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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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Crack behavior in ultrafast laser drilling of thermal barrier coated nickel superalloy
摘要： Quantitative analysis is required to explore the mechanism of crack generation in ultrafast laser drilling of thermal barrier coated nickel superalloy. In this study, a simple thermo-mechanical coupled model is established to obtain temperature history, phase transformation stress and thermal stress during drilling process, in which laser beam scanning, laser intensity attenuation, the nonlinear relationship between drilling depth and drilling time are involved. The induced stress obtained from the present model is compared with the results by digital image correlation (DIC) method. According to the crack distribution around the drilled hole, the present model is used to explain the mechanism of crack behavior in drilling of multilayer materials. Finally, the strategy using low pulse repetition rate or water jet assisted method is suggested to reduce the thermal effect in ultrafast laser drilling process.
关键词： TBC,Phase transformation stress,Thermal stress,Crack behavior,Ultrafast laser,Laser drilling
更新于2025-09-23 15:19:57
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Investigation on the Continuous Wave Mode and the ms Pulse Mode Fiber Laser Drilling Mechanisms of the Carbon Fiber Reinforced Composite
摘要： The near infrared (NIR) laser drilling of a carbon fiber reinforced polymer (CFRP) composite in the continuous wave (CW) mode and the ms pulse mode was investigated by an experiment and a numerical simulation. The relationships between the laser penetrating time, entrance hole diameter, surface heat affected zone (HAZ) width, and material ablation rate and the laser irradiation time and laser peak power densities were obtained from the experiment. For the same average power density of the laser output, 3.5 kW/cm2, it was found that the ms pulse laser mode, which had a higher peak power density, had a higher drilling efficiency. When drilling the same holes, the pulse laser mode, which had the highest peak power density of 49.8 kW/cm2, had the lowest drilling time of 0.23 s and had the smallest surface HAZ width of 0.54 mm. In addition, it was found that the laser penetrating time decreased sharply when the peak power density was higher than 23.4 kW/cm2. After analyzing the internal gas pressure by the numerical simulation, it was considered that a large internal gas pressure appeared, which resulted from polymer pyrolysis, causing a large amount of the mechanical erosion of the composite material to improve the drilling efficiency. Therefore, the ms pulse laser showed its potential and advantage in laser drilling the CFRP composite.
关键词： ms pulse,mechanical erosion,peak power density,surface HAZ,laser drilling
更新于2025-09-23 15:19:57
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Research on Wafer-Level MEMS Packaging with Through-Glass Vias
摘要： A MEMS fabrication process with through-glass vias (TGVs) by laser drilling was presented, and reliability concerns about MEMS packaging with TGV, likes debris and via metallization, were overcome. The via drilling process on Pyrex 7740 glasses was studied using a picosecond laser with a wavelength of 532 nm. TGVs were tapered, the minimum inlet diameter of via holes on 300 μm glasses was 90 μm, and the relative outlet diameter is 48 μm. It took about 9 h and 58 min for drilling 4874 via holes on a four-inch wafer. Debris in ablation was collected only on the laser inlet side, and the outlet side was clean enough for bonding. The glass with TGVs was anodically bonded to silicon structures of MEMS sensors for packaging, electron beam evaporated metal was used to cover the bottom, the side, and the surface of via holes for vertical electrical interconnections. The metal was directly contacted to silicon with low contact resistance. A MEMS gyroscope was made in this way, and the getter was used for vacuum maintenance. The vacuum degree maintained under 1 Pa for more than two years. The proposed MEMS fabrication ?ow with a simple process and low cost is very suitable for mass production in industry.
关键词： through glass via (TGV),laser drilling,MEMS devices,wafer level packaging
更新于2025-09-19 17:15:36
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An experimental investigation of laser drilling nitrile butadine (NBR) rubber
摘要： This paper focusses on understanding laser-NBR rubber interactions in particular the effect of laser wavelength and pulse width on material removal and thermal damage. Three lasers with wavelengths at 355 nm, 795 nm and 1064 nm and pulse duration at 30 ns, 10 ps and 130 fs, respectively, have been investigated for their optical absorption, heat conduction and their material removal mechanisms in high aspect ratio drilling of NBR rubber. It is interesting to find that under certain conditions, the ultrashort pulse lasers (both the femtosecond and picosecond lasers) did not lead to better results than the nanosecond UV laser in drilling hole profile (straightness and thermal damage), aspect ratio and amount of the ablated material re-deposition on the substrate surfaces. The results implied that there is heat conduction and thermal damage even with ultrashort laser pulses when the processing conditions are not appropriate. Firing laser pulses intermittently was shown to reduce thermal accumulation. Experimental studies showed that the 355-nm Nd:YAG laser (UV laser) achieved higher material removal rate with high aspect ratio as compared to the ultrashort laser pulses in drilling the NBR substrates.
关键词： NBR rubber,Pulse width effect,Picosecond laser drilling,UV laser drilling,Femtosecond laser drilling
更新于2025-09-16 10:30:52
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Swirling Gas Jet-Assisted Laser Trepanning for a Galvanometer-Scanned CO2 Laser
摘要： Laser-drilled hole arrays are part of an important field that aim to improve efficiency without affecting the quality of laser-drilled holes. In this paper, a swirling gas jet was implemented to assist with laser trepanning for a galvanometer scanned CO2 laser. The proposed swirling gas jet is based on laser trepanning. This swirling gas jet nozzle was composed of four inlet tubes to produce the flow of the vortex. Then, the plume particles were excluded, and spatter on the surface of the workpiece decreased. Thus, this approach can mitigate the problem of overcooling. This study manipulated the appropriate parameter settings, which were simulated by computational fluid dynamics software ANSYS CFX. The proposed swirling gas jet can be used with galvanometer-based scanner systems to keep the laser beam from interference by spatter. In addition, a hollow position of the vortex was achieved by using the four inlet tubes, which resulted in pressure asymmetry in the nozzle and velocity distribution on the surface of the workpiece. The experiment verified that the depth of processing could be enhanced by 110% when trepanning at a scanning speed of 30 mm/s, and that the removal of volume could be enhanced by 71% in trepanning at a diameter of 1 mm by using a swirl assistant compared with a non-assisted condition. Furthermore, the material removal rate of the swirling jet increases when the machining area of the galvanometer-based scanner is larger.
关键词： laser trepanning,laser drilling,swirling gas jet,galvanometer-based scanner systems
更新于2025-09-16 10:30:52
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Multi Response Optimization of Nd:YAG Laser Micro Drilling Characteristics of 304 Stainless Steel using Desirability Function Approach
摘要： Laser micro drilling is a non-traditional machining process for producing micro hole of various sizes and different angle in many modern industrial application, such as aerospace gas turbine, automobile industry, electronics field etc. Laser drilling is extremely high speed with high aspect ratio. However, the quality and accuracy of the holes can be excellent, if the optimal process parameter has set. It is difficult to achieve exact size of hole as per suggested by the equipment manufacturer without any consideration. So this paper addressed to investigate influence of process parameter on drilling characteristics of 304 stainless steel of 1.5 mm thickness material using Nd:YAG laser drilling through desirability function optimization technique. The effect of process parameter taken during machining operation is average power, nozzle stand-off, nitrogen gas pressure to obtain requisite hole quality. The output responses are entry circularity, exit circularity and taper angle were considered performance criteria for the experimentation. Analysis of variance (ANOVA) has been performed to find out the significant process parameter during the micro drilling process. It is found that nitrogen gas pressure is highly influencing factor on the overall response characteristics, which is about 54.62% and nozzle standoff is 2nd highest influencing parameter, which is about 27.69%.
关键词： 304 Stainless Steel,Laser Drilling Machine,Optimization,Desirability,ANOVA
更新于2025-09-16 10:30:52
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[IEEE 2019 International Wafer Level Packaging Conference (IWLPC) - San Jose, CA, USA (2019.10.22-2019.10.24)] 2019 International Wafer Level Packaging Conference (IWLPC) - Recent Breakthroughs in Tight Pitch Laser Microdrilling for Mems Guide Plates
摘要： Laser drilling of guide plates for Advanced Vertical Probecards has become a key enabling technology over the past several years. Amongst the key drivers is the switch in demand from circular shaped holes, achievable with both mechanical and laser drilling methods, to rectangular holes for MEMs style probes. These rectangular holes can only readily be produced with the use of laser technology. As semiconductor technology and wafer test advances, an additional driver is high density hole drilling, i.e. the ability to place smaller and smaller holes on tighter and tighter pitches, whilst keeping the material between adjacent holes intact. Typically, the 3D shaped profile of laser drilled holes cannot easily be controlled, with so called “entry rounding” and “taper angle” characteristics restricting tighter hole positioning. The challenge is therefore to develop new processes which essentially eliminate both entry rounding and taper to values of virtually zero. After a recent breakthrough this has now been achieved.
关键词： Laser drilling,guide plates,probe cards
更新于2025-09-16 10:30:52
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Laser micro drilling methods for perforation of aircraft suction surfaces
摘要： To reduce the fuel consumption of large passenger aircrafts the hybrid laminar flow control is a key technology. For drag reduction, several millions of holes with diameters around 50 μm at the leading edges are needed. In this paper, the perforation of such titanium sheets using the laser processes of single pulse and percussion drilling is presented. The single pulse technique is an “on-the-fly” drilling process using a pulsed fibre laser in combination with a drilling optic with coaxial gas supply. The percussion technique is a flexible drilling process using a q-switched fibre laser combined with a galvanic scanner.
关键词： percussion,micro-holes,single pulse,HLFC structures,laser drilling
更新于2025-09-16 10:30:52
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Laser drilling of micro-holes in single crystal silicon, indium phosphide and indium antimonide using a continuous wave (CW) 1070 nm fibre laser with millisecond pulse widths
摘要： The laser micro-drilling of “thru” holes, also known as via holes, in Si, InP and InSb semiconductor wafers was studied using millisecond pulse lengths from an IPG Laser Model YLR-2000 CW multimode 2 kW Ytterbium Fibre Laser and a JK400 (400 W) fibre laser, both with 1070 nm wavelength. The flexibility of this laser wavelength and simple pulsing scheme were demonstrated for semiconductor substrates of narrow (InSb Eg 0.17 eV) and wide (InP Eg 1.35 eV)) room-temperature bandgap, Eg, with respect to the photon energy of 1.1 eV. Optical microscopy and cross-sectional analysis were used to quantify hole dimensions and the distribution of recast material for all wafers and, for silicon, any microcracking for both (100) and (111) single crystal surface Si wafer orientations. It was found that the thermal diffusivity was not a sufficient parameter for predicting the relative hole sizes for the Si, InP and InSb single crystal semiconductors studied. Detailed observations for Si showed that, between the threshold energies for surface melting and the irradiance for drilling a “thru” hole from the front surface to rear surface, there was a range of irradiances for which micro-cracking occurred near the hole circumference. The directionality and lengths of these microcracks were studied for the (100) and (111) orientations and possible mechanisms for formation were discussed, including the Griffith criterion for microcracks and the failure mechanism of fatigue usually applied to welding of metals. For Si, above the irradiance for formation of a thru-hole, few cracks were observed. Future work will compare similar observations and measurements in other narrow- and wide-bandgap semiconductor wafer substrates. We demonstrated one application of this laser micro-drilling process for the micro-fabrication of a thru hole precisely-located in the centre of a silicon-based atom chip which had been patterned using semiconductor lithographic techniques. The end-user application was a source of magneto-optically trapped (MOT) cold atoms of Rubidium (87Rb) for portable quantum sensing.
关键词： microcrack,InP,Si,Griffith criterion,pulse,atom chip,Ytterbium fibre laser,semiconductor material,Fibre laser,semiconductor wafer,laser drilling,silicon,magneto-optical trap,MOT,via hole,laser micro-drilling,cold atoms,InSb,thru hole
更新于2025-09-12 10:27:22