Flexible PCB Microcircuits

Advances in electronics continue to push devices toward smaller form factors and higher data transmission speeds. Every flexible PCB microcircuit must fit within a defined space while remaining manufacturable, mechanically stable, and cost-effective. Achieving this balance requires careful attention to outline tolerances, circuit density, material selection, and process control.

As component sizes decrease, flexible microcircuits can integrate substantial functionality while also serving as passive interconnect structures. This makes them well-suited for applications where rigid boards cannot meet the required size, weight, or conformability constraints.

At a Glance: Flexible PCB Microcircuits

• Miniaturization with manufacturability: Flexible PCB microcircuits are designed to deliver high functionality in extremely small form factors while maintaining tight mechanical tolerances, controlled impedance, and cost-effective production.
• Precision flex for demanding applications: These designs support high circuit density, fine line and space geometries, and reliable electrical performance in use cases where rigid boards cannot meet size or conformability constraints.
• End-to-end engineering and production: Epec evaluates materials, bend tolerance, and stack ups through in-house design verification, prototyping, and scalable manufacturing to ensure repeatability and reliability across production volumes.

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How Small Can a Flexible PCB Be?

Application-specific requirements determine the minimum size of a flexible PCB microcircuit. Key considerations include mechanical tolerances, electrical performance targets, assembly constraints, and the need for reliable manufacturability.

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Miniature Flexible PCB Capabilities

Continuous electronics miniaturization has increased demand for flexible printed circuits with higher circuit density, improved signal performance, and enhanced mechanical reliability. Flexible PCB microcircuits enable compact, lightweight systems with complex interconnects that cannot be achieved with rigid circuit boards alone.

Epec's miniature flexible PCB technology is built to support precision and repeatability across diverse designs. Engineering teams evaluate electrical performance, bend radius tolerance, and material stack ups to help ensure designs meet customer specifications and applicable industry requirements. Full in-house capabilities support design verification, prototyping, and scalable production for both specialized low volume programs and higher volume applications.

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Miniature Flexible PCB Capabilities

The following table outlines our general capabilities for flexible microcircuits. However, every application is different so please contact us with your design questions so that we can review your application parameters.

Product	Miniature Flex Circuits
Smallest PCB Size	5mm x 5 mm
Line Width and Spacing	0.002" (0.05mm)
Copper Thickness	1/4 oz, 1/3 oz, 1/2 oz 1 oz, 2 oz, and higher
Via/ Drill Size
Minimum Drill (Mechanical) Hole Diameter	0.004" (0.1 mm)
Minimum Via (Laser) Size	2 mil (0.05 mm)
Minimum Micro Via (Laser) Size	3 mil (0.07 mm)
Solder Mask/Coverlay
Solder Mask Bridge Between Dam	3 mil (0.08 mm)
Solder Mask Registration Tolerance	2 mil (0.05mm)
Coverlay Registration	8 mil (0.20 mm)
PIC Registration	7 mil (0.18 mm)
Stiffener
Stiffener Registration	8 mil (0.28 mm)
Thickness Tolerance	10%
Smallest Stiffiner Size	0mm x 0mm
Impedance
Impedance	+/- 8%
Steel Rule Die (SRD))
Outline Tolerance	4 mil (0.1mm)
Minimum Radius	4 mil (0.1 mm)
Inside Radius	20 mil (0.51 mm)
Punch Minimum Hole Size	28 mil (0.7 mm)
Tolerance of Punch Hole Size	+/- 2 mil (0.051 mm)
Slot Width	20 mil (0.51 mm)
Tolerance of Hole to Outline	+/- 2 mil (0.05 mm)
Tolerance of Hole Edge to Outline	+/-3 mil (0.07mm)
Minimum of Trace to Outline	8 mil (0.20 mm)
Electrical Testing
Test Voltage	50 - 300V
Surface Finishes Available
Hard Gold, ENIG, ENEPIG, OSP, Immersion Silver, Immersion Tin, Plating Tin

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Applications for Flex Microcircuits

Epec's flexible PCB microcircuits support high performance and precision use cases across a wide range of industries, including:

• Semiconductor packaging and interconnect structures, such as chiponflex and system in package designs
• RF and microwave assemblies requiring controlled impedance signal routing
• High speed digital interfaces optimized for impedance matching and noise reduction
• Medical and bio-electronic devices with strict size and flexibility constraints
• Wearable electronics requiring ultra-thin, conformal circuitry
• Industrial and environmental sensors exposed to vibration, humidity, and temperature variation
• Aerospace and defense systems demanding lightweight and vibration-resistant interconnects
• Automotive electronics used in sensing, display, and battery-related systems
• Instrumentation and analytical equipment requiring repeatable electrical performance
• RFID tags and antenna designs, requiring compact, conformal integration

Manufacturing Quality and Repeatability

Advanced automated manufacturing, combined with rigorous quality control, supports consistent precision across Epec's flex microcircuit production. These processes enable tight tolerances, stable electrical performance, and robust mechanical reliability across a wide range of form factors.

The result is flexible circuitry well suited for demanding, space-constrained applications where performance and consistency are critical.

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Frequently Asked Questions

Quick Links

• What defines a flexible PCB microcircuit?
• What limits how small a flex microcircuit can be?
• Can flexible microcircuits support controlled impedance?
• Are stiffeners used in flex microcircuits?

What defines a flexible PCB microcircuit?

A flexible PCB microcircuit is a very small, high-density flex circuit designed to deliver electrical functionality while fitting within tight mechanical constraints.

What limits how small a flex microcircuit can be?

Size is limited by outline tolerances, line and space requirements, impedance control needs, and assembly considerations tied to the specific application.

Can flexible microcircuits support controlled impedance?

Yes. Controlled impedance can be maintained, including in high-volume applications, when trace geometry, materials, and processes are tightly controlled.

Are stiffeners used in flex microcircuits?

Small stiffeners may be added in localized areas to provide rigidity where needed for component mounting or interconnection.

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Customized Solutions That Meet Your Project's Needs

Epec combines design expertise, materials knowledge, and in-house manufacturing to deliver flexible PCB microcircuits that meet demanding size, performance, and reliability requirements. Contact our engineering team to review your application and discuss a custom solution.

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