What is Microvia in PCB Manufacturing
A microvia is a laser-drilled conductive aperture with a maximum diameter of 0.2mm, engineered for connecting 1–2 adjacent layers on microvia PCBs. Unlike conventional through-holes or HDI’s multi-layer interconnect vias, our microvia PCB manufacturing processes prioritize filling and plating integrity over overall board density. Each microvia is precision-machined into a conical frustum shape, a design that enhances both electrical conductivity and mechanical stability. Distinct from HDI microvias— which are optimized for high-layer count connectivity— standalone microvia PCBs serve as a precision upgrade for standard PCB architectures, elevating reliability in compact, low-layer electronic devices.
HDI Microvia Fabrication
Depending on the size of the vias, they can be mechanically drilled and plated (followed by stacking and pressing each layer), or they can be formed with a high-power laser. The latter process is constantly being improved and is preferred in high volume PCB manufacturing thanks to its high throughput. New advances in laser drilling techniques are pushing microvia sizes down to as small as 15 µm.
After drilling and cleaning, the via hole is plated, either with a sputtering process, electrolytic deposition, or electroless copper plating process. The goal in the plating process is to prevent the formation of voids, dimples, bumps, or any other structural defect in the filled via. Voids are also a reliability concern as stress can concentrate around the edge of the void where copper is thinner if stress is applied to the via structure.
During fabrication, laser-drilled microvias have a lower potential for manufacturing defects than normal vias. Mechanically-drilled microvias can have defects due to drill vibration as the drill wears out, and mechanical microvia drilling is only useful down to 6 to 8 mil diameters, depending on the fabricator’s tooling .
Via In Pad
Perhaps one of the greatest benefits of via fill is the option to implement via in pad.This process is becoming more and more popular and preferred as opposed to using the traditional “dog bone” method to transfer signal from the BGA, through the via, and on to inner layers. In this process, also known as active pad, vias are filled, planarized, plated over with copper. While the Via-In-Pad process does increase cost there can be significant benefits over conventional through hole technology.
Staggered Microvias
Like stacked vias, staggered vias also connect different layers of the board. However, they are never in direct contact with each other as their drill axes are separate, which offsets their position on adjacent layers.
Staggering the microvias involves fewer design steps. Because the drilled hole is not directly above the one below it, laser-drilled staggered vias do not need copper filling. This makes the design less complicated.
While designing a staggered via structure, the spacing between the laser-drilled holes is the primary concern. The possibility of the staggered via design depends on the vertical distance between the centers of two adjacent microvias. A viable staggered design requires the vertical separation to be more than the diameter of the microvia.
•Blind vias, buried vias, Ultra HDI PCB
•High frequency low loss PCB material
•Low loss high speed PCB materials
•R-5775, R-5785, R-5795, TU-872 SLK , TU-872 SLK SP, TU 933+, I-Tera MT40, Astra MT77, Tachyon 100G material
•EM-888, EM-888(S), EM-888(K), EM-526, EM-528, EM-528K, IT-968, IT-968 SE, IT-988G, IT-988G SE material
