What are blind holes in PCB?
Blind Via Hole, which connects the outermost circuit of the PCB with the adjacent inner layer with electroplated holes. Because the opposite side cannot be seen, it is called "blind through". In order to increase the space utilization of the PCB circuit layer, a "blind via" process has emerged. This BVH (buried/blind via hole) PCB manufacturing method requires special attention to the depth of the drilling (Z axis). This method often causes difficulties in plating in the hole, so almost no manufacturer adopts it; it can also be used in advance. The connected circuit layers are drilled in the individual circuit layers first, and then glued together. However, more precise positioning and alignment devices are required.
Blind holes are located on the top and bottom surfaces of the printed circuit board, with a certain depth, used for the connection of the surface line and the underlying inner line, the depth of the hole usually does not exceed a certain ratio (aperture).
In the non-through via technology, the application of blind vias and buried vias can greatly reduce the size and quality of BVH PCBs, reduce the number of layers, improve electromagnetic compatibility, increase the characteristics of electronic products, and realize low cost pcb manufacturing. Make the design work easier and faster. In traditional PCB design and PCBA Manufacturing, through holes can cause many problems. First, they occupy a large amount of effective space, and secondly, a large number of through holes are densely packed in one place, which also creates a huge obstacle to the inner layer wiring of the multilayer PCB. These through holes occupy the space required for the wiring, and they intensively pass through the power supply and the ground. The surface of the wire layer will also destroy the impedance characteristics of the power ground wire layer and make the power ground wire layer ineffective. And the conventional mechanical method of drilling will be 20 times the workload of non-through hole technology.
In PCB design, although the size of pads and vias have been gradually reduced, if the thickness of the board layer is not proportionally reduced, the aspect ratio of the through hole will increase, and the increase of the aspect ratio of the through hole will reduce the reliability. With the maturity of advanced laser drilling technology and plasma dry etching technology, it is possible to apply non-penetrating small blind holes and small buried holes. If the diameter of these non-penetrating vias is 0.3mm, the parasitic parameters will be About 1/10 of the original conventional hole, which improves the reliability of the PCB.
Due to the non-through via technology, there are few large vias on the PCB, which can provide more space for routing. The remaining space can be used for large-area shielding purposes to improve EMI/RFI performance. At the same time, more remaining space can also be used for the inner layer to partially shield the device and key network cables, so that it has the best electrical performance. The use of non-through vias makes it easier to fan out the device pins, making it easy to route high-density pin devices (such as BGA packaged devices), shortening the wiring length, and meeting the timing requirements of high-speed circuits.
