Mini LED copper paste printed circuit board and preparation method thereof

Abstract

The invention discloses a Mini LED copper paste printed circuit board and a preparation method thereof, the circuit board comprises a shading PI layer, a copper paste circuit layer, a bonding layer and a white cover film layer, the copper paste circuit layer is arranged on the shading PI layer in a printing mode, the bonding layer is arranged on the copper paste circuit layer and used for connecting the copper paste circuit layer and the white cover film layer, and the white cover film layer is a protective film; the total thickness of the shading PI layer, the copper paste circuit layer, the bonding layer and the white cover film layer is smaller than 0.1 mm, the surface of the copper paste circuit layer is subjected to chemical gold treatment, a Mini LED is mounted on the surface of the white cover film layer through SMT, and a 0-ohm resistor is matched. According to the preparation method, by optimizing the steps of shading PI cutting, copper paste printing, copper paste curing, white protective film false connection and SMT part printing, the technical difficulty of the Mini LED copper paste printed circuit board in the manufacturing process can be overcome, and the product quality and the production efficiency are improved.

Description

Technical Field

[0001] The invention relates to the technical field of flexible printed circuit boards, in particular to a copper paste printed circuit board and a preparation method thereof. Background Art

[0002] Copper pastes are widely used in the field of printed electronics, which utilizes a printing process to produce conductive traces and patterns on a variety of surfaces. Printed electronics is a new technology that allows electronic components and devices to be produced using additive manufacturing techniques, offering advantages such as cost-effectiveness, flexibility, and the ability to incorporate electronics into unusual forms and surfaces.

[0003] With the rapid development of electronic technology, the performance requirements of printed circuit boards, as key basic components of electronic equipment, are also increasing. There are many problems in the traditional copper foil etching process for manufacturing printed circuit boards. A large amount of chemical etchants are used in the etching process, which is not only costly but also causes serious pollution to the environment. As an emerging printed circuit board manufacturing technology, copper paste printing technology has potential advantages such as simple process, good environmental protection, and flexible circuit manufacturing. However, there is still room for improvement in copper paste formulation, printing process and subsequent treatment to meet higher performance requirements.

[0004] With the rapid development of electronic technology, Mini LED is increasingly used in the display field. Traditional printed circuit boards with copper foil substrate etched circuits face many challenges in the preparation of Mini LED application products, such as complex processes, high costs, and high environmental pressure. The copper paste printed circuit technology provides a new way to solve these problems, but there are still a series of process difficulties that need to be overcome in the actual preparation process. In order to meet the market demand for Mini LED printed circuit boards, the applicant actively explored innovations and developed a new product that uses copper paste printed circuits to replace copper foil substrate etched circuits. Through in-depth research and development of this product, it aims to improve the quality of Mini LED circuit board products, reduce costs and enhance market competitiveness, and provide the electronics industry with a more advantageous Mini LED printed circuit board preparation solution. Summary of the invention

[0005] The purpose of the present invention is to provide a reliable and environmentally friendly Mini LED copper paste printed circuit board and a manufacturing method thereof, so as to solve the problems of high cost, high pollution and limited circuit production existing in the existing printed circuit board manufacturing process.

[0006] In order to achieve the above object, the solution of the present invention is: A Mini LED copper paste printed circuit board includes a light-shielding PI layer, a copper paste circuit layer, an adhesive layer and a white cover film layer. The copper paste circuit layer is arranged on the light-shielding PI layer by printing, and the adhesive layer is arranged on the copper paste circuit layer to connect the copper paste circuit layer and the white cover film layer. The white cover film layer is a protective film; the total thickness of the light-shielding PI layer, the copper paste circuit layer, the adhesive layer and the white cover film layer is less than 0.1 mm, the surface of the copper paste circuit layer is subjected to gold treatment, and the surface of the white cover film layer is mounted with Mini LED by SMT and matched with a 0 ohm resistor.

[0007] Furthermore, the total bus width of the Mini LED copper paste printed circuit board is greater than 1.5 mm and less than 3 mm, and the line width is 1 mm.

[0008] Furthermore, a copper paste with good fluidity, good chemical resistance, voltage resistance, pre-treatment, gold-plating and resistance value meeting the requirements is selected to prepare the copper paste circuit layer.

[0009] A method for preparing a Mini LED copper paste printed circuit board comprises the following steps: Step S1. Cutting of light-shielding PI: The main material is black light-shielding PI, and a polymer layer with anti-stretching and anti-curling properties is compounded on the black light-shielding PI. The light-shielding PI uses a high-strength, low-shrinkage polyimide film with a thickness of 25-35μm. The polymer layer is composed of a cross-linked silicone polymer with a thickness of 10-15μm. Step S2. Printing copper paste on the cut light-shielding PI to form a light-shielding PI printed board with copper paste circuits; etching positioning marks on the non-functional area of ​​the light-shielding PI using a low-power laser, assembling a laser sensor for detecting the positioning marks on the printing equipment, and detecting these positioning marks by the laser sensor to accurately position the black light-shielding PI; Copper paste printing uses a fully automatic screen printer. The scraper of the fully automatic screen printer is made of titanium alloy, with a nano coating on the surface. The scraper hardness is 50-60HRC, and the scraper angle is adjusted between 60 and 70 degrees. The scraper pressure of the fully automatic screen printer is set according to the viscosity of the copper paste, printing speed and printing thickness requirements to stabilize the printing thickness at 14μm; the printing speed is 35-45PPM; Step S3. Copper paste curing: A dedicated copper paste curing fixture is used. The fixture is made of lightweight aluminum alloy and the surface is treated with a high-temperature resistant coating. The light-shielding PI printed board is always kept flat by the fixture during the curing process. The curing process uses a heating method that combines infrared heating and hot air circulation; Step S4. Laser drilling; Step S5. Pretreatment of the protective film: cleaning and drying the printed board after the circuit is cured; Step S6. Pretend to connect the white protective film, select the white protective film, add transparent positioning marks on the edge or fixed area of ​​the white protective film, and the width of the mark is 1-2mm; Step S7. Pressing the white protective film so that the white protective film is attached to the copper paste circuit layer of the printed board; Step S8. baking the white protective film to form a printed circuit board having a white protective film; Step S 9. Surface treatment - sandblasting to remove dirt and oxides from the surface of the printed circuit board; Step S10. Chemical nickel gold; Step S11. Washing and drying; Step S12. PI reinforcement by false connection and PI reinforcement by crimping; Step S13. Silk screen printing and baking characters; Step S14. Electrical testing - flying probe; Step S15. Laser contour cutting is performed on the printed circuit board that has passed the electrical test; Step S16: MQC full inspection; Step S17. SMT mounting: Mounting Mini LED and 0 ohm resistor on printed circuit board: Use a ceramic nozzle specially used for Mini LED mounting, the surface of the nozzle is treated with anti-stick coating, the nozzle is installed on the mounting machine, and the parameters of the nozzle are adjusted to match the size and surface characteristics of the Mini LED. During the mounting process, adjust the viscosity and printing amount of the solder paste, control the viscosity of the solder paste to 180-220Pa·s, and the printing amount to 0.1 - 0.2mg / pad. The solder paste is printed on the pad according to the printing parameters. The mounting machine scans the polarity mark of the Mini LED and automatically adjusts the mounting angle and position to mount the Mini LED on the pad. Step S18. Laser contouring, and contour cutting again to make the printed circuit board reach the designed size and shape; Step S19. After the package is inspected again, it is packaged and shipped, completing the production of the Mini LED copper paste printed circuit board.

[0010] Furthermore, in step S2, the screen for printing copper paste is cleaned by a pulsed high-pressure airflow combined with micro-vibration, and a plurality of pulsed high-pressure air nozzles are arranged under the screen, the pressure of the air nozzles is 0.3-0.5MPa, and the pulse frequency is 5-10Hz; a micro-vibration motor is installed on the screen frame, and the vibration frequency is 100-200Hz and the amplitude is 0.5-1mm.

[0011] Furthermore, in step S2, the depth of the positioning mark of the light-shielding PI is 5-10 μm, and the width is 100-200 μm; the positioning deviation of the black light-shielding PI is controlled within ±0.1 mm.

[0012] Furthermore, in step S17, before mounting, the polarity mark of the Mini LED is scanned by CCD, and the detection result is directly transmitted to the mounting machine control system, and the control system automatically adjusts the mounting angle and position according to the detection result.

[0013] Furthermore, in step S17, the inner diameter of the nozzle corresponds to the size of the Mini LED, and the size of the Mini LED is 0.3 - 0.5 mm.

[0014] After adopting the above scheme, the method for preparing the Mini LED copper paste printed circuit board of the present invention has the following beneficial effects: By improving the PI cutting process, the PI curling problem was effectively solved, the cutting efficiency and accuracy were improved, a good basic material was provided for subsequent processes, and the scrap rate caused by cutting problems was reduced. It is estimated that the scrap rate can be reduced by 30-50%.

[0015] By optimizing the copper paste printing process, the precise positioning of black PI is achieved, the printing thickness is precisely controlled, the copper paste loss is reduced, and the printing quality and production efficiency are improved. The deviation of printing thickness can be controlled within ±1μm, the copper paste loss is reduced by 60-80%, and the production efficiency is increased by 20-30%.

[0016] By improving the copper paste curing process, the curing efficiency is improved, the labor cost is reduced, and the uniformity and stability of the copper paste curing are ensured, the reliability of the product is improved, and the labor cost is reduced by 40-60%.

[0017] By improving the lamination process of the white protective film, the lamination efficiency and yield rate are improved, and product defects caused by lamination problems are reduced. The lamination efficiency is increased by 50-80%, and the yield rate is increased to more than 90%.

[0018] By optimizing the placement process, problems such as nozzle adhesion, solder paste bridging short circuit and material throwing were solved, the first piece confirmation and machine adjustment time were shortened, the placement quality and production efficiency were improved, the placement defect rate was reduced by 50-70%, and the first piece confirmation and machine adjustment time were shortened by 60-80%.

[0019] In summary, the preparation method of the Mini LED copper paste printed circuit board of the present invention can effectively overcome many difficulties in the existing preparation process, and compared with the process of etching the circuit, the present invention is more environmentally friendly, can reduce environmental pollution, improve product quality and production efficiency, has significant economic and social benefits, and has broad application prospects in the field of Mini LED related electronic product manufacturing. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 It is a schematic diagram of the layer structure of the copper paste printed circuit board of the present invention.

[0021] Figure 2 It is a schematic diagram of the process of the present invention. DETAILED DESCRIPTION

[0022] In order to further explain the technical solution of the present invention, the present invention is described in detail below through specific embodiments.

[0023] like Figure 1 As shown, the present invention discloses a Mini LED copper paste printed circuit board, which includes a light-shielding PI layer 1, a copper paste circuit layer 2, an adhesive layer 3 and a white cover film layer 4. The copper paste circuit layer 2 is arranged on the light-shielding PI layer 1 by printing, and the adhesive layer 3 is arranged on the copper paste circuit layer 2 to connect the copper paste circuit layer 2 and the white cover film layer 4. The white cover film layer 4 is a protective film to protect the copper paste circuit layer 2. The total thickness of the light-shielding PI layer 1, the copper paste circuit layer 2, the adhesive layer 3 and the white cover film layer 4 is less than 0.1mm, the surface of the copper paste circuit layer 2 is subjected to gold treatment, and the surface of the white cover film layer 4 is mounted with multiple MiniLEDs (for example, 46) by SMT and matched with a 0 ohm resistor. The total bus width of the Mini LED copper paste printed circuit board is greater than 1.5mm and less than 3mm, and the line width is 1mm.

[0024] The copper paste circuit layer 2 is made of copper paste with good fluidity, good chemical resistance, voltage resistance, normal pre-treatment, gold plating, and resistance that meets the requirements, and copper paste with poor fluidity, poor adhesion, large resistance, and NG chemical resistance is excluded. After testing, the copper paste of Bairou brand and model PHP9000-5F-P4 can be selected (of course, other copper pastes that meet the requirements are also applicable, and this model is only a specific embodiment of the present invention).

[0025] like Figure 2 As shown, the present invention also discloses a method for preparing a Mini LED copper paste printed circuit board, which comprises the following steps: Step S1. Cutting of light-shielding PI: The main material is black light-shielding PI, and the conventional PI is prepared with a carrier film. After roll-to-sheet cutting, the curling is serious, which makes the equipment unable to cut, and requires manual cutting, and the curling of PI will affect the printing and curing process. Therefore, the present invention composites a layer of high-molecular polymer layer with anti-stretching and anti-curling properties on the black light-shielding PI to reduce the relative displacement and curling phenomenon during the cutting process; the light-shielding PI adopts a high-strength, low-shrinkage polyimide film with a thickness of 25-35μm to provide stable support for the whole, and the high-molecular polymer layer is composed of a cross-linked silicone polymer with a thickness of about 10-15μm, which can effectively resist the stress deformation of the light-shielding PI during the cutting process. By improving the light-shielding PI, the present invention can not only ensure the effective support of the light-shielding PI, but also avoid the cutting problem caused by itself being too hard or too soft, and can overcome the process difficulty of PI curling, thereby improving the cutting efficiency, improving the cutting yield, and avoiding the curling of the light-shielding PI during cutting.

[0026] Step S2. Copper paste is printed to form a light-shielding PI printed board with copper paste circuits; in the non-functional area around the light-shielding PI, a low-power laser is used to etch tiny positioning marks with a depth of 5-10μm and a width of 100-200μm. The printing equipment is equipped with a high-precision laser sensor to detect these positioning marks to achieve fast and accurate positioning of the black light-shielding PI, and the positioning deviation can be controlled within ±0.1mm.

[0027] The printing process is carried out by using a fully automatic screen printer. The scraper of the screen printer is improved. The scraper is made of titanium alloy and coated with nano-coating on the surface. The hardness of the scraper is 50-60HRC. The scraper angle can be precisely adjusted between 60 and 70 degrees. The scraper pressure of the fully automatic screen printer is set according to the viscosity of the copper paste, the printing speed and the printing thickness requirements to ensure that the printing thickness is stable at 14μm. At the same time, the printing speed is optimized and the printing speed is precisely controlled at 35-45PPM (number of sheets printed per minute). The printing time for each sheet is about 10s-15s, which can not only ensure the printing quality but also improve the production efficiency.

[0028] In order to avoid clogging of the stencil, the present invention adopts a cleaning method combining pulsed high-pressure airflow and micro-vibration. A plurality of pulsed high-pressure air nozzles are arranged under the stencil. The pressure of the air nozzles can be adjusted between 0.3 and 0.5 MPa, and the pulse frequency is 5 to 10 Hz. At the same time, a micro-vibration motor is installed on the stencil frame, with a vibration frequency of 100 to 200 Hz and an amplitude of 0.5 to 1 mm. This cleaning method can effectively remove the copper paste adhesion on the stencil, reduce the stencil cleaning frequency to once every 10 to 15 PCS of printing, and greatly reduce the loss of copper paste.

[0029] Step S3. Copper paste curing: Use a special copper paste curing fixture. The fixture is made of lightweight aluminum alloy and the surface is treated with a special high-temperature resistant coating. The structural design of the fixture can ensure that the light-shielding PI printed board remains flat during the curing process. The curing process uses a heating method that combines infrared heating and hot air circulation. The infrared heating element can quickly transfer heat to the PI printed board, and the hot air circulation system ensures the uniformity of the temperature in the curing room, with a temperature control accuracy of within ±2°C. The combination of the curing fixture and the heating method greatly improves the curing efficiency and curing yield.

[0030] Step S4. Laser drilling; Step S5. Pretreatment of the protective film: cleaning and drying the printed board after the circuit is cured; Step S6. Pretend to connect the white protective film: select a white protective film. Since the white protective film is opaque, the present invention adds a transparent positioning mark on the edge or fixed area of ​​the protective film, and the width of the mark is 1-2mm. By adding a transparent positioning mark, it is avoided that the white protective film is opaque and the device cannot recognize it. The purpose of the fake connection of the white protective film is to ensure that the white protective film can be accurately positioned on the printing plate, so as to prepare for the subsequent crimping process.

[0031] Step S7: Press the white protective film so that the white protective film is more closely attached to the copper paste circuit layer of the printed board.

[0032] Step S 8. Bake the white protective film. Baking is an important step after the white protective film is bonded. Baking can further promote the curing of the adhesive or adhesive layer between the white protective film and the printed board to achieve the best bonding effect; baking can also help remove any residual solvent or moisture that may exist, thereby improving the stability and reliability of the white protective film. At the same time, baking can also help relieve the stress that may be generated by the white protective film during the bonding process, thereby improving the bonding quality and durability between the white protective film and the printed board. After the baking process is completed, a printed circuit board with a white protective film is formed; Step S 9. Surface treatment - sandblasting; remove dirt and oxides from the surface of the printed circuit board, improve adhesion performance and improve the surface quality of the printed circuit board.

[0033] Step S10. Chemical nickel-gold, which mainly enhances solderability and improves the overall performance of the printed circuit board. This process is a common process in the processing of flexible circuit boards and will not be described in detail.

[0034] Step S11: washing and drying, the purpose of which is to remove residual flux and other impurities on the surface of the printed circuit board, and to remove water vapor by drying to ensure the cleanliness and stability of the printed circuit board.

[0035] Step S12: Preliminary PI reinforcement and PI reinforcement by pressing. First, preliminarily fix the PI reinforcement material and ensure that it is accurately aligned with the printed circuit board before pressing the PI reinforcement. Pressing PI reinforcement is used to enhance the mechanical strength and high temperature resistance of the printed circuit board. During the PI reinforcement pressing process, the PI reinforcement material is closely attached to the flexible circuit board by heat pressing or pressure sensing to form a solid reinforcement layer.

[0036] Step S13: Silk screen printing and baking characters, the purpose of which is mainly to add necessary logos and characters on the reinforced printed circuit board for subsequent assembly, testing and maintenance. These characters may include component numbers, polarity logos, production dates, etc.

[0037] Step S14. Electrical test - flying probe. The flying probe test is to directly contact the test points on the printed circuit board through the moving test probe to detect the electrical connections on the printed circuit board to ensure that the quality of the circuit board meets the design requirements.

[0038] Step S15. Laser contouring: For printed circuit boards that have passed the electrical test, precise contour cutting is performed to meet the size and shape requirements of the product. Laser contouring is the use of laser technology to cut printed circuit boards according to preset contour patterns to ensure that the edges of the printed circuit boards are smooth and the dimensions are accurate.

[0039] Step S16. MQC full inspection: a comprehensive quality inspection conducted by MQC (Manufacture Quality Control) personnel.

[0040] Step S17. SMT assembly: mount multiple (46 in this embodiment) Mini LEDs and 0 ohm resistors. Use a ceramic nozzle specially used for mounting Mini LED lamp beads. The surface of the nozzle is treated with an anti-stick coating. The inner diameter of the nozzle corresponds to the size of the Mini LED. The size of the Mini LED is preferably between 0.3 and 0.5 mm, which can effectively avoid the nozzle adhesion problem caused by the stickiness of the Mini LED surface. At the same time, optimize the mounting process parameters, adjust the viscosity and printing amount of the solder paste, control the viscosity of the solder paste to 180-220 Pa·s, and the printing amount to 0.1-0.2 mg / pad to reduce the occurrence of solder paste bridging short circuits and material throwing.

[0041] Before mounting, the polarity mark of the Mini LED is quickly scanned by CCD, and the detection data is directly transmitted to the mounting machine control system. The control system automatically adjusts the mounting angle and position according to the detection results without manual intervention.

[0042] The present invention installs the ceramic nozzle corresponding to Mini LED on the SMT machine, and adjusts the parameters of the nozzle to match the size and surface characteristics of Mini LED. During the mounting process, the solder paste is printed on the pad using the optimized printing parameters. The SMT machine uses an integrated polarity detection and adjustment system to quickly scan the polarity mark of Mini LED and automatically adjust the mounting angle and position to accurately mount the Mini LED on the pad, while reducing the occurrence of solder paste bridging short circuit and material throwing.

[0043] Step S18: Laser contouring: perform contour cutting again to achieve the designed size and shape. Laser processing is used to improve the accuracy of the product and ensure that the fit between the various parts is tighter.

[0044] Step S19: Inspect before packaging and then package for shipment to complete the production of Mini LED copper paste printed circuit board.

[0045] The preparation method of the Mini LED copper paste printed circuit board of the present invention overcomes the technical difficulties in the production process of the Mini LED copper paste printed circuit board by improving the steps of step S1. shading PI cutting, step S2. copper paste printing, step S3. copper paste curing, step S6. false connection of white protective film, and step S17. SMT assembly, which is specifically manifested in the following aspects: By improving the PI cutting process, the PI curling problem was effectively solved, the cutting efficiency and accuracy were improved, a good basic material was provided for subsequent processes, and the scrap rate caused by cutting problems was reduced. It is estimated that the scrap rate can be reduced by 30-50%.

[0046] By optimizing the copper paste printing process, the precise positioning of black PI is achieved, the printing thickness is precisely controlled, the copper paste loss is reduced, and the printing quality and production efficiency are improved. The deviation of printing thickness can be controlled within ±1μm, the copper paste loss is reduced by 60-80%, and the production efficiency is increased by 20-30%.

[0047] By improving the copper paste curing process, the curing efficiency is improved, the labor cost is reduced, and the uniformity and stability of the copper paste curing are ensured, the reliability of the product is improved, and the labor cost is reduced by 40-60%.

[0048] By improving the lamination process of the white protective film, the lamination efficiency and yield rate are improved, and product defects caused by lamination problems are reduced. The lamination efficiency is increased by 50-80%, and the yield rate is increased to more than 90%.

[0049] By optimizing the placement process, problems such as nozzle adhesion, solder paste bridging short circuit and material throwing were solved, the first piece confirmation and machine adjustment time were shortened, the placement quality and production efficiency were improved, the placement defect rate was reduced by 50-70%, and the first piece confirmation and machine adjustment time were shortened by 60-80%.

[0050] In summary, the preparation method of the Mini LED copper paste printed circuit board of the present invention can effectively overcome many difficulties in the existing preparation process, improve the quality and production efficiency of the product, has significant economic and social benefits, and has broad application prospects in the field of Mini LED related electronic product manufacturing.

[0051] The above embodiments and drawings do not limit the product form and style of the present invention. Any appropriate changes or modifications made by ordinary technicians in the relevant technical field should be deemed to be within the patent scope of the present invention.

Claims

1. A Mini LED copper paste printed circuit board, characterized in that: include: Light-shielding PI layer, copper paste circuit layer, adhesive layer and white cover film layer. The copper paste circuit layer is arranged on the light-shielding PI layer by printing, and the adhesive layer is arranged on the copper paste circuit layer to connect the copper paste circuit layer and the white cover film layer. The white cover film layer is a protective film. The total thickness of the light-shielding PI layer, copper paste circuit layer, adhesive layer and white cover film layer is less than 0.1mm. The surface of the copper paste circuit layer is subjected to gold treatment. The surface of the white cover film layer is mounted with Mini LED by SMT and is matched with a 0 ohm resistor.

2. The Mini LED copper paste printed circuit board according to claim 1, characterized in that: The total width of the circuit board is greater than 1.5mm and less than 3mm, and the line width is 1mm.

3. The Mini LED copper paste printed circuit board according to claim 1, characterized in that: The copper paste circuit layer is prepared by selecting a copper paste with good fluidity, good chemical resistance, voltage resistance, pre-treatment, gold plating, and resistance value that meets the requirements.

4. A method for preparing a Mini LED copper paste printed circuit board according to any one of claims 1 to 3, characterized in that: The following steps are involved: Step S1. Cutting of light-shielding PI: The main material is black light-shielding PI, and a polymer layer with anti-stretching and anti-curling properties is compounded on the black light-shielding PI. The light-shielding PI adopts a high-strength, low-shrinkage polyimide film with a thickness of 25-35μm. The polymer layer is composed of a cross-linked silicone polymer with a thickness of 10-15μm. Step S2. Printing copper paste on the cut light-shielding PI to form a light-shielding PI printed board with copper paste circuits; etching positioning marks on the non-functional area of ​​the light-shielding PI using a low-power laser, assembling a laser sensor for detecting the positioning marks on the printing equipment, and detecting these positioning marks by the laser sensor to accurately position the black light-shielding PI; Copper paste printing uses a fully automatic screen printer. The scraper of the fully automatic screen printer is made of titanium alloy, with a nano coating on the surface. The scraper hardness is 50-60HRC, and the scraper angle is adjusted between 60 and 70 degrees. The scraper pressure of the fully automatic screen printer is set according to the viscosity of the copper paste, printing speed and printing thickness requirements to stabilize the printing thickness at 14μm; the printing speed is 35-45PPM; Step S3. Copper paste curing: A dedicated copper paste curing fixture is used. The fixture is made of lightweight aluminum alloy and the surface is treated with a high-temperature resistant coating. The light-shielding PI printed board is always kept flat by the fixture during the curing process. The curing process uses a heating method that combines infrared heating and hot air circulation; Step S4. Laser drilling; Step S5. Pretreatment of the protective film: cleaning and drying the printed board after the circuit is cured; Step S6. Pretend to connect the white protective film, select the white protective film, add transparent positioning marks on the edge or fixed area of ​​the white protective film, and the width of the mark is 1-2mm; Step S7. Pressing the white protective film so that the white protective film is attached to the copper paste circuit layer of the printed board; Step S8. baking the white protective film to form a printed circuit board having a white protective film; Step S 9. Surface treatment - sandblasting to remove dirt and oxides from the surface of the printed circuit board; Step S10. Chemical nickel gold; Step S11. Washing and drying; Step S12. PI reinforcement by false connection and PI reinforcement by crimping; Step S13. Silk screen printing and baking characters; Step S14. Electrical testing - flying probe; Step S15. Laser contour cutting is performed on the printed circuit board that has passed the electrical test; Step S16: MQC full inspection; Step S17. SMT mounting: Mounting Mini LED and 0 ohm resistor on printed circuit board: Use a ceramic nozzle specially used for Mini LED mounting, the surface of the nozzle is treated with anti-stick coating, the nozzle is installed on the mounting machine, and the parameters of the nozzle are adjusted to match the size and surface characteristics of the Mini LED. During the mounting process, adjust the viscosity and printing amount of the solder paste, control the viscosity of the solder paste to 180-220Pa·s, and the printing amount to 0.1 - 0.2mg / pad. The solder paste is printed on the pad according to the printing parameters. The mounting machine scans the polarity mark of the Mini LED and automatically adjusts the mounting angle and position to mount the Mini LED on the pad. Step S18. Laser contouring, and contour cutting again to make the printed circuit board reach the designed size and shape; Step S19. After the package is inspected again, it is packaged and shipped, completing the production of the Mini LED copper paste printed circuit board.

5. The method for preparing a Mini LED copper paste printed circuit board according to claim 4, characterized in that: In the step S2, the screen for printing copper paste is cleaned by a pulsed high-pressure airflow combined with micro-vibration. A plurality of pulsed high-pressure air nozzles are arranged under the screen, the pressure of the air nozzles is 0.3-0.5MPa, and the pulse frequency is 5-10Hz; a micro-vibration motor is installed on the screen frame, and the vibration frequency is 100-200Hz and the amplitude is 0.5-1mm.

6. A method for preparing a Mini LED copper paste printed circuit board according to claim 4, characterized in that: In step S2, the depth of the positioning mark of the light-shielding PI is 5-10 μm and the width is 100-200 μm; the positioning deviation of the black light-shielding PI is controlled within ±0.1 mm.

7. The method for preparing a Mini LED copper paste printed circuit board according to claim 4, characterized in that: In step S17, before mounting, the polarity mark of the Mini LED is scanned by CCD, and the detection result is directly transmitted to the mounting machine control system, and the control system automatically adjusts the mounting angle and position according to the detection result.

8. The method for preparing a Mini LED copper paste printed circuit board according to claim 4, characterized in that: In step S17, the inner diameter of the nozzle corresponds to the size of the Mini LED, and the size of the Mini LED is 0.3-0.5 mm.

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