Abstract
This article researches the effect of Sn-based solder alloys on flip-chip light-emitting diode LED (FC-LED) filament properties. SEM images, shearing force, steady-state voltage, blue light luminous flux, and junction temperature were examined to demonstrate the difference between two types of FC-LED filaments welded with two solders. The microstructure surface of Sn90Sb10 filament solder joints was smoother and had fewer voids and cracks compared with that of SAC0307 filament solder joints, which indicates that the Sn90Sb10 filaments had a higher shearing force than the SAC0307 filaments; moreover, the average shearing force was beyond 200 gf (standard shearing force). The steady-state voltage and junction temperature of the Sn90Sb10 solder-welded FC-LED filament were lower, and the Sn90Sb10 filament had a relatively higher blue light luminous flux. If high reliability of the solder joints and better photoelectric properties of the filaments are required, this Sn90Sb10 solder is the best bonding material for FC-LED filament welding.
Highlights
As a new generation of light source, the light-emitting diode (LED) has many advantages, such as energy saving, environmental protection, and no radiation emission [1,2,3]
Industrial Flip-chip LED (FC-LED) chip-bonding technologies include conductive adhesive bonding and eutectic welding [10], of which, the FC-LED filament that is bonded by eutectic welding has high reliability
More voids and cracks are present in solder joints of the SAC0307 filaments, and as evident in Figure 4a, cracks are most likely to occur the solder joints of the SAC0307 filaments, and as evident in Figure 4a, cracks are most likely to occur where voids are [19,20,21]
Summary
As a new generation of light source, the light-emitting diode (LED) has many advantages, such as energy saving, environmental protection, and no radiation emission [1,2,3]. With the growing demand of LEDs, the white LED has been industrialized [4,5]. Flip-chip LED (FC-LED) filament bulbs are gradually replacing incandescent lamps, with the advantages of lower working voltage, less power consumption, and higher luminous efficiency. Due to the output power of LED chips being improved, the FC-LED filament package process requires advanced technology [6,7,8,9]. Compared with the traditional LED packaging (wire-bonded LED) process, the FC-LED package process has improved the bonding efficiency and thermal conductivity of the FC-LED filament. Industrial FC-LED chip-bonding technologies include conductive adhesive bonding and eutectic welding [10], of which, the FC-LED filament that is bonded by eutectic welding has high reliability
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