FR1 PCB Guide: Everything About This Low-Cost Circuit Board Material

Looking for an affordable PCB substrate for your single-layer board project? FR1 PCB material offers excellent value for cost-sensitive electronics. This comprehensive guide covers everything you need to know about FR1 specifications, applications, and when to choose it over FR4.

What is FR1 PCB?

If you’ve been designing PCBs for any length of time, you’ve probably encountered the term FR1 at some point. FR1 PCB is a flame-retardant laminate material made from cellulose paper impregnated with phenol-formaldehyde (phenolic) resin. The “FR” designation stands for “Flame Retardant,” while the “1” indicates it’s the original formulation in this category of materials.

In practical terms, FR1 is a hard, flat material consisting of a paper-based substrate with a thin layer of copper bonded to one side. This creates what we call a copper-clad laminate—the foundation for etching circuit traces. The material meets IPC-4101 /21 & /22 specifications and conforms to UL94V-0 flammability standards.

I’ve worked with FR1 boards extensively in consumer electronics projects where cost was the primary driver. What makes this material particularly useful is its combination of adequate electrical properties and significantly lower cost compared to FR4. For single-layer PCB designs that don’t require through-hole plating or high-frequency performance, FR1 often makes more sense from a manufacturing economics standpoint.

FR1 PCB Material Composition and Manufacturing

Understanding the material composition helps explain why FR1 PCB behaves the way it does in various applications. The manufacturing process involves several key steps:

Paper Base Preparation

High-quality cellulose paper serves as the core material, providing the mechanical structure and thickness. This paper-based construction is fundamentally different from the woven fiberglass used in FR4, which explains many of the performance differences between these materials.

Phenolic Resin Impregnation

The paper is impregnated with phenol-formaldehyde resin, which provides flame retardancy and binding properties. This phenolic resin gives FR1 its characteristic brown color and contributes to its self-extinguishing behavior when exposed to flame.

Copper Foil Lamination

A thin copper foil (typically 1 oz or 35μm) is bonded to one side under heat and pressure. The result is a single-sided copper-clad laminate ready for circuit fabrication. The standard thickness ranges from 1.5mm to 1.6mm, roughly equivalent to two or three credit cards stacked together.

Read more about FR materils:

FR1 PCB Technical Specifications

Before selecting any PCB material, you need hard numbers. Here’s the technical data for FR1 PCB that matters for design decisions:

Property	FR1 Value
Glass Transition Temperature (Tg)	130°C (266°F)
Dielectric Constant (Dk)	4.0 – 5.5 @ 1MHz
Flammability Rating	UL94 V-0
Standard Thickness	1.5mm – 1.6mm
Copper Weight	1 oz (35μm) typical
Maximum Operating Temperature	130°C
Moisture Absorption	Moderate to High
Thermal Conductivity	0.2 – 0.3 W/m·K
Comparative Tracking Index (CTI)	≥150V
Layer Configuration	Single-sided only
IPC Standard	IPC-4101 /21 & /22

FR1 vs FR2 vs FR3 vs FR4: Complete Comparison

One of the most common questions I get from junior engineers is about the differences between FR materials. Here’s the breakdown that actually matters for material selection:

Property	FR1	FR2	FR3	FR4
Base Material	Paper + Phenolic	Cotton Paper + Phenolic	Paper + Epoxy	Fiberglass + Epoxy
Tg (°C)	130	105	105-110	130-180
Cost (Relative)	Low ($)	Low ($)	Medium ($$)	Medium-High ($$$)
Layers Supported	Single	Single/Double	Single/Double	Multi-layer
Through-Hole	Poor	Poor	Fair	Excellent
High-Frequency	No	No	Limited	Yes
Moisture Resistance	Poor	Fair	Good	Excellent
Mechanical Strength	Low	Low-Medium	Medium	High
Pb-Free Soldering	No	No	Limited	Yes
Market Share	~5%	~3%	~2%	~90%

Key Takeaway: FR4 dominates because of its versatility, but FR1 PCB remains the go-to choice when you need the lowest possible material cost and your design is a simple single-layer board. The 60% cost savings compared to FR4 adds up quickly in high-volume production runs.

Advantages of FR1 PCB Material

Despite being the most basic FR-grade material, FR1 PCB offers several compelling advantages for the right applications:

• Cost-Effective: Approximately 40-60% cheaper than FR4, making it ideal for budget-conscious projects and high-volume consumer goods.
• Excellent Punchability: The paper core allows for die-cutting and punching without the fiberglass dust issues of FR4. Entire outlines, slots, and keyholes can be cut in milliseconds.
• Lightweight: Paper core is approximately 15% lighter than FR4 at the same thickness.
• Safe Machining: Unlike FR4 which produces hazardous glass-fiber dust when milled, FR1 can be machined with minimal safety concerns. Just keep debris away from eyes and lungs.
• Simplified Design: Single-layer construction means straightforward routing without complex via strategies.
• RoHS Compliant: Meets environmental regulations for restricted substances.
• Flame Retardant: Self-extinguishing properties (UL94 V-0) provide safety in consumer applications.

Limitations and Constraints of FR1 PCB

Being honest about material limitations saves headaches down the road. Here’s where FR1 PCB falls short:

• No Multilayer Support: Limited to single-sided configurations. If you need double-sided or multilayer, look elsewhere.
• Poor Through-Hole Performance: The paper substrate doesn’t hold up well to drilling and plating processes.
• Cannot Withstand Pb-Free Reflow: Peak temperatures of ≥245°C in lead-free soldering will damage the material. Use Sn-Pb wave soldering profiles <245°C.
• Higher Dissipation Factor: Signal loss becomes significant above approximately 30MHz, making it unsuitable for RF or high-speed digital applications.
• Moisture Sensitivity: Absorbs water in humid environments, causing swelling and Dk fluctuations. Not recommended for marine or outdoor applications.
• Lower Mechanical Strength: Avoid mounting heavy components like transformers or using press-fit connectors.
• Limited Temperature Range: Operating above 130°C will cause the board to soften and lose dimensional stability.

Best Applications for FR1 PCB

FR1 PCB shines in applications where cost matters more than performance margins. Based on real-world projects, here’s where this material makes the most sense:

Consumer Electronics

1. Remote controls and TV controllers
2. Basic calculators
3. Electronic toys and novelty items
4. Simple audio equipment
5. LED lighting fixtures

Power Electronics

1. Low-cost AC/DC adapters and chargers
2. Simple power supplies
3. 120V/230V appliance controls (with proper creepage distances)

Industrial and Other Applications

• Control panels with basic functionality
• Instrumentation displays
• Button interfaces and membrane switch backing
• Prototyping and hobbyist projects
• Educational electronics kits

Design Guidelines for FR1 PCB Projects

If you’ve decided FR1 PCB is right for your project, here are practical design considerations:

Trace and Spacing Recommendations

Parameter	Minimum	Recommended
Trace Width	0.2mm (8 mil)	0.3mm+ (12 mil+)
Trace Spacing	0.2mm (8 mil)	0.3mm+ (12 mil+)
Pad Size (SMD)	0.4mm	0.5mm+
Drill Size	0.6mm	0.8mm+
Board Edge Clearance	0.3mm	0.5mm+

Soldering Process Considerations

• Use Sn-Pb solder: Keep wave or selective solder profiles below 245°C.
• Avoid BGA packages: Heavy components and lead-free reflow are not compatible with FR1.
• Surface finish options: HASL (tin-lead), ENIG, and Immersion Silver all work with FR1.
• Solder mask: Standard LPI solder mask can be applied for trace protection.

FR1 PCB Cost Analysis

Let’s talk numbers. The cost advantage of FR1 PCB becomes significant in volume production:

Factor	FR1	FR4
Raw Material Cost	~$0.90/sq ft	~$2.75/sq ft
Relative Cost	100% (baseline)	~300%
Processing	Simpler (punch/die-cut)	CNC routing required
Typical Scrap Rate	~3%	~0.5%
Best For	10,000+ units	All volumes

Pro Tip: For production runs exceeding 10,000 units with simple single-layer designs, the material cost savings with FR1 often justify any increase in handling or quality control overhead.

How to Specify FR1 PCB for Manufacturing

When ordering FR1 PCB from a manufacturer, include these specifications in your documentation:

• Material: FR1 per IPC-4101/21 or /22
• Thickness: 1.6mm (or specify)
• Copper Weight: 1oz (35μm)
• Surface Finish: HASL (Sn-Pb), ENIG, or Immersion Silver
• Solder Mask: Green LPI (or specify color)
• Silkscreen: White (single side)
• Quality Standard: IPC-A-600 Class 2 (or Class 3 if required)

Useful Resources and Downloads

For deeper technical information on FR1 PCB and related standards, these resources are worth bookmarking:

Resource	Description / Link
IPC-4101 Standard	Base materials specification for rigid PCB laminates – Available from IPC (shop.ipc.org)
IPC-TM-650 Test Methods	Testing procedures for PCB materials – IPC Association
UL 94 Flammability Standards	Flame retardant classification reference – UL Standards
DigiKey Datasheets	FR1 product datasheets from Bantam Tools and others – digikey.com
IPC-A-600 Acceptability	Visual quality standards for PCB inspection – IPC
RoHS Directive	Environmental compliance requirements – EU regulations

Frequently Asked Questions About FR1 PCB

Can FR1 PCB be used for double-sided boards?

No. FR1 PCB is designed exclusively for single-sided applications. The paper-based substrate doesn’t support the through-hole plating process required for double-sided connectivity. If you need double-sided or multilayer boards, FR4 is the standard choice, though FR2 can work for simple double-sided designs with limited via requirements.

What’s the difference between FR1 and FR2?

The primary difference is glass transition temperature. FR1 has a Tg of 130°C while FR2 is rated at 105°C. Both use paper-phenolic construction, but FR2 uses cotton paper instead of cellulose. In practice, most manufacturers who produce FR1 don’t also produce FR2 since the materials have similar costs and applications. FR1 is generally preferred when available because of its higher temperature tolerance.

Is FR1 PCB RoHS compliant?

Yes, standard FR1 PCB materials meet RoHS 2 and REACH requirements. However, keep in mind that FR1 cannot withstand lead-free reflow soldering temperatures (≥245°C), so you’ll need to use Sn-Pb solder processes which have their own compliance considerations depending on your target market.

Can I mill FR1 PCB on a desktop CNC machine?

Absolutely. FR1 is actually preferred for desktop PCB milling because it doesn’t produce the hazardous glass-fiber dust that FR4 generates. Use 0.003″ or 0.005″ PCB engraving bits for trace isolation and 1/32″ flat end mills for holes and outlines. Make sure the board is completely flat and secured with double-sided tape—Nitto tape works best for holding the material during milling.

What surface finishes work with FR1 PCB?

FR1 PCB supports several surface finishes: HASL (Hot Air Solder Leveling) with tin-lead is most common and cost-effective. ENIG (Electroless Nickel Immersion Gold) works well for better solderability and shelf life. Immersion Silver provides good performance for mixed-signal applications. OSP (Organic Solderability Preservative) is also an option for short-term storage before assembly.

Conclusion

FR1 PCB material has been serving the electronics industry for decades, and it continues to be relevant for cost-sensitive, single-layer applications. While FR4 dominates the market at 90%+ share, FR1 fills an important niche where material cost directly impacts product viability.

The key is understanding where FR1 makes sense: simple consumer electronics, toys, basic chargers, LED lighting, and high-volume products where every fraction of a cent matters. Where it doesn’t make sense: anything requiring through-holes, multilayer stackups, high-frequency signals, lead-free soldering, or operation in harsh environments.

For your next project, evaluate the technical requirements honestly. If a single-layer board with basic electrical performance meets your needs, FR1 PCB could save 40-60% on material costs—money that might be better spent elsewhere in your BOM.