| With the continuous development of a new generation of communication technology,the traditional signal frequency band has been unable to meet the requirements of high-speed data transmission and high-frequency system bandwidth,which has put forward new requirements for high-frequency devices.Therefore,devices corresponding to high-frequency systems are urgently needed packaging solutions to solve the corresponding problems.Due to the advantages of LCP with excellent dielectric constant temperature coefficient characteristics,extremely low moisture absorption and better high-frequency packaging performance,LCP flexible copper clad laminate composited with LCP as a substrate performs better for highfrequency device packaging.It is widely used in microwave/millimeter substrate packaging and has received extensive attention in the field of 5G electronic device packaging.Microscale processing is essential in high-frequency system packaging.The application of traditional methods such as mechanical stamping and chemical etching is limited due to cumbersome processing procedures and chemical pollution.Using traditional laser processing of LCP materials,affected by the thermal effect of the laser,the thermal shape of the LCP substrate will change the processing laser focus and thus affect the processing accuracy,while the LCP molecules are prone to material modification under the influence of the thermal effect,affecting the electrical properties of RF devices.In view of the above problems,in recent years,laser direct writing technology based on ultrafast lasers has been widely used in the cold processing of various organic polymer materials.Improve the surface modification of LCP materials under thermal effects.Different from general organic polymers,LCP bonds are more stable in the molten state and have stronger fluidity.Therefore,during the processing,the molten LCP molecules are difficult to be further excited by the photoinduced plasma.After the laser action is stopped,these LCP melts will reflow and solidify,which reduces the processing depth and causes problems such as rough cuts.The main research contents include the following parts:(1)Through the comparison of the characteristics of various high-frequency substrates,LCP flexible copper clad laminates are finally selected for high-frequency packaging,and then the packaging application of LCP substrates is investigated,combined with the advantages of picosecond laser processing LCP,the formulation of the experimental plan.(2)The Gaussian distribution of the picosecond laser pulse energy density was analyzed and discussed.According to the area calculation method and the experimentally measured data,the damage thresholds of the LCP material at the infrared wavelength and the ultraviolet wavelength were obtained respectively,and the appropriate one was selected by comparison.wavelength.The experimental results show that the photopolymerization of LCP at 1064 nm seriously affects the processing quality,and the wavelength of 355 nm is more suitable for the precision processing of LCP.(3)Further analyze the effects of laser power,scanning speed,repetition frequency,etc.on the etching thermodynamics of LCP materials during the ultra-fast processing of LCP substrates,and combine the physicochemical properties of liquid crystal polymer LCP to reduce melt liquid crystal reflow and improve micro scribing processing quality.By analyzing the influence of scanning speed and average power on scribing quality,it is found that when the scanning speed is 500 mm/s-700mm/s and the average laser power is 2.5W-3.5W,a better etching effect can be obtained.(4)Finally,the process of blind hole and film removal is carried out on the LCP substrate,and the optimal parameters are selected.On this basis,through the analysis of the heat-affected zone at the frame of the LCP substrate after film removal,it is further discussed how to reduce the width of the heat-affected zone at the frame during the film removal process.When the number of scanning layers is 5-6,the laser power is 2.1W-2.7W,and the scanning speed is600mm/s,the film removal effect is better.In summary,the purpose of this paper is to study the effects of laser process parameters on the ablation threshold,micro-scribing,film removal and blind vias of LCP flexible copper clad laminates through picosecond laser experiments,and to obtain optimized processing parameters.On this basis,the processed materials were characterized by laser confocal microscopy to explore the thermodynamic process of LCP materials under the action of ultrafast lasers,to solve the problem of liquid crystal recondensation during processing,and to provide high-frequency packaging of LCP materials for electronic devices.Processing provides a preliminary theoretical model. |
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