Modeling of Thin-Film Single and Multilayer Nanosecond Pulsed Laser Processing

Abstract

A complete model of nanosecond pulsed laser scribing of arbitrary thin multilayer structures is presented. The chain of events is separated according to time-scale; an initial simulation considers material response during the pulse; another combines this result with the much slower effects of heat flow away from the laser axis. The former considers heating, vaporization and phase explosion of metals in the course of a single pulse, accounting for variations in thermal conductivity and optical absorption as the material becomes superheated and approaches its critical temperature. The latter calculates the bidimensional heat flow in a complete multilayer structure over the course of a scribing operation, combining material properties and considering removal by both short-pulse ablation and long-term heating of the workpiece. Simulation results for the single pulse ablation of an aluminum target align well with published experimental data both in terms of phase-explosion threshold and ablation depth as a function offluence. Bidinierrsional heat flow simulations of a polypropylene-aluminum-polypropylene triplex structure reveal the progression of events toward steady state behavior; aluminum ejected due to short-pulse ablation and plastic removed due to conduction.

Lithium iron phosphate battery electrode integrity following high speed pulsed laser cutting

“…A reduction in thermal conduction effects at high velocity leads to lower work piece temperatures in the zone not removed by the incident laser beam, with repetition rate/ velocity and average power/velocity ratios held constant. Such an effect has been shown to result from a reduction in the proportion of laser cutting power lost to thermal conduction with an increasing Peclet number [26,30]. In the present case, oxidation is completely eliminated and microstructural degradation is limited to 50 lm, or 1.2Â the focused spot size.…”

“…Noting the near-Gaussian fluence distribution of the laser utilized for experiments, direct ablation of all exposed layers takes place where the laser pulse fluence is above the ablation threshold of the material in question. Heat accumulation and conduction in metallic layers on a much longer timescale may then lead to coating layer removal outside the exposed area [26]. Beyond the clearance width, the upper coating layer of the anode is defect free, while that of the cathode presents spherical formations associated with ejected material and melting that are approximately 5 lm in size.…”

Simulation of evaporation ablation dynamics of materials by nanosecond pulse laser of Gaussian beam and flat-top beam

“…Wu和Shin [24] 基于Drude模型计算了铝在 临界温度附近的吸收系数, 研究表明临界温度下铝 的吸收系数将降低近2 -3个数量级. Gragossian 等 [25] 评估了从室温到临界温度下材料特性的变化, 考虑了蒸发和相爆炸机制, 计算了靶材电导率、热 导率、密度以及吸收系数的时间和空间分布特性, 分 析了烧蚀深度随激光强度的变化规律. 研究表明随 着激光强度的增加, 烧蚀深度逐渐增大, 但文中数 值计算的烧蚀结果高于实验值.…”

“…为了模拟由于材料蒸发产生的靶面移动, 采用 变形网格技术, 使用以下公式表达: 爆炸发生 [20] . 在本模型中, 将靶材温度高于 的区域视为由于发生相爆炸导致移除, 这也是目前 多数仿真文献常用的计算方法 [25,17,31] . , 由于本次使用的激光为1064 nm, 因此可 忽略光电离吸收的激光能量 [27] , 本模型仅考虑由 逆韧致辐射吸收产生的等离子体屏蔽现象.…”

Nanosecond Laser Ablation: Mathematical Models, Computational Algorithms, Modeling

“…Primary attention is paid to model the dynamics of phase explosion of liquid phase of aluminum and the expansion of its fragments in the air, since explosive boiling is considered to be one of the most effective thermal mechanisms of ns laser ablation of materials. Various aspects of this problem have been studied in a number of theoretical and experimental studies [43][44][45][46][47][48][49][50][51][52][53][54][55][56], but there is still no consensus on the mechanism of the phase explosion in metals. In order to obtain detailed information on interaction of heterogeneous and homogeneous mechanisms and data on laser plume morphology, simulation of laser heating, melting, surface evaporation, and evolution of plume in the vapor-gas medium is performed within the framework of new hydrodynamic model with temperature dependences of material properties of the target and explicit tracking of interphase boundary fronts, contact boundary, and shock wave.…”