Flex PCBs – High-Density Flexible PCB Manufacturing

Flex PCBs – high-density flexible PCB manufacturing
Fine pitch capability – 3 mil / 3 mil trace width/spacing
High layer count – up to 6 layers in flexible construction
Small via technology – 0.10mm laser drilled microvias
RA copper standard – rolled annealed for reliability
High component density – for compact electronic devices
Ideal for miniaturization – smartphones, wearables, medical
Surface finish options – ENIG, Immersion Silver, OSP
Prototype to production – no MOQ for prototypes
ISO9001 & UL certified – quality you can trust

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Flex PCBs – High-Density Flexible PCB Manufacturing

As electronic devices become smaller, thinner, and more feature-rich, the demand for high-density flexible PCBs continues to grow. Standard flex PCBs with 1-2 layers and 6/6 mil trace/space are no longer sufficient for today’s compact designs.

Our high-density flex PCB manufacturing capabilities include fine-pitch traces (3/3 mil) , multi-layer flexible construction (up to 6 layers) , and microvias (0.10mm laser drilled) – enabling you to pack more functionality into less space.

What is High-Density Flex PCB?

Feature	Standard Flex PCB	High-Density Flex PCB
Trace width/spacing	6/6 mil or larger	3/3 mil or finer
Layer count	1-2 layers	4-6 layers (up to 8 on request)
Via size	0.20mm mechanical	0.10mm laser microvias
Component density	Low to medium	High to very high
Board thickness	0.15-0.3mm	0.2-0.5mm (more layers)
Typical applications	Simple flex, sensors	Smartphones, wearables, medical

High-Density Flex PCB Capabilities

Parameter	Our Capability
Layer count	1 to 6 layers (8 layers 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)	0.10mm (microvia)
Copper weight	0.5 oz or 1 oz (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
Surface finish	ENIG (preferred), Immersion Silver, OSP
Stiffeners	FR4, polyimide, metal
EMI shielding	Silver ink, copper layer, shielding film

High-Density Flex – Design Considerations

Design Element	High-Density Recommendation	Why
Trace width/spacing	3/3 mil minimum	Enables higher routing density
Via type	Laser microvias (0.10mm)	Saves space vs. mechanical vias
Via placement	Avoid bend areas	Vias crack under flex stress
Copper weight	0.5 oz preferred	Thinner copper = finer traces
Layer count	4-6 layers for complex routing	Distributes signals efficiently
Stackup symmetry	Balanced construction	Prevents warpage
Component placement	Rigid sections or stiffener areas	Flex too thin for heavy parts

High-Density Flex – Layer Stackup Examples

4-Layer High-Density Flex Stackup

Layer	Material	Thickness	Function
Coverlay	Polyimide	0.5 mil	Protection
L1 (Copper)	RA copper, 0.5 oz	0.7 mil	Signal / component
Adhesive	Acrylic	0.5 mil	Bonding
Polyimide core	DuPont Kapton	1 mil	Insulation
L2 (Copper)	RA copper, 0.5 oz	0.7 mil	Ground plane
Adhesive	Acrylic	0.5 mil	Bonding
Polyimide core	DuPont Kapton	1 mil	Insulation
L3 (Copper)	RA copper, 0.5 oz	0.7 mil	Power plane
Adhesive	Acrylic	0.5 mil	Bonding
L4 (Copper)	RA copper, 0.5 oz	0.7 mil	Signal / component
Coverlay	Polyimide	0.5 mil	Protection
Total thickness		~0.4mm

6-Layer High-Density Flex Stackup – available on request.

Microvia Technology for High-Density Flex

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
Staggered microvia	Laser + plating	0.10mm	Layer-to-layer without stacking

Microvias save significant space – a 0.10mm microvia uses ~70% less area than a 0.20mm mechanical via.

Space Savings with High-Density Flex

Feature	Standard Flex	High-Density Flex	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

Applications for High-Density Flex PCB

Application	Why High-Density Flex is Required
Smartphone	Extreme space constraints, fine-pitch BGA connections
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	Weight reduction, space efficiency
Miniature sensor module	Small footprint, multiple signals

Flexible PCB vs. High-Density Flex – Comparison

Feature	Standard Flex PCB	High-Density Flex PCB
Trace width/spacing	6/6 mil	3/3 mil (2/2 mil available)
Maximum layers	1-2 layers	4-6 layers (8 on request)
Via size	0.20mm	0.10mm microvia
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 circuits, sensors	Miniaturized products, smartphones, wearables

Manufacturing Challenges for High-Density Flex

Challenge	Our Solution
Fine trace etching	High-resolution imaging, controlled impedance
Microvia registration	Laser drilling with vision alignment
Layer-to-layer alignment	Precision tooling, automated optical alignment
Coverlay alignment (fine openings)	Laser-cut coverlay, tight registration
Yield management	Statistical process control, 100% AOI

Why Choose Our High-Density Flex PCB 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
Laser coverlay	Precise openings for fine-pitch components
Engineering support	DFM review for high-density designs
ISO9001 & UL certified	Quality guaranteed

Order Process for High-Density Flex PCB

Upload Gerber files – specify high-density requirements (trace/space, microvias)
Free DFM review – we verify fine traces, microvia registration, stackup
Receive quotation – based on density and complexity
First article (recommended) – 5-10 pieces for validation
Production – built with high-density processes
100% electrical test – including microvia continuity
Secure shipping

Designing a high-density flex PCB? Contact us for DFM review. We help optimize trace routing, via placement, and stackup for manufacturability.

Q1: What is the minimum trace width and spacing for high-density flex?

Capability	Minimum	Recommended for production
Trace width	2 mil (0.05mm)	3 mil (0.075mm)
Trace spacing	2 mil (0.05mm)	3 mil (0.075mm)

3/3 mil is our standard high-density capability. 2/2 mil available upon request (higher cost, longer lead time).

Q2: What is the maximum number of layers in a flexible PCB?

Layer Count	Suitability
1-2 layers	Standard – most common
4 layers	High-density – available
6 layers	Very high-density – available (contact us)
8+ layers	Limited – discuss with engineering

Important: More layers = thicker board = larger minimum bend radius. For dynamic flex with 4+ layers, increase bend radius accordingly.

Q3: What are microvias and when should I use them?

A: Microvias are laser-drilled vias with diameter ≤0.15mm (typically 0.10mm).

Via Type	Diameter	Space Savings	Cost
Mechanical via	0.20-0.30mm	Baseline	Lower
Laser microvia	0.10mm	~75% area reduction	Higher

Use microvias when: Board space is extremely limited, you have fine-pitch BGAs, or you need to route many signals in a small area.

Q4: Can high-density flex be used for dynamic flexing?

A: Yes – but with limitations.

Layer Count	Dynamic Flex Suitability
1-2 layers (high-density)	Excellent – thin enough for dynamic flex
4 layers (high-density)	Acceptable – requires larger bend radius (≥40x thickness)
6 layers (high-density)	Limited – thicker, larger radius needed

For dynamic flex with high-density designs, we recommend 1-2 layers with 3/3 mil traces.

Q5: Is ENIG required for high-density flex?

A: ENIG is strongly recommended for high-density flex PCBs.

Finish	Suitability for High-Density	Why
ENIG	Best	Flat surface, fine-pitch compatible
Immersion Silver	Acceptable	Good but can tarnish
OSP	Acceptable	Short shelf life
HASL	Not recommended	Uneven surface, not fine-pitch compatible

ENIG is standard for all our high-density flex orders.

Q6: How does high-density flex compare to rigid PCB for miniaturization?

Feature	Rigid PCB	High-Density Flex PCB
Fine traces (3/3 mil)	Yes	Yes
Microvias (0.10mm)	Yes (HDI)	Yes
3D packaging capability	No	Yes (folds)
Weight	Heavier	Lighter
Connectors needed	Yes (board-to-board)	No (flex connects sections)

High-density flex offers the same fine-pitch capabilities as HDI rigid, plus the ability to fold and bend.

Q7: What is the typical lead time for high-density flex?

A: High-density flex requires more processing steps.

Quantity	Typical Lead Time
Prototype (5-20 pieces)	10-12 working days
Pilot (21-100 pieces)	12-15 working days
Production (101-1,000+ pieces)	15-18 working days

Microvias and fine traces add 2-3 days vs. standard flex.

Q8: What is the minimum order quantity for high-density flex?

A: No MOQ for prototypes – we accept as few as 5 pieces.

Quantity	We Accept
5-20 pieces (prototype)	Yes – for design validation
21-100 pieces (pilot)	Yes
100+ pieces (production)	Yes

For designs with 3/3 mil traces or microvias, we strongly recommend a prototype order first.

Q9: Can you combine high-density flex with stiffeners?

A: Yes – stiffeners are commonly used on high-density flex for connector or component support.

Stiffener Type	Best For
FR4 (0.1-0.3mm)	ZIF connectors, fine-pitch components
Polyimide (0.05-0.1mm)	Thin applications
Metal (0.1-0.2mm)	Mechanical support

Stiffeners must be placed outside bend areas.

Q10: How do I get started with a high-density flex design?

A: Recommended workflow:

Design for 3/3 mil trace/spacing – use CAD rules to ensure consistency
Use microvias for dense BGA fanout – 0.10mm laser vias
Keep flex layers to 1-2 if possible – thinner = better flex life
Avoid vias in bend areas
Send Gerber files – specify high-density requirements
Free DFM review – we check trace/space, microvia registration
Order prototype (5-10 pieces) – validate before mass production

We offer free DFM review for high-density flex designs – we verify trace/space, microvia registration, and stackup.

Shipping Terms

Shipping costs are paid by the buyer.
We normally ship via DHL, UPS, FedEx, or TNT.
Alternatively, you may provide your own courier account or arrange delivery to your freight forwarder in China.

For large-volume orders, sea freight is available.

Delivery to Port (FOB Terms)

When shipping to a port, Tengxinjie is responsible for transporting the goods to the departure port.
All customs clearance, ocean freight, insurance, and onward transportation after that point are the responsibility of the buyer.

Tengxinjie can recommend reliable local freight forwarders upon request.
With the buyer’s authorization, Tengxinjie may also assist in coordinating shipping, with all related costs charged to the buyer.

Notice

The above shipping information is for reference only.
Tracking details and shipment updates will be provided once the order has been dispatched.

PCBA Shipping Delivery

Tags:3 mil trace flex PCB 4 layer flex PCB Fine Pitch Flex PCB Flex PCB Flex PCBs HDI flexible circuit board High-Density Flex PCB High-Density Flexible PCB Manufacturing Microvia Flex PCB Miniaturization flex PCB Multi-layer Flex PCB

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