MICROVIA HDI designs
In PCBs, microvias are small holes that connect layers and provide a way for signals to travel between them. They are used in high-density HDI designs to minimize copper foil thickness and allow for greater circuitry density on the board. This is especially important as electronic devices become increasingly compact while demanding higher performance and functionality.
The use of microvias reduces manual routing time for even the most complex projects, and it can save manufacturers valuable production resources. They also improve board reliability by providing a stable connection between layers and preventing solder failure due to voids or uneven plating. This is especially important for HDI boards, which typically require a higher level of copper thickness and more difficult fabrication processes than traditional designs.
microvia hdi are drilled with laser technology, which increases precision and consistency over traditional methods of drilling. This eliminates the risk of voids or short circuits, which can significantly impact the integrity of the PCB. In addition, the microvias have a smaller aspect ratio than traditional through-hole vias, which reduces mechanical stress on the substrate and allows for thinner constructions.
How do microvias contribute to MICROVIA HDI designs?
The choice of copper foil thickness for the microvia plating process can have a significant impact on the conductivity of the via and its ability to dissipate heat. Choosing the right thickness is critical to ensure adequate conductivity while minimizing manufacturing costs and maintaining manufacturability. It is also important to consider the physical thickness of the microvias, which may impact their size and shape.
After the drill process, the microvias are plated using a specialized copper plating bath. This process utilizes conformal plating to fill the body of the microvia with solid copper, avoiding the formation of voids. Achieving this result requires the use of special additives in the plating chemistry. Without them, copper will concentrate on the walls and top surface of the microvia, resulting in poor conductivity and increased voiding.
Depending on the type of PCB, different methods can be used to plate the microvias. Some are plated shut, while others are etched open to create a conductive path between the layers of the PCB. In either case, these features provide a robust and reliable connection that can support the higher speeds and currents associated with modern electronic devices.
Stacked and staggered microvias are also available for enhanced signal transmission. In the latter, the holes are arranged in a staggered pattern and located offset from each other. This arrangement helps to minimize interference between adjacent microvias, which is essential for high-speed applications.
Another option is to place the microvias directly on the component pads, which is known as a “via-in-pad” configuration. This can help to reduce signal reflections and attenuations, thereby improving circuit performance and reducing parasitic capacitance and inductance. However, this approach has been subject to some reliability issues due to internal copper wrap plating and solderability concerns.