JP6537172B2 - Printed wiring board - Google Patents

Description

  The present invention relates to a printed wiring board.

  In recent years, the amount of information communication has been increasing, and in order to respond to this, for example, in devices such as IC cards and mobile phone terminals, communications in high frequency regions such as microwaves and millimeter waves, that is, high speed transmission of electric signals ing. Therefore, a printed wiring board for high-speed transmission, which has a small transmission loss when used in a high frequency region, is required.

  As a transmission loss in a high frequency region, a dielectric loss in an insulating layer such as a base film or a cover lay adjacent to a conductive pattern of a printed wiring board can be mentioned. This dielectric loss can be reduced by using an insulating material having a small relative dielectric constant.

  Therefore, it has been proposed to use a film formed of a liquid crystal polymer having a small relative dielectric constant as a base film and a cover lay, and integrate these base film and the cover lay by thermocompression bonding ( See JP 2013-89710 A).

JP, 2013-89710, A

  As disclosed in the above publication, when laminating the base film and the coverlay by thermocompression bonding, the base film and the coverlay must be heated to a temperature close to their melting points. For this reason, at the time of thermocompression bonding, the dimensional stability of the base film is lowered and deformed, and the conductive pattern may be displaced. That is, the printed wiring board disclosed in the above publication has a disadvantage that dimensional accuracy tends to be insufficient.

  The present invention has been made based on the above-mentioned circumstances, and an object of the present invention is to provide a printed wiring board having a small dielectric loss at the time of high speed transmission and a high dimensional accuracy.

  A printed wiring board according to an aspect of the present invention made to solve the above problems comprises: a first resin film; a conductive pattern to be laminated on one surface of the first resin film; 1. A printed wiring board comprising a second resin film disposed on one side of a laminate including a resin film, and an adhesive layer filled between the second resin film and the laminate, The relative permittivity of the adhesive layer is 3 or less, and the dielectric loss tangent is 0.05 or less.

  The printed wiring board according to one aspect of the present invention has a small dielectric loss during high-speed transmission and high dimensional accuracy.

FIG. 1 is a schematic cross-sectional view showing a printed wiring board according to an embodiment of the present invention. FIG. 2 is a schematic plan view of the printed wiring board of FIG.

Description of the embodiment of the present invention
A printed wiring board according to an aspect of the present invention includes a first resin film, a conductive pattern to be laminated on one surface of the first resin film, and one of a laminate including the conductive pattern and the first resin film. A printed wiring board comprising a second resin film disposed on the surface side of the adhesive layer and an adhesive layer filled between the second resin film and the laminate, wherein the relative dielectric constant of the adhesive layer is 3 or less, dielectric loss tangent is 0.05 or less.

  The printed wiring board has a high dimension because the first resin film and the second resin film are unlikely to be deformed by bonding the second resin film and the laminate of the conductive pattern and the first resin film using an adhesive. With accuracy. Moreover, the said printed wiring board transmits a high frequency signal by a conductive pattern by being filled with the adhesive bond layer whose specific dielectric constant and dielectric loss tangent are below the said upper limit between the clearance gap of a conductive pattern, and a 2nd resin film. Dielectric loss during high speed transmission is reduced.

  If the relative permittivity of the adhesive layer is smaller than the relative permittivity of the first resin film and the second resin film, and the dielectric tangent of the adhesive layer is smaller than the dielectric tangent of the first resin film and the second resin film Good. Thus, the dielectric constant of the adhesive layer is smaller than the dielectric constant of the first resin film and the second resin film, and the dielectric loss tangent of the adhesive layer is the dielectric of the first resin film and the second resin film. By being smaller than a tangent, dielectric loss can be made smaller than thermocompression-bonding the said 1st resin film and 2nd resin film. As a result, dielectric loss during high speed transmission is further reduced.

  The adhesive layer preferably has a thermosetting resin having a curing temperature of 250 ° C. or less as a main component. Thus, since the adhesive layer can be adhered at a relatively low temperature by using a thermosetting resin having a curing temperature of 250 ° C. or less as a main component, the first resin film and the second resin can be used. The deformation of the film can be effectively prevented and the dimensional accuracy can be further improved.

  The thermosetting resin may be a modified polyphenylene ether or a styrene resin. As described above, when the thermosetting resin is a modified polyphenylene ether or a styrene resin, an adhesive layer having a relatively small dielectric constant and a dielectric loss tangent can be easily formed.

  As melting | fusing point of said 1st resin film and 2nd resin film, 250 degreeC or more is preferable. Thus, when the melting points of the first resin film and the second resin film are at least the lower limit, deformation of the first resin film and the second resin film is more reliably prevented at the time of forming the adhesive layer. The dimensional accuracy can be further improved.

  The relative dielectric constant of the first resin film and the second resin film is preferably 4 or less, and the dielectric loss tangent is preferably 0.05 or less. Thus, the dielectric loss in the first resin film and the second resin film can be reduced by setting the relative dielectric constant and the dielectric loss tangent of the first resin film and the second resin film to the upper limits or less. As a result, dielectric loss during high speed transmission is further reduced.

  The main component of the first resin film and the second resin film is preferably a fluorine resin or a liquid crystal polymer. As described above, the main component of the first resin film and the second resin film is a fluorine resin or a liquid crystal polymer, thereby easily reducing the dielectric constant and the dielectric loss tangent of the first resin film and the second resin film. Can.

  The printed wiring board may be used for high speed transmission. Thus, by being used for high-speed transmission, the advantage that the dielectric loss is small becomes remarkable.

  Here, the "specific dielectric constant" is a value measured in accordance with JIS-C2138 (2007). Moreover, "dielectric loss tangent" is a value measured at a frequency of 1 GHz in accordance with JIS-C2138 (2007). Moreover, "hardening temperature" and "melting point" are peak values of temperature change at the time of hardening or melting which are measured by differential scanning calorimetry (differential scanning calorimetry). Moreover, a "main component" means the component whose content rate is 50 mass% or more, preferably 90 mass% or more. Also, “high-speed transmission” refers to transmission of a signal whose frequency is 1 GHz or more.

Details of the Embodiment of the Present Invention
Hereinafter, an embodiment of a printed wiring board according to the present invention will be described in detail with reference to the drawings.

[Printed wiring board]
The printed wiring board of FIG. 1 is formed in a band shape in plan view, and is used as a flexible cable for high speed transmission used to transmit a high frequency signal in the longitudinal direction (the depth direction in the drawing).

  The printed wiring board includes a first resin film 1, a conductive pattern 2 laminated on one side (upper side in the drawing) of the first resin film 1, and the conductive pattern 2 and the first resin film 1. A second resin film 4 disposed on one side of the first laminate 3 and an adhesive layer 5 filled between the second resin film 4 and the first laminate 3 are provided.

  Moreover, the said printed wiring board is the 1st grand layer 6 laminated | stacked on the other surface side (lower side in the figure) of the 1st resin film 1, and one surface side of the 2nd resin film (1st resin film 1 And the second ground layer 7 stacked on the opposite side of That is, the first stacked body 3 further includes the first ground layer 6. Further, the second resin film and the second ground layer 7 constitute a second laminate 8.

  The first laminate 3 can be formed as a so-called double-sided substrate, and the second laminate 8 can be formed as a single-sided substrate. That is, the printed wiring board can be formed by bonding the first laminate 3 as a double-sided substrate and the second laminate 8 as a single-sided substrate with an adhesive forming the adhesive layer 5.

<First resin film>
The first resin film 1 is a sheet-like member having resin as a main component and having an insulating property, and isolates the conductive pattern 2 and the first ground layer 6 and supports the conductive pattern 2 and the first ground layer 6. Of the first laminate 3.

  The lower limit of the relative dielectric constant of the first resin film 1 is preferably as small as possible, but in order to meet other conditions such as insulation and mechanical strength, it is considered that 1.5 is practically the limit. On the other hand, the upper limit of the relative dielectric constant of the first resin film 1 is preferably 4 and more preferably 3. When the relative dielectric constant of the first resin film 1 exceeds the above upper limit, there is a possibility that the dielectric loss may increase when transmitting a high frequency signal by the printed wiring board.

  The lower limit of the dielectric loss tangent at a frequency of 1 GHz of the first resin film 1 is preferably as small as possible, but in reality, 0.0001 is considered to be the limit. On the other hand, the upper limit of the dielectric loss tangent at a frequency of 1 GHz of the first resin film 1 is preferably 0.05, and more preferably 0.005. When the dielectric loss tangent of the first resin film 1 at a frequency of 1 GHz exceeds the above upper limit, the transmission loss of the high frequency signal of the printed wiring board may be increased.

  The thickness of the first resin film 1 is appropriately set according to the application of the printed wiring board and the like, and is not particularly limited. However, as a general theory, the lower limit of the average thickness of the first resin film 1 5 μm is preferable, 10 μm is more preferable, and 25 μm is more preferable. On the other hand, as an upper limit of average thickness of the 1st resin film 1, 500 micrometers is preferred and 150 micrometers is more preferred. When the average thickness of the first resin film 1 is less than the above lower limit, the parasitic capacitance between the conductive pattern 2 and the first ground layer 6 may be too large, or the strength of the first resin film 1 is insufficient. May be Conversely, when the average thickness of the first resin film 1 exceeds the upper limit, the flexibility of the printed wiring board may be insufficient, or the printed wiring board may be unnecessarily thick.

  As a minimum of melting point of the 1st resin film 1, 250 ° C is preferred and 280 ° C is more preferred. On the other hand, as a maximum of melting point of the 1st resin film 1, 400 ° C is preferred and 350 ° C is more preferred. If the melting point of the first resin film 1 is less than the above lower limit, there is a possibility that the dimensional accuracy may become insufficient due to deformation at the time of solder reflow for mounting electronic parts and the like. On the contrary, when the melting point of the first resin film 1 exceeds the above upper limit, there is a possibility that the cost may be unnecessarily increased, and other characteristics such as the relative dielectric constant and the dielectric loss tangent may not be preferable. .

  As a main component of the first resin film 1, for example, a resin such as polyimide or polyethylene terephthalate can be used, but a resin having a small dielectric constant and a dielectric loss tangent is preferable. Thus, by using a resin having a small dielectric constant and dielectric loss tangent as the main component of the first resin film 1, it is possible to reduce dielectric loss when transmitting a high frequency signal by the conductive pattern 2. Examples of the resin having a small dielectric constant and dielectric loss tangent include fluorine resin and liquid crystal polymer.

  The liquid crystal polymer as the main component of the first resin film 1 includes a thermotropic type exhibiting liquid crystallinity in a molten state and a lyotropic type exhibiting liquid crystallinity in a solution state, but in the present invention, a thermotropic liquid crystal polymer It is preferable to use

  The liquid crystal polymer is, for example, an aromatic polyester obtained by synthesizing an aromatic dicarboxylic acid and a monomer such as an aromatic diol or an aromatic hydroxycarboxylic acid. Typical examples thereof are polymers obtained by polymerizing monomers of the following formulas (1), (2) and (3) synthesized from parahydroxybenzoic acid (PHB), terephthalic acid and 4,4'-biphenol A polymer obtained by polymerizing monomers of the following formulas (3) and (4) synthesized from PHB, terephthalic acid and ethylene glycol, the following formula (2) synthesized from PHB and 2,6-hydroxynaphthoic acid, The polymer etc. which superposed | polymerized the monomer of (3) and (5) can be mentioned.

  The liquid crystal polymer is not particularly limited as long as it exhibits liquid crystallinity, and each of the above polymers may be the main component (50 mol% or more in the liquid crystal polymer), and other polymers or monomers may be copolymerized. . The liquid crystal polymer may be a liquid crystal polyester amide, a liquid crystal polyester ether, a liquid crystal polyester carbonate, or a liquid crystal polyester imide.

  The liquid crystal polyesteramide is a liquid crystal polyester having an amide bond, and examples thereof include polymers obtained by polymerizing the monomers of the following formula (6) and the above formulas (2) and (4).

  The liquid crystal polymer is preferably produced by melt-polymerizing a raw material monomer corresponding to a constituent unit constituting the polymer and solid-phase polymerizing the obtained polymer (prepolymer). Thereby, a liquid crystal polymer of high molecular weight having high heat resistance, strength and rigidity can be produced with good operability. Melt polymerization may be carried out in the presence of a catalyst, and examples of this catalyst include metal compounds such as magnesium acetate, stannous acetate, tetrabutyl titanate, lead acetate, sodium acetate, potassium acetate, antimony trioxide, etc. And nitrogen-containing heterocyclic compounds such as 4- (dimethylamino) pyridine and 1-methylimidazole, and nitrogen-containing heterocyclic compounds are preferably used.

  Examples of the fluorine resin which is the main component of the first resin film 1 include polytetrafluoroethylene (PTFE), polytetrafluoroethylene / perfluoroalkylvinylether copolymer (PFA), tetrafluoroethylene / hexafluoropropylene copolymer, and the like. Polymer (FEP), tetrafluoroethylene / ethylene copolymer (ETFE), polyvinylidene fluoride (PVDF), polychlorotrifluoroethylene (PCTFE), chlorotrifluoroethylene / ethylene copolymer (ECTFE), polyfluorination Mention may be made of vinyl (PVF) and thermoplastic fluoroplastics (THV) and fluoroelastomers consisting of three monomers of tetrafluoroethylene, hexafluoropropylene and vinylidene fluoride. Also, mixtures and copolymers containing these compounds can be used.

  Among them, as the fluorine resin used as the main component of the first resin film 1, tetrafluoroethylene / hexaolopropylene copolymer (FEP), polytetrafluoroethylene / perfluoroalkyl vinyl ether copolymer (PFA) and polytetratetra Fluoroethylene (PTFE) is preferred. By using these fluorine resins, the first resin film 1 has flexibility, light transmittance, heat resistance and flame retardancy.

  The fluorine resin of the first resin film 1 is preferably crosslinked, and specifically, carbon atoms of the main chain of the polymer of the fluorine resin are preferably covalently bonded. Thus, since the deformation | transformation in solder | pewter reflow temperature for mounting of an electronic component etc. is suppressed by bridge | crosslinking a fluororesin, the dimensional accuracy of the said printed wiring board can be improved.

  As a method of crosslinking the fluorine resin, for example, a method of generating a fluorine radical by irradiating ionizing radiation may be mentioned. In addition, as a minimum of the irradiation amount of the ionizing radiation with respect to the fluororesin of the 1st resin film 1, 0.1 kGy is preferable and 1 kGy is more preferable. On the other hand, as an upper limit of the said irradiation amount, 1000 kGy is preferable and 900 kGy is more preferable. When the said irradiation amount is less than the said minimum, there exists a possibility that the bond strength with the conductive pattern 2 of the 1st resin film 1 may not fully be obtained. On the contrary, when the above-mentioned irradiation dose exceeds the above-mentioned upper limit, there is a possibility that strength reduction accompanying decomposition reaction (competitive reaction with crosslinking) of fluorocarbon resin and foaming in the interface of the 1st resin film 1 and conductive pattern 2 may occur. .

  The first resin film 1 may contain a filler, an additive and the like in addition to the above-mentioned main components such as the liquid crystal polymer and the fluorine resin.

<Conductive pattern>
The conductive pattern 2 is disposed along the longitudinal direction of the printed wiring board, and a pair of signal lines 9 serving as an electric path for transmitting high frequency signals and a pair of shields disposed substantially in parallel on both sides in the width direction of the signal lines 9. And a wiring 10. The pair of shield wires 10 are electrically connected to the first ground layer 6 and the second ground layer 7 through the through holes 11 respectively.

  The conductive pattern 2 is formed by patterning a layered conductor. The conductor for forming the conductive pattern 2 may be any one having conductivity, for example, metals such as copper, aluminum, silver, gold and the like are suitably used, and among them, copper which is inexpensive and excellent in conductivity is suitably used. Be

  The method of patterning the conductive pattern 2 is not particularly limited. For example, a method of forming the conductive pattern 2 having a desired planar shape by selectively removing the metal layer laminated on the first resin film 1 by etching Can be adopted.

  It does not specifically limit as a method to laminate a metal layer on the 1st resin film 1, For example, the adhesion method which bonds metal foil together with adhesive agent, the resin composition which is the material of the 1st resin film 1 on metal foil is applied Forming a metal layer by plating on a thin conductive layer (seed layer) several nm thick formed on the first resin film 1 by the cast method, sputtering or vapor deposition method The lamination method etc. which are stuck by can be used.

  The average thickness of the conductive pattern 2 is not particularly limited, but the lower limit of the average thickness of the conductive pattern 2 is preferably 1 μm, more preferably 5 μm. On the other hand, the upper limit of the average thickness of the conductive pattern 2 is preferably 100 μm, more preferably 50 μm, and still more preferably 25 μm. When the average thickness of the conductive pattern 2 is less than the above lower limit, the transmission loss (Joule loss) in the signal line 9 may be too large. Conversely, when the average thickness of the conductive pattern 2 exceeds the above upper limit, the flexibility of the printed wiring board may be insufficient, or the parasitic capacitance between the signal line 9 and the shield wiring 10 may be increased. Impedance matching may be difficult to obtain.

  The signal line 9 is disposed at the center along the longitudinal direction of the strip of the first resin film. The signal line 9 is configured to be connectable to an external circuit in the vicinity of the end of the printed wiring board. The connection structure of the signal line 9 to the external circuit may be, for example, a configuration that allows connection to the external circuit by a portion exposed without being covered by the second stacked body 8 or separated from other portions of the second ground layer 7. There is a configuration that can be connected to an external circuit through the land by being connected by a via to the land formed.

  The average width of the signal line 9 is not particularly limited, but the lower limit of the average width is preferably 25 μm, more preferably 60 μm, and still more preferably 70 μm. On the other hand, the upper limit of the average width is preferably 500 μm, more preferably 240 μm, and still more preferably 230 μm. If the average width is less than the lower limit, the transmission loss (copper loss) in the signal line 9 may be too large. Conversely, if the average width exceeds the upper limit, parasitic capacitance between the signal line 9 and the first ground layer 6 and the second ground layer 7 may be too large, and impedance matching may not be obtained. . Further, the variation of the width of the signal line 9 is preferably within ± 20% of the average width.

  The shield wiring 10 has a shielding function of electromagnetically shielding both sides in the width direction of the signal line 9.

  The lower limit of the average width of the shield wiring 10 is preferably 100 μm, and more preferably 200 μm. On the other hand, the upper limit of the average width of the shield wiring 10 is preferably 500 μm, and more preferably 400 μm. If the average width of the shield wiring 10 is less than the above lower limit, the conductivity of the shield wiring 10 itself may not be sufficiently obtained, and the shielding effect by the shield wiring 10 may not be sufficiently obtained. On the contrary, when the average width of the shield wiring 10 exceeds the above-mentioned upper limit, there is a possibility that the flexible printed wiring board 1 concerned may become large unnecessarily in the width direction.

  It is preferable that the thickness of each of the signal line 9 and the shield wiring 10 be substantially constant. The term "substantially constant" means that the error is within 40% of the average thickness.

  The lower limit of the average distance in the width direction between the signal line 9 and the shield wiring 10 is preferably 50 μm, more preferably 100 μm, and still more preferably 200 μm. On the other hand, as an upper limit of an average space | interval, 1000 micrometers is preferable, 600 micrometers is more preferable, and 400 micrometers is more preferable. When the above-mentioned average interval does not reach the above-mentioned lower limit, the parasitic capacitance between the signal line 9 and the shield wiring 10 becomes large, and it may be difficult to obtain the impedance matching. On the contrary, when the above-mentioned average interval exceeds the above-mentioned upper limit, there is a possibility that the flexible printed wiring board 1 concerned may become large unnecessarily in the cross direction.

  As shown in FIG. 2, a plurality of through holes 11 for connecting the shield wiring 10 to the first ground layer 6 and the second ground layer 7 are formed at intervals in the longitudinal direction (the depth direction in FIG. 1). By electrically connecting the shield wiring 10 to the first ground layer 6 and the second ground layer 7 as described above, the shielding effect of the shield wiring 10 can be further improved.

  The distance between the through holes 11 is not particularly limited, but is preferably within 1 cm. The inner diameter of the through hole 11 is not particularly limited, but is preferably 50 μm to 500 μm, for example.

<Second resin film>
The second resin film 4 is a sheet-like member having a resin as a main component and having an insulating property, and is a base material that supports the second ground layer 7. The second resin film 4 is a layer that defines a space in which the adhesive layer 5 is filled.

  The configuration of the second resin film 4 can be the same as that of the first resin film 1 described above.

<Adhesive layer>
The adhesive layer 5 is formed of an adhesive. The adhesive layer 5 is a layer that bonds together the first laminate 3 and the second laminate 8 and surrounds three sides (upper and left in the figure) of the signal lines 9 of the conductive pattern 2.

  The adhesive for forming the adhesive layer 5 is preferably an adhesive having excellent flexibility and heat resistance, and as such an adhesive, for example, modified polyphenylene ether, styrene resin, epoxy resin, butyral resin, acrylic resin Adhesives of various types such as resins are included.

  As a main component of the adhesive layer 5, that is, as a main component of the adhesive forming the adhesive layer 5, a thermosetting resin is preferable. As a minimum of hardening temperature of thermosetting resin made into the main ingredients of adhesive layer 5, 120 ° C is preferred and 150 ° C is more preferred. On the other hand, as a maximum of curing temperature of thermosetting resin made into the main ingredients of adhesive layer 5, 250 ° C is preferred, 230 ° C is more preferred, and 200 ° C is still more preferred. When the curing temperature of the thermosetting resin which is the main component of the adhesive layer 5 does not reach the above lower limit, the handling of the adhesive which is a raw material of the adhesive layer 5 may not be easy. On the other hand, when the curing temperature of the thermosetting resin which is the main component of the adhesive layer 5 exceeds the above upper limit, the first resin film 1 and the first resin film 1 are cured when the adhesive is cured to form the adhesive layer 5. [2] The resin film 4 may be deformed by heat to impair the dimensional accuracy of the printed wiring board.

  As the thermosetting resin which is the main component of the adhesive layer 5, modified polyphenylene ether and styrene resin are suitably used in that the relative dielectric constant and the dielectric loss tangent can be reduced.

  The lower limit of the relative dielectric constant of the adhesive layer 5 is preferably as small as possible, but in order to meet other conditions such as insulation and mechanical strength, it is considered that 1.5 is practically the limit. On the other hand, the upper limit of the relative dielectric constant of the adhesive layer 5 is 3, preferably 2.8, and more preferably 2.6. In addition, when the relative dielectric constant of the adhesive layer 5 exceeds the above-mentioned upper limit, there is a possibility that the dielectric loss may increase when transmitting a high frequency signal by the printed wiring board.

  The relative dielectric constant of the adhesive layer 5 is preferably smaller than that of the first resin film 1 and the second resin film 4. As described above, since the relative dielectric constant of the adhesive layer 5 is smaller than the relative dielectric constant of the first resin film 1 and the second resin film 4, the first resin film 1 and the second resin film 4 do not use an adhesive. The dielectric loss in the case of transmitting a high frequency signal by the signal line 9 of the conductive pattern 2 can be made smaller than in the case of thermocompression bonding.

  The lower limit of the dielectric loss tangent at a frequency of 1 GHz of the adhesive layer 5 is preferably as small as possible, but in reality, 0.0001 is considered to be the limit. On the other hand, the upper limit of the dielectric loss tangent at a frequency of 1 GHz of the adhesive layer 5 is 0.05, preferably 0.01, and more preferably 0.005. If the dielectric loss tangent at a frequency of 1 GHz of the adhesive layer 5 exceeds the upper limit, the transmission loss of high frequency signals of the printed wiring board may be increased.

  The dielectric loss tangent of the adhesive layer 5 is preferably smaller than the dielectric loss tangent of the first resin film 1 and the second resin film 4. Thus, since the dielectric loss tangent of the adhesive layer 5 is smaller than the dielectric loss tangent of the first resin film 1 and the second resin film 4, the first resin film 1 and the second resin film 4 can be obtained without using an adhesive. The dielectric loss in the case of transmitting a high frequency signal by the signal line 9 of the conductive pattern 2 can be made smaller than in the case of thermocompression bonding.

<First ground layer>
The first ground layer 6 is laminated on the other side (lower side) of the first resin film 1. The first ground layer 6 serves as a shield that electromagnetically shields the other side of the signal line 9 by covering the other side of the signal line 9 of the conductive pattern 2.

  The first ground layer 6 may have any shape such as a mesh pattern, but is formed in a solid shape substantially having no opening at least in a region overlapping with the signal line 9 in plan view so as to improve the shielding effect. Preferably. Further, the first ground layer 6 may form an opening (not shown) facing the signal line 9 in order to obtain a desired impedance by adjusting the parasitic capacitance with the signal line 9.

  The first ground layer 6 can have the same configuration as the conductive pattern 2 except for the planar shape.

<Second ground layer>
The second ground layer 7 is laminated on the surface on one side (upper side) of the second resin film 4. The second ground layer 7 serves as a shield that electromagnetically shields one side of the signal line 9 by covering one side of the signal line 9 of the conductive pattern 2.

  The configuration of the second ground layer 7 can be similar to that of the first ground layer 6 described above. In addition, in order to facilitate calculation of impedance, it is preferable to form an opening for impedance adjustment in only one of the first ground layer 6 and the second ground layer 7.

<Advantage>
The printed wiring board has a gap between the conductive pattern 2 (between the signal line 9 and the shield wiring 10) and an adhesive layer 5 having a small dielectric constant and a dielectric loss tangent between the signal line 9 and the second resin film 4 By being filled, the dielectric loss at the time of high-speed transmission which transmits a high frequency signal by the signal line 9 of the conductive pattern 2 is reduced.

  Moreover, the said printed wiring board adheres the 1st resin film 1 and 2nd by adhere | attaching the laminated body of the conductive pattern 2 and the 1st resin film 1, and the 2nd resin film 4 using the adhesive agent which carries out low temperature curing. Since the resin film 4 is unlikely to be deformed, it has high dimensional accuracy.

Other Embodiments
It should be understood that the embodiments disclosed herein are illustrative and non-restrictive in every respect. The scope of the present invention is not limited to the configurations of the above embodiments, but is indicated by the claims, and is intended to include all modifications within the meaning and scope equivalent to the claims. Ru.

  In the printed wiring board, the first ground layer and the second ground layer are not essential, and one or both may be omitted.

  In the printed wiring board, the conductive pattern may have no shield wiring. Also, the conductive pattern may have a plurality of signal lines. In the printed wiring board, the signal line and the shield wiring may be formed with different thicknesses or different materials.

  In the printed wiring board, the adhesive layer may not be filled in the entire gap between the second resin film and the laminate including the conductive pattern and the first resin film, but at least from the signal line in plan view. It is preferable to be filled in a region of 10 μm or less, more preferably a region of 25 μm or less, and further preferably a region of 50 μm or less.

  The said printed wiring board is not restricted to what transmits a high frequency signal, A low frequency signal may be handled.

  In addition, the printed wiring board is not limited to one used as a cable for transmitting a signal, and an electronic component may be mounted to form a circuit board.

  In addition, the printed wiring board may have a layer other than the layers described in the above embodiments, for example, a cover lay laminated on the other side of the first ground layer or one side of the second ground layer.

  Moreover, in the said printed wiring board, when laminating | stacking conductor layers, such as metal foil which forms a conductive pattern, to a 1st resin film using an adhesive agent, it is a 1st laminated body and a 2nd resin film as this adhesive agent. It is preferable to use the same adhesive as that for forming the adhesive layer filled in between.

  The printed wiring board can be suitably used, for example, as a flexible printed wiring board for high-speed transmission that transmits high frequency signals.

1 first resin film 2 conductive pattern 3 first laminate 4 second resin film 5 adhesive layer 6 first ground layer 7 second ground layer 8 second laminate 9 signal line 10 shield wiring 11 through hole

Claims (7)

A first resin film,
A conductive pattern laminated on one side of the first resin film;
A second resin film disposed on one side of a laminate including the conductive pattern and the first resin film;
A printed wiring board comprising: the second resin film; and an adhesive layer filled between the laminates,
The dielectric constant of the adhesive layer is 3 or less state, and are dielectric loss tangent of 0.05 or less,
A print in which the dielectric constant of the adhesive layer is smaller than the dielectric constant of the first resin film and the second resin film, and the dielectric loss tangent of the adhesive layer is smaller than the dielectric loss tangent of the first resin film and the second resin film Wiring board. The printed wiring board according to claim 1 , wherein the adhesive layer mainly comprises a thermosetting resin having a curing temperature of 250 ° C. or less. The printed wiring board according to claim 2 , wherein the thermosetting resin is a modified polyphenylene ether or a styrene resin. The printed wiring board according to any one of claims 1 to 3 , wherein the melting point of the first resin film and the second resin film is 250 ° C or more. The dielectric constant of the first resin film and the second resin film is 4 or less, the printed wiring board according to any one of claims 1 to 4 dielectric loss tangent is 0.05 or less. The printed wiring board according to any one of claims 1 to 5 , wherein a main component of the first resin film and the second resin film is a fluorine resin or a liquid crystal polymer. The printed wiring board according to any one of claims 1 to 6 , which is used for high speed transmission.

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