TWI863616B - Adhesive flexible substrate with high dimensional stability and preparation method thereof - Google Patents

Abstract

Disclosed are an adhesive flexible substrate with high dimensional stability and a preparation method thereof. The adhesive flexible substrate comprises: a coated modified polyimide resin film, an adhesive layer and a copper foil layer, wherein the adhesive layer is located between the coated modified polyimide resin film and the copper foil layer. In the present invention, the polymer adhesive is coated on the coated modified polyimide resin film and the copper foil layer is further laminated on the same, so all sections can be winded on the meter scale without ripening, thereby achieving the effects of improving yield, reducing loss, improving efficiency, and saving cost.

Description

Adhesive flexible substrate with high dimensional stability and preparation method thereof

This invention relates to the field of printed circuit board technology, and in particular to a flexible substrate with high dimensional stability, which can be used in high-current products such as automotive and battery panels.

Polyimide (PI) is a type of polymer with imide repeating units, which has the advantages of wide applicable temperature, chemical corrosion resistance, high strength, etc. As a special engineering material, polyimide is now widely used in aviation, aerospace, microelectronics, nano, liquid crystal, separator, laser, automotive and other fields.

The flexible substrates currently used in the automotive field are mostly adhesive flexible substrates from the perspective of reliability, and the insulating layer must use biaxially stretched polyimide resin film and cured epoxy resin adhesive to meet the needs. However, in order to reduce costs, some products on the market choose to use uniaxially stretched polyimide resin film as the insulating layer, which has poor mechanical properties and dimensional stability.

Therefore, there is still a need to develop a flexible substrate with high dimensional stability to meet the needs of the industry.

The main technical problem solved by the present invention is to provide a flexible substrate with high dimensional stability and its preparation method. Specifically, a polymer adhesive is coated on a coating-type modified polyimide resin film and a copper foil layer is pressed. All sections can be rolled up to a large number of meters and do not need to be aged. The substrate is directly coated to form a substrate, thereby achieving the effects of improving yield, reducing loss, improving efficiency, and saving costs.

In order to solve the above technical problems, the present invention provides a flexible substrate with high dimensional stability, comprising: a coating type modified polyimide resin film, an adhesive layer and a copper foil layer, wherein the adhesive layer is located between the coating type modified polyimide resin film and the copper foil layer,

The surface roughness of the copper foil layer in contact with the adhesive layer is 0.4μm to 4.0μm, the thickness of the copper foil layer is 1μm to 105μm, and the thickness of the adhesive layer is 10μm to 50μm.

In a specific embodiment, the material of the adhesive layer is selected from at least one of the group consisting of epoxy resin, acrylic resin, urethane resin, silicone rubber resin, polyparaxylene resin, dimaleimide resin and polyimide resin.

The present invention further provides a method for preparing a flexible substrate with high dimensional stability, comprising the following steps:

(1) Applying one or more layers of modified polyimide resin varnish on the carrier film;

(2) Curing the modified polyimide resin varnish layer at 50°C to 180°C to form a modified polyimide resin film;

(3) Apply an adhesive layer on the surface of the modified polyimide resin film, and then press the copper foil layer onto the adhesive layer;

(4) removing the carrier film on the modified polyimide resin film and then baking; and

(5) Slit into predetermined widths, package and roll up to obtain a single-sided adhesive flexible substrate with a coated modified polyimide resin film.

Another technical solution adopted by the present invention is to provide a method for preparing a flexible substrate with high dimensional stability, comprising the following steps:

(1) Applying one or more layers of modified polyimide resin varnish on the carrier film;

(2) Curing the modified polyimide resin varnish layer at 50°C to 180°C to form a modified polyimide resin film;

(3) Apply an adhesive layer on the surface of the modified polyimide resin film layer, press the copper foil layer onto the adhesive layer, and then place it in a dry environment for 12 to 24 hours;

(4) Removing the carrier film on the modified polyimide resin film;

(5) Applying an adhesive layer on the other surface of the modified polyimide resin film, pressing a copper foil layer onto the adhesive layer, and then baking; and

(6) Slit into predetermined widths, package and roll up to obtain a double-sided adhesive flexible substrate with a coated modified polyimide resin film.

In a specific embodiment, the material forming the carrier film is selected from at least one of polypropylene, biaxially oriented polypropylene, polyethylene terephthalate, polyimide, polyphenylene sulfide, polyethylene naphthalate, polyurethane and polyamide.

In a specific embodiment, during the pressing process, the temperature is 90°C to 150°C and the pressure is 1kgf/cm ² to 3kgf/cm ² .

In a specific embodiment, the baking temperature is 25°C to 160°C and the baking time is 12 hours to 30 hours.

In a specific implementation, during pressing, the pressure of pressing and conveying is 10N to 45N.

The beneficial effects of the present invention include:

(1) The present invention uses a coated modified polyimide resin film, which has excellent insulation performance and high dimensional stability, so as to improve the overall dimensional stability of the product and enhance the insulation effect against high voltage breakdown; and

(2) The present invention coats a polymer adhesive on a coatable modified polyimide resin film and presses a copper foil layer. All sections are rolled up in large quantities and do not require aging. They are directly coated to form a substrate, thereby achieving the effects of improving yield, reducing loss, improving efficiency, and saving costs.

100: Adhesive flexible substrate

101: Copper foil layer

102: Adhesive layer

103: Coating type modified polyimide resin film

Figure 1 is a schematic diagram of the structure of the single-sided adhesive flexible substrate of the present invention.

Figure 2 is a schematic diagram of the structure of the double-sided adhesive flexible substrate of the present invention.

The following is an explanation of the implementation of the present invention through specific implementation modes. People familiar with this art can easily understand the advantages and effects of the present invention from the contents disclosed in this manual.

It should be understood that the structures, proportions, sizes, etc. shown in the drawings attached to this specification are only used to match the contents disclosed in the specification for understanding and reading by people familiar with this technology, and are not used to limit the limiting conditions for the implementation of the present invention, so they have no substantial technical significance. Any modification of the structure, change of the proportion relationship, or adjustment of the size should still fall within the scope of the technical content disclosed by the present invention without affecting the effects and purposes that can be produced by the present invention. At the same time, the references such as "one", "upper" and "lower" in this specification are only for the convenience of description, and are not used to limit the scope of the implementation of the present invention. The changes or adjustments in their relative relationships should also be regarded as the scope of the implementation of the present invention without substantially changing the technical content. In addition, all ranges and values herein are inclusive and combinable. The present invention discloses many ranges, and any value or point falling within the range described herein is also covered by the present invention, and any value or point falling within the range described herein can be used as a minimum value or maximum value to derive lower ranges, etc.

Adhesive flexible substrate with high dimensional stability

The present invention has a highly dimensional-stable adhesive flexible substrate, comprising a coating-type modified polyimide resin film, an adhesive layer, and a copper foil layer. The adhesive layer is located between the coating-type modified polyimide resin film and the copper foil layer, and the adhesive layer is formed on at least one side of the coating-type modified polyimide resin film.

The coating type modified polyimide resin film used in the present invention may be, for example, the coating type modified polyimide resin film disclosed in Chinese Patent Application No. 202310012270.3 (named as a coating type modified polyimide resin film with a carrier film and a preparation method thereof). The specific structure and components of the coating type modified polyimide resin film are described as follows.

Coating type modified polyimide resin film with carrier layer

The coated modified polyimide resin film with a carrier layer of the present invention includes a carrier layer and at least one modified polyimide resin layer, that is, a single layer or multiple layers of modified polyimide resin layers formed by coating and curing a modified polyimide resin varnish layer once or multiple times. The present invention can avoid micropores in the coating process by coating and curing a varnish-type resin, solve the known surface micropore problem, and also help to improve the mechanical properties of the film and the operability of processing.

In a specific embodiment, the thickness of the carrier layer is 25 μm to 250 μm, for example, 25, 30, 35, 40, 45, 50, 55, 60, 65, 70, 75, 80, 85, 90, 95, 100, 110, 120, 130, 140, 150, 160, 170, 180, 190, 200, 210, 220, 230, 240 or 250 μm.

In a specific embodiment, the total thickness of the modified polyimide resin layer is 1 μm to 150 μm, for example, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 15, 20, 25, 30, 35, 40, 45, 50, 60, 65, 70, 75, 80, 85, 90, 95, 100, 110, 120, 130, 140 or 150 μm.

The coated modified polyimide resin film of the present invention has high dimensional stability due to the use of a carrier layer. Moreover, the coated modified polyimide resin film of the present invention can control the thickness through the coating process, for example, it can be coated and cured multiple times to increase the thickness, thereby producing a modified polyimide resin film with a wide range of thicknesses from 1μm to 150μm. Therefore, the present invention can simultaneously meet the thickness requirements of conventional ultra-thin films (e.g., 5μm to 7.5μm), the high thickness requirements of automotive products (e.g., 25μm, 50μm), etc.

In a specific embodiment, the modified polyimide resin varnish layer is basically composed of the following components:

(1) The polyimide resin accounts for 50 to 95% by weight, such as 50, 55, 60, 65, 70, 75, 80, 85, 90 or 95% by weight;

(2) a crosslinking agent, which is 0 to 25% by weight, for example 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 15, 20 or 25% by weight; and

(3) Inorganic fillers, accounting for 0 to 50% by weight, such as 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 15, 20, 25, 30, 35, 40, 45 or 50% by weight.

The present invention can adjust the surface release force of the modified polyimide resin layer by adjusting the type of crosslinking agent, such as the type of inorganic filler powder, and the addition ratio of the two in the modified polyimide resin varnish layer formula, so that the release force is stable and convenient for downstream processing. In this way, the modified polyimide resin layer can also have a high surface energy, which is easy to use in the bonding and coating procedures without the need for additional surface treatment processes such as corona.

At the same time, the present invention can prepare a coated modified polyimide resin film with a carrier layer having advantages such as high flame retardancy, high ionic purity, and high mechanical properties by adding different proportions and types of powders to the modified polyimide resin varnish layer formula. Among them, the modified polyimide resin layer is suitable as an insulating layer.

In a specific embodiment, the polyimide resin is obtained by polymerizing an anhydride monomer and a monomer selected from at least one of isocyanate and diamine in the presence of a solvent. In a specific embodiment, the polyimide resin is at least one of polyimide or polyamide imide.

In a specific embodiment, the crosslinking agent is selected from at least one of the group consisting of glycidylamine epoxy resin, glycidyl ester epoxy resin, epoxide alkylene compound, alicyclic epoxy resin, polyphenol glycidyl ether epoxy resin, bisphenol A epoxy resin, bisphenol F epoxy resin, aliphatic glycidyl ether epoxy resin, heterocyclic epoxy resin and mixed epoxy resin.

In a specific embodiment, the inorganic filler is selected from at least one of calcium sulfate, silicon dioxide, zinc sulfide, zirconium oxide, calcium carbonate, silicon carbide, boron nitride, aluminum oxide, talc, aluminum nitride, glass powder, quartz powder and clay, and the particle size of the inorganic filler is 0.5 μm to 10 μm, such as 0.5, 1, 1.5, 2, 2.5, 2.89, 3, 3.5, 4, 4.5, 5, 5.5, 6, 6.5, 7, 7.5, 8, 8.5, 9, 9.5 or 10 μm. As the powder content ratio changes, the flame retardant performance of the modified polyimide resin layer is also different. The higher the addition ratio of inorganic powders or mixed powders selected from such as silicon dioxide, aluminum oxide, aluminum hydroxide, calcium carbonate, etc., the higher the flame retardancy of the modified polyimide resin layer. Therefore, when there is a demand for higher flame retardancy, it is better to add one or more inorganic substances selected from aluminum hydroxide, aluminum oxide, calcium carbonate, and flame-retardant halogen, phosphorus, nitrogen or boron compounds.

In a specific embodiment, the acid anhydride is selected from at least one of the group consisting of hexafluorodianhydride (6FDA), bicyclo[2.2.2]oct-7-ene-2,3,5,6-tetracarboxylic dianhydride (B1317), 1,2-ethylenebis[1,3-dihydro-1,3-dioxoisobenzofuran-5-carboxylate], 3,3',4,4'-benzophenonetetracarboxylic dianhydride, 3,3',4,4'-biphenyltetracarboxylic dianhydride, pyromellitic dianhydride, trimellitic anhydride (TMA), and cis-abiotic anhydride.

In a specific embodiment, the isocyanate is selected from at least one of the group consisting of 4,4'-diphenylmethane diisocyanate (MDI), 2,4-toluene diisocyanate, 2,6-toluene diisocyanate, 1,5-naphthalene diisocyanate, isophorone diisocyanate, dicyclohexylmethane diisocyanate, and lysine diisocyanate.

In a specific embodiment, the solvent is selected from at least one of the group consisting of N-methylpyrrolidone, γ-butyrolactone, cyclohexanone, acetone, butanone, N,N-dimethylformamide, N,N-dimethylacetamide, pyridine, cyclohexane, dichloromethane, tetrahydrofuran, ethyl acetate, acetonitrile, 1,2-dichloroethane, trichloroethylene, triethylamine, 4-methyl-2-pentanone, toluene, and xylene.

In a specific embodiment, the diamine can be selected from 2,2-bis[4-(4-aminophenoxy)phenyl]propane (BAPP), 2,2'-bis(trifluoromethyl)diaminobiphenyl (TFMB), 2,2-bis(4-aminophenyl)hexafluoropropane, 4,4'-diaminodiphenyl ether, bis[4-(3-aminophenoxy)phenyl]sulfonamide, bis[4-(4-aminophenoxy)phenyl]sulfonamide, 2,2 - At least one of the group consisting of bis[4-(4-aminophenoxy)phenyl]hexafluoropropane, bis[4-(4-aminophenoxy)phenyl]methane, 4,4'-bis(4-aminophenoxy)biphenyl, bis[4-(4-aminophenoxy)phenyl]ethyl ether, bis[4-(4-aminophenoxy)phenyl]ketone, 1,3-bis(4'-aminophenoxy)benzene, and 1,4-bis(4-aminophenoxy)benzene.

In a specific embodiment, the synthesis of polyamide imide can be achieved by first reacting diamine and acid anhydride to generate dicarboxylic acid containing imide, and then the dicarboxylic acid reacts with isocyanate to generate amide bond to form polyamide imide.

In a specific embodiment, in the synthesis of polyamide imide, the molar ratio of all diamines/all acid anhydrides is 1/2.00 to 1/2.20, for example, 1/2.00, 1/2.05, 1/2.10, 1/2.15, 1/2.20; the molar ratio of all diamines/all isocyanates is 1/1.05 to 1/1.50, for example, 1/1.05, 1/1.10, 1/1.15, 1/1.20, 1/1.25, 1/1.30, 1/1.35, 1/1.40, 1/1.45, 1/1.50. In another specific embodiment, in the synthesis of polyimide, the molar ratio of all diamines/all anhydrides is 1/0.90 to 1/1.10, for example, 1/0.90, 1/0.95, 1/1.00, 1/1.05, 1/1.10.

In one embodiment, the polymerization is carried out in the presence of a catalyst, such as a tertiary amine, and the tertiary amine is at least one selected from the group consisting of triethylamine (Et ₃ N), isoquinoline, pyridine, N-ethylpiperidine, and benzimidazole. In another embodiment, the tertiary amine is used as a catalyst and accounts for more than 0 to 3% by weight, such as more than 0, 0.5, 1, 1.5, 2, 2.5, 3% by weight.

In a specific embodiment, the material forming the carrier layer is selected from at least one of the group consisting of polypropylene, biaxially oriented polypropylene, polyethylene terephthalate, polyimide, polyphenylene sulfide, polyethylene naphthalate, polyurethane and polyamide.

In a specific embodiment, the carrier layer is used on the outer side of the insulating layer, and its surface roughness is between 0.001 μm and 10 μm, preferably between 0.1 μm and 5.0 μm, for example, 0.001, 0.002, 0.003, 0.004, 0.005, 0.006, 0.007, 0.008, 0.009, 0.01, 0.15, 0.02, 0.03, 0.04, 0.05, 0.06, 0.07, 0.08, 0.09, 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10 μm. The present invention uses a carrier layer with a specific surface roughness to control the release force between the carrier layer and the modified polyimide resin layer, making it easier to separate the modified polyimide resin layer from the carrier layer, thereby improving the operability of the downstream terminal.

Method for preparing coated modified polyimide resin film with carrier layer

In the present invention, the preparation method of the coated modified polyimide resin film with a carrier layer includes the following steps:

(1) Applying a modified polyimide resin varnish layer on the carrier layer;

(2) curing the modified polyimide resin varnish layer at 50°C to 180°C to form a modified polyimide resin layer; and

(3) If necessary, step (1) and step (2) are not repeated or repeated once or more times on the modified polyimide resin layer to form a single layer or multiple layers of modified polyimide resin layer.

In the present invention, the preparation method of the coated modified polyimide resin film with a carrier layer may also include the following steps:

(1) Applying a modified polyimide resin varnish layer on the carrier layer;

(2) Drying the modified polyimide resin varnish layer;

(3) not repeating or repeating step (1) and step (2) once or more times on the dried modified polyimide resin varnish layer as needed; and

(4) Curing all the dried modified polyimide resin varnish layers at 50°C to 180°C to form a single layer or multiple layers of modified polyimide resin layers.

In a specific embodiment, low temperature curing is performed at 50°C to 180°C, for example, 50, 60, 70, 80, 90, 100, 110, 120, 130, 140, 150, 160, 170, 180°C. In another specific embodiment, low temperature curing is multi-stage/stage-type, each stage can be at the same or different temperature, and each stage time is also independent, for example, seven stages of low temperature curing, wherein the temperature of each stage is 50, 110, 160, 180, 180, 130, 70°C in sequence, and each stage can be performed for more than 0 minutes to 30 minutes.

In a specific embodiment, the surface roughness of the copper foil layer in contact with the adhesive layer is 0.4 μm to 4.0 μm, for example, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9, 1.0, 1.5, 2.0, 2.5, 3.0, 3.5, 4.0 μm.

In a specific embodiment, the thickness of the copper foil layer is 1 μm to 105 μm, preferably 9 μm to 70 μm, for example 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 25, 30, 35, 40, 45, 50, 55, 60, 65, 70, 75, 80, 85, 90, 95, 100, 105 μm.

In a specific embodiment, the copper foil layer may be an electrolytic copper foil (ED) and a rolled & annealed copper foil (RA).

In a specific embodiment, the thickness of the adhesive layer is 10 μm to 50 μm, for example, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 25, 30, 35, 40, 45, 50 μm.

In a specific embodiment, the material of the adhesive layer is selected from at least one of the group consisting of epoxy resin, acrylic resin, urethane resin, silicone rubber resin, polyparaxylene resin, dimaleimide resin and polyimide resin.

In a specific embodiment, the material of the carrier film is selected from at least one of polypropylene, biaxially oriented polypropylene, polyethylene terephthalate, polyimide, polyphenylene sulfide, polyethylene naphthalate, polyurethane and polyamide.

Method for preparing an adhesive flexible substrate with high dimensional stability

In the present invention, a method for preparing a flexible substrate with high dimensional stability includes the following steps:

(1) Applying one or more layers of modified polyimide resin varnish on the carrier film;

(2) Curing the modified polyimide resin varnish layer at 50°C to 180°C to form a modified polyimide resin film;

(3) Apply an adhesive layer on the surface of the modified polyimide resin film, and then press the copper foil layer onto the adhesive layer;

(4) removing the carrier film on the modified polyimide resin film and then baking; and

(5) Slit into predetermined widths, package and roll up to obtain a single-sided adhesive flexible substrate with a coated modified polyimide resin film.

In the present invention, the method for preparing a flexible substrate with high dimensional stability may also include the following steps:

(1) Applying one or more layers of modified polyimide resin varnish on the carrier film;

(2) Curing the modified polyimide resin varnish layer at 50°C to 180°C to form a modified polyimide resin film;

(3) Apply an adhesive layer on the surface of the modified polyimide resin film layer, press the copper foil layer onto the adhesive layer, and then place it in a dry environment for 12 to 24 hours;

(4) Removing the carrier film on the modified polyimide resin film;

(5) Applying an adhesive layer on the other surface of the modified polyimide resin film, pressing the copper foil layer onto the adhesive layer, and then baking; and

(6) Slit into predetermined widths, package and roll up to obtain a double-sided adhesive flexible substrate with a coated modified polyimide resin film.

In a specific embodiment, the carrier film can be removed by tearing it off, for example, using a film peeling machine or manually.

In a specific embodiment, curing of the modified polyimide resin varnish layer can be performed after all modified polyimide resin varnish layers are applied.

In a specific embodiment, the temperature during pressing is 90°C to 150°C, for example, 90, 95, 100, 105, 110, 115, 120, 125, 130, 135, 140, 145, 150°C.

In a specific embodiment, during the pressing, the pressure is 1kgf/cm ² to 3kgf/cm ² , for example, 1, 1.5, 2, 2.5, 3kgf/cm ² .

In a specific embodiment, the baking temperature is 25°C to 160°C, for example, 25, 30, 35, 40, 45, 50, 55, 60, 65, 70, 75, 80, 85, 90, 95, 100, 105, 110, 115, 120, 125, 130, 135, 140, 145, 150, 155, 160°C; the baking time is 12 hours to 30 hours, for example, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30 hours.

In another specific implementation, the baking is multi-stage/phased, each stage can be at the same or different temperature, and each stage time is also independent, for example: baking at 60℃ for 3 hours, 80℃ for 2 hours, 120℃ for 2 hours, and 160℃ for 4 hours in sequence, with a temperature control time of 1 hour between each stage, and finally taking 2 hours to cool to room temperature, a total of 16 hours.

In a specific embodiment, curing of the modified polyimide resin varnish layer can be performed after all modified polyimide resin varnish layers are applied.

In a specific embodiment, the drying temperature is, for example, 60°C.

In a specific embodiment, the pressure during the pressing and conveying process is 10N to 45N, for example, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 25, 30, 35, 40, 45N.

FIG. 1 and FIG. 2 are schematic diagrams of the structure of the adhesive flexible substrate with high dimensional stability of the present invention. In FIG. 1 , the adhesive flexible substrate 100 includes a copper foil layer 101, an adhesive layer 102, and a coating type modified polyimide resin film 103 from top to bottom; in FIG. 2 , the adhesive flexible substrate 100 includes a (first) copper foil layer 101, a (first) adhesive layer 102, a coating type modified polyimide resin film 103, a (second) adhesive layer 102, and a (second) copper foil layer 101 from top to bottom.

Implementation example

Modified polyimide resin varnish

Synthesis Example 1

41.1g of 2,2-bis[4-(4-aminophenoxy)phenyl]propane (BAPP) was dissolved in 330g of N-methylpyrrolidone (NMP), followed by the addition of 40.3g of trimellitic anhydride (TMA) and the reaction at 80°C for 1 hour. After the addition of 50ml of toluene, the temperature was raised to 170°C for dehydration and then to 190°C to evaporate the toluene. After the temperature was lowered back to room temperature, 30g of 4,4'-diphenylmethane diisocyanate (MDI) and 1.3g of triethylamine (Et3N) were added and the reaction was carried out at 120°C for 3 hours to obtain a modified polyimide resin varnish, which includes polyimide resin: polyamide imide.

Synthesis Example 2

Take 32.02g of 2,2'-bis(trifluoromethyl)diaminobiphenyl (TFMB), 21.99g of hexafluorodianhydride (6FDA), and 12.41g of bicyclo[2.2.2]oct-7-ene-2,3,5,6-tetracarboxylic dianhydride (B1317) and add them to 349g of N-methylpyrrolidone (NMP) at 80°C. Raise the temperature to 150°C, add 0.80g of N-ethylpiperidine, and then raise the temperature to 190°C for 4 hours to obtain a modified polyimide resin varnish, which includes polyimide resin: polyimide.

The above-mentioned synthesis example of modified polyimide resin varnish is only illustrative, and those with ordinary knowledge in the relevant technical field can arbitrarily replace and use known polyimide or polyamide imide synthesis formulas and methods as needed. In other words, the use of other known polyimide or polyamide imide synthesis formulas and methods does not exceed the scope of this disclosure.

Coating type modified polyimide resin film

Preparation Examples 1 to 5

Take 37.8g of trimellitic anhydride (TMA), 52.2g of 4,4'-diphenylmethane diisocyanate (MDI) and 210g of N-methylpyrrolidone (NMP), mix and react at 140°C for 2 hours to obtain a modified polyimide resin varnish, which includes polyamide imide.

Examples 1 to 5

The modified polyimide resin varnish of Preparation Examples 1 to 5 is coated on a PET carrier film with a thickness of 75 μm, and the coating step is repeated as needed; then, seven stages of low-temperature curing are performed, and the temperatures of each stage are 50, 110, 160, 180, 180, 130 and 70°C (each stage is about 1 minute) to prepare modified polyimide resin films with different thicknesses of Preparation Examples 1 to 5, which serve as the insulating layer of the adhesive flexible substrate.

Epoxy adhesive layers of different thicknesses were applied on the prepared modified polyimide resin film (i.e., the insulating layer) and then heated at 70°C and 1.5 kgf/cm ² , copper foils of different thicknesses (commercially available BHY5-82F-HA-V2, Nichi Mining Co., Ltd., loz = 35μm, 0.5oz = 18μm, 0.3oz = 12μm) were pressed onto the adhesive layer; then, the PET carrier film on the modified polyimide resin film was torn off by a film stripper, and then baked: baked at 60°C for 3 hours, 80°C for 2 hours, 120°C for 2 hours, and 160°C for 4 hours in sequence, with a temperature control time of 1 hour between each stage, and finally cooled to room temperature for 2 hours, a total of 16 hours, to prepare the adhesive flexible substrates of Examples 1 to 5. Process pressure: 40N for sending, 80N for winding, and 35N for pressing and conveying.

Comparison Examples 1 to 3

The adhesive flexible substrate is prepared according to the method of the above embodiment, except that the step of coating the varnish on the carrier film and then curing it is replaced by directly taking the commercially available biaxially stretched polyimide resin films GF100 and GF050 of PIAM and the uniaxially stretched polyimide resin film HV-25 of Ruihuatai as the insulating layer.

Table 1

In Table 1,

The test methods for breaking voltage and dielectric strength refer to ASTM D149,

The test method for dimensional stability refers to IPC-TM-650 2.2.4C,

The test methods for tensile strength, elastic modulus, and elongation refer to IPC-TM-650 2.4.19,

The test method for release force refers to ASTM D3330,

The strength test method is then carried out in accordance with IPC-TM-650 2.4.19C (5/98).

According to the test results in Table 1, the single-sided adhesive flexible copper foil substrate of the present invention has a specific configuration. Therefore, under the above-mentioned tests of adhesive force, mechanical properties, insulation and dimensional stability, it can be observed that the mechanical properties are slightly inferior, while the insulation is equivalent, and it has significantly excellent dimensional stability.

The above is only an embodiment of the present invention and does not limit the patent scope of the present invention. Any equivalent structural changes made using the contents of the present invention specification and drawings, or directly or indirectly applied in other related technical fields, are also included in the patent protection scope of the present invention.

100: Adhesive flexible substrate

101: Copper foil layer

102: Adhesive layer

103: Coating type modified polyimide resin film

Claims (6)

A method for preparing a flexible substrate with high dimensional stability, comprising the following steps: coating one or more modified polyimide resin varnish layers on a carrier film; curing the modified polyimide resin varnish layers at 50°C to 180°C to form a modified polyimide resin film, wherein the curing is a multi-stage curing, and each stage is cured at the same or different temperatures. The process lasts for more than 0 minutes to 30 minutes; an adhesive layer is coated on the surface of the modified polyimide resin film, and a copper foil layer is pressed onto the adhesive layer; the carrier film on the modified polyimide resin film is removed, and then the film is baked; and the film is slit into predetermined widths, packaged and rolled up to obtain a single-sided adhesive flexible substrate with a coated modified polyimide resin film. A method for preparing a flexible substrate with high dimensional stability, comprising the following steps: coating one or more modified polyimide resin varnish layers on a carrier film; curing the modified polyimide resin varnish layers at 50°C to 180°C to form a modified polyimide resin film, wherein the curing is a multi-stage curing, and each stage is performed at the same or different temperatures for more than 0 minutes to 30 minutes; Apply an adhesive layer, press a copper foil layer onto the adhesive layer, and then place it in a dry environment for 12 to 24 hours; remove the carrier film on the modified polyimide resin film; Apply an adhesive layer on the other surface of the modified polyimide resin film, press a copper foil layer onto the adhesive layer, and then bake; and slit into a predetermined width, package and roll up to obtain a double-sided adhesive flexible substrate with a coated modified polyimide resin film. A method for preparing a flexible substrate with high dimensional stability as described in claim 1 or 2, wherein the material forming the carrier film is selected from at least one of polypropylene, biaxially oriented polypropylene, polyethylene terephthalate, polyimide, polyphenylene sulfide, polyethylene naphthalate, polyurethane and polyamide. The method for preparing an adhesive flexible substrate having high dimensional stability as claimed in claim 1 or 2, wherein the temperature during the pressing is 90°C to 150°C and the pressure is 1kgf/cm ² to 3kgf/cm ² . A method for preparing a flexible substrate with high dimensional stability as described in claim 1 or 2, wherein the baking is performed at a temperature of 25°C to 160°C and for a time of 12 hours to 30 hours. A method for preparing a flexible substrate with high dimensional stability as described in claim 1 or 2, wherein the pressure of the pressing conveying is 10N to 45N during the pressing.

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