Method for processing circuit board with large back cavity

Abstract

The invention provides a method for processing a circuit board with a large back cavity, and the method employs a novel etching solution, and the etching solution comprises the following components: 20-30 mL / L of sulfuric acid, 5-10 g / L of a regulating agent, 40-50 mL / L of hydrogen peroxide, 2-4 g / L of a surfactant, 15-20 g / L of ethylene glycol, 40-50 g / L of a copper ion complexing agent, 6-8 g / L of a copper surface corrosion inhibitor, 1-3 g / L of a stabilizer, and 1-3 g / L of n-butylamine. By using the etching solution provided by the invention, the etching uniformity and stability of the circuit board can be improved, and a stable etching effect can be realized at different temperatures.

Description

Technical Field

[0001] The invention belongs to the technical field of circuit boards, and in particular relates to a processing method for a circuit board with a large back cavity. Background Art

[0002] Silicon microphone chamber PCB is a circuit board used to integrate micro silicon microphones (MEMS microphones). This circuit board is commonly used in various electronic devices, such as smart phones, tablets, smart speakers, etc., to achieve sound collection and processing.

[0003] In the preparation process of silicon-wheat cavity circuit boards, the selection and use of etching solution is one of the key steps. Etching solution is used to remove unnecessary metal layers and form the desired circuit pattern. However, in actual operation, the selection and use of etching solution faces multiple technical difficulties: (1) Local uneven etching may occur during the etching process, resulting in inconsistent circuit line width and affecting circuit performance. (2) Etching rate that is too fast or too slow will affect production efficiency and product quality. (3) Problems such as rough line edges and broken lines may occur during the etching process, affecting the accuracy of the circuit. (4) Unstable temperature of the etching solution is one of the common problems in the preparation of silicon-wheat cavity circuit boards, which will affect the uniformity and consistency of etching, and thus affect the quality and performance of the final product.

[0004] The etching solution in the prior art is mainly used to improve the etching rate by adding a copper ion complexing agent, but the existing etching solution still has the problem of temperature sensitivity, resulting in poor etching uniformity and consistency, and cannot meet the needs of consumers. Summary of the invention

[0005] The purpose of the present invention is to provide a method for processing a circuit board with a large back cavity.

[0006] In order to achieve the above object, the present invention provides the following technical solutions:

[0007] A method for processing a circuit board with a large back cavity comprises the following steps:

[0008] (1) Cutting: Cut the circuit board according to the design requirements and cut out the substrate;

[0009] (2) Gong plate: Clean the CNC gong machine, prepare the gong belt and the gong knife of the specified specifications, read the gong belt data, set the appropriate gong plate parameters to gong the substrate to form the inner cavity frame of the cavity plate;

[0010] (3) Lamination: Laminating the two substrates and the inner cavity frame material together and laminating them to obtain a cavity circuit board;

[0011] (4) Drilling: Drilling slots on the pressed circuit board;

[0012] (5) Electroplating: Electroplating the through holes of the drilled circuit board with a copper thickness of 24-26 μm and the blind holes with a copper thickness of 13-15 μm;

[0013] (6) Dry film: The outer layer pattern of the circuit board processed in step (5) is processed by film to make the circuit, and the PAD near the line is not compensated, while the other sides are compensated unilaterally;

[0014] (7) Etching: placing the circuit board processed in step (6) into an etching solution, etching away the non-circuit copper layer, exposing the circuit part, and obtaining the final formed circuit pattern;

[0015] The etching solution comprises the following components: 20-30 mL / L sulfuric acid, 5-10 g / L regulator, 40-50 mL / L hydrogen peroxide, 2-4 g / L surfactant, 15-20 g / L ethylene glycol, 40-50 g / L copper ion complexing agent, 6-8 g / L copper surface corrosion inhibitor, 1-3 g / L stabilizer and 1-3 g / L n-butylamine;

[0016] (8) Printing ink: Printing ink on both sides of the etched circuit board substrate, and sequentially undergoing pre-baking and exposure processes to form an ink layer;

[0017] (9) Surface treatment: After printing ink, the circuit board is subjected to outer layer circuit AOI inspection, photosensitive solder mask, and thermosetting text in turn;

[0018] (10) Forming, electrical testing, FQC, and laser drilling of acoustic holes on the cavity are performed in sequence to obtain a large back cavity circuit board.

[0019] Furthermore, the regulating agent comprises 4-vinylpyridine homopolymer with N-hydroxysuccinimide as the terminal group, aniline sulfate and dibromoneopentyl glycol in a weight ratio of 1: (1.2-1.4): (0.5-0.7).

[0020] Furthermore, the method for preparing the 4-vinylpyridine homopolymer having an N-hydroxysuccinimide terminal group comprises the following steps: by weight,

[0021] (1) 1 part of 4-vinylpyridine, 0.06-0.07 parts of dodecyl trithiocarbonate-2-methyl-propionic acid, 0.01-0.015 parts of azobisisobutyronitrile and 5-6 parts of dioxane are mixed, and the mixture is frozen-vacuumed-thawed 2-6 times under nitrogen protection, and then placed in an oil bath at 70-75° C. to react for 18-20 hours. The product is precipitated with ether and dried in vacuum to obtain a 4-vinylpyridine homopolymer with dodecyl trithiocarbonate as the terminal group;

[0022] (2) under nitrogen protection, 1 part of 4-vinylpyridine homopolymer with dodecyl trithiocarbonate as the terminal group, 0.06-0.08 parts of n-hexylamine, 0.015-0.016 parts of methylpyrazole phosphate and 4-6 parts of tetrahydrofuran are mixed, and freeze-vacuum-thaw is repeated 2-6 times, and then placed in a 25-30° C. water bath for reaction for 4-6 hours, the product is precipitated with ether, and vacuum dried to obtain a 4-vinylpyridine homopolymer with thiol as the terminal group;

[0023] (3) Under nitrogen protection, 1 part of 4-vinylpyridine homopolymer with a terminal thiol, 0.25-0.27 parts of N-acryloxysuccinimide, 0.15-0.18 parts of triethylamine and 5-7 parts of tetrahydrofuran were mixed, and the mixture was frozen-vacuumed-thawed 2-6 times and placed at 25-30°.

[0024] The reaction was carried out in a water bath at 400 °C for 25-30 h, and the product was precipitated with ether and dried in vacuo to obtain a 4-vinylpyridine homopolymer with N-hydroxysuccinimide as the terminal group.

[0025] The temperature stability of the etching solution used in the preparation process of the silicon wheat cavity circuit board has an important influence on the etching effect. Temperature instability can lead to a series of problems, which not only affect the etching quality, but also may affect the performance and reliability of the final product. When the temperature rises, the etching rate increases; when the temperature decreases, the etching rate slows down. This will lead to uneven etching, some areas may be over-etched, and other areas may be under-etched. The present invention attempts to improve the temperature stability of the etching solution by adding aniline sulfate and dibromoneopentyl glycol as regulators, but the effect is not ideal. The present invention uses 4-vinylpyridine homopolymer with N-hydroxysuccinimide as the terminal group, aniline sulfate and dibromoneopentyl glycol as regulators to improve the temperature stability of the etching solution, and can maintain balanced and stable performance within the range of 25-45°C. Because the terminal 4-vinylpyridine homopolymer has temperature responsiveness, it can change its conformation and solubility at different temperatures. This temperature responsiveness helps to adjust the viscosity and fluidity of the etching solution, thereby maintaining the stability of the etching rate. Aniline sulfate has high thermal stability and can maintain its chemical properties in a wide temperature range, thereby reducing the impact of temperature changes on the performance of the etching solution. Dibromoneopentyl glycol can adjust the viscosity of the etching solution to maintain appropriate fluidity at different temperatures, thereby maintaining a stable etching rate. The three can work together to improve the temperature stability of the etching solution.

[0026] Furthermore, the surfactant comprises sodium dodecyl sulfate, sodium dioctyl succinate sulfonate and a self-made surfactant in a weight ratio of 1: (0.3-0.6): (1.3-1.5).

[0027] Furthermore, the preparation method of the homemade surfactant includes the following steps: weighing 6-7 parts of C12-14 fatty alcohol and 1 part of boron trifluoride ether by weight, stirring at room temperature for 10-15 minutes, heating to 50-55°C, adding 3.5-4 parts of ethylene glycol diglycidyl ether, continuing to heat to 80-85°C and reacting for 4-6 hours, cooling to room temperature, adding 5-6 parts of chlorosulfonic acid dropwise, reacting at 45-50°C for 2-4 hours, cooling to room temperature, neutralizing with 5wt% NaOH to a pH of 8-8.5, distilling until crystallization occurs, and drying to obtain a homemade surfactant.

[0028] In the experiment, it was found that after adding the regulator, the temperature stability became better, but the etching rate was not ideal. The present invention attempted to add a commercially available surfactant to improve the etching rate, but the effect was not ideal. The present invention can improve the etching rate of the etching solution by compounding sodium dodecyl sulfate, dioctyl sodium sulfosuccinate and a homemade surfactant. The main reason is that the compounded surfactant can improve the surface tension of the etching solution, making it easier to wet the surface of the substrate, helping the etching solution to better contact and penetrate into the area to be etched, and improving the etching efficiency.

[0029] Furthermore, the pressing process is divided into six stages:

[0030] In the first stage, the temperature is set to 120-140°C and maintained for 5-7 minutes; the pressure is set to 1200-1400 kPa and maintained for 4-7 minutes, and the vacuum is turned on;

[0031] In the second stage, the temperature is raised to 140-160°C within 10 minutes and maintained for 20-30 minutes; the pressure is set to 2000-2400 kPa, maintained for 20-25 minutes, and the vacuum is turned on;

[0032] Stage 3: raise the temperature to 150-170°C within 10 minutes and keep it for 3-6 minutes; set the pressure to 3000-3500 kPa, keep it for 8-12 minutes, and open the vacuum;

[0033] In the fourth stage, the temperature is raised to 180-190°C within 10 minutes and maintained for 15-17 minutes; the pressure is set to 3000-3500 kPa, maintained for 20-25 minutes, and the vacuum is turned on;

[0034] The fifth stage: the temperature is set to 160-180℃ and maintained for 10-15 minutes; the pressure is reduced to 1000-1200 kPa within 10 minutes, maintained for 15-20 minutes, and the vacuum is turned on;

[0035] In the sixth stage, the temperature is lowered to 120-130°C within 15 minutes and maintained for 8-12 minutes; the pressure is set to 700-900 kPa, maintained for 15-18 minutes, and the vacuum is turned off.

[0036] Furthermore, the copper ion complexing agent comprises copper chloride, ethylenediaminetetramethylenephosphonic acid and citric acid in a weight ratio of 1: (0.6-0.8): (1.5-1.7).

[0037] Furthermore, the copper surface corrosion inhibitor is benzotriazole.

[0038] Furthermore, the hole diameter during drilling is 0.85-0.75 mm, the drilling speed of the drill bit is 80-100 krpm, the falling speed is 20-30 ipm, and the returning speed is 500-600 ipm.

[0039] Furthermore, the stabilizer comprises urea, n-butanol and propylene glycol in a weight ratio of 1:(1.5-1.7):(0.2-0.4).

[0040] Compared with the prior art, the advantages and beneficial effects of the present invention are:

[0041] 1. The present invention uses 4-vinylpyridine homopolymer with N-hydroxysuccinimide as the terminal group, aniline sulfate and dibromoneopentyl glycol as regulating agents, which can improve the temperature stability of the etching solution and maintain balanced and stable performance within the range of 25-45°C.

[0042] 2. The present invention can improve the etching rate of the etching solution by compounding sodium dodecyl sulfate, dioctyl sodium sulfosuccinate and a homemade surfactant. DETAILED DESCRIPTION

[0043] The technical solutions in the embodiments of the present invention are described clearly and completely below. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of them. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0044] The raw materials used in the following examples of the present invention are all commercially available products:

[0045] Boron trifluoride ethyl etherate, CAS: 109-63-7.

[0046] C12-14 fatty alcohol, Wuhan Jixinyibang Biotechnology Co., Ltd.

[0047] C8-10 fatty alcohol, Wuxi Baisidao New Materials Co., Ltd. CAS No. 85566-12-7.

[0048] Aniline sulfate: CAS No. 542-16-5.

[0049] Dodecyl trithiocarbonate-2-methyl-propionic acid, CAS number: 461642-78-4.

[0050] Methylpyrazole phosphate, CAS number: 202842-98-6.

[0051] N-Acryloyloxysuccinimide, CAS: 38862-24-7.

[0052] Sodium dioctyl sulfosuccinate, CAS: 7453-24.

[0053] Sulfuric acid, its volume concentration is 50%.

[0054] Hydrogen peroxide, with a volume concentration of 5%.

[0055] Propylene glycol, specifically 1,3-propanediol.

[0056] Example 1

[0057] This embodiment provides a method for processing a circuit board with a large back cavity, comprising the following steps:

[0058] (1) Cutting: Cut the circuit board according to the design requirements and cut out the substrate;

[0059] (2) Gong plate: Clean the CNC gong machine, prepare the gong belt and the gong knife of the specified specifications, read the gong belt data, set the appropriate gong plate parameters to gong the substrate to form the inner cavity frame of the cavity plate;

[0060] (3) Lamination: Laminating the two substrates and the inner cavity frame material together and laminating them to obtain a cavity circuit board;

[0061] (4) Drilling: Drilling slots on the pressed circuit board; the hole diameter during drilling is 0.80 mm, the drilling speed of the drill is 90 krpm, the falling speed is 25 i pm, and the return speed is 550 i pm;

[0062] (5) Electroplating: Electroplating the through holes of the drilled circuit board with a copper thickness of 25 μm and the blind holes with a copper thickness of 14 μm;

[0063] (6) Dry film: The outer layer pattern of the circuit board processed in step (5) is processed by film to make the circuit, and the PAD near the line is not compensated, while the other sides are compensated unilaterally;

[0064] (7) Etching: placing the circuit board processed in step (6) into an etching solution, etching away the non-circuit copper layer, exposing the circuit part, and obtaining the final formed circuit pattern;

[0065] (8) Printing ink: Printing ink on both sides of the etched circuit board substrate, and sequentially undergoing pre-baking and exposure processes to form an ink layer;

[0066] (9) Surface treatment: After printing ink, the circuit board is subjected to outer layer circuit AOI inspection, photosensitive solder mask, and thermosetting text in sequence;

[0067] (10) Forming, electrical testing, FQC, and laser drilling of acoustic holes on the cavity are performed in sequence to obtain a large back cavity circuit board.

[0068] The etching solution includes the following components: 25 mL / L sulfuric acid, 8 g / L regulating agent, 45 mL / L hydrogen peroxide, 3 g / L surfactant, 17 g / L ethylene glycol, 45 g / L copper ion complexing agent, 7 g / L copper surface corrosion inhibitor, 2 g / L stabilizer and 2 g / L n-butylamine.

[0069] The stabilizer comprises urea, n-butanol and propylene glycol in a weight ratio of 1:1.6:0.3. The copper ion complexing agent comprises copper chloride, ethylenediaminetetramethylenephosphonic acid and citric acid in a weight ratio of 1:0.7:1.6. The copper surface corrosion inhibitor is benzotriazole.

[0070] The regulating agent comprises 4-vinylpyridine homopolymer with N-hydroxysuccinimide as the terminal group, aniline sulfate and dibromoneopentyl glycol (i.e. 2,2-bis(bromomethyl)-1,3-propylene glycol) in a weight ratio of 1:1.3:0.6.

[0071] The method for preparing a 4-vinylpyridine homopolymer having an N-hydroxysuccinimide terminal group comprises the following steps: by weight:

[0072] (1) 1 part of 4-vinylpyridine, 0.065 parts of dodecyl trithiocarbonate-2-methyl-propionic acid, 0.012 parts of azobisisobutyronitrile and 5.5 parts of dioxane (i.e., 1,4-dioxane) were mixed, and the mixture was frozen-vacuumed-thawed three times under nitrogen protection, and then placed in an oil bath at 72° C. for reaction for 19 hours. The product was precipitated with ether and dried in vacuum to obtain a 4-vinylpyridine homopolymer with dodecyl trithiocarbonate as the terminal group;

[0073] (2) Under nitrogen protection, 1 part of 4-vinylpyridine homopolymer with dodecyl trithiocarbonate as the terminal group, 0.07 parts of n-hexylamine, 0.0155 parts of methylpyrazole phosphate and 5 parts of tetrahydrofuran were mixed, and freeze-vacuum-thawed were repeated three times, and then placed in a 27° C. water bath for reaction for 5 hours. The product was precipitated with diethyl ether and vacuum dried to obtain a 4-vinylpyridine homopolymer with thiol as the terminal group;

[0074] (3) Under nitrogen protection, 1 part of 4-vinylpyridine homopolymer with a thiol terminal group, 0.26 parts of N-acryloyloxysuccinimide, 0.17 parts of triethylamine and 6 parts of tetrahydrofuran were mixed, and freeze-vacuum-thawed were repeated three times, and then placed in a 27°C water bath to react for 27 hours. The product was precipitated with ether and vacuum dried to obtain a 4-vinylpyridine homopolymer with an N-hydroxysuccinimide terminal group.

[0075] The surfactant comprises sodium dodecyl sulfate, sodium dioctyl succinate sulfonate and a self-made surfactant in a weight ratio of 1:0.5:1.4.

[0076] The preparation method of a homemade surfactant comprises the following steps: weighing 6.5 parts of C12-14 fatty alcohol and 1 part of boron trifluoride ether by weight, stirring at room temperature for 12 minutes, heating to 52°C, adding 3.7 parts of ethylene glycol diglycidyl ether, continuing to heat to 82°C for reaction for 5 hours, cooling to room temperature, dripping 5.5 parts of chlorosulfonic acid, reacting at 42°C for 3 hours, cooling to room temperature, neutralizing with 5wt% NaOH to a pH of 8.2, distilling until crystallization occurs, and drying to obtain a homemade surfactant.

[0077] The pressing process is divided into six stages:

[0078] In the first stage, the temperature is set to 120°C and maintained for 5 minutes; the pressure is set to 1200 kPa and maintained for 4 minutes, and the vacuum is turned on;

[0079] In the second stage, the temperature was raised to 140°C within 10 minutes and maintained for 20 minutes; the pressure was set to 2000 kPa and maintained for 20 minutes, and the vacuum was turned on;

[0080] In the third stage, the temperature was raised to 150°C within 10 minutes and maintained for 3 minutes; the pressure was set to 3000 kPa, maintained for 8 minutes, and the vacuum was turned on;

[0081] In the fourth stage, the temperature was raised to 180°C within 10 minutes and maintained for 15 minutes; the pressure was set to 3000 kPa, maintained for 20 minutes, and the vacuum was turned on;

[0082] The fifth stage: the temperature is set to 160°C and maintained for 10 minutes; the pressure is reduced to 1000 kPa within 10 minutes, maintained for 15 minutes, and the vacuum is turned on;

[0083] In the sixth stage, the temperature was lowered to 120°C within 15 minutes and maintained for 8 minutes; the pressure was set to 700 kPa, maintained for 15 minutes, and the vacuum was turned off.

[0084] Example 2

[0085] This embodiment provides a method for processing a circuit board with a large back cavity, comprising the following steps:

[0086] (1) Cutting: Cut the circuit board according to the design requirements and cut out the substrate;

[0087] (2) Gong plate: Clean the CNC gong machine, prepare the gong belt and the gong knife of the specified specifications, read the gong belt data, set the appropriate gong plate parameters to gong the substrate to form the inner cavity frame of the cavity plate;

[0088] (3) Lamination: Laminating the two substrates and the inner cavity frame material together and laminating them to obtain a cavity circuit board;

[0089] (4) Drilling: Drilling slots on the pressed circuit board; the hole diameter during drilling is 0.85 mm, the drilling speed of the drill is 80 krpm, the falling speed is 20 ipm, and the return speed is 600 ipm;

[0090] (5) Electroplating: Electroplating the through holes of the drilled circuit board with a copper thickness of 26 μm and the blind holes with a copper thickness of 15 μm;

[0091] (6) Dry film: The outer layer pattern of the circuit board processed in step (5) is processed by film to make the circuit, and the PAD near the line is not compensated, while the other sides are compensated unilaterally;

[0092] (7) Etching: placing the circuit board processed in step (6) into an etching solution, etching away the non-circuit copper layer, exposing the circuit part, and obtaining the final formed circuit pattern;

[0093] (8) Printing ink: Printing ink on both sides of the etched circuit board substrate, and sequentially undergoing pre-baking and exposure processes to form an ink layer;

[0094] (9) Surface treatment: After printing ink, the circuit board is subjected to outer layer circuit AOI inspection, photosensitive solder mask, and thermosetting text in sequence;

[0095] (10) Forming, electrical testing, FQC, and laser drilling of acoustic holes on the cavity are performed in sequence to obtain a large back cavity circuit board.

[0096] The etching solution includes the following components: 30 mL / L sulfuric acid, 5 g / L regulating agent, 50 mL / L hydrogen peroxide, 2 g / L surfactant, 20 g / L ethylene glycol, 50 g / L copper ion complexing agent, 6 g / L copper surface corrosion inhibitor, 3 g / L stabilizer and 1 g / L n-butylamine.

[0097] The stabilizer comprises urea, n-butanol and propylene glycol in a weight ratio of 1:1.6:0.2. The copper ion complexing agent comprises copper chloride, ethylenediaminetetramethylenephosphonic acid and citric acid in a weight ratio of 1:0.6:1.7. The copper surface corrosion inhibitor is benzotriazole.

[0098] The regulating agent comprises 4-vinylpyridine homopolymer with N-hydroxysuccinimide as the terminal group, aniline sulfate and dibromoneopentyl glycol in a weight ratio of 1:1.2:0.7.

[0099] The method for preparing a 4-vinylpyridine homopolymer having an N-hydroxysuccinimide terminal group comprises the following steps: by weight:

[0100] (1) 1 part of 4-vinylpyridine, 0.07 parts of dodecyl trithiocarbonate-2-methyl-propionic acid, 0.01 parts of azobisisobutyronitrile and 6 parts of dioxane were mixed, and the mixture was frozen-vacuumed-thawed three times under nitrogen protection, and then placed in an oil bath at 70° C. for reaction for 20 hours. The product was precipitated with ether and dried in vacuum to obtain a 4-vinylpyridine homopolymer with dodecyl trithiocarbonate as the terminal group;

[0101] (2) Under nitrogen protection, 1 part of 4-vinylpyridine homopolymer with dodecyl trithiocarbonate as the terminal group, 0.06 parts of n-hexylamine, 0.016 parts of methylpyrazole phosphate and 6 parts of tetrahydrofuran were mixed, and freeze-vacuum-thawed were repeated three times, and then placed in a 25° C. water bath for reaction for 6 hours. The product was precipitated with ether and vacuum dried to obtain a 4-vinylpyridine homopolymer with thiol as the terminal group;

[0102] (3) Under nitrogen protection, 1 part of 4-vinylpyridine homopolymer with a thiol terminal group, 0.27 parts of N-acryloyloxysuccinimide, 0.15 parts of triethylamine and 7 parts of tetrahydrofuran were mixed, and freeze-vacuum-thawed were repeated three times, and then placed in a 30°C water bath to react for 30 hours. The product was precipitated with ether and vacuum dried to obtain a 4-vinylpyridine homopolymer with an N-hydroxysuccinimide terminal group.

[0103] The surfactant comprises sodium dodecyl sulfate, sodium dioctyl succinate sulfonate and a self-made surfactant in a weight ratio of 1:0.3:1.5.

[0104] The preparation method of a homemade surfactant comprises the following steps: weighing 7 parts of C12-14 fatty alcohol and 1 part of boron trifluoride ether by weight, stirring at room temperature for 15 minutes, heating to 50°C, adding 4 parts of ethylene glycol diglycidyl ether, continuing to heat to 85°C for reaction for 6 hours, cooling to room temperature, dripping 5 parts of chlorosulfonic acid, reacting at 45°C for 4 hours, cooling to room temperature, neutralizing with 5wt% NaOH to a pH of 8.5, distilling until crystallization occurs, and drying to obtain a homemade surfactant.

[0105] The pressing process is divided into six stages:

[0106] In the first stage, the temperature is set to 140°C and maintained for 7 minutes; the pressure is set to 1400 kPa and maintained for 7 minutes, and the vacuum is turned on;

[0107] In the second stage, the temperature was raised to 160°C within 10 minutes and maintained for 30 minutes; the pressure was set to 2400 kPa, maintained for 25 minutes, and the vacuum was turned on;

[0108] In the third stage, the temperature was raised to 170°C within 10 minutes and maintained for 6 minutes; the pressure was set to 3500 kPa, maintained for 12 minutes, and the vacuum was turned on;

[0109] In the fourth stage, the temperature was raised to 190°C within 10 minutes and maintained for 17 minutes; the pressure was set to 3500 kPa, maintained for 25 minutes, and the vacuum was turned on;

[0110] In the fifth stage, the temperature is set to 180°C and maintained for 15 minutes; the pressure is reduced to 1200 kPa within 10 minutes, maintained for 20 minutes, and the vacuum is turned on;

[0111] In the sixth stage, the temperature was lowered to 130°C within 15 minutes and maintained for 12 minutes; the pressure was set to 900 kPa, maintained for 18 minutes, and the vacuum was turned off.

[0112] Comparative Example 1

[0113] The difference between this comparative example and Example 1 is that the etching solution includes the following components: 25 mL / L sulfuric acid, 2 g / L regulating agent, 45 mL / L hydrogen peroxide, 8 g / L surfactant, 17 g / L ethylene glycol, 45 g / L copper ion complexing agent, 4 g / L copper surface corrosion inhibitor, 5 g / L stabilizer and 2 g / L n-butylamine.

[0114] Comparative Example 2

[0115] The difference between this comparative example and Example 1 is that the regulating agent comprises 4-vinylpyridine homopolymer with N-hydroxysuccinimide as the terminal group, aniline sulfate and dibromoneopentyl glycol in a weight ratio of 1:1:1.

[0116] Comparative Example 3

[0117] The difference between this comparative example and Example 1 is that the regulating agent comprises aniline sulfate and dibromoneopentyl glycol in a weight ratio of 1.3:0.6.

[0118] Comparative Example 4

[0119] The difference between this comparative example and Example 1 is that the surfactant includes sodium dodecyl sulfate, dioctyl sodium sulfosuccinate and a homemade surfactant in a weight ratio of 1:1:1.

[0120] Comparative Example 5

[0121] The difference between this comparative example and Example 1 is that the surfactant includes sodium dodecyl sulfonate, dioctyl sodium sulfosuccinate and sodium dodecyl sulfate in a weight ratio of 1:0.5:1.4.

[0122] Comparative Example 6

[0123] The difference between this comparative example and Example 1 is that the C12-14 fatty alcohol is replaced by a C8-10 fatty alcohol.

[0124] Performance Testing

[0125] The circuit boards prepared in Examples 1-2 and Comparative Examples 1-6 were subjected to performance tests at different temperatures according to GB / T315282015. The test results are shown in Table 1 below:

[0126] Table 1 Performance test results

[0127]

[0128] From the above performance test results, it can be seen that the etching solutions of Examples 1-2 have good etching effects and high stability at different temperatures, especially Example 1 has the most outstanding comprehensive performance, which is mainly due to the synergistic effect between the components.

[0129] However, since the necessary technical solutions were not adopted in the comparative examples, the corresponding performance tests were obviously worse than those of the embodiments. In comparative example 1, the ratio of the components was changed, and it can be seen that the overall effect decreased. In comparative example 2, the ratio of the regulator was different, and it can be seen from the results that the stability effect of the etching solution temperature decreased. In comparative example 3, no 4-vinylpyridine homopolymer with an end group of N-hydroxysuccinimide was added to the regulator, and the stability effect of the etching solution temperature decreased. In comparative example 4, the ratio of surfactants was different, in comparative example 5, the types of surfactants were different, and the raw materials for preparing the homemade surfactants in comparative example 5 were different, all of which would reduce the etching speed to varying degrees. The above experimental results further prove the importance of the technical solutions defined in the present invention for its technical effects.

[0130] The above is a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principles of the present invention. These improvements and modifications should also be regarded as the scope of protection of the present invention.

Claims

1. A method for processing a circuit board with a large back cavity, characterized in that: The following steps are involved: (1) Cutting: Cut the circuit board according to the design requirements and cut out the substrate; (2) Gong plate: Clean the CNC gong machine, prepare the gong belt and the gong knife of the specified specifications, read the gong belt data, set the appropriate gong plate parameters to gong the substrate to form the inner cavity frame of the cavity plate; (3) Lamination: Laminating the two substrates and the inner cavity frame material together and laminating them to obtain a cavity circuit board; (4) Drilling: Drilling slots on the pressed circuit board; (5) Electroplating: Electroplating the through holes of the drilled circuit board with a copper thickness of 24-26 μm and the blind holes with a copper thickness of 13-15 μm; (6) Dry film: The outer layer pattern of the circuit board processed in step (5) is processed by film to make the circuit, and the PAD near the line is not compensated, while the other sides are compensated unilaterally; (7) Etching: placing the circuit board processed in step (6) into an etching solution, etching away the non-circuit copper layer, exposing the circuit part, and obtaining the final formed circuit pattern; The etching solution comprises the following components: 20-30 mL / L sulfuric acid, 5-10 g / L regulator, 40-50 mL / L hydrogen peroxide, 2-4 g / L surfactant, 15-20 g / L ethylene glycol, 40-50 g / L copper ion complexing agent, 6-8 g / L copper surface corrosion inhibitor, 1-3 g / L stabilizer and 1-3 g / L n-butylamine; (8) Printing ink: Printing ink on both sides of the etched circuit board substrate, and sequentially undergoing pre-baking and exposure processes to form an ink layer; (9) Surface treatment: After printing ink, the circuit board is subjected to outer layer circuit AOI inspection, photosensitive solder mask, and thermosetting text in turn; (10) Forming, electrical testing, FQC, and laser drilling of acoustic holes on the cavity are performed in sequence to obtain a large back cavity circuit board.

2. The method for processing a circuit board with a large back cavity according to claim 1, characterized in that: The regulating agent comprises 4-vinylpyridine homopolymer with N-hydroxysuccinimide as the terminal group, aniline sulfate and dibromoneopentyl glycol in a weight ratio of 1: (1.2-1.4): (0.5-0.7).

3. The method for processing a circuit board with a large back cavity according to claim 2, characterized in that: The method for preparing a 4-vinylpyridine homopolymer having an N-hydroxysuccinimide terminal group comprises the following steps: by weight: (1) 1 part of 4-vinylpyridine, 0.06-0.07 parts of dodecyl trithiocarbonate-2-methyl-propionic acid, 0.01-0.015 parts of azobisisobutyronitrile and 5-6 parts of dioxane are mixed, and the mixture is frozen-vacuumed-thawed 2-6 times under nitrogen protection, and then placed in an oil bath at 70-75° C. to react for 18-20 hours. The product is precipitated with ether and dried in vacuum to obtain a 4-vinylpyridine homopolymer with dodecyl trithiocarbonate as the terminal group; (2) under nitrogen protection, 1 part of 4-vinylpyridine homopolymer with dodecyl trithiocarbonate as the terminal group, 0.06-0.08 parts of n-hexylamine, 0.015-0.016 parts of methylpyrazole phosphate and 4-6 parts of tetrahydrofuran are mixed, and freeze-vacuum-thaw is repeated 2-6 times, and then placed in a 25-30° C. water bath for reaction for 4-6 hours, the product is precipitated with ether, and vacuum dried to obtain a 4-vinylpyridine homopolymer with thiol as the terminal group; (3) Under nitrogen protection, 1 part of 4-vinylpyridine homopolymer with a thiol terminal group, 0.25-0.27 parts of N-acryloyloxysuccinimide, 0.15-0.18 parts of triethylamine and 5-7 parts of tetrahydrofuran are mixed, freeze-vacuum-thaw is repeated 2-6 times, and then placed in a 25-30° C. water bath to react for 25-30 hours. The product is precipitated with ether and vacuum dried to obtain a 4-vinylpyridine homopolymer with an N-hydroxysuccinimide terminal group.

4. The method for processing a circuit board with a large back cavity according to claim 1, characterized in that: The surfactant comprises sodium dodecyl sulfonate, sodium dioctyl sulfosuccinate and a self-made surfactant in a weight ratio of 1: (0.3-0.6): (1.3-1.5).

5. The method for processing a circuit board with a large back cavity according to claim 4, characterized in that: The preparation method of a homemade surfactant comprises the following steps: weighing 6-7 parts of C12-14 fatty alcohol and 1 part of boron trifluoride ether by weight, stirring at room temperature for 10-15 minutes, heating to 50-55°C, adding 3.5-4 parts of ethylene glycol diglycidyl ether, continuing to heat to 80-85°C for reaction for 4-6 hours, cooling to room temperature, dripping 5-6 parts of chlorosulfonic acid, reacting at 45-50°C for 2-4 hours, cooling to room temperature, neutralizing with NaOH to a pH of 8-8.5, distilling until crystallization occurs, and drying to obtain a homemade surfactant.

6. The method for processing a circuit board with a large back cavity according to claim 1, characterized in that: The pressing process is divided into six stages: In the first stage, the temperature is set to 120-140°C and maintained for 5-7 minutes; the pressure is set to 1200-1400 kPa and maintained for 4-7 minutes, and the vacuum is turned on; In the second stage, the temperature is raised to 140-160°C within 10 minutes and maintained for 20-30 minutes; the pressure is set to 2000-2400 kPa, maintained for 20-25 minutes, and the vacuum is turned on; Stage 3: raise the temperature to 150-170°C within 10 minutes and keep it for 3-6 minutes; set the pressure to 3000-3500 kPa, keep it for 8-12 minutes, and open the vacuum; In the fourth stage, the temperature is raised to 180-190°C within 10 minutes and maintained for 15-17 minutes; the pressure is set to 3000-3500 kPa, maintained for 20-25 minutes, and the vacuum is turned on; The fifth stage: the temperature is set to 160-180℃ and maintained for 10-15 minutes; the pressure is reduced to 1000-1200 kPa within 10 minutes, maintained for 15-20 minutes, and the vacuum is turned on; In the sixth stage, the temperature is lowered to 120-130°C within 15 minutes and maintained for 8-12 minutes; the pressure is set to 700-900 kPa, maintained for 15-18 minutes, and the vacuum is turned off.

7. The method for processing a circuit board with a large back cavity according to claim 1, characterized in that: The copper ion complexing agent comprises copper chloride, ethylenediaminetetramethylenephosphonic acid and citric acid in a weight ratio of 1: (0.6-0.8): (1.5-1.7).

8. The method for processing a circuit board with a large back cavity according to claim 1, characterized in that: The copper surface corrosion inhibitor is benzotriazole.

9. The method for processing a circuit board with a large back cavity according to claim 1, characterized in that: The hole diameter during drilling is 0.85-0.75mm, the drilling speed of the drill bit is 80-100krpm, the falling speed is 20-30ipm, and the returning speed is 500-600ipm.

10. The method for processing a circuit board with a large back cavity according to claim 1, characterized in that: The stabilizer comprises urea, n-butanol and propylene glycol in a weight ratio of 1:(1.5-1.7):(0.2-0.4).

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