A stack-up primarily consists of metal foil, prepreg, and copper-clad laminate (core).
Metal foil: Copper is the most commonly used metal foil in PCB construction.
Prepreg: It is an interwoven glass cloth impregnated in epoxy resin. The resin is left semi-cured.
Copper-clad laminate: Single or multiple plies of prepreg bonded together along with the top and bottom copper foil makes a copper-clad laminate. This is also known as the core.
What are the power and ground layers in multilayer PCB stackup?
The power plane is a copper layer connected to the power supply. It is often designated as VCC in PCB design. The main function of the power plane is to provide a steady voltage supply to the PCB. In multi-layered boards, if a component needs to draw power then it is simply connected to the via that makes contact with the power plane. Similarly, the ground plane is a plane of flat copper connected to the common ground point in the PCB.
Advantages of using power/ground planes
- The power and ground pins of the components can easily be connected to the power and ground planes.
- It provides a clear current return path, especially for high-speed signals. This in turn reduces the EMI (electromagnetic interference).
- The power planes have a larger current carrying capacity than the traces. This also reduces the operating temperature of the PCB.
What is PCB lamination?
The lamination is the process of placing the stack-up under extreme temperature and pressure to bond prepreg and copper foil to the base PCB inner layers. The temperature and pressure values are mentioned in the datasheets of the chosen PCB materials.
What is the standard board thickness?
The thickness of a PCB mainly depends on factors such as copper thickness, materials used, number of layers, and the operating environment. The standard thickness of a conventional board is around 62 mils (1.57mm). Today, PCBs have become more complex as the copper layer weight and the layer count have increased for various applications. Due to this, the PCBs tend to become thicker. Manufacturers, based on the customer’s request, are now fabricating PCBs with two new standard thicknesses, 93 mils (2.36mm) and 125 mils (3.17mm) (150% and 200% of old standard thickness).
Why we need multilayer PCB？
In this modern era, electronic devices are becoming more complex and consist of a higher number of components and circuits. It becomes a tedious task to accommodate the complex circuits in a single-layered PCB. This problem can be solved by adding layers to the stack-up.
Let us have a look at few advantages of multilayer boards:
- They are capable of accommodating complex circuits that are required for modern electronic devices.
- Having more layers means the board is thicker and, therefore, more durable than single-sided PCBs.
- Multi-layer boards require more planning and intensive production processes, so they are of a higher quality than other types of boards.
- Using multiple PCB components would require multiple connection points. Multi-layer boards, on the other hand, are designed to work with a single connection point, simplifying the design of the electronic device and further reducing the weight.