Printed Circuit Boards (PCBs) are fundamental components in modern electronics, providing the backbone for electrical connections and supporting various electronic components. Among the different types of PCBs, 2-layer PCBs are commonly used in a wide range of applications due to their balance of complexity and cost-effectiveness. In this blog, we’ll explore the benefits, applications, and design considerations of 2-layer PCBs.
What is a 2-Layer PCB?
A 2-layer PCB, also known as a double-sided PCB, consists of two layers of conductive material (usually copper) separated by an insulating substrate. These layers allow for more complex circuit designs compared to single-layer PCBs, as they provide additional routing options and space for components.
How does a double-layer PCB work?
A double-layer PCB, also known as a 2-layer PCB, works by providing two conductive layers (usually made of copper) separated by an insulating layer. Here’s a step-by-step explanation of how it functions:
1. Structure
- Top Layer: One side of the PCB has a layer of copper where components can be mounted and where conductive traces (paths for electric signals) are etched.
- Insulating Substrate: This is typically made of a material like FR-4 (a fiberglass-reinforced epoxy laminate) that electrically insulates the two copper layers.
- Bottom Layer: The other side of the PCB has another layer of copper, similar to the top layer, which can also have components and conductive traces.
2. Conductive Paths
- Traces: Conductive paths are etched onto both the top and bottom copper layers. These traces are the pathways that allow electric signals to travel between components.
- Vias: These are small holes drilled through the PCB and plated with copper to create electrical connections between the top and bottom layers. Vias allow signals to pass from one layer to the other.
3. Component Mounting
- Components can be mounted on either the top or bottom layer. Surface mount technology (SMT) components are soldered directly onto the surface of the copper layers, while through-hole components have leads that pass through holes in the board and are soldered on the opposite side.
4. Signal Routing
- Top Layer Routing: Some of the signal paths are routed on the top layer. This might include connections between nearby components and initial stages of more complex routing paths.
- Bottom Layer Routing: Additional signal paths are routed on the bottom layer. This helps in managing more complex circuits by providing more space for routing without crossing traces.
5. Power and Ground Planes
- Often, one of the layers (usually the bottom) is used predominantly for power distribution (like a power plane) and grounding (ground plane). This helps in stabilizing the circuit and reducing electrical noise.
6. Electrical Connection and Function
- Power Supply: Power is supplied to the components through the power plane and routed traces.
- Signal Transmission: Electric signals travel through the traces and vias, allowing components to communicate and perform their functions.
- Grounding: A common ground plane helps in providing a stable reference point for the electric signals and aids in reducing electromagnetic interference (EMI).
7. Overall Function
- The PCB serves as a platform that physically supports the components and provides the necessary electrical connections between them. By having two layers, the 2-layer PCB can accommodate more complex circuits and higher component density than a single-layer PCB, allowing for more advanced and compact electronic devices.
2 Layer PCB Thickness
The thickness of a 2-layer PCB typically ranges from 1.2 mm to 1.6 mm (approximately 0.047 to 0.063 inches). This includes the two copper layers, each typically 35 µm (1 oz per square foot) thick, and the insulating substrate, which makes up the bulk of the thickness. The exact thickness can vary based on specific design requirements and manufacturing processes.
2 layer board stack-up
A 2-layer PCB stack-up consists of the following layers, from top to bottom:
- Top Copper Layer: The topmost layer of copper where components are placed and traces are routed.
- Prepreg or Dielectric Layer: An insulating material, typically made of FR-4, that separates the two copper layers and provides electrical insulation.
- Bottom Copper Layer: The bottom layer of copper used for additional routing and component placement.
- Solder Mask Layers: Protective coatings applied to both the top and bottom copper layers to prevent solder bridges and protect the traces.
- Solder Mask Layers: Protective coatings applied to both the top and bottom copper layers to prevent solder bridges and protect the traces.
This stack-up allows for a compact and efficient layout of electronic circuits by utilizing both sides of the PCB for routing and component placement.
