A manufacturing method of a highly reliable flexible circuit board with a surface treatment on a tin layer

Abstract

The present invention discloses a manufacturing method for a highly reliable flexible circuit board with surface treatment of a tin layer. The flexible circuit board is manufactured according to design data and in a structure of a panelized board; the manufacturing method includes the steps of: manufacturing the panelized board to form a flexible core board; printing conductive paste on the flexible core board to form a printed core board; passing the printed core board through reflow soldering and undergoing subsequent process treatment to form a flexible circuit board; the overall solution is based on the method of printing solder paste on the surface of the flexible circuit board and passing it through reflow soldering to form an effective surface treatment of the tin layer, replacing the traditional process of spraying tin; based on the designed board body structure and positioning hole structure, using a first support plate and a second support plate to match the designed structure, realizing a continuous, complete, and high-precision processing process of the conductive paste, and using reflow soldering treatment to form a flexible circuit board with good surface treatment of the tin layer, improving problems such as board body deformation, tin pollution, and even board body tearing, and reducing manual processing.

Description

Technical Field

[0001] The present invention relates to the field of flexible circuit board processing, and particularly to a method for manufacturing a highly reliable flexible circuit board with surface treatment of a tin layer. Background Art

[0002] For some circuit boards applied to communication products, computers and other products, hot air solder leveling is used for surface treatment, which has advantages such as low cost and easy soldering. The essence of hot air solder leveling is to place the board to be processed into a molten tin bath, and while taking it out of the tin bath, use hot air to blow off the excess tin on the surface and in the holes of the printed circuit board, and the remaining tin is evenly coated on the pads and the inner walls of the through holes to form the surface treatment process.

[0003] When a flexible circuit board needs to use hot air solder leveling for surface treatment, due to the softness of the board, the flexible board needs to be fixed on a rigid support frame during hot air solder leveling and then processed together.

[0004] However, when the flexible circuit board is relatively thin or the finished board is required to have high flexibility, during hot air solder leveling, the molten tin bath and strong hot air will have a strong impact on the board, resulting in problems such as board deformation, tin pollution, and even board tearing. If a support board with a dense skeleton is used for support, for a flexible circuit board with a small size and a large hot air solder leveling density, after hot air solder leveling, it will be difficult for the support board to be processed in subsequent processes, resulting in a high dependence on manual operation during the processing and easy damage to the board.

[0005] Based on the above background art and problems, a method for manufacturing a flexible circuit board with surface treatment of a tin layer to replace hot air solder leveling is needed. Summary of the Invention

[0006] Aiming at the problems of board deformation, tin pollution, and even board tearing in the hot air solder leveling of flexible circuit boards in the prior art, as well as the problems of dependence on manual labor and easy damage to the board, the present invention provides a method for manufacturing a highly reliable flexible circuit board with surface treatment of a tin layer. The flexible circuit board is made according to design data and in a panelized structure. The manufacturing method includes the following steps:

[0007] S10: Manufacturing the panelized board into a flexible core board;

[0008] S20: Printing conductive paste on the flexible core board to form a printed core board;

[0009] S30: Passing the printed core board through reflow soldering and performing post-process treatment to form the flexible circuit board.

[0010] Further, the puzzle board is designed with forming lines. The area within the forming lines is the effective area, and other areas are invalid areas. The manufacturing of the flexible core board includes: pre-sizing the invalid areas on the edges of the puzzle board to form auxiliary tool areas, and then manufacturing circuit patterns to form the flexible core board; the circuit patterns include first-side pads distributed on the first side of the flexible core board, second-side pads on the second side, and core board through holes penetrating the flexible core board.

[0011] Further, the printing of the conductive paste includes: manufacturing a first supporting pad, fixing the second side of the flexible core board relative to the first supporting pad, manufacturing a first stencil, the mesh holes of the first stencil corresponding to the core board through holes and the first-side pads; printing the conductive paste on the first side to form a single-sided printed core board.

[0012] Further, the first supporting pad is made with a first pad groove body, and the first pad groove body is distributed corresponding to the core board through holes; the auxiliary tool area is made with printing positioning holes, and the first supporting pad is made with hanging pins corresponding to the printing positioning holes. The fixing is to fix the positioning holes to the hanging pins to fix the flexible core board.

[0013] Further, the printing of the conductive paste includes: manufacturing a second supporting pad, setting the first side of the single-sided printed core board relative to the second supporting pad to fix the single-sided printed core board, manufacturing a second stencil, the mesh holes of the second stencil corresponding to the second-side pads; printing the conductive paste on the second side to form a double-sided printed core board;

[0014] Further, the second supporting pad is composed of a frame board and a supporting board. The frame board is made with a frame grid skeleton and frame grid through slots. The frame grid skeleton is distributed corresponding to the auxiliary tool area. The supporting board corresponds to the frame grid through slots and is detachably placed in the frame grid through slots. The surface of the supporting board corresponding to the first side is made with pad grooves, some of the pad grooves corresponding to the first-side pads and some corresponding to the core board through holes. The supporting board is made with pin holes; the surface of the frame grid skeleton is made with an adhesive layer.

[0015] Further, use pins to fix the supporting board to the tabletop of the printing equipment through the pin holes, put the frame grid skeleton around the supporting board, align the single-sided printed core board with the supporting board, and adhere it to the frame grid skeleton through the adhesive layer. Print the conductive paste through the second stencil to form a double-sided printed core board.

[0016] Further, the conductive paste is solder paste. The conductive paste fills the core board through holes and covers the first-side pads and the second-side pads.

[0017] Further, subjecting the printed core board to reflow soldering includes: removing the double-sided printed core board together with the grid frame after printing the conductive paste to form the printed core board, and placing the printed core board in the reflow soldering equipment for heating to form a welded board.

[0018] Further, the post-processing includes: drilling the core board through-holes corresponding to the welded board.

[0019] The technical solution of the present invention is overall based on the method of printing solder paste on the surface of a flexible circuit board and subjecting it to reflow soldering to form an effective tin layer surface treatment, replacing the traditional spray tin processing method.

[0020] Further, first pre-expand the board body to provide a basis for subsequent fixing and transfer processing, effectively ensuring that the internal processing of the original board body is not affected; by designing a first support backing plate and performing printing of conductive paste processing on the first side, further designing a second support backing plate and performing printing of conductive paste processing on the second side, the effect of effectively covering the first-side pads and the second-side pads with conductive paste on both sides and filling the through-holes is formed.

[0021] Further, based on the printing of conductive solder on the first side, design a second support plate composed of a support plate and a frame plate. After printing the conductive paste on the second side, the frame plate is removed together with the double-sided printed core board to form the supporting effect of the frame plate on the flexible board body, and then they are subjected to reflow soldering together to complete the process of effective melting and covering of the solder paste. The first support plate and the second support plate ensure the supportability of the flexible board body and ensure the continuity of processing.

[0022] Further, for the through-holes filled with solder, use the method of back drilling or laser ablation to form via holes, improving the processing accuracy of the via holes and ensuring the good application of the plug holes.

[0023] The overall technology forms the basis for the subsequent processing by designing the board body structure and the positioning hole structure, and uses the first support plate and the second support plate to match the designed structure to achieve a continuous, complete, and high-precision processing process of the conductive paste. Then, reflow soldering and post-processing are used to form a flexible circuit board with a good tin layer surface treatment, effectively improving problems such as board body deformation, tin pollution, and even board body tearing, and reducing the degree of manual participation in the processing process to avoid problems such as easy damage of the board body. Description of the Drawings

[0024] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the drawings required for the description of the embodiments or the prior art. Obviously, the drawings in the following description are only some embodiments of the present invention. For those of ordinary skill in the art, without creative efforts, other drawings can be obtained based on the structures shown in these drawings.

[0025] Figure 1 It is the main process flow chart included in the embodiment of the present invention;

[0026] Figure 2 It is a schematic cross-sectional structure diagram of the flexible core board formed in this embodiment;

[0027] Figure 3 It is a schematic cross-sectional structure diagram of printing the conductive paste on the first side in this embodiment;

[0028] Figure 4 It is a schematic cross-sectional structure diagram of printing the conductive paste on the second side in this embodiment;

[0029] Figure 5 It is a schematic cross-sectional structure diagram of removing the printed core board in this embodiment;

[0030] Figure 6 It is a schematic plan view of the printed core board in this embodiment;

[0031] Figure 7 It is a schematic cross-sectional structure diagram of the printed core board after reflow soldering in this embodiment;

[0032] Figure 8 It is a schematic cross-sectional structure diagram of the flexible circuit board in this embodiment.

[0033] Description of the attached drawing reference numerals: 10, flexible core board; 100, insulating dielectric layer; 1110, forming line; 1120, outer shape line of the panel; 1210, auxiliary tool area; 1310, first-side pad; 1320, second-side pad; 1410, through hole of the core board; 1510, printing positioning hole; 1520, forming positioning hole; 10J, conductive paste; 10D, single-sided printed core board; 20, first stencil; 2110, mesh holes of the first stencil; 30, first support backing plate; 3110, groove body of the first backing plate; 3120, hanging nail; 40A, first tabletop; 40B, second tabletop; 410, pin hole on the tabletop; 40X, pin; 10S, double-sided printed core board; 50, second stencil; 5110, mesh holes of the second stencil; 60, second support backing plate; 610, frame board; 610A, frame grid; 610B, frame through slot; 620, support plate; 6110, adhesive layer; 6210, backing plate groove; 6220, pin hole; 70, printed core board; 80, welding plate; 90, flexible circuit board; 910, through hole.

[0034] The realization, functional features and advantages of the object of the present invention will be further described with reference to the embodiments and the accompanying drawings. Detailed implementation manners

[0035] Next, the technical solutions in the embodiments of the present invention will be clearly and completely described in conjunction with the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without making creative efforts belong to the scope of protection of the present invention.

[0036] It should be noted that all directional indications (such as up, down, left, right, front, back, inside, outside, etc.) in the embodiments of the present invention are only used to explain the relative positional relationship and movement conditions between components in a specific posture (as shown in the accompanying drawings). If the specific posture changes, the directional indications will also change accordingly.

[0037] In addition, the descriptions such as "first" and "second" in the present invention are only for descriptive purposes, and cannot be understood as indicating or implying their relative importance or implicitly indicating the quantity of the indicated technical features. Thus, the features defined with "first" and "second" may explicitly or implicitly include at least one such feature. In the description of the present invention, "a plurality" means at least two, such as two, three, etc., unless otherwise specifically defined.

[0038] In addition, the technical solutions between the various embodiments of the present invention can be combined with each other, but it must be based on the ability of those of ordinary skill in the art to implement. When the combination of technical solutions is contradictory or cannot be implemented, it should be considered that such a combination of technical solutions does not exist and is not within the scope of protection required by the present invention.

[0039] Please refer to Figure 1 ; Figure 1 which is the main process flow chart included in the embodiment of the present invention.

[0040] The manufacturing method of the highly reliable flexible circuit board with surface treatment of the tin layer according to the embodiment of the present invention includes Figure 1 the main manufacturing process flow, which will be described in detail in the following steps.

[0041] Please refer to Figure 2 ; Figure 2 which is a schematic cross-sectional structure diagram of the flexible core board formed in this embodiment.

[0042] Step S10:

[0043] Manufacture a flexible core board 10 from a panel.

[0044] In this embodiment, the panel is designed with a forming line 1110. The area within the forming line 1110 is the effective area, and other areas are invalid areas. Manufacturing the flexible core board 10 includes: enlarging the invalid areas at the edges of the panel in advance to form an auxiliary tool area 1210, and then manufacturing a circuit pattern to form the flexible core board 10; the circuit pattern includes a first-side pad 1310 distributed on the first side of the flexible core board 10, a second-side pad 1320 on the second side, and a core board through hole 1410 penetrating the flexible core board 10. The flexible core board 10 includes an insulating dielectric layer 100.

[0045] Enlarge the panel in advance, which is to enlarge the area outward from the panel outline line 1120 of the original panel, and enlarge all four sides of the panel surface for manufacturing tool holes such as printing positioning holes 1510 (and other tool patterns used in the processing).

[0046] During the processing of the flexible circuit board 90, operations such as alignment, positioning, and electroplating clamping are required. Therefore, it is necessary to manufacture the flexible circuit board in the form of a panel. The edge of the board body formed by the panel is an invalid area, which is used to distribute hole patterns such as forming positioning holes 1520 and tool patterns used for alignment processing. In the final forming process, the invalid area is removed to form the finished flexible circuit board 90.

[0047] In this embodiment, since the single-sided printed core board 10D needs to be adhered to the grid framework 610A later, and after processing, the grid framework 610A needs to be removed. At this time, the double-sided printed core board 10S on this part adhered to the grid framework 610A is also removed. Therefore, before manufacturing the flexible core board 10, that is, the panel needs to be pre-expanded, and a part for subsequent removal needs to be reserved while maintaining its original size; that is, pre-expansion design is carried out when designing the data. When cutting the material, the material is cut according to the pre-expanded size and processed.

[0048] Optionally, the size of the single-sided pre-expansion is 100 μm to 5 mm to ensure the supportability and accuracy during the processing.

[0049] The flexible core board 10 is manufactured to form pads and vias for the subsequent printing of the conductive paste 10J. During the actual processing, generally, the pads 1310 on the first side and the pads 1320 on the second side are asymmetric. Therefore, corresponding support plates 620 on both sides need to be designed for processing later; among them, the core board via 1410 is a via after electroplating, that is, a conductive via. The manufacturing process is "core board drilling → full-board electroplating → manufacturing the outer layer pattern". The conductive via can provide an effective copper adhesion hole basis for the subsequent printing of the conductive paste 10J and the melting adhesion of the conductive paste 10J.

[0050] Please refer to Figures 3 to 7 ; Figure 3 It is a schematic cross-sectional structure diagram of printing the conductive paste on the first side in this embodiment; Figure 4 It is a schematic cross-sectional structure diagram of printing the conductive paste on the second side in this embodiment; Figure 5 It is a schematic cross-sectional structure diagram of removing the printed core board in this embodiment; Figure 6 It is a schematic plan structure diagram of the printed core board in this embodiment; Figure 7 It is a schematic cross-sectional structure diagram of the printed core board after reflow soldering in this embodiment.

[0051] Step S20:

[0052] Print the conductive paste 10J on the flexible core board 10 to form a printed core board 70.

[0053] In this embodiment, printing the conductive paste 10J includes: manufacturing the first support pad 30, fixing the second side of the flexible core board 10 relative to the first support pad 30, manufacturing the first stencil 20, the mesh holes 2110 of the first stencil corresponding to the core board vias 1410 and the pads 1310 on the first side; printing the conductive paste 10J on the first side to form a single-sided printed core board 10D (as Figure 3 shown).

[0054] Optionally, the thickness of the first support pad 30 is 0.5 mm to 3.0 mm.

[0055] Since the flexible core board 10 is made of a flexible material and does not have self-supporting properties, when printing the conductive paste 10J, it is necessary to use the support plate 620 as a support and fixation to provide printable supportability.

[0056] In this embodiment, it is necessary to print the conductive paste 10J into the core board through-hole 1410 and onto the surface of the pad. Therefore, stencil printing in the soldering process is adopted to achieve the effects of precise positioning and precise printing. Compared with screen printing or offset printing, it has higher processing accuracy.

[0057] Optionally, the size of the mesh holes 2110 of the first stencil corresponding to the first-side pads 1310 is equal to the size of the first-side pads 1310, or is greater than the size of the first-side pads 1310 by 20 μm to 30 μm on one side; the size of the mesh holes 2110 of the first stencil corresponding to the core board through-holes 1410 is equal to the size of the core board through-holes 1410 including the hole rings, or is greater than the size of the core board through-holes 1410 including the hole rings by 20 μm to 30 μm on one side; when the size conditions permit, a pre-large on one side can improve the alignment accuracy and enable the printed conductive paste 10J to cover the pads or the core board through-holes 1410.

[0058] In this embodiment, the first support backing plate 30 is made with a first backing plate groove 3110, and the first backing plate groove 3110 is distributed corresponding to the core board through-holes 1410; the auxiliary tool area 1210 is made with printing positioning holes 1510, and the first support backing plate 30 is made with hanging pins 3120 corresponding to the printing positioning holes 1510. To fix, the printing positioning holes 1510 are fixed to the hanging pins 3120 to fix the flexible core board 10.

[0059] Since printing the conductive paste 10J requires filling the core board through-holes 1410 completely, it is necessary to ensure the air conduction performance during printing. Therefore, the first support backing plate 30 needs to be made with a first backing plate groove 3110 so that the core board through-holes 1410 will not have problems with gas blockage when printing the conductive paste 10J. Optionally, the first backing plate groove 3110 can be a through groove or a half groove, and the depth of the half groove is 0.5 mm to 2.5 mm.

[0060] It is worth noting that if the through-holes are processed by drilling in the previous process, the corresponding holes are drilled in the backing plate used for drilling, and the backing plate after drilling can be used as the first backing plate groove 3110.

[0061] In this embodiment, printing the conductive paste 10J includes: making a second support backing plate 60, setting the first side of the single-sided printed core board 10D opposite to the second support backing plate 60 to fix the single-sided printed core board 10D, making a second stencil 50, and the mesh holes 5110 of the second stencil corresponding to the second-side pads 1320; printing the conductive paste 10J on the second side to form a double-sided printed core board 10S.

[0062] Similar to the printing of the first side, conductive paste 10J is printed on the pads 1320 of the second side by means of stencil printing. Since the conductive paste 10J has been filled in the core board vias 1410 during the printing of the first side, there is no need to fill it again on the second side.

[0063] In this embodiment, the second support backing plate 60 is composed of a frame plate 610 and a support plate 620. The frame plate 610 is made with a grid framework 610A and grid through slots 610B. The grid framework 610A is distributed corresponding to the auxiliary tool area 1210. The support plate 620 corresponds to the grid through slots 610B and is detachably placed in the grid through slots 610B. The surface of the support plate 620 corresponding to the first side is made with backing plate slots 6210. Some of the backing plate slots 6210 correspond to the pads 1310 on the first side, and some of the backing plate slots 6210 correspond to the core board vias 1410. The support plate 620 is made with pin holes 6220; the surface of the grid framework 610A is made with an adhesive layer 6110.

[0064] In this embodiment, the printing of the conductive paste 10J includes: fixing the support plate 620 to the table surface of the printing equipment through the pin holes 6220 using pins 40X, that is, fixing it to the second table surface 40B through the table surface pin holes 410, sleeving the grid framework 610A around the support plate 620, aligning the single-sided printed core board 10D with the support plate 620, optionally aligning through alignment holes or alignment targets, and adhering it to the grid framework 610A through the adhesive layer 6110, and printing the conductive paste 10J through the second stencil 50 to form a double-sided printed core board 10S (as Figure 4 shown).

[0065] Since the conductive paste 10J has been printed on the first side, when making the second side, it is necessary to prevent problems such as smearing, collision, and scratching of the conductive paste 10J on the first side. Therefore, it needs to be vertically taken out and vertically placed during processing, or an automated mechanical device can also be used to suck and place it. And the second support backing plate 60 needs to be made with backing plate slots 6210 to provide space to prevent defects such as smearing for the conductive paste 10J that has been printed on the first side.

[0066] In addition to being distributed corresponding to the auxiliary tool area 1210, if there is no further special processing required before subsequent forming, the grid framework 610A can also be optionally distributed corresponding to the invalid area inside the plate body. That is, the grid framework 610A can be set corresponding to the invalid area of the plate body to provide stronger support for the overall plate body and facilitate better support during subsequent reflow soldering processing.

[0067] It should be noted that after the conductive paste 10J on the second side is printed in the subsequent printing process, the double-sided printed core board 10S and the frame board 610 need to be removed together. At the same time, the support board 620 needs to be fixedly retained on the second table 40B without being removed. That is, by adopting the method of jointly removing and processing the frame board 610 and the double-sided printed core board 10S, the support board 620 can be firmly fixed on the second table 40B through the pin 40X, while the frame board 610 is tightly sleeved on the support board 620 and fixed by relying on the support board 620, forming the effect that the subsequent frame board 610 is easy to remove while the support board 620 is not removed. Optionally, to improve the printing accuracy of the double-sided printed core board 10S, the frame board 610 can also be fixed by the method of pin fixation. After printing, the pin is pulled out to remove the frame board 610.

[0068] Optionally, the thickness of the support board 620 is the same as that of the frame board 610, which can provide a flat supporting force and prevent the board surface from being uneven.

[0069] Optionally, the material of the support board 620 and the thickness material of the frame board 610 can be optionally FR-4 material, aluminum plate, PVC and other materials with supporting force.

[0070] Optionally, the adhesive layer 6110 is one of acrylic glue, epoxy resin glue or polyolefin glue. The adhesive layer 6110 can effectively adhere the single-sided printed core board 10D to the frame board 610 to fix the single-sided printed core board 10D. The fusion method (before the multilayer circuit board lamination process) can also be used for hot melt adhesion.

[0071] It should be noted that when printing the conductive paste 10J on the first side, the first support board 30 also needs to be fixed on the first table 40A.

[0072] In this embodiment, the conductive paste 10J is solder paste. The conductive paste 10J fills the through holes 1410 of the core board and covers the first-side pads 1310 and the second-side pads 1320.

[0073] In this embodiment, solder paste is printed on the board surface of the flexible circuit board 90 by means of stencil printing, and then processed by a reflow soldering device in the subsequent process, forming the effect of effectively covering the pads and the through holes 1410 of the core board with a tin surface, replacing the traditional spray tin (hot air leveling) processing method in the prior art, which has problems such as being too soft to perform spray tin processing, causing excessive damage to the board itself, resulting in excessive deformation, tin pollution and even tearing.

[0074] Please refer to Figure 8 ; Figure 8 It is a schematic cross-sectional structure diagram of the flexible circuit board of this embodiment.

[0075] Step S30:

[0076] The printed core board 70 is subjected to reflow soldering and undergoes post - process treatment to form a flexible circuit board 90.

[0077] In this embodiment, subjecting the printed core board 70 to reflow soldering includes: removing the double - sided printed core board 10S together with the frame skeleton 610A after printing the conductive paste 10J (as Figure 5 shown), to form the printed core board 70, that is, the double - sided printed core board 10S and the frame skeleton 610A together form the printed core board 70 (as Figure 6 shown), placing the printed core board 70 in a reflow soldering device for heating to form a welded board 80 (as Figure 7 shown).

[0078] Based on the support and protection of the double - sided printed core board 10S by the frame skeleton 610A, the printed solder paste is heated and melted by the reflow soldering device, so that the solder paste firmly adheres to the surfaces of the first - side pads 1310 and the second - side pads 1320, and the hole walls and hole rings of the core board through - holes 1410, forming a protection on the tin surface (and providing a solderability basis for subsequent welding of components); the heating process parameter curve of the reflow soldering is determined according to the type of solder paste used and the pad types, quantities, and structures of the double - sided printed core board 10S.

[0079] In this embodiment, the post - process treatment includes: drilling the core board through - holes 1410 corresponding to the welded board 80 to form through - holes 910 (as Figure 8 shown); it also includes performing shaping processing on the printed core board 70 that has undergone reflow soldering.

[0080] If the aperture of the core board through - hole 1410 is relatively small and it needs to be used as a plug - in hole, after reflow soldering, the molten solder paste will block the hole, and the hole can be opened by using the method of back - drilling to form an effective plug - in hole. It should be noted that since the board body of the flexible circuit board 90 is relatively thin, the laser ablation method can also be used to burn through the blocked tin in the hole.

[0081] It should be noted that due to the high precision of the circuit board in the actual design and processing process, the actual structure diagram and the dimensions such as the thickness between layers and the line width are in the micron level. For example, the thickness of each layer is generally between 5μm and 50μm. If the specification drawings are made according to the actual ratio, there will be a problem of unclear illustration. Therefore, in order to more clearly represent the implementation process of the manufacturing method, the drawings in this embodiment are all enlarged schematic diagrams of the technical features, which do not represent the dimensions of the actual structure diagram, nor do they represent an enlarged diagram of the actual structure diagram in proportion.

[0082] The above are only the preferred embodiments of the present invention, and do not limit the patent scope of the present invention accordingly. Any equivalent structural transformation made by using the content of the specification and drawings of the present invention under the inventive concept of the present invention, or any direct / indirect application in other related technical fields is included in the patent protection scope of the present invention.

Claims

1. A manufacturing method of a highly reliable flexible circuit board with a surface-treated tin layer. The flexible circuit board is manufactured according to design data and in a panelized structure; It is characterized in that The manufacturing method includes the following steps: S10: Manufacture the panelized structure into a flexible core board; The panelized structure is designed with a forming line. The area within the forming line is the effective area, and other areas are invalid areas. The manufacturing of the flexible core board includes: pre-sizing the invalid areas on the board edges of the panelized structure to form an auxiliary tool area, and then manufacturing a circuit pattern to form the flexible core board; the circuit pattern includes a first-side pad distributed on the first side of the flexible core board, a second-side pad on the second side, and a core board through-hole penetrating the flexible core board; S20: Print conductive paste on the flexible core board to form a printed core board; The printing of the conductive paste includes: manufacturing a first support pad, fixing the second side of the flexible core board relative to the first support pad, manufacturing a first stencil, the mesh holes of the first stencil corresponding to the core board through-holes and the first-side pads; printing the conductive paste on the first side to form a single-sided printed core board; The first support pad is manufactured with a first pad groove body, and the first pad groove body is distributed corresponding to the core board through-holes; The printing of the conductive paste includes: manufacturing a second support pad, setting the first side of the single-sided printed core board corresponding to the second support pad to fix the single-sided printed core board, manufacturing a second stencil, the mesh holes of the second stencil corresponding to the second-side pads; printing the conductive paste on the second side to form a double-sided printed core board; The second support pad is composed of a frame board and a support board. The frame board is manufactured with a frame grid skeleton and frame grid through-holes. The frame grid skeleton is distributed corresponding to the auxiliary tool area. The support board corresponds to the frame grid through-holes and is detachably placed in the frame grid through-holes. The surface of the support board corresponding to the first side is manufactured with pad grooves, some of the pad grooves corresponding to the first-side pads and some corresponding to the core board through-holes. The support board is manufactured with pin holes; the surface of the frame grid skeleton is manufactured with an adhesive layer; The printing of the conductive paste includes: using pins to fix the support board to the tabletop of the printing equipment through the pin holes, sleeving the frame grid skeleton around the support board, aligning the single-sided printed core board with the support board, and adhering it to the frame grid skeleton through the adhesive layer, and printing the conductive paste through the second stencil to form a double-sided printed core board; S30: Pass the printed core board through reflow soldering and perform post-process treatment to form the flexible circuit board; Passing the printed core board through reflow soldering includes: removing the double-sided printed core board together with the frame grid skeleton after printing the conductive paste to form the printed core board, and placing the printed core board in a reflow soldering equipment for heating to form a welded board.

2. The manufacturing method of a highly reliable flexible circuit board with a surface-treated tin layer according to claim 1, wherein, The auxiliary tool area is manufactured with printing positioning holes, and the first support pad is manufactured with hanging pins corresponding to the printing positioning holes. The fixing is to fix the positioning holes to the hanging pins to fix the flexible core board.

3. The manufacturing method of a highly reliable flexible circuit board with surface treatment of a tin layer according to claim 2, characterized in that, The conductive paste is solder paste, and the conductive paste fills the through holes of the core board and covers the first side pads and the second side pads.

4. The manufacturing method of a highly reliable flexible circuit board with a surface-treated tin layer according to claim 1, characterized in that The post-processing includes: drilling the through holes of the core board corresponding to the welding plate.

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