● The plated hole
● The non-plated thru-hole
As it is known to all, PCB pads are normally divided into two types: a soldered surface-mount pad and a soldered thru-hole pad. Moreover, the latter one can be also classified to two kinds. And here is the classification of soldered thru-hole pad: the plated thru-hole and the non-plated thru-hole.
The plated thru-hole
The plated thru-hole(PLTH) is a pad in almost any shape with a hole through it. The wall of the hole is plated with copper, sometimes solder or some other protective plating is also suitable. The plating flows into the hole from external area, thickening the hole wall. The plated thru-hole possesses the following advantages:
* Support the solder flow from the top to the bottom, eliminating soldering of both sides.
* Dissipation of heat when soldering.
* Connection from the top to the bottom layer regardless of component insertion.
* Necessary for internal pad connection in multilayer board.
The non-plated thru-hole
With the classification of soldered thru-hole pad, we’ve got another one: the non-plated thru-hole(NPTH), which is a pad without plating in the hole. The pad is frequently used for single-sided boards or holes that have mounting hardware. Generally speaking, the unplated holes will have a area around the hole clear of any copper (just like the board edge) to prevent shorting between copper layers and components which may be placed through.
In all, the classification of soldered thru-hole pad is the plated thru-hole and the non-plated thru-hole, namely, PLTH and NPTH. In some cases, if there isn’t a plated hole in the board, we can omit the plating process. This not only reduces the overall cost (but in turn increases pad size), but also reduces available surface area.