Isola FR408HR mid-loss laminate
Isola FR408HR PCB: Mid-Loss, High-Tg FR-4 for Faster Digital
FR408HR is Isola’s lead-free, mid-loss FR-4 resin system: Tg 190 °C (DSC), Td 360 °C, Dk about 3.65 and Df about 0.0095 at 10 GHz. It bridges standard high-Tg FR-4 and low-loss laminates such as Megtron 6.
- Tg (DSC)
- 190 °C
- Td
- 360 °C
- Dk @ 10 GHz
- 3.65
- Df @ 10 GHz
- 0.0095
What is FR408HR
What is Isola FR408HR?
Isola FR408HR is a high-performance, lead-free FR-4 resin system reinforced with E-glass. It has a Tg of 190 °C by DSC (230 °C by DMA), a Td of 360 °C, and a Dk of about 3.65 with Df of about 0.0095 at 10 GHz. Isola positions it as a mid-loss laminate that is CAF resistant, survives six 260 °C reflows and processes like FR-4.
FR408HR is common in networking, storage and computing boards where standard high-Tg FR-4 loses too much signal but a full low-loss laminate is not needed. It meets IPC-4101 /98, /99, /101 and /126.
Properties
Isola FR408HR typical properties.
| Property | Typical value | Method |
|---|---|---|
| Tg (DSC) | 190 °C | IPC-TM-650 2.4.25C |
| Td (TGA, 5% weight loss) | 360 °C | IPC-TM-650 2.4.24.6 |
| T260 / T288 | 60 / > 30 min | IPC-TM-650 2.4.24.1 |
| Z-axis CTE pre-Tg / post-Tg | 55 / 230 ppm/°C | IPC-TM-650 2.4.24C |
| Z-axis expansion, 50–260 °C | 2.8% | IPC-TM-650 2.4.24C |
| X/Y CTE pre-Tg | 16 ppm/°C | IPC-TM-650 2.4.24C |
| Dk @ 1 GHz / 2 GHz / 10 GHz | 3.69 / 3.68 / 3.65 | 2.5.5.9 / Bereskin stripline |
| Df @ 1 GHz / 2 GHz / 10 GHz | 0.0091 / 0.0092 / 0.0095 | 2.5.5.9 / Bereskin stripline |
| Thermal conductivity | 0.4 W/m·K | ASTM E1952 |
| Electric strength | 70 kV/mm (1741 V/mil) | IPC-TM-650 2.5.6.2A |
| CTI | Class 2 (250–399 V) | UL 746A |
| Moisture absorption | 0.061% | IPC-TM-650 2.6.2.1A |
| Flammability / RTI | UL 94 V-0 / 130 °C | UL 94 / UL 796 |
When to use
When to choose Isola FR408HR.
FR408HR suits designs that have outgrown standard FR-4 but do not need a premium low-loss material: 10G and 25G Ethernet line cards, PCIe Gen 3/4 boards, storage controllers and FPGA boards with moderate channel lengths. Its Df of about 0.0095 is roughly half that of typical high-Tg FR-4, and its 190 °C Tg and CAF resistance carry it through repeated lead-free assembly.
For 56G or 112G PAM4 channels, or long backplane traces, move to Megtron 6 or 7. For boards that only need thermal margin, a high-Tg FR-4 such as Shengyi S1000-2M or Isola 370HR costs less.
FR408HR vs others
Isola FR408HR vs 370HR vs Megtron 6.
| Laminate | Tg | Df @ ≈ 10 GHz (approx.) | Positioning |
|---|---|---|---|
| Isola 370HR | 180 °C | ≈ 0.02 | High-Tg, CAF-resistant FR-4 |
| Isola FR408HR | 190 °C | ≈ 0.0095 | Mid-loss FR-4 |
| ITEQ IT-180A | 180 °C | ≈ 0.016 | High-Tg FR-4 |
| Panasonic Megtron 6 | ≈ 185 °C | ≈ 0.004 | Low loss, 25–56G |
Stack-up
Stack-up guidance on FR408HR.
FR408HR laminate is offered from 2 to 30 mil (0.05 to 0.75 mm) with ½, 1 and 2 oz copper, in HTE grade 3 or reverse-treated (RTF) foil, and with E-glass, square-weave or mechanically spread glass. For high-speed differential pairs we prefer spread glass and RTF copper: spread glass reduces fiber-weave skew and RTF lowers conductor loss.
- Use construction-specific Dk/Df for impedance and loss budgets
- Prefer spread glass for fine-pitch differential pairs
- Specify RTF copper on high-speed layers
- Balance copper and prepreg on mirrored layers
I-Speed & Tachyon
Isola I-Speed and Tachyon 100G.
Isola’s lower-loss systems sit above FR408HR. I-Speed is a low-loss laminate for faster serial links, and Tachyon 100G is an ultra-low-loss material for 100G-class channels. If your drawing calls out one of these, we build on it and confirm stock at quote; if you are choosing, we compare it with Megtron grades on loss, cost and lead time for your channel.
Reliability
Lead-free and CAF reliability.
Isola rates FR408HR for six 260 °C reflows and six 288 °C solder floats, with CAF resistance and a 30% improvement in z-axis expansion over competitive products in its class. That makes it a good fit for thick boards and HDI builds that see several lamination and assembly cycles. Boards should still be stored dry and baked if moisture exposure limits are exceeded.
RFQ
What to include in an FR408HR RFQ.
- Laminate name and grade exactly as on your drawing, or “or equivalent” if substitution is allowed
- “Isola FR408HR” or IPC-4101 /98, /99, /101, /126 if an equivalent is acceptable
- Glass style and copper type (e.g. spread glass, RTF) on high-speed layers
- Data rates and channel lengths
- Layer count, finished thickness and tolerance
- Impedance targets and reference layers
- IPC class, quantity and schedule
FAQ
Material questions.
What is the Tg of Isola FR408HR?
190 °C by DSC and 230 °C by DMA, with a Td of 360 °C.
What are the Dk and Df of FR408HR?
About 3.65 and 0.0095 at 10 GHz, and 3.69 and 0.0091 at 1 GHz, per the Isola data sheet.
FR408HR vs Megtron 6: which do I need?
FR408HR for 10–25G channels of moderate length at lower cost; Megtron 6 for 25–56G and longer channels where loss must be lower.
Is FR408HR lead-free compatible?
Yes. Isola rates it for six 260 °C reflow cycles.
Is FR408HR CAF resistant?
Yes, Isola lists CAF resistance among its performance attributes.
Can FR408HR be used in HDI?
Yes. It supports multiple lamination cycles and via filling.
Ready when your files are
Send your stack-up for a material check.
Upload Gerber, ODB++ or IPC-2581 data. Every quote includes a written engineering DFM review, typically within one business day.