This application is based upon and claims the benefit of priority from Japanese Patent Application No. 2014-183029, filed Sep. 9, 2014, the entire contents of which are incorporated herein by reference.
Embodiments described herein relate generally to a method for manufacturing a flexible printed circuit board module with a reinforcing board, and an intermediate structure of a flexible printed circuit board.
A reinforcing board is often attached to a flexible printed circuit board for reinforcement. Such a reinforcing board is useful when parts such as switches or connectors are mounted on the flexible printed circuit board or the flexible printed circuit board is mounted to another device. In the related art, a reinforcing board is attached to the flexible printed circuit board with an adhesive film or a sheet. That is, an adhesive film or sheet that has a predetermined shape is first disposed in a predetermined position of a flexible printed circuit board using a positioning pin, and then a reinforcing board is disposed on the adhesive sheet using the positioning pin. Finally, the reinforcing board is pressed against the flexible printed circuit board while heating the adhesive film or sheet.
One or more embodiments are directed to provide a method for manufacturing a flexible printed circuit board with a reinforcing board more easily and efficiently.
In general, according to one embodiment, a method for manufacturing a flexible printed circuit module, includes discharging an adhesive material from an inkjet head towards one or more target regions of a flexible printed circuit board, semi-curing the adhesive material on the flexible printed circuit board, placing one or more reinforcement members on a surface of the adhesive material, and pressing the one or more reinforcement members against the flexible printed circuit board while heating the adhesive material, such that the one or more reinforcement members are fixed on the flexible printed circuit board.
Embodiments will be described with reference to the drawings.
This disclosure describes some components using different names. The names are only examples and these components may be represented by other names. Components not represented by different names may also be represented by other names.
In addition, since the drawings are illustrated schematically, the relationship between the thickness, the planar size and the ratio between the thicknesses of layers, and the like maybe different from the actual ones. In addition, parts having a different relationship of sizes or a different ratio of sizes between drawings may be included.
First, a working panel 100 that defines and includes a plurality of FPCs 110 immediately before reinforcing boards are mounted is prepared in a usual manner (
Next, an adhesive is applied to the reinforcement target portion 111 (see
Next, the insulating adhesive layer 310 is semi-cured, an insulating reinforcing board 400 is disposed thereon, and a reinforcing board 410 is pressed against the adhesive layer 310 under heating, to cure the adhesive, and, through the cured adhesive. As a result, the FPC 110 and the reinforcing board 410 are firmly bonded together. The insulating reinforcing board 410 to be used may be made of polyimide, polyethylene terephthalate (PET), liquid crystal polymer (LCP), glass epoxy, or the like.
Since the insulating adhesive used here has a thermosetting property as described above, the insulating adhesive normally includes a thermosetting agent.
In addition, the adhesive layer has substantially the same planar shape as the plane (that is, the surface in contact with the adhesive layer) of the reinforcing board to be disposed later (the same in the following embodiments).
A second embodiment is the same as the first embodiment except that the second embodiment uses a conductive adhesive and a conductive reinforcing board.
That is, referring to
Next, the conductive adhesive layer 320 is semi-cured, a conductive reinforcing board 420 is disposed thereon, and the reinforcing board 420 is pressed against the adhesive layer 320 under heating, to cure the adhesive, and, through the cured adhesive. As a result, the FPC 110 and the reinforcing board 420 are firmly bonded together. The conductive reinforcing board 420 to be used may be made of copper, aluminum, SUS, or the like.
Also in this case, since the conductive adhesive has a thermosetting property, the conductive adhesive includes a thermosetting agent.
Since the reinforcing board is conductive in the present embodiment, electrical connection to the ground pattern of the FPC is effective in noise reduction such as electromagnetic interference (EMI) reduction and in heat radiation of the heating component mounted on the FPC.
A third embodiment is the same as the first embodiment except that the third embodiment uses an insulating adhesive and a conductive reinforcing board.
That is, referring to
Next, the insulating adhesive layer 310 is semi-cured, the conductive reinforcing board 420 is disposed thereon, and the reinforcing board 420 is pressed against the adhesive layer 310 under heating, to cure the adhesive, and, through the cured adhesive. As a result, the FPC 110 and the reinforcing board 420 are firmly bonded. The conductive reinforcing board 420 used in the second embodiment may be used as the conductive reinforcing board 420 in the present embodiment.
Since the reinforcing board is conductive and the adhesive is insulating in the embodiment, heat of the heating component mounted on the FPC is effectively radiated.
A fourth embodiment is the same as the first embodiment except that the adhesive layer includes a portion including an insulating adhesive and a portion including a conductive adhesive adjacent to the portion including an insulating adhesive, and uses a conductive reinforcing board.
That is, referring to
Next, an adhesive layer 300 including insulating adhesive layer parts 311 and 312 and the conductive adhesive layer part 321 is semi-cured, the conductive reinforcing board 420 is disposed thereon, and the reinforcing board 420 is pressed against the adhesive layer 300 under heating, to cure the adhesive, and, through the cured adhesive. As a result, the FPC 110 and the reinforcing board 420 are firmly bonded. The conductive reinforcing board 420 used in the second embodiment may be used as this conductive reinforcing board 420.
In the embodiment, since the reinforcing board is conductive, electrical connection to the ground pattern of the FPC achieves noise reduction such as electromagnetic interference (EMI) reduction. In the part of insulating adhesive, wiring with an electric potential different from that of the ground may be disposed on the surface of the FPC.
According to a fifth embodiment, the FPC is reinforced at a plurality of positions. Further, the FPC according to the fifth embodiment includes a plurality of reinforcing boards, and the adhesive layers with which the reinforcing boards and the FPC are bonded together have different thicknesses.
That is, referring to
Next, the insulating adhesive layers 310a and 310b are semi-cured, reinforcing boards 400a and 400b are disposed on these layers, and the reinforcing boards 400a and 400b are pressed against the adhesive layers 310a and the 310b under heating, to cure the adhesive, and, through the adhesives. As a result, the FPC 110 and the reinforcing boards 400a and 400b are firmly bonded.
That is, in the present embodiment, the flexible printed circuit board includes the first and second reinforcement target portions and the first and second reinforcing boards are bonded to the flexible printed circuit board in the first and second reinforcement target portions through the adhesive layers with different thicknesses.
One example in which adhesive layers with different thicknesses are preferable to be formed as described above is the case in which one reinforcing board has an area larger than that of the other reinforcing board. Since a layer with a larger area is likely to warp, a thicker adhesive layer is required to absorb the warpage. The flexible printed circuit board with a reinforcing board manufactured in this case includes the flexible circuit board, the first reinforcing board bonded to the flexible circuit board through the first adhesive layer, and the second reinforcing board bonded to the flexible circuit board through the second adhesive layer, and the second reinforcing board has an area larger than that of the first reinforcing board and the second adhesive layer is thicker than the first adhesive layer.
Another example in which adhesive layers with different thicknesses are preferable to be formed is the case in which one reinforcing board has surface roughness smaller than that of the other reinforcing board. Since a reinforcing board with smaller surface roughness such as a metal plate is not easily bonded, a thicker adhesive layer is preferred. A reinforcing board made of synthetic resin is an example of a reinforcing board with large surface roughness. The flexible printed circuit board with a reinforcing board manufactured in this case includes the flexible circuit board, the first reinforcing board bonded to the flexible circuit board through the first adhesive layer, and the second reinforcing board bonded to the flexible circuit board through the second adhesive layer, and the second reinforcing board has surface roughness smaller than that of the first reinforcing board and the second adhesive layer is thicker than the first adhesive layer.
An ink jet printing system may be used to easily form adhesive layers with different thicknesses on a single FPC.
In the sixth embodiment, the FPC includes a step section including an inclined plane and a three-dimensional shaped reinforcing board including a step section corresponding to the step section of the FPC is bonded to the step section of the FPC.
That is, with referring to
Next, the adhesive layer 330 is semi-cured, the reinforcing board 400 is disposed on the semi-cured adhesive layer 300, and the reinforcing board 400 is pressed against the adhesive layer 330 under heating, to cure the adhesive, and, through the adhesive. As a result, the FPC 110 and the reinforcing board 400 are firmly bonded together. The reinforcing board 400 includes a step portion corresponding to the step portion of the FPC 110.
An ink jet printing system may be used to easily apply an adhesive to a three-dimensional shaped portion of the FPC with such a three-dimensional shape.
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As a result, the reinforcing board 22 has the ground electric potential and functions as a shield member for EMI prevention. In addition, the reinforcing board 22 is thermally connected to the board 21 through the conductive adhesive layer 31 and the ground pattern 25. As a result, the reinforcing board 22 made of metal functions as a radiating member for the board 21.
On the other hand, an insulating adhesive layer 32 (nonconductive adhesive layer) is provided between the reinforcing board 22 and the wiring pattern 26. The insulating adhesive layer 32 bonds the reinforcing board 22 and the first plane 21a of the board 21 together and insulates the reinforcing board 22 from the wiring pattern 26. This prevents a short circuit between the wiring pattern 26 and the conductive reinforcing board 22.
Next, an exemplary method for manufacturing the FPC 11 will be described.
Referring to
Next, a conductive adhesive is similarly applied to the opening 32a of the insulating adhesive layer 32 using an ink jet printing system, and the conductive adhesive layer 31 is formed. Through this process, the conductive adhesive layer 31 contacts and is electrically connected to the ground pattern 25. Next, the insulating adhesive and the conductive adhesive are semi-cured, and the insulating adhesive layer 32 and the conductive adhesive layer 31 are disposed between the board 21 and the conductive reinforcing board 22 and then crimped by applying heat and pressure.
Through this process, the conductive reinforcing board 22 is bonded to the board 21 through the conductive adhesive layer 31 and electrically connected to the ground pattern 25 through the conductive adhesive layer 31. In addition, the conductive reinforcing board 22 is bonded to the board 21 through the insulating adhesive layer 32.
As a result, the printed circuit board 11 including the conductive reinforcing board 22 is provided. The insulating adhesive and the conductive adhesive have a thermosetting property, as described above.
The insulating adhesive layer 32 may be formed by applying an insulating adhesive to the first plane 21a of the board 21 instead of using the above manufacturing method.
In the printed circuit board 11 with such a structure, the wiring efficiency may be improved. That is, when the reinforcing board is mounted on the printed circuit board, the ground pattern with an area substantially the same as that of the shape of the reinforcing board is provided on the surface of the board, generally. In this case, since the ground pattern occupies a large area on the surface of the board, wiring patterns for power sources and signals cannot be disposed in the region. As a result, the number of layers and the size of the PFC are increased.
On the other hand, the FPC 11 according to the present embodiment includes the board 21, the ground pattern 25 provided on the board 21, the wiring pattern 26 provided on the board 21, the conductive reinforcing board 22, and the insulating adhesive layer 32. The conductive reinforcing board 22 covers the ground pattern 25 and the wiring pattern 26 and is electrically connected to the ground pattern 25. The insulating part is provided between the conductive reinforcing board 22 and the wiring pattern 26.
In such a structure, a part of the region on the surface of the board 21 covered with the conductive reinforcing board 22 may be used as a region in which the wiring pattern 26 and the via 27 are provided. This improves the wiring efficiency. In addition, the improvement of the wiring efficiency reduces the number of layers in the board 21, thereby achieving reduction in the thickness and the size of the printed circuit board 11.
In the embodiment, the insulating part provided between the conductive reinforcing board 22 and the wiring pattern 26 is the insulating adhesive layer 32. The insulating adhesive layer 32 bonds the conductive reinforcing board 22 and the board 21. In such a structure, even if the wiring pattern 26 is provided in the region covered with the conductive reinforcing board 22, the bonding force between the board 21 and the conductive reinforcing board 22 may be ensured sufficiently. This improves the reliability of the printed circuit board 11.
In the embodiment, the insulating adhesive layer 32 is formed like a frame surrounding the ground pattern 25. In such a structure, a relatively large area may be assigned to the region in which the wiring pattern 26 is provided and the bonding force between the board 21 and the conductive reinforcing board 22 may be ensured sufficiently. This further improves the wiring efficiency of the printed circuit board 11.
The embodiment further includes the conductive adhesive layer 31 provided between the conductive reinforcing board 22 and the ground pattern 25. The conductive adhesive layer 31 bonds the conductive reinforcing board 22 and the board 21. Such a structure further increases the bonding force between the board 21 and the conductive reinforcing board 22 and improves reliability of the printed circuit board 11.
In the embodiment, the insulating adhesive layer 32 is formed like a frame, and the opening 32a facing the ground pattern 25 is formed therein. The conductive adhesive layer 31 is provided within the opening 32a of the insulating adhesive layer 32. In such a structure, even if the insulating adhesive layer 32 is provided between the board 21 and the conductive reinforcing board 22, an electrical connection between the board 21 and the conductive reinforcing board 22 maybe ensured.
According to the first to seventh embodiments, the adhesive is applied to the reinforcement target portion of an FPC using an ink jet printing system. Accordingly, at least a part of a surface of the adhesive semi-cured after the adhesive is applied to the reinforcement target portion of the FPC reflects the contour of droplets ejected from the inkjet head. Here, “reflects the contour of droplets” represents not only the case in which the contour of droplets is the same as the surface shape of the adhesive, but also the case in which the contour of droplets is deformed due to their own weight, and it generally means that the surface of the adhesive layer is non-flat (wavy). It may be said that the flexible printed circuit board (intermediate) with such a semi-cured adhesive layer includes the flexible printed circuit board 110 including the reinforcement target portion and the semi-cured adhesive layer 300 applied to the reinforcement target portion, and at least a part of a surface 300a of the adhesive layer reflects the contour of droplets ejected from the ink jet head, as illustrated in
In the above embodiments, since an adhesive for bonding the FPC and the reinforcing board together is ejected and applied using an ink jet printing system, the number of processes maybe reduced and the accuracy of positioning during application of the adhesive becomes higher as compared with a bonding method using an adhesive sheet in the related art. In addition, when using an adhesive sheet, unnecessary parts generated due to die-cutting need to be discarded. However, since an adhesive is applied using an ink jet system in the above embodiments, no adhesive material is wasted and, if a failed FPC is present in the working panel, it is possible not to apply an adhesive to the failed FPC. In an ink jet system, three-dimensional reinforcing board, which cannot be achieved by an adhesive sheet, may also be used easily and the thickness of the adhesive may be partially changed easily.
Accordingly, according to one or more of the above embodiments, a flexible printed circuit board with a reinforcing board may be manufactured more easily and efficiency.
While certain embodiments have been described, these embodiments have been presented by way of example only, and are not intended to limit the scope of the inventions. Indeed, the novel embodiments described herein may be embodied in a variety of other forms; furthermore, various omissions, substitutions and changes in the form of the embodiments described herein may be made without departing from the spirit of the inventions. The accompanying claims and their equivalents are intended to cover such forms or modifications as would fall within the scope and spirit of the inventions.
Number | Date | Country | Kind |
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2014-183029 | Sep 2014 | JP | national |