JP2006173310A - Circuit board - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a circuit board allowing the characteristic impedance to be controlled at a high accuracy. <P>SOLUTION: The circuit board has a signal wiring having a first and second signal wiring parts on one surface of a base, and a ground layer having a first and second mesh wiring parts forming parallelepiped openings with intersections of lines in two directions. The first and second signal wiring parts bend at specified angles, and is disposed so that the longer diagonal lines of the opening parallelepiped figures approximately align with the wiring directions of the first and second signal wiring parts, respectively. <P>COPYRIGHT: (C)2006,JPO&amp;NCIPI

Description

  The present invention relates to a circuit board.

  Conventionally, a circuit board for controlling the characteristic impedance of a signal wiring portion is provided with a signal wiring layer, an insulating layer, and a ground layer. Here, the ground layer serves as an electrical reference plane that defines the characteristic impedance of the signal wiring layer. Generally, the characteristic impedance is often selected to be around 50Ω for single end and around 100Ω for differential. However, if this value is to be realized with a relatively thin circuit board such as a flexible circuit board, the line width of the signal wiring portion often has to be a thin line of about 50 μm or less. If the line width of the signal wiring section is too thin, the accuracy of characteristic impedance and transmission characteristics will deteriorate. Therefore, in order to keep the characteristic impedance to a desired value on the flexible circuit board, the ground layer should be meshed. Often has a pattern shape.

  Such a mesh pattern of the ground layer conventionally has a square opening. However, when a ground layer having a square opening is used, there is a large difference in the overlap area between the mesh and the signal wiring portion depending on whether the signal wiring portion is located at the mesh opening or at the mesh intersection. Has occurred. Due to this difference, there has been a problem that fluctuations in characteristic impedance become large.

  In order to solve such a problem, a thin film multilayer wiring board is disclosed in which the angle of the mesh opening with respect to the signal wiring portion is regulated and the signal wiring portion does not overlap the intersection of the mesh (for example, Patent Document 1).

However, even in the thin film multilayer wiring board as described above, it is difficult to control the characteristic impedance with high accuracy for a circuit board in which the signal wiring portion is bent and wired.

JP 7-32463 A

  An object of the present invention is to provide a circuit board capable of controlling characteristic impedance with high accuracy.

Such an object is achieved by the present invention described in the following (1) to (8).
(1) A signal wiring portion having a first signal wiring portion and a second signal wiring portion provided on one surface side of the base substrate, and a parallelogram opening with two lines intersecting each other. A circuit board having a ground layer having a first mesh wiring portion and a second mesh wiring portion to be formed, wherein the first signal wiring portion and the second signal wiring portion are at a predetermined angle. And the first mesh wiring portion is arranged so that the longer diagonal of the parallelogram of the opening substantially coincides with the wiring direction of the first signal wiring portion, and The circuit board, wherein the second mesh wiring portion is arranged so that the longer diagonal of the parallelogram of the opening substantially coincides with the wiring direction of the second signal wiring portion.
(2) a third signal wiring portion having a curved portion between the first signal wiring portion and the signal wiring portion having the second signal wiring portion provided on one surface side of the base substrate; A circuit board having a ground layer having a first mesh wiring portion, a second mesh wiring portion, and a third mesh wiring portion in which lines in two directions intersect to form a parallelogram opening. And
The first mesh wiring portion is arranged such that the longer diagonal of the parallelogram of the opening substantially coincides with the wiring direction of the first signal wiring portion, and the second mesh wiring portion Is arranged such that the longer diagonal of the parallelogram of the opening substantially coincides with the wiring direction of the second signal wiring portion, and the third mesh-like wiring portion has the longer side of the parallelogram. A circuit board, wherein a diagonal line is arranged so as to substantially coincide with a tangential direction formed in the vicinity of the middle of the third signal wiring portion.
(3) The circuit board according to (1) or (2), wherein the ground layer is stacked with an insulating layer between the signal wiring portion.
(4) The circuit board according to any one of (1) to (3), wherein the ground layer is provided on the other surface side of the base substrate.
(5) The circuit board according to any one of (1) to (4), wherein the first mesh-shaped wiring portion is opened in a diamond shape.
(6) The circuit board according to any one of (1) to (5), wherein the second mesh-shaped wiring portion is open in a diamond shape.
(7) The opening of the first mesh wiring portion is inclined at 5 to 40 degrees with respect to the first signal wiring portion, according to any one of (1) to (6) above. Circuit board.
(8) The opening of the second mesh wiring portion is inclined at 5 to 40 degrees with respect to the second signal wiring portion, according to any one of (1) to (7) above. Circuit board.

According to the present invention, a circuit board capable of controlling characteristic impedance with high accuracy can be obtained.
Moreover, when a resin film is used as the base substrate 2, a flexible circuit board excellent in flexibility can be obtained.
In addition, when polyimide is used as the resin constituting the resin film, it is excellent in heat resistance and mechanical properties.

Hereinafter, the circuit board of the present invention will be described in detail based on preferred embodiments shown in the accompanying drawings.
FIG. 1 is a sectional side view showing an example of a circuit board of the present invention. FIG. 2 is a plan view showing a perspective view of a signal wiring portion and a mesh wiring portion of a part of the circuit board of the present invention. FIG. 3 is a plan view transparently showing a signal wiring portion and a mesh wiring portion of a part of another circuit board. FIG. 4 is a cross-sectional side view showing an example of another circuit board. FIG. 5 is a cross-sectional side view showing an example of another circuit board.
As shown in FIG. 1, the circuit board 1 is provided on the upper side (upper side in FIG. 1) of the base substrate 2 and on the upper side of the signal wiring part 3 (upper side in FIG. 1). The first insulating layer 4a and the first covering layer 5a provided on the upper side (the upper side in FIG. 1) of the first insulating layer 4a are provided, while the lower side of the base substrate 2 is provided. The ground layer 6 is disposed on the lower side (lower side in FIG. 1), the second insulating layer 4b is disposed on the lower side (lower side in FIG. 1), and the second covering layer 5b is disposed on the lower side. Is provided.

  Hereinafter, each component will be described.

The base substrate 2 is in the form of a film and has a function to be a core of the circuit board 1.
Examples of the base substrate 2 include a resin film and a ceramic wiring board. Among these, a resin film is preferable. Thereby, the flexibility of the circuit board 1 can be improved.
Examples of the resin 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.

  The thickness of the base substrate 2 is not particularly limited, but is preferably 25 μm or more, and particularly preferably 28 to 50 μm. If the thickness is less than the lower limit value, it may be necessary to make the signal line width so thin that it becomes difficult to process. In this case, the desired characteristic impedance value must be obtained unless the mesh opening of the ground layer is made very large. May not be obtained. On the other hand, if the thickness exceeds the upper limit, the rigidity becomes high, and it may be difficult to use the flexible printed circuit board (FPC) characterized by flexibility.

The signal wiring unit 3 has a function of transmitting a high-speed and stable electric signal.
As shown in FIG. 1, the signal wiring portion 3 is provided on one surface side (upper side in FIG. 1) of the base substrate 2. The signal wiring part 3 may be provided directly on the base substrate 2 or may be provided via an adhesive.
The signal wiring unit 3 includes a first signal wiring unit 31 and a second signal wiring unit 32. The first signal wiring portion 31 and the second signal wiring portion 32 are bent at a predetermined angle at the bent boundary line 7.
The reason why the signal wiring portion 3 is bent at a predetermined angle is not particularly limited, but examples thereof include an improvement in wiring density. Furthermore, the wiring density has been improved in recent years, and it is often difficult to draw the shortest distance with a straight line even for high-speed transmission signals.

Specifically, as shown in FIG. 2, a plurality of signal wiring sections 3 are formed with a plurality of second signal wiring sections 32 that are bent from the linear first signal wiring section 31 with an angle of approximately 45 degrees. Has been.
In FIG. 2, the signal wiring portion 3 is formed with a plurality of second signal wiring portions 32 that are bent from the linear first signal wiring portion 31 with an angle of approximately 45 degrees. However, the angle is not limited to this, and may be an angle of approximately 10 to 40 degrees.
The first signal wiring unit 31 and the second signal wiring unit 32 are arranged in parallel with a predetermined interval.

  The distance between the signal wiring parts 3 is not particularly limited, but is preferably 2 to 6 times the width of the signal wiring parts 3, particularly preferably 3 to 5 times. Within this range, the electrical influence between the signal lines is almost negligible, and high-density circuit design is often possible.

  The distal end portion and the proximal end portion of the signal wiring portion 3 are joined to a mounting pad of a component (not shown) to transmit an electrical signal and function as the circuit board 1.

  As shown in FIG. 1, a first insulating layer 4 a is provided so as to cover the signal wiring portion 3. Examples of the material constituting the first insulating layer 4a include acrylic resins, epoxy resins, polyimide resins, and liquid crystal polymers. Among these, an epoxy resin is preferable. Thereby, heat resistance and flexibility can be improved. In the case of the liquid crystal polymer, the electrical characteristics can be further improved. This is because the liquid crystal polymer has a low relative dielectric constant and is excellent in high-speed signal transmission.

  Although the thickness of the 1st insulating layer 4a is not specifically limited, It is preferable that it is 5-40 micrometers, and 10-30 micrometers is especially preferable. If the thickness is less than the lower limit value, circuit embedding may be insufficient. If the thickness exceeds the upper limit value, the amount of smearing of the insulating layer 4 may increase, or the multilayer printed wiring board may have interlayer connection reliability. It may decrease.

As shown in FIG. 1, a first covering layer 5a is provided adjacent to the first insulating layer 4a. The first coating layer 5a is preferably made of a resin material.
Examples of the resin constituting the resin material include polyester resins, polyimides, and liquid crystal polymers. Among these, polyimide is preferable. Thereby, heat resistance and flexibility can be improved.

  Although the thickness of the 1st coating layer 5a is not specifically limited, It is preferable that it is 5-50 micrometers, and 10-30 micrometers is especially preferable. If the thickness is less than the lower limit value, the strength of the resin layer may be reduced, and if the thickness exceeds the upper limit value, slidability and flexibility may be reduced.

In addition, the 1st insulating layer 4a may be integrally formed in the 1st coating layer 5a as an adhesive bond layer of the 1st coating layer 5a.
In this case, the first coating layer 5a is composed of a resin layer and an adhesive layer. In this case, the resin material constituting the resin layer includes, for example, a polyester resin, a polyimide, a liquid crystal polymer, and the like, similarly to the resin material constituting the first covering layer 5a. Among these, polyimide is preferable. Thereby, heat resistance and flexibility can be improved.
In this case, the material constituting the adhesive layer may be, for example, an acrylic resin, an epoxy resin, a polyimide resin, or the like, similar to the material constituting the first insulating layer 4a. Among these, an epoxy resin is preferable. Thereby, heat resistance and flexibility can be improved.

The ground layer 6 includes a first mesh wiring portion 61 and a second mesh wiring portion 62 that form parallelogram openings by intersecting lines in two directions.
The circuit board 1 according to the present invention includes a signal wiring portion 3 and a ground layer 6 via a base substrate 2, and the ground layer 6 includes a first mesh wiring portion 61 and a second mesh wiring portion 62. And a plurality of mesh-like wiring sections.
In the conventional ground layer, the ground layer is formed by one mesh-like wiring portion having a square opening. For this reason, when the signal wiring portion is bent, a large difference occurs in the facing area between the mesh-like wiring portion and the signal wiring portion, thereby causing a large change in characteristic impedance.
On the other hand, in the present invention, since the installation angle of each mesh-like wiring part constituting the ground layer 6 is changed corresponding to the bending of the signal wiring part 3, even if the signal wiring part 3 is bent, high accuracy is achieved. In addition, the characteristic impedance can be controlled.

  As shown in FIG. 2, the first mesh wiring portion 61 is opened in a diamond shape, and the longer diagonal line substantially coincides with the wiring direction of the first signal wiring portion 31. Thereby, the stability of characteristic impedance can be improved. The opening of the first mesh wiring portion 61 is not particularly limited as long as it is a parallelogram, but is preferably a rhombus. In this case, it is possible to minimize the fluctuation of the characteristic impedance when the diagonal lines of the signal wiring and the mesh pattern do not completely match.

  Each opening of the first mesh wiring portion 61 may have different sizes, but it is preferable that all the sizes are the same. Thereby, in particular, the impedance can be controlled with high accuracy.

Similarly to the first mesh-like wiring part 61, the second mesh-like wiring part 62 forms a parallelogram opening by intersecting lines in two directions.
As shown in FIG. 2, the second mesh wiring portion 62 is joined to the first mesh wiring portion 61 in the vicinity of the bent boundary line 7. In the vicinity of the bent boundary line 7, the second mesh wiring portion 62 and the first mesh wiring portion 61 may or may not be connected.

  As shown in FIG. 2, the second mesh wiring portion 62 is opened in a rhombus shape, and the longer diagonal line substantially coincides with the wiring direction of the second signal wiring portion 32. The opening of the second mesh wiring part 62 is not particularly limited as long as it is a parallelogram, but is preferably a rhombus.

  The ratio of the longer diagonal line to the shorter diagonal line (longer diagonal line / shorter diagonal line) of the opening of the first mesh-like wiring portion 61 opening in the rhombus and the first opening in the rhombus The ratio of the longer diagonal line to the shorter diagonal line (longer diagonal line / shorter diagonal line) of the opening of the mesh-shaped wiring portion 62 of 2 may be the same or different, but the same It is preferable that

  The aperture ratio of the first mesh wiring portion 61 and the aperture ratio of the second mesh wiring portion 62 may be the same or different, but are preferably the same.

  Each opening of the second mesh wiring portion 62 may have a different size, but it is preferable that all the sizes are the same. Thereby, in particular, the impedance can be controlled with high accuracy.

  The thickness of the first mesh wiring portion 61 and the thickness of the second mesh wiring portion 62 may be the same or different, but are preferably the same.

  The material constituting the first mesh wiring portion 61 and the material constituting the second mesh wiring portion 62 may be the same or different, but are preferably the same.

As shown in FIG. 1, a second insulating layer 4b is provided below the ground layer 6 (the lower side in FIG. 1).
Examples of the material constituting the second insulating layer 4b include acrylic resins, epoxy resins, polyimide resins, and the like. Among these, an epoxy resin is preferable. Thereby, heat resistance and flexibility can be improved.

  The materials constituting the first insulating layer 4a and the second insulating layer 4b may be the same or different.

  Although the thickness of the 2nd insulating layer 4b is not specifically limited, It is preferable that it is 5-40 micrometers, and 10-30 micrometers is especially preferable. If the thickness is less than the lower limit value, circuit embedding may be insufficient. If the thickness exceeds the upper limit value, the amount of smearing of the insulating layer 4 may increase, or the multilayer printed wiring board may have interlayer connection reliability. It may decrease.

  The thickness of the first insulating layer 4a and the thickness of the second insulating layer 4b may be the same or different.

As shown in FIG. 1, a second covering layer 5b is provided adjacent to the second insulating layer 4b. The second coating layer 5b is preferably made of a resin material.
Examples of the resin constituting the resin material include polyester resins, polyimides, and liquid crystal polymers. Among these, polyimide is preferable. Thereby, heat resistance and flexibility can be improved.

  The resin material constituting the first coating layer 5a and the resin material constituting the second coating layer 5b may be the same or different.

  Although the thickness of the 2nd coating layer 5b is not specifically limited, It is preferable that it is 5-50 micrometers, and 10-30 micrometers is especially preferable. If the thickness is less than the lower limit value, the strength of the resin layer may be reduced, and if the thickness exceeds the upper limit value, slidability and flexibility may be reduced.

  The thickness of the first coating layer 5a and the thickness of the second coating layer 5b may be the same or different.

The second insulating layer 4b may be integrally formed with the second coating layer 5b as an adhesive layer of the second coating layer 5b.
In this case, the second coating layer 5b is composed of a resin layer and an adhesive layer. In this case, the resin material constituting the resin layer includes, for example, a polyester resin, polyimide, liquid crystal polymer, and the like, similarly to the resin material constituting the second coating layer 5b described above. Among these, polyimide is preferable. Thereby, heat resistance and flexibility can be improved.
In this case, the material constituting the adhesive layer may be, for example, an acrylic resin, an epoxy resin, a polyimide resin, or the like, similar to the material constituting the second insulating layer 4b described above. Among these, an epoxy resin is preferable. Thereby, heat resistance and flexibility can be improved.

As described above, the circuit board 1 of the present invention has been described based on a preferred embodiment. However, the present invention is not limited to this. For example, the position and number of the signal wiring portions 3, the position and number of the ground layer 6, and the like. It may be different from the embodiment described above.
Hereinafter, a specific example will be described regarding differences from the above-described embodiment.
As shown in FIG. 3, the first mesh wiring portion 61 is arranged such that the longer diagonal of the parallelogram of the opening substantially coincides with the wiring direction of the first signal wiring portion 31, and The second mesh-like wiring part 62 is arranged so that the longer diagonal of the parallelogram of the opening substantially coincides with the wiring direction of the second signal wiring part 32, and the third mesh-like wiring part 63 is The longer diagonal of the parallelogram may be arranged so as to substantially coincide with the tangential direction formed near the middle of the third signal wiring portion 33.

  As shown in FIG. 4, on the circuit board 1, the ground layer 6 is provided only between the signal wiring portion 3 and the first covering layer 5a via the first insulating layer 4a.

  Further, as shown in FIG. 5, the circuit board 1 includes a ground layer 6a provided on the lower side of the base substrate 2 (lower side in FIG. 4) and a signal wiring portion via the first insulating layer 4a. 3 and a ground layer 6b provided between the first covering layer 5a.

  Although the circuit board 1 of the present invention has been described above, the circuit board 1 of the present invention can be used as a part or the whole of a flexible circuit board or a rigid circuit board.

EXAMPLES Hereinafter, although this invention is demonstrated based on an Example and a comparative example, this invention is not limited to this.
Example 1
A polyimide film was used as a base substrate, and a first signal wiring portion and a second signal wiring portion were formed on one side of the base substrate. Further, the first signal wiring portion and the second signal wiring portion are bent with an angle of approximately 45 degrees.
A cover film having an adhesive layer (insulating layer 4) was disposed so as to cover the signal wiring.

Next, the ground layer shown below was formed on the surface of the base substrate opposite to the surface on which the signal wiring was formed.
The ground layer includes a first mesh wiring portion in which lines in two directions intersect to form a rhombus opening, and a second mesh in which lines in two directions intersect to form a rhombus opening, respectively. And a wiring section. In the first mesh wiring portion, the longer diagonal line of the rhombus almost coincided with the wiring direction of the first signal wiring portion. In the second mesh wiring portion, the longer diagonal line of the rhombus substantially coincides with the wiring direction of the second signal wiring portion. In addition, the material which comprises the mesh part of the said 1st mesh-like wiring part and the said 2nd mesh-like wiring part was copper.
Further, a cover film having an adhesive layer (insulating layer 4) was disposed so as to cover the ground layer to obtain a circuit board as shown in FIG.

(Example 2)
Further, a circuit board as shown in FIG. 2 is formed in the same manner as in Example 1 except that the ground layer is provided between the first signal wiring portion and the second signal wiring portion and the cover film. Obtained.

(Comparative Example 1)
Example 1 except that a single mesh-like wiring part having a square opening is used instead of the ground layer composed of the first mesh-like wiring part and the second mesh-like wiring part. And so on.

The circuit board obtained in each example had an excellent impedance value, and was excellent for high-speed signal transmission.
In addition, the circuit boards obtained in each example were excellent in flexibility and connection reliability.

  The present invention can be used for a printed wiring board, a flexible printed wiring board, a multilayer flexible printed wiring board, and the like, and is particularly suitably used for a circuit board used as a component of an electronic device and a printed wiring board constituting the circuit board. .

It is a sectional side view showing an example of a circuit board of the present invention. It is a top view which shows transparently the signal wiring part and mesh-shaped wiring part of a part of circuit board of this invention. It is a top view which shows perspectively the signal wiring part and mesh-shaped wiring part of a part of other circuit board. It is a cross-sectional side view which shows an example of another circuit board. It is a cross-sectional side view which shows an example of another circuit board.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Circuit board 2 Base base material 3 Signal wiring part 31 1st signal wiring part 32 2nd signal wiring part 33 3rd signal wiring part 4 Insulating layer 4a 1st insulating layer 4b 2nd insulating layer 5a 1st Coating layer 5b second coating layer 6 ground layer 6a ground layer 6b ground layer 61 first mesh wiring portion 62 second mesh wiring portion 63 third mesh wiring portion 7 bent boundary line

Claims (8)

A signal wiring portion having a first signal wiring portion and a second signal wiring portion provided on one surface side of the base substrate;
A circuit board having a first mesh-like wiring portion and a ground layer having a second mesh-like wiring portion, in which lines in two directions intersect each other to form a parallelogram opening,
The first signal wiring portion and the second signal wiring portion are bent at a predetermined angle,
The first mesh wiring portion is arranged such that the longer diagonal of the parallelogram of the opening substantially coincides with the wiring direction of the first signal wiring portion, and the second mesh wiring portion Are arranged so that the longer diagonal line of the parallelogram of the opening substantially coincides with the wiring direction of the second signal wiring portion. A third signal wiring portion having a curved portion between the first signal wiring portion and the signal wiring portion having the second signal wiring portion provided on one surface side of the base substrate;
A circuit board having a first mesh wiring portion, a second mesh wiring portion, and a ground layer having a third mesh wiring portion, in which lines in two directions intersect to form a parallelogram opening, respectively. There,
The first mesh wiring portion is arranged such that the longer diagonal of the parallelogram of the opening substantially coincides with the wiring direction of the first signal wiring portion, and the second mesh wiring portion Is arranged such that the longer diagonal of the parallelogram of the opening substantially coincides with the wiring direction of the second signal wiring portion, and the third mesh-like wiring portion has the longer side of the parallelogram. A circuit board, wherein a diagonal line is arranged so as to substantially coincide with a tangential direction formed in the vicinity of the middle of the third signal wiring portion.   The circuit board according to claim 1, wherein the ground layer is stacked between the signal wiring portion via an insulating layer.   The circuit board according to claim 1, wherein the ground layer is provided on the other surface side of the base substrate.   5. The circuit board according to claim 1, wherein the first mesh-shaped wiring portion is open in a diamond shape. 6.   The circuit board according to any one of claims 1 to 5, wherein the second mesh-shaped wiring portion is open in a diamond shape.   The circuit board according to claim 1, wherein the opening of the first mesh wiring portion is inclined by 5 to 40 degrees with respect to the first signal wiring portion.   The circuit board according to claim 1, wherein an opening of the second mesh wiring portion is inclined by 5 to 40 degrees with respect to the second signal wiring portion.

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