BRIEF DESCRIPTION OF THE DRAWINGS
The accompanying drawings are included to provide a further understanding of the invention, and are incorporated in and constitute a part of this specification. The drawings illustrate embodiments of the invention and, together with the description, serve to explain the principles of the invention.
FIG. 1 is a schematic cross-sectional view showing a conventional flexible printed circuit board (FPC).
FIG. 2 is a schematic view showing an electrical connection approach for connecting a FPC to a printed circuit board (PCB).
FIG. 3 is a schematic cross-sectional view showing other conventional FPC.
FIG. 4 is a schematic cross-sectional view showing a flexible circuit board according to one embodiment of the present invention.
FIG. 5 is a schematic cross-sectional view showing that a flexible circuit board of the present invention is electrically connected to a PCB by using a hot bar reflow process.
FIGS. 6A to 6F are schematic, cross-sectional diagrams illustrating the process flow for fabricating a flexible circuit board according to the present invention.
FIG. 7 is a schematic diagram showing a display apparatus including the above-mentioned flexible circuit board.
FIG. 8 is a schematic block diagram showing an electronic device having the display panel as shown in FIG. 7.
DESCRIPTION OF THE EMBODIMENTS
Reference will now be made in detail to the present preferred embodiments of the invention, examples of which are illustrated in the accompanying drawings. Wherever possible, the same reference numbers are used in the drawings and the description to refer to the same or like parts.
FIG. 4 is a schematic cross-sectional view showing a flexible circuit board according to one embodiment of the present invention. Please refer to FIG. 4, the flexible circuit board 400 mainly comprises a base film 410, a first conductive layer 420, a second conductive layer 430 and an adhesive layer 440. The base film 410 has a first surface 410a and a second surface 410b, and it is made of a flexible material such as polyimide, polyester, polyethylene terephthalate resin (PET) and the like. The first conductive layer 420 is disposed on the first surface 410a of the base film 410 directly and has a thermal bonding region A′ adapted for a thermal bonding process. In one embodiment of the present invention, the first conductive layer 420 can be a copper foil having a patterned circuit. The second conductive layer 430 is disposed above the second surface 410b of the base film 410, and it can also be a copper foil having a patterned circuit. The second conductive layer 430 is adhered to the base film 410 through the adhesive layer 440, and it is patterned in advance such that the adhesive layer 440 does not overlap the thermal bonding region A′.
The first passivation layer 450 is selectively disposed on the first conductive layer 420 for protecting the first conductive layer 420, and the first passivation layer 450 does not overlap the thermal bonding region A′. Similarly, the second passivation layer 460 is selectively disposed on the second conductive layer 430 for protecting the second conductive layer 430. Besides, one or more conductive plugs 470 are selectively formed in the base film 410 and the adhesive layer 440 for electrically connecting the first conductive layer 420 and the second conductive layer 430.
FIG. 5 is a schematic cross-sectional view showing that a flexible circuit board of the present invention is electrically connected to a PCB by using a thermal bonding process. The flexible circuit board 400 and a PCB 200 are bonded together by using a thermal bonding process, and a hot bar reflow process is taken as an example in the following for illustration. Please refer to FIG. 5, in the flexible circuit board 400 of the present invention, the adhesive layer 440 does not overlap the thermal bonding region A′. Therefore, when pressure and heat are applied through a hot bar 300 to the thermal bonding region A′ of the flexible circuit board 400 so as to melt the first conductive layer 420 and pre-solder pastes 210 of a PCB 200, no adhesive layer disposed above the thermal bonding region A′ would be damaged due to the high operation temperature. Therefore, the reliability of electrical connection between flexible circuit board 400 and the PCB 200 can be improved.
FIGS. 6A to 6F are schematic, cross-sectional diagrams illustrating the process flow for fabricating a flexible circuit board according to the present invention. First, please refer to FIG. 6A, a base film 410 is provided with a first conductive layer 420 disposed on the lower surface thereof, and the first conductive layer 420 has a thermal bonding region A′. In one embodiment of the present invention, the first conductive layer 420 disposed on the base film 410 is formed by deposition, such as sputtering, or lamination. Next, please refer to FIG. 6B, a second conductive layer 430 is provided with an adhesive layer 440 disposed thereon. Finally, please refer to FIG. 6C, the base film 410 and the second conductive layer 430 are bonded together. The adhesive layer 440 is disposed between the base film 410 and the second conductive layer 430, and the adhesive layer 440 does not overlap the thermal bonding region A′. Thus far, the basic structure of the flexible circuit board is formed according to the above processes.
Besides, please refer to FIG. 6D, before bonding the base film 410 and the second conductive layer 430 together, the method may further comprise a step of forming a first passivation layer 450 on the first conductive layer 420. The first passivation layer 450 is adapted for protecting the first conductive layer 420 and it also exposes the thermal bonding region A′. Further, please refer to FIG. 6E, the second conductive layer 430 shown in FIG. 6B can be provided on a second passivation layer 460 which is adapted for protecting the second conductive layer 430, and the second conductive layer 430 is disposed between the second passivation layer 460 and the adhesive layer 440. However, the fabrication sequence of the first passivation layer 450 and the second passivation layer 460 are not limited in the present invention.
In one embodiment of the present invention, the base film 410 shown in FIG. 6D and the second conductive layer 430 shown in FIG. 6E can be bonded together to form the flexible circuit board 400′ shown in FIG. 6F. Besides, one or more conductive plugs (not shown) can be formed in the base film 410 and the adhesive layer 440 to electrically connect the first conductive layer 420 and the second conductive layer 430 according to the requirement.
FIG. 7 is a schematic diagram showing a display apparatus including the above-mentioned flexible circuit board. Please refer to FIG. 7, the display apparatus 500 mainly comprises a display panel 510, a PCB 520 and at least one flexible circuit board 530. The display panel 510 may be an LCD display panel, a plasma display panel or an organic electroluminescence display panel, and the type of the display panel 510 is not limited in the present invention. The PCB 520 is disposed at one side of the display panel 510, and the flexible circuit board 530 is adapted for electrically connecting the display panel 510 and the PCB 520. The flexible circuit board 530 is the same as that shown in FIG. 4, so it is not repeated herein.
FIG. 8 is a schematic block diagram showing an electronic device having the display panel as shown in FIG. 7. Please refer to FIG. 8, the electronic device 600 of the present invention mainly comprises a display apparatus 500 as shown in FIG. 7 and an input apparatus 610 electrically connected thereto. The components of the display apparatus 500 are shown in FIG. 7, so it is not repeated herein. The input apparatus 610 is adapted for receiving commands input by users and transmitting the commands to the display apparatus 500.
In summary, the adhesive layer does not overlap the thermal bonding region in the flexible circuit board. Therefore, when performing a thermal bonding process, such as a hot bar reflow process, no adhesive layer would be damaged due to the high operation temperature, and the reliability of electrical connection between flexible circuit board and PCB can be improved. Besides, compared with the conventional FPC, one conductive layer is formed on one side of the base film by sputtering, and the other conductive layer is adhered to the other side of the base film through an adhesive layer in the present invention. Thus, the production cost of the flexible circuit board can be reduced.
It will be apparent to those skilled in the art that various modifications and variations can be made to the structure of the present invention without departing from the scope or spirit of the invention. In view of the foregoing, it is intended that the present invention cover modifications and variations of this invention provided they fall within the scope of the following claims and their equivalents.
Patent Application
20070285905
