Electronic manufacturing can be divided into four levels: semiconductor manufacturing (Level 0), PCB/integrated circuit packaging/passive components/process materials manufacturing (Level 1), board-level assembly (Level 2), and system-level assembly (Level 3). The integrated circuit assembly discussed in this chapter belongs to Level 2 of electronic manufacturing (board-level assembly), which primarily refers to the process of soldering packaged integrated circuits onto a PCB to achieve thermal, electrical, and mechanical connections between the integrated circuit and the PCB through board-level assembly solder joints.