Isola FR408HR 4-Layer and 6-Layer PCBs with ENIG Finish
1.Introduction to Core Technologies
FR408HR is a high-performance FR-4 resin system developed by Isola Group, specifically designed for multilayer PCB applications where maximum thermal performance and reliability are required. This material features a high glass transition temperature (Tg) of 190°C (DSC) and is reinforced with electrical grade E-glass fabric.
FR408HR represents a significant advancement in FR-4 technology, offering a 30% improvement in Z-axis expansion and 25% more electrical bandwidth (lower loss) compared to competitive products. The material is also laser fluorescing and UV blocking, ensuring maximum compatibility with Automated Optical Inspection (AOI) systems, optical positioning systems, and photo-imageable solder mask imaging.
2.Key Performance Characteristics:
Tg 190°C (DSC) for lead-free compatibility
Td 360°C at 5% weight loss
T260 >60 min, T288 >30 min for reflow reliability
Z-axis CTE: 55 ppm/°C pre-Tg, 2.8% total expansion
Dk 3.68 at 2 GHz, 3.65 at 10 GHz
Df 0.0092 at 2 GHz, 0.0095 at 10 GHz
Dielectric breakdown >50 kV
Moisture absorption 0.061%
UL 94 V-0 flame retardant
CTI Class 2 (250-399V)
Peel strength 1.14 N/mm for low-profile foil
3.Benefits
Bridges standard FR-4 and high-performance materials
Reliable through multiple lead-free reflow cycles
Lower loss enables higher data rates
AOI-compatible with laser fluorescing properties
Stable Dk across frequency for impedance control
Long-term durability in demanding environments
Compatible with resin-filled vias and sequential lamination
4. FR408HR Data Sheet Summary
| Property |
Conditions |
Typical Value |
Unit |
Test Method |
| Glass Transition Temperature (Tg) | DSC | 190 | °C | IPC-TM-650 2.4.25C |
| Decomposition Temperature (Td) | 5% weight loss | 360 | °C | IPC-TM-650 2.4.24.6 |
| T260 | TMA | >60 | Minutes | IPC-TM-650 2.4.24.1 |
| T288 | TMA | >30 | Minutes | IPC-TM-650 2.4.24.1 |
| Z-Axis CTE | Pre-Tg | 55 | ppm/°C | IPC-TM-650 2.4.24C |
| Z-Axis CTE | Post-Tg | 230 | ppm/°C | IPC-TM-650 2.4.24C |
| Z-Axis CTE | 50-260°C (Total) | 2.8 | % | IPC-TM-650 2.4.24C |
| X/Y-Axis CTE | Pre-Tg | 16 | ppm/°C | IPC-TM-650 2.4.24C |
| Thermal Conductivity | - | 0.4 | W/m·K | ASTM E1952 |
| Dielectric Constant (Dk) | @ 100 MHz | 3.72 | - | IPC-TM-650 2.5.5.3 |
| Dielectric Constant (Dk) | @ 1 GHz | 3.69 | - | IPC-TM-650 2.5.5.9 |
| Dielectric Constant (Dk) | @ 2 GHz | 3.68 | - | Bereskin Stripline |
| Dielectric Constant (Dk) | @ 5 GHz | 3.64 | - | Bereskin Stripline |
| Dielectric Constant (Dk) | @ 10 GHz | 3.65 | - | Bereskin Stripline |
| Dissipation Factor (Df) | @ 100 MHz | 0.0072 | - | IPC-TM-650 2.5.5.3 |
| Dissipation Factor (Df) | @ 1 GHz | 0.0091 | - | IPC-TM-650 2.5.5.9 |
| Dissipation Factor (Df) | @ 2 GHz | 0.0092 | - | Bereskin Stripline |
| Dissipation Factor (Df) | @ 5 GHz | 0.0098 | - | Bereskin Stripline |
| Dissipation Factor (Df) | @ 10 GHz | 0.0095 | - | Bereskin Stripline |
| Volume Resistivity | After moisture | 4.4 x 10⁷ | MΩ-cm | IPC-TM-650 2.5.17.1 |
| Volume Resistivity | Elevated temp | 9.4 x 10⁷ | MΩ-cm | IPC-TM-650 2.5.17.1 |
| Surface Resistivity | After moisture | 2.6 x 10⁶ | MΩ | IPC-TM-650 2.5.17.1 |
| Surface Resistivity | Elevated temp | 2.1 x 10⁸ | MΩ | IPC-TM-650 2.5.17.1 |
| Dielectric Breakdown | - | >50 | kV | IPC-TM-650 2.5.6B |
| Arc Resistance | - | 137 | Seconds | IPC-TM-650 2.5.1B |
| Electric Strength | Laminate & prepreg | 70 (1741) | kV/mm (V/mil) | IPC-TM-650 2.5.6.2A |
| Comparative Tracking Index (CTI) | - | Class 2 (250-399) | Volts | UL 746A / ASTM D3638 |
| Peel Strength | Low profile foil | 1.14 (6.5) | N/mm (lb/in) | IPC-TM-650 2.4.8C |
| Peel Strength | Very low profile | 0.96 (5.5) | N/mm (lb/in) | IPC-TM-650 2.4.8.2A |
| Peel Strength | Standard profile | 0.90 (5.1) | N/mm (lb/in) | IPC-TM-650 2.4.8.3 |
| Moisture Absorption | - | 0.061 | % | IPC-TM-650 2.6.2.1A |
| Flammability | Laminate & prepreg | V-0 | Rating | UL 94 |
| Relative Thermal Index (RTI) | - | 130 | °C | UL 796 |
5.1 6-Layer FR408HR PCB Specifications
| Item |
Specification |
| Product Type | 6-Layer High-Performance PCB |
| Material | Isola FR408HR |
| Layer Count | 6 Layers |
| Copper Thickness | 1oz per layer (approx. 35μm) |
| Finished Thickness | 1.60mm |
| Surface Finish | ENIG (Electroless Nickel Immersion Gold) |
| Solder Mask | Blue (Top and Bottom) |
| Silkscreen | White (Top and Bottom) |
| Via Process | 0.2mm - 0.4mm vias with resin filling |
| Dimensions | 79mm x 105mm = 1 PCS |
5.2 4-Layer FR408HR PCB Specifications
| Item |
Specification |
| Product Type | 4-Layer High-Performance PCB |
| Material | Isola FR408HR |
| Layer Count | 4 Layers |
| Copper Thickness | 1oz per layer (approx. 35μm) |
| Finished Thickness | 1.58mm |
| Surface Finish | ENIG (Electroless Nickel Immersion Gold) |
| Solder Mask | Blue (Top and Bottom) |
| Silkscreen | White (Top and Bottom) |
| Via Process | Blind vias L1-L3 |
| Dimensions | 96mm x 115mm = 1 PCS |
6.1 PCB Stackup (6-Layer Rigid Structure)
L1 (Top): 1oz copper
Prepreg Layer
L2: 1oz copper
Core Layer
L3: 1oz copper
Prepreg Layer
L4: 1oz copper
Core Layer
L5: 1oz copper
Prepreg Layer
L6 (Bottom): 1oz copper
6.2 4-Layer PCB (1.58mm):
L1 (Top): 1oz copper
Prepreg Layer
L2: 1oz copper
Core Layer
L3: 1oz copper
Prepreg Layer
L4 (Bottom): 1oz copper
7.Typical Applications
Telecommunications: Base stations, routers, switches
High-Speed Networking: Ethernet switches, servers, data centers
Industrial Control: PLCs, motor drives, industrial computers
Automotive Electronics: ADAS, infotainment, powertrain modules
Medical Devices: Diagnostic equipment, imaging systems
Test & Measurement: Oscilloscopes, spectrum analyzers
Aerospace & Defense: Avionics, radar, communication systems
High-Reliability Computing: Servers, storage systems
8.Quality Assurance
Artwork Format: Gerber RS-274-X
Quality Standard: IPC-Class-2
Availability: Worldwide
9.Conclusion
These 6-layer and 4-layer FR408HR PCBs combine Isola's advanced mid-loss laminate technology with ENIG surface finish and specialized via processes, delivering reliable thermal performance and signal integrity for demanding multilayer applications in telecommunications, industrial, automotive, and aerospace sectors.
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