JP2002124741A - Flexible printed board - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a flexible printed board of a structure that the generation of a disconnection of a metal foil and a deviation of the mounting position of a mounting component due to a mounting of the mounting component on the bended part of the board is prevented and a freedom can be given to the structural design of the board. SOLUTION: In a flexible printed board 1 of a structure that a metal foil 4 consisting of copper and the like is formed on the surface of a filmy substrate base 3 and a coverlay 5 is covered on the foil 4 in such a way as to cover the foil 4, when a land region 2 to connect a mounting component terminal 7 on the end part of the board 1 with the coverlay 5 is provided, one part of the coverlay 5 is widely removed in the longitudinal direction of the board 1 to form the prescribed shape of a coverlay notch part 9 and the width of the coverlay 5 is made roughly equal with the width of the mounting component terminal 7, whereby a positioning of the terminal 7 to the coverlay 5 is facilitated and the bending angle of the board 1 is turned into a smooth curve in the notch part 9 to prevent stresses from being concentrated on the board 1 and a disconnection of the foil 4 is prevented from being generated.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a flexible printed circuit board (FRP) used for connecting electronic equipment and the like, and more particularly, to a shape of a land area formed at an end of the flexible printed circuit board.

[0002]

2. Description of the Related Art Conventionally, flexible printed circuit boards have been widely used in electronic equipment such as computer equipment. FIG. 5 shows the structure of this type of flexible printed circuit board.
This will be described with reference to FIG. 5A and 5B are diagrams schematically showing the structure of a component mounting area at the end of a conventional flexible printed board. FIG. 5A is a plan view of the flexible printed board.
(B) is a cross-sectional view taken along line BB 'after mounting components.
(C) is a sectional view showing a state where the flexible printed board is bent.

[0005] As shown in FIG. 5, a conventional flexible printed board 1 is made of a flexible printed board base material 3.
A metal foil 4 on which a circuit pattern is formed is adhered on both sides of the substrate with an adhesive or the like, and a coverlay 5 is adhered thereon with an adhesive or the like. Further, the coverlay 5 of the land area 2 on which the electronic components and the like are mounted at the end of the flexible printed circuit board 1 is removed, and the mounted component terminals 7 are fixed to the land area 2 by the solder layer 6.

[0004] Such a flexible printed circuit board 1 is usually used by being bent to connect the vicinity of the mounting component terminals 7 to another flexible printed circuit board.
In particular, with the recent miniaturization of electronic devices, the bending angle has become steep.

[0005]

However, the above-mentioned conventional flexible printed circuit board 1 has the following problems.

The land area 2 of the flexible printed circuit board 1 has a cover lay 5 that is linearly arranged in the width direction of the flexible printed circuit board 1 in accordance with the shape of the mounted component terminals 7 in order to prevent the displacement of the mounted component terminals 7. The mounting component terminals 7 are aligned at the end face of the cover lay 5 and connected by the solder layer 6. Since the flexibility between the coverlay 5 and the solder layer 6 is extremely different, when the flexible printed circuit board 1 is bent, as shown in FIG.
Stress concentrates on the boundary region between the metal foil 4 and the metal foil 4 in that region, and the disconnection 8 occurs.

Further, in order to prevent the disconnection 8 of the metal foil 4, the land area 2 is formed to be larger than the shape of the mounting component terminal 7, and the concentrated stress at the time of bending is dispersed to disconnect the metal foil 4. Although there is a method of preventing such a problem, in the case of such a structure, particularly when a flat component is mounted, since the land area 2 is larger than the mounted component terminal 7, the position of the mounted component terminal 7 can be accurately determined. It is difficult to perform soldering by controlling the position, and a positional shift occurs.

Further, in order to prevent the metal foil 4 from being broken, it is necessary to consider the structure and layout so that no component mounting position is provided at the bent portion of the flexible printed circuit board 1. In the design of No. 1, there is a restriction.

SUMMARY OF THE INVENTION The present invention has been made in view of the above problems, and its main objects are to break a metal foil by mounting a mounting component on a bent portion of a flexible printed circuit board, and to displace a mounting position of the mounting component. To prevent the occurrence of
It is an object of the present invention to provide a flexible printed circuit board having a degree of freedom in structural design.

[0010]

According to the present invention, a metal foil and a coverlay for covering the metal foil are formed on the surface of a strip-shaped base film, and the coverlay is formed at an end thereof. In the flexible printed circuit board in which the component terminal connection area from which is removed is provided, and the component terminal is positioned with reference to at least a part of the removal boundary surface of the cover lay, the cover lay has a width of the flexible printed board. In the direction, the cover lay is formed with substantially the same width as the component terminal to be mounted, and in the longitudinal direction of the flexible printed circuit board, the cover lay is widely removed in a part of the width direction of the component terminal, and has a predetermined shape. A notch is formed.

In the present invention, the width and depth of the notch are such that, when the flexible printed circuit board is bent, bending stress is dispersed in the notch, and the metal foil has a gentle curve without disconnection. Preferably, it is set to a predetermined value for bending.

Further, in the present invention, the notch portion may be formed in a rectangular shape, and may be disposed substantially at the center of the flexible printed circuit board in the width direction.

Further, in the present invention, the notch may be formed in a rectangular shape, and may be provided at both ends in the width direction of the flexible printed circuit board.

As described above, according to the structure of the present invention, the notch is provided at the boundary of the cover lay forming the component terminal connection area at the end of the flexible printed circuit board.
Eliminating the sudden difference in hardness between the component terminal area and the coverlay, the stress generated when bending the flexible printed circuit board can be distributed to the cutouts of the coverlay,
Thereby, disconnection of the metal foil at the bent portion can be prevented.

[0015]

BEST MODE FOR CARRYING OUT THE INVENTION In a preferred embodiment of a flexible printed board according to the present invention, a metal foil 4 made of copper or the like is formed on the surface of a film-shaped substrate base 3 so as to cover the metal foil 4. When the land area 2 for connecting the component terminals at the end of the flexible printed circuit board 1 is provided on the flexible printed circuit board covered with the cover lay 5, a part of the cover lay 5 is removed widely in the longitudinal direction of the flexible printed circuit board 1. Is formed, and the width of the cover lay 5 is made substantially equal to the width of the mounted component terminal 7, so that the positioning of the mounted component terminal 7 is facilitated. Prevent the concentration of stress by making the bending angle of the printed circuit board 1 a smooth curve and prevent the metal foil 4 from breaking. It can be.

[0016]

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a block diagram showing an embodiment of the present invention;

Embodiment 1 First, a flexible printed circuit board according to a first embodiment of the present invention will be described with reference to FIGS. FIG. 1 is a diagram showing a shape of a land area at an end of a flexible printed circuit board according to a first embodiment of the present invention. FIGS. 2A and 2B are diagrams showing the relationship between the land area of the flexible printed circuit board and the shapes of the mounted component terminals, wherein FIG. 2A is a top view and FIG. 2B is a perspective view thereof. FIGS. 3A and 3B are diagrams showing a state in which the flexible printed circuit board is bent, wherein FIG. 3A is a sectional view and FIG. 3B is a perspective view thereof.

As shown in FIG. 3A, in the flexible printed circuit board of this embodiment, a metal foil 4 made of a metal such as copper or aluminum is bonded to both sides of a flexible board base material 3 made of polyester, polyimide or the like. The metal foil 4 is etched to form a circuit pattern. A coverlay 5 made of a polymer film or the like is attached to one surface of the flexible substrate base material 3 with an adhesive or the like.

The cover lay 5 at the end of the flexible printed circuit board 1 is removed to form a land area 2 on which electronic components and the like are mounted. In this embodiment, as shown in FIG. The flexible printed circuit board 1 is not removed linearly in the width direction of the flexible printed circuit board 1,
The present invention is characterized in that the cover lay 5 is removed so that a cutout 9 in which the metal foil 4 is exposed is formed at the center. Then, as shown in FIG. 2A, a mounting component terminal 7 such as an electronic component is connected to the land region 2 via a solder layer 6.

The relationship between the notch 9 provided in the land area 2 of the flexible printed board 1 and the effect of preventing disconnection will be described with reference to FIGS. As shown in FIG. 2, the width of the cover lay 5 is substantially the same as the width of the mounted component terminal 7, and the mounted component terminal 7 is positioned at the end of the cover lay 5 and soldered.

As shown in FIG. 3, when the flexible printed circuit board 1 is bent in the vicinity of the mounting component terminals 7, a cutout 9 from which the coverlay 5 is removed is provided. The distance between the mounting component terminal 7 and the coverlay 5 is increased, and a sharp difference in hardness is eliminated. Therefore, the bending angle with respect to the bending direction can be made gentle, and the problem that the metal foil 4 is broken at the bent portion as in the conventional example can be avoided.

As described above, according to the structure of the flexible printed circuit board 1 of this embodiment, the coverlay 5 is formed with the same dimensions as the terminals 7 of the electronic components to be soldered, so that the components are not soldered. The displacement of the mounting position can be prevented. Further, by providing the cutouts 9 in the coverlay 5, the stress generated when the flexible printed circuit board 1 is bent can be dispersed in the cutouts 9 to prevent concentration of the stress, whereby the bending angle becomes gentle. Thus, disconnection of the metal foil 4 at the bent portion can be prevented.

In this embodiment, the size of the cutout 9 of the coverlay 5 is not specified, but the position, width and depth of the cutout 9 are determined by the size of the electronic component to be mounted and the cover. The optimum position and value can be set according to the hardness of the lay 5 and the bending angle. For example, as the width and depth of the notch 9 are larger, the bending angle of the bent portion can be reduced, but the width of the notch 9 is about 1/2 to 1/3 of the width of the flexible printed circuit board. Is set, the concentration of stress can be efficiently reduced.

Embodiment 2 Next, a flexible printed circuit board according to a second embodiment of the present invention will be described with reference to FIG. FIG. 4 is a top view showing the shape of the land area of the flexible printed circuit board according to the second embodiment of the present invention. In the present embodiment, the shape of the notch provided in the land area is changed, and the configuration of the other portions is the same as that of the first embodiment.

The flexible printed circuit board of this embodiment is
A metal foil 4 on which a circuit pattern is formed is attached to a flexible printed board base member 3 with an adhesive or the like, and a coverlay 5 is attached thereon with an adhesive or the like. Then, the land area 2 is formed by removing the cover lay 5 of the flexible printed circuit board. In this embodiment, the cover lay 5 remains in the central portion of the flexible printed circuit board 1 and the cutout portions 9 are formed on both sides. The coverlay 5 is removed as described above. Then, the mounted component terminal 7 is connected to the land area 2. In this embodiment, the center of the mounted component terminal 7 is positioned at the end of the cover lay 5,
Soldered.

With the flexible printed circuit board having such a structure, the notch formed in the coverlay 5 when the flexible printed circuit board 1 is bent in the vicinity of the mounting component terminals 7 as in the first embodiment. By 9
A sharp difference in hardness between the solder layer 6 for fixing the mounted component terminals 7 and the coverlay 5 is eliminated, and the bending angle with respect to the bending direction can be made gentle. Then, the stress generated at the time of bending the flexible printed board 1 is dispersed in the cutout portions 9 to prevent the concentration of the stress and to prevent the metal foil 4 from breaking.

In the above-described first and second embodiments, an example has been described in which the cutout 9 of the coverlay 5 is provided at the center or both sides of the flexible printed circuit board 1. However, the present invention is limited to the above-described embodiment. However, it is sufficient that the cutout 9 from which the coverlay 5 is removed is formed at the end of the component mounting area. For example, a number of cutouts 9 are provided in the width direction of the flexible printed circuit board 1. Alternatively, notches 9 having different shapes may be provided side by side, or the shapes of the notches 9 may be arcs.

[0028]

As described above, according to the flexible printed board of the present invention, the following effects can be obtained.

A first effect of the present invention is that disconnection of a metal foil when a flexible printed board is bent can be prevented. The reason is that the stress at the time of bending can be dispersed by the cutout portion provided in the coverlay.

A second effect of the present invention is that the degree of freedom in designing a flexible printed circuit board shape can be improved. The reason is that due to the disconnection prevention effect,
This is because a land region can be freely provided in a bent portion of the flexible substrate.

[Brief description of the drawings]

FIG. 1 is a top view showing a land area of a flexible printed circuit board according to a first embodiment of the present invention.

FIG. 2 is a diagram showing a structure near a land area of the flexible printed circuit board according to the first embodiment of the present invention;
(A) is a top view and (b) is a perspective view thereof.

FIGS. 3A and 3B are diagrams showing a structure near a land area in a state where the flexible printed board according to the first embodiment of the present invention is bent, wherein FIG. 3A is a sectional view and FIG.

FIG. 4 is a top view showing a land area of a flexible printed circuit board according to a second embodiment of the present invention.

5A and 5B are diagrams showing a structure of a conventional flexible printed circuit board, wherein FIG. 5A is a top view, FIG. 5B is a sectional view taken along line BB ′, and FIG. 5C is a sectional view in a state where the board is bent. is there.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Flexible printed circuit board 2 Land area 3 Flexible printed circuit board base 4 Metal foil 5 Coverlay 6 Mounting component terminal 7 Solder layer 8 Disconnection part 9 Notch part

Claims (4)

[Claims] A metal foil and a coverlay for covering the metal foil are formed on the surface of the base film, and a component terminal connection area from which the coverlay is removed is disposed at an end thereof; In a flexible printed circuit board in which the component terminals are positioned on the basis of at least a part of a removal boundary surface of a ray, the cover lay has a width substantially the same as the component terminals to be mounted in a width direction of the flexible printed circuit board. In the longitudinal direction of the flexible printed board, the coverlay is widely removed in a part of the width direction of the component terminal, and a cutout having a predetermined shape is formed. substrate. 2. The predetermined width and width of the notch portion, when bending the flexible printed circuit board, bending stress is dispersed in the notch portion, and the metal foil is bent into a gentle curved shape without disconnection. 2. The flexible printed circuit board according to claim 1, wherein the value is set to: 3. The flexible printed circuit board according to claim 1, wherein the cutout portion is formed in a rectangular shape, and is disposed at a substantially central portion in a width direction of the flexible printed circuit board. . 4. The flexible printed circuit board according to claim 1, wherein the cutout portion is formed in a rectangular shape, and is disposed at both ends in the width direction of the flexible printed circuit board.