A method for enhancing the bonding strength between polymer film and metal coating

Abstract

The present invention relates to a method for enhancing the bonding strength between a polymer film and a metal coating, comprising the following steps: (1) vacuum metallization to form a base layer; (2) laser melting treatment; and (3) metallization. The present invention utilizes the characteristics of ultrathin metal melting point reduction, surface energy reduction-driven spheroidization, and rapid high-energy treatment to soften the surface of the polymer film. By precisely controlling laser energy, the method significantly enhances the bonding strength between the polymer film and the metal coating. Furthermore, the method has certain universality and broad application prospects.

Description

Technical Field

[0001] The invention belongs to the field of electronic material processing, and in particular relates to a method for enhancing the bonding strength between a polymer film and a metal plating layer. Background Art

[0002] With the rapid development of the electronics industry, the performance of electronic products has been further improved, their appearance has become smaller and lighter, and electronic circuit boards have become more sophisticated. The development of high-performance electronic materials is imperative, and so is the improvement of the performance of metallized films. Metallized films are widely used in the electronic materials field, such as capacitors using metallized films as electrodes, power batteries composed of composite current collectors, and ultra-thin flexible copper-clad laminates used in high-precision circuit boards.

[0003] Conventional metallized films have a prominent problem, namely the weak bonding between the film and the metal layer. This problem is usually solved by using adhesives, but the use of adhesives brings new problems such as poor thermal stability and thermal bulging. At the same time, the use of adhesives will inevitably increase the thickness of the metallized film, making the preparation of ultra-thin metallized films more difficult. Therefore, the research and development of ultra-thin metallized films cannot avoid the problem of glue-free. The current optimal solution is to use vacuum coating technology to deposit a metal conductive layer on the polymer film, and then use electroplating to thicken the metal conductive layer to meet the requirements of thin film metallization. Vacuum coating technology can make the film layer thinner while ensuring that the metal conductive layer is uniform and dense, but the defect of this method is that the bonding strength between the vacuum-coated metal layer and the polymer film substrate does not meet the use requirements, and the use of coating modification, ion implantation, different ion source pretreatments, etc. cannot improve the bonding strength between the metal layer and the polymer film substrate to a very high level.

[0004] In order to achieve the demand for improving the performance of metallized films, it is very important to develop a method to improve the bonding strength between the vacuum-coated metal layer and the polymer film substrate. Summary of the Invention

[0005] The present invention provides a method for enhancing the bonding strength between a polymer film and a metal coating, which solves the problem of weak bonding between the two and achieves a leap in the performance of the metallized film.

[0006] The present invention provides a method for enhancing the bonding strength between a polymer film and a metal coating, comprising the following steps:

[0007] (1) Pre-treating the polymer film with an ion source in a vacuum coating device to remove the passivation layer on the surface of the film; after the treatment, using vacuum coating technology to coat the film surface with a metal base layer;

[0008] (2) Using a high-energy laser to melt the metal base layer, after cooling and solidification, the metal base layer becomes spherical and embedded in the surface layer of the polymer film substrate;

[0009] (3) Using vacuum coating technology to continue to coat a metal layer on the surface of the polymer film, so that the metal layer and the metal base layer are combined to form a film, and then the metal layer is thickened to the target thickness.

[0010] The polymer film material in step (1) is one or more of polyimide, polyethylene, polypropylene, polystyrene, polyethylene terephthalate, polyethylene naphthalate, polytetrafluoroethylene, and polyacrylonitrile, and has a thickness of 3 μm to 300 μm.

[0011] The ion source in step (1) is one or more of an anode layer ion source, a Hall ion source, a Kaufman ion source, and an ICP ion source, and the vacuum degree is 2.0-3.0*10 -5 Torr, ion source power is 1 to 10 kW, and processing time is 1 to 30 min.

[0012] The metal used for the metal base layer in step (1) includes one of Cu, Ni, Co, Cr, Zn, Fe, Mo, Ti, V, Mn, W or an alloy thereof, and has a thickness of 1 to 20 nm.

[0013] The process parameters of the metal coating base layer in step (1) are: the sputtering power is set to 1-10KW, and the amount of Ar gas filled is 100-200SCCM.

[0014] The power range of the high-energy laser in step (2) is 200W to 3000W, the exposure time is 0.002s to 5s; the diameter of the laser beam is 0.005mm to 2mm, the lateral scanning speed of the laser beam is 0 to 1500mm / s, and the incident angle of the laser beam is between 0 and 90°; the melting processing speed is set to 0.1-1m2 / min.

[0015] The high-energy laser in step (2) may use one or more high-energy laser devices.

[0016] The cooling and solidification in step (2) is performed by applying the bottom surface of the polymer film to a cooling roller at a temperature of -5 to -25°C.

[0017] The metal used for the vacuum-plated metal layer in step (3) is one of Cu, Ni, Co, Cr, Zn, Fe, Mo, Ti, V, Mn, W or an alloy thereof, and has a thickness of 1 to 500 nm.

[0018] The process parameters of the metal coating in step (3) are: the sputtering power is set to 1-10KW, and the amount of Ar gas filled is 100-200SCCM.

[0019] In the step (3), the thickening to the target thickness is performed by using vacuum coating technology and / or electroplating technology.

[0020] This method uses a high-energy laser beam to rapidly melt the vacuum-coated base metal layer, cooling and solidifying it into metal microspheres. Simultaneously, the laser's thermal effect rapidly softens the surface of the polymer substrate, allowing the metal microspheres to be embedded in the polymer film's surface. The subsequent metal layer, then bonded to the base metal, forms a film. This metal layer, formed in this way, contains numerous "rivets" embedded in the polymer film's surface, significantly enhancing the bonding strength between the two.

[0021] Beneficial effects

[0022] (1) The present invention can effectively enhance the bonding strength between polymer films and metal coatings on a variety of film substrates. The method is universal and has a wide range of applications.

[0023] (2) The present invention has no special requirements on the type and thickness of the base metal, and can effectively improve the bonding strength between the base film and the metal layer, and can meet the requirements of special metallized film layers required by different industries.

[0024] (3) The high-energy laser processing step in the present invention can achieve precise control of the degree of interlocking between the metal layer and the base film by adjusting parameters such as laser power, lateral scanning speed, exposure time and spot diameter, thereby achieving the purpose of enhancing the bonding strength between the metal layer and the film. The degree of enhanced bonding strength can be adjusted according to actual needs, and the feasibility window range is relatively wide, which is convenient for process control in industrial production.

[0025] (4) The metal layer after high-energy laser treatment of the present invention can continue to be vacuum plated with other metal layers or directly electroplated to thicken it, thereby enhancing the bonding strength between the polymer film and the metal coating while ensuring product production efficiency.

[0026] (5) The method of enhancing the bonding strength between the polymer film and the metal coating by high-energy laser treatment of the present invention does not generate additional wastewater, waste gas and solid pollution waste, which is in line with the concept of high efficiency and environmental protection. DETAILED DESCRIPTION

[0027] Below in conjunction with specific embodiment, further set forth the present invention.Should be understood that these embodiments are only used to illustrate the present invention and are not used in limiting the scope of the present invention.In addition, should be understood that after reading the content taught by the present invention, those skilled in the art can make various changes or modifications to the present invention, and these equivalent forms fall equally within the scope limited by the appended claims of the application.

[0028] Example 1

[0029] A roll of 12.5μm thick polyimide film with a width of 550mm is fixed on the unwinding roller of the vacuum coating equipment. The parameters of the guide roller and the tension roller are adjusted to appropriate values ​​to ensure that the film will not wrinkle due to unwinding and rewinding during the vacuum coating process and to ensure that the rewinding speed is stable at 4m / min.

[0030] Set the initial vacuum degree of the vacuum coating equipment to 2.0*10 -5 Torr, and after reaching the set vacuum degree, argon gas was introduced with 1KW power of RF ion source for pretreatment for 120s; after the pretreatment, the film was ion beam sputtered through the target area to form a 20nm Cr layer as a base metal layer, the sputtering power was set to 2KW, and the amount of Ar gas filled was 120SCCM.

[0031] After the base metal layer is plated, the film passes through the high-energy laser area, the laser power is set to 1000W, the laser beam diameter is 0.01mm, the lateral scanning speed of the laser beam is 100mm / s, the incident angle is 70°, and the melting process speed is set to 0.55m 2 / min, the number of lasers is 4, and the temperature of the cooling roller is set at -15℃ to ensure that the film after laser treatment can be quickly cooled and reconstructed to tightly combine the Cr layer and polyimide.

[0032] After the treatment, a 50nm thick Cu layer is sputtered as a seed layer. The sputtering power is set to 2kW and the Ar gas volume is 120 SCCM. After the vacuum coating is completed, the rolled polyimide film is transferred to the electroplating line for thickening to the required thickness specification.

[0033] Example 2

[0034] The difference from Example 1 is that the Cr base layer is replaced with a NiCr alloy base layer (Ni:Cr=4:1). Other than that, the preparation method is the same as that of Example 1.

[0035] Example 3

[0036] The difference from Example 1 is that the Cr base layer is replaced with a Cu base layer. Other than that, the preparation method is the same as that of Example 1.

[0037] Example 4

[0038] The difference from Example 1 is that the laser power is set to 1200W, the laser beam diameter is 0.01mm, the lateral scanning speed of the laser beam is 100mm / s, the incident angle is 70°, and the melting processing speed is set to 0.55m 2 / min, the number of lasers is 4, and other than that, the preparation method is consistent with that of Example 1.

[0039] Example 5

[0040] The difference from Example 1 is that the laser power is set to 700 W, the laser beam diameter is 0.01 mm, the lateral scanning speed of the laser beam is 100 mm / s, the incident angle is 70°, the melting processing speed is set to 0.55 m2 / min, and the number of lasers is 4. Other than that, the preparation method is consistent with that of Example 1.

[0041] Comparative Example 1

[0042] The difference from Example 1 is that the high-energy laser treatment process is not performed, and the Cu seed layer is directly sputtered after the base layer is sputtered. Other than that, the preparation method is consistent with that of Example 1.

[0043] Comparative Example 2

[0044] The difference from Example 1 is that the high-energy laser treatment process is not performed, and the Cr base layer is replaced with a NiCr alloy base layer (Ni:Cr=4:1). Other than that, the preparation method is the same as that of Example 1.

[0045] Comparative Example 3

[0046] The difference from Example 1 is that the high-energy laser treatment process is not performed, and the Cr base layer is replaced with a Cu base layer. Other than that, the preparation method is the same as that of Example 1.

[0047] Binding strength evaluation method and result analysis

[0048] Random samples were taken from the same roll of electroplated, thickened metallized film and copper-plated to a thickness of 18 μm according to standard peel strength testing methods. Each sample from the Examples and Comparative Examples was heated in an air oven at 200°C for two hours. The heated samples were then secured to a flat support plate and the peel strength was measured using a PT50N tester manufactured by Minebea Co., Ltd. according to the peel strength test method specified in JIS-C6481 (1996). A higher peel strength indicates a stronger bond between the sample's metal layer and the polymer film.

[0049] The following table shows the peel strength test results:

[0050]

[0051]

[0052] Analysis of peel strength test results:

[0053] 1. Comparison of the peel strengths of Example 1 and Comparative Example 1, Example 2 and Comparative Example 2, and Example 3 and Comparative Example 3 shows that high-energy laser treatment of the base metal can effectively improve the bonding strength between the metal layer and the polymer film in the metallized film.

[0054] 2. By comparing the peel strengths of Example 1, Example 4, and Example 5, it can be seen that the bonding strength between the metal layer and the polymer film can be controlled by controlling the laser beam power of the high-energy laser melting process.

[0055] 3. Comparison of the peel strengths of Examples 1, 2, and 3 shows that the bonding strength between the metal layer and the polymer film is related to the type of the base metal. Preferably, Cr is used as the base metal for a better bonding strength.

[0056] In summary, high-energy laser treatment of metallized film to form the underlying metal layer creates a large number of "rivets" embedded in the surface of the polymer film, significantly enhancing the bonding between the two. This allows the metallized film to be thinner and gel-free while maintaining performance, representing a significant breakthrough in improving the performance of metallized film materials. This method has significant economic value and can be widely applied in the production process of polymer metallized films, such as ultra-thin FCCLs, composite current collector copper and aluminum foils, and metallized film capacitors.

Claims

1. A method for enhancing the bonding strength between a polymer film and a metal coating, comprising the following steps; (1) Pre-treating the polymer film with an ion source in a vacuum coating device to remove the passivation layer on the film surface; after the treatment, a metal base layer is plated on the film surface using vacuum coating technology; (2) A high-energy laser is used to melt the metal base layer, and after cooling and solidification, the metal base layer becomes spherical and embedded in the surface layer of the polymer film substrate; the power range of the high-energy laser is 200W~3000W, the exposure time is 0.002s~5s; the laser beam diameter is 0.005mm~2mm, the lateral scanning speed of the laser beam is 0~1500 mm / s, and the laser beam incident angle is between 0~90°; the melting processing speed is set to 0.1-1m² / min; the cooling and solidification is performed by applying the bottom surface of the polymer film to a cooling roller, and the temperature is -5~-25℃; (3) Use vacuum coating technology to continue to coat a metal layer on the surface of the polymer film, so that the metal layer and the metal base layer are combined to form a film, and then the metal layer is thickened to the target thickness.

2. The method according to claim 1, wherein: The polymer film material in step (1) is one or more of polyimide, polyethylene, polypropylene, polystyrene, polyethylene terephthalate, polyethylene naphthalate, polytetrafluoroethylene, and polyacrylonitrile, and has a thickness of 3 μm to 300 μm.

3. The method according to claim 1, wherein: The ion source in step (1) is one or more of an anode layer ion source, a Hall ion source, a Kaufman ion source, and an ICP ion source, and the vacuum degree is (2.0-3.0)×10 -5 Torr, ion source power is 1~10KW, and processing time is 1~30min.

4. The method according to claim 1, wherein: The metal used for the metal base layer in step (1) includes one of Cu, Ni, Co, Cr, Zn, Fe, Mo, Ti, V, Mn, W or an alloy thereof, and has a thickness of 1 to 20 nm.

5. The method according to claim 1, wherein: The high-energy laser in step (2) may use one or more high-energy laser devices.

6. The method according to claim 1, wherein: The metal used for the vacuum-plated metal layer in step (3) is one of Cu, Ni, Co, Cr, Zn, Fe, Mo, Ti, V, Mn, W or an alloy thereof, and has a thickness of 1 to 500 nm.

7. The method according to claim 1, wherein: In step (3), the thickening to the target thickness is performed using vacuum coating technology and / or electroplating technology.

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