... , BGA chip’s auctual heating tempreture is also different. Because in unit space, the more the quantity of heat, the higher the ... . If some corners hold out against components, we can stagger it for 1-2mm, or turn the middle screwed mandril higher, only ... ’t touch solder by hands, once infected in sweat or oil stain, also can result in welding’s fail. Remmeber:Details decide success ...