Jul 27, 2020
The application of laser on PCB mainly includes cutting, drilling, marking, etc., especially cutting. Compared with the traditional die-cutting process, laser cutting is a non-contact processing, without expensive molds, and the production cost is greatly reduced; in addition, the traditional process is difficult to solve a series of problems such as burrs, dust, stress, and inability to process curves. After the laser is focused, the spot is only ten micrometers in diameter, which can meet the processing needs of high-precision cutting and drilling, and solve a series of problems left over in the traditional process. This advantage is catering to the development trend of sophisticated circuit design and is an ideal tool for PCB, FPC, and PI film cutting.
In fact, the application of PCB laser cutting technology in the PCB industry started early, but the early use of CO2 laser cutting has a greater thermal impact and lower efficiency. It has not been able to achieve better development, and only in some special fields (such as scientific research) , Military industry, etc.). With the development of laser technology, more and more light sources can be used in the PCB industry, and a breakthrough has been found for the industrial application of laser cutting PCB.
The lasers currently used in FPC and PI film cutting are mainly nanosecond solid-state ultraviolet lasers, and their wavelength is generally 355nm. Compared with 1064nm infrared and 532nm green light, 355nm ultraviolet has higher single-photon energy, higher material absorption rate, less thermal impact, and higher processing accuracy.
From the principle point of view, pulsed laser cutting materials can be divided into two situations: one is the principle of photochemistry, which uses the laser single photon energy to reach or exceed the chemical bond energy of the material and break certain chemical bonds of the material to achieve cutting; the other is light According to the physical principle, when the laser single photon energy is lower than the chemical bond energy of the material, relying on the very high energy density at the focused spot, exceeding the vaporization threshold of the material, the material is vaporized instantaneously and the material is cut. But when actually cutting FPC or PI film with ultraviolet laser, photochemical and photophysical cutting principles exist at the same time.
In the photophysical effect, heat will be generated and accumulated, and the temperature of the material will continue to rise. When the temperature is higher than 600℃, the material will be carbonized.
It can be seen that when the material is constant, the greater the laser pulse width, the greater the diffusion distance of the thermal energy generated by the laser on the material, and the greater the thermal damage to the material. Therefore, narrower pulse width contributes to better processing effect.