Study On Micro-drilling Technology Based On Nanosecond Pulsed Laser

Silicon nitride?Si₃N₄?ceramic substrates,due to its high hardness,insulation,thermal resistance,wear resistance,and chemical stability,play an important role in rigid printed circuit board applications,such as machinery,electronics,aerospace ect.al.As one of flexible PCB boards the IC carrier board and the adhesive double-sided copper clad board are commonly used in some small,portable and wearable devices such as mobile phones,digital cameras,PDAs,LCMs,and drones.With the advanced development of electronics the products become miniaturization,portability,high density,and high performance,and thus the required micro-holes will become much smaller.As a result,the problem of micro-drilling has attracted people's attention.Because of the complexity and integration of materials,traditional ways of micro-drilling have become difficult to completely satisfy the processing tasks.Laser technology,as one of the special machining technologies,has the advantages of high precision,high quality,and high efficiency in the field of micro-drilling.Thus,the laser processing becomes an alternative approach to solve this problem.In this research,the nanosecond pulse laser was employed to study the micro-drilling mechanism of Si₃N₄ ceramic substrate,IC carrier board,and plastic double-sided copper clad board in order to explore the mechanisms of laser micro-drilling.The effects of laser average power,repetition frequency,and scanning speed on quality of micro-drilling were systematically studied.Also,the quality of Si₃N₄ ceramic substrate micro-hole in different media,and the relationship between quality and efficiency by used laser to micro-drilling different apertures were studied in details as well.The main results obtained from the thesis were stated as follows:The relative poor quality of micro-hole on Si₃N₄ ceramic substrates was machined using the small average power,the high repetition frequency,and the high scanning speed.Excessive ablation occurred under the high average power and small scanning speed.Thus,it is necessary to select appropriate laser parameters for micro-drilling.The different processing environment has significant effect on laser micro-drilling,and the quality of micro-holes is mainly characterized by the average diameter,circularities,roughness,recast layer,and heat affected zone.The relationship between quality and efficiency by laser micro-drilling with different diameters on Si₃N₄ ceramic substrate was also studied and characterized by the quality of micro-holes and time of required processing.On the other hand,IC carrier board and plastic double-sided copper clad board were machined by laser micro-drilling.There was little effect on the quality of micro-hole by the repetition frequency,but the average power and scanning speed had a great influence on the quality of micro-hole.Each individual material was machined by same process,but exhibited different results,due to the different characteristics of the material.The better quality of micro-hole on IC carrier board was obtained via the use of the smaller scanning speed.On the other hand,the superior quality of micro-hole on plastic double-sided copper clad board was obtained using the high scanning speed.The relationship between quality and efficiency with different laser apertures on PCB was studied and characterized by the quality of micro-holes and time of required processing.The present research provides the very fundamentally scientific base and processing reference on laser micro-drilling of Si₃N₄ ceramic substrates and PCB substrates,which would be further explored in the near future.