JP2011114251A - Flexible printed circuit board and method of manufacturing the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a flexible printed circuit board with superior productivity. <P>SOLUTION: The flexible printed circuit board 1 is constituted by stacking a first circuit board 20 and a second circuit board 40 with an adhesive layer 30 interposed therebetween, and forming a hollow 31 between the first and second circuit boards 20 and 40. A sub-hollow 32 communicating with the hollow 31 is formed in the adhesive layer 30 outside a region to become a product 10, and in at least one of the first and second circuit boards 20 and 40, through-holes 25 and 45 which are open to the sub-hollow at an opening are formed, and closed with air-permeable and waterproof closing members 51 and 52. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a flexible printed wiring board in which a hollow portion is formed.

  A multiple flexible wiring board is known in which a hollow portion is formed in a flexible wiring board corresponding part to be a product (see, for example, Patent Document 1).

JP 2007-142045 A

  In the above-described multiple flexible wiring board, for example, when a heating process such as reflow is performed, it is necessary to form a through hole that releases the pressure in the hollow portion in order to prevent abnormal appearance of the product due to expansion of the hollow portion.

  On the other hand, when performing a wet process such as plating, for example, it is necessary to close the through hole in order to prevent liquid from entering the hollow portion.

  That is, this multiple flexible wiring board has a problem in that it is inferior in productivity because it requires an operation of opening the through hole during the heating process and closing the through hole during the wet process.

  The problem to be solved by the present invention is to provide a flexible printed wiring board excellent in productivity and a method for manufacturing the same.

  The flexible printed wiring board according to the present invention is a flexible printed circuit board in which a first circuit board and a second circuit board are laminated via an adhesive layer, and a hollow portion is formed between the first and second circuit boards. In the printed wiring board, a sub-hollow portion communicating with the hollow portion is formed outside a region to be a product in the adhesive layer, and at least one of the first or second circuit boards has the opening at the opening portion. A through-hole opening in the sub-hollow part is formed, and the through-hole is closed by a closing member having air permeability and waterproofness.

  In the above invention, the closing member may be a film-like member attached to at least one of the first or second circuit board so as to close the opening.

  The manufacturing method of the flexible printed wiring board includes a first pattern forming step for forming the first opening pattern to be the hollow portion in the adhesive layer, and a second opening pattern to be the sub hollow portion. A second pattern forming step for forming the adhesive layer; a through hole forming step for forming the through hole in at least one of the first or second circuit board; and the through hole being blocked by the blocking member. And a laminating step of laminating the first circuit board and the second circuit board via the adhesive layer.

  In the flexible printed wiring board according to the present invention, a first circuit board and a second circuit board are laminated via an adhesive layer, and a hollow portion is provided between the first circuit board and the second circuit board. In the flexible printed wiring board formed with, the communication layer is formed with a communication path that communicates the hollow portion to the outside, and the communication path is blocked by a blocking member having air permeability and waterproofness. It is characterized by.

  The manufacturing method of the flexible printed wiring board includes the first pattern forming step of forming the first opening pattern to be the hollow portion in the adhesive layer, and the second opening pattern to be the communication path, A second pattern forming step formed on the adhesive layer; a filling step of filling at least a part of the second opening pattern with the blocking member; and the first circuit board and the first through the adhesive layer. And a laminating step of laminating the two circuit boards.

  In the above invention, the blocking member may be made of porous polytetrafluoroethylene.

  According to the present invention, since the through-hole is closed by the closing member having air permeability and waterproofness, the productivity of the flexible printed wiring board can be improved.

FIG. 1 is a plan view of a flexible printed wiring board according to the first embodiment of the present invention. FIG. 2 is a cross-sectional view taken along line II-II in FIG. FIG. 3 is a cross-sectional view taken along line III-III in FIG. FIG. 4 is an enlarged cross-sectional view of a portion IV in FIG. FIG. 5 is a plan view of the first closing member as seen from the direction V in FIG. FIG. 6 is a cross-sectional view of a main part showing a first modification of the flexible printed wiring board in the first embodiment of the present invention. FIG. 7 is a cross-sectional view of a main part showing a second modification of the flexible printed wiring board in the first embodiment of the present invention. FIG. 8 is a flowchart showing a method for manufacturing a flexible printed wiring board according to the first embodiment of the present invention. FIG. 9 is a perspective view showing a method for manufacturing a flexible printed wiring board according to the first embodiment of the present invention. FIG. 10 is a plan view of a flexible printed wiring board according to the second embodiment of the present invention. 11 is a cross-sectional view taken along line XI-XI in FIG. 12 is a cross-sectional view taken along line XII-XII in FIG. 13 is an enlarged cross-sectional view taken along line XIII-XIII in FIG. FIG. 14 is a flowchart showing a method for manufacturing a flexible printed wiring board according to the second embodiment of the present invention. FIG. 15 is a perspective view showing a method for manufacturing a flexible printed wiring board according to the second embodiment of the present invention. FIG. 16 is a graph showing the results of the high temperature vacuum test in the example of the present invention.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

<< first embodiment >>
1 is a plan view of a flexible printed wiring board according to the present embodiment, FIG. 2 is a cross-sectional view taken along line II-II in FIG. 1, FIG. 3 is a cross-sectional view taken along line III-III in FIG. 2 is an enlarged cross-sectional view of a portion IV, FIG. 5 is a plan view of the first closing member as seen from the direction V in FIG. 4, and FIGS. 6 and 7 are main portions showing a modification of the flexible printed wiring board in the present embodiment. It is sectional drawing.

  As shown in FIG. 1, the flexible printed wiring board 1 in the present embodiment includes four product parts 10 (parts divided by solid lines and provided with a pattern in the figure). The product portion 10 is cut and separated from the flexible printed wiring board 1 to become a flexible printed wiring board as a product, and is incorporated into a hinge portion of a mobile phone, a game machine, or the like, for example. The product portion 10 includes two product rectangular portions 11 and 12 and a product inclined portion 13 that connects the product rectangular portions 11 and 12. In FIG. 1, portions defined by broken lines are a hollow portion 31 and a sub hollow portion 32 in an adhesive layer 30 to be described later.

  As shown in FIG. 2, the flexible printed wiring board 1 includes a first circuit board 20, an adhesive layer 30, a second circuit board 40, a first closing member 51, a second closing member 52, It has.

  The first circuit board 20 includes a first insulating substrate 21, a first circuit layer 22, a second circuit layer 23, and a first coverlay film 24.

  The first insulating substrate 21 is flexible and is made of, for example, polyimide.

  As shown in FIG. 2, the first circuit layer 22 is laminated on the upper surface of the first insulating substrate 21, and is made of, for example, copper formed in a predetermined wiring pattern.

  The second circuit layer 23 is laminated on the lower surface of the first insulating substrate 21 and is made of copper formed in a predetermined wiring pattern, for example, like the first circuit layer 22.

  As shown in FIG. 2, the first coverlay film 24 is laminated on the first circuit layer 22 to protect the first circuit layer 22. The first coverlay film 24 is composed of a first insulating film 24a and a first coverlay adhesive layer 24b.

  The first insulating film 24 a is located on the uppermost layer of the first circuit board 20. The first insulating film 24a has flexibility and insulating properties, and is made of, for example, a film made of polyimide.

  The first coverlay adhesive layer 24b bonds the first insulating film 24a and the first circuit layer 22, and is made of an adhesive made of, for example, an epoxy resin.

  As shown in FIGS. 2 and 4, the first circuit board 20 is formed with a first through hole 25 that allows the hollow portion 31 (described later) to communicate with the outside through the sub-hollow portion 32 (described later). ing. The first through hole 25 penetrates the first circuit board 20 below the sub hollow portion 32 of the adhesive layer 30 and opens at the first opening 24c. In addition, this 1st opening part 24c is located in the part corresponding to the sub hollow part 32 (after-mentioned) of the contact bonding layer 30 in the 1st insulating film 24a. The cross-sectional shape of the first through hole 25 is circular (inner diameter D1), but is not particularly limited and may be rectangular.

  As shown in FIG. 2, the adhesive layer 30 is laminated between the first circuit board 20 and the second circuit board 40 to bond them together. The adhesive layer 30 is made of an adhesive made of, for example, an epoxy resin. A hollow portion 31 and a sub hollow portion 32 are formed in the adhesive layer 30.

  As shown in FIGS. 2 and 3, the hollow portion 31 is a cavity formed between the first and second circuit boards 20 and 40 in the adhesive layer 30 and corresponds to a part of the product portion 10. Formed in the region. In addition, this hollow part 31 is provided in order to improve the flexibility of the product part 10 (flexible printed wiring board used as a product).

  As shown in FIG. 3, the hollow portion 31 includes hollow rectangular portions 31a and 31b and a hollow inclined portion 31c.

  The hollow rectangular portions 31a and 31b are formed in the product rectangular portions 11 and 12 of the product portion 10 in a region corresponding to a half on the product inclined portion 13 side from the central portion. The widths of the hollow rectangular portions 31a and 31b are relatively larger than the widths of the product rectangular portions 11 and 12. In FIG. 3, a part defined by a broken line is the product part 10.

  The hollow inclined portion 31 c is a portion connecting the hollow rectangular portions 31 a and 31 b and is formed in a region corresponding to the product inclined portion 13. Further, the width of the hollow inclined portion 31 c is relatively larger than the width of the product inclined portion 13.

  The sub-hollow portion 32 is a portion with a pattern in FIG. 3 and is formed outside the region to be a product (outside the region of the product portion 10) and communicates with the hollow rectangular portion 31a. In addition, you may connect the sub hollow part 32 with the hollow rectangular part 31b and the hollow inclination part 31c. Moreover, although the sub hollow part 32 is a rectangle in the figure, the shape is not specifically limited.

  As shown in FIG. 2, the second circuit board 40 includes a second insulating substrate 41, a third circuit layer 42, a fourth circuit layer 43, and a second coverlay film 44. Have.

  The second insulating substrate 41 is flexible and is made of, for example, polyimide.

  As shown in FIG. 2, the third circuit layer 42 is laminated on the lower surface of the second insulating substrate 41, and is made of, for example, copper formed in a predetermined wiring pattern.

  The fourth circuit layer 43 is laminated on the upper surface of the second insulating substrate 41, and is made of, for example, copper formed in a predetermined wiring pattern, similarly to the third circuit layer 42.

  As shown in FIG. 2, the second coverlay film 44 is laminated on the third circuit layer 42 to protect the third circuit layer 42. The second coverlay film 44 is composed of a second insulating film 44a and a second coverlay adhesive layer 44b.

  The second insulating film 44 a is located in the lowermost layer of the second circuit board 40. The second insulating film 44a has flexibility and insulating properties, and is made of, for example, a film made of polyimide.

  The second coverlay adhesive layer 44b bonds the second insulating film 44a and the second circuit layer 42, and is made of an adhesive made of, for example, an epoxy resin.

  As shown in FIGS. 2 and 4, the second circuit board 40 is formed with a second through hole 45 that allows the hollow portion 31 to communicate with the outside via the sub hollow portion 32. The second through hole 45 penetrates the second circuit board 40 above the sub hollow portion 32 of the adhesive layer 30 and opens at the second opening 44c. The second opening 44c is located in a portion of the second insulating film 44a corresponding to the sub hollow portion 32 of the adhesive layer 30. In the present embodiment, the cross-sectional shape of the second through hole 45 is circular (inner diameter D1), but is not particularly limited and may be rectangular.

  As shown in FIGS. 2 and 4, the first closing member 51 closes the first through hole 25 with the first opening 24 c. The first closing member 51 has a film shape, and includes a first closing film 51a and a first closing adhesive layer 51b.

  The first closing film 51a has air permeability and waterproofness. In the present embodiment, “breathability” is a concept that allows moisture to pass through in addition to allowing air to pass therethrough, and “waterproofness” refers to repelling liquid in addition to preventing intrusion of liquid ( It is a concept including water repellency. That is, the first closing film 51a is configured not to allow liquid to pass while allowing air or moisture to pass.

  The first closing film 51a is made of, for example, a moisture permeable waterproof material or a hollow fiber. Furthermore, as a moisture-permeable and waterproof material, porous polytetrafluoroethylene (PTFE: Polytetrafluoro-ethylene) having many pores smaller than the diameter of water droplets (100 μm to 6000 μm) and larger than the diameter of water vapor molecules (0.0004 μm) is formed. Ethylene (for example, Gore-Tex (registered trademark)) can be exemplified. Further, the first closing film 51a has a heat resistance of 250 ° C. or higher. Thereby, performance (particularly air permeability) can be maintained even in a heating process such as reflow. Moreover, this 1st obstruction | occlusion film 51a has the outstanding chemical resistance.

  As shown in FIG. 5, the first closing film 51a has a circular shape, and its outer diameter D2 is relatively larger than the inner diameter D1 of the first through hole 25 (D2> D1). ). Therefore, the first closing film 51a can completely close the first through hole 25.

  As shown in FIG. 4, the first closing adhesive layer 51b is laminated on the lower surface of the first closing film 51a, and bonds the first closing film 51a and the first insulating film 24a. The first closing adhesive layer 51b is made of an adhesive made of an epoxy resin, for example.

  As shown in FIGS. 4 and 5, the first closing adhesive layer 51 b is formed with a first closing opening 51 c that exposes the first closing film 51 a at the center portion. The first closing opening 51c is located coaxially with the first through hole 25, and the inner diameter D3 of the first closing opening 51c is substantially equal to the inner diameter D1 of the first through hole 25. They are the same (D3≈D1). For this reason, in the heating process such as reflow, the air (pressure) in the hollow portion 31 is smoothly released through the first closing film 51a without being blocked by the first closing adhesive layer 51b.

  As shown in FIGS. 2 and 4, the second closing member 52 closes the second through hole 45 with the second opening 44 c. The second closing member 52 is in the form of a film like the first closing member 51, and includes a second closing film 52a and a second closing adhesive layer 52b.

  Similar to the first closing film 51a of the first closing member 51, the second closing film 52a has air permeability and waterproofness so as not to allow liquid to pass while allowing air and moisture to pass. It has become. The material of the second closing film 52a is substantially the same as the material of the first closing film 51a of the first closing member 51, and the shape and size of the second closing film 52a are the same as the first closing film 51a. It is substantially the same as the shape and size of the film 51a.

  As shown in FIG. 4, the second closing adhesive layer 52b is laminated on the upper surface of the second closing film 52a, and bonds the second closing film 52a and the second insulating film 44a. The material of the second closing adhesive layer 52b is substantially the same as the material of the first closing adhesive layer 51b of the first closing member 51, and the shape and size of the second closing adhesive layer 52b are the same. It is substantially the same as the shape and size of one closing adhesive layer 51b.

  In the present embodiment, the through holes 25 and 45 are formed in the first circuit board 20 and the second circuit board 40, respectively, but the through holes 25 and 45 are formed in either one of the circuit boards 20 and 40. The through holes 25 and 45 may not be formed in the other circuit boards 20 and 40. For example, as shown in FIG. 6, the first through hole 25 may be formed only in the first circuit board 20 and closed with the first closing member 51.

  In this embodiment, one sub hollow portion 32 and two through holes 25 and 45 are formed for one hollow portion 31, but a plurality of sub hollow portions 32 are provided for one hollow portion 31. May be formed in the adhesive layer 30, and the through holes 25 and 45 corresponding to the plurality of sub hollow portions 32 may be formed in the circuit boards 20 and 40, respectively. As described above, the air permeability between the hollow portion 31 and the outside is improved by forming the plurality of sub-hollow portions 32 and the through holes 25 and 45 for one hollow portion 31. Here, in the air permeability between the hollow portion 31 and the outside, it is preferable that the number of the sub-hollow portion 32 and the through holes 25 and 45 is larger.

  In the present embodiment, the first and second closing members 51, 52 are the first and second coverlay films 24, 44 (on the side of the sub hollow portion 32 in the first and second circuit boards 20, 40). The first and second closing members 51 and 52 are attached to the second and fourth circuit layers 23 and 43 (outside in the first and second circuit boards 20 and 40). May be.

  Moreover, as shown in FIG. 7, you may make the inside of the 1st and 2nd through-holes 25 and 45 fill with the closure members 53a and 53b. In addition, the closing members 53a and 53b have air permeability and waterproofness similarly to the first and second closing members 51 and 52.

  As described above, in this embodiment, the sub-hollow portion 32 communicating with the hollow portion 31 is formed outside the product region (outside the product portion 10) in the adhesive layer 30, and the first and second circuits are formed. First and second through holes 25 and 45 opened in the sub hollow portion 32 are formed in the substrates 20 and 40, and the first and second blocking members 51 and 52 having waterproof properties are used. Since the through holes 25 and 45 are closed, for example, intrusion of liquid into the hollow portion 31 is suppressed in a wet process using a liquid such as plating or cleaning.

  In addition, since the first and second closing members 51 and 52 have air permeability, the first and second closing members 51 and 52 are attached to the first and second circuit boards 20 and 40. Even if a heating process such as plasma desmear treatment or reflow is performed on the flexible printed wiring board 1 in a state, the pressure in the hollow portion 31 is released to the outside, and the appearance abnormality of the product portion 10 due to the expansion of the hollow portion 31 is suppressed. Has been. Thus, the quality of the product part 10 is also improved by suppressing the expansion of the hollow part 31.

  As described above, the flexible printed wiring board 1 in the present embodiment is a heating process for the flexible printed wiring board 1 in a state where the first and second closing members 51 and 52 are attached to the flexible printed wiring board 1. Both the wet process and the wet process can be performed, and it is not necessary to remove the first and second closing members 51 and 52 for each process. For this reason, the productivity of the flexible printed wiring board is improved.

  In the present embodiment, as shown in FIG. 2, the first and second circuit boards are configured such that the first and second closing members 51 and 52 close the first and second openings 24c and 44c. 20 and 40, and the first and second closing members 51 and 52 are accommodated in the sub-hollow portion 32. Therefore, the first and second closing members 51 and 52 are peeled (dropped) by an external force. It is suppressed.

  Next, the manufacturing method of the flexible printed wiring board 1 in this embodiment is demonstrated.

  FIG. 8 is a flowchart showing a method for manufacturing a flexible printed wiring board according to this embodiment, and FIG. 9 is a perspective view showing a method for manufacturing a flexible printed wiring board according to this embodiment.

  As shown in FIG. 8, the manufacturing method of the flexible printed wiring board 1 in the present embodiment includes an opening pattern forming step S10, a sub-opening pattern forming step S20, a through-hole forming step S30, a closing step S40, Step S50.

  In the opening pattern forming step S <b> 10, as shown in FIG. 9, an opening pattern 33 a that becomes the hollow portion 31 is formed in the film-like adhesive layer 30. Such an opening pattern 33a can be formed by punching, for example, and in this embodiment, four opening patterns 33a are formed in a lump. Alternatively, the opening pattern 33a may be formed by masking a portion to be the opening pattern 33a and screen printing an adhesive to be the adhesive layer 30 on the first circuit board 20.

  In the sub-opening pattern forming step S20, as shown in FIG. 9, a sub-opening pattern 33b to be the sub-hollow portion 32 is formed in the film-like adhesive layer 30. Such sub-opening patterns 33b can be formed, for example, by punching. In the present embodiment, the four sub-opening patterns 33b are formed in a lump. Alternatively, the sub-opening pattern 33b may be formed by masking a portion to be the sub-opening pattern 33b and screen printing an adhesive to be the adhesive layer 30. Further, the sub opening pattern forming step S20 may be performed simultaneously with the opening pattern forming step S10.

  In the through-hole forming step S30, as shown in FIG. 9, the first and second through-holes 25, 45 are formed in regions corresponding to the sub-opening patterns 33b of the adhesive layer 30 in the first and second circuit boards 20, 40. Form. As shown in FIG. 6, the first through hole 25 may be formed only in the first circuit board 20. Such through holes 25 and 45 can be formed by, for example, drilling.

  In the closing step S40, as shown in FIG. 9, the upper surface of the first circuit board 20 and the lower surface of the second circuit board 40 are closed so as to close the first and second through holes 25, 45 from the adhesive layer 30 side. The first and second closing members 51 and 52 are pasted to each other.

  In the lamination step S50, as shown in FIG. 9, the first and second circuit boards 20 and 40 are laminated via the adhesive layer 30 with the first and second coverlay films 24 and 44 facing each other. To do. At this time, the opening pattern 33a of the adhesive layer 30 is made to correspond to a part of the product part 10, the sub-opening pattern 33b is made to correspond to the outside of the product part 10, and the first and second closing members 51 and 52 are The first and second circuit boards 20 and 40 and the adhesive layer 30 are aligned so as to be accommodated in the sub-opening pattern 33b.

  Thus, the hollow part 31 is formed in the adhesive layer 30 by the opening pattern 33 a being sandwiched between the first and second circuit boards 20 and 40. Further, the sub hollow portion 32 is formed in the adhesive layer 30 by sandwiching the sub opening pattern 33 b between the first and second circuit boards 20 and 40.

  The flexible printed wiring board 1 manufactured in this way is subjected to mounting of electronic components and plating treatment, and the product portion 10 is cut and separated to become a flexible printed wiring board as a product.

  In the method for manufacturing the flexible printed wiring board 1 in the present embodiment, the first and second through holes 25 and 45 are closed by the first and second closing members 51 and 52 having air permeability and waterproofness. In the process, both the heating process and the wet process can be performed on the flexible printed wiring board 1 with the first and second closing members 51 and 52 attached, and the first and second processes for each process are performed. Removal of the blocking members 51 and 52 is not necessary. For this reason, the productivity of the flexible printed wiring board is improved.

<< Second Embodiment >>
Next, a second embodiment will be described.

  10 is a plan view of the flexible printed wiring board according to the present embodiment, FIG. 11 is a sectional view taken along line XI-XI in FIG. 10, FIG. 12 is a sectional view taken along line XII-XII in FIG. It is an expanded sectional view along the XIII-XIII line of FIG.

  The flexible printed wiring board 1a in the present embodiment is different from the first embodiment in that the communication path 34 is formed in the adhesive layer 30 and the closing member 54, but other configurations are the same as in the first embodiment. It is the same as the form. Only the differences from the first embodiment will be described below, and portions having the same configuration as in the first embodiment will be denoted by the same reference numerals and description thereof will be omitted.

  As shown in FIG. 10, a communication path 34 that allows the hollow portion 31 to communicate with the outside is formed in the adhesive layer 30 of the flexible printed wiring board 1 a in the present embodiment. In the present embodiment, two communication paths 34 are formed for one hollow portion 31, but only one communication path 34 may be formed. Further, three or more communication passages 34 may be formed for one hollow portion 31. In FIG. 10, a part defined by a solid line and provided with a pattern is the product part 10, and a part defined by a broken line is the hollow part 31 and the communication path 34.

  As shown in FIGS. 10 and 12, the communication path 34 is connected to the hollow rectangular portions 31 a and 31 b at one end and connected (opened) to the outside at the other end. Note that one end of the communication passage 34 may be connected to the hollow inclined portion 31c, and is not particularly limited. Moreover, as shown in FIG. 13, the communication path 34 has a rectangular cross section. In FIG. 12, a part defined by a broken line is the product part 10.

As shown in FIG. 12, the width l ₁ of the communication path 34 is relatively smaller than the widths l ₂ and l ₃ of the product rectangular portions 11 and 12 (l ₁ <l ₂ , l ₁ <l ₃ ). For this reason, the adhesive layer 30 is necessarily interposed between the first and second circuit boards 20 and 40 at the end portions of the product rectangular portions 11 and 12 of the product portion 10.

  As shown in FIGS. 11 to 13, the communication path 34 is closed by a closing member 54.

  The closing member 54 includes a closing film 54a, a third closing adhesive layer 54b, and a fourth closing adhesive layer 54c.

  The closing film 54a is made of substantially the same material as the first and second closing films 51a and 52a of the first and second closing members 51 and 52 in the first embodiment. It is waterproof. The closing film 54a is a cube (see FIG. 15) corresponding to the shape of the communication path 34.

  The 3rd obstruction | occlusion adhesion layer 54b is laminated | stacked on the lower surface of the obstruction | occlusion film 54a, and adhere | attaches the obstruction | occlusion film 54a and the 1st coverlay film 24 (1st insulating film 24a). On the other hand, the 4th obstruction | occlusion adhesive layer 54c is laminated | stacked on the upper surface of the obstruction | occlusion film 54a, and adhere | attaches the obstruction | occlusion film 54a and the 2nd coverlay film 44 (2nd insulating film 44a). These third and fourth adhesive layers 54b and 54c are made of an adhesive made of, for example, an epoxy resin.

  In the present embodiment, the entire communication path 34 is filled with the closing member 54, but the closing member 54 may be filled only in a part of the communication path 34. In order to improve the air permeability, it is desirable that the length of the communication path 34 in the Y direction in FIG. 12 is shortened and the cross section in FIG.

  Further, by forming three or more communication passages 34 for one hollow portion 31 and filling the communication passages 34 with a closing member 54, the air permeability between the hollow portion 31 and the outside is further improved. To do.

  As described above, in the present embodiment, the communication path 34 is formed in the adhesive layer 30 and the communication path 34 is closed by the blocking member 54 having air permeability and waterproofness. In the state attached to the flexible printed wiring board 1a, both the heating process and the wet process can be performed on the flexible printed wiring board 1a, and the removal of the closing member 54 for each process is not necessary. For this reason, the productivity of the flexible printed wiring board 1a is improved. Moreover, the quality of the product part 10 also improves by suppressing expansion of the hollow part 31 similarly to 1st Embodiment.

  Next, the manufacturing method of the flexible printed wiring board 1a in this embodiment is demonstrated.

  FIG. 14 is a flowchart showing a method for manufacturing a flexible printed wiring board in the present embodiment, and FIG. 15 is a perspective view showing a method for manufacturing a flexible printed wiring board in the present embodiment.

  The manufacturing method of the flexible printed wiring board 1a in the present embodiment is different from the first embodiment in the communication path forming step S60 and the filling step S70, but the other configurations are the same as those in the first embodiment. . Only the differences from the first embodiment will be described below, and portions having the same configuration as in the first embodiment will be denoted by the same reference numerals and description thereof will be omitted.

  In the communication path forming step S60, as shown in FIG. 15, a communication path opening pattern 35 to be the communication path 34 is formed in the film-like adhesive layer 30. Such a communication path opening pattern 35 can be formed by punching, for example, and in this embodiment, eight communication path opening patterns 35 are formed in a lump. Note that the communication path opening pattern 35 may be formed by masking a portion that becomes the communication path 34 and screen-printing an adhesive that becomes the adhesive layer 30 on the first circuit board 20. Further, the communication path forming step S60 may be performed simultaneously with the opening pattern forming step S10.

  Next, the adhesive layer 30 on which the communication path opening pattern 35 is formed is laminated on the first coverlay film 24 of the first circuit board 20.

  In the filling step S70, as shown in FIG. 15, the blocking member 54 is filled into the communication path opening pattern 35 of the adhesive layer 30. The blocking member 54 (blocking film 54a) is a cube corresponding to the communication path opening pattern 35, and a third blocking adhesive layer 54b is laminated on the lower surface. For this reason, the closing member 54 is fixed in the communication path opening pattern 35 by inserting the closing member 54 into the communication path opening pattern 35.

  A closing member 54 is attached to the lower surface (second coverlay film 44) of the second circuit board 40 in advance according to the pitch of the communication path opening pattern 35, and the second circuit board 40 is laminated in the stacking step S50. The closing member 54 may be filled in the communication path opening pattern 35 at the same time as laminating the adhesive layer 30.

  In the manufacturing method of the flexible printed wiring board 1a in the present embodiment, as in the first embodiment, the heating process and the wet process are performed on the flexible printed wiring board 1a with the closing member 54 attached in the subsequent processes. Both can be implemented, and the removal of the closing member 54 for each step is not necessary. For this reason, the productivity of the flexible printed wiring board is improved.

  Moreover, the manufacturing method of the flexible printed wiring board 1a in this embodiment has few processes compared with the manufacturing method of the flexible printed wiring board 1 of 1st Embodiment. For this reason, the productivity of flexible printed wiring is further improved.

  Moreover, productivity of a flexible printed wiring board further improves by performing filling process S70 and lamination process S50 simultaneously as mentioned above.

  In the embodiment described above, the opening pattern 33a corresponds to an example of the first opening pattern of the present invention, and the sub opening pattern 33b or the communication path opening pattern 35 corresponds to an example of the second opening pattern of the present invention. The opening pattern forming step S10 corresponds to an example of the first pattern forming step of the present invention, and the sub-opening pattern forming step S20 or the communication path forming pattern forming step S60 is an example of the second pattern forming step of the present invention. It corresponds to.

  FIG. 16 is a graph showing the results of the high temperature vacuum test in the examples.

  Below, the effect of the present invention was confirmed by examples and comparative examples that further embody the present invention. The following examples and comparative examples are for confirming the effect of suppressing expansion in the hollow portion of the flexible printed wiring board of the embodiment described above.

<Example 1>
In Example 1, 100 samples of the flexible printed wiring board having the same structure as that of the first embodiment described above were prepared. In the sample of Example 1, the total volume of the hollow part and the sub-hollow part was set to 5 mm ³ .

  The sample of Example 1 was subjected to a high-temperature vacuum test in which the temperature was 150 ° C. and the atmospheric pressure was about 66 kPa for 60 minutes (n = 100). I investigated. Table 1 and FIG. 16 show the results of the high temperature vacuum test (occurrence rate of appearance abnormality). As shown in Table 1, the appearance abnormality occurrence rate of Example 1 is zero, and Example 1 is not displayed in FIG. 16 (hereinafter, Examples 2-5, Examples 7-11, and comparison) The same applies in Example 1.)

＜実施例２＞
実施例２では、中空部と副中空部の体積の合計を１０ｍｍ^３としたこと以外は、実施例１と同一構造のフレキシブルプリント配線板のサンプルを１００個作成した。この実施例２のサンプルに対し、実施例１と同様の要領で高温真空試験を行った。実施例２についての高温真空試験の結果（外観異常の発生率）を表１及び図１６に示す。

<Example 2>
In Example 2, 100 samples of flexible printed wiring boards having the same structure as Example 1 were prepared except that the total volume of the hollow part and the sub-hollow part was 10 mm ³ . The sample of Example 2 was subjected to a high temperature vacuum test in the same manner as in Example 1. Table 1 and FIG. 16 show the results of the high temperature vacuum test for Example 2 (occurrence rate of appearance abnormality).

<Example 3>
In Example 3, 100 flexible printed wiring board samples having the same structure as Example 1 were prepared except that the total volume of the hollow part and the sub-hollow part was 20 mm ³ . The sample of Example 3 was subjected to a high temperature vacuum test in the same manner as in Example 1. The results of the high-temperature vacuum test for Example 3 are shown in Table 1 and FIG.

<Example 4>
In Example 4, 100 flexible printed wiring board samples having the same structure as Example 1 were prepared except that the total volume of the hollow part and the sub-hollow part was 30 mm ³ . The sample of Example 4 was subjected to a high temperature vacuum test in the same manner as in Example 1. The results of the high-temperature vacuum test for Example 4 are shown in Table 1 and FIG.

<Example 5>
In Example 5, 100 samples of the flexible printed wiring board having the same structure as Example 1 were prepared except that the total volume of the hollow part and the sub-hollow part was 50 mm ³ . The sample of Example 5 was subjected to a high temperature vacuum test in the same manner as in Example 1. The results of the high-temperature vacuum test for Example 5 are shown in Table 1 and FIG.

<Example 6>
In Example 6, 100 samples of the flexible printed wiring board having the same structure as Example 1 were prepared except that the total volume of the hollow part and the sub-hollow part was 100 mm ³ . The sample of Example 6 was subjected to a high temperature vacuum test in the same manner as in Example 1. The results of the high-temperature vacuum test for Example 6 are shown in Table 1 and FIG.

<Example 7>
In Example 7, 100 samples of the flexible printed wiring board having the same structure as that of the second embodiment described above were prepared. In the sample of Example 7, the volume of the hollow portion was set to 5 mm ³ . The sample of Example 7 was subjected to a high temperature vacuum test in the same manner as in Example 1. The results of the high-temperature vacuum test for Example 7 are shown in Table 1 and FIG. In addition, since the sub hollow part was not formed in the sample of this Example 7, only the volume of the hollow part was displayed in "the sum total of the volume of a hollow part and a sub hollow part" in Table 1 and FIG. The same applies to Examples 8 to 12 below).

<Example 8>
In Example 8, 100 samples of the flexible printed wiring board having the same structure as Example 7 were prepared except that the volume of the hollow portion was 10 mm ³ . The sample of Example 8 was subjected to a high temperature vacuum test in the same manner as in Example 1. The results of the high-temperature vacuum test for Example 8 are shown in Table 1 and FIG.

<Example 9>
In Example 9, 100 samples of flexible printed wiring boards having the same structure as Example 7 were prepared except that the volume of the hollow portion was 20 mm ³ . The sample of Example 9 was subjected to a high temperature vacuum test in the same manner as in Example 1. The results of the high-temperature vacuum test for Example 9 are shown in Table 1 and FIG.

<Example 10>
In Example 10, 100 samples of a flexible printed wiring board having the same structure as Example 7 were prepared except that the volume of the hollow portion was 30 mm ³ . The sample of Example 10 was subjected to a high temperature vacuum test in the same manner as in Example 1. The results of the high-temperature vacuum test for Example 10 are shown in Table 1 and FIG.

<Example 11>
In Example 11, 100 samples of flexible printed wiring boards having the same structure as Example 7 were prepared except that the volume of the hollow portion was 50 mm ³ . The sample of Example 11 was subjected to a high temperature vacuum test in the same manner as in Example 1. The results of the high-temperature vacuum test for Example 11 are shown in Table 1 and FIG.

<Example 12>
In Example 12, 100 samples of flexible printed wiring boards having the same structure as Example 7 were prepared except that the volume of the hollow portion was 100 mm ³ . The sample of Example 12 was subjected to a high temperature vacuum test in the same manner as in Example 1. The results of the high-temperature vacuum test for Example 12 are shown in Table 1 and FIG.

<Comparative Example 1>
In Comparative Example 1, a flexible printed wiring board having the same structure as that of Example 1 except that the sub-hollow portion is not formed in the adhesive layer and the through holes are not formed in the first and second circuit boards. A sample was created. In addition, the volume of the hollow part of the sample of Comparative Example 1 was set to 5 mm ³ . A high temperature vacuum test was performed on the sample of Comparative Example 1 in the same manner as in Example 1. The results of the high temperature vacuum test for Comparative Example 1 are shown in Table 1 and FIG. In addition, only the volume of the hollow part was displayed in "Total of the volume of the hollow part and the sub hollow part" in Table 1 and FIG. 16 (hereinafter, the same applies in Comparative Examples 2 to 6).

<Comparative example 2>
In Comparative Example 2, 100 flexible printed wiring board samples having the same structure as Comparative Example 1 were prepared except that the volume of the hollow portion was 10 mm ³ . A high temperature vacuum test was performed on the sample of Comparative Example 2 in the same manner as in Example 1. The results of the high temperature vacuum test for Comparative Example 2 are shown in Table 1 and FIG.

<Comparative Example 3>
In Comparative Example 3, 100 flexible printed wiring board samples having the same structure as Comparative Example 1 were prepared except that the volume of the hollow portion was 20 mm ³ . A high temperature vacuum test was performed on the sample of Comparative Example 3 in the same manner as in Example 1. The results of the high temperature vacuum test for Comparative Example 3 are shown in Table 1 and FIG.

<Comparative example 4>
In Comparative Example 4, 100 samples of flexible printed wiring boards having the same structure as Comparative Example 1 were prepared except that the volume of the hollow portion was 30 mm ³ . A high temperature vacuum test was performed on the sample of Comparative Example 4 in the same manner as in Example 1. The results of the high temperature vacuum test for Comparative Example 4 are shown in Table 1 and FIG.

<Comparative Example 5>
In Comparative Example 5, 100 flexible printed wiring board samples having the same structure as Comparative Example 1 were prepared, except that the volume of the hollow portion was 50 mm ³ . A high temperature vacuum test was performed on the sample of Comparative Example 5 in the same manner as in Example 1. The results of the high temperature vacuum test for Comparative Example 5 are shown in Table 1 and FIG.

<Comparative Example 6>
In Comparative Example 6, 100 flexible printed wiring board samples having the same structure as Comparative Example 1 were prepared except that the volume of the hollow portion was 100 mm ³ . A high temperature vacuum test was performed on the sample of Comparative Example 6 in the same manner as in Example 1. The results of the high temperature vacuum test for Comparative Example 6 are shown in Table 1 and FIG.

<Discussion>
As shown in Table 1 and FIG. 16, in Comparative Example 2, 45% had abnormal appearance, and in Comparative Example 3, 95% had abnormal appearance. Moreover, in Comparative Examples 4 to 6, all (100%) samples had abnormal appearance.

  On the other hand, in Examples 1-5 and Examples 7-11, the appearance abnormality was zero. Here, in Example 6 and Example 12, the appearance abnormality occurred, but the appearance abnormality occurrence rate of Example 6 was 5%, and the appearance abnormality occurrence rate of Example 12 was 15%. It was something. From this, it can be seen that the samples of Examples 1 to 12 have the appearance abnormality of the product part suppressed under high temperature vacuum.

  The embodiment described above is described for facilitating the understanding of the present invention, and is not described for limiting the present invention. Therefore, each element disclosed in the above embodiment is intended to include all design changes and equivalents belonging to the technical scope of the present invention.

DESCRIPTION OF SYMBOLS 1, 1a ... Flexible printed wiring board 10 ... Product part 20, 40 ... Circuit board 21, 41 ... Insulating board 22, 23 ... Circuit layer 24, 44 ... Cover-lay film 24c, 44c ... Opening part 25, 45 ... Through-hole DESCRIPTION OF SYMBOLS 30 ... Adhesive layer 31 ... Hollow part 32 ... Sub hollow part 33a ... Opening pattern 33b ... Sub opening pattern 34 ... Communication path 35 ... Communication path opening pattern 51, 52, 53a, 53b, 54 ... Closure member 51a, 52a, 54a ... Occlusion film

Claims (7)

A flexible printed wiring board in which a first circuit board and a second circuit board are laminated via an adhesive layer, and a hollow portion is formed between the first and second circuit boards,
Outside the region to be a product in the adhesive layer, a sub hollow portion communicating with the hollow portion is formed,
At least one of the first or second circuit board is formed with a through-hole that opens to the sub-hollow portion at the opening,
The flexible printed wiring board, wherein the through hole is closed by a closing member having air permeability and waterproofness. The flexible printed wiring board according to claim 1,
The flexible printed wiring board, wherein the closing member is a film-like member attached to at least one of the first or second circuit board so as to close the opening. A flexible printed wiring board in which a first circuit board and a second circuit board are laminated via an adhesive layer, and a hollow portion is formed between the first circuit board and the second circuit board. And
In the adhesive layer, a communication path for communicating the hollow portion to the outside is formed,
The flexible printed wiring board, wherein the communication path is closed by a closing member having air permeability and waterproofness. The flexible printed wiring board according to any one of claims 1 to 3,
The flexible printed wiring board, wherein the closing member is made of porous polytetrafluoroethylene. It is a manufacturing method of the flexible printed wiring board according to claim 1 or 2,
A first pattern forming step of forming a first opening pattern to be the hollow portion in the adhesive layer;
A second pattern forming step of forming a second opening pattern to be the sub-hollow portion in the adhesive layer;
A through hole forming step of forming the through hole in at least one of the first or second circuit board;
A closing step of closing the through hole with the closing member;
A method of manufacturing a flexible printed wiring board, comprising: a laminating step of laminating the first circuit board and the second circuit board via the adhesive layer. It is a manufacturing method of the flexible printed wiring board according to claim 3,
A first pattern forming step of forming a first opening pattern to be the hollow portion in the adhesive layer;
A second pattern forming step of forming a second opening pattern serving as the communication path in the adhesive layer;
A filling step of filling at least a part of the second opening pattern with the blocking member;
A method of manufacturing a flexible printed wiring board, comprising: a laminating step of laminating the first circuit board and the second circuit board via the adhesive layer. It is a manufacturing method of the flexible printed wiring board according to claim 5 or 6,
The method for manufacturing a flexible printed wiring board, wherein the blocking member is made of porous polytetrafluoroethylene.

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