You can observe that there are many small and large holes in the PCB, which are densely packed with small holes, each designed for a specific purpose. These holes can be broadly classified into PTH (Plating Through Hole) and NPTH (Non Plating Through Hole). In fact, there are other holes in the circuit board that do not run through the board.
PCB terminology explained: through-hole, blind hole, buried hole.
1. How to distinguish between PTH and NPTH these two types of through-hole?
You can tell if there are bright plating marks on the wall of the hole, a hole with plating marks is PTH, a hole without plating marks is NPTH.
2. What is the purpose of NPTH?
NPTH holes are usually larger than PTH, as they are mostly used for locking screws and some are used for attaching connectors to the outside. Some are also used for positioning test fixtures on the edge of the board.
3. What are PTHs used for? And what is Via?
Generally there are two uses for PTH holes in the board, one is for soldering traditional DIP part pins, the diameter of these holes must be larger than the diameter of the solder pins of the part, so that the part can be inserted into the hole.
The other smaller PTH, usually called via, is used to connect and conduct the copper foil circuit between two or more layers of a circuit board (PCB), because the PCB is made of many layers of copper foil stacked and accumulated, each layer of copper foil (copper) will be laid between a layer of insulation, which means that the copper foil layers can not interoperate with each other, the signal connection is by Via is not visible from the outside because it has no holes at all. Via is also a type of PTH because the purpose of via is to conduct the different layers of copper foil and requires plating to do so.
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