1. Micro-etch copper surface for good solderability and quick IMC generation, followed by water wash and hot air drying. 2. Use 1.2m infrared heating tube for preheating, board transmission speed depends on size and thickness. 3. Tin melting tank contains 430kg of 63/37 eutectic solder alloy, with ethylene glycol oil floated on tin noodles. 4. Use cold air blowing to remove flux residue and prevent uneven tin surface on pads.