The capability extract shows in thirty seconds what runs as standard and what carries a surcharge.
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To the data check →Standard FR-4 reaches its flammability class with brominated flame retardants. Halogen-free laminates get there with phosphorus and metal hydroxides instead — which changes the smoke behaviour in a fire, and changes how the material behaves in your reflow oven.
"Halogen-free" is a defined threshold rather than an absolute: under 900 ppm bromine, under 900 ppm chlorine, and under 1500 ppm combined, per IEC 61249-2-21. The point is not the residual trace but what replaces the flame retardant — phosphorus compounds and aluminium hydroxide instead of brominated resin.
The reason it matters is fire behaviour in confined spaces. Burning brominated resin produces dense, corrosive, toxic smoke; in a tunnel or a rail carriage that is what harms people before the fire does. EN 45545-2 exists for exactly that scenario, and it is the single most common reason a project specifies halogen-free — environmental policy is usually the second.
EN 45545-2 is not optional in European rolling stock. If your product goes into a carriage, this material group is where the conversation starts.
In a fire the material produces markedly less dense and less corrosive smoke — which in an enclosed space is the difference that the standard is written around.
Halogen-free and High-Tg grades combine, so a thick railway multilayer does not have to choose between compliance and thermal margin.
| Property | Value | Test / note |
|---|---|---|
| Bromine content | < 900 ppm | IEC 61249-2-21 |
| Chlorine content | < 900 ppm | IEC 61249-2-21 |
| Total Br + Cl | < 1500 ppm | Combined limit |
| Glass transition Tg | 150 – 175 °C | Standard and High-Tg grades both available |
| Td | > 330 °C | Comparable to High-Tg FR-4 |
| Dk (1 GHz) | 4.3 – 4.8 | Slightly higher than standard FR-4 |
| Water absorption | 0.20 – 0.35 % | Notably higher — this drives the handling rules |
| Flammability | UL 94 V-0 | Achieved without halogenated retardant |
Guide values for pre-selection. Binding values are confirmed per project against your data.
The points below are what most often comes back as a query after data review. Settling them before layout freeze saves a loop.
These laminates absorb roughly twice the moisture of standard FR-4. After more than a few weeks of storage, bake before reflow — trapped moisture flashes to steam and delaminates the board.
Vacuum packing with a humidity indicator is not over-caution here, it is the normal handling regime. Boards left open on a shelf for a month will need baking.
Halogen-free is a material property; EN 45545-2 is a tested classification of the finished assembly at a hazard level. Tell us the required HL level so we choose a laminate with the right evidence.
The mineral fillers raise the dielectric constant a little. On an impedance-controlled build this changes the stack-up calculation — mention the material when you send target impedances.
No, and they are often confused. RoHS restricts lead, cadmium, mercury and a handful of other substances; it says nothing about bromine in flame retardants. Practically all our material is RoHS compliant. Halogen-free is a separate, additional requirement.
Around 10 – 25 % over standard FR-4, depending on grade and availability. Combined with High-Tg the surcharges roughly stack.
Thermally and mechanically it is comparable to standard FR-4, and High-Tg grades are comparable to High-Tg FR-4. The two real differences are moisture uptake and a slightly higher Dk.
Not usually — IATF 16949 does not require it. Some manufacturers specify it under their own environmental policy, so check the customer specification rather than the standard.
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