Transmission circuit board and manufacturing method thereof

Abstract

A transmission circuit board is divided into a bending area and a transmission area; the transmission circuit board includes: a flexible substrate layer; an inner circuit layer formed on the substrate layer; a first covering film layer formed on the inner circuit layer located in the bending area; a first dielectric layer formed on the inner circuit layer located in the transmission area; a first outer circuit layer formed on the first dielectric layer, the first outer circuit layer including a first outer circuit; a second covering film layer formed on the first outer circuit layer; and a first shielding layer formed on the second and first covering film layers; the first shielding layer includes an end and a bottom, the two ends are formed on the second covering film layer and are electrically connected to the first outer circuit, and the bottom is formed on the first covering film. The present invention also relates to a method for manufacturing a transmission circuit board. The transmission circuit board provided by the present invention has good dynamic bending ability and a long service life.

Description

Technical Field

[0001] The present invention relates to the field of circuit boards, and in particular to a transmission circuit board and a manufacturing method thereof. Background Art

[0002] With the development of wearable electronic technology, circuit boards need higher flexibility to meet the needs of various parts of the body. At the same time, the advent of the 5G era has made the industry have higher requirements for the frequency and efficiency of wireless transmission. How to meet the dual needs of flexibility and high-speed transmission has become a hot topic in circuit board research and development.

[0003] The current transmission line adopts a stripline design, in which the signal line runs through the middle layer, and the two sides of the signal line are ground layers. Blind holes or through holes are designed at both ends of the transmission line to guide the signal line to the outer layer to form signal line terminals. The thicker the transmission line, the less signal loss the signal line has during high-frequency transmission. However, as the thickness increases, the transmission line no longer has the ability to bend dynamically, and it is difficult to be used in wearable products that require dynamic bending and have life requirements. Summary of the invention

[0004] In view of this, the present invention provides a transmission line with good dynamic bending capability and long service life.

[0005] In addition, it is also necessary to provide a method for manufacturing the transmission line as described above.

[0006] A transmission circuit board, the transmission circuit board is divided into a bending area and a first transmission area and a second transmission area located on both sides of the bending area; the transmission circuit board comprises: a substrate layer, the substrate layer is flexible; an inner circuit layer formed on a surface of the substrate layer; a first covering film layer formed on the inner circuit layer located in the bending area; a first dielectric layer formed on the inner circuit layer located in the first transmission area and the second transmission area; a first outer circuit layer formed on the first dielectric layer, the first outer circuit layer includes a first outer circuit; a second covering film layer formed on the first outer circuit layer; and a first shielding layer formed on the second covering film layer and the first covering film layer; the first shielding layer includes two ends and a bottom, the two ends are formed on the second covering film layer and are electrically connected to the first outer circuit respectively, and the bottom is formed on the first covering film layer.

[0007] In one embodiment, the transmission circuit board also includes: a third covering film layer formed on the substrate layer located in the bending area and away from the inner circuit layer; a second dielectric layer formed on the substrate layer located in the first transmission area and the second transmission area and away from the inner circuit layer; a second outer circuit layer formed on the second dielectric layer; and a fourth covering film layer formed on the second outer circuit layer.

[0008] Furthermore, the transmission circuit board also includes a second shielding layer formed on the third covering film layer and the fourth covering film layer; the structure of the second shielding layer is the same as that of the first shielding layer, and the second shielding layer is electrically connected to the second outer circuit layer.

[0009] In another embodiment, the transmission circuit board also includes: a third shielding layer formed on at least the substrate layer located in the bending area and away from the inner circuit layer; a third covering film formed on the third shielding layer located in the bending area; a second dielectric layer formed on the substrate layer located in the first transmission area and the second transmission area and away from the inner circuit layer; a second outer circuit layer formed on the second dielectric layer; and a fourth covering film layer formed on the second outer circuit layer.

[0010] Furthermore, part of the glue layer of the second covering film layer flows onto the first covering film layer to form two first glue overflow parts; the first shielding layer also includes two connecting parts, and the two connecting parts respectively connect the two ends and the bottom; the first glue overflow part is filled in the first space formed by the two connecting parts, the first covering film layer, the first dielectric layer and the first outer circuit layer; part of the glue layer of the fourth covering film layer flows onto the third covering film layer to form two second glue overflow parts; the second glue overflow part is filled in the second space formed by the two connecting parts of the second shielding layer, the third covering film layer, the second dielectric layer and the second outer circuit layer.

[0011] Furthermore, the inner circuit layer includes at least one signal circuit and at least two inner ground circuits located on both sides of the signal circuit; the first outer circuit layer also includes at least two signal line terminals and a first outer circuit, and the two ends of each signal circuit are electrically connected to the two signal line terminals through copper pillars respectively; the first outer circuit includes at least one ground terminal, and the inner ground circuit is electrically connected to the ground terminal through a via; the via is formed in the first transmission area and the second transmission area, and is not formed in the bending area.

[0012] A method for manufacturing a transmission circuit board as described above comprises: providing a copper-clad substrate, the copper-clad substrate being divided into a bending area and a first transmission area and a second transmission area located on both sides of the bending area; the copper-clad substrate comprising a flexible substrate layer and a first inner copper foil layer formed on the substrate layer; manufacturing the first inner copper foil layer to form an inner circuit layer, the inner circuit layer comprising at least one signal circuit and at least two inner ground circuits located on both sides of the signal circuit; laminating a first covering film layer on the inner circuit layer located in the bending area; laminating a first single-sided copper-clad substrate on the inner circuit layer located in the first transmission area and the second transmission area through a first adhesive layer, the first single-sided copper-clad substrate comprising a first inner circuit layer formed in the first transmission area and the second transmission area. A first dielectric layer on the layer and a first outer copper foil layer formed on the first dielectric layer; at least two blind holes are drilled from the first outer copper foil layer to the two ends of each of the signal lines, and copper pillars are formed by filling the at least two blind holes with electroplated copper through selective electroplating; the first outer copper foil layer is made into a first outer circuit layer; the first outer circuit layer includes a first outer circuit and at least two signal line terminals, and the first outer circuit is electrically insulated from the signal line terminals; a second covering film layer is pressed on the first outer circuit layer; a first shielding layer is formed on the second covering film layer and the first covering film layer, the first shielding layer includes two ends and a bottom, the two ends are formed on the second covering film layer and are respectively electrically connected to the first outer circuit, and the bottom is formed on the first covering film.

[0013] Furthermore, while laminating the first covering film layer, the step is also included: laminating the third covering film layer on the substrate layer located in the bending area; while laminating the first copper-clad substrate and thereafter, the step is also included: laminating a second single-sided copper-clad substrate on the substrate layer located in the first transmission area and the second transmission area through a second adhesive layer, the second single-sided copper-clad substrate including a second dielectric layer formed on the substrate layer located in the first transmission area and the second transmission area and a second outer copper foil layer formed on the second dielectric layer; while drilling to form the blind hole, the step is also included: forming a plurality of vias in the first transmission area and the second transmission area, and the vias are not formed in the bending area; while forming the first outer circuit layer, the step is also included: forming the second outer copper foil layer to form a second outer circuit layer; the vias electrically connect the first outer circuit, the inner ground circuit and the second outer circuit layer; while laminating the second covering film layer, the step is also included: laminating the fourth covering film layer on the second outer circuit layer.

[0014] In one embodiment, the copper-clad substrate also includes a second inner copper foil layer formed on the other opposite surface of the substrate layer. While forming the inner circuit layer, it also includes the steps of: making the second inner copper foil layer into a third shielding layer, and the third covering film layer is formed on the third shielding layer.

[0015] In another embodiment, the method further includes forming a second shielding layer on the fourth covering film layer and the third covering film layer, wherein the structure of the second shielding layer is the same as that of the first shielding layer, and the second shielding layer is electrically connected to the second outer circuit layer.

[0016] The transmission circuit board and its manufacturing method provided by the present invention use a flexible material as a substrate layer, set a bending zone between the first transmission zone and the second transmission zone, only add layers on the inner circuit layer located in the first transmission zone and the second transmission zone to form a first outer circuit zone, and form a first shielding layer on the first outer circuit layer. The bending zone of the transmission circuit board only includes an inner circuit layer and a substrate layer, so that the transmission circuit board can have good dynamic bending ability, thereby extending the service life of the transmission circuit board. In addition, the first shielding layer includes two ends and a bottom connecting the end and the bottom. The end of the first shielding layer is electrically connected to the outer circuit of the outer circuit layer, and the bottom of the first shielding layer is formed on the first covering film layer in the bending zone, which can not only make the first shielding layer grounded while playing a shielding role, but also avoid signal backflow, thereby improving the shielding effect. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 A cross-sectional view of a copper-clad substrate provided in accordance with a first embodiment of the present invention.

[0018] Figure 2 For the general Figure 1 The first inner copper foil layer is made into an inner circuit layer, forming a cross-sectional view of an inner circuit substrate.

[0019] Figure 3 For Figure 2 A cross-sectional view of the bending region after the first covering film layer and the third covering film layer are formed is shown.

[0020] Figure 4 For Figure 3 The cross-sectional view is shown after the first single-sided copper clad substrate and the second single-sided copper clad substrate are pressed together in the first transmission area and the second transmission area respectively.

[0021] Figure 5 For Figure 4 A cross-sectional view of a first single-sided copper-clad substrate after at least two blind holes are formed thereon is shown.

[0022] Figure 6For selective electroplating Figure 5 Cross-sectional view of the blind via after it is filled with electroplated copper.

[0023] Figure 7 For the general Figure 6 The cross-sectional view of the first and second outer copper foil layers of the first and second single-sided copper clad substrates after being manufactured to form the first and second outer circuit layers.

[0024] Figure 8 For Figure 7 The cross-sectional view is shown after the second and fourth covering film layers are laminated on the first and second outer circuit layers.

[0025] Fig. 9 For Figure 8 The cross-sectional view shows a solder mask formed on the ground terminal in the first outer layer circuit exposed in the third covering film layer, and a nickel-gold layer formed on the signal terminal and part of the first outer layer circuit exposed from the third covering film layer.

[0026] Fig.10 For Fig. 9 The cross-sectional view of a transmission circuit board after the first and second shielding layers are formed on the second and fourth covering film layers is shown. The cross-sectional view of the transmission circuit board is a cross-sectional view along the extension direction of the transmission circuit board.

[0027] Fig.11 A cross-sectional view along the extension direction of a transmission circuit board provided for the second embodiment of the present invention.

[0028] Main component symbols

[0029]

[0030]

[0031]

[0032] The following specific implementation manner will further illustrate the present invention in conjunction with the above-mentioned drawings. DETAILED DESCRIPTION

[0033] In order to further explain the technical means and effects adopted by the present invention to achieve the predetermined invention purpose, the following is combined with the attached Figure 1-11 The specific implementation, structure, features and efficacy of the transmission circuit board and the manufacturing method thereof provided by the present invention are described in detail as follows. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of them. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0034] It should be noted that when an element is considered to be "connected" to another element, it may be directly connected to the other element or there may be a centrally disposed element at the same time. When an element is considered to be "disposed on" another element, it may be directly disposed on the other element or there may be a centrally disposed element at the same time.

[0035] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as those commonly understood by those skilled in the art of the present invention. The terms used herein in the specification of the present invention are only for the purpose of describing specific embodiments and are not intended to limit the present invention. The term "and / or" used herein includes any and all combinations of one or more related listed items.

[0036] See also Figure 1-10 The present invention provides a method for manufacturing a transmission circuit board 100, comprising the steps of:

[0037] Step S1, see Figure 1 , a copper clad substrate 10 is provided.

[0038] The copper clad substrate 10 is divided into a bending area 101 and a first transmission area 102 and a second transmission area 103 located at two sides of the bending area 101 .

[0039] In this embodiment, the copper clad substrate 10 is a single-sided copper clad substrate. Specifically, the copper clad substrate 10 includes a flexible substrate layer 11 and a first inner copper foil layer 12 formed on a surface of the substrate layer 11 .

[0040] In other embodiments, the copper clad substrate 10 may also be a double-sided copper clad substrate.

[0041] The material of the substrate layer 11 is one of polyimide (PI), modified polyimide (MPI), polyethylene terephthalate (PET) or polyethylene naphthalate (PEN), polyethylene (PE), Teflon (Teflon), liquid crystal polymer (LCP), polyvinylchloride polymer (PVC), ABF (Ajinomoto Build-up Film) materials, etc. Preferably, the material of the substrate layer 11 is PI or MPI.

[0042] Step S2, see Figure 2 The first inner copper foil layer 12 is manufactured to form an inner circuit layer 13 to form an inner circuit substrate 110 .

[0043] The first inner copper foil layer 12 is manufactured into the inner circuit layer 13 through an image transfer process.

[0044] The inner circuit layer 13 includes at least one signal circuit 131 and at least two ground circuits 132 located on both sides of the signal circuit 131 . The ground circuit 132 is electrically insulated from the signal circuit 131 .

[0045] Step S3, see Figure 3 A first covering film layer 14 and a third covering film layer 15 are respectively laminated on two opposite surfaces of the inner circuit substrate 110 located in the bending area 101 .

[0046] Specifically, in this embodiment, the first covering film layer 14 is formed on the inner circuit layer 13 , and the third covering film layer 15 is formed on the substrate layer 11 .

[0047] In other embodiments, the third covering film layer 15 may not be formed.

[0048] Step S4, see Figure 4 A first single-sided copper clad substrate 201 and a second single-sided copper clad substrate 202 are pressed onto opposite surfaces of the inner layer circuit substrate 110 located in the first transmission area 102 and the second transmission area 103 through a first adhesive layer 23 and a second adhesive layer 26 respectively.

[0049] In this embodiment, the first single-sided copper clad substrate 201 is formed on the inner circuit layer 13 through the first adhesive layer 23, and the second single-sided copper clad substrate 202 is formed on the first base material layer 11 through the second adhesive layer 26. In other embodiments, the first single-sided copper clad substrate 201 and the second single-sided copper clad substrate 202 can also be formed on opposite surfaces of the inner circuit substrate 110 by direct lamination or other methods.

[0050] The first single-sided copper clad substrate 201 includes a first dielectric layer 21 and a first outer copper foil layer 22 formed on the first dielectric layer 21. In this embodiment, the first adhesive layer 23 is formed on the inner circuit layer 13 located in the first transmission area 102 and the second transmission area 103, and the first dielectric layer 21 is formed on the first adhesive layer 23.

[0051] The second single-sided copper clad substrate 202 includes a second dielectric layer 24 and a second outer copper foil layer 25 formed on the second dielectric layer 24. In this embodiment, the second adhesive layer 26 is formed on the substrate layer 11 located in the first transmission area 102 and the second transmission area 103, and the second dielectric layer 24 is formed on the second adhesive layer 26.

[0052] The first dielectric layer 21 and the second dielectric layer 24 are made of at least one of materials with low dielectric loss such as liquid crystal polymer (LCP), polytetrafluoroethylene (PTFE), and modified polyimide (MPI).

[0053] In this embodiment, the first outer copper foil layer 22 and the second outer copper foil layer 25 are made of rolled copper foil (HA copper foil) and electrolytic copper foil (ED copper foil).

[0054] In other implementations, the second single-sided copper clad substrate 202 may not be formed.

[0055] Step S5, see Figure 5-6 At least two blind holes 27 are formed by recessing the first outer copper foil layer 22 toward both ends of each signal line 131 , and copper pillars 28 are formed by filling the at least two blind holes 27 with electroplated copper through selective electroplating.

[0056] In this embodiment, a plurality of vias (not shown) are formed in the first transmission area 102 and the second transmission area 103, and the vias are not formed in the bending area 101. The vias are electrically connected to the ground terminal 3121 (see below) of the first outer layer circuit 312, the ground circuit 132 and the second outer layer circuit 321 (see below).

[0057] The two ends of each signal line 131 are exposed from at least two blind holes 27 , and the two ends of each copper column 28 are electrically connected to the two ends of the corresponding signal line 131 and the first outer copper foil layer 22 .

[0058] In this embodiment, the blind via 27 passes through the first outer copper foil layer 22 , the first dielectric layer 21 , and the first adhesive layer 23 .

[0059] Step S6, see Figure 7 The first outer copper foil layer 22 and the second outer copper foil layer 25 are respectively manufactured to form a first outer circuit layer 31 and a second outer circuit layer 32 .

[0060] The first outer circuit layer 31 and the second outer circuit layer 32 are formed by an image transfer process.

[0061] The first outer circuit layer 31 includes at least two signal terminals 311 and at least one first outer circuit 312, and the first outer circuit 312 includes at least one ground terminal 3121. The ground terminal 3121 is electrically connected to the ground circuit 132 and the second outer circuit. The signal terminal 311 is electrically insulated from the ground terminal 3121. The signal terminal 311 can be used for component mounting, connection with other circuit boards or antennas, etc. The ground terminal 3121 can be used to connect electronic components that need to be grounded.

[0062] In other implementations, the first outer layer circuit 312 may not include the ground terminal 3121 .

[0063] The two ends of each signal line 131 are electrically connected to the two signal terminals 311 through the two copper pillars 28 formed in the two blind holes 27 .

[0064] The second outer circuit layer 32 includes at least one second outer circuit 321 .

[0065] Step S7, see Figure 8 A second covering film layer 33 is pressed on the first outer circuit layer 31 , and a fourth covering film layer 34 is pressed on the second outer circuit layer 32 .

[0066] In this embodiment, the second covering film layer 33 and the fourth covering film layer 34 extend by a length of 0.1 to 0.4 microns at the gap formed between the first covering film layer 14 and the third covering film layer 15 , respectively, and the adhesive layers of the second covering film layer 33 and the fourth covering film layer 34 overflow.

[0067] Specifically, during the lamination process, the glue layer of the second covering film layer 33 flows onto the first covering film layer 14 , thereby forming two first glue overflow portions 330 formed by the glue layer at the gap between the second covering film layer 33 and the first covering film layer 14 .

[0068] During the lamination process, the glue layer of the fourth covering film layer 34 flows onto the third covering film layer 15 , thereby forming two second glue overflow portions 340 formed by the glue layer at the gap between the fourth covering film layer 34 and the third covering film layer 15 .

[0069] The second cover film layer 33 is formed with at least two first openings 331, at least one third opening 333 and at least one fourth opening 334. One of the at least two first openings 331 and the third opening 333 are located in the first transmission area 102, and the other of the at least two first openings 331 and the fourth opening 334 are located in the second transmission area 103. At least two signal terminals 311 and at least two ground terminals 3121 are exposed from the at least two first openings 331, respectively. Part of the first outer layer circuit 312 is exposed from the third opening 333 and the fourth opening 334, respectively.

[0070] At least one fifth opening 341 and at least one sixth opening 342 are formed on the fourth covering film layer 34 . The fifth opening 341 is located in the first transmission region 102 , and the sixth opening 342 is located in the second transmission region 103 .

[0071] Step S8, see Fig. 9 A solder mask 36 is formed on the ground terminal 3121, and a nickel-gold layer 35 is formed on the signal terminal 311, the first outer layer circuit 312 exposed from the third opening 333 and the fourth opening 334, and the second outer layer circuit 321 exposed from the fifth opening 341 and the sixth opening 342.

[0072] Step S9, see Fig.10 A first shielding layer 41 is formed on the second covering film layer 33 and the first covering film layer 14, and a second shielding layer 42 is formed on the fourth covering film layer 34 and the third covering film layer 15, the first shielding layer 41 is electrically connected to the first outer layer line 312, and the second shielding layer 42 is electrically connected to the second outer layer line 321, so as to obtain the transmission circuit board 100.

[0073] The first shielding layer 41 includes two ends 411, a bottom 412, and two connecting parts 413 respectively connecting the two ends 411 and the bottom 412. The two ends 411 are formed on the second covering film layer 33 and are respectively electrically connected to the first outer layer circuit 312, the bottom 412 is formed on the first covering film layer 14, and the connecting part 413 is attached to the first overflow glue part 330. Specifically, the first overflow glue part 330 is filled in the first space 104 formed by the two connecting parts 413, the first covering film layer 14, the first dielectric layer 21 and the first outer layer circuit layer 31, which can solve the problem of poor filling of the first shielding layer 41 due to high step difference, thereby solving the problem of breakage of the first shielding layer 41.

[0074] The structure of the second shielding layer 42 is the same as that of the first shielding layer 41. The connecting portion of the second shielding layer 42 is attached to the second overflowing glue portion 340. Specifically, the first overflowing glue portion 330 is filled in the second space 105 formed by the connecting portion of the second shielding layer 42, the third covering film layer 15, the second dielectric layer 24 and the second outer circuit layer 32, which can solve the problem of poor filling of the second shielding layer 42 caused by the high step difference, thereby solving the problem of the breakage of the second shielding layer 42.

[0075] Specifically, the two ends 411 of the first shielding layer 41 are electrically connected to the first outer layer circuit 312 exposed from the third opening 333 and the fourth opening 334, respectively, and the two ends of the second shielding layer 42 are electrically connected to the second outer layer circuit 321 exposed from the fifth opening 341 and the sixth opening 342, respectively.

[0076] In other implementations, the second shielding layer 42 may not be included.

[0077] See also Fig.10 The first embodiment of the present invention further provides a transmission circuit board 100, which is divided into a bending area 101 and a first transmission area 102 and a second transmission area 103 located on both sides of the bending area 101. The transmission circuit board 100 includes a flexible substrate layer 11, an inner circuit layer 13 formed on a surface of the substrate layer 11, a first covering film layer 14 formed on the inner circuit layer 13 located in the bending area 101, a first adhesive layer 23 formed on the inner circuit layer 13 located in the first transmission area 102 and the second transmission area 103, a first dielectric layer 21 formed on the first adhesive layer 23, a first outer circuit layer 31 formed on the first dielectric layer 21, a second covering film layer 33 formed on the first outer circuit layer 31, and a first shielding layer 41 formed on the second covering film layer 33 and the first covering film layer 14.

[0078] The material of the substrate layer 11 is one of polyimide (PI), modified polyimide (MPI), polyethylene terephthalate (PET) or polyethylene naphthalate (PEN), polyethylene (PE), Teflon (Teflon), liquid crystal polymer (LCP), polyvinylchloride polymer (PVC), ABF (Ajinomoto Build-up Film) materials, etc. Preferably, the material of the substrate layer 11 is PI or MPI.

[0079] The inner circuit layer 13 includes at least one signal circuit 131 . The line width of the signal circuit 131 in the bending area 101 is smaller than the width of the signal circuit 131 in the first transmission area 102 and the second transmission area 103 .

[0080] The material of the first dielectric layer 21 is at least one of materials with low dielectric loss such as liquid crystal polymer (LCP), polytetrafluoroethylene (PTFE), and modified polyimide (MPI).

[0081] The first outer circuit layer 31 includes at least two signal terminals 311 and at least one first outer circuit 312. The first outer circuit 312 includes at least one ground terminal 3121. The signal terminal 311 is electrically insulated from the ground terminal 3121. The signal terminal 311 can be used for component mounting, connection with other circuit boards or antennas, etc. The ground terminal 3121 can be used for grounding.

[0082] In other implementations, the first outer layer circuit 312 may not include the ground terminal 3121 .

[0083] The two ends of each signal line 131 are electrically connected to the two signal terminals 311. In this embodiment, the transmission circuit board 100 further includes at least two blind holes 27 formed from the first outer circuit layer 31 to the two ends of each signal line 131, and at least two blind holes 27 are filled with copper pillars 28 formed by electroplating copper. The two ends of each signal line 131 are electrically connected to the two signal terminals 311 through the two copper pillars 28 formed in the two blind holes 27.

[0084] The first dielectric layer 21 is bonded to the inner circuit layer 13 located in the first transmission area 102 and the second transmission area 103 through the first adhesive layer 23. The blind via 27 penetrates the first outer copper foil layer 22, the first dielectric layer 21 and the first adhesive layer 23.

[0085] During the lamination process, the adhesive layer of the second covering film layer 33 flows onto the first covering film layer 14 , thereby forming two first adhesive overflow portions 330 formed by the adhesive layer at the gap between the second covering film layer 33 and the first covering film layer 14 .

[0086] The second cover film layer 33 is formed with at least two first openings 331, at least one third opening 333 and at least one fourth opening 334. One of the at least two first openings 331 and the third opening 333 are located in the first transmission area 102, and the other of the at least two first openings 331 and the fourth opening 334 are located in the second transmission area 103. At least two signal terminals 311 and at least two ground terminals 3121 are exposed from the at least two first openings 331, respectively. Part of the first outer layer circuit 312 is exposed from the third opening 333 and the fourth opening 334, respectively.

[0087] A solder mask 36 is formed on the ground terminal 3121 , and a nickel-gold layer 35 is formed on the signal terminal 311 and the second outer layer circuit 321 exposed from the first outer layer circuit 312 exposed from the third opening 333 and the fourth opening 334 .

[0088] The first shielding layer 41 includes two ends 411, a bottom 412, and two connecting parts 413 respectively connecting the two ends 411 and the bottom 412. The two ends 411 are formed on the second covering film layer 33 and are respectively electrically connected to the first outer layer circuit 312, the bottom 412 is formed on the first covering film layer 14, and the connecting part 413 is attached to the first overflow glue part 330. Specifically, the first overflow glue part 330 is filled in the first space 104 formed by the two connecting parts 413, the first covering film layer 14, the first dielectric layer 21 and the first outer layer circuit layer 31, which can solve the problem of poor filling of the first shielding layer 41 due to high step difference, thereby solving the problem of breakage of the first shielding layer 41.

[0089] The transmission circuit board 100 further includes a third covering film layer 15 formed on the substrate layer 11 located in the bending area 101, a second adhesive layer 26 formed on the substrate layer 11 located in the first transmission area 102 and the second transmission area 103, a second dielectric layer 24 formed on the second adhesive layer 26, a second outer circuit layer 32 formed on the second dielectric layer 24, a fourth covering film layer 34 formed on the second outer circuit layer 32, and a second shielding layer 42 formed on the third covering film layer 15 and the fourth covering film layer 34. The structure of the second shielding layer 42 is the same as that of the first shielding layer 41, and the second shielding layer 42 is electrically connected to the second outer circuit layer 32. At least one fifth opening 341 and at least one sixth opening 342 are formed on the fourth covering film layer 34, the fifth opening 341 is located in the first transmission area 102, and the sixth opening 342 is located in the second transmission area 103. The second outer circuit layer 32 further includes at least one second outer circuit 321. Part of the second outer circuit 321 is exposed from the fifth opening 341 and the sixth opening 342. Two ends of the second shielding layer 42 are electrically connected to the second outer circuit 321 exposed from the fifth opening 341 and the sixth opening 342, respectively.

[0090] During the lamination process, the glue layer of the fourth covering film layer 34 will flow onto the third covering film layer 15, thereby forming two second glue overflow portions 340 formed by the glue layer at the step difference between the fourth covering film layer 34 and the third covering film layer 15. Among them, the connecting portion of the second shielding layer 42 is attached to the second glue overflow portion 340. Specifically, the first glue overflow portion 330 is filled in the second space 105 formed by the connecting portion of the second shielding layer 42, the third covering film layer 15, the second dielectric layer 24 and the second outer circuit layer 32, which can solve the problem of poor filling of the second shielding layer 42 caused by the high step difference, thereby solving the problem of the breakage of the second shielding layer 42.

[0091] The second dielectric layer 24 is made of at least one of liquid crystal polymer (LCP), polytetrafluoroethylene (PTFE), modified polyimide (MPI), and other materials with low dielectric loss.

[0092] A nickel-gold layer 35 is also formed on the second outer layer circuit 321 exposed from the fifth opening 341 and the sixth opening 342 .

[0093] The ground terminal 3121 , the ground circuit 132 and the second outer layer circuit 321 are electrically connected through a plurality of vias. The vias are located in the first transmission area 102 and the second transmission area 103 , and are not located in the bending area 101 .

[0094] In addition, in this embodiment, the thickness of the first dielectric layer 21 and the second dielectric layer 24 are respectively greater than the thickness of the substrate layer 11, the thickness of the first adhesive layer 23 is the same as the thickness of the second adhesive layer 26, and the thickness of the first dielectric layer 21 is the same as the thickness of the second dielectric layer 24, so as to improve the performance of the transmission circuit board 100.

[0095] In addition, in this embodiment, the first shielding layer 41 and the second shielding layer 42 both have a conductive layer (not shown), the conductive layer is made of Ag, and the thickness of Ag is controlled to be 0.1 to 0.5 microns. Of course, the first shielding layer 41 and the second shielding layer 42 may also be used without a conductive layer, in which case the shielding effect of the first shielding layer 41 and the second shielding layer 42 is relatively poor.

[0096] See also Fig.11The second embodiment of the present invention further provides a transmission circuit board 200, and the structure of the transmission circuit board 200 is basically the same as that of the transmission circuit board 100, except that: the transmission circuit board 200 does not include a second shielding layer 42, but includes a third shielding layer 43 formed on the substrate layer 11 located in the bending area 101, and the third covering film layer 15 is formed on the third shielding layer 43, and the third shielding layer 43 has a shielding effect.

[0097] The third shielding layer 43 may be solid copper or grid-shaped copper. When the third shielding layer is grid-shaped copper, the copper exposure rate of the third shielding layer 43 is greater than 50%.

[0098] Accordingly, the manufacturing method of the transmission circuit board 200 provided in the second embodiment of the present invention is different from the manufacturing method of the transmission circuit board 100 in that:

[0099] In step S1 , the copper clad substrate 10 further includes a second inner copper foil layer 44 formed on the base material layer 11 .

[0100] In step S2 , the second inner copper foil layer 44 is manufactured to form a third shielding layer 43 .

[0101] In step S3 , the third covering film layer 15 is formed on the third shielding layer 43 .

[0102] In step S9 , the second shielding layer is not formed.

[0103] The transmission circuit board and the manufacturing method thereof provided by the present invention adopt a flexible material as a substrate layer, set a bending area between a first transmission area and a second transmission area, only add layers on the inner layer circuit layer located in the first transmission area and the second transmission area to form a first outer layer circuit area, and form a first shielding layer on the first outer layer circuit layer, 1) the bending area of ​​the transmission circuit board only includes an inner layer circuit layer and a substrate layer, so that the transmission circuit board can have good dynamic bending ability, thereby extending the service life of the transmission circuit board; 2) the first shielding layer includes two ends and a bottom connecting the end and the bottom, the end of the first shielding layer is electrically connected to the outer layer circuit of the outer layer circuit layer and the first shielding layer is electrically connected to the outer layer circuit of the outer layer circuit layer. The bottom of the shielding layer is formed on the first covering film layer in the bending area. Since the grounding terminal is part of the outer grounding circuit and is electrically connected to the grounding circuit of the inner circuit layer, the first shielding layer can be grounded, so that the first shielding layer can be grounded while playing a shielding role, avoiding signal backflow and improving the shielding effect; 3) The glue layer of the second covering film layer will flow to the first covering film during pressing, thereby forming an overflow portion formed by the glue layer at the gap between the second covering film layer and the first covering film layer. The overflow portion is in contact with the first shielding layer, which can solve the problem of poor filling of the first and second shielding layers caused by the high gap, thereby solving the problem of breakage of the first and second shielding layers.

[0104] The above is only a preferred embodiment of the present invention and is not intended to limit the present invention in any form. Although the present invention has been disclosed as a preferred embodiment as above, it is not intended to limit the present invention. Any technician familiar with this profession can make some changes or modify the technical contents disclosed above into equivalent embodiments without departing from the scope of the technical solution of the present invention. However, any simple modification, equivalent change and modification made to the above embodiments based on the technical essence of the present invention without departing from the content of the technical solution of the present invention still falls within the scope of the technical solution of the present invention.

Claims

1. A transmission circuit board, the transmission circuit board is divided into a bending area and a first transmission area and a second transmission area located on both sides of the bending area; characterized in that: The transmission circuit board comprises: a substrate layer, wherein the substrate layer is flexible; an inner circuit layer formed on a surface of the substrate layer; a first covering film layer formed on the inner circuit layer located in the bending area; a first dielectric layer formed on the inner wiring layer located in the first transmission area and the second transmission area; a first outer circuit layer formed on the first dielectric layer; a second covering film layer formed on the first outer circuit layer; and a first shielding layer formed on the second covering film layer and the first covering film layer; the first shielding layer includes two ends and a bottom, the two ends are formed on the second covering film layer and are respectively electrically connected to the first outer layer circuit, and the bottom is formed on the first covering film; Part of the glue layer of the second covering film layer flows onto the first covering film layer to form two first overflowing glue parts; the first shielding layer also includes two connecting parts, the two connecting parts are formed on the first overflowing glue parts of the second covering film layer, and the two connecting parts are respectively connected to the two ends and the bottom; the first overflowing glue part is filled in the first space formed by the two connecting parts, the first covering film layer, the first dielectric layer and the first outer circuit layer.

2. The transmission circuit board according to claim 1, characterized in that: The transmission circuit board also includes: a third covering film layer formed on the substrate layer in the bending region; a second dielectric layer formed on the substrate layer located in the first transmission area and the second transmission area; a second outer circuit layer formed on the second dielectric layer; and A fourth covering film layer is formed on the second outer circuit layer.

3. The transmission circuit board according to claim 2, characterized in that: The transmission circuit board also includes a second shielding layer formed on the third covering film layer and the fourth covering film layer; the structure of the second shielding layer is the same as that of the first shielding layer, and the second shielding layer is electrically connected to the second outer circuit layer.

4. The transmission circuit board according to claim 1, characterized in that: a third shielding layer formed at least on the substrate layer in the bending region and away from the inner circuit layer; a third covering film formed on the third shielding layer located in the bending region; A second dielectric layer formed on the substrate layer located in the first transmission area and the second transmission area and away from the inner circuit layer; a second outer circuit layer formed on the second dielectric layer; A fourth covering film layer is formed on the second outer circuit layer.

5. The transmission circuit board according to claim 3, characterized in that: Part of the glue layer of the fourth covering film layer flows onto the third covering film layer to form two second overflowing glue parts; the second overflowing glue parts fill the second space formed by the two connecting parts of the second shielding layer, the third covering film layer, the second dielectric layer and the second outer circuit layer.

6. The transmission circuit board according to claim 1, characterized in that: The inner circuit layer includes at least one signal circuit and at least two inner ground circuits located on both sides of the signal circuit; the first outer circuit layer also includes at least two signal line terminals and a first outer circuit, the first outer circuit includes at least one ground terminal, and the two ends of the signal circuit are respectively electrically connected to the two signal line terminals through copper pillars; the inner ground circuit is electrically connected to the ground terminal through a via; the via is formed in the first transmission area and the second transmission area, and is not formed in the bending area.

7. A method for manufacturing a transmission circuit board according to any one of claims 1 to 6, characterized in that: include: A copper-clad substrate is provided, wherein the copper-clad substrate is divided into a bending area and a first transmission area and a second transmission area located on both sides of the bending area; the copper-clad substrate comprises a flexible substrate layer and a first inner copper foil layer formed on the substrate layer; The first inner copper foil layer is manufactured to form an inner circuit layer, wherein the inner circuit layer includes at least one signal circuit and at least two inner ground circuits located on both sides of the signal circuit; Laminating a first covering film layer on the inner circuit layer located in the bending area; A first single-sided copper-clad substrate is pressed onto the inner circuit layer located in the first transmission area and the second transmission area through a first adhesive layer, wherein the first single-sided copper-clad substrate includes a first dielectric layer formed on the inner circuit layer located in the first transmission area and the second transmission area and a first outer copper foil layer formed on the first dielectric layer; Drilling at least two blind holes from the first outer copper foil layer to both ends of each signal line, and filling the at least two blind holes with electroplated copper to form copper pillars by selective electroplating; The first outer copper foil layer is made into a first outer circuit layer; the first outer circuit layer includes a first outer circuit and at least two signal line terminals; the signal line terminals are electrically connected to two ends of the signal circuit through copper pillars; Laminating a second covering film layer on the first outer circuit layer; A first shielding layer is formed on the second covering film layer and the first covering film layer. The first shielding layer includes two ends and a bottom. The two ends are formed on the second covering film layer and are electrically connected to the first outer layer circuit respectively. The bottom is formed on the first covering film.

8. The method for manufacturing a transmission circuit board according to claim 7, characterized in that: While laminating the first covering film layer, the method further includes the steps of: laminating a third covering film layer on the substrate layer located in the bending area; The process of laminating the first single-sided copper-clad substrate also includes the following steps: A second single-sided copper-clad substrate is pressed onto the base material layer located in the first transmission area and the second transmission area through a second adhesive layer, wherein the second single-sided copper-clad substrate includes a second dielectric layer formed on the base material layer located in the first transmission area and the second transmission area and a second outer copper foil layer formed on the second dielectric layer; While drilling to form the blind hole, the steps are also included: A plurality of via holes are formed in the first transmission area and the second transmission area, and no via holes are formed in the bending area; While forming the first outer circuit layer, the process also includes the following steps: The second outer copper foil layer is made into a second outer circuit layer; the via hole electrically connects the first outer circuit, the inner ground circuit and the second outer circuit layer; While laminating the second covering film layer, the steps also include: A fourth covering film layer is laminated on the second outer circuit layer.

9. The method for manufacturing a transmission circuit board according to claim 8, characterized in that: The copper-clad substrate also includes a second inner copper foil layer formed on the other opposite surface of the substrate layer. While forming the inner circuit layer, it also includes the steps of: making the second inner copper foil layer into a third shielding layer, and forming the third covering film layer on the third shielding layer.

10. The method for manufacturing a transmission circuit board according to claim 8, characterized in that: Also includes the steps: A second shielding layer is formed on the fourth covering film layer and the third covering film layer. The structure of the second shielding layer is the same as that of the first shielding layer. The second shielding layer is electrically connected to the second outer circuit layer.

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