PCB Appliance in Telecommunication Industry
In the field of communication, different applications have different PCB requirements. Generally speaking, FPC and HDI are more used for mobile communication terminals, and large-area, high-level rigid PCBs are mostly used for communication devices.
Compared with rigid copper clad laminates, FPC is commonly referred to as "flex board", and the core layer is generally a flexible substrate such as polyimide (PI) or polyester film. FPC features thin, flexible, and high wiring, achieving the integration of component assembly and wire bonding. FPC was first used in the space shuttle, military equipment and other fields. Due to its lightness, softness and folding resistance, FPC quickly penetrated into the public at the end of the 20th century. It was mainly used in consumer electronics such as mobile phones, notebook computers, PDAs, and LCDs.
HDI is called high-density interconnected printed circuit board. Its main feature is to carry more devices and achieve more functions in the smallest possible area. The development of HDI has promoted the development of 2G-5G mobile communication terminals, and also made high-performance touch screen mobile phones possible. In addition, HDI is also used in the field of avionics and military equipment. In 2016, the global HDI board production value reached 7.68 billion US dollars, accounting for 14% of the PCB output value, with a compound annual growth rate of 2.70%.
HDI requires ultra-high wiring density to minimize the footprint of the motherboard inside the smart-phone. HDI is made by stacking layers of common core plates, and it is necessary to realize the connection between any layers by drilling, in-hole plating and the like.
Therefore, HDI needs to be as thin and multi-layered as possible to greatly increase the density of components and save the wiring area required for PCB. The HDI can be classified into a first-order HDI, a second-order HDI, a high-order HDI, and the like according to the number of adjacent layers directly connected through the blind holes. HDI laser drilling, plating hole plugs and other processes are more difficult and have higher added value.