The semiconductor packaging industry requires ultrathin device wafers to achieve high-density vertical integration and high performance. However, ultrathin wafers with thicknesses below 30 mu m are prone to warpage and fracture. To address this issue, various temporary bonding and debonding technologies have been developed. Among these, laser debonding has attracted significant attention because it enables stress-free separation of temporary bonding wafers. In addition, it provides higher throughput (wafers per hour) than conventional mechanical peel-off methods. In this study, two types of temporary bonding wafers with standard and inverse structures were prepared to investigate the optimal bonding material configuration. Furthermore, two-dimensional transient heat transfer simulations were performed for both structures to understand the thermal response during laser debonding. A 308 nm excimer laser with a homogenized flat-top beam was irradiated through the glass side of both temporary bonding wafers, and comparative studies on various processing parameters were performed. The results indicate that an optimized energy density enables successful debonding without damage to the device wafer, and that the inverse structure is suitable for applications in advanced semiconductor packaging.
Recent innovations in UV and visible laser sources have led to more efficient and precise processes for electronic applications. This study presents a detailed comparison of blue (450 nm) and green (515 nm) laser wavelengths against established infrared (975.3 nm) sources. Through qualitative comparisons, we analyse energy coupling and absorptivity in solder and terminal materials, identifying significant performance differences across the wavelength spectrum. A double integrating sphere setup is used to capture in-situ diffuse and laser back reflections, enabling a thorough evaluation of energy deposition during soldering. Correlating data from detectors in both spheres provides a more holistic understanding of energy behaviour, supporting improved emission-based control techniques such as pyrometry. Our results demonstrate that shorter wavelengths-particularly blue and green- offer enhanced energy absorption, leading to more efficient soldering with reduced damage on surrounding components. Across the tested alloys, visible wavelengths increased static absorptivity versus 975 nm by up to similar to 50%, and green (515 nm) reduced the activation energy for OK joints by similar to 24% relative to blue (450 nm) and similar to 50% relative to IR. Shear testing on header-via samples showed comparable peak forces for blue and green (similar to 200 N) and lower values for IR (similar to 180 N). The findings not only advance laser soldering technology but also support its broader industrial adoption, aiding the transition toward greater electrification and sustainability in manufacturing.
Micro-drilling with ultrashort laser pulses is becoming increasingly popular due to its productivity and precision. Applications such as water filtration and vibrating mesh nebulizers require micro-holes with an exit diameter of less than 5 & micro;m and a high aspect ratio often greater than 10. At high aspect ratios multiple effects arise, that increase in complexity and for which an analytical explanation is not yet found. One of these effects, multi-reflection, remains particularly enigmatic. Although simulations for the shape of laser drilled holes do exist, they often fail to predict the geometries of micro-holes adequately. This paper presents an alternative approach for simulating ultrashort pulse laser micro drilling to enable accurate predictions of geometries. A model approach to address the multi-reflection effect is provided and the contribution of different effects on the generation of USP laser drilled holes are discussed.
Laser-based patterning of high-quality submicron patterns on large-area substrates remains a significant challenge. In this study, photoresist films of varying thicknesses are deposited on silicon surfaces by spin coating to achieve patterning. The samples are exposed to nanosecond laser pulses (lambda = 532 nm, tau = 8 ns). The formation of laser-induced periodic surface structures (LIPSS) on silicon surface when restricted by the photoresist film in air was investigated. The results show that the period of LIPSS on the silicon surface remains consistent (similar to 530 +/- 5 nm) under different film thickness (d = 420 nm and 620 nm). With the constraint of photoresist film, the minimum threshold for LIPSS formation on the silicon surface was similar to 14 mJ/cm(2) (d = 420 nm). The formation mechanism of LIPSS is attributed to the interference between the incident laser beam and surface scattering waves, as well as plasma enhancement within the confined layer. Studies have shown that by restricting plasma within the thin film to prepare wavelength periodic structures on the silicon surface, the energy coupling efficiency in laser direct writing can be significantly enhanced, thereby improving the laser-material interaction effect. This study provides important references and support for the potential applications of laser micro processing technology in layered structures.
Nickel phthalocyanine (NiPc) nanoparticles were synthesized by laser ablation in liquid (LAL). The particle size, morphology, and optical properties were controlled by adjusting the laser fluence and irradiation time. SEM and DLS analyses indicated that higher laser fluence and irradiation time promoted the formation of smaller and more uniform nanoparticles. UV-Vis spectroscopy confirmed that the characteristic Q-band absorption of NiPc remained after laser processing, indicating that the molecular structure remained stable. The nanoparticles were transferred into chloroform and deposited as thin films by spin coating. Film thickness and optical absorbance increased with deposition volume, while surface morphology remained consistent. This work demonstrates a controllable, surfactant-free approach to producing NiPc nanoparticle thin films with stable optical properties, offering potential for future solution-processed optoelectronic applications.
