There are three major types of holes/drills on PCB: Vias, Blind Hole and Buried Hole.
Vias
This is a major type of holes used to connect the copper circuits and the conductive patterns located in different layers. Because PCB is pressed by several copper foils layers, between every copper foil layer there is an isolating layer, the communication between copper foils layers shall rely on the vias. The vias cannot place with DIP components or other enhanced materials.
Blind Hole
This is the hole to connect outer layers circuit to inner layers circuits, as we can't see through the hole, so we call it blind. This is to maximum the usage of space on PCB design.
The blind hole starts in TOP layer or BOT layer, with a certain depth, to connect surface circuit with internal circuit. The hole depth can not exceed a certain number, depend on the hole size (aspect ratio). The depth control is so hard therefore very few PCB factories use this way to make blind hole, they normally pre-drill the holes while making corresponding layers of circuit, then press them together, this will require precision in press procedure.
Buried Hole
It means the hole is "buried" in the internal layers of PCB, it has no connection with outer layer.
Buried hole can not be made after press, so the pre-drill process is a must. Press relevant inner layers and then copper plating to the holes, then finally all layers pressed together. It is harder than vias and blind hole so it is the most expensive one. The buried hole is used only to make high density PCB to enlarge the area that other layers can use.
The drilling process is very important because the electric performance depends on it and the components stands on it. So if the drilling process is failed, the PCB can not function at all.
Here at Inno Circuit we have top quality of PCB with VIAS, Blind Hole and Buried Hole, welcome to contact us.
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