JP2010161232A - Flexible printed wiring board and electronic device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a flexible printed wiring board which prevents disconnection caused by repetitious bending deformation with severer great strain even when it is used for a long period of time, and has excellent durability; and to provide an electronic device. <P>SOLUTION: The flexible printed wiring board 10 includes mounting parts 11, 12 positioned on both ends and wiring parts 3, 5 of two layers which wire between the mounting parts, and is curved in a direction intersecting with a face of the FPC (flexible printed wiring board) 10. The wiring part 5 as an outer side layer is longer, a clearance S is formed between the respective layers, and the layers are aligned at both of the ends. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a flexible printed wiring board and an electronic device, and more specifically to a flexible printed wiring board and an electronic device that are incorporated in an electronic device such as a portable terminal and undergo bending deformation.

  A multilayer flexible printed wiring board incorporated in a portable terminal and used for conductively connecting the electronic circuit of the input key side casing and the circuit of the display section side casing is constantly subjected to bending deformation. The conventional multilayer flexible printed wiring board has a multilayer integrated structure in which each wiring conductor layer and insulating layer including the bent portion are uniformly joined with an adhesive, so the bending deformation resistance is low. There were cases where the wiring conductor was cracked and disconnected due to bending deformation several times. For this reason, the structure of the multilayer flexible printed wiring board which provided the non-joining part which does not adhere to the wiring layer of a bending deformation part, adhere | attaches and laminates | stacks parts other than a bending part was made | formed (patent document 1). Thereby, resistance to repeated bending deformation can be improved.

Japanese Patent Laid-Open No. 7-312497

However, in the case of a slide-type mobile terminal in which the input key side case and the display side case are slid, the multilayer flexible printed wiring board that spans both has a large bending radius locally at a portion between them. Repeated strain bending deformation. Thinning of mobile terminals has been promoted, and the gap between the housings tends to be small every time the model is changed, and the bending radius is also very small. For this reason, in the method disclosed in Patent Document 1 in which a non-bonded portion is simply provided in a bending deformation portion, a large strain is generated in the wiring layer outside the bending, and there is a high possibility of disconnection.
An object of the present invention is to provide a flexible printed wiring board having excellent durability and an electronic device that does not cause a disconnection even when used for a long period of time against repeated bending deformation of a severer large strain. To do.

  The flexible printed wiring board of the present invention includes mounting portions located at both ends and a plurality of overlapping wiring portions that wire between the mounting portions. In this flexible printed wiring board, the plurality of wiring sections have different lengths, and the plurality of wiring sections having different lengths are overlapped in the order of the length and aligned at both ends. It is curved to the side away from the part.

  For example, when two housings of an electronic device slide, a flexible printed wiring board that conductively connects between wiring boards in these housings is repeatedly subjected to a large bending local bending deformation. As described above, by forming a wiring portion that is curved and becomes longer toward the outside, there is no portion where a large strain is generated anywhere in the outer layer (outer layer) to the inner layer (inner layer) even when subjected to repeated bending deformation. That is, when the lengths of the outer layer and the inner layer are equal, it is forced to have a long peripheral length outside the bend, and attempts to increase the peripheral length by distortion. The smaller the bending radius, the larger the strain on the outside with the same thickness (the thickness of the inner layer and the outer layer). However, as in the present invention, by dealing with bending deformation in advance and making the wiring part longer toward the outer side, in the outer layer, the strain is almost the same as the layer at the neutral position of the bending deformation (layer at the center of the multilayer). Will occur. In addition, the inner layer and the outer layer do not interfere with each other due to the bending deformation described above. For this reason, even if a flexible printed wiring board repeats severe bending deformation of a small radius, it becomes difficult to disconnect, and can obtain high repetition durability. It should be noted that “curving to the side away from the shorter wiring portion” means to bend convexly in a direction away from the short wiring portion. In addition, the mounting part refers to the area where the terminal part connected to the other mounting board is located in the mounting, and even if it is multi-layered, all areas overlapping in the plane where the terminal part is located are mounted. It goes without saying that wiring between the wiring portions of each layer may be included.

  A plurality of wiring portions and their mounting portions can be formed by being folded from the form of a single flexible printed wiring board formed integrally on a single sheet. This eliminates the need for adhesives, interlayer wiring connections, and the like required when individual layers are made into multiple layers, thereby reducing member costs and manufacturing man-hours. Bending is easier than bonding and can greatly reduce manufacturing costs.

  Of the multiple wiring parts, the terminal part is located at both ends of the longest wiring part located on the outermost side or the shortest wiring part located on the innermost side, or on the mounting part at one end, and located between them. Therefore, it is possible to adopt a configuration in which there is no terminal portion on the mounting portions at both ends of the intermediate length wiring portion, and the wiring is continuous at the mounting portion at the end of the adjacent wiring portion. Thereby, it is not necessary to connect the wiring between the layers by interposing the anisotropic conductive sheet between the multilayer mounting portions, and very excellent economic efficiency can be obtained. The terminal portion provided on the surface layer (exposed surface, ie, outermost layer and innermost layer) is arranged only in one layer of the outermost layer and the innermost flexible printed wiring layer, or is distributed to both layers one by one. Arranged. Which is determined depends on the position of the mounting portion of the wiring board in the housing of the electronic device. In addition, when this flexible printed wiring board is formed of two layers, there is no remaining flexible printed wiring layer between them, and it is composed of an outermost flexible printed wiring layer and an innermost flexible printed wiring layer. The

  In the state before the flexible printed wiring board is folded, the length direction of each wiring section is radiated in the order of the wiring section length from the longest wiring section and its mounting section to the shortest wiring section and its mounting section. It is possible to adopt a structure that is located along the direction and sandwiches a radial extraction space between adjacent wiring portions and their mounting portions. As a result, the number of folding can be reduced and the folding line can be shortened, and a multilayer flexible printed wiring board that can be regarded as a substantially rectangular shape can be created by, for example, two short folding lines. As a result, the number of folding steps can be shortened.

  A notch can be provided at the end of the fold in the fold. Thereby, the folding can be facilitated. The notch may be at both ends or at one end.

  The mounting portion and / or the wiring portion can be provided with a positioning hole for determining an overlapping position in folding. This makes it easy to perform the folding work accurately.

  The mounting part can be formed with a double-sided board, and the wiring part can be formed with a single-sided board. Although all may be formed of a single-sided plate, the above configuration can increase the rigidity of the mounting portion and form a high-strength mounting portion. Also, there are more options for the mounting method, and a more appropriate method can be selected from many mounting methods.

  It can be used by bending and sliding in a U-shape so that the longer part of the wiring part is on the outside. As a result, even when repeatedly sliding in use, it is possible to avoid a bent bent state, and durability can be improved.

  It is possible to adopt a structure in which a gap is formed between a plurality of overlapping wiring portions. Thus, it becomes easy to reliably prevent the above-mentioned hip breakage.

  An electronic apparatus according to the present invention is characterized in that any of the flexible printed wiring boards described above is incorporated. Thus, a highly durable electronic device that does not cause a problem even when used for a long time can be obtained.

  According to the flexible printed wiring board of the present invention, it is possible to have excellent durability with no fear of disconnection even when used for a long period of time against repeated bending deformation of severer large strain.

It is a perspective view which shows the portable terminal (electronic device) in Embodiment 1 of this invention. It is a longitudinal cross-sectional view of the portable terminal of FIG. It is a perspective view of FPC in this Embodiment. It is a top view which shows the FPC single-piece body of the state before producing FPC of FIG. It is a figure which shows the state which bent and adhered the FPC single-piece body. It is a figure which shows the state which folded and bonded the surplus part from the state of FIG. FIG. 7 is a schematic cross-sectional view of the FPC in FIG. 6. 8A and 8B are diagrams illustrating a usage state of the FPC in FIG. 7, in which FIG. 7A illustrates one bent state, and FIG. 7B illustrates a slid state. 6 is a diagram showing a modification of the first embodiment. FIG. It is a perspective view which shows FPC in Embodiment 2 of this invention. It is a figure which shows the separate FPC sublayer of FPC of FIG. 10, (a) shows an inner-layer side FPC sublayer, (b) shows an outer-layer side FPC sublayer.

(Embodiment 1)
FIG. 1 is a perspective view showing a portable terminal (electronic device) 50 according to Embodiment 1 of the present invention. In the portable terminal 50, the input unit 54 and the display unit 53 having the display device 56 are slid by the slide unit 58. The slide part 58 is formed by an outer frame 58a provided in the display unit housing and an inner frame 58b provided in the input unit housing.

FIG. 2 is a longitudinal sectional view of the portable terminal 50 shown in FIG. The mobile phone 50 is provided with an input unit casing 41 positioned at the input unit 54 and a display unit casing 31 positioned at the display unit 53, and both are connected by a slide unit 58. The input unit housing 41 includes a first housing 41a and a second housing 41b that are connected to each other, and a through portion 41h is provided on the display unit side of the first housing 41a. Similarly, the display unit casing 31 includes a first casing 31a and a second casing 31b that are connected to each other, and a through-hole 31h is provided on the input unit side of the second casing 31b. .
The input unit housing 41 accommodates an input key substrate 45 of a mobile phone, and the display unit housing 31 accommodates a display unit substrate 35. Information input on the input key substrate 45 is delivered to the display unit substrate 35 via a flexible printed wiring board (hereinafter referred to as FPC) 10. The FPC 10 wire-connects the input key substrate 45 and the display unit substrate 35 through the through portions 31h and 41h. The FPC 10 has a wiring portion 3 that forms an inner layer and a wiring portion 5 that is longer than the wiring portion 3 and forms an outer layer, and is curved in a direction intersecting the surface of the layer. Mounting portions 11 and 12 are formed at both ends of the wiring portions 3 and 5. Terminal portions are provided on the mounting surfaces of the mounting portions 11 and 12, and are electrically connected to the terminal portions of the substrates 35 and 45 of the display portion and the input portion. The inner-layer wiring portion 3 and the outer-layer wiring portion 5 are separated from each other, as shown in FIG. 2, but are not necessarily separated in a bent state due to bending deformation during use. The gap g between the second housing 31b of the display unit and the first housing 41a of the input unit tends to be very small due to a demand for thinning the mobile terminal 50. For this reason, when the display unit casing 31 and the input unit casing 41 slide, in the conventional FPC in which the outer layer and the inner layer are integrated via the resin layer, a large stress is caused by bending deformation with a small radius locally. May occur, causing problems such as FPC destruction. However, as shown in FIG. 2, in the FPC 10 according to the present embodiment, the curved outer layer wiring portion 5 and the inner layer wiring portion 3 are separated from each other, so that one deformation does not affect the other. For this reason, since the thin wiring part deforms independently, it does not lead to large stress generation.

  FIG. 3 is a perspective view showing an example of the FPC 10. The FPC 10 is curved in a direction intersecting the plane of the layers, and the outer layer wiring portion 5 and the inner layer wiring portion 3 are separated with the gap S therebetween. In the following description, each layer formed from the wiring portion and its mounting portion may be referred to as an FPC sublayer. The FPC 10 is folded from a single sheet, and the mounting portions 11 and 12 are bonded. Also, although not shown here, the mounting portion 12 has a side that does not interfere with mounting when it is folded. It is bent and glued. A terminal portion T is provided on the back surface 11 b of the mounting portion 11 and the back surface 12 b of the mounting portion 12.

  FIG. 4 is a plan view of the single FPC 9 before folding. For the FPC single piece 9, it is preferable to use an FPC sub-layer having a single-sided wiring portion that elastically deforms flexibly for both the wiring portions 3 and 5 and the mounting portions 11 and 12. The inner layer wiring portion 3 and the outer layer wiring portion 5 extend radially at an angle across the radial extraction space H. It is important that the length of the outer wiring portion 5 is slightly longer than the length of the inner wiring portion 3. The lengths of the wiring portions of the four mounting portions 11a, 11b, 12a, and 12b are aligned. The back surface 11b of the mounting portion 11 and the back surface 12b of the mounting portion 12 are both exposed surfaces (outermost layer or innermost layer) after being folded and bonded, but terminal portions T are provided on the back surfaces 11b and 12b. That is, the back surface on the inner layer side is the mounting surface. Inner layer wiring portion 3 and mounting portions 11b and 12b at both ends thereof form one FPC sublayer, and similarly outer layer wiring portion 5 and mounting portions 11a and 12a at both ends thereof form one FPC sublayer. . In the present embodiment, the terminal portions T are provided on the mounting portions 11 b and 12 b located at both ends of the inner layer wiring portion 3. Some of the terminals of the terminal portion T are connected to wiring from the inner layer wiring portion 3 and others are connected to wiring from the outer layer wiring portion 5. The wiring 21 from the outer layer wiring portion 5 to the terminal of the terminal portion T intersects with the creases 25 and 27.

A method of folding the FPC 10 shown in FIG. 3 from the single FPC 9 shown in FIG. 4 will be described. Here, if the cuts 25k are provided at both ends or one of the folds 25 and 27 before the crease 25 is attached, the crease 25 can be accurately folded when the crease 25 is attached or folded. Also, by folding each fold 25 of the FPC single body 9, the mounting portion 11a, when 11b and back to back, and to back-to-back mounting portions 12a, 12b, and may be provided with positioning holes _h 1 to h _8, for example positioning holes h it is possible to improve the accuracy by combining a ₁ and h _4.
In addition, when forming FPC10 by folding, the crease | fold 25 in the mounting part 12 is folded so that it may become a ridgeline of a mountain. In the surplus part F that is surplus when folded with the crease 25, the distance between the center crease 25 and the two creases 27 at the boundary with each mounting part is substantially the same.

  First, the mounting portion 11 is folded with a crease 25, and the surfaces 11a and 11b are back-to-back, and the mounting portion 12 is folded with a crease 25, and the surfaces 12a and 12b are back-to-back. As shown, the mounting portions 11a and 11b and 12a and 12b are aligned and aligned. As for the wiring portion, the outer layer wiring portion 5 is curved outward from the inner layer wiring portion 3. In FIG. 5, the outer layer wiring portion 5 is curved so as to be lifted from the paper surface. In FIG. 5, the surplus part F protrudes largely from the rectangle. The surplus portion F cannot be cut off because there is a wiring 21 from the outer layer wiring portion 5 toward the terminal portion T. For this reason, as shown in FIG. 6, it bend | folds along the crease | fold 27 to the outer layer side which does not become an obstacle of mounting, and adhere | attaches on an outer layer with an adhesive agent.

  FIG. 7 is a schematic cross-sectional view of the FPC according to the present embodiment, produced by the above folding method. In a free state, the inner layer wiring part 3 and the outer layer wiring part 5 are separated from each other, and the outer layer inner line part 5 is curved outward. When this is bent with the inner layer wiring portion 3 inward, as shown in FIG. 8 (a), the outer layer wiring portion 5 is long, so that the tensile stress in the outer layer in the multilayer FPC solidified integrally with a conventional resin is obtained. An increase can be prevented. Further, when the display unit housing and the input unit housing are slid in such a state, as shown in FIG. 8B, the inner layer wiring unit 3 and the outer layer wiring unit 5 do not affect each other. Due to the deformation, the inner layer wiring portion and the outer layer wiring portion do not interfere with each other and generate a large stress unlike the conventional case. As a result, it can be used stably for a long time without causing any problems.

(Modification of Embodiment 1)
FIG. 9 is a diagram showing a modification of the first embodiment of the present invention. In the first embodiment, the terminal portions T are provided on the exposed surfaces of the mounting portions 11b and 12b on the inner layer side. However, depending on the position of the mounting part of the display part substrate 35 or the input part board 45, it may be preferable to provide the terminal part T on the exposed surface of the mounting parts 12a, 11a on the outer layer side. Examples of the positions of the mounting portions of the display unit substrate 35 and the input unit substrate 45 shown in FIG. In some cases, it is advantageous in terms of electronic device design to provide one terminal portion on the exposed surface of the inner-layer mounting portion and the other terminal portion on the exposed surface of the outer-layer mounting portion.
Sometimes.

(Embodiment 2—Laminated body of individual FPC sub-layers)
FIG. 10 is a cross-sectional view showing an FPC according to Embodiment 2 of the present invention. 11A and 11B are diagrams showing two FPC sub-layers. FIG. 11A shows an FPC sub-layer 73 with a short wiring portion length, and FIG. 11B shows an FPC sub-layer 75 with a long wiring portion length. The present embodiment is characterized in that two FPC sub-layers 73 and 75 having different lengths of the wiring portions 73c and 75c are stacked. The stacking is performed by stacking the mounting portions of the two FPC sublayers 73 and 75. The mounting portions 73a and 75a are aligned, and the mounting portions 73b and 75b are aligned and stacked to form the entire mounting portions 81 and 82. The wiring portion 75c having the longer length is curved outward to open the gap S by the above-described lamination.
The mounting parts 75a and 73a have no continuous wiring. In order to conductively connect the terminals provided on both mounting portions facing each other, a pressure P is applied with an anisotropic conductive film 85 interposed. Similarly, it is preferable that the wiring is continuous in the mounting portions 75b and 73b.
As shown in FIG. 10, the wiring portions 75c and 73c are single-sided plates, and the mounting portions 73a, 73b, 75a, and 75b are double-sided plates. Since the mounting portion has high rigidity and no problem even if it is hard, a double-sided plate may be used. In the single-sided plate, a copper layer is formed on one side of a resin substrate that is an insulating layer, and the copper layer is patterned by etching or the like to form a wiring layer. A cover insulating layer is formed on the copper wiring layer with an adhesive layer interposed therebetween. In the double-sided board, a copper layer is formed on both sides of the resin substrate, and an adhesive layer is interposed on both sides to form a cover insulating layer. In the double-sided board, since copper layers are provided on both sides, the rigidity becomes high, and a force is required to move the bent part accompanying the slide. For this reason, it is good to use a single-sided board for a wiring part. In order to use the mounting portions 73a, 73b, 75a, and 75b as double-sided plates and the wiring portions 73c and 75c as single-sided plates, the double-sided plates are used, and only one side of the wiring portions 73c and 75c is removed by etching. It is good.
According to the present embodiment, the same action as in the first embodiment can be obtained for the bending durability of the FPC. However, use for the anisotropic conductive film 85, a mechanism of a pressure load, etc. are required.

  Although the embodiments and examples of the present invention have been described above, the embodiments and examples of the present invention disclosed above are merely examples, and the scope of the present invention is the implementation of these inventions. It is not limited to the form. The scope of the present invention is indicated by the description of the scope of claims, and further includes meanings equivalent to the description of the scope of claims and all modifications within the scope.

  According to the present invention, it is possible to obtain a multi-layer FPC having high repetition durability against bending with a small radius. Furthermore, by folding and bonding using a single FPC according to the multilayer structure, the number of parts can be reduced and labor saving in the manufacturing process can be promoted.

3 Inner layer wiring portion, 3a, 3b Inner layer wiring portion surface, 5 Outer layer wiring portion, 5a, 5b Outer layer wiring portion surface, 10 FPC, 11, 12 mounting portion, 11a, 12a mounting portion surface, 11b, 12b mounting portion rear surface , 14 Adhesive layer, 21 Wiring, 25 fold, 25k notch, 27 fold, 31 Display housing, 31a First housing, 31b
Second housing, 31h penetrating portion, 35 display portion substrate, 41 input portion housing, 41a first housing, 41b second housing, 41h penetrating portion, 45 input key substrate, 50 portable terminal (electronic device), 53 Display unit, 54 input unit, 56 display screen, 58 slide unit, 58a outer frame, 58b inner frame, 73 inner layer side FPC sublayer, 73a, 73b mounting unit, 75 outer layer side FPC sublayer, 75a, 75b mounting unit, 81 , 82 mounting portion, F surplus portion, g gap between housings, h _{1 to} h ₈ positioning holes, H blank space, S gap, T terminal portion.

Claims (10)

A flexible printed wiring board comprising a mounting portion located at both ends, and a plurality of overlapping wiring portions for wiring between the mounting portions,
The plurality of wiring portions have different lengths, and the plurality of wiring portions having different lengths are overlapped in order of length and aligned at both ends.
A flexible printed wiring board, wherein each wiring portion is curved toward a side away from a shorter wiring portion.   The plurality of wiring portions and their mounting portions are formed by being folded from a single flexible printed wiring board formed integrally on a single sheet. The flexible printed wiring board as described.   Among the plurality of wiring parts, the longest wiring part located on the outermost side, or the shortest wiring part located on the innermost side, both of the mounting parts on both ends or on one mounting part, have a terminal part, 3. The flexible device according to claim 2, wherein the mounting portion at both ends of the intermediate-length wiring portion is not provided with a terminal portion, and the wiring is continuous at the mounting portion at the end of the adjacent wiring portion. Printed wiring board.   In the state before the flexible printed wiring board is folded, from the longest wiring portion and its mounting portion to the shortest wiring portion and its mounting portion, the length direction of each wiring portion in the order of the wiring portion length. 4. The flexible printed wiring board according to claim 2, wherein the flexible printed wiring board is located along a radial direction, and a radial extraction space is interposed between adjacent wiring portions and mounting portions thereof. 5.   The flexible printed wiring board according to claim 2, wherein a cut is provided at an end of the fold in the folding.   The flexible printed wiring board according to claim 1, wherein a positioning hole for determining an overlapping position in folding is provided in the mounting portion and / or the wiring portion.   The flexible printed wiring board according to claim 1, wherein the mounting part is formed of a double-sided board, and the wiring part is formed of a single-sided board.   The flexible printed wiring board according to any one of claims 1 to 7, wherein the flexible printed wiring board is used by being bent and slid in a U shape so that the longer one of the wiring portions is on the outside.   The flexible printed wiring board according to claim 1, wherein a gap is formed between the plurality of overlapping wiring portions. An electronic apparatus comprising the flexible printed wiring board according to any one of claims 1 to 9.

Images