Non-adhesive double-sided flexible copper-clad plate and preparation method thereof

Abstract

The invention provides a non-adhesive double-sided flexible copper-clad plate and a preparation method thereof. The adhesive-free double-sided flexible copper-clad plate comprises a first copper foil, a first thermosetting polyimide layer, a first thermoplastic polyimide layer, a second thermoplastic polyimide layer, a second thermosetting polyimide layer and a second copper foil which are sequentially stacked, the preparation raw materials of the first thermosetting polyimide layer and the second thermosetting polyimide layer respectively comprise a catalyst; the preparation raw materials of the first thermoplastic polyimide layer and the second thermoplastic polyimide layer do not comprise a catalyst. The preparation raw materials of the thermosetting polyimide layer and the thermoplastic polyimide layer in the adhesive-free double-sided flexible copper-clad plate are designed, so that the contradiction between the imidization temperature and the performance of the copper-clad plate is solved, and the adhesive-free double-sided flexible copper-clad plate which has excellent mechanical property, higher interlayer binding force and excellent heat resistance is prepared. And the adhesive-free double-sided flexible copper-clad plate has the advantages of good adhesion resistance, good dip soldering resistance and good pressing performance.

Description

Technical Field

[0001] The present invention belongs to the technical field of copper clad laminate materials, and particularly relates to a non-adhesive double-sided flexible copper clad laminate and a preparation method thereof. Background Art

[0002] At present, the mainstream production methods of non-adhesive double-sided flexible copper clad laminates are coating method and lamination method, and the former has better performance. The coating method is further divided into symmetric lamination method and asymmetric lamination method. The symmetric lamination method is to symmetrically laminate a single-sided substrate with the structure of copper foil (Cu) / thermosetting polyimide (PI) / thermoplastic polyimide (TPI) to obtain a non-adhesive double-sided substrate; the asymmetric lamination method is to laminate a single-sided substrate with the structure of copper foil (Cu) / thermoplastic polyimide (TPI) / thermosetting polyimide (PI) / thermoplastic polyimide (TPI) with copper foil to obtain a non-adhesive double-sided substrate. For the non-adhesive double-sided flexible copper clad laminate prepared by the asymmetric lamination method, since the copper foil and TPI are arranged adjacent to each other, it causes problems such as insufficient heat resistance and low flame retardant grade of the material; while for the non-adhesive double-sided flexible copper clad laminate prepared by the symmetric lamination method, TPI is wrapped in the inner layer, and its heat resistance and flame retardant grade are significantly improved. Therefore, the non-adhesive double-sided flexible copper clad laminate prepared by the symmetric lamination method has attracted wide attention.

[0003] CN1929716A discloses a technical solution for preparing a non-adhesive double-sided flexible copper clad laminate by the symmetric lamination method. The technical solution includes: successively coating a PI precursor and a TPI precursor on a copper foil, obtaining a single-sided substrate through thermal imidization, and then symmetrically laminating and curing the single-sided substrate to obtain a double-sided substrate. However, since the imidization rate of TPI is greater than that of PI, when the imidization temperature is high, the imidization rate of PI is high and good performance can be obtained, but because the imidization rate of TPI is too high and the surface energy is too small, it will cause poor lamination, and further lead to problems such as processing explosion of the board; when the imidization temperature is low, the imidization rate of PI is insufficient and the performance does not meet the requirements. Therefore, this method has a contradiction between the imidization temperature and the performance, and it is also impossible to provide a non-adhesive double-sided flexible copper clad laminate with both good mechanical properties and high processing performance.

[0004] Therefore, how to provide a material that has both excellent mechanical properties, high interlayer bonding strength, good dip soldering resistance and good lamination performance has become an urgent technical problem to be solved at present. Summary of the Invention

[0005] Aiming at the deficiencies of the prior art, the purpose of the present invention is to provide a non - adhesive double - sided flexible copper clad laminate and its preparation method. In the present invention, by designing that the preparation raw materials of the first thermosetting polyimide layer and the second thermosetting polyimide layer both include a catalyst, while the preparation raw materials of the first thermoplastic polyimide layer and the second thermoplastic polyimide layer do not include a catalyst, the contradiction between the imidization temperature and the performance of the copper clad laminate is solved, and a non - adhesive double - sided flexible copper clad laminate with excellent mechanical properties, high interlayer bonding force, good dip - soldering resistance and good lamination performance is prepared.

[0006] To achieve this purpose, the present invention adopts the following technical solutions:

[0007] In the first aspect, the present invention provides a non - adhesive double - sided flexible copper clad laminate, which includes a first copper foil, a first thermosetting polyimide layer, a first thermoplastic polyimide layer, a second thermoplastic polyimide layer, a second thermosetting polyimide layer and a second copper foil stacked in sequence;

[0008] The preparation raw materials of the first thermosetting polyimide layer and the second thermosetting polyimide layer both include a catalyst;

[0009] The preparation raw materials of the first thermoplastic polyimide layer and the second thermoplastic polyimide layer do not include a catalyst.

[0010] In the present invention, by designing that the preparation raw materials of the first thermosetting polyimide layer and the second thermosetting polyimide layer both include a catalyst, while the preparation raw materials of the first thermoplastic polyimide layer and the second thermoplastic polyimide layer do not include a catalyst, the imidization rate of the first thermosetting polyimide layer and the second thermosetting polyimide layer is accelerated, so that the composite layers between the first thermoplastic polyimide layer and the first thermosetting polyimide layer, and between the second thermoplastic polyimide layer and the second thermosetting polyimide layer can obtain thermosetting polyimide layers with excellent performance, thermoplastic polyimide layers with good self - adhesion and thermoplastic polyimide layers with high surface energy at a lower imidization temperature. The double - sided substrate obtained by symmetric composite has excellent mechanical properties, high interlayer bonding force, good dip - soldering resistance and good lamination performance, and will not delaminate or burst.

[0011] It should be noted that in the present invention, the catalysts in the preparation raw materials of the first thermosetting polyimide layer and the second thermosetting polyimide layer can be the same or different.

[0012] The following are the preferred technical solutions of the present invention, but not the limitations on the technical solutions provided by the present invention. Through the following preferred technical solutions, the purpose and beneficial effects of the present invention can be better achieved and realized.

[0013] As a preferred technical solution of the present invention, the first thermosetting polyimide layer and the second thermosetting polyimide layer are each independently prepared from a thermosetting polyimide precursor solution; it should be noted that in the present invention, the raw materials for preparing the thermosetting polyimide precursor solution of the first thermosetting polyimide layer and the second thermosetting polyimide layer may be the same or different.

[0014] The raw materials for preparing the thermosetting polyimide precursor solution include the following components:

[0015] Diamine compound A, tetracarboxylic dianhydride compound A, and a catalyst.

[0016] As a preferred technical solution of the present invention, the molar ratio of the diamine compound A to the tetracarboxylic dianhydride compound A is (0.95 - 1.05):1, for example, it can be 0.95:1, 0.96:1, 0.97:1, 0.98:1, 0.99:1, 1:1, 1.01:1, 1.02:1, 1.03:1, 1.04:1, or 1.05:1, etc.

[0017] Preferably, the molar ratio of the tetracarboxylic dianhydride compound A to the catalyst is 1:(0.8 - 2.2), for example, it can be 1:0.8, 1:0.85, 1:0.9, 1:0.95, 1:1, 1:1.05, 1:1.1, 1:1.15, 1:1.3, 1:1.4, 1:1.5, 1:1.6, 1:1.7, 1:1.8, 1:1.9, 1:2.0, 1:2.1, 1:2.2, etc.

[0018] In the present invention, by controlling the amount of the catalyst within a specific range and controlling the imidization rate of the first thermosetting polyimide layer and the second thermosetting polyimide layer within a specific range, a thermosetting polyimide layer with excellent performance, a thermoplastic polyimide layer with good self - adhesiveness, and a thermoplastic polyimide layer with high surface energy can be obtained at a relatively low imidization temperature. If the amount of the catalyst is too small, the imidization rate of the first thermosetting polyimide layer and the second thermosetting polyimide layer is relatively low, and the performance of the adhesive - free double - sided flexible copper clad laminate prepared therefrom is poor; if the amount of the catalyst is too large, the catalytic activity is high, which will cause the thermosetting polyimide precursor solution to gel, affecting the use of the glue.

[0019] Preferably, the diamine compound A is selected from any one or a combination of at least two of p-phenylenediamine (p-PDA), m-phenylenediamine (m-PDA), 4,4'-oxydianiline (4,4'-ODA), 3,4'-oxydianiline (3,4'-ODA), 4,4'-methylenedianiline (4,4'-MDA), 4,4'-bis(4-aminophenoxy)biphenyl (4,4'-BAPB), 4,4'-diaminodiphenylsulfone (4,4'-DDS), 4,4'-diaminobenzanilide (4,4'-DABA), and 2-(4-aminophenyl)-5-aminobenzoxazole (APBOA).

[0020] Preferably, the tetracarboxylic dianhydride compound A is selected from any one or a combination of at least two of pyromellitic dianhydride (PMDA), 3,3',4,4'-biphenyltetracarboxylic dianhydride (BPDA), and 3,3',4,4'-benzophenonetetracarboxylic dianhydride (s-BTDA).

[0021] Preferably, the catalyst is selected from any one or a combination of at least two of p-hydroxybenzoic acid (PHA), quinoline (QL), benzimidazole (BI), benzotriazole (BTA), triethylamine (Et-3N), and 1,8-diazabicyclo[5.4.0]undec-7-ene (DBU).

[0022] Preferably, the raw materials for preparing the thermosetting polyimide precursor solution further include solvent A.

[0023] Preferably, the solvent A is selected from any one or a combination of at least two of N,N-dimethylacetamide (DMAc), N,N-dimethylformamide (DMF), and N-methylpyrrolidone (NMP);

[0024] Preferably, the addition amount of the solvent A is preferably such that the solid content of the thermosetting polyimide precursor solution reaches 0.1% to 30% (for example, it can be 0.1%, 1%, 5%, 10%, 15%, 20%, 25%, or 30%, etc.), and it can be formulated according to actual needs.

[0025] As a preferred technical solution of the present invention, the thermosetting polyimide precursor solution is prepared by the following method, and the method includes the following steps:

[0026] After mixing the diamine compound A and the solvent A, add the tetracarboxylic dianhydride compound A thereto, carry out a polymerization reaction, and then add the catalyst thereto to obtain the thermosetting polyimide precursor solution.

[0027] It should be noted that during the process of adding the tetracarboxylic dianhydride compound A to the mixture of the diamine compound A and the solvent A, the tetracarboxylic dianhydride compound A can be added in multiple portions (exemplarily including but not limited to 3 times).

[0028] Preferably, the polymerization reaction is carried out in an inert gas atmosphere, and the inert gas atmosphere includes a nitrogen atmosphere.

[0029] Preferably, the temperature of the polymerization reaction is -10 to 25 °C (for example, it can be -10 °C, -5 °C, 0 °C, 10 °C, 20 °C, 21 °C, 22 °C, 23 °C, 24 °C or 25 °C, etc.), and the time is 8 to 24 h (for example, it can be 8 h, 10 h, 12 h, 14 h, 16 h, 18 h, 19 h, 20 h, 21 h, 22 h, 23 h or 24 h, etc.).

[0030] As a preferred technical solution of the present invention, it is characterized in that the first thermoplastic polyimide layer and the second thermoplastic polyimide layer are each independently prepared from a thermoplastic polyimide precursor solution; it should be noted that in the present invention, the raw materials for preparing the precursor solutions of the first thermoplastic polyimide layer and the second thermoplastic polyimide layer can be the same or different.

[0031] The raw materials for preparing the thermoplastic polyimide precursor solution include the following components:

[0032] Diamine compound B and tetracarboxylic dianhydride compound B.

[0033] As a preferred technical solution of the present invention, the molar ratio of the diamine compound B to the tetracarboxylic dianhydride compound B is (0.95 to 1.05):1, for example, it can be 0.95:1, 0.96:1, 0.97:1, 0.98:1, 0.99:1, 1:1, 1.01:1, 1.02:1, 1.03:1, 1.04:1 or 1.05:1, etc.

[0034] Preferably, the diamine compound B is selected from any one or a combination of at least two of 2,2-bis[4-(4-aminophenoxy)phenyl]propane (BAPP), 1,3-bis(3-aminophenoxy)benzene (APB), 1,3-bis(4'-aminophenoxy)benzene (TPE-R), 4,4'-bis(4-aminophenoxy)biphenyl (BAPB), 4,4'-bis(3-aminophenoxy)diphenyl sulfone (BAPS-M), 4,4'-bis(3-aminophenoxy)biphenyl (BAPB-M).

[0035] Preferably, the tetracarboxylic dianhydride compound B is selected from any one or a combination of at least two of 3,3',4,4'-biphenyltetracarboxylic dianhydride (BPDA), 3,3',4,4'-benzophenone tetracarboxylic dianhydride (s-BTDA), 2,3,3',4'-diphenylether tetracarboxylic dianhydride (a-ODPA), and 4,4'-(4,4'-isopropyl diphenoxy) bis(phthalic anhydride) (BPADA).

[0036] Preferably, the raw materials for preparing the thermoplastic polyimide precursor solution further include a solvent B.

[0037] Preferably, the solvent B is selected from any one or a combination of at least two of N,N-dimethylacetamide (DMAc), N,N-dimethylformamide (DMF), and N-methylpyrrolidone (NMP).

[0038] Preferably, the addition amount of the solvent B is such that the solid content of the thermoplastic polyimide precursor solution reaches 0.1% to 30% (for example, it can be 0.1%, 1%, 5%, 10%, 15%, 20%, 25%, or 30%, etc.), and it can be prepared according to actual needs. As a preferred technical solution of the present invention, the thermoplastic polyimide precursor solution is prepared by the following method, and the method includes the following steps:

[0039] After mixing the diamine compound B and the solvent B, the tetracarboxylic dianhydride compound B is added thereto, and a polymerization reaction is carried out to obtain the thermoplastic polyimide precursor solution.

[0040] Similarly, it should be noted that during the process of adding the tetracarboxylic dianhydride compound B to the mixture of the diamine compound B and the solvent B, the tetracarboxylic dianhydride compound B can be added in multiple times (exemplarily including but not limited to 3 times).

[0041] Preferably, the polymerization reaction is carried out in an atmosphere of a protective gas, and the atmosphere of the protective gas includes a nitrogen atmosphere.

[0042] Preferably, the temperature of the polymerization reaction is -10 to 25 °C (for example, it can be -10 °C, -5 °C, 0 °C, 10 °C, 20 °C, 21 °C, 22 °C, 23 °C, 24 °C, or 25 °C, etc.), and the time is 8 to 24 h (for example, it can be 8 h, 10 h, 12 h, 14 h, 16 h, 18 h, 19 h, 20 h, 21 h, 22 h, 23 h, or 24 h, etc.).

[0043] In the present invention, the imidization process in the above steps (1) and (2) is carried out in an atmosphere of a protective gas, and the protective gas includes nitrogen.

[0044] As a preferred technical solution of the present invention, the thicknesses of the first thermosetting polyimide layer and the second thermosetting polyimide layer are each independently 8 to 20 μm, and may be, for example, 8 μm, 8.2 μm, 8.4 μm, 8.6 μm, 8.8 μm, 9 μm, 9.2 μm, 9.4 μm, 9.6 μm, 9.8 μm, 10 μm, 11 μm, 12 μm, 13 μm, 14 μm, 15 μm, 16 μm, 17 μm, 18 μm, 19 μm or 20 μm, etc.

[0045] Preferably, the thicknesses of the first thermoplastic polyimide layer and the second thermoplastic polyimide layer are each independently 2 to 4 μm, and may be, for example, 2 μm, 2.2 μm, 2.4 μm, 2.6 μm, 2.8 μm, 3 μm, 3.2 μm, 3.4 μm, 3.6 μm, 3.8 μm or 4 μm, etc.

[0046] The thicknesses of the first copper foil and the second copper foil are not limited, and any copper foil applicable to the adhesive-free double-sided flexible copper clad laminate can be used in the present invention. Preferably, the thicknesses of the first copper foil and the second copper foil are each independently 9 to 70 μm, and may be, for example, 9 μm, 10 μm, 11 μm, 12 μm, 13 μm, 14 μm, 15 μm, 18 μm, 27 μm, 35 μm, 53 μm or 70 μm, etc.

[0047] Second, the present invention provides a method for preparing an adhesive-free double-sided flexible copper clad laminate as described in the first aspect. The preparation method includes the following steps:

[0048] (1) Coating a thermosetting polyimide precursor solution on one side surface of the first copper foil and drying to obtain a precursor dry film of the first thermosetting polyimide layer;

[0049] Coating a thermoplastic polyimide precursor solution on the surface of the precursor dry film of the first thermosetting polyimide layer and drying to obtain a precursor dry film of the first thermoplastic polyimide layer;

[0050] Performing imidization treatment on the precursor dry film of the first thermosetting polyimide layer and the precursor dry film of the first thermoplastic polyimide layer to obtain a first copper foil, a first thermosetting polyimide layer and a first thermoplastic polyimide layer which are sequentially stacked;

[0051] (2) Coating a thermosetting polyimide precursor solution on one side surface of the second copper foil and drying to obtain a precursor dry film of the second thermosetting polyimide layer;

[0052] Coating a thermoplastic polyimide precursor solution on the surface of the precursor dry film of the second thermosetting polyimide layer and drying to obtain a precursor dry film of the second thermoplastic polyimide layer;

[0053] The precursor dry film of the second thermosetting polyimide layer and the precursor dry film of the second thermoplastic polyimide layer are imidized to obtain a second copper foil, a second thermosetting polyimide layer, and a second thermoplastic polyimide layer that are stacked.

[0054] (3) The first thermoplastic polyimide layer obtained in step (1) and the second thermoplastic polyimide layer obtained in step (2) are compounded to obtain the adhesive-free double-sided flexible copper clad laminate.

[0055] As a preferred technical solution of the present invention, the temperatures of the two dryings in step (1) are each independently 60 to 200 °C (for example, 60 °C, 80 °C, 100 °C, 120 °C, 140 °C, 160 °C, 180 °C, or 200 °C, etc.), and the times are each independently 10 to 60 min (for example, 10 min, 20 min, 30 min, 40 min, 50 min, or 60 min, etc.).

[0056] The temperatures of the two dryings in step (2) are each independently 60 to 200 °C (for example, 60 °C, 80 °C, 100 °C, 120 °C, 140 °C, 160 °C, 180 °C, or 200 °C, etc.), and the times are each independently 10 to 60 min (for example, 10 min, 20 min, 30 min, 40 min, 50 min, or 60 min, etc.).

[0057] Preferably, the temperature of the imidization treatment in step (1) is 280 to 350 °C (for example, 280 °C, 290 °C, 300 °C, 310 °C, 320 °C, 330 °C, 340 °C, or 350 °C, etc.), and the time is 10 to 60 min (for example, 10 min, 20 min, 30 min, 40 min, 50 min, or 60 min, etc.).

[0058] Preferably, the temperature of the imidization treatment in step (2) is 280 to 350 °C (for example, 280 °C, 290 °C, 300 °C, 310 °C, 320 °C, 330 °C, 340 °C, or 350 °C, etc.), and the time is 10 to 60 min (for example, 10 min, 20 min, 30 min, 40 min, 50 min, or 60 min, etc.).

[0059] Preferably, the compounding method in step (3) includes: roll pressing or laminating at a high temperature; or, at a low temperature, after roll pressing or laminating, curing.

[0060] Preferably, the temperature of the high temperature is 300 to 350 °C (for example, 300 °C, 310 °C, 320 °C, 330 °C, 340 °C, or 350 °C, etc.).

[0061] Preferably, the temperature of the low temperature is 220 to 280 °C (such as 220 °C, 230 °C, 240 °C, 250 °C, 260 °C, 270 °C or 280 °C, etc.).

[0062] Preferably, the temperature of the curing is 250 to 300 °C (such as 250 °C, 260 °C, 270 °C, 280 °C, 290 °C or 300 °C, etc.), and the time is 0.5 to 3 h (such as 0.5 h, 1 h, 1.5 h, 2 h, 2.5 h or 3 h, etc.).

[0063] As a preferred technical solution of the present invention, the preparation method of the adhesive-free double-sided flexible copper clad laminate specifically includes the following steps:

[0064] (1) Coating a thermosetting polyimide precursor solution on one side surface of the first copper foil, and drying at 60 to 200 °C for 10 to 60 min to obtain a precursor dry film of the first thermosetting polyimide layer;

[0065] Coating a thermoplastic polyimide precursor solution on the surface of the precursor dry film of the first thermosetting polyimide layer, and drying at 60 to 200 °C for 10 to 60 min to obtain a precursor dry film of the first thermoplastic polyimide layer;

[0066] At 280 to 350 °C, in a protective gas atmosphere, imidization treatment is carried out on the precursor dry film of the first thermosetting polyimide layer and the precursor dry film of the first thermoplastic polyimide layer for 10 to 60 min to obtain the first copper foil, the first thermosetting polyimide layer and the first thermoplastic polyimide layer stacked in sequence;

[0067] (2) Coating a thermosetting polyimide precursor solution on one side surface of the second copper foil, and drying at 60 to 200 °C for 10 to 60 min to obtain a precursor dry film of the second thermosetting polyimide layer;

[0068] Coating a thermoplastic polyimide precursor solution on the surface of the precursor dry film of the second thermosetting polyimide layer, and drying at 60 to 200 °C for 10 to 60 min to obtain a precursor dry film of the second thermoplastic polyimide layer;

[0069] At 280 to 350 °C, in a protective gas atmosphere, imidization treatment is carried out on the precursor dry film of the second thermosetting polyimide layer and the precursor dry film of the second thermoplastic polyimide layer for 10 to 60 min to obtain the second copper foil, the second thermosetting polyimide layer and the second thermoplastic polyimide layer stacked;

[0070] (3) Aligning the first thermoplastic polyimide layer obtained in step (1) and the second thermoplastic polyimide layer obtained in step (2), and performing roll pressing or laminating at 300 to 350 °C to obtain the adhesive-free double-sided flexible copper clad laminate;

[0071] Alternatively, align the first thermoplastic polyimide layer obtained in step (1) and the second thermoplastic polyimide layer obtained in step (2), perform roll pressing or lamination at 220-280°C, and then cure at 250-300°C for 0.5-3 h to obtain the adhesive-free double-sided flexible copper clad laminate.

[0072] Compared with the prior art, the present invention has the following beneficial effects:

[0073] (1) In the present invention, by designing that the preparation raw materials of the first thermosetting polyimide layer and the second thermosetting polyimide layer both include a catalyst, while the preparation raw materials of the first thermoplastic polyimide layer and the second thermoplastic polyimide layer do not include a catalyst, and controlling the dosage of the catalyst within a specific range, a thermosetting polyimide layer with excellent performance, a thermoplastic polyimide layer with good self-adhesion, and a thermoplastic polyimide layer with high surface energy can be obtained at a relatively low imidization temperature. The adhesive-free double-sided flexible copper clad laminate obtained by symmetric lamination has excellent mechanical properties, high interlayer bonding strength, good dip soldering resistance, and good lamination performance, and will not delaminate or burst. After testing the dip soldering resistance under normal conditions and after damp heat treatment, the adhesive-free double-sided flexible copper clad laminate does not show any delamination problems. Its interlayer bonding strength is 16.3-18.6 N / cm, the tensile strength is 365.71-398.96 MPa, and the elongation at break is 48.91-60.48%.

[0074] (2) In the present invention, a thermosetting polyimide layer with excellent performance and a thermoplastic polyimide layer with good self-adhesion can be obtained at a relatively low imidization temperature, and then an adhesive-free double-sided flexible copper clad laminate with excellent comprehensive performance is prepared, reducing the energy consumption per unit product and the production cost. BRIEF DESCRIPTION OF THE DRAWINGS

[0075] Figure 1 is a schematic structural diagram of the adhesive-free double-sided flexible copper clad laminate provided in Example 1 of the present invention;

[0076] Among them, 1 - first copper foil, 2 - first thermosetting polyimide layer, 3 - first thermoplastic polyimide layer, 4 - second thermoplastic polyimide layer, 5 - second thermosetting polyimide layer, 6 - second copper foil. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0077] The technical solutions of the present invention will be further described below in conjunction with the drawings and specific embodiments. Those skilled in the art should understand that the embodiments are only for helping to understand the present invention and should not be construed as specific limitations of the present invention.

[0078] Some components used in the following preparation examples and comparative preparation examples are described as shown in Table 1 below:

[0079] Table 1

[0080]

[0081] Production Examples A1 to A7, Comparative Production Example M1

[0082] Production Examples A1 to A7 and Comparative Production Example M1 each provide a thermosetting polyimide precursor solution (the thermosetting polyimide precursor solutions provided by Production Examples A1 to A7 are successively denoted as A1 to A7, and the thermosetting polyimide precursor solution provided by Comparative Production Example M1 is denoted as M1). The raw materials and amounts used for preparing the thermosetting polyimide precursor solution are as shown in Table 2 below. The amounts of each raw material in the following Table 2 are all in terms of the amount of substance.

[0083] The preparation method of the thermosetting polyimide precursor solution is as follows:

[0084] In a nitrogen atmosphere, after stirring and mixing the diamine compound A and the solvent A evenly, trimellitic anhydride compound A is added thereto in 3 portions, the stirring speed is 150 revolutions / min, and a polymerization reaction is carried out at 15 °C for 20 h, and then a catalyst is added thereto and stirred for 4 h to obtain the thermosetting polyimide precursor solution.

[0085] Table 2

[0086]

[0087] Production Examples B1 to B3, Comparative Production Example N1

[0088] Production Examples B1 to B3 and Comparative Production Example B1 each provide a thermoplastic polyimide precursor solution (the thermoplastic polyimide precursor solutions provided by Production Examples B1 to B3 are successively denoted as B1 to B3, and the thermoplastic polyimide precursor solution provided by Comparative Production Example N1 is denoted as N1). The raw materials and amounts used for preparing the thermosetting polyimide precursor solution are as shown in Table 3 below. The amounts of each raw material in the following Table 3 are all in terms of the amount of substance.

[0089] The preparation method of the thermoplastic polyimide precursor solution is as follows:

[0090] In a nitrogen atmosphere, after stirring and mixing the diamine compound B and the solvent B evenly, trimellitic anhydride compound B is added thereto in 3 portions, the stirring speed is 150 revolutions / min, and a polymerization reaction is carried out at 15 °C for 20 h, and optionally a catalyst is added thereto and stirred for 4 h to obtain the thermoplastic polyimide precursor solution.

[0091] Table 3

[0092]

[0093]

[0094] Example 1

[0095] Examples 1 - 7 and Comparative Examples 1 - 4 respectively provide an adhesive - free double - sided flexible copper clad laminate. The adhesive - free double - sided flexible copper clad laminate includes a first copper foil 1, a first thermosetting polyimide layer 2, a first thermoplastic polyimide layer 3, a second thermoplastic polyimide layer 4, a second thermosetting polyimide layer 5, and a second copper foil 6 which are stacked in sequence;

[0096] Among them, the first copper foil 1 and the second copper foil 6 are 12 - μm - thick electrolytic copper foils;

[0097] The thicknesses of the first thermosetting polyimide layer 2 and the second thermosetting polyimide layer 5 are 9 μm;

[0098] The thicknesses of the first thermoplastic polyimide layer 3 and the second thermoplastic polyimide layer 4 are 3 μm.

[0099] The preparation method of the above - mentioned adhesive - free double - sided flexible copper clad laminate is as follows:

[0100] (1) Fix the electrolytic copper foil on a flat glass plate, coat the thermosetting polyimide precursor solution on the matte surface of the electrolytic copper foil, and dry it at 80 °C for 30 min to obtain the precursor dry film of the first thermosetting polyimide layer;

[0101] Coat the thermoplastic polyimide precursor solution on the surface of the precursor dry film of the first thermosetting polyimide layer, and dry it at 80 °C for 30 min to obtain the precursor dry film of the first thermoplastic polyimide layer;

[0102] Under nitrogen protection, perform imidization treatment on the precursor dry film of the first thermosetting polyimide layer and the precursor dry film of the first thermoplastic polyimide layer for 60 min to obtain the first copper foil, the first thermosetting polyimide layer, and the first thermoplastic polyimide layer stacked in sequence;

[0103] (2) Fix another electrolytic copper foil on a flat glass plate, coat the thermosetting polyimide precursor solution on the matte surface of the electrolytic copper foil, and dry it at 80 °C for 60 min to obtain the precursor dry film of the second thermosetting polyimide layer;

[0104] Coat the thermoplastic polyimide precursor solution on the surface of the precursor dry film of the second thermosetting polyimide layer, and dry it at 80 °C for 30 min to obtain the precursor dry film of the second thermoplastic polyimide layer;

[0105] Under nitrogen protection, imidization treatment was carried out on the precursor dry film of the second thermosetting polyimide layer and the precursor dry film of the second thermoplastic polyimide layer for 60 minutes to obtain a second copper foil, a second thermosetting polyimide layer, and a second thermoplastic polyimide layer stacked together;

[0106] (3) Align the first thermoplastic polyimide layer obtained in step (1) and the second thermoplastic polyimide layer obtained in step (2), and carry out roll pressing or laminating under nitrogen protection at 350 °C to obtain the adhesive-free double-sided flexible copper clad laminate;

[0107] Among them, the specific sources of the thermosetting polyimide precursor solution and the thermoplastic polyimide precursor solution used in step (1) and step (2), and the imidization temperature in step (1) and step (2) are shown in Table 4 below.

[0108] Table 4

[0109]

[0110] Test the properties of the adhesive-free double-sided flexible copper clad laminates provided in the above examples and comparative examples. The specific test methods are as follows:

[0111] Immersion soldering resistance: Tested according to IPC-TN-650 2.4.13, and the test treatment conditions are normal state (A) and after damp heat treatment (PCT 121 °C / 1.5 kPa / 2 hr; C-24 / 85 / 85) respectively.

[0112] Interlayer bonding strength: Tested according to IPC-TN-650 2.4.9.

[0113] Tensile strength: Tested according to IPC-TN-650 2.4.19.

[0114] Elongation at break: Tested according to IPC-TN-650 2.4.19.

[0115] The above performance test results are shown in Table 5 below:

[0116] Table 5

[0117]

[0118] As can be seen from the above, in the present invention, by designing that the raw materials for preparing the first thermosetting polyimide layer and the second thermosetting polyimide layer both include a catalyst, while the raw materials for preparing the first thermoplastic polyimide layer and the second thermoplastic polyimide layer do not include a catalyst, and controlling the amount of the catalyst within a specific range, at a relatively low imidization temperature, a thermosetting polyimide layer with excellent performance, a thermoplastic polyimide layer with good self-adhesion and a thermoplastic polyimide layer with high surface energy can be obtained. The adhesive-free double-sided flexible copper clad laminate obtained by symmetric lamination has both excellent mechanical properties and high interfacial bonding strength, and also has good dip soldering resistance and good lamination performance, and will not delaminate or burst. After testing its dip soldering resistance under normal conditions and after damp heat treatment, the adhesive-free double-sided flexible copper clad laminate will not show delamination problems. Its interfacial bonding strength is 16.3 - 18.6 N / cm, the tensile strength is 365.71 - 398.96 MPa, and the elongation at break is 48.91 - 60.48%.

[0119] As can be seen from Examples 1 - 7, if the amount of the catalyst in the first thermosetting polyimide layer / second thermosetting polyimide layer of the adhesive-free double-sided flexible copper clad laminate is too small (Example 6), the comprehensive performance of the adhesive-free double-sided flexible copper clad laminate will decrease; if the amount of the catalyst in the first thermosetting polyimide layer / second thermosetting polyimide layer of the adhesive-free double-sided flexible copper clad laminate is too large (Example 7), the thermosetting polyimide precursor solution A7 will gel and cannot be used to prepare the adhesive-free double-sided flexible copper clad laminate.

[0120] As can be seen from the data of Examples 1 - 5 and Comparative Examples 1 - 5, if the first thermosetting polyimide layer / second thermosetting polyimide layer of the adhesive-free double-sided flexible copper clad laminate does not use a catalyst (Comparative Examples 1 - 3), at a relatively low imidization temperature, delamination problems will gradually occur in the prepared adhesive-free double-sided flexible copper clad laminate as the imidization temperature rises, and the higher the imidization temperature, the more serious the delamination problem, and its mechanical properties are poor; if both the first thermosetting polyimide layer / second thermosetting polyimide layer and the first thermoplastic polyimide layer / second thermoplastic polyimide layer of the adhesive-free double-sided flexible copper clad laminate use a catalyst (Comparative Examples 4 - 5), even at a relatively low imidization temperature, delamination will occur in the adhesive-free double-sided flexible copper clad laminate, and the higher the imidization temperature, the more serious the delamination problem.

[0121] In summary, in the present invention, by designing that the raw materials for preparing the first thermosetting polyimide layer and the second thermosetting polyimide layer both include a catalyst, while the raw materials for preparing the first thermoplastic polyimide layer and the second thermoplastic polyimide layer do not include a catalyst, and controlling the dosage of the catalyst within a specific range, at a relatively low imidization temperature, a catalyst-free double-sided flexible copper clad laminate can be obtained, which has excellent mechanical properties, high interlayer bonding strength, good dip soldering resistance, good lamination performance, and does not delaminate or explode.

[0122] The applicant declares that the present invention uses the above embodiments to illustrate the detailed structural features and detailed process flows of the present invention, but the present invention is not limited to the above detailed structural features and detailed process flows, that is, it does not mean that the present invention must rely on the above detailed structural features and detailed process flows to be implemented. Those skilled in the art should understand that any improvement to the present invention, the equivalent replacement of the components selected for the present invention, the addition of auxiliary components, the selection of specific methods, etc., the equivalent replacement of the raw materials of the present invention products, the addition of auxiliary components, the selection of specific methods, etc., all fall within the protection scope and the disclosure scope of the present invention.

Claims

1. A non-adhesive double-sided flexible copper clad laminate, characterized in that, The adhesive-free double-sided flexible copper clad laminate comprises a first copper foil, a first thermosetting polyimide layer, a first thermoplastic polyimide layer, a second thermoplastic polyimide layer, a second thermosetting polyimide layer and a second copper foil which are sequentially stacked; The preparation raw materials of the first thermosetting polyimide layer and the second thermosetting polyimide layer both include a catalyst; The preparation raw materials of the first thermoplastic polyimide layer and the second thermoplastic polyimide layer do not include a catalyst.

2. The non-adhesive type double-sided flexible copper clad laminate according to claim 1, characterized in that, The first thermosetting polyimide layer and the second thermosetting polyimide layer are each independently prepared from a thermosetting polyimide precursor solution; The preparation raw materials of the thermosetting polyimide precursor solution include the following components: Diamine compound A, tetracarboxylic dianhydride compound A and a catalyst.

3. The non-adhesive double-sided flexible copper clad laminate according to claim 2, wherein, The molar ratio of the diamine compound A to the tetracarboxylic dianhydride compound A is (0.95 - 1.05):1; Preferably, the molar ratio of the tetracarboxylic dianhydride compound A to the catalyst is 1:(0.8 - 2.2); Preferably, the diamine compound A is selected from any one or a combination of at least two of p-phenylenediamine, m-phenylenediamine, 4,4'-diaminodiphenyl ether, 3,4'-diaminodiphenyl ether, 4,4'-diaminodiphenylmethane, 4,4'-bis(4-aminophenoxy)biphenyl, 4,4'-diaminobenzophenone, 4,4'-diaminobenzanilide, 2-(4-aminophenyl)-5-aminobenzoxazole; Preferably, the tetracarboxylic dianhydride compound A is selected from any one or a combination of at least two of pyromellitic dianhydride, 3,3',4,4'-biphenyltetracarboxylic dianhydride, 3,3',4,4'-benzophenone tetracarboxylic dianhydride; Preferably, the catalyst is selected from any one or a combination of at least two of hydroxybenzoic acid, quinoline, benzimidazole, benzotriazole, triethylamine and 1,8-diazabicyclo; Preferably, the preparation raw materials of the thermosetting polyimide precursor solution further include solvent A; Preferably, the solvent A is selected from any one or a combination of at least two of N,N-dimethylacetamide, N,N-dimethylformamide, N-methylpyrrolidone.

4. The non-adhesive double-sided flexible copper clad laminate according to claim 2 or 3, wherein The thermosetting polyimide precursor solution is prepared by the following method, and the method includes the following steps: After mixing the diamine compound A and the solvent A, adding the tetracarboxylic dianhydride compound A thereto, carrying out a polymerization reaction, and then adding the catalyst thereto to obtain the thermosetting polyimide precursor solution.

5. The adhesive-free double-sided flexible copper clad laminate according to any one of claims 1-4, characterized in that, The first thermoplastic polyimide layer and the second thermoplastic polyimide layer are each independently prepared from a thermoplastic polyimide precursor solution; The preparation raw materials of the thermoplastic polyimide precursor solution include the following components: Diamine compound B and tetracarboxylic dianhydride compound B.

6. The adhesive-free double-sided flexible copper clad laminate according to claim 5, wherein The molar ratio of the diamine compound B to the tetracarboxylic dianhydride compound B is (0.95 - 1.05):1; Preferably, the diamine compound B is selected from any one or a combination of at least two of 2,2-bis[4-(4-aminophenoxy)phenyl]propane, 1,3-bis(3-aminophenoxy)benzene, 1,3-bis(4'-aminophenoxy)benzene, 4,4'-bis(4-aminophenoxy)biphenyl, 4,4'-bis(3-aminophenoxy)diphenyl sulfone, and 4,4'-bis(3-aminophenoxy)biphenyl; Preferably, the tetracarboxylic dianhydride compound B is selected from any one or a combination of at least two of 3,3',4,4'-biphenyltetracarboxylic dianhydride, 3,3',4,4'-benzophenone tetracarboxylic dianhydride, 2,3,3',4'-diphenylether tetracarboxylic dianhydride, and 4,4'-(4,4'-isopropylidenediphenoxy)bis(phthalic anhydride); Preferably, the raw materials for preparing the thermoplastic polyimide precursor solution further include a solvent B; Preferably, the solvent B is selected from any one or a combination of at least two of N,N-dimethylacetamide, N,N-dimethylformamide (DMF), and N-methylpyrrolidone.

7. The adhesive-free double-sided flexible copper clad laminate according to claim 5 or 6, characterized in that The thermoplastic polyimide precursor solution is prepared by the following method, which includes the following steps: After mixing the diamine compound B and the solvent B, add the tetracarboxylic dianhydride compound B thereto, and carry out a polymerization reaction to obtain the thermoplastic polyimide precursor solution.

8. The adhesive-free double-sided flexible copper clad laminate according to any one of claims 1-7, characterized in that, The thicknesses of the first thermosetting polyimide layer and the second thermosetting polyimide layer are each independently 8 - 20 μm; Preferably, the thicknesses of the first thermoplastic polyimide layer and the second thermoplastic polyimide layer are each independently 2 - 4 μm.

9. A method for preparing a glue-free double-sided flexible copper clad laminate according to any one of claims 1-8, characterized in that, The preparation method includes the following steps: (1) Coat a thermosetting polyimide precursor solution on one side surface of a first copper foil, and dry it to obtain a precursor dry film of the first thermosetting polyimide layer; Coat a thermoplastic polyimide precursor solution on the surface of the precursor dry film of the first thermosetting polyimide layer, and dry it to obtain a precursor dry film of the first thermoplastic polyimide layer; Carry out imidization treatment on the precursor dry film of the first thermosetting polyimide layer and the precursor dry film of the first thermoplastic polyimide layer to obtain a first copper foil, a first thermosetting polyimide layer, and a first thermoplastic polyimide layer that are sequentially stacked; (2) Coat a thermosetting polyimide precursor solution on one side surface of a second copper foil, and dry it to obtain a precursor dry film of the second thermosetting polyimide layer; Coat a thermoplastic polyimide precursor solution on the surface of the precursor dry film of the second thermosetting polyimide layer, and dry it to obtain a precursor dry film of the second thermoplastic polyimide layer; Carry out imidization treatment on the precursor dry film of the second thermosetting polyimide layer and the precursor dry film of the second thermoplastic polyimide layer to obtain a second copper foil, a second thermosetting polyimide layer, and a second thermoplastic polyimide layer that are stacked; (3) Compound the first thermoplastic polyimide layer obtained in step (1) and the second thermoplastic polyimide layer obtained in step (2) to obtain the adhesive-free double-sided flexible copper clad laminate.

10. The preparation method according to claim 9, characterized in that, The temperature of the imidization treatment in step (1) is 280 - 350 °C, and the time is 10 - 60 min; Preferably, the temperature of the imidization treatment in step (2) is 280 to 350 °C, and the time is 10 to 60 min.

Images