Resin composition, resin composition film, and use thereof

Abstract

The present application relates to the processing technology field of printed wiring soft and hard combination board, and particularly relates to a resin composition, a resin composition film and application thereof, wherein the resin composition contains 50-60 parts of main body resin, 0-20 parts of filler, 0-2 parts of thixotropic agent and 0-50 parts of solvent by weight. The resin composition in the present application selects polyimide as the main component of the resin composition film, and the resin composition film not only has excellent high-temperature resistance, etching resistance, bending resistance and other properties, but also has the characteristics of being easily removed by alkali dissolution, that is, the film can be completely removed by alkali dissolution without any residue, and can be applied to the processing and treatment process of the soft and hard combination board as a protective film, and has the advantages of pad protection and glue blocking application.

Description

Technical Field

[0001] This invention relates to the field of printed circuit board processing technology, specifically to resin compositions, resin composition films, and their applications. Background Technology

[0002] Rigid-flex PCBs (FPCBs) are circuit boards formed by bonding flexible printed circuit boards (FPCs) and rigid printed circuit boards (PCBs) together according to relevant process requirements. They possess the characteristics of both flexible and rigid PCBs and can be used in products with special requirements. Because they have both flexible and rigid areas, rigid-flex PCBs greatly help save internal space, reduce finished product volume, and improve product performance. However, rigid-flex PCBs still face challenges such as numerous production processes, high manufacturing difficulty, and low yield rates. As multi-layered rigid-flex PCBs gradually become an important part of printed circuit boards, the manufacturing process requirements for rigid-flex PCBs are becoming increasingly stringent.

[0003] Currently, the fabrication of rigid-flex PCBs can be achieved by hollowing out the flexible bending areas of the prepreg, then stacking the flexible and rigid circuit boards together by lamination, and finally removing the rigid layer of the flexible areas using laser depth control to expose the flexible circuit board and form the rigid-flex PCB. However, the hollowed-out areas of the prepreg will create cavities and steps, resulting in depressions after the outer substrate is laminated. During the fabrication of the outer circuitry, the dry film lamination process may fail to bond properly to the substrate due to these depressions and steps, leading to dry film cracking. This can cause the wire patterns to break and open during etching due to the lack of dry film protection. Alternatively, a filler material can be added to the hollowed-out areas of the prepreg before lamination to fill the hollowed-out areas. However, the thickness of this filler material needs to be consistent with the thickness of the prepreg stack. If the filler material is too thin... The depressions also exist; if the filler is too thick, the board surface will bulge, affecting processing. When the prepreg is not perforated, the rigid circuit board and the prepreg are not isolated in the flexible bending area, which will cause the prepreg in the dynamic flexible bending area to stick together because it is not perforated. At present, the main solution is to add a protective film to the fine window area on the cover film of the flexible circuit board. After the rigid circuit board is stacked and pressed, the protective film is removed to avoid the rigid circuit board and the flexible circuit board sticking together during the pressing process.

[0004] In the fabrication of rigid-flex PCBs, the aforementioned protective film not only prevents the rigid and flexible circuit boards from bonding during lamination but also prevents oxidation of the copper surface in precision windowed areas due to prolonged exposure. In existing technologies, various products can be used as the aforementioned protective film, and their removal methods generally depend on their composition and type. For example, water-soluble protective films can be removed with high-temperature pure water, but residues are easily left, or they are not resistant to chemicals, generally failing to meet application requirements; epoxy-based peelable films, while removable, lack sufficient bending resistance, and the peeling operation is relatively difficult; existing polyimide peelable films, using hyperbranched polyimide, while possessing high-temperature resistance, require direct peeling of the entire film, making the peeling process cumbersome; furthermore, other existing protective films suffer from varying degrees of poor high-temperature resistance, insufficient mechanical properties, and inadequate peel strength stability. Summary of the Invention

[0005] The purpose of this invention is to overcome the shortcomings of the prior art and provide a resin composition for rigid-flex PCBs. The film formed by the resin composition after drying can be completely removed by alkali dissolution, thus overcoming the problems of water-soluble adhesive films being difficult to remove completely and leaving residues, and epoxy peelable adhesives only being able to be removed by peeling operations in the prior art.

[0006] To achieve the above objectives, the present invention provides the following technical solution: In a first aspect, the present invention provides a resin composition comprising, by weight, the following components: 50-60 parts of a main resin, 0-20 parts of a filler, 0-2 parts of a thixotropic agent, and 0-50 parts of a solvent; The main resin includes the structural unit shown in formula (1), and any one or more structural units shown in formula (2), formula (3), and formula (4); The structural unit shown in equation (1) accounts for at least 50% of the total weight of the structural units; Equation (1) Equation (2) Equation (3) Equation (4) In formulas (1) to (4), X and A are independent divalent organic groups. X is selected from any one of di(trifluoromethyl)methylene, carbonyl, sulfone, dimethylmethylene, or oxygen atom. X in formulas (1) to (4) can be the same or different. A is selected from any one of di(trifluoromethyl)methylene, sulfone, oxymethylene, oxygen atom, dimethylmethylene, or methylene. R is a hydroxyl or sulfonic acid group. Y is a divalent organic group. Y is selected from any one of di(trifluoromethyl)methylene or dimethylmethylene. R1 is an alkylene group with 3 to 9 carbon atoms. R2, R3, R4, and R5 are independent alkylene groups or aromatic groups with 1 to 8 carbon atoms. m represents an integer greater than 1.

[0007] Preferably, the raw materials used to synthesize the above-mentioned polyimide segments include dianhydrides such as 4,4'-(hexafluoroisopropylidene) phthalic anhydride, 3,4,3',4'-benzophenone tetracarboxylic dianhydride, 3,3',4,4'-diphenyl sulfone tetracarboxylic dianhydride, 4,4'-(isopropylidene) phthalic anhydride, and 4,4'-oxobisphthalic anhydride, as well as bis(3-amino-4-hydroxyphenyl)hexafluoropropane, bis(3-amino-4-hydroxyphenyl) sulfone, and bis(3-amino-4-hydroxyphenyl) Ethers, 3-sulfonic acid-4,4'-diaminodiphenyl ether, bis(3-amino-4-hydroxyphenyl)propane, bis(3-amino-4-hydroxyphenyl)methane, 2,2-bis[4-(5-amino-2-pyridoxy)phenyl]hexafluoropropane, 2,2-bis[4-(5-amino-2-pyridoxy)phenyl]propane, 3,3-di-tert-butylbenzidine, 1,3-bis(3-aminopropyl)tetramethyldisiloxane, amino-terminated polydimethylsiloxane, etc., or diamines of formula (5): Equation (5) In equation (5), n is an integer from 1 to 20, and m is an integer from 1 to 10. The value of m in equation (5) and the value of m in equation (4) are independent of each other.

[0008] In this invention, polyimide with pyridine units or 3,3-di-tert-butylbenzidine and siloxane diamine in its polyimide skeleton is selected as the main resin component in the resin composition. By adding fillers, thixotropic agents and solvents, the addition amount of each component is adjusted to 50-60 parts of the main resin, 0-20 parts of fillers, 0-2 parts of thixotropic agents and 0-50 parts of solvents. The resulting resin composition, after film formation, has the properties of high temperature resistance, etching resistance, bending resistance and especially easy removal of alkali solubility. Formula (1) in the main resin is the basic structure, and formulas (2) / (3) / (4) are the modifying components. Formula (1) has basically met the requirements in terms of heat resistance, bending resistance, adhesion and solubility, but there is still room for further improvement. Therefore, formulas (2) / (3) / (4) are used for modification. The role of each modifying component (chain segment / functional group): Formula (2) contains a pyridine group. Pyridine possesses solubility, adhesiveness, processability, and optical properties (transmittance, transparency). Pyridine molecules are highly polar, and the lone pair of electrons on the nitrogen atom can form hydrogen bonds with water, resulting in good solubility and improved removal efficiency and completeness. Furthermore, the hydrocarbon group in the pyridine structure gives it considerable affinity for organic molecules, good compatibility with other components in the composition, and good adhesion to some organic hierarchical structures (such as adhesive layers and substrate layers in circuit boards). The lone pair of electrons on the nitrogen atom can form complexes with some metal ions such as Ag, Ni, and Cu, thus providing good adhesion to metal layers or metal parts (circuit lines, pads, etc.) in circuit boards. In the pyridine ring, the nitrogen atom has both an electron-withdrawing inductive effect and an electron-withdrawing conjugation effect, thereby endowing polyimide with good optical properties (normally, due to electron transfer in the polyimide structure, polyimide films are generally yellow; this structure can improve the transmittance and transparency of polyimide, thus improving visibility). However, the structure of formula (2) has poor heat resistance to the phenyl ether fragment and is easily decomposed by heat; moreover, the long and flexible chain segment will also affect the heat resistance and dimensional stability. Formula (3) contains tert-butyl, which can increase solubility, increase polymer processability, and facilitate film removal; improve optical transmittance; and increase Tg without reducing thermal stability as with the introduction of flexible linking groups or long alkyl chains. However, the introduction of tert-butyl in the side chain and the increase in inter-chain entanglement may increase viscosity and affect the coatability of the composition; Formula (4) contains siloxane, which can improve flexibility and adhesion, but it will lead to a decrease in Tg, a decrease in heat resistance, and an increase in CTE.

[0009] In summary, appropriately introducing formulas (2) / (3) / (4) can modify formula (1), but each of formulas (2) / (3) / (4) has its own drawbacks, so the proportion of each formula must be controlled. Experimental data shows that formula (1) needs to be at least 50% for the resulting resin composition to exhibit good film-forming properties, flexibility, folding resistance, heat resistance, dimensional stability, coatability, processability, and optical properties after film formation.

[0010] The polyimide selected in this invention is often used in combination with photosensitizers, resulting in a resin composition with excellent photosensitivity, thus finding wide application in photosensitive solder resist inks. Currently, no research has been found on using the polyimide selected in this invention as a component of the protective film in the processing of rigid-flex PCBs. Commonly used protective films are generally epoxy-based or other peelable adhesive films that can be used as protective films, mainly used to isolate flexible circuit boards from prepregs. The protective film is then peeled off after lamination, increasing workload and reducing processing efficiency, and all of these processes have some degree of shortcomings in the performance of the protective film.

[0011] The cover film (i.e., solder resist dry film) on the surface of flexible circuit boards is generally made of acrylic resin or polyimide. Before other operations, the cover film undergoes photothermal dual curing (exposure followed by heat treatment). After photothermal dual curing, the entire cover film forms a stable cross-linked system that is not easily corroded or damaged. However, the film formed by the resin composition of this invention has excellent alkali solubility. When used as a protective film in the rigid-flex PCB processing, after the rigid-flex PCB lamination process, the protective film can be dissolved and removed by alkali dissolution without damaging the original cover film on the flexible circuit board, thus improving processing efficiency. Furthermore, this resin composition is ink-like and can be directly applied to the areas of the flexible circuit board that need protection by brushing, and then dried into a protective film. This is convenient and avoids the problem of some existing protective films on the market that can only be attached to the flexible circuit board by pasting and lamination, leading to the need to cut off the protective film on the surface of the areas that do not need protection later.

[0012] The alkali-soluble removal of the resin composition after film formation referred to in this invention includes two situations: (1) the film layer is completely dissolved in the alkaline solution, that is, all molecular chains are dissolved by alkali; (2) the film layer is partially dissolved in the alkaline solution, that is, only part of the film layer is dissolved by the alkali solution, forming fragments of a certain size. The remaining fragments can be completely removed by rinsing. That is, some molecular chains in the film, and polyimide with a high acid value react with alkali and are dissolved by alkali, thereby destroying the structure of the entire film. After achieving the purpose of film fragmentation, the remaining film fragments can be removed by rinsing.

[0013] Preferably, the mass ratio of the structural units represented by formulas (1), (2), (3), and (4) in the main resin is 100:(0-50):(0-20):(0-30) by weight.

[0014] This invention adjusts the content ratio of each structural unit in the main resin to within the range of 100:(0~50):(0~20):(0~30). When the resulting resin composition film has good high temperature resistance, etching resistance, bending resistance, and especially easy removal of alkali-soluble substances, it achieves better performance.

[0015] Preferably, the main resin includes at least main resin a and main resin b; main resin a includes the structural unit shown in formula (1), and any one or more structural units shown in formula (2), formula (3), and formula (4), and the acid value of main resin a is 0 to 50 mg KOH / g; main resin b includes the structural unit shown in formula (1), and any one or more structural units shown in formula (2), formula (3), and formula (4), and the acid value of main resin b is 50 to 200 mg KOH / g.

[0016] In the resin composition of this invention, at least two polyimides are selected and compounded to form the main resin components, corresponding to main resin a and main resin b, respectively. To ensure that the film formed by this resin composition is unaffected in other properties (e.g., high temperature resistance, etching resistance, bending resistance) and has good alkali-soluble removal properties, the overall acid value of the compounded main resin needs to be controlled within a suitable range. When the overall acid value of the main resin is too low, the protective film formed by the resin composition may not be completely removed by alkali. When the overall acid value of the main resin is too high, the protective film may be corroded and damaged by the etching solution during subsequent etching operations, thereby damaging the copper foil in the fine windowed area and failing to achieve the protective effect. Further preferably, the mass ratio of main resin a to main resin b is (0.25–1):1.

[0017] Preferably, the main resin includes at least main resin c and main resin d; main resin c includes the structural unit shown in formula (1), and any one or more structural units shown in formula (2), formula (3), and formula (4), and the number average molecular weight of main resin c is 50,000 to 80,000; main resin d includes the structural unit shown in formula (1), and any one or more structural units shown in formula (2), formula (3), and formula (4), and the number average molecular weight of main resin d is 20,000 to 30,000.

[0018] To ensure that the protective film formed by this resin composition exhibits better high-temperature resistance, folding resistance, and etching resistance, the type of polyimide used in the compounding is subject to high requirements. At least two polyimides must be selected for compounding, and both must contain polyimides with a number average molecular weight of 50,000–80,000 and a number average molecular weight of 20,000–30,000. The polyimide with a number average molecular weight of 50,000–80,000 contains rigid segments, while the polyimide with a number average molecular weight of 20,000–30,000 contains flexible segments. By compounding these two types of polyimides, the protective film formed by the resin composition can have good mechanical properties (flexibility), is not prone to cracking, and can withstand bending. Furthermore, the presence of flexible segments ensures that the formed protective film has good adhesion to the copper surface.

[0019] Further preferably, the glass transition temperature of the main resin c is not lower than 330°C, and the glass transition temperature of the main resin d is 150-180°C. The requirement that one of the polyimides has a glass transition temperature above 330°C ensures that the protective film is not easily damaged by high temperatures during high-temperature processing, mainly reflecting the requirement for high-temperature resistance. A polyimide with a glass transition temperature of 150-180°C allows for free movement of the chain segments, resulting in good ink flowability, and also further ensures the toughness of the film.

[0020] Preferably, the viscosity of the resin composition at 25°C is 120–220 dPa·s. Excessive viscosity is detrimental to coating, while insufficient viscosity and excessive fluidity may lead to edge runs, uneven surfaces, or the composition covering non-target areas.

[0021] Preferably, the filler includes pigments and inorganic fillers, wherein the inorganic filler includes one or more of non-metals, metals, and metal oxides.

[0022] The addition of filler components can improve the physical and mechanical properties of resin compositions, such as extending the pot life, reducing the coefficient of thermal expansion and shrinkage, and improving the strength, heat resistance, aging resistance, and water resistance of the film. As an additive, filler primarily functions by occupying volume. Due to the presence of filler, the polyimide molecular chains can no longer occupy all the original space, thus fixing the connected chain segments to some extent. Because of the dimensional stability of filler, the movement of molecular chains in the polyimide interfacial region is restricted, leading to an increase in glass transition temperature, heat distortion temperature, and shrinkage rate, while improving elastic modulus, hardness, stiffness, and impact strength.

[0023] Filler components can be divided into pigments and other fillers. Other fillers are mainly inorganic fillers, such as silicon dioxide, barium sulfate, barium titanate, calcium carbonate, silicon nitride, aluminum nitride, boron nitride, aluminum hydroxide, magnesium hydroxide, magnesium carbonate, mica, talc, organobentonite, Noiburg silica, glass powder, clay, mineral wool, aluminosilicates, calcium silicates, non-fibrous glass, and other non-metallic fillers; metallic fillers such as copper, gold, silver, palladium, and silicon; and metal oxide fillers such as alumina, magnesium oxide, titanium oxide, zinc oxide, and iron oxide. These can be used alone or in combination of two or more.

[0024] Other fillers mentioned above can be treated with silane coupling agents to give their surfaces vinyl, styrene, methacryloyl, acryloyl, hydroxy, carboxyl, isocyanate, amino, imino, epoxy, oxacyclobutane, mercapto, methoxymethyl, ethoxyethyl, ethoxymethyl, oxazoline, etc. The presence of these groups can improve the compatibility of inorganic fillers in the entire resin composition system, and may even make inorganic fillers reactive.

[0025] Pigments can be organic or inorganic, including but not limited to black pigments such as: carbon black, graphite, iron oxide, titanium black, iron oxide, anthraquinone, cobalt oxide, copper oxide, manganese, antimony oxide, nickel oxide, perylene, aniline, molybdenum sulfide, bismuth sulfide, etc.; blue pigments such as: phthalocyanine, anthraquinone, etc., and metal-substituted phthalocyanine compounds may also be used; red pigments such as: monoazo, diazo, azo lake, benzimidazolone, perylene. The pigments include: diketopyrrolopyrrole, condensed azo, anthraquinone, and quinacridone; yellow pigments, such as monoazo, diazo, condensed azo, benzimidazolone, isoindolinone, and anthraquinone; green pigments, such as phthalocyanine and anthraquinone, and metal-substituted phthalocyanine compounds can also be used; white pigments, such as rutile or anatase titanium dioxide and barium sulfate; and purple, orange, and brown fillers can be added as needed.

[0026] Preferably, the thixotropic agent comprises one or more of the following: fine-grained silica, silica gel, asbestos, kaolin, attapulgite, emulsion-processed vinyl chloride compounds, polyamide additives, modified urea additives, wax additives, organobentonite, hydrogenated castor oil, metallic soaps, cellulose derivatives such as hydroxyethyl cellulose, polyvinyl alcohol, polyacrylate, montmorillonite, and hydrotalcite. The addition of the thixotropic agent can improve the film-forming properties of the coating and inhibit sagging.

[0027] Preferably, the solvent includes one or more of the following: ketones, aromatic hydrocarbons, glycol ethers, glycol ether acetates, esters, alcohols, aliphatic hydrocarbons, and petroleum-based solvents.

[0028] The addition of solvents can make the components in the resin composition dissolve better, so that the resin composition can be coated normally. The solvent components in the resin composition of the present invention can be ketones, aromatic hydrocarbons, glycol ethers, glycol ether acetates, esters, alcohols, aliphatic hydrocarbons, petroleum solvents, etc.

[0029] Specifically, these can be N-methyl-2-pyrrolidone, N-ethyl-2-pyrrolidone, γ-butyrolactone, N,N-dimethylformamide, N,N-dimethylacetamide, dimethyl sulfoxide, m-cresol, ethanol, propanol, ethylene glycol, propylene glycol, butanone, acetone, cyclopentanone, methyl ethyl ketone, cyclohexanone, α-acetyl-γ-butyrolactone, tetramethylurea, tetrahydrofuran, 1,3-dimethyl-2-imidazolinone, N-cyclohexyl-2-pyrrolidone, and hexamethylphosphoramide. The following solvents can be selected: pyridine, toluene, xylene, tetramethylbenzene, carbitol, methyl carbitol, butyl carbitol, propylene glycol monomethyl ether, diethylene glycol dimethyl ether, dipropylene glycol diethyl ether, triethylene glycol monoethyl ether, ethyl acetate, butyl acetate, dipropylene glycol methyl ether acetate, propylene glycol ethyl ether acetate, propylene glycol butyl ether acetate, octane, decane, petroleum ether, petroleum naphtha, hydrogenated petroleum naphtha, and solvent naphtha. Preferably, a mixture of two solvents is used, one being a high-boiling-point solvent and the other a low-boiling-point solvent. Using a mixture of high- and low-boiling-point solvents yields the best overall coating performance, often with better film hardness than a single solvent. This is because the evaporation rate of the low-boiling-point solvent and the solubility of the high-boiling-point solvent work synergistically, resulting in higher hardness, better surface finish, and higher gloss. The specific solvents selected for the mixture can be chosen from the list above.

[0030] More preferably, the composition further includes an antifoaming agent or a leveling agent.

[0031] Defoamers quickly remove air bubbles from a system and are commonly used in high-viscosity systems to remove microbubbles. Leveling agents improve leveling properties, enhance surface smoothness, improve scratch resistance, prevent sticking, and minimize surface defects. The addition of defoamers or leveling agents can improve the smoothness of the coating surface after the resin composition has formed, inhibit the formation of voids in the coating, and maintain the leveling properties of the coating after solvent evaporation.

[0032] The main agent used as a defoamer or leveling agent in a resin composition can be a compound such as organosilicon, modified organosilicon, mineral oil, vegetable oil, aliphatic alcohol, fatty acid, metal soap, fatty acid amide, polyoxyalkylene glycol, polyoxyalkylene alkyl ether, polyoxyalkylene fatty acid ester, etc.

[0033] In a second aspect, the present invention provides a resin composition film formed by curing the resin composition described above.

[0034] The resin composition film can be customized to the desired color by adding pigments according to the needs of downstream circuit board manufacturers. Preferably, considering the visibility and ease of observation of the rigid-flex PCB manufacturing process, the resin composition film has a thickness of 5-15 μm, an L* value of 35-100, an a* value of -100 to -25, and a b* value of -20 to 100.

[0035] Preferably, the curing temperature is 90–200°C and the time is 10–60 min.

[0036] Preferably, the above-mentioned resin composition film can be removed by alkali dissolution. More preferably, the alkali solution is a 5% to 20% sodium hydroxide solution at a temperature of 40 to 80°C.

[0037] Thirdly, the present invention provides the application of the above-described resin composition or the resin composition film in rigid-flex PCBs.

[0038] The present invention has the following beneficial effects: (1) In this invention, polyimide is selected as the main component for forming the resin composition film. The resin composition film not only has excellent high temperature resistance, etching resistance, and bending resistance, but also has the characteristic of being easily removed by alkali dissolution. The film can be completely removed by alkali dissolution without any residue. (2) This invention optimizes the structural composition of polyimide and selects different types of polyimide for compounding to make up for the single performance of a single polyimide, realize the complementarity of physicochemical properties between different types of polyimide, achieve the optimal synergistic effect between each component, and thus obtain a resin composition film with good physicochemical properties. (3) The film formed by the resin composition in this invention can be used as a protective film in the processing of rigid-flex boards. Because the film formed has excellent high temperature resistance, pressure resistance and folding resistance, and does not react with PP, it has the advantages of both pad protection and adhesive resistance. It can be applied to the protection of fine openings. The resin composition is applied to the opening protection area and dried into a film, or the film formed by the resin composition is directly attached to the flexible area to prevent the copper surface of the opening from oxidizing or being damaged by chemical etching, and to isolate the flexible circuit board from the prepreg, and to prevent the flexible circuit board from sticking to the rigid circuit board during pressing. Detailed Implementation

[0039] The present invention will be further described below with reference to specific embodiments in the specification. Those skilled in the art will be able to implement the present invention based on these descriptions. Furthermore, the embodiments of the present invention described below are generally only some, not all, of the embodiments of the present invention. Therefore, all other embodiments obtained by those skilled in the art based on the embodiments of the present invention without inventive effort should fall within the scope of protection of the present invention.

[0040] The specific raw materials of each main resin in the following embodiments are shown in Table 1, and the specific composition of each main resin is shown in Table 2.

[0041] Table 1. Raw materials that make up the main resin Table 2 Specific Composition of Each Main Resin Note: In the table, 'a' represents the main resin a with an acid value of 0-50 mg KOH / g, 'b' represents the main resin b with an acid value of 50-200 mg KOH / g, 'c' represents the main resin c with a glass transition temperature of not less than 330℃, and 'd' represents the main resin d with a glass transition temperature of 150-180℃.

[0042] For details on the fillers, thixotropic agents, and solvents corresponding to different numbers in the following examples, please refer to Table 3.

[0043] Table 3. Fillers, Thixotropic Agents and Solvents F1 filler silicon dioxide F2 filler Calcium carbonate F3 filler Phthalocyanine Green G1 thixotropic agents Polyamide wax G2 thixotropic agents Organic bentonite H1 solvent N-Methylpyrrolidone Example 1 In this embodiment, the viscosity of the resin composition is 189 dPa·s, and the specific composition is shown in Table 4: Table 4. Composition of the resin composition (parts by weight) The composition in this embodiment was applied to the curved part of the flexible board (the application method was screen printing, squeegee at 75°, mesh 120), and cured into a film (25cm×25cm) under a heat condition of 150°C for 30 minutes.

[0044] Example 2 In this embodiment, the viscosity of the resin composition is 192 dPa·s, and the specific composition is shown in Table 5: Table 5. Composition of the resin composition (parts by weight) The composition was applied to the curved part of the flexible board (coating method: screen printing, squeegee at 75°, mesh 120), and cured into a film (25cm×25cm) under a heat of 150°C for 30 minutes.

[0045] Example 3 In this embodiment, the viscosity of the resin composition is 206 dPa·s, and the specific composition is shown in Table 6: Table 6. Composition of the resin composition (parts by weight) The composition was applied to the curved part of the flexible board (coating method: screen printing, squeegee at 75°, mesh 120), and cured into a film (25cm×25cm) under a heat of 150°C for 30 minutes.

[0046] Example 4 In this embodiment, the viscosity of the resin composition is 193 dPa·s, and the specific composition is shown in Table 7: Table 7. Composition of the resin composition (parts by weight) The composition was applied to the curved part of the flexible board (coating method: screen printing, squeegee at 75°, mesh 120), and cured into a film (25cm×25cm) under a heat of 150°C for 30 minutes.

[0047] Example 5 In this embodiment, the viscosity of the resin composition is 197 dPa·s, and the specific composition is shown in Table 8: Table 8. Composition of the resin composition (parts by weight) The composition was applied to the curved part of the flexible board (coating method: screen printing, squeegee at 75°, mesh 120), and cured into a film (25cm×25cm) under a heat of 150°C for 30 minutes.

[0048] Example 6 In this embodiment, the viscosity of the resin composition is 199 dPa·s, and the specific composition is shown in Table 9: Table 9. Composition of the resin composition (parts by weight) The composition was applied to the curved part of the flexible board (coating method: screen printing, squeegee at 75°, mesh 120), and cured into a film (25cm×25cm) under a heat of 150°C for 30 minutes.

[0049] Example 7 In this embodiment, the viscosity of the resin composition is 206 dPa·s, and the specific composition is shown in Table 10: Table 10 Composition of the resin composition (parts by weight) The composition was applied to the curved part of the flexible board (coating method: screen printing, squeegee at 75°, mesh 120), and cured into a film (25cm×25cm) under a heat of 150°C for 30 minutes.

[0050] Example 8 In this embodiment, the viscosity of the resin composition is 193 dPa·s, and the specific composition is shown in Table 11: Table 11 Composition of the resin composition (parts by weight) The composition was applied to the curved part of the flexible board (coating method: screen printing, squeegee at 75°, mesh 120), and cured into a film (25cm×25cm) under a heat of 150°C for 30 minutes.

[0051] Example 9 In this embodiment, the viscosity of the resin composition is 205 dPa·s, and the specific composition is shown in Table 12: Table 12 Composition of the resin composition (parts by weight) The composition was applied to the curved part of the flexible board (coating method: screen printing, squeegee at 75°, mesh 120), and cured into a film (25cm×25cm) under a heat of 150°C for 30 minutes.

[0052] Example 10 In this embodiment, the viscosity of the resin composition is 162 dPa·s, and the specific composition is shown in Table 13: Table 13 Composition of the resin composition (parts by weight) The composition was applied to the curved part of the flexible board (coating method: screen printing, squeegee at 75°, mesh 120), and cured into a film (25cm×25cm) under a heat of 150°C for 30 minutes.

[0053] Example 11 In this embodiment, the viscosity of the resin composition is 182 dPa·s, and the specific composition is shown in Table 14: Table 14 Composition of the resin composition (parts by weight) The composition was applied to the curved part of the flexible board (coating method: screen printing, squeegee at 75°, mesh 120), and cured into a film (25cm×25cm) under a heat of 150°C for 30 minutes.

[0054] Example 12 In this embodiment, the viscosity of the resin composition is 176 dPa·s, and the specific composition is shown in Table 15: Table 15 Composition of the resin composition (parts by weight) The composition was applied to the curved part of the flexible board (coating method: screen printing, squeegee at 75°, mesh 120), and cured into a film (25cm×25cm) under a heat of 150°C for 30 minutes.

[0055] Example 13 In this embodiment, the viscosity of the resin composition is 143 dPa·s, and the specific composition is shown in Table 16: Table 16 Composition of the resin composition (parts by weight) The composition was applied to the curved part of the flexible board (coating method: screen printing, squeegee at 75°, mesh 120), and cured into a film (25cm×25cm) under a heat of 150°C for 30 minutes.

[0056] Example 14 In this embodiment, the viscosity of the resin composition is 129 dPa·s, and the specific composition is shown in Table 17: Table 17 Composition of the resin composition (parts by weight) The composition was applied to the curved part of the flexible board (coating method: screen printing, squeegee at 75°, mesh 120), and cured into a film (25cm×25cm) under a heat of 150°C for 30 minutes.

[0057] Example 15 In this embodiment, the viscosity of the resin composition is 191 dPa·s, and the specific composition is shown in Table 18: Table 18 Composition of the resin composition (parts by weight) The composition was applied to the curved part of the flexible board (coating method: screen printing, squeegee at 75°, mesh 120), and cured into a film (25cm×25cm) under a heat of 150°C for 30 minutes.

[0058] Example 16 In this embodiment, the viscosity of the resin composition is 123 dPa·s, and the specific composition is shown in Table 19: Table 19 Composition of the resin composition (parts by weight) The composition was applied to the curved part of the flexible board (coating method: screen printing, squeegee at 75°, mesh 120), and cured into a film (25cm×25cm) under a heat of 150°C for 30 minutes.

[0059] Example 17 In this embodiment, the viscosity of the resin composition is 160 dPa·s, and the specific composition is shown in Table 20: Table 20 Composition of the resin composition (parts by weight) The composition was applied to the curved part of the flexible board (coating method: screen printing, squeegee at 75°, mesh 120), and cured into a film (25cm×25cm) under a heat of 150°C for 30 minutes.

[0060] Example 18 In this embodiment, the viscosity of the resin composition is 165 dPa·s, and the specific composition is shown in Table 21: Table 21 Composition of the resin composition (parts by weight) The composition was applied to the curved part of the flexible board (coating method: screen printing, squeegee at 75°, mesh 120), and cured into a film (25cm×25cm) under a heat of 150°C for 30 minutes.

[0061] Comparative Example 1 The viscosity of the resin composition in this comparative example is 226 dPa·s, and its specific composition is shown in Table 22. Table 22 Composition of the resin composition (parts by weight) The composition was applied to the curved part of the flexible board (coating method: screen printing, squeegee at 75°, mesh 120), and cured into a film (25cm×25cm) under a heat of 150°C for 30 minutes.

[0062] Comparative Example 2 The viscosity of the resin composition in this comparative example is 103 dPa·s, and its specific composition is shown in Table 23. Table 23 Composition of the resin composition (parts by weight) The composition was applied to the curved part of the flexible board (coating method: screen printing, squeegee at 75°, mesh 120), and cured into a film (25cm×25cm) under a heat of 150°C for 30 minutes.

[0063] Comparative Example 3 The viscosity of the resin composition in this comparative example is 241 dPa·s, and its specific composition is shown in Table 24. Table 24 Composition of the resin composition (parts by weight) The composition was applied to the curved part of the flexible board (coating method: screen printing, squeegee at 75°, mesh 120), and cured into a film (25cm×25cm) under a heat of 150°C for 30 minutes.

[0064] Comparative Example 4 The viscosity of the resin composition in this comparative example is 193 dPa·s, and its specific composition is shown in Table 25. Table 25 Composition of the resin composition (parts by weight) The composition was applied to the curved part of the flexible board (coating method: screen printing, squeegee at 75°, mesh 120), and cured into a film (25cm×25cm) under a heat of 150°C for 30 minutes.

[0065] [Performance Evaluation] 1. Heat resistance The semi-finished "flexible board + resin composite film" after curing was placed at 220℃ for 3 hours. Observe whether there is discoloration, pinholes, wrinkling or even peeling, and record and rate it: A: No discoloration, no pinholes, no wrinkling, no peeling; B: Discoloration, no pinholes, no wrinkling, no peeling; C: Discoloration, pinholes, no wrinkling, no peeling; D: Discoloration, pinholes, wrinkling, peeling.

[0066] 2. Flexibility Referring to JIS-C-5-016 standard 8.7, the semi-finished product of "flexible and rigid bonded board + resin composition film" after curing into a film is bent at 180° with the resin composition film as the outer side, and the bending level is recorded according to the following standards: A: No obvious creases or cracks on the film; B: Creases appear on the film, but no cracks appear; C: There are some cracks on the film; D: The film breaks.

[0067] 3. Demembranous properties The semi-finished product of "soft and hard bonded board + resin composition film" after curing was immersed in 10% sodium hydroxide film removal solution at 50°C. The film peeling was observed, and the film removal time, the size of the film fragments and whether there were any residues were recorded.

[0068] 4. Leveling properties Record the thickness at the edge of the semi-finished product "hard and soft bonded board + resin composition film" after curing. Then, slice the semi-finished product from the middle and measure the film thickness at the center (referred to as film thickness). Calculate the difference between the film thickness at the center and the thickness at the edge.

[0069] 5. Chemical resistance The semi-finished product of "rigid-soft bonded board + resin composition film" after curing was placed in a 10% hydrochloric acid aqueous solution for 10 minutes. The surface was observed for blistering, discoloration, floating and peeling, etc., and the results were recorded and rated as follows: A: No change in appearance; B: Discoloration on the surface; C: Floating, thin peeling and deep soldering of the cured film.

[0070] The performance test results are shown in Table 26: Table 26 Performance Test Results The performance test results above show that the acid values ​​of the resin combinations in Example 2 and Example 1 are different, and the film removal speed of the resin composition film obtained in Example 2 is faster than that obtained in Example 1. The Tg values ​​of the resin compositions in Example 3 and Example 1 are different, and the heat resistance of the resin composition film obtained in Example 3 is worse than that obtained in Example 1. The main resin in Example 4 is obtained by compounding two main resins a and b with different acid values, and the resulting resin composition film is easier to remove than that obtained in Example 1. The main resins in Examples 5 to 7 are all obtained by compounding two main resins a and b with different acid values, and the content of diamine monomer 4 in the main resin of Example 5 is relatively low. The flexibility of the resin compositions in Examples 6 and 7 was worse than that in Example 4. The main resins a and b in Examples 6 and 7 were adjusted compared to Example 4, resulting in resin compositions with poorer water resistance than those in Example 4. However, the film removal properties of the resin compositions in Examples 6 and 7 were better than those in Example 4. In Example 8, the main resin was obtained by blending two main resins c and d with different glass transition temperatures. The resulting resin composition film had better heat resistance and flexibility than the resin composition film obtained in Example 1. In Examples 9 and 10, the content of the main resin changed compared to Example 1. In Example 9, the content of the main resin was higher than in Example 1, thus the viscosity of the resin composition was correspondingly higher. In Example 10, the content of the main resin was lower than in Example 1. Conversely, the resin composition in Example 11 had a higher viscosity than that in Example 10, resulting in poorer heat resistance after film formation; the resin composition in Example 12 had a higher viscosity than that in Example 10, resulting in better heat resistance after film formation and faster film removal; the resin composition in Example 13 had a lower viscosity than that in Example 10, resulting in faster film removal; the resin composition in Example 14 had a lower viscosity than that in Example 10, resulting in poorer heat resistance after film formation and faster film removal; in Examples 15 and 16, the filler component content changed compared to Example 10, with the filler component content increasing in Example 15, and the corresponding resin composition viscosity increasing accordingly, while the opposite was true in Example 16; in Examples 17 and 18, the thixotropic agent was added compared to Example 10. The dosage was adjusted. In Example 17, no thixotropic agent was added, resulting in poor smoothness of the resin composition film. In Example 18, the amount of thixotropic agent added was increased, resulting in better smoothness of the resin composition film. Compared with Example 1, the weight percentage of formula (1) in the main resin of Comparative Example 1 was less than 50%, resulting in poor heat resistance, flexibility, film removal and leveling properties of the resin composition film. Compared with Example 14, the content of the main resin in Comparative Example 2 was lower, resulting in a resin composition that could not be coated due to its low viscosity, and insufficient protective coverage on the rigid-flex liner. Compared with Example 3, the content of the main resin in Comparative Example 3 was higher, resulting in a resin composition that could not be coated due to its high viscosity and uneven composition.Compared to Example 1, Comparative Example 4 had a much higher acid value in its main resin, resulting in very poor water resistance after the resin composition was formed.

[0071] In summary, this application addresses the existing technical challenge of completely removing or cumbersomely removing protective films. Based on the actual needs of the product, it purposefully selects the type of main resin in the resin composition, optimizes the structural units and their proportions within the main resin, and rationally adjusts the amounts of fillers, thixotropic agents, and solvents. The resulting resin composition, after film formation, exhibits excellent high-temperature resistance, etching resistance, bending resistance, and especially easy removal due to alkali solubility. If the composition or amount of some components in the resin composition does not meet the conditions described in this application, the performance of the resulting resin composition film will be significantly weakened, affecting normal use.

Claims

1. A resin composition, characterized in that, The product comprises, by weight, the following components: 50-60 parts of main resin, 0-20 parts of filler, 0-2 parts of thixotropic agent, and 0-50 parts of solvent; wherein the main resin comprises the structural unit shown in formula (1), and any one or more structural units shown in formula (2), formula (3), and formula (4); the structural unit shown in formula (1) accounts for at least 50% of the total structural units by weight. Equation (1) ； Equation (2) ； Equation (3) ； Equation (4) ； In formulas (1) to (4), X and A are independent divalent organic groups, X is selected from any one of di(trifluoromethyl)methylene, carbonyl, sulfone, dimethylmethylene, and oxygen atom, X in formulas (1) to (4) can be the same or different, A is selected from any one of di(trifluoromethyl)methylene, sulfone, methyl oxide, oxygen atom, dimethylmethylene, or methylene; R is a hydroxyl or sulfonic acid group; Y is a divalent organic group, Y is selected from any one of di(trifluoromethyl)methylene or dimethylmethylene; R1 is an alkylene group with 3 to 9 carbon atoms; R2, R3, R4, and R5 are independent alkylene groups or aromatic groups with 1 to 8 carbon atoms; m represents The number of components is an integer greater than or equal to 1; wherein the content of filler and thixotropic agent is not 0, and the resin composition does not contain photosensitizer and crosslinking agent; the main resin includes at least main resin a and main resin b; main resin a includes the structural unit shown in formula (1), and any one or more structural units shown in formula (2), formula (3), and formula (4), and the acid value of main resin a is 0 to 50 mg KOH / g; main resin b includes the structural unit shown in formula (1), and any one or more structural units shown in formula (2), formula (3), and formula (4), and the acid value of main resin b is 50 to 200 mg KOH / g; wherein the acid values ​​of main resin a and b are different.

2. The resin composition according to claim 1, characterized in that, The mass ratio of the structural units represented by formulas (1), (2), (3), and (4) in the main resin is 100:(0-50):(0-20):(0-30).

3. The resin composition according to claim 1, characterized in that, The mass ratio of the main resin a to the main resin b is (0.25~1):

1.

4. A resin composition as described in claim 1 or 2, characterized in that, The main resin includes at least main resin c and main resin d; main resin c includes the structural unit shown in formula (1), and any one or more structural units shown in formula (2), formula (3), and formula (4), and the number average molecular weight of main resin c is 50,000 to 80,000; main resin d includes the structural unit shown in formula (1), and any one or more structural units shown in formula (2), formula (3), and formula (4), and the number average molecular weight of main resin d is 20,000 to 30,000.

5. The resin composition according to claim 4, characterized in that, The glass transition temperature of the main resin c is not lower than 330°C, and the glass transition temperature of the main resin d is 150-180°C.

6. A resin composition as described in claim 1 or 2, characterized in that, The viscosity of the resin composition at 25°C is 120–220 dPa·s.

7. A resin composition film, characterized in that, The resin composition film is formed by curing the resin composition according to any one of claims 1 to 6.

8. The resin composition film according to claim 7, characterized in that, The resin composition film has a thickness of 5–15 μm, an L* value of 35–100, an a* value of -100–-25, and a b* value of -20–100.

9. The use of the resin composition according to any one of claims 1 to 6 or the resin composition film according to claim 7 or 8 in rigid-flex PCBs.

Images