Beyond Design: Skip-layer Routing—The Waveguide Structure That Makes 224G Possible
Designers Notebook: Old vs. New School System-level Packaging—Flip-Chip to Chiplets
Elementary, Mr. Watson: Builders of the Dream
The continuous push toward higher functionality, miniaturization, and performance in modern electronic devices—such as smartphones, wearables, and advanced computing platforms—has intensified the demand for high-density interconnect (HDI) printed circuit boards. Central to HDI performance is the reliable formation of blind microvias (BMVs), which serve as critical interlayer connections in modified semi-additive processes (mSAP).
As BMV geometries shrink and core materials become thinner (≤25 µm), conventional electrolytic copper plating systems encounter significant challenges: achieving sufficient copper coverage inside the via while minimizing unwanted surface deposition that inhibits fine line/space (L/S) capabilities. Furthermore, inconsistencies arising from glass fiber protrusions, copper overhang, wedge formations, and drilling variability can negatively impact via reliability.
To address these challenges, a newly developed electrolytic flash copper plating system introduces major innovations in anode design, electrolyte distribution, contamination control, and transport precision. These advancements collectively deliver superior uniformity, improved microvia copper structure, enhanced system sustainability, and lower cost of ownership.
Figure 1: Low copper thickness on top for good L/S capability and high copper thickness on bottom for good reliability.
Process Background and Core Advantages of Flash Plating
The previous generation of flash copper plating systems gained substantial industry adoption due to an efficient wet‑in‑wet integration between electroless copper deposition and electrolytic flash copper reinforcement. Key advantages of this approach include:
- Prevention of oxidation: Direct transition between process steps avoids drying-induced oxidation on electroless copper, preserving interface quality and improving metallurgical bonding.
- Enhanced BMV reliability: The process effectively reinforces copper in BMV wedges, masks glass protrusions, and levels irregular drilling defects, leading to durable via structures.
- Superior copper-to-copper epitaxy: A highly uniform crystallographic transition between electroless and electrolytic copper improves electrical and mechanical reliability.
These strengths form the performance baseline for the newly enhanced plating system.
To continue reading this article, which originally appeared in the May 2026 issue of I-Connect007 Magazine, click here.
