ABSTRACT
A substrate is a board onto which a number of individual electrical components, devices, and modules are integrated into functional electronic systems. The development of integrated circuit chip technology and assembly technology has resulted in increasingly high requirements for the performance of substrates. Organic substrates feature low electrical permittivity, a simple fabrication process, and low cost. For the subtractive process, a wiring pattern is formed by removing some needless parts from copper foil, which is coated on the substrate before the process, with chemical etchant. According to the numbers of conductive wiring layer, commonly used organic substrates mainly fall into the following categories: single-sided boards, double-sided boards, and multilayer boards. Multilayer boards are widely used to obtain larger wiring area and more flexible wiring rules. During wiring design with the computer aided design tool, the line width and spacing and other parameters must be designed according to the requirements of electrical parameters, positioning accuracy, and sizes of vias.
