This is one topic I wish someone had taught me when I first started designing boards. Back then, finding content online wasn’t as easy as it is today. Vias are essentially small holes that create electrical connections between different layers of a PCB. Whether a PCB has just 1 layer or several, vias are the key to connecting layers and routing signals between them.
The most common via is the Through-hole via, drilled from the top to the bottom layer, connecting one or more layers in between. It doesn’t need to connect all layers, but the hole goes completely through the PCB. It’s the cheapest option due to easy manufacturing (drill once through all layers). However, it takes up space, and you can’t place parts or pads on both sides unless you use a via-in-pad. If the signal doesn’t connect the top and bottom layers, the metallic hole can create stubs(We can discuss this in the future) that cause reflections in high-speed designs.
Blind Vias connect one outer layer to one or more inner layers but do not go all the way through the board. Useful when you want to save on space and can do part mounting on the other layer that you haven’t connected to.
Buried Vias as the name suggests, is buried inside the PCB, in the inner layers, with no direct connection to the 2 outer layers. Pros: Excellent for multi-layer PCBs, no impact on the outer layers, great for high-density designs. Both Buried and Blind vias are expensive as they require multiple stacking and drilling processes.
Micro vias are a special type of via with an aspect ratio of 1:1 or less and a hole depth of less than 0.25mm, typically used for single-layer transitions. Unlike traditional cylindrical vias, micro vias have a conical structure that tapers from one layer to the next. Categorized into two types: Stacked Vias, where multiple micro vias are aligned vertically across different layers (one on top of the other), and Staggered Vias, where vias are placed on different layers but do not align directly with each other.
Always weigh the trade-offs between cost and space requirements for your next PCB design.
