Glue filling process of glass-fiber-free PP (polypropylene) substitute resin

Abstract

The invention discloses a glue filling process of glass-fiber-free PP (polypropylene) substitute resin. The glue filling process comprises the following steps: step 1, preparing materials; step 2, feeding and drilling; step 3, PTH and electroplating; step 4, primary film drying; step 5, primary etching; step 6, AOI detection; step 7, pressing; step 8, curing post-treatment; step 9, performance testing; the non-glass-fiber PP is adopted to replace traditional common PP, the unique material characteristics, such as higher resin content and better fluidity, of the non-glass-fiber PP are utilized, resin printing and glue filling are not needed in the pressing process, and the problem of glue shortage in pressing can be effectively solved; resin printing glue filling and resin grinding procedures are omitted, the production process is simplified, the number of procedures is reduced, and therefore the production cost is reduced, and the production period is shortened.

Description

Technical Field

[0001] The present invention relates to the technical field of circuit board processing, and specifically to a glue filling process using fiberglass-free PP to replace resin. Background Art

[0002] In the production process of printed circuit boards, for products with specific copper thickness requirements, such as circuit boards with a copper thickness of 5 oz, in the traditional process when using ordinary PP (semi-cured sheet), in order to solve the problem of lack of glue in lamination, resin printing and filling and resin grinding processes are required. The existing patent CN114245617A discloses a lamination method for improving poor glue filling, but this method still relies on a complex resin coating process and does not fundamentally solve the problem of high cost. In addition, the patent CN222472066U proposes a positioning device for resin grinding of printed circuit boards. Although it improves the grinding efficiency to a certain extent, it fails to change the current situation of the cumbersome production process and long cycle. These processes have obvious drawbacks. On the one hand, they result in high costs, and the resin filling and grinding costs for each set of products are relatively high; on the other hand, they increase the complexity of the production process and extend the production cycle. Therefore, there is an urgent need for a method that can replace the traditional resin filling process to reduce costs, improve production efficiency, and at the same time ensure the quality and performance of products. Summary of the Invention

[0003] The purpose of the present invention is to provide a glue filling process using fiberglass-free PP to replace resin, so as to solve the problems raised in the above background art.

[0004] To achieve the above purpose, the present invention provides the following technical solution: A glue filling process using fiberglass-free PP to replace resin, including the following steps:

[0005] Step 1. Material preparation: Select fiberglass-free PP as the lamination material, prepare the CORE board as the raw material, and conduct appearance inspection and size measurement;

[0006] Step 2. Material delivery and drilling: After delivering the raw materials, use high-precision drilling equipment for drilling, control the drilling parameters, and clean the debris in the holes after drilling;

[0007] Step 3. PTH and electroplating: Conduct chemical copper plating and electroplating treatment on the drilled board to metallize the hole walls and increase the copper layer thickness;

[0008] Step 4. First dry film: Coat a dry film on the surface of the electroplated board and conduct film laminating and exposure treatment;

[0009] Step 5. First etching: Develop and etch the exposed board to form a circuit pattern;

[0010] Step Six, AOI Detection: Use an automatic optical inspection device to perform circuit pattern inspection on the etched board;

[0011] Step Seven, Lamination: Combine the CORE board and the glass fiber-free PP in a laminated structure, place them in a lamination device, control the temperature, pressure, and time parameters during lamination, adopt vacuum lamination technology, and cool to room temperature after lamination;

[0012] Step Eight, Post-Curing Treatment: Use a numerically controlled routing machine for profile machining, blow off the dust on the board surface with high-pressure air, and after ultrasonic cleaning, place the board in a constant temperature and humidity chamber for 2 - 4 hours to eliminate the internal stress generated during lamination;

[0013] Step Nine, Performance Testing: Perform board thickness measurement, thermal stress testing, microsection analysis, and electrical property testing on the cleaned board.

[0014] Preferably, the material preparation in Step One is specifically as follows: Select glass fiber-free PP with a resin content of 65% - 75% and a glass transition temperature ≥ 150°C, and its melt flow rate needs to meet 1.2 - 1.8 g / 10 min (190°C, 2.16 kg) to ensure uniform resin fluidity during lamination; perform flatness inspection on the CORE board, with the flatness error ≤ 0.1%, wipe the surface with alcohol to remove oil stains and oxides, and control the roughness at Ra ≤ 1.2 μm; control the storage environment of the glass fiber-free PP at a temperature of 20 ± 5°C and a humidity ≤ 40% RH, with a storage period not exceeding 3 months, and it needs to be placed at room temperature for more than 4 hours for rewarming before use.

[0015] Preferably, the material feeding and drilling in Step Two are specifically as follows: Generate drilling NC codes according to the CAD design file, adopt coordinate compensation technology to correct the board expansion and contraction error, with the error compensation accuracy ≤ ±5 μm; use a six-axis linkage numerically controlled drilling machine equipped with a diamond-coated drill bit, and the drill bit life ≥ 5000 holes / bit; the first drilling depth is 1 / 2 of the board thickness, and after retracting the tool and discharging chips, complete the drilling of the remaining depth to avoid drill breakage and delamination of the hole wall; the drilling parameters are a rotational speed of 25000 - 30000 rpm, a feed rate of 0.08 - 0.12 mm / rev, a hole position accuracy of ±25 μm, and a hole diameter tolerance of ±10 μm; perform deburring treatment after drilling, use a brush wheel for mechanical grinding, with the brush rotational speed of 1500 - 2000 rpm and the grinding pressure of 5 - 10 N / cm 2 , ensuring that the hole wall roughness Ra ≤ 1.6 μm.

[0016] Preferably, in step three, the PTH and electroplating are as follows: caustic degreaser sodium hydroxide is used, with a concentration of 50 - 70 g / L, a temperature of 50 - 60 °C, a treatment time of 3 - 5 minutes, and the surface contact angle after degreasing ≤ 30°; sodium persulfate solution is used, with a concentration of 80 - 100 g / L, a temperature of 30 - 40 °C, and an etching rate controlled at 1.5 - 2.0 μm / min to form a uniformly rough surface; colloidal palladium activation solution is used, with a concentration of 20 - 30 ppm, a temperature of 25 - 30 °C, and a treatment time of 5 - 8 minutes to ensure that the distribution density of catalytic active sites on the hole wall ≥ 10^6 per cm 2 ;

[0017] The composition of the electroless copper plating solution for electroless copper plating is 15 - 20 g / L of copper sulfate, 8 - 12 ml / L of formaldehyde, and 50 - 60 g / L of EDTA sodium salt, with a temperature of 30 - 35 °C and a pH value of 12.5 - 13.5; during the electroless copper plating process, air stirring is used, with an air pressure of 0.2 - 0.3 MPa, the electroless copper plating thickness is controlled at 0.8 - 1.2 μm, and the continuity of the copper layer on the hole wall ≥ 99.5%;

[0018] The electroplating solution for electroplating treatment uses a high - acid and low - copper system, including 180 - 220 g / L of sulfuric acid, 60 - 80 g / L of copper sulfate, and 50 - 80 ppm of chloride ions, with a leveling agent and a brightening agent added; pulse electroplating technology is used, with a current density of 15 - 25 A / dm 2 , a duty cycle of 1:3, a period of 50 ms, an electroplating temperature of 25 - 30 °C, the uniformity of the copper layer thickness ≤ ±5%, and the target thickness according to the design requirements; after electroplating, copper thickness detection is carried out. An X - ray thickness gauge is used, with the number of detection points per sheet of board ≥ 10, and the single - point thickness deviation ≤ ±5%.

[0019] Preferably, in step four, the single - layer dry film is as follows: a dry film with etching resistance is selected, with a thickness of 15 - 30 μm selected according to the circuit accuracy, a photosensitivity ≥ 30 mJ / cm 2 , a resolution ≤ 50 μm; the temperature of the roller of the laminating machine is controlled at 105 - 115 °C, the pressure is 150 - 200 Psi, and the laminating speed is 1.2 - 1.5 m / min; after laminating, static treatment is carried out, with a static time of 15 - 20 minutes to make the dry film fully adhere to the copper surface, and the bubble defect rate ≤ 0.1%; a parallel - light exposure machine is used, with a light intensity uniformity ≥ 95%, and the exposure energy is controlled at 80 - 120 mJ / cm 2 , using the positive - negative film alignment technology, with an alignment accuracy of ±25 μm, using a 50 - μm - thick film, and a dot reduction degree ≥ 98%.

[0020] Preferably, the single etching in step five is as follows: in the developing step, the developer is a sodium carbonate solution with a concentration of 2.5 - 3.5%, a temperature of 30 - 35°C, a developing time of 40 - 60 seconds, and a developing speed of 15 - 20 μm / min; after developing, residue detection is carried out. Observation is made with a 50 - fold microscope, and the residue rate ≤ 0.5%; in the etching step, the acidic etching solution is ferric chloride and hydrochloric acid, with a ferric chloride concentration of 45 - 55 g / L, a hydrochloric acid concentration of 10 - 15 g / L, a temperature of 45 - 55°C, and an etching rate controlled at 25 - 35 μm / min; the spray etching method is adopted, with a spray pressure of 0.3 - 0.5 MPa, and the etching line width accuracy controlled within ±10%, and the minimum line width / line pitch ≥ 50 μm; in the film removal step, a sodium hydroxide solution is used, with a sodium hydroxide solution concentration of 5 - 8%, a temperature of 50 - 60°C, to remove the residual dry film, and the treatment time is 3 - 5 minutes. After film removal, the surface insulation resistance ≥ 10^9 Ω; after film removal, surface cleaning is carried out, rinsing with DI water, with a conductivity ≤ 10 μS / cm, a drying temperature of 80 - 100°C, and a drying time of 10 - 15 minutes.

[0021] Preferably, the AOI detection in step six is as follows: a high - precision linear array camera AOI device is adopted, with a resolution ≥ 12 μm / pixel and a detection speed ≥ 100 cm 2 / s; the detection items include open - circuit / short - circuit detection, line width / line pitch measurement, line width / line pitch measurement, and notch / burr detection;

[0022] Open - circuit / short - circuit detection: The current pulse method is adopted, with a detection voltage of 5 - 10 V and a leakage current threshold ≤ 1 μA; Line width / line pitch measurement: Automatically extract the edge contour, with a measurement accuracy of ±5 μm and a tolerance range of ±10% of the design value;

[0023] Notch / burr detection: The image edge detection algorithm is adopted, with a minimum detection size of 50 μm;

[0024] After detection, defect repair is carried out: For open - circuit defects, the laser wire - filling technology is adopted, with a wire - filling accuracy of ±10 μm and a wire width ≥ 70 μm; for short - circuit defects, the laser cutting technology is adopted, with a cutting width ≤ 50 μm and a cutting depth ≥ 2 / 3 of the copper layer thickness.

[0025] Preferably, the lamination in step seven is as follows: A symmetric stacking design is adopted, with the CORE board and glass - free PP stacked alternately, and copper foil protective layers are provided on the top and bottom layers, with a thickness of 18 - 35 μm; The inter - layer positioning adopts a pin positioning system, with a positioning accuracy of ±25 μm, and the tolerance of the pin diameter and hole diameter fit is ±10 μm;

[0026] The lamination parameters are:

[0027] Heating stage: Raise the temperature from room temperature to 120°C at a rate of 3°C / min, maintain for 10 minutes to remove volatiles; then raise the temperature to 180±5°C at a rate of 5°C / min, and gradually increase the pressure to 100Psi during the heating process;

[0028] Holding pressure stage: at 180°C, the pressure is controlled in stages, first at 200 Psi for 15 minutes to allow the resin to fully flow, then increased to 300-350 Psi for 45 minutes to complete the curing, with pressure uniformity ≤±5%;

[0029] Cooling stage: Turn off the heating system and use circulating water for cooling at a cooling rate of ≤5℃ / min until the plate temperature drops below 50℃ to avoid internal stress concentration;

[0030] Vacuum control: During the lamination process, the vacuum degree is maintained at ≤10mbar, and the vacuum leakage rate is monitored in real time at ≤5mbar / min to ensure that the air removal rate between layers is ≥99%;

[0031] Demolding treatment: After pressing, the plate is naturally cooled to room temperature, and a release agent is used. The release agent is a silicone-based release agent with a concentration of 0.5-1.0% to assist in demolding and avoid damaging the surface copper foil.

[0032] Preferably, the post-curing treatment in step eight is specifically as follows: using a CNC gong machine for shape processing, with a tool speed of 20000-25000rpm, a feed speed of 800-1200mm / min, a shape dimensional accuracy of ±50μm, and a burr height of ≤50μm; using high-pressure air with a pressure of 0.5-0.7MPa to blow away the dust on the board surface, and combining ultrasonic cleaning with a frequency of 40kHz and a time of 5-8 minutes. After cleaning, the surface ion contamination is ≤1.5μg / cm 2 , calculated as NaCl; place the board in a constant temperature and humidity chamber with a temperature of 50±5°C and a humidity of 60±5% RH for 2-4 hours to eliminate the internal stress generated during the pressing process, and the warpage is ≤0.7%.

[0033] Preferably, the performance test in step nine is specifically as follows: plate thickness measurement: using a micrometer to measure 5 points in total, including the four corners and the center of the plate, with the thickness tolerance controlled within ±5% of the design value;

[0034] Thermal stress test: carried out in accordance with IPC-TM-650 standard, with the tin furnace temperature at 289±5℃, the tinning time at 10±1 seconds, and the number of cycles at 3 times. Visual inspection showed no board explosion, delamination, or blistering, and section inspection showed no breakage of the copper layer on the hole wall.

[0035] Slice analysis: Five slices are made, which are the four corners and the center of the board respectively. The interfacial bonding strength between layers is observed under a microscope with a magnification of 50 - 200 times. The peeling strength between the glass fiber-free PP and the CORE board is ≥1.5 N / mm, and the adhesion between the copper foil and the substrate is ≥3 N / cm.

[0036] Electrical property test: A flying probe tester is used for conduction testing. The test voltage is 10 V, the resistance threshold is ≤50 mΩ, the test coverage rate is 100%, and the yield rate is ≥99.5%.

[0037] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0038] The glass fiber-free PP is used to replace the traditional ordinary PP. By utilizing the unique material properties of the glass fiber-free PP, such as higher resin content and better fluidity, the problem of lack of glue in lamination can be effectively solved without resin printing and filling during the lamination process; the resin printing and filling and resin grinding processes are cancelled, the production process is simplified, the number of processes is reduced, thereby reducing the production cost and shortening the production cycle; the parameters such as temperature, pressure, and time in the lamination process are optimized and designed. Combining with the characteristics of the glass fiber-free PP, a reasonable lamination curve is formulated to ensure that the glass fiber-free PP can be fully melted, flowed, and cured during the lamination process to form a high-quality laminated structure. At the same time, in the processes of drilling, electroplating, etching, etc., the relevant process parameters are precisely controlled to ensure the processing quality of each process. Description of the Drawings

[0039] Figure 1 is the process flow chart of the present invention;

[0040] Figure 2 is the stack diagram of the embodiment of the present invention;

[0041] Figure 3 is the thermal stress test chart of the present invention;

[0042] Figure 4 is the board thickness measurement chart of the present invention. Detailed Embodiments

[0043] Next, in combination with the embodiments of the present invention, the technical solutions in the embodiments of the present invention will be clearly and completely described. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the protection scope of the present invention.

[0044] Please refer to Figures 1-4 , the present invention provides a glue filling process for replacing resin with glass fiber-free PP, including the following steps:

[0045] Step 1. Material Preparation: Select non-glass fiber PP as the lamination material, prepare the CORE board as the raw material, and conduct appearance inspection and dimensional measurement; select non-glass fiber PP with a resin content of 65%-75% and a glass transition temperature of ≥150°C, and its melt flow rate should meet 1.2-1.8 g / 10 min (190°C, 2.16 kg) to ensure uniform resin fluidity during lamination; conduct flatness inspection on the CORE board, with the flatness error ≤0.1%, wipe the surface with alcohol to remove oil stains and oxides, and control the roughness at Ra ≤1.2 μm; control the storage environment of non-glass fiber PP at a temperature of 20±5°C and a humidity of ≤40% RH, with a storage period not exceeding 3 months, and it needs to be allowed to warm up at room temperature for more than 4 hours before use;

[0046] Step 2. Material Issuance and Drilling: After issuing the raw materials, use high-precision drilling equipment for drilling, control the drilling parameters, and clean the debris in the holes after drilling; specifically for material issuance and drilling, generate drilling NC codes according to the CAD design document, adopt coordinate compensation technology to correct the expansion and contraction error of the board, with the error compensation accuracy ≤±5 μm; use a six-axis linkage CNC drilling machine equipped with a diamond-coated drill bit, and the drill bit life ≥5000 holes / bit; the first drilling depth is 1 / 2 of the board thickness, and after retracting the tool to evacuate chips, complete the drilling of the remaining depth to avoid drill breakage and hole wall delamination; the drilling parameters are a rotational speed of 25000-30000 rpm, a feed rate of 0.08-0.12 mm / rev, a hole position accuracy of ±25 μm, and a hole diameter tolerance of ±10 μm; after drilling, conduct deburring treatment, use a brush wheel for mechanical grinding, with the brush rotational speed of 1500-2000 rpm and the grinding pressure of 5-10 N / cm 2 to ensure that the hole wall roughness Ra ≤1.6 μm;

[0047] Step 3. PTH and Electroplating: Conduct chemical copper deposition and electroplating treatment on the drilled board to metallize the hole wall and increase the copper layer thickness; specifically for PTH and electroplating, use sodium hydroxide as the alkaline degreaser, with the concentration of sodium hydroxide being 50-70 g / L, the temperature being 50-60°C, and the treatment time being 3-5 minutes. After degreasing, the surface contact angle ≤30°; use a sodium persulfate solution, with the concentration of the sodium persulfate solution being 80-100 g / L, the temperature being 30-40°C, and the etching rate controlled at 1.5-2.0 μm / min to form a uniform rough surface; use a colloidal palladium activation solution, with the concentration of the colloidal palladium activation solution being 20-30 ppm, the temperature being 25-30°C, and the treatment time being 5-8 minutes to ensure that the distribution density of catalytic active points on the hole wall ≥10^6 pieces / cm 2 ;

[0048] The composition of the electroless copper plating solution is 15 - 20 g / L of copper sulfate, 8 - 12 ml / L of formaldehyde, and 50 - 60 g / L of EDTA sodium salt. The temperature is 30 - 35 °C, and the pH value is 12.5 - 13.5. During the electroless copper plating process, air stirring is used with a gas pressure of 0.2 - 0.3 MPa. The thickness of the electroless copper plating is controlled within 0.8 - 1.2 μm, and the continuity of the copper layer on the hole wall is ≥99.5%.

[0049] The electroplating solution for electroplating treatment uses a high - acid and low - copper system, which includes 180 - 220 g / L of sulfuric acid, 60 - 80 g / L of copper sulfate, and 50 - 80 ppm of chloride ions. A leveling agent and a brightening agent are added. Pulse electroplating technology is adopted with a current density of 15 - 25 A / dm 2 , a duty cycle of 1:3, a period of 50 ms, an electroplating temperature of 25 - 30 °C, the thickness uniformity of the copper layer is ≤±5%, and the target thickness is based on the design requirements. After electroplating, copper thickness detection is carried out using an X - ray thickness gauge. The number of detection points for each sheet of board is ≥10, and the thickness deviation of a single point is ≤±5%.

[0050] Step 4: First dry film: Coat a dry film on the surface of the electroplated board and perform laminating and exposure treatments. Specifically for the first dry film, a dry film with etching resistance is selected. The thickness is selected as 15 - 30 μm according to the line accuracy, and the photosensitivity is ≥30 mJ / cm 2 , the resolution is ≤50 μm. The temperature of the roller of the laminating machine is controlled at 105 - 115 °C, the pressure is 150 - 200 Psi, and the laminating speed is 1.2 - 1.5 m / min. After laminating, a standing treatment is carried out for 15 - 20 minutes to make the dry film fully adhere to the copper surface, and the bubble defect rate is ≤0.1%. A parallel - light exposure machine is used with a light intensity uniformity of ≥95%, and the exposure energy is controlled at 80 - 120 mJ / cm 2 , using the positive - negative film alignment technology with an alignment accuracy of ±25 μm, a 50 - μm - thick film is used, and the dot reduction degree is ≥98%. Specifically for the first dry film, a dry film with etching resistance is selected. The thickness is selected as 15 - 30 μm according to the line accuracy, and the photosensitivity is ≥30 mJ / cm 2 , the resolution is ≤50 μm. The temperature of the roller of the laminating machine is controlled at 105 - 115 °C, the pressure is 150 - 200 Psi, and the laminating speed is 1.2 - 1.5 m / min. After laminating, a standing treatment is carried out for 15 - 20 minutes to make the dry film fully adhere to the copper surface, and the bubble defect rate is ≤0.1%. A parallel - light exposure machine is used with a light intensity uniformity of ≥95%, and the exposure energy is controlled at 80 - 120 mJ / cm 2 , using the positive - negative film alignment technology with an alignment accuracy of ±25 μm, a 50 - μm - thick film is used, and the dot reduction degree is ≥98%.

[0051] Step Five: Primary Etching: Develop and etch the exposed board to form a circuit pattern. Specifically for primary etching, in the developing step, the developing solution is sodium carbonate solution with a concentration of 2.5 - 3.5%, a temperature of 30 - 35°C, a developing time of 40 - 60 seconds, and a developing speed of 15 - 20μm / min. After developing, perform residue glue detection. Observe with a 50 - fold microscope, and the residue glue rate ≤ 0.5%. In the etching step, the acidic etching solution is ferric chloride and hydrochloric acid, with a ferric chloride concentration of 45 - 55g / L, a hydrochloric acid concentration of 10 - 15g / L, a temperature of 45 - 55°C, and the etching rate is controlled at 25 - 35μm / min. Use spray etching method, with a spray pressure of 0.3 - 0.5MPa, and the etching line width accuracy is controlled within ±10%, and the minimum line width / line pitch ≥ 50μm. In the film removal step, use sodium hydroxide solution with a concentration of 5 - 8% and a temperature of 50 - 60°C to remove the residual dry film. The treatment time is 3 - 5 minutes. After film removal, the surface insulation resistance ≥ 10^9Ω. After film removal, perform surface cleaning. Rinse with DI water, with a conductivity ≤ 10μS / cm, a drying temperature of 80 - 100°C, and a drying time of 10 - 15 minutes.

[0052] Step Six: AOI Detection: Use an automatic optical detection device to detect the circuit pattern of the etched board. Specifically for AOI detection, use a high - precision linear array camera AOI device with a resolution ≥ 12μm / pixel and a detection speed ≥ 100cm 2 / s. The detection items include open - circuit / short - circuit detection, line width / line pitch measurement, line width / line pitch measurement, and notch / burr detection.

[0053] Open - circuit / short - circuit detection: Use the current pulse method, with a detection voltage of 5 - 10V and a leakage current threshold ≤ 1μA. Line width / line pitch measurement: Automatically extract the edge contour, with a measurement accuracy of ±5μm and a tolerance range of ±10% of the design value.

[0054] Notch / burr detection: Use an image edge detection algorithm, with a minimum detection size of 50μm.

[0055] After detection, perform defect repair: For open - circuit defects, use laser wire - filling technology, with a wire - filling accuracy of ±10μm and a wire width ≥ 70μm. For short - circuit defects, use laser cutting technology, with a cutting width ≤ 50μm and a cutting depth ≥ 2 / 3 of the copper layer thickness.

[0056] Step 7. Lamination: Combine the CORE board and the glass-free PP in a stacked structure and place them in a lamination device. Control the temperature, pressure, and time parameters during the lamination process using vacuum lamination technology. Cool to room temperature after lamination. Specifically, the lamination is performed using a symmetrical stacking design, with the CORE board and the glass-free PP stacked alternately. The top and bottom layers are provided with a copper foil protective layer with a thickness of 18-35μm. The interlayer positioning adopts a pin positioning system with a positioning accuracy of ±25μm and a tolerance of ±10μm between the pin diameter and the hole diameter.

[0057] The pressing parameters are:

[0058] Heating stage: Raise the temperature from room temperature to 120°C at a rate of 3°C / min, maintain for 10 minutes to remove volatiles; then raise the temperature to 180±5°C at a rate of 5°C / min, and gradually increase the pressure to 100Psi during the heating process;

[0059] Holding pressure stage: at 180°C, the pressure is controlled in stages, first at 200 Psi for 15 minutes to allow the resin to fully flow, then increased to 300-350 Psi for 45 minutes to complete the curing, with pressure uniformity ≤±5%;

[0060] Cooling stage: Turn off the heating system and use circulating water for cooling at a cooling rate of ≤5℃ / min until the plate temperature drops below 50℃ to avoid internal stress concentration;

[0061] Vacuum control: During the lamination process, the vacuum degree is maintained at ≤10mbar, and the vacuum leakage rate is monitored in real time at ≤5mbar / min to ensure that the air removal rate between layers is ≥99%;

[0062] Demolding treatment: After lamination, the plate is naturally cooled to room temperature, and a release agent is used. The release agent is a silicone-based release agent with a concentration of 0.5-1.0% to assist in demoulding and avoid damaging the surface copper foil;

[0063] Step 8. Post-curing treatment: Use CNC gong machine for shape processing, use high-pressure air to blow off the dust on the board surface, and after ultrasonic cleaning, place the board in a constant temperature and humidity chamber for 2-4 hours to eliminate the internal stress generated during the pressing process; the post-curing treatment is specifically, using CNC gong machine for shape processing, the tool speed is 20000-25000rpm, the feed speed is 800-1200mm / min, the shape dimensional accuracy is ±50μm, and the burr height is ≤50μm; use high-pressure air with a pressure of 0.5-0.7MPa to blow off the dust on the board surface, and cooperate with ultrasonic cleaning with a frequency of 40kHz and a time of 5-8 minutes. The surface ion contamination after cleaning is ≤1.5μg / cm 2, calculated as NaCl; place the board in a constant temperature and humidity chamber at 50±5℃ and 60±5% RH for 2-4 hours to eliminate the internal stress generated during the pressing process, and the warpage is ≤0.7%;

[0064] Step 9: Performance test: After cleaning, perform thickness measurement, thermal stress test, slice analysis and electrical test on the plate. Specifically, the performance test includes: plate thickness measurement: use a micrometer to measure 5 points in the four corners and the center of the plate, and the thickness tolerance is controlled within ±5% of the design value.

[0065] Thermal stress test: carried out in accordance with IPC-TM-650 standard, with the tin furnace temperature at 289±5℃, the tinning time at 10±1 seconds, and the number of cycles at 3 times. Visual inspection showed no board explosion, delamination, or blistering, and section inspection showed no breakage of the copper layer on the hole wall.

[0066] Slice analysis: Make 5 slices, each of which is from the four corners and the center of the board. Observe the interlayer bonding strength under a 50-200x microscope. The peel strength between the glass-free PP and the CORE board is ≥1.5N / mm, and the adhesion between the copper foil and the substrate is ≥3N / cm.

[0067] Electrical test: Use flying probe tester for continuity test, test voltage 10V, resistance threshold ≤50mΩ, test coverage 100%, yield ≥99.5%.

[0068] When implementing:

[0069] Taking the L308CB001DJMP4 glass fiber-free PP alternative resin filling process as an example, the specific implementation steps are as follows:

[0070] 1. Material preparation

[0071] Select glass fiber-free PP with a resin content of 70% and good fluidity. Prepare CORE board with a specification of 100±13um.

[0072] 2. Material delivery and drilling

[0073] The CORE plate is sent to the drilling process and drilled using a CNC drilling machine. The drilling diameter is 0.5mm, the drilling depth is determined according to the thickness of the plate, the drilling speed is 20,000 rpm, and the feed rate is 0.1mm / rev. After drilling is completed, the debris in the hole is cleaned.

[0074] 3. PTH and electroplating

[0075] The CORE board after drilling is degreased, roughened, and activated, and then electroless copper plating is carried out with a copper plating thickness of 5 um. Then electroplating is carried out. The electroplating solution is copper sulfate solution, the temperature is controlled at 25 °C, the current density is 20 A / dm2, and the electroplating time is 30 minutes to make the copper layer thickness reach 5 oz (about 175 um).

[0076] 4. First dry film

[0077] The dry film is attached to the surface of the electroplated CORE board using a laminating machine. The laminating temperature is 100 °C, the pressure is 100 Psi, and the speed is 1 m / min. After laminating, exposure is carried out with an exposure time of 60 seconds and a light intensity of 100 mJ / cm2.

[0078] 5. First etching

[0079] After developing, etching is carried out using ferric chloride etching solution. The temperature of the etching solution is 50 °C, the etching time is 10 minutes, and the board is cleaned after etching is completed.

[0080] 6. AOI inspection

[0081] The etched board is inspected through AOI equipment to ensure that the circuit pattern meets the design requirements.

[0082] 7. Lamination

[0083] The processed CORE board and non-glass fiber PP are combined in a laminated structure and placed in a vacuum laminating machine. The lamination process is as follows: heating from 80 °C to 180 °C at a rate of 5 °C per minute, while the pressure is gradually increased from 50 Psi to 300 Psi, maintaining at 180 °C and 300 Psi for 60 minutes, and then slowly cooling to room temperature.

[0084] 8. Performance testing

[0085] Various performance tests are carried out on the laminated board, including board thickness measurement, thermal stress test, and inspection of the hole wall after drilling and electroplating. The results show that the board thickness meets the design requirements, no phenomena such as board explosion, delamination, and blistering are found in the thermal stress test, the hole wall quality is good, and all performances meet the customer's requirements.

[0086] Although the present invention has been described in detail with reference to the foregoing embodiments, for those skilled in the art, they can still modify the technical solutions described in the foregoing embodiments, or perform equivalent replacements for some of the technical features. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principle of the present invention shall be included within the protection scope of the present invention.

Claims

1. A filling process for fiberglass-free PP substitute resin, characterized in that: It includes the following steps: Step 1, Material preparation: Select non-glass fiber PP as the lamination material, prepare the CORE board as the raw material, and conduct appearance inspection and dimension measurement; Step 2, Material distribution and drilling: After distributing the raw materials, use high-precision drilling equipment to drill, control the drilling parameters, and clean the debris in the holes after drilling; Step 3, PTH and electroplating: Conduct electroless copper plating and electroplating on the drilled board to metallize the hole walls and increase the copper layer thickness; Step 4, First dry film: Coat the dry film on the surface of the electroplated board, and conduct film laminating and exposure; Step 5, First etching: Develop and etch the exposed board to form a circuit pattern; Step 6, AOI inspection: Use automatic optical inspection equipment to inspect the circuit pattern of the etched board; Step 7, Lamination: Combine the CORE board and non-glass fiber PP according to the laminated structure, place them in the lamination equipment, control the temperature, pressure and time parameters during lamination, adopt vacuum lamination technology, and cool to room temperature after lamination; Step 8, Post-curing treatment: Use a numerically controlled router for profile machining, blow off the dust on the board surface with high-pressure air, and after ultrasonic cleaning, place the board in a constant temperature and humidity chamber for 2 - 4 hours to eliminate the internal stress generated during lamination; Step 9, Performance testing: Conduct board thickness measurement, thermal stress testing, microsection analysis and electrical property testing on the cleaned board.

2. The filling process of a fiberglass-free PP substitute resin according to claim 1, characterized in that: Specifically for the material preparation in Step 1, select non-glass fiber PP with a resin content of 65% - 75% and a glass transition temperature ≥ 150°C, and its melt flow rate should meet 1.2 - 1.8 g / 10 min to ensure uniform resin fluidity during lamination; conduct flatness inspection on the CORE board, with the flatness error ≤ 0.1%, wipe the surface with alcohol to remove oil stains and oxides, and control the roughness at Ra ≤ 1.2 μm; control the storage environment of non-glass fiber PP at a temperature of 20 ± 5°C and a humidity ≤ 40% RH, with a storage period not exceeding 3 months, and it needs to be placed at room temperature for more than 4 hours for temperature recovery before use.

3. The filling process of a glass fiber-free PP alternative resin according to claim 1, characterized in that: In the second step, the material feeding and drilling are specifically as follows: Generate drilling NC code according to the CAD design document, and use coordinate compensation technology to correct the expansion and contraction error of the board, with the error compensation accuracy ≤ ±5μm; Use a six-axis linkage numerical control drilling machine equipped with a diamond-coated drill bit, and the drill bit life ≥ 5000 holes / bit; The first drilling depth is 1 / 2 of the board thickness, and after retracting the tool and discharging chips, complete the drilling of the remaining depth to avoid drill breakage and delamination of the hole wall; The drilling parameters are a rotational speed of 25000 - 30000 rpm, a feed rate of 0.08 - 0.12 mm / rev, a hole position accuracy of ±25μm, and a hole diameter tolerance of ±10μm; After drilling, perform deburring treatment, using a brush wheel for mechanical grinding, with a brush rotational speed of 1500 - 2000 rpm and a grinding pressure of 5 - 10 N / cm 2 , ensuring that the surface roughness of the hole wall Ra ≤ 1.6μm.

4. The filling process of a fiberglass-free PP alternative resin according to claim 1, characterized in that: In the third step, the PTH and electroplating are specifically as follows: sodium hydroxide, an alkaline degreasing agent, is used with a concentration of 50 - 70 g / L, a temperature of 50 - 60 °C, and a treatment time of 3 - 5 minutes. After degreasing, the surface contact angle ≤ 30°; a sodium persulfate solution is used with a concentration of 80 - 100 g / L, a temperature of 30 - 40 °C, and an etching rate controlled at 1.5 - 2.0 μm / min to form a uniformly rough surface; a colloidal palladium activation solution is used with a concentration of 20 - 30 ppm, a temperature of 25 - 30 °C, and a treatment time of 5 - 8 minutes to ensure that the distribution density of catalytic active sites on the pore wall ≥ 10^6 / cm 2 ; The composition of the electroless copper plating solution for electroless copper plating is 15 - 20 g / L of copper sulfate, 8 - 12 ml / L of formaldehyde, 50 - 60 g / L of EDTA sodium salt, the temperature is 30 - 35°C, and the pH value is 12.5 - 13.5; air stirring is adopted during electroless copper plating, with an air pressure of 0.2 - 0.3 MPa, the electroless copper plating thickness is controlled at 0.8 - 1.2 μm, and the continuity of the copper layer on the hole wall ≥ 99.5%; The electroplating solution for electroplating treatment uses a high-acid and low-copper system, containing 180-220 g / L of sulfuric acid, 60-80 g / L of copper sulfate, 50-80 ppm of chloride ions, and leveling agents and brighteners are added; Pulse electroplating technology is adopted, with a current density of 15-25 A / dm 2 , duty cycle 1:3, period 50 ms, electroplating temperature 25-30 °C, copper layer thickness uniformity ≤ ±5%, target thickness according to design requirements; After electroplating, copper thickness detection is carried out, using an X-ray thickness gauge, with the number of detection points per sheet of plate ≥ 10, and the single-point thickness deviation ≤ ±5%.

5. A caulking process for a glass fiber-free PP alternative resin according to claim 1, characterized in that: In the fourth step, the single dry film specifically refers to an etching-resistant dry film with a thickness of 15 - 30 μm selected according to the circuit accuracy and a photosensitivity of ≥ 30 mJ / cm 2 , a resolution of ≤ 50 μm; the temperature of the roller of the laminator is controlled at 105 - 115 °C, the pressure is 150 - 200 Psi, and the laminating speed is 1.2 - 1.5 m / min; after laminating, static treatment is carried out for 15 - 20 minutes to fully bond the dry film to the copper surface, and the defective rate of bubbles is ≤ 0.1%; a parallel light exposure machine is used with a light intensity uniformity of ≥ 95%, and the exposure energy is controlled at 80 - 120 mJ / cm 2 , the yin-yang film alignment technology is adopted with an alignment accuracy of ± 25 μm, the thickness of the film used is 50 μm, and the dot reduction degree is ≥ 98%.

6. The filling process of a fiberglass-free PP alternative resin according to claim 1, characterized in that: The one-time etching in step five is specifically as follows: in the developing step, the developer is a sodium carbonate solution, the concentration of the sodium carbonate solution is 2.5-3.5%, the temperature is 30-35° C., the developing time is 40-60 seconds, and the developing speed is 15-20 μm / min; after development, residual adhesive is detected, and a residual adhesive rate is ≤0.5% under a 50x microscope; in the etching step, the acidic etching solution is ferric chloride and hydrochloric acid, the ferric chloride concentration is 45-55 g / L, the hydrochloric acid concentration is 10-15 g / L, the temperature is 45-55° C., and the etching rate is controlled at 25-35 μm / min; a spray etching method is adopted, the spray pressure is 0.3-0.5 MPa, the etching line width accuracy is controlled at ±10%, and the minimum line width / line spacing is ≥50 μm; In the film removal step, a sodium hydroxide solution is used with a concentration of 5-8% and a temperature of 50-60°C to remove the residual dry film. The treatment time is 3-5 minutes, and the surface insulation resistance after film removal is ≥10^9Ω; after film removal, the surface is cleaned and rinsed with DI water. The conductivity is ≤10μS / cm, the drying temperature is 80-100°C, and the drying time is 10-15 minutes.

7. A caulking process for a glass fiber-free PP alternative resin according to claim 1, characterized in that: The AOI detection in step six specifically uses a high-precision linear array camera AOI device with a resolution of ≥12μm / pixel and a detection speed of ≥100cm 2 / s. The detection items include open circuit / short circuit detection, line width / line spacing measurement, line width / line spacing measurement, and notch / burr detection; Open / short circuit detection: uses current pulse method, detection voltage 5-10V, leakage current threshold ≤1μA; line width / line spacing measurement: automatically extracts edge contours, measurement accuracy ±5μm, tolerance range ±10% design value; Notch / burr detection: Using image edge detection algorithm, the minimum detection size is 50μm; Defect repair is performed after detection: For open circuit defects, laser line repair technology is used with a repair accuracy of ±10μm and a wire width of ≥70μm; for short circuit defects, laser cutting technology is used with a cutting width of ≤50μm and a cutting depth of ≥2 / 3 of the copper layer thickness.

8. A caulking process for a glass fiber-free PP substitute resin according to claim 1, characterized in that: The lamination in step seven is specifically performed by adopting a symmetrical stacking design, with CORE boards and glass-free PP boards stacked alternately, and a copper foil protective layer with a thickness of 18-35 μm provided on the top and bottom layers; a pin positioning system is used for inter-layer positioning, with a positioning accuracy of ±25 μm and a matching tolerance of ±10 μm between the pin diameter and the hole diameter; The pressing parameters are: Heating stage: Raise the temperature from room temperature to 120°C at a rate of 3°C / min, maintain for 10 minutes to remove volatiles; then raise the temperature to 180±5°C at a rate of 5°C / min, and gradually increase the pressure to 100Psi during the heating process; Holding pressure stage: at 180°C, the pressure is controlled in stages, first at 200 Psi for 15 minutes to allow the resin to fully flow, then increased to 300-350 Psi for 45 minutes to complete the curing, with pressure uniformity ≤±5%; Cooling stage: Turn off the heating system and use circulating water for cooling at a cooling rate of ≤5℃ / min until the plate temperature drops below 50℃ to avoid internal stress concentration; Vacuum control: During the lamination process, the vacuum degree is maintained at ≤10mbar, and the vacuum leakage rate is monitored in real time at ≤5mbar / min to ensure that the air removal rate between layers is ≥99%; Demolding treatment: After pressing, the plate is naturally cooled to room temperature, and a release agent is used. The release agent is a silicone-based release agent with a concentration of 0.5-1.0% to assist in demolding and avoid damaging the surface copper foil.

9. The filling process of a fiberglass-free PP substitute resin according to claim 1, characterized in that: The post-curing treatment in the eighth step is specifically as follows: the contour machining is carried out by a numerically controlled milling machine, the tool rotation speed is 20,000 - 25,000 rpm, the feed rate is 800 - 1200 mm / min, the contour dimension accuracy is ±50 μm, and the burr height is ≤50 μm; high-pressure air with a pressure of 0.5 - 0.7 MPa is used to blow off the dust on the board surface, and ultrasonic cleaning is carried out in cooperation, with a frequency of 40 kHz and a time of 5 - 8 minutes. After cleaning, the surface ion contamination degree is ≤1.5 μg / cm 2 , calculated as NaCl; the board is placed in a constant temperature and humidity chamber with a temperature of 50 ± 5°C and a humidity of 60 ± 5% RH for 2 - 4 hours of intermediate treatment to eliminate the internal stress generated during the lamination process, and the warpage degree is ≤0.7%.

10. A filling process for a glass fiber-free PP alternative resin according to claim 1, characterized in that: The performance test in Step 9 is specifically as follows: board thickness measurement: use a micrometer to measure 5 points at the four corners and the center of the board, and the thickness tolerance is controlled within ±5% of the design value; Thermal stress test: Conducted in accordance with the IPC-TM-650 standard, the solder pot temperature is 289 ± 5 °C, the solder dipping time is 10 ± 1 second, the number of cycles is 3 times, visually inspect for no board explosion, delamination, or blistering, and observe under a microsection that the copper layer on the hole wall is not fractured; Microsection analysis: Make 5 microsections, which are respectively at the four corners and the center of the board. Observe the interfacial bonding strength between layers under a microscope with a magnification of 50 - 200 times. The interfacial peel strength between the glass fiber PP and the CORE board is ≥ 1.5 N / mm, and the adhesion between the copper foil and the substrate is ≥ 3 N / cm; Electrical property test: Conduct a conduction test using a flying probe tester, with a test voltage of 10 V, a resistance threshold of ≤ 50 mΩ, a test coverage rate of 100%, and a yield rate of ≥ 99.5%.

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