Pad is the basic constituent elements of the surface mount assembly used to form the land pattern of the circuit board, that is, various combinations of pads designed for special component types. There is nothing more frustrating than the poor design of the pad structure. When a pad structure is not designed correctly, it is sometimes difficult and sometimes impossible to achieve the desired weld point. Pad in English has two words: Land and Pad, which can often be used interchangeably; however, in function, Land is a two-dimensional surface feature for surface mount components, while pad is a three-dimensional feature. As a general rule, land does not include plated through holes (PTH, plated through-hole). Bypass holes (via) are plated through holes that connect different circuit layers. The blind via connects the outermost layer with one or more inner layers, and the buried bypass holes are only connected to the inner layer.