Ultra-HDI PCB Manufacturing
Ultra-fine traces. High-density routing. Advanced PCB fabrication.
Sierra Circuits offers industry-leading Ultra-HDI (UHDI) PCB manufacturing, pushing the boundaries of miniaturization and signal integrity. Our advanced processes support ultra-fine feature sizes essential for next-generation semiconductor, aerospace, and medical applications.
With mSAP (modified Semi-Additive Process) technology, we achieve 2 mil (50 µm) trace and space with exceptional precision and trapezoidal trace profile control. All boards are manufactured in the USA at our state-of-the-art facility in Silicon Valley.
Ultra-HDI PCB Specifications
PCB Type
Ultra-HDI Rigid, Flex, and Rigid-Flex
Max Layers
Up to 30+ Layers
UHDI Layers
Any Layer HDI / mSAP Technology
Min Trace/Space
2 mil (50 µm)
Board Size
Up to 18" x 24"
Technology
Modified Semi-Additive Process (mSAP)
Copper Plating
Pulse Plated Copper / SAP
Manufacturing Location
USA (Sierra Circuits)
Trace and Copper Clearances
Trace to Trace
2 mil (50 µm)
Trace to Pad
2 mil (50 µm)
Pad to Pad
2 mil (50 µm)
Min Hole to Trace
5 mil (125 µm)
UHDI Materials
- Isola family: 185HR, 370HR, P95, P96, I-Tera MT40, Tachyon 100G, Astra MT77
- Panasonic family: Felios, Megtron 6, Megtron 7
- AGC (Nelco) family: Meteorwave 8000, N4000-13EP, N4000-13, N4000-6, N4000-29
- Flat and spread glass are typically required for UHDI routing zones
- PTFE materials are not available for UHDI fabrication at this time
Surface Finish Capabilities
UHDI Configuration
Available Surface Finishes
All UHDI Layers
ENEPIG (Recommend), ENIG+
UHDI Mixed Technology
ENEPIG, ENIG+, Hard Gold (selective only), Immersion Silver (selective only)
Note: Surface finishes for UHDI are subject to design review based on trace/pad configuration and density.
UHDI Design and Manufacturing Requirements
Fine-Line Routing: Designs are limited to specific fine-line routing zones to maintain yield and reliability.
Copper Thickness: Ultra-fine features require precise copper weight control, typically starting with thin base foils.
Microvia Structures: Stacked and staggered microvias must follow specific aspect ratio guidelines for reliable plating.
Copper Distribution: Uniform copper density across the panel is critical for consistent mSAP etching results.
Power Routing: Heavy power/ground requirements should be managed on non-UHDI layers where possible.
Stack-up Design: Symmetrical stack-ups are required to prevent warping during multiple lamination cycles.
Panel Design: All UHDI designs are processed on standard Sierra Circuits panels for optimal manufacturing control.
Production Lead Times
Ultra-HDI PCB lead times are highly dependent on the total layer count and the number of sequential lamination cycles required by the design. For planning purposes, an estimate of one week per lamination cycle should be used. Final production schedules are confirmed during the technical quotation process based on the complexity and volume of the order.
U.S. UHDI PCB Manufacturing
All Ultra-HDI PCBs are manufactured exclusively by Sierra Circuits in the United States. Our vertically integrated process includes comprehensive engineering review, advanced fabrication, precise automated optical inspection (AOI), and electrical testing. All quotations, orders, and technical support are handled directly by Sierra Circuits' domestic engineering team.
Certifications & Registrations
ITAR
ISO 13485:2016
ISO 9001:2015
NIST
UL
RoHS
REACH
IPC-A-600 Class 3
AS9100D
MIL-PRF-31032
J-STD-001ES