Multilayer PCB stackup

The multilayer PCB stackup refers to the arrangement and configuration of the different layers that make up a

multilayer printed circuit board (PCB). The stackup determines the order, composition, and characteristics of each

layer, including conductive layers, insulating layers, and other components. The stackup design is a crucial aspect

of multilayer PCB fabrication and directly impacts the electrical performance and signal integrity of the PCB.

Here is a general description of a typical multilayer PCB stackup:

Signal Layers: The signal layers contain the conductive traces that carry electrical signals. These layers are

typically made of copper and can vary in number, depending on the complexity of the circuit design. The signal

layers are sandwiched between insulating layers to prevent short circuits.

Power and Ground Planes: Power and ground planes are dedicated layers that provide a stable reference for power

distribution and signal return paths. These planes help reduce noise and provide a solid ground reference for

signal integrity. Power and ground planes are often placed adjacent to each other, with multiple layers allocated

for power and ground depending on the design requirements.

Insulating Layers (Prepregs): Insulating layers, also known as prepregs, are made of non-conductive materials such

as fiberglass-reinforced epoxy. These layers are placed between the signal layers and help isolate and separate

them. The number of insulating layers can vary depending on the desired PCB thickness and the number of signal

layers.

Soldermask Layers: Soldermask layers are applied to the outer surfaces of the PCB to protect the copper traces from

oxidation and provide insulation between components during soldering. The soldermask layer is typically green in

color, but other colors can also be used.

Silkscreen Layers: Silkscreen layers are used to print component markings, reference designators, logos, and other

information on the PCB. These layers are applied over the soldermask and help identify components and provide

assembly instructions.

The actual stackup configuration can vary depending on the specific requirements of the PCB design, such as

impedance control, signal integrity, power distribution, and thermal management. Different stackup configurations

may include additional layers for controlled impedance, shielding, or other specialized purposes.

It's important to note that the specific details of the multilayer PCB stackup, such as the number of signal

layers, power and ground planes, and the arrangement of insulating layers, are determined based on the design

requirements and considerations of the PCB designer.