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[IEEE 2018 19th International Conference on Electronic Packaging Technology (ICEPT) - Shanghai (2018.8.8-2018.8.11)] 2018 19th International Conference on Electronic Packaging Technology (ICEPT) - A novel organic coating assisted laser drilling method for TSV fabrication
摘要： Through-silicon vias (TSVs) is a promising three-dimensional packaging solution in post-Moore's law era in the semiconductor industry. The fabrication of through silicon via plays an important role in three-dimensional packaging. Laser drilling is widely used in TSVs fabrication. However, the geometry quality of laser drilling is unsatisfied and heat affected zone (HAZ) is intrinsic. In this work, a novel organic coating assisted picosecond UV laser drilling method is proposed to obtain high-quality TSVs, the HAZ was noticeably eliminated and the TSVs quality was significantly improved. The effects of the organic thickness and laser power on the TSVs' quality were also studied in detail. It is found that the diameter of vias decreases with the increase of the organic thickness and decrease of the laser power. The minimum diameter of TSV obtained by this method is about 15 μm while the aspect ratio is beyond 30. Most importantly, by coating with the organic layer, the minimized via diameter can be decreased to about only 70% of the laser spot size which breaks the limit that the minimized via should be larger than or at least equal to the laser spot size. These findings will be helpful for TSV technology development in modern three-dimensional packaging.
关键词： ultraviolet picosecond laser drilling,through silicon via,heat affected zone elimination,organics coating method
更新于2025-09-23 15:22:29
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Microstructure and Characteristic of Biomedical Titanium Alloy Based on Picosecond Laser Micromachining
摘要： Laser micromachining has become a hotspot in recent years due to its high precision, non-contact and adjustable parameter. In this paper, TC4 titanium alloy implant samples were conducted to obtain specific surface textures through picosecond laser. The laser parameters which directly influenced the microstructure and characteristic of surface textures were optimized within the context of laser power, scanning speed and scanning number via response surface methodology. The microstructure was evaluated using scanning electron microscope (SEM) while the feature size of the surface textures was measured through surface 3D profiler. In addition, endothelial cell culture was conducted to investigate the biofunctionalization of samples with specific surface textures. It demonstrated that well-structured textures played an important role in promoting cell adhesion and proliferation for titanium alloy implants.
关键词： Picosecond laser micromachining,Microstructure,Biofunctionalization,Titanium alloy
更新于2025-09-23 15:22:29
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<i>In situ</i> structural kinetics of picosecond laser-induced heating and fragmentation of colloidal gold spheres
摘要： Fragmentation of colloidal 54 nm gold nanoparticles by picosecond laser pulses is recorded by time-resolved X-ray scattering, giving access to structural dynamics down to a 80 ps resolution. Lattice temperature and energy dissipation have been quantified to verify that the maximum applied fluence of 1800 J m?2 heats up the particles close to boiling. Already within 30 ns, particles with significantly lower particle sizes of 2 to 3 nm are detected, which hints towards an ultrafast process either by a thermal phase explosion or Coulomb instability. An arrested growth is observed on a microsecond time scale resulting in a final particle size of 3–4 nm with high yield. In this context, the fragmentation in a NaCl/NaOH solution seems to limit growth by electrostatic stabilization of fragments, whereas it does not modify the initial product sizes. The laser-induced fragmentation process is identified as a single-step, instantaneous reaction.
关键词： Coulomb instability,fragmentation,thermal phase explosion,time-resolved X-ray scattering,picosecond laser pulses,gold nanoparticles
更新于2025-09-23 15:21:01
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Wettability Control of Copper Surface Using Picosecond Laser for Enhancing Condensation Heat Transfer
摘要： One of the most important and widely visualized process taking place in nature is condensation. Superhydrophobic surfaces, which facilitates dropwise condensation has been the principal area of research in the last decade or so. Fabrication of superhydrophobic surface can be achieved by either surface modification using mechanical process, surface treatment like coating or by the combination of both. But, the major drawback of coating is its durability and vulnerability. So, in this work we have fabricated a robust surface by means of picosecond laser machining. Apart from being a simple process, this method has an advantage of cutting down the surface fabrication time by several hours as compared to other methods like one-step immersion, electro-deposition, top-down fabrication method, etc. In our work three different work specimens irradiated with different laser power were studied for its surface morphologies by scanning electron microscope (SEM) images and its wettability was measured using contact angle meter. It is found that the wettability of surface changes with different laser power and hence it is possible to control the wettability by adjusting the laser parameters. Condensation experiment was carried out on these different surfaces and its performance was compared with plain surface.
关键词： Wettability control,micro grooves,Condensation heat transfer,Contact angle,Picosecond laser
更新于2025-09-23 15:21:01
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Experimental study on direct fabrication of micro channel on fused silica by picosecond laser
摘要： Ultrafast laser ablation, known for its high precision and the depressed thermal influence during processing, is fevered in micro channel fabrication on the glass bulk. In present work, a micro channel structure fabricated on fused silica bulk by a picosecond pulsed laser is parametrically investigated with different processing environments, scanning velocities, pulse energies, hatch distances and repetitive scans. The best processing parameters are determined through the material remove rate and the bottom surface roughness of the channel. Moreover, the fabrication defect attributed to the heat accumulation effect is analyzed by Raman spectrum. A scanning strategy is put forward to compensate the asymmetry in the cross section of the micro channels.
关键词： Heat accumulation,Surface roughness,Scanning strategy,Micro channel,Picosecond laser
更新于2025-09-23 15:21:01
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Phase Change Behavior of Sn <sub/>20</sub> Sb <sub/>80</sub> /Si?Nano-Composite Multilayer?Thin?Films
摘要： Nano-composite multilayer Sn20Sb80/Si thin films were studied by thermal, electrical and optical methods. Compared with Sn20Sb80, Sn20Sb80/Si film was proved to be a more promising candidate for phase change memory device applications because of its higher crystallization temperature (246?C) and larger crystallization activation energy (2.6 eV). The bandgap was broadened with the increase of Si layer thickness. The crystallization of Sn20Sb80 was restrained after the adding of more Si film layers confirmed by X-ray diffraction patterns. A smoother surface was obtained with the root-mean-square surface roughness of 0.753 nm for [Sn20Sb80(3nm)/Si(7nm)]5 thin film. The measurement using the picosecond laser technique showed that [Sn20Sb80(3nm)/Si(7nm)]5 thin film could achieve the crystalline-to-amorphous phase transform within 2.8 ns irradiated by the laser pulse.
关键词： bandgap,nano-composite multilayer thin films,picosecond laser technique,crystallization activation energy,Phase change memory,surface roughness,Sn20Sb80/Si,crystallization temperature
更新于2025-09-23 15:21:01
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The Influence of Laser Ablation Parameters on the Holes Structure of Laser Manufactured Graphene Paper Microsieves
摘要： The graphene paper microsieves can be applied in the ?ltration of biological ?uids or separation of solid particles from exploitation ?uids. To produce graphene paper microsieves for speci?c applications, good control over fabrication should be achieved. In this study, a laser ablation method using a picosecond laser was applied to fabricate graphene paper microsieves. Holes in the microsieves were drilled using pulsed laser radiation with a pulse energy from 5 to 100 μJ, a duration of 60 ps, a wavelength of 355 nm, and a repetition rate of 1 kHz. The impact method was applied using 10 to 100 pulses to drill one hole. To produce holes of a proper diameter which could separate biological particles of a certain size (≥10 μm), optimum parameters of graphene paper laser ablation were de?ned using the MATLAB software taking into account laser pulse energy, repetition rate, and a desired hole diameter. A series of structural tests were carried out to determine the quality of an edge and a hole shape. Experimental results and Laguerre–Gauss calculations in MATLAB were then compared to perform the analysis of the distribution of di?raction fringes. Optimum experimental parameters were determined for which good susceptibility of the graphene paper to laser processing was observed.
关键词： laser manufacturing,graphene paper,picosecond laser,graphene paper microsieves,laser ablation
更新于2025-09-23 15:19:57
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Effect of single pulsed picosecond and 100 nanosecond laser cleaning on surface morphology and welding quality of aluminium alloy
摘要： Removing the oxide film and dirt on the surface of the aluminium alloy can improve the welding quality of the aluminium alloy. In this paper, the characteristics of picosecond and 100 nanosecond pulsed laser cleaning aluminium alloys are explored by changing the average laser power, spot overlap ratio and scanning trajectory overlap rate. The results show that the oxide laser removal depth and diameter are related to the average power. As the average laser power increases, the depth and diameter of the ablation pit increase. At the same average power, the nanosecond laser ablation depth is greater than the picosecond laser. To achieve good surface quality, the nanosecond laser requires a higher overlap rate than the picosecond laser. The high overlap rate results in a nanosecond laser cleaning efficiency that is much lower than that of a picosecond laser. More importantly, the surface quality obtained by picosecond laser cleaning is much better than nanosecond laser cleaning. In addition, the welding experiment shows that the laser cleaning pre-treatment can effectively improve the welding quality.
关键词： Welding quality,Surface micromorphology,Picosecond laser,Laser cleaning,Process strategy
更新于2025-09-23 15:19:57
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Damage-free patterning of thermally sensitive CIGS thin-film solar cells: Can nanosecond pulses outperform ultrashort laser pulses?
摘要： Nanosecond pulses are usually not considered as a suitable candidate for low-damage processing of heat-sensitive materials due to high thermal effects and significant melt formation. Many studies have shown, that CIGS is thermally sensitive material and ultrashort lasers have been chosen as the primary source for the processing of CIGS cells. However, we report on the P3 scribing of CIGS thin-film solar cells with the ns pulse duration at the wavelength of 2.5 μm – a wavelength close to the mid-infrared region and compare the results with the ps pulses covering traditional wavelengths of 355 nm, 532 nm, 1064 nm, and 1342 nm. In our case, 6 ns pulses at 2.5 μm wavelength outperformed the picosecond laser sources operating at VIS and NIR wavelength range. The minimal P3 scribe conductivity of 4.7 mS/m was achieved for ns laser patterning, corresponding to simulated CIGS module efficiency loss of just 0.01%. We proposed that high absorption in the transparent conductive oxide - TCO efficiently shielded the underlying CIGS with only a fraction of energy reaching the back-contact. Finally, results show that nanosecond pulses can be as competitive as picosecond ones for P3 processing of high-efficiency CIGS devices.
关键词： CIGS,Nanosecond laser,Scribing,Picosecond laser,VIS and NIR wavelength range,Thin-film
更新于2025-09-23 15:19:57
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Successful and quick treatment of nevus of Ota with 755nm picosecond laser in Chinese
摘要： Nevus of Ota, also known as nevus fusco-caeruleus ophthalmo-maxillaris, is a benign dermal melanocytosis. In the past, this disease was usually treated by Q-switched laser therapy, but the course of treatment was relatively long. In recent years, it has been reported that 755nm picosecond laser, which was firstly reported to treat tattoos, is also effective in the treatment of nevus of Ota. Here, we report six cases of nevus of Ota which were treated with 755nm picosecond laser in Chinese people. We find amazingly that these lesions almost disappeared after only one or two sessions of treatment.
关键词： 755nm picosecond laser,treatment,nevus of Ota
更新于2025-09-23 15:19:57