Method for removing surface cover film from flexible board copper wiring

Abstract

The present application relates to a kind of flexible plate copper circuit surface covering film removal method, first with single solvent soak softening covering film resin layer, obtain first intermediate state;Then the PI layer of first intermediate state covering film is heat treated, so that PI layer film bubble, delamination, fall off, obtain second intermediate state;Finally, second intermediate state is cleaned, and residual solvent is absorbed, and after drying, third intermediate state is obtained, i.e., finished surface resin layer and PI layer are cleaned, and copper circuit is not damaged;If necessary, ultraviolet laser treatment can be added after obtaining third intermediate state, and the resin remaining on the flexible plate is removed in depth, which provides the possibility for effective failure analysis of flexible plate.

Description

Technical Field

[0001] This invention relates to the field of electronic information development technology, and more specifically, to a method for removing the coating film from the surface of copper circuits on flexible boards. Background Technology

[0002] With the rapid development of the electronic information industry, printed circuit boards (PCBs) play a crucial role as the "foundation" of electronic circuits. Among them, flexible printed circuit boards (FPCs) have become star products in the current electronic industry due to their high wiring density, light weight, thinness, and good bending properties.

[0003] Flexible copper-clad laminates (FCLs) are mainly composed of three categories of materials: insulating base film materials, metal conductor foils, and adhesives. The most widely used insulating base film materials for FCLs are polyester film (PET) and polyimide film (PI); the most widely used metal conductor foils are electrolytic copper foil (ED) and rolled copper foil (RA). During FPC manufacturing, the conductor metal foil is etched into patterns such as copper lines and pads; the most widely used adhesives are mainly divided into two categories: acrylic adhesives and epoxy adhesives.

[0004] The flexible cover film mainly consists of two parts: a surface PI layer and a resin layer underneath the PI layer. Epoxy resin is the most commonly used resin layer. Before lamination, the epoxy resin layer of the cover film is in a semi-cured state. During the lamination process, the PI layer faces outwards, and the resin side is bonded to the flexible circuit board. Under high temperature and pressure, the resin layer melts and flows, bonding with the copper foil circuitry and filling the gaps between the flexible circuits. It then cures at high temperature, firmly adhering to the surface of the flexible circuitry and protecting the copper conductors from oxidation and corrosion. Therefore, once the cover film resin is cured and bonded to the flexible circuitry, it is very difficult to peel off. This is especially true when quality defects occur under the cover film, making failure analysis particularly difficult. The cover film must be removed first, and traditionally, this is done using harsh methods such as open flame burning, which damages the inner copper circuitry and severely affects the "first failure site" of the sample. Summary of the Invention

[0005] Based on this, the purpose of the present invention is to provide a method for removing the cover film with minimal impact on the inner copper circuitry of a flexible board.

[0006] The method for removing the surface coating film of the flexible board copper circuit of the present invention includes:

[0007] The resin layer of the covering film is soaked and softened to obtain the first intermediate state;

[0008] The first intermediate state of the PI film covering layer is heat-treated to obtain the second intermediate state;

[0009] The second intermediate state is cleaned and dried to obtain the third intermediate state.

[0010] In some embodiments, soaking and softening the cover film resin layer includes immersing the flexible plate containing the cover film in a constant-temperature softening agent solution at 40–150°C for 3–60 minutes.

[0011] In some embodiments, the softener is selected from solvents such as ethanolamine, diethanolamine, triethanolamine, butanone, phenol, and methylphenol.

[0012] In some implementations, the plasticizer has a purity of 99% or higher.

[0013] In some implementations, the heat treatment includes blowing the covering film with a hot air gun.

[0014] In some implementations, the hot air gun temperature is 100–350°C, and the purging time is 1–5 minutes.

[0015] In some embodiments, the cleaning process includes ultrasonic cleaning of the second intermediate state with ethanol followed by ultrasonic cleaning with deionized water.

[0016] In some implementations, the ultrasonic cleaning time for ethanol is 3 to 8 minutes, and the ultrasonic cleaning time for deionized water is also 3 to 8 minutes.

[0017] In some embodiments, the method may further include ultraviolet laser treatment of the third intermediate state.

[0018] In some implementations, the wavelength of the ultraviolet laser is 200–500 nm, and the burning time is 150–250 μs / cycle.

[0019] The method for removing the surface coating film of flexible board copper circuits adopted in this application starts from the structure and composition system of the coating film, separates the resin layer and PI layer to obtain the first and second intermediate states, and then obtains the third intermediate state, i.e., the finished product, after cleaning and drying. It uses fewer types and amounts of reagents, is low in cost, highly efficient, and highly operable. The entire operation does not damage the copper circuit and inner layer structure. It is suitable for processing small samples, valuable samples, and unique samples, with a wide range of applications. At the same time, the entire process takes less time and is more efficient, and also ensures the authenticity and effectiveness of the failure analysis of flexible boards. Attached Figure Description

[0020] To more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the specific embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0021] Figure 1 This is a scanning electron microscope image at 2000x magnification after the surface covering film of the flexible board copper circuit in Embodiment 1 of the present invention has been removed.

[0022] Figure 2 This is a scanning electron microscope image at 8000x magnification after the surface covering film of the flexible board copper circuit in Embodiment 1 of the present invention has been removed.

[0023] Figure 3 This is a scanning electron microscope image at 400x magnification after the surface cover film of the flexible board copper circuit in Embodiment 1 of the present invention has been removed.

[0024] Figure 4 This is a scanning electron microscope image at 2000x magnification after the surface covering film of the flexible board copper circuit in Embodiment 1 of the present invention has been removed.

[0025] Figure 5 This is a scanning electron microscope image of the flexible board copper circuit surface after the cover film has been removed in Embodiment 2 of the present invention;

[0026] Figure 6 This is a scanning electron microscope image of the flexible board copper circuit surface after the cover film has been removed in Embodiment 3 of the present invention;

[0027] Figure 7 This is a scanning electron microscope image of the flexible board copper circuit surface after the cover film has been removed in Embodiment 4 of the present invention;

[0028] Figure 8 This is a scanning electron microscope image of the flexible board copper circuit surface after the cover film has been removed in Embodiment 4 of the present invention;

[0029] Figure 9 This is a metallographic microscope image of the flexible board copper circuit surface after the cover film has been removed in Comparative Example 1 of the present invention.

[0030] Figure 10 This is a metallographic microscope image of the flexible board copper circuit surface after the cover film has been removed in Comparative Example 2 of the present invention. Detailed Implementation

[0031] Reference will now be made to detailed embodiments of the present invention, one or more of which are described below. Each example is provided for explanation and not for limitation of the invention. In fact, it will be apparent to those skilled in the art that various modifications and variations can be made to the invention without departing from its scope or spirit. For example, features described or illustrated as part of one embodiment may be used in another embodiment to produce further embodiments.

[0032] Therefore, this invention is intended to cover such modifications and variations falling within the scope of the appended claims and their equivalents. Other objects, features, and aspects of the invention are disclosed in or will be apparent from the following detailed description. It will be understood by those skilled in the art that this discussion is merely a description of exemplary embodiments and is not intended to limit the broader aspects of the invention.

[0033] In this invention, the technical features described in an open-ended manner include both closed-ended technical solutions composed of the listed features and open-ended technical solutions that include the listed features.

[0034] It is understood that the terms “first,” “second,” etc., used in this application may be used herein to describe various elements, but these elements are not limited by these terms. These terms are only used to distinguish one element from another.

[0035] In this invention, numerical ranges are involved. Unless otherwise specified, the numerical ranges are considered continuous and include the minimum and maximum values ​​of the range, as well as every value between the minimum and maximum values. Furthermore, when the range refers to integers, it includes every integer between the minimum and maximum values ​​of the range. Additionally, when multiple ranges are provided to describe features or characteristics, the ranges may be merged. In other words, unless otherwise specified, all ranges disclosed herein should be understood to include any and all subranges to which they are included.

[0036] In this article, when referring to units for data ranges, if the unit is only followed by the right endpoint, it means that the units for the left and right endpoints are the same. For example, 200–500nm means that the units for the left endpoint “200” and the right endpoint “500” are both nm (nanometers).

[0037] This invention provides a method for peeling off a cover film with minimal impact on the inner layer circuitry of a flexible board.

[0038] The method for removing the surface coating film of the flexible board copper circuit of the present invention includes:

[0039] The resin layer of the covering film is soaked and softened to obtain the first intermediate state;

[0040] The PI layer in the first intermediate state is heat-treated to obtain the second intermediate state;

[0041] The second intermediate state is cleaned and dried to obtain the third intermediate state.

[0042] In some embodiments, soaking and softening the cover film resin layer involves immersing the flexible plate containing the cover film in a constant-temperature softening agent solution at 40–150°C for 3–60 minutes. The soaking time is synergistic with temperature; as the temperature increases, the soaking time can be adaptively shortened.

[0043] In some embodiments, the softener is selected from reagents such as ethanolamine, diethanolamine, triethanolamine, butanone, phenol, and methylphenol, preferably an ethanolamine solution. The softener has a purity of 99% or higher.

[0044] In some embodiments, the resin layer may be acrylic resin, epoxy resin or polyester resin.

[0045] In some embodiments, temperature control during immersion can be achieved by first placing the softener in a beaker, heating the beaker to a constant temperature in a water bath, and then immersing the flexible plate containing the cover film in the softener. The softener is continued until it penetrates into the resin layer beneath the cover film, thus obtaining the first intermediate state.

[0046] In some embodiments, the temperature of the softener is 40–150°C. Specifically, the temperature of the softener includes, but is not limited to, 40°C, 50°C, 65°C, 80°C, 95°C, 110°C, 130°C, and 150°C. Preferably, the temperature of the softener is 40–65°C.

[0047] The soaking time is 3 to 60 minutes, specifically including but not limited to 3 minutes, 10 minutes, 20 minutes, 30 minutes, 40 minutes, 50 minutes, and 60 minutes. Preferably, the soaking time is 3 to 20 minutes.

[0048] The temperature setting for the plasticizer is related to the type of resin material. Different resin materials have different glass transition temperatures (Tg values). For example, the Tg value of acrylic resin is 20–120℃, that of epoxy resin is 40–65℃, and that of polyester resin is 50–70℃. When the resin layer is acrylic resin, the plasticizer temperature can be 40–120℃, and the soaking time can be 3–30 minutes; when the resin layer is epoxy resin, the plasticizer temperature can be 40–65℃, and the soaking time can be 3–20 minutes; when the resin layer is polyester resin, the plasticizer temperature can be 50–70℃, and the soaking time can be 3–20 minutes. For example, when the resin layer is epoxy resin, diethanolamine can be used as the plasticizer, with the plasticizer temperature set to 40℃ and the soaking time 3–20 minutes; alternatively, methyl ethyl ketone (MEK) can be used as the plasticizer, with the plasticizer temperature set to 60℃ and the soaking time 3–10 minutes.

[0049] In some embodiments, the plasticizer has a purity of 99% or higher, specifically 99%, 99.5%, 99.7%, 99.8%, or 100%. An analytical grade solution is preferred.

[0050] During the penetration process, the softener reacts with the resin layer, gradually dissolving and softening it. This reduces the physical and chemical adhesion between the resin layer and the copper circuitry. However, the PI layer, due to its excellent properties, remains unaffected and continues to cover the outermost layer. This step uses a single type of highly pure chemical, effectively isolating the copper circuitry from air and moisture. Furthermore, the reaction temperature is low, making the impact on the copper circuitry of the flexible board negligible during heating. Throughout the process, the PI layer remains on the surface of the copper circuitry, effectively protecting it from oxidation, corrosion, and other damage. The soaking process is also quick and efficient.

[0051] In some embodiments, the heat treatment includes blowing the covering film with a hot air gun. The hot air gun temperature is 100–350°C, and the blowing time is 1–5 minutes. This continues until the PI layer film bubbles, delaminates, and detaches, resulting in a second intermediate state with the PI layer and resin layer removed.

[0052] In some embodiments, the temperature of the hot air gun is 100–350°C. Specifically, the temperature of the hot air gun includes, but is not limited to, 100°C, 150°C, 200°C, 250°C, 300°C, and 350°C. Preferably, it is 300–350°C, and more preferably, it is 330°C.

[0053] In some embodiments, the purging time is 1 to 5 minutes. Specifically, the purging time includes, but is not limited to, 1 minute, 2 minutes, 3 minutes, 4 minutes, and 5 minutes. Preferably, it is 2 to 4 minutes, and more preferably, it is 3 minutes.

[0054] Hot air purging utilizes the fact that the softener in the first intermediate state has already penetrated into the epoxy resin molecular chain. The large molecules in the softener cause the resin layer's performance to deteriorate after immersion in the softener. Simultaneously, upon heating, the smaller molecules, including the softener, vaporize, causing a dramatic expansion and blistering / delamination of the resin layer, leading to the PI layer detaching. When using a hot air gun for purging, the PI layer remains attached to the circuit surface until blistering and delamination occur, at which point purging stops. The PI layer protects the copper circuitry, preventing oxidation at high temperatures. Compared to traditional open flame burning methods, this provides more comprehensive protection for the copper circuitry and the sample. Furthermore, the hot air gun purging process allows for precise temperature settings, making the entire process safe, controllable, and easy to operate.

[0055] In some embodiments, if the PI layer cannot be successfully peeled off after soaking, softening, and heat treatment, the aforementioned two steps can be repeated until a second intermediate state with the PI layer and resin layer removed is obtained.

[0056] In some embodiments, the cleaning process includes first ultrasonically cleaning the second intermediate state with ethanol to remove excess softener from the flexible plate surface, then ultrasonically cleaning the remaining ethanol from the flexible plate surface with deionized water, and finally drying to obtain the third intermediate state.

[0057] In some implementations, anhydrous ethanol is used for ultrasonic cleaning.

[0058] In some implementations, the ultrasonic cleaning time for ethanol is 3 to 8 minutes, and the ultrasonic cleaning time for deionized water is also 3 to 8 minutes.

[0059] Specifically, the ultrasound time includes, but is not limited to, 3 min, 4 min, 5 min, 6 min, 7 min, and 8 min. Preferably, the ultrasound time is 4 to 6 min, and more preferably, it is 5 min.

[0060] In some implementations, if there are still residues on the circuit surface after ultrasonic cleaning with ethanol and deionized water, the aforementioned two ultrasonic cleaning steps can be repeated until the residues are completely cleaned in the third intermediate state.

[0061] In some embodiments, this method may further include ultraviolet laser treatment of the third intermediate state. Typically, the third intermediate state obtained through the aforementioned three steps is sufficient to completely remove the PI layer and resin layer from the copper circuit surface required for detection and failure analysis, thus completing the removal process of the coating film on the flexible board copper circuit surface. If some samples require further deep cleaning to remove the resin from the circuit surface and between the circuits, ultraviolet laser deep cleaning of residual resin can be performed based on the third intermediate state.

[0062] In some embodiments, the ultraviolet laser has a wavelength of 200–500 nm, a burning time of 150–250 μs / cycle, a pulse width of 7.0–9.0 μs, and an energy of 6.0–8.0 mJ.

[0063] In some embodiments, the wavelength of the ultraviolet laser is 200–500 nm. Specifically, the wavelength includes, but is not limited to, 200 nm, 250 nm, 300 nm, 350 nm, 400 nm, 450 nm, and 500 nm. Preferably, it is 260–360 nm, and more preferably, it is 266 nm or 355 nm.

[0064] In some embodiments, the calcination time is 150–250 μs / cycle. Specifically, the calcination time includes, but is not limited to, 150 μs / cycle, 170 μs / cycle, 190 μs / cycle, 210 μs / cycle, 230 μs / cycle, and 350 μs / cycle. Preferably, it is 190–210 μs / cycle, and more preferably, it is 210 μs / cycle.

[0065] In some implementations, the pulse width is 7.0 to 9.0 μs. Specifically, the pulse width includes, but is not limited to, 7.0 μs, 7.5 μs, 8.0 μs, 8.5 μs, and 9.0 μs.

[0066] In some implementations, the energy is 6.0 to 8.0 mJ, specifically including but not limited to 6.0 mJ, 6.5 mJ, 7.0 mJ, 7.5 mJ, and 8.0 mJ.

[0067] Ultraviolet lasers utilize the high photon energy in the ultraviolet region to destroy long molecular chains of organic materials, breaking them into smaller molecular chains and decomposing macromolecules into small particles, making them easier to peel off. Moreover, due to their high energy, they can remove small resin particles by using only photochemical ablation without generating high-energy heat. Thus, they achieve the effect of removing organic matter without damaging the surface of copper circuits.

[0068] The method for removing the coating film from the copper circuit surface of flexible boards adopted in this application starts from the structure and composition system of the coating film, separating the resin layer and the PI layer separately, and then obtaining a third intermediate state through cleaning and drying. This method uses fewer types and amounts of reagents, resulting in low cost, high efficiency, and high operability. The entire process does not damage the copper circuit and inner layer structure, making it suitable for processing small, valuable, and unique samples. It has a wide range of applications, and the entire process is time-efficient, resulting in higher effectiveness, while also ensuring the authenticity and validity of the failure analysis of flexible boards. When residual resin remains in the third intermediate state, ultraviolet laser can be used for targeted deep cleaning, which also does not damage the copper circuit and further ensures the removal effect of the coating film on the flexible copper-clad laminate.

[0069] Example 1

[0070] Add a softener to an analytical grade ethanolamine solution in a beaker, then transfer the beaker to a water bath at 40°C. After the ethanolamine solution temperature stabilizes, immerse a flexible copper-clad laminate with a coating film on its surface in the beaker for 20 minutes to obtain the first intermediate state.

[0071] Take the first intermediate state out of the beaker, spread it out flat, and fix it on the table with the covering film facing up; set the temperature of the hot air gun to 330℃ and blow the covering film on the surface of the flexible board for 4 minutes to obtain the second intermediate state.

[0072] The second intermediate was placed in an ultrasonic cleaner containing anhydrous ethanol and ultrasonically cleaned for 5 minutes to remove excess softener from the surface. Then it was transferred to an ultrasonic cleaner containing deionized water and ultrasonically cleaned for 5 minutes to remove residual ethanol from the surface. After drying, the third intermediate was obtained.

[0073] The surface of the copper circuit after the cover film was peeled off was observed using a scanning electron microscope, such as... Figure 1 The results show that most of the resin on the circuit surface has been completely removed, but some resin residue remains in certain areas; microcracks are exposed on the copper circuit surface, and the cracks are clearly visible, meeting the technical requirements for detection and failure analysis. Using secondary electron mode, the magnification is 2000x. Figure 1 Magnified to 8000 times Figure 2 As shown, the copper surface morphology is clearly visible, and there is no resin residue on the textured surface.

[0074] Ultraviolet laser was used to deeply remove residual resin from the circuit surface and between circuits. The wavelength was 355 nm, the pulse width was 7.0–9.0 μs, the energy was 8.0 mJ, the ablation time was 200 μs / batch, and the ablation was continuous for 5 min, resulting in the following: Figure 3 The circuit shown, with a magnification of 400x, exhibits a clear surface with no resin residue; using a secondary electron mode, [the following text is incomplete and requires further context to translate accurately]. Figure 3 Magnified to 2000 times Figure 4 As shown, the surface of the circuit is intact and undamaged.

[0075] Example 2

[0076] Add a softener to an analytical grade triethanolamine solution in a beaker, then transfer the beaker to an oil bath at 300°C. After the triethanolamine solution temperature stabilizes, immerse a flexible copper-clad laminate with a coating film on its surface in the beaker for 3 minutes to obtain the first intermediate state.

[0077] Take the first intermediate state out of the beaker, spread it out flat, and fix it on the table with the covering film facing up; set the temperature of the hot air gun to 350℃ and blow the covering film on the surface of the flexible board for 1 minute to obtain the second intermediate state.

[0078] The second intermediate was placed in an ultrasonic cleaner containing anhydrous ethanol and ultrasonically cleaned for 3 minutes to remove excess softener from the surface. Then it was transferred to an ultrasonic cleaner containing deionized water and ultrasonically cleaned for 4 minutes to remove residual ethanol from the surface. After drying, the third intermediate was obtained.

[0079] The surface of the copper circuit after the cover film was peeled off was observed using a scanning electron microscope, such as... Figure 5 The resin on the surface of the circuit was found to have been completely removed, with no residue remaining.

[0080] Example 3

[0081] Add a softener to an analytical grade methyl ethyl ketone solution in a beaker, then transfer the beaker to an oil bath at 65°C. After the methyl ethyl ketone solution temperature stabilizes, immerse a flexible copper-clad laminate with a coating film on its surface in the beaker for 15 minutes to obtain the first intermediate state.

[0082] Take the first intermediate state out of the beaker, spread it out flat, and fix it on the table with the covering film facing up; set the temperature of the hot air gun to 300℃ and blow the covering film on the surface of the flexible board for 8 minutes to obtain the second intermediate state.

[0083] The second intermediate was placed in an ultrasonic cleaner containing anhydrous ethanol and ultrasonically cleaned for 5 minutes to remove excess softener from the surface. Then it was transferred to an ultrasonic cleaner containing deionized water and ultrasonically cleaned for 6 minutes to remove residual ethanol from the surface. After drying, the third intermediate was obtained.

[0084] The surface of the copper circuit after the cover film was peeled off was observed using a scanning electron microscope, such as... Figure 6 The resin on the surface of the circuit was found to have been completely removed, with no residue remaining.

[0085] Example 4

[0086] Add a softener to an analytical grade diethanolamine solution in a beaker, then transfer the beaker to a water bath at 40°C. After the diethanolamine solution temperature stabilizes, immerse a flexible copper-clad laminate with a coating film on its surface in the beaker for 20 minutes to obtain the first intermediate state.

[0087] Take the first intermediate state out of the beaker, spread it out flat, and fix it on the table with the covering film facing up; set the temperature of the hot air gun to 330℃ and blow the covering film on the surface of the flexible board for 4 minutes to obtain the second intermediate state.

[0088] The second intermediate was placed in an ultrasonic cleaner containing anhydrous ethanol and ultrasonically cleaned for 5 minutes to remove excess softener from the surface. Then it was transferred to an ultrasonic cleaner containing deionized water and ultrasonically cleaned for 5 minutes to remove residual ethanol from the surface. After drying, the third intermediate was obtained.

[0089] The surface of the copper circuit after the cover film was peeled off was observed using a scanning electron microscope, such as... Figure 7 The results show that most of the resin on the surface of the circuit has been completely removed, but some areas still have resin residue; the microcracks on the surface of the copper circuit are exposed and clearly visible, which meets the technical requirements for detection and failure analysis.

[0090] Residual resin on and between circuit surfaces was deeply removed using an ultraviolet laser at a wavelength of 355 nm, a pulse width of 7.0–9.0 μs, an energy of 6.0 mJ, and an ablation time of 200 μs / batch, with continuous ablation for 8 min, yielding the following results: Figure 8 The scanning electron microscope image shown shows that there is no resin residue on the surface of the circuit, and the surface morphology is clear.

[0091] Comparative Example 1

[0092] Add a softener to an analytical grade ethanolamine solution in a beaker, then transfer the beaker to a water bath at 40°C. After the ethanolamine solution temperature stabilizes, immerse a flexible copper-clad laminate with a coating film on its surface in the beaker for 20 minutes to obtain the first intermediate state.

[0093] Take the first intermediate state out of the beaker, spread it out flat, and fix it on the table with the covering film facing up; set the temperature of the hot air gun to 600℃ and blow the covering film on the surface of the flexible board for 4 minutes to obtain the second intermediate state.

[0094] The second intermediate was placed in an ultrasonic cleaner containing anhydrous ethanol and ultrasonically cleaned for 5 minutes to remove excess softener from the surface. Then it was transferred to an ultrasonic cleaner containing deionized water and ultrasonically cleaned for 5 minutes to remove residual ethanol from the surface. After drying, the third intermediate was obtained.

[0095] The surface of the copper circuit after the cover film was peeled off was observed using a scanning electron microscope, such as... Figure 9 The results showed that the resin on the circuit surface was completely removed; at the same time, the exposed copper circuit surface underwent copper oxidation and discoloration (purple-black) due to excessive temperature from the blower, which altered the microstructure of the area to be observed on the circuit surface and did not meet the requirements for detection and failure analysis.

[0096] Comparative Example 2

[0097] The flexible copper-clad laminate with a covering film on its surface is subjected to high-temperature burning using an open flame, and the baking continues until the PI layer separates from the flexible copper-clad laminate, thus obtaining the first intermediate state.

[0098] The first intermediate state was immersed in a leavening solution prepared with deionized water, a leavening agent, and sodium hydroxide until the resin layer softened to obtain the second intermediate state. The temperature of the leavening solution was 90°C, and the immersion time was 2.5 hours. The volume ratio of deionized water, leavening agent, and sodium hydroxide was 63:15:1.

[0099] The softened resin layer on the surface was removed by rubbing the second intermediate state with a frosted eraser.

[0100] The surface of the copper circuit after the cover film was peeled off was observed using a scanning electron microscope, such as... Figure 10 The results showed that most of the resin on the circuit surface had been completely removed, but some areas still had resin residue. At the same time, the exposed copper circuit surface was severely damaged, with defects such as deformation, burning, and oxidation, which did not meet the requirements for testing and failure analysis.

[0101] The technical features of the above embodiments can be combined in any way. For the sake of brevity, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0102] The embodiments described above are merely illustrative of several implementations of the present invention, and while the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the invention patent. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention, and these all fall within the protection scope of the present invention. Therefore, the protection scope of this invention patent should be determined by the appended claims.

Claims

1. A method for removing the coating film on the surface of copper circuits on a flexible board, characterized in that, include: The process of soaking and softening the cover film resin layer includes immersing a flexible plate containing the cover film in a softening agent solution, wherein the softening agent is selected from ethanolamine, diethanolamine, triethanolamine, butanone, phenol, and methylphenol to obtain a first intermediate state. The PI layer in the first intermediate state is heat-treated until the PI layer falls off to obtain the second intermediate state; The second intermediate state is cleaned and dried to obtain the third intermediate state.

2. The method according to claim 1, characterized in that, Immerse the flexible sheet containing the covering film in a constant temperature softener solution at 40~150℃ for 3~60 min.

3. The method according to claim 2, characterized in that, The plasticizer has a purity of 99% or higher.

4. The method according to claim 1, characterized in that, The heat treatment includes blowing the covering film with a hot air gun.

5. The method according to claim 4, characterized in that, The temperature of the hot air gun is 100~350℃, and the blowing time is 1~5 min.

6. The method according to claim 1, characterized in that, The cleaning process includes ultrasonic cleaning of the second intermediate state with ethanol, followed by ultrasonic cleaning with deionized water.

7. The method according to claim 6, characterized in that, The ultrasonic cleaning time with ethanol or deionized water is 3-8 minutes.

8. The method according to claim 1, characterized in that, The method further includes ultraviolet laser processing of the third intermediate state.

9. The method according to claim 8, characterized in that, The wavelength of the ultraviolet laser treatment is 200~500 nm, and the calcination time is 150~250 μs / time.

Images