The boards are prepared with solder paste on the pads that the components will be placed on. Solder paste is a sticky substance made of solder beads and flux th

The boards are prepared with solder paste on the pads that the components will be placed on. Solder paste is a sticky substance made of solder beads and flux that will later turn into solid solder connections after being melted. It's also sticky enough to keep the components from flying away during the process. These machines are called "pick and place" machines.