How to Build a Multilayer PCB Stack-up
A multilayer PCB has more than two layers in its stack-up. Stack-up is one of the most important aspects of your design. It describes how layers are arranged in a multilayer board. An accurately stacked board will reduce electromagnetic emissions, crosstalk , and improve the signal integrity .
In this article, we will have a look at the following points:
What is a PCB stack-up?
6 layer PCB stack-up (thickness in inches)
Stack-up describes the construction of a multilayer board in sequential order. It provides vital information like material thickness and copper weights required to fabricate a PCB . Stack-ups are also referred to as build-ups. The stack-up also gives the details of trace width for different controlled impedance traces such as 50ohms, 100ohms differential. An example of a 6-layer stack-up is shown in the above image.
What are the different layers present in a circuit board?
Different layers present in a PCB
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.
Glass fiber weave
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.
Power and ground layers in PCB stack-up
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 connections of the components can be easily accessed.
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 .
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What is the standard board thickness?
The thickness of a PCB mainly depends on factors such as copper thickness,...