Substrate materials for printed circuit boards (PCBs) generally fall into two categories: rigid substrates and flexible substrates. The most common type of rigid substrate is the copper-clad laminate (CCL). These are manufactured by impregnating reinforcing materials with a resin adhesive, drying and cutting the layers, stacking them into a preform, applying copper foil, and then subjecting the assembly to high temperature and high pressure using steel molds in a hot press. Prepreg-a material commonly used in multilayer PCBs-is essentially an intermediate product from the CCL manufacturing process (typically consisting of glass fabric impregnated with resin and then dried). So, do you know what components make up a circuit board?
1. A circuit board is primarily composed of pads, vias, mounting holes, traces (conductive paths), electronic components, connectors, copper fills, and electrical boundaries. The functions of these elements are as follows:
Pads: Metal-plated areas used for soldering the leads (pins) of electronic components.
Vias: Metal-plated or non-plated holes; metal-plated vias are used to electrically connect component leads between different layers of the board.
Mounting Holes: Used to secure the circuit board in place.
Traces (Conductive Paths): Copper patterns that form electrical networks, connecting the leads of various components.
Connectors: Components used to establish connections between different circuit boards.
Copper Fills (Copper Pour): Copper areas-often connected to the ground network-used to effectively reduce impedance.
Electrical Boundaries: These define the physical dimensions of the circuit board; no components may be placed beyond these boundaries.
2. Circuit boards go by various names, including PCBs, aluminum-based boards, high-frequency boards, heavy-copper boards, impedance-controlled boards, ultra-thin boards, and printed (copper-etched) circuit boards. Circuit boards enable the miniaturization and visualization of electronic circuits, playing a crucial role in the mass production of fixed circuits and the optimization of component layout within electronic devices. They are commonly referred to as printed wiring boards (PWBs) or printed circuit boards (PCBs).
3. Based on the number of layers, circuit boards are broadly classified into three categories: single-sided boards, double-sided boards, and multilayer boards. First, there is the single-sided board. In this most basic type of PCB, components are concentrated on one side, while the conductive traces are located on the other. Because the traces appear on only one side, it is called a single-sided circuit board. Single-sided boards are generally simple to manufacture and low in cost, but their drawback is that they cannot be used for overly complex products.
A double-sided board is an extension of the single-sided board; it is used when single-layer routing cannot meet the requirements of an electronic product. Both sides feature copper cladding and conductive traces, which can be connected between the two layers via "vias" (vertical interconnect accesses) to form the necessary network connections.
A multi-layer board consists of three or more conductive pattern layers, separated by insulating material and laminated together, with the conductive layers interconnected as required. Multi-layer circuit boards are a product of the evolution of electronic information technology toward higher speeds, greater functionality, larger capacity, smaller size, thinner profiles, and lighter weight.
Based on their physical characteristics, circuit boards are categorized into flexible printed circuits (FPC), rigid printed circuit boards (PCB), and rigid-flex printed circuit boards (FPCB).
