JP2009055071A - Circuit board and its manufacturing method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a circuit board configured so as to sufficiently reduce crosstalk noise and easily achieve multilayer structurization, and its manufacturing method. <P>SOLUTION: The circuit board is provided with insulating layers 11a and 11b and a wiring layer 12 interposed between the insulating layers. An inter-wiring insulating part 12b whose dielectric constant is made lower than the insulating layers 11a and 11b is provided mutually between respective signal wiring 12a to be the wiring layers 12. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a circuit board in which crosstalk noise is suppressed and a manufacturing method thereof, and more particularly to a circuit board having a multilayer structure and a manufacturing method thereof.

  With the recent increase in the speed of computers, high-speed operation of semiconductor chips is required, and on circuit boards on which semiconductor chips are mounted, signal wiring is assumed to be a transmission line in order to realize high-speed signal transmission. The design is done. Further, in recent semiconductor chips, the number of input / output terminals has been remarkably increased, so that signal wirings on a circuit board have to be arranged with high density, and it has been necessary to narrow the arrangement interval between signal wirings. However, when signal wirings through which high-speed signals flow are arranged close to each other, noise such as crosstalk occurs due to the influence of parasitic components generated between the signal wirings, especially inter-wiring capacitance (floating capacitance) and mutual inductance. Will end up.

And from the necessity of realizing the suppression of crosstalk noise while narrowing the interval between the signal wirings, a configuration as in Patent Document 1, that is, a groove is provided between adjacent signal wirings formed on the circuit board. It has been proposed to adopt the following configuration. That is, in this prior art, as shown in FIG. 12, a groove 103 is formed between pedestals 102 provided at predetermined positions of the circuit board 101, and inner leads 104 that are signal wirings are provided on each pedestal 102. Since air having a low dielectric constant exists between the pedestals 102 on which the inner leads 104 are formed, parasitic components generated between them, particularly between the wirings, are formed. The capacity can be reduced. As a result, according to this technique, it is possible to reduce the arrangement interval of the signal wiring while suppressing the crosstalk noise.
Japanese Patent Laid-Open No. 9-246425 Japanese Patent Laid-Open No. 08-330300

  However, when the configuration disclosed in Patent Document 1 and shown in FIG. 12 is adopted, a groove 103 is formed between pedestals 102 provided at predetermined positions of the circuit board 101. Since it is necessary to form the inner lead 104, it is inevitable that the manufacturing process is troublesome and requires a lot of labor. Further, a general circuit board is required to have a multilayer structure. However, as long as the configuration as shown in FIG. 12 in which the groove 103 is provided between the bases 102 on which the inner leads 104 are formed, the multilayer circuit board is required. It becomes difficult to realize the structure.

  The present invention was devised in view of these disadvantages, and it is possible to sufficiently reduce crosstalk noise, and a circuit board configured to easily realize a multilayer structure, and The purpose is to provide a manufacturing method thereof.

  The circuit board according to claim 1 of the present invention includes an insulating layer and a wiring layer interposed between these insulating layers, and each of the signal wirings serving as the wiring layers An inter-wiring insulating portion having a lower dielectric constant than the insulating layer is provided between them. A circuit board according to a second aspect of the present invention is the circuit board according to the first aspect, wherein the insulating layer has a ratio lower than that of the first resin component and the first resin component that decreases in viscosity with pressurization and heating. It is formed from a dielectric material containing a second resin component or an inorganic component that has a large dielectric constant and does not decrease in viscosity with pressurization and heating. It is formed only from the 1st resin component contained in the dielectric material which becomes.

  A circuit board according to a third aspect of the present invention is the circuit board according to the first aspect, wherein the inter-wiring insulating portion is formed by adding fine particles having a small relative dielectric constant to a dielectric material to be an insulating layer. It is characterized by being. In the configuration according to any one of claims 1 to 3, since the inter-wiring insulation portions having a lower dielectric constant than that of the insulating layer are provided between the signal wirings, they are arranged close to each other. As a result of reducing the wiring capacitance directly generated between the signal wirings, crosstalk noise can be suppressed. When these configurations are employed, the advantage that the circuit board can be easily formed into a multilayer structure is also ensured.

  A circuit board manufacturing method according to a fourth aspect of the present invention is a method employed when manufacturing the circuit board according to the second or third aspect, and is a dielectric that decreases in dielectric constant with light irradiation. A step of laminating a material on an insulating layer, a step of patterning the laminated dielectric material with light irradiation and reducing the dielectric constant, and forming an inter-wiring insulating portion; and an inter-wiring insulating portion And a step of forming a signal wiring therebetween. The method for manufacturing a circuit board according to claim 5 of the present invention is a method employed when manufacturing the circuit board according to claim 2 or claim 3, wherein the viscosity of the circuit board decreases with pressurization and heating. 1st insulation which consists of a dielectric material containing 1 resin component and 2nd resin component or an inorganic component which has a relative dielectric constant larger than 1st resin component, and does not reduce viscosity with pressurization and heating A step of forming a layer, a step of forming a plurality of signal wirings on the first insulating layer, and a first insulating layer in which the signal wiring is formed on a second insulating layer made of the same dielectric material as the first insulating layer And the step of forming the second insulating layer is characterized by adopting pressure and heating conditions that lower the viscosity of only the first resin component.

  A method for manufacturing a circuit board according to claim 6 of the present invention is a method employed when manufacturing the circuit board according to claim 2 or 3, wherein a plurality of signals are formed on an insulating layer made of a dielectric material. A step of forming a wiring, a step of filling the same dielectric material as the insulating layer between the signal wirings to form an insulating portion between the wirings, and a dielectric constant smaller than that of the dielectric material to be the insulating layer And a step of injecting fine particles into the inter-wiring insulating portion. The manufacturing method according to any one of claims 4 to 6 also secures the advantage that a multilayered circuit board in which crosstalk noise is suppressed can be manufactured inexpensively and easily.

  According to the circuit board according to the present invention, the inter-wiring insulating portion having a lower dielectric constant than the insulating layer is provided between the signal wirings serving as the wiring layers, so that crosstalk noise can be sufficiently reduced. As a result, it is possible to easily realize a multilayer structure of the circuit board. In addition, according to the method for manufacturing a circuit board according to the present invention, it is possible to easily and inexpensively manufacture a circuit board in which crosstalk noise is suppressed.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

(Reference example)
FIG. 1 is a cross-sectional view showing a simplified configuration of a circuit board according to a reference example, FIG. 2 is a process cross-section showing a manufacturing method thereof, and FIG. 3 is for explaining the reason why crosstalk noise can be suppressed. It is explanatory drawing. In this reference example, the circuit board has a single-layer structure. However, the circuit board is not limited to the single-layer structure, and may be a circuit board having a two-layer or more layer structure. Of course.

  As shown in FIG. 1, the circuit board according to this reference example includes an insulating layer 1 made of a dielectric material, and a wiring layer 2 and a grounding layer 3 that face each other with the insulating layer 1 interposed therebetween. A plurality of signal wires 2a constituting the wiring layer 2 are provided on one surface (upper surface in the figure) of the insulating layer 1 having a predetermined thickness by being arranged in parallel, while the other surface of the insulating layer 1 On the (lower surface in the figure), a ground layer 3 which is a ground electrode having a planar shape is provided. In this circuit board, the signal wiring 2a is not provided and the insulating layer is not provided, rather than the first region 1a of the insulating layer 1 specified by being sandwiched between each of the signal wirings 2a and the ground layer 3. The dielectric constant of the second region 1b of the insulating layer 1 located between the first regions 1a is reduced. That is, in this insulating layer 1, the relative permittivity of the second region 1b is set to be smaller than the relative permittivity of the first region 1a.

  That is, the insulating layer 1 included in the circuit board here is a dielectric material that changes so that the relative dielectric constant decreases with light irradiation, such as an epoxy resin containing a diazo compound. Is formed using a dielectric material that is a simple resin composition, and is disposed between the first regions 1a of the insulating layer 1 sandwiched between each of the signal wirings 2a and the ground layer 3 The second region 1b of the insulating layer 1 is irreversibly lowered in dielectric constant with light irradiation. When the circuit board having such a configuration is manufactured, as shown in FIG. 2, a plurality of signal wirings 2a to be the wiring layer 2 are formed in parallel on one surface of the insulating layer 1, and these A method of irradiating a laser beam 4 having a predetermined wavelength from above the one surface side of the insulating layer 1 on which the signal wiring 2a is formed is employed. The ground layer 3 is not limited to a planar ground electrode. For example, the ground layer 3 may not be planar but may be a linear ground electrode corresponding to each of the signal wirings 2a. Of course, the power supply electrode may be used instead of the ground electrode.

  By the way, when the configuration of the circuit board according to the present reference example is adopted, it is possible to suppress the crosstalk noise generated between the signal wirings 2a arranged in proximity to each other. The reason why the crosstalk noise can be suppressed will be described with reference to FIG. First, it is a general fact that the crosstalk noise is proportional to the capacitance between the signal wirings 2a arranged adjacent to each other, and although not shown, a dielectric is provided between the parallel arranged flat plates. The capacity when sandwiching is expressed by εS / d, where S is the plate area, d is the distance between the plates, and ε is the relative dielectric constant of the dielectric. However, the capacity is expressed as εS / d only when it is possible to assume that the electric field between the plates is uniform without considering the influence of the edges of the plates, as shown in FIG. In fact, in the end region of the flat plate 105 arranged in parallel, the electric field cannot be zero. Note that the arrows in FIG. 3 indicate lines of electric force.

  That is, the influence of the edge of the parallel plate 105 is also described in detail in Feiman physics and electromagnetism (written by Miyajima Tatsuoki, 1982, Vol. 3, p. 65-80). Is that the charge density is somewhat increased in the other end region 107 of the flat plate 105 arranged in parallel, and the capacitance between them is larger than in the case where the influence of the edge is not taken into account. It is described that the capacity is calculated using a numerical value obtained by extending d by 3/8. Therefore, considering this and considering the electrostatic capacitance between the signal wirings 2a, the capacitance generated between the signal wirings 2a included in the circuit board having the configuration shown in FIG. 1 is the same as that shown in FIG. Therefore, the capacitance is smaller than the capacity generated between the signal wirings 2a included in the circuit board that is not irradiated with light.

  This is because the circuit board according to this reference example, that is, the first region 1a of the insulating layer 1 sandwiched between each of the signal wirings 2a and the ground layer 3, as shown in FIG. The circuit board in which the second region 1b of the insulating layer 1 has a lower dielectric constant and the circuit board shown in FIG. 2 for explaining the manufacturing method, that is, the entire insulating layer 1 without being irradiated with light. 3 is considered to be only a difference in dielectric constant in the other end region 107 of the flat plate 105 shown in FIG. This is because the wiring capacity generated between the signal wirings 2a is smaller as the value is smaller. Therefore, in the case of the circuit board according to this reference example, the second region 1b of the insulating layer 1 located between the adjacent signal wirings 2a has a lower dielectric constant than the first region 1a. Parasitic components generated between these signal wirings 2a, in particular, inter-wiring capacitance is reduced, and crosstalk noise is suppressed.

(Embodiment 1)
4 is a simplified cross-sectional view showing the configuration of the circuit board according to the first embodiment, FIG. 5 is a process cross-sectional view showing the manufacturing method, and FIG. 6 is a process cross-sectional view showing a modification procedure of the manufacturing method. 7 is an explanatory diagram for explaining the reason why crosstalk noise can be suppressed even by a circuit board having a modified configuration. In the present embodiment, the circuit board has a single-layer structure. However, the circuit board is not limited to a single-layer structure, and may be a circuit board having a two-layer or more layer structure. Of course.

  As shown in FIG. 4, the circuit board according to the present embodiment is formed using a dielectric material such as glass epoxy, glass ceramic, or a resin component, and is disposed at least in a pair of positions. Insulating layers 11a and 11b and a wiring layer 12 interposed between these insulating layers 11a and 11b, and a wiring layer 12 sandwiched between the insulating layers 11a and 11b Includes a plurality of signal wires 12a arranged in parallel. An inter-wiring insulating portion 12b having a lower dielectric constant than the insulating layers 11a and 11b is provided between the signal wirings 12a. By the way, the circuit board having such a configuration is manufactured after adopting a method including a procedure as shown in FIG.

  First, a first insulating layer 11a made of a first dielectric material such as glass epoxy is formed, and a wiring conductor 13 is laminated on the first insulating layer 11a. After the deposition, a resist layer 14 is formed on the wiring conductor 13, and an opening 14a is formed at each position corresponding to the inter-wiring insulating portion 12b in the resist layer 14 as shown in FIG. . Subsequently, when the wiring conductor 13 is etched through the resist layer 14, a plurality of signal wirings 12a that are arranged in parallel and become the wiring layer 12 are formed as shown in FIG. 5B. Next, a dielectric material having a relative dielectric constant smaller than that of the first dielectric material forming the first insulating layer 11a, for example, a second dielectric material 15 made of only epoxy resin is prepared. As shown in FIG. 5C, after covering the entire surface of the first insulating layer 11a including the resist layer 14 with the second dielectric material 15, the resist layer 14 is removed. As shown, the inter-wiring insulating portion 12b having a lower dielectric constant than that of the first insulating layer 11a is provided between the signal wirings 12a arranged in parallel on the first insulating layer 11a.

  Thereafter, although not shown in the drawing, if the second dielectric layer 11b is formed on the wiring layer 12 after using the first dielectric material which is the same as the first insulating layer 11a, the circuit board shown in FIG. It will be manufactured. Note that the first dielectric material is not necessarily glass epoxy and the second dielectric material 15 is necessarily an epoxy resin. For example, the first dielectric material is an inorganic material such as ceramic. In this case, a porous and insulating inorganic material can be used as the second dielectric material 15. In the case of the circuit board having the configuration according to the present embodiment, the signal wirings 12a serving as the wiring layers 12 interposed between the insulating layers 11a and 11b are more than the insulating layers 11a and 11b. In addition, since the inter-wiring insulating portion 12b having a low dielectric constant is interposed, the inter-wiring capacitance generated between the adjacent signal wirings 12a is reduced, and crosstalk noise is suppressed. It will be. Such a configuration also ensures the advantage that a multilayered circuit board can be easily manufactured.

  By the way, in the present embodiment, the manufacturing method having the procedure as shown in FIG. 5 is adopted. However, the manufacturing method is not limited to such a method, and the procedure as shown in FIG. 6 is used. It is also possible to manufacture a circuit board by employing a manufacturing method. Therefore, hereinafter, a modified procedure of the method of manufacturing a circuit board will be described with reference to FIG. In FIG. 6, the same or corresponding parts as those in FIGS. 4 and 5 are denoted by the same reference numerals.

  First, a resin composition that is patterned with light irradiation and has a low dielectric constant, for example, a dielectric material 16 made of a resin composition that cures with light irradiation is prepared, and is shown in FIG. Thus, the prepared dielectric material 16 is deposited and laminated on the first insulating layer 11a. Then, as shown in FIG. 6B, when a mask film 17 is laminated on the dielectric material 16 and light irradiation is performed through the mask film 17, exposure and development accompanying light irradiation are performed. As a result, the dielectric material 16 is patterned and the dielectric constant is lowered. Further, as shown in FIG. 6C, after removing the portion of the dielectric material 16 that was not irradiated with light to form the opening 16a, as shown in FIG. 6D, a plating method or the like is performed. After the adoption, the conductor material to be the signal wiring 12a is filled into the opening 16a of the dielectric material 16.

  That is, in this case, only the portion irradiated with light in the dielectric material 16 remains without being removed, and the remaining portion is the inter-wiring insulating portion in which the dielectric constant is reduced. 12b. Subsequently, as shown in FIG. 6E, if the second insulating layer 11b is formed on the wiring layer 12 after using the same dielectric material as that of the first insulating layer 11a, the structure shown in FIG. A circuit board is manufactured. In this case, the dielectric material 16 is generally a resin composition containing a diazo compound, and when such a manufacturing method is adopted, the wiring portion is patterned by exposure and development of the resin composition. Therefore, the fine pattern can be formed rather than the patterning by the conventional etching, and as a result, the advantage that the wiring density can be increased is secured.

  Furthermore, in the circuit board according to the present embodiment, the dielectric constant lower than that of the insulating layers 11a and 11b between the signal wirings 12a constituting the wiring layer 12 after being interposed between the insulating layers 11a and 11b. However, the present invention is not limited to such a configuration and is not shown in the drawing, but a configuration as a modified example as described below may be adopted. Conceivable. That is, a resin composition having a dielectric loss larger than that of the dielectric material used as the insulating layers 11a and 11b is used as the second dielectric material 15, and the resin composition as the second dielectric material 15 is printed between the signal wirings 12a. In addition, the resin composition is used as the inter-wiring insulating portion 12b.

  And considering the circuit board having such a modified configuration, when the state between the signal wirings provided in this circuit board is represented by an electrical equivalent circuit, as schematically shown in FIG. The signal transmission path between the terminals a and b is expressed as a relationship between the series connection of the resistance component R1 and the line capacitance C related to dielectric loss and the parallel connection of these and the insulation resistance component R2 related to leakage current. Therefore, if the equivalent circuit as shown in FIG. 7 is realized with a circuit board, in the frequency band where the impedance of the line capacitance C is small, the signal between the terminals a and b increases as the resistance component R1 increases. It will be understood that transmission will deteriorate and crosstalk noise will be suppressed. In addition, in the direction in which the signal in the same signal wiring 12a is transmitted, the electric field passing through the inter-wiring insulating portion 12b made of a resin composition having a large dielectric loss is weak, so there is a risk of causing a deterioration in transmission loss. There will be no.

(Embodiment 2)
FIG. 8 is a cross-sectional view showing a simplified configuration of the circuit board according to the second embodiment, and FIG. 9 is a process cross-section showing the manufacturing method. In the present embodiment, the circuit board has a single-layer structure. However, the circuit board is not limited to a single-layer structure, and may be a circuit board having a two-layer or more layer structure. Of course.

  As shown in FIG. 8, the circuit board according to the present embodiment includes a pair of upper and lower insulating layers 21a and 21b and a wiring layer 22 interposed between the insulating layers 21a and 21b. The wiring layer 22 includes a plurality of signal wirings 22a arranged in parallel. An inter-wiring insulating portion 22b having a lower dielectric constant than that of the insulating layers 21a and 21b is provided between the signal wirings 22a serving as the wiring layers 22. That is, the insulating layers 21a and 21b here have a first resin component such as an epoxy resin that decreases in viscosity with pressurization and heating, and a relative dielectric constant larger than that of the first resin component, so Accordingly, a dielectric that is a resin composition comprising a solid component such as glass fiber or aramid nonwoven fiber that does not decrease in viscosity, that is, a second resin component or an inorganic component stronger than the first resin component On the other hand, the inter-wiring insulating portion 22b is formed using only the first resin component contained in the dielectric material to be the insulating layers 21a and 21b.

  By the way, the circuit board having such a structure is manufactured after adopting a method including a procedure as shown in FIG. First, a first resin component that decreases in viscosity with pressurization and heating, and a second resin component or inorganic that has a relative dielectric constant greater than that of the first resin component and does not decrease in viscosity with pressurization and heating After forming a first insulating layer 21a using a dielectric material containing a solid component as a component, a plurality of signal wirings 22a are formed on one surface (the upper surface in the figure) of the first insulating layer 21a. Form a pattern. Then, a gap 23 as shown in FIG. 9A is generated between each of these signal wirings 22a. Subsequently, as shown in FIG. 9B, the second insulating layer 21b made of the same dielectric material as the first insulating layer is formed on the first insulating layer 21a on which the signal wiring 22a is formed under reduced pressure conditions. It is formed by stacking.

  And when forming the 2nd insulating layer 21b, it is performed to employ | adopt the pressurization and heating conditions which only a 1st resin component makes viscosity low, and a solid component does not make viscosity low. Then, the low-viscosity first resin component oozes out from the first and second insulating layers 21a and 21b, and the oozed first resin component is filled in the gaps 23 and between the wirings. It becomes the insulation part 22b. As a result, an inter-wiring insulating portion 22b having a dielectric constant lower than that of the insulating layers 21a and 21b is provided between the signal wirings 22a that are sandwiched by the insulating layers 21a and 21b and become the wiring layer 22. It is done.

  In the case of the circuit board having such a configuration, the dielectric constant is lower than that of the insulating layers 21a and 21b with respect to each other of the signal wirings 22a which are interposed between the insulating layers 21a and 21b and become the wiring layers 22. Since the inter-wiring insulating portion 22b is provided, the inter-wiring capacitance generated between the adjacent signal wirings 21a is reduced. As a result, the advantage that crosstalk noise is suppressed is ensured. The In addition, when this configuration is adopted, a circuit board having a multilayer structure can be easily manufactured.

(Embodiment 3)
FIG. 10 is a cross-sectional view showing a simplified configuration of the circuit board according to the third embodiment, and FIG. 11 is a process cross-section showing the manufacturing method. In the present embodiment, the circuit board has a single-layer structure. However, the circuit board is not limited to a single-layer structure, and may be a circuit board having a two-layer or more layer structure. Of course.

  As shown in FIG. 10, the circuit board according to the present embodiment includes a pair of upper and lower insulating layers 31a and 31b and a wiring layer 32 interposed between the insulating layers 31a and 31b. The wiring layer 32 includes a plurality of signal wirings 32a arranged in parallel. An inter-wiring insulating portion 32b having a lower dielectric constant than the insulating layers 31a and 31b is provided between the signal wirings 32a serving as the wiring layers 32. That is, the insulating layers 31a and 31b here are formed using a dielectric material such as glass epoxy or glass ceramic, and the inter-wiring insulating portion 32b is the same as the insulating layers 31a and 31b. Fine particles having a small relative dielectric constant, for example, fine particles such as Teflon (registered trademark) particles and ceramic particles having a hollow sphere shape are added to the dielectric material.

  As shown in FIG. 11, this circuit board is manufactured by a method comprising the following procedure. First, after using the first dielectric material such as glass epoxy or glass ceramic and forming the first insulating layer 31a disposed on the lower side, one surface of the first insulating layer 31a (in the figure, A plurality of signal wirings 32a are formed on the upper surface). Then, a gap 33 as shown in FIG. 11A is generated between each of these signal wirings 32a. Therefore, a second dielectric material having a dielectric constant lower than that of the first dielectric material, that is, a second dielectric material 34 to which fine particles having a small relative dielectric constant are added is prepared, and the signal wiring 32a is prepared. When the second dielectric material 34 is printed on one surface of the first insulating layer 31a on which is formed, as shown in FIG. 11B, in the gaps 33 generated between the signal wirings 32a, The second dielectric material 34 is filled.

  Then, the second dielectric material 34 filled in the gap 33 is the inter-wiring insulating portion 32b having a lower dielectric constant than that of the insulating layer 31a, and continues to be the same as the first insulating layer 31a. When the second insulating layer 31b is formed on the wiring layer 32 including the signal wiring 32a and the inter-wiring insulating portion 32b after using the first dielectric material, the circuit board shown in FIG. 10 is manufactured. It will be. That is, in the case of the circuit board having such a configuration, the dielectric constant of the signal wirings 32a interposed between the insulating layers 31a and 31b and serving as the wiring layer 32 is lower than that of the insulating layers 31a and 31b. Since the inter-wiring insulating portion 32b is interposed, the inter-wiring capacitance generated between the adjacent signal wirings 32a is reduced, and crosstalk noise is suppressed. Such a configuration also ensures the advantage that a multilayered circuit board can be easily manufactured.

  By the way, in the present embodiment, the dielectric material that becomes the inter-wiring insulating portion 32b, that is, the dielectric material that has a lower dielectric constant than the dielectric material that becomes the insulating layers 31a and 31b has a relative dielectric constant. Although it is assumed that small fine particles are added, such a dielectric material is not necessarily used. Although not shown, an insulating layer is formed against the gap 33 formed between each of the signal wirings 32a. FIG. 10 shows a case where a dielectric material equivalent to the dielectric materials 31a and 31b is filled and fine particles having a small relative dielectric constant are injected after adopting a method such as thermal spraying. A circuit board similar to the above is easily manufactured. And even if it is a circuit board manufactured according to such a procedure, of course, crosstalk noise is suppressed.

It is sectional drawing which simplifies and shows the structure of the circuit board which concerns on a reference example. It is process cross section which shows the manufacturing method. It is explanatory drawing for demonstrating the reason which suppression of crosstalk noise becomes possible. 2 is a cross-sectional view showing a simplified configuration of a circuit board according to Embodiment 1. FIG. It is process sectional drawing which shows the manufacturing method. It is process sectional drawing which shows the deformation | transformation procedure of the manufacturing method. It is explanatory drawing for demonstrating the reason which suppression of crosstalk noise is attained also by the circuit board made into the modification example structure. FIG. 6 is a cross-sectional view showing a simplified configuration of a circuit board according to a second embodiment. It is process cross section which shows the manufacturing method. FIG. 6 is a cross-sectional view showing a simplified configuration of a circuit board according to a third embodiment. It is process cross section which shows the manufacturing method. It is sectional drawing which simplifies and shows the structure of the circuit board which concerns on the conventional form.

Explanation of symbols

11a, 11b, 21a, 21b, 31a, 31b Insulating layer 12, 22, 32 Wiring layer 12a, 22a, 32a Signal wiring 12b, 22b, 32b Insulating part between wirings

Claims (6)

A circuit board comprising an insulating layer and a wiring layer interposed between these insulating layers,
A circuit board characterized in that an inter-wiring insulating portion having a lower dielectric constant than that of an insulating layer is provided between signal wirings serving as wiring layers. The circuit board according to claim 1,
The insulating layer includes a first resin component that decreases in viscosity with pressurization and heating, and a second resin component that has a relative dielectric constant greater than that of the first resin component and does not decrease in viscosity with pressurization and heating, or It is formed from a dielectric material containing an inorganic component, and the inter-wiring insulating portion is formed only from the first resin component contained in the dielectric material that becomes the insulating layer. Feature circuit board. The circuit board according to claim 1,
The circuit board, wherein the inter-wiring insulating portion is formed by adding fine particles having a small relative dielectric constant to a dielectric material to be an insulating layer.   A process of laminating a dielectric material whose dielectric constant is lowered with light irradiation on the insulating layer, and patterning the laminated dielectric material with light irradiation and lowering the dielectric constant, A method for manufacturing a circuit board, comprising: a step of forming; and a step of forming a signal wiring between each of the inter-wiring insulating portions.   A first resin component that decreases in viscosity with pressurization and heating, and a second resin component or inorganic component that has a relative dielectric constant greater than that of the first resin component and does not decrease in viscosity with pressurization and heating. A step of forming a first insulating layer made of the contained dielectric material, a step of forming a plurality of signal wirings on the first insulating layer, and a second insulation made of the same dielectric material as the first insulating layer Forming a layer on the first insulating layer on which the signal wiring is formed, and in the step of forming the second insulating layer, pressurization and heating in which only the first resin component is reduced in viscosity A method of manufacturing a circuit board, characterized by adopting conditions.   A step of forming a plurality of signal wirings on an insulating layer made of a dielectric material, a step of filling the same dielectric material between the signal wirings with each other to form an inter-wiring insulating portion, and an insulating layer And a step of injecting fine particles having a relative dielectric constant smaller than that of the dielectric material into the inter-wiring insulating portion.

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