Microvias Can Be Used in High-Speed Digital Designs

The heart of every electronic device is the printed circuit board (PCB). As PCBs become more advanced and powerful, they also grow smaller. To keep up with this trend, PCB manufacturers must use microvias to connect layers and establish conductive pathways throughout the device. However, there are several important factors that must be taken into consideration to ensure the long-term reliability of microvias.

One of the most significant factors affecting the performance of microvias is their aspect ratio, which refers to the relationship between the diameter of the via and its depth. When this ratio is too large, the microvia is prone to fracture, specifically near its neck region. This is caused by the plating process, which curves copper inward around the barrel of the via, concentrating stress in that area and making it more susceptible to cracking.

To reduce the risk of this issue, designers can use a staggered arrangement or a design with a low aspect ratio. However, this does not necessarily eliminate the possibility of failure at the interface between two stacked microvias. Ultimately, designers must balance the benefits of using microvias against the need to ensure their design will be able to withstand the rigors of manufacturing and field operation.

How Microvias Can Be Used in High-Speed Digital Designs

Another factor that can influence the performance of a microvia is the material used to fill it. In order to prevent voids from forming, the manufacturer must carefully select the type of fill material as well as the plating process. It is vital that these steps are performed correctly, as they play an essential role in ensuring the longevity of the microvia structure.

When a PCB is subjected to extreme temperature changes, the substrate expands and exerts high stresses on the thin copper plating of the microvias. This can lead to failure of the plated interface between microvias, or between a microvia and its pad.

To mitigate this risk, the PCB manufacturer must ensure that the fill and plating processes are consistent and defect-free. This includes ensuring that the material selected for the fill is compatible with the plating process and that the copper plating is free of voids. It is also crucial that the manufacturer test for these issues prior to production to ensure that the final microvia structures will function as intended.

Proper PCB layout is essential to the success of a microvia-based design, as it can help to minimize signal loss and latency. This includes implementing proper trace widths, spacing, and impedance control, as well as using materials with lower dielectric constants to reduce signal losses. It is also vital to consider the layout of signal traces when designing for high-speed digital devices, as these signals are very sensitive to EMI interference.

The bottom line is that while microvias are an effective solution for connecting the various layers of a PCB, they can be challenging to place in high-speed digital designs. This is due to the fact that the conductive paths must be placed accurately, while not interfering with other traces or components. Additionally, precise lamination and testing processes are required to ensure the integrity of the microvias.