JP4838006B2 - Flexible printed wiring board - Google Patents

Description

  The present invention relates to a printed wiring board, and more particularly to a flexible printed wiring board with controlled impedance.

  In recent years, printed wiring boards having a multilayer structure in which a signal layer, a ground layer, a power supply layer, and the like are laminated are used for high-density wiring of electronic devices. Some printed wiring boards having a multilayer structure have signal lines wired as signal layers on one side of an insulating layer and the other side as a ground plane. A ground surface of a printed wiring board using a flexible substrate may have a mesh structure in order to improve flexibility. As a mesh structure of the ground surface, there is a disclosure of a printed wiring board that performs impedance control by using a mesh structure composed of lines parallel to signal lines and perpendicular lines (see, for example, Patent Document 1).

  However, if the ground layer has a mesh structure composed of lines parallel to the signal lines and perpendicular lines, the impedance differs depending on the positional relationship between the signal lines and the mesh structure. For example, as shown in FIG. 4, the impedance is compared when the signal line 100 is positioned between the mesh structure of the ground line 200 and when the signal line 101 is positioned on the mesh structure of the ground line 200 and matches. Then, when the signal line 100 and the signal line 101 have the same width, the impedance is higher in the case of the signal line 101. Further, in order to eliminate the difference in impedance depending on the positional relationship between the mesh structure such as the signal line 100 and the signal line 101, controlling the impedance by changing the width of each signal line complicates the design work. To do.

Further, as shown in FIG. 5, even when the signal lines 102 and 103 are in a square mesh structure and the signal lines 102 and 103 have a 45 ° angle relationship with the mesh structure of the ground line 200, the impedances of the signal lines 102 and 103 are respectively They are different (details will be described later).
JP 2003-133659 A

  An object of this invention is to provide the flexible printed wiring board which has the positional relationship of the signal line | wire which controls an impedance, and the mesh structure of a ground line.

According to one embodiment of the present invention, a flexible insulating layer, one surface of the insulating layer, a ground wire provided in a square or rectangular mesh structure, and another surface of the insulating layer provided with the ground wire The gist of the invention is a flexible printed wiring board including signal lines that are extended and wired so as not to be parallel to all straight lines connecting any intersections of the ground line and the mesh structure.
According to another aspect of the present invention, a flexible insulating layer, a ground wire provided in a square or rectangular mesh structure on one surface of the insulating layer, and another surface of the insulating layer provided with the ground wire Further, the gist of the present invention is a flexible printed wiring board provided with each of a straight line intersecting only with an intersection of the ground line and the mesh structure and a signal line extended and wired at an angle of 7 °.

  ADVANTAGE OF THE INVENTION According to this invention, the flexible printed wiring board which has the positional relationship of the signal line | wire which controls an impedance, and the mesh structure of a ground line can be provided.

  Embodiments of the present invention will be described below with reference to the drawings. In the following description of the drawings, the same or similar parts are denoted by the same or similar reference numerals. However, the drawings are schematic, and the relationship between the thickness and the planar dimensions, the ratio of the thickness of each layer, and the like are different from the actual ones. Therefore, specific thicknesses and dimensions should be determined in light of the following description. Moreover, it is a matter of course that portions having different dimensional relationships and ratios are included between the drawings.

  As shown in FIGS. 1 and 2, the flexible printed wiring board according to the embodiment of the present invention is provided in a mesh structure with a flexible insulating layer 3 and a ground layer 2 on one surface of the insulating layer 3. The ground line 20 and the other surface of the insulating layer 3 on which the ground line 20 is provided are wired as the signal layer 1 so as not to be parallel to each of the ground line 20 and a straight line that intersects only the intersection of the mesh structure. The signal line 10 is provided.

  As the insulating layer 3, for example, a flexible substrate such as a polyimide substrate, a polyethylene terephthalate (PET) substrate, or a polyethylene naphthalate (PEN) substrate can be used. The thickness of the insulating layer 3 can be 25 μm, 12.5 μm, 8 μm, 6 μm, or the like.

  The ground layer 2 is provided to prevent noise or the like generated in the signal line 10 of the signal layer 1. The ground wire 20 has a mesh structure so as not to impair the flexibility of the flexible printed wiring board. The ground lines 20 form a mesh structure by intersecting vertically. The pattern width of the ground line 20 can employ 10 to 500 μm, preferably 50 to 300 μm, and more preferably 70 to 150 μm. The thickness of the ground line 20 may be 35 μm, 18 μm, 12 μm, 9 μm, or the like.

  The signal line 10 is formed by patterning the insulating layer 3 with a rolled copper foil or an electrolytic copper foil. For the signal line 10, a metal foil other than copper foil can be used as a conductor. The pattern width of the signal line 10 may be 10 to 500 μm, preferably 50 to 300 μm, and more preferably 70 to 150 μm. The signal line 10 may have a thickness of 35 μm, 18 μm, 12 μm, 9 μm, or the like.

  In FIG. 1, the signal line 10 is shown as a single line, but may be plural. When there are a plurality of signal lines 10, the pitch width of the signal lines 10 can employ 10 to 500 μm, preferably 60 to 300 μm, and more preferably 70 to 150 μm. When a plurality of signal lines 10 are wired, auxiliary conductors (not shown) may be wired between the signal lines 10. The auxiliary conducting wire is connected to the ground layer 2 on the back surface through a through hole to prevent noise between the signal lines 10.

  A coverlay or resist protective film based on an insulating polyimide film or the like having excellent flexibility even after bonding on the ground line 20 except for the connection terminal portion of the signal line 10 (see FIG. (Not shown). The exposed conductor such as the connection terminal portion of the signal line 10 that is not protected by the protective film is subjected to surface treatment by preflux treatment, hot air leveler (HAL), electrolytic solder plating, electroless solder plating, or the like.

(Example)
The comparison with the Example using the flexible printed wiring board concerning embodiment of this invention and a prior art example is shown.

  As an example, the flexible printed wiring board uses a polyimide substrate having a thickness of 25 μm for the insulating layer 3. The signal line 10 and the ground line 20 are formed of a copper foil having a thickness of 18 μm bonded to both surfaces of the insulating layer 3 with an adhesive thickness of 10 μm. As the protective film, a 12.5 μm thick polyimide film bonded with an adhesive thickness of 25 μm is used as a coverlay.

  In the embodiment of the present invention, the positional relationship of the mesh structure of the signal line 10 and the ground line 20 is a position where the signal line 10 intersects at 38 ° and 52 ° at the intersection of the mesh structure as shown in FIG. It is related.

  As shown in FIG. 5, in the conventional example 1 compared with the embodiment of the present invention, the positional relationship between the mesh structure of the signal line and the ground line is that the signal line 103 intersects the mesh structure at 45 °, The positional relationship is arranged so as to pass through the intersection. Further, as a conventional example 2, the positional relationship between the mesh structure of the signal line and the ground line is a positional relationship in which the signal line 102 intersects the mesh structure at 45 ° and does not pass through the intersection of the mesh structure.

  The relationship between the signal line width and the characteristic impedance in the example, the conventional example 1, and the conventional example 2 is shown in the graph of FIG. According to the graph of FIG. 3, the conventional example 1 and the conventional example 2 have different characteristic impedances depending on the positional relationship between the mesh structure of the signal line and the ground line. On the other hand, the embodiment of the present invention does not depend on the positional relationship between the signal line and the mesh structure of the ground line.

  Therefore, according to the flexible printed wiring board according to the embodiment of the present invention, the signal line 10 is extended and wired so as not to be parallel to the ground line 20 and the line connecting the intersections of the mesh structure formed by the ground line 20. Therefore, since the impedance does not depend on the positional relationship between the signal line 10 and the mesh structure of the ground line 20, it is not necessary to control the impedance. Further, since it is not necessary to control the impedance, it is not necessary to control the impedance by changing the width of each signal line, and the design work can be simplified.

(Other embodiments)
As described above, the present invention has been described according to the embodiment. However, it should not be understood that the description and drawings constituting a part of this disclosure limit the present invention. From this disclosure, various alternative embodiments, examples and operational techniques should be apparent to those skilled in the art.

  For example, in the embodiment, the flexible printed wiring board is shown in three layers, but it is not limited to three layers, and a plurality of multilayer printed wiring boards may be used.

  Thus, it should be understood that the present invention includes various embodiments and the like not described herein. Therefore, the present invention is limited only by the invention specifying matters in the scope of claims reasonable from this disclosure.

It is a top view which shows the positional relationship of the signal structure of the flexible printed wiring board which concerns on embodiment of this invention, and the mesh structure of a ground line. It is a typical sectional view of a flexible printed wiring board concerning an embodiment of the invention. It is a graph which shows the result of having compared the flexible printed wiring board which concerns on embodiment of this invention, and a prior art example. It is a top view (the 1) which shows the positional relationship of the conventional signal wire | line and the mesh structure of a ground line. It is a top view (the 2) which shows the positional relationship of the conventional signal wire | line and the mesh structure of a ground wire.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Signal layer 2 ... Ground layer 3 ... Insulating layer 10, 100, 101, 102, 103 ... Signal line 20,200 ... Ground line

Claims (2)

An insulating layer having flexibility;
On one surface of the insulating layer, a ground line provided in a square or rectangular mesh structure;
A signal line extended and wired on the other surface of the insulating layer provided with the ground line so as not to be parallel to all the straight lines connecting the ground line and an arbitrary intersection of the mesh structure. A flexible printed wiring board. An insulating layer having flexibility;
On one surface of the insulating layer, a ground line provided in a square or rectangular mesh structure;
The other surface of the insulating layer provided with the ground line is provided with a signal line that extends and forms an angle of 7 ° with each of the straight lines that intersect only the intersection of the ground line and the mesh structure. A flexible printed wiring board characterized by

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