IPC-WP/TR-584 Explained: Complete Guide to Halogen-Free PCB Materials and Flame Retardants

Few topics in PCB materials generate more confusion than “halogen-free.” Ask ten engineers what halogen-free means, and you’ll get ten different answers. Some think it means zero halogens. Others confuse it with RoHS compliance. Many don’t realize that the common FR-4 laminate sitting in their stockroom contains brominated flame retardants that, while perfectly legal, may not meet their customer’s environmental requirements.

IPC-WP/TR-584 exists to cut through this confusion. This white paper represents IPC’s official position on halogen-free materials for the electronics industry, developed over six years by a team spanning the entire electronics supply chain. It defines what “halogen-free” actually means, explains why the thresholds were set where they are, and addresses the common misconceptions that lead to specification errors and supply chain problems.

If you’re specifying PCB materials, qualifying suppliers, or trying to understand why your customer suddenly requires halogen-free boards, this document is essential reading.

What Is IPC-WP/TR-584?

IPC-WP/TR-584, officially titled “IPC White Paper and Technical Report on the Use of Halogenated Flame Retardants in Printed Circuit Boards and Assemblies (Correcting the Misunderstandings on ‘Halogen-Free’),” establishes IPC’s position on halogen content in electronics materials. The document was first released in 2003, with Revision A published in September 2007.

The document applies to materials for interconnecting electronics including copper-clad laminates, prepregs, resin-coated copper foils (RCC), flexible materials, and solder masks. It reflects the state of information and technology as of May 2007, though the fundamental definitions and thresholds remain the industry reference today.

Why Halogen-Free Matters

Halogens—specifically bromine and chlorine—have been used as flame retardants in PCB laminates for decades. They’re effective, economical, and well-understood. So why the push to eliminate them?

Environmental and Health Concerns

The problem isn’t halogens themselves, but what happens when halogenated materials burn or are improperly disposed of:

The EU’s RoHS Directive banned two specific brominated flame retardants—polybrominated biphenyls (PBB) and polybrominated diphenyl ethers (PBDE)—in 2006. However, RoHS does not ban all brominated flame retardants. Tetrabromobisphenol A (TBBPA), the most common flame retardant in FR-4 laminates, remains legal under RoHS.

This distinction is crucial: RoHS compliance does not equal halogen-free.

Market and Customer Requirements

Beyond regulations, market forces drive halogen-free adoption:

The “9-9-15” Rule: IPC-WP/TR-584 Halogen Thresholds

IPC-WP/TR-584 defines “halogen-free” using specific concentration limits, commonly called the “9-9-15” rule:

These thresholds didn’t appear arbitrarily. They emerged from negotiations between Japanese industry (represented by JPCA) and U.S./European stakeholders during the development of IEC 61249-2-21. The compromise balanced detection capabilities, manufacturing tolerances, and practical achievability.

Why Not Zero?

“Halogen-free” doesn’t mean zero halogens for several practical reasons:

The 900 ppm threshold represents a practical limit that ensures intentional halogenated flame retardants are absent while allowing for incidental trace content.

Which Halogens Are Covered?

While halogens include fluorine, chlorine, bromine, iodine, and astatine, IPC-WP/TR-584 focuses on bromine and chlorine because:

Fluorine’s exclusion is notable. PTFE-based high-frequency laminates contain fluorine as an intrinsic part of the resin system, not as a flame retardant. At the time IPC-WP/TR-584 was written, fluorine in PTFE was not considered an environmental or health concern, though this may change with evolving PFAS regulations.

Comparing Halogen-Free Standards

IPC-WP/TR-584 isn’t the only standard addressing halogen content. Understanding how it relates to other specifications prevents confusion:

The slight difference in JEDEC JS709 (1000 ppm vs. 900 ppm) reflects ongoing industry debates about harmonization. When specifying materials, always confirm which standard your customer requires.

Halogenated vs. Halogen-Free Flame Retardants

Understanding flame retardant chemistry helps explain why halogen-free materials behave differently.

Traditional Halogenated Flame Retardants

Brominated flame retardants work by releasing bromine radicals during combustion that interrupt the flame chemistry:

TBBPA remains the most common flame retardant in standard FR-4 laminates. It’s effective, well-characterized, and not currently banned. However, it doesn’t meet halogen-free requirements.

Halogen-Free Flame Retardant Alternatives

Halogen-free laminates typically use phosphorus-based, nitrogen-based, or combination flame retardant systems:

When phosphorus-containing resin burns, it decomposes into polyphosphoric acid that dehydrates the polymer surface, forming a protective carbonized char layer. This physically separates the fuel from oxygen and heat.

Halogen-Free PCB Material Properties

Halogen-free materials aren’t just “FR-4 without bromine.” The different flame retardant chemistry affects multiple material properties:

The reduced drill life is significant for PCB fabricators. Halogen-free laminates tend to be more rigid, accelerating drill wear. This cost gets passed through to the assembled board price.

Common Halogen-Free Laminate Materials

Major laminate suppliers offer halogen-free alternatives:

When selecting materials, verify that both the laminate AND the solder mask meet halogen-free requirements. A halogen-free laminate with standard solder mask doesn’t produce a halogen-free board.

Testing Methods for Halogen Content

IPC-WP/TR-584 references specific test methods for verifying halogen content:

The oxygen bomb combustion method followed by ion chromatography provides the most accurate results. The older semi-open flask method has been shown to underreport halogen content in some cases.

For incoming inspection, XRF (X-ray fluorescence) provides rapid screening but cannot definitively distinguish between halogen sources. A positive XRF result requires follow-up with combustion testing.

Read more IPC Standards:

MIL-PRF-38534: Hybrid Microcircuits Military Specification Guide for Engineers

MIL-PRF-31032: The Definitive Guide to Military-Grade PCB Requirements

MIL-PRF-19500: Military Semiconductor Device Specification Explained

MIL-PRF-123: High-Reliability Ceramic Capacitor Military Standard

MIL-I-46058CMIL-I-46058C: Military Conformal Coating Specification Complete Guide

MIL-HDBK-263: ESD Control Handbook & Implementation Guide

J-STD-075 Guide: PSL Classification for Passive Components & Assembly Process Limits

J-STD-035 Guide: Acoustic Microscopy for IC Package Inspection & Defect Detection

J-STD-033 Guide: MSD Handling, Floor Life, Baking & Dry Storage Requirements

J-STD-032 Explained: Ball Grid Array Ball Construction & Performance Specs

J-STD-027 Guide: Mechanical Outline Standard for Flip Chip & CSP Packages

J-STD-020 Guide: MSL Classification, Reflow Profiles & Moisture Sensitivity Testing

IPC/WHMA-A-620 Explained: Complete Guide to Cable & Wire Harness Standards

IPC-SG-141: Complete Guide to S-Glass Fabric Specifications for PCB Laminates

IPC-QF-143: Complete Guide to Quartz Fabric Specifications for RF/Microwave PCB Laminates

Specifying Halogen-Free Materials

When writing specifications for halogen-free PCBs:

What to Include

Common Specification Mistakes

Manufacturing Considerations

Switching to halogen-free materials affects both PCB fabrication and assembly:

PCB Fabrication

Assembly

Note that halogen-free flux requirements are separate from laminate requirements. A board assembled with halogen-free laminate but standard flux may not meet overall halogen-free requirements depending on customer specifications.

Useful Resources for IPC-WP/TR-584 Implementation

Official Standards and Documentation

Industry Resources

Related IPC Standards

Frequently Asked Questions About IPC-WP/TR-584

Is halogen-free the same as RoHS compliant?

No, and this is one of the most common misconceptions. RoHS restricts specific substances including two brominated flame retardants (PBB and PBDE), but it does not restrict all halogens. Tetrabromobisphenol A (TBBPA), the most widely used flame retardant in FR-4 laminates, is fully RoHS compliant but contains bromine at levels far exceeding halogen-free thresholds. A standard FR-4 board can be 100% RoHS compliant while containing 15-20% bromine by weight. Always specify halogen-free requirements separately from RoHS compliance.

Why does IPC-WP/TR-584 allow 900 ppm instead of requiring zero halogens?

The 900 ppm threshold reflects practical limitations in testing and manufacturing. Analytical test methods have detection limits around 50 ppm, with lab-to-lab variation that can exceed 100 ppm. Trace halogen contamination exists in many raw materials used in electronics manufacturing. Setting the limit at 900 ppm ensures that intentional halogenated flame retardants are absent while providing margin for incidental contamination and measurement uncertainty. Achieving absolute zero would require extraordinary measures with no additional environmental benefit.

Do I need halogen-free solder mask if my laminate is halogen-free?

Yes, if your requirement is for a halogen-free PCB assembly. Standard solder masks may contain halogenated compounds. Specifying only halogen-free laminate while using standard solder mask results in a board that doesn’t meet overall halogen-free requirements. Always specify that both laminate materials and solder mask must meet IPC-WP/TR-584 thresholds. Verify with your PCB supplier that they’re using qualified halogen-free solder mask, not just halogen-free laminate.

Does IPC-WP/TR-584 restrict fluorine in PTFE laminates?

No, the current version of IPC-WP/TR-584 focuses on bromine and chlorine only. Fluorine was excluded because, at the time the document was written, fluorine in PTFE laminates was not considered an environmental or health concern—the fluorine is intrinsic to the polymer structure, not added as a flame retardant. However, this may change. Evolving regulations around PFAS (per- and polyfluoroalkyl substances) could eventually affect PTFE materials. If your application specifically requires fluorine-free materials, you’ll need to specify this separately from IPC-WP/TR-584 compliance.

How do I verify that materials meet IPC-WP/TR-584 requirements?

Request test reports from your material suppliers showing halogen content tested per EN 14582 (oxygen bomb combustion) with analysis by ion chromatography. The report should show bromine ≤900 ppm, chlorine ≤900 ppm, and total Br+Cl ≤1500 ppm. For incoming inspection, XRF screening provides quick verification but positive results should be confirmed with combustion testing. Many laminate suppliers provide certificates of compliance that reference IPC-4101 slash sheets for halogen-free materials. Ensure your purchase orders specifically require halogen-free materials and request certification documentation.

Conclusion

IPC-WP/TR-584 provides the authoritative industry definition for halogen-free PCB materials. The “9-9-15” thresholds—900 ppm maximum bromine, 900 ppm maximum chlorine, 1500 ppm total—have become the global standard referenced by IEC, JPCA, and incorporated into IPC-4101 laminate specifications.

Understanding this document prevents the specification errors and supply chain confusion that arise from ambiguous halogen-free requirements. It clarifies why RoHS compliance doesn’t equal halogen-free, why zero halogen content isn’t required or practical, and why fluorine-containing PTFE materials are currently excluded from restrictions.

For engineers specifying materials, the key takeaways are straightforward: reference IPC-WP/TR-584 or IEC 61249-2-21 thresholds explicitly, include both laminate and solder mask in your requirements, specify the EN 14582 test method, and require supplier certification. Following these practices ensures your halogen-free specifications are clear, achievable, and verifiable.

The halogen-free transition continues to evolve with changing regulations and market expectations. While IPC-WP/TR-584 reflects 2007 technology, its fundamental definitions remain the industry baseline. As new concerns emerge around PFAS and other compounds, expect continued refinement of halogen-related requirements—making a solid understanding of the current framework even more valuable.