Low-Temperature and Medium-Temperature Solders for Mini LED Packaging

2022-06-15

With the higher requirements for the display, more and more manufacturers tend to reduce the pixel size of the display screen to achieve higher resolution. Compared with the traditional LCD screen, the mini LED backlight board uses a smaller LED as the light source, which can control the brightness of the backlight more accurately to improve the display quality. However, it significantly increases the number of solder joints. COB, IMD, and SMD are the main technologies adopted for Mini LED packaging. To achieve efficient packaging, it is necessary to choose an appropriate solder. The mainstream mini LED packaging solders are low-temperature and medium-temperature solders paste/epoxy solder pastes. Solders made of tin-bismuth-silver or tin-silver-copper alloy can meet the peak reflow temperature requirements. Due to the increase of LED chips, the die bond time is also significantly prolonged. The degradation of solder properties such as viscosity and thixotropy may affect the soldering yield and lead to failure. Therefore, the solder should maintain a long online working time and stable performance.

The low-temperature and medium-temperature solder pastes/epoxy solder pastes produced by Fitech have excellent sphericity, wettability, stable viscosity, and thixotropy. The products are suitable for dispensing and printing processes, producing metallurgical connections on the pads to improve the solder joint reliability. Water-soluble and no-clean solder products are available. After soldering, the components have no offset, and the solder joints are firm, which effectively ensures the reliability of soldering. In addition, due to the small size (50-200μm) and pitch (p<1.2mm) of Mini LED chips, traditional solder paste can no longer meet the packaging requirements. The solder particles tend to be miniaturized. Fitech has the leading ultra-fine manufacturing technology to produce T6-T10 solder powders. T8 SAC and SnBiAg ultra-fine solders are the flagship product made by advanced liquid phase molding technology. The small particle size can reach 2-8μm, which can satisfy ultra-fine-pitch soldering.