PCB & PCBA Manufacturer
FPC PCB – FPC Circuit Board for High-Density Interconnect
As electronic devices become smaller, thinner, and more powerful, the demand for high-density interconnect (HDI) capabilities in flexible circuits has grown dramatically. Standard flex PCBs with 1-2 layers and 6/6 mil trace/space are no longer sufficient for today’s compact designs.
Our FPC PCB for high-density interconnect combines the space-saving benefits of flexible circuits with the fine-pitch capabilities of HDI technology – including 3/3 mil trace/space, 0.10mm microvias, and multi-layer flexible construction (up to 6 layers) .
What is High-Density Interconnect (HDI) FPC?
| Feature | Standard FPC | HDI FPC (Our Capability) |
|---|---|---|
| Trace width/spacing | 6/6 mil or larger | 3/3 mil or finer (2 mil available) |
| Via size | 0.20mm mechanical | 0.10mm laser microvias |
| Layer count | 1-2 layers | 4-6 layers (8 on request) |
| Component density | Low to medium | High to very high |
| Board thickness | 0.1-0.2mm (1-2 layer) | 0.2-0.5mm (4-6 layer) |
| BGA pitch support | >0.5mm (not recommended) | 0.4mm and below |
Why High-Density Interconnect for FPC?
| Benefit | How HDI FPC Delivers |
|---|---|
| More routing in less space | 3/3 mil traces vs. 6/6 mil = 2x routing density |
| Smaller vias | 0.10mm microvias save 75% area vs. 0.20mm |
| More layers for complex circuits | 4-6 layers for dense BGA fanout |
| Eliminates multiple boards | One HDI FPC replaces several rigid boards |
| 3D packaging capability | Folds to fit curved enclosures |
| Signal integrity | Continuous traces – no connectors |
HDI FPC – Technical Specifications
| Parameter | Our HDI FPC Capability |
|---|---|
| Layer count | 1 to 6 layers (8 on request) |
| Min trace width/spacing | 3 mil / 3 mil (0.075mm) – 2 mil available |
| Min drill size (mechanical) | 0.15mm |
| Min drill size (laser microvia) | 0.10mm (0.08mm on request) |
| Copper weight | 0.5 oz or 1 oz |
| Copper type | RA copper standard |
| Board thickness (1-2 layer) | 0.1mm – 0.2mm |
| Board thickness (4-6 layer) | 0.3mm – 0.5mm |
| Min coverlay opening | 0.2mm (0.15mm with laser) |
| Microvia types | Blind, buried, stacked, staggered |
| Surface finish | ENIG (preferred for HDI) |
| BGA pitch support | Down to 0.4mm (0.35mm on request) |
HDI FPC – Microvia Technology
| Via Type | Drill Method | Minimum Size | Best For |
|---|---|---|---|
| Mechanical via | Mechanical drill | 0.15mm | Cost-effective, larger designs |
| Laser microvia | CO2 or UV laser | 0.10mm | High-density, space-constrained |
| Stacked microvia | Laser + plating | 0.10mm | Multiple layer connections in same location |
| Staggered microvia | Laser + plating | 0.10mm | Layer-to-layer without stacking |
| Via-in-pad | Laser + fill | 0.10mm | BGA pads – saves space |
HDI FPC – Layer Stackup Examples
4-Layer HDI FPC with Microvias
| Layer | Function | Via Type |
|---|---|---|
| L1 (Coverlay) | Protection | – |
| L1 (Copper) | Signal / components | Microvia to L2 |
| Insulation | Polyimide core | – |
| L2 (Copper) | Ground plane | Mechanical or microvia |
| Insulation | Polyimide core | – |
| L3 (Copper) | Power plane | Mechanical via |
| Insulation | Polyimide core | – |
| L4 (Copper) | Signal / components | Microvia to L3 |
| L4 (Coverlay) | Protection | – |
6-Layer HDI FPC – available on request with stacked or staggered microvias.
Space Savings with HDI FPC
| Feature | Standard FPC | HDI FPC | Space Savings |
|---|---|---|---|
| Trace width/spacing | 6/6 mil | 3/3 mil | 50% reduction |
| Via diameter | 0.20mm | 0.10mm | 75% area reduction |
| Layers for same routing | 4 layers | 2 layers (finer traces) | 50% layer reduction |
| Board size (example) | 50mm x 30mm | 35mm x 20mm | ~50% area reduction |
| Component pitch support | >0.5mm | 0.4mm (0.35mm on request) | Finer BGA support |
HDI FPC vs. Standard FPC – Comparison
| Feature | Standard FPC | HDI FPC |
|---|---|---|
| Trace width/spacing | 6/6 mil | 3/3 mil (2 mil available) |
| Via size | 0.20mm | 0.10mm microvia |
| Layer count | 1-2 layers | 4-6 layers (8 on request) |
| BGA pitch support | >0.5mm | 0.4mm and below |
| Component density | Low-medium | High-very high |
| Board thickness | 0.1-0.2mm | 0.2-0.5mm |
| Cost | Lower | Higher (finer features = more processing) |
| Best for | Simple flex circuits | Miniaturized products, smartphones, wearables |
Applications for HDI FPC
| Application | Why HDI FPC is Required |
|---|---|
| Smartphone | Extreme space constraints, fine-pitch BGA (0.4mm) |
| Smartwatch / fitness band | Tiny form factor, high component density |
| Hearing aid | Ultra-compact, fine traces (2/2 mil) |
| Medical implantable-adjacent | Small size, high reliability |
| Endoscope camera module | High-density interconnects in small tip |
| AR/VR glasses | Thin, lightweight, dense routing |
| Drone / UAV flight controller | Weight reduction, space efficiency |
| Miniature sensor module | Small footprint, multiple signals |
| 4K/8K camera module | High-speed signals, dense BGA fanout |
| RF module (5G, WiFi 6/7) | Controlled impedance, fine pitch |
Design Guidelines for HDI FPC
| Design Element | HDI FPC Recommendation | Why |
|---|---|---|
| Trace width/spacing | 3/3 mil minimum | Enables higher routing density |
| Via type | Laser microvias (0.10mm) | Saves space vs. mechanical vias |
| Microvia fill | Copper-filled for via-in-pad | Supports BGA soldering |
| BGA fanout | Microvias under BGA pads | Maximizes routing channels |
| Layer count | 4-6 layers for complex routing | Distributes signals efficiently |
| Stackup symmetry | Balanced construction | Prevents warpage |
| Bend radius | ≥30x thickness (dynamic) | Prevents copper fatigue |
| Via placement | Avoid bend areas | Vias crack under flex stress |
HDI FPC – BGA Fanout Strategies
| BGA Pitch | Recommended HDI FPC Approach |
|---|---|
| 0.5mm | 2-4 layer FPC with microvias |
| 0.4mm | 4-6 layer FPC with via-in-pad microvias |
| 0.35mm | 6+ layer FPC with stacked microvias (contact us) |
| 0.3mm | Specialized process – discuss with engineering |
Why Choose Our HDI FPC Manufacturing?
| Feature | What You Get |
|---|---|
| 3/3 mil trace/spacing | Fine-pitch capability for miniaturization |
| 0.10mm microvias | Space-saving via technology |
| 4-6 layer flex | High-density routing in flexible construction |
| RA copper standard | Reliable for dynamic flexing |
| Via-in-pad capability | BGA fanout under the pad |
| Engineering support | DFM review for HDI flex designs |
| ISO9001 & UL certified | Quality guaranteed |
Order Process for HDI FPC
Upload Gerber files – specify HDI requirements (3/3, microvias, stackup)
Free DFM review – we verify fine traces, microvia registration, stackup
Receive quotation – based on HDI complexity
First article (recommended) – 5-10 pieces for validation
Production – built with HDI processes
100% electrical test – including microvia continuity
Secure shipping
Designing a high-density flexible circuit? Contact us for DFM review. We help optimize trace routing, microvia placement, and stackup for manufacturability.
