A pi adhesive, a pi film and a warpage-resistant fccl product prepared therefrom

Abstract

The application belongs to the technical field of flexible copper-clad plate production, and particularly relates to a PI glue, a PI film prepared from the PI glue and further discloses a warpage-resistant FCCL product prepared from the PI film. The raw materials for preparing the PI glue include dianhydride monomers, diamine monomers and sheet fillers, and the dianhydride monomers and the diamine monomers are in-situ polymerized on the surface of the sheet fillers. The PI glue adds appropriate sheet fillers as a skeleton and is dispersed in the PI glue on the basis of a traditional PI glue system, so that the coefficient of thermal expansion (CTE) of the PI glue is effectively reduced, the deformation of the PI glue during thermal cyclization to form a film is reduced, the dimensional stability of the PI film and the dimensional stability of a subsequent FCCL product are improved, and the application requirements of the FCCL product can be met.

Description

Technical Field

[0001] This invention belongs to the field of flexible copper clad laminate production technology, specifically relating to a PI adhesive, a PI film with dimensional stability, and further disclosing a warp-resistant FCCL product prepared therefrom. Background Technology

[0002] In recent years, with the development of communication technology, personal electronic products have gradually become thinner. The electronic components and circuits within these products mainly use flexible copper clad laminates (FCCLs) as substrates, which requires FCCL circuits to become increasingly miniaturized and denser. As the cover film for traditional flexible copper clad laminates, polyimide films are also becoming the mainstream product, increasingly sought after, with even thinner shapes, such as ultra-thin films below 10μm.

[0003] However, the disadvantages of this ultra-thin polyimide film are its relatively low elastic modulus and relatively high coefficient of thermal expansion compared to copper foil. This results in low peel strength and poor dimensional stability in single-sided flexible copper-clad laminates. This is because the low modulus of the polyimide insulation layer makes it difficult to provide good support, causing excessive deformation of the copper foil during peeling, leading to low peel strength on the single side. Conversely, the high coefficient of thermal expansion of the polyimide insulation layer, during the thermal imidization process in the flexible copper-clad laminate manufacturing process, causes the PI adhesive to shrink, leading to warping and other problems in the single-sided flexible copper-clad laminate. In severe cases, it may even shrink and roll into a cylindrical shape, seriously affecting the product's dimensional stability and subsequent applications.

[0004] Chinese patent CN112955497A discloses a method for preparing an ultrathin polyimide film with improved dimensional stability. This method prepares the polyimide film using an imidization precursor composition comprising a first polyamic acid prepared by polymerization of a first dianhydride and a first diamine, a second polyamic acid prepared by polymerization of a second dianhydride and a second diamine, and an inorganic filler. This method effectively solves the dimensional stability problem of ultrathin polyimide films with a thickness of less than 10.0 μm, achieving a modulus of over 4 GPa and a coefficient of thermal expansion of 8 ppm / ℃-10 ppm / ℃. However, the preparation method of this polyimide film is relatively complex.

[0005] Therefore, developing a PI adhesive system suitable for forming dimensionally stable FCCL products, thereby obtaining FCCL products with more stable application performance, is of positive significance for the development of thinner products. Summary of the Invention

[0006] To address the aforementioned technical problems, the first objective of this invention is to provide a PI adhesive that has superior bonding ability with copper foil, and the adhesive itself has a low coefficient of expansion. FCCL products prepared using this PI adhesive exhibit excellent dimensional stability and good warping resistance.

[0007] The second objective of this invention is to provide a PI film with better dimensional stability, wherein the film has better adhesion to the copper foil substrate and better warping resistance.

[0008] The third objective of this invention is to provide an FCCL product with superior warpage resistance.

[0009] Therefore, the present invention provides a PI adhesive, wherein the raw materials for preparing the PI adhesive include dianhydride monomer, diamine monomer and sheet filler, and the dianhydride monomer and the diamine monomer are polymerized in situ on the surface of the sheet filler.

[0010] Specifically, the sheet-like filler includes one or a mixture of several of the following: silicon oxide, silicon carbide, talc, aluminum oxide, montmorillonite, and mica.

[0011] Preferably, the particle size D50 of the sheet filler is 2-10 μm, more preferably 2.8-8 μm, and even more preferably 2.8 μm;

[0012] Preferably, the specific surface area of ​​the sheet-like packing is 7-15 m². 2 / g, with a preferred specific surface area of ​​12m². 2 / g.

[0013] Specifically, the amount of the sheet-like filler added is 5-15 wt% of the total amount of the diamine monomer and dianhydride monomer.

[0014] Specifically, the PI adhesive:

[0015] The diamine monomers include p-phenylenediamine, m-phenylenediamine, 3,3'-dimethylbenzidine, 2,2'-dimethylbenzidine, 2,4-diaminotoluene, 2,6-diaminotoluene, 3,5-diaminobenzoic acid, 4,4'-diaminodiphenyl ether, 3,4'-diaminodiphenyl ether, 4,4'-diaminodiphenylmethane (methylenediamine), 3,3'-dimethyl-4,4'-diaminobiphenyl, 2,2'-dimethyl-4,4'-diaminobiphenyl, 2,2'-bis(trifluoromethyl)-4,4'-diaminobiphenyl, 3,3'-dimethyl-4,4'-diaminodiphenylmethane, and 3,3'-dicarboxylic acid. 4,4'-diaminodiphenylmethane, 3,3',5,5'-tetramethyl-4,4'-diaminodiphenylmethane, bis(4-aminophenyl)sulfide, 4,4'-diaminobenzoylaniline, 3,3'-dimethoxybenzidine, 2,2'-dimethoxybenzidine, 3,3'-diaminodiphenyl ether, 3,4'-diaminodiphenyl ether, 4,4'-diaminodiphenyl ether, 3,3'-diaminodiphenyl sulfide, 3,4'-diaminodiphenyl sulfide, 4,4'-diaminodiphenyl sulfide, 3,3'-diaminodiphenyl sulfone, 3,4'-diaminodiphenyl sulfone Diphenyl sulfone, 4,4'-diaminodiphenyl sulfone, 3,3'-diaminobenzophenone, 4,4'-diaminobenzophenone, 3,3'-diamino-4,4'-dichlorobenzophenone, 3,3'-diamino-4,4'-dimethoxybenzophenone, 3,3'-diaminodiphenylmethane, 3,4'-diaminodiphenylmethane, 4,4'-diaminodiphenylmethane, 2,2-bis(3-aminophenyl)propane, 2,2-bis(4-aminophenyl)propane, 2,2-bis(3-aminophenyl)-1,1,1,3,3,3-hexafluoropropane, 2 2-Bis(4-aminophenyl)-1,1,1,3,3,3-hexafluoropropane, 3,3'-diaminodiphenyl sulfoxide, 3,4'-diaminodiphenyl sulfoxide, 4,4'-diaminodiphenyl sulfoxide, 1,3-bis(3-aminophenyl)benzene, 1,3-bis(4-aminophenyl)benzene, 1,4-bis(3-aminophenyl)benzene, 1,4-bis(4-aminophenyl)benzene, 1,3-bis(4-aminophenoxy)benzene, 1,4-bis(3-aminophenoxy)benzene, 1,3-bis(3-aminophenoxy)-4-trifluoromethylbenzene, 3,3 '-Diamino-4-(4-phenyl)phenoxybenzophenone, 3,3'-diamino-4,4'-di(4-phenylphenoxy)benzophenone, 1,3-bis(3-aminophenyl sulfide)benzene, 1,3-bis(4-aminophenyl sulfide)benzene, 1,4-bis(4-aminophenyl sulfide)benzene, 1,3-bis(3-aminophenyl sulfone)benzene, 1,3-bis(4-aminophenyl sulfone)benzene, 1,4-bis(4-aminophenyl sulfone)benzene, 1,3-bis[2-(4-aminophenyl)isopropyl]benzene, 1,4-bis[2-(3-aminophenyl)isopropyl]benzene, 1,4-bis[2-(4-aminophenyl)isopropyl]benzene, 3,3'-bis(3-aminophenoxy)biphenyl, 3,3'-bis(4-aminophenoxy)biphenyl, 4,4'-bis(3-aminophenoxy)biphenyl, 4,4'-bis(4-aminophenoxy)biphenyl, bis[3-(3-aminophenoxy)phenyl]ether, bis[3-(4-aminophenoxy)phenyl]ether, bis[4-(3-aminophenoxy)phenyl]ether, bis[4-(4-aminophenoxy)phenyl]ether, bis[3-(3-aminophenoxy)phenyl]one, bis[3-(4-aminophenoxy)phenyl]one [Phenylacetyl]ketone, bis[4-(3-aminophenoxy)phenyl]ketone, bis[4-(4-aminophenoxy)phenyl]ketone, bis[3-(3-aminophenoxy)phenyl]sulfide, bis[3-(4-aminophenoxy)phenyl]sulfide, bis[4-(3-aminophenoxy)phenyl]sulfide, bis[4-(4-aminophenoxy)phenyl]sulfide, bis[3-(3-aminophenoxy)phenyl]sulfone, bis[3-(4-aminophenoxy)phenyl]sulfone, bis[4-(3-aminophenoxy)phenyl]sulfone bis[4-(4-aminophenoxy)phenyl]sulfone, bis[3-(3-aminophenoxy)phenyl]methane, bis[3-(4-aminophenoxy)phenyl]methane, bis[4-(3-aminophenoxy)phenyl]methane, bis[4-(4-aminophenoxy)phenyl]methane, 2,2-bis[3-(3-aminophenoxy)phenyl]propane, 2,2-bis[3-(4-aminophenoxy)phenyl]propane, 2,2-bis[4-(3-aminophenoxy)phenyl]propane, 2,2-bis[4-( At least one of the following: [4-aminophenoxy)phenyl]propane, 2,2-bis[3-(3-aminophenoxy)phenyl]-1,1,1,3,3,3-hexafluoropropane, 2,2-bis[3-(4-aminophenoxy)phenyl]-1,1,1,3,3,3-hexafluoropropane, 2,2-bis[4-(3-aminophenoxy)phenyl]-1,1,1,3,3,3-hexafluoropropane, and 2,2-bis[4-(4-aminophenoxy)phenyl]-1,1,1,3,3,3-hexafluoropropane;

[0016] The dianhydride monomers include pyromellitic dianhydride, oxydiphthalic anhydride, 3,3',4,4'-biphenyltetracarboxylic dianhydride, 2,3,3',4'-biphenyltetracarboxylic dianhydride, diphenyl sulfone-3,4,3',4'-tetracarboxylic dianhydride, bis(3,4-dicarboxyphenyl)sulfide dianhydride, 2,2-bis(3,4-dicarboxyphenyl)-1,1,1,3,3,3-hexafluoropropane dianhydride, 2,3,3',4'-benzophenone tetracarboxylic dianhydride, 3,3',4,4'-benzophenone tetracarboxylic dianhydride, bis(3,4-dicarboxyphenyl)methane dianhydride, 2,2-bis(3,4-dicarboxyphenyl)propane dianhydride, and p-phenylenebis(phenylene) Triacetic acid monoester anhydride), p-biphenylene di(triacetic acid monoester anhydride), m-tert-phenyl-3,4,3',4'-tetracarboxylic acid dianhydride, p-tert-phenyl-3,4,3',4'-tetracarboxylic acid dianhydride, 1,3-bis(3,4-dicarboxyphenoxy)phthalic anhydride, 1,4-bis(3,4-dicarboxyphenoxy)phthalic anhydride, 1,4-bis(3,4-dicarboxyphenoxy)biphenyl dianhydride, 2,2-bis[(3,4-dicarboxyphenoxy)phenyl]propane dianhydride, 2,3,6,7-naphthalenetetracarboxylic dianhydride, 1,4,5,8-naphthalenetetracarboxylic dianhydride, and at least one of 4,4'-(2,2-hexafluoroisopropylidene)diphthalic anhydride;

[0017] The molar ratio of the diamine monomer to the dianhydride monomer is 1:0.98-0.99.

[0018] The present invention also discloses a PI film prepared from the PI adhesive.

[0019] This invention also discloses a method for preparing the PI adhesive, comprising the steps of dispersing the sheet-like filler in the diamine monomer, and adding the dianhydride monomer for in-situ polymerization and curing into a film. Specifically, in the method for preparing the PI film, the filler is added by first pre-dispersing and then performing in-situ polymerization. Here, in-situ polymerization refers to adding the dianhydride after the filler particles are dispersed in the diamine, at which point the dianhydride reacts with the diamine, and the synthesized PI molecules are distributed around the filler particles.

[0020] Specifically, the pre-dispersion method is carried out by a reciprocating oscillator, and the oscillation speed of the reciprocating oscillator is 20-70 rpm, preferably 40-60 rpm.

[0021] The present invention also discloses the use of the PI adhesive or the PI film in the preparation of FCCL products.

[0022] The present invention also discloses an FCCL product, comprising copper foil and the PI adhesive or the PI film;

[0023] The PI adhesive is disposed on at least one surface of the copper foil, or the PI film is pressed onto at least one surface of the copper foil.

[0024] Specifically, the FCCL product mentioned above:

[0025] In the FCCL product, the surface roughness Rz of the electrolytic copper foil on the side closest to the PI adhesive or PI film is 1-3 μm, preferably 1.5-2.5 μm.

[0026] Specifically, the FCCL product described in this invention:

[0027] Preferably, in the FCCL product, the peel strength between the copper foil and the PI adhesive is greater than or equal to 7.5 N / cm, more preferably greater than 8 N / cm;

[0028] Preferably, the dimensional fluctuation range of the FCCL product is ≤10. ;

[0029] Preferably, the elongation of the FCCL product is 5-30%;

[0030] Preferably, the FCCL product has a warpage resistance of less than 1.5 cm;

[0031] Preferably, the FCCL product has heat resistance that can withstand tin bleaching treatment at 360°C for 30 seconds without bubbling.

[0032] The present invention also discloses a method for preparing the FCCL product, comprising:

[0033] The step of applying the PI adhesive to the surface of the copper foil and curing it;

[0034] or,

[0035] The steps include coating both sides of the PI film with thermoplastic adhesive and pressing the two copper foils together.

[0036] or,

[0037] The steps include preparing a PI film using the PI adhesive according to the method, and coating both sides of the PI film with thermoplastic adhesive and pressing the two copper foils together.

[0038] The PI adhesive of this invention, based on the traditional PI adhesive system, adds appropriate sheet fillers dispersed in the PI film as a skeleton, which significantly reduces the coefficient of thermal expansion (CTE) of the PI film, thereby reducing product deformation and improving the dimensional stability of the PI film and subsequent FCCL products; at the same time, the PI adhesive has good adhesion to copper foil, which can meet the application requirements of FCCL products.

[0039] The PI adhesive of the present invention uses sheet-like filler particles, and preferably the particle size / size of the inorganic filler is not greater than 19μm. The sheet-like filler can increase the shrinkage resistance of the PI adhesive or PI film by having a more extended specific surface area, thereby improving its bonding ability and dimensional stability.

[0040] The FCCL product of this invention, based on the excellent properties of sheet filler, and by using in-situ polymerization to improve the uniformity of filler dispersion, improves the bonding performance of PI adhesive, reduces the coefficient of thermal expansion (CTE) of PI film, effectively improves the warpage resistance of the FCCL product, reduces product deformation, and ensures the dimensional stability of the FCCL product. Detailed Implementation

[0041] Preparation Examples 1-6

[0042] In the following preparation examples 1-6 of the present invention, the raw materials for preparing the PI adhesive include a diamine monomer, a dianhydride monomer, and a sheet-like filler dispersed in the PI adhesive. The diamine monomer is selected from 3,4'-diaminodiphenyl ether, and the dianhydride monomer is selected from 4,4'-biphenyl dianhydride. The mass ratio of the diamine monomer, the dianhydride monomer, and the inorganic filler is 1:1:0.2.

[0043] The selection and characteristics of the sheet-like fillers in Preparation Examples 1-6 are shown in Table 1 below.

[0044] Table 1. Characteristics of the inorganic fillers added in Preparation Examples 1-6

[0045] serial number Element form Particle size D50 Specific surface area Preparation Example 1 Montmorillonite flakes 8μm 7m2 / g Preparation Example 2 talcum powder flakes 2.8μm 12m² / g Preparation Example 3 Aluminum oxide flakes 8μm 8m2 / g Preparation Example 4 Aluminum oxide flakes 8μm 7m2 / g Preparation Example 5 Aluminum oxide flakes 8μm 6m2 / g Preparation Example 6 Aluminum oxide flakes 8μm 16m² / g

[0046] Comparative Preparation Example 1

[0047] The raw material system of the PI adhesive in this comparative preparation example is the same as that in preparation examples 1-6, except that the inorganic filler is not added.

[0048] Comparative Preparation Example 2

[0049] The raw material system of the PI adhesive in this comparative preparation example is the same as that in preparation examples 1-6, except that the filler is spherical titanium dioxide.

[0050] Comparative preparation example 3

[0051] The raw material system of the PI adhesive in this comparative preparation example is the same as that in preparation examples 1-6, except that the filler is fumed silica.

[0052] Comparative preparation example 4

[0053] The raw material system of the PI adhesive in this comparative preparation example is the same as that in preparation examples 1-6, except that the filler is spherical aluminum oxide.

[0054] Comparative preparation example 5

[0055] The raw material system of the PI adhesive in this comparative preparation example is the same as that in preparation examples 1-6, except that the filler is a three-dimensional multifaceted aluminum oxide.

[0056] It should be noted that the above preparation examples only use a common 3,4'-diaminodiphenyl ether (diamine monomer) and 4,4'-biphenyl ether dianhydride (dianhydride monomer) system to demonstrate the PI adhesive formulation and its effect. In fact, in the PI adhesive formulation of this invention, the diamine monomer and dianhydride monomer only need to be conventional PI adhesive-forming systems. The improving effect of the sheet-like filler is not affected by the diamine monomer and dianhydride monomer; the addition of the sheet-like filler can effectively improve the performance of the PI adhesive, thereby improving the application performance of the PI film and FCCL products.

[0057] Examples 1-6

[0058] In Examples 1-6 of the present invention, the PI film was prepared using the PI adhesive system described in Examples 1-6, and the performance of the PI film was tested.

[0059] The method for preparing the PI membrane includes: taking a selected amount of the filler and dispersing it in a diamine monomer, pre-dispersing it under the action of a reciprocating oscillator (50 rpm), and then adding a selected amount of dianhydride monomer. At this time, the dianhydride reacts with the diamine to solidify into a membrane, and the filler particles are uniformly distributed in the PI membrane.

[0060] Comparative Examples 1-5

[0061] In Comparative Examples 1-5 of the present invention, the PI films were prepared using the PI adhesive system described in Comparative Preparation Examples 1-5, and the performance of the PI films was tested.

[0062] The preparation method of the PI film is the same as in Examples 1-6.

[0063] The performance of the PI films prepared in Examples 1-6 and Comparative Examples 1-5 were tested respectively. The specific test parameters and test standards included:

[0064] PI film tensile strength test method: Reference standard: IPC-TM-650;

[0065] PI film elastic modulus test method: Reference standard: IPC-TM-650;

[0066] PI film elongation test method: Reference standard: IPC-TM-650;

[0067] Test method for the coefficient of thermal expansion of PI film: Tested using TMA (thermomechanical analyzer);

[0068] The test results for the above parameters are shown in Table 2 below.

[0069] Table 2 Performance results of PI film

[0070]

[0071] As can be seen, the addition of sheet-like fillers to the PI adhesive of the present invention allows the inorganic sheet-like fillers to act as the skeleton of the PI film during the curing and molding process, effectively increasing the elastic modulus of the PI film and reducing the coefficient of thermal expansion of the PI film. Although the tensile strength and elongation are reduced, they can still meet the application requirements of flexible copper clad laminates.

[0072] The performance test results of PI in the comparative scheme show that the granular filler does not significantly improve the elastic modulus and thermal expansion coefficient of the PI film, which may be because the granular filler is difficult to form a continuous support structure.

[0073] Application examples

[0074] Application Examples 1-6 of the present invention respectively use the PI adhesive products described in Preparation Examples 1-6 to prepare the required FCCL products. Comparative Application Examples 1-5 of the present invention respectively use the PI adhesive products described in Comparative Preparation Examples 1-5 to prepare the required FCCL products.

[0075] In Application Examples 1-6 and Comparative Application Examples 1-5 of the present invention, the FCCL products have the same structure, which is a single-sided panel structure. Specifically, the structure is copper foil-PI adhesive, that is, a single-sided flexible copper-clad board formed by curing a layer of copper foil and a layer of PI adhesive coated on the surface of the copper foil.

[0076] The performance test results of the FCCL products described in Application Examples 1-6 and Comparative Application Examples 1-5 are shown in Table 3 below.

[0077] Table 3 Performance results of FCCL products

[0078]

[0079] As can be seen, the addition of sheet fillers to the PI adhesive of this invention effectively increases the peel strength of single-sided flexible copper-clad laminates and reduces the shrinkage of the PI adhesive. Due to their shape characteristics, sheet fillers easily form continuous irregular structures, acting as a support in the adhesive film. Therefore, the PI adhesive with added sheet fillers exhibits excellent mechanical properties. This not only reduces the deformation of the adhesive surface caused by the peeling of the copper foil from the PI layer, increasing the adhesion of the single-sided panel, but also reduces the thermal shrinkage of the PI layer, resulting in excellent performance in terms of dimensional expansion, contraction, and warpage of the single-sided panel.

[0080] However, the performance test results of the FCCL product described in the comparative application example show that the granular filler does not significantly improve the mechanical properties of the PI adhesive. In summary, the FCCL product of this invention, based on the excellent properties of the flake filler added to the PI adhesive and employing in-situ polymerization to improve the uniformity of filler dispersion, improves the adhesive performance of the PI adhesive, reduces the coefficient of thermal expansion (CTE) of the PI film, effectively improves the warpage resistance of the FCCL product, reduces product deformation, and ensures the dimensional stability of the FCCL product.

[0081] Obviously, the above embodiments are merely illustrative examples for clear explanation and are not intended to limit the implementation. Those skilled in the art will recognize that other variations or modifications can be made based on the above description. It is neither necessary nor possible to exhaustively list all possible implementations here. However, obvious variations or modifications derived therefrom are still within the scope of protection of this invention.

Claims

1. A PI adhesive, characterized in that, The raw materials for preparing the PI adhesive include dianhydride monomer, diamine monomer, and sheet filler, wherein the dianhydride monomer and the diamine monomer are polymerized in situ on the surface of the sheet filler; The sheet-like filler is one or a mixture of several of the following: silicon dioxide, silicon carbide, talc, aluminum oxide, montmorillonite, and mica. The particle size D50 of the sheet-like filler is 2-10 μm, and the specific surface area of ​​the sheet-like filler is 7-15 m². 2 / g.

2. The PI adhesive according to claim 1, characterized in that, The amount of the sheet-like filler added is 5-15 wt% of the total amount of the diamine monomer and dianhydride monomer.

3. The PI adhesive according to claim 1 or 2, characterized in that: The diamine monomers include p-phenylenediamine, m-phenylenediamine, 3,3'-dimethylbenzidine, 2,2'-dimethylbenzidine, 2,4-diaminotoluene, 2,6-diaminotoluene, 3,5-diaminobenzoic acid, 4,4'-diaminodiphenyl ether, 3,4'-diaminodiphenyl ether, 2,2'-bis(trifluoromethyl)-4,4'-diaminobiphenyl, 3,3'-dimethyl-4,4'-diaminodiphenylmethane, 3,3',5,5'-tetramethyl-4,4'-diaminodiphenylmethane, 4,4'-diaminobenzoylaniline, 3,3'-dimethoxybenzidine, 3,3'-diaminodiphenyl ether, 4,4'-diaminodiphenyl sulfide, 3,3'-diaminodiphenyl sulfone, 4,4'-diaminodiphenyl sulfone, 3,3'-diaminodibenzophenone, and 4,4'-diaminodibenzophenone. At least one of the following: 3,3'-diaminodiphenylmethane, 3,4'-diaminodiphenylmethane, 4,4'-diaminodiphenylmethane, 2,2-bis(4-aminophenyl)propane, 1,3-bis(4-aminophenoxy)benzene, 1,4-bis(3-aminophenoxy)benzene, 4,4'-bis(3-aminophenoxy)biphenyl, 4,4'-bis(4-aminophenoxy)biphenyl, bis[4-(3-aminophenoxy)phenyl]sulfone, bis[4-(4-aminophenoxy)phenyl]sulfone, 2,2-bis[4-(3-aminophenoxy)phenyl]propane, 2,2-bis[4-(4-aminophenoxy)phenyl]propane, and 2,2-bis[4-(4-aminophenoxy)phenyl]-1,1,1,3,3,3-hexafluoropropane; The dianhydride monomer includes at least one of 4,4'-biphenyl ether dianhydride, pyromellitic dianhydride, 3,3',4,4'-biphenyltetracarboxylic dianhydride, 2,3,3',4'-biphenyltetracarboxylic dianhydride, 3,3',4,4'-benzophenone tetracarboxylic dianhydride, 1,4-bis(3,4-dicarboxyphenoxy)phenyl dianhydride, 2,3,6,7-naphthalenetetracarboxylic dianhydride, and 1,4,5,8-naphthalenetetracarboxylic dianhydride; The molar ratio of the diamine monomer to the dianhydride monomer is 1:0.98-0.

99.

4. A PI film prepared from the PI adhesive according to any one of claims 1-3.

5. A method for preparing the PI film according to claim 4, characterized in that, The process includes the steps of dispersing the sheet-like filler in the diamine monomer, and the steps of adding the dianhydride monomer for in-situ polymerization and curing into a film.

6. Use of the PI adhesive according to any one of claims 1-3 or the PI film according to claim 4 for the preparation of FCCL products.

7. An FCCL product, characterized in that, Includes copper foil and the PI adhesive according to any one of claims 1-3 or the PI film according to claim 4; The PI adhesive is coated on at least one side of the copper foil, or the PI film is pressed onto at least one side of the copper foil.

8. The FCCL product according to claim 7, characterized in that, In the FCCL product, the surface roughness Rz of the copper foil near the PI adhesive or PI film is 1-3 μm.

9. A method for preparing the FCCL product of claim 7 or 8, characterized in that, include: The step of applying the PI adhesive according to any one of claims 1-3 to the surface of the copper foil and then curing it; or, The steps of coating both sides of the PI film according to claim 4 with thermoplastic adhesive and pressing the two copper foils together; or, The steps of preparing a PI film according to the method of claim 5 using the PI adhesive of any one of claims 1-3, and coating both sides of the PI film with thermoplastic adhesive and pressing the two copper foils together.

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