Printed Wiring Boards (PWB) made by Sequential Build-Up (SBU) processes have found a wide application in semiconductor packaging substrates and system in package substrates, besides usage as a conventional printed wiring board. Its capability for high density circuits can contain multi-functional electronic circuits within a small surface area and can achieve light weight and low-profile products with improved electric characteristics. A number of processes and materials were developed and are used for each application in each electronic product. The advancement of printed wiring boards is expected to continue, driven by the requirements from electronic products. Technical development activities are needed to satisfy these requirements. Activities are still high in the development of embedded passive technology, which will equip printed wiring boards with the functions of passive components resistance (R), capacitance (C) and inductance (L) - as well as the conventional interconnection functions of conductors between components. This technology will dramatically change the structure of printed wiring boards and complicate the fabrication processes. Material development will be a key issue in the case of embedded resistors and capacitors.
