Abstract
This paper investigates the effect of two different welding methods, direct welding (DW) and vacuum furnace welding (VFW), on flip-chip light-emitting diode (FC-LED) filament properties. Shearing force, SEM, steady-state voltage, steady-state luminous flux, and change of photoelectric performance with aging time were employed to characterize the differences in filament properties between the two welding methods. The shearing test revealed that the average shearing force of the VFW group was higher than that of the DW group, but the two groups followed the standard. Furthermore, the microstructure of the VFW group fault was more smoother, and the voids were fewer and smaller based on the SEM test results. The steady-state voltage and luminous flux revealed that the VFW group had a more concentrated voltage and a higher luminous flux. The aging data revealed that the steady-state voltage change rate of both groups was not very different, and both luminous flux maintenance rates of the VFW group were higher than those of the DW group, but all were within the standard range. In conclusion, if there is a higher requirement for filament in a practical application, such as the filament is connected in series or in parallel and needs a higher luminous flux, it can be welded using vacuum furnace welding. If the focus is on production efficiency and the high performance of filaments is not required, direct welding can be used.
Highlights
The light-emitting diode (LED), which is the most promising cold light source in the 21st century due to its energy-saving, environmental protection, high reliability, and flexible design qualities and other advantages, has been widely developed and applied in the field of lighting [1]
Due to the good thermal conductivity of aluminum substrate, the direct welding method can make solder paste reach the melting point quickly and shorten the time needed for welding
It can be seen that the shearing force of the chip using the two welding methods is higher (VFW)
Summary
The light-emitting diode (LED), which is the most promising cold light source in the 21st century due to its energy-saving, environmental protection, high reliability, and flexible design qualities and other advantages, has been widely developed and applied in the field of lighting [1]. Due to the good thermal conductivity of aluminum substrate, the direct welding method can make solder paste reach the melting point quickly and shorten the time needed for welding. Using this method, the solder joint is exposed to air, and the solder paste is oxidized during the welding process. Much research has been conducted about different welding methods used on LED, there is limited literature reporting relevant studies for the comparison of direct welding and vacuum furnace welding. By using the above testing methods, the shearing force, the microstructure of the solder joint after the shear failure test, the steady-state voltage, the luminous flux, and the main wavelength curve were obtained, respectively. The suitable welding methods can be selected according to the different production requirements
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