Applying Monte Carlo Simulation to Analyze the Open Scenario in the Assembly of Electronic Components

The emergence of environmental awareness, particularly regarding green packaging, has caused SAC305, a tin-silver-copper alloy (Sn 96.5%, Ag 3%, and Cu 0.5%), to become a widely used lead-free solder material. The use of SAC305 increases in temperature requirements for reflow soldering roughly 15 °C-35 °C compared with that of the use of Sn63Pb37, a conventional tin-lead solder. However, component and printed circuit board (PCB) warpage may occur when subject to high temperature, leading to open solder joints and other defects. The ball grid array (BGA), quad flat pack, and dual-flat no-lead (DFN-8) packaging components of server PCBs were tested in this paper. First, the height of the component contacts, printing thickness of the solder paste, and PCB and component warpage were examined, and geometric principles were applied to establish an open solder joint model for nonflat solder joints. Subsequently, the Monte Carlo simulation method was used to sample the aforementioned parameters randomly and calculate the distance between the contacts at the bottom of the electronic component and the surface of the solder paste. A threshold value was used to determine whether the contacts at the bottom of the components were connected to the surface of the solder paste and independently evaluate the occurrence of open solder joints before and during reflow soldering.