Surface Mount Technology (SMT) is developed from traditional through-hole technology (THT), THT&SMT equipment，but is different from traditional THT.

From the perspective of assembly process technology, the fundamental difference between SMT and THT is "sticking" and "blocking". The difference between the two is also reflected in the substrate, components, component shapes, solder joint shapes and assembly process methods.

On traditional THT printed circuit boards, components and solder joints are located on both sides of the board; on SMT boards, solder joints and components are located on the same side of the board. Therefore, on SMT printed circuit boards, the through holes are only used to connect the wires on both sides of the board, and the number of holes is much smaller and the diameter of the holes is much smaller. This can greatly improve the assembly density of the circuit board

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