A low-temperature self-adhesive high-modulus polyimide film for filters and its application

Abstract

The present invention discloses a low-temperature self-adhesive high-modulus polyimide film for filters and its application. The polyimide film material provided by the present invention is made of the following raw materials: a polyamic acid solution, a low-temperature curing agent, a curing agent modifier, and an adhesion promoter; the polyamic acid solution is obtained by reacting an aromatic diamine with a dianhydride compound. The non-photosensitive and filler-free PI film material proposed by the present invention can simultaneously meet the characteristics of high modulus, high tensile strength, excellent adhesion performance, low-temperature curing, etc., and can meet the standards of a smooth surface after a dry etching process and no residual substances on the surface after cleaning.

Description

Technical Field

[0001] The invention belongs to the technical field of polymer materials, and in particular relates to a low-temperature self-adhesive high-modulus polyimide film for filters and an application thereof. Background Art

[0002] Polyimide (PI for short) occupies a very important position in the semiconductor field with its excellent mechanical properties, electrical insulation properties, chemical resistance and thermal stability. It has been widely used in IC front-end, advanced packaging, RF components, high-power electronic devices, flexible circuits and display panels.

[0003] With the continuous emergence of emerging semiconductor structures, especially the rapid development of wafer-level packaging filters and micro-electromechanical systems (MEMS), the number of devices directly attached with polyimide films as structural layers has gradually increased, showing its broad market prospects and unlimited potential.

[0004] SAW filter wafer-level packaging is a technology that major filter manufacturers are currently focusing on. Among them, the cavity structure of the interdigital transducer is an indispensable component in particle accelerators and electronic devices. Its core function is to finely adjust and screen the electromagnetic waves passing through. In this structure, the side wall membrane (Wall) and the top membrane (Roof) constitute the basic framework of the cavity, and they together form a closed space. In terms of structural design, the close combination of the wall and the roof is crucial, which not only ensures the effective transmission of electromagnetic waves, but also maintains the integrity of the structure. In order to achieve this, the adhesion between the two must meet extremely high standards to ensure that there will be no energy leakage or loss under the action of the electromagnetic field. In addition, as the supporting layer of the entire structure, the top membrane also bears additional mechanical loads, so it needs to have higher strength and stability. This usually means that in material selection and structural design, special consideration needs to be given to the bearing capacity and durability of the top to ensure the reliability and efficiency of the entire filter cavity in long-term operation.

[0005] At present, the top film technology uses a photosensitive PI film doped with inorganic fillers. For example, Chinese patent CN117701233A discloses a photosensitive polyimide glue suitable for coating and its coating method. The glue is made of raw materials including the following components: alkaline water-soluble resin, photocrosslinking agent, photoinitiator, inhibitor, inorganic filler, dispersant, defoamer, leveling agent, anti-settling agent, solvent, etc., and the viscosity of the glue is controlled between 800-1500cps. The glue can reach 48h at room temperature without sedimentation. After baking, the coated film can obtain a good uniformity of film thickness, reaching within ±1μm deviation, and there are no defects such as pores, vertical stripes, and filler condensation points on the surface. Although this type of film is doped with fillers to enhance strength, it needs to use an exposure and development process, and the inorganic filler therein is easy to precipitate to form residues, which directly weakens the quality of the opening after photolithography, affects the performance of the device, and the composite material system itself limits the further improvement of the film modulus. Therefore, high-performance non-photosensitive PI top film has become a cutting-edge direction in the market demand for space construction devices.

[0006] In terms of temperature technology, the traditional method of preparing high modulus polyimide (PI) film layers relies on high-temperature curing technology, which aims to build a solid PI film layer on the device surface by promoting the imidization process of polyimide. This process ensures that the polyimide resin can be fully cross-linked to build a stable three-dimensional network architecture, thereby greatly enhancing the thermal stability and mechanical strength of the material. However, in the field of advanced wafer-level packaging technology, facing the precise manufacturing process and fragile internal components, the high temperature challenges brought by traditional high-temperature curing methods are particularly prominent, which may cause irreversible damage to subsequent processing procedures and internal components of the package. Therefore, the market demand for high-performance low-temperature cured PI is also becoming increasingly urgent.

[0007] It can be seen that the above patents and various commercially available photosensitive polyimides cannot simultaneously meet the characteristics of high modulus, high tensile strength, excellent adhesion performance, low-temperature curing, etc., and cannot meet the standards of a smooth surface after dry etching process and no residual substances on the surface after cleaning.

[0008] In view of this, the present invention is proposed. Summary of the invention

[0009] The purpose of the present invention is to provide an innovative polyimide material, which can significantly reduce the curing temperature while maintaining the excellent properties of the original material, such as thermal stability and mechanical strength, and adapt to various subsequent process requirements of wafer-level packaging. It not only solves the problems caused by high temperature, but also opens up a new way to improve packaging quality, optimize production processes, and reduce costs. It has broad application prospects.

[0010] In order to achieve the above object, the technical solution adopted by the present invention is as follows:

[0011] In a first aspect, the present invention provides a polyimide film material, which is made of raw materials including the following parts by weight: 100 parts of polyamic acid solution, 3-40 parts of low-temperature curing agent, 5-40 parts of curing agent modifier, and 0.5-25 parts of adhesion promoter; the polyamic acid solution is obtained by reacting aromatic diamine and dianhydride compound.

[0012] In view of the problems of filler residue and high-temperature curing in the existing photosensitive PI films doped with inorganic fillers, the present invention proposes a non-photosensitive and filler-free PI film material, which can simultaneously meet the characteristics of high modulus, high tensile strength, excellent adhesion performance, low-temperature curing, etc., and can achieve the standards of a smooth surface after dry etching process and no residual substances on the surface after cleaning.

[0013] In the present invention, the aromatic diamine is selected from one or more of 4,4'-diaminodiphenyl ether, 2,2'-dimethylbenzidine, 4,4'-(1,3-propylenedioxy)diphenylamine, 2,2-bis(3-amino-4-hydroxyphenyl)hexafluoropropane, 2,2-bis[4-(4-aminophenoxybenzene)]hexafluoropropane, 4-[4-(4-aminophenoxy)phenoxy]aniline, 2,2'-bis(trifluoromethyl)diaminobiphenyl, 4,4'-bis(4-aminophenoxy)biphenyl, p-phenylenediamine, m-phenylenediamine, and 1,3-bis(3-aminopropyl)-1,1,3,3-tetramethyldisiloxane.

[0014] In a specific embodiment, the aromatic diamine is a combination of p-phenylenediamine and 1,3-bis(3-aminopropyl)-1,1,3,3-tetramethyldisiloxane, wherein the molar fraction of p-phenylenediamine is 92-97%.

[0015] In another specific embodiment, the aromatic diamine is a combination of p-phenylenediamine and 4,4'-diaminodiphenyl ether, wherein the molar fraction of p-phenylenediamine is 70%.

[0016] In another specific embodiment, the aromatic diamine is a combination of p-phenylenediamine and hexafluoromethylbenzene diamine, wherein the molar fraction of p-phenylenediamine is 70%.

[0017] In the present invention, the dianhydride compound is selected from one or more of 3,3',4,4'-biphenyltetracarboxylic dianhydride, pyromellitic anhydride, 3,3',4,4'-benzophenonetetracarboxylic dianhydride, cyclobutanetetracarboxylic dianhydride, 1,2,4,5-cyclohexanetetracarboxylic dianhydride, dicyclohexyl-3,4,3',4'-tetracarboxylic dianhydride, hexafluoro dianhydride, 4,4'-biphenyl ether dianhydride, 2,3,3',4'-diphenyl ether tetracarboxylic dianhydride, 3,3',4,4'-diphenyl sulfone tetracarboxylic dianhydride, and 2,3,3',4'-biphenyltetracarboxylic dianhydride.

[0018] In a specific embodiment, the dianhydride compound is 3,3',4,4'-biphenyltetracarboxylic dianhydride.

[0019] In another specific embodiment, the dianhydride compound is 3,3',4,4'-benzophenone tetracarboxylic dianhydride.

[0020] In another specific embodiment, the dianhydride compound is pyromellitic dianhydride.

[0021] In the present invention, the molar ratio of the aromatic diamine to the dianhydride compound is 1:(0.8-1), specifically, 1:0.98.

[0022] In the present invention, the low temperature curing agent is selected from one or more of imidazole, quinoline, isoquinoline, 1,2-dimethylimidazole and 2,5-dimethylpyrrole.

[0023] In the present invention, the curing agent modifier is selected from one or more of lactone, cyanate, isocyanate, anhydride, toluene diisocyanate, hexamethylene diisocyanate, hexamethylene diisocyanate, and isophorone diisocyanate.

[0024] In the present invention, the adhesion promoter is selected from γ-aminopropyl trimethoxysilane, γ-aminopropyl triethoxysilane, γ-glycidyloxypropyl trimethoxysilane, γ-glycidyloxypropyl triethoxysilane, 3-methacryloxypropyl dimethoxymethylsilane, 3-methacryloxypropyl trimethoxysilane, 3-ureidopropyl trimethoxysilane, 3-ureidopropyl triethoxysilane, 3-isocyanate trimethoxysilane, 3-isocyanate triethoxysilane, 3-mercaptopropyl trimethoxysilane, 3-mercaptopropyl triethoxysilane, One or more of trimethoxysilane, vinyltrimethoxysilane, N-phenyl-3-aminopropyltrimethoxysilane, 3-(triethoxysilyl)propylsuccinic anhydride, N-(3-diethoxymethylsilylpropyl)succinimide, N-(3-diethoxymethylsilylpropyl)phthalamic acid, benzophenone-3,3'-bis(N-[3-triethoxysilyl]propylamide)-4,4'-dicarboxylic acid and benzene-1,4-bis(N-[3-triethoxysilyl]propylamide)-2,5-dicarboxylic acid.

[0025] In a second aspect, the present invention provides a method for preparing the above-mentioned polyimide film material, comprising the following steps:

[0026] S1. Under nitrogen protection, aromatic diamine and dianhydride compound are polymerized to obtain a polyamic acid solution;

[0027] S2, mixing the polyamic acid solution with a low-temperature curing agent, a curing agent modifier, and an adhesion promoter, and reacting to obtain a polyamic acid solution;

[0028] S3, coating the polyamic acid solution on the surface of the substrate, and curing it to obtain a polyimide film.

[0029] In the above step S1, the organic solvent used in the polymerization reaction is selected from one or more of N-methylpyrrolidone, N,N-dimethylacetamide, N,N-dimethylformamide, dimethyl sulfoxide, γ-butyrolactone, β-propiolactone, acetone, methyl ethyl ketone, cyclohexanone, ethyl acetate, 3-methoxybutyl acetate, propylene glycol methyl ether acetate, tetrahydrofuran, dioxane, ethyl lactate, ethylene glycol diethyl ether, ethylene glycol monomethyl ether and ethylene glycol dimethyl ether.

[0030] In the above step S3, the coating conditions are: the coating rod thickness is 100-500 μm, and the coating rate is 2-20 mm / s.

[0031] Preferably, the coating rod has a thickness of 200 μm and a coating rate of 10 mm / s.

[0032] The curing conditions are: temperature 90-100° C., preferably 95° C., and time 30-40 min, preferably 35 min.

[0033] The substrate may be glass, a wafer, or the like.

[0034] In a specific embodiment, the preparation of the polyimide film is carried out according to the following steps: a desired release film is pasted on a clean glass plate; then the prepared low-temperature curable polyimide solution is evenly scraped on the surface of the release film, the coating rod size is set to 200 μm, and the coating rate is 10 mm / s to ensure the flatness and uniformity of the coating; then, the coated glass plate is transferred to a nitrogen-filled oven for pre-curing to obtain a polyimide film; finally, a protective layer release film is laminated on the polyimide film by a laminator.

[0035] In a third aspect, the present invention further provides a SAW filter, which contains the above-mentioned polyimide film material. The polyimide film material is used as a top film material.

[0036] In a specific embodiment, the specific steps of the SAW filter WLP packaging are as follows: in a dust-free environment, on a wafer that has completed the IDT and PAD processes, use photosensitive PI glue or film to complete the wall film and patterning, then use the polyimide film material described in the present invention to complete the Roof film, tear off the release film, perform low-temperature curing treatment, and then use a laser to perform a hole opening process on the Roof film to achieve a hole that meets the requirements; after completing the hole opening detection, perform the post-process Pillar and Bump process to finally complete the SAW filter WLP packaging.

[0037] Compared with the prior art, the present invention has the following beneficial effects:

[0038] Taking the top film of the filter cavity as an example, the present invention innovatively proposes a new type of low-temperature PI film material. This material not only has excellent strength, which is sufficient to stably support the upper molded structure and ensure the stability and reliability of the overall structure of the cavity, but also can be well adhered to the side wall of the filter, thereby meeting the high sensitivity of the wafer structure to temperature, and maintaining stable performance even under low temperature conditions. By using a modifier to protect the low-temperature curing agent, it can be unprotected during low-temperature curing (for example, 250°C) during application, restore the activity of the curing agent, and improve stability. At the same time, the dry etching process can be used to achieve patterning. BRIEF DESCRIPTION OF THE DRAWINGS

[0039] Figure 1 The PI film material provided by the present invention is used in the WLP packaging process of the SAW filter; in the figure: (a) represents PAD; (b) represents IDT; (c) represents Wall; (d) represents non-photosensitive filler-free Roof film; (e) represents Pillar; and (f) represents Bump.

[0040] Figure 2 This is a comparison diagram of the local enlarged effects of non-photosensitive unfilled roof adhesive film and photosensitive roof adhesive film doped with inorganic fillers; among them, the upper picture is non-photosensitive unfilled roof adhesive film, and the lower picture is photosensitive roof adhesive film doped with inorganic fillers. DETAILED DESCRIPTION

[0041] The present invention will be further described below in conjunction with specific embodiments, but the present invention is not limited to the following embodiments.

[0042] Unless otherwise specified, the experimental methods used in the following examples are conventional methods.

[0043] Unless otherwise specified, the reagents, materials, instruments, etc. used in the following examples can be obtained from commercial sources.

[0044] Synthesis example 1

[0045] In a 1L three-necked round-bottom flask equipped with a mechanical stirrer, a thermometer and a nitrogen protection device, 0.095 mol (10.27 g) of p-phenylenediamine (aromatic diamine) and 0.005 mol (1.24 g) of 1,3-bis(3-aminopropyl)-1,1,3,3-tetramethyldisiloxane (aromatic diamine) were dissolved in 300 g of NMP. After complete dissolution, 0.098 mol (28.83 g) of 3,3',4,4'-biphenyltetracarboxylic dianhydride (BPDA) (dianhydride compound) and an appropriate amount of NMP were added, and stirred at a constant temperature (25°C) for 12 h to obtain a polyamic acid solution (also known as polymer A1).

[0046] Synthesis example 2

[0047] In a 1L three-necked round-bottom flask equipped with a mechanical stirrer, a thermometer and a nitrogen protection device, 0.097 mol (10.49 g) of p-phenylenediamine and 0.003 mol (0.75 g) of 1,3-bis(3-aminopropyl)-1,1,3,3-tetramethyldisiloxane were dissolved in 300 g of NMP. After complete dissolution, 0.098 mol (28.83 g) of 3,3',4,4'-biphenyltetracarboxylic dianhydride (BPDA) and an appropriate amount of NMP were added, and the mixture was stirred at a constant temperature (25°C) for 12 h to obtain a polyamic acid solution (also known as polymer A2).

[0048] Synthesis example 3

[0049] In a 1L three-necked round-bottom flask equipped with a mechanical stirrer, a thermometer and a nitrogen protection device, 0.092mol (9.95g) of p-phenylenediamine and 0.008mol (1.99g) of 1,3-bis(3-aminopropyl)-1,1,3,3-tetramethyldisiloxane were dissolved in 300g of NMP. After complete dissolution, 0.098mol (28.83g) of 3,3',4,4'-biphenyltetracarboxylic dianhydride (BPDA) and an appropriate amount of NMP were added, and the mixture was stirred at a constant temperature (25°C) for 12h to obtain a polyamic acid solution (also known as polymer A3).

[0050] Synthesis example 4

[0051] In a 1L three-necked round-bottom flask equipped with a mechanical stirrer, a thermometer and a nitrogen protection device, 0.097 mol (10.49 g) of p-phenylenediamine and 0.003 mol (0.75 g) of 1,3-bis(3-aminopropyl)1,1,3,3-tetramethyldisiloxane were dissolved in 300 g of NMP. After complete dissolution, 0.098 mol (31.58 g) of 3,3',4,4'-benzophenone tetraacid dianhydride (BTDA) and an appropriate amount of NMP were added, and the mixture was stirred at a constant temperature (25°C) for 12 h to obtain a polyamic acid solution (also known as polymer A4).

[0052] Synthesis example 5

[0053] In a 1L three-necked round-bottom flask equipped with a mechanical stirrer, a thermometer and a nitrogen protection device, 0.097 mol (10.49 g) of p-phenylenediamine and 0.003 mol (0.75 g) of 1,3-bis(3-aminopropyl)1,1,3,3-tetramethyldisiloxane were dissolved in 300 g of NMP. After complete dissolution, 0.098 mol (21.38 g) of pyromellitic dianhydride (PMDA) and an appropriate amount of NMP were added, and the mixture was stirred at a constant temperature (25°C) for 12 h to obtain a polyamic acid solution (also known as polymer A5).

[0054] Synthesis example 6

[0055] In a 1L three-necked round-bottom flask equipped with a mechanical stirrer, a thermometer and a nitrogen protection device, 0.070 mol (7.57 g) of p-phenylenediamine (PDA) and 0.030 mol (6.01 g) of 4,4'-diaminodiphenyl ether (ODA) were dissolved in 300 g of NMP. After complete dissolution, 0.098 mol (28.83 g) of 3,3',4,4'-biphenyltetracarboxylic dianhydride (BPDA) and an appropriate amount of NMP were added, and the mixture was stirred at a constant temperature (25°C) for 12 h to obtain a polyamic acid solution (also known as polymer A6).

[0056] Synthesis Example 7

[0057] In a 1L three-necked round-bottom flask equipped with a mechanical stirrer, a thermometer and a nitrogen protection device, 0.070 mol (7.57 g) of p-phenylenediamine (PDA) and 0.030 mol (9.61 g) of hexafluoromethylbenzenediamine were dissolved in (TFMB) 300 g of NMP. After complete dissolution, 0.098 mol (28.83 g) of 3,3',4,4'-biphenyltetracarboxylic dianhydride (BPDA) and an appropriate amount of NMP were added, and stirred at a constant temperature (25°C) for 12 h to obtain a polyamic acid solution (also known as polymer A7).

[0058] Synthesis example 8

[0059] In a 1L three-necked round-bottom flask equipped with a mechanical stirrer, a thermometer and a nitrogen protection device, add 0.10mol (31.02g) 3,3',4,4'-diphenyl ether tetracarboxylic anhydride (ODPA), 26.03g 2-hydroxyethyl methacrylate (HEMA), 3.96g pyridine and 130g NMP, stir at room temperature for 6h to generate the corresponding aromatic diacid diethyl ester. The above product is reacted with 23.79g SOCl2 at 0-10℃ for 2h and at room temperature for 4h to generate the corresponding ODPE diacyl chloride diethyl ester.

[0060] In a 1L three-necked round-bottom flask equipped with a mechanical stirrer, a thermometer and a nitrogen protection device, 0.1mol (20.02g) of 4,4'-diaminodiphenyl ether and 158g of NMP were added and stirred to dissolve to form a homogeneous transparent solution; the temperature of the reaction liquid was cooled to below 10°C using an ice bath, and the above-prepared ODPE-diethyl dichloride was added dropwise to the NMP solution of 4,4-diaminodiphenyl ether (ODA) for 0.5h, and the reaction was carried out at room temperature for 10h; 1.48g of phthalic anhydride was then added and the stirring was continued for 1h; the reaction liquid was poured into 5L of deionized water, solids were precipitated, filtered, and vacuum dried to obtain primary polyamic acid ester resin; the resin was dissolved in tetrahydrofuran to form a solution, and residual metal or non-metal ions were removed by adsorption of anionic and cationic resins to obtain high-purity polyimide precursor resin solids (also known as polymer A8).

[0061] Example 1

[0062] In a clean room equipped with a yellow light, 20 g of A1 was weighed, 0.015 mol (1.02 g) of imidazole (low-temperature curing agent), 0.018 mol (3.13 g) of toluene diisocyanate (curing agent modifier), and 3 g of γ-aminopropyltriethoxysilane (adhesion promoter) were added, and the mixture was stirred for 10 h to obtain solution S1.

[0063] Paste the required release film on a clean glass plate. Evenly scrape the prepared solution S1 on the surface of the release film, set the coating rod size to 200μm, and the coating rate to 10mm / s to ensure the flatness and uniformity of the coating. Then, transfer the coated glass plate to a nitrogen-filled oven for pre-curing at 95℃ for 35min to obtain a polyimide film, and finally press the release film on the polyimide film using a laminator.

[0064] Example 2

[0065] The difference from Example 1 is that the 0.015 mol of imidazole in Example 1 is increased to 0.030 mol (2.04 g), and the 0.024 mol of toluene diisocyanate is increased to 0.033 mol (5.75 g), to obtain solution S2.

[0066] Example 3

[0067] The difference from Example 1 is that the 0.015 mol of imidazole in Example 1 is increased to 0.040 mol (2.72 g), and the 0.024 mol of toluene diisocyanate is increased to 0.043 mol (7.49 g), to obtain solution S3.

[0068] Example 4

[0069] The difference from Example 1 is that 0.015 mol of imidazole in Example 1 is replaced by 0.015 mol (1.44 g) of 1,2-dimethylimidazole to obtain solution S4.

[0070] Example 5

[0071] The difference from Example 2 is that 0.033 mol of toluene diisocyanate in Example 2 is replaced by 0.033 mol (1.42 g) of isocyanate to obtain solution S5.

[0072] Example 6

[0073] The difference from Example 2 is that 0.033 mol of toluene diisocyanate in Example 2 is replaced by 0.033 mol (5.55 g) of hexamethylene diisocyanate to obtain solution S6.

[0074] Example 7

[0075] The difference from Example 2 is that 0.030 mol of imidazole in Example 2 is replaced by 0.030 mol (2.85 g) of 2,5-dimethylpyrrole to obtain solution S7.

[0076] Example 8

[0077] The difference from Example 2 is that 0.030 mol of imidazole in Example 2 is replaced by 0.030 mol (3.87 g) of isoquinoline to obtain solution S8.

[0078] Example 9

[0079] The difference from Example 2 is that 20 g of A1 in Example 2 is replaced by 20 g of A2 to obtain solution S9.

[0080] Example 10

[0081] The difference from Example 2 is that 20 g of A1 in Example 2 is replaced by 20 g of A3 to obtain solution S10.

[0082] Embodiment 11

[0083] The difference from Example 2 is that 20 g of A1 in Example 2 is replaced by 20 g of A4 to obtain solution S11.

[0084] Example 12

[0085] The difference from Example 2 is that 20 g of A1 in Example 2 is replaced by 20 g of A5 to obtain solution S12.

[0086] Example 13

[0087] The difference from Example 2 is that 20 g of A1 in Example 2 is replaced by 20 g of A6 to obtain solution S13.

[0088] Embodiment 14

[0089] The difference from Example 2 is that 20 g of A1 in Example 2 is replaced by 20 g of A7 to obtain solution S14.

[0090] Comparative Example 1

[0091] The difference from Example 1 is that no imidazole and isocyanate are added, and solution D1 is obtained.

[0092] Paste the required release film on a clean glass plate. Evenly scrape the prepared D1 on the surface of the release film, set the coating rod size to 200μm, and the coating rate to 10mm / s to ensure the flatness and uniformity of the coating. Then, transfer the coated glass plate to a nitrogen-filled oven for pre-curing at 95℃ for 35min to obtain a polyimide film, and finally use a laminator to laminate the release film on the polyimide film.

[0093] Comparative Example 2

[0094] The difference from Example 14 is that 3 g of γ-aminopropyltriethoxysilane is not added to obtain solution D2.

[0095] Paste the required release film on a clean glass plate. Evenly scrape the prepared D2 on the surface of the release film, set the coating rod size to 200μm, and the coating rate to 10mm / s to ensure the flatness and uniformity of the coating. Then, transfer the coated glass plate to a nitrogen-filled oven for pre-curing at 95℃ for 35min to obtain a polyimide film, and finally press the release film on the polyimide film using a laminator.

[0096] Comparative Example 3

[0097] In a clean room equipped with a yellow light lamp, 50 g of polyimide precursor solid resin A8 was weighed and dissolved in 100 g of NMP solvent to form a homogeneous solution; photocurable monomer 10 g of ethylene glycol diethyl ether methacrylate (4EM), oxime photoinitiator PDO, 1.5 g of γ-aminopropyltriethoxysilane, 0.5 g of N-nitrosodiphenylamine and 20 g of ultrasonically dispersed silicon powder were stirred at room temperature for 1 hour to form a negative PSPI photoresist solution containing methacrylate side chains.

[0098] Paste the required release film on a clean glass plate. Evenly scrape the prepared solution S1 on the surface of the release film, set the coating rod size to 200μm, and the coating rate to 10mm / s to ensure the flatness and uniformity of the coating. Then, transfer the coated glass plate to a nitrogen-filled oven for pre-curing at 95℃ for 35min to obtain a polyimide film, and finally press the release film on the polyimide film using a laminator.

[0099] Performance Testing

[0100] The following are the values ​​of the curing performance at 250°C.

[0101]

[0102] Application Examples

[0103] This application example provides a SAW filter WLP package, such as Figure 1 As shown, the steps are as follows:

[0104] S1. Prepare wafers that have completed IDT (interdigital transducer) and PAD processes;

[0105] S2. Use photosensitive PI glue or film to complete the wall filming and graphics;

[0106] S3. Use the non-photosensitive and filler-free roof adhesive film of the present invention to apply the film. After the application of the film is completed, remove the protective film and perform a curing treatment. The curing conditions are: temperature 95° C., time 35 minutes.

[0107] S4. Use laser to make holes in the roof film to achieve holes that meet the requirements;

[0108] S5. Complete the hole opening detection.

[0109] S6. Complete the Pillar and Bump processes of the post-process and complete the SAW filter WLP packaging.

[0110] In order to verify the effect of the non-photosensitive filler-free roof adhesive film provided by the present invention, a photosensitive roof adhesive film doped with inorganic fillers was used as a comparison, and the internal structure of two different roof films was tested. The results are as follows: Figure 2 As shown in the partial enlarged picture, it can be seen that the interior of the non-photosensitive and filler-free roof film is uniform PI resin (as shown in the figure above), while the interior and surface of the photosensitive roof film doped with inorganic fillers contain filler components (as shown in the figure below).

[0111] Although the present invention has been described in detail above with general descriptions and specific embodiments, it is obvious to those skilled in the art that some modifications or improvements may be made thereto based on the present invention. Therefore, these modifications or improvements made without departing from the spirit of the present invention all fall within the scope of protection claimed by the present invention.

Claims

1. A polyimide adhesive film for SAW filter wafer-level packaging, which is formed by curing a release film and a polyimide film material; The polyimide film material is made of the following raw materials in parts by weight: 100 parts of polyamic acid solution, 3-40 parts of low-temperature curing agent, 5-40 parts of curing agent modifier, and 0.5-25 parts of adhesion promoter; The polyamic acid solution is obtained by reacting a diamine compound with a dianhydride compound; The molar ratio of the diamine compound to the dianhydride compound is 1:(0.8-1); The diamine compound is a combination of p-phenylenediamine and 1,3-bis(3-aminopropyl)-1,1,3,3-tetramethyldisiloxane; The dianhydride compound is 3,3',4,4'-biphenyltetracarboxylic dianhydride or 3,3',4,4'-benzophenone tetracarboxylic dianhydride; The low temperature curing agent is one or more of imidazole, isoquinoline, and 2,5-dimethylpyrrole; The curing agent modifier is isocyanate or toluene diisocyanate; The adhesion promoter is γ-aminopropyltriethoxysilane; The curing conditions are: temperature of 90-100° C. and time of 30-40 min.

2. The method for preparing the polyimide film according to claim 1, comprising the following steps: S1. Under nitrogen protection, the diamine compound and the dianhydride compound are polymerized to obtain a polyamic acid solution; S2, mixing the polyamic acid solution with a low-temperature curing agent, a curing agent modifier, and an adhesion promoter, and reacting to obtain a polyamic acid solution; S3, coating the polyamic acid solution on the surface of the substrate, and curing it to obtain a polyimide film; The substrate is a substrate with a release film attached to the surface; A release film is then pressed onto the surface of the polyimide film to obtain the polyimide adhesive film.

3. The preparation method according to claim 2, characterized in that: In step S1, the organic solvent used in the polymerization reaction is selected from one or more of N-methylpyrrolidone, N,N-dimethylacetamide, N,N-dimethylformamide, dimethyl sulfoxide, γ-butyrolactone, β-propiolactone, acetone, methyl ethyl ketone, cyclohexanone, ethyl acetate, 3-methoxybutyl acetate, propylene glycol methyl ether acetate, tetrahydrofuran, dioxane, ethyl lactate, ethylene glycol diethyl ether, ethylene glycol monomethyl ether and ethylene glycol dimethyl ether.

4. The preparation method according to claim 2, characterized in that: The curing conditions are: temperature of 90-100°C and time of 30-40min; The coating is performed using a coating rod; the coating rod has a thickness of 100-500 μm and a coating rate of 2-20 mm / s.

5. A SAW filter, comprising a top film material; the top film material is the polyimide film according to claim 1.

6. A SAW filter WLP packaging method, comprising the following steps: in a dust-free environment, on a wafer that has completed the IDT and PAD processes, using photosensitive PI glue or film to complete the wall filming and patterning, then using the polyimide film described in claim 1 to complete the roof filming, tearing off the release film, performing a low-temperature curing treatment, and then using a laser to perform a hole opening process on the roof film to achieve a hole that meets the requirements; after completing the hole opening detection, performing the post-process Pillar and Bump process to finally complete the SAW filter WLP packaging.

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