The basic method of CO2 laser processing thin film is to expand the laser beam, and then focus on the film product, the material in the focus is instantly vaporized, so as to realize the cutting of the material, and finally obtain various shapes of film products.
With the development of thin film technology, various non-metallic films are widely used in military industrial products and 3C electronic products. Non-metallic film products can be used for shielding and sealing, waterproof sealing, heat conduction, insulation, appearance decoration, appearance protection, etc. The thickness of these films is generally between 0.1mm~2mm, and the application scenes are various in shapes. Due to the limitations of traditional manufacturing methods - knife cutting or mold forming, laser cutting has been widely used in non-metallic film forming.
The output laser wavelength of CO2 lasers is 10.6um, and the absorptivity of non-metal film is higher than other wavelength lasers, so CO2 laser is preferred for film processing and shaping. The basic method of CO2 laser processing film is to expand the laser beam, and then focus on the film product, the material in the focus is instantly vaporized, so as to realize the cutting of the material, and finally obtain various shapes of film products. There are two common CO2 laser processing equipment: galvanometer scanning processing equipment and flying optical path scanning processing equipment. RF excited diffusion cooling slab waveguide CO2 laser has many advantages such as good laser beam quality, high peak power, maintenance-free, small size, etc., it has become the first choice for thin film cutting and forming.
SPT Laser Q Series CO2 RF Laser
Using radio frequency CO2 laser cutting and forming equipment to produce film products has the following advantages:
Computerized graphics, no mold required - cost saving, quick response to market demand, with both small batch proofing and mass production;
What you see is what you get - low requirements for operators, saving labor costs;
Maintenance-free, no consumables - saving time, labor, and cost.
PET Phone film
Film processing products require neat edges, no jaggedness, small heat-affected area, small cutting edge slope, and no residue accumulation on the edges. There are many factors that affect the processing effect of RF CO2 laser processing equipment. The following is a qualitative analysis of the factors that affect the film processing effect:
1. Wavelength —— RF CO2 laser has four wavelengths -- 10.6um, 9.3um, 10.2um and 9.6um. Most of the non-metallic materials are organic plastic products and polymer products. Organic matter is very sensitive to changes in light absorption rate and light wavelength。 With small differences in wavelength, the difference in absorbance will be very large. The difference in laser absorption rate of materials has a fundamental impact on the processing effect, so the choice of wavelength is the first to affect the processing effect. Commercial RF CO2 lasers can reliably obtain these four wavelengths. The lasers have a maintenance-free service life of more than 20,000 hours, and can be used again after a simple inflation. A reasonably maintained RF CO2 laser has a life span of more than 100,000 hours.
2. Laser power —— RF CO2 laser’s output power varies from a few watts to thousands of watts. Select the appropriate power and laser according to the thickness of the film cutting, the cutting speed, and the absorption of the material. Under normal circumstances, when the CO2 laser power used in cutting is not more than 80% of the maximum output power of the laser, it is easy to get the best performance and effect.
3. The focal length of the focus lens——the focal length of the focus lens directly affects the size of the focusing spot, so it is very important to choose a proper focus length of a focus lens. For cutting equipment with flying light path, the focal length is generally selected between 1 inch and 2.5 inches. At the same focal length, there are plano-convex lenses and meniscus lenses to choose from. In general, the focal spot of a meniscus lens is smaller than that of a plano-convex lens. For CO2 laser galvanometer scanning processing equipment, the focal length of the focus field lens is generally 80~160mm. For galvanometer scanning processing equipment that requires particularly fine effects, a telecentric scanning field lens is required.
4. Film cutting speed - The cutting speed determines the laser processing time and the amount of laser energy absorbed by the film material, which in turn affects the size of the cutting heat-affected zone. For film cutting and the flying light path, the cutting speed is usually greater than 100mm/s. The speed of galvanometer scanning laser processing is usually greater than 500mm/s. If the cutting speed reaches several kilometers per second, attention should be paid to the coordination of laser modulation frequency and speed to obtain a smooth edge.
5. Focus position - although the film is very thin, it also has a certain thickness. The focus position is on the upper surface of the material, the middle of the material, the lower surface of the material, and even the upper defocus and the lower defocus. The choice of different focus positions can affect the processing efficiency and processing effect.
6. Laser mode - Laser mode describes the distribution of laser energy in the cross section of the laser beam perpendicular to the transmission direction. The laser mode is divided into transverse mode and longitudinal mode. Most RF CO2 lasers are in transverse mode. In application, the RF CO2 laser mode is simply divided into fundamental mode and multimode. In order to obtain fine processing effects, the fundamental mode spot is often selected. For a laser with a fundamental mode output, its beam quality factor M2 is relatively small, generally less than 1.5. According to the calculation formula of focusing spot:
Spot is the diameter of the focused spot, λ is the laser wavelength, F is the focal length of the focus lens, and D is the size of the spot incident on the focus lens. It can be seen from the calculation formula that the size of the focused spot is proportional to the beam quality factor M2. Therefore, selecting the fundamental mode and selecting a laser with a small beam quality factor can obtain a small focused spot and a better processing effect.
7. Auxiliary gas- Auxiliary gas can blow away the smoke generated at the incision, prevent waste and smoke from polluting the optical lens, divert the laser thermal energy, so that the laser energy can be more concentrated on the material, and enhance the laser cutting performance. According to cutting needs, you can choose different gases that support combustion or flame retardancy.
8. Thin film material material- When laser is cutting materials, the action process is very complicated. Generally speaking, when laser cutting plastics and other polymer materials, it includes the conversion of light energy to heat energy, the conversion and distribution of heat energy on the workpiece, and heat exchange between workpiece and surrounding environment. In short, one of the basic optical properties of thin film materials is absorption and conversion. The laser energy absorbed by the thin film material in a unit time determines the overall absorption energy. The laser light energy is irradiated on the surface of the material, and then converted into heat energy, and the surface temperature is relatively high. The sum of the energy of the heating material, the vaporized material, and the moving vaporization zone constitutes the energy distribution on the material.
PET film Polyester film
The PET material, which is a common film material, is an IMD film material with excellent performance, and is a thermoplastic polymer material with a complex molecular chain structure and aggregated structure. PET is a composite material with excellent physical and chemical properties because of its excellent mechanical and heat transfer properties, thermal stability and optical transparency. The following table shows the thermal properties of PET film materials. From the table, it can be found that the melting temperature of PET materials is always 261°C, whether it is a single-layer film material, after aminating or a multilayer PET film material.
| Sample | Onset(℃) | Tm (℃) | △Tm (℃) | △Hm (J/g) |
| Original PET | 251.88±2.34 | 261.31±0.60 | 16.29 | 17.25±0.01 |
| A/C PET | 250.88±0.01 | 262.20±1.52 | 17.86 | 22.50±0.05 |
| Nanolayered film | 250.67±0.09 | 262.82±1.18 | 18.29 | 31.33±0.11 |
Thermal properties of PET film materials
From the analysis of the thermal performance of PET film, there is little difference between different samples. What determines the cutting effect and efficiency is the absorption efficiency of the PET film for the laser. The absorption coefficient of the PET film for the 10.6um wavelength is 0.5, so 10.6um laser can be used to cut PET film. In some recent PET film experiments, when 9.3um laser, 10.2um laser, or 9.6um laser is selected, the effect is better than 10.6um laser, which also shows the importance of laser wavelength selection for film cutting.
The above analysis shows that the core device of the RF CO2 laser cutting film equipment is a laser. Correct selection of the laser wavelength and matching the absorptivity of the material is the basis for achieving the best cutting effect, and then with a reasonable selection of the whole machine components and appropriate process parameters, the best effect and efficiency can be obtained. Of course, there are other software parameters that affect thin film laser cutting, such as Q frequency, release time, processing leads, and so on.
