What is Build-up
In the PCB industry, “Build-up” refers to the specific sequence or order in which the copper layers of a printed circuit board (PCB) are defined by the designer. This sequence determines the arrangement and configuration of the copper layers in the PCB stack-up, which is crucial for ensuring proper electrical connectivity and functionality of the PCB.
The build-up process involves several considerations. Firstly, the layer count is determined, which refers to the number of copper layers in the PCB. A higher layer count implies a more complex build-up. Secondly, the selection of appropriate pre-preg and core materials is crucial. These materials, which are dielectric materials, separate the copper layers and can vary based on the specific requirements of the PCB design. Additionally, the build-up includes specifying the thickness of the copper layers, both on the outer and inner layers of the PCB. This information is essential for achieving the desired conductivity and performance of the PCB. The build-up also takes into account factors such as manufacturability, IPC class requirements, the use of high-density interconnect (HDI) technology, via aspect ratios, control impedance, and surface finishes.