Resin laminated substrate and method for manufacturing resin laminated substrate

Abstract

This resin laminated substrate comprises: a plurality of resin layers laminated on each other; and conductors disposed outside and inside the laminated plurality of resin layers. The plurality of resin layers include a first resin layer (11), a second resin layer (12), and third resin layers (13a, 13b, 13c) that are laminated on each other in the stated order. The conductors include first conductor layers (21a, 21b), second conductor layers (22a-22h), and interlayer connection conductors (23a1, 23a2, 23e, 23f, 23g, 23h). The first conductor layers (21a, 21b) are disposed on a lower main surface (11ds) of the first resin layer (11). The interlayer connection conductors or the second conductor layers overlapping a portion of the first resin layer (11) when viewed in the thickness direction of the third resin layers (13a, 13b, 13c), are disposed on the third resin layers. The second resin layer (12) is a thermoplastic resin. The melting point of the second resin layer (12) is lower than the melting point of the first resin layer (11). At least the second resin layer (12) has air bubbles.

Description

Resin laminated substrate and method for manufacturing the same

[0001] The present invention relates to a resin laminated substrate including a plurality of resin layers that are stacked together to form a part of a laminate, and conductor layers that are disposed on the exterior and interior of the laminate, and a method for manufacturing the same.

[0002] For example, Patent Document 1 discloses a method for manufacturing a multilayer wiring board that includes a step of thermocompressing multiple laminated resin sheets together using a batch multilayer pressing method, and a multilayer wiring board manufactured by such a method.

[0003] The multilayer wiring board described in Patent Document 1 uses multiple wiring layers, and the multiple wiring layers are connected by inner vias. A manufacturing method for this multilayer board includes the steps of: forming a conductor pattern that will become the wiring layer on the surface of a thermoplastic resin sheet; positioning a laminate formed by stacking multiple resin sheets between a first press plate and a second press plate; and disposing a compressible cushion sheet formed of a graphite sheet obtained by pressing expanded graphite between the laminate and at least one of the first press plate and the second press plate; and heating and pressing the laminate in the stacking direction between the first press plate and the second press plate.

[0004] Patent No. 5927946

[0005] In the manufacturing method of a multilayer wiring board described in Patent Document 1, the remaining copper ratio and the arrangement of the interlayer connecting conductors in each layer differ, which results in a deterioration in the uniformity (coplanarity) of the resin layer surface and the copper foil surface (substrate surface) of the multilayer wiring board after pressing.

[0006] SUMMARY OF THE INVENTION It is therefore an object of the present invention to provide a resin laminated substrate with improved surface uniformity and a method for producing the same.

[0007] (1) A resin laminated substrate as an example of the present disclosure comprises: a plurality of resin layers stacked on top of each other; and conductors arranged outside and inside the plurality of stacked resin layers; the plurality of resin layers include a first resin layer, a second resin layer, and a third resin layer stacked on top of each other in order; the conductors include a first conductor layer, a second conductor layer, and an interlayer connection conductor; the first resin layer has an upper main surface and a lower main surface facing each other; the second resin layer has an upper main surface and a lower main surface facing each other; the upper main surface of the first resin layer is in contact with the lower main surface of the second resin layer; the first conductor layer is arranged on the lower main surface of the first resin layer; the second conductor layer or the interlayer connection conductor is arranged on the third resin layer, overlapping a portion of the first conductor layer when viewed in a thickness direction of the third resin layer; the second resin layer is a thermoplastic resin; the melting point of the second resin layer is lower than the melting point of the first resin layer; and at least the second resin layer has bubbles.

[0008] (2) The method for producing a resin laminated substrate according to the present disclosure is characterized in that the second resin layer is heat-pressed in a state in which the melting point of the second resin layer is lower than the heat-pressing temperature and the melting point of the first resin layer is higher than the heat-pressing temperature.

[0009] According to the present invention, a resin laminated substrate with improved surface uniformity can be obtained.

[0010] FIG. 1 is a cross-sectional view showing each resin layer structure that is a part of a resin laminated substrate according to a first embodiment. FIG. 2 is a cross-sectional view of a resin laminated substrate 1 formed by heat pressing. FIG. 3 is a cross-sectional view of a resin laminated substrate 1A according to the first embodiment, which is different from the resin laminated substrate shown in FIG. 2. FIG. 4 is a cross-sectional view showing each resin layer structure that is a part of a resin laminated substrate according to a second embodiment. FIG. 5 is a cross-sectional view showing each resin layer structure that is a part of a resin laminated substrate according to a third embodiment. FIG. 6 is a cross-sectional view of a resin laminated substrate 3 formed by heat pressing. FIG. 7 is a cross-sectional view showing each resin layer structure that is a part of a resin laminated substrate according to a fourth embodiment. FIG. 8 is a cross-sectional view of a resin laminated substrate 4 formed by stacking the resin layers shown in FIG. 7 and heat pressing them with a rigid member. FIG. 9 is a cross-sectional view of a resin laminated substrate 4A according to a fourth embodiment, which is different from the resin laminated substrate 4 shown in FIG. 8. FIG. 10 is a perspective view showing each resin layer structure that is a part of a resin laminated substrate according to a fifth embodiment. FIG. 11 is a cross-sectional view showing each resin layer structure that is a part of a resin laminated substrate according to the fifth embodiment. Fig. 12 is a cross-sectional view of a resin laminated substrate 5 formed by laminating the resin layers shown in Fig. 11 and hot pressing them with a rigid member. Fig. 13 is a cross-sectional view of a resin laminated substrate 5A according to a fifth embodiment, which is different from the resin laminated substrate shown in Fig. 12.

[0011] Hereinafter, several specific examples will be given with reference to the drawings to illustrate multiple embodiments for carrying out the present invention. The same reference numerals are used for the same parts in each drawing. For ease of explanation and understanding of the main points, the embodiments are shown divided into multiple embodiments for convenience of explanation. However, partial substitution or combination of the configurations shown in different embodiments is possible. From the second embodiment onwards, a description of matters common to the first embodiment will be omitted, and only differences will be described. In particular, similar effects resulting from similar configurations will not be mentioned in each embodiment.

[0012] First Embodiment Fig. 1 is a cross-sectional view showing the structure of each resin layer that is a part of a resin laminated substrate according to a first embodiment. Fig. 2 is a cross-sectional view of a resin laminated substrate 1 formed by hot pressing.

[0013] The resin laminated substrate 1 includes a plurality of resin layers stacked on top of one another and conductors disposed on the exterior and interior of the plurality of stacked resin layers. In Figures 1 and 2, the first resin layer 11, the second resin layer 12, and the third resin layers 13a, 13b, and 13c are the "resin layers." The first conductor layers 21a and 21b, the second conductor layers 22a to 22h, and the interlayer connection conductors 23a1, 23a2, 23e, 23f, 23g, and 23h are the "conductors."

[0014] The first resin layer 11, the second resin layer 12, and the third resin layers 13a, 13b, and 13c are all made of LCP (liquid crystal polymer), PTFE (fluororesin), PI (polyimide), etc., but have different melting points. At least the second resin layer 12 is made of a thermoplastic resin.

[0015] 1, the first resin layer 11 has an upper main surface 11us and a lower main surface 11ds that face each other, and the second resin layer 12 has an upper main surface 12us and a lower main surface 12ds that face each other.

[0016] The upper main surface 11us of the first resin layer 11 is in contact with the lower main surface 12ds of the second resin layer 12. In other words, the first resin layer 11 and the second resin layer 12 are in direct contact with each other, and no conductor layer is disposed between the first resin layer 11 and the second resin layer 12.

[0017] First conductor layers 21 a and 21 b are disposed on the lower main surface 11 ds of the first resin layer 11 .

[0018] The third resin layer 13a is provided with an interlayer connection conductor 23a2 and a second conductor layer 22a that overlap the first conductor layer 21a when viewed in the thickness direction of the third resin layer 13a. The third resin layer 13a is also provided with a second conductor layer 22b.

[0019] The third resin layer 13b is provided with interlayer connection conductors 23e and 23f and second conductor layers 22e and 22f that overlap the second conductor layer 22b when viewed in the thickness direction of the third resin layer 13b. The third resin layer 13b is also provided with second conductor layers 22c and 22d.

[0020] An interlayer connection conductor 23g is disposed on the third resin layer 13c, overlapping the second conductor layer 22d when viewed in the thickness direction of the third resin layer 13c. An interlayer connection conductor 23h is also disposed on the third resin layer 13c. Second conductor layers 22g and 22h are also disposed on the third resin layer 13c, overlapping the interlayer connection conductors 23g and 23h.

[0021] The second conductor layers 22b, 22e, and 22f and the interlayer connection conductors 23e and 23f overlap the first conductor layer 21b when viewed in the thickness direction of the third resin layer.

[0022] The second resin layer 12 is a thermoplastic resin, and the melting point of the second resin layer 12 is lower than the melting point of the first resin layer 11. In other words, in terms of the difference in melting point, the first resin layer 11 is a high-melting-point resin, and the second resin layer 12 is a low-melting-point resin.

[0023] Furthermore, the melting point of the second resin layer 12 is lower than the heat-pressing temperature, and the melting point of the first resin layer 11 is higher than the heat-pressing temperature. Therefore, during heat-pressing, the second resin layer 12 becomes flexible earlier than the first resin layer 11, and the second resin fills the air bubbles in the second resin layer 12, effectively improving the coplanarity of the outer surface of the first resin layer 11.

[0024] The second resin layer 12 is a porous material containing numerous bubbles Fo. Therefore, when a partial pressure difference is applied to the second resin layer 12 in the thickness direction during heat pressing, the amount of depression of the second resin layer 12 varies depending on the pressure. That is, the more highly pressurized the second resin layer 12, the more depression there is. Therefore, the second resin layer 12 can also be called a buffer layer (a layer with cushioning properties), a pressure relaxation layer, and an irregularity absorption layer.

[0025] The first resin layer 11 made of a high melting point resin is pressed while maintaining high rigidity during the heat press.

[0026] 1 are formed on the first resin layer 11, the second resin layer 12, and the third resin layers 13a, 13b, and 13c, and are then heat-pressed with a flat pressing member. That is, the pressing member presses and heats the first resin layer 11, the second resin layer 12, and the third resin layers 13a, 13b, and 13c of the laminate.

[0027] 2 is a cross-sectional view of a resin laminated substrate 1 formed by stacking the resin layers shown in FIG. 1 and hot-pressing them with a press member. The second resin layer 12, which is an inner layer, is a low-melting-point resin layer made of a thermoplastic porous material, rather than the first resin layer 11, which is the outermost layer. Thus, by hot-pressing a laminate of multiple resin layers, a resin laminated substrate 1 with high coplanarity on the side of the first resin layer, which is the outermost layer, is obtained. Therefore, according to this embodiment, the coplanarity of the first conductor layer 21b formed on the outermost layer of the first resin layer 11 is improved.

[0028] 1 are integrated into the third resin layer 13. The second conductor layers 22g and 22h formed on the top surface of the third resin layer 13c are embedded along the top surface of the third resin layer 13. This flattens the top surface of the resin laminated substrate 1.

[0029] However, in a batch laminated substrate using a plurality of thermoplastic resin layer sheets, the coplanarity of the surface layers deteriorates during pressing due to factors such as the density distribution of the inner layer conductors.

[0030] In contrast, according to this embodiment, even if thickness variations occur in various locations due to differences in conductor density in the inner layers, the low-temperature resin absorbs the unevenness during heat pressing, allowing (equal) pressure to be applied to each interlayer connection conductor while maintaining the coplanarity of the surface layers. This reduces unevenness in the stress applied to the conductor patterns in the outermost layer, improving the coplanarity of the conductor patterns in the outermost layer. Furthermore, because the melting point of the first resin layer 11 in the outermost layer is higher than the melting point of the resin in the second resin layer 12 in the inner layer, the third resin layer made of a relatively high-melting-point resin maintains its rigidity during heat pressing, suppressing misalignment and sinking (burial amount) of the conductor patterns in the outermost layer, and improving the coplanarity of the conductor patterns in the outermost layer.

[0031] Furthermore, according to this embodiment, since no conductor layer is disposed between the first resin layer 11 and the second resin layer 12, the air in the bubbles of the first resin layer 11 can easily flow into the bubbles of the second resin layer 12. This makes it easier for the second resin layer 12 to deform when pressurized, thereby maintaining the coplanarity of the outer surface of the first resin layer 11.

[0032] Furthermore, according to this embodiment, the second resin layer 12, which is a low-melting-point resin, is a thermoplastic resin, so it does not harden during heat pressing, the resin flows into the air bubbles with high efficiency, and the coplanarity of the outer surface of the first resin layer 11 is maintained.

[0033] Furthermore, according to this embodiment, the resin flows into the air bubbles in the second resin layer to such an extent that not all of the air bubbles are filled (air bubbles remain) during heat pressing. Because the air bubble rate (the proportion of air bubbles in the resin, which can also be called the "void ratio") is high to such an extent, the coplanarity of the conductor patterns in the outermost layer is improved in response to large differences in distribution density of the conductor layers.

[0034] Furthermore, it is preferable that the air bubbles in the second resin layer 12 are crushed (the air bubbles are filled with resin) so that the air bubble content of the second resin layer 12 approaches the air bubble content of the first resin layer 11. This maintains high strength of the second resin layer, and increases the rigidity of the entire resin laminated substrate.

[0035] It does not matter whether the above-mentioned heat pressing is carried out under atmospheric pressure or under vacuum.

[0036] Furthermore, when the first resin layer 11 and the second resin layer 12 are attached to each other, a reaction may occur between the first resin layer 11 and the second resin layer 12 due to the heat press, causing a gradient in the distribution of the air void content. Even in this case, this is included in the category of the structure of the present invention in which the upper main surface of the first resin layer and the lower main surface of the second resin layer are in contact with each other.

[0037] Examples of methods for forming a porous resin layer are as follows: (a) mixing compressed gas into heated resin to form bubbles; (b) mixing a foaming agent into resin and heating it to foam and form bubbles; (c) mixing a solvent into resin and heating it to vaporize the solvent to form bubbles.

[0038] Fig. 3 is a cross-sectional view of a resin laminated substrate 1A according to a first embodiment, which is different from the resin laminated substrate shown in Fig. 2. This resin laminated substrate 1A is configured by forming a protective film 3a on the lower surface of the resin laminated substrate 1 shown in Fig. 2 and forming a protective film 3b on the upper surface of the resin laminated substrate 1. The configuration of the resin laminated substrate 1 in Fig. 3 is the same as that shown in Fig. 2.

[0039] The protective films 3a and 3b are provided by applying a solder resist, for example, or by attaching a coverlay layer made of PI (polyimide) or the like.

[0040] In this way, by providing the protective films 3a and 3b on the top and bottom surfaces of the resin laminated substrate 1, the conductor layers exposed on the outer surfaces can be protected.

[0041] Although a single resin laminated substrate is illustrated in Figures 1, 2, and 3, when a plurality of resin laminated substrates are manufactured simultaneously, a plurality of units of the resin laminated substrates shown in Figures 1, 2, and 3 may be stacked in a continuous state, heat-pressed, and then separated into individual (single) resin laminated substrates.

[0042] 2 and 3, for example, conductor layer 22b is a signal conductor of the transmission line, and conductor layer 21b is an opposing ground conductor layer. A microstrip line is formed by conductor layer 21b, conductor layer 22b, and parts of first resin layer 11, second resin layer 12, and third resin layer 13 between conductor layer 21b and conductor layer 22b. In addition, conductor layers 22e and 22f and interlayer connection conductors 23e and 23f function as signal lines for conductor layer 22b, which serves as a signal conductor.

[0043] According to this embodiment, the coplanarity of the resin laminated substrate is improved, thereby reducing variations in the thickness of the resin layers above and below the transmission line portion, and suppressing variations in the characteristic impedance of the transmission line.

[0044] In this embodiment, a resin laminated substrate having a transmission line is exemplified, but the present invention is not limited to this and can be applied to substrates having various conductor layers. For example, an example of a resin laminated substrate having an antenna function in which a radiating element is provided in the first resin layer 11 will be shown later.

[0045] Second Embodiment In the second embodiment, a resin laminated substrate in which the configurations of the first resin layer 11 and the second resin layer 12 of the resin laminated substrate shown in the first embodiment are different will be exemplified.

[0046] FIG. 4 is a cross-sectional view showing the structure of each resin layer that is part of a resin laminate substrate according to the second embodiment. As illustrated in the first embodiment, the second resin layer 12 is a porous material containing numerous bubbles Fo. In the second embodiment, the first resin layer 11 is also a porous material containing numerous bubbles Fo. However, the second resin layer 12, which is a low-melting-point resin, has a higher porosity than the first resin layer 11, which is a relatively high-melting-point resin. Therefore, when there is a partial pressure difference applied in the thickness direction between the first resin layer 11 and the second resin layer 12, the amount of depression of the first resin layer 11 and the second resin layer 12 varies depending on the pressure. In other words, the second resin layer 12 is more depressed in the areas subjected to higher pressure. Therefore, both the first resin layer 11 and the second resin layer 12 can also be referred to as a buffer layer (a layer with cushioning properties), a pressure relaxation layer, and an irregularity absorption layer.

[0047] According to this embodiment, air bubbles into which the resin flows during heat pressing are also present in the first resin layer 11, providing many escape routes for the molten resin. Therefore, by increasing the air bubble content of the second resin layer 12, which is the more easily deformed low-melting-point resin, these air bubbles are more easily crushed. Furthermore, as in the first embodiment, the first resin layer 11, made of a high-melting-point resin, is pressurized during heat pressing while maintaining its high rigidity compared to the second resin layer. This is expected to further improve the coplanarity of the outer surface of the first resin layer 11. Furthermore, by relatively increasing the air bubble content of the second resin layer 12, the dielectric constant of the second resin layer 12 can be reduced. Therefore, a desired characteristic impedance can be obtained even with a thicker line width. This also reduces transmission loss in the signal transmission path.

[0048] Third Embodiment In a third embodiment, a cross-sectional deformation (uneven shape) of a conductor layer in an inner layer of a third resin layer is illustrated. Also, in this third embodiment, a resin laminate substrate having electronic components mounted on its outer surface is illustrated.

[0049] Fig. 5 is a cross-sectional view showing the structure of each resin layer that is a part of the resin laminated substrate according to the third embodiment, and Fig. 6 is a cross-sectional view of the resin laminated substrate 3 formed by hot pressing.

[0050] The resin laminated substrate 1 includes multiple resin layers stacked on top of each other and conductors disposed on the exterior and interior of the multiple stacked resin layers. In Figures 5 and 6, the first resin layer 11, the second resin layer 12, and the third resin layers 13a, 13b, and 13c are the "resin layers." The first conductor layers 21a, 21c, and 21d, the second conductor layers 22a to 22h, and the interlayer connection conductors 23a1, 23a2, 23e, 23g, and 23h are the "conductors."

[0051] 5, the first resin layer 11 has an upper main surface 11us and a lower main surface 11ds that face each other, and the second resin layer 12 has an upper main surface 12us and a lower main surface 12ds that face each other.

[0052] The upper main surface 11us of the first resin layer 11 is in contact with the lower main surface 12ds of the second resin layer 12.

[0053] First conductor layers 21 a , 21 c , and 21 d are disposed on the lower main surface 11 ds of the first resin layer 11 .

[0054] The third resin layer 13a is provided with an interlayer connection conductor 23a2 and a second conductor layer 22a that overlap the first conductor layer 21a when viewed in the thickness direction of the third resin layer 13a. The third resin layer 13a is also provided with a second conductor layer 22b.

[0055] An interlayer connection conductor 23e overlapping the second conductor layer 22b when viewed in the thickness direction of the third resin layer 13b is disposed on the third resin layer 13b. Also, a second conductor layer 22e overlapping the interlayer connection conductor 23e is disposed on the third resin layer 13b. Also, second conductor layers 22c and 22d are disposed on the third resin layer 13b.

[0056] An interlayer connection conductor 23g overlapping the second conductor layer 22d when viewed in the thickness direction of the third resin layer 13c is disposed on the third resin layer 13c. An interlayer connection conductor 23h is also disposed on the third resin layer 13c. Second conductor layers 22g and 22h overlapping the interlayer connection conductors 23g and 23h are also disposed on the third resin layer 13c.

[0057] The second resin layer 12 is a thermoplastic resin, and the melting point of the second resin layer 12 is lower than the melting point of the first resin layer 11. In other words, in terms of the difference in melting point, the first resin layer 11 is a high-melting-point resin, and the second resin layer 12 is a low-melting-point resin.

[0058] The second resin layer 12 is a porous material containing numerous bubbles Fo. Therefore, when a partial pressure difference is applied to the second resin layer 12 in the thickness direction during heat pressing, the amount of depression varies depending on the pressure. That is, the more highly pressurized the second resin layer 12, the more depression there is. Therefore, the second resin layer 12 can also be called a buffer layer (a layer with cushioning properties), a pressure relaxation layer, and an irregularity absorption layer.

[0059] The first resin layer 11 made of a high melting point resin is pressed during the heat press while maintaining its high rigidity compared to the second resin layer.

[0060] The first resin layer 11, the second resin layer 12, and the third resin layers 13a, 13b, and 13c on which the conductor layers and interlayer connection conductors shown in Figure 5 are formed are stacked and heat-pressed with a rigid member having a flat surface.

[0061] 6 is a cross-sectional view of a resin laminated substrate 3 formed by laminating the resin layers shown in FIG. 5 and hot-pressing them with a rigid member to form a protective film 3a on the lower surface of the resin laminated substrate and a protective film 3b on the upper surface of the resin laminated substrate. The second resin layer 12, which is an inner layer, is a low-melting-point resin layer made of a thermoplastic porous material, rather than the first resin layer 11, which is the outermost layer. By hot-pressing the laminated body of multiple resin layers, the conductor layer 22b deforms in response to upward pressure from the conductor layers 21c and 21d, but a resin laminated substrate 3 is obtained in which the first resin layer 11, which is the outermost layer, and the first conductor layers 21c and 21d have high coplanarity.

[0062] Terminals 71c, 71d of the electronic component 7 are mounted on the first conductor layers 21c, 21d by soldering or the like. Even when the electronic component is mounted on the outer surface of the resin laminated substrate 3 as in this embodiment, the high coplanarity of the first conductor layers 21c, 21d makes it easy and reliable to mount the electronic component 7.

[0063] Fourth Embodiment In a fourth embodiment, a resin laminated substrate in which electronic components are mounted will be exemplified.

[0064] Fig. 7 is a cross-sectional view showing the structure of each resin layer that is a part of the resin laminated substrate according to the fourth embodiment. Fig. 8 is a cross-sectional view of a resin laminated substrate 4 formed by laminating the resin layers shown in Fig. 7 and hot pressing them with a rigid member.

[0065] The resin laminated substrate 4 includes multiple resin layers stacked on top of each other and conductors disposed on the exterior and interior of the multiple stacked resin layers. In Figures 7 and 8, the first resin layer 11, the second resin layer 12, and the third resin layers 13a, 13b, and 13c are the "resin layers." The first conductor layers 21a and 21b, the second conductor layers 22a, 22c to 22h, and the interlayer connection conductors 23a1, 23a2, 23e, 23f, 23g, and 23h are the "conductors."

[0066] First conductor layers 21 a and 21 b are disposed on the lower main surface of the first resin layer 11 .

[0067] Through holes for inserting (embedding) electronic components 7 are formed in the third resin layer 13a, and the electronic components 7 are inserted into the through holes. Terminals 71e, 71f of the electronic components 7 contact the interlayer connection conductors 23e, 23f. A first conductor layer 21b is disposed in the first resin layer 11 at a position overlapping the electronic components 7 when viewed in the thickness direction of the first resin layer 11. The electronic components 7 are components such as ICs, chip capacitors, and chip inductors.

[0068] According to this embodiment, high coplanarity can be maintained during heat pressing of the first conductor layer 21b of the resin laminated substrate 4. Generally, when electronic components are embedded in a resin laminated substrate, the coplanarity of the outer surface of the resin laminated substrate deteriorates, but the presence of the second resin layer 12, which is a low-melting point resin layer, improves the coplanarity of the outer surface of the resin laminated substrate.

[0069] Fig. 9 is a cross-sectional view of a resin laminated substrate 4A according to a fourth embodiment, which is different from the resin laminated substrate 4 shown in Fig. 8. This resin laminated substrate 4A is configured by forming a protective film 3a on the lower surface of the resin laminated substrate 4 shown in Fig. 8 and forming a protective film 3b on the upper surface of the resin laminated substrate 4. The configuration of the resin laminated substrate 4 in Fig. 9 is the same as that shown in Fig. 8.

[0070] In this way, by providing the protective films 3a and 3b on the top and bottom surfaces of the resin laminated substrate 4, the conductor layers exposed on the outer surface can be protected.

[0071] Fifth Embodiment In a fifth embodiment, a resin laminated substrate provided with an antenna will be exemplified.

[0072] Fig. 10 is a perspective view showing each resin layer structure that is a part of the resin laminated substrate according to the fifth embodiment. Fig. 11 is a cross-sectional view showing each resin layer structure that is a part of the resin laminated substrate according to the fifth embodiment. Fig. 12 is a cross-sectional view of a resin laminated substrate 5 formed by stacking the resin layers shown in Fig. 11 and hot pressing them with a rigid member.

[0073] The resin laminated substrate 1 includes multiple resin layers stacked on top of each other and conductors disposed on and inside the multiple resin layers. In Figures 10 and 11, the first resin layer 11, the second resin layer 12, and the third resin layers 13a, 13b, and 13c are the "resin layers." The first conductor layers 21a and 21g, the second conductor layers 22g1, 22g2, 22g3, 22g4, 22g5, 22g, 22s, 22a, 22b, 22c, and 22s, and the interlayer connection conductors 23a1, 23a2, 23b1, 23b2, 23c1, 23c2, 23c3, and 23c4 are the "conductors."

[0074] The second resin layer 12 is a thermoplastic resin, and the melting point of the second resin layer 12 is lower than the melting point of the first resin layer 11. In other words, in terms of the difference in melting point, the first resin layer 11 is a high-melting-point resin, and the second resin layer 12 is a low-melting-point resin.

[0075] The second resin layer 12 is a porous material having a large number of bubbles Fo. Therefore, when a pressure difference is applied to the second resin layer 12 in the thickness direction during heat pressing, the amount of depression varies depending on the pressure.

[0076] The first resin layer 11 made of a high melting point resin is pressed during the heat press while maintaining its high rigidity compared to the second resin layer.

[0077] The first conductor layer 21a is a radiating element, and the second conductor layer 22g is an opposing ground layer opposing the first conductor layer 21a. The first conductor layer 21a is electrically connected to the second conductor layer 22c via interlayer connection conductors 23c1, 23c2, 23c3, and 23c4. The first conductor layer 21a, the second conductor layers 22g and 22c, and the interlayer connection conductors 23c1, 23c2, 23c3, and 23c4 form a patch antenna.

[0078] The second conductor layer 22s is a signal conductor, and the second conductor layers 22a and 22b are electrically connected to the second conductor layer 22s via interlayer connection conductors 23a1, 23a2, 23b1, and 23b2. The second conductor layers 22s, 22a, and 22b and the interlayer connection conductors 23a1, 23a2, 23b1, and 23b2 form a microstrip line or a strip line. The second conductor layers 22g1, 22g2, 22g3, 22g4, and 22g5 and the interlayer connection conductors that connect them in the layer direction are at ground potential and act as shield electrodes that shield the microstrips.

[0079] The dielectric constant of the first resin layer 11, which is the outermost layer with a high melting point and on which the conductor layer 21a serving as the radiating element is formed, is higher than the dielectric constant of the second resin layer 12, which is the inner layer having pores. In this way, the high dielectric constant in the vicinity of the first conductor layer 21a serving as the radiating element allows the antenna to be miniaturized due to the wavelength compression effect.

[0080] On the other hand, since the dielectric constant in the vicinity of the conductor layer 22s, which is the signal line, is relatively low, the transmission loss due to the dielectric loss (Df) can be reduced.

[0081] Fig. 13 is a cross-sectional view of a resin laminated substrate 5A according to a fifth embodiment, which is different from the resin laminated substrate shown in Fig. 12. This resin laminated substrate 5A is configured by forming a protective film 3a on the lower surface of the resin laminated substrate 1 shown in Fig. 12 and forming a protective film 3b on the upper surface of the resin laminated substrate 1. The configuration of the resin laminated substrate 5 in Fig. 13 is the same as that shown in Fig. 12.

[0082] According to this embodiment, the variation in the distance between the first conductor layer 21 a serving as the radiating element and the second conductor layer 22 g serving as the opposing ground conductor layer is reduced, thereby suppressing the variation in the resonant frequency of the antenna. Note that the above effect can also be achieved by providing the second conductor layer serving as the radiating element on the second resin layer side and providing the first conductor layer serving as the opposing ground conductor layer on the first resin layer side.

[0083] In each of the above-described embodiments, an example has been shown in which a conductor layer such as copper foil is provided on only one side of each resin layer prior to lamination by hot pressing, but a conductor layer may be formed partially or entirely on both sides of a desired resin layer.

[0084] In addition, in each of the above-described embodiments, the resin laminated substrate is exemplified as including a first resin layer, a second resin layer, and a third resin layer stacked in this order, with the first resin layer and the third resin layer being the outermost layers, but a pair of the first resin layer and the second resin layer may be provided on both sides of the resin laminated substrate. That is, the resin laminated substrate may be constructed by stacking layers in the order of [first resin layer], [second resin layer], [third resin layer], [second resin layer], and [first resin layer], and then heat-pressing the layers.

[0085] Finally, the present invention is not limited to the above-described embodiments. Those skilled in the art can make appropriate modifications and variations. The scope of the present invention is defined not by the above-described embodiments but by the claims. Furthermore, the scope of the present invention includes modifications and variations from the embodiments within the scope of the claims and their equivalents.

[0086] The resin laminated substrate and the method for producing a resin laminated substrate of the present invention may be provided in the following embodiments.

[0087] <1> A resin laminated substrate comprising: a plurality of resin layers stacked on top of each other; and conductors disposed outside and inside the plurality of stacked resin layers; the plurality of resin layers include a first resin layer, a second resin layer, and a third resin layer stacked on top of each other in that order; the conductors include a first conductor layer, a second conductor layer, and an interlayer connection conductor; the first resin layer has an upper main surface and a lower main surface facing each other; the second resin layer has an upper main surface and a lower main surface facing each other; the upper main surface of the first resin layer contacts the lower main surface of the second resin layer; the first conductor layer is disposed on the lower main surface of the first resin layer; the second conductor layer or the interlayer connection conductor is disposed on the third resin layer, overlapping a portion of the first conductor layer when viewed in a thickness direction of the third resin layer; the second resin layer is a thermoplastic resin, the melting point of the second resin layer is lower than the melting point of the first resin layer; and at least the second resin layer has bubbles.

[0088] <2> The resin laminated substrate according to <1>, wherein the second resin layer has a higher void content than the first resin layer.

[0089] <3> The resin laminated substrate according to <1> or <2>, wherein the first resin layer and the second resin layer are in direct contact with each other, and no conductor layer is disposed between the first resin layer and the second resin layer.

[0090] <4> The resin laminated substrate according to any one of <1> to <3>, wherein the second conductor layer is disposed on the third resin layer, overlapping at least a portion of the first conductor layer when viewed in the thickness direction of the third resin layer, and at least a portion of the first conductor layer is a radiating element, and the second conductor layer overlapping at least a portion of the first conductor layer is a ground conductor; or at least a portion of the second conductor layer is a radiating element, and the first conductor layer overlapping at least a portion of the second conductor layer is a ground conductor.

[0091] <5> The resin laminated substrate according to <4>, wherein the radiating element is disposed on the first resin layer, and the dielectric constant of the first resin layer is higher than the dielectric constant of the second resin layer, or the radiating element is disposed on the third resin layer, and the dielectric constant of the third resin layer is higher than the dielectric constant of the first resin layer.

[0092] <6> The resin laminated substrate according to any one of <1> to <5>, wherein a protective film is formed on an outer surface of a laminate including the plurality of resin layers stacked on one another and the conductors disposed on the outside and inside of the plurality of stacked resin layers.

[0093] <7> The resin laminated substrate according to any one of <1> to <6>, wherein an electronic component is disposed in the third resin layer at a position overlapping the first conductor layer.

[0094] <8> The resin laminated substrate according to any one of <1> to <7>, wherein the lower main surface of the first resin layer is an outermost layer of a laminate including the plurality of resin layers stacked on one another and the conductors disposed outside and inside the plurality of stacked resin layers, and a part of the first conductor layer is disposed on the lower main surface of the first resin layer.

[0095] <9> A method for manufacturing a resin laminated substrate, comprising: a plurality of resin layers stacked on one another; and conductors arranged outside and inside the plurality of stacked resin layers; the plurality of resin layers include a first resin layer, a second resin layer, and a third resin layer stacked on one another in order; the conductors include a first conductor layer, a second conductor layer, and an interlayer connection conductor; the first resin layer has an upper main surface and a lower main surface facing each other; the second resin layer has an upper main surface and a lower main surface facing each other; the upper main surface of the first resin layer is in contact with the lower main surface of the second resin layer; the first conductor layer is arranged on the lower main surface of the first resin layer; and the second conductor layer or the interlayer connection conductor is arranged on the third resin layer, the second resin layer being such that it overlaps with a part of the first conductor layer when viewed in a thickness direction of the third resin layer; a method for producing a resin laminated substrate, wherein the first resin layer, the second resin layer, and the third resin layer are heat-pressed in a laminated state at a temperature lower than a melting point of the first resin layer and higher than a melting point of the second resin layer.

[0096] Fo...air bubbles 1, 1A, 3, 4, 4A, 5, 5A...resin laminated substrate 3a, 3b...protective film 7...electronic component 11...first resin layer 11ds...lower main surface 11us...upper main surface 12...second resin layer 12ds...lower main surface 12us...upper main surface 13, 13a, 13b, 13c...third resin layer 21a, 21b, 21c, 21d, 21g...first conductor layer 22a, 22b, 22c, 22d, 22e, 22f, 22g, 22h, 22s...second conductor layer 22g1, 22g2, 22g3, 22g4, 22g5...second conductor layer Interlayer connection conductors 23a1, 23a2, 23b1, 23b2, 23c1, 23c2, 23c3, 23c4... Interlayer connection conductors 23e, 23f, 23g, 23h... Interlayer connection conductors 23c1, 23c2, 23c3, 23c4... Interlayer connection conductors 71c, 71d, 71e, 71f... Terminals

Claims

1. A resin laminated substrate comprising a plurality of resin layers stacked on top of each other and conductors disposed on the exterior and interior of the plurality of stacked resin layers, the plurality of resin layers including a first resin layer, a second resin layer and a third resin layer stacked on top of each other in that order, the conductors including a first conductor layer, a second conductor layer and an interlayer connection conductor, the first resin layer having upper and lower main surfaces opposing each other, the second resin layer having upper and lower main surfaces opposing each other, the upper main surface of the first resin layer contacting the lower main surface of the second resin layer, the first conductor layer being disposed on the lower main surface of the first resin layer, the second conductor layer or the interlayer connection conductor being disposed on the third resin layer so as to overlap a portion of the first conductor layer when viewed in the thickness direction of the third resin layer, the second resin layer being a thermoplastic resin, the melting point of the second resin layer being lower than the melting point of the first resin layer, and at least the second resin layer having air bubbles.

2. The resin laminated substrate according to claim 1, wherein the second resin layer has a higher void content than the first resin layer.

3. A resin laminated substrate as described in claim 1 or claim 2, wherein the first resin layer and the second resin layer are in direct contact with each other, and no conductor layer is disposed between the first resin layer and the second resin layer.

4. A resin laminated substrate as described in any one of claims 1 to 3, wherein the third resin layer is provided with the second conductor layer overlapping at least a portion of the first conductor layer when viewed in the thickness direction of the third resin layer, and at least a portion of the first conductor layer is a radiating element, and the second conductor layer overlapping at least a portion of the first conductor layer is a ground conductor, or at least a portion of the second conductor layer is a radiating element, and the first conductor layer overlapping at least a portion of the second conductor layer is a ground conductor.

5. The resin laminated board according to claim 4, wherein the radiating element is disposed on the first resin layer, and the dielectric constant of the first resin layer is higher than the dielectric constant of the second resin layer, or the radiating element is disposed on the third resin layer, and the dielectric constant of the third resin layer is higher than the dielectric constant of the first resin layer.

6. A resin laminated board according to any one of claims 1 to 5, in which a protective film is formed on the outer surface of a laminate consisting of the multiple resin layers stacked on top of each other and the conductors disposed on the outside and inside of the multiple resin layers stacked on top of each other.

7. The resin laminated board according to any one of claims 1 to 6, wherein an electronic component is disposed in a position overlapping said first conductor layer and within said third resin layer.

8. A resin laminated substrate as described in any one of claims 1 to 7, wherein the lower main surface of the first resin layer is the outermost layer of a laminate consisting of the multiple resin layers stacked on top of each other and the conductors disposed on the outside and inside of the multiple resin layers stacked on top of each other, and a portion of the first conductor layer is disposed on the lower main surface of the first resin layer.

9. A method for manufacturing a resin laminated substrate comprising a plurality of resin layers laminated on one another and a conductor disposed on the outside and inside of the plurality of laminated resin layers, the plurality of resin layers including a first resin layer, a second resin layer and a third resin layer laminated on one another in order, the conductor including a first conductor layer, a second conductor layer and an interlayer connection conductor, the first resin layer having an upper main surface and a lower main surface opposed to each other, the second resin layer having an upper main surface and a lower main surface opposed to each other, the upper main surface of the first resin layer being in contact with the lower main surface of the second resin layer, the first conductor layer being disposed on the lower main surface of the first resin layer, and the second conductor layer or the interlayer connection conductor being disposed on the third resin layer so as to overlap a part of the first conductor layer when viewed in the thickness direction of the third resin layer, wherein the second resin layer is a thermoplastic resin and has air bubbles therein before the heat pressing, the melting point of the second resin layer is lower than the melting point of the first resin layer, a heat pressing step of laminating the first resin layer, the second resin layer, and the third resin layer at a temperature lower than a melting point of the first resin layer and higher than a melting point of the second resin layer.

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