SMD Hand Soldering Methods:
Method 1 – Pin by pin Used for : two pin components (0805 caps & res), pitches >= 0.0315″ in Small Outline Package, (T)QFP and SOT (Mini 3P).
Method 2 – Flood and suck Used for : pitches <= 0.0315″ in Small Outline Package and (T)QFP
Method 3 – Solder paste Used for BGA, MLF / MLA packages; where the pins are underneath the part and inaccessible.
BGA or Ball Grid Array is one type of packaging for surface-mounted PCBs (where components are actually ‘mounted’ or affixed on the surface of the printed circuit board). A BGA package simply looks like a thin wafer of semi-conducting material that has circuit components on only one face. The Ball Grid Array package is called such because it is basically an array of metal alloy balls arranged in a grid. These BGA Balls are normally Tin/Lead (Sn/Pb 63/37) or Tin/Lead/Silver (Sn/Pb/Ag)