PCB (Printed Circuit Board), also known as Printed Circuit Board in Chinese, is an important electronic component that supports electronic components and serves as the carrier for electrical connections of electronic components. Due to its use of electronic printing technology, it is called a "printed" circuit board.

　　Its main function is to avoid manual wiring errors due to the consistency of similar printed boards in electronic equipment, and to achieve automatic insertion or installation of electronic components, automatic soldering, and automatic detection, ensuring the quality of electronic equipment, improving labor productivity, reducing costs, and facilitating maintenance.

　　HDI boards refer to high-density interconnect circuit boards. The boards with blind hole electroplating and secondary pressing are all HDI boards, which are divided into first, second, third, fourth, and fifth order HDIs. For example, the motherboard of the iPhone 6 is a fifth order HDI.

　　Simply burying holes does not necessarily mean HDI.