The difference between buried vias and blind vias
Buried vias and blind vias are two common processes in PCB processing. Understand the differences, advantages and disadvantages of buried vias and blind vias, so you need to choose the appropriate via type.
Characteristics of buried vias and blind vias
Blind vias are a type of connection that connects inner circuits to outer circuits. Blind holes connect the inner and outer layers of traces, and the holes only reach part of the board, so their existence is not visible from the appearance. Therefore, blind holes are characterized by saving space, improving conduction effect and beautiful appearance, and are suitable for various complex circuit board designs. Buried vias are the type of vias that connect the wiring between inner layers. The wiring between inner layers does not reach both sides of the board. Buried holes can also increase the stiffness of the board and avoid adverse effects such as obstruction of the board by via holes or damage to the board caused by improper drilling. This kind of hole can make the distance between pads shorter in denser areas of the PCB. For example, glass and high TG board circuit designs often use buried holes to avoid more complex outer layer via holes and poor board production.
Application
In the layout of high-density circuit boards, a complete design space is usually required to obtain cost advantages and occupy as little space as possible. Therefore, using blind vias in these circuit boards can reduce space usage and increase line routing flexibility. Blind holes are particularly suitable for mobile phones, PDAs, MP3s and other small portable electronic devices. When designing for higher circuit densities, the traditional use of blind vias is no longer sufficient. Buried vias have gradually become the main type of vias connecting inner layer traces. In multilayer boards, the application of buried vias can increase the connection methods of internal wiring, thereby improving signal transmission efficiency and line capacity. Buried hole technology is used in high-end electronic products such as mobile phones and flat-panel TVs.
Manufacturing process and precautions for buried vias and blind vias
Blind hole production requires higher costs and complex manufacturing processes because the hole must be machined only in a local area. During production, attention must be paid to process and machine tool requirements. For example, laser drilling has the function of penetrating the thickness of the plate. The accuracy and direction of drilling must be controlled to avoid production failure due to interference and other factors. The production of buried vias is a combination of drilling, copper plating, cutting and other processing techniques. Compared with blind vias, the production process is simple, has good stability, and is not prone to shortcomings such as production failure. It should be noted that since the connection method of buried holes is mainly based on the inner layer, the pads need to be converted, and the number of layers of the board, the arrangement method and the processing sequence need to be determined so that each buried hole can be connected to the designated position as accurately as possible inner wiring.
When it is necessary to connect inner layer circuits during the PCB manufacturing process, we can choose blind holes or buried holes to achieve this. When choosing, various factors should be considered comprehensively, such as circuit density, cost, production difficulty, etc. Mastering the differences and applications of buried vias and blind vias is of great significance to improving the flexibility and efficiency of circuit board design.
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