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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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A Novel Design of Through-Hole Depth On-Machine Optical Measuring Equipment for Automatic Drilling and Riveting
摘要： In the aerospace manufacturing industry, it is impossible to achieve precise and efficient automatic drilling and riveting for largescale composite board parts. The bottleneck is that the depth detection of rivet holes still relies on manual operation, which seriously affects the assembly efficiency and stability of composite board parts. In order to realize accurate and efficient on-machine automatic measurement for through holes in the automatic drilling and riveting process of largescale composite board parts, this paper presents a novel hole depth measuring device. Its mechanical structure is developed based on our newly designed measurement scheme and optical path, the purpose of which is to convert the hole depth data into displacement data of the probe motion. Its electrical hardware consists of three units: a laser transceiver unit to pick up laser spots; a displacement measuring unit to capture the probe movement in real time; and a driving unit to achieve motion control of the probe. Finally, the experimental results indicated that the proposed method and device are capable of performing automatic measurements for through-hole depth. In addition, factors affecting the measuring accuracy and stability of the device are initially analyzed and discussed, which lay a foundation for subsequent research on error compensation and probe calibration.
关键词： image processing,depth detection,automatic drilling and riveting,through-hole depth,large-scale composite board,on-machine measurement
更新于2025-09-23 15:22:29
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[Laser Institute of America ICALEO?? 2017: 36th International Congress on Applications of Lasers & Electro-Optics - Atlanta, Georgia, USA (October 22a??26, 2017)] International Congress on Applications of Lasers & Electro-Optics - Transformation of Gaussian beams into M-beams for advanced microvia drilling
摘要： Typical laser systems produce Gaussian laser beams that may not be suitable for high precision materials processing. This study considers laser microvia drilling of multilayer polymeric substrates for high density interconnects of microelectronics devices. Closely spaced microvias reduce the interconnect distance between the processors to meet the ever increasing demand for transferring large volumes of data at high rates. CO2 lasers of 9.3 μm wavelength is commonly used for drilling microvias in current polymeric substrates because of their higher absorption coefficient at this wavelength than at 10.6 μm wavelength of conventional CO2 lasers. High absorption coefficient provides a volumetric heating mechanism of shallow depth to enable surface-controlled vaporization of the polymeric materials. Gaussian or top-hat laser beams generally leave carbonized polymeric residue at the bottom corner and on the side wall of the microvias, and this residue hinders the subsequent microsoldering of electronic devices to the interconnects. The formation of the residue can be reduced using M-beams for microvia drilling. A thermal model is developed to determine the intensity distribution of the M-beam. To achieve this M-beam from a Gaussian beam, a lens system is designed using the Fresnel diffraction model. Drilling experiments have been conducted using an M-beam and the shape and size of the microvia are found to match the theoretical predictions very well.
关键词： microvia drilling,high density interconnects,Gaussian beams,CO2 lasers,M-beams,polymeric substrates
更新于2025-09-23 15:21:01
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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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Laser micro drilling of 316L stainless steel orthopedic implant: A study
摘要： It has recently been shown that there is a requirement of inclined micro hole with smooth side walls (without cracks and burr), high aspect ratio, low taper, reduced heat affected zone (HAZ) and thin recast layer on orthopedic implant. So with the aim of improving hole quality characteristics and functionality of implant a multi-objective optimization of laser micro drilling with argon as an assist gas is addressed in this study. A hybrid statistical approach based on grey relational analysis (GRA) and coefficient of variation (COV) is proposed to analyse the experimental data. The key process variables responsible for quality improvement are identified. Four statistical tests are performed to compare the hybrid and GRA approach. Further, it was found that the proposed hybrid is more superior to GRA in terms of computational time and ease of computation. It is also observed that focal point position and diode current have striking effect of hole quality. An important implication of this paper is that thin recast layer, small HAZ width and spatter area were observed, when argon was used as an assist gas.
关键词： Assist gas,Laser micro-drilling,Grey relational analysis,Coefficient of variation,Orthopedic implant,Statistical test,Eccentric holes
更新于2025-09-23 15:19:57
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Investigation of hole quality in drilled Ti/CFRP/Ti laminates using CO2 laser
摘要： The machinability of titanium (Ti) and carbon fiber reinforced plastic (CFRP) (Ti/CFRP/Ti) laminates using CO2 laser is presented in this work. The effect of line energy and laser frequency on output responses such as heat affected zone (HAZ), taper angle (TA), metal composite interface (MCI) damage, surface roughness, dross height, and circularity were investigated. Line energy - the most influential parameter - demonstrated a threshold behavior; no drilling was observed below a certain line energy. Scanning acoustic microscopy (SAM), scanning electron microscopy (SEM), micro-computed tomography (μ-CT), and other imaging techniques were used to establish a correlation between laser parameters and CO2 laser machined damage in Ti/CFRP/Ti laminates. The results show that using a higher frequency and lower line energy can significantly improve the hole quality. However, dross free holes with minimum taper can be obtained using higher line energy.
关键词： Surface roughness,Circularity,Micro-hardness,CO2 laser,Dross height,HAZ,Drilling,Ti/CFRP/Ti,MCI damage factor,TA
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 study of geometrical characteristic in low power fiber laser drilling of Monel k-500 superalloy
摘要： Precise holes in advanced dif?cult to cut nickel-based superalloys can be drilled with ease by the method of ?ber laser drilling. Laser trepanned drilling has become more acceptable laser percussion drilling as it can produce better hole quality and generate macro or micro size hole. On the basis of geometrical quality feature like hole taper for drilling small diameter hole in dif?cult to cut Monel k-500 superalloy sheet laser trepanned drilling process performance studies have been made in the present research paper. The laser drilling has become a highly non-linear and complex process as there is involvement of different and large process parameters. Application of response surface methodology (RSM) has been made for attaining optimization by way of handling the non-linearity and complexity. Input process parameters like sawing angle, power setting, duty cycle, pulse frequency and trepanning speed have been used in this study. A well-designed experimental matrix has supplied essential data to ?nd out the in?uence of signi?cant process parameters on characteristic of the hole taper. Development of reliable empirical models has been achieved to relate different quality characteristic.
关键词： Hole taper,RSM,Laser trepan drilling,Monel k-500,Fiber laser
更新于2025-09-19 17:13:59
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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