in FIGS. 7, 16, 17, and 18. In FIG. DETAILED DESCRIPTION OF THE INVENTION

[0012] The resin film with a conductor layer of the present invention, the laminated substrate of the present invention, and the method for producing the resin film with a conductor layer of the present invention will be described below. Note that the present invention is not limited to the following configurations and may be modified as appropriate within the scope of the present invention. Furthermore, the present invention also includes combinations of the individual preferred configurations described below.

[0013] The resin film with a conductor layer of the present invention comprises a resin film containing a thermoplastic resin and having voids formed therein, and a conductor layer adjacent to at least one main surface of the resin film in a stacking direction, wherein the position of the end face of the resin film on the conductor layer side is defined as a first position, a position away from the first position in the stacking direction by a distance of 1 / 3 of the thickness of the resin film is defined as a second position, and a position away from the second position in the stacking direction toward the opposite side of the first position by a distance of 1 / 3 of the thickness of the resin film is defined as a third position, and the voids are unevenly distributed between the first position and the second position such that the number of voids between the first position and the second position is greater than the number of voids between the second position and the third position.

[0014] FIG. 1 is a cross-sectional view showing an example of a resin film with a conductor layer according to the present invention.

[0015] A resin film 10 with a conductor layer shown in FIG. 1 has a resin film 1 and a conductor layer 2 in the stacking direction.

[0016] In this specification, the term "film" is synonymous with "sheet," and the two are not distinguished by thickness.

[0017] In this specification, the lamination direction corresponds to the direction along the thickness direction of the resin film that constitutes the conductor layer-attached resin film.

[0018] The resin film 1 has a first main surface 1a and a second main surface 1b that face each other in the thickness direction HD.

[0019] The thickness of the resin film 1 is preferably 10 μm or more and 250 μm or less.

[0020] The first direction MD and the second direction TD are included in the in-plane directions perpendicular to the thickness direction HD. More specifically, the first direction MD is a direction perpendicular to the thickness direction HD, and the second direction TD is a direction perpendicular to the thickness direction HD and the first direction MD. In other words, the thickness direction HD, the first direction MD, and the second direction TD are perpendicular to each other.

[0021] The conductor layer 2 is adjacent to at least one main surface side, here the first main surface 1a side, of the resin film 1. More specifically, the conductor layer 2 is provided on the first main surface 1a of the resin film 1.

[0022] Examples of materials that can be used to form the conductor layer 2 include copper, silver, aluminum, stainless steel, nickel, gold, and alloys containing at least one of these metals.

[0023] The conductor layer 2 is made of, for example, a metal foil, and is preferably made of copper foil among other metal foils. In this case, metals other than copper may be present on the surface of the copper foil.

[0024] The resin film 1 contains a thermoplastic resin.

[0025] Examples of thermoplastic resins contained in the resin film 1 include liquid crystal polymers (LCPs), fluororesins, thermoplastic polyimide resins, polyether ether ketone resins (PEEKs), polyphenylene sulfide resins (PPSs), cyclic polyolefin resins (COPs), and polyphenylene ether resins (PPEs).

[0026] The thermoplastic resin contained in the resin film 1 is preferably a liquid crystal polymer. That is, the resin film 1 is preferably a liquid crystal polymer film. Among thermoplastic resins, liquid crystal polymers have the properties of having a small dielectric constant and low moisture absorption, and therefore, in a laminated substrate manufactured using a liquid crystal polymer film, the effects of the liquid crystal polymer are easily exhibited, such as improved dielectric properties in the high frequency range and reduced changes in dielectric properties due to moisture absorption.

[0027] When a laminated substrate is manufactured using a liquid crystal polymer film and a conductor layer, for example, when via holes penetrating the liquid crystal polymer film are plated to form interlayer connection conductors connected to the conductor layer, stress applied from the liquid crystal polymer film can cause cracks in the interlayer connection conductors. Similarly, when a laminated substrate is manufactured by a batch lamination method using a structure in which via holes provided in a liquid crystal polymer film with a conductor layer are filled with conductive paste, stress applied from the liquid crystal polymer film can cause cracks in the interlayer connection conductors, which are solidified conductive paste. As a result, the connection reliability of the interlayer connection conductors in a laminated substrate manufactured using a liquid crystal polymer film can be reduced.

[0028] On the other hand, when the resin film 1 is a liquid crystal polymer film, the resin film 1 is decomposed in supercritical methanol. 13 In a C-NMR spectrum, when the integral value of the peak derived from the benzene ring is CA, the integral value of the peak derived from the naphthalene ring is CB, and the integral value of the peak derived from the carboxymethyl group is CC, it is preferable that (CA+CB) / CC is 1.25 or more and 1.65 or less.

[0029] In the liquid crystal polymer film, when (CA+CB) / CC is 1.65 or less, the linear expansion coefficient in the thickness direction can be reduced. Furthermore, when (CA+CB) / CC is 1.25 or more, the liquid crystal polymer film can be easily processed into a film state, and further, the processability when using the liquid crystal polymer film to manufacture a laminate substrate can be improved. Therefore, when (CA+CB) / CC is 1.25 or more and 1.65 or less, the linear expansion coefficient in the thickness direction can be reduced, and the processability when using the liquid crystal polymer film to manufacture a film state and further, the processability when using the liquid crystal polymer film to manufacture a laminate substrate can be improved.

[0030] When a laminated substrate having interlayer connection conductors is manufactured using a liquid crystal polymer film having a (CA+CB) / CC ratio of 1.25 or more and 1.65 or less, stress is less likely to be applied to the interlayer connection conductors from the liquid crystal polymer film due to the small linear expansion coefficient in the thickness direction of the liquid crystal polymer film. Therefore, in a laminated substrate manufactured using a liquid crystal polymer film having a (CA+CB) / CC ratio of 1.25 or more and 1.65 or less, cracks are less likely to occur in the interlayer connection conductors, and as a result, the connection reliability of the interlayer connection conductors is less likely to decrease.

[0031] Furthermore, when a laminated substrate is manufactured by a batch lamination method using a liquid crystal polymer film having a (CA+CB) / CC ratio of 1.25 or more and 1.65 or less, the temperature of the heat press does not need to be high, so the liquid crystal polymer is less likely to decompose during heat press processing.

[0032] In the case of a liquid crystal polymer film, if (CA+CB) / CC is smaller than 1.25, the constituent materials are hard and difficult to deform, making it difficult to process into a film, and furthermore, the processability when manufacturing a laminated substrate using the liquid crystal polymer film may be reduced.

[0033] In a liquid crystal polymer film, if (CA+CB) / CC is greater than 1.65, the linear expansion coefficient in the thickness direction becomes large, and therefore, in a laminated substrate having interlayer connection conductors manufactured using a liquid crystal polymer film, the connection reliability of the interlayer connection conductors may decrease.

[0034] In the liquid crystal polymer film, (CA+CB) / CC is preferably 1.35 or more and 1.65 or less.

[0035] (CA+CB) / CC is calculated as follows.

[0036] First, the conductor layer of the conductor-layer-attached liquid crystal polymer film is etched to remove the liquid crystal polymer film. Alternatively, the conductor-layer-attached liquid crystal polymer film is removed from a laminate substrate having the conductor-layer-attached liquid crystal polymer film, and then the conductor layer of the removed conductor-layer-attached liquid crystal polymer film is etched to remove the liquid crystal polymer film.

[0037] Next, the liquid crystal polymer film and methanol are placed in a high-temperature, high-pressure reactor. The reactor is then purged with argon and heated to obtain a solution containing the liquid crystal polymer film. If the high-temperature, high-pressure reactor is a closed system, simply heating the reactor to, for example, 240°C or higher vaporizes the methanol, causing the system to reach its critical pressure, resulting in the methanol entering a supercritical state. The solution is then vacuum-dried to remove the solvent, yielding a powder of the liquid crystal polymer film decomposed in supercritical methanol. The powder of the liquid crystal polymer film decomposed in deuterated methanol is then dissolved, for example, at a ratio of 0.02 g per 1 ml of deuterated methanol, to obtain a sample for NMR measurement.

[0038] Next, NMR measurement is performed on the NMR measurement sample, 13 Obtain a C-NMR spectrum; 13From the C-NMR spectrum, the integral value of the peak derived from the benzene ring, the integral value of the peak derived from the naphthalene ring, and the integral value of the peak derived from the carboxymethyl group are determined and designated as CA, CB, and CC, respectively.

[0039] Here, for example, when the liquid crystal polymer constituting the liquid crystal polymer film contains only type II wholly aromatic polyester, the peak derived from the benzene ring, more specifically, the peak derived from methyl p-hydroxybenzoate, corresponds to a peak with a chemical shift in the range of 113 ppm to 115 ppm (114 ± 1 ppm). Furthermore, the peak derived from the naphthalene ring, more specifically, the peak derived from methyl 6-hydroxy-2-naphthoate, corresponds to a peak with a chemical shift in the range of 107 ppm to 109 ppm (108 ± 1 ppm). Furthermore, the peak derived from the carboxymethyl group, more specifically, the peak derived from the methyl group from the ester, corresponds to a peak with a chemical shift in the range of 49 ppm to 51 ppm (50 ± 1 ppm).

[0040] From the CA, CB, and CC obtained above, (CA+CB) / CC is calculated.

[0041] Alternatively, CA, CB, and CC may be calculated as converted values when the integral value of the peak derived from deuterated methanol is set to 100, and then (CA+CB) / CC may be calculated.

[0042] The (CA+CB) / CC ratio can be controlled by, for example, using multiple types of wholly aromatic polyesters with different monomer primary structures as liquid crystal polymers and adjusting the blending ratio of these liquid crystal polymers during the production of the liquid crystal polymer film. Alternatively, a liquid crystal polymer having a monomer primary structure in which the (CA+CB) / CC ratio is in the range of 1.25 to 1.65 may be used during the production of the liquid crystal polymer film.

[0043] Further effects of a liquid crystal polymer film having a (CA+CB) / CC ratio of 1.25 or more and 1.65 or less will be described below.

[0044] A conventional method for reducing the linear expansion coefficient in the thickness direction of a liquid crystal polymer film is to form the film using a liquid crystal polymer with a small volume expansion coefficient when producing the liquid crystal polymer film. However, in addition to this method, the following method also exists.

[0045] Another conventional method is to produce a liquid crystal polymer film by using a mixed resin of a liquid crystal polymer and an inorganic filler.

[0046] However, because the surface of inorganic fillers is highly active, moisture is easily adsorbed onto the surface of inorganic fillers. Therefore, in laminated substrates manufactured using liquid crystal polymer films containing inorganic fillers, the dielectric properties are easily changed due to moisture absorption. To address this issue, the inorganic fillers are sometimes surface-treated with coupling agents or the like to reduce the surface activity of the inorganic fillers, but even with such surface treatment, moisture adsorption onto the inorganic filler surface cannot be sufficiently suppressed. Furthermore, the inclusion of inorganic fillers in liquid crystal polymer films tends to reduce the breaking elongation.

[0047] In contrast, a liquid crystal polymer film having a (CA+CB) / CC ratio of 1.65 or less can have a small linear expansion coefficient in the thickness direction. In other words, a liquid crystal polymer film having a (CA+CB) / CC ratio of 1.65 or less does not need to contain an inorganic filler in order to reduce the linear expansion coefficient in the thickness direction. This reduces the dielectric properties of a liquid crystal polymer film with a conductor layer having a liquid crystal polymer film with a (CA+CB) / CC ratio of 1.65 or less and a laminate substrate having the liquid crystal polymer film with the conductor layer, which are less likely to change due to moisture absorption. Furthermore, the breaking elongation of the liquid crystal polymer film is less likely to decrease.

[0048] Yet another conventional method involves irradiating a liquid crystal polymer film with ionizing radiation to crosslink the liquid crystal polymer.

[0049] However, in order to reduce the linear expansion coefficient of the liquid crystal polymer film in the thickness direction, it is necessary to irradiate the film with a high dose of ionizing radiation, which increases the production cost of the liquid crystal polymer film.

[0050] In contrast, a liquid crystal polymer film having a (CA+CB) / CC ratio of 1.65 or less can have a small linear expansion coefficient in the thickness direction. In other words, when producing a liquid crystal polymer film having a (CA+CB) / CC ratio of 1.65 or less, it is not necessary to irradiate the film with a high dose of ionizing radiation in order to reduce the linear expansion coefficient in the thickness direction. This reduces the production cost of the liquid crystal polymer film.

[0051] For liquid crystal polymer film, the powder of the decomposition product of the liquid crystal polymer film decomposed in supercritical methanol was dissolved in deuterated methanol at a ratio of 0.02 g per 1 ml of methanol. 13 In the C-NMR spectrum, when the integral value of the peak derived from deuterated methanol is taken as 100, the CA is preferably 1.05 or more and 1.80 or less.

[0052] In the liquid crystal polymer film, if the CA under the above conditions is smaller than 1.05, the storage modulus may become large.

[0053] In the liquid crystal polymer film, if the CA under the above conditions is greater than 1.80, the linear expansion coefficient in the thickness direction may become large.

[0054] For liquid crystal polymer film, the powder of the decomposition product of the liquid crystal polymer film decomposed in supercritical methanol was dissolved in deuterated methanol at a ratio of 0.02 g per 1 ml of methanol. 13 In the C-NMR spectrum, when the integral value of the peak derived from deuterated methanol is taken as 100, C is preferably 1.20 or more and 1.70 or less.

[0055] In the liquid crystal polymer film, if CB under the above conditions is smaller than 1.20, the linear expansion coefficient in the thickness direction may become large.

[0056] In the liquid crystal polymer film, if CB under the above conditions is larger than 1.70, the storage modulus may become large.

[0057] For liquid crystal polymer film, the powder of the decomposition product of the liquid crystal polymer film decomposed in supercritical methanol was dissolved in deuterated methanol at a ratio of 0.02 g per 1 ml of methanol. 13 In the C-NMR spectrum, when the integral value of the peak derived from deuterated methanol is taken as 100, CC is preferably 1.60 or more and 2.50 or less.

[0058] In the liquid crystal polymer film, if CC under the above conditions is less than 1.60, the storage modulus may become large.

[0059] In the liquid crystal polymer film, if CC under the above conditions is greater than 2.50, the linear expansion coefficient in the thickness direction may become large.

[0060] The peaks derived from deuterated methanol correspond to peaks in the chemical shift range of 47 ppm or more and 48 ppm or less (47.5±0.5 ppm).

[0061] The resin film 1 has holes 1h formed therein.

[0062] In the resin film 10 with a conductor layer, holes 1h are provided inside the resin film 1, thereby reducing the dielectric constant of the resin film 1. As a result, the dielectric properties of a laminated substrate manufactured using the resin film 10 with a conductor layer are improved in the high frequency range. Furthermore, when the resin film 1 is a liquid crystal polymer film, the dielectric properties of the laminated substrate in the high frequency range are significantly improved, in addition to the effects of the liquid crystal polymer.

[0063] In the resin film 10 with a conductor layer, when the position of the end face of the resin film 1 on the conductor layer 2 side, here the first main surface 1a, is defined as the first position E1, the position away from the first position E1 in the stacking direction by a distance of 1 / 3 of the thickness of the resin film 1 is defined as the second position E2, and the position away from the second position E2 in the stacking direction toward the opposite side of the first position E1 by a distance of 1 / 3 of the thickness of the resin film 1, is defined as the third position E3, the voids 1h are unevenly distributed between the first position E1 and the second position E2 so that the number of voids between the first position E1 and the second position E2 is greater than the number of voids between the second position E2 and the third position E3.

[0064] In the resin film 10 with a conductor layer, the holes 1h are unevenly distributed between the first position E1 and the second position E2 in the resin film 1 as described above, and therefore the holes 1h are unevenly distributed near the conductor layer 2. In a laminated substrate manufactured using the resin film 10 with a conductor layer, if the conductor layer 2 is a signal line that transmits signals, and the holes 1h are unevenly distributed near the conductor layer 2, in this case the signal line, the dielectric constant near the signal line decreases, which makes it easier to reduce transmission loss in the high frequency range and, as a result, makes it easier to improve transmission characteristics in the high frequency range.

[0065] In this specification, the second position in the resin film is defined by a plane extending in an in-plane direction perpendicular to the stacking direction at a position away from the interface between the resin film and the conductor layer included in the first position by a distance of 1 / 3 of the thickness of the resin film that overlaps the conductor layer in the stacking direction.

[0066] In this specification, the third position in the resin film is defined by a plane extending in an in-plane direction perpendicular to the stacking direction, at a position away from the second position toward the opposite side of the first position, a distance of 1 / 3 of the thickness of the resin film as when determining the second position.

[0067] The number of voids between the first and second positions is determined as follows. First, the resin film of a conductor-layered resin film or a laminated substrate having a conductor-layered resin film (described below) is checked in advance for the presence of voids when viewed from the thickness direction. Images of the cross section along the thickness direction when the region between the first and second positions is viewed from the in-plane direction are then taken with a scanning electron microscope (SEM). In this way, cross-sectional images of the region between the first and second positions in the resin film are taken at five to ten different in-plane positions. The size of each cross-sectional image is set to 75 μm long and 125 μm wide (e.g., the size of the field of view when viewed at 1000x magnification). All the taken cross-sectional images are then analyzed using image analysis software to count the number of voids in all the cross-sectional images. The average value per cross-sectional image (one field of view), calculated from the total number of voids obtained, is determined as the number of voids between the first and second positions.

[0068] The number of pores between the second position and the third position is determined in the same manner as the number of pores between the first position and the second position. If the presence of pores cannot be confirmed in all cross-sectional images (cross-sectional images at 5 or more locations and 10 or less locations) taken of the region between the second position and the third position on the resin film, the number of pores between the second position and the third position is determined to be 0.

[0069] In this specification, the phrase "voids are unevenly distributed between the first position and the second position" means that, unlike the multilayer wiring board described in Patent Document 1 (see Figure 1 of Patent Document 1), the number of voids between the first position and the second position is extremely greater than the number of voids between the second position and the third position, and preferably means that the number of voids between the second position and the third position is 1 / 5 or less of the number of voids between the first position and the second position.

[0070] In the resin film 1, when a position in the lamination direction away from the first position E1 by a distance of ¼ of the thickness of the resin film 1 is defined as a fourth position (not shown), and a position in the lamination direction away from the fourth position toward the opposite side of the first position E1 by a distance of ¼ of the thickness of the resin film 1 is defined as a fifth position (not shown), it is preferable that the holes 1h are unevenly distributed between the first position E1 and the fourth position so that the number of holes between the first position E1 and the fourth position is greater than the number of holes between the fourth position and the fifth position. In this case, the transmission characteristics in the high frequency range of a laminated substrate manufactured using the conductor layer-equipped resin film 10 are more likely to be improved.

[0071] On the other hand, if the voids 1h are not unevenly distributed between the first position E1 and the second position E2 but are present throughout the thickness direction HD of the resin film 1, the mechanical strength of the resin film 1 and, ultimately, the mechanical strength of the conductor-layer-equipped resin film 10 will decrease. From this perspective, it is preferable that there are substantially no voids 1h between the second position E2 and the third position E3. "There are substantially no voids between the second position and the third position" means that the number of voids between the second position and the third position is 5 or less, preferably 3 or less.

[0072] As shown in FIG. 1, the holes 1h may be present only between the first position E1 and the second position E2.

[0073] As described above, the conductor layer-equipped resin film 10 can realize a conductor layer-equipped resin film that contains a thermoplastic resin and can improve dielectric properties in the high frequency range.

[0074] The diameter of the holes 1h present between the first position E1 and the second position E2 is preferably 20 μm or less.

[0075] When the pore diameter of the pores 1h is 20 μm or less, the mechanical strength of the resin film 1, and therefore the mechanical strength of the conductor layer-attached resin film 10, is less likely to decrease.

[0076] On the other hand, if the voids 1h are unevenly distributed in the vicinity of the conductor layer 2, the voids 1h may reduce the adhesion between the resin film 1 and the conductor layer 2. In contrast, if the voids 1h have a diameter of 20 μm or less, even if the voids 1h are unevenly distributed in the vicinity of the conductor layer 2, the adhesion between the resin film 1 and the conductor layer 2 is less likely to reduce.

[0077] If the pore diameter of the pores 1h is larger than 20 μm, the mechanical strength of the resin film 1 and, in turn, the mechanical strength of the conductor layer-attached resin film 10 may decrease. Furthermore, if the pore diameter of the pores 1h is larger than 20 μm, the adhesion between the resin film 1 and the conductor layer 2 may decrease.

[0078] The diameter of the holes 1h is preferably 5 μm or more.

[0079] If the pore diameter of the pores 1h is smaller than 5 μm, the number of pores 1h required to achieve the same porosity will be too large compared to when the pore diameter of the pores 1h is 5 μm or greater. Therefore, when the resin film with a conductor layer or the laminated substrate having the resin film with a conductor layer is bent, the pores 1h may become a source of cracks, and as a result, the mechanical strength of the resin film with a conductor layer or the laminated substrate having the resin film with a conductor layer may be reduced.

[0080] The pore diameter of the pores present between the first and second positions is determined as follows. First, the pore area is confirmed in advance by viewing the resin film of a conductor-layered resin film or a laminated substrate having a conductor-layered resin film (described below) from the thickness direction. Then, an image of a cross section along the thickness direction when the region between the first and second positions is viewed from the in-plane direction is taken with a scanning electron microscope. In this way, cross-sectional images of the region between the first and second positions in the resin film are taken at five to ten different positions in the in-plane direction. The size of each cross-sectional image is set to 75 μm in length and 125 μm in width (e.g., the size of the field of view when viewed at 1000x magnification). Then, image analysis software is performed on all the taken cross-sectional images to measure the equivalent circle diameter of all the pores in all the cross-sectional images. The maximum value of the obtained measurements is determined as the pore diameter of the pores present between the first and second positions.

[0081] In the viscoelastic properties showing the relationship between the loss tangent and temperature of the resin film 1, the integral value of the loss tangent in the temperature range from 40° C. to the melting point of the thermoplastic resin contained in the resin film is preferably 29.7 or less.

[0082] The integral value of the loss tangent of a resin film in the temperature range from 40°C to the melting point of the thermoplastic resin contained in the resin film can be determined as follows. First, the conductor layer of a resin film with a conductor layer is etched to remove the resin film. Alternatively, the resin film with a conductor layer is removed from a laminate substrate having the resin film with a conductor layer, as described below, and then the conductor layer of the removed resin film with a conductor layer is etched to remove the resin film. Next, a dynamic viscoelasticity measuring device is used to measure the temperature dependence of the loss tangent of the resin film in a temperature range from at least 40°C to the melting point of the thermoplastic resin contained in the resin film, thereby obtaining a graph showing the relationship between the loss tangent of the resin film and temperature. The integral value of the loss tangent is then determined by integrating the graph showing the relationship between the loss tangent of the resin film and temperature in the temperature range from 40°C to the melting point of the thermoplastic resin contained in the resin film.

[0083] The melting point of the thermoplastic resin contained in the resin film is determined as follows. First, the resin film is heated using a differential scanning calorimeter until it is completely melted. Next, the resulting melt is cooled and then heated again. The temperature corresponding to the endothermic peak observed during this heating process is determined as the melting point of the thermoplastic resin contained in the resin film. Note that if the endothermic peak is difficult to observe using the above-mentioned method, the melting point of the thermoplastic resin contained in the resin film is determined by texture observation under crossed Nicols conditions using a polarizing microscope.

[0084] When the integral value of the loss tangent of the resin film 1 under the above conditions is 29.7 or less, the resin film 1 has a small viscous component in the loss tangent of its viscoelastic properties and is less likely to soften even at high temperatures. The effects obtained when the resin film 1 has such properties will be described below with reference to an example of a method for producing the conductor layer-equipped resin film 10 shown in FIG.

[0085] The method for producing a resin film with a conductor layer of the present invention comprises the steps of: preparing a laminate having the resin film and the conductor layer in a stacking direction by providing a conductor layer adjacent to at least one main surface of a resin film containing a thermoplastic resin; and providing voids inside the resin film by heat-treating the laminate, wherein in the step of providing voids, when the position of the end face of the resin film on the conductor layer side is defined as a first position, a position spaced 1 / 3 of the thickness of the resin film from the first position in the stacking direction is defined as a second position, and a position spaced 1 / 3 of the thickness of the resin film from the second position in the stacking direction toward the opposite side of the first position is defined as a third position, the voids are provided so as to be unevenly distributed between the first position and the second position such that the number of voids between the first position and the second position is greater than the number of voids between the second position and the third position.

[0086] <Step of Producing Laminate> 2, 3, and 4 are cross-sectional views schematically illustrating steps of producing a laminate in one example of the method for producing a resin film with a conductor layer of the present invention.

[0087] First, a resin film 1 containing a thermoplastic resin is prepared as shown in Fig. 2. As shown in Fig. 2, a first main surface 1a of the resin film 1 is not a completely flat surface but is a rough surface with projections and depressions.

[0088] The resin film 1, for example, a liquid crystal polymer film, is produced using a resin material containing a liquid crystal polymer by a known method such as that described in JP-A-2-3430. As a method for producing the resin film 1, for example, a liquid crystal polymer film, T-die film-forming and stretching methods, laminate stretching methods, inflation methods, etc. are industrially advantageous.

[0089] Furthermore, as shown in FIG. 3, a conductor layer 2 is prepared.

[0090] 4, a conductor layer 2 is provided adjacent to at least one main surface side of the resin film 1, in this case the first main surface 1a side, to produce a laminate 15 having the resin film 1 and the conductor layer 2 in the stacking direction. At this time, for example, the conductor layer 2 is pressure-bonded to the first main surface 1a of the resin film 1.

[0091] In the laminate 15, the first main surface 1a of the resin film 1 is a rough surface, and therefore a space 15h is provided between the resin film 1 and the conductor layer 2 in the in-plane direction.

[0092] In the step of producing the laminate, the arithmetic mean height Sa of the main surface of the resin film 1 on the side where the conductor layer 2 is provided, here the first main surface 1a, is preferably 240 nm or more.

[0093] When the arithmetic mean height Sa of the main surface of the resin film 1 on which the conductor layer 2 is provided, here the first main surface 1a, is 240 nm or more, the spaces 15h are more likely to be provided over a wider area between the resin film 1 and the conductor layer 2. As a result, in the step of providing voids described below, voids resulting from the spaces 15h are more likely to be provided over a wider area in the resin film 1 near the conductor layer 2. Therefore, in the resin film with a conductor layer obtained later, the number of voids in the resin film 1 near the conductor layer 2 is more likely to be large.

[0094] In the step of producing the laminate, the arithmetic mean height Sa of the main surface of the resin film 1 on the side where the conductor layer 2 is provided, here the first main surface 1a, is preferably 350 nm or less.

[0095] The arithmetic mean height Sa of the principal surface of the resin film on the side where the conductor layer is to be provided is determined as follows: First, a non-contact laser microscope is used to capture images of nine fields of view at a magnification of 20x of the area of the principal surface of the resin film where the conductor layer is to be provided. Then, image analysis software is performed on all the captured images to measure the arithmetic mean height Sa of the principal surface of the resin film in each image, and the maximum value of the obtained measurements is determined to be the arithmetic mean height Sa of the principal surface of the resin film on the side where the conductor layer is to be provided.

[0096] <Step of forming holes> The laminate 15 is heat-treated to provide voids inside the resin film 1. When the laminate 15 is heat-treated, the resin film 1 flows, thereby incorporating spaces 15h inside the resin film 1. As a result, voids resulting from the spaces 15h are provided inside the resin film 1. More specifically, as shown in FIG. 1 , in the resin film 1, the position of the end face of the resin film 1 on the conductor layer 2 side (here, the first main surface 1a) is defined as a first position E1, a position spaced 1 / 3 of the thickness of the resin film 1 from the first position E1 in the stacking direction is defined as a second position E2, and a position spaced 1 / 3 of the thickness of the resin film 1 from the second position E2 toward the opposite side of the first position E1 in the stacking direction is defined as a third position E3. The voids 1h are distributed unevenly between the first position E1 and the second position E2 so that the number of voids between the first position E1 and the second position E2 is greater than the number of voids between the second position E2 and the third position E3.

[0097] In this manner, the conductor layer-attached resin film 10 shown in FIG. 1 is produced.

[0098] As described above, when the viscoelastic properties of the resin film 1, which indicate the relationship between the loss tangent and temperature, are such that the integral value of the loss tangent in the temperature range from 40°C to the melting point of the thermoplastic resin is 29.7 or less, the resin film 1 has a small viscous component in the loss tangent of the viscoelastic properties and is resistant to softening even at high temperatures. When the resin film 1 has such properties, the resin film 1 is resistant to softening, and the shape of the irregularities provided on the first principal surface 1a of the resin film 1 is easily maintained. Therefore, even when the laminate 15 is heat-treated in the above-described void-providing step, gas contained in the spaces 15h originating from the irregularities provided on the first principal surface 1a of the resin film 1 is less likely to escape to the outside of the resin film 1. As a result, the gas contained in the spaces 15h is easily trapped inside the resin film 1, and as shown in FIG. 1, voids 1h are easily formed inside the resin film 1, more specifically, near the conductor layer 2.

[0099] In the resin film with a conductor layer of the present invention, the conductor layer may be in a planar form that spreads over the entire surface, as in the resin film with a conductor layer 10 shown in Figure 1, but the conductor layer may also be in a patterned form patterned into wiring or the like.

[0100] FIG. 5 is a cross-sectional view showing an example of a resin film with a conductor layer according to the present invention, which is different from that shown in FIG.

[0101] A resin film 10' with a conductor layer shown in FIG. 5 has a resin film 1 and a conductor layer 2' in the stacking direction.

[0102] The conductor layer 2' is adjacent to the first main surface 1a side of the resin film 1. More specifically, the conductor layer 2' is provided on a part of the first main surface 1a of the resin film 1.

[0103] The conductor layer 2' is formed, for example, by pressure-bonding a conductor layer to the first main surface 1a of the resin film 1 and then etching the conductor layer into a pattern shape. Alternatively, the conductor layer 2' may be formed by pressure-bonding a pre-patterned conductor layer to the first main surface 1a of the resin film 1.

[0104] In the resin film 10' with a conductor layer, when the position of the end face of the resin film 1 on the conductor layer 2' side, here the position of the first main surface 1a, is defined as the first position E1, the position away from the first position E1 in the stacking direction by a distance of 1 / 3 of the thickness of the resin film 1 is defined as the second position E2, and the position away from the second position E2 in the stacking direction toward the opposite side of the first position E1 by a distance of 1 / 3 of the thickness of the resin film 1, is defined as the third position E3, the voids 1h are unevenly distributed between the first position E1 and the second position E2 so that the number of voids between the first position E1 and the second position E2 is greater than the number of voids between the second position E2 and the third position E3.

[0105] In the conductor layer-equipped resin film 10', the voids 1h are present not only in the vicinity of the region where the conductor layer 2' is provided but also in the vicinity of the region where the conductor layer 2' is not provided on the first main surface 1a of the resin film 1. That is, in the conductor layer-equipped resin film 10', the voids 1h are present not only in the region that overlaps with the conductor layer 2' when viewed from the thickness direction HD but also in the region that does not overlap with the conductor layer 2' when viewed from the thickness direction HD.

[0106] The resin film with a conductor layer of the present invention may have a conductor layer adjacent to only one main surface of the resin film, as in the resin film with a conductor layer 10 shown in Figure 1, but may also have, in addition to the conductor layer adjacent to one main surface of the resin film, another conductor layer adjacent to the other main surface of the resin film.

[0107] FIG. 6 is a cross-sectional view showing an example of a resin film with a conductor layer according to the present invention, which is different from the examples shown in FIGS.

[0108] A resin film 10'' with a conductor layer shown in FIG. 6 has a resin film 1'', a conductor layer 2 and a conductor layer 2'' arranged in the stacking direction.

[0109] The resin film 1'' has a first main surface 1a'' and a second main surface 1b'' that face each other in the thickness direction HD.

[0110] The conductor layer 2 is adjacent to the first main surface 1a'' side of the resin film 1''. More specifically, the conductor layer 2 is provided on the first main surface 1a'' of the resin film 1''.

[0111] The conductor layer 2'' is adjacent to the second main surface 1b'' side of the resin film 1''. More specifically, the conductor layer 2'' is provided on the second main surface 1b'' of the resin film 1''.

[0112] The resin film 1'' contains a thermoplastic resin.

[0113] The resin film 1'' has holes 1h formed therein.

[0114] In the conductor layer-equipped resin film 10'', the position of the end face of the resin film 1'' on the conductor layer 2 side, here the position of the first main surface 1a'', is defined as the first position E1, the position away from the first position E1 in the stacking direction by a distance of 1 / 3 of the thickness of the resin film 1'' is defined as the second position E2, and the position away from the second position E2 in the stacking direction toward the opposite side from the first position E1 by a distance of 1 / 3 of the thickness of the resin film 1'' is defined as the third position E3. The voids 1h are unevenly distributed between the first position E1 and the second position E2 so that the number of voids between the first position E1 and the second position E2 is greater than the number of voids between the second position E2 and the third position E3. In other words, in the conductor layer-equipped resin film 10'', the voids 1h are unevenly distributed near the conductor layer 2.

[0115] In the conductor layer-equipped resin film 10'', in addition to the voids 1h, voids 1h'' are provided inside the resin film 1''. In the conductor layer-equipped resin film 10'', the position of the end face of the resin film 1'' on the conductor layer 2'' side (here, the position of the second main surface 1b'') is defined as a first position E1'', a position away from the first position E1'' in the stacking direction by a distance of one-third of the thickness of the resin film 1'' is defined as a second position E2'', and a position away from the second position E2'' in the stacking direction toward the opposite side from the first position E1'' by a distance of one-third of the thickness of the resin film 1'' is defined as a third position E3''. The voids 1h'' are unevenly distributed between the first position E1'' and the second position E2'' such that the number of voids between the first position E1'' and the second position E2'' is greater than the number of voids between the second position E2'' and the third position E3''. That is, in the conductor layer-equipped resin film 10'', the voids 1h'' are unevenly distributed near the conductor layer 2''.

[0116] The laminated substrate of the present invention is characterized by comprising the conductor layer-provided resin film of the present invention.

[0117] FIG. 7 is a cross-sectional view showing an example of the laminated substrate of the present invention.

[0118] 7 includes a resin film with a conductor layer 10A, a resin film with a conductor layer 10B, and a resin film with a conductor layer 10C, stacked in this order in the stacking direction. That is, in the laminated substrate 50, the resin film with a conductor layer 10A, the resin film with a conductor layer 10B, and the resin film with a conductor layer 10C are stacked in this order in the stacking direction.

[0119] The conductor layer-attached resin film 10A includes a resin film 1A and a conductor layer 2A.

[0120] The resin film 1A has a first main surface 1Aa and a second main surface 1Ab that face each other in the thickness direction HD.

[0121] The conductor layer 2A is adjacent to the first main surface 1Aa of the resin film 1A. The conductor layer 2A is also adjacent to the second main surface 1Bb of the resin film 1B, which will be described later.

[0122] The resin film 1A contains a thermoplastic resin.

[0123] The resin film 1A has holes 1Ah formed therein.

[0124] In the conductor layer-equipped resin film 10A, the position of the end face of the resin film 1A on the conductor layer 2A side (here, the first main surface 1Aa) is defined as a first position EA1, a position away from the first position EA1 in the stacking direction by a distance of one-third of the thickness of the resin film 1A is defined as a second position EA2, and a position away from the second position EA2 in the stacking direction toward the opposite side from the first position EA1 by a distance of one-third of the thickness of the resin film 1A is defined as a third position EA3. The pores 1Ah are unevenly distributed between the first position EA1 and the second position EA2 such that the number of pores between the first position EA1 and the second position EA2 is greater than the number of pores between the second position EA2 and the third position EA3. That is, in the conductor layer-equipped resin film 10A, the pores 1Ah are unevenly distributed near the conductor layer 2A.

[0125] The conductor layer-attached resin film 10B has a resin film 1B, a conductor layer 2B, a conductor layer 2B', and a conductor layer 2B''.

[0126] The resin film 1B has a first main surface 1Ba and a second main surface 1Bb that face each other in the thickness direction HD.

[0127] The conductor layer 2B, the conductor layer 2B', and the conductor layer 2B'' are adjacent to the first main surface 1Ba side of the resin film 1B. The conductor layer 2B, the conductor layer 2B', and the conductor layer 2B'' are also adjacent to the second main surface 1Cb side of the resin film 1C described later.

[0128] The resin film 1B contains a thermoplastic resin.

[0129] The resin film 1B has holes 1Bh formed therein.

[0130] In the conductor layer-equipped resin film 10B, when the position of the end face of the resin film 1B facing the conductor layer 2B, the conductor layer 2B', and the conductor layer 2B" (here, the first main surface 1Ba) is defined as a first position EB1, a position away from the first position EB1 by a distance of one-third of the thickness of the resin film 1B in the stacking direction is defined as a second position EB2, and a position away from the second position EB2 toward the opposite side from the first position EB1 by a distance of one-third of the thickness of the resin film 1B in the stacking direction is defined as a third position EB3, the voids 1Bh are unevenly distributed between the first position EB1 and the second position EB2 such that the number of voids between the first position EB1 and the second position EB2 is greater than the number of voids between the second position EB2 and the third position EB3. That is, in the conductor layer-equipped resin film 10B, the voids 1Bh are unevenly distributed near the conductor layer 2B, the conductor layer 2B', and the conductor layer 2B".

[0131] In the resin film 10B with a conductor layer, when viewed in a cross section along the stacking direction and an in-plane direction perpendicular to the stacking direction, as shown in Figure 7, it is preferable that the voids 1Bh are present so as to extend from the main surface (here, the bottom surface) in the stacking direction of the conductor layer 2B, the conductor layer 2B', and the conductor layer 2B'' to the side surface (here, the left side surface and the right side surface) in the in-plane direction of the conductor layer 2B, the conductor layer 2B', and the conductor layer 2B''.

[0132] The conductor layer-attached resin film 10C includes a resin film 1C and a conductor layer 2C.

[0133] The resin film 1C has a first main surface 1Ca and a second main surface 1Cb that face each other in the thickness direction HD.

[0134] The conductor layer 2C is adjacent to the first main surface 1Ca side of the resin film 1C.

[0135] The resin film 1C contains a thermoplastic resin.

[0136] The resin film 1C has holes 1Ch formed therein.

[0137] In the conductor layer-equipped resin film 10C, the position of the end face of the resin film 1C on the conductor layer 2C side (here, the first main surface 1Ca) is defined as a first position EC1, a position away from the first position EC1 by a distance of one-third of the thickness of the resin film 1C in the stacking direction is defined as a second position EC2, and a position away from the second position EC2 in the stacking direction toward the opposite side from the first position EC1 by a distance of one-third of the thickness of the resin film 1C is defined as a third position EC3. The pores 1Ch are unevenly distributed between the first position EC1 and the second position EC2 such that the number of pores between the first position EC1 and the second position EC2 is greater than the number of pores between the second position EC2 and the third position EC3. That is, in the conductor layer-equipped resin film 10C, the pores 1Ch are unevenly distributed near the conductor layer 2C.

[0138] The conductor layer 2B is preferably provided across the interface between the resin film 1B and the resin film 1C, as shown in Fig. 7. This allows the interface between the conductor layer 2B and the resin film 1B and the interface between the conductor layer 2B and the resin film 1C to be shifted in the stacking direction from the interface between the resin film 1B and the resin film 1C, thereby suppressing peeling at the interface between the conductor layer 2B and the resin film 1B and the interface between the conductor layer 2B and the resin film 1C.

[0139] Like the conductor layer 2B, the conductor layer 2B' and the conductor layer 2B'' are preferably provided across the interface between the resin film 1B and the resin film 1C.

[0140] 7 shows the interface between resin film 1B and resin film 1C, but in reality, this interface does not have to be clearly visible. When the interface between resin film 1B and resin film 1C is not clearly visible, in a cross section along the stacking direction as shown in FIG. 7, a plane that passes through the center in the stacking direction of the cross section of conductor layer 2B and extends along an in-plane direction perpendicular to the stacking direction is considered to be the interface between resin film 1B and resin film 1C.

[0141] In the laminated substrate 50, the dielectric properties in the high frequency range are improved because pores are provided inside the resin films 1A, 1B, and 1C. Furthermore, when the resin films 1A, 1B, and 1C are liquid crystal polymer films, the dielectric properties of the laminated substrate 50 in the high frequency range are significantly improved, in addition to the effects of the liquid crystal polymer.

[0142] As described above, in the resin film with conductor layer 10A, the resin film with conductor layer 10B, and the resin film with conductor layer 10C, pores are concentrated near the conductor layer, similar to the resin film with conductor layer 10. Therefore, when the conductor layer is a signal line for transmitting a signal, in the laminate substrate 50 manufactured using the resin film with conductor layer 10A, the resin film with conductor layer 10B, and the resin film with conductor layer 10C, the dielectric constant is reduced near the signal line, similar to the laminate substrate manufactured using the resin film with conductor layer 10, and therefore transmission loss in the high frequency range is likely to be reduced, and as a result, transmission characteristics in the high frequency range are likely to be improved.

[0143] In all of the conductor layer-equipped resin films 10A, 10B, and 10C, when the first position, second position, and third position are defined as described above, it is preferable that the voids are unevenly distributed between the first position and the second position, but in some of the conductor layer-equipped resin films, the voids may be unevenly distributed between the first position and the second position. In other words, as long as the laminated substrate 50 has at least one conductor layer-equipped resin film in which the voids are unevenly distributed between the first position and the second position, the laminated substrate 50 may have a conductor layer-equipped resin film in which the voids are present other than between the first position and the second position, or may have a conductor layer-equipped resin film in which the voids are not provided inside the resin film.

[0144] The preferred features of the conductor layer-equipped resin film 10A, the conductor layer-equipped resin film 10B, and the conductor layer-equipped resin film 10C are the same as the preferred features of the above-mentioned conductor layer-equipped resin film 10. In other words, the preferred features of the resin film 1A, the resin film 1B, and the resin film 1C are the same as the preferred features of the above-mentioned resin film 1.

[0145] The thicknesses of resin film 1A, resin film 1B, and resin film 1C may be the same as one another, may be different from one another, or may be partially different as shown in FIG.

[0146] The constituent materials of conductor layer 2A, conductor layer 2B, conductor layer 2B', conductor layer 2B'', and conductor layer 2C are similar to the constituent materials of conductor layer 2, and include, for example, copper, silver, aluminum, stainless steel, nickel, gold, and alloys containing at least one of these metals.

[0147] Like the conductor layer 2, the conductor layer 2A, the conductor layer 2B, the conductor layer 2B', the conductor layer 2B'', and the conductor layer 2C are made of, for example, a metal foil, and among metal foils, it is preferable that they are made of copper foil. In this case, a metal other than copper may be present on the surface of the copper foil.

[0148] The constituent materials of the conductor layer 2A, the conductor layer 2B, the conductor layer 2B', the conductor layer 2B'', and the conductor layer 2C are preferably the same as one another, but may be different from one another or may be partially different from one another.

[0149] The thicknesses of the conductor layer 2A, the conductor layer 2B, the conductor layer 2B', the conductor layer 2B'', and the conductor layer 2C may be the same as each other as shown in FIG. 7, or may be different from each other, or may be partially different.

[0150] As shown in FIG. 7, it is preferable that the laminated substrate 50 further has an interlayer connection conductor that penetrates the resin film in the stacking direction but does not penetrate the conductor layer in the stacking direction, and is arranged to be connected to the conductor layer.

[0151] The laminated substrate 50 shown in FIG. 7 further includes an interlayer connection conductor 20A, an interlayer connection conductor 20B, an interlayer connection conductor 20C, and an interlayer connection conductor 20D.

[0152] The interlayer connection conductor 20A is provided so as to penetrate the resin film 1B in the stacking direction but not the conductor layer 2B' in the stacking direction, and to be connected to the conductor layer 2B'. More specifically, the interlayer connection conductor 20A penetrates the resin film 1B in the stacking direction and is connected to the conductor layer 2B' on the first main surface 1Ba side of the resin film 1B. The interlayer connection conductor 20A is also connected to the conductor layer 2A on the second main surface 1Bb side of the resin film 1B. In other words, the conductor layer 2A and the conductor layer 2B' are electrically connected via the interlayer connection conductor 20A.

[0153] The interlayer connection conductor 20B is provided at a position spaced apart from the interlayer connection conductor 20A so as to penetrate the resin film 1B in the stacking direction but not through the conductor layer 2B'' in the stacking direction, so as to be connected to the conductor layer 2B''. More specifically, the interlayer connection conductor 20B is provided at a position spaced apart from the interlayer connection conductor 20A so as to penetrate the resin film 1B in the stacking direction and to be connected to the conductor layer 2B'' on the first main surface 1Ba side of the resin film 1B. Furthermore, the interlayer connection conductor 20B is connected to the conductor layer 2A on the second main surface 1Bb side of the resin film 1B, at a position spaced apart from the interlayer connection conductor 20A. In other words, the conductor layer 2A and the conductor layer 2B'' are electrically connected via the interlayer connection conductor 20B.

[0154] The interlayer connection conductor 20C is provided so as to penetrate the resin film 1C in the stacking direction but not the conductor layer 2C in the stacking direction, so as to be connected to the conductor layer 2C. More specifically, the interlayer connection conductor 20C penetrates the resin film 1C in the stacking direction and is connected to the conductor layer 2C on the first main surface 1Ca side of the resin film 1C. The interlayer connection conductor 20C is also connected to the conductor layer 2B' on the second main surface 1Cb side of the resin film 1C. In other words, the conductor layer 2B' and the conductor layer 2C are electrically connected via the interlayer connection conductor 20C.

[0155] The interlayer connection conductor 20D is provided at a position spaced apart from the interlayer connection conductor 20C, penetrating the resin film 1C in the stacking direction but not penetrating the conductor layer 2C in the stacking direction, so as to be connected to the conductor layer 2C. More specifically, the interlayer connection conductor 20D is connected to the conductor layer 2C on the first main surface 1Ca side of the resin film 1C, while penetrating the resin film 1C in the stacking direction, at a position spaced apart from the interlayer connection conductor 20C. Furthermore, the interlayer connection conductor 20D is connected to the conductor layer 2B" on the second main surface 1Cb side of the resin film 1C, at a position spaced apart from the interlayer connection conductor 20C. In other words, the conductor layer 2B" and the conductor layer 2C are electrically connected via the interlayer connection conductor 20D.

[0156] In this way, in the laminated substrate 50, the conductor layer 2A and the conductor layer 2C are electrically connected via the interlayer connection conductor 20A, the conductor layer 2B', and the interlayer connection conductor 20C. In addition, in the laminated substrate 50, the conductor layer 2A and the conductor layer 2C are also electrically connected via the interlayer connection conductor 20B, the conductor layer 2B'', and the interlayer connection conductor 20D.

[0157] The interlayer connection conductor 20A is formed, for example, by plating the inner wall of a via hole that penetrates the resin film 1B in the thickness direction HD but reaches the conductor layer 2B' without penetrating the conductor layer 2B' in the thickness direction HD, or by filling it with a conductive paste and then performing a heat treatment.

[0158] The interlayer connection conductors 20B, 20C, and 20D are formed in the same manner as the interlayer connection conductor 20A, except that they are formed at different positions.

[0159] When the interlayer connection conductors 20A, 20B, 20C, and 20D are formed by plating, examples of metals constituting each interlayer connection conductor include copper, tin, silver, etc., and among these, copper is preferred.

[0160] When interlayer connection conductors 20A, 20B, 20C, and 20D are formed by heat treatment of a conductive paste, examples of metals contained in each interlayer connection conductor include copper, tin, and silver. Among these, each interlayer connection conductor preferably contains copper, and more preferably contains copper and tin. For example, when interlayer connection conductor 20A contains copper and tin and conductor layer 2B' is made of copper foil, interlayer connection conductor 20A and conductor layer 2B' undergo an alloying reaction at low temperatures, making electrical conduction between them easier. The same applies to other combinations of interlayer connection conductors and conductor layers.

[0161] When the interlayer connection conductors 20A, 20B, 20C, and 20D are formed by heat treatment of a conductive paste, the resin contained in each interlayer connection conductor preferably includes at least one thermosetting resin selected from the group consisting of epoxy resin, phenolic resin, polyimide resin, silicone resin or modified resin thereof, and acrylic resin, or at least one thermoplastic resin selected from the group consisting of polyamide resin, polystyrene resin, polymethacrylic resin, polycarbonate resin, and cellulose-based resin.

[0162] The laminated substrate 50 is used, for example, as an electronic circuit board.

[0163] In the laminated substrate 50, the conductor layer 2B may be a signal line that transmits a signal. That is, the laminated substrate 50 may have the conductor layer 2B as a signal line that transmits a signal. In this case, the laminated substrate 50 forms a transmission line.

[0164] In the laminated substrate 50, when the conductor layer 2B is a signal line that transmits signals, as shown in Figure 7, when viewed in a cross section along the stacking direction and an in-plane direction perpendicular to the stacking direction, it is preferable that the voids 1Bh are present so as to wrap around from the main surface (here, the bottom surface) of the conductor layer 2B in the stacking direction to the side surfaces (here, the left and right sides) of the conductor layer 2B in the in-plane direction.

[0165] When the conductor layer 2B functions as a signal line to transmit signals, an electric field tends to concentrate at the corners of the conductor layer 2B. In contrast, if the air holes 1Bh are present so as to extend from the main surface of the conductor layer 2B in the stacking direction to the side surface of the conductor layer 2B in the in-plane direction, the air holes 1Bh will be present so as to cover the corners of the conductor layer 2B, which tends to reduce transmission loss in the high frequency range and, as a result, tends to improve transmission characteristics in the high frequency range.

[0166] The laminated substrate 50 may have a conductor layer 2B as a signal line for transmitting a signal, and may have conductor layers 2A and 2C as ground electrodes, in which case the laminated substrate 50 forms a stripline-type transmission line.

[0167] When the laminated substrate 50 constitutes the above-mentioned transmission line, the conductor layer 2B may be a signal line that transmits a high-frequency signal.

[0168] When the laminate substrate 50 forms a transmission line, the holes 1Bh are unevenly distributed in the conductor layer 2B, i.e., in the vicinity of the signal line, reducing the dielectric constant in the vicinity of the signal line. Therefore, when the laminate substrate 50 forms a transmission line, transmission loss in the high frequency range tends to be reduced, and as a result, transmission characteristics in the high frequency range tend to be improved.

[0169] The laminated substrate 50 is manufactured, for example, by the following method.

[0170] <Process for producing a resin film with a conductor layer> 8, 9, and 10 are cross-sectional views schematically illustrating steps of producing a resin film with a conductor layer in one example of a method for producing a laminated substrate of the present invention.

[0171] As shown in FIG. 8, a conductor layer-attached resin film 10A is produced in which a conductor layer 2A is provided adjacent to the first main surface 1Aa of a resin film 1A.

[0172] The conductor layer-equipped resin film 10A is produced, for example, in the same manner as the conductor layer-equipped resin film 10. As a result, in the conductor layer-equipped resin film 10A, the holes 1Ah are provided so as to be unevenly distributed near the conductor layer 2A.

[0173] As shown in FIG. 9, a conductor layer-attached resin film 10B is produced in which a conductor layer 2B, a conductor layer 2B', and a conductor layer 2B'' are provided adjacent to the first main surface 1Ba of the resin film 1B.

[0174] The conductor layer-equipped resin film 10B is produced, for example, in the same manner as the conductor layer-equipped resin film 10. As a result, in the conductor layer-equipped resin film 10B, the pores 1Bh are provided so as to be unevenly distributed near the conductor layer 2B, the conductor layer 2B', and the conductor layer 2B''.

[0175] When producing the resin film 10B with a conductor layer, for example, a conductor layer is pressure-bonded to the first main surface 1Ba of the resin film 1B, and then the conductor layer is etched to pattern the conductor layer 2B, conductor layer 2B', and conductor layer 2B''. Alternatively, the conductor layer 2B, conductor layer 2B', and conductor layer 2B'' are prepared in advance, and each conductor layer is pressure-bonded to the first main surface 1Ba of the resin film 1B.

[0176] As shown in FIG. 10, a conductor layer-attached resin film 10C is produced in which a conductor layer 2C is provided adjacent to the first main surface 1Ca of a resin film 1C.

[0177] The conductor layer-equipped resin film 10C is produced, for example, in the same manner as the conductor layer-equipped resin film 10. As a result, in the conductor layer-equipped resin film 10C, the holes 1Ch are provided so as to be unevenly distributed near the conductor layer 2C.

[0178] <Process for forming via holes> 11 and 12 are cross-sectional views showing a process of forming via holes in an example of a method for producing a laminated substrate according to the present invention.

[0179] 11, a via hole 21A is formed in a conductor layer-equipped resin film 10B so as to penetrate the resin film 1B in the thickness direction HD but reach the conductor layer 2B' without penetrating the conductor layer 2B' in the thickness direction HD, thereby exposing a part of the conductor layer 2B' from the via hole 21A.

[0180] Furthermore, a via hole 21B is formed in the conductor layer-equipped resin film 10B at a position spaced apart from the position where the via hole 21A is to be formed, so as to penetrate the resin film 10B in the thickness direction HD but not the conductor layer 2B'' in the thickness direction HD, and reach the conductor layer 2B''. As a result, a part of the conductor layer 2B'' is exposed from the via hole 21B.

[0181] In this way, the via holes 21A and 21B are formed in the conductor layer-equipped resin film 10B. At this time, the via holes 21A and 21B may be formed at the same time or at different times.

[0182] 12, a via hole 21C is formed in a conductor layer-equipped resin film 10C so as to penetrate the resin film 1C in the thickness direction HD but reach the conductor layer 2C without penetrating the conductor layer 2C in the thickness direction HD, thereby exposing a part of the conductor layer 2C from the via hole 21C.

[0183] Furthermore, a via hole 21D is formed in the conductor layer-included resin film 10C at a position spaced apart from the position where the via hole 21C is to be formed, so as to penetrate the resin film 1C in the thickness direction HD but not the conductor layer 2C in the thickness direction HD, and reach the conductor layer 2C, thereby exposing a part of the conductor layer 2C from the via hole 21D.

[0184] In this way, the via holes 21C and 21D are formed in the conductor layer-equipped resin film 10C. At this time, the via holes 21C and 21D may be formed at the same time or at different times.

[0185] When forming the via holes 21A, 21B, 21C, and 21D, it is preferable to irradiate the conductor layer-attached resin film with laser light from the resin film side.

[0186] <Process of filling conductive paste> 13 and 14 are cross-sectional views schematically illustrating a step of filling a conductive paste in an example of a method for producing a laminated substrate of the present invention.

[0187] 13, in a resin film 10B with a conductor layer, a conductive paste 22A is filled into a via hole 21A. In addition, in a resin film 10B with a conductor layer, a conductive paste 22B is filled into a via hole 21B. At this time, the conductive paste 22A and the conductive paste 22B may be filled at the same time or at different times.

[0188] 14, in a resin film 10C with a conductor layer, a conductive paste 22C is filled into a via hole 21C. In addition, in a resin film 10C with a conductor layer, a conductive paste 22D is filled into a via hole 21D. At this time, the conductive pastes 22C and 22D may be filled at the same time or at different times.

[0189] Examples of methods for filling the conductive paste 22A, the conductive paste 22B, the conductive paste 22C, and the conductive paste 22D include a screen printing method and a vacuum filling method.

[0190] The conductive paste 22A, the conductive paste 22B, the conductive paste 22C, and the conductive paste 22D each contain, for example, a metal and a resin.

[0191] Examples of metals contained in each of the conductive pastes 22A, 22B, 22C, and 22D include copper, tin, silver, etc. Among these, each of the conductive pastes preferably contains copper, and more preferably contains copper and tin.

[0192] The resin contained in each of the conductive pastes 22A, 22B, 22C, and 22D preferably includes at least one thermosetting resin selected from the group consisting of epoxy resin, phenolic resin, polyimide resin, silicone resin or modified resin thereof, and acrylic resin, or at least one thermoplastic resin selected from the group consisting of polyamide resin, polystyrene resin, polymethacrylic resin, polycarbonate resin, and cellulose-based resin.

[0193] Each of the conductive pastes 22A, 22B, 22C, and 22D may further contain a vehicle, a solvent, a thixotropic agent, an activator, and the like.

[0194] Examples of the vehicle include rosin-based resins made from rosin and derivatives thereof such as modified rosin, synthetic resins made from rosin and derivatives thereof such as modified rosin, and mixtures of these resins.

[0195] Examples of rosin-based resins made from rosin and derivatives thereof such as modified rosin include gum rosin, tall rosin, wood rosin, polymerized rosin, hydrogenated rosin, formylated rosin, rosin ester, rosin-modified maleic acid resin, rosin-modified phenolic resin, rosin-modified alkyd resin, and various other rosin derivatives.

[0196] Examples of synthetic resins made of rosin and derivatives thereof such as modified rosin include polyester resins, polyamide resins, phenoxy resins, and terpene resins.

[0197] Examples of solvents include alcohols, ketones, esters, ethers, aromatic solvents, and hydrocarbons. Specific examples of these solvents include benzyl alcohol, ethanol, isopropyl alcohol, butanol, diethylene glycol, ethylene glycol, glycerin, ethyl cellosolve, butyl cellosolve, ethyl acetate, butyl acetate, butyl benzoate, diethyl adipate, dodecane, tetradecene, α-terpineol, terpineol, 2-methyl-2,4-pentanediol, 2-ethylhexanediol, toluene, xylene, propylene glycol monophenyl ether, diethylene glycol monohexyl ether, ethylene glycol monobutyl ether, diethylene glycol monobutyl ether, diethylene glycol monoethyl ether, diisobutyl adipate, hexylene glycol, cyclohexanedimethanol, 2-terpinyloxyethanol, 2-dihydroterpinyloxyethanol, and mixtures thereof. Among these, terpineol, ethylene glycol monobutyl ether, diethylene glycol monobutyl ether, and diethylene glycol monoethyl ether are preferred.

[0198] Examples of thixotropic agents include hydrogenated castor oil, carnauba wax, amides, hydroxy fatty acids, dibenzylidene sorbitol, bis(p-methylbenzylidene)sorbitols, beeswax, stearic acid amide, hydroxystearic acid ethylene bisamide, etc. Furthermore, these thixotropic agents may contain, as necessary, fatty acids such as caprylic acid, lauric acid, myristic acid, palmitic acid, stearic acid, and behenic acid, hydroxy fatty acids such as 1,2-hydroxystearic acid, antioxidants, surfactants, amines, etc.

[0199] Examples of the activator include amine hydrohalides, organic halogen compounds, organic acids, organic amines, and polyhydric alcohols.

[0200] Examples of amine hydrohalides include diphenylguanidine hydrobromide, diphenylguanidine hydrochloride, cyclohexylamine hydrobromide, ethylamine hydrochloride, ethylamine hydrobromide, diethylaniline hydrobromide, diethylaniline hydrochloride, triethanolamine hydrobromide, and monoethanolamine hydrobromide.

[0201] Examples of the organic halogen compound include chlorinated paraffin, tetrabromoethane, dibromopropanol, 2,3-dibromo-1,4-butanediol, 2,3-dibromo-2-butene-1,4-diol, and tris(2,3-dibromopropyl)isocyanurate.

[0202] Examples of organic acids include malonic acid, fumaric acid, glycolic acid, citric acid, malic acid, succinic acid, phenylsuccinic acid, maleic acid, salicylic acid, anthranilic acid, glutaric acid, suberic acid, adipic acid, sebacic acid, stearic acid, abietic acid, benzoic acid, trimellitic acid, pyromellitic acid, and dodecanoic acid.

[0203] Examples of organic amines include monoethanolamine, diethanolamine, triethanolamine, tributylamine, aniline, and diethylaniline.

[0204] Examples of polyhydric alcohols include erythritol, pyrogallol, and ribitol.

[0205] <Step of forming interlayer connection conductors> FIG. 15 is a cross-sectional view showing a step of forming an interlayer connection conductor in an example of a method for producing a laminated substrate of the present invention.

[0206] As shown in Fig. 15, a conductor layer-equipped resin film 10A, a conductor layer-equipped resin film 10B filled with conductive paste 22A and conductive paste 22B, and a conductor layer-equipped resin film 10C filled with conductive paste 22C and conductive paste 22D are laminated in this order in the lamination direction. The laminated films are arranged so that the surface (top surface) of the conductor layer-equipped resin film 10A facing the conductor layer 2A is in contact with the surface (bottom surface) of the conductor layer-equipped resin film 10B facing the resin film 1B, and so that the surface (top surface) of the conductor layer-equipped resin film 10B facing the conductor layer 2B' and conductor layer 2B'' is in contact with the surface (bottom surface) of the conductor layer-equipped resin film 10C facing the resin film 1C. For ease of explanation, Fig. 15 shows the conductor layer-equipped resin films spaced apart from each other.

[0207] The resulting laminate is then subjected to heat pressing by applying pressure in the lamination direction while being heated, thereby pressure-bonding the conductor layer-equipped resin film 10A to the conductor layer-equipped resin film 10B, and pressure-bonding the conductor layer-equipped resin film 10B to the conductor layer-equipped resin film 10C.

[0208] Here, when the resin film 10B with a conductor layer and the resin film 10C with a conductor layer are pressure-bonded together, the resin film 1B contains a thermoplastic resin, so the conductor layers 2B, 2B', and 2B'' are pressed into the resin film 1B. As a result, the voids 1Bh also move together with the conductor layers 2B, 2B', and 2B'', and so the voids 1Bh extend from the main surfaces of the conductor layers 2B, 2B', and 2B'' in the stacking direction to the side surfaces of the conductor layers 2B, 2B', and 2B'' in the in-plane direction. In this way, the configuration in which the voids 1Bh are present so as to wrap around from the main surfaces in the stacking direction of the conductor layers 2B, 2B', and 2B'' to the side surfaces in the in-plane direction of the conductor layers 2B, 2B', and 2B'' is achieved by a co-lamination method using a resin film 10B with a conductor layer in which voids 1Bh are provided inside a resin film 1B containing a thermoplastic resin, more specifically, by co-laminating a resin film 10B with a conductor layer and a resin film 10C with a conductor layer.

[0209] Furthermore, conductive paste 22A, conductive paste 22B, conductive paste 22C, and conductive paste 22D solidify during hot pressing to become interlayer connection conductor 20A, interlayer connection conductor 20B, interlayer connection conductor 20C, and interlayer connection conductor 20D, respectively. In this manner, interlayer connection conductor 20A, interlayer connection conductor 20B, interlayer connection conductor 20C, and interlayer connection conductor 20D are formed in via hole 21A, via hole 21B, via hole 21C, and via hole 21D, respectively.

[0210] When forming the interlayer connection conductors 20A, 20B, 20C, and 20D, instead of filling the via holes with conductive paste, the inner walls of the via holes may be plated with a metal such as copper, tin, or silver.

[0211] In this way, the laminated substrate 50 shown in FIG. 7 is manufactured.

[0212] The laminated substrate of the present invention may further include a side conductor on a side surface along the lamination direction.

[0213] FIG. 16 is a cross-sectional view showing an example of the laminated substrate of the present invention, which is different from that shown in FIG.

[0214] The multilayer substrate 50' shown in FIG. 16 has the same configuration as the multilayer substrate 50 shown in FIG. 7, and further includes side conductors 30 on the side surfaces along the lamination direction.

[0215] The side conductor 30 can function as a shield electrode that shields electromagnetic waves. Therefore, when the laminated substrate 50' has the side conductor 30, the electromagnetic wave shielding properties of the side surface of the laminated substrate 50' tend to be improved.

[0216] The side conductor 30 is preferably connected to a conductor layer. In the laminate substrate 50' shown in Fig. 16, the side conductor 30 is connected to the conductor layer 2A, the conductor layer 2B', the conductor layer 2B'', and the conductor layer 2C. As a result, when the conductor layer 2A and the conductor layer 2C function as ground electrodes as described above, the side conductor 30 functions as a shield electrode and also as a ground electrode.

[0217] Examples of materials that can be used to form the side conductors 30 include copper, tin, and silver.

[0218] The side conductors 30 are formed by plating the side surfaces of the laminate of conductor layer-attached resin films with a metal such as copper, tin, or silver by sputtering or the like.

[0219] The laminated substrate 50' has, in addition to the side conductor 30, interlayer connection conductors 20A, 20B, 20C, and 20D, but does not necessarily have to have these interlayer connection conductors.

[0220] The laminated substrate of the present invention may have three resin films with conductor layers, such as the laminated substrate 50 shown in Figure 7 and the laminated substrate 50' shown in Figure 16, but may also have only one resin film with a conductor layer.

[0221] FIG. 17 is a cross-sectional view showing an example of the laminated substrate of the present invention, which is different from the examples shown in FIGS.

[0222] The laminated substrate 50A shown in FIG. 17 has the conductor layer-equipped resin film 10' shown in FIG. 5 and a resin film 1' in the lamination direction.

[0223] The resin film 1' is in contact with the surface (upper surface) of the conductor layer-equipped resin film 10' on the conductor layer 2' side, which includes part of the first main surface 1a of the resin film 1.

[0224] In the laminated substrate 50A, as shown in Figure 17, when viewed in a cross section along the stacking direction and an in-plane direction perpendicular to the stacking direction, it is preferable that the voids 1h extend from the main surface (here, the bottom surface) in the stacking direction of the conductor layer 2' to the side surfaces (here, the left and right sides) in the in-plane direction of the conductor layer 2'.

[0225] FIG. 18 is a cross-sectional view showing an example of the laminated substrate of the present invention, which is different from the examples shown in FIGS. 7, 16, and 17. In FIG.

[0226] The laminated substrate 50A' shown in FIG. 18 has, in the lamination direction, the resin film 10' with a conductor layer shown in FIG. 5 and a resin film 1 different from the resin film 1 of the resin film 10' with a conductor layer.

[0227] The two resin films 1 are laminated in the lamination direction so that their first main surfaces 1a are in contact with each other.

[0228] In the laminated substrate 50A', as shown in Figure 18, when viewed in a cross section along the stacking direction and an in-plane direction perpendicular to the stacking direction, it is preferable that the voids 1h exist so as to extend from one main surface (here, the bottom surface) and the other main surface (here, the top surface) in the stacking direction of the conductor layer 2' to the side surfaces (here, the left side surface and the right side surface) in the in-plane direction of the conductor layer 2'.

[0229] The laminated substrate 50A' is manufactured, for example, as follows. First, two resin films 10' with conductor layers are prepared. Next, the conductor layer 2' is etched from one of the resin films 10' with conductor layers to remove the resin film 1. Then, the resin film 1 removed from one of the resin films 10' with conductor layers and the other resin film 10' with conductor layers are laminated in the lamination direction so that the first main surfaces 1a of the resin films 1 are in contact with each other, thereby manufacturing the laminated substrate 50A'.

[0230] In the manufacturing method of the laminated substrate 50A' described above, when preparing a resin film 1 having holes 1h for laminating onto a resin film 10' with a conductor layer, the resin film 1 is extracted by etching the conductor layer 2' of the resin film 10' with a conductor layer, but it is also possible to simply use a resin film 1 having holes 1h.

[0231] In the laminated substrate 50A' manufactured in the above manner, as shown in Figure 18, the voids 1h are present along the first main surface 1a of each resin film 1, and extend from both main surfaces (here, the bottom and top surfaces) in the stacking direction of the conductor layer 2' to the side surfaces (here, the left and right surfaces) in the in-plane direction of the conductor layer 2'.

[0232] The laminated substrate of the present invention may have two resin films with conductor layers.

[0233] FIG. 19 is a cross-sectional view showing an example of the laminated substrate of the present invention, which is different from the examples shown in FIGS. 7, 16, 17, and 18. In FIG.

[0234] The laminated substrate 50B shown in FIG. 19 has two conductor layer-equipped resin films 10 shown in FIG. 1 in the lamination direction.

[0235] The two conductor layer-equipped resin films 10 are laminated in the lamination direction so that the second main surfaces 1b of the resin films 1 are in contact with each other.

[0236] The above describes examples of the laminated substrate of the present invention having only one resin film with a conductor layer, two resin films with a conductor layer, and three resin films with a conductor layer, but the laminated substrate of the present invention may also have four or more resin films with a conductor layer.

[0237] In the laminated substrate of the present invention, the resin film may be plastically deformed. In the laminated substrate of the present invention, the resin film contains a thermoplastic resin, and therefore can be plastically deformed by, for example, heat.

[0238] In the laminated substrate of the present invention, when the resin film is plastically deformed, the resin film and the conductor layer may be bent together. In conventional laminated substrates in which voids are provided inside the resin film, such as the multilayer wiring substrate described in Patent Document 1, when the resin film and the conductor layer are bent together, the voids may become a source of cracks. In contrast, in the laminated substrate of the present invention, the voids are unevenly distributed near the conductor layer, so that even when the resin film and the conductor layer are bent together, the voids are unlikely to become a source of cracks. [Example]

[0239] EXAMPLES Hereinafter, examples will be shown that more specifically disclose the conductor layer-attached resin film of the present invention, but the present invention is not limited to the following examples.

[0240] As the thermoplastic resins, the following liquid crystal polymers A, B, C, and D were prepared.

[0241] <Liquid Crystal Polymer A> As liquid crystal polymer A, a type II fully aromatic polyester was prepared, which was a copolymer of 75 mol% 6-hydroxy-2-naphthoic acid and 25 mol% p-hydroxybenzoic acid, and had a melting point of 320°C and a melt viscosity of 111 Pa·s.

[0242] <Liquid Crystal Polymer B> As liquid crystal polymer B, a type II fully aromatic polyester was prepared, which was a copolymer of 75 mol% 6-hydroxy-2-naphthoic acid and 25 mol% p-hydroxybenzoic acid, and had a melting point of 320°C and a melt viscosity of 74 Pa·s.

[0243] <Liquid Crystal Polymer C> As liquid crystal polymer C, a type II fully aromatic polyester was prepared, which was a copolymer of 20 mol% 6-hydroxy-2-naphthoic acid and 80 mol% p-hydroxybenzoic acid, and had a melting point of 325°C and a melt viscosity of 98 Pa·s.

[0244] <Liquid Crystal Polymer D> As liquid crystal polymer D, a type II fully aromatic polyester was prepared, which was a copolymer of 75 mol% 6-hydroxy-2-naphthoic acid and 25 mol% p-hydroxybenzoic acid, and had a melting point of 320°C and a melt viscosity of 79 Pa·s.

[0245] The melt viscosity of liquid crystal polymer A, liquid crystal polymer B, liquid crystal polymer C, and liquid crystal polymer D was measured at a temperature of 330°C and a shear rate of 1000 s -1 The measurements were carried out under the following conditions.

[0246] [Example 1] The liquid crystal polymer film with a conductor layer of Example 1 was produced by the following method.

[0247] <Step of Producing Laminate> First, a liquid crystal polymer film was produced by the above-mentioned known film-forming method using a resin material containing a liquid crystal polymer in the blending ratio shown in Table 1.

[0248] One of the principal surfaces of the liquid crystal polymer film was roughened with concaves and convexes. The arithmetic mean height Sa of the principal surface of the liquid crystal polymer film, which would later become the principal surface on which a conductor layer was formed, was measured using the above-mentioned method using a non-contact laser microscope. The results are shown in Table 1.

[0249] In addition, copper foil "WS" manufactured by Furukawa Electric Co., Ltd. was prepared as the conductor layer.

[0250] The conductor layer was then pressed onto one main surface of the liquid crystal polymer film to produce a laminate having the liquid crystal polymer film and the conductor layer in the stacking direction. In the laminate, since one main surface of the liquid crystal polymer film was rough, a space was provided between the liquid crystal polymer film and the conductor layer in the in-plane direction.

[0251] <Step of forming holes> The laminate was heat-treated to produce a liquid crystal polymer film with a conductor layer of Example 1, in which voids were provided inside the liquid crystal polymer film.

[0252] [Examples 2 to 7 and Comparative Example 1] The liquid crystal polymer films with conductor layers of Examples 2 to 7 and Comparative Example 1 were produced in the same manner as the liquid crystal polymer film with conductor layers of Example 1, except that the liquid crystal polymer films were produced using a resin material containing a liquid crystal polymer in the blending ratio shown in Table 1.

[0253] In Table 1, liquid crystal polymer A, liquid crystal polymer B, liquid crystal polymer C, and liquid crystal polymer D are shown as "A," "B," "C," and "D," respectively.

[0254] [evaluation] The following evaluations were carried out on the conductor layer-attached liquid crystal polymer films of Examples 1 to 7 and Comparative Example 1. The results are shown in Table 1.

[0255] < 13 C-NMR spectrum First, the conductor layer of the liquid crystal polymer film with the conductor layer was etched to remove the liquid crystal polymer film.

[0256] Next, 5 g of liquid crystal polymer film and 200 cc of methanol were placed in an OM Labotec high-temperature, high-pressure reactor (MMJ-500). The reactor was then purged with argon and heated at 280°C for 15 minutes to obtain a solution containing the liquid crystal polymer film. The heating process vaporized the methanol, and the pressure in the system reached its critical pressure, resulting in the methanol entering a supercritical state. The solution was then vacuum-dried to remove the solvent, yielding a powder of the liquid crystal polymer film decomposed in supercritical methanol. 0.014 g of the liquid crystal polymer film decomposition powder was then dissolved in 0.7 ml of deuterated methanol to obtain a sample for NMR measurement.

[0257] Next, NMR measurement is performed on the NMR measurement sample using a JEOL Fourier transform nuclear magnetic resonance measurement device "JNM-ECP600" to obtain the following: 13 C-NMR spectra were obtained. 13 From the C-NMR spectrum, the integral value of the peak derived from the benzene ring, the integral value of the peak derived from the naphthalene ring, and the integral value of the peak derived from the carboxymethyl group were determined and designated as CA, CB, and CC, respectively.

[0258] Here, the peaks derived from benzene rings, more specifically, peaks derived from methyl p-hydroxybenzoate, were defined as peaks with a chemical shift in the range of 113 ppm to 115 ppm (114±1 ppm). The peaks derived from naphthalene rings, more specifically, peaks derived from methyl 6-hydroxy-2-naphthoate, were defined as peaks with a chemical shift in the range of 107 ppm to 109 ppm (108±1 ppm). The peaks derived from carboxymethyl groups, more specifically, peaks derived from methyl groups derived from esters, were defined as peaks with a chemical shift in the range of 49 ppm to 51 ppm (50±1 ppm).

[0259] From the CA, CB, and CC obtained above, (CA+CB) / CC was calculated.

[0260] <Viscoelastic properties> First, the conductor layer was etched from the liquid crystal polymer film with a conductor layer to obtain a liquid crystal polymer film. Next, using a TA Instruments dynamic viscoelasticity measuring device "RSA-G2," the temperature dependence of the loss tangent of the liquid crystal polymer film was measured under the following conditions: dynamic strain: 0.25%, frequency: 0.5 Hz, heating rate: 10°C / min, and temperature range: 40°C to the melting point of the liquid crystal polymer contained in the liquid crystal polymer film. A graph showing the relationship between the loss tangent of the liquid crystal polymer film and temperature was obtained. The graph showing the relationship between the loss tangent of the liquid crystal polymer film and temperature was then integrated over the temperature range from 40°C to the melting point of the thermoplastic resin contained in the liquid crystal polymer film to obtain the integral value of the loss tangent.

[0261] The melting point of the thermoplastic resin contained in the liquid crystal polymer film was measured as follows. First, using a Hitachi High-Tech Science DSC7000X differential scanning calorimeter, the liquid crystal polymer film was heated at a heating rate of 20°C / min until it was completely melted. Next, the resulting melt was cooled to 175°C at a heating rate of 20°C / min and then heated again at a heating rate of 20°C / min. The temperature corresponding to the endothermic peak observed during this heating process was determined as the melting point of the thermoplastic resin contained in the liquid crystal polymer film. When an endothermic peak was difficult to observe using the above-mentioned method, the melting point of the thermoplastic resin contained in the liquid crystal polymer film was determined by texture observation under crossed Nicols conditions using a polarizing microscope.

[0262] <Vacancy position> Cross-sectional images of the area where the liquid crystal polymer film and the conductor layer overlap in the conductor layer-attached liquid crystal polymer film were taken using a scanning electron microscope. These cross-sectional images were taken at five or more locations and no more than ten locations in the in-plane direction. All of the cross-sectional images were then analyzed using image analysis software to confirm the locations of all voids in all cross-sectional images of the liquid crystal polymer film. The first location was the edge of the liquid crystal polymer film facing the conductor layer, the second location was a position separated by one-third of the thickness of the liquid crystal polymer film in the stacking direction from the first location, and the third location was a position separated by one-third of the thickness of the liquid crystal polymer film in the stacking direction from the second location toward the opposite side of the first location. The evaluation criteria were as follows: ◯ (Good): A void was present between the first and second positions. × (bad): A void was not present between the first position and the second position, but was present between the second position and the third position, or no void was present.

[0263] <Number of holes> For the liquid crystal polymer film with a conductor layer, the presence of voids was confirmed in advance by viewing the film from the thickness direction. Images of the cross section along the thickness direction when the region between the first and second positions was viewed from the in-plane direction were then taken using a scanning electron microscope. In this way, cross-sectional images of the region between the first and second positions in the liquid crystal polymer film were taken at five or more and ten or less different positions in the in-plane direction. The size of each cross-sectional image was 75 μm long and 125 μm wide (e.g., the size of the field of view when viewed at 1000x magnification). All the cross-sectional images were then analyzed using image analysis software to count the number of voids in each cross-sectional image. The average value per cross-sectional image (one field of view) calculated from the total number of voids obtained was defined as the number of voids between the first and second positions.

[0264] The number of voids between the second position and the third position was determined in the same manner as the number of voids between the first position and the second position. If the presence of voids could not be confirmed in all cross-sectional images (cross-sectional images at 5 or more locations and 10 or less locations) taken of the region between the second position and the third position in the liquid crystal polymer film, the number of voids between the second position and the third position was determined to be 0.

[0265] <Pore diameter> For the liquid crystal polymer film with a conductor layer, the presence of voids was confirmed in advance by viewing the film from the thickness direction. Images of the cross section along the thickness direction when the region between the first and second positions was viewed from the in-plane direction were then taken using a scanning electron microscope. In this way, cross-sectional images of the region between the first and second positions in the liquid crystal polymer film were taken at five or more and ten or less different positions in the in-plane direction. The size of each cross-sectional image was 75 μm long and 125 μm wide (e.g., the size of the field of view when viewed at 1000x magnification). Image analysis software was then performed on all the taken cross-sectional images to measure the equivalent circle diameter of all voids in all cross-sectional images. The maximum value of the obtained measurements was determined to be the void diameter of the voids existing between the first and second positions.

[0266] <Porosity> For the liquid crystal polymer film with a conductor layer, a planar image along the in-plane direction when the main surface on which the conductor layer was provided was viewed in plan from the thickness direction was taken using an optical microscope at a magnification of 100. The planar image was then analyzed using image analysis software to measure the area ratio of pores per 10 mm square area in the planar image, and the obtained measurement value was defined as the porosity between the first position and the second position.

[0267] [Table 1]

[0268] As shown in Table 1, in the conductor layer-attached liquid crystal polymer films of Examples 1 to 7, the pores were unevenly distributed between the first position and the second position, and as a result, the pores were unevenly distributed near the conductor layer.

[0269] The reason why voids were formed near the conductor layer in the conductor layer-equipped liquid crystal polymer films of Examples 1 to 7 is believed to be because, during the production of the conductor layer-equipped liquid crystal polymer films of Examples 1 to 7, liquid crystal polymer films with an integrated value of the loss tangent in the viscoelastic properties of 29.7 or less, i.e., liquid crystal polymer films with a small viscous component in the loss tangent in the viscoelastic properties and that do not soften even at high temperatures, were used. Because a liquid crystal polymer film with such properties was used during the production of the conductor layer-equipped liquid crystal polymer films of Examples 1 to 7, it is believed that, even when the laminate was heat-treated in the step of providing the voids, gas contained in the spaces originating from the irregularities formed on one main surface of the liquid crystal polymer film was less likely to escape to the outside of the liquid crystal polymer film. As a result, in the conductor layer-equipped liquid crystal polymer films of Examples 1 to 7, gas contained in the spaces was more likely to be trapped inside the liquid crystal polymer film, which is believed to have made it easier for voids to be formed inside the liquid crystal polymer film, more specifically, near the conductor layer.

[0270] The conductor layer-attached liquid crystal polymer films of Examples 4 to 7 had a higher number of voids and a higher porosity between the first position and the second position than the conductor layer-attached liquid crystal polymer films of Examples 2 and 3. This is thought to be because, when the conductor layer-attached liquid crystal polymer films of Examples 4 to 7 were produced, a liquid crystal polymer film having an arithmetic mean height Sa of 240 nm or more on the main surface on which the conductor layer was provided was used.

[0271] On the other hand, in the conductor layer-attached liquid crystal polymer film of Comparative Example 1, no pores were present inside the liquid crystal polymer film.

[0272] The reason why voids were not formed inside the conductor layer-equipped liquid crystal polymer film of Comparative Example 1 is believed to be because a liquid crystal polymer film with an integrated loss tangent in the viscoelastic properties of more than 29.7 was used during the production of the conductor layer-equipped liquid crystal polymer film of Comparative Example 1, i.e., a liquid crystal polymer film with a high viscous component in the loss tangent of the viscoelastic properties that easily softens at high temperatures. Because a liquid crystal polymer film with such properties was used during the production of the conductor layer-equipped liquid crystal polymer film of Comparative Example 1, when the laminate was heat-treated in the step of forming the voids, the shape of the irregularities formed on one main surface of the liquid crystal polymer film was difficult to maintain, and gas contained in spaces originating from the irregularities was likely to escape to the outside of the liquid crystal polymer film. As a result, it is believed that the gas contained in the spaces was difficult to absorb into the liquid crystal polymer film in the conductor layer-equipped liquid crystal polymer film of Comparative Example 1, and therefore voids were not formed inside the liquid crystal polymer film. [Explanation of symbols]

[0273] 1, 1', 1'', 1A, 1B, 1C Resin film 1a, 1a'', 1Aa, 1Ba, 1Ca First main surface of resin film 1b, 1b'', 1Ab, 1Bb, 1Cb Second main surface of resin film 1h, 1h'', 1Ah, 1Bh, 1Ch vacancy 2, 2', 2'', 2A, 2B, 2B', 2B'', 2C conductor layer 10, 10', 10'', 10A, 10B, 10C Resin film with conductor layer 15 Laminate 15h space 20A, 20B, 20C, 20D Interlayer connecting conductor 21A, 21B, 21C, 21D via holes 22A, 22B, 22C, 22D Conductive Paste 30 Side conductor 50, 50', 50A, 50A', 50B laminated board E1, E1'', EA1, EB1, EC1 1st position E2, E2'', EA2, EB2, EC2 2nd position E3, E3'', EA3, EB3, EC3 3rd position HD thick direction MD 1st direction TD 2nd direction

Claims

1. a resin film containing a thermoplastic resin and having pores formed therein; a conductor layer adjacent to only the first main surface side of a first main surface and a second main surface facing each other in a thickness direction of the resin film, the thermoplastic resin is a liquid crystal polymer, the liquid crystal polymer contains a wholly aromatic polyester which is a copolymer of 6-hydroxy-2-naphthoic acid and p-hydroxybenzoic acid; In a viscoelastic property showing the relationship between the loss tangent and temperature of the resin film, the integral value of the loss tangent in a temperature range from 40°C to the melting point of the thermoplastic resin contained in the resin film is 29.7 or less, a second position is a position away from the first position in the stacking direction by a distance of 1 / 3 of the thickness of the resin film, and a third position is a position away from the second position in the stacking direction toward the opposite side of the first position by a distance of 1 / 3 of the thickness of the resin film, the voids are unevenly distributed between the first position and the second position such that the number of voids between the first position and the second position is greater than the number of voids between the second position and the third position, and such that the number of voids between the first position and the second position is greater than the number of voids between the position of the second main surface and the third position.

2. The resin film was decomposed in supercritical methanol. １３ 2. The resin film with a conductor layer according to claim 1, wherein, in a C-NMR spectrum, when an integral value of a peak derived from a benzene ring is CA, an integral value of a peak derived from a naphthalene ring is CB, and an integral value of a peak derived from a carboxymethyl group is CC, (CA+CB) / CC is 1.25 or more and 1.65 or less.

3. The resin film with a conductor layer according to claim 1 , wherein the pores present between the first position and the second position have a pore diameter of 20 μm or less.

4. A laminated substrate comprising the resin film with a conductor layer according to any one of claims 1 to 3.

5. the conductor layer is a signal line for transmitting a signal, The laminated substrate of claim 4, wherein when viewed in a cross section along the stacking direction and an in-plane direction perpendicular to the stacking direction, the voids are present so as to extend from the main surface of the conductor layer in the stacking direction to the side surface of the conductor layer in the in-plane direction.

6. The laminated substrate according to claim 4 , wherein the resin film is plastically deformed.

7. The laminated substrate according to claim 6 , wherein the resin film and the conductor layer are integrally bent.

8. a step of providing a conductor layer adjacent to only the first main surface side of a resin film, the resin film including a thermoplastic resin, the thermoplastic resin being a liquid crystal polymer, out of a first main surface and a second main surface facing each other in a thickness direction of the resin film, thereby producing a laminate having the resin film and the conductor layer in a stacking direction; and a step of heat-treating the laminate to form voids inside the resin film, In the step of producing the laminate, the liquid crystal polymer contains a wholly aromatic polyester which is a copolymer of 6-hydroxy-2-naphthoic acid and p-hydroxybenzoic acid; In a viscoelastic property showing the relationship between the loss tangent and temperature of the resin film, the integral value of the loss tangent in a temperature range from 40°C to the melting point of the thermoplastic resin contained in the resin film is 29.7 or less, the first main surface of the resin film is a rough surface having projections and recesses; a second position is a position away from the first position in the stacking direction by a distance of 1 / 3 of the thickness of the resin film, and a third position is a position away from the second position in the stacking direction toward the opposite side of the first position by a distance of 1 / 3 of the thickness of the resin film, the holes are unevenly distributed between the first position and the second position so that the number of holes between the first position and the second position is greater than the number of holes between the second position and the third position, and so that the number of holes between the first position and the second position is greater than the number of holes between the second position and the third position.

9. 9. The method for producing a resin film with a conductor layer according to claim 8, wherein in the step of producing the laminate, an arithmetic mean height Sa of the main surface of the resin film on which the conductor layer is provided is 240 nm or more.

Images