Multi-layer flexible circuit board with reliable shielding performance and manufacturing method thereof

Abstract

The invention discloses a multi-layer flexible circuit board with reliable shielding performance and a manufacturing method thereof. The method comprises the following steps: providing a multi-layer circuit substrate; the multi-layer circuit substrate is provided with an inner-layer signal line, an inner-layer grounding line and an outer-layer signal line; pasting a protective film on the multi-layer circuit substrate to form a grounding opening exposed from the protective film, and obtaining an initial multi-layer circuit board; performing primary shape punching to form a shielding film filling groove; a shielding film is pasted, so that electric conduction is formed between the first shielding film attached to the outer surface of the initial multilayer circuit board and the grounding opening, the second shielding film filled in the shielding film filling groove wraps the inner layer signal line, the inner layer grounding line and the outer layer signal line in the signal area, and a semi-finished product multilayer circuit board is obtained; and performing secondary shape punching based on the shielding film filling groove to obtain the target multilayer circuit board. A good signal shielding effect is achieved, excessive material layers do not need to be laminated, and meanwhile the bending performance of the multi-layer board is considered.

Description

Technical Field

[0001] The invention relates to the field of flexible circuit board manufacturing, and in particular to a multilayer flexible circuit board with reliable shielding performance and a manufacturing method thereof. Background Art

[0002] With the birth and development of flexible printed circuit boards (FPCBs), flexible printed circuit boards have increasingly higher requirements for signal transmission, especially for consumer electronics products for 5G applications, which require that the signal loss be as small as possible while ensuring the bending performance of the circuit board.

[0003] At present, for multi-layer flexible circuit boards with signal transmission requirements, the production method is usually as follows: Figure 1 As shown, after the inner flexible substrate (taking a double-sided board as an example, including an inner insulating layer 1 and an inner conductive layer 2) circuit is manufactured, the outer flexible substrate (a single-sided board, including an outer insulating layer 3 and an outer conductive layer 4) is directly pressed with the adhesive layer 5 to form a multi-layer board, and the inner grounding wire 22 and the inner signal line 21 on the inner flexible substrate are protected by the protective films 6 on the front and back sides. A hole is drilled from the protective films 6 on the front and back sides to the inner signal line 21, and the inner grounding wire 22 and the circuit on the outer conductive layer 4 are electroplated with copper through the hole 43, and the outer conductive layer 4 is shielded and protected by the outer protective film 6. The multi-layer flexible circuit board manufactured in this way is thicker, which will lead to a decrease in the bending performance of the flexible circuit board; at the same time, the problem of signal loss through the intermediate insulating material has not been solved, and the only area near the cross section of the hole has a high vertical shielding effect, and the signal loss in other areas is still large.

[0004] That is to say, in the current manufacturing method, in order to reduce line signal loss, it is necessary to increase the thickness of the material or use a metal layer to shield the signal line on the circuit board, which will lead to a decrease in the bending performance of the circuit board and fail to meet the existing bending performance requirements.

[0005] Therefore, it is necessary to develop a new production technology that can take into account the requirements of shielding performance and bending performance for multi-layer flexible circuit boards with signal transmission requirements, to ensure that the manufactured multi-layer flexible circuit boards have excellent bending performance and low signal loss, while having highly reliable shielding performance. Summary of the invention

[0006] In view of this, an embodiment of the present invention provides a multilayer flexible circuit board with reliable shielding performance and a manufacturing method thereof, so as to solve the problem that the existing multilayer flexible circuit board manufacturing technology cannot take into account the requirements of shielding performance and bending performance.

[0007] The present invention provides a method for manufacturing a multilayer flexible circuit board with reliable shielding performance, the method comprising:

[0008] A multilayer circuit substrate is provided; wherein the multilayer circuit substrate has an inner layer signal line, an inner layer ground line and an outer layer signal line, and the inner layer signal line and the outer layer signal line are electrically connected;

[0009] Applying a protective film to the multilayer circuit substrate, and forming a ground opening exposed from the protective film on the multilayer circuit substrate to obtain an initial multilayer circuit board;

[0010] Performing a profile punching operation on the initial multi-layer circuit board to form a shielding film filling groove on the initial multi-layer circuit board;

[0011] A shielding film is applied to the initial multilayer circuit board after the first shape punching, so that electrical conduction is formed between the first shielding film attached to the outer surface of the initial multilayer circuit board and the ground opening, and the second shielding film filled in the shielding film filling groove wraps the inner signal line, the inner ground line and the outer signal line in the signal area defined by the second shielding film, so as to obtain a semi-finished multilayer circuit board;

[0012] Based on the shielding film filling groove, the semi-finished multi-layer circuit board is punched out for a second time to obtain a target multi-layer circuit board.

[0013] Optionally, providing a multilayer circuit substrate includes:

[0014] providing an inner flexible substrate and an outer flexible substrate respectively;

[0015] Performing circuit fabrication on the inner layer flexible substrate to form the inner layer signal line and the inner layer ground line to obtain an inner layer circuit board;

[0016] Laminating the outer flexible substrate onto the inner circuit board to obtain a multi-layer flexible substrate;

[0017] The outer layer circuit is manufactured on the multi-layer flexible substrate, and the outer layer signal line which is conductive with the inner layer signal line is formed on the multi-layer flexible substrate to obtain the multi-layer circuit substrate.

[0018] Optionally, a ground opening area matching the ground opening is reserved on the outer flexible substrate on the multi-layer circuit substrate;

[0019] The step of attaching a protective film to the multilayer circuit substrate and forming a ground opening exposed from the protective film on the multilayer circuit substrate to obtain an initial multilayer circuit board comprises:

[0020] Providing the protective film, and based on the reserved ground opening area, punching the protective film to form a protective film opening on the protective film;

[0021] Based on the ground opening area and the protective film opening, the protective film after opening punching is adhered to the multilayer circuit substrate, so that the ground opening exposed from the protective film opening is formed on the ground opening area to obtain the initial multilayer circuit board.

[0022] Optionally, an effective area is provided on the initial multi-layer circuit board, a waste area is provided outside the effective area, a stacking direction from the outer flexible substrate to the inner flexible substrate in the initial multi-layer circuit board is assumed to be an x ​​direction, a tiling direction from the effective area to the waste area is assumed to be a y direction, and an extension direction of the inner signal line is assumed to be a z direction;

[0023] The method of punching the initial multi-layer circuit board once to form a shielding film filling groove on the initial multi-layer circuit board includes:

[0024] Taking the outer edge of the effective area close to the waste area as a reference, determining a punching position along the y direction;

[0025] Based on the primary punching position, in the waste area, the initial multi-layer circuit board is punched once along the x direction, and the shielding film filling groove that penetrates the initial multi-layer circuit board along the x direction is formed at the primary punching position; wherein the length direction of the shielding film filling groove is parallel to the z direction, and the length of the inner layer signal line, the length of the outer layer signal line, and the length of the inner layer grounding line are all less than or equal to the length of the shielding film filling groove.

[0026] Optionally, the distance between the outer edge of the effective area and the primary punching position along the y direction is greater than or equal to 0.1 mm.

[0027] Optionally, the width of the shielding film filling groove along the y direction ranges from 0.6 to 1.2 mm.

[0028] Optionally, the method of performing secondary shape punching on the semi-finished multilayer circuit board based on the shielding film filling groove to obtain a target multilayer circuit board includes:

[0029] Taking the primary punching position as a reference, determining the secondary punching position along the y direction;

[0030] Based on the secondary punching position, in the waste area, the semi-finished multilayer circuit board is subjected to secondary shape punching along the x direction, so that the effective area and the waste area in the semi-finished multilayer circuit board are separated to obtain the target multilayer circuit board.

[0031] Optionally, the distance between the secondary punching position and the primary punching position along the y direction ranges from 0.1 to 0.2 mm.

[0032] Optionally, the width of the punching groove formed by the secondary profile punching along the y direction ranges from 0.6 to 1.2 mm.

[0033] Optionally, the initial multilayer circuit board after the first shape punching is pasted with a shielding film, so that the first shielding film pasted on the outer surface of the initial multilayer circuit board is electrically conductive with the ground opening, and the second shielding film filled in the shielding film filling groove wraps the inner signal line, the inner ground line and the outer signal line in the signal area defined by the second shielding film, to obtain a semi-finished multilayer circuit board, including:

[0034] Provide shielding film materials;

[0035] Based on the shielding film filling groove, the initial multi-layer circuit board after one-time shape punching is pasted with a shielding film, so that the shielding film filling groove is filled with the shielding film material to form the second shielding film, and the first shielding film is formed on the outer surface of the initial multi-layer circuit board to obtain the semi-finished multi-layer circuit board; wherein, the second shielding film wraps the inner signal line, the inner ground line and the outer signal line in the signal area defined by the second shielding film, and electrical conductivity is formed between the first shielding film and the ground opening.

[0036] In addition, the present invention also provides a multi-layer flexible circuit board with reliable shielding performance, which is manufactured using the aforementioned manufacturing method.

[0037] The beneficial effects of the present invention are as follows: first, by manufacturing a multi-layer circuit substrate, basic components with signal transmission requirements are manufactured respectively, including an inner signal line, an inner ground line and an outer signal line, and the inner and outer signal lines are electrically connected to ensure that the final circuit board can transmit signals; then a protective film is attached and the ground opening is exposed from the protective film, so that the signal line is protected by the protective film and the grounding function of the circuit board is ensured based on the ground opening; the initial multi-layer circuit board is punched once to form a shielding film filling groove, which is convenient for filling the shielding film material based on the shielding film filling groove, so that all basic components in the signal area are wrapped in the area defined by the second shielding film, and then further wrapped in the signal area of ​​the entire circuit board; on the other hand, it is convenient to form a first shielding film on the outer surface of the initial multi-layer circuit board that can be electrically connected to the ground opening, that is, the grounding function is realized based on the first shielding film and the ground opening, and a good signal shielding effect is realized based on the second shielding film, which effectively reduces the signal loss of the circuit; finally, a secondary punching is performed based on the shielding film filling groove formed after the first punching, so as to realize the product shape punching of the entire target multi-layer circuit board and obtain the multi-layer flexible circuit board product actually required;

[0038] The multilayer flexible circuit board with reliable shielding performance and the manufacturing method thereof of the present invention are based on the shielding film filling groove formed after one-time shape punching. The first shielding film and the second shielding film can be formed respectively only by bonding the shielding film on the outer layer, which not only ensures the grounding function of the circuit board, but also achieves a good signal shielding effect, effectively reduces the signal loss of the line, and ensures that the entire multilayer board has excellent shielding performance; the process is simple, saves materials, does not need to laminate too many material layers, can effectively reduce the thickness of the entire multilayer board, and takes into account the bending performance of the multilayer board. BRIEF DESCRIPTION OF THE DRAWINGS

[0039] The features and advantages of the present invention will be more clearly understood by referring to the accompanying drawings, which are schematic and should not be construed as limiting the present invention in any way. In the accompanying drawings:

[0040] Figure 1 The cross-sectional structure diagram of a multi-layer flexible circuit board with signal transmission requirements manufactured by conventional technology is shown;

[0041] Figure 2 A flow chart showing a method for manufacturing a multi-layer flexible circuit board with reliable shielding performance in Embodiment 1 of the present invention is shown;

[0042] Figure 3 The cross-sectional structure diagram of the inner layer flexible substrate in the first embodiment of the present invention is shown;

[0043] Figure 4The cross-sectional structure diagram of the inner layer circuit board obtained after circuit manufacturing in the first embodiment of the present invention is shown;

[0044] Figure 5 The cross-sectional structure diagram of the outer layer flexible substrate in the first embodiment of the present invention is shown;

[0045] Figure 6 A cross-sectional structural diagram showing a cross-sectional structure of a multi-layer flexible substrate obtained by laminating an outer layer flexible substrate to an inner layer circuit board in the first embodiment of the present invention;

[0046] Figure 7 A diagram showing a multi-layer circuit substrate obtained after the outer layer circuit is manufactured in the first embodiment of the present invention;

[0047] Figure 8 A cross-sectional structural diagram of an initial multi-layer circuit board formed in the first embodiment of the present invention is shown;

[0048] Fig. 9 The cross-sectional structure diagram of the initial multi-layer circuit board after one-time punching in the first embodiment of the present invention is shown;

[0049] Fig.10 The cross-sectional structure diagram of the semi-finished multilayer circuit board obtained after the shielding film is attached in the first embodiment of the present invention is shown;

[0050] Fig.11 The cross-sectional structure diagram of the target multi-layer circuit board obtained after the secondary shape punching in the first embodiment of the present invention is shown.

[0051] The description of each reference numeral is as follows:

[0052] 1. Inner insulation layer, 2. Inner conductive layer, 3. Outer insulation layer, 4. Outer conductive layer, 5. Adhesive layer, 6. Protective film, 7. Grounding opening, 8. Primary punching position, 9. Shielding film filling groove, 10. First shielding film, 11. Second shielding film, 12. Secondary punching position, 13. Punching groove, 21. Inner signal line, 22. Inner grounding line, 41. Outer signal line, 42. Grounding opening area, 43. Hole, 100. Effective area, 200. Waste area. DETAILED DESCRIPTION

[0053] In order to make the purpose, technical solution and advantages of the embodiments of the present invention clearer, the technical solution in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative work are within the scope of protection of the present invention.

[0054] Embodiment 1

[0055] This embodiment provides a method for manufacturing a multi-layer flexible circuit board with reliable shielding performance, such as Figure 2 As shown, including:

[0056] S1: providing a multilayer circuit substrate; wherein the multilayer circuit substrate has an inner signal line, an inner ground line and an outer signal line, and the inner signal line and the outer signal line are electrically connected;

[0057] S2: attaching a protective film to the multilayer circuit substrate, and forming a ground opening exposed from the protective film on the multilayer circuit substrate to obtain an initial multilayer circuit board;

[0058] S3: performing a punching operation on the initial multi-layer circuit board to form a shielding film filling groove on the initial multi-layer circuit board;

[0059] S4: affixing a shielding film to the initial multilayer circuit board after the first shape punching, so that electrical conduction is formed between the first shielding film affixed on the outer surface of the initial multilayer circuit board and the ground opening, and the second shielding film filled in the shielding film filling groove wraps the inner signal line, the inner grounding line and the outer signal line in the signal area defined by the second shielding film, to obtain a semi-finished multilayer circuit board;

[0060] S5: Based on the shielding film filling groove, the semi-finished multi-layer circuit board is punched for a second time to obtain a target multi-layer circuit board.

[0061] In this embodiment, firstly, a multilayer circuit substrate is manufactured to respectively manufacture basic components with signal transmission requirements, including an inner signal line, an inner ground line and an outer signal line, and the inner and outer signal lines are electrically conductive to ensure that the final circuit board can transmit signals; then a protective film is attached and the ground opening is exposed from the protective film, so that the signal line is protected by the protective film and the grounding function of the circuit board is ensured based on the ground opening; the initial multilayer circuit board is punched once to form a shielding film filling groove, which is convenient for filling the shielding film material based on the shielding film filling groove, so that all basic components in the signal area are wrapped in the area defined by the second shielding film, and then further wrapped in the signal area of ​​the entire circuit board; on the other hand, it is convenient to form a first shielding film on the outer surface of the initial multilayer circuit board that can be electrically conductive with the ground opening, that is, the grounding function is realized based on the first shielding film and the ground opening, and a good signal shielding effect is realized based on the second shielding film, which effectively reduces the signal loss of the circuit; finally, a secondary punching is performed based on the shielding film filling groove formed after the first punching, so as to realize the product shape punching of the entire target multilayer circuit board and obtain the multilayer flexible circuit board product actually required.

[0062] The method for manufacturing a multi-layer flexible circuit board with reliable shielding performance in this embodiment is based on the shielding film filling groove formed after a single shape punching. The first shielding film and the second shielding film can be formed separately only by bonding the shielding film on the outer layer, which not only ensures the grounding function of the circuit board, but also achieves a good signal shielding effect, effectively reduces the signal loss of the line, and ensures that the entire multi-layer board has excellent shielding performance; the process is simple, saves materials, and does not require the lamination of too many material layers, which can effectively reduce the thickness of the entire multi-layer board, while taking into account the bending performance of the multi-layer board.

[0063] The following describes in detail each step of the manufacturing method of this embodiment.

[0064] In this embodiment S1, a multilayer circuit substrate is provided, including:

[0065] S11: providing an inner flexible substrate and an outer flexible substrate respectively;

[0066] S12: performing circuit fabrication on the inner layer flexible substrate to form the inner layer signal line and the inner layer ground line to obtain an inner layer circuit board;

[0067] S13: Laminating the outer flexible substrate onto the inner circuit board to obtain a multi-layer flexible substrate;

[0068] S14: manufacturing an outer layer circuit for the multi-layer flexible substrate, forming the outer layer signal line conductively connected to the inner layer signal line on the multi-layer flexible substrate, and obtaining the multi-layer circuit substrate.

[0069] Through the above process, basic components required for signal transmission can be formed on the inner flexible substrate and the outer flexible substrate respectively, so as to ensure that the final circuit board has the signal transmission function, and provide a circuit board substrate for the production of multi-layer flexible circuit boards with both bending performance and shielding performance.

[0070] Among them, the circuit production of the inner layer flexible substrate includes conventional processes such as dry film pasting, exposure and development, and etching. The outer layer circuit production of the multi-layer flexible substrate includes conventional processes such as drilling, copper plating in the hole, dry film pasting, exposure and development, and etching. These conventional processes all use conventional operating methods, and the specific details will not be repeated here.

[0071] Specifically, the inner flexible substrate includes any one of a double-sided board and a multi-layer board, and the outer flexible substrate includes any one of a single-sided board, a double-sided board and a multi-layer board.

[0072] Based on the above inner flexible substrate and outer flexible substrate, it is convenient to form a multi-layer flexible circuit board with three or more layers.

[0073] For the convenience of explanation, the inner layer flexible substrate provided in this embodiment takes a double-sided board as an example, and its cross-sectional structure is as follows: Figure 3 As shown, the cross-sectional structure of the inner layer circuit board obtained after circuit production is as follows Figure 4 As shown; the outer layer flexible substrate provided in this embodiment takes a single-sided board as an example, and its cross-sectional structure is as follows Figure 5 The cross-sectional structure of the multi-layer flexible substrate obtained by laminating it to the inner circuit board is as shown in Figure 6 As shown, the cross-sectional structure of the multi-layer circuit substrate obtained after the multi-layer flexible substrate is made into an outer layer circuit is as follows Figure 7 As shown. Figure 3 In the figure, 1 is the inner insulating layer, 2 is the inner conductive layer; Figure 4 In the figure, 21 and 22 are respectively one of the inner conductive layers 2 (an inner conductive layer located in the inner layer of the entire multilayer board, i.e. Figure 4 Inner signal lines and inner ground lines are formed on the inner conductive layer located on the upper side; Figure 5 In the figure, 3 is the outer insulating layer, 4 is the outer conductive layer; Figure 6 and Figure 7 In the figure, 5 is a glue layer used for laminating the inner circuit board and the outer flexible substrate, 41 is an outer conductive layer 4 and another inner conductive layer 2 (an inner conductive layer located on the outer layer of the entire multilayer board, i.e. Figure 4 An outer signal line is formed on the inner conductive layer located at the lower side.

[0074] For the multilayer circuit substrate (i.e. Figure 7 The outer flexible substrate on the multi-layer circuit substrate is provided with a ground opening area matching the ground opening, that is, Figure 7 42, the ground opening area 42 is used for subsequently forming a ground opening.

[0075] This embodiment S2 includes:

[0076] S21: providing the protective film, and based on the reserved ground opening area, punching the protective film to form a protective film opening on the protective film;

[0077] S22: Based on the ground opening area and the protective film opening, the protective film after the opening is punched is adhered to the multi-layer circuit substrate, so that the ground opening exposed from the protective film opening is formed on the ground opening area, and the initial multi-layer circuit board is obtained.

[0078] The protective film is pre-punched with an opening through the above process, which not only facilitates the subsequent precise fitting of the protective film to protect the signal lines in the multi-layer circuit substrate, but also facilitates the precise exposure of the grounding opening from the opening of the protective film, thereby facilitating the subsequent formation of the grounding opening through the grounding opening process and ensuring the grounding function of the grounding opening.

[0079] The number of the ground openings can be one or more, all of which are located within the effective area of ​​the entire initial multi-layer circuit board. The specific number depends on the specific product design.

[0080] The cross-sectional structure of the initial multi-layer circuit board formed in this embodiment is as follows: Figure 8 As shown, in Figure 8 In the figure, 6 is a protective film, and 7 is a grounding opening, of which there are two in total.

[0081] Specifically, when the initial multilayer circuit board (i.e. Figure 8 After the initial multi-layer circuit board shown in FIG.

[0082] Based on the ground opening, ink solder resist and chemical nickel-gold are sequentially performed on the initial multi-layer circuit board.

[0083] By sequentially applying ink solder mask and chemical nickel gold, it is convenient to make a ground pad at the interface opening, fully ensuring the grounding function of the entire multilayer board.

[0084] The above-mentioned ink solder mask and chemical nickel gold are conventional processes in the field of flexible circuit board production, and both adopt conventional operating methods. The specific details will not be repeated here.

[0085] for Figure 8 The initial multilayer circuit board shown in the figure has an effective area, and a waste area is provided outside the effective area. The effective area and the waste area are respectively Figure 8 100 and 200 in it.

[0086] Among them, the inner signal line, outer signal line and ground opening are all located in the effective area of ​​the initial multi-layer circuit board, which is equivalent to the functional area of ​​the multi-layer board; the outside of the effective area is a waste area, which can be used for subsequent shape punching.

[0087] exist Figure 8 In the initial multilayer circuit board, the stacking direction from the outer flexible substrate to the inner flexible substrate is assumed to be the x direction (specifically Figure 8 The tiling direction of the effective area to the waste area is the y direction (due to Figure 8 There are two ground openings in the figure. For the ground opening on the left, the y direction specifically refers to Figure 8 The y direction is from right to left in the figure, and for the ground opening on the right, the y direction is specifically Figure 8 The inner signal line extends in the z direction (i.e. Figure 8 In the direction from front to back or from back to front, Figure 8 not shown).

[0088] This embodiment S3 includes:

[0089] S31: Taking the outer edge of the effective area close to the waste area as a reference, determining a punching position along the y direction;

[0090] S32: Based on the primary punching position, in the waste area, the initial multi-layer circuit board is punched once along the x direction, and the shielding film filling groove that penetrates the initial multi-layer circuit board along the x direction is formed at the primary punching position; wherein the length direction of the shielding film filling groove is parallel to the z direction, and the length of the inner layer signal line, the length of the outer layer signal line, and the length of the inner layer grounding line are all less than or equal to the length of the shielding film filling groove.

[0091] By taking the outer edge of the effective area close to the waste area as a reference and searching along the y direction, the punching position for subsequent primary punching can be accurately determined; then, taking this position as a reference, a primary punching is performed in the waste area along the x direction, so as to facilitate the shape processing of the signal area that wraps all the basic components in the effective area, that is, to form a shielding film filling groove that can subsequently confine the inner signal line, the outer signal line and the inner ground line to the signal area, thereby facilitating the subsequent bonding using only the shielding film material, thereby improving the signal shielding performance of the multilayer board and reducing signal loss.

[0092] for Figure 8 In the initial multilayer circuit board shown, the outer edges of the effective area 100 near the waste area 200 include the left outer edge and the right outer edge, which are equivalent to the left and right boundaries where the effective area 100 intersects with the waste area 200. Since the left boundary is on the left side of a grounding opening 7 on the left, the corresponding primary punching position 8 determined along the y direction (from right to left) is also on the left side of the grounding opening 7, and thus the shielding film filling groove 9 formed by the primary contour punching is on the left side of the grounding opening 7, as shown in FIG. Fig. 9 As shown; the right boundary is on the right side of a ground opening 7 on the right, and the corresponding primary punching position 8 determined along the y direction (from left to right) is also on the right side of the ground opening 7, and then the shielding film filling groove 9 formed by the primary shape punching is on the right side of the ground opening, as shown Fig. 9As shown. For other numbers of ground openings, since there must be two left and right boundaries where the effective area 100 and the waste area 200 intersect, and all ground openings and signal lines are located in the effective area, a punching position is determined based on the left and right boundaries as a reference, and then a shape punching is performed based on the punching position to form two shielding film filling grooves, and all ground openings and signal lines are located in the area defined by the two shielding film filling grooves.

[0093] Preferably, in the above-mentioned primary punching process, the distance between the outer edge of the effective area and the primary punching position along the y direction is greater than or equal to 0.1 mm.

[0094] Since punching has processing errors, the above-mentioned spacing limitation can avoid the influence of punching of the effective area and each basic component in the effective area in the processing error of one-time punching, thereby ensuring the functionality of the grounding opening and the functionality of each signal line in the effective area respectively; and can ensure that the second shielding film formed in the subsequent shielding film filling groove wraps the basic components of the multilayer board in the signal area, thereby achieving excellent signal shielding performance.

[0095] exist Fig. 9 In the embodiment, the distance between the outer edge of the effective area 100 and the primary punching position 8 along the y direction is specifically d1, and d1 satisfies ≥0.1 mm.

[0096] Preferably, in the above-mentioned one-time punching process, the width of the shielding film filling groove along the y direction ranges from 0.6 to 1.2 mm.

[0097] By filling the shielding film groove with the above-mentioned width, it is convenient to form a second shielding film of sufficient width by filling the shielding film material, so that it can exert the best signal shielding performance; at the same time, it can also maintain a sufficient width during the subsequent secondary shape processing, thereby avoiding the influence of the subsequent secondary shape processing on its shielding performance.

[0098] exist Fig. 9 In the figure, the width of the shielding film filling groove 9 along the y direction is specifically w1, and this w1 satisfies 0.6≤w1≤1.2 mm.

[0099] This embodiment S4 includes:

[0100] S41: providing shielding film materials;

[0101] S42: Based on the shielding film filling groove, a shielding film is pasted on the initial multi-layer circuit board after one-time punching, so that the shielding film filling groove is filled with the shielding film material to form the second shielding film, and the first shielding film is formed on the outer surface of the initial multi-layer circuit board to obtain the semi-finished multi-layer circuit board; wherein, the second shielding film wraps the inner signal line, the inner ground line and the outer signal line in the signal area defined by the second shielding film, and electrical conductivity is formed between the first shielding film and the ground opening.

[0102] By filling the shielding film filling groove, it is easy to form a second shielding film that completely wraps the inner signal line, inner grounding line and outer signal line in the signal area, ensuring that the second shielding film exerts the best signal shielding performance; by forming the first shielding film on the outer surface of the initial multi-layer circuit board, on the basis of ensuring the signal shielding performance, the electrical conductivity of the grounding opening is ensured to achieve the grounding performance.

[0103] The cross-sectional structure of the semi-finished multilayer circuit board obtained after the shielding film is attached in this embodiment is as follows: Fig.10 As shown, in Fig.10 In the figure, 10 is a first shielding film formed on the outer surface of the initial multilayer circuit board, and 11 is a second shielding film formed in the shielding film filling groove.

[0104] Specifically, the shielding film material of this embodiment is metal, and the first shielding film and the second shielding film formed are both metal shielding films, which can not only make the first shielding film contact with the grounding opening to form electrical conductivity, but also make the signal lines and grounding lines inside the multilayer board all wrapped by metal materials, thereby achieving good signal shielding effect and reducing line signal loss.

[0105] This embodiment S5 includes:

[0106] S51: Taking the primary punching position as a reference, determining a secondary punching position along the y direction;

[0107] S52: Based on the secondary punching position, in the waste area, the semi-finished multilayer circuit board is subjected to secondary shape punching along the x direction, so that the effective area and the waste area in the semi-finished multilayer circuit board are separated to obtain the target multilayer circuit board.

[0108] In the secondary shape punching process, the primary punching position is used as a reference, and then searching along the y direction can accurately determine the secondary punching position for subsequent product shape processing; this position is convenient for the subsequent separation of the effective area and the waste area to form the final required multi-layer board product, and will not affect the second shielding film, ensuring its signal shielding performance; when the secondary punching position is determined, the secondary shape punching is performed along the x direction in the waste area based on this position, which can accurately achieve the separation of the effective area and the waste area, ensure the manufacturing accuracy of the product shape processing, and obtain a high product yield of the target multi-layer circuit board.

[0109] In this embodiment, the cross-sectional structure of the target multilayer circuit board obtained after the secondary shape punching is as follows: Fig.11 As shown, in Fig.11 In the figure, 12 is the secondary punching position, and 13 is the punching groove formed by the secondary shape punching.

[0110] Preferably, in the secondary contour punching process, the distance between the secondary punching position and the primary punching position along the y direction ranges from 0.1 to 0.2 mm.

[0111] Through the above spacing range, it is possible to realize product shape processing and fully avoid the influence of processing errors in secondary shape punching on the punching of the second shielding film, thereby ensuring the excellent signal shielding performance of the second shielding film.

[0112] Preferably, in the secondary profile punching process, the width of the punching groove formed by the secondary profile punching is in the range of 0.6 to 1.2 mm along the y direction.

[0113] The punching grooves in the above width range can effectively separate the effective area from the waste area, and ensure that the second shielding film has a sufficient width, so that the signal shielding performance of the second shielding film will not be affected by the secondary shape punching.

[0114] exist Fig.11 In the embodiment, the distance between the secondary punching position 12 and the primary punching position 8 along the y direction is specifically d2, and the range of d2 is 0.1-0.2 mm; the width of the punching groove 13 along the y direction is specifically w2, and the range of w2 is 0.6-1.2 mm.

[0115] Embodiment 2

[0116] This embodiment provides a multi-layer flexible circuit board with reliable shielding performance, which is manufactured by using the manufacturing method of the multi-layer flexible circuit board with reliable shielding performance described in the first embodiment.

[0117] This embodiment is based on the shielding film filling groove formed after a single shape punching. The first shielding film and the second shielding film can be formed separately only by bonding the shielding film on the outer layer, which not only ensures the grounding function of the circuit board, but also achieves a good signal shielding effect, effectively reduces the signal loss of the line, and ensures that the entire multi-layer board has excellent shielding performance; the process is simple, saves materials, and does not require the lamination of too many material layers. It can effectively reduce the thickness of the entire multi-layer board, while taking into account the bending performance of the multi-layer board.

[0118] The manufacturing method of the multilayer flexible circuit board with reliable shielding performance in this embodiment is the same as the method steps described in the first embodiment. Therefore, for details not provided in this embodiment, please refer to the first embodiment and the second embodiment. Figures 1 to 11 The specific description of this embodiment will not be repeated in detail.

[0119] Although the embodiments of the present invention have been described in conjunction with the accompanying drawings, those skilled in the art may make various modifications and variations without departing from the spirit and scope of the present invention, and such modifications and variations are all within the scope defined by the appended claims.

Claims

1. A method for manufacturing a multilayer flexible circuit board with reliable shielding performance, characterized in that: The method comprises: A multilayer circuit substrate is provided; wherein the multilayer circuit substrate has an inner layer signal line, an inner layer ground line and an outer layer signal line, and the inner layer signal line and the outer layer signal line are electrically connected; Applying a protective film to the multilayer circuit substrate, and forming a ground opening exposed from the protective film on the multilayer circuit substrate to obtain an initial multilayer circuit board; Performing a profile punching operation on the initial multi-layer circuit board to form a shielding film filling groove on the initial multi-layer circuit board; A shielding film is applied to the initial multilayer circuit board after the first shape punching, so that electrical conduction is formed between the first shielding film attached to the outer surface of the initial multilayer circuit board and the ground opening, and the second shielding film filled in the shielding film filling groove wraps the inner signal line, the inner ground line and the outer signal line in the signal area defined by the second shielding film, so as to obtain a semi-finished multilayer circuit board; Based on the shielding film filling groove, the semi-finished multi-layer circuit board is punched out for a second time to obtain a target multi-layer circuit board.

2. The method according to claim 1, characterized in that: The multi-layer circuit substrate is provided, comprising: providing an inner flexible substrate and an outer flexible substrate respectively; Performing circuit fabrication on the inner layer flexible substrate to form the inner layer signal line and the inner layer ground line to obtain an inner layer circuit board; Laminating the outer flexible substrate onto the inner circuit board to obtain a multi-layer flexible substrate; The outer layer circuit is manufactured on the multi-layer flexible substrate, and the outer layer signal line which is conductive with the inner layer signal line is formed on the multi-layer flexible substrate to obtain the multi-layer circuit substrate.

3. The method according to claim 2, characterized in that: A ground opening area matching the ground opening is reserved on the outer flexible substrate on the multi-layer circuit substrate; The step of attaching a protective film to the multilayer circuit substrate and forming a ground opening exposed from the protective film on the multilayer circuit substrate to obtain an initial multilayer circuit board comprises: Providing the protective film, and based on the reserved ground opening area, punching the protective film to form a protective film opening on the protective film; Based on the ground opening area and the protective film opening, the protective film after opening punching is adhered to the multilayer circuit substrate, so that the ground opening exposed from the protective film opening is formed on the ground opening area to obtain the initial multilayer circuit board.

4. The method according to claim 2, characterized in that: The initial multi-layer circuit board is provided with an effective area, and a waste area is provided outside the effective area. The stacking direction from the outer flexible substrate to the inner flexible substrate in the initial multi-layer circuit board is assumed to be the x direction, the tiling direction from the effective area to the waste area is assumed to be the y direction, and the extension direction of the inner signal line is assumed to be the z direction; The method of punching the initial multi-layer circuit board once to form a shielding film filling groove on the initial multi-layer circuit board includes: Taking the outer edge of the effective area close to the waste area as a reference, determining a punching position along the y direction; Based on the primary punching position, in the waste area, the initial multi-layer circuit board is punched once along the x direction, and the shielding film filling groove that penetrates the initial multi-layer circuit board along the x direction is formed at the primary punching position; wherein the length direction of the shielding film filling groove is parallel to the z direction, and the length of the inner layer signal line, the length of the outer layer signal line, and the length of the inner layer grounding line are all less than or equal to the length of the shielding film filling groove.

5. The method according to claim 4, characterized in that: The distance between the outer edge of the effective area and the primary punching position along the y direction is greater than or equal to 0.1 mm.

6. The method according to claim 4, characterized in that: The width of the shielding film filling groove along the y direction ranges from 0.6 to 1.2 mm.

7. The method according to claim 4, characterized in that: The method of performing secondary shape punching on the semi-finished multilayer circuit board based on the shielding film filling groove to obtain a target multilayer circuit board comprises: Taking the primary punching position as a reference, determining the secondary punching position along the y direction; Based on the secondary punching position, in the waste area, the semi-finished multilayer circuit board is subjected to secondary shape punching along the x direction, so that the effective area and the waste area in the semi-finished multilayer circuit board are separated to obtain the target multilayer circuit board.

8. The method according to claim 7, characterized in that: The distance between the secondary punching position and the primary punching position along the y direction ranges from 0.1 to 0.2 mm.

9. The manufacturing method according to claim 7, characterized in that: The width of the punched groove formed by the secondary profile punching along the y direction ranges from 0.6 to 1.2 mm.

10. The production method according to any one of claims 1 to 9, characterized in that: The shielding film is applied to the initial multilayer circuit board after the first shape punching, so that the first shielding film attached to the outer surface of the initial multilayer circuit board is electrically conductive with the ground opening, and the second shielding film filled in the shielding film filling groove wraps the inner signal line, the inner grounding line and the outer signal line in the signal area defined by the second shielding film, to obtain a semi-finished multilayer circuit board, including: Provide shielding film materials; Based on the shielding film filling groove, the initial multi-layer circuit board after one-time shape punching is pasted with a shielding film, so that the shielding film filling groove is filled with the shielding film material to form the second shielding film, and the first shielding film is formed on the outer surface of the initial multi-layer circuit board to obtain the semi-finished multi-layer circuit board; wherein, the second shielding film wraps the inner signal line, the inner ground line and the outer signal line in the signal area defined by the second shielding film, and electrical conductivity is formed between the first shielding film and the ground opening.

11. A multi-layer flexible circuit board with reliable shielding performance, characterized in that: The method is produced according to any one of claims 1 to 10.

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