HDI means high-density interconnection, and HDI board is a blind buried via circuit board. A blind hole refers to a hole in the inside that can be seen from the outside, but there is no penetration, and the road slab with a line cannot be seen on the other side; a buried hole is a hole that only exists in the inner layer and is completely invisible from the outside. Blind and buried vias are different from through holes. Generally speaking, the diameter of blind holes is very small (usually no more than 0.15 mm), and it is difficult to machine by mechanical means, so laser drilling is usually used. Therefore, the processing technology of PCB with blind and buried holes is: cutting-internal circuit-laser drilling (drilling blind and buried holes)-electroplating filling or resin plugging-pressing-drilling through holes-the follow-up process is the same as ordinary PCB processing.

HDI boards are high-density interconnected circuit boards. The boards that are plated through blind holes and pressed twice are all HDI boards, which are divided into first-order, third-order, fourth-order, and fifth-order HDI. For example, the motherboard of iPhone 6 is fifth-order HDI. Simply burying a hole is not necessarily HDI.

The proofing of blind and buried vias is calculated based on the area, such as how much is a square, and then calculate the total area. Butyl circuit boards are introduced in more detail, and you get what you pay for. Generally, better circuit boards have different prices. The high technical content of the blind and buried via circuit boards will naturally lead to higher prices.

Through holes are one of the important components of multilayer printed circuit boards, and the drilling cost usually accounts for 30%-40% of the manufacturing cost of the printed circuit board. Simply put, each hole on the PCB can be called a via. From a functional point of view, vias can be divided into two categories: one is used as an electrical connection between layers; second, it is used to fix or locate equipment. In terms of process, these through holes are generally divided into three categories, namely blind holes, buried holes and through holes. The blind holes are located on the top and bottom surfaces of the printed circuit board and have a certain depth for connecting the surface circuit and the bottom internal circuit. The depth of the hole usually does not exceed a certain ratio (pore size). Buried hole refers to the connection hole located in the inner layer of the printed circuit board, which does not extend to the surface of the printed circuit board. The above-mentioned two kinds of holes are located in the inner layer of the circuit board, and are completed by a through-hole forming process before lamination, and several inner layers can overlap during the through-hole forming process. The third type is called a through hole, which penetrates the entire circuit board and can be used for internal interconnection or as a component mounting positioning hole. Because through holes are technically easier to implement and lower cost, most printed circuit boards use it instead of the other two types of via holes.