The difference between blind via and buried via circuit board

With the development of high-density, high-precision electronic products, the same requirements are imposed on circuit boards. In the circuit board industry, from the end of the 20th century to the beginning of the 21st century, the circuit board electronics industry has advanced by leaps and bounds, and electronic technology has rapidly improved. Along with the small size, lightness and thinness of electronic products, printed circuit boards have developed flexible boards, rigid-flexible boards, blind& buried via circuit boards and the like.

 
When it comes to blind& buried via, we first start with traditional multi-layer boards. The structure of a standard multi-layer circuit board is a process including an inner layer line and an outer layer line, followed by drilling, and metallization in the hole to achieve the internal connection function of each layer line. However, due to the increase in line density, the packing form of parts is constantly updated. In order to allow a limited board area can place more high-performance parts, in addition to the thinner line width, the aperture is also reduced from 1 mm in the DIP to 0.6 mm in SMD, and further reduced to 0.4 mm or less. But the surface area is still occupied, so that there are buried via and blind via. The buried via and blind via are defined as follows:

A. Blind via

Applied to the communication between the surface layer and one or more inner layers, one side of the hole is on one side of the board and then passes to the inside of the board.
 

B. Buried Via

 
The through hole between the inner layers can not be seen after lamination, so it is not necessary to occupy the area of the outer layer. The upper and lower sides of the hole are in the inner layer of the board, in other words, the hole is buried inside the board.