Printed circuit board (PCB) is a structural component formed by insulating material supplemented by conductor wiring. The final product is assembled with integrated circuits, transistors, diodes, passive components (resistors, capacitors, connectors, etc.) and various other electronic components.

Through wire connection, electronic signal connection and function can be formed. Thus, a printed circuit board is a platform for connecting components to form the base for connecting parts.

2 Step HDI Board

HDI board

Printed circuit board is not a general end product, so the definition of the name is a little confused, for example: the PC used by the motherboard, called the motherboard but not directly called the circuit board, although there are circuit boards in the motherboard but not the same, so the industry evaluation of the two related but not the same. Another example: an integrated circuit component is called an IC board because it is mounted on a circuit board, but it is not the same as a printed circuit board.

As electronic products tend to be multi-functional and complex, the contact distance of integrated circuit components decreases, the speed of signal transmission increases, the number of wiring increases, and the length of interpoint wiring locally shortens, which requires the application of high-density line configuration and micro-hole technology to achieve the goal. Wiring and bonding are basically difficult to achieve for single and double baords, so circuit boards tend to be multilayered.  Moreover, due to the continuous increase of signal lines, more power layers and connecting layers are necessary for design. All these make Multilayer Printed Circuit boards more common.

For the electrical requirements of high-speed signal, the circuit board must provide impedance control with alternating current characteristics, high frequency transmission capability, and reduction of unnecessary radiation (EMI). With stripline, microstrip structure, multilayer design became necessary. In order to reduce the quality of signal transmission, the insulation materials with low dielectric coefficient and low attenuation rate will be adopted. In order to match the miniaturization and array of electronic components, the circuit board will constantly increase its density to meet the demand. The appearance of assembly methods of BGA (Ball Grid Array), CSP (Chip Scale Package), DCA (Direct Chip Attachment) and other group parts promotes the printed circuit board to the unprecedented high density state.

Any hole less than 150um in diameter is called Microvia in the industry. The circuit made by using the geometric structure technology of this microhole can improve the efficiency of assembly, space utilization and so on. At the same time, it is also necessary for the miniaturization of electronic products.

For such a structure of the circuit board products, the industry has a number of different names to call such a circuit board. For example, European and American companies used to call such products SBU (Sequence Build Up Process) because their programs were constructed in a sequential way. As for the Japanese companies, because the hole structure produced by such products is much smaller than the previous hole structure, the manufacturing technology of such products is called "Micro Via Process". Some people call the traditional Multilayer Board MLB (Multilayer Board), so they call it BUM (Build Up Multilayer Board).

In order to avoid confusion, the IPC circuit board association (IPC) of the United States proposed to call such a product the common name of High Density IntrerconnecTIon Technology. However, this does not reflect the characteristics of the circuit board, so most circuit board manufacturers refer to such products as HDI boards or the full Chinese name "high density interconnection technology". But because of the smoothness of the spoken word, some people call these products "high-density circuit boards" or HDI boards.

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