CN111479395B

CN111479395B - Preparation method of glue-free flexible copper-clad plate

Info

Publication number: CN111479395B
Application number: CN202010380876.9A
Authority: CN
Inventors: 刘金刚; 肖潇; 武晓; 郭晨雨; 张燕; 毕洪生
Original assignee: China University of Geosciences Beijing
Current assignee: China University of Geosciences Beijing
Priority date: 2017-07-28
Filing date: 2017-07-28
Publication date: 2021-02-19
Anticipated expiration: 2037-07-28
Also published as: CN107266683B; CN111479395A; CN107266683A

Abstract

The invention discloses a preparation method of a glue-free flexible copper-clad plate. The thermoplastic polyimide film-based non-adhesive flexible copper clad laminate and the preparation method thereof are disclosed. The invention overcomes the thermoplasticity of the PI film and the high T thereof_gThe mutual restriction relationship between thermoplasticity and low CTE of the film exists, and the prepared PI film has excellent comprehensive properties including good thermoplasticity and high T_gThe copper clad laminate has the advantages of low CTE, good bonding strength with copper foil, smooth appearance, light weight, thinness, softness, flexibility and the like, and can be applied to devices such as microelectronics, photoelectrons, wearable electronic products and the like.

Description

Preparation method of glue-free flexible copper-clad plate

Technical Field

The invention belongs to the technical field of preparation of functional polyimide films, and particularly relates to a thermoplastic polyimide film and a non-adhesive flexible copper-clad plate prepared from the same.

Background

In recent years, Flexible Copper Clad Laminates (FCCL) have become more widely used in the electronics and display industry. FCCL generally refers to a flexible laminated composite material formed by coating a copper foil on a polymer insulating base film. The flexible printed circuit board (FPC) manufactured by the FCCL has the advantages of light weight, thinness, softness, flexibility and the like, and is widely applied to the fields of portable electronic equipment such as mobile phones, digital cameras, notebook computers, wearable electronic products and the like, liquid crystal televisions, instruments and meters and the like. The traditional FCCL adopts a 3-layer structure formed by Polyimide (PI)/adhesive/copper foil, wherein the adhesive layer is thermosetting resin such as acrylate and epoxy resin, the heat resistance and the dimensional stability of the adhesive are poor, and the adhesive is degraded at high temperature, so that the circuit board is warped and layered. The new FCCL developed in recent years is composed of only PI and copper foil without using an adhesive. The non-adhesive FCCL is higher in thermal stability and dimensional stability and thinner in thickness, and is widely applied to the high-tech fields of advanced integrated circuit packaging, wearable display and the like.

In the double-layer glue-free FCCL, the PI film has the functions of an insulating base film and an adhesive, so that the requirements of insulativity, dimensional stability, thermal property, mechanical property and adhesive property must be met at the same time. In order to prevent the final FCCL from suffering from defects such as warpage, dimensional stability requires that the Coefficient of Thermal Expansion (CTE) of the PI insulation base film be matched as much as possible with the copper foil (CTE: -17 ppm/. degree. C.). In terms of adhesion performance, in order to allow the PI base film and the copper foil to be well laminated, the PI base film is required to have good thermoplasticity (high temperature moldability) and adhesion to copper as high as possible. In terms of heat resistance, in order to ensure that the final FCCL has excellent thermal stability, the glass transition temperature (T) of the PI-based film is required on the premise of ensuring the hot-pressing process_g) As high as possible. Therefore, the development of a thermoplastic resin composition having good thermoplasticity and high T_gLow CTE and high adhesion PI-based films are of great interest for the development of FCCL.

In general, the thermoplasticity of PI films and their high T_gThe thermoplastic and its low CTE tend to be in a mutually limiting relationshipThe means of high PI film thermoplasticity comprises introducing flexible ether bond (-O-), sulfone group (-SO2-), and other groups, which tend to reduce the T of the film_gIn particular, the CTE value of the film is increased. For example, CN1869103 reports a class of thermoplastic PI films using a flexible diamine, bis [4- (3-aminophenoxy) phenyl]Sulfone (BAPS-m) and aromatic tetracarboxylic dianhydride by polymerization reaction. T of thermoplastic PI film prepared from BAPS-m and pyromellitic dianhydride (PMDA)_g308.16 ℃ but with a CTE as high as 61.56 ppm/DEG C; t of thermoplastic PI film prepared from BAPS-m and 3,3',4,4' -biphenyltetracarboxylic dianhydride (sBPDA)_g247.73 ℃ but with a CTE as high as 51.56 ppm/DEG C. To produce low CTE thermoplastic PI films, rigid dianhydride monomers are often copolymerized with flexible diamine monomers and rigid diamine monomers. For example, CN105348528 discloses a thermoplastic polyimide film and a preparation method thereof. The film adopts

rigid dianhydride

3,3',4,4' -biphenyl tetracid dianhydride (sBPDA) and flexible diamine 2,2' -bis [4- (4-aminophenoxy) phenyl]Propane (BAPP) and another rigid aromatic diamine, 2- (4-aminophenyl) -5-aminobenzimidazole are copolymerized to prepare a polyamic acid (PAA) solution, then the solution is coated on a copper foil, and FCCL is prepared after imidization at high temperature. The film had a CTE (50-250 ℃) of 17-19 ppm/DEG C and a peel strength with copper foil of 0.8N/mm. Although the thermoplastic PI film has a low CTE value, the adhesiveness with the copper foil is good<1.0N/mm, it is difficult to meet the application requirement of high performance FCCL (PI/Cu)>1.0N/mm)。

In recent years, a method of preparing a thermoplastic PI film using isomerized 2,3,3',4' -diphenyl ether tetracarboxylic dianhydride (aODPA) and an aromatic diamine has been widely regarded. For example, CN102532543B discloses a class of thermoplastic PI films prepared by copolymerizing aODPA with 2,3,3',4' -biphenyltetracarboxylic dianhydride (bpda) and an aromatic diamine. When the film is heated to a certain temperature, the modulus of the film can be rapidly reduced to a certain level in a narrow temperature range to form a resin with certain viscoelasticity, and the heat bonding between the PI film and the PI film or other metal substrates can be realized under pressure. However, the reported chemical structure of the PI film contains a large number of flexible ether bond segments, which imparts excellent self-heating sealability to the film, but at the same time, it is also apparent thatReduce the T of the film_gAnd increases the CTE value thereof.

Therefore, how to impart excellent thermoplasticity to PI films while maintaining high T thereof_gLow CTE, and high adhesion to copper foil are issues of concern in the FCCL field.

Disclosure of Invention

In order to overcome the defects of the existing FCCL preparation method, the PI film is endowed with excellent thermoplasticity and simultaneously keeps high T_gLow CTE and high adhesion with copper foil, the invention provides a method for preparing a thermoplastic polyimide film. The polyimide film prepared by the method has good insulativity, dimensional stability, thermal property, mechanical property and bonding property, and can be used for preparing double-layer non-adhesive FCCL. Meanwhile, the invention also provides a non-glue flexible copper clad laminate prepared based on the thermoplastic polyimide film and a preparation method thereof. The flexible copper-clad plate prepared by the method is flat and has no warpage, has the advantages of light weight, thinness, softness, flexibility and the like, and can be widely applied to the fields of portable electronic equipment such as mobile phones, digital cameras, notebook computers, wearable electronic products and the like, liquid crystal televisions, instruments and meters and the like.

In order to achieve the aim, the invention adopts the following technical scheme:

a thermoplastic polyimide film is characterized in that the thermoplastic polyimide film is a compound with a general formula structure shown in a formula I,

in the structural general formula of the formula I, Ar can be selected from one of PDA, ODA, pODA and 3APBI groups:

in the formula I, n represents the mole number of 2- (4-aminophenyl) -5-aminobenzimidazole (4APBI), and n is an integer of 1-100. m represents the mole number of other aromatic diamine, and m is an integer of 0-100.

A preparation method of a thermoplastic polyimide film comprises the following steps:

1) dissolving aromatic diamine in an aprotic strong polar solvent, stirring to form a homogeneous solution, adding aromatic dianhydride aODPA in batches, and reacting for a certain time at a certain temperature to obtain a polyamic acid (PAA) solution;

2) adding toluene and isoquinoline into the PAA solution, heating to a certain temperature, and reacting for a period of time to obtain a soluble PI solution;

3) precipitating the soluble polyimide solution into absolute ethyl alcohol to obtain PI resin;

4) separating, washing and drying the PI resin to obtain soluble PI resin, namely the compound shown in the formula I;

5) dissolving PI resin in an organic solvent according to a certain solid content (weight percentage) to obtain a PI solution;

6) and coating the PI solution on a clean glass plate, and curing for a certain time at a certain temperature to obtain the PI film.

The aromatic diamine monomer in the step 1) is selected from 2- (4-aminophenyl) -5-aminobenzimidazole (4APBI) or a mixture of 4APBI and other aromatic diamines.

The other aromatic diamine is selected from 1, 4-p-Phenylenediamine (PDA), 4' -diaminodiphenyl ether (4,4' -ODA), 2-phenyl-4, 4' -diaminodiphenyl ether (pODA), 2- (3-aminophenyl) -5-aminobenzimidazole (3APBI) and a mixture thereof mixed according to any proportion.

The aprotic strongly polar solvent in the step 1) is at least one selected from N-methylpyrrolidone (NMP), m-cresol, N-Dimethylformamide (DMF), N-dimethylacetamide (DMAc), dimethyl sulfoxide (DMSO) and butyrolactone, and is preferably m-cresol. The dosage of the solvent is 10-30% of the solid content in the reaction system by mass percent, and preferably 15-20%.

In the step 1), the molar ratio of the aromatic dianhydride monomer to the aromatic diamine is (1.20-1.00):1.00, (0.40-0), preferably (1.10-1.05):1.00, (0.20-0.10); the reaction time is 10 to 30 hours, preferably 20 to 25 hours, and the reaction temperature is 0 to 35 ℃, preferably 15 to 25 ℃.

In the step 2), the reaction temperature is 160-200 ℃, preferably 180-190 ℃; the reaction time is 1 to 30 hours, preferably 3 to 10 hours.

In step 5), the solid content of the PI resin is 1-20% (weight percent), preferably 10-15% (weight percent). The organic solvent is selected from N-methylpyrrolidone (NMP), N-dimethylacetamide (DMAc), dimethyl sulfoxide (DMSO), N-Dimethylformamide (DMF) and a mixture of N, N-Dimethylformamide (DMF) in any proportion.

In the step 6), the final curing temperature of the PI solution is 200-300 ℃, preferably 250-280 ℃; the final curing time is from 0.5 to 5 hours, preferably from 1 to 3 hours.

The preparation method of the non-gel FCCL is characterized by comprising the following steps:

1) carrying out hot-die pressing on a thermoplastic PI film prepared from the compound shown in the formula I and a copper foil for a period of time at a certain temperature and under a certain pressure;

2) and naturally cooling the molded product to obtain the non-adhesive FCCL.

In the step 1), the mould pressing temperature is at the PI film T_gAbove 5-50 ℃, preferably T_g15-25 ℃ above; the molding pressure is between 0.1 and 5MPa, preferably between 0.3 and 1 MPa; the molding time is 1-60min, preferably 10-30 min.

The FCCL can be applied to devices such as microelectronics, optoelectronics, wearable electronics and the like.

The invention has the advantages and beneficial effects that: overcomes the thermoplasticity and high T of the PI film_gThe mutual restriction relationship between thermoplasticity and low CTE of the film exists, and the prepared PI film has excellent comprehensive properties including good thermoplasticity and high T_gLow CTE, and good bond strength to copper foil, FCCL made therefrom is flat in appearance.

Drawings

The invention is further illustrated by the following figures and examples.

FIG. 1 shows IR spectra of PI films prepared in examples 1 to 5.

FIG. 2 is a DSC chart of the polyimide films prepared in examples 1 to 5.

FIG. 3 is a TGA spectrum of the polyimides prepared in examples 1-5.

FIG. 4 shows DMA spectra of the polyimide films prepared in examples 1 to 5.

FIG. 5 is a TMA spectrum of the polyimide films prepared in examples 1 to 5.

Fig. 6 shows the appearance of FCCL prepared in example 1, example 2 and comparative example 1.

Detailed Description

The molecular weights of the polymers obtained in the following examples were all measured by the GPC method, and the obtained molecular weights were all number average molecular weights.

The performance evaluation method of the PI film obtained in the following examples is as follows:

1) glass transition temperature evaluation method:

a) calorimetric Differential Scanning (DSC): the prepared PI film was tested in a calorimetric differential scanner (TA, USA, Q100 series) at a temperature rise rate of 10 deg.C/min.

b) Dynamic thermomechanical analysis (DMA): the prepared PI film was tested in a dynamic thermo-mechanical analyzer (TA, USA, Q800 series) at a temperature rise rate of 5 deg.C/min and a frequency of 1 Hz.

2) Thermal decomposition temperature evaluation method: the prepared PI film was tested in a thermogravimetric analyzer (TA, USA, Q50 series) at a temperature ramp rate of 10 deg.C/min.

3) Method for evaluating adhesive strength: and respectively sealing the front side and the back side of the prepared PI film and the copper foil on a heat sealing press (IDM company, L0003-5 type experimental hot press) at a certain temperature and pressure for a period of time to obtain the PI/Cu composite film. And carrying out a peeling test according to the industry standard QB/T2358-98 to obtain the peeling strength.

Example 1: preparation of polyimide (m ═ 0) from aODPA and 4APBI

22.426g (100mmol) of 4APBI and 200g of m-cresol are added into a 1000mL three-necked bottle provided with a nitrogen inlet, a water separator and a thermometer, and stirred until the mixture is dissolved to form a homogeneous solution; 31.022g (100mmol) of aODPA and 103g of m-cresol solvent are added into the solution, and after the materials are added, the mixture is stirred and reacted for 2 hours to obtain viscous polyamic acid solution with the solid content of 15 wt%. 3g of isoquinoline and 350g of toluene were added to the polyamic acid solution, dehydrated by heating for 3 hours, and then distilled to remove toluene. The reaction temperature is adjusted to 180 ℃ and the reaction is carried out for 5 h. Cooling, spinning and crushing to obtain the polyimide resin powder. The polyimide resin was dissolved in N-methylpyrrolidone (NMP) to prepare a 15 wt% solution. Evenly coating the solution on a clean glass plate through an automatic film coating machine, placing the clean program temperature control drying box in 100 levels, and heating and curing according to the following program: 80 ℃/3 h; 120 ℃/1 h; 150 ℃/1 h; 180 ℃/1 h; 250 ℃/1 h; 280 ℃/1 h. Naturally cooling to room temperature. And (3) soaking the glass plate in deionized water, and stripping to obtain the PI film. The structure of the PI film is as follows:

the number average molecular weight of the compound is 49800g/mol, and n is 100; the thermal properties are shown in table 1; t of the film_g379 deg.C; CTE (50-250 ℃) 16.8 ppm/K; the thermal decomposition temperature (5% weight loss temperature) is 543 ℃; the infrared spectrum is shown in figure 1, the DSC spectrum is shown in figure 2, the TGA spectrum is shown in figure 3, the DMA spectrum is shown in figure 4, and the TMA spectrum is shown in figure 5.

The prepared PI film was compounded with a copper foil (297 mm. times.210 mm. times.0.025 mm) and press-molded on a high-temperature press. Film T with mould pressing temperature of PI _g20 ℃ above, namely 399 ℃; the mould pressing pressure is 0.5 MPa; the molding time was 30 min. After natural cooling, FCCL was obtained as shown in FIG. 6. The prepared FCCL is flat in surface and free of warping.

Example 2: preparation of polyimide (n ═ 50; m ═ 50) from 4APBI and 3APBI and aODPA in a 50:50 (molar ratio)

A1000 mL three-necked flask equipped with a nitrogen inlet, water trap and thermometer was charged with 11.213g (50mmol) of 4APBI and 11.213g (50mmol) of 2- (3-aminophenyl) -5-aminobenzimidazole (3APBI) and 200g of m-cresol and stirred until dissolved to form a homogeneous solution; 31.022g (100mmol) of aODPA and 103g of m-cresol solvent are added into the solution, and after the materials are added, the mixture is stirred and reacted for 2 hours to obtain viscous polyamic acid solution with the solid content of 15 wt%. 3g of isoquinoline and 350g of toluene were added to the polyamic acid solution, dehydrated by heating for 3 hours, and then distilled to remove toluene. The reaction temperature is adjusted to 180 ℃ and the reaction is carried out for 5 h. Cooling, spinning and crushing to obtain the polyimide resin powder. The polyimide resin was dissolved in N, N-dimethylacetamide (DMAc) to prepare a 15 wt% solution. Evenly coating the solution on a clean glass plate through an automatic film coating machine, placing the clean program temperature control drying box in 100 levels, and heating and curing according to the following program: 80 ℃/3 h; 120 ℃/1 h; 150 ℃/1 h; 180 ℃/1 h; 250 ℃/1 h; 280 ℃/1 h. Naturally cooling to room temperature. And (3) soaking the glass plate in deionized water, and stripping to obtain the PI film. The structure of the PI film is as follows:

the number average molecular weight of the compound is 49810g/mol, n is 50, and m is 50; the thermal properties are shown in table 1; t of the film_gThe temperature is 348 ℃; CTE (50-250 ℃) 24.6 ppm/K; the thermal decomposition temperature (5% weight loss temperature) is 547 ℃; the infrared spectrum is shown in figure 1, the DSC spectrum is shown in figure 2, the TGA spectrum is shown in figure 3, and the TMA spectrum is shown in figure 5.

The prepared PI film was compounded with a copper foil (297 mm. times.210 mm. times.0.025 mm) and press-molded on a high-temperature press. Film T with mould pressing temperature of PI _g20 ℃ above, namely 368 ℃; the mould pressing pressure is 0.5 MPa; the molding time was 30 min. After natural cooling, FCCL was obtained as shown in FIG. 6. The FCCL prepared was relatively flat with only slight warping at the edges.

Comparative example 1: preparation of polyimide from aODPA and PDA (n ═ 0, m ═ 100)

10.814g (100mmol) of PDA and 200g of m-cresol are added into a 1000mL three-necked bottle with a nitrogen inlet, a water separator and a thermometer, and stirred until dissolved to form a homogeneous solution; 31.022g (100mmol) of aODPA and 37g of m-cresol solvent are added into the solution, and after the materials are added, the mixture is stirred and reacted for 2 hours to obtain viscous polyamic acid solution with the solid content of 15 wt%. 3g of isoquinoline and 350g of toluene were added to the polyamic acid solution, dehydrated by heating for 3 hours, and then distilled to remove toluene. The reaction temperature is adjusted to 180 ℃ and the reaction is carried out for 5 h. Cooling, spinning and crushing to obtain the polyimide resin powder. The polyimide resin was dissolved in N, N-dimethylacetamide (DMAc) to prepare a 15 wt% solution. Evenly coating the solution on a clean glass plate through an automatic film coating machine, placing the clean program temperature control drying box in 100 levels, and heating and curing according to the following program: 80 ℃/3 h; 120 ℃/1 h; 150 ℃/1 h; 180 ℃/1 h; 250 ℃/1 h; 280 ℃/1 h. Naturally cooling to room temperature. And (3) soaking the glass plate in deionized water, and stripping to obtain the PI film. The structure of the PI film is as follows:

the thermal properties are shown in table 1; t of the film_g337 ℃ under the weight of a steel plate; CTE (50-250 ℃) 50 ppm/K; the thermal decomposition temperature (5% weight loss temperature) is 526 ℃; the infrared spectrum is shown in figure 1, the DSC spectrum is shown in figure 2, the TGA spectrum is shown in figure 3, the DMA spectrum is shown in figure 4, and the TMA spectrum is shown in figure 5.

The prepared PI film was compounded with a copper foil (297 mm. times.210 mm. times.0.025 mm) and press-molded on a high-temperature press. Film T with mould pressing temperature of PI_gAbove 20 ℃, namely 357 ℃; the mould pressing pressure is 0.5 MPa; the molding time was 30 min. After natural cooling, FCCL was obtained as shown in FIG. 6. The FCCL prepared had a severely warped surface.

Comparative example 2: preparation of polyimide from aODPA and 4,4' -ODA (n ═ 0, m ═ 100)

20.024g (100mmol) of 4,4' -ODA and 200g of m-cresol were added into a 1000mL three-necked flask equipped with a nitrogen inlet, a water separator and a thermometer, and stirred until dissolved to form a homogeneous solution; 31.022g (100mmol) of aODPA and 89g of m-cresol solvent are added into the solution, and after the materials are added, the mixture is stirred and reacted for 2 hours to obtain viscous polyamic acid solution with the solid content of 15 wt%. 3g of isoquinoline and 350g of toluene were added to the polyamic acid solution, dehydrated by heating for 3 hours, and then distilled to remove toluene. The reaction temperature is adjusted to 180 ℃ and the reaction is carried out for 5 h. Cooling, spinning and crushing to obtain the polyimide resin powder. The polyimide resin was dissolved in N, N-dimethylacetamide (DMAc) to prepare a 15 wt% solution. Evenly coating the solution on a clean glass plate through an automatic film coating machine, placing the clean program temperature control drying box in 100 levels, and heating and curing according to the following program: 80 ℃/3 h; 120 ℃/1 h; 150 ℃/1 h; 180 ℃/1 h; 250 ℃/1 h; 280 ℃/1 h. Naturally cooling to room temperature. And (3) soaking the glass plate in deionized water, and stripping to obtain the PI film. The structure of the PI film is as follows:

the thermal properties are shown in table 1; t of the film_g284 ℃ is calculated; CTE (50-250 ℃) 62 ppm/K; the thermal decomposition temperature (5% weight loss temperature) is 537 ℃; the infrared spectrum is shown in figure 1, the DSC spectrum is shown in figure 2, the TGA spectrum is shown in figure 3, the DMA spectrum is shown in figure 4, and the TMA spectrum is shown in figure 5.

The prepared PI film was compounded with a copper foil (297 mm. times.210 mm. times.0.025 mm) and press-molded on a high-temperature press. Film T with mould pressing temperature of PI_gAbove 20 ℃, namely 357 ℃; the mould pressing pressure is 0.5 MPa; the molding time was 30 min. After natural cooling, FCCL is obtained, and the surface of the prepared FCCL is seriously warped.

Comparative example 3: preparation of polyimide from aODPA and pODA (n ═ 0, m ═ 100)

27.633g (100mmol) of pODA and 200g of m-cresol were added to a 1000mL three-necked flask equipped with a nitrogen inlet, a water separator and a thermometer, and stirred until dissolved to form a homogeneous solution; 31.022g (100mmol) of aODPA and 132g of m-cresol solvent are added into the solution, and after the materials are added, the mixture is stirred and reacted for 2 hours to obtain viscous polyamic acid solution with the solid content of 15 wt%. 3g of isoquinoline and 350g of toluene were added to the polyamic acid solution, dehydrated by heating for 3 hours, and then distilled to remove toluene. The reaction temperature is adjusted to 180 ℃ and the reaction is carried out for 5 h. Cooling, spinning and crushing to obtain the polyimide resin powder. The polyimide resin was dissolved in N, N-dimethylacetamide (DMAc) to prepare a 15 wt% solution. Evenly coating the solution on a clean glass plate through an automatic film coating machine, placing the clean program temperature control drying box in 100 levels, and heating and curing according to the following program: 80 ℃/3 h; 120 ℃/1 h; 150 ℃/1 h; 180 ℃/1 h; 250 ℃/1 h; 280 ℃/1 h. Naturally cooling to room temperature. And (3) soaking the glass plate in deionized water, and stripping to obtain the PI film. The structure of the PI film is as follows:

the thermal properties are shown in table 1; t of the film_g258 ℃ under the condition of no water; CTE (50-200 ℃) 122.9 ppm/K; the thermal decomposition temperature (5% weight loss temperature) is 551 ℃; the infrared spectrum is shown in figure 1, the DSC spectrum is shown in figure 2, the TGA spectrum is shown in figure 3, and the TMA spectrum is shown in figure 5.

The prepared PI film was compounded with a copper foil (297 mm. times.210 mm. times.0.025 mm) and press-molded on a high-temperature press. Film T with mould pressing temperature of PI_gAbove 22 ℃, namely 280 ℃; the mould pressing pressure is 0.5 MPa; the molding time was 30 min. After natural cooling, FCCL is obtained, and the surface of the prepared FCCL is seriously warped.

TABLE 1 Properties of polyimide film

As can be seen by summarizing the data in Table 1, the PI films prepared in example 1 have an excellent balance of properties, including a high T_gLow CTE, and good bond strength to copper foil, FCCL made therefrom is flat in appearance. Example 2A 50% (molar ratio) relatively flexible 3APBI was introduced based on example 1, and as a result T_gThe decrease, the CTE increase slightly, and the FCCL prepared therefrom is relatively flat with only slight edge warping. Comparative examples 1 to 3 do not contain any rigid 4APBI component, and therefore have a high CTE,T_grelatively low, the prepared FCCL warps severely. It can be seen that the embodiments of the present invention proposed using isomerized aODPA dianhydride with rigid imidazole-containing diamines to produce high heat resistance, low CTE, and good adhesion to copper foil are feasible. The embodiment has good industrialization prospect.

Finally, it should be noted that: the above examples are merely illustrative for clearly illustrating the present invention and are not intended to limit the embodiments. Other variations and modifications will be apparent to persons skilled in the art in light of the above description. And are neither required nor exhaustive of all embodiments. And obvious variations or modifications therefrom are intended to be within the scope of the invention.

Claims

1. The preparation method of the adhesive-free flexible copper-clad plate is characterized by comprising the following steps:

1) hot-pressing the thermoplastic polyimide film, i.e. the thermoplastic PI film and the copper foil at the temperature of the PI film T_gThe hot die pressing is carried out at the temperature of 15-25 ℃, and the hot die pressing pressure is between 0.3-1 MPa; the hot molding time is 10-30 min;

2) naturally cooling the hot-pressed product to obtain a non-adhesive flexible copper clad laminate, namely FCCL;

the FCCL is applied to microelectronic, optoelectronic and wearable electronic product devices;

the thermoplastic polyimide film has the following structure:

wherein n is an integer of 1 to 100;

the preparation method of the thermoplastic PI film comprises the following steps:

(1) under the protection of nitrogen, dissolving 2- (4-aminophenyl) -5-aminobenzimidazole in an aprotic strong polar solvent m-cresol, stirring to form a homogeneous solution, adding aromatic dianhydride aODPA in batches, and reacting at 15-25 ℃ for 20-25 hours to obtain a polyamide acid PAA solution;

wherein, the dosage of the aprotic strong polar solvent is that the mass percentage of the solid in the reaction system reaches 15-20%;

(2) adding toluene and isoquinoline into the PAA solution, heating to 190 ℃ at 180 ℃, and reacting for 3-10h to obtain a soluble PI solution;

(3) precipitating the soluble polyimide solution into absolute ethyl alcohol to obtain PI resin;

(4) separating, washing and drying the PI resin to obtain soluble PI resin;

(5) dissolving PI resin in an organic solvent according to a certain solid content to obtain a PI solution;

the solid content of the PI resin is 10-15%; the organic solvent is selected from N-methyl pyrrolidone, N-dimethyl acetamide, dimethyl sulfoxide, N-dimethyl formamide and a mixture formed by mixing the N-methyl pyrrolidone, the N, N-dimethyl acetamide, the dimethyl sulfoxide and the N, N-dimethyl formamide according to any proportion;

(6) coating the PI solution on a clean glass plate, and carrying out temperature programming curing: 80 ℃/3 h; 120 ℃/1 h; 150 ℃/1 h; 180 ℃/1 h; 250 ℃/1 h; and (4) preparing a PI film at 280 ℃/1 h.