JP2016162854A - Printed wiring board - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a printed wiring board capable of relatively accurately adjusting an impedance.SOLUTION: A printed wiring board comprises: an interlayer 1 having an insulation quality; a conductive pattern 2 laminated to one surface side of the interlayer 1; and a first ground layer 3 laminated to the other surface side of the interlayer. The conductive pattern 2 includes a connection part 5, the first ground layer 3 includes an opening 6 in a region overlapping the connection part 5 in plan view, and a radius of the maximum inscription circle in the region overlapping the connection part 5 of the opening 6 is equal to 1/2 of the radius of the maximum inscription circle of the connection part 5 or more. It is preferable that the connection part 5 be a land part. It is preferable that the minimum interval of the first ground layer 3 and the connection part 5 in the plan view is equal to an average interval of the conductive pattern 2 and the first ground layer 3 in thickness direction. It is preferable that the first ground layer 3 overlaps the region other than the connection part 5 of the conductive pattern 2 and a neighborhood of the connection part in the plan view. It is preferable that a relative dielectric constant of the interlayer 1 is equal to 4 or less.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a printed wiring board.

  The printed wiring board is used for transmitting high-frequency signals, digital signals, and the like. As such a printed wiring board, a printed wiring board with a shielding function having a stripline structure, a microstrip structure, or the like is used in order to prevent noise and crosstalk. In the stripline structure and the microstrip structure, a signal line is disposed on one surface side of a dielectric layer, and a ground layer is laminated on the other surface side of the dielectric layer.

  By the way, impedance matching with other components is particularly required for printed wiring boards that transmit high-frequency signals. When the dielectric layer is thinned in order to reduce the thickness of the printed wiring board with a shield function, the parasitic capacitance (capacitance) between the ground layer that performs the shield function and the signal line increases, and the impedance tends to decrease. If the width of the signal line is reduced, the parasitic capacitance can be reduced, but there is a disadvantage that transmission loss in the signal line increases.

  As means for solving such inconvenience, it has been proposed to adjust the impedance to a desired value by providing an opening in the first ground layer, thereby reducing the facing area between the ground layer and the signal line ( (See JP 2007-123740 A).

JP 2007-123740 A

  In the printed wiring board disclosed in the above publication, the parasitic capacitance between the signal line and the ground layer can be adjusted. However, a printed wiring board is generally formed with a conductive pattern having a connection portion wider than the signal line in order to connect the signal line to another layer or an external circuit. The parasitic capacitance between layers cannot be ignored. Examples of such a connection portion include a land portion for mounting electronic components by solder, a conductive portion formed around a hole for forming an interlayer connection via, a contact portion for connector connection, and the like. It is done.

  Additional conductors are laminated or connected to the connecting portion by mounting electronic components or the like. When a further conductor is laminated or connected to the connection portion in this way, the parasitic capacitance between the connection portion and the ground layer substantially changes. In many cases, it is difficult to control the amount of change in parasitic capacitance due to the lamination or connection of conductors to the connection portion, resulting in a disadvantage that the impedance of the printed wiring board varies.

  The present invention has been made in view of the above disadvantages, and an object of the present invention is to provide a printed wiring board capable of adjusting impedance relatively accurately.

  A printed wiring board according to one aspect of the present invention made to solve the above problems includes an insulating intermediate layer, a conductive pattern laminated on one surface side of the intermediate layer, and the other of the intermediate layers. A printed wiring board having a first ground layer laminated on the surface side of the first conductive layer, wherein the conductive pattern has a connection portion, and the first ground layer has an opening in a region overlapping the connection portion in plan view. And the radius of the maximum inscribed circle of the overlapping area with the connection portion of the opening is not less than ½ of the radius of the maximum inscribed circle of the connection portion.

  The printed wiring board according to one embodiment of the present invention can adjust the impedance relatively accurately.

FIG. 1 is a schematic exploded perspective 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. 3 is a cross-sectional end view taken along line AA of the printed wiring board of FIG. 4 is a cross-sectional end view taken along the line BB of the printed wiring board of FIG. FIG. 5 is a schematic exploded perspective view showing a printed wiring board of an embodiment different from FIG. FIG. 6 is a schematic cross-sectional end view corresponding to FIG. 3 of the printed wiring board of FIG. FIG. 7 is a schematic exploded perspective view showing a printed wiring board according to an embodiment different from those in FIGS. 1 and 5. 8 is a schematic cross-sectional end view corresponding to FIG. 3 of the printed wiring board of FIG.

[Description of Embodiment of the Present Invention]
A printed wiring board according to an aspect of the present invention includes an insulating intermediate layer, a conductive pattern stacked on one surface side of the intermediate layer, and a first layer stacked on the other surface side of the intermediate layer. A printed wiring board including a ground layer, wherein the conductive pattern has a connection portion, the first ground layer has an opening in a region overlapping the connection portion in plan view, and the connection portion of the opening The radius of the maximum inscribed circle of the overlapping region is ½ or more of the radius of the maximum inscribed circle of the connecting portion.

  The printed wiring board has an opening in an area where the first ground layer overlaps with the connection part in plan view, and a radius of a maximum inscribed circle of the overlapping area with the connection part of the opening is within the maximum of the connection part. The parasitic capacitance between the first ground layer and the connection portion is relatively small due to being ½ or more of the radius of the tangent circle, and the parasitic capacitance between the first ground layer and the connection portion is the overall impedance. Does not significantly affect. As a result, the influence of the parasitic capacitance change between the first ground layer and the connection portion on the impedance of the entire printed wiring board due to the connection of the electronic component or circuit to the connection portion is small, and the design of other portions The impedance can be adjusted relatively accurately.

  The connection part may be a land part. Thus, the accuracy of impedance adjustment becomes more remarkable by forming an opening in a region overlapping with the land portion of the first ground layer in plan view.

  The inner edge of the opening surrounds the entire periphery of the connection portion in plan view, and the minimum distance in plan view between the first ground layer and the connection portion is the thickness direction between the conductive pattern and the first ground layer. It should be greater than the average interval. As described above, the inner edge of the opening surrounds the entire periphery of the connection portion in a plan view, and the minimum distance in the plan view between the first ground layer and the connection portion is between the conductive pattern and the first ground layer. The parasitic capacitance between the connection portion and the first ground layer is greater than the parasitic capacitance between the signal line portion other than the connection portion of the conductive pattern and the first ground layer by being equal to or greater than the average interval in the thickness direction. Therefore, the impedance can be adjusted more accurately.

  The first ground layer may overlap with the connection portion of the conductive pattern and a region other than the vicinity of the connection portion in plan view. Thus, when the first ground layer overlaps with the region other than the connection portion and the vicinity of the connection portion of the conductive pattern in plan view, the region other than the connection portion and the vicinity of the connection portion of the conductive pattern, that is, a signal line. Loss at the time of high-frequency signal transmission can be reduced by the shielding effect of the first ground layer.

  The relative dielectric constant of the intermediate layer is preferably 4 or less. Thus, the dielectric loss at the time of the said conductive pattern transmitting a high frequency signal can be reduced by making the relative dielectric constant of the said intermediate layer below the said upper limit.

  It is preferable to further include a second ground layer laminated on one surface side of the conductive pattern via an insulating layer. As described above, by further including the second ground layer laminated on one surface side of the conductive pattern via the insulating layer, both surface sides of the conductive pattern are electromagnetically shielded by the ground layer. Therefore, it is possible to further reduce signal transmission loss and improve signal transmission efficiency.

  The first ground layer or the second ground layer may have an opening overlapping the conductive pattern in plan view. As described above, when the first ground layer or the second ground layer has an opening overlapping the conductive pattern in a plan view, the impedance can be adjusted efficiently by adjusting the facing area between the ground layer and the conductive pattern.

  The “connecting portion” means a region for electrically connecting the conductive pattern to other components, and includes those provided for connection to other layers inside the printed wiring board. . The “maximum inscribed circle” of the connecting portion means a circle having the largest diameter among the perfect circles inscribed at three or more points on the outline of the connecting portion. And may overlap. The “land part” includes not only a part for mounting an electronic component or the like, but also a conductor part arranged around a through hole of a via for making an interlayer connection inside the printed wiring board. “Near the connection part” means a range in which the distance from the outer edge of the connection part is not more than 10 times, preferably not more than 5 times the radius of the maximum inscribed circle of the connection part. The “relative dielectric constant” is a value measured in accordance with JIS-C2138 (2007).

[Details of the embodiment of the present invention]
Hereinafter, each embodiment of the printed wiring board according to the present invention will be described in detail with reference to the drawings.

[First embodiment]
The printed wiring board shown in FIGS. 1 to 4 is laminated on an insulating intermediate layer 1, a conductive pattern 2 laminated on one surface side of the intermediate layer 1, and the other surface side of the intermediate layer 1. First ground layer 3.

  The printed wiring board is formed in a substantially band shape and is used for transmitting an electrical signal in the longitudinal direction.

<Intermediate layer>
The intermediate layer 1 is a layered member that is formed in a substantially band shape and ensures the strength of the printed wiring board, and preferably has flexibility. The intermediate layer 1 can be composed of, for example, a sheet-like member whose main component is a resin.

  Specifically, a resin film can be used as the sheet-like member constituting the intermediate layer 1. As the main component of this resin film, for example, polyimide, polyethylene terephthalate or the like can be used, but it is preferable to use a liquid crystal polymer (LCP) having excellent electrical characteristics.

  The lower limit of the relative dielectric constant of the intermediate layer 1 is preferably as small as possible. However, in order to satisfy other conditions such as insulation and mechanical strength, 1.5 is considered to be the limit in practice. On the other hand, the upper limit of the relative dielectric constant of the intermediate layer 1 is preferably 4, and more preferably 3. When the relative dielectric constant of the intermediate layer 1 exceeds the above upper limit, the dielectric loss may increase when a high-frequency signal is transmitted through the printed wiring board.

  The lower limit of the dielectric loss tangent at a frequency of 1 GHz of the intermediate layer 1 is preferably as small as possible, but in reality, 0.0001 is considered the limit. On the other hand, the upper limit of the dielectric loss tangent of the intermediate layer 1 at a frequency of 1 GHz is preferably 0.05, and more preferably 0.005. When the dielectric loss tangent of the intermediate layer 1 at a frequency of 1 GHz exceeds the above upper limit, there is a possibility that the transmission loss of the high-frequency signal of the printed wiring board becomes large. The “dielectric loss tangent” is a value measured according to JIS-C2138 (2007).

  The thickness of the intermediate layer 1 is appropriately set according to the use of the printed wiring board and the like, and is not particularly limited. In general, the lower limit of the average thickness of the intermediate layer 1 is preferably 5 μm. 10 μm is more preferable, and 25 μm is even more preferable. On the other hand, the upper limit of the average thickness of the intermediate layer 1 is preferably 500 μm, and more preferably 150 μm. When the average thickness of the intermediate layer 1 is less than the lower limit, the parasitic capacitance between the conductive pattern 2 and the first ground layer 3 may be excessively increased, or the strength of the intermediate layer 1 may be insufficient. . On the contrary, when the average thickness of the intermediate layer 1 exceeds the above upper limit, the flexibility of the printed wiring board may be insufficient or the printed wiring board may be unnecessarily thick.

  The liquid crystal polymer forming the intermediate layer 1 includes a thermotropic type exhibiting liquid crystallinity in a molten state and a lyotropic type exhibiting liquid crystallinity in a solution state. In the present invention, it is preferable to use a thermotropic liquid crystal polymer. .

  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. A typical example is a polymer 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, Examples thereof include a polymer obtained by polymerizing the monomers (3) and (5).

  The liquid crystal polymer is not particularly limited as long as it exhibits liquid crystallinity, and the above-mentioned polymers are the main components (in the liquid crystal polymer, 50 mol% or more), 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 polyester amide is a liquid crystal polyester having an amide bond, and examples thereof include a polymer obtained by polymerizing monomers of the following formula (6) and the above formulas (2) and (4).

  The liquid crystal polymer is preferably produced by melt polymerization of raw material monomers corresponding to the constituent units constituting the liquid crystal polymer, and solid-phase polymerization of the obtained polymer (prepolymer). Thereby, a high molecular weight liquid crystal polymer 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. Examples of this catalyst include metal compounds such as magnesium acetate, stannous acetate, tetrabutyl titanate, lead acetate, sodium acetate, potassium acetate, and antimony trioxide, And nitrogen-containing heterocyclic compounds such as 4- (dimethylamino) pyridine and 1-methylimidazole, and nitrogen-containing heterocyclic compounds are preferably used.

  The intermediate layer 1 may include a filler, an additive, and the like in addition to the main component such as the liquid crystal polymer.

<Conductive pattern>
The conductive pattern 2 is formed by patterning a conductor, and has a strip-shaped signal line portion 4 and a connection portion 5 provided continuously to the signal line portion 4.

  The conductor for forming the conductive pattern 2 may be any conductor as long as it has conductivity. For example, metals such as copper, aluminum, silver, and gold are preferably used, and among them, copper that is inexpensive and excellent in conductivity is preferably used. It is done.

  The patterning method of 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 intermediate layer 1 by etching is adopted. can do.

  The method for laminating the metal layer on the intermediate layer 1 is not particularly limited. For example, an adhesion method in which a metal foil is bonded with an adhesive, a casting method in which a resin composition that is a material of the intermediate layer 1 is applied on the metal foil, Sputtering / plating method in which a metal layer is formed by plating on a thin conductive layer (seed layer) having a thickness of several nanometers formed on the intermediate layer 1 by sputtering or vapor deposition, laminating method in which a metal foil is attached by hot pressing, etc. 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 and 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 even more preferably 25 μm. When the average thickness of the conductive pattern 2 is less than the above lower limit, the transmission loss in the signal line portion 4 may be too large. On the other hand, when the average thickness of the conductive pattern 2 exceeds the upper limit, the flexibility of the printed wiring board may be insufficient.

(Signal line)
The signal line unit 4 is a path for transmitting an electrical signal. The signal line portion 4 is disposed so as to extend in the longitudinal direction at the center portion in the width direction of the intermediate layer 1 in plan view.

  The signal line portion 4 is usually formed with a substantially constant width, and the variation is preferably within ± 20% of the average width W. The lower limit of the average width W of the signal line portion 4 is preferably 25 μm, more preferably 60 μm, and further preferably 70 μm. On the other hand, the upper limit of the average width W of the signal line portion 4 is preferably 500 μm, more preferably 240 μm, and further preferably 230 μm. When the average width W of the signal line portion 4 is less than the lower limit, the transmission loss in the signal line portion 4 may be too large. On the other hand, when the average width W of the signal line portion 4 exceeds the above upper limit, the parasitic capacitance with the first ground layer 3 becomes too large, and impedance matching may not be obtained.

(Connection part)
In the printed wiring board of FIG. 1, the connection portion 5 is a land portion for connecting the signal line portion 4 and wiring to an external circuit or an electronic component. The connection portions 5 are typically disposed at both ends of the signal line portion 4, respectively. The wiring or the electronic component can be connected to the connecting portion 5 using, for example, solder.

  Therefore, the conductors of wiring and electronic parts are connected to the connection part 5 which is a land part by laminating solder or the like. Due to the connection between the wiring and the electronic component, the effective facing area and the facing distance between the connecting portion 5 and the first ground layer 3 change, and the parasitic capacitance between the connecting portion 5 and the first ground layer 3 changes. . Since the internal structure of the printed wiring board has small variations from product to product, it is possible to set the parasitic capacitance between the internal structures to a substantially constant value. Since it is difficult to manage the printed wiring board, it is not easy to make the parasitic capacitance between the connecting portion 5 and other components constant when the printed wiring board is used. For this reason, the effective impedance of the printed wiring board is relatively reduced by reducing the parasitic capacitance between the connection portion 5 and the first ground layer 3 where the variation of the value when using the printed wiring board is large. It can be adjusted accurately.

  The shape of the connecting portion 5 is not particularly limited, but may be any shape such as a circle, an ellipse, and a rectangle, and is generally a circle as illustrated.

  The lower limit of the radius R1 of the maximum inscribed circle of the connecting portion 5 (the radius of the connecting portion 5 when the shape is circular) is preferably 0.8 times the average width W of the signal line portion 4, and more preferably 1 time. preferable. On the other hand, the upper limit of the radius R1 of the maximum inscribed circle of the connecting portion 5 is preferably 5 times the average width W of the signal line portion 4, and more preferably 3 times. When the radius R1 of the maximum inscribed circle of the connecting portion 5 is less than the lower limit, when the width of the signal line portion 4 is reduced to increase the density of the printed wiring board, the electrical connection to the conductive pattern 2 is May not be easy. Conversely, when the radius R1 of the maximum inscribed circle of the connection part 5 exceeds the upper limit, the parasitic capacitance between the connection part 5 and the first ground layer 3 may become unnecessarily large, May grow unnecessarily.

<First ground layer>
The first ground layer 3 is formed with a larger width than the signal line portion 4 so as to overlap with the signal line portion 4 of the conductive pattern 2 in a plan view by a conductive material. The first ground layer 3 is preferably formed in a solid shape on substantially the other surface of the other side of the intermediate layer 1 except for the connecting portion 5 and the vicinity thereof. Further, the first opening 6 is formed in the first ground layer 3 so as to overlap the connection portion 5 of the conductive pattern 2 in plan view.

  The average distance from the side edge of the signal line portion 4 of the conductive pattern 2 to the side edge of the first ground layer 3 (average protrusion length in the width direction from the signal line portion 4 of the first ground layer 3 in plan view). As a minimum, 1 time of the average width of the signal line part 4 is preferable, and 1.5 times is more preferable. On the other hand, the upper limit of the average distance from the side edge of the signal line portion 4 of the conductive pattern 2 to the side edge of the first ground layer 3 is preferably 20 times the average width of the signal line portion 4 and more preferably 10 times. When the average distance from the side edge of the signal line portion 4 of the conductive pattern 2 to the side edge of the first ground layer 3 is less than the lower limit, the shielding effect of the signal line portion 4 by the one ground layer 3 may be insufficient. There is. Conversely, if the average distance from the side edge of the signal line portion 4 of the conductive pattern 2 to the side edge of the first ground layer 3 exceeds the upper limit, the width of the printed wiring board may be unnecessarily increased.

  On the other hand, as shown in FIG. 2, the first ground layer 3 overlaps a region other than the connection portion 5 of the conductive pattern 2, that is, a region excluding both ends of the signal line portion 4. Thereby, since the 1st ground layer 3 has the shielding effect which electromagnetically shields signal line part 4, loss at the time of a signal line part transmitting a high frequency signal can be reduced.

  Examples of a material for forming the first ground layer 3 include metals such as copper and aluminum, and copper that is inexpensive and excellent in conductivity is particularly preferably used.

  The average thickness of the first ground layer 3 can be the same as that of the conductive pattern 2.

(First opening)
As described above, the first opening 6 is formed so as to overlap the connection portion 5 in plan view. As the planar shape of the first opening 6, the connection portion 5 has a similar geometrical center of gravity, or the distance between the inner peripheral edge of the first opening 6 and the outer peripheral edge of the connection portion 5 is the entire first opening 6. Although it is preferable to make the shape constant over the circumference, any shape in which the distance between the inner peripheral edge of the first opening 6 and the outer peripheral edge of the connecting portion 5 changes may be adopted.

  The lower limit of the radius R2 of the maximum inscribed circle in the overlapping area of the first opening 6 with the connection portion 5 is 1/2 times the radius R1 of the maximum inscribed circle of the connection portion 5, and preferably 1 time. Double is more preferable, and 2.5 times is more preferable. On the other hand, the upper limit of the radius R2 is preferably 10 times the radius R1 of the maximum inscribed circle of the connecting portion 5, more preferably 7 times, and more preferably 5 times. When the radius R2 is less than the lower limit, the parasitic capacitance between the first ground layer 3 and the connection portion 5 increases, and there is a possibility that variation in impedance of the printed wiring board cannot be sufficiently suppressed. Conversely, when the radius R2 exceeds the upper limit, the shielding effect of the signal line portion 4 by the first ground layer 3 may be insufficient.

  Further, the first opening 6 is preferably formed so that the first ground layer 3 surrounds the entire periphery of the connection portion 5 while being spaced apart. That is, the first opening 6 is preferably formed so as to include the entire connection portion 5 in a plan view. At this time, the radius R2 of the maximum inscribed circle of the overlapping area of the first opening 6 with the connection portion 5 is more than 1 times the radius R1 of the maximum inscribed circle of the connection portion 5. In this way, by forming the first opening 6 so as to include the connection portion 5, the parasitic capacitance between the first ground layer 3 and the connection portion 5 is further reduced, and the variation in impedance of the printed wiring board is reduced. The suppression effect can be further promoted.

  In this case, the lower limit of the minimum distance in plan view between the first ground layer 3 and the connection portion 5 is preferably one times the radius R1 of the maximum inscribed circle of the connection portion 5, and the maximum inscribed circle of the connection portion 5 is preferred. Is preferably 1.2 times the radius R1, and more preferably 1.5 times the radius R1 of the maximum inscribed circle of the connecting portion 5. On the other hand, the upper limit of the minimum distance in plan view between the first ground layer 3 and the connecting portion 5 is preferably 10 times the radius R1 of the maximum inscribed circle of the connecting portion 5, and the maximum inscribed circle of the connecting portion 5 is 5 times the radius R1 is more preferable. When the minimum distance in plan view between the first ground layer 3 and the connection portion 5 is less than the lower limit, the parasitic capacitance between the first ground layer 3 and the connection portion 5 cannot be sufficiently reduced, There is a possibility that the effect of suppressing variation in impedance of the printed wiring board cannot be made remarkable. Conversely, when the minimum distance in plan view between the first ground layer 3 and the connection portion 5 exceeds the upper limit, the shielding effect of the signal line portion 4 by the first ground layer 3 may be insufficient.

  Furthermore, the lower limit of the minimum distance in plan view between the first ground layer 3 and the connection portion 5 is preferably one times the average distance T1 in the thickness direction between the conductive pattern 2 and the first ground layer 3. 2 and the first ground layer 3 are more preferably 1.5 times the average distance T1 in the thickness direction. On the other hand, the upper limit of the minimum distance in plan view between the first ground layer 3 and the connection portion 5 is preferably 20 times the average distance T1 between the conductive pattern 2 and the first ground layer 3 in the thickness direction. 10 times the average distance T1 in the thickness direction between 2 and the first ground layer 3 is more preferable. When the minimum distance in plan view between the first ground layer 3 and the connection portion 5 is less than the lower limit, the connection portion is compared with the parasitic capacitance between the signal line portion 4 and the first ground layer 3 of the conductive pattern. The parasitic capacitance between the first and second ground layers 3 cannot be sufficiently reduced, and the effect of suppressing variation in impedance of the printed wiring board may not be noticeable. Conversely, when the minimum distance in plan view between the first ground layer 3 and the connection portion 5 exceeds the upper limit, the shielding effect of the signal line portion 4 by the first ground layer 3 may be insufficient.

<Advantages>
Since the printed wiring board has a small parasitic capacitance between the first ground layer 3 and the connection portion 5 of the conductive pattern 2 and does not greatly affect the overall impedance, the printed wiring board is connected to the connection portion 5 by connecting an electronic component or a circuit. The influence of the change in the parasitic capacitance between the ground layer 3 and the connection portion 5 on the impedance of the entire printed wiring board is small. For this reason, the said printed wiring board can adjust an impedance comparatively accurately by the design of another part.

  In addition, since the first ground layer 3 overlaps most of the signal line portions 4 of the conductive pattern 2 in plan view, the printed wiring board can shield the signal line portions 4 and accurately transmit electric signals. Can do.

[Second Embodiment]
5 and 6 includes an insulating first intermediate layer 11, a conductive pattern 12 laminated on one surface side of the first intermediate layer 11, and the other of the first intermediate layer 11. A first ground layer 13 laminated on the surface side of the first intermediate layer 1, a second intermediate layer 14 laminated on one surface of the laminated body of the first intermediate layer 1 and the conductive pattern 12, and having an insulating property; And a second ground layer 15 laminated on one surface side.

  The configuration of the first intermediate layer 11, the conductive pattern 12, and the first ground layer 13 in the printed wiring board of the present embodiment is the same as that of the intermediate layer 1, the conductive pattern 2, and the first ground layer 3 in the printed wiring board of the first embodiment. The configuration is the same.

  Specifically, the conductive pattern 12 has a signal line portion 16 and a connection portion 17, and a first opening 18 is formed in the first ground layer 13. About the structure of these signal wire | line parts 16, the connection part 17, and the 1st opening 18, it is the same as that of the structure of the signal wire | line part 4, the connection part 5, and the 1st opening 6 in the printed wiring board of 1st embodiment.

  Therefore, detailed description of the configuration of the first intermediate layer 11, the conductive pattern 12, and the first ground layer 13, and the configuration of the signal line portion 16, the connection portion 17, and the first opening 18 in the printed wiring board of the present embodiment is omitted. To do.

<Second intermediate layer>
The second intermediate layer 14 has a base film 19 on which the second ground layer 15 is laminated on one surface, and an adhesive layer 20 that is laminated on the other surface of the base film 19. That is, in the printed wiring board, the adhesive layer 20 includes a single-sided substrate in which the second ground layer 15 is formed on the base film 19 and a double-sided substrate in which the conductive pattern 12 and the first ground layer 13 are formed on the first intermediate layer 11. Are formed by bonding.

(Base film)
The base film 19 has a film opening 21 that surrounds the connection portion 17 of the conductive pattern 12 and the vicinity thereof in a plan view, that is, surrounds the entire periphery of the connection portion 17 in a plan view. The configuration of the base film 19 can be the same as the configuration of the intermediate layer 1 in the printed wiring board of the first embodiment except that the film opening 21 is provided.

  As the planar shape of the film opening 21, the similar shape in which the center of gravity coincides with the connection portion 17, or the distance between the inner periphery of the film opening 21 and the outer periphery of the connection portion 17 is constant over the entire periphery of the connection portion 17. A shape is preferable, but any other shape may be adopted.

(Adhesive layer)
The adhesive layer 20 has an adhesive opening 22 that overlaps the film opening 21 in plan view.

  Although it does not specifically limit as an adhesive agent which comprises the adhesive bond layer 20, What has a thermosetting resin as a main component is preferable, and it is temperature lower than melting | fusing point of the material which comprises the base film 19 and the 1st intermediate | middle layer 11. What hardens | cures is more preferable. The “main component” means a component having the largest mass content, preferably a component contained in an amount of 50% by mass or more.

  The lower limit of the curing temperature of the thermosetting resin that is the main component of the adhesive layer 20 is preferably 120 ° C., more preferably 150 ° C. On the other hand, the upper limit of the curing temperature of the thermosetting resin that is the main component of the adhesive layer 20 is preferably 250 ° C., more preferably 200 ° C. When the curing temperature of the thermosetting resin that is the main component of the adhesive layer 20 is less than the lower limit, the handling of the adhesive that is the raw material of the adhesive layer 20 may not be easy. Conversely, when the curing temperature of the thermosetting resin as the main component of the adhesive layer 20 exceeds the above upper limit, the base film 19 or the first intermediate is formed when the adhesive layer 20 is formed by curing the adhesive. The layer 11 may be deformed by heat and impair the dimensional accuracy of the printed wiring board.

  Although it does not specifically limit as a thermosetting resin used as the main component of the adhesive bond layer 20, A thing with a small non-dielectric constant and dielectric loss is preferable. Examples of the thermosetting resin having a small non-dielectric constant and dielectric loss include modified polyphenylene ether and styrene resin.

  The relative dielectric constant of the adhesive layer 20 is not particularly limited, but the upper limit of the relative dielectric constant of the adhesive layer 20 is preferably 4.0, and more preferably 3.0. When the relative dielectric constant of the adhesive layer 20 exceeds the upper limit, the presence of the adhesive layer 20 may increase the apparent dielectric constant of the entire second intermediate layer 14.

  The dielectric loss tangent of the adhesive layer 20 is not particularly limited, but the upper limit of the dielectric loss tangent of the adhesive layer 20 is preferably 0.1, and more preferably 0.01. When the dielectric loss tangent of the adhesive layer 20 exceeds the above upper limit, the presence of the adhesive layer 20 may increase the apparent dielectric loss tangent of the entire second intermediate layer 14.

  As a minimum of average thickness of adhesive bond layer 20, 15 micrometers is preferred and 20 micrometers is more preferred. On the other hand, the upper limit of the average thickness of the adhesive layer 20 is preferably 100 μm, and more preferably 50 μm. When the average thickness of the adhesive layer 20 is less than the lower limit, the adhesive strength between the first intermediate layer 11 and the second intermediate layer 14 may be insufficient. On the other hand, when the average thickness of the adhesive layer 20 exceeds the upper limit, the flexibility of the printed wiring board may be insufficient.

<Second ground layer>
The second ground layer 15 covers one side of the signal line portion 16 of the conductive pattern 12 to make the shield of the signal line portion 16 more reliable, thereby further reducing signal transmission loss and signal transmission efficiency. To improve.

  The second ground layer 15 has a second opening 23 that overlaps the film opening 21 and the adhesive opening 22 of the second intermediate layer 14 in plan view.

  The configuration of the second ground layer 15 is the same as that of the first ground layer 3 in the printed wiring board of the first embodiment and the first ground layer 13 in the printed wiring boards of FIGS. It can be.

(Second opening)
The second opening 23, together with the film opening 21 and the adhesive opening 22, provides a space for electrical connection such as external wiring and electronic components to the connection portion 17 of the first conductive pattern 12. Further, the second opening 23 is configured so that the second ground layer 15 separates and surrounds the connection portion 17 in a plan view, that is, the second ground layer 15 does not overlap with the connection portion 17. The parasitic capacitance between the connection part 17 of the pattern 12 and the second ground layer 15 is reduced.

  The relationship between the minimum distance in plan view of the first ground layer 13 and the connection portion 17 and the radius of the maximum inscribed circle of the connection portion 17 and the average in the thickness direction between the conductive pattern 12 and the first ground layer 13. The relationship with the interval T1 is the relationship between the minimum interval in plan view between the second ground layer 15 and the connection portion 17 and the radius of the maximum inscribed circle of the connection portion 17, and between the conductive pattern 12 and the second ground layer 15. It can be read as a relationship with the average interval T2 in the thickness direction.

[Third embodiment]
7 and 8 includes an insulating first intermediate layer 31, a conductive pattern 32 laminated on one surface side of the first intermediate layer 31, and the other surface of the intermediate layer 31. The first ground layer 33 laminated on the side, the second intermediate layer 34 laminated on one surface side of the conductive pattern 32, and the first intermediate layer 34 laminated on one surface side of the second intermediate layer 34. 2 ground layers 35.

<First intermediate layer>
The first intermediate layer 31 is formed in a solid shape without holes so as to exist in the entire printed wiring board in a plan view.

  The first intermediate layer 31 has a base film 36 on which the first ground layer 33 is laminated on the other surface, and an adhesive layer 37 that is laminated on one surface of the base film 36. That is, in the printed wiring board, the adhesive layer 37 includes a single-sided board in which the first ground layer 33 is formed on the base film 36 and a double-sided board in which the conductive pattern 32 and the second ground layer 35 are formed on the second intermediate layer 34. Are formed by bonding.

  The configurations of the base film 36 and the adhesive layer 37 in the printed wiring board of the present embodiment are the same as the configurations of the base film 19 and the adhesive layer 20 in the printed wiring board of the second embodiment, except for the lamination position and the planar shape. It can be.

<Conductive pattern>
The conductive pattern 32 is formed by patterning a conductor, and has a strip-shaped signal line portion 38 and a connection portion 39 provided continuously to the signal line portion 38.

  The material and average thickness of the conductive pattern 32 in the printed wiring board of the present embodiment can be the same as those of the conductive pattern 2 in the printed wiring board of the first embodiment. The signal line portion 38 of the conductive pattern 32 in the printed wiring board of the present embodiment can be the same as the signal line portion 4 of the conductive pattern 2 in the printed wiring board of the first embodiment.

(Connection part)
The connecting portion 39 is necessary for forming a through hole (a conductor for forming the through hole is not shown in FIG. 7) for electrically connecting to a terminal portion 43 of the second ground layer 35 described later. It is a land part.

  The shape of the connecting portion 39 is not particularly limited, but is generally an annular shape as illustrated.

  The radius of the maximum inscribed circle of the connection portion 39 of the conductive pattern 32 in the printed wiring board of this embodiment is the same as the radius of the maximum inscribed circle of the connection portion 5 of the conductive pattern 2 in the printed wiring board of the first embodiment. It can be.

<First ground layer>
The first ground layer 33 is formed with a larger width than the signal line portion 38 so as to overlap the signal line portion 38 of the conductive pattern 32 in a plan view with a conductive material. The first ground layer 33 is preferably formed in a solid shape on substantially the entire other side of the first intermediate layer 31 except for the connection portion 39 and the vicinity thereof. Further, the first opening 40 is formed in the first ground layer 33 in a region overlapping the connecting portion 39 of the conductive pattern 32 and the vicinity thereof in a plan view.

  The configuration of the first ground layer 33 and the first opening 40 in the printed wiring board of the present embodiment is the same as the configuration of the first ground layer 3 and the first opening 6 of the printed wiring board of the first embodiment. Can do.

<Second intermediate layer>
A through hole 41 is formed in the second intermediate layer 34 to form the through hole for electrically connecting the connection portion 39 of the conductive pattern 32 and the terminal portion 43 (described later) of the second ground layer 35. Is done.

  The configuration of the second intermediate layer 34 in the printed wiring board of the present embodiment can be the same as that of the intermediate layer 1 in the printed wiring board of the first embodiment, except that the through hole 41 is formed.

<Second ground layer>
The second ground layer 35 covers one side of the signal line portion 38 of the conductive pattern 32 to make the shield of the signal line portion 38 more reliable, thereby further reducing signal transmission loss and increasing the signal transmission efficiency. improves.

  The second ground layer 35 includes a second opening 42 formed in a region overlapping with the connection portion 39 of the conductive pattern 32 and the vicinity thereof in a plan view, and the connection portion 39 of the conductive pattern 32 in the second opening 42. It has the terminal part 43 formed so that it may correspond substantially by planar view, and the some adjustment opening 44 formed so that it may overlap with the signal wire | line part 38 of the conductive pattern 32 by planar view.

  The configuration of the second ground layer 35 is the same as that of the first ground layer 3 in the printed wiring board of the first embodiment and the first ground layer 13 in the printed wiring board of the present embodiment, except for the stacking position and planar shape. be able to.

(Second opening)
Similar to the first opening 40 of the first ground layer 13, the second opening 42 is formed to reduce the parasitic capacitance between the connection portion 39 of the conductive pattern 32 and the second ground layer 35. The relationship between the minimum distance in plan view between the first ground layer 33 and the connection portion 39 and the radius of the maximum inscribed circle of the connection portion 39 and the thickness direction between the conductive pattern 32 and the first ground layer 33 are shown. The relationship with the average interval T1 is the relationship between the minimum interval between the second ground layer 35 and the connection portion 39 in plan view, the radius of the maximum inscribed circle of the connection portion 39, and the conductive pattern 32 and the second ground layer 35. It can be read as the relationship with the average interval T2 in the thickness direction.

(Terminal part)
The terminal part 43 is electrically connected to the connection part 39 of the conductive pattern 32. An external circuit or an electronic component is connected to the terminal portion 43. That is, the terminal portion 43 is a relay terminal for indirectly connecting the conductive pattern 32 to an external circuit or electronic component.

  Further, as shown in FIG. 8, the terminal portion 43 is formed by laminating a connection conductor 45 such as copper or nickel on the inner periphery of the through hole 41 of the second intermediate layer 34 to form a through hole. It is also a land part used for electrically connecting the part 43 and the conductive pattern 32. In addition, about a through hole, since it can be set as a well-known structure, detailed description is abbreviate | omitted.

<Adjustment opening>
The adjustment opening 44 is formed to adjust the impedance of the printed wiring board by adjusting the facing area between the second ground layer 35 and the conductive pattern 32. The adjustment opening 44 is generally formed in a part of the signal line portion 38 in the longitudinal direction of the conductive pattern 32 so as to overlap the entire width of the signal line portion 38.

<Advantages>
In the printed wiring board, the parasitic capacitance between the connection portion 39 of the conductive pattern 32 and the first ground layer 33 and the parasitic capacitance between the connection portion 39 and the second ground layer 35 are different from those of the signal line portion 38 and the first ground layer 35. The parasitic capacitance between the ground layer 33 and the parasitic capacitance between the signal line portion 38 and the second ground layer 35 is smaller. For this reason, since the parasitic capacitance related to the signal line portion 38 does not greatly affect the overall impedance, the printed wiring board adjusts the impedance relatively accurately by adjusting the area of the adjustment opening 44 facing the conductive pattern 32. be able to.

[Other Embodiments]
The embodiment disclosed this time should be considered as illustrative in all points and not restrictive. The scope of the present invention is not limited to the configuration of the embodiment described above, but is defined by the scope of the claims, and is intended to include all modifications within the meaning and scope equivalent to the scope of the claims. The

  In the printed wiring board, the intermediate layer may be formed of only an adhesive layer, or may have a laminated structure of three or more layers.

  The printed wiring board may further include a layer other than those described in the above embodiment, for example, a cover lay or a solder resist.

  In the printed wiring board, an adjustment opening may be formed in the first ground layer.

  Further, in the printed wiring board, the conductive pattern laminated on the intermediate layer may have a plurality of signal line portions, and extend to other patterns other than the signal line portions and the connection portions, for example, both sides of the signal line portions. You may further have the shield part etc. which exist.

  The printed wiring board may further have a through-hole structure that penetrates the ground layer and the intermediate layer.

  The said printed wiring board can be used suitably as a flexible printed wiring board which transmits a high frequency signal, for example.

DESCRIPTION OF SYMBOLS 1 1st intermediate | middle layer 2 Conductive pattern 3 1st ground layer 4 Signal line part 5 Connection part (land part)
6 First opening 11 First intermediate layer 12 Conductive pattern 13 First ground layer 14 Second intermediate layer 15 Second ground layer 16 Signal line portion 17 Connection portion 18 First opening 19 Base film 20 Adhesive layer 21 Film opening 22 Adhesion Agent opening 23 Second opening 31 First intermediate layer 32 Conductive pattern 33 First ground layer 34 Second intermediate layer 35 Second ground layer 36 Base film 37 Adhesive layer 38 Signal line portion 39 Connection portion (land portion)
40 1st opening 41 Through-hole 42 2nd opening 43 Terminal part 44 Adjustment opening 45 Connection conductor R1, R2 Radius T1, T2 Average space | interval W Average width

Claims (7)

A printed wiring board comprising an insulating intermediate layer, a conductive pattern laminated on one surface side of the intermediate layer, and a first ground layer laminated on the other surface side of the intermediate layer,
The conductive pattern has a connection part,
The first ground layer has an opening in a region overlapping with the connection portion in plan view,
A printed wiring board in which a radius of a maximum inscribed circle in a region overlapping with the connection portion of the opening is ½ or more of a radius of the maximum inscribed circle of the connection portion.   The printed wiring board according to claim 1, wherein the connection portion is a land portion. The inner edge of the opening surrounds the entire circumference of the connection part in plan view,
3. The printed wiring board according to claim 1, wherein a minimum distance in a plan view between the first ground layer and the connection portion is equal to or greater than an average distance in a thickness direction between the conductive pattern and the first ground layer.   4. The printed wiring board according to claim 1, wherein the first ground layer overlaps with a region other than the connection portion and the vicinity of the connection portion of the conductive pattern in a plan view.   The printed wiring board according to any one of claims 1 to 4, wherein a relative dielectric constant of the intermediate layer is 4 or less.   The printed wiring board according to any one of claims 1 to 5, further comprising a second ground layer laminated on one surface side of the conductive pattern via an insulating layer.   The printed wiring board according to claim 6, wherein the first ground layer or the second ground layer has an opening overlapping the conductive pattern in plan view.

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