Paper-Epoxy Boards That Bridge the Gap Between Ultra-Budget Phenolic and Full Glass-Epoxy FR4 PCB
What Is High-Tg FR-4?
High-Tg FR-4 is a glass-cloth epoxy laminate qualified under IPC-4101 /126, /129, /130, etc. Compared with standard FR-4 (Tg ≈ 135 °C), it provides:
| Parameter | Standard FR-4 | High-Tg FR-4 | Why It Matters |
| Glass-transition temp (Tg) | 135–150 °C | 170–200 °C | Withstands 260 °C Pb-free reflow & multiple rework cycles |
| Z-axis CTE (below Tg) | 65–70 ppm/°C | 45–55 ppm/°C | Minimises via-barrel fatigue and pad cratering |
| εr @ 1 GHz | 4.3–4.5 | ≈ 4.2 | Predictable impedance to >25 Gb/s |
| Loss tangent @ 1 GHz | 0.020 | ≈ 0.015 | Lower insertion loss for SERDES lanes |
| Peel strength (Cu 35 µm) | 1.05 N/mm | ≥ 1.10 N/mm | Robust against pad-lift during rework |
FR1 PCB
FR2 PCB
FR3 PCB
HIGHPCB is one of the largest Epoxy PCB Board and Rigid PCB manufacturing factories in China, click on the link to see more.
Key Advantages
Lead-Free Reliability
survives JEDEC J-STD-020 reflow up to 260 °C without de-lam or CAF.
High-Speed Signal Integrity
tight Dk/Df spread enables 28 Gb/s PCIe® Gen 4/5, 10 GbE, USB4®.
Thermal Cycling Endurance
low Z-CTE prevents barrel cracks in −40 → +125 °C mission profiles.
Mechanical Strength
glass cloth resists torque from press-fit connectors & heavy heat-sinks.
Multilayer Scalability
supports 4 – 16+ layers, blind/buried vias, copper-filled microvias.
Typical Applications
| Sector | Example Boards |
| Automotive | ADAS camera ECU, 77 GHz radar front-end, EV BMS stack |
| Data-Com & Server | 25–28 Gb/s backplanes, network switches, AI accelerator cards |
| Industrial Drive | 600 V IGBT gate boards, 48 V DC-bus converters |
| LED Lighting | 80–150 W constant-current drivers with Pb-free wave solder |
| Aerospace & Defense | Ku-band transceivers, rugged SBCs, phased-array control PCBs |
Manufacturing Flow (High-Tg FR-4 Multilayer)
| Step | Process Highlight | Critical Control |
| Stack-up & DFM | Impedance modelling, CAF risk check | ΔDk ≤ 0.05 across cores |
| Drilling | 100 µm laser microvia, 0.20 mm mechanical PTH | Aspect ≤ 10:1 |
| Desmear & Cu-seed | Plasma + electroless 1 µm | No epoxy smear residue |
| Copper Build-up | 25 µm electrolytic on PTH; via fill for VIPPO | Void ≤ 5 % X-ray |
| Imaging & Etch | LDI 25 µm lines / spaces | Etch factor 3 : 1 |
| Solder Mask | LPI PSR-4000 or Taiyo SD15 | Mask clearance ≥ 80 µm |
| Finish Options | ENIG • ENEPIG • Imm Ag • OSP | Au 0.05 µm ± 0.02 |
| Reliability Test | IST, T-260/T-288, AOI, Flying-probe | ΔR/R < 5 % after 10 × reflow |
Design Guidelines
| Item | Recommended Value |
| Min line / space | 75 µm (2.95 mil) LDI standard; 50 µm achievable |
| Min via (laser) | 0.10 mm drill, 0.20 mm land |
| Controlled-impedance tolerance | ± 8 % single-end, ± 6 % diff (≤ 12 layer) |
| Copper weight options | 1 oz outer, 0.5–2 oz inner; 3 oz for power planes |
| Thickness range | 1.0 – 3.2 mm; keep dielectric > 75 µm for 100 Ω diff @ FR-4 Dk |
| Thermal reliefs | Match spoke width to plane Cu weight per IPC-2152 |
| Via-in-pad (VIPPO) | Copper-fill + planarize; ideal for BGA 0.8/0.65 mm pitch |
Thermal tip: For sustained board temps > 130 °C (e.g., under-hood), specify Tg ≥ 180 °C and Td ≥ 360 °C to ensure 1000-h reliability.
High-Tg vs. Standard FR-4 – Quick Comparison
| Metric | Standard FR-4 | High-Tg FR-4 |
| Tg (°C) | 135–150 | 170–200 |
| Pb-Free Reflow | Risk of delam after 3× cycles | Pass ≥ 6× cycles @ 260 °C |
| Z-axis CTE (ppm/°C) | 65–70 | 45–55 |
| Max Layer Count* | 1–8 | 1–16+ |
| Cost Factor | 0.8 | 1.0 |
*practical in 1.6 mm thickness with 0.25 mm min drill
Support All Types of PCB Fabrication
Biggest PCB Manufacturers
Why Source High-Tg FR-4 Boards from HighPCB?
- IPC-4101 /126, /129, /130 certified materials in stock – no MOQs.
- Stack-up simulation & Dk/Df certificate supplied with every quote.
- Microvia reliability proven: < 1 % void rate, 0 failures in 1000-cycle IST.
- Quick-turn: 7 days for 6-layer, 10 days for 10-layer production.
- End-to-end manufacturing – SMT, x-ray inspection, conformal coat, functional burn-in.
Ready to elevate your product’s thermal and signal-integrity headroom?
Request an instant high-Tg FR-4 quotation from HighPCB today and tap into our design-for-reliability expertise.
FAQ
1. Does high-Tg always mean halogen-free?
Not necessarily. High-Tg and halogen-free are independent specs. HighPCB offers both halogen-free high-Tg (IPC-4101 /129) and standard high-Tg (IPC-4101 /126).
2. Can I mix high-Tg cores with standard prepregs?
Yes, but keep Tg of all layers within 10 °C to avoid resin-rich interfaces and wicking.
3. What impedance can I hold on 8-layer 1.6 mm stack-up?
50 Ω single-ended and 90 Ω differential with 100 µm dielectric and 35 µm copper; HighPCB provides full field-solver reports.
4. What’s the largest panel size?
Up to 510 × 610 mm routed (20 × 24 in) with ± 0.10 mm registration.
