Reflow soldering is processing the welding flux into a certain size of granular or powder, mixed with appropriate adhesive, making it a certain liquid paste

HDI board refers to High Density Interconnect, namely High Density Interconnect board

Fire training program were launched at 16:30 on July 10

Diode schematic symbols of electronic circuit - Diode, LED, Zener diode, Schottky diode, photodiode