Study On Drilling Technology Of FPC With Different Polarized Light

With the development of modern high-tech,Flexible Printed Circuit Board(referred to as FPC)of high density and pore diameter are put forward higher requirements,the traditional mechanical processing method has been unable to meet the demand.Femtosecond laser micromachining has the advantages of high machining accuracy,small thermal effect and low damage threshold.It is widely used in drilling.Polarization is one of the basic parameters of laser,and has an important influence on the characteristics of micro machining.In this paper,the characteristics of FPC micro machined by femtosecond laser beams with different polarization states are investigated:Firstly,the action mechanism of laser and material and the process of four steps of laser action on metal material processing hole are introduced.This paper discusses two kinds of drilling methods of laser impact drilling and contour detour at present.In addition,the theory and feasibility of using the area method to measure the damage threshold is deduced.The optical path and the experimental system are designed to measure the damage threshold of FPC in the single pulse of femtosecond laser pulse is25.44J/cm~2.Secondly,the physical and geometrical description of several kinds of polarization beams and the vector light field of four kinds of polarization states are introduced.The principle of phase modulation of spatial light modulator and the principle of 4f optical system.And the design of optical principle diagram,using computer generated hologram by spatial light modulator,combined with the fast axis of 1/2 wave plate and1/4 plate and horizontal angle control line polarized light,circularly polarized,radially polarized and azimuthally polarized beams.Finally,it designs and constructs a machining experiment system,which consists of femtosecond laser,spatial light modulator,CCD camera and 3D mobile platform.Based on the analysis of the processing characteristics of the FPC micro hole,the influence of the pulse energy on the aperture and the different polarized light beam on the roundness and the ablation degree of they are analyzed.The experimental results show that the aperture of axisymmetric radial polarized light and angle polarized light is slightly larger than linear polarization and circular polarization.Linear polarized light ablation was the most serious,the roundness of the worst;ablation of circularly polarized light is better than linear polarized roundness;radially polarized and angular polarized light general ablation and roundness than the first two,and the radially polarized micro quality better.And then for the project part of the indicators of processing experiments.