TWI395533B - Method for manufacturing a flex-rigid circuit board - Google Patents

Description

Soft and hard composite circuit board manufacturing method

The present invention relates to a method of fabricating a circuit board, and more particularly to a method of fabricating a soft and hard composite circuit board.

As the electronics market continues to grow and diversify, the use of circuit boards is diversified. In most electronic products, boards are an indispensable component. The circuit board is used to carry electronic components and circuits between the electronic components. The circuit board can be divided into a rigid circuit board, a flexible circuit board, and a soft and hard composite circuit board. The soft and hard composite circuit board has high design flexibility, so it can be widely applied in various electronic products.

A conventional soft and hard composite circuit board is a circuit that first forms a rigid circuit board and a circuit of a flexible circuit board, and then the rigid circuit board and the flexible circuit board are joined in an appropriate manner. For example, a recess is formed in the interlayer on the side of the rigid circuit board, and then one end of the flexible circuit board is inserted into the recess and fixed, and a connection hole is formed above the joint between the rigid circuit board and the hard and soft circuit board. , to electrically connect the rigid circuit board and the flexible circuit board.

Another conventional connection method is that a soft board having a size similar to a hard board is interposed between two hard boards, and both ends of the board are sandwiched by two hard boards. Then, an electrical connection hole is formed on the rigid circuit board to electrically connect the rigid circuit board to the hard and soft circuit board.

The above manufacturing methods are difficult to achieve a reliable automated production process. Moreover, in the first method described above, the reliability and mechanical strength of the joint of the soft and hard board are not good, and it is easy to fall off or the electrical contact is poor. In the second method described above, when the electrical connection hole is formed, one end of the semi-finished product of the flexible circuit board is a rigid circuit board, and the other end is a flexible circuit board, which is inconvenient in performing subsequent processes or transportation. Therefore, there is still a need for a manufacturing method that can improve the above problems.

An object of the present invention is to provide a soft and hard composite circuit board and a manufacturing method thereof, which can realize automated manufacturing, improve product yield and reliability.

The above method of manufacturing a soft and hard composite circuit board includes the following steps. A first rigid substrate is provided. The opposite sides of the first rigid substrate respectively have a first surface and a second surface. The first predetermined removal region edge of one of the first rigid substrates has a first cutting line and a second cutting line, wherein the first and second cutting lines extend through the first rigid substrate. Attaching a first adhesive layer to the second surface of the first rigid substrate, the first adhesive layer having a first opening corresponding to the first predetermined removal region to expose a portion of the second surface of the first rigid substrate. A flexible circuit board is disposed on the portion of the first adhesive layer and over the first predetermined removal region of the first rigid substrate. Adhering the second adhesive layer to a portion of the flexible circuit board and the first adhesive layer not covered by the flexible circuit board, wherein the second adhesive layer has a second opening, and the position of the second opening corresponds to the first Above the opening. Attaching a second rigid substrate and a second adhesive layer, the opposite sides of the second rigid substrate respectively have a first surface and a second surface, wherein the second surface of the second rigid substrate contacts the second adhesive layer, and One of the second rigid substrate has a second predetermined removal region edge having a third cutting line and a fourth cutting line penetrating through the second rigid substrate, and the third cutting line position corresponds to the first cutting line position, and the fourth cutting The line position corresponds to above the second cutting line position.

The soft and hard composite circuit board comprises: a first rigid substrate having a first conductive line and a first cutting removal area, and a second rigid substrate having a second conductive line and a second cutting removal area And a flexible circuit board having at least one first conductive layer, wherein the position of the second cut removal region corresponds to the first cut removal region of the first rigid substrate. The circuit board further includes a first adhesive layer having a first surface and a second surface on opposite sides thereof, the first surface is adhered to the first rigid substrate, and the second surface is adhered to the flexible circuit board The first adhesive layer has a first opening to expose a portion of the flexible circuit board, and the first cutting removal region of the first rigid substrate exposes a portion of the first adhesive layer; and a second adhesive layer has opposite sides Each has a first surface and a second surface. The first surface is adhered to the second rigid substrate, and the second surface is adhered to the flexible circuit board. The second adhesive layer has a second opening to expose a portion of the flexible circuit. a second adhesive removal region of the second rigid substrate exposing a portion of the second adhesive layer, wherein the second surface of the first adhesive layer and the second surface portion of the second adhesive layer are bonded to each other; and A connecting hole passes through the first adhesive layer and the first rigid substrate to electrically connect the first conductive line of the first rigid substrate and the first conductive layer of the flexible circuit board.

1 to 9 are views showing a manufacturing process of a manufacturing method according to an embodiment of the present invention. Referring to FIGS. 1A and 1B, the first rigid substrate 100 is first provided. 1A is a top view of the first rigid substrate 100, and FIG. 1B is a schematic cross-sectional view taken along line 1B to 1B of FIG. 1A. As shown in FIG. 1B, the opposite sides of the first rigid substrate 100 have a first surface 101 and a second surface 102, respectively, and the first surface 101 has a first copper layer 103 (first metal layer) thereon. Of course, the second surface 102 may also have an alignment mark (not shown) formed by another metal layer (for example, a copper layer). In one embodiment, the first rigid substrate 100 is a thermoset material, such as a fiberglass cloth substrate (eg, Flame Retardant 4, FR4 substrate), which has been widely used in printed circuit boards.

As shown in FIG. 1A, a first cutting line 110 and a second cutting line 120 are formed at an edge of the first predetermined removal region 105 of the first rigid substrate 100, and the first and second cutting lines 110, 120 are top to bottom. The first rigid substrate 100 is penetrated. The method of forming the first and second cutting lines 110, 120 is not particularly limited, and for example, a die cutting (or steel die cutting) or a laser cutting technique can be utilized. The positions and lengths of the first and second cutting lines 110, 120 are designed according to product requirements, and are not particularly limited.

Referring to FIGS. 2A and 2B , a first adhesive layer 200 is formed on the second surface 102 of the first rigid substrate 100 , and the first adhesive layer 200 has a first opening 210 thereon to expose a portion of the first rigid substrate 100 . The second surface 102. The method of forming the first opening 210 of the first adhesive layer 200 is not particularly limited. For example, a punching machine or a laser cutting machine can be utilized. The first adhesive layer 200 covers the first and second cutting lines 110, 120, and the first and second cutting lines 110, 120 are substantially parallel to one side of the first opening 210. In one embodiment, the method of forming the first adhesive layer 200 on the first rigid substrate 100 is to laminate an adhesive adhesive on the second surface 102 of the first rigid substrate 100 using a quick press. . In another embodiment, the first adhesive layer 200 can be attached to the first rigid substrate 100 by simultaneously providing external pressure and high temperature. The first adhesive layer 200 may be a thermoplastic polymer material which softens and melts after being heated to have adhesiveness.

Next, referring to FIGS. 3A and 3B , the flexible circuit board 300 is disposed on the first adhesive layer 200 , and the flexible circuit board 300 spans the first opening 210 of the first adhesive layer 200 . In an embodiment, the flexible circuit board 300 includes a first portion 310, a second portion 320, and an intermediate portion 330. The intermediate portion 330 substantially corresponds to the first opening 210, the first portion 310 extends from one end of the intermediate portion 330 across the first cutting line 110, and the second portion 320 extends from the other end of the intermediate portion 330 across the second cutting line 120. As shown in Figures 3A and 3B. The opposite sides of the first adhesive layer 200 respectively have a first surface 201 and a second surface 202. The first surface 201 is adhered to the first rigid substrate 100, and the flexible circuit board is adhered to the second surface 202. In one embodiment, the flexible circuit board 300 is pre-bonded to the first adhesive layer 200 using an attaching machine, for example, by using an applicator to provide a temperature of about 120 ° C, the first portion 310 of the flexible circuit board 300 and The second portion 320 is pre-attached to the first adhesive layer 200.

In a specific embodiment, the flexible circuit board 300 includes a first protective layer 301, a first conductive layer 302, an insulating layer 303, a second conductive layer 304, and a second protective layer 305. The above layers may be sequentially arranged from bottom to top. As shown in Fig. 3C, the invention is not limited thereto. The first and second conductive layers 302, 304 can be, for example, patterned copper layers (copper lines) for transmitting electrical energy or signals. The first and second protective layers 301, 305 are used to protect the first and second conductive layers 302, 304 from scratching or damage of the first and second conductive layers 302, 304. The insulating layer 303 and the first and second protective layers 301 and 305 may be, for example, a polymer material of polyamidamine. In one embodiment, the first protective layer 301 is disposed on the outer surface of the flexible circuit board 300 adjacent to the first adhesive layer 200, and the second protective layer 305 is disposed on the flexible circuit board 300 opposite to the first adhesive layer 200. An outer surface. The insulating layer 303 is disposed between the first protective layer 301 and the second protective layer 305; the first conductive layer 302 is disposed between the insulating layer 303 and the first protective layer 301; and the second conductive layer 304 is disposed on the insulating layer 303 Between the second protective layer 305 and the second protective layer 305.

Next, referring to FIGS. 4A and 4B, the second adhesive layer 400 is formed on the partial flexible circuit board 300 and on the first adhesive layer 200 not covered by the flexible circuit board 300. The second adhesive layer 400 has a second opening 420 , and the second opening 420 is substantially the same size as the first opening 210 of the first adhesive layer 200 and is located above the first opening 210 . The method of forming the second adhesive layer 400 may be the same as the first adhesive layer 200, and will not be repeated here.

Then, as shown in FIGS. 5A and 5B, the second rigid substrate 500 is placed on the second adhesive layer 400. As shown in FIG. 5B, the opposite sides of the second rigid substrate 500 respectively have a first surface 501 and a second surface 502. The first surface 501 has a second copper layer 503 (second metal layer) thereon, and the second rigid layer The second surface 502 of the substrate 500 contacts the second adhesive layer 400. In other words, the opposite sides of the second adhesive layer 400 have a first surface 401 and a second surface 402 respectively. The first surface 401 is adhered to the second rigid substrate, and the second surface 402 is adhered to the flexible circuit board 300. The edge of the second predetermined removal region 505 on the second rigid substrate 500 has a third cutting line 530 and a fourth cutting line 540, and the third cutting line 530 and the fourth cutting line 540 respectively penetrate the second rigid substrate 500, and The third cutting line 530 of the two rigid substrate 500 is located substantially above the first cutting line 110, and the fourth cutting line 540 is located substantially above the second cutting line 120. In one embodiment, the layers between the second rigid substrate 500 and the first rigid substrate 100 are tightly pressed together using a press to provide external pressure and a suitable temperature, which are familiar to those skilled in the art. In a particular embodiment, the lengths of the third and fourth cutting lines 530, 540 are the same as the first and second cutting lines 110, 120, respectively, but the invention is not limited thereto. The method of forming the third and fourth dicing lines 530, 540 on the second rigid substrate 500 may be the same as or different from the method of forming the first and second dicing lines 110, 120 on the first rigid substrate 100. In one embodiment, the third and fourth cutting lines 530, 540 are formed on the second rigid substrate 500, and then the pressing step is performed. In another embodiment, after the pressing step, the third and fourth cutting lines 530, 540 are formed on the second rigid substrate 500 using, for example, laser cutting techniques.

Alternatively, please refer to FIG. 5C. Before forming the second adhesive layer 400, a filling layer 410 may be disposed on the first adhesive layer 200, and then a second adhesive layer 400 may be formed on the filling layer 410. In this embodiment, the filling layer 410 is disposed between the first adhesive layer 200 and the second adhesive layer 400, so that the required amount of the first adhesive layer 200 and the second adhesive layer 400 can be reduced. The material of the filling layer 410 may be a hard or soft material, and a chemically stable material may be used. For example, the fill layer 410 can be a metallic material such as copper or a non-metallic material such as an epoxy substrate.

In an embodiment, after the step is completed, or after the first adhesive layer is disposed on the first rigid substrate, the first connection hole 601 and the second connection hole 602 are formed on the first rigid substrate 100, and After the second adhesive layer is disposed on the second rigid substrate, a third connection hole 603 and a fourth connection hole 604 are formed on the second rigid substrate 500, as shown in FIGS. 6A and 6B. The first and second connecting holes 601 and 602 penetrate the first rigid substrate 100, the first adhesive layer 200, and the first protective layer 301 of the flexible circuit board 300, so that the first conductive portion of the first portion 310 of the flexible circuit board 300 The layer 302 can be exposed through the first connection hole 601, and the first conductive layer 302 in the second portion 320 of the flexible circuit board 300 can be exposed through the second connection hole 602. Similarly, the third and fourth connecting holes 604 extend through the second rigid substrate 500, the second adhesive layer 400, and the second protective layer 305 of the flexible circuit board 300 from top to bottom, so that the first portion 310 of the flexible circuit board 300 The second conductive layer 304 in the second conductive layer 304 may be exposed through the third connection hole 603, and the second conductive layer 304 in the second portion 320 of the flexible circuit board 300 may be exposed through the fourth connection hole 604.

After the first, second, third, and fourth connection holes 601, 602, 603, and 604 are formed, the first electrical connection layer 610 is formed in the first and second connection holes 602, and the third and fourth connections are formed. A second electrical connection layer 620 is formed in the hole 604. The first electrical connection layer 610 and the second electrical connection layer 620 can be completed in the same step. For example, the first and second electrical connection layers 610, 620 are simultaneously formed by electroless plating (or electroless plating). Therefore, the first conductive layer 302 in the flexible circuit board 300 is electrically connected to the first copper layer 103 of the first rigid substrate 100 via the first electrical connection layer 610, and the second conductive layer 304 in the flexible circuit board 300 is electrically connected. The second copper layer 503 of the second rigid substrate 500.

In the above manufacturing method, the first copper layer 103 and the second copper layer 503 may be further patterned. Patterning the first and second copper layers 103, 503 can be performed after forming the first and second electrical connection layers 610, 620. In one embodiment, the first and second copper layers 103, 503 are patterned by a conventional development and etching process to form a product such as a first conductive line 107 and a second on the first rigid substrate 100. The second conductive line 507 on the rigid substrate 500 is as shown in FIGS. 6A and 6B.

Referring to FIG. 7, in an embodiment, after the above steps are completed, a fifth cutting line 650 is formed, which can penetrate all the layers between the first rigid substrate 100 and the second rigid substrate 500 from top to bottom. That is, the fifth cutting line 650 is penetrated from the first surface 101 of the first rigid substrate 100 to the first surface 501 of the second rigid substrate 500. The fifth cutting line 650, the third cutting line 530, and the fourth cutting line 540 at least substantially enclose the intermediate portion 330 of the flexible circuit board 300. In one embodiment, as shown in FIG. 7, the fifth cutting line 650 includes 651, 652, and 653 indicated on the left side of FIG. 7, and 654, 655, and 656 indicated on the right side of FIG. The fifth cutting line is labeled 652 and the portion labeled 655 is substantially along the sides of the intermediate portion 330 of the flexible circuit board 300, respectively, and the fifth cutting line is labeled 652 and 655 and the third cutting line 530 and fourth. The cutting line 540 generally encloses a second predetermined removal region 505 of the second rigid substrate 500. The portion of the fifth cutting line designated 652 and 655 and the first cutting line 110 and the second cutting line 120 substantially enclose a first predetermined removal region 105 of the circuit board 300. Since the fifth cutting line 650 is penetrated from the second rigid substrate 500 to the first rigid substrate 100, the portion of the fifth cutting line marks 651, 652, 653 and the area enclosed by the boundary 630 may also be completely removed, while The portion of the fifth cut line designation 654, 655, 656 and the area enclosed by the boundary 640 may also be completely removed. Figure 8 is a top view showing the removal of the above two parts.

Then, the second rigid substrate 500 located above the intermediate portion 330 of the flexible circuit board 300 is removed, and the first rigid substrate 100 located under the intermediate portion 330 of the flexible circuit board 300 is removed. As shown in FIGS. 9A and 9B, in an embodiment, the second rigid substrate 500 located at a portion above the intermediate portion 330 has only a second adhesive layer 400 having a small area in the vicinity of the third and fourth cutting lines 530, 540. Therefore, the second rigid substrate 500 between the third cutting line 530 and the fourth cutting line 540 at a portion above the intermediate portion 330 can be easily removed. Similarly, the first rigid substrate 100 between the first cutting line 110 and the second cutting line 120 at a portion below the intermediate portion 330 may be removed to expose the intermediate portion 330 of the flexible circuit board 300. Therefore, in FIG. 9A, the first portion 310 of the flexible circuit board 300 is connected to one multilayer hard circuit board 510, and the second portion 320 of the flexible circuit board 300 is connected to the other multilayer hard circuit board 520. A two-layer rigid circuit board is connected between the flexible circuit boards 300 to complete a soft and hard composite circuit board.

Of course, in the above manufacturing method, there are other embodiments. For example, the fifth cutting line encloses a closed area with the other cutting lines and removes all layers in this area. For example, the fifth cutting line 650 includes only 652 indicated on the left side of FIG. 7 and 655 indicated on the right side of FIG. Therefore, only the second rigid substrate 500 and the first rigid substrate 100 above and below the intermediate portion 330 of the flexible circuit board 300 will be removed.

In other embodiments, the second adhesive layer 400 described above may be formed on the second surface 502 of the second rigid substrate 500, and then subjected to pressing and subsequent steps, which will be described in detail below.

The second rigid substrate 500 is prepared before or after or at the same time as the structure shown in FIG. 3B. As described above, the opposite sides of the second rigid substrate 500 respectively have a first surface 501 and a second surface 502, and The second hard substrate 500 has a second copper layer 503 on the first surface thereof. And forming a third cutting line 530 and a fourth cutting line 540 on the second rigid substrate 500 according to the arrangement of the first and second cutting lines 110, 120 on the first rigid substrate 100, and the third and fourth cutting lines 530, 540 extend through the second rigid substrate 500.

Next, a second adhesive layer 400 is formed on the second surface 502 of the second rigid substrate 500. The second adhesive layer 400 has a second opening 420 to expose a portion of the second surface 502, and the second adhesive layer 400 covers the third and fourth cutting lines 530, 540. In an embodiment, the third and fourth cutting lines 540 are substantially parallel to the perimeter of the second opening 420.

Then, the second rigid substrate 500 on which the second adhesive layer 400 is formed is pressed together with the first rigid substrate 100 on which the flexible circuit board 300 is disposed, so that the flexible circuit board 300 is placed on the first adhesive layer 200 and Between two adhesive layers 400. The third cutting line 530, the fourth cutting line 540, and the second opening 420 are respectively located above the first cutting line 110, the second cutting line 120, and the first opening 210, and complete the structure as shown in FIG. 5B. Subsequent processes can then be performed, such as forming a via, an electrical connection layer, or a process of patterning the first copper layer and the second copper layer.

Of course, there are other embodiments in the above manufacturing method. For example, after completing the structure as shown in FIG. 6B, the build-up process of the board can be performed. Referring to FIG. 6C, in an embodiment, the first build-up board 710, the second build-up board 720, and the third build-up board 730 are sequentially formed on the first surface 501 of the second rigid substrate 500, and A fourth build-up layer 740, a fifth build-up plate 750, and a sixth build-up plate 760 are sequentially formed on the first surface 101 of the first rigid substrate 100. The first build-up board 710, the second build-up board 720, and the third build-up board 730 have a first circuit 712, a second circuit 722, and a third circuit 732, respectively. The fourth build-up board 740, the fifth build-up board 750, and the sixth build-up board 760 have a fourth circuit 742, a fifth circuit 752, and a sixth circuit 762, respectively. The above-mentioned build-up board can be used to increase the conductive line. For example, different circuit patterns can be formed on different build-up boards to form a three-degree space circuit structure, and the build-up board can be, for example, an FR4 substrate. The fabrication of the build-up circuit structure on the board is well known to those skilled in the art. It should be noted, however, that in an embodiment of the present invention, when the first build-up layer 710, the second build-up layer 720, and the third build-up layer 730 are formed, the first build-up layer 710, the second build-up layer 720, and the third increase must be added. Cutting lines (714, 716, 724, 726, 734, 736) corresponding to the third and fourth cutting lines 530, 540 are formed in the layer 730, and corresponding to the first and the second in the fourth build-up layer 740, the fifth build-up layer 750, and the sixth build-up layer 760. The cutting lines (744, 746, 754, 756, 764, 766) of the two cutting lines 110, 120 are as shown in Fig. 6C.

After the above steps are completed, the fifth cut line 650 is formed through all of the build-up structures (710, 720, 730, 740, 750, 760) and all layers between the first rigid substrate 100 to the second rigid substrate 500. The manner in which the fifth cutting line 650 is formed is as described above and as shown in FIG. Next, the area enclosed by the fifth cutting line and the boundary is removed, as described above and shown in FIG. Then, the second rigid substrate 500 and the first, second and third build-up layers (710, 720, 730) located above the intermediate portion 330 of the flexible circuit board 300 are removed, and the first portion under the intermediate portion 330 of the flexible circuit board 300 is removed. A rigid substrate 100 and fourth, fifth and sixth build-up layers (740, 750, 760) are exposed to expose the intermediate portion 330 of the flexible circuit board 300. The soft and hard composite circuit boards are completed as described above and shown in FIGS. 9A and 9C.

It will be apparent from the above-described embodiments of the present invention that the application of the present invention can have the following advantages. (1) The flexible circuit board is sandwiched between two rigid substrates in a planar manner, and the flexible bonding board can be completed by using an automatic bonding machine to achieve automation, and manual steps can be reduced to increase the volume rate. (2) The connection between the rigid substrate and the flexible circuit board is stable and the reliability is high. (3) During the fabrication process, the predetermined removal area of the rigid substrate 500 is retained, so that the flexible circuit board is protected from being formed in the formation of the connection hole, the electrical connection layer, the patterned metal layer, or other build-up process. Damage, improve the yield of soft and hard composite boards.

Although the present invention has been disclosed in the above embodiments, it is not intended to limit the present invention, and the present invention can be modified and modified without departing from the spirit and scope of the present invention. The scope is subject to the definition of the scope of the patent application attached.

100. . . First rigid substrate

101. . . First surface

102. . . Second surface

103. . . First copper layer

105. . . First scheduled removal area

107. . . First conductive line

110. . . First cutting line

120. . . Second cutting line

200. . . First adhesive layer

201. . . First surface of the first adhesive layer

202. . . Second surface of the first adhesive layer

210. . . First opening

300. . . Flexible circuit board

301. . . First protective layer

302. . . First conductive layer

303. . . Insulation

304. . . Second conductive layer

305. . . Second protective layer

310. . . First

320. . . Second part

330. . . Middle part

400. . . Second adhesive layer

401. . . First surface of the second adhesive layer

402. . . Second surface of the second adhesive layer

410. . . Fill layer

420. . . Second opening

500. . . Second rigid substrate

501. . . First surface

502. . . Second surface

503. . . Second copper layer

505. . . Second scheduled removal area

507. . . Second conductive line

510,520. . . Multi-layer rigid circuit board

530. . . Third cutting line

540. . . Fourth cutting line

601. . . First connection hole

602. . . Second connection hole

603. . . Third connection hole

604. . . Fourth connection hole

610. . . First electrical connection layer

620. . . Second electrical connection layer

630,640. . . boundary

650,651,652,653,654,655,656. . . Fifth cutting line

710. . . First build-up board

712. . . First circuit

720. . . Second build-up board

722. . . Second circuit

730. . . Third build-up board

732. . . Third circuit

740. . . Fourth build-up board

742. . . Fourth circuit

750. . . Fifth build-up board

752. . . Fifth circuit

760. . . Sixth build-up board

762. . . Sixth circuit

1 to 9 are views showing a manufacturing process of a manufacturing method according to an embodiment of the present invention.

330. . . Middle part

530. . . Third cutting line

540. . . Fourth cutting line

630,640. . . boundary

650,651,652,653,654,655,656. . . Fifth cutting line

Claims (11)

A method for manufacturing a soft and hard composite circuit board, comprising: providing a first rigid substrate, wherein opposite sides of the first rigid substrate respectively have a first surface and a second surface, and one of the first rigid substrates is first predetermined The edge of the removal region has a first cutting line and a second cutting line, wherein the first and second cutting lines extend through the first rigid substrate; and a first adhesive layer is adhered to the second surface of the first rigid substrate And the first adhesive layer has a first opening corresponding to the first predetermined removal area to expose a portion of the second surface of the first rigid substrate; and a flexible circuit board is disposed on a portion of the first adhesive layer a first adhesive removal region of the first rigid substrate; a second adhesive layer adhered to the portion of the flexible circuit board and the first adhesive layer not covered by the flexible circuit board, wherein the second adhesive layer The layer has a second opening, and the second opening position corresponds to the first opening; a second rigid substrate and the second adhesive layer are adhered, and the opposite sides of the second rigid substrate respectively have a first surface as well as a second surface, wherein the second surface of the second rigid substrate contacts the second adhesive layer, and the second predetermined removal region edge of the second rigid substrate has a third cutting line extending through one of the second rigid substrates And a fourth cutting line, and wherein the third cutting line corresponds to the top of the first cutting line, and the fourth cutting line corresponds to the second cutting line. The method of claim 1, wherein the flexible circuit board comprises: an intermediate portion located above the first opening; a first portion extending from the one end of the intermediate portion across the first cut And a second portion extending from the other end of the intermediate portion across the second cutting line. The method of claim 2, wherein the flexible circuit board comprises: a first protective layer disposed on an outer surface of the flexible circuit board adjacent to the first adhesive layer; and a second protective layer disposed on the a flexible circuit board adjacent to the other outer surface of the second adhesive layer; an insulating layer disposed between the first protective layer and the second protective layer; a first conductive layer disposed on the insulating layer and the Between the first protective layers; and a second conductive layer disposed between the insulating layer and the second protective layer. The method of claim 3, after the first rigid substrate is disposed on the first adhesive layer, further comprising: forming a first connection hole to expose the first portion located in the first portion of the flexible circuit board a conductive layer; and a second connection hole to expose the first conductive layer in the second portion of the flexible circuit board; wherein the first and second connection holes penetrate the first rigid substrate, the first The adhesive layer and the first protective layer of the flexible circuit board. The method of claim 3, after configuring the second rigid substrate on the second adhesive layer, further comprising: Forming a third connection hole to expose the second conductive layer located in the first portion of the flexible circuit board; and forming a fourth connection hole to expose the second portion located in the second portion of the flexible circuit board a conductive layer; wherein the third and fourth connecting holes penetrate the second rigid substrate, the second adhesive layer, and the second protective layer of the flexible circuit board. The method of claim 1, wherein the first rigid substrate has a first metal layer on the first surface and a second metal layer on the first surface of the second rigid substrate. The method of claim 6, after forming the third and fourth connection holes, further comprising: forming a first electrical connection layer in the first and second connection holes to electrically connect the first conductive a layer and the first metal layer; and forming a second electrical connection layer in the third and fourth connection holes to electrically connect the second conductive layer and the second metal layer. The method of claim 7, after forming the first and second electrical connection layers, further comprising the steps of: patterning the first metal layer and the second metal layer. The method of claim 8, after patterning the first and second metal layers, further comprising: forming at least one buildup structure on the first surface. The method of claim 8, after patterning the first and second metal layers, further comprising: forming a fifth cutting line, wherein the fifth cutting line, the third cutting line, and the fourth cutting line At least substantially surrounding the intermediate portion of the flexible circuit board, and wherein the fifth cutting line extends from the first surface of the first rigid substrate to the first surface of the second rigid substrate. The method of claim 10, after forming the fifth cutting line, further comprising: removing a portion of the first rigid substrate located under the intermediate portion of the flexible circuit board; and removing the portion located on the flexible circuit board A portion of the second rigid substrate above the intermediate portion.