Electronics Manufacturing, Guide, PCB Manufacturing

Buried Vias PCB: Advantages, Applications, and Implementation

Buried Vias

Introduction to All Kinds of Vias in PCBs

In multilayer PCB to transfer signals between different layers of the board small copper-plated holes called vias are used. With the help of vias external layers of PCB can be connected with the internal layers, thus vias are an essential part of multilayer PCB design PCBs of modern Telecommunication devices have a very complex layout and space management is very crucial as routing is very tight due to dense component placement. Vias help in managing the limited space on PCBs. There are various types of vias used in PCB design such as:

  1. Through-Hole Vias
  2. Blind Vias
  3. Buried Vias
  4. Microvias
  5. Stacked Vias
  6. Staggered Vias
  7. Via-in-pad
  8. Filled and Capped Vias

In this article, we are going to briefly discuss Buried Vias that exist in the buried vias PCB such as their advantages over other types of vias their applications and their implementation which includes the major design considerations, and manufacturing process cost implications. We are going to discuss about the standards used for testing and inspection of buried vias that exist in the buried vias PCB  and the best practices for using Buried Vias then we will take an insight into future trends and innovations related to Buried Vias.

What are Buried Vias?

Buried Vias are vias used to connect the different internal layers of a PCB without disturbing the external layers. The Buried Vias comes in handy while designing a PCB of complex design as it helps in maximising the surface area for external layers. Thus, more area is available for component placement and routing.

Comparison of Buried Vias, Blind Vias and Through-hole Vias

Up until now, we have discussed the applications and advantages of Buried Vias. But there are other types of vias also exist. Blind Vias and Through Hole Vias are the most popular vias that are used to enhance the performance of PCBs. The following table describes the differences between through-hole, blind and buried vias based on different features.

Features Through-Hole Vias Blind Vias Buried vias
Layers

Connected

All layers External layers to internal layers Internal Layers
Manufacturing Simple drilling through the entire stack Precision drilling or laser drilling Multistep lamination and drilling
Cost Low Higher than through hole Higher due to complexity
Space Utilization Uses on every layer Space from internal layers is saved Maximum space on external layers
Signal Integrity Long stubs possess issues with resonance A shorter path improves signal integrity Minimised stub effects provide the best results
Inspection Easy More difficult Most challenging
Applications Standard PCBs High-density interconnect (HDI) PCBs High-density interconnect (HDI) PCBs

From the table above it is clear that the Buried Vias implementation of buried vias gives optimal performance. But due to its very advantages, its manufacturing and inspection are the most challenging, resulting in higher production costs.

Advantages of Buried Vias

Advantages of Buried Vias

Since we have discussed the applications of Buried Vias now let’s discuss the advantages offered by it through the following points-

  • More Space for Components and Routing: There is more space for components and routing since vias that exist in the buried vias PCB are confined to internal layers and external layers are free.
  • Enhanced Signal Integrity: The length of signal paths is reduced which results in minimal signal reflections and interferences hence signal integrity is enhanced.
  • Reduce the Parasitic Capacitance and Inductance: It reduces the parasitic capacitance and inductance which improves the device’s overall performance.
  • Implementation of Complex and Dense Routing: Implementation of complex and dense routing schemes is possible due to it which results in high-performance PCB designs.

 

Applications of Buried Vias

Buried vias that exist in the buried vias PCB have vast applications in electronics and communication engineering. It is used in every sector where PCBs of complex design are required. The sectors where Buried vias in PCB found their applications are-

  • High-Density Interconnect (HDI) PCBs: High-Density Interconnect PCBs as compared to traditional PCBs contain a higher density of components per unit area leaving very little space for routing here Buried Vias helps in managing complex interconnections without wasting valuable surface space
  • Advanced Telecommunication Equipment: Modern Telecommunication Equipment performs high-speed signal transmission and complex signal processing while maintaining signal integrity. Buried Vias improves the signal integrity and reduces crosstalk which enables the telecommunication circuit to operate at higher frequencies.
  • Consumer Electronics: It is utilised in electronic devices like smartphones, tablets, and smartwatches to make them more compact.
  • Automotive Electronics: it is applied in the different parts of vehicles such as various control systems such as advanced driver assistance system (ADAS). It is also used in a vehicle’s infotainment system. Reliable connections in multilayer PCBs of such control systems are essential for safety-critical applications.
  • Aerospace and Defence: Buried Vias in PCB is heavily used in avionics, communication systems, and control systems of aircraft, missiles, satellites, drones etc due to its high reliability as well as the fact that it makes a system more compact which is very crucial when weight and space management is the main concern.
  • Computer and Networking: As we know it improves signal integrity greatly which is very desirable for high-speed data transfer and complex processing tasks this it can be implemented in hardware such as servers, data storage devices and high-performance computing systems.

 

Best Practices of Using Buried Vias

Best Practices of Using Buried Vias

Now let’s take a look at the best practices for using Buried Vias as careful planning and adherence are required while designing a PCB that uses this type of vias. These are some of the best practices that should be that should be implemented while designing such vias in PCBs:

  • Make sure that it is only connecting the internal layers of the PCB.
  • The length of the via should be kept as short as possible to minimise inductance and capacitance.
  • Heat management is very crucial thus proper spacing is necessary to manage heat effectively.
  • Vias should not compromise the mechanical integrity of PCB.
  • The drilling and plating should be precise hence to ensure the accuracy laser drilling is preferred.
  • The end product should be inspected carefully and robust testing methods should be used such as X-ray or cross-section analysis.
  • The cost of production should be compared with other types of vias to balance performance with manufacturing cost.
  • Placement of vias and other specifications should be well documented in the design files along with clear instructions for the manufacturer.

Conclusion

To conclude this article let’s take a look at the future trends and innovations. Additive manufacturing techniques such as 3D printing can enhance the design flexibility. Implementation of Nanotechnology could provide smaller and more precise vias in the future. The addition of  Nanotechnology also opens the gates for miniaturisation and more widespread use of denser layouts.

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