A permanganate composition for use in removing solder flux residues from microvias of printed circuit boards and a method for removing solder flux residues from printed circuit boards

Abstract

The application provides a permanganate composition for removing glue residue from micro-holes of a printed circuit board and a method for removing glue residue from the printed circuit board, and relates to the technical field of printed circuit board manufacturing. Raw materials of the permanganate composition for removing glue residue from micro-holes of the printed circuit board include a permanganate, an alkali metal hydroxide, a hyperbranched polyglycerol and water; the mass concentration of the permanganate is 40-70 g / L, the mass concentration of the alkali metal hydroxide is 30-60 g / L, and the mass concentration of the hyperbranched polyglycerol is 0.5-5 g / L. Compared with a conventional linear surfactant which is oxidized and decomposed within 24 hours, the permanganate composition significantly reduces the frequency of tank replacement and the cost of waste liquid treatment.

Description

Technical Field

[0001] This application relates to the field of printed circuit board manufacturing technology, and in particular to a permanganate composition for removing adhesive residue from micropores of printed circuit boards and a method for removing adhesive residue from printed circuit boards. Background Technology

[0002] As electronic products become thinner, lighter, and more integrated, high-density interconnect (HDI) boards and integrated circuit substrates have become mainstream technologies. These high-end circuit boards extensively use micro-blind vias and ultra-high aspect ratio vias to achieve interlayer interconnection. The diameter of micro-blind vias is typically less than 50μm, and the aspect ratio of vias generally exceeds 10:1.

[0003] During the drilling process of multilayer boards, the high temperature generated by the friction between the drill bit and the resin substrate causes the epoxy resin at the hole wall to melt, forming adhesive residue. This residue covers the surface of the inner copper ring. If it is not thoroughly removed, the electroplated copper layer cannot form a reliable connection with the inner copper ring during subsequent hole metallization, resulting in open circuit failure. Therefore, removing adhesive residue is an indispensable and critical step before hole metallization.

[0004] Currently, the industry widely uses the alkaline permanganate method for removing epoxy resin residue. This process utilizes the strong oxidizing properties of potassium permanganate or sodium permanganate under high-temperature, strongly alkaline conditions to oxidize and decompose the epoxy resin whose pore walls have swelled. However, existing technologies have the following drawbacks when treating micropores: First, traditional permanganate solutions have a high surface tension (typically 70–80 mN / m), making it difficult to effectively wet micropores with a pore size less than 50 μm and a depth-to-diameter ratio greater than 8:1. Because the solution cannot fully penetrate to the bottom of the pore, uneven resin etching occurs within the pores, often resulting in no etching at the bottom or residual resin residue on the pore walls.

[0005] Second, the reaction rate of the existing chemical solution varies significantly at different locations within the hole. In the orifice region, the turbulence intensity of the chemical solution is high and the exchange rate is fast. The oxidation reaction rate of permanganate on the resin is much higher than in the center region of the hole, resulting in excessive etching of the resin at the orifice and the formation of a trumpet-shaped defect. At the same time, the inner copper ring shrinks inward due to excessive lateral etching, which seriously affects the reliability of subsequent electroplating.

[0006] Third, to improve wettability, some existing technologies attempt to add conventional surfactants, such as polyethylene glycol and alkylphenol polyoxyethylene ethers. However, these linear surfactants are extremely unstable in high-temperature, high-alkali, and strong oxidizing environments, and are usually oxidized and decomposed within 24 hours of operation, resulting in short tank life, high tank replacement frequency, and increased production costs.

[0007] Fourth, existing processes rely on a single method to control the degumming process, typically using only timed soaking to complete the treatment. This lacks effective control over the reaction process within the pores, making it difficult to adapt to the diverse needs of boards with different pore sizes and aspect ratios.

[0008] In summary, developing a permanganate degumming composition and its supporting process that can effectively wet micropores, achieve uniform etching from the pore opening to the bottom, and have long-term stability is a technical problem that urgently needs to be solved in this field. Summary of the Invention

[0009] The purpose of this application is to provide a permanganate composition for removing adhesive residue from micropores of printed circuit boards and a method for removing adhesive residue from printed circuit boards, so as to solve the problems of poor wettability of permanganate adhesive residue removal solution on micropores, uneven etching at the orifice and bottom of the orifice, and insufficient stability of additives in the prior art.

[0010] To achieve the above objectives, the first aspect of this application provides a permanganate composition for removing adhesive residue from micropores of printed circuit boards, the raw materials of which include permanganate, alkali metal hydroxide, hyperbranched polyglycerol and water; The permanganate has a mass concentration of 40-70 g / L, the alkali metal hydroxide has a mass concentration of 30-60 g / L, and the hyperbranched polyglycerol has a mass concentration of 0.5-5 g / L.

[0011] Optionally, the permanganate composition used for removing adhesive residue from microvias of printed circuit boards meets at least one of the following conditions: (1) The permanganate includes sodium permanganate and / or potassium permanganate; (2) The alkali metal hydroxides include potassium hydroxide and / or sodium hydroxide.

[0012] Optionally, the hyperbranched polyglycerol has a number-average molecular weight of 2000-10000 Da and a branching degree ≥0.6; The hyperbranched polyglycerol comprises a three-dimensional dendritic molecular structure with hydroxyl functional groups on its surface.

[0013] Optionally, the raw materials of the permanganate composition for removing adhesive residue from micropores of printed circuit boards also include auxiliary stabilizers; The auxiliary stabilizers include sodium silicate and / or phosphonates; The mass concentration of the auxiliary stabilizer is 0.1-1 g / L.

[0014] A second aspect of this application provides a method for removing adhesive residue from a printed circuit board, comprising: The drilled printed circuit board is placed in a swelling agent for swelling treatment to obtain a swollen printed circuit board. The expanded printed circuit board is placed in a desmearing working solution for desmearing treatment to obtain a desmeared printed circuit board. The printed circuit board after removing the adhesive residue is placed in a neutralizing agent for neutralization treatment to obtain the treated printed circuit board. The descaling working solution includes the permanganate composition used for descaling micropores in printed circuit boards.

[0015] Optionally, the method for removing adhesive residue from printed circuit boards satisfies at least one of the following conditions: (1) The leavening agent includes at least one of diethylene glycol monobutyl ether, ethylene glycol phenyl ether and N-methylpyrrolidone; (2) The neutralizing agent includes at least one of hydroxylamine sulfate, oxalic acid and citric acid; (3) The surface tension of the degumming working fluid is 30-35 mN / m.

[0016] Optionally, the method for removing adhesive residue from printed circuit boards satisfies at least one of the following conditions: (1) The temperature of the bulking treatment is 70-85℃ and the time is 5-10 min; (2) The temperature for the degumming treatment is 70-85℃ and the time is 5-15 min; (3) The temperature of the neutralization treatment is 40-50℃ and the time is 3-8min.

[0017] Optionally, the degumming treatment includes a first degumming treatment and a second degumming treatment performed sequentially; the temperature of the first degumming treatment is 70-75℃ and the time is 2-4 min; the temperature of the second degumming treatment is 80-85℃ and the time is 4-10 min.

[0018] Optionally, during the degumming process, periodic pressure pulses are applied. The periodic pressure pulses have a pulse frequency of 0.5-2 Hz, a pressure difference of 0.1-0.3 MPa, a pulse waveform of sine wave or square wave, and a duty cycle of 40%-60%.

[0019] The method for removing adhesive residue from printed circuit boards meets at least one of the following conditions: (1) When the micropore diameter in the expanded printed circuit board is ≤50μm, the pulse frequency is 1.5-2 Hz; when the micropore diameter in the expanded printed circuit board is greater than 50μm and less than 80μm, the pulse frequency is 1.0-1.5 Hz; when the micropore diameter in the expanded printed circuit board is ≥80μm, the pulse frequency is 0.5-1.0 Hz. (2) When the hole depth-to-diameter ratio in the expanded printed circuit board is <8:1, the pressure difference is 0.1-0.15 MPa; when the hole depth-to-diameter ratio in the expanded printed circuit board is between 8 and 12:1, the pressure difference is 0.15-0.25 MPa; when the hole depth-to-diameter ratio in the expanded printed circuit board is >12:1, the pressure difference is 0.25-0.3 MPa.

[0020] Compared with the prior art, the beneficial effects of this application include: The permanganate composition for removing adhesive residue from micropores in printed circuit boards provided in this application uses hyperbranched polyglycerol as a wetting agent, which can reduce the surface tension of the permanganate working solution from 70-80 mN / m in traditional solutions to 30-35 mN / m, significantly improving its wetting ability in micropores. Hyperbranched polyglycerol possesses unique "adaptive" molecular conformational change characteristics. In the high-shear region at the orifice, the molecular chains stretch and align at high flow rates, forming a dynamic protective layer that slows down the oxidation rate of the resin at the orifice by the adhesive residue removal working solution. In the low-shear region at the bottom of the orifice, the molecules are coiled into spherical shapes, resulting in low resistance to diffusion of the adhesive residue removal working solution. The three-dimensional dendritic structure of hyperbranched polyglycerol gives it excellent chemical stability in high-temperature, strong alkaline, and strong oxidizing environments. Compared to conventional linear surfactants, which are oxidized and decomposed within 24 hours, this significantly reduces the frequency of tank changes and waste liquid treatment costs.

[0021] The method for removing adhesive residue from printed circuit boards provided in this application is applicable to the removal of adhesive residue from various types of circuit boards, from conventional multilayer boards to high-end HDI boards and IC carrier boards, and has wide process adaptability. Attached Figure Description

[0022] To more clearly illustrate the technical solutions of the embodiments of this application, the accompanying drawings used in the embodiments will be briefly described below. It should be understood that the following drawings only show some embodiments of this application and should not be regarded as a limitation on the scope of this application.

[0023] Figure 1 This is a photograph of the material to be processed provided in Example 1; Figure 2 This is a physical image of the processed sheet material provided in Example 1. Detailed Implementation

[0024] During the research and development process, those skilled in the art generally hold a technical bias, believing that permanganate will rapidly decompose under high temperature (≥70℃), high alkalinity (pH>13), and strong oxidizing conditions, making it impossible for any organic additive to exist stably for a long time. Therefore, the industry usually avoids adding organic polymers or only adds inorganic salts. This application overcomes the above-mentioned technical bias and discovers that hyperbranched polyglycerol with a specific three-dimensional dendritic structure, due to its highly branched molecular backbone and dense terminal hydroxyl groups, can resist the strong oxidizing attack of permanganate and maintain its structural integrity in harsh environments, thus solving the long-standing technical obstacle that organic additives cannot be used for long-term application in degumming slag solutions. At the same time, conventional linear surfactants (such as polyethylene glycol and alkylphenol polyoxyethylene ethers) are prone to main chain breakage under strong oxidizing environments, while the unique spherical conformation of hyperbranched polyglycerol hinders its oxidative degradation pathway and significantly improves its stability. This discovery cannot be expected through simple substitution or conventional experiments.

[0025] First, the solution provided in this application will be explained in more detail as follows: The first aspect of this application provides a permanganate composition for removing adhesive residue from micropores of printed circuit boards, the raw materials of which include permanganate, alkali metal hydroxide, hyperbranched polyglycerol and water; The permanganate has a mass concentration of 40-70 g / L, the alkali metal hydroxide has a mass concentration of 30-60 g / L, and the hyperbranched polyglycerol has a mass concentration of 0.5-5 g / L.

[0026] Optionally, the mass concentration of permanganate can be any value between 40 g / L, 45 g / L, 50 g / L, 55 g / L, 60 g / L, 65 g / L, 70 g / L, or 40-70 g / L; the mass concentration of alkali metal hydroxide can be any value between 30 g / L, 35 g / L, 40 g / L, 45 g / L, 50 g / L, 55 g / L, 60 g / L, or 30-60 g / L; and the mass concentration of hyperbranched polyglycerol can be any value between 0.5 g / L, 1 g / L, 1.5 g / L, 2 g / L, 2.5 g / L, 3 g / L, 3.5 g / L, 4 g / L, 4.5 g / L, 5 g / L, or 0.5-5 g / L.

[0027] In some embodiments, the permanganate composition for removing adhesive residue from micropores of printed circuit boards satisfies at least one of the following conditions: (1) The permanganate includes sodium permanganate and / or potassium permanganate; Preferably, the permanganate includes sodium permanganate; It should be noted that sodium permanganate, due to its higher solubility and lower impurity content, is beneficial in reducing sedimentation in the bath solution. (2) The alkali metal hydroxides include potassium hydroxide and / or sodium hydroxide.

[0028] In some embodiments, the hyperbranched polyglycerol has a number-average molecular weight of 2000-10000 Da and a branching degree ≥0.6; Optionally, the number-average molecular weight of hyperbranched polyglycerol can be any value between 2000 Da, 3000 Da, 4000 Da, 5000 Da, 6000 Da, 7000 Da, 8000 Da, 9000 Da, 10000 Da, or 2000-10000 Da, and the degree of branching can be any value between 0.65, 0.7, 0.8, 0.9, or >0.6. The hyperbranched polyglycerol comprises a three-dimensional dendritic molecular structure with hydroxyl functional groups on its surface.

[0029] It is worth noting that, compared with conventional linear surfactants, hyperbranched polyglycerol has excellent chemical stability under high temperature and strong alkaline conditions. After continuous operation for 96 hours at 80℃, with a NaOH concentration of 50 g / L and a sodium permanganate concentration of 50 g / L, its molecular structure remains intact with a residual rate of ≥85%.

[0030] In some embodiments, the raw materials of the permanganate composition for removing adhesive residue from micropores of printed circuit boards further include auxiliary stabilizers; The auxiliary stabilizers include sodium silicate and / or phosphonates; The mass concentration of the auxiliary stabilizer is 0.1-1 g / L.

[0031] Optionally, the mass concentration of the auxiliary stabilizer can be any value between 0.1 g / L, 0.2 g / L, 0.3 g / L, 0.4 g / L, 0.5 g / L, 0.6 g / L, 0.7 g / L, 0.8 g / L, 0.9 g / L, 1 g / L, or 0.1-1 g / L.

[0032] It is important to note that the role of the auxiliary stabilizer is to inhibit the non-specific adsorption of hyperbranched polyglycerol on the metal surface of the equipment, ensuring that the hyperbranched polyglycerol maintains an effective concentration in the liquid solution (the working solution for removing sludge).

[0033] A second aspect of this application provides a method for removing adhesive residue from a printed circuit board, comprising: The drilled printed circuit board is placed in a swelling agent for swelling treatment to obtain a swollen printed circuit board. The expanded printed circuit board is placed in a desmearing working solution for desmearing treatment to obtain a desmeared printed circuit board. The printed circuit board after removing the adhesive residue is placed in a neutralizing agent for neutralization treatment to obtain the treated printed circuit board. The descaling working solution includes the permanganate composition used for descaling micropores in printed circuit boards.

[0034] In some embodiments, the method for removing adhesive residue from printed circuit boards satisfies at least one of the following conditions: (1) The leavening agent includes at least one of diethylene glycol monobutyl ether, ethylene glycol phenyl ether and N-methylpyrrolidone; (2) The neutralizing agent includes at least one of hydroxylamine sulfate, oxalic acid and citric acid; (3) The surface tension of the degumming working fluid is 30-35 mN / m.

[0035] Optionally, the surface tension of the descaling working fluid can be any value between 30 mN / m, 31 mN / m, 32 mN / m, 33 mN / m, 34 mN / m, 35 mN / m, or 30-35 mN / m.

[0036] In some embodiments, after the descaling working fluid has been running continuously for 96 hours, the residual rate of hyperbranched polyglycerol remains above 85%, and the service life of the bath is extended by more than 4 times. Furthermore, in the descaling treatment, the inner copper ring can be protected because excessive etching of the orifice is effectively suppressed, and the lateral etching of the inner copper ring is reduced from more than 8μm in the traditional process to about 2μm, effectively preventing reliability risks caused by shrinkage of the inner pad.

[0037] It should be noted that, in some embodiments, for microblind holes with a pore size of 50 μm and a depth-to-diameter ratio of 10:1, the complete wetting time of the solution (removing adhesive residue working solution) provided in this application is shortened by more than 80% compared with traditional solutions.

[0038] In some embodiments, the method for removing adhesive residue from printed circuit boards satisfies at least one of the following conditions: (1) The temperature of the bulking treatment is 70-85℃ and the time is 5-10 min; Optionally, the temperature of the bulking treatment can be any value between 70℃, 75℃, 80℃, 85℃ or 70-85℃, and the time can be any value between 5min, 6min, 7min, 8min, 9min, 10min or 5-10min. (2) The temperature for the degumming treatment is 70-85℃ and the time is 5-15 min; Optionally, the temperature for removing adhesive residue can be any value between 70℃, 75℃, 80℃, 85℃ or 70-85℃, and the time can be any value between 5min, 6min, 7min, 8min, 9min, 10min, 11min, 12min, 13min, 14min, 15min or 5-15min. (3) The temperature of the neutralization treatment is 40-50℃ and the time is 3-8min.

[0039] Optionally, the neutralization temperature can be any value between 40°C, 45°C, 50°C or 40-50°C, and the time can be any value between 3 min, 4 min, 5 min, 6 min, 7 min, 8 min or 3-8 min.

[0040] In some embodiments, the degumming treatment includes a first degumming treatment and a second degumming treatment performed sequentially; the temperature of the first degumming treatment is 70-75°C and the time is 2-4 min; the temperature of the second degumming treatment is 80-85°C and the time is 4-10 min.

[0041] Optionally, the temperature of the first degumming treatment can be any value between 70℃, 71℃, 72℃, 73℃, 74℃, 75℃ or 70-75℃, and the time can be any value between 2 min, 3 min, 4 min or 2-4 min; the temperature of the second degumming treatment can be any value between 80℃, 81℃, 82℃, 83℃, 84℃, 85℃ or 80-85℃, and the time can be any value between 4 min, 5 min, 6 min, 7 min, 8 min, 9 min, 10 min or 4-10 min.

[0042] It should be noted that the first degumming treatment stage mainly utilizes the low surface tension of hyperbranched polyglycerol to achieve full wetting of micropores; the high temperature of the second degumming treatment promotes the oxidation reaction rate of permanganate, achieving effective etching of the resin on the pore walls.

[0043] In some embodiments, periodic pressure pulses are applied during the degumming process. The periodic pressure pulses have a pulse frequency of 0.5-2 Hz, a pressure difference of 0.1-0.3 MPa, a sine wave or square wave waveform, and a duty cycle of 40%-60%.

[0044] Optionally, the pulse frequency of the periodic pressure pulse can be any value between 0.5 Hz, 1 Hz, 1.5 Hz, 2 Hz or 0.5-2 Hz, the pressure difference can be any value between 0.1 MPa, 0.2 MPa, 0.3 MPa or 0.1-0.3 MPa, and the duty cycle can be any value between 40%, 45%, 50%, 55%, 60% or 40-60%.

[0045] It is important to note that the pulse waveform should be either a sine wave or a square wave. A sine wave is beneficial for achieving a smooth transition in the flow of the liquid (de-gumming working fluid) and is suitable for thin plates with small pore sizes that are sensitive to impact. A square wave provides a steeper pressure change and generates a stronger "impact-back suction" effect, which is beneficial for carrying out the reaction products at the bottom of the pore. The duty cycle should be controlled at 40%-60% to ensure a balanced time distribution between the pressure peak and trough values, which ensures that the liquid (de-gumming working fluid) fully enters the pore while allowing sufficient time for the reaction products to be discharged from the pore.

[0046] The adhesive residue removal process, combined with the "impact-back suction" effect of periodic pressure pulses, effectively promotes the exchange and renewal of the chemical solution within the holes, making the etching depth from the hole opening to the bottom more consistent. Experimental data shows that after adopting the adhesive residue removal method for printed circuit boards of this application, the etching depth ratio between the hole bottom and the hole opening is increased from 0.15 in the traditional process to over 0.90.

[0047] In some embodiments, the method for removing adhesive residue from printed circuit boards satisfies at least one of the following conditions: (1) When the pore size of the micropores in the expanded printed circuit board is ≤50μm, the pulse frequency is 1.5-2 Hz; Optionally, when the pore size of the micropores in the expanded printed circuit board is any value of 1μm, 10μm, 20μm, 30μm, 40μm, 50μm or ≤50μm, the pulse frequency can be any value between 1.5 Hz, 1.6 Hz, 1.7 Hz, 1.8 Hz, 1.9 Hz, 2 Hz or 1.5-2 Hz; When the pore size of the micropores in the expanded printed circuit board is greater than 50μm and less than 80μm, the pulse frequency is 1.0-1.5 Hz; Optionally, when the pore size of the micropores in the expanded printed circuit board is 55μm, 60μm, 65μm, 70μm, 75μm or greater than 50μm and less than 80μm, the pulse frequency can be any value between 1 Hz, 1.1 Hz, 1.2 Hz, 1.3 Hz, 1.4 Hz, 1.5 Hz or 1-1.5 Hz; When the pore size of the micropores in the expanded printed circuit board is ≥80μm, the pulse frequency is 0.5-1.0 Hz; Optionally, when the pore size of the micropores in the expanded printed circuit board is any value of 80μm, 90μm, 100μm, 110μm, 120μm, 150μm, 200μm or ≥80μm, the pulse frequency can be any value between 0.5 Hz, 0.6 Hz, 0.7 Hz, 0.8 Hz, 0.9 Hz, 1 Hz or 0.5-1 Hz; It is important to note that the pulse frequency setting is negatively correlated with the micropore diameter of the expanded printed circuit board and positively correlated with the hole depth. Higher pulse frequencies help overcome capillary resistance within the micropores and promote the permanganate composition used for removing adhesive residue from the micropores of printed circuit boards to enter the bottom area of ​​the hole. (2) When the hole depth-to-diameter ratio in the expanded printed circuit board is <8:1, the pressure difference is 0.1-0.15 MPa; when the hole depth-to-diameter ratio in the expanded printed circuit board is between 8 and 12:1, the pressure difference is 0.15-0.25 MPa; when the hole depth-to-diameter ratio in the expanded printed circuit board is >12:1, the pressure difference is 0.25-0.3 MPa.

[0048] Optionally, when the hole depth-to-diameter ratio in the expanded printed circuit board is <8:1, the pressure difference can be any value between 0.1 MPa, 0.11 MPa, 0.12 MPa, 0.13 MPa, 0.14 MPa, 0.15 MPa, or 0.1-0.15 MPa; when the hole depth-to-diameter ratio in the expanded printed circuit board is between 8 and 12:1, the pressure difference can be any value between 0.15 MPa, 0.2 MPa, 0.25 MPa, or 0.15-0.25 MPa; when the hole depth-to-diameter ratio in the expanded printed circuit board is >12:1, the pressure difference can be any value between 0.25 MPa, 0.26 MPa, 0.27 MPa, 0.28 MPa, 0.29 MPa, 0.3 MPa, or 0.25-0.3 MPa.

[0049] It is important to note that the pressure differential setting is positively correlated with the aspect ratio of the expanded printed circuit board; a larger pressure differential provides a stronger driving force for the exchange of permanganate composition used for removing adhesive residue from the micropores of the printed circuit board, ensuring effective renewal of the solution (adhesive residue removal working fluid) in high aspect ratio pores.

[0050] It is also important to note the synergistic effect of the working fluid and pressure pulse parameters in removing slag: This application combines hyperbranched polyglycerol with periodic pressure pulses, generating a synergistic effect driven by both chemical and physical processes. Specifically, hyperbranched polyglycerol reduces the surface tension of the working fluid to 30-35 mN / m, allowing the solution to spontaneously enter the micropores. However, it is difficult to achieve rapid renewal of the high aspect ratio region within the pore under static or low flow conditions. Periodic pressure pulses, through an "impact-reabsorption" effect, force periodic exchange of the solution within the pores. More importantly, hyperbranched polyglycerol molecules possess "adaptive" conformational change characteristics—in the high-shear / high-flow-rate region at the pore opening (pulse high-pressure stage), the molecular chains stretch and align to form a dynamic protective layer, mitigating excessive etching at the pore opening; in the low-shear region at the pore bottom, the molecules coil into spherical shapes, reducing the resistance to solution diffusion. This synergy increases the etching depth ratio from the pore opening to the pore bottom from 0.15 in traditional processes to over 0.90. Furthermore, the matching of pulse parameters (frequency, pressure difference) with the low surface tension of the degumming working fluid maximizes the exchange efficiency of the chemical solution within the high aspect ratio pores (≥12:1), achieving a 100% permeability. Comparative experiments (Comparative Example 3) demonstrate that even with the same composition, without pulse application, the bottom / mouth etching depth ratio is only 0.42; while with conventional compositions, even with pulse application (similar to Comparative Example 1), the uniformity remains poor due to excessively high surface tension and the lack of adaptive molecular protection. Therefore, the degumming working fluid and the specific pressure pulse process of this application constitute a non-obvious synergistic technical solution.

[0051] The implementation schemes of this application will be described in detail below with reference to specific embodiments. However, those skilled in the art will understand that the following embodiments are only for illustrating this application and should not be regarded as limiting the scope of this application. Unless otherwise specified in the embodiments, conventional conditions or conditions recommended by the manufacturer shall apply. Reagents or instruments used without specified manufacturers are all conventional products that can be purchased commercially.

[0052] Example 1 The first aspect of this embodiment provides a permanganate composition for removing adhesive residue from micropores of printed circuit boards, which, by weight-volume concentration, has the following composition: Sodium permanganate: 50 g / L, sodium hydroxide: 45 g / L, hyperbranched polyglycerol: 2 g / L (number average molecular weight 5000 Da, degree of branching 0.65), sodium silicate: 0.3 g / L, balance: deionized water.

[0053] Among them, hyperbranched polyglycerol is prepared by glycidyl ring-opening polymerization, and its three-dimensional dendritic structure contains dense hydroxyl functional groups on its surface.

[0054] The above raw materials are mixed and stirred until completely homogeneous to obtain a permanganate composition (i.e., desmearing working solution) for removing adhesive residue from micropores of printed circuit boards, with a surface tension of 33 mN / m.

[0055] The second aspect of this embodiment provides a method for removing adhesive residue from a printed circuit board. The board to be treated is a 12-layer high-end HDI board with micro-blind vias having a diameter of 45μm, a depth-to-diameter ratio of 9:1, and a through-hole aspect ratio of 12:1. The specific steps are as follows: (1) Soaking: Place the board in a soaking agent (ethylene glycol monobutyl ether) and treat at 80°C for 8 minutes; (2) Removal of adhesive residue: The board is placed in the adhesive residue removal working solution. Two-stage temperature control is adopted. In the first stage, the board is treated at 72°C for 3 minutes. At this time, the circulation pump is turned off and the working solution is allowed to stand. The low surface tension of the solution is used to achieve natural wetting of the micropores. In the second stage, the temperature is raised to 82°C, the circulation pump is turned on and periodic pressure pulses are applied. The treatment time is 8 minutes. The pressure pulse parameters are set as follows: pulse frequency 1.8 Hz, pressure difference 0.22 MPa, sine waveform, duty cycle 50%. (3) Neutralization: Place the board in the neutralizing agent and treat at 45°C for 5 minutes; (4) Wash and dry to obtain the treated board.

[0056] After processing using the above process, the cross-section of the micro-blind holes was observed under a scanning electron microscope after the processed plate was cut. The results showed that the etching depth at the hole opening was 3.2 μm, the etching depth at the bottom of the hole was 2.9 μm, and the etching depth ratio of the bottom of the hole to the hole opening was 0.91; the side etching amount of the inner copper ring was 2.0 μm; the hole wall roughness was uniform, there was no residual adhesive, and the through hole penetration rate was 100%.

[0057] Actual photos of the boards to be treated (without glue residue removed) are shown below. Figure 1 As shown in the image, a photograph of the processed board is shown below. Figure 2 As shown.

[0058] Example 2 The difference between this embodiment and Embodiment 1 is that the board to be processed is a conventional 8-layer multilayer board with a through-hole diameter of 0.3 mm and a depth-to-diameter ratio of 6:1. The pressure pulse parameters are adjusted as follows: pulse frequency 0.8 Hz, pressure difference 0.12 MPa, square waveform, and duty cycle 50%.

[0059] Treatment results: The etching depth at the orifice was 3.5 μm, the etching depth at the bottom of the orifice was 3.2 μm, and the etching depth ratio at the bottom of the orifice was 0.91; the lateral etching amount of the inner copper ring was 1.8 μm; the orifice wall was clean and free of residual adhesive.

[0060] Example 3 The difference between this embodiment and Example 1 is that the amount of hyperbranched polyglycerol added is 0.8 g / L, and the surface tension of the working fluid is measured to be 35 mN / m. The pressure pulse parameters are set as follows: pulse frequency 1.5 Hz, pressure difference 0.18 MPa, sine waveform, and duty cycle 55%.

[0061] Treatment results: The etching depth at the orifice was 3.6 μm, the etching depth at the bottom of the orifice was 2.8 μm, and the etching depth ratio at the bottom of the orifice was 0.78; the lateral etching amount of the inner copper ring was 2.8 μm.

[0062] Compared to Example 1, the uniformity is slightly reduced but still significantly better than the conventional process.

[0063] Example 4 This embodiment uses the composition of Example 1, but no periodic pressure pulses are applied during the removal of adhesive residue; only conventional circulating soaking treatment is used.

[0064] Processing results: The etching depth at the orifice was 3.8 μm, the etching depth at the bottom of the orifice was 1.6 μm, and the etching depth ratio at the bottom of the orifice was 0.42; the lateral etching of the inner copper ring was 3.5 μm; and the permeability of the through hole was 82%.

[0065] Comparative Example 1 The difference from Example 1 is that this comparative example uses a traditional potassium permanganate descaling solution with the following composition: 60 g / L potassium permanganate and 50 g / L sodium hydroxide, without adding any wetting agent. No pressure pulses are applied during the descaling process; conventional soaking treatment is used.

[0066] Processing results: The etching depth at the orifice was 5.2 μm, the etching depth at the bottom of the orifice was 0.8 μm, and the etching depth ratio at the bottom of the orifice was 0.15; the lateral etching of the inner copper ring was 8.5 μm; and the permeability of the through hole was only 65%.

[0067] Comparative Example 2 The difference from Example 1 is that this comparative example uses conventional linear surfactant polyethylene glycol (PEG-6000) instead of hyperbranched polyglycerol, with an addition amount of 2 g / L. Other components and process parameters are the same as in Example 1.

[0068] Treatment results: The initial surface tension of the working solution was 45 mN / m. After 24 hours of operation, the surface tension rebounded to 68 mN / m, indicating that the solution had failed. The test results for the treated plates within 24 hours were as follows: etching depth at the orifice was 4.5 μm, etching depth at the bottom of the orifice was 1.5 μm, and the ratio of bottom to orifice etching depth was 0.33; the lateral etching depth of the inner copper ring was 6.2 μm.

[0069] Comparative Example 3 The difference from Example 1 is that no alkali metal hydroxide is added to the permanganate composition used for removing adhesive residue from micropores of printed circuit boards.

[0070] Comparative Example 4 The difference from Example 1 is that the permanganate composition used for removing adhesive residue from micropores of printed circuit boards does not contain hyperbranched polyglycerol.

[0071] Comparative Example 5 The difference from Example 1 is that the mass concentration of permanganate is 25 g / L, the mass concentration of alkali metal hydroxide is 20 g / L, and the mass concentration of hyperbranched polyglycerol is 0.3 g / L.

[0072] The comparison of the degumming effects of the above embodiments and comparative examples is summarized in Table 1.

[0073] Table 1 Effect of removing adhesive residue

[0074] As shown in Table 1, this application significantly improves the uniform etching ability of permanganate solution on micropores through the synergistic effect of hyperbranched polyglycerol and periodic pressure pulses. Examples 1 and 2 achieved an excellent etching depth ratio of 0.91 at the bottom of the hole to the opening of the hole, with the lateral etching amount of the inner copper ring controlled within 2 μm, and the permeability of the 12:1 high aspect ratio through-holes reaching 100%. Although Example 4 uses the permanganate composition for removing adhesive residue from micropores of printed circuit boards provided in this application, there is still a significant difference in uniformity and permeability without the pressure pulse process. Comparative Example 1 shows that traditional solutions cannot effectively treat micropores; Comparative Example 2 shows that conventional surfactants have poor stability and limited improvement in uniformity.

[0075] The difference between Comparative Example 3 and Example 1 is that no alkali metal hydroxide is added. At this time, the solution is weakly alkaline and cannot effectively expand and oxidize the epoxy resin. Although the hyperbranched polyglycerol still maintains the surface tension at 33 mN / m, the etching depth at the orifice is only 0.5 μm and the etching depth at the bottom of the orifice is 0.1 μm, which is basically ineffective in removing glue residue. In Comparative Example 4, without the addition of hyperbranched polyglycerol, the surface tension of the working fluid rose to 72 mN / m. Despite the application of the same periodic pressure pulses, the pore mouth etching depth reached 4.8 μm while the pore bottom etching depth was only 1.0 μm due to the inability of the solution to effectively wet the micropores and the lack of adaptive molecular protection. The pore bottom / pore mouth etching ratio was only 0.21, and the porosity was 68%. In Comparative Example 5, the concentrations of permanganate (25 g / L) and alkali metal hydroxide (20 g / L) were both lower than the lower limits of this application, resulting in significantly insufficient oxidation capacity of the degumming working solution, which could not effectively erode the expanded epoxy resin on the pore walls. At the same time, the concentration of hyperbranched polyglycerol (0.3 g / L) was also lower than the lower limit of 0.5 g / L, and the surface tension of the working solution only dropped to 46 mN / m, which was much higher than the 30-35 mN / m achieved in the examples of this application. The micropore wettability was poor, and the low content of hyperbranched polyglycerol made it difficult to form an effective dynamic protective layer in the high shear area of ​​the pore opening. This resulted in a large difference between the pore opening erosion depth (2.2 μm) and the pore bottom erosion depth (0.9 μm), with a pore bottom / pore opening erosion depth ratio of only 0.41 and poor uniformity. In addition, due to insufficient alkalinity, the permanganate decomposition rate was slowed down, and the effective life of the bath solution was extended to 72 hours, but the overall degumming effect (pore penetration rate of only 72%) was far from meeting the production requirements. This comparative example shows that the concentrations of each component need to work synergistically within the range defined in this application in order to achieve excellent microporous descaling performance. If the concentration of any key component is too low, the overall effect will be significantly degraded.

[0076] This application also conducted stability tests on hyperbranched polyglycerol, as detailed below: The permanganate composition for removing adhesive residue from micropores of printed circuit boards described in Example 1 was subjected to an aging test at 85°C with continuous operation of a circulating pump. Samples were taken at 24, 48, 72, and 96 hours to determine the sodium permanganate concentration and the residual rate of hyperbranched polyglycerol. The sodium permanganate concentration was determined by redox titration, and the residual rate of hyperbranched polyglycerol was determined by gel permeation chromatography to measure the peak area change.

[0077] Test results: Initial concentration: Sodium permanganate 50.2 g / L, hyperbranched polyglycerol relative content 100%; 24 hours: Sodium permanganate concentration 49.8 g / L, residual hyperbranched polyglycerol 97%; 48 hours: Sodium permanganate concentration 48.5 g / L, residual hyperbranched polyglycerol 92%; 72 hours: Sodium permanganate concentration 46.2 g / L, residual hyperbranched polyglycerol 88%; 96 hours: Sodium permanganate concentration 43.5 g / L, hyperbranched polyglycerol residue rate 85%.

[0078] The results show that the permanganate composition for removing adhesive residue from micropores of printed circuit boards provided in this application still maintains a hyperbranched polyglycerol residual rate of over 85% after 96 hours of continuous operation, which is much higher than that of conventional surfactants (which completely decompose within 24 hours), demonstrating its excellent stability.

[0079] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of this application, and are not intended to limit them. Although this application has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features therein. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of this application.

[0080] Furthermore, those skilled in the art will understand that although some embodiments herein include certain features included in other embodiments but not others, combinations of features from different embodiments are intended to be within the scope of this application and form different embodiments. For example, any of the claimed embodiments can be used in any combination. The information disclosed in this background section is intended only to enhance the understanding of the general background of this application and should not be construed as an admission or in any way implying that such information constitutes prior art known to those skilled in the art.

Claims

1. A permanganate composition for removing adhesive residue from micropores of printed circuit boards, characterized in that, Its raw materials include permanganate, alkali metal hydroxide, hyperbranched polyglycerol and water; The permanganate has a mass concentration of 40-70 g / L, the alkali metal hydroxide has a mass concentration of 30-60 g / L, and the hyperbranched polyglycerol has a mass concentration of 0.5-5 g / L.

2. The permanganate composition for removing adhesive residue from micropores of printed circuit boards according to claim 1, characterized in that, At least one of the following conditions must be met: (1) The permanganate includes sodium permanganate and / or potassium permanganate; (2) The alkali metal hydroxides include potassium hydroxide and / or sodium hydroxide.

3. The permanganate composition for removing adhesive residue from micropores of printed circuit boards according to claim 1, characterized in that, The hyperbranched polyglycerol has a number-average molecular weight of 2000-10000 Da and a branching degree ≥0.6; The hyperbranched polyglycerol comprises a three-dimensional dendritic molecular structure with hydroxyl functional groups on its surface.

4. The permanganate composition for removing adhesive residue from micropores of printed circuit boards according to claim 1, characterized in that, The raw materials of the permanganate composition for removing adhesive residue from micropores of printed circuit boards also include auxiliary stabilizers; The auxiliary stabilizers include sodium silicate and / or phosphonates; The mass concentration of the auxiliary stabilizer is 0.1-1 g / L.

5. A method for removing adhesive residue from printed circuit boards, characterized in that, include: The drilled printed circuit board is placed in a swelling agent for swelling treatment to obtain a swollen printed circuit board. The expanded printed circuit board is placed in a desmearing working solution for desmearing treatment to obtain a desmeared printed circuit board. The printed circuit board after removing the adhesive residue is placed in a neutralizing agent for neutralization treatment to obtain the treated printed circuit board. The descaling working solution includes the permanganate composition for removing descaling from micropores of printed circuit boards as described in any one of claims 1-4.

6. The method for removing adhesive residue from printed circuit boards according to claim 5, characterized in that, At least one of the following conditions must be met: (1) The leavening agent includes at least one of diethylene glycol monobutyl ether, ethylene glycol phenyl ether and N-methylpyrrolidone; (2) The neutralizing agent includes at least one of hydroxylamine sulfate, oxalic acid and citric acid; (3) The surface tension of the degumming working fluid is 30-35 mN / m.

7. The method for removing adhesive residue from printed circuit boards according to claim 5, characterized in that, At least one of the following conditions must be met: (1) The temperature of the bulking treatment is 70-85℃ and the time is 5-10 min; (2) The temperature for the degumming treatment is 70-85℃ and the time is 5-15 min; (3) The temperature of the neutralization treatment is 40-50℃ and the time is 3-8min.

8. The method for removing adhesive residue from printed circuit boards according to claim 6, characterized in that, The adhesive residue removal process includes a first adhesive residue removal process and a second adhesive residue removal process performed sequentially; the temperature of the first adhesive residue removal process is 70-75℃ and the time is 2-4 min; the temperature of the second adhesive residue removal process is 80-85℃ and the time is 4-10 min.

9. The method for removing adhesive residue from printed circuit boards according to any one of claims 5-8, characterized in that, During the degumming process, periodic pressure pulses are also applied. The pulse frequency of the periodic pressure pulses is 0.5-2 Hz, the pressure difference is 0.1-0.3 MPa, the pulse waveform is a sine wave or a square wave, and the duty cycle is 40%-60%.

10. The method for removing adhesive residue from printed circuit boards according to claim 9, characterized in that, At least one of the following conditions must be met: (1) When the micropore diameter in the expanded printed circuit board is ≤50μm, the pulse frequency is 1.5-2 Hz; when the micropore diameter in the expanded printed circuit board is greater than 50μm and less than 80μm, the pulse frequency is 1.0-1.5 Hz; when the micropore diameter in the expanded printed circuit board is ≥80μm, the pulse frequency is 0.5-1.0 Hz. (2) When the hole depth-to-diameter ratio in the expanded printed circuit board is <8:1, the pressure difference is 0.1-0.15 MPa; when the hole depth-to-diameter ratio in the expanded printed circuit board is between 8 and 12:1, the pressure difference is 0.15-0.25 MPa; when the hole depth-to-diameter ratio in the expanded printed circuit board is >12:1, the pressure difference is 0.25-0.3 MPa.

Images