Stacked microvias can be vulnerable to interface separation under high thermal expansion ($z$-axis CTE). To ensure long-term interconnect reliability: (1) We apply plasma dry etching combined with chemical permanganate desmear to clean microvia bottoms down to the target pad; (2) We run automated vertical continuous plating (VCP) with specialized copper filling additives to yield dimple depths < 5 µm; and (3) Every production batch undergoes solder float testing (288°C for 10 seconds, 3 cycles) and metallurgical microsectioning under IPC-6012 Class 3 criteria.

We achieve fine line width and spacing down to 40 µm / 40 µm (1.6 mil / 1.6 mil) on volume production using German Laser Direct Imaging (LDI) and automated vacuum etching compensation systems. For high-speed digital and RF lines, we simulate stackups using Polar SI9000 field solvers and maintain single-ended (50Ω) and differential (90Ω, 100Ω) controlled impedance tolerances strictly within ±5%, verified 100% via panel-level Time-Domain Reflectometry (TDR) coupon testing.

VIPPO (Via-in-Pad Plated Over), also known as POFV (Plated Over Filled Via), is a process where microvias or through-vias located directly inside component solder pads are vacuum-plugged with non-conductive epoxy resin, thermally cured, planarized flush via ceramic grinding, and electroplated with copper. This creates a flat, solid metallic surface (< 15 µm coplanarity variation), eliminating solder drainage into via barrels during reflow and allowing microvias to sit directly beneath 0.30 mm to 0.40 mm pitch BGA pads.

Utilizing German multi-beam CO2 and UV laser systems, we achieve microvia hole diameters down to 50 µm to 75 µm (2 to 3 mil). Our standard microvia aspect ratio is maintained at 0.8:1 to 1:1, which ensures optimum chemical fluid exchange during desmear and enables 100% void-free electroplated copper filling. For mechanical buried core vias, we support drill sizes down to 0.15 mm (6 mil).

We fabricate a complete spectrum of HDI builds from standard 1+N+1 (Type I) and 2+N+2 (Type II) up to 3+N+3 and Any-Layer HDI (ELIC - Every Layer Interconnect, Type IV) up to 14+ layers. Our manufacturing supports stacked microvias, staggered microvias, and buried-via-in-core constructions. Our DFM engineering team performs stackup symmetry analysis, dielectric prepreg selection, and thermal balance checks to ensure warpage remains strictly < 0.5% on finished panels.