The main advantages of pcb board SMT over the older through-hole technique are:
Smaller components. As of 2012 smallest was 0.4 × 0.2 mm (0.016 × 0.008 in: 01005). pcb board Expected to sample in 2013 are 0.25 × 0.125 mm (0.010 × 0.005 in, size not yet standardized)
Much higher component density (components per unit area) and many more connections per component.
Lower initial cost and time of pcb board setting up for production.
Fewer holes need to be drilled.
Simpler and faster automated assembly. Some placement machines are capable of placing more pcb board than 136,000 components per hour.
Small errors in component placement are corrected automatically as the surface tension of molten solder pulls components into alignment with solder pads.
Components can be placed on both sides of the circuit board.
Lower resistance and inductance at the connection; consequently, fewer unwanted RF signal effects and better and more predictable high-frequency performance.
Better mechanical pcb board performance under shake and vibration conditions.
Many SMT parts cost less than equivalent through-hole parts pcb board.
Better EMC compatibility (lower radiated emissions) due to the smaller radiation loop area (because of the smaller package) and the pcb board smaller lead inductance.
