Blind and buried vias fabrication is an effective method to improve the density of multi-layer plate, reduce the number of layers and the size of plate surface, and greatly reduce the number of plated through vias.
Most of the buried and blind vias are small vias with diameters ranging from 0.05 mm to 0.15 mm. Buried vias are manufactured on the inner thin plate by double panel technology, while blind vias are manufactured by small via drilling CNC machine which controls Z axis depth. Laser drilling, plasma etching and photoinduced drilling are widely used in the manufacture of blind vias.
With the development of electronic products to high density and high precision, the same requirements are put forward for circuit boards. The most effective way to increase the density of PCB is to reduce the number of through vias, precisely set blind vias and bury vias.
Basic knowledge of blind and buried vias:
When it comes to blind and buried vias fabrication, we begin with the traditional multi-layer board. The standard multi-layer board structure is composed of inner circuit and outer circuit, and then uses boreholes, as well as the process of metallization in the via, to achieve the internal connection function of each layer of circuit. But because of the increase of line density, the encapsulation methods of parts are constantly updated. In order to make the limited PCB area and place more parts with higher performance, besides the thinner line width, the aperture is reduced from 1 mm of DIP Jack to 0.6 mm of SMD, and further reduced to less than 0.4 mm. But it will still occupy surface area, so there are blind and buried vias.
Design and fabrication of buried vias:
The manufacturing process of buried vias is more complex than that of traditional multilayer boards, and the cost is also higher. It has a very high density, double-sided SMD design board, there will be upper and lower outer layer, I/O guide via interference with each other, especially VIP (Via-in-pad) design is a problem. Blind via can solve this problem. In addition, with the prevalence of radio communication, the design of the circuit must reach the range of RF (Radio frequency), which is more than 1 GHz. The blind via design can meet this requirement.