Laser Drilling Micro-vias​

HDI and Micro-Vias

As PCBs continue to shrink in size and grow in complexity, it’s essential for your PCB fabricator to adapt. As a designer, you know that traditional processes are constantly evolving, with new techniques emerging to meet the demands of High-Density Interconnect (HDI) technology. At Stream PCB, we are committed to staying ahead of the curve!

HDI is one of our specialties, and it goes beyond just fine lines in the foil pattern. It also involves Sequential Build-Up (SBU) and the use of laser-drilled Microvias, ensuring that your designs are innovative and meet the latest industry standards.

Sequential Build-Up

Multilayer technology utilizing Sequential Build-Up (SBU) involves adding one layer of dielectric and foil pattern at a time, allowing for the processing of HDI Micro-Vias before adding the next layer.


These layers are added in pairs, one on each side of the substrate, to balance the stresses. For instance, layers can be added in increments such as 1, 2, 3, etc., on each side of the substrate (N), or in a pattern like 1+N+1, 2+N+2, 3+N+3, and so on.

Laser-Drilled Microvias

Laser-drilled Microvias minimize the space needed by conventional through-the-board vias. Their smaller diameter frees up more space for additional circuit traces. A Microvia connects only one layer of foil to the next, leaving layers above and below available for additional circuit traces, which increases overall circuit density.As each layer of SBU is added, a laser drills a hole from the outer layer of foil through the dielectric to the next inner layer of foil. This hole is then plated and filled. If another layer of SBU is added, the Micro-Via becomes buried Not all fabricators fill their Micro-Vias, but at Stream PCB, we fill the Micro-Vias with solid metal to ensure stronger connections and better thermal management, improving the overall reliability of the board. High-density I/O components sometimes require Via-In-Pads (VIP) to connect traces to all solder pads. When VIPs are used, filling the Micro-Via helps maintain a smooth pad, allowing for better reflow of solder. Filling also allows Micro-Vias to be stacked on top of each other, connecting three or more layers of foil, which further enhances the density of the circuit. Contact Stream PCB for more information about HDI technology at sales@streampcb.com.

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