As printed circuit boards continue to shrink in size, the available surface area for wiring and components becomes increasingly constrained. In such cases, cavity PCBs present an effective solution.
What is a Cavity PCB?
A cavity in a PCB refers to a hole (cutout) that extends from the outer copper layer to the inner copper layer, but does not fully penetrate the board. By placing components within these cavities, their height can be reduced, making the entire circuit board more compact. This allows for greater functionality and layout optimization within a limited space. Additionally, cavities create more space and increase the distance between components, reducing interference and enhancing the reliability and performance of the circuit. Furthermore, cavities can be used to expand the heat dissipation surface area, which is particularly important for small, high-power circuit boards. By designing heat dissipation structures in the concave cavities, heat can be efficiently dissipated, ensuring the stable operation of components even under heavy loads.
Types of Cavity PCBs
The latest revision of the IPC standard for rigid PCBs, IPC-6012F, defines three types of recessed cavities and their associated criteria:
- Type 1: No copper plating or metallization inside the cavity.
- Type 2: Copper on the top/bottom or walls (but not both) of the cavity. This is the most common type of cavity.
Multiple inset cavities in a PCB. [Image source: IPC]
- Type 3: The cavity walls and floor area are both copper-plated.
Cavities containing copper inside, such as traces and pads, are referred to as Type 2 cavities. If the cavity walls are partially plated with copper, this would be classified as a Type 3 cavity.
In some cases, the cavity can be completely filled with copper, a process known as copper coining. This is often done to create a large heat sink inside the PCB. When placed beneath a component, the copper coin significantly improves heat transfer within the board. If the copper coin is connected to an electrical plane or positioned near a large electrical plane, it facilitates heat dissipation away from the heat source. This technique can also be used to bond components to the case, where the coin and case together form a large heat sink.
Learn more about Copper Coin PCBs in the following video:
Advantages of Cavity PCBs
- Reduces product size and weight
- Increases assembly density
- Improves overall product performance
- Meets the high-speed and high-information requirements of communication devices
- Enhances the stability of surface-mounted components
- Expands the heat dissipation area
Applications of Cavity PCBs
- RF and microwave applications
- Telecommunications
- Central hybrid automotive systems
- High-current circuits
- Power amplifiers
- DC power supplies
- Motor control modules
- Electric vehicle powertrains
- High-speed computing
In high-frequency antenna circuit boards, removing unnecessary layers can minimize signal loss, which is crucial for antenna structures. Therefore, PCBs with cavities are particularly suitable for wireless communication applications, such as smartphones and related infrastructure. Additionally, the waste heat generated by power components can be more effectively managed through targeted material removal.
If you have any questions about PCBs and PCBA, please feel free to contact me at info@wellcircuits.com
