IC Substrate PCBs are the emerging link between the PCB and the semiconductor itself and miniaturisation is the key.
Working on feature sizes, which a few years ago were out of capability in PCB manufacture, it involves manufacturing PCBs in miniature on different materials, akin to where the semiconductor industry was 5 to 10 years ago.
Materials can range from rigid materials such as woven epoxies similar to FR4, through pure polyimide as used in flex PCBs to ceramics such as aluminium oxide and aluminium nitride. Due to the need for miniaturization, HDI technology is employed also.
Typical applications are for smartphones as well as computing, consumer electronics and military/aerospace.