How to Define Layer Stackup for 4 Layer PCB: Simple Guide
To define a
4 layer PCB stackup, arrange layers as Top Signal, Ground Plane, Power Plane, and Bottom Signal. Specify the thickness and material for each layer to ensure proper electrical performance and manufacturability.Syntax
Defining a 4 layer PCB stackup involves specifying the order and type of each layer along with their thickness and material properties.
- Top Layer: Signal layer for routing important traces.
- Inner Layer 1: Ground plane for reference and noise reduction.
- Inner Layer 2: Power plane to supply voltage.
- Bottom Layer: Signal layer for additional routing.
- Dielectric Thickness: Insulating material thickness between layers.
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Layer Stackup Definition: 1. Top Layer - Signal (e.g., 1 oz copper) 2. Prepreg - Dielectric (e.g., 0.1 mm) 3. Inner Layer 1 - Ground Plane (1 oz copper) 4. Core - Dielectric (e.g., 0.2 mm) 5. Inner Layer 2 - Power Plane (1 oz copper) 6. Prepreg - Dielectric (0.1 mm) 7. Bottom Layer - Signal (1 oz copper)
Example
This example shows a typical 4 layer PCB stackup with layer order, copper thickness, and dielectric thickness for good signal integrity.
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Layer | Type | Thickness (mm) | Description ------------------------------------------------- 1 | Signal (Top) | 0.035 | Routing layer 2 | Dielectric | 0.1 | Prepreg insulation 3 | Ground Plane | 0.035 | Reference ground 4 | Core | 0.2 | Core insulation 5 | Power Plane | 0.035 | Power supply 6 | Dielectric | 0.1 | Prepreg insulation 7 | Signal (Bot) | 0.035 | Routing layer
Output
Layer 1: Top Signal (0.035 mm copper)
Layer 2: Prepreg (0.1 mm dielectric)
Layer 3: Ground Plane (0.035 mm copper)
Layer 4: Core (0.2 mm dielectric)
Layer 5: Power Plane (0.035 mm copper)
Layer 6: Prepreg (0.1 mm dielectric)
Layer 7: Bottom Signal (0.035 mm copper)
Common Pitfalls
Common mistakes when defining a 4 layer PCB stackup include:
- Placing power and ground planes too far apart, increasing impedance.
- Using uneven dielectric thickness causing signal integrity issues.
- Not specifying copper thickness, leading to current capacity problems.
- Ignoring manufacturer stackup guidelines causing fabrication delays.
Always verify stackup with your PCB fabricator before finalizing.
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Wrong Stackup Example: 1. Top Signal 2. Power Plane 3. Ground Plane 4. Bottom Signal Right Stackup Example: 1. Top Signal 2. Ground Plane 3. Power Plane 4. Bottom Signal
Quick Reference
| Layer | Type | Typical Thickness (mm) | Purpose |
|---|---|---|---|
| 1 | Top Signal | 0.035 | Routing signals |
| 2 | Prepreg (Dielectric) | 0.1 | Insulation |
| 3 | Ground Plane | 0.035 | Reference and noise reduction |
| 4 | Core (Dielectric) | 0.2 | Insulation |
| 5 | Power Plane | 0.035 | Power distribution |
| 6 | Prepreg (Dielectric) | 0.1 | Insulation |
| 7 | Bottom Signal | 0.035 | Routing signals |
Key Takeaways
Arrange layers as Top Signal, Ground Plane, Power Plane, and Bottom Signal for a 4 layer PCB.
Specify copper and dielectric thicknesses to ensure signal integrity and manufacturability.
Place ground and power planes close with proper dielectric to reduce noise and impedance.
Always confirm stackup details with your PCB manufacturer before production.
Avoid uneven dielectric layers and incorrect layer order to prevent electrical issues.