PCB Materials Guide: FR4 vs Aluminum vs Flex vs Rogers

Why I Wrote This Guide

After 15+ years in PCB manufacturing and reviewing thousands of customer designs, I've noticed something: material selection is where most engineers either nail it or completely miss the mark. I've seen $50,000 RF projects fail because someone used FR4 "to save money." I've also seen companies waste budget on Rogers material for a simple LED driver that would've worked fine with standard FR4.

This guide is my attempt to give you the straight talk on PCB materials—no marketing fluff, just real-world experience from someone who's seen what works and what doesn't.

Quick Comparison: All 4 Materials at a Glance

Before we dive deep, here's your cheat sheet:

**Hommer's Take**: If you're unsure which material you need, you probably need FR4. Seriously. It handles 80% of applications just fine.

FR4: The Workhorse of the Industry

What Is FR4?

FR4 (Flame Retardant, Grade 4) is a composite material made from woven fiberglass cloth and epoxy resin. It's been the backbone of the electronics industry since the 1960s—and for good reason.

Why Everyone Uses FR4

Pros: - ✅ Extremely cost-effective (baseline for all pricing) - ✅ Readily available worldwide - ✅ Supports 1 to 40+ layers - ✅ Well-understood manufacturing processes - ✅ Good mechanical strength - ✅ Decent electrical insulation

Cons: - ❌ Poor thermal conductivity (0.3 W/mK) - ❌ High signal loss above 1-2 GHz - ❌ Dk varies with frequency (±10% tolerance) - ❌ Higher moisture absorption

When to Use FR4

FR4 is your default choice for: - Consumer electronics - Industrial control systems - Low-frequency analog circuits - Digital circuits under 1 GHz - Prototype PCBs (fast and cheap iteration) - General-purpose applications

FR4 Variants Worth Knowing

For our HDI PCB services, we typically recommend High-Tg FR4 as the baseline.

Aluminum PCB (MCPCB): The Thermal Champion

What Is Aluminum PCB?

Metal Core PCB (MCPCB) uses an aluminum substrate instead of traditional FR4. The structure is simple: copper circuit layer → dielectric layer → aluminum base.

The Thermal Advantage Is Real

Here's a number that matters: aluminum conducts heat 600x better than FR4.

The dielectric layer is the bottleneck, but even so, aluminum PCBs dissipate heat 3-10x more efficiently than FR4.

When Aluminum Makes Sense

Perfect applications: - LED lighting (the #1 use case) - Power electronics - Motor drivers - Automotive lighting - Any design with components that run hot

Not suitable for: - Multilayer designs (max 4 layers practical) - High-frequency circuits - Complex mixed-signal designs

Check our aluminum PCB capabilities for detailed specifications.

Real Cost Analysis

**Hommer's Reality Check**: Yes, aluminum PCBs cost 2-3x more than FR4 per unit. But here's what most cost calculators miss—if you're designing LED products, you'd need to add a separate heatsink to FR4 anyway. An aluminum PCB often eliminates that cost entirely, plus simplifies assembly.

Same total cost, but the aluminum solution is more reliable with better thermal performance.

Flex PCB (Polyimide): The Shape-Shifter

What Is Flex PCB?

Flexible PCBs use polyimide (PI) film instead of rigid fiberglass. This allows the board to bend, fold, and conform to 3D shapes.

Key Properties of Polyimide

Types of Flex Circuits

1. **Single-sided flex**: Simplest, lowest cost
2. **Double-sided flex**: More routing options
3. **Multilayer flex**: Up to 12 layers
4. **Rigid-flex**: Best of both worlds—see our [rigid-flex PCB service](/services/flex)

When to Use Flex

Flex PCBs excel in: - Wearables and medical implants - Folding/sliding mechanisms - Camera modules - Aerospace (weight reduction) - Automotive (engine compartment) - Any application with space constraints or movement

The Real Cost of Flex

Flex PCBs cost 4-6x more than equivalent FR4. But consider this:

Traditional approach with FR4: - 3 separate PCBs - 2 cable assemblies - 4 connectors - Multiple assembly steps

Flex PCB approach: - 1 integrated flex circuit - 0 cables - 0 connectors - Single assembly step

I've seen projects where switching to flex actually *reduced* total system cost by 30% while improving reliability.

Rogers: The High-Frequency King

What Is Rogers Material?

Rogers Corporation produces specialized high-frequency laminates that outperform FR4 at frequencies above 500 MHz. These materials use ceramic-filled PTFE or hydrocarbon systems instead of epoxy-glass.

The Numbers That Matter

That Dk tolerance is everything for RF design. A 10% variation in FR4 means your 50Ω trace might actually be 45Ω or 55Ω. With Rogers, you hit your target impedance consistently.

Signal Loss Comparison

At 10 GHz over a 10cm trace: - FR4: ~3 dB loss - Rogers RO4350B: ~0.8 dB loss

That's nearly 4x less signal degradation. For a radar module or 5G antenna, this difference determines whether your product works or doesn't.

Rogers Product Lines

For most commercial projects, RO4350B is the sweet spot—good performance at a (relatively) reasonable price.

Our RF/high-frequency PCB service supports all major Rogers materials.

Hybrid Stackups: The Smart Approach

**Hommer's Pro Tip**: You don't always need 100% Rogers. A hybrid stackup—Rogers on outer layers for RF traces, FR4 on inner layers for power/ground—can cut costs by 40-50% while maintaining RF performance.

This is what we typically recommend for cost-sensitive 5G and WiFi 6 designs.

Head-to-Head: Making the Right Choice

FR4 vs Aluminum

FR4 vs Rogers

Flex vs Everything Else

Material Selection Decision Tree

Not sure where to start? Follow this:

Step 1: Does your circuit need to bend or fold? - Yes → Flex PCB or Rigid-Flex - No → Continue

Step 2: Does your design have high heat dissipation (>5W concentrated)? - Yes → Aluminum MCPCB - No → Continue

Step 3: Does your circuit operate above 1 GHz? - Yes → Rogers or high-performance FR4 - No → Standard FR4

Step 4: Is impedance control critical (±5% or better)? - Yes → Rogers or FR408HR - No → Standard FR4

When in doubt, send us your design files for a free DFM review. We'll tell you exactly what material makes sense.

Cost Optimization Strategies

1. Don't Over-Specify

I see this constantly: engineers specify Rogers material "just to be safe" for a 433 MHz remote control. FR4 handles that frequency just fine. Use the simplest material that meets your requirements.

2. Consider Total System Cost

A $2 PCB that needs $5 in additional heatsinks and mechanical parts isn't cheaper than a $4 aluminum PCB that eliminates all of that.

3. Prototype Smart

Prototype with FR4 first to validate your design, then switch to specialized materials for production if needed. Don't prototype on Rogers—the lead time and cost will slow your development cycle.

4. Volume Matters

*Approximate pricing for 100x100mm, 2-layer*

At volume, even Rogers becomes reasonably affordable.

FAQ

Can I mix materials in one PCB?

Yes! Hybrid stackups are common. You can combine Rogers outer layers with FR4 inner layers, or integrate flex sections into rigid boards (rigid-flex).

What's the minimum order for specialty materials?

At PCB Portugal: - FR4: No MOQ (even 1pc) - Aluminum: No MOQ - Flex: 5 pcs minimum - Rogers: 5 pcs minimum

How do I specify materials in my Gerber files?

Include a README or fabrication notes specifying: - Material type (e.g., "Rogers RO4350B") - Dielectric thickness - Copper weight - Any special requirements

Which material has the best shelf life?

All standard materials have 6-12 month shelf life when stored properly. Flex PCBs can be more sensitive to humidity—store in sealed bags with desiccant.

Conclusion: My Honest Recommendations

After manufacturing millions of PCBs across all material types, here's my summary:

Start with FR4 unless you have a specific reason not to. It's proven, affordable, and handles most applications.

Use Aluminum when thermal management is a primary concern—especially for LED products. The slightly higher cost usually pays for itself in reliability.

Consider Flex when physical constraints or connector elimination justify the investment. The cost premium is significant, but the design freedom is unmatched.

Reserve Rogers for genuine high-frequency applications where FR4 measurably fails to meet your specs. Don't use it "just because"—your budget will thank you.

Have questions about material selection for your specific project? Contact our engineering team or use our instant quote calculator to compare options.

Related Reading

If you found this material comparison useful, you might also want to check out these related guides:

• **[HDI vs Standard Multilayer PCB](/blog/hdi-vs-standard-multilayer-pcb)** - Once you have chosen your material, understand when HDI technology makes sense for your layer stackup
• **[PCB Testing Methods Compared](/blog/pcb-testing-methods-comparison)** - Learn how different materials affect your testing strategy (especially X-ray for aluminum thermal vias)
• **[Turnkey vs Consignment Assembly](/blog/turnkey-vs-consignment-pcba)** - Material availability can influence your assembly model choice

References

1. [IPC-4101](https://www.ipc.org/) - Specification for Base Materials
2. [Rogers Corporation Technical Resources](https://www.rogerscorp.com/advanced-electronics-solutions)
3. [DuPont Pyralux Flex Materials](https://www.dupont.com/electronic-materials.html)

*This guide was written by Hommer Zhao, founder of PCB Portugal, based on 15+ years of hands-on experience in PCB fabrication and assembly. Last updated: December 2024.*