Research Of Micro Line Formation Technology On FR-4 Copper Clad Laminate Based On Femtosecond Laser

Femtosecond laser is well konwn to us for its extremely high peak power and ultra-short duration,which makes it possible to process any material with non-thermal influence.By this way,high precision and good processing quality can be attained easily by femtoseocnd laser,therefore it shows unparalleled superiority in the field of micro processing.With the rapid development of microelectronics,the integration of PCB keeps improving and the R & D period of the products continues shortening,leads to the increasingly urgent demands for micro conductive lines and rapid template production.To solve the above problems,a study on the direct etching of copper clad laminate by femtosecond laser is performed in this paper,in order to realize high etching quality of micro lines on FR-4 copper clad laminate with the cold processing and selective etching characteristics of femtosecond laser.The main contents are as follows:(1)Mechanisms of the interaction between femtosecond laser and metal material are discussed from mechanism of laser energy absorption and the phase transition process of metal.By means of simplifying Two Temperature Model,we obtained an analytic formula for the depth of single-pulse femtosecond laser ablation materials.We can see that the ablation mechanism of metal materials includes the evaporation of superheated liquid and the phase change explosion based on a phase diagram for describing the dynamic characteristics.(2)Based on Two Temperature Model,numerical simulation of the electron and lattice temperatures in the material are performed by MATLAB.The five influential factors,such as electron thermal conductivity,electron lattice coupling coefficient,laser energy density,pulse width and material depth,which are on change of electron lattice temperature change are analyzed mainly form the following several aspects: electron peak temperature,the electron temperature rise rate,the time and temperature of electron lattice coupling to the balance heat.(3)The influences of the average power,scanning speed,scanning times,defocusing amount and line spacing on the depth of the etching depth,the roughness and the micro morphology are gained with the method of single factor etching of FR-4 copper clad laminate with femtosecond laser.Besides the influence of these process parameters on the etching depth and the etching roughness is obtained through orthogonal design.The results shows that the influence of the scanning times is the greatest and the scanning speed is the smallest no matter the etching depth or the etching roughness is considered as the measure index.In addition,the optimum processing parameters are obtained by the comprehensive balance method.(4)Study of femtosecond laser micro circuit etching on the surface of copper clad laminate by optimizing process parameters.In order to get the exact line width,the factors affecting the size of the forming wire are analyzed by the design contrast test.It is proved that the copper layer can be completely removed by the femtosecond laser etching with the optimizing parameters,and do not cause damage to the substrate material as well.The etching process of micro conductive lines,including single and parallel wires has been realized,a conductive line with a width of 50?m and a line spacing of 20?m is produced,and the width and spacing of lines can be controlled in the micron scale range.The results show that direct etching of FR-4 copper clad laminate with optimizing parameters femtosecond laser can achieve high quality window etching and high precision micro conductive lines.Compared with the traditional line forming process,this new line forming craft can simplify process flow,improve the efficiency and reduce environmental pollution.