Thermoplastic polyimide adhesive for bonding copper-clad plate layers as well as preparation method and application of thermoplastic polyimide adhesive

Abstract

The invention discloses a thermoplastic polyimide adhesive for copper-clad plate interlayer bonding and a preparation method and application thereof, and belongs to the technical field of flexible electronic materials.The preparation method of the thermoplastic polyimide adhesive comprises the following steps that 4, 4 '-diaminodiphenyl ether is dissolved in an aprotic polar solvent, and a solution A is obtained; adding a first batch of anhydride into the solution A, and stirring for reaction to obtain a solution B; furyl diamine is added into the solution B, stirring reaction is carried out, and a solution C is obtained; and adding a second batch of anhydride into the solution C, and stirring for reaction to obtain the thermoplastic polyimide adhesive. The thermoplastic polyimide adhesive prepared by the invention has good heat resistance, has high bonding and peeling strength with a copper foil, and has better application in the fields of high-temperature binders and multi-layer flexible copper-clad plates; compared with traditional full-aromatic polyimide, the furyl-containing thermoplastic polyimide adhesive prepared by the method is easier to dissolve in an aprotic polar solvent after imidization, and solution processing is facilitated.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of flexible electronic materials, in particular to a thermoplastic polyimide glue for interlayer bonding of copper-clad plates and a preparation method and application thereof. BACKGROUND

[0002] Flexible electronics is the core development branch of the new generation of electronic information industry. The core devices such as flexible copper-clad plate (FCCL), flexible PCB and ultra-thin flexible sensor are developing towards light and thin, high bending resistance, high temperature resistance and high reliability. One of the core technical bottlenecks is the selection and adaptation of high-performance interfacial bonding system, and the core requirement is to realize the firm combination of copper foil or electroplated copper layer and flexible substrate, while meeting the requirements of interface non-cracking during bending and stable performance under high and low temperature conditions. The traditional bonding system has many shortcomings: the temperature resistance of epoxy resin glue is insufficient, which cannot adapt to the high temperature process and service environment of high-end flexible electronics; the thermosetting polyimide glue has excellent temperature resistance, but it cannot be remelted after curing, and it needs high pressure curing, which is easy to damage the ultra-thin substrate, and it has no thermoplasticity, so the bending resistance cannot meet the tens of thousands of bending requirements of flexible devices; ordinary acrylate and polyurethane glue has poor solvent resistance and high temperature aging failure, which cannot adapt to the harsh application scenarios of flexible electronics.

[0003] On the other hand, polyimide materials have extremely temperature resistance, environmental resistance and excellent dielectric performance due to the rigid imide ring structure, and become the core substrate and bonding material of high-end flexible electronics. Thermoplastic polyimide (TPI) has melt reprocessing property due to the absence of cross-linking structure in the molecular chain, which breaks through the limitations of thermosetting polyimide glue that cannot be reprocessed and has poor adaptability, while retaining the core advantages of polyimide materials such as temperature resistance (long-term 200-260℃), moisture resistance, radiation resistance and good matching of copper foil thermal expansion coefficient, becoming the preferred material for interfacial bonding of flexible electronics.

[0004] In the prior art, there are two application modes of TPI. The first mode is that TPI simultaneously assumes the functions of bonding and substrate support. In this mode, the TPI glue layer needs to reach a thickness of 50-100μm to realize support, but it has the shortcomings of insufficient modulus and poor dimensional stability, which easily leads to device warping and greatly increases the thickness of the device, which does not meet the development needs of light and thin flexible electronics, and is only suitable for a few special ultra-thin substrate scenarios. The second mode is that TPI is only used as an intermediate bonding layer without the function of substrate, which is the core technical direction that adapts to the production needs of most flexible electronics. In this mode, the thickness of the TPI glue layer is controlled within 3-25μm, which is only responsible for the interfacial bonding of copper foil and flexible substrate (PI / PET film), and the substrate support function is assumed by independent PI or PET film, which not only avoids the performance shortcomings of TPI as a substrate, but also maximizes its bonding advantages, realizing the core requirements of light and thin, high bending resistance and high reliability of the device.

[0005] In addition, during the preparation and service of the flexible circuit, small defects such as solder cracking, line gap, local delamination of the substrate, and pin peeling often occur. The thermoplastic polyimide glue is used for repairing in the mode of "only making an adhesive sealing layer, not replacing the original circuit substrate", which can restore the integrity and reliability of the circuit without damaging the original flexibility and structure of the circuit, and is the core solution for the precision repair of flexible electronics. The main features of the repair scene are that the glue layer needs to penetrate into various gaps, and the flowability of the glue layer needs to be controllable and the insulation of the cured glue layer needs to be excellent.

[0006] Therefore, it is of great practical significance to develop a thermoplastic polyimide glue with excellent heat resistance and good bonding strength, to make a flexible copper-clad plate with the glue, to replace the adhesive layer in the traditional copper-clad plate, to avoid the performance short board of PI as the substrate, or to prepare a thermoplastic polyimide glue with better flowability for repairing small defects in the circuit. SUMMARY

[0007] The purpose of the present application is to provide a thermoplastic polyimide glue for interlayer bonding of copper-clad plates and a preparation method and application thereof, to solve the problems raised in the background art.

[0008] To achieve the above-mentioned purpose, the present application provides the following technical solutions:

[0009] A preparation method of a thermoplastic polyimide glue for interlayer bonding of copper-clad plates, comprising the following steps:

[0010] 4,4'-diaminodiphenyl ether is dissolved in an aprotic polar solvent to obtain solution A;

[0011] A first batch of acid anhydride is added to solution A, and stirred and reacted to obtain solution B;

[0012] Furanyl diamine is added to solution B, and stirred and reacted to obtain solution C;

[0013] A second batch of acid anhydride is added to solution C, and stirred and reacted to obtain the thermoplastic polyimide glue.

[0014] Further, the temperature of the stirring and reaction is controlled at -20℃ to 20℃.

[0015] Further, the 4,4'-diaminodiphenyl ether and the furanyl diamine are both diamine monomers; the ratio of the total amount of substance of the diamine monomers to the total amount of substance of the two batches of acid anhydride is 1:(1-1.02); the mole percentage content of the first batch of acid anhydride in the two batches of acid anhydride is 5%-15% less than the mole percentage content of 4,4'-diaminodiphenyl ether in the diamine monomers.

[0016] Further, the mole ratio of the furanyl diamine is 1:1-19:1.

[0017] Further, the furan-based diamine is 2,5-furan dimethylamine; and the acid anhydride is one or more of 3,3',4,4'-biphenyl tetracarboxylic dianhydride, 3,3',4,4'-benzophenone tetracarboxylic dianhydride, and 4,4'-oxydiphthalic anhydride.

[0018] Further, the aprotic polar solvent is one or more of N,N-dimethylacetamide, N-methylpyrrolidone, and N,N-dimethylformamide.

[0019] Another object of the present application is to provide a thermoplastic polyimide glue prepared by the above method.

[0020] Another object of the present application is to provide an application of the above thermoplastic polyimide glue in interlayer bonding of flexible copper-clad plates, wherein the thermoplastic polyimide glue is coated between the substrate and the copper foil of the flexible copper-clad plate; and the thermoplastic polyimide glue is cured into a thermoplastic polyimide glue film by gradient temperature rising.

[0021] Another object of the present application is to provide a low-viscosity glue solution prepared by diluting the above thermoplastic polyimide glue and then adding acetic anhydride and triethylamine for reaction.

[0022] Another object of the present application is to provide an application of the above low-viscosity glue solution in defect repair of flexible copper-clad plates.

[0023] The present application provides a preparation method of a thermoplastic polyimide glue for interlayer bonding of copper-clad plates, which has the following effects compared with the prior art:

[0024] 1. The furan ring and flexible chain segment introduced by the furan-based diamine can reduce the softening temperature and the curing initiation temperature of the polyimide prepolymer, facilitating low-temperature forming and processing, and thus meeting the requirement of thermoplasticity;

[0025] 2. The structure of the furan ring and the flexible chain segment can significantly reduce the regularity of the polymer molecules, so that the glue film prepared subsequently has good film-forming property;

[0026] 3. The rigid structure of the furan ring can significantly improve the Tg;

[0027] 4. The batch feeding mode of the diamine monomer and the acid anhydride makes the furan-based diamine more uniformly distributed in the polyimide segment, so that the advantages brought by the furan-based diamine are more stably reflected;

[0028] 5. The thermoplastic polyimide glue prepared by the present application has good heat resistance, high peel strength with copper foil, and good application in the field of high-temperature adhesives and multi-layer flexible copper-clad plates.

[0029] 6. Compared with traditional fully aromatic polyimide, the furan-containing thermoplastic polyimide adhesive prepared by this invention is more soluble in aprotic polar solvents after imidization, which facilitates solution processing and thus prepares a low-viscosity adhesive solution. Attached Figure Description

[0030] Figure 1 The reaction route diagram shows the preparation method of the thermoplastic polyimide adhesive for interlayer bonding of copper-clad laminates provided in the embodiments of the present invention. Detailed Implementation

[0031] The technical solutions of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0032] like Figure 1 As shown, in one embodiment of the present invention, a thermoplastic polyimide adhesive for interlayer bonding of copper clad laminates is provided, the preparation method of which includes the following steps:

[0033] S1. Under inert gas protection, 4,4'-diaminodiphenyl ether is dissolved in an aprotic polar solvent to obtain solution A;

[0034] S2. With the temperature controlled between -20℃ and 20℃, add the first batch of acid anhydride powder to solution A, stir and react for 3-5 hours to obtain solution B;

[0035] S3. Add furanyldiamine to solution B and stir for 2-3 hours to obtain solution C;

[0036] S4. Control the temperature between -20℃ and 20℃, add the second batch of acid anhydride to solution C, stir and react for 3-5 hours to obtain a viscous polyamic acid solution, which is the thermoplastic polyimide glue with an apparent viscosity of 20000-50000cps.

[0037] In the above steps, it can be understood that 4,4'-diaminodiphenyl ether and furanyldiamine are both diamine monomers, and the molar ratio of furanyldiamine is 1:1-19:1, that is, furanyldiamine accounts for 5%-50% of the total amount of diamine monomers, preferably 10%.

[0038] It should be noted that, in the embodiments of the present invention, the furanyl diamine is selected as 2,5-furan dimethylamine, but it is not limited to this, and other diamine monomers containing furan rings and flexible segments can also be selected.

[0039] The ratio of the total amount of substance of the diamine monomers to the total amount of substance of the two batches of acid anhydrides (the first batch of acid anhydrides and the second batch of acid anhydrides) is 1:(1-1.02); the molar percentage content of the first batch of acid anhydrides in the two batches of acid anhydrides is 5%-15% less than the molar percentage content of 4,4'-oxydianiline in the diamine monomers, preferably 10% less.

[0040] Preferably, the acid anhydride is independently one or more of 3,3',4,4'-biphenyl tetracarboxylic dianhydride (BPDA), 3,3',4,4'-benzophenone tetracarboxylic dianhydride (BTDA), and 4,4'-oxydiphthalic anhydride (ODPA).

[0041] Preferably, the aprotic polar solvent is one or more of N,N-dimethylacetamide, N-methylpyrrolidone, and N,N-dimethylformamide. The amount of the aprotic polar solvent added is 4.5-8 times, more preferably 4 times, the total amount of mass of all solid materials (including all diamine monomers and acid anhydrides);

[0042] Preferably, the inert gas is one or more of nitrogen, helium, and argon.

[0043] In another embodiment of the present application, there is also provided an application of the above-mentioned thermoplastic polyimide adhesive in the interlayer bonding of a flexible copper-clad plate, wherein the thermoplastic polyimide adhesive is coated between the substrate and the copper foil of the flexible copper-clad plate; and the thermoplastic polyimide adhesive is cured into a thermoplastic polyimide adhesive film through gradient temperature curing.

[0044] Specifically, the coating method is as follows: the thermoplastic polyimide adhesive is diluted with an aprotic polar solvent (the same as that used in the preparation process) to a solid content of 5%-15%, and then applied to the substrate, and the liquid surface is leveled with a doctor blade. The solid content thickness after coating is 3-25 μm.

[0045] The gradient temperature curing process is as follows: 50-70℃ for 40-80 minutes, 90-110℃ for 40-80 minutes, 110-130℃ for 40-80 minutes, 140-160℃ for 40-80 minutes, 170-190℃ for 40-80 minutes, and 190-210℃ for 40-80 minutes; and the temperature rising rate in the temperature rising procedure is 1-3 min / ℃.

[0046] In the embodiment of the present application, the thermoplastic polyimide adhesive is prepared into an adhesive film by removing the solvent and pre-curing and cyclization, and then applied to the flexible copper-clad plate, which can provide large-area bonding capacity.

[0047] In another embodiment of the present application, a low viscosity glue solution is also provided, which is prepared by diluting the above-mentioned thermoplastic polyimide glue to a solid content of 5%-10%, and then adding acetic anhydride and triethylamine to react. The low viscosity glue solution can be used for repairing micro-defects of flexible copper-clad plate.

[0048] Specifically, the preparation method of the low viscosity glue solution is as follows: taking the above-mentioned polyamide acid solution after polymerization, adding it into a reaction kettle, diluting it with an aprotic polar solvent (the same as the solvent used in the preparation process) to obtain a slurry; then mixing acetic anhydride and triethylamine, and then dropping them into the slurry, stirring and reacting at room temperature for 12-24 hours to obtain a polyimide low viscosity glue solution with an apparent viscosity of 300-800 cps; wherein the molar ratio of the added acetic anhydride, triethylamine and carboxylic acid groups in the slurry is: n(carboxylic acid group):n(acetic anhydride):n(triethylamine)=1:(0.4-0.6):(0.2-0.3).

[0049] In the embodiment of the present application, the prepolymer of the above-mentioned thermoplastic polyimide glue is partially cyclized to prepare a low viscosity glue solution with better fluidity, which can be used for repairing micro-defects such as solder crack, circuit gap, and interlayer gap filling during the use of flexible copper-clad plate.

[0050] The following examples are cases of the present application in actual application, which are only exemplary and not limited.

[0051] Example 1: The embodiment provides a thermoplastic polyimide glue for interlayer bonding of copper-clad plate, and the preparation method thereof comprises the following steps:

[0052] S1, 50g of 4,4'-diamino diphenyl ether, 563.43g of N,N-dimethylacetamide are put into a reaction bottle, and stirred and dissolved under nitrogen protection to obtain solution A;

[0053] S2, after the dissolution is completed, the solution A is cooled to-15℃, and 69.886g of 4,4'-oxybisphthalic anhydride is added, and then stirred and reacted at the temperature for 5 hours to obtain solution B;

[0054] S3, 3.5g of 2,5-furandimethylamine is added to the solution B and stirred and reacted for 2 hours to obtain solution C;

[0055] S4, the temperature of the solution C is controlled at-15℃, and 17.471g of 4,4'-oxybisphthalic anhydride is added, and then stirred and reacted at the temperature for 5 hours, and after the reaction is completed, a viscous polyamide acid solution is obtained, which is the thermoplastic polyimide glue, and the apparent viscosity thereof is measured to be 31500 cps.

[0056] The thermoplastic polyimide glue is prepared into a thermoplastic polyimide glue film as follows: first, a clean and oil-free glass plate is taken, the polyamide acid solution is diluted with N,N-dimethylacetamide to a solid content of 10%, and then is applied on the surface of the glass plate and is leveled with a scraper; then, is placed in a vacuum oven with gradient temperature rising: 60°C for 60 minutes, 100°C for 60 minutes, 120°C for 60 minutes, 150°C for 60 minutes, 180°C for 60 minutes, 200°C for 60 minutes, and the temperature rising rate in the temperature rising procedure is 2 min / °C; after cooling, a thermoplastic polyimide glue film is obtained.

[0057] In addition, the thermoplastic polyimide glue is prepared into a low-viscosity glue solution as follows: 50 g of the polyamide acid solution after polymerization is taken into a reaction bottle, 50 g of N,N-dimethylacetamide is added for dilution, and a slurry is obtained; then, 2.041 g of acetic anhydride and 1.012 g of triethylamine are mixed and are dropped into the diluted slurry, and the reaction is stirred at room temperature for 24 hours, and a polyimide low-viscosity glue solution is obtained, and the apparent viscosity thereof is measured to be 370 cps.

[0058] Example 2: The embodiment provides a thermoplastic polyimide glue for interlayer bonding of copper-clad plates, and a preparation method thereof includes the following steps:

[0059] S1, 50 g of 4,4'-diamino diphenyl ether and 539.3 g of N,N-dimethylacetamide are put into a reaction bottle, and are dissolved under stirring with nitrogen protection to obtain solution A;

[0060] S2, after the dissolution, solution A is cooled to-15°C, 70.692 g of 4,4'-oxydiphthalic anhydride is added, and then is stirred at the temperature for 5 hours to obtain solution B;

[0061] S3, 1.658 g of 2,5-furandimethylamine is added to solution B and is stirred for 2 hours to obtain solution C;

[0062] S4, the temperature of solution C is controlled at-15°C, 12.475 g of 4,4'-oxydiphthalic anhydride is added, and then is stirred at the temperature for 5 hours, and after the reaction is completed, a viscous polyamide acid solution is obtained, which is the thermoplastic polyimide glue, and the apparent viscosity thereof is measured to be 38700 cps.

[0063] The thermoplastic polyimide glue is prepared into a thermoplastic polyimide glue film as follows: first, a clean and oil-free glass plate is taken, the polyamide acid solution is diluted with N,N-dimethylacetamide to a solid content of 10%, and then is applied on the surface of the glass plate and is leveled with a scraper; then, is placed in a vacuum oven with gradient temperature rising: 60℃ for 60 minutes, 100℃ for 60 minutes, 120℃ for 60 minutes, 150℃ for 60 minutes, 180℃ for 60 minutes, 200℃ for 60 minutes, and the temperature rising rate in the temperature rising procedure is 2min / ℃; after cooling, a thermoplastic polyimide glue film is obtained.

[0064] In addition, the thermoplastic polyimide glue is prepared into a low-viscosity glue solution as follows: 50g of the polyamide acid solution after polymerization is taken into a reaction bottle, 50g of N,N-dimethylacetamide is added for dilution, and a slurry is obtained; then, 2.03g of acetic anhydride and 1.006g of triethylamine are mixed and are dropped into the diluted slurry, and the reaction is stirred at room temperature for 24 hours, and a polyimide low-viscosity glue solution is obtained, and the apparent viscosity thereof is measured to be 485cps.

[0065] Example 3: The embodiment provides a thermoplastic polyimide glue for interlayer bonding of copper-clad plates, and a preparation method thereof includes the following steps:

[0066] S1, 50g of 4,4'-diamino diphenyl ether and 622.67g of N,N-dimethylacetamide are put into a reaction bottle, and are dissolved under stirring under nitrogen protection to obtain solution A;

[0067] S2, after the dissolution, solution A is cooled to-15℃, and 68.455g of 4,4'-oxydiphthalic anhydride is added, and then is stirred at the temperature for 5 hours to obtain solution B;

[0068] S3, 7.876g of 2,5-furandimethylamine is added to solution B and is stirred for 2 hours to obtain solution C;

[0069] S4, the temperature of solution C is controlled at-15℃, and 29.338g of 4,4'-oxydiphthalic anhydride is added, and then is stirred at the temperature for 5 hours, and after the reaction is completed, a viscous polyamide acid solution is obtained, which is the thermoplastic polyimide glue, and the apparent viscosity thereof is measured to be 23700cps.

[0070] The thermoplastic polyimide glue is prepared into a thermoplastic polyimide glue film as follows: first, a clean and oil-free glass plate is taken, the polyamide acid solution is diluted with N,N-dimethylacetamide to a solid content of 10%, and then is applied on the surface of the glass plate and is leveled with a scraper; then, the glass plate is placed in a vacuum oven and is subjected to gradient temperature rising: 60°C for 60 minutes, 100°C for 60 minutes, 120°C for 60 minutes, 150°C for 60 minutes, 180°C for 60 minutes, and 200°C for 60 minutes, and the temperature rising rate is 2 min / °C in the temperature rising procedure; and after cooling, the thermoplastic polyimide glue film is obtained.

[0071] In addition, the thermoplastic polyimide glue is prepared into a low-viscosity glue solution as follows: 50 g of the polyamide acid solution after polymerization is added into a reaction bottle, 50 g of N,N-dimethylacetamide is added for dilution, and a slurry is obtained; then, 2.067 g of acetic anhydride and 1.025 g of triethylamine are mixed and are added dropwise into the diluted slurry, and the mixture is stirred at room temperature for 24 hours, and a polyimide low-viscosity glue solution is obtained, and the apparent viscosity thereof is 330 cps.

[0072] Example 4: The embodiment provides a thermoplastic polyimide glue for interlayer bonding of copper-clad plates, and a preparation method thereof includes the following steps:

[0073] S1, 50 g of 4,4'-diamino diphenyl ether and 576.97 g of N,N-dimethylacetamide are added into a reaction bottle, and are stirred and dissolved under nitrogen protection to obtain solution A;

[0074] S2, after the dissolution, solution A is cooled to -15°C, 72.594 g of 3,3',4,4'-benzophenone tetracarboxylic dianhydride is added, and then is stirred at the temperature for 5 hours to obtain solution B;

[0075] S3, 3.5 g of 2,5-furandimethylamine is added into solution B and is stirred for 2 hours to obtain solution C;

[0076] S4, the temperature of solution C is controlled at -15°C, 18.148 g of 3,3',4,4'-benzophenone tetracarboxylic dianhydride is added, and then is stirred at the temperature for 5 hours, and after the reaction is completed, a viscous polyamide acid solution is obtained, which is the thermoplastic polyimide glue, and the apparent viscosity thereof is 34500 cps.

[0077] The thermoplastic polyimide glue is prepared into a thermoplastic polyimide glue film in the following manner: first, a clean and oil-free glass plate is taken, the polyamide acid solution is diluted with N,N-dimethylacetamide to a solid content of 10%, and then applied to the surface of the glass plate and leveled with a spatula; then, it is placed in a vacuum oven with gradient heating: 60°C for 60 minutes, 100°C for 60 minutes, 120°C for 60 minutes, 150°C for 60 minutes, 180°C for 60 minutes, and 200°C for 60 minutes, with a heating rate of 2 min / °C in the heating program; after cooling, a thermoplastic polyimide glue film is obtained.

[0078] In addition, the thermoplastic polyimide glue is prepared into a low-viscosity glue solution in the following manner: 50 g of the polyamide acid solution after polymerization is added to a reaction bottle, and 50 g of N,N-dimethylacetamide is added for dilution to obtain a slurry; then, 1.993 g of acetic anhydride and 0.988 g of triethylamine are mixed and added dropwise to the diluted slurry, and stirred at room temperature for 24 hours to obtain a polyimide low-viscosity glue solution, with an apparent viscosity of 478 cps.

[0079] The comparative example provides a thermoplastic polyimide glue, and the preparation method thereof comprises the following steps:

[0080] S1, 50 g of 4,4'-diamino diphenyl ether and 514.49 g of N,N-dimethylacetamide are added to a reaction bottle, and stirred and dissolved under nitrogen protection to obtain solution A;

[0081] S2, after dissolution, solution A is cooled to -15°C, and 70.759 g of 4,4'-oxydiphthalic anhydride is added, and then stirred at this temperature for 5 hours to obtain solution B;

[0082] S3, the temperature of solution B is controlled at -15°C, and 7.862 g of 4,4'-oxydiphthalic anhydride is added, and then stirred at this temperature for 5 hours, and after the reaction is completed, a viscous polyamide acid solution is obtained, which is a thermoplastic polyimide glue, with an apparent viscosity of 32000 cps.

[0083] The thermoplastic polyimide glue is prepared into a thermoplastic polyimide glue film in the following manner: first, a clean and oil-free glass plate is taken, the polyamide acid solution is diluted with N,N-dimethylacetamide to a solid content of 10%, and then applied to the surface of the glass plate and leveled with a spatula; then, it is placed in a vacuum oven with gradient heating: 60°C for 60 minutes, 100°C for 60 minutes, 120°C for 60 minutes, 150°C for 60 minutes, 180°C for 60 minutes, and 200°C for 60 minutes, with a heating rate of 2 min / °C in the heating program; after cooling, a thermoplastic polyimide glue film is obtained.

[0084] In addition, the thermoplastic polyimide glue is prepared into a low viscosity glue solution as follows: 50 g of the polyamic acid solution after polymerization is taken into a reaction bottle, 50 g of N,N-dimethylacetamide is added for dilution to obtain a slurry; then, 2.012 g of acetic anhydride and 0.997 g of triethylamine are mixed and then dropped into the diluted slurry, and the mixture is stirred at room temperature for 24 hours to obtain a polyimide low viscosity glue solution, and the apparent viscosity of which is measured to be 478 cps.

[0085] Performance test: the thermoplastic polyimide glue film and the polyimide low viscosity glue solution prepared in the above examples 1-4 and the comparative example are respectively tested for the following performance: glass transition temperature (Tg), thermal initial decomposition temperature (Td5%), thermal expansion coefficient, thermal conductivity coefficient, and peel strength. It should be noted that the internal structures of the glue film and the low viscosity glue solution are the same, so the test results of the other performance items of the two product forms are similar, and therefore only one test is performed; and the peel strength has two items, which are the test results of the two product forms. The specific test results are shown in Table 1:

[0086] Table 1: Performance test results of glue film and low viscosity glue solution

[0087]

[0088] From the test results in Table 1, it can be seen that compared with the wholly aromatic polyimide glue product without adding furan-based diamine, the thermoplastic polyimide glue product prepared in the examples of the present application has better heat resistance and peel strength, and the peel strength of the glue film and the low viscosity glue solution product can meet the requirements of the application scenarios such as flexible electronic copper-clad plate. In addition, the thermoplastic polyimide glue product prepared in the examples of the present application has a low thermal expansion coefficient and good heat dissipation performance.

[0089] Based on the above ideal embodiments according to the present application, through the above description, relevant personnel can make various changes and modifications without deviating from the technical idea of the present application. The technical scope of the present application is not limited to the contents in the specification.

Claims

1. A method for preparing a thermoplastic polyimide adhesive for interlayer bonding of copper clad laminates, characterized in that, Includes the following steps: 4,4'-diaminodiphenyl ether was dissolved in an aprotic polar solvent to obtain solution A; The first batch of acid anhydride was added to solution A, and the mixture was stirred to react, resulting in solution B. Add furanyldiamine to solution B, stir the reaction to obtain solution C; A second batch of acid anhydride was added to solution C, and the mixture was stirred to obtain the thermoplastic polyimide adhesive.

2. The method for preparing the thermoplastic polyimide adhesive for interlayer bonding of copper-clad laminates according to claim 1, characterized in that, The temperature of the stirring reaction is controlled between -20℃ and 20℃.

3. The method for preparing the thermoplastic polyimide adhesive for interlayer bonding of copper-clad laminates according to claim 1, characterized in that, The 4,4'-diaminodiphenyl ether and furanyldiamine are both diamine monomers; the ratio of the total amount of the diamine monomers to the total amount of the two batches of acid anhydrides is 1:(1-1.02); the molar percentage of the first batch of acid anhydrides in the two batches of acid anhydrides is 5%-15% less than the molar percentage of 4,4'-diaminodiphenyl ether in the diamine monomers.

4. The method for preparing the thermoplastic polyimide adhesive for interlayer bonding of copper-clad laminates according to claim 1, characterized in that, The molar ratio of furanyldiamine is 1:1 to 19:

1.

5. The method for preparing the thermoplastic polyimide adhesive for interlayer bonding of copper-clad laminates according to claim 1, 3, or 4, characterized in that, The furanyldiamine is 2,5-furandimethylamine; the anhydride is independently one or more of 3,3',4,4'-biphenyltetracarboxylic dianhydride, 3,3',4,4'-benzophenonetetracarboxylic dianhydride, and 4,4'-oxobisphthalic anhydride.

6. The method for preparing the thermoplastic polyimide adhesive for interlayer bonding of copper clad laminates according to claim 1, wherein the aprotic polar solvent is one or more of N,N-dimethylacetamide, N-methylpyrrolidone, and N,N-dimethylformamide.

7. A thermoplastic polyimide adhesive prepared by any one of claims 1-6.

8. The application of the thermoplastic polyimide adhesive as described in claim 7 in the interlayer bonding of flexible copper-clad laminates, characterized in that, The flexible copper-clad laminate is coated with the thermoplastic polyimide adhesive between the substrate and the copper foil; the thermoplastic polyimide adhesive is cured into a thermoplastic polyimide film by gradient heating.

9. A low-viscosity adhesive, characterized in that, The low-viscosity adhesive is prepared by diluting the thermoplastic polyimide adhesive of claim 7 and then adding acetic anhydride and triethylamine to react.

10. The application of the low-viscosity adhesive as described in claim 9 in the repair of defects in flexible copper-clad laminates.

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