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[IEEE 2018 7th Electronic System-Integration Technology Conference (ESTC) - Dresden, Germany (2018.9.18-2018.9.21)] 2018 7th Electronic System-Integration Technology Conference (ESTC) - Integration with Light
摘要： This paper reports the use of Laser-induced Forward Transfer (LIFT) technology for printing of multilayer flexible circuitries and the fabrication of micro-bumps for flip-chip bonding of packaged LEDs and bare die microcomponents. Bonding of passive and functional surface mount devices (SMD) on low-temperature polyethylene terephthalate (PET) foils have been demonstrated using two selective bonding techniques. Firstly, using a high intensity near-infrared (NIR) lamp, a bare die NFC chip was bonded on micro-bumps formed with LIFT printed isotropic conductive adhesive (ICA) within less than a minute. Secondly, using a high intensity Xenon lamp, passive components and packaged LEDs were bonded within 5 seconds on micro-bumps formed with conventional Sn–Ag–Cu (SAC) lead-free alloys. In the both cases, due to selective light absorption, a limited temperature increase was observed in the PET substrates allowing successful bonding of components onto the delicate polyethylene foil substrates using conventional interconnect materials.
关键词： LIFT,low temperature bonding,NIR curing,conductive adhesive,lead-free SAC solder,photonic soldering,flip-chip bonding,laser printing
更新于2025-09-23 15:23:52
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AIP Conference Proceedings [AIP Publishing INTERNATIONAL SYMPOSIUM ON GREEN AND SUSTAINABLE TECHNOLOGY (ISGST2019) - Perak, Malaysia (23–26 April 2019)] INTERNATIONAL SYMPOSIUM ON GREEN AND SUSTAINABLE TECHNOLOGY (ISGST2019) - Lead-free solders for ribbon interconnection of crystalline silicon PERC solar cells with infrared soldering
摘要： We report about the analysis of Pb-free, low-temperature solders for the ribbon-interconnection of PERC solar cells with an industrial infrared stringer. Five solders (SnPb, SnBi-A, SnBi-B, SnBiAg and a proprietary lead-free, low-temperature (PLFLT) alloy) are characterized with di?erential scanning calorimetry to determine the melting and solidi?cation temperature. It is found that SnBi-B, SnBiAg, and the PLFLT composition melt in a temperature range between 137 ?C to 171 ?C instead of a single temperature. Solidi?cation occurs at a 3 K to 11 K lower temperature (undercooling). Mono-crystalline silicon PERC cells are contacted using an industrial stringer. The microstructure of the solder bonds is investigated with scanning electron microscopy. For the SnBi-A-solder, large and brittle Bi-phases are identi?ed. The SnBi-B, SnBiAg and PLFLT solder show a ?ner grain structure. The added Ag in SnBiAg forms an intermetallic compound of Ag3Sn close to the Cu-core of the ribbon. The peel strength of the connected solar cells with the Pb-free solders is on average 1 N mm?1 or slightly higher. Some bonds show low adhesion. The observed fracture mode is mainly failure at the busbar metallization to solar cell irrespective of the solder type. However, the occasionally observed solder residues on the metallization clearly reveal brittle fracture for the Pb-free solders, which is not observed for SnPb. First reliability tests show similar degradation of 1 % to 2 % for all solders.
关键词： ribbon interconnection,infrared soldering,lead-free solders,crystalline silicon PERC solar cells
更新于2025-09-16 10:30:52
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[IEEE 2019 25th International Workshop on Thermal Investigations of ICs and Systems (THERMINIC) - Lecco, Italy (2019.9.25-2019.9.27)] 2019 25th International Workshop on Thermal Investigations of ICs and Systems (THERMINIC) - Investigation of Thermomechanical Local Stress Induced in Assembled GaN LEDs
摘要： Bonding of LEDs on substrates by soldering or sintering induce stresses in the LEDs. Raman spectroscopy is employed to investigate the local stress. Nine blue emitting gallium nitride (GaN) LEDs were first investigated at room temperature before the bonding process. Then, two LEDs were reflow soldered on Al-IMS with ENIG metallization and four LEDs were soldered on Cu substrate using 25 μm AuSn preform. Three LEDs were sintered under pressureless sintering conditions on Cu substrate using an Ag sinter paste. All assemblies were investigated between -50 °C and 180 °C. The change in position of the GaN Raman band E2(high) at ca. 568 cm-1 was used to characterise the thermomechanical stress. The obtained values are in the MPa order of magnitude and allow us to conclude that the dielectric layer of the Al-IMS relaxes the stress very efficiently. Moreover, the samples prepared via Ag-sintering show a reduced stress, which indicate that the stress is relaxed by the soft and ductile property of silver.
关键词： sintering,thermomechanical stress,Raman spectroscopy,soldering,GaN LEDs
更新于2025-09-12 10:27:22
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The Measurement of Optical Interconnect Module Post-Soldering Alignment Offsets and The Study of Its Influence on Optical Coupling Efficiency
摘要： In the process of the optical interconnection module soldering assembly, the mismatch of the thermal expansion coefficient between the substrate and PCB would result in the production of alignment offset between light source devices and light-coupled devices, which would lead to light power loss. It is of great significance to study on the optical interconnect module alignment offset in the assembly process to improve optical interconnect module coupling efficiency. In the present study, an optical interconnection module key position post soldering shift offset measurement system was established, and an optical interconnection module experimental sample was prepared. The key position post soldering shift in the X and Y directions were measured. The 3D finite element analysis model of a typical optical interconnect module was established, and post soldering shift offsets were calculated after the finite elements analysis of the reflow soldering temperature load. The coupling efficiency simulation model of the optical interconnection module was established using the ZEMAX software, and the coupling efficiency was calculated according to the alignment offset measured in the experiment. The results revealed the following: The post soldering alignment offsets in the X and Y direction were 0.316 μm and 0.422 μm, respectively, and the synthetic alignment offset was 0.527 μm. The post soldering alignment offset calculated using the finite element simulation model was 0.436 μm, and its error was 17.2%, when compared with the measured value. The coupling efficiency of the optical interconnection module was 85.804% when the post soldering alignment offset was 0.527 μm.
关键词： Reflow soldering,Optical interconnect module,Multimode fiber,Alignment offset,Coupling efficiency
更新于2025-09-09 09:28:46