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The Specifications of Pcb Blind and Buried Vias

Do you know the specifications of PCB blind and buried vias? Before we talk about the specifications of PCB blind and buried vias, we need to explain PCB blind and buried vias.


PCB blind via, as the name suggests, cannot be seen. Blind via PCB refers to the through hole connecting the inner layer which cannot be seen on the surface of finished board. PCB blind via with a certain depth, is located on the top and bottom surface of PCB, which is used to connect the surface circuit and the lower inner circuit. The depth of the hole usually does not exceed a certain ratio (aperture). That is to say, it is of certain specifications.


It can be seen from the literal that the PCB buried vias are hidden in the board. In a multilayer board, a buried via is a through hole connecting any circuit layer in a multilayer PCB which does not extend to the surface of the circuit board.


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What are the specifications of PCB blind and buried vias?


The blind via making method requires special attention to the proper drilling depth (Z axis). If attention is not paid, it will be difficult to electroplate in the hole. The circuit layers that need to be connected in advance can be drilled in individual circuit layers and then bonded together. However, precise positioning and alignment devices are needed.


The manufacturing process of buried vias can not be achieved by drilling after bonding. Drilling must be carried out in one circuit layer. After the local bonding of the inner layer, it must be electroplated first, and finally all the bonding can be achieved. It takes more time than the original through hole and blind hole, so the price is the highest. This process is usually used only for high density circuit boards to increase the usable space of other circuit layers.


For example, the line width of most devices is: the blind via is 0.1 mm, 0.125 mm or 0.15 mm, and the buried hole can be 0.15 mm, 0.2 mm or 0.25 mm. And laser drilling and mechanical drilling are different, depending on the process equipment.


In the industry, there are also small pore sizes of 0.2 mm and 0.1 mm. The specific specification depends on the requirements of PCB design and the equipment capacity of the manufacturing plant. For example, in the ordinary PCB factory, if there is a common mechanical hole, the minimum requirement is 6mil. According to the unit conversion, it is a mechanical drill 0.2mm. According to the unit conversion, it is a mechanical drill 0.2mm. The design is recommended to be 0.3 mm or more, and the tolerance of aperture is ± 0.075 mm. (1mil = 0.0254mm)


If it is radium perforation, it can be relatively smaller, and the minimum hole diameter can be 4 mil (0.1 mm). Generally, it mainly depends on the design requirements of the hole. For example, if the current is high, the outer diameter should be larger, and the hole can be smaller.

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