JP2010212320A - Flexible printed wiring board - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To prevent the occurrence of cracks in a flexible printed wiring board with a reinforcing material. <P>SOLUTION: A flexible printed wiring board 19 has a body and a reinforcing material 16. The body includes a base film and a wiring pattern 22 formed on the surface of the base film. The base film is provided with each protrusion 80 protruding to the outside with respect to a part where each protrusion is adjacent to each other. The reinforcing material 16 is stuck to the body in a region surrounded by a boundary line 85, extending from the outer edge of each protrusion 80 and crossing the base film, and one side of the outer edge of the base film separated by the boundary line 85. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a flexible printed wiring board with a reinforcing material.

  The flexible printed wiring board is formed by forming a wiring pattern of a conductor such as copper foil on one or both sides of a base film and further covering the surface with a coverlay. There is also a multilayer flexible printed wiring board in which a plurality of wiring patterns are laminated with an insulating film interposed therebetween. Flexible printed wiring boards have flexibility and are used in liquid crystal displays, mobile phones, notebook PCs and the like.

  When components are mounted on a flexible printed wiring board or when a flexible printed board is inserted into a connector, a certain degree of thickness and hardness are required. In response to such a requirement, a reinforcing material having an appropriate thickness and hardness may be attached to the flexible printed circuit board.

  A step is formed on the boundary between the portion where the reinforcing material is present and the portion where the reinforcing material is not present in the flexible printed circuit board to which the reinforcing material is attached. For this reason, when stress is applied at the time of outer shape processing at the time of manufacturing or bending of the substrate at the time of use, cracks may occur starting from the intersection of the step and the outer edge. Thus, for example, Patent Document 1 to Patent Document 3 disclose a method of making the crack less likely to occur by changing the edge of the reinforcing material to a shape other than a straight line.

Japanese Patent Laid-Open No. 5-34127 Japanese Patent Laid-Open No. 10-135581 JP 2007-317981 A

  When the shape of the edge of the reinforcing material is changed to a shape other than a straight line as described in Patent Document 1 to Patent Document 3, the number of processing steps may be larger than that of a reinforcing material having a straight edge. is there. In addition, when the shape of the edge of the reinforcing material is a shape other than a straight line, it is necessary to increase the positioning accuracy when the reinforcing material is attached. For this reason, if the shape of the edge of a reinforcing material is made into shapes other than a straight line, the cost required for manufacture will increase.

  Then, an object of this invention is to make it difficult to produce a crack in a flexible printed wiring board with a reinforcing material, suppressing the increase in the cost required for manufacture.

  In order to solve the above-described problems, the present invention includes a main body having a flexible film and a wiring pattern formed on the surface of the film, and a reinforcing material attached to the main body. In the flexible printed wiring board, the main body portion is formed with a protruding portion that decreases in width as the boundary line of the reinforcing material is approached from the outer edge of the main body portion toward the inside of the main body portion. It is characterized by.

  Further, the present invention provides a flexible printed wiring board, a main body having a flexible film, a wiring pattern formed on the surface of the film, and a reinforcing material attached to the main body, The wiring pattern includes a terminal located at an end of the film and a pattern extending from the terminal, and the film has a pair of protruding portions protruding in a direction crossing the pattern extending from the terminal. It is formed, The boundary line of the said reinforcing material is extended between the said one pair of protrusion parts, It is characterized by the above-mentioned.

  ADVANTAGE OF THE INVENTION According to this invention, it can be made hard to produce a crack in a flexible printed wiring board with a reinforcing material, suppressing the increase in the cost required for manufacture.

It is a bottom view in one embodiment of a flexible printed wiring board concerning the present invention. It is a top view in one embodiment of a flexible printed wiring board concerning the present invention. FIG. 3 is a sectional view taken along arrows III-III in FIGS. 1 and 2. It is a flowchart of the manufacturing method in one Embodiment of the flexible printed wiring board which concerns on this invention. It is a top view of the base plate in which the copper foil pattern was formed in one Embodiment of the flexible printed wiring board which concerns on this invention. It is a bottom view of the base plate in which the copper foil pattern was formed in one Embodiment of the flexible printed wiring board which concerns on this invention. It is a top view of the base plate with which the coverlay was adhere | attached in one Embodiment of the flexible printed wiring board which concerns on this invention. It is a top view of the base plate with which the reinforcement board was adhere | attached in one Embodiment of the flexible printed wiring board which concerns on this invention.

  An embodiment of a flexible printed wiring board according to the present invention will be described with reference to the drawings. Note that this description is merely an example, and the present invention is not limited to this embodiment, and can be implemented in various forms.

  FIG. 1 is a bottom view of an embodiment of a flexible printed wiring board according to the present invention. FIG. 2 is a top view of the flexible printed wiring board in the present embodiment. 3 is a cross-sectional view taken along arrows III-III in FIGS. 1 and 2.

  The flexible printed wiring board 19 of the present embodiment has a main body portion and a reinforcing material 16. The main body includes a base film 10 and a first cover lay 11 and a second cover lay 12 that cover both surfaces of the base film. The base film 10 is a thin film serving as a base material for the wiring pattern 22 formed on the surface thereof, and is formed of a flexible insulating material. The first cover lay 11 and the second cover lay 12 are thin films that protect the wiring pattern 22 formed on the surface of the base film 10 and have functions as plating and solder masks. Similarly, it is formed of a flexible insulating material.

  The base film 10, the first cover lay 11, and the second cover lay 12 are all formed in a film shape with a thickness of about 30 μm using translucent polyimide or the like. Here, the base film 10 is a single layer, but a multi-layer base film in which one or more wiring patterns are formed may be used.

  A wiring pattern 22 is formed between the base film 10 and the second coverlay 12. A part of the wiring pattern 22 is a terminal 17 that is exposed without being covered by the second coverlay 12. The terminal 17 is obtained by forming an electroplating 25 with a conductor such as gold on the surface of a wiring pattern 22 formed with a conductor foil such as copper. That is, the signal line 35 or the ground line 36 extends from the terminal 17.

  The base film 10 is formed, for example, in a shape combining a large rectangle and a small rectangle 81 extending from one side of the rectangle. The terminal 17 is formed in the vicinity of the side facing the portion of the small rectangle 81 that contacts the large rectangle.

  Projections 80 are respectively formed on a pair of sides sandwiching a direction extending from the large rectangle of the small rectangle 81. That is, the base film 10 is formed with a pair of projecting portions 80 that project in a direction crossing the pattern of the signal line 35 or the ground wire 36 extending from the terminal 17. These protrusions 80 protrude, for example, 0.4 mm or more from the small rectangle 81 toward the outside, that is, the opposite side to the region where the base film 10 is present.

  Further, a wiring pattern 22 may be formed between the base film 10 and the first coverlay 11. The wiring pattern 22 formed between the base film 10 and the first cover lay 11 penetrates the base film 10 with the wiring pattern 22 formed between the base film 10 and the second cover lay 12. The connection via 23 is connected. The wiring patterns 22 on both surfaces of the base film 10 connected to the same connection via 23 are electrically connected by a connection conductor covering the inner surface of the connection via 23.

  The first coverlay 11 is bonded to the base film 10 and the wiring pattern 22 with an adhesive 13. The second coverlay 12 is bonded to the base film 10 and the wiring pattern 22 with an adhesive 14.

  A reinforcing material 16 is bonded to the surface of the first cover lay 11 with an adhesive 15 on the back side of a part of the terminal 17. The material of the reinforcing material 16 may be any material as long as the required thickness and hardness can be obtained, for example, polyester.

  The reinforcing material 16 is smaller than the base film 10. Further, at least a part of the reinforcing material 16 has a shape along the outer edge of the base film 10. The starting point 82 of the boundary line 85 of the reinforcing material 16 from the outer edge of the base film 10 toward the inside of the base film 10 is located at the protrusion 80. The protruding portion 80 is a portion that becomes smaller as the width of the base film 10 across the boundary line 85 approaches the starting point 82.

  The reinforcing material 16 includes a boundary line 85 that crosses the base film 10 by connecting between the outer edges of the two projecting portions 80, and a terminal 17 on the outer edge of the base film 10 that is partitioned by the boundary line 85. It is affixed to the area surrounded by That is, the boundary line 85 of the reinforcing member 16 extends between the pair of protrusions 80. The reinforcing material 16 is provided so that the boundary line 85 is a straight line.

  The outer edge of the tip of the protrusion 80 is, for example, formed in an arc shape that protrudes outward and has a polar radius of 0.2 mm or more. The starting point 82 of the boundary line 85 of the reinforcing material 16 is located in such an arc-shaped portion. The outer edge 83 of the connecting portion between the projecting portion 80 and the adjacent portion of the projecting portion 80 is, for example, inwardly, that is, in an arc shape with a curvature radius of 0.2 mm or more in a direction toward the region where the base film 10 exists. Is formed.

  FIG. 4 is a flowchart of the manufacturing method in the present embodiment. FIG. 5 is a top view of a base plate on which a copper foil pattern is formed in the present embodiment. FIG. 6 is a bottom view of the base plate on which the copper foil pattern is formed in the present embodiment. FIG. 7 is a top view of the base plate to which the coverlay is bonded in the present embodiment. FIG. 8 is a top view of the base plate to which the reinforcing plate is bonded in the present embodiment.

  In the present embodiment, first, drilling is performed on the double-sided copper-clad plate (S1). The double-sided copper-clad plate is obtained by attaching copper foil to both sides of the base film 10. The thickness of the copper foil is about 30 μm. In this double-sided copper-clad plate, connection vias 23 are formed by drilling holes at positions where the wiring patterns 22 on both sides of the base film 10 are connected and positions where the wiring patterns 22 and the power supply patterns 21 are connected.

  Next, after performing a cleaning process as necessary, electroless plating is performed to form a connection conductor on the inner surface of the connection via 23 (S2). The connection conductor may be formed by performing electroplating after electroless plating.

  Then, surface treatment is given to copper foil as needed, and a resist film is formed on the copper foil surface (S3). A pattern is baked on the resist film by applying a photomask corresponding to the wiring pattern 22 and performing exposure. Further, the pattern is developed and etched to form a predetermined copper foil pattern on the surface of the base film 10 (S4). Thereafter, the remaining resist film is peeled off (S5).

  In FIG. 5 and FIG. 6, the dotted line indicates the contour processing line 34. The outline processing line 34 is a virtual line indicating the outline of the flexible printed wiring board 19 that is finally cut out. The wiring pattern 22 and the like remaining on the final flexible printed wiring board 19 are all formed inside the outer shape processing line 34, that is, on the wiring pattern 22 side. In the present embodiment, a case where two flexible printed wiring boards 19 are manufactured from one rectangular base film 10 is shown. One flexible printed wiring board 19 may be manufactured from one base film 10, or three or more flexible printed wiring boards 19 may be manufactured.

  A wiring pattern 22 including a terminal portion 37, a signal line 35 connected to the terminal portion 37, a ground wire 36 connected to the terminal portion 37, and the like is formed inside the outer shape processing line 34 of the etched base plate 43. ing. In the middle of some of the signal lines 35, a connection via forming part 38 in which the connection via 23 is formed for connection to the signal line 35 on the back side is provided.

  The copper foil 32 is left almost entirely on the outside of the outer shape processing line 34 of the etched base plate 43, that is, on the opposite side to the wiring pattern 22. The power supply pattern 21 is connected to each of the electrically independent terminal portions 37. Each power feeding pattern 21 extends from the copper foil 32 outside the outer shape processing line 34 across the outer shape processing line 34.

  After the etching process is completed, the first cover lay 11 and the second cover lay 12 are bonded to the etched base plate 43 (S7). The coverlay to be bonded to the base plate 43 is previously punched (S6).

  In the second cover lay 12, a notch 51 for exposing the terminal portion 37 and a notch 52 for exposing the power feeding portion 53 are formed in step S6. The cutout portion 52 that exposes the power feeding portion 53 is formed at, for example, a corner portion. The notch part 51 that exposes the terminal part 37 and the notch part 52 that exposes the power feeding part 53 may be formed as one continuous region. The first cover lay 11 and the second cover lay 12 are bonded to both surfaces of the etched base plate 43 with adhesives 13 and 14 to form a base plate 44 to which the cover lay is bonded.

  Next, an electrolytic plating process is performed by supplying power to the copper foil 32 exposed in the notch 52 of the base plate 44 to which the coverlay is bonded (S8). Thereby, the electrolytic plating 25 is formed on the surface of the wiring pattern 22 of the terminal portion 37.

  Thereafter, the reinforcing material 16 is attached to a predetermined position on the back surface of the terminal portion 37 of the base film 10 (S9). The reinforcing material 16 is attached in a single band shape across the two outer shape processing lines 34 corresponding to the two flexible printed wiring boards 19.

  Next, a force is applied to the base plate 45 to which the reinforcing material 16 is bonded in a direction in which the base plate 45 is sheared in the thickness direction of the base plate 45 by pressing with a die having a shape along the outer shape processing line 34. For example, an upward force is applied to the inside of the contour processing line 34, and a downward force is applied to the outside of the contour processing line 34. Thereby, the two flexible printed wiring boards 19 are cut out from the base plate 45. In this way, the flexible printed wiring board 19 is obtained by cutting the base plate 45 to which the reinforcing material 16 is attached along the outer shape processing line 34 (S10).

  In the flexible printed wiring board 19 to which the reinforcing material 16 is affixed, a crack is likely to be generated based on the intersection of the step formed at the end of the reinforcing material 16 and the outer edge. For example, a crack may occur due to a shearing force during pressing in outline processing. Furthermore, even if the crack generated during pressing is very small, the crack may develop due to subsequent external stress. Even when the outer shape is processed with a laser or the like, even if no crack is generated during the outer shape processing, a crack may be generated due to external stress during subsequent assembly or use.

  However, in the flexible printed wiring board 19 of the present embodiment, the step generated by attaching the reinforcing member 16 is located at the boundary line 85 that extends from the outer edge of the protrusion 80 and crosses the base film 10. That is, the intersection of the step and the outer edge where cracks are likely to occur is located at the protruding portion 80. For this reason, the concentration of stress at the intersection between the step where the crack is likely to occur and the outer edge is alleviated, and the crack is less likely to occur.

  Further, even if the wiring pattern 22 is formed along the outer edge of the portion adjacent to the protruding portion 80, the necessity of forming the wiring pattern 22 up to the protruding portion 80 is small. For this reason, even if a crack occurs based on the intersection between the step and the outer edge generated at the end of the reinforcing member 16, the possibility of affecting the wiring pattern 22 is small.

  Furthermore, by making the shape of the outer edge of the tip of the protrusion 80 arc, the number of places where stress tends to concentrate on the tip of the protrusion 80 is reduced, and cracks are less likely to occur. Further, by making the shape of the outer edge of the connecting portion between the projecting portion 80 and its adjacent portion arc-shaped, the concentration of stress on that portion is reduced and cracks are less likely to occur.

  In the present embodiment, the shape of the boundary line 85 is not limited to a specific shape. Therefore, it is not necessary to process the reinforcing material 16 in a specific shape in advance before attaching the reinforcing material 16 to the base plate 44. Furthermore, it is not necessary to increase the positioning accuracy more than necessary when the reinforcing material 16 is attached. On the other hand, the protrusion 80 can be formed by changing a mold for cutting out from the base plate 45. For this reason, the cost required for manufacturing the flexible printed wiring board 19 of the present embodiment does not increase so much as compared to the conventional case.

DESCRIPTION OF SYMBOLS 10 ... Base film, 11 ... 1st coverlay, 12 ... 2nd coverlay, 13 ... Adhesive agent, 14 ... Adhesive agent, 15 ... Adhesive agent, 16 ... Reinforcement material, 17 ... Terminal, 19 ... Flexible printed wiring Plate 21, Power supply pattern 22, Wiring pattern 23, Connection via 25, Electroplating 32, Copper foil 34, Outline processed wire 35, Signal line 36, Ground wire 37, Terminal portion 38 Connection via forming part, 43 ... element plate, 44 ... element plate, 45 ... element plate, 51 ... notch part, 52 ... notch part, 53 ... feeding part, 80 ... projecting part, 82 ... starting point, 85 ... boundary line

Claims (6)

In a flexible printed wiring board having a main body having a flexible film and a wiring pattern formed on the surface of the film, and a reinforcing material attached to the main body,
The main body is formed with a protruding portion that decreases in width as it approaches the starting point of the boundary line of the reinforcing member from the outer edge of the main body toward the inside of the main body. Flexible printed wiring board.   The flexible printed wiring board according to claim 1, wherein the vicinity of the starting point of the main body is formed in an outwardly convex arc shape.   3. The flexible printed wiring board according to claim 1, wherein an outer edge of a connection portion between a portion where the protruding portion is adjacent and the protruding portion is formed in an inwardly protruding arc shape. 4.   4. The flexible printed wiring according to claim 1, wherein at least two of the protrusions are formed, and the boundary line extends between the two protrusions. 5. Board.   The flexible printed wiring board according to any one of claims 1 to 4, wherein the boundary line is a straight line. A main body having a flexible film and a wiring pattern formed on the surface of the film;
Reinforcing material affixed to the main body,
Comprising
The wiring pattern includes a terminal located at an end of the film and a pattern extending from the terminal,
The film has a pair of protrusions protruding in a direction crossing the pattern extending from the terminal,
The flexible printed wiring board, wherein a boundary line of the reinforcing material extends between the pair of protrusions.

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