A: Stacked microvias are microvia technology used in printed circuit boards (PCBs) and electronic packaging. Microvias are tiny, drilled holes in PCBs that connect different layers of the board, allowing for the routing of electrical signals. Stacked microvias are designed to provide additional routing flexibility and enable high-density interconnections in modern electronic devices.

Here’s how stacked microvias work and what sets them apart:

  1. Vertical Stacking: Unlike traditional microvias, typically single holes that connect adjacent layers of a PCB, stacked microvias involve multiple microvias stacked on top of each other, forming a vertical connection between various layers of the PCB. This vertical stacking allows for more complex and dense routing.
  2. Increased Routing Density: Stacked microvias enable a higher routing density than single microvias. This is particularly useful in modern electronics such as smartphones, tablets, and wearables, where miniaturization and space-saving are critical.
  3. Reduced Signal Propagation Delay: Because stacked microvias provide shorter and more direct connections between layers, they can help reduce signal propagation delays, making them suitable for high-speed and high-frequency applications.
  4. Improved Thermal Management: These vias can also be used to design PCBs for improved thermal management. By connecting multiple layers with stacked microvias, heat can be dissipated more efficiently through the PCB, which is essential for devices with high-power components.
  5. Complex PCB Designs: They are often used in complex PCB designs where there is a need for multiple signal layers, power distribution, and ground planes. They allow designers to create intricate, multilayered PCBs without compromising performance or reliability.
  6. Advanced Manufacturing Techniques: Manufacturing stacked microvias requires precise drilling and plating processes, which can be more complex and expensive than traditional microvias. Advanced PCB fabrication techniques are often used to create these stacked structures.
  7. Signal Integrity and Reliability: While these types of vias offer many advantages, they also introduce additional design challenges related to signal integrity and reliability. Careful design and manufacturing processes are essential to ensure the stacked microvias meet the required electrical and mechanical specifications.

In summary, stacking microvias is a technology used in advanced PCB designs to achieve higher routing densities and support modern electronic devices’ miniaturization and performance demands. They are essential in applications where space constraints and signal integrity are critical considerations.

Below are three examples of typical vias, whether standard via or microvia; the concepts are similar. To learn more about the basic vias (Through-hole, Blind, and Buried), see this FAQ: Explain Printed Circuit Board Vias.