Rigid flex PCB bare circuit board contains several fabricated properties, such as cut-outs, slots, and the end product’s overall shape. The biggest number of these properties are the holes that are drilled into the board. The role of these holes can be divided into three classes:

1. Via Holes 

Small holes plated with metal can be applied to transmit electrical signals, power, and ground through the PCB layers. These holes are called vias, and there are various types based on the requirements. 

Through-hole. A Through-hole is a standard via that extends from the upper to the lower part of the board. These vias link traces or planes to various layers. 

Buried. A buried via starts and ends on the inner Rigid flex PCB layers without extending to the surface layers. They consume less space than through-hole vias, making them suitable for high-density interconnect (HDI) boards. Nevertheless, buried vias are also costly to create.  

Blind. These vias start from surface layers but only percolate through halfway the board. Earlier on, we mentioned that blind vias are expensive to create but create adequate space for routing. Their shorter barrel can enhance the signal quality of high-speed communication lines. 

Micro. Micro vias contain smaller holes than others because they are made using laser machines. They are typically two layers deep because of the challenges of plating smaller holes. Micro vias are suitable for HDI boards or high pin-count fine-pitch gadgets, like BGAs that require insertable escape vias.