A processing method of a large back cavity cavity circuit board

Abstract

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

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of circuit boards, and particularly relates to a processing method of a large back cavity chamber circuit board. BACKGROUND

[0002] Silicon microphone chamber circuit board (Silicon Microphone Chamber PCB) is a circuit board used for integrated micro silicon microphone (MEMS microphone). This kind of circuit board is usually used in various electronic devices, such as smart phones, tablet computers, smart speakers, etc., to realize the collection and processing of sound.

[0003] In the preparation process of the silicon microphone chamber circuit board, the selection and use of etching solution is one of the key steps. The etching solution is used to remove the unnecessary metal layer to form the required circuit pattern. However, in actual operation, the selection and use of etching solution faces multiple technical difficulties: (1) Local etching may not be uniform during etching, resulting in inconsistent circuit line width, affecting circuit performance. (2) Too fast or too slow etching rate will affect production efficiency and product quality. (3) Problems such as line edge roughness and line breakage may occur during etching, affecting the accuracy of the circuit. (4) Temperature instability of etching solution is one of the common problems in the preparation of silicon microphone chamber circuit board, which will affect the uniformity and consistency of etching, and further affect the quality and performance of the final product.

[0004] The etching solution in the prior art mainly adds copper ion complexing agent to improve the etching rate, but the existing etching solution still has temperature sensitivity problems, resulting in poor uniformity and consistency of etching, which cannot meet the needs of consumers. SUMMARY

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

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

[0007] A processing method of a large back cavity chamber circuit board, comprising the following steps:

[0008] (1) Cutting: cutting the circuit board according to the size required by the design, and cutting the substrate;

[0009] (2) Rounding: cleaning the numerical control rounding machine, preparing the rounding belt and the specified specification rounding tool, reading the rounding belt data, and setting appropriate rounding parameters to round the substrate to form the inner cavity frame of the cavity plate;

[0010] (3) Pressing: stacking two substrates and the inner cavity frame material together, and pressing to obtain the cavity circuit board;

[0011] (4) Drilling: drilling grooves on the circuit board after pressing;

[0012] (5) Electroplating: electroplating the circuit board after drilling to make the thickness of the through-hole copper 24-26 μm and the thickness of the blind-hole copper 13-15 μm;

[0013] (6) Dry film: processing the outer pattern of the circuit board after step (5) to make lines, and not compensating for the PAD near lines, and compensating for other edges;

[0014] (7) Etching: putting the circuit board after step (6) into etching solution to etch the non-line copper layer, expose the line part, and get the final shaped line pattern;

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

[0016] (8) Printing ink: printing ink on both sides of the circuit board substrate after etching, and sequentially going through the processes of pre-baking and exposure to make the ink form an ink layer;

[0017] (9) Surface treatment: sequentially performing outer line AOI detection, photosensitive solder mask, and heat-set text on the circuit board after printing ink;

[0018] (10) sequentially performing molding, electrical measurement, FQC, and laser drilling acoustic holes on the cavity to get a large back cavity circuit board.

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

[0020] Further, the preparation method of the 4-vinylpyridine homopolymer with N-hydroxysuccinimide end group comprises the following steps:

[0021] (1) mixing 1 part of 4-vinylpyridine, 0.06-0.07 parts of dodecyltrithiocarbonate-2-methyl-propionic acid, 0.01-0.015 parts of azobisisobutyronitrile, and 5-6 parts of dioxane under nitrogen protection, repeating freezing-vacuumizing-thawing for 2-6 times, and then placing in a 70-75℃ oil bath for 18-20h, precipitating the product with diethyl ether, and vacuum drying to get 4-vinylpyridine homopolymer with dodecyltrithiocarbonate end group;

[0022] (2) Under nitrogen protection, 1 part of 4-vinylpyridine homopolymer with dodecyltrithiocarbonate end 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 the freezing-vacuumizing-thawing is repeated for 2-6 times, then it is placed in a 25-30℃ water bath for 4-6 hours, the product is precipitated with diethyl ether, and after vacuum drying, 4-vinylpyridine homopolymer with thiol end group is obtained;

[0023] (3) Under nitrogen protection, 1 part of 4-vinylpyridine homopolymer with thiol end group, 0.25-0.27 parts of N-acryloyloxy succinimide, 0.15-0.18 parts of triethylamine and 5-7 parts of tetrahydrofuran are mixed, and after the freezing-vacuumizing-thawing is repeated for 2-6 times, it is placed in a 25-30℃ water bath for 25-30 hours, the product is precipitated with diethyl ether, and after vacuum drying, 4-vinylpyridine homopolymer with N-hydroxysuccinimide end group is obtained.

[0024]

[0025] The temperature stability of the etching solution used in the preparation process of the silicon microphone cavity circuit board has an important influence on the etching effect. Temperature instability can cause a series of problems that 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 cause 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 a regulator, but the effect is not ideal. The present invention uses 4-vinylpyridine homopolymer with N-hydroxysuccinimide end group, aniline sulfate and dibromoneopentyl glycol as a regulator to improve the temperature stability of the etching solution, which can maintain balanced and stable performance within the range of 25-45℃. Because the end group 4-vinylpyridine homopolymer has temperature responsiveness, it can change its conformation and solubility at different temperatures, which helps to adjust the viscosity and flowability of the etching solution, thereby maintaining the stability of the etching rate. Aniline sulfate has high thermal stability and can maintain its chemical properties unchanged within 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 flowability at different temperatures, thereby maintaining the stability of the etching rate. The three work together to improve the temperature stability of the etching solution.

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

[0027] ​Further, the preparation method of the self-made surfactant comprises the following steps: 6-7 parts of C12-14 fatty alcohol, 1 part of boron trifluoride diethyl ether are weighed, stirring at room temperature for 10-15 min, when the temperature is increased to 50-55 DEG C, 3.5-4 parts of ethylene glycol glyceryl ether are added, the temperature is continuously increased to 80-85 DEG C and reacted for 4-6 h, then the temperature is decreased to room temperature, 5-6 parts of chlorosulfonic acid is added dropwise, the reaction is carried out at 45-50 DEG C for 2-4 h, the temperature is decreased to room temperature, 5 wt% NaOH is used for neutralization until the pH is 8-8.5, distillation is carried out until crystals appear, drying is carried out, and the self-made surfactant is obtained.

[0028] It is found in the experiment that the temperature stability is good after adding the regulating agent, but the etching rate is not ideal, the application attempts to add a commercially available surfactant for improving the etching rate effect, and the effect is not ideal. The etching rate of the etching solution can be improved by compounding sodium dodecyl sulfonate, sodium dioctyl succinate and the self-made surfactant. Mainly, the surfactant after compounding can improve the surface tension of the etching solution, so that it is easier to wet the substrate surface, and it is helpful for the etching solution to better contact and penetrate into the etching area, and the etching efficiency is improved.

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

[0030] In the first stage, the temperature is set to 120-140 DEG C, the time is kept for 5-7 min, the pressure is set to 1200-1400 kPa, the time is kept for 4-7 min, and the vacuum is opened;

[0031] In the second stage, the temperature is increased to 140-160 DEG C within 10 min, the time is kept for 20-30 min, the pressure is set to 2000-2400 kPa, the time is kept for 20-25 min, and the vacuum is opened;

[0032] In the third stage, the temperature is increased to 150-170 DEG C within 10 min, the time is kept for 3-6 min, the pressure is set to 3000-3500 kPa, the time is kept for 8-12 min, and the vacuum is opened;

[0033] In the fourth stage, the temperature is increased to 180-190 DEG C within 10 min, the time is kept for 15-17 min, the pressure is set to 3000-3500 kPa, the time is kept for 20-25 min, and the vacuum is opened;

[0034] In the fifth stage, the temperature is set to 160-180 DEG C, the time is kept for 10-15 min, the pressure is decreased to 1000-1200 kPa within 10 min, the time is kept for 15-20 min, and the vacuum is opened;

[0035] Six sections, reduce the temperature to 120-130 DEG C within 15 min, keep 8-12 min; pressure setting is 700-900 kPa, keep time 15-18 min, and close the vacuum.

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

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

[0038] Further, the hole diameter during drilling is 0.85-0.75 mm, the drill bit drilling speed is 80-100 krpm, the drop speed is 20-30 ipm, and the return speed is 500-600 ipm.

[0039] Further, 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 application has the following advantages and beneficial effects:

[0041] 1. The 4-vinylpyridine homopolymer with an end group of N-hydroxysuccinimide, aniline sulfate and dibromoneopentyl glycol are used as the control agent, the temperature stability of the etching solution can be improved, and the performance can be kept balanced and stable within the range of 25-45 DEG C.

[0042] 2. The etching rate of the etching solution can be improved by compounding sodium dodecyl sulfonate, sodium dioctyl succinate and the self-made surfactant. DETAILED DESCRIPTION

[0043] The technical solutions in the embodiments of the application will be clearly and completely described below. Obviously, the described embodiments are only a part of the embodiments of the application, rather than all the embodiments. Based on the embodiments in the application, all other embodiments obtained by those skilled in the art without creative work fall within the protection scope of the application.

[0044] The raw materials used in the following embodiments of the application are all commercially available goods:

[0045] Boron trifluoride diethyl ether, CAS: 109-63-7.

[0046] C12-14 fatty alcohol, Wuhan Jixin Yibang Biological Technology Co., Ltd.

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

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

[0049] Dodecyltrithiocarbonate-2-methyl-propionic acid, CAS No.: 461642-78-4.

[0050] Methylpyrazole phosphate, CAS No.: 202842-98-6.

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

[0052] Sodium dioctylsulfosuccinate, CAS: 7453-24.

[0053] Sulfuric acid, 50% by volume concentration.

[0054] Hydrogen peroxide, 5% by volume concentration.

[0055] Propylene glycol, in particular 1,3-propylene glycol.

[0056] Example 1

[0057] The present embodiment provides a processing method of a large back cavity circuit board, comprising the following steps:

[0058] (1) Cutting: cutting the circuit board according to the size required by the design, and opening the substrate;

[0059] (2) Plate milling: cleaning the numerical control milling machine, preparing the milling belt and the milling cutter of the specified specification, reading the milling belt data, and setting appropriate milling parameters to mill the substrate to form the inner cavity frame of the cavity plate;

[0060] (3) Pressing: stacking two substrates and the inner cavity frame material together, and pressing to obtain a cavity circuit board;

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

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

[0063] (6) Dry film: processing the outer layer pattern of the circuit board treated in step (5) by film processing to make a circuit, and the PAD near the line is not compensated, while the other edges are single-sided compensated;

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

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

[0066] (9) Surface treatment: sequentially performing outer layer circuit AOl detection, photosensitive solder mask, and hot-set text on the circuit board after printing ink;

[0067] (10) sequentially performing molding, electrical testing, FQC, and laser drilling acoustic holes on the cavity to obtain a large back cavity circuit board.

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

[0069] The stabilizer comprises urea, n-butanol, and propylene glycol at a weight ratio of 1:1.6:0.3. The copper ion complexing agent comprises copper chloride, ethylenediaminetetra(methylene phosphonic acid), and citric acid at 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 end groups, aniline sulfate, and dibromoneopentyl glycol (i.e., 2,2-bis(bromomethyl)-1,3-propanediol) at a weight ratio of 1:1.3:0.6.

[0071] The preparation method of the 4-vinylpyridine homopolymer with N-hydroxysuccinimide end groups comprises the following steps:

[0072] (1) mixing 1 part of 4-vinylpyridine, 0.065 parts of dodecyltrithiocarbonate-2-methyl-propionic acid, 0.012 parts of azobisisobutyronitrile, and 5.5 parts of dioxane (i.e., 1,4-dioxane) under nitrogen protection, repeating freezing-vacuumizing-thawing three times, then placing in a 72°C oil bath for 19h, precipitating the product with diethyl ether, and vacuum drying to obtain 4-vinylpyridine homopolymer with dodecyltrithiocarbonate end groups;

[0073] (2) mixing 1 part of 4-vinylpyridine homopolymer with dodecyltrithiocarbonate end groups, 0.07 parts of n-hexylamine, 0.0155 parts of methylpyrazole phosphate, and 5 parts of tetrahydrofuran under nitrogen protection, repeating freezing-vacuumizing-thawing three times, then placing in a 27°C water bath for 5h, precipitating the product with diethyl ether, and vacuum drying to obtain 4-vinylpyridine homopolymer with thiol end groups;

[0074] (3) 1 part of 4-vinylpyridine homopolymer with thiol end group, 0.26 part of N-acryloyloxy succinimide, 0.17 part of triethylamine and 6 parts of tetrahydrofuran were mixed under nitrogen protection, and after being frozen, vacuumed and thawed for three times, the mixture was placed in a water bath at 27℃ for 27 hours. The product was precipitated with ether, and after being vacuum dried, 4-vinylpyridine homopolymer with N-hydroxysuccinimide end group was obtained.

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

[0076] The preparation method of the self-made surfactant includes the following steps: 6.5 parts of C12-14 fatty alcohol and 1 part of boron trifluoride ether are weighed, stirred at room temperature for 12 min, 3.7 parts of ethylene glycol diglycidyl ether is added when the temperature is increased to 52℃, and the temperature is continuously increased to 82℃ for 5 hours, and then the temperature is decreased to room temperature. 5.5 parts of chlorosulfonic acid is added dropwise, and the reaction is carried out at 42℃ for 3 hours. The temperature is decreased to room temperature, and the pH is neutralized to 8.2 with 5wt% NaOH. Distillation is carried out until crystals appear, and the self-made surfactant is obtained after drying.

[0077] In the pressing process, the pressing is divided into six stages:

[0078] In the first stage, the temperature is set to 120℃, and the time is kept for 5 min; the pressure is set to 1200kPa, and the time is kept for 4 min, and the vacuum is opened;

[0079] In the second stage, the temperature is increased to 140℃ within 10 min, and the time is kept for 20 min; the pressure is set to 2000kPa, and the time is kept for 20 min, and the vacuum is opened;

[0080] In the third stage, the temperature is increased to 150℃ within 10 min, and the time is kept for 3 min; the pressure is set to 3000kPa, and the time is kept for 8 min, and the vacuum is opened;

[0081] In the fourth stage, the temperature is increased to 180℃ within 10 min, and the time is kept for 15 min; the pressure is set to 3000kPa, and the time is kept for 20 min, and the vacuum is opened;

[0082] In the fifth stage, the temperature is set to 160℃, and the time is kept for 10 min; the pressure is decreased to 1000kPa within 10 min, and the time is kept for 15 min, and the vacuum is opened;

[0083] In the sixth stage, the temperature is decreased to 120℃ within 15 min, and the time is kept for 8 min; the pressure is set to 700kPa, and the time is kept for 15 min, and the vacuum is closed.

[0084] Example 2

[0085] The embodiment provides a processing method of a large back cavity cavity circuit board, and comprises the following steps:

[0086] (1) Cutting: cutting the circuit board according to the size required by the design, and opening the substrate;

[0087] (2) Milling: cleaning the numerical control milling machine, preparing the milling belt and the milling cutter with the specified specification, reading the milling belt data, and setting the appropriate milling parameters to mill the substrate to form the inner cavity frame of the cavity plate;

[0088] (3) Pressing: stacking two substrates and the inner cavity frame material together, and pressing to obtain the cavity circuit board;

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

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

[0091] (6) Dry film: processing the outer layer pattern of the circuit board treated in step (5) by film processing to form a circuit, and not compensating for the PAD near the line, and other single-sided compensation;

[0092] (7) Etching: placing the circuit board treated in step (6) into an etching solution to etch the non-circuit copper layer and expose the circuit part to obtain the final shaped circuit pattern;

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

[0094] (9) Surface treatment: sequentially performing outer layer circuit AO I detection, photosensitive solder mask, and heat-set text on the circuit board after printing ink;

[0095] (10) sequentially performing molding, electrical measurement, FQC, and laser drilling of the acoustic hole on the cavity to obtain the large back cavity cavity circuit board.

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

[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, ethylenediaminetetramethylene phosphonic acid and citric acid in a weight ratio of 1:0.6:1.7. The copper surface corrosion inhibitor is benzotriazole.

[0098] The regulator includes 4-vinylpyridine homopolymer with N-hydroxysuccinimide end group, aniline sulfate and dibromoneopentyl glycol in a weight ratio of 1:1.2:0.7.

[0099] The preparation method of the 4-vinylpyridine homopolymer with N-hydroxysuccinimide end group includes the following steps: in terms of weight fraction,

[0100] (1) 1 part of 4-vinylpyridine, 0.07 parts of dodecyltrithiocarbonate-2-methyl-propionic acid, 0.01 parts of azobisisobutyronitrile and 6 parts of dioxane are mixed, and after being repeated three times of freezing-vacuumizing-thawing, it is placed in a 70℃ oil bath for reaction for 20h, the product is precipitated with diethyl ether, and vacuum dried to obtain 4-vinylpyridine homopolymer with dodecyltrithiocarbonate end group;

[0101] (2) 1 part of 4-vinylpyridine homopolymer with dodecyltrithiocarbonate end group, 0.06 parts of n-hexylamine, 0.016 parts of methylpyrazole phosphate and 6 parts of tetrahydrofuran are mixed under nitrogen protection, and after being repeated three times of freezing-vacuumizing-thawing, it is placed in a 25℃ water bath for reaction for 6h, the product is precipitated with diethyl ether, and vacuum dried to obtain 4-vinylpyridine homopolymer with thiol end group;

[0102] (3) 1 part of 4-vinylpyridine homopolymer with thiol end group, 0.27 parts of N-acryloyloxy succinimide, 0.15 parts of triethylamine and 7 parts of tetrahydrofuran are mixed under nitrogen protection, and after being repeated three times of freezing-vacuumizing-thawing, it is placed in a 30℃ water bath for reaction for 30h, the product is precipitated with diethyl ether, and vacuum dried to obtain 4-vinylpyridine homopolymer with N-hydroxysuccinimide end group.

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

[0104] The preparation method of the self-made surfactant includes the following steps: in terms of weight fraction, 7 parts of C12-14 fatty alcohol and 1 part of boron trifluoride ether are weighed, stirred at room temperature for 15min, when the temperature is increased to 50℃, 4 parts of ethylene glycol glycidyl ether is added, the temperature is continuously increased to 85℃ for reaction for 6h, and then decreased to room temperature, 5 parts of chlorosulfonic acid is added dropwise for reaction for 4h at 45℃, and then decreased to room temperature, neutralized to pH 8.5 with 5wt% NaOH, distilled until crystals appear, and dried to obtain the self-made surfactant.

[0105] In the pressing process, pressing is carried out in six stages:

[0106] First stage, temperature set at 140°C, hold for 7 min; pressure set at 1400 kPa, hold for 7 min, and open vacuum;

[0107] Second stage, temperature raised to 160°C in 10 min, hold for 30 min; pressure set at 2400 kPa, hold for 25 min, and open vacuum;

[0108] Third stage, temperature raised to 170°C in 10 min, hold for 6 min; pressure set at 3500 kPa, hold for 12 min, and open vacuum;

[0109] Fourth stage, temperature raised to 190°C in 10 min, hold for 17 min; pressure set at 3500 kPa, hold for 25 min, and open vacuum;

[0110] Fifth stage, temperature set at 180°C, hold for 15 min; pressure reduced to 1200 kPa in 10 min, hold for 20 min, and open vacuum;

[0111] Sixth stage, temperature reduced to 130°C in 15 min, hold for 12 min; pressure set at 900 kPa, hold for 18 min, and close vacuum.

[0112] Comparative Example 1

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

[0114] Comparative Example 2

[0115] The difference between this comparative example and Example 1 is that the regulator comprises 4-vinylpyridine homopolymer with N-hydroxysuccinimide end 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 regulator 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 comprises sodium dodecyl sulfonate, sodium dioctyl succinate sulfonate, and self-made surfactant in a weight ratio of 1:1:1.

[0120] Comparative Example 5

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

[0122] Comparative Example 6

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

[0124] Performance test

[0125] The circuit boards prepared according to Examples 1-2 and Comparative Examples 1-6 were subjected to performance tests at different temperatures according to GB / T315282015, and 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 effect and high stability at different temperatures, and the comprehensive performance of Example 1 is the most outstanding, which is mainly due to the synergistic effect between the components.

[0129] The comparative examples, however, do not use the necessary technical solutions, resulting in a significant difference in the corresponding performance tests compared to the examples. In Comparative Example 1, the component ratio is changed, and it can be seen that the comprehensive effect decreases. In Comparative Example 2, the ratio of the control agent is different, and from the results it can be seen that the temperature stability of the etching solution decreases. In Comparative Example 3, the 4-vinylpyridine homopolymer with N-hydroxysuccinimide as the end group is not added to the control agent, and the temperature stability of the etching solution decreases. In Comparative Example 4, the ratio of the surfactant is different, in Comparative Example 5, the types of surfactants are different, and in Comparative Example 5, the raw materials for preparing the self-made surfactant are different, all of which will reduce the etching speed to varying degrees. The above experimental results further prove the importance of the technical solutions defined in the present application to its technical effects.

[0130] The above is a preferred embodiment of the present application. It should be noted that for those skilled in the art, without departing from the principles of the present application, a number of improvements and refinements can be made, and these improvements and refinements should also be considered within the scope of protection of the present application.

Claims

1. A method for fabricating a large back cavity circuit board, characterized in that, include: (1) Cutting: Cut the circuit board to the dimensions required by the design and cut out the substrate; (2) Routing: Clean the CNC router, prepare the router tape and the specified router cutter, read in the router tape data, set the appropriate router parameters to router the substrate to form the inner cavity frame of the cavity plate. (3) Pressing: The two substrates and the inner cavity frame material are stacked together and pressed to obtain the cavity circuit board; (4) Drilling: Drilling slots into the laminated circuit board; (5) Electroplating: Electroplating the circuit board after drilling to 24-26μm thick copper for through holes and 13-15μm thick copper for blind holes. (6) Dry film: The outer layer pattern of the circuit board after step (5) is processed with film to make the circuit. The PAD near the line is not compensated, while the other sides are compensated one side only. (7) Etching: The circuit board processed in step (6) is placed in the etching solution to etch away the non-circuit copper layer, exposing the circuit part and obtaining the final shaped circuit pattern. The etching solution includes: sulfuric acid 20-30 mL / L, conditioning agent 5-10 g / L, hydrogen peroxide 40-50 mL / L, surfactant 2-4 g / L, ethylene glycol 15-20 g / L, copper ion complexing agent 40-50 g / L, copper surface corrosion inhibitor 6-8 g / L, stabilizer 1-3 g / L, and n-butylamine 1-3 g / L; the conditioning agent includes 4-vinylpyridine homopolymer with N-hydroxysuccinimide end group in a weight ratio of 1:(1.2-1.4):(0.5-0.7), aniline sulfate, and dibromoneopentyl glycol; the copper ion complexing agent includes copper chloride and ethylenediaminetetramethylene in a weight ratio of 1:(0.6-0.8):(1.5-1.7). The copper surface corrosion inhibitor is benzotriazole; the stabilizer includes urea, n-butanol and propylene glycol in a weight ratio of 1:(1.5-1.7):(0.2-0.4); the surfactant includes sodium dodecyl sulfonate, sodium dioctyl succinate sulfonate and a self-made surfactant in a weight ratio of 1:(0.3-0.6):(1.3-1.5); the preparation method of the self-made surfactant includes the following steps: weigh 6-7 parts of C12-14 fatty alcohol and 1 part of boron trifluoride ethyl ether by weight, stir at room temperature for 10-15 min, heat to 50-55℃, add 3.5-4 parts of ethylene glycol diglycidyl ether, and continue to heat to 80-85℃. React at ℃ for 4-6 hours, cool to room temperature, add 5-6 parts of chlorosulfonic acid, react at 45-50℃ for 2-4 hours, cool to room temperature, neutralize with NaOH to pH 8-8.5, distill until crystals appear, dry to obtain the self-made surfactant; (8) Printing ink: Ink is printed on both sides of the etched circuit board substrate, and the ink is formed into an ink layer by a process of pre-baking and exposure. (9) Surface treatment: After the ink is printed, the circuit board is subjected to AOI inspection of the outer layer circuit, photosensitive solder resist, and thermosetting text in sequence. (10) The molding, electrical testing, FQC and laser drilling of the acoustic holes on the cavity are carried out in sequence to obtain the large back cavity circuit board.

2. The processing method of the large back cavity circuit board according to claim 1, characterized in that, The preparation method of 4-vinylpyridine homopolymer with N-hydroxysuccinimide end group includes the following steps: (1) by weight, 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 under nitrogen protection, the mixture is subjected to freezing-vacuuming-thawing repeated 2-6 times, and then placed in an oil bath at 70-75℃ for 18-20h. The product is precipitated with diethyl ether and dried under vacuum to obtain 4-vinylpyridine homopolymer with dodecyl trithiocarbonate end group; (2) under nitrogen protection, 1 part of 4-vinylpyridine homopolymer with dodecyl trithiocarbonate end group, 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. 0.08 parts of n-hexylamine, 0.015-0.016 parts of methylpyrazole phosphate and 4-6 parts of tetrahydrofuran were mixed, and the freezing-vacuuming-thawing process was repeated 2-6 times. Then, the mixture was placed in a water bath at 25-30°C for 4-6 hours. The product was precipitated with diethyl ether and dried under vacuum to obtain a 4-vinylpyridine homopolymer with thiol end groups. (3) Under nitrogen protection, 1 part of 4-vinylpyridine homopolymer with thiol end groups, 0.25-0.27 parts of N-acryloyloxysuccinimide, 0.15-0.18 parts of triethylamine and 5-7 parts of tetrahydrofuran were mixed, and the freezing-vacuuming-thawing process was repeated 2-6 times. Then, the mixture was placed in a water bath at 25-30°C for 25-30 hours. The product was precipitated with diethyl ether and dried under vacuum to obtain a 4-vinylpyridine homopolymer with N-hydroxysuccinimide end groups.

3. The processing method of the large back cavity circuit board according to claim 1, characterized in that, The pressing process consists of six stages: Stage 1: Temperature set at 120-140℃, maintained for 5-7 minutes; pressure set at 1200-1400 kPa, maintained for 4-7 minutes, with vacuum applied; Stage 2: Temperature increased to 140-160℃ within 10 minutes, maintained for 20-30 minutes; pressure set at 2000-2400 kPa, maintained for 20-25 minutes, with vacuum applied; Stage 3: Temperature increased to 150-170℃ within 10 minutes, maintained for 3-6 minutes; pressure set at 3000-3500 kPa, maintained for 8-12 minutes, with vacuum applied; Stage 4: Temperature increased to 180-190℃ within 10 minutes, maintained for 15-17 minutes; pressure set at 3000 kPa... 3500 kPa, maintain for 20-25 minutes, and apply vacuum; Stage 5, temperature set to 160-180℃, maintain for 10-15 minutes; within 10 minutes, reduce pressure to 1000-1200 kPa, maintain for 15-20 minutes, and apply vacuum; Stage 6, within 15 minutes, reduce temperature to 120-130℃, maintain for 8-12 minutes; set pressure to 700-900 kPa, maintain for 15-18 minutes, and apply vacuum.

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

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