Capacitance pen refill production process integrating PCB in-mold injection molding and three-dimensional circuit forming

Abstract

The invention relates to the technical field of intelligent manufacturing, and particularly discloses a capacitive pen refill production process integrating in-mold injection molding and three-dimensional circuit forming of a PCB (Printed Circuit Board), which comprises the following steps: designing and manufacturing a three-layer or four-layer PCB containing three bonding pads and circuits, connecting each bonding pad with the circuit in one layer of PCB, the other end of each circuit is connected with a surface circuit formed after laser forming of the injection molding part; fixing the PCB in an injection mold, and carrying out injection molding to form a plastic matrix containing a taper hole; after the plastic matrix is subjected to injection molding, laser activation, chemical coarsening, palladium activation, chemical copper plating or nickel base layer plating and thickened copper plating treatment are sequentially carried out to form a three-dimensional circuit; and sequentially carrying out magnetic suspension polishing grinding or chemical polishing, chemical nickel plating and hole sealing treatment on the three-dimensional circuit. According to the invention, by integrating the in-mold injection molding of the PCB, the laser forming of the three-dimensional circuit and the post-treatment process, a conventional plastic material can be adopted besides an LDS material, so that the cost of raw materials is greatly reduced.

Description

Technical Field

[0001] This invention belongs to the field of intelligent manufacturing technology, specifically relating to a capacitive pen refill production process that integrates in-mold injection molding of PCB board and three-dimensional circuit forming. Background Technology

[0002] The current mainstream manufacturing method for capacitive pen refills is to assemble multiple metal and plastic (insulating) parts.

[0003] When assembling hardware components, the cumulative tolerances of multiple hardware components result in poor consistency of the electronic pen refill after assembly, unstable product quality, and large signal fluctuations, affecting the performance and power consumption of the electronic pen and making it difficult to meet high-quality requirements. At the same time, the manufacturing mode of producing and assembling multiple hardware components and plastic parts is inefficient and has high manufacturing costs. Summary of the Invention

[0004] The purpose of this invention is to provide a manufacturing process for capacitive pen refills that integrates in-mold injection molding of PCB board and three-dimensional circuit forming, so as to solve the problems mentioned in the background art.

[0005] To achieve the above objectives, the present invention provides the following technical solution:

[0006] A manufacturing process for capacitive pen refills that integrates in-mold injection molding of PCB board and three-dimensional circuit forming includes the following steps:

[0007] (1) Design and manufacture three- or four-layer PCB boards, wherein one end of the circuit of the upper and lower PCB boards is connected to the PCB pads, and the other end is exposed and connected to the circuit of the plastic surface through the through hole formed by subsequent in-mold injection molding and laser circuit forming; one end of the circuit of the middle PCB board is connected to the pads, and the other end is exposed on the top of the pen refill body structure formed by in-mold injection molding.

[0008] (2) Fix the PCB board in the mold for in-mold injection molding, and injection molding forms a plastic substrate with a tapered hole, and simultaneously forms a thread for pen cap assembly to replace the metal nut; the plastic thread is covered by a metal layer after subsequent laser forming and electroplating to ensure the hardness and wear resistance of the thread; the tapered hole and the exposed circuit of the PCB board that need to be connected later are aligned. During injection molding, the plastic must not cover the corresponding exposed area of ​​the PCB board, otherwise the corresponding circuit cannot be connected to the PCB circuit during subsequent laser circuit forming.

[0009] (3) The surface of the plastic substrate is subjected to laser activation, chemical roughening and palladium activation as needed (if the material is LDS material, chemical roughening and palladium activation are not required), chemical plating of nickel or copper base layer, and then copper plating thickening treatment to form a three-dimensional circuit.

[0010] (4) The copper layer of the three-dimensional circuit is chemically polished or magnetically levitated and ground, then chemically nickel-plated and surface-sealed.

[0011] (5) Use convolutional neural networks to automatically identify line defects and combine them with impedance analysis algorithms to detect continuity reliability.

[0012] Preferably, the bottom diameter of the tapered hole in step (2) is 0.15-0.4 mm, and the taper of one side is preferably ≥25°, so that the inner side of the hole can be fully activated during laser forming.

[0013] Preferably, the conventional plastic material in step (2) is one of PC, PC+ABS or nylon; the material can be LDS modified material or non-LDS modified material. When non-LDS modified PC, PC+ABS or nylon material is used, subsequent chemical plating requires additional chemical roughening and palladium activation treatment.

[0014] Preferably, in step (3), the laser activation uses a fiber laser device with a wavelength of 1064nm and the parameters are: power 10-60W, scanning speed 1500-5000mm / s, laser frequency 20-150kHz, energy 30%-80%, and filling gap 0.04-0.07mm.

[0015] Preferably, the chemical roughening required in step (3) uses any of the following systems:

[0016] System 1: 200-300 g / L chromic anhydride, 50-150 mL / L sulfuric acid, 50-70℃, treatment for 3-10 minutes;

[0017] System 2: Sodium hydroxide 30-60 g / L, temperature 60-80℃, treatment for 2-15 minutes;

[0018] System 3: Sodium hydroxide 30-50 g / L, potassium permanganate 50-100 g / L, temperature 50-70℃, treatment for 2-12 minutes.

[0019] Preferably, if magnetic levitation polishing and grinding is used in step (4), the process parameters are: magnetic field strength 3000Gs, φ0.2mm iron-based magnetic abrasive (containing alumina abrasive particles), grinding speed 300rpm, and processing time 3 minutes.

[0020] Preferably, the materials used for chemical polishing in step (4) include triacid polishing slurry, hydrogen peroxide-based polishing slurry, and environmentally friendly copper polishing slurry, with the following slurry ratios and process parameters:

[0021] The formula for the tri-acid polishing solution includes 20%-30% nitric acid, 50% sulfuric acid, 0.3%-0.8% hydrochloric acid, 1%-5% brightener, and the balance being water;

[0022] The hydrogen peroxide-based polishing solution formula includes 250 ml / L hydrogen peroxide, 12 ml / L sulfuric acid, 20 ml / L brass polishing additive, and the remainder is water;

[0023] The environmentally friendly copper polishing solution formula includes 60-140g of persulfate, 200-350ml of 92.5wt%-98.0wt% concentrated sulfuric acid, 0-60ml of 85.0wt% concentrated phosphoric acid, 1-10g of citric acid, 2-10g of ferrous sulfate heptahydrate, 0-3g of sodium chloride, 0-6g of urea, 0.2-1.0g of sodium dodecyl sulfate, and the balance being water.

[0024] Preferably, the specific operation of electroless nickel plating in step (4) is as follows:

[0025] Solution formulation (taking 1L of water as an example): Nickel sulfate (NiSO4·7H2O) 20-30g (slightly less than the high-temperature formulation to avoid a rough coating);

[0026] Sodium hypophosphite (NaH2PO2·H2O) 25-35g (slightly increase the concentration to compensate for insufficient reducing activity at low temperature);

[0027] 15-25g of trisodium citrate + 10-20ml of lactic acid (complex complexation enhances the stability of nickel ions, and the key is that it does not precipitate at low temperatures);

[0028] Sodium acetate 15-25g (to stabilize pH and avoid pH fluctuations at low temperatures affecting the reaction);

[0029] Thiourea 0.5-1 mg / L + potassium iodide 1-3 mg / L (the plating solution is more prone to spontaneous decomposition at low temperatures, and the two stabilizers work together to inhibit this. Do not use too much, otherwise it will slow down the deposition).

[0030] Process requirements: Temperature: 50~65℃ (the most commonly used range; below 50℃, deposition is too slow, and above 70℃, it approaches high temperature and loses the advantage of low temperature);

[0031] pH value: 4.0~5.0 (slightly lower than the high temperature formula, adjust with dilute sulfuric acid or ammonia water, slightly higher pH will easily cause precipitation);

[0032] Deposition rate: 5-12 μm / h (the rate will be slower at low temperatures, which is normal and results in a finer coating).

[0033] Preferably, the parameters for the sealing process in step (4) are:

[0034] The sealing agent contains 3-5% silane coupling agent and 0.5% nano-alumina particles with a particle size of 50nm;

[0035] Processing conditions: Soak at 40-50℃ for 5-8 minutes, then dry with hot air at 60℃ for 10 minutes.

[0036] Compared with the prior art, the beneficial effects of the present invention are:

[0037] (1) By integrating in-mold injection molding of PCB board with optimized three-dimensional circuit forming and post-processing, the cost of raw materials can be greatly reduced when using conventional plastic materials, and waste can be further reduced by recycling and reusing injection head; the "chemical polishing or magnetic levitation polishing" post-processing chain effectively eliminates laser processing marks, improves the flatness and smoothness of the circuit surface, and the optimized conical hole structure design improves the high reliability of conduction and signal stability between the plastic surface circuit and the PCB board circuit.

[0038] (2) Integrated injection molding combined with laser 3D circuit manufacturing reduces the number of multi-component assembly steps and improves the consistency of product size and performance; during plastic injection molding, the threaded injection molding is replaced by metal covering during subsequent copper and nickel plating, further reducing costs and increasing efficiency. The various chemical roughening solutions provided enhance the adaptability to different conventional plastic materials and improve process flexibility; the sealing treatment forms a dense protective film on the plating surface, improving the product's corrosion resistance and service life. Attached Figure Description

[0039] Figure 1 This is a flowchart of the present invention. Detailed Implementation

[0040] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0041] Example 1:

[0042] Please see Figure 1 As shown, a manufacturing process for a capacitive pen refill integrating in-mold injection molding of a PCB board and three-dimensional circuit forming includes the following steps:

[0043] (1) Design and manufacture three- or four-layer PCB boards, wherein one end of the circuit of the upper and lower PCB boards is connected to the PCB pads, and the other end is exposed where it needs to be connected to the external circuits. The circuits are connected to the plastic surface through the through holes formed by subsequent in-mold injection molding and laser circuit forming; one end of the circuit of the middle PCB board is connected to the pads, and the other end is exposed on the top of the pen refill body structure formed by in-mold injection molding.

[0044] (2) Fix the PCB board in the mold for in-mold injection molding and form a plastic substrate with tapered holes and threads required for pen cap assembly. Align the tapered holes with the exposed lines on the PCB board that need to be connected later. During injection molding, the plastic must not cover the corresponding exposed area of ​​the PCB board, otherwise the corresponding lines will not be able to be connected to the PCB lines during subsequent laser circuit forming.

[0045] (3) The surface of the plastic substrate is subjected to laser activation, chemical roughening and palladium activation as needed (if the material is LDS material, chemical roughening and palladium activation are not required), chemical plating of nickel or copper base layer, and then copper plating thickening treatment to form a three-dimensional circuit.

[0046] (4) The three-dimensional circuit is sequentially subjected to chemical polishing or magnetic levitation polishing, chemical nickel plating and sealing treatment.

[0047] (5) Use convolutional neural networks to automatically identify line defects and combine them with impedance analysis algorithms to detect continuity reliability.

[0048] In one embodiment of the present invention, the bottom diameter of the tapered hole in step (2) is 0.15-0.4 mm, and the single-sided taper is ≥25°.

[0049] In one embodiment of the present invention, the conventional plastic material in step (2) is PC, and the injection head is recyclable and reusable.

[0050] In one embodiment of the present invention, the laser activation in step (3) uses a fiber laser device with a wavelength of 1064nm and the parameters are: power 10-60W, scanning speed 1500-5000mm / s, laser frequency 20-150kHz, energy 30%-80%, and filling gap 0.04-0.07mm.

[0051] In one embodiment of the present invention, the chemical roughening in step (3) employs the following system:

[0052] Sodium hydroxide 30-60 g / L, temperature 60-80℃, treatment for 8-15 minutes.

[0053] In one embodiment of the present invention, the parameters for magnetic levitation polishing and grinding in step (4) are: magnetic field strength 3000Gs, φ0.2mm iron-based magnetic abrasive (containing alumina abrasive grains), grinding speed 300rpm, and processing time 3 minutes.

[0054] If chemical polishing is used, the polishing slurry preparation ratio and process parameters are as follows:

[0055] Tri-acid polishing solution formula: The components and proportions are 20%-30% nitric acid, 50% sulfuric acid, 0.3%-0.8% hydrochloric acid, 1%-5% brightener, and the balance is water;

[0056] The above formula is characterized by good gloss, high pickling efficiency, and low cost.

[0057] Hydrogen peroxide polishing solution formula: The components and proportions are 250ml / L hydrogen peroxide, 12ml / L sulfuric acid, 20ml / L brass polishing additive, and the balance is water;

[0058] The above formula is characterized by excellent polishing brightness, near-mirror gloss, and environmental friendliness without pollution.

[0059] The formula for a new type of environmentally friendly copper polishing solution is as follows: 60-140g of persulfate, 200-350ml of 92.5wt%-98.0wt% concentrated sulfuric acid, 0-60ml of 85.0wt% concentrated phosphoric acid, 1-10g of citric acid, 2-10g of ferrous sulfate heptahydrate, 0-3g of sodium chloride, 0-6g of urea, 0.2-1.0g of sodium dodecyl sulfate, and the balance being water.

[0060] The above formula is characterized by stable and long-lasting effects, virtually smokeless operation, and rich color after polishing of copper materials, achieving a mirror-like finish, which meets the requirements of clean industrial production.

[0061] In one embodiment of the present invention, the electroless nickel plating in step (4) is specifically performed as follows:

[0062] I. Solution formulation (taking 1L of water as an example):

[0063] Main salt: Nickel sulfate (NiSO4·7H2O) 20-30g (slightly less than the high-temperature formula to avoid a rough coating);

[0064] Reducing agent: Sodium hypophosphite (NaH2PO2·H2O) 25-35g (slightly increase the concentration to compensate for insufficient reducing activity at low temperatures);

[0065] Complexing agent: 15-25g of trisodium citrate + 10-20ml of lactic acid (compound complexation, which enhances the stability of nickel ions and, importantly, prevents precipitation at low temperatures);

[0066] Buffer: Sodium acetate 15-25g (to stabilize pH and avoid pH fluctuations at low temperatures affecting the reaction);

[0067] Stabilizer: 0.5-1 mg / L thiourea + 1-3 mg / L potassium iodide (the plating solution is more prone to spontaneous decomposition at low temperatures, so the two stabilizers work together to inhibit this. Do not use too much, otherwise it will slow down the deposition).

[0068] II. Key Process Requirements

[0069] Temperature: 50~65℃ (the most commonly used range; below 50℃, deposition is too slow, and above 70℃ it is close to high temperature, losing the advantage of low temperature);

[0070] pH value: 4.0~5.0 (slightly lower than the high temperature formula, adjust with dilute sulfuric acid or ammonia water, slightly higher pH will easily cause precipitation);

[0071] Deposition rate: 5-12 μm / h (the rate will be slower at low temperatures, which is normal and results in a finer coating);

[0072] In one embodiment of the present invention, the parameters for the sealing process in step (4) are:

[0073] The sealing agent contains 3-5% silane coupling agent and 0.5% nano-alumina particles with a particle size of 50nm;

[0074] Processing conditions: Soak at 40-50℃ for 5-8 minutes, then dry with hot air at 60℃ for 10 minutes.

[0075] Example 2:

[0076] Please see Figure 1 As shown, a manufacturing process for a capacitive pen refill integrating in-mold injection molding of a PCB board and three-dimensional circuit forming includes the following steps:

[0077] (1) PCB board pretreatment: Design a PCB board that is compatible with the pen refill function, including the necessary signal lines and sensing interfaces, and its size must be precisely matched with the plastic substrate. Perform surface cleaning treatment on the PCB board: use 5% sodium hydroxide solution for ultrasonic cleaning with a power of 300W for 5 minutes to remove oil and oxide layer; then rinse with deionized water and dry at 60℃. On the PCB board where three-dimensional circuits need to be connected, reserve the exposed circuit area without the cover layer, and process positioning holes (tolerance controlled within ±0.02mm) to ensure that it can be accurately positioned with the plastic substrate during in-mold injection.

[0078] (2) In-mold injection molding of the plastic substrate: The plastic substrate is manufactured using in-mold injection molding, and the material is conventional PC plastic. The mold design includes a positioning structure to ensure the relative positional accuracy between the PCB board and the plastic substrate. A tapered hole is reserved on the surface of the substrate, and its core parameters are: the bottom diameter is controlled within the range of 0.15-0.4mm, and the single-sided taper is not less than 25° to ensure that there are no blind spots on the inner wall of the hole during laser scanning, thereby improving the uniformity of subsequent plating. The bottom of the tapered hole must be precisely aligned with the exposed lines on the PCB board without significant positional deviation. This is ensured by the synergistic effect of the mold positioning structure and the positioning hole on the PCB board. The injection molding process parameters are set as follows: barrel temperature 240℃ in the front section, 250℃ in the middle section, and 260℃ in the nozzle; injection pressure 80-120 bar; holding time 5-10s; and cooling time 15-20s. To reduce material loss, the sprue generated during injection molding is crushed, screened, and recycled for reuse.

[0079] (3) Laser activation and forming of three-dimensional circuits

[0080] The process employs a 1064nm fiber laser with key parameters set as follows: power 10-60W, scanning speed 1500-5000mm / s, laser frequency 20-150kHz, energy range 30%-80%, and fill spacing 0.04-0.07mm. This process creates the desired micro-roughness structure on the surface of the plastic substrate and the inner wall of the tapered hole.

[0081] Based on the properties of the plastic material, three optional treatment systems are provided. In this embodiment, PC material is selected, and system 2 is the optimal roughening system.

[0082] System 1 (chromic anhydride-sulfuric acid system, applicable to PC, PC+ABS): Use a solution containing 200-300 g / L chromic anhydride and 50-150 mL / L 98% sulfuric acid, and treat at 50-70℃ for 2-10 minutes;

[0083] System 2 (Sodium hydroxide system, applicable to PC and PC+ABS): Use a solution containing 30-60 g / L of sodium hydroxide and treat at 60°C for 2-15 minutes (preferred conditions for PC materials are 60-70°C × 10 minutes);

[0084] System 3 (Sodium hydroxide-potassium permanganate system, suitable for difficult-to-roughen materials such as nylon): Use a solution containing 30-50 g / L sodium hydroxide and 50-100 g / L potassium permanganate, and treat at 50-70℃ for 2-12 minutes;

[0085] Chemical copper plating (base layer): The activated and roughened parts are immersed in a plating solution containing 15g / L copper sulfate, 8g / L formaldehyde, and 35g / L EDTA-2Na. The pH value of the plating solution is controlled at 11-12, the temperature is 40℃, and the treatment is carried out for 12 minutes to form a uniform copper base layer on the activated surface.

[0086] To further enhance conductivity, the components were transferred to a thickened plating solution (containing 20g / L copper sulfate, 20g / L formaldehyde, 40g / L potassium sodium tartrate, pH 11-12) and treated at 40℃ for 2 hours.

[0087] (4) Joint post-processing

[0088] Magnetic levitation polishing and grinding is performed using a magnetic polishing machine with a magnetic field strength of 3000Gs, using φ0.2mm iron-based magnetic abrasive (containing alumina abrasive grains), setting the grinding speed to 300rpm, and the processing time to 3 minutes, to provide a smooth base for subsequent coating.

[0089] If chemical polishing is used, the specific operation is as follows:

[0090] Tri-acid polishing solution formula: The components and proportions are 20%-30% nitric acid, 50% sulfuric acid, 0.3%-0.8% hydrochloric acid, 1%-5% brightener, and the balance is water;

[0091] The above formula is characterized by good gloss, high pickling efficiency, and low cost.

[0092] Hydrogen peroxide polishing solution formula: The components and proportions are 250ml / L hydrogen peroxide, 12ml / L sulfuric acid, 20ml / L brass polishing additive, and the balance is water;

[0093] The above formula is characterized by excellent polishing brightness, near-mirror gloss, and environmental friendliness without pollution.

[0094] The formula for a new type of environmentally friendly copper polishing solution is as follows: 60-140g of persulfate, 200-350ml of 92.5wt%-98.0wt% concentrated sulfuric acid, 0-60ml of 85.0wt% concentrated phosphoric acid, 1-10g of citric acid, 2-10g of ferrous sulfate heptahydrate, 0-3g of sodium chloride, 0-6g of urea, 0.2-1.0g of sodium dodecyl sulfate, and the balance being water.

[0095] The above formula is characterized by stable and long-lasting effects, virtually smokeless operation, and rich color after polishing of copper materials, achieving a mirror-like finish, which meets the requirements of clean industrial production.

[0096] The specific polishing time can be slightly adjusted according to the coating thickness and the effect after polishing, and is generally 2 to 5 minutes.

[0097] Electroless nickel plating:

[0098] I. Solution formulation (taking 1L of water as an example):

[0099] Main salt: Nickel sulfate (NiSO4·7H2O) 20-30g (slightly less than the high-temperature formula to avoid a rough coating);

[0100] Reducing agent: Sodium hypophosphite (NaH2PO2·H2O) 25-35g (slightly increase the concentration to compensate for insufficient reducing activity at low temperatures);

[0101] Complexing agent: 15-25g of trisodium citrate + 10-20ml of lactic acid (compound complexation, which enhances the stability of nickel ions and, importantly, prevents precipitation at low temperatures);

[0102] Buffer: Sodium acetate 15-25g (to stabilize pH and avoid pH fluctuations at low temperatures affecting the reaction);

[0103] Stabilizer: 0.5-1 mg / L thiourea + 1-3 mg / L potassium iodide (the plating solution is more prone to spontaneous decomposition at low temperatures, so the two stabilizers work together to inhibit this. Do not use too much, otherwise it will slow down the deposition).

[0104] II. Key Process Requirements

[0105] Temperature: 50~65℃ (the most commonly used range; below 50℃, deposition is too slow, and above 70℃ it is close to high temperature, losing the advantage of low temperature);

[0106] pH value: 4.0~5.0 (slightly lower than the high temperature formula, adjust with dilute sulfuric acid or ammonia water, slightly higher pH will easily cause precipitation);

[0107] Deposition rate: 5-12 μm / h (the rate will be slower at low temperatures, which is normal and results in a finer coating).

[0108] After completing the electroless nickel plating, a sealing treatment is performed: the component is immersed in a sealing agent composed of 3-5% silane coupling agent (such as KH-550), 0.5% nano alumina particles (particle size 50nm), and the remainder deionized water. It is soaked at 40-50℃ for 5-8 minutes to allow the sealing agent to fully penetrate into the micropores of the nickel layer. Finally, the component is placed in a 60℃ hot air circulating oven to dry for 10 minutes to form a dense protective film.

[0109] (5) Finished product inspection:

[0110] The product must pass the following four tests:

[0111] Electrical performance testing: Ensure good circuit continuity and stable and reliable signal transmission.

[0112] Appearance inspection: The surface should have a high gloss finish, free from any defects such as pinholes, peeling, or scratches, and the reflection should be uniform and consistent.

[0113] Mechanical performance testing: The coating adhesion must be qualified, and no peeling should be verified by 3M tape testing.

[0114] Antioxidant performance test: It should perform well in the salt spray test to prove that it has sufficient corrosion resistance.

[0115] Example 3:

[0116] Please see Figure 1 As shown, a manufacturing process for a capacitive pen refill integrating in-mold injection molding of a PCB board and three-dimensional circuit forming includes the following steps:

[0117] (1) PCB board pretreatment

[0118] The PCB board uses FR-4 substrate (0.8mm thickness) and is designed with 3 sets of signal transmission lines. Three 0.3mm × 0.3mm exposed trace areas are reserved at the locations where 3D traces need to be connected, and φ1.0mm positioning holes are machined (tolerance strictly controlled within ±0.02mm). During the pretreatment stage, surface oil is thoroughly removed by ultrasonic cleaning, followed by drying at 60℃ for 30 minutes to ensure the substrate cleanliness meets the requirements of subsequent processes.

[0119] (2) In-mold injection molding of plastic matrix

[0120] Standard PC plastic material is used, and injection molding is performed using a mold with a positioning structure. A tapered hole is pre-drilled on the substrate surface, with the following key parameters: bottom diameter 0.2mm (meeting the 0.15-0.4mm range), single-sided taper 28° (above the 25° lower limit), and precise alignment with exposed circuitry on the PCB board with no significant positional deviation. The injection molding process parameters are set as follows: barrel front section 240℃, middle section 250℃, nozzle 260℃; first-stage injection pressure 80bar (filling stage), second-stage pressure 100bar (holding stage), holding time 8s, cooling time 15s.

[0121] (3) Laser activation and forming of three-dimensional circuits

[0122] First, activation treatment was performed using a 1064nm fiber laser with parameters set to a scanning speed of 2000mm / s, a frequency of 50kHz, an energy of 50% (approximately 15 watts), and a fill spacing of 0.05mm, forming a uniform micro-rough structure on the plastic surface and the inner wall of the tapered hole. Chemical roughening was then performed: a sodium hydroxide system (concentration 50g / L) was used, treated at 65℃ for 10 minutes. Next, chemical copper plating was completed in two steps: the base layer plating solution reacted at 40℃ for 12 minutes to form the initial copper layer; the thickening layer was treated at 40℃ for 2 hours to ensure the conductivity of the circuit met the standards.

[0123] (4) Joint post-processing

[0124] Magnetic levitation polishing and grinding is performed using a magnetic polishing machine with a magnetic field strength of 3000Gs, using φ0.2mm iron-based magnetic abrasive (containing alumina abrasive grains), setting the grinding speed to 300rpm, and the processing time to 3 minutes, to provide a smooth base for subsequent coating.

[0125] Electroless nickel plating:

[0126] I. Solution formulation (taking 1L of water as an example):

[0127] Main salt: Nickel sulfate (NiSO4·7H2O) 20-30g (slightly less than the high-temperature formula to avoid a rough coating);

[0128] Reducing agent: Sodium hypophosphite (NaH2PO2·H2O) 25-35g (slightly increase the concentration to compensate for insufficient reducing activity at low temperatures);

[0129] Complexing agent: 15-25g of trisodium citrate + 10-20ml of lactic acid (compound complexation, which enhances the stability of nickel ions and, importantly, prevents precipitation at low temperatures);

[0130] Buffer: Sodium acetate 15-25g (to stabilize pH and avoid pH fluctuations at low temperatures affecting the reaction);

[0131] Stabilizer: 0.5-1 mg / L thiourea + 1-3 mg / L potassium iodide (the plating solution is more prone to spontaneous decomposition at low temperatures, so the two stabilizers work together to inhibit this. Do not use too much, otherwise it will slow down the deposition).

[0132] II. Key Process Requirements

[0133] Temperature: 50~65℃ (the most commonly used range; below 50℃, deposition is too slow, and above 70℃ it is close to high temperature, losing the advantage of low temperature);

[0134] pH value: 4.0~5.0 (slightly lower than the high temperature formula, adjust with dilute sulfuric acid or ammonia water, slightly higher pH will easily cause precipitation);

[0135] Deposition rate: 5-12 μm / h (the rate will be slower at low temperatures, which is normal and results in a finer coating);

[0136] It also includes workpiece pretreatment: similar to high temperature, it is necessary to thoroughly degrease, remove rust, and activate (for example, soaking in 10% dilute sulfuric acid for 1-2 minutes), otherwise the bonding strength will be poor;

[0137] It also includes plating solution maintenance: low-temperature plating solutions have a slightly shorter lifespan (3-5 cycles), so nickel sulfate and sodium hypophosphite should be added regularly, and the pH should be adjusted after each addition.

[0138] After electroless nickel plating, a sealing treatment is performed: the component is immersed in a sealing agent composed of 3-5% silane coupling agent (such as KH-550), 0.5% nano-alumina particles (50nm particle size), and the remainder deionized water. The component is immersed at 40-50℃ for 5-8 minutes to allow the sealing agent to fully penetrate the micropores of the bright nickel layer. Finally, the component is dried in a 60℃ hot air circulating oven for 10 minutes to form a dense protective film.

[0139] 5. Finished product inspection results

[0140] The finished product passed comprehensive testing:

[0141] Electrical performance: The circuit has good conductivity, and the resistance value meets the design requirements;

[0142] Appearance: The surface has a mirror-like finish, with uniform and flawless reflection;

[0143] Environmental reliability: Excellent performance in salt spray testing, with no obvious corrosion observed;

[0144] Mechanical properties: The coating showed no peeling after 3M tape adhesion testing.

[0145] Example 4:

[0146] Based on the basic process framework of Example 1 and the specific parameter configuration of Example 2, this example further introduces an intelligent control system, and the specific steps are as follows:

[0147] (1) In the PCB preprocessing stage of Example 2, the precision control of the image recognition positioning system is added to ensure that the positioning hole processing error is ≤ ±0.01mm;

[0148] (2) The conical hole structure parameters (bottom diameter 0.2mm / taper 28°) of Example 2 are used in the in-mold injection stage. A new real-time position calibration algorithm is added: the PCB positioning hole coordinates are obtained by the infrared sensor embedded in the mold, the conical hole injection offset is calculated iteratively based on the least squares method, and the piezoelectric ceramic fine adjustment mechanism is driven to compensate for the position deviation so that the alignment deviation is ≤5μm.

[0149] (3) Based on the laser activation parameters (1064nm / 15W / 2000mm / s) in Example 2, a dynamic control system is added: a machine learning model (based on the random forest algorithm) is used to analyze the surface reflection spectrum of the material in real time, dynamically optimize the laser power / scanning speed (1500-4000mm / s) / energy (30%-80%), monitor the state of the roughening solution through an ion concentration sensor (automatic replenishment when the impedance change is ≥15%), and optimize the flow path of the plating solution (the hanger is tilted 15°-30°) using fluid dynamics simulation.

[0150] (4) In the post-processing stage, the magnetic levitation polishing (3000Gs / 300rpm / 3min) and layered nickel plating process in Example 2 are integrated with a closed-loop control system: the grinding time is adaptively adjusted based on surface roughness detection (1-5min), and the reflectivity of the coating is monitored in real time by a laser interferometer. When the reflectivity is ≥85%, the polishing is terminated by a PID controller.

[0151] (5) Use convolutional neural networks to automatically identify line defects and combine them with impedance analysis algorithms to detect continuity reliability.

[0152] In one embodiment of the present invention, the real-time position calibration algorithm in step (2) includes: obtaining the coordinates of the PCB positioning hole through the infrared sensor embedded in the mold, iteratively calculating the offset of the conical hole injection position based on the least squares method, and driving the piezoelectric ceramic fine-tuning mechanism to compensate for the position deviation.

[0153] In one embodiment of the present invention, the method for constructing the machine learning model in step (3) is as follows: collect surface reflection spectrum data under different power / speed combinations as training set, take surface roughness Ra = 0.2-0.5μm as optimization target, establish parameter mapping relationship through random forest algorithm and embed it into laser controller;

[0154] The specific steps for establishing parameter mapping relationships in the random forest algorithm include:

[0155] Step 1: High-dimensional spectral feature extraction and dimensionality reduction

[0156] Collect reflection spectrum data (wavelength range 380-1100nm) during laser processing to construct the original dataset:

[0157] Among them, s i ∈200 represents a 200-channel spectral vector, p i =[P i ,v i E i ] represents laser parameters (power, velocity, energy), y i The measured surface roughness Ra;

[0158] The spectral signal is decomposed using wavelet packet transform (WPT) to extract energy entropy features: (M = 8-level decomposition);

[0159] Step 2: Multi-objective random forest modeling

[0160] The objective function simultaneously constrains the surface roughness Ra and the machining efficiency η (which is positively correlated with the scanning speed):

[0161] stRa∈[0.2,0.5]μm;

[0162] Random forest structure:

[0163] Construct 100 decision trees, each randomly selected. One feature (d = 11: 8 spectral features + 3 laser parameters); using the mixing impurity function: I hybrid =α·MSE(Ra)+(1-α)·Entropy(η);

[0164] Where α = 0.7 is the roughness weight, and η is discretized into three levels: high efficiency, medium efficiency, and low efficiency.

[0165] Storage parameter optimization solution set: P opt ={p|Ra(p)∈[0.2,0.5]};

[0166] Step 3: Dynamic Parameter Mapping and Real-Time Control

[0167] Real-time acquisition of current spectral features f t Traverse all decision trees and extract the P of the terminal nodes. opt Solution set;

[0168] Calculate the Pareto front solution:

[0169] Select the solution p* that is closest to the target Ra = 0.35 and output it to the laser controller;

[0170] Step 4: Self-learning model update

[0171] Closed-loop feedback optimization:

[0172] For every 100 processing cycles completed, new data D is collected. new Perform incremental learning:

[0173] Calculate the prediction residuals of the old model:

[0174] For δ i Weighted training is performed on samples ≥0.1μm;

[0175] Dynamically adjust feature weights: Update the wavelet packet decomposition layer M to minimize the residual.

[0176] In one embodiment of the present invention, the fluid dynamics simulation model in step (3) specifically includes: establishing a three-dimensional flow field model of a conical hole, simulating the flow velocity distribution of the plating solution, defining the boundary conditions as an inlet flow velocity of 0.5-1.2 m / s and an outlet pressure of 0 Pa, and outputting the optimal hanger tilt angle of 15°-30° through finite element analysis.

[0177] In one embodiment of the present invention, the AI ​​quality inspection system in step (5) includes: training a ResNet50 network with 1000+ labeled microscopic images of the line, measuring the line resistance by the four-probe method, and analyzing the signal noise spectrum by combining Fourier transform.

[0178] In one embodiment of the present invention, the ion concentration sensor in step (3) is an electrochemical impedance spectroscopy sensor, which monitors the impedance value Z of the roughening solution in real time, and triggers the plating solution replenishment mechanism when |ΔZ / Z0|≥15%.

[0179] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A manufacturing process for capacitive pen refills that integrates in-mold injection molding of PCB board and three-dimensional circuit forming, characterized in that, Includes the following steps: (1) Design and manufacture a three- or four-layer PCB board with three pads and lines, each pad is connected to a line in a layer of PCB board, and the other end of each line is connected to the surface line formed after laser forming of the injection molded part, and a positioning hole is processed. (2) Fix the PCB board in the injection mold, and injection mold to form a plastic substrate with a conical hole. The precise positioning of the PCB positioning hole ensures that the injection conical hole is aligned with the exposed circuit of the PCB. During in-mold injection, the thread used for pen refill assembly is formed at the same time to replace the metal nut. (3) After injection molding, laser activation, chemical roughening and palladium activation (when using non-LDS modified materials) are sequentially performed on the plastic surface, followed by chemical copper or nickel base layer and copper thickening treatment to form a three-dimensional circuit. (4) Perform magnetic levitation polishing or chemical polishing, chemical nickel plating and sealing treatment on the three-dimensional circuit in sequence. (5) Use convolutional neural networks to automatically identify line defects and combine them with impedance analysis algorithms to detect continuity reliability.

2. The capacitive pen refill manufacturing process integrating in-mold injection molding of PCB board and three-dimensional circuit forming according to claim 1, characterized in that, The bottom diameter of the tapered hole in step (2) is 0.15-0.4mm, and the single-sided taper is preferably ≥25°. During injection molding, the metal nut for assembling the pen cap with the pen refill is directly replaced by the injection-molded thread.

3. The capacitive pen refill manufacturing process integrating in-mold injection molding and three-dimensional circuit forming on a PCB board according to claim 1, characterized in that, The conventional plastic material mentioned in step (2) is PC, PC+ABS, or nylon, and is either an LDS modified material or a non-LDS modified material.

4. The capacitive pen refill manufacturing process integrating in-mold injection molding of PCB board and three-dimensional circuit forming according to claim 1, characterized in that, In step (3), the laser activation uses a fiber laser device with a wavelength of 1064nm and the following parameters: power 10-60W, scanning speed 1500-5000mm / s, laser frequency 20-150kHz, energy 30%-80%, and fill spacing 0.04-0.07mm.

5. The capacitive pen refill manufacturing process integrating in-mold injection molding and three-dimensional circuit forming on a PCB board according to claim 1, characterized in that, In step (3), the chemical roughening process employs any of the following systems: System 1: Chromium trioxide 200-300 g / L, sulfuric acid 50-150 mL / L, temperature 50-70℃, treatment for 2-10 minutes; System 2: Sodium hydroxide 30-60 g / L, temperature 60-80℃, treatment for 2-15 minutes; System 3: Sodium hydroxide 30-50 g / L, potassium permanganate 50-100 g / L, temperature 50-70℃, treatment for 2-12 minutes.

6. The capacitive pen refill manufacturing process integrating in-mold injection molding and three-dimensional circuit forming on a PCB board according to claim 1, characterized in that, The parameters for magnetic levitation polishing and grinding in step (4) are: magnetic field strength 3000Gs, φ0.2mm iron-based magnetic abrasive, grinding speed 100 to 500rpm, and processing time 3 to 15 minutes.

7. The capacitive pen refill manufacturing process integrating in-mold injection molding and three-dimensional circuit forming on a PCB board according to claim 1, characterized in that, The materials used in the chemical polishing in step (4) include triacid polishing liquid, hydrogen peroxide polishing liquid and environmentally friendly copper polishing liquid; The formula for the tri-acid polishing solution includes 20%-30% nitric acid, 50% sulfuric acid, 0.3%-0.8% hydrochloric acid, 1%-5% brightener, and the balance being water; The hydrogen peroxide-based polishing solution formula includes 250 ml / L hydrogen peroxide, 12 ml / L sulfuric acid, 20 ml / L brass polishing additive, and the remainder is water; The environmentally friendly copper polishing solution formula includes 60-140g of persulfate, 200-350ml of 92.5wt%-98.0wt% concentrated sulfuric acid, 0-60ml of 85.0wt% concentrated phosphoric acid, 1-10g of citric acid, 2-10g of ferrous sulfate heptahydrate, 0-3g of sodium chloride, 0-6g of urea, 0.2-1.0g of sodium dodecyl sulfate, and the balance being water.

8. The capacitive pen refill manufacturing process integrating in-mold injection molding and three-dimensional circuit forming on a PCB board according to claim 1, characterized in that, The solution ratio and process parameters for electroless nickel plating in step (4) are as follows: Nickel sulfate (NiSO4·7H2O) 20-30g; sodium hypophosphite (NaH2PO2·H2O) 25-35g; trisodium citrate 15-25g and lactic acid 10-20ml; sodium acetate 15-25g; thiourea 0.5-1mg / L + potassium iodide 1-3mg / L, with the nickel layer thickness controlled at 2 to 5 micrometers; Temperature: 50~65℃; pH value: 4.0~5.0; deposition rate: 5~12μm / h.

9. The capacitive pen refill manufacturing process for integrated PCB board in-mold injection molding and three-dimensional circuit forming according to claim 1, wherein the parameters for the sealing treatment in step (4) are: The sealing agent contains 3-5% silane coupling agent and 0.5% nano-alumina particles with a particle size of 50nm; Processing conditions: Soak at 40-50℃ for 5-8 minutes, then dry with hot air at 60℃ for 10 minutes.

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