Technical
Assembly
Technical
Assembly
What is PCB Stack-up?
PCB stack-up design refers to the arrangement of copper layers and insulating layers in a specific order before the layout design of the circuit board. A good stack-up structure can reduce the vulnerability of the circuit to external noise and minimize impedance and crosstalk issues in high-speed PCB layouts.
Why is PCB Stack-up Necessary?
In modern precision instruments, the conductors on the circuit board can span kilometers in length. As devices become more feature-rich and smaller in size, single-layer circuit boards can no longer meet the demands. To address this, multi-layer PCBs were developed.
The Emergence of Multi-layer PCBs
Single-layer boards have limited space and small routing areas, leading to lower performance, higher material consumption, and larger size. Multi-layer PCBs solve this by stacking multiple layers, significantly increasing routing space within the same area.
Advantages of PCB Stack-up
• More Routing Space: Increased flexibility in routing.
• Better Heat Dissipation: Uniform heat distribution.
• Reduced Electromagnetic Interference (EMI).
• Enhanced Electromagnetic Compatibility (EMC).
• Minimized Impedance Mismatch.
Key Points in PCB Stack-up Design
The main elements of stack-up layer design include determining the number of conductive copper layers and insulating layers, their stacking order, and the dielectric thickness which determines the spacing between copper layers. It also involves deciding which copper layers to use for signal routing to avoid crossing and overlapping, determining the impedance of signal transmission lines, and identifying layers for shielding, power planes, and ground planes.
1. Avoid Crossings and Overlaps
- Conductive paths should avoid crossing and overlapping to prevent signal interference and short circuits.
2. Radiating Power Lines
- Power lines on the same layer should be distributed radially to shorten the total length and reduce voltage drop and noise.
3. Close Proximity Routing
- Power and ground lines should be routed close together to reduce the area of current loops and minimize noise interference.
4. Adjacent Power and Ground Lines
- Power and ground lines should be as close as possible to reduce various current loop areas, thereby enhancing power stability and signal integrity.
5. Dual-layer PCB Design
- For dual-layer PCBs, place a ground line closely beneath the signal line on the other side of the board. The ground line should be as wide as possible to minimize loop area, improving anti-interference capability.
6. Minimum Impedance Return Path
- Each signal layer in the PCB stack-up must have a closely coupled reference layer, preferably a ground plane or power plane.
7. Minimize Spacing Between Adjacent Power-Ground Planes
- This provides a larger parasitic capacitance.
8. Large Area Reference Layers for Electromagnetic Shielding
- Large, continuous power and ground plane copper foils provide electromagnetic shielding to protect inner signal traces.
GreatPCB Stack-up Standards
GreatPCB stack-ups range from 4 to 18 layers, with thicknesses from 0.4mm to 6.0mm. Inner copper thickness ranges from 0.5oz to 2oz, while outer copper thickness ranges from 0.5oz to 6oz.
Below is GreatPCB’s standard lamination structure. For custom requirements, please email us, and we will promptly provide the corresponding stack-up model parameters.
