Inquire: Call 0086-755-23203480, or reach out via the form below/your sales contact to discuss our design, manufacturing, and assembly capabilities.
Quote: Email your PCB files to Sales@pcbsync.com (Preferred for large files) or submit online. We will contact you promptly. Please ensure your email is correct.
Notes: For PCB fabrication, we require PCB design file in Gerber RS-274X format (most preferred), *.PCB/DDB (Protel, inform your program version) format or *.BRD (Eagle) format. For PCB assembly, we require PCB design file in above mentioned format, drilling file and BOM. Click to download BOM template To avoid file missing, please include all files into one folder and compress it into .zip or .rar format.
If your product ships into the EU, Japan, China, or any market with active e-waste regulation, “RoHS compliant” is a baseline requirement — not a differentiator. But somewhere between reading the regulation and writing a fabrication note, a lot of engineers stop short of understanding what halogen-free actually demands of a laminate and where the DS-7409HF halogen-free grade fits in the Doosan DS-7409 family.
The DS-7409HF is Doosan’s halogen-free, high-Tg copper clad laminate — the “H” suffix denoting the high glass transition temperature, the “F” denoting the halogen-free resin system. It targets the segment of multilayer PCB designs where two requirements converge simultaneously: the need for a material that clears the bromine and chlorine thresholds defined in IEC 61249-2-21, and the thermal reliability margins demanded by lead-free SAC305 assembly. This article explains what those requirements actually mean at the chemistry level, how the DS-7409HF halogen-free specification meets them, and what performance trade-offs you need to manage when specifying it.
For the complete Doosan laminate range, sourcing guidance, and fabricator support, visit Doosan PCB.
What “Halogen-Free” Actually Means — and What It Does Not
The phrase “halogen-free” in PCB laminates has a precise technical definition under IEC 61249-2-21, the governing international standard. A laminate qualifies as halogen-free when its chlorine content is at or below 900 ppm by weight, its bromine content is at or below 900 ppm by weight, and the combined total of chlorine and bromine does not exceed 1,500 ppm by weight. These thresholds apply to the cured laminate and prepreg, not to the final assembled board, which can introduce halogens via solder flux, conformal coating, or surface finish.
This is a point that trips up many compliance teams. A PCB built on halogen-free laminate is not automatically a halogen-free board. Every material in the stack — solder mask, flux, coating, and surface treatment — must be independently verified against the same thresholds for the assembled product to carry a halogen-free claim.
Why Halogens Were There in the First Place
Standard FR-4 achieves its UL 94 V-0 flame retardancy using tetrabromobisphenol A (TBBPA), a brominated compound that reacts into the epoxy cross-link network during laminate cure. TBBPA is effective: a relatively small loading — typically around 18–20% of the uncured resin by weight — produces a well-cured, dimensionally stable laminate that passes the UL 94 vertical burn test. The bromine atoms interrupt the combustion chain reaction in the gas phase when the material burns, suppressing flame spread.
The problem is the by-product. When TBBPA-containing laminates burn, they can release hydrogen bromide (HBr), brominated dioxins, and brominated furans — combustion products that are corrosive, highly toxic, and environmentally persistent. As electronics end-of-life volumes grew through the 1990s and 2000s, these by-products from incineration of e-waste drove regulatory action. The EU RoHS directive (2002/95/EC, revised as 2011/65/EU) restricted polybrominated biphenyls (PBB) and polybrominated diphenyl ethers (PBDE) outright. TBBPA was subsequently added to the substances of very high concern (SVHC) list under REACH. The trajectory of regulation is clear, and volume electronics OEMs have been ahead of the formal requirements for years.
What Replaces Bromine in DS-7409HF Halogen-Free
Doosan’s halogen-free system uses a phosphorus-nitrogen (P-N) reactive flame retardant chemistry integrated into the epoxy resin matrix — not as an additive that could migrate or leach, but as a reactive component that becomes part of the cured polymer network. This distinction matters for long-term stability.
Phosphorus-based systems provide flame retardancy through a different mechanism than halogens. During combustion, phosphorus compounds thermally decompose to generate polyphosphoric acid. This dehydrating acid promotes the formation of a carbonaceous char layer on the polymer surface. The char acts as a physical barrier between the burning substrate and the oxygen supply, slowing further combustion. Nitrogen compounds, when incorporated as a synergist, release inert nitrogen gas during decomposition — diluting the flammable gas concentration in the flame zone and reducing combustion intensity. The combined P-N mechanism achieves UL 94 V-0 classification without any halogenated species.
DS-7409HF Halogen-Free Key Specifications
Table 1: DS-7409HF Halogen-Free Core Properties
Property
Typical Value
Test Method
Unit
Glass Transition Temperature (Tg, DSC)
≥170
IPC-TM-650 2.4.25c
°C
Decomposition Temperature (Td, TGA 5% wt loss)
~295–310
IPC-TM-650 2.4.40
°C
T-260 (time to delamination at 260 °C)
≥10
IPC-TM-650 2.4.24.1
min
Z-axis CTE (α1, below Tg)
~40–50
IPC-TM-650 2.4.41
ppm/°C
Peel Strength (1 oz Cu, condition A)
≥1.5
IPC-TM-650 2.4.8
N/mm
Dielectric Constant (Dk, 1 GHz)
~4.3–4.5
IPC-TM-650 2.5.5.9
—
Dissipation Factor (Df, 1 GHz)
~0.015–0.018
IPC-TM-650 2.5.5.9
—
Water Absorption (D-24/23 °C)
≤0.12
IPC-TM-650 2.6.2
%
Bromine Content
≤900
IEC 61249-2-21
ppm
Chlorine Content
≤900
IEC 61249-2-21
ppm
Total Halogens (Cl + Br)
≤1,500
IEC 61249-2-21
ppm
Flammability
V-0
UL 94
—
RoHS / REACH Compliance
Yes
—
—
The T-260 value of ≥10 minutes is directly relevant to lead-free assembly. SAC305 reflow peaks at 245–260 °C for 20–40 seconds, and thick multilayer boards can accumulate meaningful dwell time at elevated temperatures across multiple assembly passes, rework cycles, and thermal excursions during wave soldering. A T-260 of ≥10 minutes provides substantially more headroom than the ~3 minutes typical of standard difunctional FR-4, reducing delamination risk in high-layer-count or rework-intensive production flows.
The Dk of ~4.3–4.5 at 1 GHz is slightly higher than Doosan’s TBBPA-based standard DS-7409 base grade (~4.2). This is a known characteristic of phosphorus-nitrogen resin systems: replacing bromine atoms with phosphorus and nitrogen modifies the polymer dipole behaviour in a way that marginally increases Dk. For designs operating below ~2 GHz on impedance-controlled traces, this difference is manageable through adjusted trace geometry. For 5G mmWave or high-speed SerDes above 10 Gbps, it is a factor worth checking against your impedance budget — and where Doosan’s DS-7409DV or DV(N) family (low-loss, halogen-free) may be the more appropriate specification.
RoHS, REACH, and the Compliance Documentation Chain
What the Regulations Actually Require From the Laminate
RoHS 2 (EU Directive 2011/65/EU) restricts 10 substances in electrical and electronic equipment. PBB and PBDE are on the restricted list at 0.1% (1,000 ppm) by weight of homogeneous material. TBBPA is listed as a substance of very high concern (SVHC) under REACH. The DS-7409HF halogen-free resin system eliminates TBBPA entirely as a flame retardant, placing bromine content well below the 900 ppm IEC 61249-2-21 threshold and comfortably below the 1,000 ppm RoHS restriction level.
Table 2: Halogen Content Thresholds — Standard vs DS-7409HF vs Regulatory Limits
Parameter
Standard FR-4 (TBBPA)
DS-7409HF Halogen-Free
IEC 61249-2-21 Limit
RoHS 2 Limit
Bromine (Br) content
~15,000–20,000 ppm
≤900 ppm
≤900 ppm
1,000 ppm (PBB/PBDE)
Chlorine (Cl) content
~500–1,500 ppm
≤900 ppm
≤900 ppm
N/A (not restricted)
Total halogens (Cl + Br)
~16,000–22,000 ppm
≤1,500 ppm
≤1,500 ppm
—
TBBPA present
Yes — reactive into matrix
No
—
SVHC (REACH)
Antimony trioxide (synergist)
Often present
No
—
Not restricted currently
The documentation a fabricator needs to substantiate halogen-free laminate claim typically includes: the laminate CoC (Certificate of Conformance) citing IEC 61249-2-21 compliance with lot-specific halogen test results, Doosan’s RoHS declaration for the DS-7409HF grade, and the MSDS/SDS for the laminate and prepreg. Doosan provides RoHS and MSDS downloads directly from their product pages. For products going into EU markets, the REACH SVHC substance declaration should also be requested from the fabricator for the complete bill of materials.
Halogen-Free Is Not Automatically RoHS Compliant — And Vice Versa
This distinction causes real compliance errors. RoHS restricts specific substances (lead, cadmium, mercury, Cr6+, PBB, PBDE, and four phthalates). It does not require halogen-free materials. A board built on standard FR-4 with TBBPA can be fully RoHS compliant — TBBPA itself is not banned by RoHS, only PBB and PBDE are. Conversely, a halogen-free board built to IEC 61249-2-21 is not automatically RoHS compliant unless the surface finish, solder, flux, and other materials are also checked against the RoHS substance list.
Performance Trade-offs When Specifying DS-7409HF Halogen-Free
Table 3: DS-7409HF vs Standard High-Tg FR-4 vs Halogen-Free Competitors
Property
DS-7409HF (HF, Tg ≥170 °C)
Standard High-Tg FR-4 (Tg 140 °C)
Isola GreenSpeed HF
Panasonic R1566W (HF)
Tg (DSC)
≥170 °C
130–140 °C
~150–170 °C
~150–155 °C
Td
~295–310 °C
~270–280 °C
~320 °C
~310 °C
T-260
≥10 min
~2–3 min
~20 min
~15 min
Dk (1 GHz)
~4.3–4.5
~4.5–4.8
~4.2
~4.1
Df (1 GHz)
~0.015–0.018
~0.020–0.025
~0.013
~0.014
Water absorption
≤0.12%
~0.20%
~0.10%
~0.10%
Halogen-free (IEC 61249-2-21)
Yes
No
Yes
Yes
Processing vs standard FR-4
Same
Same
Same
Same
The Dk and Df of the DS-7409HF are slightly elevated compared to Isola GreenSpeed and Panasonic R1566W. Those materials use different halogen-free resin chemistry tuned for lower loss, which is reflected in both their electrical properties and their cost premium. For the majority of industrial multilayer designs without high-frequency signal integrity requirements, the DS-7409HF Dk of ~4.3–4.5 and Df of ~0.015–0.018 are fully adequate. The practical benefit is a material that processes identically to standard FR-4 on existing equipment with no drilling, desmear, or lamination parameter changes.
Moisture Absorption — The Overlooked Advantage
One performance benefit that rarely gets the attention it deserves: the water absorption of halogen-free P-N epoxy laminates is genuinely lower than standard FR-4. The mechanism is straightforward — phosphorus and nitrogen have lower electronegativity than bromine, so the polymer bonds in a P-N resin system are less polar, reducing the material’s affinity for hydrogen bonding with water molecules. The DS-7409HF’s water absorption of ≤0.12% compares favourably with the ~0.20% typical of standard FR-4.
Lower moisture absorption reduces several failure modes: moisture-induced Tg depression (absorbed water acts as a plasticiser, lowering the effective Tg of the laminate), delamination risk during preheating ahead of soldering, and conductive anodic filament (CAF) formation risk in fine-pitch via patterns at humidity. For products deployed in industrial or outdoor environments where the PCB assembly sees sustained elevated humidity, this is a meaningful reliability advantage of the DS-7409HF halogen-free grade over its brominated counterpart.
Applications Where DS-7409HF Halogen-Free Is the Right Call
Table 4: DS-7409HF Application Fit Matrix
Application Segment
Why DS-7409HF Fits
Alternative if Insufficient
Automotive body/chassis ECU
AEC-Q200-aligned material, halogen-free often OEM mandated, Tg ≥170 °C for underhood ambient
DS-7409DV if >6 GHz signal lanes required
Industrial control & HVAC
Extended operating temperature, humidity resistance, RoHS mandated for EU market access
Same grade — typically fully adequate
Medical device PCBs (Class II/III)
Reduced toxic off-gassing in enclosed housings, REACH substance control important
Q1: Does specifying DS-7409HF require any fabrication process changes compared to standard FR-4?
No — this is one of the most practically important characteristics of the DS-7409HF halogen-free grade. The reactive phosphorus-nitrogen resin system is formulated to process on standard FR-4 fabrication equipment without modification. Drilling parameters, desmear chemistry (permanganate or plasma), lamination press cycles, etching, and standard ENIG, HASL, or OSP surface finish processes all remain unchanged. Fabricators qualified on the standard DS-7409 family can run DS-7409HF with no re-qualification of drill or lamination parameters. This is not universally true across the halogen-free laminate market — some P-N systems require adjusted lamination temperatures or desmear chemistry, but Doosan has specifically engineered the DS-7409HF for drop-in processability.
Q2: Is DS-7409HF the right material for designs that need both halogen-free compliance and high-speed signal integrity above 5 GHz?
Not as the primary specification. The DS-7409HF’s Dk of ~4.3–4.5 and Df of ~0.015–0.018 at 1 GHz are appropriate for general multilayer designs, but signal attenuation at 5 GHz and above becomes a meaningful concern with Df at this level. For halogen-free designs requiring 5G mmWave, 25G/100G Ethernet SerDes, or other high-frequency signal lanes, the DS-7409DV (halogen-free, Tg 225 °C DMA, Dk ~3.48 at 10 GHz, Df ~0.003) or DS-7409DV(N) ultra-low-loss grade should be the specification. The DS-7409HF is optimised for the mid-performance segment: full halogen-free compliance plus high-Tg lead-free reliability at a cost point well below the low-loss premium grades.
Q3: How do I verify that a board built on DS-7409HF actually meets IEC 61249-2-21 at the laminate level?
The primary verification method is oxygen bomb combustion followed by ion chromatography (IC), per IPC-TM-650 2.3.41 or IEC 61189-2-712. The combustion method ensures both covalently bonded halogens (which do not dissolve in water for simple water extraction tests) and ionically bonded halogens are captured and quantified. This matters because TBBPA is a covalently bonded halogen — a simple water leach test will not detect it. Any fabricator or laminate supplier quoting halogen-free compliance should be able to provide lot-level test reports from oxygen bomb combustion IC testing, not just a generic CoC. Request Doosan’s RoHS declaration and the lot CoC for the DS-7409HF prepreg used in your specific build.
Q4: What is the cost premium for DS-7409HF halogen-free vs the standard DS-7409 base grade?
Expect a material cost premium of approximately 15–25% over equivalent standard high-Tg FR-4 laminate at the laminate/prepreg level. This range reflects phosphorus-nitrogen flame retardant system chemistry that is more expensive than TBBPA, and moderately tighter process controls around cross-contamination with brominated materials at the laminate manufacturer level. At the finished PCB level, the premium is diluted by other cost drivers (copper weight, layer count, surface finish, via filling) and typically translates to 5–10% of total PCB cost for a standard 8–12 layer industrial multilayer. For markets requiring halogen-free laminate certification, the cost of non-compliance or delayed market access vastly exceeds this premium.
Q5: Does halogen-free laminate affect CAF (conductive anodic filament) reliability?
This is an important question for high-density designs with fine via pitch. CAF formation — copper migration along the glass fibre/resin interface driven by electrochemical processes under moisture and applied voltage — is a known failure mode in dense multilayer boards. The evidence from industry testing, including iNEMI’s HFR-Free High Reliability PCB Project, indicates that well-formulated halogen-free epoxy laminates perform equivalently to or better than brominated FR-4 for CAF resistance. The lower moisture absorption of P-N resin systems (DS-7409HF ≤0.12% vs standard FR-4 ~0.20%) reduces the electrolytic pathway availability for copper migration. For safety-critical medical or automotive applications with via pitch below 0.8 mm, specify SIR (surface insulation resistance) and CAF testing to IPC-TM-650 2.6.25 as a qualification requirement — this holds for any laminate system, halogen-free or not.
For the complete Doosan CCL product range, halogen-free grade comparisons, and fabricator qualification support, visit Doosan PCB.
Inquire: Call 0086-755-23203480, or reach out via the form below/your sales contact to discuss our design, manufacturing, and assembly capabilities.
Quote: Email your PCB files to Sales@pcbsync.com (Preferred for large files) or submit online. We will contact you promptly. Please ensure your email is correct.
Notes: For PCB fabrication, we require PCB design file in Gerber RS-274X format (most preferred), *.PCB/DDB (Protel, inform your program version) format or *.BRD (Eagle) format. For PCB assembly, we require PCB design file in above mentioned format, drilling file and BOM. Click to download BOM template To avoid file missing, please include all files into one folder and compress it into .zip or .rar format.
