Halogen free PCB is a printed circuit board non-contain any halogen elements, During PCB manufacturing, the concerned halogen elements like Chlorine and Bromine do have some benefits however these do not outweigh their negative impact that can be caused in our day to day life. As a responsible PCB manufacturer, We are committed to producing circuit boards under environmentally friendly conditions
We are using following raw material to manufacture halogen free PCBs :
Halogen free PCB material, base on JPCA-ES-01-2003 standard: a copper-clad which the content of C1, Br less than 0.09%wt, it is called for halogen free PCB. (at the same time, the total value of Cr+Br ≤0.15％[1500PPM). Halogen free material: TU883, Isola DE156, Green speed series, S1165/S1165M, S0165, and so on. The EU has a strict import requirements from July 2006 ,the requirements details is the PCB products should be without halogen, mercury, hexavalent chromium, polybrominated biphenyls, polybrominated biphenyls ether .
Introduction
Halogen free printed circuit boards (PCBs) are becoming increasingly common thanks to environmental legislation and the drive for more sustainable electronics. But what exactly makes a PCB halogen free? This article provides a detailed examination of halogen free PCB materials, properties, manufacturing processes, applications, and benefits.
What is a Halogen?
Halogens are a class of reactive elements in group 17 on the periodic table. They consist of:
- Fluorine (F)
- Chlorine (Cl)
- Bromine (Br)
- Iodine (I)
These elements exhibit high reactivity and are commonly used in many chemical compounds across industries.
The Need for Halogen Free PCBs
Many traditional PCB laminate materials utilize brominated flame retardants (BFRs) to reduce flammability. However, halogens like bromine can produce toxic substances when burned. Regulatory initiatives like the Restriction of Hazardous Substances (RoHS) directive now limit halogens in electronics. Additionally, halogen free PCBs avoid corrosion issues and allow safer recycling.
Definition of Halogen Free Materials
While no universal standard exists, common criteria for halogen free materials are:
- Chlorine – < 900 ppm
- Bromine – < 900 ppm
- Total halogens – < 1500 ppm
Materials meeting these halogen limits are considered halogen free for PCB applications. Some standards require even lower concentrations.
Halogen Free Epoxy Resins
Epoxy resin is used to impregnate the glass fabric layers in FR-4 PCB laminates. Special formulations are needed for halogen free boards:
- Dicyandiamide (DCA) – Hardener that contains no halogens
- Halogen Free Flame Retardants – Replace brominated versions while maintaining fire resistance
- Modified epoxy backbone – May alter epoxy structure while keeping properties
Common halogen free epoxy resins include Tetrabrombisphenol A (TBBPA) free, epoxy phenol novolac, multifunctional epoxy, BMI, and DCA types.
Halogen Free Substrates
Popular halogen free substrate materials include:
- FR-4 – Modified bromine free version of standard FR-4 laminate
- Polyimide – Inherently halogen free polymer substrate
- I-Tera MT – Panasonic proprietary halogen free material
- RCF – Isola resin coated foil, halogen free
- BT Epoxy – Bismaleimide triazine, higher performance
Many material suppliers now offer halogen free FR-4 and other laminates to meet market needs.
Properties of Halogen Free PCB Materials
Halogen free PCB materials offer the following characteristics:
Electrical – Stable dielectric constant and low loss for high speed signals
Thermal – Withstand high temperature processes and thermal cycling
Mechanical – Good strength, durability, and drillability
Fire Resistance – Meet flammability standards without halogens
Moisture Absorption – Low moisture uptake and superior dimensional stability
Chemical Resistance – Withstand exposure to solder, acids, solvents etc.
With careful material selection, halogen free boards can match most properties of conventional PCB laminates.
Benefits of Halogen Free Materials
Halogen free PCB materials provide several benefits:
- Environmental Sustainability – Avoid toxic chemicals and byproducts
- Regulatory Compliance – Meet strict halogen bans in Europe, China etc.
- Improved Reliability – Reduce risk of corrosion and metal migration
- Easier Recycling – Less hazardous materials at end of life
- Responsible Branding – Improve public image for customers
This makes halogen free materials ideal for contemporary environmentally conscious electronics.
Challenges of Halogen Free Materials
However, halogen free materials also pose some challenges:
Cost – Halogen free resins remain more expensive than standard FR-4.
Availability – Some exotic substrate options have limited global supply.
Processes – May require adjustments to lamination cycles and drilling.
Testing – Validation required to meet halogen thresholds.
But continual progress is improving access and cost as adoption grows.
Testing for Halogens
Several analytical techniques can quantify halogen content:
- Combustion Ion Chromatography – Burns sample to free halogens for detection
- X-ray Fluorescence Spectroscopy – Use X-rays to stimulate halogen emissions
- Total Organic Halogen Analysis – Measures total organically bound halogens
- Headspace Analysis – Detects halogen gas emissions released during heating
- Wet Chemical Methods – Solution-based titration approaches
Certified third-party labs can validate halogen concentrations to guarantee compliance.
Halogen Testing Standards
Relevant industry testing standards include:
- IPC-4101 – Validates halogen content in base laminate materials
- IEC 61249-2-21 – Tests PCB laminate halogens after fabrication
- UL 746A – Determines halogens in laminate samples via combustion
- IEC 61249-2-41 – Detects total halogen content in laminate resins
Testing should be performed on both base materials and finished PCBs.
Halogen Free PCB Fabrication
Halogen free PCB manufacturing involves:
- Sourcing – Obtain certified halogen free substrate materials
- Inner Layer Processing – Standard imaging and etching
- Lamination – Adjusted temperature and pressure profiles
- Drilling – Carbide bits, optimized feeds and speeds
- Plating – Electroless copper followed by electrolytic copper
- Soldermask – Liquid photoimageable or dry film
- Finishing – HASL, immersion tin, ENIG, other surface finishes
- Testing – Validate halogen content to ppm levels
Fabrication is similar with some adaptations in processes like lamination and drilling.
Applications for Halogen Free PCBs
Halogen free PCBs are mandated or recommended for:
- Consumer Electronics – Mobile phones, laptops, wearables
- Automotive – Engine control units, infotainment, sensors
- Aerospace/Military – Avionics, guidance systems
- Medical – Implantables, imaging equipment
- Green Energy – Solar, batteries, wind turbines
Any application with flammability risks or susceptible to corrosion over long operating lifetimes.
Supply Chain Considerations
To guarantee halogen free end products:
- Material Disclosures – Require disclosures from suppliers at all tiers
- CoC Agreements – Certificate of Conformance from partners
- Incoming Testing – Spot check incoming materials
- Process Control – Prevent crossover contamination
- Documentation – Full traceability for materials and chemistry
Careful partnership with the full supply chain is key to success.
Cost Analysis
The cost premium for halogen free materials is shrinking but remains:
| PCB Type | Typical Cost | Halogen Free Cost | Premium |
|---|---|---|---|
| 2-4 Layer FR-4 | $5-10/ft2 | $7-12/ft2 | ~20% |
| 6-8 Layer FR-4 | $15-25/ft2 | $20-35/ft2 | ~30% |
| 4-6 Layer Polyimide | $40-80/ft2 | $55-95/ft2 | ~30% |
Table 1: Cost comparison of standard versus halogen free PCB materials
In high volumes, lower costs can be negotiated with laminate suppliers.
Future Outlook
Halogen free PCB adoption will increase due to:
- Tightening environmental regulations
- Push for sustainable electronics
- Growing performance of halogen free materials
- Reduced costs and expanded supply chains
Within 5-10 years halogen free PCBs could become the default for many applications.
Conclusion
Overall halogen free PCB technology enables environmentally responsible electronics with low flammability risk and improved longevity. With global momentum toward eliminating hazardous chemicals, halogen free substrates and chemistry deliver green yet high performance PCB fabrication. Thanks to extensive R&D, halogen free boards can now match most design needs at reasonable costs. Look for halogen free PCB materials to rapidly gain share across all industries in the coming decade.
FAQs
Q: What are the major benefits of halogen free PCBs?
A: Main benefits are reduced flammability, avoidance of toxic fumes when burned, reduced corrosion, and improved recyclability.
Q: What industries most need halogen free PCBs?
A: Sectors like aerospace, automotive, medical, and renewables have the greatest needs due to safety and reliability demands.
Q: How much more do halogen free PCBs cost?
A: There is typically a 20-30% cost premium for halogen free materials depending on the PCB technology.
Q: What is the most common halogen free PCB material?
A: Modified FR-4 with bromine free epoxy is the most popular thanks to its balance of cost and performance.
Q: How can you tell if a PCB is halogen free?
A: Certificates of compliance from manufacturers along with third-party halogen testing can reliably validate halogen free status.
