JP4683381B2 - Circuit board - Google Patents

Description

  The present invention relates to a ground layer and a circuit board in which signal wiring is disposed with respect to the ground layer through an insulator layer.

For example, a circuit board on which a device operating in a high frequency band is mounted has a characteristic impedance (hereinafter also referred to as Z0) of a signal transmission path (hereinafter also referred to as signal wiring) in order to suppress signal reflection and waveform distortion. It is necessary to match the input / output impedance of the device.
In order to match the characteristic impedance of the signal transmission path described above, a strip structure or a microstrip structure in which a ground layer is opposed to a signal transmission path (strip line) having an appropriate pattern width with an insulator layer having an appropriate thickness interposed therebetween Is adopted.

The ground layer in the circuit board structure described above serves as an electrical reference plane that defines the characteristic impedance of the signal transmission path. In general, the characteristic impedance is often selected to be around 50Ω at a single end and around 100Ω at a differential.
On the other hand, the characteristic impedance of the circuit board described above is the ratio of the reactance L per unit length of the signal transmission path and the capacitance C per unit area between the signal transmission path and the ground layer (reactance L / capacitance C). The value approximated by the square root of.

By the way, in recent years, thin rigid boards and flexible circuit boards are frequently used as circuit boards for mounting the above-described devices. When such circuit boards are adopted, of course, the signal transmission path for the ground layer is naturally used. The interlayer is narrow (thin), and the value of the capacitance C between the two increases almost in inverse proportion to the dimension between the layers.
Therefore, in the above-described thin multilayer circuit board, in order to obtain the desired Z0, the width of the signal transmission path is narrower (thinner) than that of a conventional thick circuit board, A means for suppressing the increase in the capacitance C must be employed.

Thus, in order to obtain a desired Z0, when trying to form a thin signal wiring, there is a case where the signal wiring has to be made so thin that it is difficult to process. Even if the signal wiring can be processed, the thinner the signal wiring, the higher the processing accuracy and the ratio of line width variation, and the Z0 variation increases accordingly.
For this reason, there arises a problem that signal reflection and waveform distortion occur in the signal wiring portion where the change in Z0 is large. Furthermore, since the wiring resistance value of the signal wiring is increased, there is a problem that the higher the signal frequency supplied to the signal wiring, the worse the transmission characteristics.

Therefore, in order to solve the above-described technical problem, the ground layer formed as a so-called solid pattern layer is coppered into a square mesh shape so that the opposing area between the ground layer and the signal wiring per unit area is reduced. Proposals have been made to ensure the width of the signal wiring by making it substantially small. This is shown in Patent Document 1 shown below.
JP 7-32463 A

  By the way, in recent electronic devices having a folding structure such as mobile phones, and mobile devices such as video cameras that are becoming smaller and lighter, composite substrates of flexible substrates and rigid substrates are often used. By eliminating the need for connectors and the like that have been used to connect conventional multilayer wiring boards and flexible wiring boards, it is possible to reduce the weight of products, reduce the number of parts, and the number of assembly steps.

  A printed wiring board in which a rigid portion is formed on a part of a flexible wiring board on which signal wiring is formed as described above is also called a rigid flex wiring board. In such a rigid-flex wiring board, when a strip structure or a microstrip structure in which the ground layer is formed in a mesh shape as described above is to be adopted, it is formed in a mesh shape between the flexible substrate and the rigid substrate. A configuration for connecting the ground layers thus formed is required.

  That is, the ground layer in the rigid substrate portion generally employs a configuration in which the copper foil is removed in a mesh shape by means such as etching. On the other hand, for the ground layer in the flexible substrate portion described above, a configuration in which, for example, a silver paste is used as a material and is printed in a mesh shape is preferably employed in order to ensure flexibility.

In this case, the specification of the ground layer in the flexible substrate portion formed by the printing described above is set so as to match the mesh-like specification of the ground layer in the rigid substrate portion. very difficult.
Therefore, at present, means for forming the ground layer in the flexible substrate portion by printing is employed so that the end portion of the ground layer in the flexible substrate portion is surely superimposed on the end portion of the ground layer in the rigid substrate portion. ing.

FIG. 11 schematically shows an example thereof, and reference numeral 1A shows a configuration example of a part of the ground layer in the above-mentioned rigid substrate, which is formed by meshing a copper foil by means such as etching. The state extracted in the shape is shown.
Reference numeral 1B shows a configuration example of a part of the ground layer in the flexible substrate described above, which shows a state in which a mesh-like punched portion is formed and printed using, for example, silver paste as a material. That is, the ground layer 1A made of copper foil and the ground layer 1B made by printing are formed so that the mesh shape, arrangement pitch, and the like of both are substantially the same.

Then, as shown in FIG. 12, the ground layer 1B is formed by printing so that the end portion of the ground layer 1B in the flexible substrate overlaps the end portion of the ground layer 1A in the rigid substrate. , 1B is configured such that there is no gap in the horizontal direction.
Although not shown in FIG. 12, the ground layers 1 </ b> A and 1 </ b> B are configured such that a contact is secured in an area where no mesh is formed. Although not shown, for example, a film-like base substrate as an insulator layer is formed on the ground layers 1A and 1B, and the signal wiring 3 indicated by a chain line faces the ground layer through the base substrate. Are arranged as follows.

By the way, the overlapping portion of the ground layers 1A and 1B shown in FIG. 12 is adjusted so that the mesh portion of the ground layer 1B formed by printing is vertically aligned with the mesh portion of the ground layer 1A. . In other words, it is ideal that the mesh portions of the ground layers 1A and 1B coincide with each other and no deviation occurs between the mesh portions.
However, as described above, the tolerance management of the ground layer 1B formed by printing is very difficult, and a deviation occurs in the mesh portion at the overlapping position.

  FIG. 12 illustrates a case where a shift of 1/6 pitch occurs with respect to the pitch P of each mesh in the longitudinal direction of the signal wiring 3. As is clear from the example shown in the figure, the regularity of the mesh configuration is lost in the overlapped portion due to the shift, and the area of the mesh opening in the overlapped portion is considerably reduced. In other words, the substantial remaining rate (area ratio) of the ground layer excluding the mesh opening in the overlapped portion increases, resulting in a mismatch in the characteristic impedance for the signal wiring 3 in the overlapped portion. .

  The present invention has been made paying attention to the technical problems described above, and in the overlapping portion of each ground layer formed in a mesh shape, an increase in the residual rate of the ground layer caused by a shift between the two is achieved. It is an object of the present invention to provide a circuit board that can be significantly reduced and that can suppress a variation in characteristic impedance on a signal wiring in an overlapping portion of a ground layer.

  The circuit board according to the present invention, which has been made to solve the above-mentioned problems, has a large number of four-sided holes formed in the first and second ground layers, and one of the first and second ground layers. A circuit board in which a signal wiring portion is disposed via an insulator layer on the first and second ground layers including the overlapped portion, and the first ground in the overlapped portion A first conductor formed in a stripe shape is formed on the layer connected to the first ground layer, and the first conductor is formed on the second ground layer in the overlapping portion. The second conductor formed in a stripe shape in the crossing direction is connected to the second ground layer, and is characterized in that it is formed.

  In this case, it is preferable that the intervals between the first conductors formed in the stripe shape are equal, and the intervals between the second conductors formed in the stripe shape are also equal. .

  In a preferred embodiment, the first conductor formed in a stripe shape connected to the first ground layer and the ground layer is formed of a copper foil, and the second ground layer and the ground The second conductor connected to the layer and formed in a stripe shape is made of a paste material in which conductive particles are dispersed.

  In this case, conductive particles of silver, copper, or carbon are dispersed in the paste material, and preferably formed as a second ground layer and a striped second conductor on the insulator layer by a printing technique. Is done.

  The substrate including the first conductor formed in a stripe shape with the first ground layer preferably forms a rigid substrate, and the second ground layer is formed in the stripe shape with the second ground layer. A substrate including a conductor is configured as a flexible substrate.

  In one preferable embodiment for specifically realizing the circuit board, the insulator layer has the signal wiring portion laminated on one surface and the ground layer disposed on the other surface. The insulator layer is preferably configured using a film-like base substrate.

  According to the circuit board having the above-described configuration, the ground layer in the overlapping portion has the first conductor formed in one stripe shape and the first conductor formed in the stripe shape in the direction crossing the first conductor. Since the two conductors are superposed on each other, even if a deviation occurs in the superposition of the first and second ground layers, the regularity of the mesh configuration in the superposed portion is greatly lost due to the deviation. Can be prevented.

That is, in the first and second ground layers, even if there is a deviation in the overlay, each mesh composed of the first conductor formed in a stripe shape and the second conductor is formed. The size and pitch are in the same relationship.
As a result, it is possible to provide a circuit board that can suppress a variation in characteristic impedance on the signal wiring in the overlapping portion of the ground layer.

  FIG. 1 shows one preferred laminated configuration example that can be adopted by the circuit board according to the present invention, which is a configuration example of the above-described rigid flex wiring board. That is, the portion indicated by the left and right symbols A indicates a rigid portion, and the portion indicated by B in the center indicates a flexible portion.

The ground layer 1A constituting the rigid portion A and the ground layer 1B constituting the flexible portion B are respectively formed on one surface of the insulator layer 2 (the lower surface shown in FIG. 1). Further, the signal wiring 3 is formed on the other surface (upper side surface shown in FIG. 1) of the insulating layer 2 through the insulating layer 2, thereby forming a microstrip structure.
In this embodiment, a film-like base substrate that will be described in detail later is employed as the insulator layer 2.

On the upper side surface of the signal wiring 3 arranged on the upper side surface of the base substrate (insulator layer) 2, an insulator layer 4 functioning as a second insulator layer is laminated. A first covering layer 5 that functions as a front cover layer is formed on the upper surface of the insulator layer 4.
On the other hand, a second covering layer 6 that functions as a back cover layer is formed on the lower surface of the ground layer 1A in the above-described rigid portion A.

  2 is an enlarged view of the overlapping portion of the ground layers 1A and 1B in the vicinity of the boundary between the rigid portion A and the flexible portion B, that is, the portion C shown in FIG. 1, and is seen through from a direction perpendicular to the surface of the circuit board. It is shown by. In FIG. 2, the ground layer 1 </ b> A constituting the rigid part A and the ground layer 1 </ b> B constituting the flexible part B are mainly shown.

  As shown in FIG. 2, the ground layer 1 </ b> A constituting the rigid portion A is made of copper foil and is laminated on the lower surface of the base substrate 2 described above. A large number of mesh-shaped (four-sided) holes 1a are formed over substantially the entire surface excluding the upper and lower side edges. This hole 1a can be formed by, for example, a processing technique using an etching solution.

On the other hand, the ground layer 1B constituting the flexible portion B is formed on the lower surface of the base substrate 2 by using a silver paste, for example, by a printing technique. Similarly, in this ground layer 1B, silver paste is printed so as to form a large number of mesh-shaped (four-sided) punched holes 1b over almost the entire surface excluding the upper and lower side edges.
In this case, the hole 1a formed in the ground layer 1A and the hole 1b formed in the ground layer 1B are formed so that the mesh shape, the arrangement direction, the arrangement pitch, and the like are substantially equal. .

As shown in FIG. 1 and FIG. 2, a through hole is formed in a part of the second covering layer 6 in an unformed portion of the through holes 1 a and 1 b in the vicinity of the boundary between the rigid portion A and the flexible portion B. (Indicated by the symbol D) is formed.
Therefore, when the ground layer 1B is formed using the silver paste described above, a part of the silver paste contacts (contacts) the ground layer 1A of the rigid portion A through the through hole D. Both ground layers 1A and 1B are configured to be electrically connected.
In FIG. 2, reference numeral 3 indicates a signal wiring disposed opposite to the ground layers 1 </ b> A and 1 </ b> B including the overlapping portion.

3 to 6 show a preferred first embodiment of the ground layers 1A and 1B. That is, FIG. 3 shows the configuration of the striped conductors formed on the ground layers in the overlapping portion of the ground layer 1A of the rigid portion A and the ground layer 1B of the flexible portion B. .
FIG. 4 illustrates an ideal state in which the striped conductors shown in FIG. 3 are overlapped and there is no deviation in the overlapping state between the two. It is shown in a transparent state.

As shown in FIG. 3, a first conductor 1c formed in a stripe shape is formed in a region corresponding to the overlapping portion of the ground layer 1A, and these are electrically connected to the first ground layer 1A. Connected.
As shown in FIG. 3, the first conductors 1c are formed so as to be inclined in one direction, and the intervals between the conductors 1c are formed equally.
That is, each conductor 1c is formed at the same interval as the copper foil pattern that forms the mesh-shaped hole 1a formed in the first ground layer 1A. This is the same as the formation of the first ground layer 1A. Formed simultaneously.

Further, as shown in FIG. 3, the second conductor 1d is formed so as to be inclined in a direction crossing the first conductor 1c, and the intervals between the conductors 1d are formed to be equal. Has been.
That is, the second conductors 1d are also formed at the same interval as the printed pattern that forms the mesh-shaped holes 1b formed in the second ground layer 1B. At the time of formation, it is formed by printing.

When the first and second conductors 1c and 1d in the stripe shape shown in FIG. 3 are overlapped with no deviation in both due to the configuration of each overlapping portion described above, it is shown in FIG. In this way, the mesh-shaped holes are regularly arranged across the ground layers 1A to 1B including the overlapping portion.
Therefore, the signal wiring 3 as opposed to this can obtain a constant characteristic impedance in the line direction, and can prevent deterioration of transmission characteristics particularly in a high frequency signal region.

By the way, as shown in FIG. 4, in the ideal case where there is no deviation in the overlapping of the ground layers 1A and 1B, the mesh-shaped holes are regularly arranged. The same applies to the example shown in FIG.
However, according to the combined configuration of the first and second conductors 1c and 1d shown in FIG. 3, the regularity of the mesh arrangement configuration is maintained even when the ground layers 1A and 1B are misaligned. There will be no major collapse.

  FIG. 5 illustrates an example of this, and FIG. 5 shows the ground layers 1A and 1B in which mesh-like holes are formed as seen in FIG. The example shown in FIG. 5 shows a case where a deviation of 1/6 pitch has occurred with respect to the pitch P of each mesh in the signal wiring arrangement direction, similarly to the example shown in FIG. ing.

  According to this, although a little irregularity occurs in the shape of the mesh-shaped hole formed in each end of the ground layers 1A, 1B, the mesh-shaped formed in the overlapping portion of the ground layers 1A, 1B. The punched holes have the same mesh shape and the same arrangement pitch as the punched holes 1a and 1b formed in the ground layers 1A and 1B, respectively.

  Therefore, when compared with the example shown in FIG. 8 shown with the same shift amount as the example shown in FIG. 5, the substantial remaining rate of the ground layer (excluding the mesh opening in the overlapping portion of the ground layers 1 </ b> A and 1 </ b> B ( The change in area ratio is very small. As a result, it is possible to solve the problem of causing a mismatch in the characteristic impedance with respect to the signal wiring 3 in the overlapping portion.

In addition, the example shown in FIG. 6 shows a case where the ground layer 1B is shifted downward with respect to the ground layer 1A, which is 1/6 pitch with respect to the arrangement pitch in the vertical direction of each mesh. This shows a state of being shifted.
In the example shown in FIG. 6 as well, although there are some irregularities in the shape of the mesh-shaped holes formed at the ends of the ground layers 1A and 1B, they are formed at the overlapping portions of the ground layers 1A and 1B. The mesh-shaped holes to be formed have the same mesh shape and the same arrangement pitch as the holes 1a and 1b formed in the ground layers 1A and 1B, respectively.

  Therefore, according to the circuit board shown in the embodiment described above, the first and second ground layers, regardless of which direction the misalignment occurs in the overlapping portion of the first and second ground layers, The change in the facing area of the signal wiring 3 with respect to the ground layer in the overlapping portion can be extremely reduced.

  Therefore, it is possible to fundamentally improve the problem of mismatching in the characteristic impedance with respect to the signal wiring in the overlapped portion. Especially in the circuit board on which a device operating in a high frequency band is mounted, signal reflection and waveform distortion Therefore, it is possible to provide a circuit board having good signal transmission characteristics.

  Next, specific examples of each layer that can be suitably employed in the laminated structure of the circuit board shown in FIG. 1 will be described. The base substrate 2 functioning as a central insulator layer forming the microstrip structure shown in FIG. 1 has a function of becoming a core of a circuit board. Examples of the material of the base substrate 2 include a resin film and a fiber substrate.

Examples of the material constituting the resin film include polyimide resins such as polyimide resins, polyamide resins, and polyamideimide resins, thermosetting resins such as epoxy resins, and thermoplastic resins such as liquid crystal polymers.
Among these, a polyimide resin or a liquid crystal polymer is preferable. For example, in the case of polyimide resin, it is excellent in heat resistance and mechanical properties and is easy to obtain. In the case of a liquid crystal polymer, it is suitable for high-speed signal transmission due to its low relative dielectric constant, and it has excellent dimensional stability due to its low hygroscopicity.

  Examples of the fiber base material include glass fiber base materials such as glass fiber cloth and glass non-woven cloth, or inorganic fiber base materials such as fiber cloth and non-fiber cloth containing inorganic compounds other than glass, aromatic polyamide resins, and polyamide resins. And organic fiber base materials composed of organic fibers such as aromatic polyester resin, polyester resin, polyimide resin, and fluororesin. Among these base materials, a glass fiber base material typified by a glass fiber fabric can be suitably employed in terms of strength and water absorption.

  The thickness of the base substrate 2 is not particularly limited, but is preferably 12 μm or more, particularly preferably 25 to 50 μm. By setting the thickness of the base substrate 2 to be equal to or greater than the lower limit, it becomes easy to make the signal line width equal to or greater than the processing limit. On the other hand, by reducing the thickness to the upper limit or less, rigidity is increased. It is possible to keep the characteristics of a thin substrate such as a flexible circuit board as flexible.

In addition, as the base substrate 2 described above, a laminated plate in which a substrate is impregnated with a resin can also be adopted.
In this case, preferable examples of the base material include glass fiber base materials such as glass fiber cloth and glass non-woven cloth, or inorganic fiber base materials such as fiber cloth and non-fiber cloth containing inorganic compounds other than glass, aromatic polyamide resins, Examples thereof include organic fiber base materials composed of organic fibers such as polyamide resin, aromatic polyester resin, polyester resin, polyimide resin, and fluororesin. Among these base materials, glass fiber base materials represented by glass fiber fabric are particularly preferable in terms of strength and water absorption.
Moreover, as said resin, thermosetting resins, such as an epoxy resin type and an acrylic resin type, are preferable, for example, Among these, an epoxy resin type is especially preferable from a heat resistant surface.

The signal wirings 3 arranged on one surface of the base substrate 2 may be provided directly on the base substrate 2 or may be provided via an adhesive. The arrangement interval of the signal wirings constituting the signal wiring 3 is not particularly limited, but is preferably 2 to 6 times the width of the signal wiring 3, and particularly preferably 3 to 5 times.
Within this range, the electrical influence between the signal wirings is in a range that can be almost ignored, and high-density circuit design is often possible. The signal wiring 3 is bonded to a mounting pad such as a semiconductor device (not shown) in the above-described rigid portion A and functions as a circuit board.

As the second insulator layer 4 covering the signal wiring 3, for example, an acrylic resin, an epoxy resin, a polyimide resin, a liquid crystal polymer, or the like can be suitably used. Among these, an epoxy resin is preferable. Thereby, heat resistance and flexibility can be improved.
On the other hand, when the liquid crystal polymer is used, it is possible to take advantage of the characteristics that the relative dielectric constant is low and the high-speed signal transmission characteristics are excellent.

  Although the thickness of the said insulator layer 4 is not specifically limited, It is preferable that it is 5-40 micrometers, and 10-30 micrometers is especially preferable. By making the thickness of the insulator layer 4 equal to or higher than the lower limit value, a decrease in circuit embeddability is suppressed, and by setting the thickness to be equal to or lower than the upper limit value, an increase in the amount of spots of the insulator layer 4 is suppressed, and the interlayer Adhesion reliability can be maintained.

  The first covering layer 5 laminated on the upper surface of the insulator layer 4 is preferably made of a resin material. As this resin material, for example, a polyester resin, polyimide, liquid crystal polymer, or the like can be preferably used. Among these, polyimide is particularly preferable. Thereby, heat resistance and flexibility can be improved.

  Although the thickness of the said coating layer 5 is not specifically limited, Preferably it is 5-50 micrometers, and 10-30 micrometers is especially preferable. By making the thickness of the coating layer 5 equal to or greater than the lower limit value, it becomes easy to maintain the strength of the resin layer within a practical range, and by making the thickness less than the upper limit value, slidability and flexibility are maximized. It becomes easy to make.

The insulator layer 4 may be formed integrally with the first coating layer 5 as an adhesive layer of the first coating layer 5.
In this case, the first coating layer 5 is composed of a resin layer and an adhesive layer. In this case, as the resin material constituting the resin layer, for example, a polyester-based resin, polyimide, liquid crystal polymer, or the like is used similarly to the resin material constituting the first covering layer 5 described above.
Among these, it is preferable to use polyimide. Thereby, heat resistance and flexibility can be improved.

  In this case, the material constituting the adhesive layer is, for example, an acrylic resin, an epoxy resin, a polyimide resin, as in the material constituting the insulator layer 4 functioning as the second insulator layer described above. Resin or the like can be used. Among these, an epoxy resin is preferable, and thereby heat resistance and flexibility can be improved.

The ground layer disposed on the back side of the base substrate 2 is made of copper foil in the rigid portion A as already described, and the ground layer 1A is matched with the characteristic impedance of the signal wiring 3 described above. The quadrangular holes 1a are regularly formed.
The quadrilateral hole 1a may be formed in a diamond shape as shown in FIG. 2, for example, but it may be formed in a square shape. As the means for forming these punched holes 1a, a processing technique using a known etching solution can be suitably employed as already described.

On the other hand, in the flexible part B, the ground layer 1B formed on the back surface side of the base substrate 2 is preferably formed by printing means using silver paste as already described. In this case, instead of the silver paste, a paste in which conductive particles of copper, carbon or the like are dispersed can be used.
In short, the characteristic impedance of the signal wiring 3 facing the ground layer 1B can be matched by using the paste material in which the conductive particles are dispersed to form the diamond-shaped or square-shaped hole 1b. it can.

  In the already described first embodiment, the ground layers 1A and 1B of the rigid part A and the flexible part B are respectively formed with the same shape of the holes 1a and 1b with the same pitch. According to the above, it is possible to facilitate the matching of the characteristic impedance to the signal wiring, but the present invention is not necessarily limited to the above-described configuration, and the second and third embodiments shown in FIGS. Can be adopted.

On the other hand, the second covering layer 6 formed on the back side of the ground layer 1A in the rigid portion A is preferably made of a resin material. Examples of the resin material include polyester resins, polyimides, and liquid crystal polymers. Among these, polyimide is preferable. Further, the resin material constituting the first coating layer 5 and the resin material constituting the second coating layer 6 may be the same or different.
Further, the thickness of the second coating layer 6 is not particularly limited, but can be formed to the same thickness as that of the first coating layer 5 already described.

FIGS. 7 and 8 show a second embodiment of the circuit board according to the present invention. FIG. 7 shows the ground layer 1A of the rigid portion A and the flexible portion B as in FIG. In the overlapping portion of the ground layer 1B, a configuration example of a striped conductor formed in each ground layer is shown.
Further, FIG. 8 is similar to FIG. 4 described above, and illustrates the overlapping state of the two when the stripe-shaped conductors are overlapped. This is shown in a state where both ground layers 1A and 1B are seen through. ing.

In the second embodiment shown in FIGS. 7 and 8, particularly in the ground layer 1B of the flexible part B, the width dimension of the conductive part is formed to a certain extent in relation to the formation of the ground layer by a printing technique. The example which can be suitably employ | adopted when the restrictions which cannot be shown is shown.
In the case of this example, the size of the mesh-shaped hole 1b is increased corresponding to the increase in the width of the conductive portion of the ground layer 1B, and the substantial remaining rate of the ground layer 1B excluding the mesh opening portion. Is formed so as to be substantially equal to the remaining rate of the ground layer 1A of the rigid portion A.

  According to the configuration described above, although the pitch of the second conductors 1d formed in the stripe shape in the ground layer 1B is larger than the pitch of the first conductors 1c formed in the stripe shape in the ground layer 1A. When these are overlapped, as shown in FIG. 8, the remaining ratio of the ground layer in the overlapped portion is substantially equal to that of the ground layer 1A and the ground layer 1B.

  In addition, even if there is a deviation in the overlay of the ground layers 1A and 1B, although the irregularities in the shape of the mesh-shaped punch holes formed at the end portions of the ground layers 1A and 1B may occur, The regularity due to the mesh-shaped holes formed in the mating portion does not change, and the remaining rate of the ground layer is equal to the remaining rate of the ground layers 1A and 1B as described above.

  Therefore, also in the second embodiment shown in FIGS. 7 and 8, the same operational effects as those of the embodiment shown in FIGS. 3 to 6 described above can be obtained.

  FIG. 9 and FIG. 10 show a third embodiment of the circuit board according to the present invention, which is similar to the example shown in FIG. 7 and FIG. The configuration example of the conductors 1c and 1d in the shape of the shape and the overlapping state of both are described.

The example shown in FIGS. 9 and 10 shows a case where the remaining ratios of the conductive portions in the ground layers 1A and 1B are inevitably different. In the example shown in the figure, the ground layer 1B shows a case where the remaining ratio of the conductive portion is larger than that of the ground layer 1A.
That is, as shown in FIG. 9, in the ground layers 1A and 1B, the first and second conductors 1c and 1d formed in stripes are formed with substantially the same pitch, but the first conductor The width of the second conductor 1d is larger than the width (thickness) of 1c.

According to the configuration described above, when the conductors 1c and 1d are overlapped, as shown in FIG. 10, the remaining ratio of the ground layer in the overlapped portion is the remaining of the ground layer 1A and the ground layer 1B. It becomes the middle value of the rate.
In addition, even if there is a deviation in the overlay of the ground layers 1A and 1B, although the irregularities in the shape of the mesh-shaped punch holes formed at the end portions of the ground layers 1A and 1B may occur, The regularity due to the mesh-shaped holes formed in the mating portions does not change, and the residual ratio is an intermediate value between the ground layers 1A and 1B as described above.

  According to the embodiment shown in FIG. 9 and FIG. 10, even when the remaining ratio of the conductive portions in the ground layers 1A and 1B is inevitably different, the remaining ratio of the conductive portions in the overlapped portion. Is an intermediate value between the ground layers 1A and 1B, so that it is possible to suppress a large change in the characteristic impedance in the signal wiring facing this, and to suppress the occurrence of signal reflection due to mismatching. Become.

In the above description, an example in which the present invention is applied to a rigid flex wiring board in which a rigid portion is formed on a part of a flexible wiring board is shown. Of course, the circuit board can be employed.
Moreover, although the embodiment described above exemplifies a circuit board adopting a microstrip structure, the present invention is also applicable to a circuit board having a strip structure in which signal wiring is sandwiched from above and below by a ground layer. Can do.

  Furthermore, the ground layer in the above-described embodiment may be configured to be applied with a circuit reference potential, or the operation power supply of each device may be superimposed. Therefore, the potential applied to the ground layer is not particularly limited.

  The circuit board according to the present invention can be used for a circuit board that functions to control the characteristic impedance of a printed wiring board, a flexible printed wiring board, a multilayer flexible printed wiring board, and the like, and particularly a circuit for mounting a device that operates in a high frequency band. It can employ | adopt suitably for a board | substrate.

It is sectional drawing which showed one preferable laminated structural example which the circuit board concerning this invention can employ | adopt. FIG. 2 is an enlarged perspective view showing a portion C in FIG. 1 seen through from a direction orthogonal to the surface of the circuit board. FIG. 3 is a perspective view according to the first embodiment, in which overlapping portions of the ground layers shown in FIG. 2 are separately shown. It is the perspective view in 1st Embodiment which showed the ideal state without a shift | offset | difference in the overlapping part of each ground layer. It is the perspective view in 1st Embodiment which showed the state which has some shift | offset | differences in the left-right direction in the overlapping part of each ground layer. It is the perspective view in 1st Embodiment which similarly showed the state which has a some shift | offset | difference to an up-down direction. It is the perspective view in 2nd Embodiment which showed separately the overlapping part of each ground layer. It is a perspective view in a 2nd embodiment which made each ground layer overlap. It is the perspective view in 3rd Embodiment which showed separately the overlapping part of each ground layer. It is a perspective view in a 3rd embodiment which made each ground layer into an overlapping state. It is the perspective view which separated and showed the overlapping part of the ground layer by the conventional structure. FIG. 12 is a perspective view showing a state where there is a slight shift in the left-right direction in the overlapping portion of the ground layer shown in FIG. 11.

Explanation of symbols

1A Ground layer (rigid board side)
1B Ground layer (flexible board side)
1a, 1b Hole 1c 1st conductor 1d 2nd conductor 2 Insulator layer (base substrate)
3 Signal wiring 4 Insulator layer (second insulator layer)
5 Front cover layer (first coating layer)
6 Back cover layer (second coating layer)
A Rigid part B Flexible part

Claims (6)

A plurality of quadrilateral holes are formed in each of the first and second ground layers, and a part of the first and second ground layers are overlapped with each other, and the first and second portions including the overlap portions are included. A circuit board in which signal wiring is disposed on the ground layer via an insulator layer,
In the first ground layer in the overlapped portion, a first conductor formed in a stripe shape is formed connected to the first ground layer,
A second conductor formed in a stripe shape in a direction crossing the first conductor is connected to the second ground layer in the second ground layer in the overlapping portion. A circuit board characterized by the above.   The intervals between the first conductors formed in the stripe shape are equal to each other, and the intervals between the second conductors formed in the stripe shape are also equal to each other. The circuit board according to claim 1.   The first conductor formed in a stripe shape connected to the first ground layer and the ground layer is formed of a copper foil, and formed in a stripe shape connected to the second ground layer and the ground layer. 3. The circuit board according to claim 1, wherein the second conductor is made of a paste material in which conductive particles are dispersed.   The circuit board according to claim 3, wherein conductive particles of silver, copper, or carbon are dispersed in the paste material.   A substrate including a first conductor formed in a stripe shape with the first ground layer constitutes a rigid substrate, and a substrate including a second conductor formed in a stripe shape with the second ground layer is provided. The circuit board according to any one of claims 1 to 4, wherein the circuit board comprises a flexible substrate.   The circuit board according to any one of claims 1 to 5, wherein the insulator layer is formed of a film-like base substrate.

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