Patent Publication Number: US-9900997-B2

Title: Manufacturing method of a rigid flex board module

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     This application is a divisional application of and claims the priority benefit of a prior application Ser. No. 14/093,660, filed on Dec. 2, 2013, now U.S. Pat. No. 9,253,898, which claims the priority benefit of Taiwan application serial no. 102130435, filed on Aug. 26, 2013. The entirety of each of the above-mentioned patent applications is hereby incorporated by reference herein and made a part of this specification. 
    
    
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The instant disclosure relates to a rigid flex board module and the manufacturing method of the same; in particular, to a rigid flex board module including a high-density interconnected circuit board and the manufacturing method of the same. 
     2. Description of Related Art 
     Conventional rigid flex board module includes a flexible circuit board, a rigid circuit board and an adhesive layer. The flexible circuit board typically includes a bending portion and a jointing portion connected to the bending portion. The rigid circuit board is disposed on the jointing portion and exposes the bending portion to provide flexible yet rigid properties. 
     The trend of 3C product such as smart phones, liquid crystal displays, PC tablets and laptops has been toward multifunction, so that the high density circuitry in rigid flex board modules is indispensable. 
     SUMMARY OF THE INVENTION 
     The object of the instant disclosure is to provide a rigid flex board module having partial high-density interconnected circuit design and a manufacturing method for the rigid flex board module. 
     In order to achieve the aforementioned objects, according to an embodiment of the instant disclosure, a rigid flex board module is provided, which includes a rigid flex circuit board and a high-density interconnected circuit board. The rigid flex circuit board includes a flexible circuit board, a first rigid circuit board and a first adhesive layer. The flexible circuit board includes a bending portion and a jointing portion connected to the bending portion. The first rigid circuit board is disposed on the jointing portion exposing the bending portion. The first rigid circuit board is electrically connected to the flexible circuit board. The first adhesive layer is connected to the first rigid circuit board and the jointing portion. The high-density interconnected circuit board is disposed in and electrically connected to the first rigid circuit board. 
     The instant disclosure also provides a manufacturing method for providing the rigid flex board module. The method includes providing a rigid flex initial substrate including a flexible circuit board, a first rigid substrate, and a first insulating layer. The flexible circuit board includes a bending portion and a jointing portion connected to the bending portion. The first rigid substrate is arranged above the flexible circuit board and the first insulating layer connects the first rigid substrate and the flexible circuit board. A second opening is formed on the rigid flex initial substrate and through the first rigid substrate and the first insulating layer. A high-density interconnected circuit layer is disposed in the second opening. A pair of insulating adhesive layers is formed on two sides of the rigid flex initial substrate. A pair of multi-layer circuit layers is formed on the insulating adhesive layers. A plurality of conductive posts is formed in the insulating adhesive layers such that the multi-layer circuit layers, the high-density interconnected circuit layer, and the rigid flex initial substrate are electrically connected to each other. Successively, portions of the first rigid substrate, portions of the first insulating layer, portions of the insulating adhesive layer, and portions of the multi-layer circuit layer above the bending portion are removed. 
     In summary, the instant disclosure provides a rigid flex board module and the manufacturing method for the same. The rigid flex board module includes a rigid flex circuit board and a high-density interconnected circuit board. The high-density interconnected circuit board is disposed in the rigid flex circuit board where high density circuit design is preferred. Since the high-density interconnected circuit board and the rigid flex circuit board in the manufacturing method of the instant disclosure can be separately designed, circuitry can first be designed on the high-density interconnected circuit board to reduce poor overall yield due to poor installation of the high-density interconnected circuit board in the rigid flex circuit board, thus increase yield. 
     In order to further understand the instant disclosure, the following embodiments and illustrations are provided. However, the detailed description and drawings are merely illustrative of the disclosure, rather than limiting the scope being defined by the appended claims and equivalents thereof. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1A  is a cross-section view of a rigid flex board module in accordance with a first embodiment of the instant disclosure; 
         FIG. 1B to 1G  are cross-sectional views of a manufacturing method for the rigid flex board module in accordance with the first embodiment of the instant disclosure; 
         FIG. 2A to 2B  are cross-sectional views of the manufacturing method for the rigid flex board module in accordance with a second embodiment of the instant disclosure; and 
         FIG. 3  is a cross-sectional view of the rigid flex board module in accordance with a second embodiment of the instant disclosure. 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     The aforementioned illustrations and detailed descriptions are exemplarities for the purpose of further explaining the scope of the instant disclosure. Other objectives and advantages related to the instant disclosure will be illustrated in the subsequent descriptions and appended drawings. 
     Please refer to  FIG. 1A . A rigid flex module  1  includes a rigid flex circuit board  10 ″, a high-density interconnected circuit board  800 , two pairs of multi-layer circuit layers  410 ′,  420 ′, a plurality of conductive posts  900 , and a through hole H. 
     As shown in  FIG. 1A , the rigid flex circuit board  10 ″ also includes a flexible circuit board  100 ′, a first adhesive layer  200 ″, a first rigid circuit board  300 ″, a second adhesive layer  600 ″, and a second rigid circuit board  700 ″. The flexible circuit board  100 ′ includes a bending portion B and a jointing portion A connected to the bending portion B. The first rigid circuit board  300 ″ and the second rigid circuit board  700 ″ are disposed on two sides of the flexible circuit board  100 ′. Specifically, the first rigid circuit board  300 ″ and the second rigid circuit board  700 ″ are disposed on two sides of the jointing portion A of the flexible circuit board  100 ′, which exposes the bending portion B. The first adhesive layer  200 ″ is connected to the first rigid circuit board  300 ″ and one of the sides of the jointing portion A, and the second adhesive layer  600 ″ is connected to the second rigid circuit board  700 ″ and the other side of the jointing portion A. 
     Moreover, in the instant embodiment, the quantity of the jointing portion A is two and the quantity of the bending portion B is one, in which the one bending portion B is arranged between the two jointing portions A. However, the configuration of the bending and jointing portions A, B is not limited hereto. In another embodiment, one jointing portion A is connected to one bending portion B. In addition, the respective quantity of both the jointing portion A and bending portion B can be more than one, and one bending portion B is arranged between two jointing portion. 
     Furthermore, in the instant embodiment, the rigid flex circuit board  10 ″ includes the flexible circuit board  100 ′, the first rigid circuit board  300 ″, and the second rigid circuit board  700 ″, where the flexible circuit board  100 ′ is arranged between the first rigid circuit board  300 ″ and the second rigid circuit board  700 ″. However, the quantities of the flexible circuit board and the rigid circuit board are not limited in the instant disclosure. In another embodiment, the flexible circuit board may only include one layer of flexible circuit board, and one layer of rigid circuit board arranged on top of the jointing portion of the flexible circuit board. 
     Notably, the flexible circuit board  100 ″, the first rigid circuit board  300 ″ and the second rigid circuit board  700 ″ include a plurality of insulating layers and circuit layers (one layer of insulating layer and one layer of circuit layer are shown in figures). The first adhesive layer  200 ″ and the second adhesive layer  600 ″ can be made of polypropylene (PP) resin, but not limited hereto. The first adhesive layer  200 ″ and the second adhesive layer  600 ″ can also be made of other polymer adhesives. 
     In  FIG. 1A , the high-density interconnected circuit board  800  is disposed in the rigid flex circuit board  10 ″ and is electrically connected to the first rigid circuit board  300 ″, the flexible circuit board  100 ′ and the second rigid circuit board  700 ″. Specifically, the rigid flex module  1  has a second opening h 2 . The second opening h 2  is formed through the first rigid circuit board  300 ″, the flexible circuit board  100 ′ and the second rigid circuit board  700 ″. Moreover, the second opening h 2  may have a cross-sectional shape of a non-point symmetric pattern, such as the shape of a lightning bolt, whereas the high-density interconnected circuit board  800  has a cross-sectional shape identical to that of the second opening h 2 . Since the cross-sectional shape of the second opening h 2  is a non-point symmetric pattern, the high-density interconnected circuit board  800  can be properly disposed in the second opening h 2 , which facilitates the conductive posts  900  forming downstream can be properly and electrically connected to the pads (not labeled in figures) on the high-density interconnected circuit board  800 . 
     Notably, the high-density interconnected circuit board  800  is formed by a plurality of insulating layers and circuit layers. In terms of thickness of the high-density interconnected circuit board  800 , the total number of circuit layer is larger than the total number of the rigid flex circuit board  10 ″, or larger than the total number of the first rigid circuit board  300 ″, the flexible circuit board  100 ′, and the second rigid circuit board  700 ″ combined. In other words, the density of the circuit layer of the high-density interconnected circuit board  800  is larger than the circuit layer density of the rigid flex circuit board  10 ″. In addition, the high-density interconnected circuit board  800  in the instant embodiment amounts to one as shown in  FIG. 1A . However, in another embodiment, the quantity of the high-density interconnected circuit board  800  is more than one, and not limited hereto. 
     Moreover, the high-density interconnected circuit board  800  is disposed in the rigid flex circuit board  10 ″ in the instant embodiment. In practice, the high-density interconnected circuit board  800  and the rigid flex circuit board  10 ″ can be separately designed. The design of the rigid flex circuit board  10 ″ can be relatively simple, in which the second opening h 2  is formed in the rigid flex circuit board  10 ″ at a region where dense circuitry may be required, then separately design the high-density interconnected circuit board  800 , and dispose the high-density interconnected circuit board  800  into the second opening h 2 . The rigid flex board module  1  of the instant disclosure can first select the high-density interconnected circuit board  800 , which reduces poor installation of the high-density interconnected circuit board  800  and increases yield, whereas the conventional arts, the high-density interconnected circuit board  800  is directly design on the module to provide dense circuitry. 
     Furthermore in  FIG. 1A , the rigid flex board module  1  further includes two pairs of multi-layer circuit layers  410 ′,  420 ′, the conductive posts  900  and the through hole H. The multi-layer circuit layers  410 ′ are disposed on two sides of both the rigid flex circuit board  10 ′ and the high-density interconnected circuit board  800 . In other words, the first rigid circuit board  300 ″, the flexible circuit board  100 ′, the second rigid circuit board  700 ″, and the high-density interconnected circuit board  800  are arranged between the pair of multi-layer circuit layers  410 ′. Specifically, one of the multi-layer circuit layers  410 ′ is attached to one side of the first rigid circuit board  300 ″ and one side of the high-density interconnected circuit board  800 , whereas the other multi-layer circuit layer  410 ′ is attached to one side of the second rigid circuit board  700 ″, and the other side of the high-density interconnected circuit board  800 . Moreover, the multi-layer circuit layers  410 ′ expose the bending portion B. 
     Notably, the multi-layer circuit layers  410 ′ includes at least one adhesive layer and at least one circuit layer (not shown in figures). The adhesive layer is made of polypropylene or other polymer adhesives, but not limited hereto. The multi-layer circuit layers  420 ′ are respectively disposed on the multi-layer circuit layers  410 ′ exposing the bending portion B. The conductive posts  900  provide electrical connectivity between the multi-layer circuit layers  410 ′, the multi-layer circuit layers  420 ′, the high-density interconnected circuit board  800 , the first rigid circuit board  300 ″, and the second rigid circuit board  700 ″. The through hole H passes through the rigid flex circuit board  10 ″ in order to interconnect internal circuits of the rigid flex circuit board  10 ″. 
     Aforementioned is the structure of the rigid flex board module  1  of the instant embodiment. The instant disclosure also includes a manufacturing method for the rigid flex board module  1 . Please refer to  FIG. 1B to 1G . As shown in  FIG. 1B , the first step includes providing a rigid flex initial substrate  10 . The rigid flex initial substrate  10  includes a flexible circuit board  100 , a pair of release layers  500 , a first insulating layer  200 , a first rigid substrate  300 , a second insulating layer  600 , and a second rigid substrate  700 . The flexible circuit board  100  includes a bending portion B, and a jointing portion A connected to the bending portion B. The release layers  500  are respectively disposed on two sides of the flexible circuit board  100  covering the bending portion B. The first rigid substrate  300  and the second rigid substrate  700  are respectively disposed on two release layer  500 s and the flexible circuit board  100  covers the jointing portion A and the bending portion B of the flexible circuit board  100 . The first insulating layer  200  is connected between the first rigid substrate  300  and the flexible circuit board  100 , whereas the second insulating layer  600  is connected between the second rigid substrate  700  and the flexible circuit board  100 . 
     Notably, the flexible circuit board  100 , the first rigid substrate  300  and the second rigid substrate  700  include a plurality of insulating layers and circuit layers (figure shows only one insulating layer and one circuit layer). 
     In addition, one bending portion B is arranged between two jointing portions in the instant embodiment, but not limited hereto. In another embodiment, only one jointing portion A is connected to one bending portion B. Besides, the quantities of the jointing portion A and the bending portion B can be more than one, as long as one bending portion B is arranged between two jointing portions A. 
     Moreover, the rigid flex initial circuit board  10  includes the first rigid substrate  300 , the second rigid substrate  700 , and the flexible circuit board  100  arranged between the first and second rigid substrate  300 ,  700  in the instant embodiment. However, the quantities of the flexible circuit board  100  and the rigid circuit boards are not limited to examples provided herein. In another embodiment, the rigid flex initial circuit board  10  can only include a layer of rigid substrate and a layer of flexible circuit board. 
     Please refer to  FIG. 1C . A pair of first openings h 1  is formed in the rigid flex initial substrate  10 ′ corresponding to the position of the bending portion B. As shown in  FIG. 1C , one of the first openings h 1  is formed through the first rigid substrate  300 ′ and the first insulating layer  200 ′ to expose one of the sides of one release layer  500  on the flexible circuit board  100 . The other first opening h 1  is formed through the second rigid substrate  700 ′ and the second insulating layer  600 ′ to expose one of the sides of another release layer  500 . In other words, the first openings h 1  expose two sides of the bending portion B of flexible circuit board  100  while the pair of release layers  500  can protect the flexible circuit board where the bending portion B is located. 
     Notably, portions of each of the following the first rigid substrate  300 ″, the first insulating layer  200 ″, the second insulating layer  600 ″, the second rigid substrate  700 ″ are removed by ultraviolet laser, routing or punching. In addition, the release layers  500  on two sides of the bending portion B can be protective layers of the flexible circuit board  100 ′ to prevent damages therefrom during removal. 
     Please refer to  FIG. 1D . One second opening h 2  is formed in the rigid flex circuit board  10 ″ corresponding to the position of the jointing portion A. As shown in  FIG. 1D , the second opening h 2  passes through the first rigid substrate  300 ″, the first insulating layer  200 ″, the flexible circuit board  100 ″, the second insulating layer  600 ″, and the second rigid substrate  700 ″. Notably, the second opening h 2  may have a cross-sectional shape of a non-point symmetric pattern such as a lightning bolt. Moreover, the second opening h 2  can be formed by ultraviolet laser (UV), routing, or punching. Thereafter, forming a through hole H in the rigid flex circuit board  10 ″. The through hole H passes through the first rigid substrate  300 ″, the first insulating layer  200 ″, the flexible circuit board  100 ′, the second insulating layer  600 ″, and the second rigid substrate  700 ″. The through hole H is for electrically jointing the internal circuits of the rigid flex circuit board  10 ″. 
     Please refer to  FIG. 1E . The rigid flex circuit board  10 ″ is disposed on a carrier  20 . The carrier  20  has a plurality of fixing members  22  to fix the rigid flex circuit board  10 ″. The fixing members  22  extend onto the first rigid circuit board  300 ″. The carrier  20  also has a buffer material  30  and a multi-layer circuit layer  410  arranged thereon. The second rigid substrate  700 ″ of the rigid flex circuit board  10 ″ is attached on the multi-layer circuit layer  410 . 
     Notably, the multi-layer circuit layer  410  includes at least one adhesive layer and at least one circuit layer (not labeled in figures), and the multi-layer circuit layer  410  has a first opening h 1  parallel to the second opening h 2 . The adhesive layer can be made of polypropylene resin or other polymer adhesives, but not limited hereto. Furthermore, the buffer layer  30  can be made of polyethylene terephthalate (PET), but not limited hereto. The buffer layer  30  is arranged between the multi-layer circuit layer  410  and the carrier  20  to prevent attachment therebetween. 
     Thereafter, the high-density interconnected circuit board  800  is disposed in the second opening h 2 . Notably, the high-density interconnected circuit board  800  has a cross-sectional shape of a non-point symmetric patter, which is identical to the cross-sectional shape of the second opening h 2 , such that the high-density interconnected circuit board  800  can be fittingly align with and disposed in the second opening h 2 . 
     Furthermore, the high-density interconnected circuit board  800  is also formed by a plurality of adhesive layers, insulating layers, and circuit layers. The total number of circuit layers of the high-density interconnected circuit board  800  is larger than the total number of circuit layers of the rigid flex circuit board  10 ″. The total number of circuit layers of the rigid flex circuit board  10 ″ includes the total number of layers of the first rigid substrate  300 ″, the flexible circuit board  100 ′, and the second rigid substrate  700 ″. In addition, as shown in  FIG. 1E , one high-density interconnected circuit board  800  is in the instant embodiment, but the quantity is not limited hereto. In another embodiment, the high-density interconnected circuit board  800  can be more than one. 
     Notably, one high-density interconnected circuit board  800  is disposed in the rigid flex circuit board  10 ″ in the instant embodiment. In practice, the high-density interconnected circuit board  800  and the rigid flex circuit board  10 ″ can be separately designed. The design of the rigid flex circuit board  10 ″ can be relatively simple and less layers. The second opening h 2  is formed in the rigid flex circuit board  10 ″ at a region where dense circuitry may be required, then separately design the high-density interconnected circuit board  800 , and dispose the high-density interconnected circuit board  800  into the second opening h 2 . The rigid flex board module  1  of the instant disclosure can first select the high-density interconnected circuit board  800 , which reduces poor installation of the high-density interconnected circuit board  800  and increases yield, whereas the conventional arts, the high-density interconnected circuit board  800  is directly design on the module to provide dense circuitry. 
     The other multi-layer circuit layer  410  covers on the first rigid substrate  300 ″ and the high-density interconnected circuit board  800  such that the rigid flex circuit board  10 ″ and the high-density interconnected circuit board  800  are arranged between the pair of multi-layer circuit layers  410 . Then, the buffer layer  30  is disposed on the upper multi-layer circuit layer  410 . The buffer layer  30  is to protect the multi-layer circuit layer  410 . Notably, the fixing member  22  of the carrier  20  extends onto the upper multi-layer circuit layer  410  and the buffer layer  30 , which fixes the multi-layer circuit layer  410  and the buffer layer  30  to the rigid flex circuit board  10 ″, to facilitate subsequent attachment steps. 
     Moreover, heat is added to the adhesive layer of the multi-layer circuit layers  410  such that the adhesives fill up the first openings h 1 , which provides adhesion between the rigid flex circuit board  10 ″ and the high-density interconnected circuit board  800 . After heating, the adhesive layer resembles a semi-liquid form and has adhesive properties, which temporarily fixes the rigid flex circuit board  10 ″ and the high-density interconnected circuit board  800  between the multi-layer circuit layers  410 . 
     Please refer to  FIG. 1F . The carrier  20  and the buffer layer  30  are removed, and a pair of multi-layer circuit layers  420  is formed on the multi-layer circuit layers  410 . The multi-layer circuit layer  420  also includes at least one adhesive layer and a circuit layer (not labeled in figures, the adhesive layer is made of the same materials as the multi-layer circuit layer  410 ). The step where the multi-layer circuit layer  420  is formed on the multi-layer circuit layer  410  further includes the multi-layer circuit layer  420  attached on the multi-layer circuit layer  410 . Thereafter, heat is added and pressed in order to fix the multi-layer circuit layers  420  on two sides of the high-density interconnected circuit board  800  and the rigid flex circuit board  10 ″. 
     After heat is added and pressed, the adhesive layer solidifies due to phase transition and cannot return to the original state. Notably, when the adhesive layer is heated, portions of the adhesive layer flow to a gap between the high-density interconnected circuit board  800  and the second opening h 2 , such that the high-density interconnected circuit board  800  is fixed in the rigid flex circuit board  10 ″. 
     Please refer to  FIG. 1G . A plurality of conductive posts  900  is formed. Conductive posts  900  can provide electrical connections between the multi-layer circuit layer  420 , multi-layer circuit layer  410 , rigid flex circuit board  10 ″, and the high-density interconnected circuit board  800 . 
     Please refer again to  FIG. 1A . The release layer  500  is removed to expose the bending portion B on two sides of the flexible circuit board  100 ′, thus forming the rigid flex board module  1 . Since the bending portion B of the flexible circuit board  100 ′ is exposed, the rigid flex board module  1  can be bent to provide rigid yet flexible properties. 
     In summary, the first embodiment of the instant disclosure firstly form the first opening h 1 , the second opening h 2 , then multi-layering are performed to form the multi-layer circuit layers  410 ,  420  on two sides of the rigid flex circuit board  10 ″, thus forming the rigid flex board module  1 . 
     Please refer to  FIG. 2A  as the continuation from  FIG. 1B  which provides the steps after the rigid flex initial substrate  10 . Notably, the structure of the rigid flex initial substrate  10  in  FIG. 2A  is similar to the structure in previous embodiment. 
     In the instant embodiment, after one rigid flex initial substrate  10  is provided, one second opening h 2  and one through hole H are formed in the rigid flex circuit board  10 ″. The second opening h 2  is correspondingly formed at the position of the jointing portion A. The second opening h 2  is formed through the first rigid substrate  300 ″, the first insulating layer  200 ″, the flexible circuit board  100 ″, the second insulating layer  600 ″, and the second rigid substrate  700 ″. The cross-sectional shape and the formation of the second opening h 2  and the through hole H are similar to the previous embodiment. 
     Please refer to  FIG. 2B . The rigid flex circuit board  10 ″ is disposed on one carrier  20 . The carrier  20  has a plurality of fixing members  22  to fix the rigid flex circuit board  10 ″. The carrier  20  has a buffer layer  30  and a multi-layer circuit layer  410  thereon. The rigid flex circuit board  10 ″ is arranged above the carrier  20 , and the second rigid substrate  700 ″ of the rigid flex circuit board  10 ″ is attached on the multi-layer circuit layer  410 . 
     The high-density interconnected circuit board  800  is then disposed in the second opening h 2 . Notably, the high-density interconnected circuit board  800  has a cross-sectional shape same as the second opening h 2 , such that the high-density interconnected circuit board  800  can align with and fittingly disposed in the second opening h 2 . As shown in  FIG. 2B , another multi-layer circuit layer  410  and buffer layer  30  cover over the first rigid substrate  300 ″ and the high-density interconnected circuit board  800 . Heat is then added such that the rigid flex circuit board  10 ″ and the high-density interconnected circuit board  800  are fixed between the multi-layer circuit layers  410 . 
     Please refer to  FIG. 1A . One pair of multi-layer circuit layer  420  is formed on the multi-layer circuit layer  410 . After heat is added and pressed, the multi-layer circuit layer  420  is fixed at two sides of the rigid flex circuit board  10 ″, the high-density interconnected circuit board  800 , and the multi-layer circuit layer  410 . Moreover, a plurality of conductive posts  900  are formed such that the multi-layer circuit layers  420 , the multi-layer circuit layers  410 , the rigid flex circuit board  10 ″, and the high-density interconnected circuit board  800  are electrically connected to each other. 
     Successively, a pair of first openings h 1  is formed in the rigid flex initial substrate  10 ′ corresponding to the position of the bending portion B. The pair of first openings h 1  exposes the bending portion B on two sides of the flexible circuit board  100 , thus forming the rigid flex board module  1 . The first openings h 1  can be formed by ultraviolet (UV) laser, routing, or punching. In addition, since the flexible circuit board  100 ′ exposes the bending portion B, the rigid flex board module  1  can be bent to provide flexible yet rigid properties. 
     In summary, in the second embodiment of the instant disclosure, the second openings h 2  are first formed, and the multi-layer circuit layers  410 ,  420  are formed on two sides of the rigid flex circuit board  10 ″. Successively, the pair of first openings h 1  is formed to expose the bending portion B on two sides of the flexible circuit board  100 . Thus, the rigid flex board module  1  is formed. 
     Notably in the first embodiment of the instant disclosure, the multi-layer circuit layer  410  having the first opening h 1  is pressed after the first opening h 1  is formed, which is more preferred for rigid flex board module  1  having a relatively thick first rigid substrate  300 ″, in order to reduce the poor accuracy in forming the openings or poor yield due to the relatively thick substrate. In the second embodiment, the procedure differs in that the first opening h 1  is formed specifically at the position of the first opening h 1  in the last step, which is more preferred for the rigid flex board module  1  having a relatively thin first rigid substrate  300 ″. 
     Moreover, the first and the second embodiments of the instant disclosure differ in the sequence of forming the first opening h 1 , second opening h 2 , and the multi-layering. Other structures such as the high-density interconnected circuit board  800  are substantially the same as previous embodiment, thus not further discussed. 
     Please refer to  FIG. 3 . The structure of the rigid flex board module  1 ′ is substantially the same as the previous embodiment, which also includes the rigid flex circuit board  10 ″, the high-density interconnected circuit board  800 , two pairs of multi-layer circuit layer  410 ′,  420 ′, and the plurality of conductive posts  900 . The rigid flex circuit board  10 ″ further includes the flexible circuit board  100 ′, the first adhesive layer  200 ″, the first rigid circuit board  300 ″, the second adhesive layer  600 ″, and the second rigid circuit board  700 ″. 
     However, the rigid flex board module  1 ′ of the instant embodiment differs from the rigid flex board module  1  of the first embodiment in that the rigid flex board module  1 ′ has a first second opening h 2 ′ which passes through the first rigid circuit board  300 ″ and the first adhesive layer  200 ″. The high-density interconnected circuit board  800 ′ can fittingly align with and be disposed in the second opening h 2 ′. Notably, the total number of circuit layer of the high-density interconnected circuit board  800 ′ is larger than the total number of circuit layer of the first rigid circuit board  300 ″ and the first adhesive layer  200 ″ combined. In other words, the density of circuits in the circuit layer of the high-density interconnected circuit board  800 ′ is higher than the density of circuits in the first rigid circuit board  300 ″ and the first adhesive layer  200 ″ combined. 
     Furthermore, in another embodiment, the second opening h 2 ′ can also passes through the second adhesive layer  600 ″, and the second rigid circuit board  700 ″. The total number of circuit layer of the high-density interconnected circuit board  800 ′ is larger than the total number of circuit layer of the second adhesive layer  600 ″ and the second rigid circuit board  700 ″ combined. The position of the high-density interconnected circuit board  800 ′ is not limited hereto. 
     In summary, the instant disclosure provides a rigid flex board module a manufacturing method of the same. The rigid flex board module includes a rigid flex circuit board and a high-density interconnected circuit board. The high-density interconnected circuit board is disposed in the rigid flex circuit board in regions thereof where high density circuitry is preferred. Since the high-density interconnected circuit board and the rigid flex circuit board can be separately designed, yield rate of the rigid flex circuit board can be successively increased. 
     The figures and descriptions supra set forth illustrated the preferred embodiments of the instant disclosure; however, the characteristics of the instant disclosure are by no means restricted thereto. All changes, alternations, combinations or modifications conveniently considered by those skilled in the art are deemed to be encompassed within the scope of the instant disclosure delineated by the following claims.