Circuit board with hot-bar fingers and processing technology thereof

Abstract

The invention provides a processing technology of a circuit board with hot-bar fingers. The processing technology comprises the following steps of S1, providing a flexible circuit board substrate; s2, manufacturing a hot-bar through hole penetrating through the substrate of the flexible circuit board, and plating copper; s3, arranging a dry film on the substrate of the flexible circuit board, exposing, developing, etching, and manufacturing a circuit and a hot-bar finger pattern to obtain the flexible circuit board; s4, carrying out browning treatment on the flexible circuit board, and pasting a protective film; s5, printing solder resist ink at the position, corresponding to the Hot-bar finger, of the flexible circuit board; and S6, cutting the polyimide layer in the hot-bar finger region to form a hot-bar finger bonding pad, and obtaining the circuit board with the hot-bar finger. A digital processing mode combining pattern etching and laser cutting is adopted, laser spots are extremely small, and the positioning precision can reach the micron level.

Description

Technical Field

[0001] This invention relates to the field of flexible circuit board manufacturing technology, and in particular to a circuit board with hot-bar fingers and its processing technology. Background Technology

[0002] Hot-bar welding technology is widely used for connecting flexible circuit boards to rigid boards or other components due to its high precision and reliability. Traditional hot-bar finger processing typically employs etching, cover film windowing, and die-cutting. However, with the miniaturization and high density of electronic products, this traditional process faces the following severe challenges: 1. Precision bottleneck: Die-cutting has inherent mechanical tolerances. For ultra-fine hot-bar fingers with a pin pitch of less than 0.2mm, the precision (usually only ±0.05mm or higher) and consistency are difficult to guarantee, and edge burrs and other issues are also prominent; 2. Deformation effect: Physical stress during the die-cutting process can easily cause micro-deformation or stretching of the flexible board, resulting in slight displacement of the finger position and affecting the alignment accuracy of subsequent welding; 3. Cost and flexibility: High-precision die manufacturing is expensive, and once the design changes, the die must be remade, resulting in long cycles and poor flexibility.

[0003] Therefore, existing technologies cannot meet the current demands for ultra-high precision electronic assembly, and a completely new processing method is urgently needed. Summary of the Invention

[0004] The purpose of this invention is to overcome and supplement the deficiencies in the existing technology, and to provide a circuit board with hot-bar fingers and its processing technology. The processed hot-bar finger structure has micron-level precision and avoids mechanical stress deformation.

[0005] The technical solution adopted in this invention is: A manufacturing process for a circuit board with hot-bar fingers, comprising the following steps: Step S1. Provide a flexible circuit board substrate, the substrate including polyimide layer and set in polyimide layer Upper copper foil and lower copper foil; Step S2. At least one hot-bar through hole is made on the flexible circuit board substrate at the position corresponding to the hot-bar finger, and copper plating is performed on the flexible circuit board substrate and the hot-bar through hole to form a copper plating layer. Step S3. A dry film is placed on the copper-plated flexible circuit board substrate, and then exposed, developed, and etched so that the upper and lower copper foils near each hot-bar via are etched away. Then, the circuit and hot-bar finger pattern are fabricated to obtain the flexible circuit board. Step S4. Perform browning treatment on the flexible circuit board, then apply a protective film, and quickly press and bake the protective film; Step S5. Print solder resist ink on the flexible circuit board at the positions corresponding to the Hot-bar fingers; Step S6. Use laser cutting to cut the Hot-bar finger area. polyimide layer Cut the circuit board to form hot-bar finger pads, resulting in a circuit board with hot-bar fingers.

[0006] Preferably, in the processing technology of the circuit board with hot-bar fingers, the diameter of the hot-bar through hole in step S2 is 0.1mm-0.3mm, and alignment holes are also provided on the flexible circuit board substrate.

[0007] Preferably, the processing technology of the circuit board with hot-bar fingers includes: in step S3, exposure is performed using direct laser imaging and segmentation alignment process, with the alignment hole serving as the target hole for segmentation alignment. During exposure, an auxiliary etching section is set at the tip of the hot-bar fingers. One end of the auxiliary etching section is close to the through hole, and the other end extends to the lower end of the flexible circuit board substrate. The width of the auxiliary etching section is 75-200um. An arc-shaped line matching the shape of the through hole is set at the end of the auxiliary etching section close to the through hole. The distance between the end of the auxiliary etching section close to the through hole and the through hole is 15-35um.

[0008] Preferably, the processing technology of the circuit board with hot-bar fingers includes the following steps: in step S4, the browning rate is 3.0-5.5 m / min, the fast pressing temperature is 170-190℃, the pressure is 60-100 kg, the time is 120-200 seconds, the baking temperature is 150-170℃, and the baking time is 60-90 minutes.

[0009] Preferably, in the processing of the circuit board with hot-bar fingers, the solder resist ink in step S5 is a flexible ink that is resistant to bending.

[0010] Preferably, in the processing technology of the circuit board with hot-bar fingers, the laser used in step S6 is an ultraviolet laser or a green laser.

[0011] Preferably, the processing technology of the circuit board with hot-bar fingers includes, after step S6, the following steps: surface treatment of the hot-bar finger pads, specifically electroless nickel-palladium-gold plating, hard gold plating, or electroless tin plating; when electroless nickel-palladium-gold plating, the thickness of nickel is 200-1000u”, the thickness of palladium is 2-10u”, and the thickness of gold is 2-10u”; when electroless hard gold plating, the thickness of nickel is 200-1000u” and the thickness of gold is 5-50u”; when electroless tin plating, the thickness of tin is 1-3um.

[0012] Preferably, the manufacturing process of the circuit board with hot-bar fingers includes a pin pitch of no more than 0.1 mm.

[0013] Preferably, the manufacturing process of the circuit board with hot-bar fingers includes, between step S5 and step S6, the following step: Step S51. Provide a low-flow prepreg and copper foil, and perform windowing treatment on the corresponding bending area of ​​the low-flow prepreg, without treating the copper foil; Step S52. The low-flow prepreg and copper foil are sequentially placed on both sides of the flexible circuit board and pressed together to form a rigid-flex board; Step S53. Drill holes, electroplat, apply circuit patterns, and solder resist to the laminated rigid-flex PCB. Step S54. Perform surface treatment on the exposed hot-bar finger pads.

[0014] Preferably, the processing technology of the circuit board with hot-bar fingers includes: in step S54, the surface treatment specifically involves electroless nickel-palladium-gold plating, electroplating hard gold, or electroless tin plating.

[0015] A circuit board with hot-bar fingers is manufactured using the processing technology for circuit boards with hot-bar fingers.

[0016] Advantages of this invention: (1) The circuit board with hot-bar fingers of the present invention and its processing technology abandon the traditional mold punching and adopt a digital processing method that combines pattern etching and laser cutting. The laser spot is extremely small and the positioning accuracy can reach the micron level. It can easily realize the production of ultra-high precision hot-bar fingers with pin spacing ≤0.1mm and position accuracy within ±0.02mm, thus solving the precision bottleneck of the traditional process.

[0017] (2) The circuit board with hot-bar fingers of the present invention and its processing technology have no physical stamping during the entire processing process, which completely eliminates the deformation and stretching caused by mechanical stress on the flexible substrate, ensuring the absolute stability and consistency of the position of the hot-bar fingers, and laying a solid foundation for subsequent precise alignment and welding.

[0018] (3) The circuit board with hot-bar fingers of the present invention and its processing technology, by printing solder resist ink first and then laser opening, can form a solder resist dam with uniform thickness and steep edge around the hot-bar fingers, which can effectively prevent the flow and bridging of solder paste during soldering, thereby obtaining a more precise and reliable soldering effect.

[0019] (4) The circuit board with hot-bar fingers of the present invention and its processing technology are directly driven by digital files for laser processing, without the need to make any physical molds, which greatly shortens the new product development cycle, reduces the cost of small batch and multi-variety production, and meets the needs of rapid iteration of electronic products. Attached Figure Description

[0020] Figure 1 This is a schematic diagram of the substrate planar diagram in step S1 of the present invention.

[0021] Figure 2 This is a schematic diagram of the substrate after drilling and electroplating in step S2 of the present invention.

[0022] Figure 3 This is a schematic diagram of the line exposure plane in step S3 of the present invention.

[0023] Figure 4 This is a schematic diagram of the line etching plane in step S3 of the present invention.

[0024] Figure 5 This is a schematic diagram of the protective film application in step S4 of the present invention.

[0025] Figure 6 This is a schematic diagram of the printing ink in step S5 of the present invention.

[0026] Figure 7 This is a cross-sectional view of Embodiment 1 of the present invention.

[0027] Figure 8 This is a cross-sectional view of Embodiment 2 of the present invention.

[0028] Figure 9 This is a schematic diagram of the laser cutting plane in step S6 of embodiment 1 of the present invention.

[0029] Figure 10 This is a comparative planar schematic diagram of traditional punching and laser cutting according to Embodiment 1 of the present invention. Detailed Implementation

[0030] The present invention will be further described below with reference to specific accompanying drawings and embodiments.

[0031] Example 1 like Figures 1-7 A manufacturing process for a circuit board with hot-bar fingers, comprising the following steps: Step S1. Provide a flexible circuit board substrate 1, the substrate 1 including Polyimide layers 1-6 and set in polyimide layer 1-6 The upper copper foil 1-1 and the lower copper foil 1-2, the flexible circuit board substrate 1 has a thickness of 25μm, the manufacturer is Taihong (Electronic) Materials Co., Ltd., and the model is 2UPDR1003JA; Step S2. At least one Hot-bar through hole 1-4 with a diameter of 0.1 mm and an alignment hole are made on the flexible circuit board substrate 1 at the position corresponding to the Hot-bar finger. Copper plating is performed on the flexible circuit board substrate 1 and the Hot-bar through hole 1-4 to form a copper plating layer 1-3, so that the thickness of the flexible circuit board substrate 1 reaches 18 μm. Step S3. A dry film 2 is placed on the copper-plated flexible circuit board substrate 1, and exposed and developed to form circuits and hot-bar finger patterns. Then, an acidic copper chloride etching solution is used to etch so that the upper copper foil 1-1 and the lower copper foil 1-2 near each hot-bar via 1-4 are etched away to create circuits and hot-bar finger patterns, and obtain a flexible circuit board. Based on the alignment holes, the flexible circuit board substrate 1 is segmented and aligned using direct laser imaging and segmentation alignment processes. The alignment holes serve as target holes for segmentation alignment. During exposure, auxiliary etching sections 1-5 are set at the tip of the hot-bar finger. One end of the auxiliary etching section 1-5 is close to the through hole 1-4, and the other end extends to the lower end of the flexible circuit board substrate 1. The width of the auxiliary etching section 1-5 is 75um. An arc-shaped line matching the shape of the through hole 1-4 is set at the end of the auxiliary etching section 1-5 close to the through hole 1-4. The distance between the end of the auxiliary etching section 1-5 close to the through hole 1-4 and the through hole 1-4 is 25um.

[0032] Step S4. The flexible circuit board is subjected to browning treatment at a browning rate of 4.5 m / min. Then, a 25 μm thick polyimide cover film of model FGA0525 is applied as protective film 3. The manufacturer is Taihong (Electronic) Materials Co., Ltd. Protective film 3 is subjected to fast pressing and baking. The fast pressing temperature is 180℃, the pressure is 60 kg, and the time is 180 seconds. The baking temperature is 150℃ and the baking time is 60 minutes. Step S5. Print flexible ink that is resistant to bending onto the flexible circuit board at the position corresponding to the Hot-bar fingers to form solder resist ink layer 4. The solder resist ink manufacturer is Sun Ink Co., Ltd., and the model is PSR-9000 FLX501OR. Step S6. Use ultraviolet laser to perform high-precision alignment and 4-section laser cutting of the Hot-bar finger area. Polyimide layers 1-6 Cut the pads to form hot-bar fingers with a pin pitch of 0.08mm. Step S7. Perform surface treatment on the hot-bar finger pads. Specifically, perform electroless nickel-palladium-gold plating with a nickel layer thickness of 3 μm, a palladium layer thickness of 0.05 μm, and a gold layer thickness of 0.03 μm to obtain a circuit board with hot-bar fingers.

[0033] Measurements showed that the circuit board with hot-bar fingers prepared in Example 1 had finished hot-bar fingers whose spacing accuracy and external dimensions fully met the design requirements, and whose edges were neat and burr-free, providing perfect conditions for subsequent micro-pitch hot-press welding.

[0034] Figure 9 The circuit board with hot-bar fingers prepared in Example 1 of this invention is an example of a circuit board. Figure 10 This is a schematic planar comparison of traditional punching and laser cutting according to Embodiment 1 of the present invention. Figure 10 Figure 5 shows the effect of the circuit board obtained by laser cutting in Example 1, and Figure 6 shows the effect of the circuit board obtained by traditional punching. Figure 9 and Figure 10 It can be concluded that the laser spot of the circuit board prepared in Embodiment 1 of the present invention is extremely small, and the positioning accuracy can reach the micrometer level. It can easily realize the ultra-high precision Hot-bar finger manufacturing with pin spacing ≤0.1mm and position accuracy within ±0.02mm, thus solving the precision bottleneck of traditional processes.

[0035] Example 2 like Figures 1-6 and Figure 8 A manufacturing process for a circuit board with hot-bar fingers, comprising the following steps: Step S1. Provide a flexible circuit board substrate 1, the substrate 1 including Polyimide layers 1-6 and set in polyimide layer 1-6 The upper copper foil 1-1 and the lower copper foil 1-2, the thickness of the flexible circuit board substrate 1 is 20μm, the manufacturer of the flexible circuit board substrate is Doosan Electronics Co., Ltd., and the model is DSflex-600 122012R; Step S2. At least one Hot-bar through hole 1-4 with a diameter of 0.15mm and an alignment hole are made on the flexible circuit board substrate 1 at the position corresponding to the Hot-bar finger. A segmentation alignment target is set, and copper plating is performed on the flexible circuit board substrate 1 and the Hot-bar through hole 1-4 to form a copper plating layer 1-3, so that the thickness of the flexible circuit board substrate 1 reaches 18μm. Step S3. A dry film 2 is placed on the copper-plated flexible circuit board substrate 1, and exposed and developed to form circuits and hot-bar finger patterns. Then, an acidic etching solution is used to etch so that the upper copper foil 1-1 and the lower copper foil 1-2 near each hot-bar via 1-4 are etched away to create circuits and hot-bar finger patterns, and a flexible circuit board is obtained. Based on the alignment holes, the flexible circuit board substrate 1 is segmented and aligned using direct laser imaging and segmentation alignment processes. The alignment holes serve as target holes for segmentation alignment. During exposure, auxiliary etching sections 1-5 are set at the tip of the hot-bar finger. The auxiliary etching sections 1-5 avoid the position of the hot-bar through-hole 1-4. One end of the auxiliary etching section 1-5 is close to the through-hole 1-4, and the other end extends to the lower end of the flexible circuit board substrate 1. The width W of the auxiliary etching section 1-5 is 100um. An arc-shaped line that matches the shape of the through-hole 1-4 is set at the end of the auxiliary etching section 1-5 close to the through-hole 1-4. The distance L between the end of the auxiliary etching section 1-5 close to the through-hole 1-4 and the through-hole 1-4 is 35um.

[0036] Step S4. The flexible circuit board is subjected to browning treatment at a browning rate of 4.8 m / min. Then, a 25 μm thick polyimide cover film of model FGA0525 is applied as protective film 3. The manufacturer of the polyimide cover film is Taihong (Electronic) Materials Co., Ltd. Protective film 3 is subjected to fast pressing and baking. The fast pressing temperature is 190℃, the pressure is 70 kg, and the time is 180 seconds. The baking temperature is 160℃ and the baking time is 60 minutes.

[0037] Step S5. Print flexible ink that is resistant to bending onto the flexible circuit board at the position corresponding to the Hot-bar fingers to form solder resist ink layer 4. The manufacturer of the solder resist ink is Sun Ink Co., Ltd., and the model is PSR-9000 FLX501OR. Step S51. Provide a low-flow prepreg 5 and a copper foil 6, and perform windowing treatment on the corresponding bending area of ​​the low-flow prepreg 5. The copper foil 6 is not treated. Step S52. The low-flow prepreg 5 and copper foil 6 are sequentially placed on both sides of the flexible circuit board and pressed together to form a rigid-flex board; Step S53. Drill holes, electroplat, apply circuit patterns, and solder resist to the laminated rigid-flex PCB. During drilling production, 1 piece / stack is used, the drill bit life is set to 800 holes, and electroplating is carried out using a vertical continuous electroplating line, with hole copper set to 12um and surface copper set to 28um. The specific steps for fabricating the circuit pattern are as follows: First, clean the copper surface to remove oxides and increase its roughness to improve the adhesion between the dry film and the copper surface during lamination. Then, press the dry film (model PM338, manufactured by DuPont Electronic Materials Co., Ltd.) onto the copper foil 6. Next, expose and develop the film, and finally etch it to obtain the desired circuit pattern.

[0038] Solder resist: First, clean the board surface with the circuit pattern to remove foreign objects and oxides from the circuit pattern, increase the roughness of the circuit, and improve the adhesion between the ink and the circuit. Then, print ink on the upper and lower layers of the board and pre-bake it. Then, expose, develop and bake it to complete the solder resist production.

[0039] Step S54. Perform surface treatment on the exposed hot-bar finger pads. Specifically, perform electroless nickel-palladium-gold plating with a nickel layer thickness of 3 μm, a palladium layer thickness of 0.05 μm, and a gold layer thickness of 0.03 μm. Step S6. Use ultraviolet laser or green laser to laser cut the polyimide layer 1-6 in the Hot-bar finger area to form Hot-bar finger pads. The pin pitch of the Hot-bar fingers is 0.05mm, resulting in a circuit board with Hot-bar fingers.

[0040] Measurements showed that the circuit board with hot-bar fingers prepared in Example 2 had finished hot-bar fingers whose spacing accuracy and external dimensions fully met the design requirements, and whose edges were neat and burr-free, providing perfect conditions for subsequent micro-pitch hot-press welding.

[0041] Finally, it should be noted that the above specific embodiments are only used to illustrate the technical solutions of the present invention and not to limit it. Although the present invention has been described in detail with reference to examples, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of the present invention without departing from the spirit and scope of the technical solutions of the present invention, and all such modifications or substitutions should be covered within the scope of the claims of the present invention.

Claims

1. A manufacturing process for a circuit board with hot-bar fingers, characterized in that: Includes the following steps: Step S1. Provide a flexible circuit board substrate (1), the flexible circuit board substrate (1) includes Polyimide layers (1-6) and set in The polyimide layers (1-6) Upper copper foil (1-1) and lower copper foil (1-2); Step S2. At least one Hot-bar through hole (1-4) is made on the flexible circuit board substrate (1) at the position corresponding to the Hot-bar finger, and copper plating is performed on the flexible circuit board substrate (1) and the Hot-bar through hole (1-4) to form a copper plating layer (1-3). Step S3. A dry film (2) is placed on the copper-plated flexible circuit board substrate (1), and then exposed, developed and etched so that the upper copper foil (1-1) and lower copper foil (1-2) near each hot-bar via (1-4) are etched away. Then, the circuit and hot-bar finger pattern are made to obtain the flexible circuit board. Step S4. The flexible circuit board is browned, and then a protective film (3) is applied. The protective film (3) is then pressed and baked. Step S5. Print solder resist ink on the flexible circuit board at the position corresponding to the Hot-bar finger to form a solder resist ink layer (4). Step S6. Use laser cutting to cut the Hot-bar finger area. Polyimide layers (1-6) Cut the circuit board to form hot-bar finger pads, resulting in a circuit board with hot-bar fingers.

2. The processing technology of the circuit board with hot-bar fingers according to claim 1, characterized in that: In step S2, the diameter of the hot-bar through holes (1-4) is 0.1mm-0.3mm, and alignment holes are also provided on the flexible circuit board substrate (1).

3. The processing technology of the circuit board with hot-bar fingers according to claim 2, characterized in that: In step S3, the exposure adopts laser direct imaging and segmentation alignment process. The alignment hole is used as the target hole for segmentation alignment. During exposure, an auxiliary etching section (1-5) is set at the tip of the hot-bar finger. One end of the auxiliary etching section (1-5) is close to the through hole (1-4), and the other end extends to the lower end of the flexible circuit board substrate (1). The width of the auxiliary etching section (1-5) is 75-200um. An arc line that matches the shape of the through hole (1-4) is set at the end of the auxiliary etching section (1-5) close to the through hole (1-4). The distance between the end of the auxiliary etching section (1-5) close to the through hole (1-4) and the through hole (1-4) is 15-35um.

4. The processing technology of the circuit board with hot-bar fingers according to claim 1, characterized in that: In step S4, the browning rate is 3.0-5.5 m / min, the fast pressing temperature is 170-190℃, the pressure is 60-100 kg, the time is 120-200 seconds, the baking temperature is 150-170℃, and the baking time is 60-90 min.

5. The processing technology of the circuit board with hot-bar fingers according to claim 1, characterized in that: The solder resist ink mentioned in step S5 is a flexible ink that is resistant to bending.

6. The processing technology of the circuit board with hot-bar fingers according to claim 1, characterized in that: The laser mentioned in step S6 is an ultraviolet laser or a green laser.

7. The processing technology of the circuit board with hot-bar fingers according to claim 1, characterized in that: Step S6 is followed by: surface treatment of the Hot-bar finger pads, specifically electroless nickel-palladium-gold plating, hard gold plating, or electroless tin plating; when electroless nickel-palladium-gold plating, the thickness of nickel is 200-1000u”, the thickness of palladium is 2-10u”, and the thickness of gold is 2-10u”; when electroless hard gold plating, the thickness of nickel is 200-1000u” and the thickness of gold is 5-50u”; when electroless tin plating, the thickness of tin is 1-3um.

8. The processing technology of the circuit board with hot-bar fingers according to claim 1, characterized in that: The pin pitch of the hot-bar finger is no greater than 0.1mm.

9. The processing technology of the circuit board with hot-bar fingers according to claim 1, characterized in that: Between steps S5 and S6, the following also applies: Step S51. Provide a low-flow prepreg (5) and copper foil (6), and perform window opening treatment on the bending area corresponding to the low-flow prepreg (5); Step S52. The low-flow prepreg (5) and copper foil (6) are sequentially placed on both sides of the flexible circuit board and pressed together to form a rigid-flex board; Step S53. Drill holes, electroplat, apply circuit patterns, and solder resist to the laminated rigid-flex PCB. Step S54. Perform surface treatment on the exposed hot-bar finger pads.

10. A circuit board with a hot-bar finger, characterized in that, It is manufactured using the processing technology described in any one of claims 1-9.

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