CN115198256A

CN115198256A - Reducing solution for electroless copper plating of polyimide film and preparation method and application thereof

Info

Publication number: CN115198256A
Application number: CN202210827169.9A
Authority: CN
Inventors: 邵永存; 冼博达; 李晓红; 章晓冬; 刘江波; 童茂军
Original assignee: Shanghai Tiancheng Chemical Co ltd
Current assignee: Shanghai Tiancheng Chemical Co ltd
Priority date: 2022-07-13
Filing date: 2022-07-13
Publication date: 2022-10-18

Abstract

The reducing solution for electroless copper plating comprises the combination of dimethylamino borane, boric acid, a sulfur-containing additive and deionized water, and the sulfur-containing additive is added, so that an electroless copper plating layer treated by the reducing solution for electroless copper plating has high bonding strength with the polyimide film, high coverage and excellent impact resistance, and the problems of bubbles and the like are avoided.

Description

Reducing solution for electroless copper plating of polyimide film and preparation method and application thereof

Technical Field

The invention belongs to the technical field of copper plating, and particularly relates to a reducing solution for chemical copper plating of a polyimide film, and a preparation method and application thereof.

Background

Polyimide (PI) has good heat resistance, chemical stability and mechanical property, is one of the most important substrates in flexible electronic devices, and is widely applied to the field of communication. A Flexible Copper Clad Laminate (FCCL) with polyimide as a base material is an electronic composite material for realizing a metallized copper layer on the surface of the polyimide base material through a certain process, and can be used for static deflection and dynamic interconnection of electronic devices.

However, polyimide is a non-conductor, and a conductive film must be prepared in advance for electroplating, and the conductive film is prepared by using chemical plating before electroplating by a common method; before chemical plating, the base material must be pretreated, and the pretreatment generally comprises the steps of oil removal, coarsening, reduction, activation, dispergation (or reduction) and the like; meanwhile, after the nonmetal is activated by palladium ions, palladium ions are adsorbed on the nonmetal, and the chemical plating is difficult to perform through catalysis initiation, so that the chemical plating can be performed after the palladium ions are reduced into palladium simple substances, and the reduction of the palladium ions into the palladium simple substances is usually performed in a reducing solution.

CN104250730A discloses an ionic palladium reduction solution and a method for carrying out nonmetal chemical plating by adopting the ionic palladium reduction solution, wherein the ionic palladium reduction solution is an aqueous solution containing hydrazine hydrate, alkali metal hydroxide and ammonia water; the method for carrying out non-metal chemical plating by adopting the ionic palladium reducing solution comprises the steps of firstly carrying out activation treatment on a coarsened non-metal part to be plated by adopting the ionic palladium activating solution, then placing the part in the ionic palladium reducing solution for carrying out reduction treatment, and finally soaking the part in chemical plating solution for carrying out chemical plating. The ionic palladium reduction solution provided by the invention is very environment-friendly, has stable service life, excellent reduction effect and can improve the activation effect.

CN111885832A discloses a neutralization reducing liquid for PCB glue removal post-treatment, a preparation method and application thereof. The neutralizing and reducing liquid for PCB degumming post-treatment provided by the invention takes water as a solvent and comprises the following components in mass concentration: 1-200 g/L of reducing agent, 10-600 g/L of inorganic acid, 0.001-10 g/L of surfactant and 0.001-10 g/L of chelating agent, wherein the inorganic acid is hydrochloric acid and/or nitric acid. When the neutralizing and reducing solution for PCB degumming post-treatment is used for a POFV plate, particularly when the POFV plate is manufactured by a copper deposition technology of ionic palladium activation, the probability of plating leakage of a hole cover is remarkably reduced.

However, due to the structure of the polyimide material itself, problems such as poor coverage, low bonding strength to the substrate, and blistering are likely to occur when electroless copper plating is performed on the polyimide surface.

Therefore, there is a need for developing a reducing solution for electroless copper plating for polyimide films, which effectively solves the problems of poor coating coverage, low bonding strength to a substrate, and blistering.

Disclosure of Invention

Aiming at the defects of the prior art, the invention aims to provide a reducing solution for electroless copper plating of a polyimide film, and a preparation method and application thereof.

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

in a first aspect, the present invention provides a reducing solution for electroless copper plating of a polyimide film, comprising dimethylaminoborane, boric acid, a sulfur-containing additive, and deionized water.

The reducing solution for electroless copper plating of the polyimide film comprises the combination of the dimethylamino borane, the boric acid, the sulfur-containing additive and the deionized water, and the sulfur-containing additive is added into the reducing solution, so that the unfavorable decomposition of the dimethylamino borane in the reducing process can be reduced, the palladium ions can be fully reduced into metal palladium, the metal palladium can be better adsorbed on the polyimide film, the bonding strength between an electroless copper plating layer and the polyimide film and the coverage of the electroless copper plating layer are improved, the obtained copper-plated polyimide film also has excellent impact resistance, and the problems of air bubbles and the like can be avoided.

Preferably, the reducing solution for electroless copper plating comprises 1-30 mL of dimethylamino borane, 1-25 g of boric acid, 0.5-50 mg of sulfur-containing additive and the balance of deionized water, wherein the volume of the reducing solution for electroless copper plating is 1L.

The dimethylaminoborane may be 2mL, 4mL, 6mL, 8mL, 10mL, 12mL, 14mL, 16mL, 18mL, 20mL, 22mL, 24mL, 26mL, 28mL, or the like, based on 1L of the reducing solution for electroless copper plating; the boronic acid can be 2g, 4g, 6g, 8g, 10g, 12g, 14g, 16g, 18g, 20g, 22g, or 24g, etc.; the sulfur-containing additive may be 1mg, 5mg, 10mg, 15mg, 20mg, 25mg, 30mg, 35mg, 40mg, or 45mg, and the like.

As a preferable technical scheme of the invention, the reducing solution for the electroless copper plating is limited to contain 1-30 mL/L of dimethylaminoborane, 1-25 g/L of boric acid and 0.5-50 mg/L of sulfur-containing additive, so that the highest bonding strength and coverage degree between an electroless copper plating layer and a polyimide film after the reduction solution for the electroless copper plating is treated can be ensured.

Preferably, the reducing solution for electroless copper plating has a sulfur additive content of 7 to 15mg, for example, 7.5mg, 8mg, 8.5mg, 9mg, 9.5mg, 10mg, 10.5mg, 11mg, 12mg, 13mg, 14mg, or the like, based on 1L of the reducing solution for electroless copper plating.

As a preferred technical scheme of the invention, the concentration of the sulfur-containing additive in the reducing solution for electroless copper plating is limited to be 7-15 mg/L, so that the adhesion of an electroless copper plating layer obtained after the reduction solution for electroless copper plating is treated is higher, and the thermal shock is more excellent, on one hand, if the concentration of the sulfur-containing additive is lower than 7mg/L, more unfavorable decomposition of methylamino borane can be caused, so that the metal palladium can not be better adsorbed on a polyimide film, and the adhesion of the electroless copper plating layer is not firm; on the other hand, if the concentration of the sulfur-containing additive is higher than 15mg/L, the dimethylaminoborane may not sufficiently reduce palladium ions, so that electroless copper plating may not completely cover the polyimide film.

Preferably, the additive comprises any one of 2- (hydroxymethyl) benzothiazole, mercaptobenzothiazole, 2-mercaptoethanol-1-ol, cystamine dihydrochloride, 2-methylthio-benzimidazole, 2-methylthio-ethylamine or 2,2' -thiobis (ethanol-1-ol) or a combination of at least two thereof, and further preferably 2-mercaptoethanol-1-ol.

In a second aspect, the present invention provides a method for producing the reducing solution for electroless copper plating according to the first aspect, the method comprising: and mixing dimethylamino borane, boric acid, an additive and deionized water to obtain the reducing solution for electroless copper plating.

As a preferred technical scheme of the invention, the preparation method comprises the following steps:

(1) Mixing dimethylamino borane, boric acid and deionized water to obtain a mixed solution;

(2) And (2) mixing the mixed solution obtained in the step (1) with an additive to obtain the reducing solution for electroless copper plating.

In a third aspect, the present invention provides a copper plating method for a polyimide film, the copper plating method comprising: the polyimide film is activated by an ionic palladium activation solution, then reduced in a reducing solution for electroless copper plating as described in the first aspect, then electroless copper plating is performed in an electroless copper plating solution, and finally electrolytic copper plating is performed to complete the copper plating of the polyimide film.

Preferably, the ionic palladium activation solution comprises a complexing agent, palladium ions and a surfactant.

Preferably, the ionic palladium activation solution has a pH of 8.5 to 9.5, for example, 8.6, 8.7, 8.8, 8.9, 9, 9.1, 9.2, 9.3, or 9.4.

Preferably, the mass of the palladium ion is 50 to 300mg, such as 100mg, 150mg, 200mg or 250mg, etc., based on 1l of the ionic palladium activator.

Preferably, the temperature of the activation treatment is 45 to 55 ℃, for example 46 ℃, 47 ℃, 48 ℃, 49 ℃, 50 ℃, 51 ℃, 52 ℃, 53 ℃ or 54 ℃ and the like.

Preferably, the activation treatment time is 30 to 120s, such as 40s, 50s, 60s, 70s, 80s, 90s, 100s, 110s, or the like.

Preferably, the temperature of the reduction treatment is 30 to 40 ℃, for example, 31 ℃, 32 ℃, 33 ℃, 34 ℃, 35 ℃, 36 ℃, 37 ℃, 38 ℃, or 39 ℃ or the like.

Preferably, the time of the reduction treatment is 30 to 60s, for example 35s, 40s, 45s, 50s, 55s, or the like.

Preferably, the electroless copper plating solution comprises a complexing agent, copper ions, a reducing agent and a stabilizing agent.

Preferably, the electroless copper plating solution has a pH of 9 to 13, for example 9.5, 10, 10.5, 11, 11.5, 12, 12.5, or the like.

Preferably, the electroless copper plating temperature is 28 to 35 ℃, such as 29 ℃, 30 ℃, 31 ℃, 32 ℃, 33 ℃ or 34 ℃ and the like.

Preferably, the electroless copper plating time is 5-7 min, such as 5.2min, 5.4min, 5.6min, 5.8min, 6min, 6.2min, 6.4min, 6.6min or 6.8 min.

In a fourth aspect, the present invention provides a copper-plated polyimide film produced by the copper plating method according to the third aspect.

In a fifth aspect, the invention provides a use of the copper-plated polyimide film according to the fourth aspect in a flexible electronic device.

Compared with the prior art, the invention has the following beneficial effects:

the reducing solution for electroless copper plating of the polyimide film comprises the combination of dimethylamino borane, boric acid, a sulfur-containing additive and deionized water, the sulfur-containing additive is added into the reducing solution, so that an electroless copper plating layer treated by the reducing solution for electroless copper plating and the polyimide film have higher bonding strength and coverage, and after a thermal shock test, the thickness of the polyimide film is 25cm ² The number of blisters appearing in the copper-plated polyimide film of (a) was 0 to 8, indicating that it had excellent impact resistance.

Drawings

FIG. 1 is a photograph of the electroless copper plated polyimide film provided in step (3) of application example 1 after being subjected to a tape adhesion test;

FIG. 2 is a photograph of the electroless copper-plated polyimide film provided in step (3) of application example 2 after being subjected to a tape adhesion test;

fig. 3 is a photograph of the electroless copper plated polyimide film provided in step (3) of application example 3 after being subjected to a tape adhesion test;

FIG. 4 is a photograph of the electroless copper-plated polyimide film provided in step (3) of application example 4 after being subjected to a tape adhesion test;

FIG. 5 is a photograph of the electroless copper-plated polyimide film provided in step (3) of application example 5 after being subjected to a tape adhesion test;

FIG. 6 is a photograph of the electroless copper-plated polyimide film provided in step (3) of application example 6 after being subjected to a tape adhesion test;

FIG. 7 is a photograph of an electroless copper-plated polyimide film provided in step (3) of application example 7 after undergoing a tape adhesion test;

fig. 8 is a photograph of the electroless copper plated polyimide film provided in step (3) of application example 8 after being subjected to a tape adhesion test;

FIG. 9 is a photograph of the electroless copper-plated polyimide film obtained in step (3) of application example 9, after being subjected to a tape adhesion test;

FIG. 10 is a photograph of an electroless copper-plated polyimide film provided in step (3) of application example 10 after undergoing a tape adhesion test;

FIG. 11 is a photograph of the electroless copper-plated polyimide film obtained in step (3) of application example 111, after being subjected to a tape adhesion test;

FIG. 12 is a photograph of an electroless copper-plated polyimide film provided in step (3) of application example 12 after undergoing a tape adhesion test;

fig. 13 is a photograph of the electroless copper-plated polyimide film provided in step (3) of application example 13 after being subjected to a tape adhesion test;

fig. 14 is a photograph of the electroless copper plated polyimide film provided in step (3) of application example 14 after being subjected to a tape adhesion test;

FIG. 15 is a photograph of an electroless copper-plated polyimide film, provided in step (3) of comparative application example 1, after being subjected to a tape adhesion test;

fig. 16 is a photograph of an electroless copper-plated polyimide film provided in step (3) of comparative application example 2 after a tape adhesion test.

Detailed Description

The technical solution of the present invention is further explained by the following embodiments. It should be understood by those skilled in the art that the examples are only for the understanding of the present invention and should not be construed as the specific limitations of the present invention.

Example 1

A reducing solution for electroless copper plating of polyimide films comprises 15mL/L of dimethylamino borane, 15g/L of boric acid, 8mg/L of 2-mercaptoethane-1-ol and the balance of deionized water;

the preparation method of the reducing solution for electroless copper plating provided by the embodiment comprises the following steps:

(2) And (2) mixing the mixed solution obtained in the step (1) with 2-mercaptoethanol-1-ol to obtain the reducing solution for electroless copper plating.

Example 2

A reducing solution for electroless copper plating of polyimide films comprises 5mL/L of dimethylamino borane, 5g/L of boric acid, 7mg/L of mercaptobenzothiazole and the balance of deionized water;

(2) And (2) mixing the mixed solution obtained in the step (1) with mercaptobenzothiazole to obtain the reducing solution for electroless copper plating.

Example 3

A reducing solution for electroless copper plating of polyimide films comprises 30mL/L of dimethylamino borane, 30g/L of boric acid, 15mg/L of 2-mercaptoethane-1-ol and the balance of deionized water;

Example 4

A reducing solution for electroless copper plating of a polyimide film, which differs from example 1 only in that the concentration of 2-mercaptoethan-1-ol is 7mg/L, and the other components, concentrations and preparation methods are the same as those of example 1.

Example 5

A reducing solution for electroless copper plating of a polyimide film, which is different from example 1 only in that the concentration of 2-mercaptoethane-1-ol is 15mg/L, and the other components, concentrations and preparation methods are the same as those of example 1.

Example 6

A reducing solution for electroless copper plating of polyimide film which is different from example 1 only in that the concentration of 2-mercaptoethane-1-ol is 0.5mg/L and the other components, concentrations and preparation methods are the same as those of example 1.

Example 7

A reducing solution for electroless copper plating of a polyimide film, which is different from example 1 only in that the concentration of 2-mercaptoethane-1-ol is 50mg/L, and the other components, concentrations and preparation methods are the same as those of example 1.

Example 8

A reducing solution for electroless copper plating of polyimide film, which is different from example 1 only in that 2- (hydroxymethyl) benzothiazole is used instead of mercaptoethane-1-ol, and other components, concentrations and preparation methods are the same as example 1.

Example 9

A reducing solution for electroless copper plating of polyimide film, which is different from example 1 only in that 2-methylthio-benzimidazole is used in place of mercaptoethane-1-ol, and other components, concentrations and preparation methods are the same as those of example 1.

Example 10

A reducing solution for electroless copper plating of polyimide film is different from that of example 1 only in that 2-methylthioethylamine is used instead of mercaptoethan-1-ol, and other components, concentrations and preparation methods are the same as those of example 1.

Example 11

A reducing solution for electroless copper plating of a polyimide film is different from that of example 1 only in that the concentration of dimethylaminoborane is 35mL/L, and other components, concentrations and preparation methods are the same as those of example 1.

Example 12

A reducing solution for electroless copper plating of polyimide film, which is different from example 1 only in that the concentration of boric acid is 30g/L, and other components, concentrations and preparation methods are the same as those of example 1.

Example 13

A reducing solution for electroless copper plating of polyimide film, which differs from example 1 only in that cystamine dihydrochloride is used instead of mercaptoethan-1-ol, and the other components, concentrations and preparation methods are the same as example 1.

Example 14

A reducing solution for electroless copper plating of polyimide film, which is different from example 1 only in that 2,2' -thiobis (ethan-1-ol) is used in place of mercaptoethan-1-ol, and other components, concentrations and preparation methods are the same as example 1.

Comparative example 1

A reducing solution for electroless copper plating of a polyimide film, which is different from example 1 only in that 2-mercaptoethane-1-ol is not added, and other components, amounts and preparation methods are the same as those of example 1.

Comparative example 2

A reducing solution for electroless copper plating of a polyimide film is different from that of example 2 only in that mercaptobenzothiazole is not added, and other components, the use amounts and the preparation method are the same as those of example 2.

Application example 1

A copper plating method of a polyimide film specifically comprises the following steps:

(1) Activating the polyimide film for 100 seconds in activating solution which has the pH value of 8 and the temperature of 50 ℃ and contains sodium dodecyl sulfate, palladium ions and acetic acid to obtain the activated polyimide film;

(2) Reducing the activated polyimide film obtained in the step (1) in a reducing solution (example 1) for electroless copper plating at 40 ℃ for 60 seconds to obtain a reduced polyimide film;

(3) Chemically plating copper on the polyimide film subjected to reduction treatment obtained in the step (2) in a chemical copper plating solution containing tartaric acid, formaldehyde, copper ions and potassium cyanide at 30 ℃ for 6min to obtain a polyimide film subjected to chemical copper plating;

(4) And (4) electroplating the polyimide film subjected to electroless copper plating obtained in the step (3) in electroplating solution with current density of 1.6-2.0 ASD for 60min to obtain the copper-plated polyimide film.

Application examples 2 to 14

A copper plating method for a polyimide film was different from that of application example 1 only in that the reducing solutions for electroless copper plating provided in example 1 were replaced with the reducing solutions for electroless copper plating obtained in examples 2 to 14, respectively, and the steps and parameters were the same as those of application example 1.

Comparative application examples 1 to 2

A copper plating method for a polyimide film differs from application example 1 only in that the reducing solutions for electroless copper plating provided in example 1 were replaced with the reducing solutions for electroless copper plating obtained in comparative examples 1 to 2, respectively, and the characteristic steps and parameters were the same as in application example 1.

And (3) performance testing:

(1) Adhesive force of the adhesive tape: adhering a 3M adhesive tape to an electroless copper plating layer formed on the surface of the polyimide film subjected to electroless copper plating treatment provided in the step (3) of the application examples 1 to 14 and the comparative application examples 1 to 2, then applying firm pressure with a thumb to peel the adhesive tape at 180 degrees, repeating the adhering and peeling steps for 6 times, and observing the appearance of the surface of the copper-plated polyimide film to judge the adhesive force condition of the adhesive tape;

specifically, the photographs of the electroless copper-plated polyimide films obtained in the steps (3) of application examples 1 to 14 and comparative application examples 1 to 2, which were subjected to the tape adhesion test, are shown in fig. 1 to 16, respectively: as can be seen from fig. 1 to 5, after 6 times of tape peeling tests, the electroless copper plating layer on the surface of the polyimide film is still intact and hardly drops, which indicates that the adhesion between the electroless copper plating layer and the polyimide film is high; as can be seen from fig. 6 to 14, after 6 tape peeling tests, a part of the electroless copper plating layer on the polyimide surface was peeled off (the darker portion in the figure is the peeled portion), which shows that the concentration of the sulfur-containing additive, the kind of the sulfur-containing additive, the concentration of the dimethylaminoborane and the concentration of the boric acid in the reducing solution for electroless copper plating all affect the adhesion between the electroless copper plating layer and the polyimide film; as can be seen from fig. 15 to 16, after 6 tape peeling tests, the chemically plated copper layer on the surface of the polyimide film was peeled off in a large area, which indicates that the adhesion between the chemically plated copper layer and the polyimide film was poor when electroless copper plating was performed after reduction treatment with a reducing solution without adding a sulfur-containing additive.

(2) Thermal shock performance: the polyimide films (the thickness of the copper layer is about 25 mu m) obtained in the application examples 1-14 and the comparative application examples 1-2 after copper electroplating are placed in an oven at 150 ℃ for baking for 4h, and cooled to room temperature in a dryer; soaking the dried copper-plated polyimide film in a tin furnace at 288 ℃ for 10s, cooling to room temperature, circulating for 6 times, and observing the thickness of the film to 25cm ² The number of blisters on the surface of the polyimide film.

The copper-plated polyimide films provided in application examples 1 to 14 and comparative application examples 1 to 2 were tested according to the above test method (2), and the test results are shown in table 1:

TABLE 1

As can be seen from the data in table 1:

examples 1 to 14 were conducted to provide copper-plated polyimides treated with the reducing solution for electroless copper platingThe amine film had excellent thermal shock properties, specifically, the copper-plated polyimide films provided in application examples 1 to 14 were 25cm after the thermal shock test ² The number of the inner bubbles is only 0-8, and the number of the bubbles of the copper-plated polyimide film treated by the reducing solution for electroless copper plating obtained without adding the sulfur-containing additive is 15-18, which is obviously increased greatly.

And further comparing application example 1 with application examples 6 to 14, it can be seen that the concentrations of the sulfur-containing additive, the dimethylaminoborane and the boric acid or the types of the dimethylaminoborane are not in the preferable range defined by the invention, so that the copper-plated polyimide film after thermal shock test has increased number of bubbles and reduced thermal shock performance.

The applicant states that the present invention is described by the above examples to describe a reducing solution for electroless copper plating of polyimide film, and a preparation method and application thereof, but the present invention is not limited to the above examples, that is, the present invention is not limited to the above examples. It should be understood by those skilled in the art that any modifications of the present invention, equivalent substitutions of the raw materials of the product of the present invention, and the addition of auxiliary components, selection of specific modes, etc., are within the scope and disclosure of the present invention.

Claims

1. The reducing solution for electroless copper plating of the polyimide film is characterized by comprising a combination of dimethylaminoborane, boric acid, a sulfur-containing additive and deionized water.

2. The reducing solution for electroless copper plating according to claim 1, wherein the reducing solution for electroless copper plating comprises 1 to 30mL of dimethylaminoborane, 1 to 25g of boric acid, 0.5 to 50mg of a sulfur-containing additive, and the balance of deionized water, based on 1L of the reducing solution for electroless copper plating.

3. The reducing solution for electroless copper plating according to claim 1 or 2, wherein the content of the sulfur-containing additive in the reducing solution for electroless copper plating is 7 to 15mg based on 1L of the reducing solution for electroless copper plating.

4. The reducing solution for electroless copper plating according to any one of claims 1 to 3, wherein the sulfur-containing additive comprises any one of 2- (hydroxymethyl) benzothiazole, mercaptobenzothiazole, 2-mercaptoethan-1-ol, cystamine dihydrochloride, 2-methylthio-benzimidazole, 2-methylthio-ethylamine or 2,2' -thiobis (ethan-1-ol), or a combination of at least two thereof, preferably 2-mercaptoethan-1-ol.

5. The method for producing the reducing solution for electroless copper plating of polyimide films according to any one of claims 1 to 4, characterized by comprising: and mixing dimethylamino borane, boric acid, a sulfur-containing additive and deionized water to obtain the reducing solution for electroless copper plating.

6. The method of claim 5, comprising the steps of:

(2) And (2) mixing the mixed solution obtained in the step (1) with a sulfur-containing additive to obtain the reducing solution for electroless copper plating.

7. A copper plating method for a polyimide film, the copper plating method comprising: the polyimide film is activated by an ionic palladium activation solution, then reduced in a reducing solution for electroless copper plating according to any one of claims 1 to 4, then electroless copper plated in an electroless copper plating solution, and finally electroplated copper, thereby completing the copper plating of the polyimide film.

8. The copper plating method according to claim 7, wherein the ionic palladium activating solution includes a complexing agent, palladium ions, and a surfactant;

preferably, the pH value of the ionic palladium activation solution is 8.5-9.5;

preferably, the mass of the palladium ions is 50-300 mg calculated by 1l of the ionic palladium activation solution;

preferably, the temperature of the activation treatment is 45-55 ℃;

preferably, the time of the activation treatment is 30 to 120s;

preferably, the temperature of the reduction treatment is 30-40 ℃;

preferably, the time of the reduction treatment is 30 to 60s;

preferably, the electroless copper plating solution comprises a complexing agent, copper ions, a reducing agent and a stabilizing agent;

preferably, the pH value of the electroless copper plating solution is 9-13;

preferably, the temperature of the electroless copper plating is 28-35 ℃;

preferably, the electroless copper plating time is 5-7 min.

9. A copper-plated polyimide film, characterized in that it is produced by the copper plating method according to claim 7 or 8.

10. Use of the copper-coated polyimide film according to claim 9 in a flexible electronic device.