In typical scenarios, resistors and capacitors on a PCB are directly soldered onto the board surface. However, the embedded resistor and embedded capacitor process involve embedding resistors and capacitors within the internal layers of the PCB. This type of printed circuit board consists of layers from bottom to top: the first dielectric layer, buried resistors, signal trace layer, and the second dielectric layer. The portion of embedded resistors without a signal trace layer is covered by a polymer isolation layer, and the surface of this polymer isolation layer is intentionally roughened with a surface roughness (Rz) greater than 0.01 μm. The polymer isolation layer at the corners has a minimum thickness of 0.1 μm.
The advantages of the buried resistor and buried capacitor process include:
Space-saving:
By embedding resistors and capacitors directly into the internal layers of the board, it's possible to save space on the PCB, resulting in a more compact overall circuit board.
Reduced circuit noise:
Embedding resistors and capacitors within the internal layers can decrease electromagnetic interference and noise, enhancing circuit stability and resistance to interference.
Improved signal integrity:
The embedded resistor and buried capacitor process can minimize signal transmission delay and reflection losses, thereby enhancing the integrity and reliability of signal transmission.
Decreased PCB thickness:
With resistors and capacitors embedded in the internal layers, the thickness of the PCB can be reduced, resulting in a thinner and more lightweight circuit board.
However, the embedded resistor and capacitor process can be relatively complex in terms of manufacturing and maintenance, as resistors and capacitors cannot be directly observed or replaced. Additionally, this process is typically employed in high-end electronic products and comes with higher costs.
When dealing with high-density circuit designs, embedded resistor and embedded capacitor technology becomes particularly useful. In conventional PCB layouts, resistors and capacitors are often surface-mounted onto the PCB surface. This approach can lead to increased PCB footprint and potential surface-related noise and interference.
The embedded resistor and embedded capacitor process addresses these issues by directly embedding resistors and capacitors within the internal layers of the PCB.
Here are the detailed steps of the PCB embedded resistor and embedded capacitor process:
Internal Layer Fabrication:
In the production of the PCB, aside from the conventional layers such as outer and inner layers, specialized internal layers are created specifically for the embedded resistor and embedded capacitor components. These internal layers will encompass the areas where resistors and capacitors are to be embedded. The fabrication of these internal layers typically employs similar techniques to regular PCB manufacturing, such as plating and etching.
Resistor/Capacitor Package:
Resistors and capacitors in the embedded resistor and embedded capacitor process adopt unique packaging forms designed for embedding within the PCB's internal layers. These packages are often slim to suit the PCB's thickness and possess good thermal conductivity.
Embedding Resistors/Capacitors:
During the internal layer fabrication process, the embedded resistor and embedded capacitor components are embedded within the PCB's internal layers. This can be achieved through various methods, such as utilizing specialized compression techniques to embed them between the internal layer materials or using laser technology to etch voids in the internal layer material, followed by filling in the resistors and capacitors.
Connection Layers:
After completing the embedded resistor and embedded capacitor internal layers, they are connected to other conventional layers (such as outer layers). This connection can be accomplished using standard PCB manufacturing techniques like lamination and drilling.
In summary, the embedded resistor and embedded capacitor process is a highly integrated technology that embeds resistors and capacitors within the internal layers of a PCB. It saves space, reduces noise, enhances signal integrity, and makes the PCB thinner and lighter. However, due to the complexity of manufacturing and maintenance as well as increased costs, this process is typically employed in high-end electronic products that demand elevated performance.
