Flexible circuit board lap joint structure and LED lamp strip

Abstract

The utility model discloses a flexible circuit board lap joint structure, an LED lamp strip and a flexible circuit board lap joint method, the flexible circuit board lap joint structure comprises segmented circuit units which are connected in the length direction, and each segmented circuit unit comprises an upper circuit layer, an insulating base material layer and a lower circuit layer. The connecting ends of the segmented circuit units are overlapped up and down to form an overlapping section, a pure adhesive film is arranged between the connecting ends for bonding, the upper circuit layer in the segmented circuit unit positioned on the upper layer of the overlapping section further extends to form an extending end, and the extending end is downwards overlapped on the upper circuit layer of the overlapped segmented circuit unit. According to the lap joint structure of the flexible circuit board, the extension end is arranged to be lapped on the other segmented circuit unit through the segmented circuit unit, so that the thickness of the lap joint is reduced, and the flexibility of the lap joint is ensured; the lap joint sections are bonded through the pure adhesive films, the connection strength is good, the function is reliable, and follow-up process manufacturing is facilitated.

Description

Technical Field

[0001] The utility model relates to an LED strip, in particular to a flexible circuit board overlapping structure and an LED strip. Background Art

[0002] Currently, the production of LED strips adopts the following processes respectively:

[0003] (1) As shown in Figure 1 , a continuous round die cutting process is used to process the circuit board. It is a pure mechanical processing to produce a continuous and uninterrupted circuit board, including a bottom film layer c1, a lower copper layer c2, an insulating carrier c3, an upper copper layer c4, and a surface film layer c5 that are laminated by a die cutting machine. It has the following characteristics: 1. It is a pure mechanical processing without chemical materials and water; 2. It has continuous and uninterrupted production, high speed, time-saving and energy-saving, and the production speed can reach more than 5 to 10 times that of the anti-etching ink printing and etching process; 3. The process is single and the product consistency is excellent; 4. About 30% of the waste copper can be recycled and reused; 5. It can only process circuit boards with a thickness of more than 0.5 mm. (2) As shown in Figure 2 , 3 , for the production of a 50-cm circuit board, a single circuit board made by the anti-etching ink printing and etching process, which consists of a bottom film layer c1, a lower copper layer c2, an insulating carrier c3, an upper copper layer c4, and a surface film layer c5. The anti-etching ink printing and etching process: 1. The ink has a low value, a small amount of chemical materials, less water consumption, and can continuously process about 3 meters of circuit board, which is suitable for processing 0.3 - 0.4 mm circuits. It needs to be processed separately in single sheets. The head and tail of the circuit board are overlapped layer by layer, and conduction blind holes c6 are respectively provided at the overlapping ends. Lap soldering c7 is provided on the blind holes c6 and the overlapping ends therebetween, and they are welded into one body through the lap soldering c7. (3) As shown in Figure 2 , 3 , for the production of a 50-cm circuit board, a single circuit board made by the exposure, development, transfer circuit processing and etching process, which consists of a bottom film layer c1, a lower copper layer c2, an insulating carrier c3, an upper copper layer c4, and a surface film layer c5. The single-sheet exposure, development, transfer circuit processing and etching process: It is used to produce precision circuit boards with a thickness of less than 0.3 mm and can only be produced in single sheets. The head and tail of the circuit board are overlapped layer by layer, and conduction blind holes c6 are respectively provided at the overlapping ends. Lap soldering c7 is provided in the blind holes c6 and on the overlapping ends, and they are welded into one body through the lap soldering c7.

[0004] For the above three traditional printed circuit board processing methods, first, due to different precision requirements for line width and line spacing, their respective equipment and the environmental requirements of the production site for the equipment are different, and their supporting consumables are also different. Secondly, since copper foil is very prone to wrinkling, scratching, and oxidation. Double-sided printed circuit boards generally use the same process to process their two circuit layers to improve the yield of their finished products. Taking the most precise circuit layer as the criterion, for example, in a double-sided printed circuit board, if the line width and line spacing requirements for one circuit layer are 0.5 mm and those for the other side are 0.25 mm, then the production of both of its two circuit layers should adopt the exposure, development, and etching process. Moreover, since the technical essentials of the three processing technologies are also different, in the traditional printed circuit board production process, it is impossible to combine the above three processes, use two different processes to process the same printed circuit board, and achieve a printed circuit board with different precision requirements for two circuit layers. Currently, the above three printed circuit board processing technologies cannot be combined to produce a printed circuit board with an uninterrupted length direction.

[0005] An LED strip is a lighting or decorative product that mounts light-emitting LED lamp beads on a long strip-shaped printed circuit board. Its main feature is long-strip-shaped lighting. The length direction can reach more than 50 meters. The printed circuit boards used are single-sided, double-sided, and multi-layer long strip-shaped printed circuit boards. For example, Figure 2 , 3 As shown, generally, several unit circuits are paralleled and joined together according to requirements. According to the manufacturing capacity of the printed circuit board factory, they are generally joined together for production in 50 cm lengths. Then, several products with a length of 50 cm are connected into lengths of 3 meters, 5 meters, 10 meters, 20 meters, or longer by soldering at the first layer. Its feature is that each unit circuit is a unit product and can be used independently. The several unit circuits within the production unit length (about 50 cm or so) of the printed circuit board joined together according to the manufacturing capacity of the printed circuit board factory are connected in parallel by a single return unit. The single circuit units can be cut and used independently, that is, the long-strip-shaped LED strip product is composed of several single circuit units connected in parallel, and the single circuit units can be cut and used independently.

[0006] The production process of the LED strip printed circuit board respectively adopts electroplating technology and etching technology. Limited by the manufacturing capacity of the printed circuit board factory, it is generally produced in single sheets of about 50 cm. With the breakthrough of the manufacturing capacity of the printed circuit board factory, there are also printed circuit boards that can adopt the etching process of screen continuous printing and the manufacturing process with an infinitely extendable length direction by round knife die cutting. However, they can only produce relatively simple LED strips with fewer lamp beads.

[0007] For LED strips with multiple lamp beads (such as more than 240) within a 1-meter length range required by the market or those that need to achieve multiple colors (such as more than 3 colors) on the same LED strip. For example, Figure 2 and Figure 3As shown, the line width and line spacing are generally below 0.3 mm. For such a circuit board, only single-piece production with a length of about 50 cm can be adopted. Circuit boards with such requirements are generally produced by combining electroplating, exposure and development for circuit transfer, and etching processes. Then, after the LED strip factory mounts electronic components such as lamp beads on the circuit board, they are soldered together every 50 cm for the first layer and used. There are several disadvantages to using this process. First, single-piece mounting of lamp beads is already a backward process in the LED strip factory. Second, the head and tail of every 50 cm are connected by soldering. Due to manual soldering, it is impossible to ensure that the spacing between lamp beads at the docking joint is equidistant. Whether each strip of LED strip is connected into a straight line cannot be guaranteed, nor can its horizontal and vertical angles. Third, the 50-cm layers are connected by soldering. Problems such as false soldering at the soldering joints, breakage at the soldering joints during the later glue-pulling process, and breakage at the soldering joints due to stress during use and installation often occur.

[0008] The prior art using the above-mentioned soldering method, such as Chinese Utility Model Patent ZL2010205739430, a double-sided LED circuit board and component with soldering connection for conduction. The traditional splicing method for circuit boards is butt joint or overall lapping, and then the interfaces are soldered together. The strength of the soldering joint in the butt joint method is insufficient and it is easy to break, and the product quality cannot be guaranteed; in the overall lapping method, the thickness of the interface is too thick, the flexibility is insufficient, it is easy to break when folded, and it is not conducive to subsequent process production.

[0009] Therefore, how to achieve the technical effect of uninterrupted length of the flexible circuit board for an LED strip, design a flexible circuit board lapping structure with good connection strength and reliable functions, and adopt different processes for different circuit layers to realize a flexible circuit board lapping method with uninterrupted length in the length direction of the circuit layer is the main technical problem to be solved by the present utility model. Summary of the Invention

[0010] In view of the above technical problems, the present utility model provides a flexible circuit board lapping structure and an LED strip. The flexible circuit board lapping structure sets extension ends of segmented circuit units to lap on another segmented circuit unit, reducing the thickness of the lapping part, ensuring the flexibility of the lapping part, having good connection strength and reliable functions, and being conducive to subsequent process production; the LED strip has the effect of uninterrupted length in the length direction and can be cut to any length as needed; the flexible circuit board lapping method is simple and easy to implement.

[0011] To achieve the above object, the technical solution of the present utility model is:

[0012] A flexible circuit board lapping structure includes segmented circuit units connected in the length direction. Each segmented circuit unit includes an upper circuit layer, an insulating substrate layer, and a lower circuit layer. The connection ends of the segmented circuit units are stacked and lapped vertically to form a lapping segment, and a pure adhesive film is provided therebetween for adhesion. The upper circuit layer in the segmented circuit unit located above the lapping segment and / or the lower circuit layer in the segmented circuit unit located below the lapping segment further extend to form extension ends, and the extension ends are lapped downward on the upper circuit layer of the segmented circuit unit to be lapped.

[0013] The tail end of the previous segmented circuit unit of the above flexible circuit board lapping structure is lapped on the front end of the next segmented circuit unit, and they can also be lapped in the opposite direction. The lapping segments formed by corresponding vertical stacking and lapping are bonded into one body through a pure adhesive film. Correspondingly, extension ends are provided on the circuit layers of the segmented circuit units, and the circuit layers are lapped on the circuit layers of another segmented circuit unit through the extension ends of the circuit layers, so as to solve the technical problems of the climbing height limit of soldering connection and circuit connection by enhancing the lapping length between the surface circuit layers through the extension ends. The thickness at the lapping part is reduced, and the flexibility at the lapping part is ensured; a pure adhesive film is provided between the lapping segments for adhesion, the connection strength is good, the function is reliable, which is beneficial to subsequent process manufacturing.

[0014] In a further optimized scheme, the lower circuit layer in the segmented circuit unit located above the lapping segment and / or the upper circuit layer in the segmented circuit unit located below the lapping segment further extend to form extension ends. These extension ends are convenient for lapping with other segmented circuit units.

[0015] In a further optimized scheme, the extension ends and the corresponding circuit layers are electrically connected into one body through soldering or laser welding or ultrasonic or cold welding. The extension ends of the segmented circuit units are electrically connected and mechanically connected into one body through soldering or laser welding or ultrasonic or cold welding, ensuring the realization of the connection strength and the circuit connection function.

[0016] In a further optimized scheme, the lapping segment is formed by the lapping between the insulating substrate layers. The lapping between the insulating substrate layers solves the technical problems such as fracture and breakage at the welding part in the traditional technology.

[0017] In a further optimized scheme, the extension ends are also lapped on the corresponding circuit layers through a pure adhesive film. The connection strength at the lapping part is ensured, and it is not easy to break or be pulled off.

[0018] In a further optimized scheme, protective film layers are provided on the outer surfaces of the upper circuit layer and the lower circuit layer of the segmented circuit unit. The protective film layers enhance the tensile capacity of the circuit board and increase the strength at the connection part of the circuit board.

[0019] An LED light strip includes a flexible circuit board, and the flexible circuit board has the flexible circuit board lapping structure described in any one of the above. The flexible circuit board of the LED light strip forms a circuit board that is uninterrupted in the length direction through continuous splicing between segmented circuit units, achieving the effect of an uninterrupted length direction of the LED light strip. Cut it as long as needed.

[0020] A flexible circuit board lapping method includes the following steps.

[0021] Step 1: The upper circuit layer at the tail end of the segmented circuit unit located in the upper layer of the lapping section and / or the lower circuit layer in the segmented circuit unit located in the lower layer of the lapping section form an extended end.

[0022] Step 2: Bond a pure adhesive film to the lower surface of the tail end of the segmented circuit unit located in the upper layer of the lapping section or bond a pure adhesive film to the upper surface of the head end of the segmented circuit unit located in the lower layer of the lapping section.

[0023] Step 3: Stack and lap the tail end of the segmented circuit unit located in the upper layer of the lapping section on the head end of another segmented circuit unit. The lapping sections are bonded together through a pure adhesive film, and the extended ends of the circuit layers are lapped on the corresponding circuit layers.

[0024] Connect continuously according to the above steps to form a circuit board substrate that is continuously and infinitely extended in the length direction.

[0025] The above flexible circuit board lapping method bonds the mutually pressed layers by fitting a pure adhesive film, ensuring good connection strength and reliable functions of the processed lapping structure, which is beneficial to subsequent process manufacturing and avoids fracture and breakage at the lap joint.

[0026] For a further optimized solution, the flexible circuit board lapping method includes the following steps.

[0027] In Step 1, when processing and fitting the segmented circuit unit, preset an upper circuit layer and a lower circuit layer that have extended ends relative to the tail end and / or head end of the insulating substrate layer.

[0028] In Step 2, bond a pure adhesive film to the outer surface of the lower circuit layer along the cut at the tail end of the substrate board.

[0029] The extended lapping end of the insulating substrate layer of the lower segmented circuit unit is lapped on the lower circuit layer of the upper segmented circuit unit and is bonded to each other through a pure adhesive film, avoiding the technical problems of fracture and breakage at the welding joint in the traditional technology, having good connection strength and reliable functions, and being beneficial to subsequent process manufacturing.

[0030] For a further optimized solution, in Step 1, by removing the edge part of the insulating substrate layer, making it retract inside the upper circuit layer to form an upper circuit layer with an extended end.

[0031] In step 2, the pure adhesive film is flush with the insulating substrate layer or the upper circuit layer.

[0032] Different layers are used for overlapping to meet the process requirements of different products.

[0033] In a further optimized solution, in step 1, at the head end interface of the segmented circuit unit, the upper circuit layer, the upper circuit layer and the insulating substrate layer or the upper circuit layer and the lower circuit layer are removed. Different layers are used to form an extended end for overlapping to meet the process requirements of different products.

[0034] In a further optimized solution, it further includes step 4. According to the design requirements, the upper circuit layer and the lower circuit layer of the upper substrate in the previous step are respectively laminated with a protective film layer, heated and pressed by a rolling press, and then wound up. Laminating the protective film layer on both the upper and lower sides enhances the tensile capacity of the circuit board and increases the strength of the connection part of the circuit board.

[0035] In a further optimized solution, it further includes step 5. The extended end is overlapped on the corresponding circuit layer, and they are electrically connected into one body through soldering or laser welding or ultrasonic or cold welding. The extended end of the segmented circuit unit and another segmented circuit unit are electrically connected into one body through soldering or laser welding or ultrasonic or cold welding, ensuring the connection strength and the realization of the circuit connection function.

[0036] The utility model has the following technical advantages compared with the prior art:

[0037] In this flexible circuit board overlapping structure, the extended end of the segmented circuit unit is overlapped on another segmented circuit unit, reducing the thickness at the overlapping part and ensuring the flexibility at the overlapping part; a pure adhesive film is provided between the overlapping segments for adhesion, with good connection strength and reliable functions, which is beneficial to subsequent process manufacturing;

[0038] The flexible circuit board of this LED light strip forms a circuit board that is uninterrupted in the length direction through continuous splicing between segmented circuit units, achieving the effect of an uninterrupted LED light strip in the length direction, and can be cut to the required length as needed;

[0039] This flexible circuit board overlapping method uses different layers for overlapping, and the pure adhesive film is pasted on different layers to achieve connection and meet the process requirements of different products. Through heating and pressing by a rolling press, it ensures good connection strength and reliable functions of the processed overlapping structure, and avoids breakage and pulling breakage at the overlapping part. Description of the Drawings

[0040] Figure 1 It is a schematic structural diagram of a circuit board processed by a traditional continuous round die cutting process;

[0041] Figure 2 It is a schematic structural diagram of a single circuit board processed by a traditional non-electroplating (blind hole) process;

[0042] Figure 3It is a schematic structural diagram of a single-sided circuit board processed by the traditional electroplating process;

[0043] Figure 4a It is a schematic diagram of the lap joint of the left and right segmented circuit units in the first embodiment of the flexible circuit board lap joint structure of the present invention Figure 1 ;

[0044] Figure 4b It is a schematic diagram of the first embodiment Figure 2 ;

[0045] Figure 4c It is a schematic diagram of the first embodiment Figure 3 ;

[0046] Figure 5a It is a schematic diagram of the lap joint of the left and right segmented circuit units in the second embodiment of the flexible circuit board lap joint structure of the present invention Figure 1 ;

[0047] Figure 5b It is a schematic diagram of the second embodiment Figure 2 ;

[0048] Figure 5c It is a schematic diagram of the second embodiment Figure 3 ;

[0049] Figure 6a It is a schematic diagram of the lap joint of the left and right segmented circuit units in the third embodiment of the flexible circuit board lap joint structure of the present invention Figure 1 ;

[0050] Figure 6b It is a schematic diagram of the third embodiment Figure 2 ;

[0051] Figure 6c It is a schematic diagram of the third embodiment Figure 3 ;

[0052] Figure 7a It is a schematic diagram of the lap joint of the left and right segmented circuit units in the fourth embodiment of the flexible circuit board lap joint structure of the present invention Figure 1 ;

[0053] Figure 7b It is a schematic diagram of the fourth embodiment Figure 2 ;

[0054] Figure 7c It is a schematic diagram of the fourth embodiment Figure 3 ;

[0055] Figure 8 It is a schematic diagram of the segmented circuit unit after cutting in the fifth specific embodiment of the flexible circuit board lap joint structure of the present invention;

[0056] Figure 9 It is a plan view of the circuit layer on the segmented circuit unit in the embodiment of the flexible circuit board lap joint structure of the present invention;

[0057] Figure 10 is Figure 8 Schematic diagram of the lap joint structure in Embodiment Five;

[0058] Figure 11 is the schematic diagram of the segmented circuit unit after cutting in Embodiment Six of the flexible circuit board lap joint structure of the present utility model;

[0059] Figure 12 is Figure 11 Schematic diagram of laminating a pure adhesive film;

[0060] Figure 13 is Figure 12 Schematic diagram of the lap joint structure in Embodiment Six;

[0061] Figure 14 is Figure 13 Schematic diagram of laminating protective film layers on the upper and lower outer surfaces in Embodiment Six;

[0062] Figure 15 is the schematic diagram of the segmented circuit unit after cutting in Embodiment Seven of the flexible circuit board lap joint structure of the present utility model;

[0063] Figure 16 is Figure 15 Schematic diagram of the lap joint structure in Embodiment Seven;

[0064] Figure 17 is the schematic diagram of laser cutting of the segmented circuit unit in Embodiment Eight of the flexible circuit board lap joint structure of the present utility model;

[0065] Figure 18 is Figure 17 Schematic diagram of laser cutting the insulating substrate layer, the lower circuit layer and the pure adhesive film in the lap joint section;

[0066] Figure 19 is Figure 18 Schematic diagram of the pure adhesive film only retracting inside the upper circuit layer;

[0067] Figure 20 is the schematic diagram of laser cutting the two segmented circuit units in the lap joint section in Embodiment Nine of the flexible circuit board lap joint structure of the present utility model;

[0068] Figure 21 is Figure 20 Schematic diagram of the lap joint structure in Embodiment Nine;

[0069] Figure 22 is the front view of the insulating substrate layer in Embodiment Five;

[0070] Figure 23 is the front view of the upper circuit layer in Embodiment Five;

[0071] Figure 24It is a schematic diagram of laser welding in an embodiment of the lap joint structure of the flexible printed circuit board of the present utility model Figure 1 ;

[0072] Figure 25 It is a schematic diagram of laser welding in an embodiment of the lap joint structure of the flexible printed circuit board of the present utility model Figure 2 。

[0073] In the figure: segmented circuit unit A, upper circuit layer 1, insulating substrate layer 2, lower circuit layer 3, pure adhesive film 4, protective film layer 5, long slot hole 6, positioning hole 7, extension end a, and lap joint end b. Specific embodiments

[0074] The present utility model will be further described in detail below in conjunction with the embodiments in the accompanying drawings.

[0075] As Figures 4a to 25 shown, there are specifically nine embodiments of the lap joint structure of the flexible printed circuit board of the present utility model.

[0076] As Figure 4a , Figure 4b and Figure 4c shown, an embodiment 1 of a lap joint structure of a flexible printed circuit board includes a segmented circuit unit A connected in the length direction. The segmented circuit unit A includes an upper circuit layer 1, an insulating substrate layer 2, and a lower circuit layer 3. The insulating substrate layer 2 is provided with adhesive layers on both sides, which respectively bond the upper circuit layer 1 and the lower circuit layer 3.

[0077] As Figure 4a shown, the connection ends of the segmented circuit unit A are overlapped and joined up and down to form a lap joint section, and a pure adhesive film 4 is provided therebetween for bonding. The upper circuit layers 1 in the segmented circuit units A located above and below the lap joint section respectively extend to form extension ends a. The pure adhesive film 4 is attached to the outer surface of the lower circuit layer 3 of the upper segmented circuit unit A and is flush with its end face.

[0078] As Figure 4b shown, the extension end a is laid down on the upper circuit layer 1 in the lower segmented circuit unit A and is electrically connected as a whole; the pure adhesive film 4 is flush with the end of the upper circuit layer 1 of the lower segmented circuit unit A and is pasted together with it. The electrical connection and mechanical connection of the extension end of the segmented circuit unit with another segmented circuit unit are realized through soldering or laser welding to ensure the connection strength and the realization of the circuit connection function.

[0079] As Figure 4c shown, the outer surfaces of the upper circuit layer 1 of the upper segmented circuit unit A and the lower circuit layer 3 of the lower segmented circuit unit A are attached with a protective film layer 5. The protective film layer 5 enhances the tensile capacity of the circuit board and increases the strength at the connection of the circuit board.

[0080] The flexible printed circuit board (FPCB) overlapping structure has an extended end of a segmented circuit unit overlapping on another segmented circuit unit. A pure adhesive film is provided between the overlapping segments for bonding, resulting in good connection strength and reliable functionality, which is beneficial for subsequent process manufacturing.

[0081] As Figure 5a , Figure 5b and Figure 5c shown, in the second embodiment of a flexible printed circuit board overlapping structure, the difference from the first embodiment is that the lower circuit layer 3 of the lower segmented circuit unit A is provided with an extended end a, and this extended end a is overlapped upward on the lower circuit layer 3 in the upper segmented circuit unit A and electrically connected as a whole. The provision of extended ends on both the upper and lower segmented circuit units A enhances the connection strength of the circuit board.

[0082] As Figure 6a , Figure 6b and Figure 6c shown, in the third embodiment of a flexible printed circuit board overlapping structure, the difference from the first embodiment is that the extended end a of the upper circuit layer 1 of the upper segmented circuit unit A is removed, and the lower circuit layer 3 of the lower segmented circuit unit A is provided with an extended end a, and this extended end a is overlapped upward on the lower circuit layer 3 in the upper segmented circuit unit A and electrically connected as a whole.

[0083] As Figure 7a , Figure 7b and Figure 7c shown, in the fourth embodiment of a flexible printed circuit board overlapping structure, the difference from the first embodiment is that the lower circuit layer 3 of the upper segmented circuit unit A is provided with an extended end a, and one end of the pure adhesive film 4 is flush with the end of the insulating substrate layer 2 of the upper segmented circuit unit A, and the other end is flush with the end of the upper circuit layer 1 of the lower segmented circuit unit.

[0084] As Figure 8 and Figure 10 shown, in the fifth embodiment of a flexible printed circuit board overlapping structure, the upper circuit layer 1 and the lower circuit layer 3 in the upper segmented circuit unit A located in the upper overlapping segment are respectively extended to form extended ends a. Figure 9 The figure shows a schematic plan view of the upper circuit layer 1.

[0085] As Figure 10As shown in the figure, the pure adhesive film 4 is attached to the outer surface of the lower circuit layer 3 of the segmented circuit unit A on the upper layer. One end of the pure adhesive film 4 is flush with the extension end a, and the other end extends beyond the end of the upper circuit layer 1 of the lower segmented circuit unit. The extension end a of the upper circuit layer 1 is laid down on the extension end a of the lower circuit layer 3, and then they are together on the upper circuit layer 1 of the overlapping segmented circuit unit A and electrically connected as a whole. The extension ends are electrically connected as a whole by soldering or laser welding. The extension end of the segmented circuit unit is electrically connected and mechanically connected as a whole through soldering or laser welding to ensure the connection strength and the realization of the circuit connection function.

[0086] In this flexible circuit board overlapping structure, the extension ends are set on the segmented circuit unit to overlap on another segmented circuit unit, reducing the thickness at the overlapping part and ensuring the flexibility at the overlapping part. A pure adhesive film is provided between the overlapping segments for adhesion, with good connection strength and reliable functions, which is beneficial to subsequent process manufacturing.

[0087] As Figures 11 to 14 shown, in Embodiment 6 of a flexible circuit board overlapping structure, the extension end a is formed by extending the upper circuit layer 1 in the segmented circuit unit A located on the upper layer of the overlapping segment. The insulating substrate layer 2, the lower circuit layer 3 and the pure adhesive film 4 are flush and have no extension.

[0088] As Figure 13 shown, the extension end a of the upper circuit layer 1 in the upper segmented circuit unit A is laid down on the upper circuit layer 1 of the segmented circuit unit A to be overlapped and electrically connected as a whole, and the extension end a is electrically connected by soldering or laser welding.

[0089] As Figure 14 shown, the protective film layer 5 is respectively attached to the outer surface of the upper circuit layer 1 in the upper segmented circuit unit A and the outer surface of the lower circuit layer 3 in the lower segmented circuit unit A. The protective film layer 5 of the upper circuit layer at the tail end of the left segmented circuit unit A is extended to the upper circuit layer 1 at the head end of the right segmented circuit unit A (i.e., the overlapping interface of the protective film layer 5 of the upper circuit layer is on the right circuit board), and the protective film layer 5 of the lower circuit layer 3 at the head end of the right segmented circuit unit A is extended to the lower circuit layer 3 at the tail end of the left circuit board (i.e., the overlapping interface of the protective film layer 5 of the lower circuit layer 3 is on the left circuit board) to enhance the tensile strength of the circuit board at the interface. If the protective film layers 5 of the upper and lower circuit layers of the segmented circuit unit A are not extended (i.e., flush with the circuit layers), the upper circuit layer 1 and the lower circuit layer 3 of the segmented circuit unit A use the method of printing solder resist ink instead of the protective film layer 5, and the effect is the same.

[0090] As Figures 15 to 16As shown in the figure, in the seventh embodiment of the flexible printed circuit board overlapping structure, an upper circuit layer 1 in a segmented circuit unit A located on the upper layer of the overlapping section extends to form an extended end a. The insulating substrate layer 2 is flush with the lower circuit layer 3 and has no extension, and the pure adhesive film 4 extends to be flush with the extended section.

[0091] As Figure 16 shown in the figure, the extended end a of the upper circuit layer 1 in the upper segmented circuit unit A is pressed downward onto the pure adhesive film 4 and is overlapped together on the upper circuit layer 1 of the segmented circuit unit A to be overlapped, and they are electrically connected as a whole. The extended end a is electrically connected by soldering or laser welding.

[0092] As Figures 17 to 19 shown in the figure, in the eighth embodiment of the flexible printed circuit board overlapping structure, the overlapping section of the upper segmented circuit unit A is cut by laser cutting with an adjustable cutting depth to remove the insulating substrate layer 2 and the lower circuit layer 3, forming an extended end a of the upper circuit layer 1. The pure adhesive film 4 can be flush with the lower circuit layer 3 or retract within the extended end a beyond the lower circuit layer 3.

[0093] As Figures 20 to 21 shown in the figure, in the ninth embodiment of the flexible printed circuit board overlapping structure, the overlapping section is an overlap formed between the insulating substrate layers 2. The upper circuit layer 1 in the upper segmented circuit unit A extends to form an extended end a, the insulating substrate layer 2 extends to form an overlapping end b, the overlapping end b retracts within the extended end a, and the pure adhesive film 4 is attached from the lower circuit layer 3 to the insulating substrate layer 2 and is flush with the overlapping end b.

[0094] As Figure 21 shown in the figure, the extended end a of the upper circuit layer 1 in the upper segmented circuit unit A is overlapped downward on the upper circuit layer 1 of the segmented circuit unit A to be overlapped. The insulating substrate layer 2 of the segmented circuit unit A to be overlapped also extends to form an overlapping end b that overlaps on the lower circuit layer of the upper segmented circuit unit A, and a pure adhesive film 4 is provided therebetween for adhesion. The insulating substrate layer 2 of the lower segmented circuit unit A extends the overlapping end b to overlap on the lower circuit layer of the upper segmented circuit unit A, and they are adhered to each other through the pure adhesive film 4, avoiding the technical problems of fracture and breakage at the welding point in the traditional technology, having good connection strength, reliable functions, and being beneficial to subsequent process manufacturing.

[0095] As Figure 21 shown in the figure, a protective film layer 5 is provided on the outer surfaces of the upper circuit layer 1 and the lower circuit layer 3 of the segmented circuit unit A, and the protective film layer 5 extends beyond the corresponding overlapping sections respectively. The protective film layer 5 is laminated in a staggered manner to another circuit layer to enhance the tensile capacity of the printed circuit board and increase the strength at the connection of the printed circuit board.

[0096] Figure 10 The figure shows a schematic diagram of soldering in the embodiment. Figure 24 And Figure 25 The figure shows a schematic diagram of laser welding in the embodiment.

[0097] The utility model also discloses an LED light strip, which includes a flexible circuit board having the flexible circuit board overlapping structure described above. The flexible circuit board of the LED light strip forms a continuous circuit board in the length direction through continuous splicing between segmented circuit units, achieving the effect of uninterrupted length in the LED light strip. It can be cut to the length required.

[0098] The utility model also discloses a method for overlapping flexible circuit boards. Before overlapping the flexible circuit boards, the production of the base material board and the circuit layer needs to be completed.

[0099] Production of the base material board:

[0100] 1. Cut the PI film with adhesive on both sides into sheets of 530 mm × 250 mm, and punch positioning holes 7 according to design requirements;

[0101] 2. According to the positioning holes 7, at the overlapping end of the segmented circuit unit A, make a long slot hole 6 of 0.5 mm × 243 mm according to design requirements by using CNC drilling (or it can also be made by die punching or cutting) (as Figure 22 );

[0102] 3. Bond copper foils on both sides, press them together by a quick press (180 °C × 60 seconds) and cure them at 150 °C × 60 minutes;

[0103] 4. Re-process the positioning holes 7 according to the positioning holes 7 of the insulating base material layer 2.

[0104] Production of the circuit layer:

[0105] 1. For the base material board produced above, process the via holes of the circuit board according to the positioning holes 7 by using a CNC drilling machine;

[0106] 2. Produce the upper circuit layer 1 and the lower circuit layer 3 of the segmented circuit unit A through processes such as electroplating and bonding dry film, alignment exposure, and developing and etching.

[0107] The method for overlapping flexible circuit boards includes the following steps:

[0108] S1. Cut off the two short sides of the base material of the segmented circuit unit A with the upper circuit layer 1 and the lower circuit layer 3 processed along the cutting line. A long slot hole 6 is made at the overlapping end of the insulating base material layer 2, and the long side of the long slot hole 6 is cut off (as Figure 23 ), forming an upper circuit layer 1 with an extended end a and a lower circuit layer 3 with an extended end a (as Figure 8 );

[0109] S2. Bond a pure adhesive film 4 (250 mm × 5 mm) on the outer surface of the lower circuit layer 3 along the cut at the end of the base material board;

[0110] S3. Press the end joint of a segmented circuit unit A, i.e., the extended end a of the upper circuit layer 1 and the extended end a of the lower circuit layer 3, onto the head end of another segmented circuit unit A according to the calibrated connection wires, and feed them into a rolling press for heating and pressing (as Figure 10 );

[0111] S4. Continuously splice according to the above steps to form a circuit board substrate that is infinitely extended in the length direction;

[0112] S5. Press and bond the upper circuit layer 1 and the lower circuit layer 3 of the substrate in the above step with protective film layers 5 respectively according to the design requirements through a rolling press for heating and pressing, and then wind it up.

[0113] The above flexible circuit board splicing method makes long slot holes at the end joint of the insulating substrate layer as positioning marks for cutting, which is convenient for accurately cutting the layers to be cut; by bonding the pure adhesive film to paste the mutually pressed layers and heating and pressing through a rolling press, it ensures that the connection strength of the processed splicing structure is good, the function is reliable, which is beneficial to subsequent process manufacturing and avoids breakage and tensile fracture at the joint.

[0114] Another splicing method is to cut off the lower circuit layer 3 at the end of the segmented circuit unit A that is not combined with the insulating substrate layer 2 in step S1, that is, cut off the extended end a of the lower circuit layer 3 (as Figure 11 ). Different layers are used for splicing to meet different product process requirements.

[0115] Another splicing method is to replace step S2 with pasting a pure adhesive film 4 along the cutting edge of the upper circuit layer 1 on the outer surface of the lower circuit layer 3. The pure adhesive film is pasted on different layers to achieve connection and meet different product process requirements.

[0116] After the above flexible circuit board is spliced, it is also necessary to carry out the production of the subsequent process section of the circuit board and the application of pasting electricity.

[0117] Production of the subsequent process section of the circuit board:

[0118] ① Print character marks on the long strip-shaped circuit board substrate with double-sided protective film pressed according to the design requirements;

[0119] ② Cut the circuit board into strips by a roll slitter;

[0120] ③ Carry out pad protection treatment such as antioxidant treatment, gold plating or tin plating.

[0121] Application of pasting electricity:

[0122] ① Open a solder paste stencil for the circuit board produced in the above step;

[0123] ② Print solder paste at the joint of the circuit board and mount electronic components;

[0124] ③Transfer the circuit board with components mounted to the reflow soldering furnace and perform reflow soldering at 245°C for 10 minutes;

[0125] ④Conduct final product testing, packaging, etc.

[0126] After the above steps, a long strip-shaped LED light strip with complete functions and infinitely extendable and composed of segmented circuit units is completed.

[0127] Another flexible circuit board lapping method disclosed by this utility model requires the completion of substrate board manufacturing and circuit layer manufacturing before lapping the flexible circuit board.

[0128] Substrate board manufacturing:

[0129] 1. Double-sidedly laminate a 35-micron copper foil on a double-sided adhesive PI film, cure it at 160°C for 120 minutes, and cut it into sheet materials of 530 mm × 250 mm;

[0130] 2. According to the design data, use CNC equipment to process positioning holes and via holes.

[0131] Circuit layer manufacturing:

[0132] Manufacture the upper circuit layer and the lower circuit layer of the circuit board from the above-completed sheet material substrate through processes well-known in the circuit board industry, such as electroplating, laminating dry film, alignment exposure, development, and etching.

[0133] This flexible circuit board lapping method includes the following steps

[0134] Step 1: Cut off the short sides along the copper edges at both ends of the segmented circuit unit A with the upper circuit layer 1 and the lower circuit layer 3 processed;

[0135] Step 2: Use a laser cutter with adjustable cutting depth to cut off the lower circuit layer 3 and the insulating substrate layer 2 from the outer edge inward at the tail-end interface of the segmented circuit unit A, leaving only the upper circuit layer 1, forming an upper circuit layer 1 with an extended end a (as Figure 18 );

[0136] Step 3: Bond a pure adhesive film 4 (250 mm × 5 mm) to the outer surface of the lower circuit layer 3 at the tail end of the circuit substrate. The pure adhesive film 4 can be flush with the upper circuit layer 1 (as Figure 15 ) or retracted 0.5 mm inside the upper circuit layer 1 (as Figure 19 ) or flush with the lower circuit layer 3 (as Figure 18 );

[0137] Step 4: Press and bond the extended end a at the tail-end lapping position of one circuit board to the head end of another circuit board according to the calibrated connection line and send it into a rolling press for heating and pressing (as Figure 13 );

[0138] Step 5: Continuously splice according to the above steps to form a circuit board substrate that is infinitely extended in the length direction.

[0139] Step 6: Press and laminate the upper circuit layer 1 and the lower circuit layer 3 of the substrate in the above step respectively with the protective film layer 5 through a rolling press for heating, and then wind it up.

[0140] The above flexible circuit board overlapping method uses a laser cutter with adjustable cutting depth to cut different layers, with accurate position and high precision. By laminating the layers pressed against each other with a pure adhesive film and heating and pressing through a rolling press, the connection strength of the overlapping structure after processing is good, the function is reliable, which is beneficial to subsequent process manufacturing, and avoids breakage and pulling breakage at the overlapping part.

[0141] Another overlapping method is that in Step 2, only a part of the outer edge of the insulating substrate layer 2 is cut off so that it retracts inside the upper circuit layer 1; in Step 3, the pure adhesive film 4 is flush with the upper circuit layer 1 or flush with the insulating substrate layer 2. Different layers are used for overlapping to meet different product process requirements, and the pure adhesive film 4 is pasted on different layers to achieve connection to meet different product process requirements.

[0142] Another overlapping method can cut off the upper circuit layer 1, the upper circuit layer 1 and the insulating substrate layer 2 or the upper circuit layer 1 and the lower circuit layer 3 at the head end interface of the segmented circuit unit A in Step 4 by using a laser cutter with adjustable cutting depth. Different layers are used for overlapping to meet different product process requirements.

[0143] Similarly, the lower circuit can also be used to form an extended end to overlap with an adjacent segmented circuit unit, and the specific overlapping method is similar to the above method.

[0144] This flexible circuit board overlapping structure overlaps on another segmented circuit unit by setting an extended end for the segmented circuit unit, reducing the thickness at the overlapping part and ensuring the flexibility at the overlapping part; a pure adhesive film is provided between the overlapping segments for adhesion, with good connection strength and reliable function, which is beneficial to subsequent process manufacturing;

[0145] The flexible circuit board of this LED light strip forms a circuit board that is uninterrupted in the length direction through continuous splicing between segmented circuit units, achieving the effect of being uninterrupted in the length direction of the LED light strip, and can be cut to the required length as needed;

[0146] This flexible circuit board overlapping method makes a long slot hole at the overlapping end of the insulating substrate layer as a positioning mark for cutting, which is convenient for accurately cutting the layers that need to be cut; or uses a cutting device with adjustable cutting depth to cut different layers, with accurate position and high precision; by laminating the layers pressed against each other with a pure adhesive film and heating and pressing through a rolling press, the connection strength of the overlapping structure after processing is good, the function is reliable, avoiding breakage and pulling breakage at the overlapping part, and different layers are used for overlapping and the pure adhesive film is pasted on different layers to meet different product process requirements.

[0147] In summary, as described in the specification and illustrated in the drawings, the practical new model has been made into an actual sample and tested through multiple uses. Judging from the test results, it is proved that the practical new model can achieve the expected purpose, and its practicability is beyond doubt. The above-mentioned embodiments are only used to conveniently illustrate the content of the practical new model, rather than imposing a formal restriction on it; any equivalent embodiments made by those with common general knowledge in the technical field, without departing from the technical features and similar features of the practical new model, and making partial changes or modifications by using the technical content disclosed by the practical new model, fall within the protection scope of the practical new model.

Claims

1. A flexible printed circuit board overlapping structure, comprising segmented circuit units (A) connected in the length direction, the segmented circuit units (A) including an upper circuit layer (1), an insulating substrate layer (2) and a lower circuit layer (3), characterized in that, The connection ends of the segmented circuit units (A) are stacked and overlapped vertically and horizontally to form an overlapping segment, and a pure adhesive film (4) is provided therebetween for adhesion. The upper circuit layer (1) of the segmented circuit unit (A) located on the upper layer of the overlapping segment and / or the lower circuit layer (3) in the segmented circuit unit (A) located on the lower layer of the overlapping segment further extend to form an extended end (a), and the extended end (a) is overlapped on the corresponding circuit layer.

2. The flexible printed circuit board overlapping structure according to claim 1, wherein: The lower circuit layer (3) of the segmented circuit unit (A) located on the upper layer of the overlapping segment and / or the upper circuit layer (1) in the segmented circuit unit (A) located on the lower layer of the overlapping segment further extend to form an extended end (a).

3. The flexible printed circuit board overlapping structure according to claim 1 or 2, characterized in that: The extended end (a) and the corresponding circuit layer are electrically connected into one body by soldering or laser welding or ultrasonic or cold welding.

4. A flexible printed circuit board overlapping structure according to claim 1, wherein: The overlapping segment is formed by overlapping between the insulating substrate layers (2).

5. A flexible circuit board overlapping structure according to claim 1, characterized in that: The extended end (a) is also overlapped on the corresponding circuit layer through the pure adhesive film (4).

6. A flexible circuit board overlapping structure according to claim 1 or 2, characterized in that: The outer surfaces of the upper circuit layer (1) and the lower circuit layer (3) of the segmented circuit unit (A) are provided with a protective film layer (5).

7. An LED strip light, comprising a flexible circuit board, characterized in that: The flexible printed circuit board has the flexible printed circuit board overlapping structure according to any one of claims 1 to 6.

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