Product Description
Material Overview – F4BM255 (Wangling)
F4BM255 is a PTFE (polytetrafluoroethylene) woven glass fabric copper-clad laminate produced by Taizhou Wangling Insulation Materials Factory. It is engineered for microwave and RF applications requiring low dielectric loss, stable dielectric constant across temperature, and excellent dimensional stability .
The material is manufactured by scientifically formulating PTFE resin with woven glass fabric and laminating under strict process control.
This construction provides:
Glass reinforcement – improves dimensional stability and reduces thermal expansion
PTFE dielectric – delivers ultra-low loss and stable Dk
ED copper foil – standard electrodeposited copper (F4BM series)
Key Material Characteristics
| Feature |
Benefit |
| Dk = 2.55 ± 0.05 @ 10 GHz |
Low and stable dielectric constant – consistent impedance across frequency . |
| Df = 0.0013 @ 10 GHz |
Very low dissipation factor – minimizes insertion loss . |
| Dk temperature coefficient = -110 ppm/°C |
Stable Dk across -55°C to +150°C – essential for outdoor/automotive applications . |
| Tg > 280°C (DSC) |
High thermal stability – supports lead-free assembly . |
| Td = 360°C |
Excellent thermal decomposition resistance – robust for harsh environments . |
| XY CTE = 16–21 ppm/°C |
Good dimensional stability – matches copper for reliable PTHs . |
| Z-axis CTE = 173 ppm/°C |
Low Z-axis expansion – reduces PTH stress during thermal cycling . |
| Moisture Absorption ≤ 0.08% |
Maintains electrical stability in humid environments . |
| Thermal Conductivity = 0.33 W/m·K |
Adequate heat dissipation for RF power circuits . |
| UL 94 V-0 |
Meets safety requirements . |
Typical Applications
- Microwave Antennas
- RF Power Distribution
- Phase Shifters
- Satellite Communications
- Radar Systems
Material Datasheet – Consolidated Properties (F4BM255)
| Property Category |
Property |
Test Condition |
Typical Value |
Unit |
| Electrical |
Dielectric Constant (Dk) |
10 GHz |
2.55 ± 0.05 |
– |
| Dissipation Factor (Df) |
10 GHz |
0.0013 |
– |
| Dissipation Factor (Df) |
20 GHz |
0.0018 |
– |
| Dk Temperature Coefficient |
-55°C to +150°C |
-110 |
ppm/°C |
| Volume Resistivity |
Normal |
≥ 6 × 10⁶ |
MΩ·cm |
| Surface Resistivity |
Normal |
≥ 1 × 10⁶ |
MΩ |
| Dielectric Strength (Z-axis) |
5kV, 500V/s |
> 25 |
kV/mm |
| Breakdown Voltage (XY-axis) |
5kV, 500V/s |
> 34 |
kV |
| Thermal |
Thermal Stress (260°C, 10s × 3) |
Solder float |
No delamination |
– |
| CTE – XY direction |
-55°C to 288°C |
16–21 |
ppm/°C |
| CTE – Z direction |
-55°C to 288°C |
173 |
ppm/°C |
| Thermal Conductivity (Z-axis) |
– |
0.33 |
W/(m·K) |
| Continuous Operating Temp |
– |
-55 to +260 |
°C |
| Flammability |
UL 94 |
V-0 |
Rating |
| Mechanical |
Peel Strength (1oz ED copper) |
Normal |
> 1.8 |
N/mm |
| Peel Strength (1oz RTF copper) |
Normal |
> 1.6 |
N/mm |
| Density |
Normal |
2.25 |
g/cm³ |
| Physical |
Water Absorption |
24h @ 20±2°C |
≤ 0.08 |
% |
| Composition |
Core Material |
– |
PTFE + Woven Glass |
– |
| Copper Foil (F4BM) |
– |
ED Copper |
– |
Standard Availability
| Parameter |
Options |
| Copper Foil (F4BM) |
0.5oz (18µm), 1oz (35µm), 1.5oz (50µm), 2oz (70µm) |
| Standard Panel Sizes |
460×610mm, 500×600mm, 850×1200mm, 914×1220mm, 1000×1200mm |
| Custom Sizes |
300×250mm, 350×380mm, 500×500mm, 840×840mm, 1000×1500mm |
| Thickness Range |
0.1mm (min for Dk ≤ 2.65) to 12.0mm |
| Size Restriction |
For thickness ≤0.2mm or ≥4.0mm: max panel 500×610mm |
Custom PCB – Double-Sided F4BM255 with 2oz Copper & ENIG Finish
This double-sided board demonstrates our capability to handle long-format F4BM255 PCBs with heavy copper and tight dimensional tolerances .
Basic Specifications
| Item |
Specification |
| Layer Count |
2 layers |
| Base Material |
Wangling F4BM255 – 3.0mm dielectric thickness |
| Finished Board Thickness |
3.1mm (3.0mm dielectric + 2 × 0.035mm copper) |
| Finished Copper Weight |
2oz / 2oz (70µm) – both sides |
| Copper Foil Type |
ED copper (F4BM series) |
| Surface Finish |
ENIG (Immersion Gold) |
| Solder Mask (Top) |
Green |
| Silkscreen (Top) |
White |
| Solder Mask (Bottom) |
None (bare copper) |
| Silkscreen (Bottom) |
None |
| Board Dimensions |
521mm × 59mm (1 piece, ±0.15mm tolerance) |
| Minimum Trace/Space |
7/7 mils |
| Minimum Hole Size |
0.4mm |
| Via Plating Thickness |
20µm |
| Via Structure |
No blind vias – through-hole only |
| Components |
28 |
| Total Pads |
194 (148 through-hole, 46 top SMT) |
| Nets |
2 |
| Quality Standard |
IPC-6012 Class 2 |
| Artwork Format |
Gerber RS-274-X |
Why F4BM255 for This Design?
| Requirement |
How F4BM255 Addresses It |
| Microwave frequency operation |
Df = 0.0013 @ 10 GHz, Df = 0.0018 @ 20 GHz – minimal insertion loss for RF signal integrity . |
| Stable dielectric constant |
Dk = 2.55 ± 0.05 – consistent impedance across the long 521mm format . |
| High-power RF handling |
2oz copper (70µm) reduces DC resistance and improves thermal dissipation . |
| Temperature stability |
Dk TC = -110 ppm/°C – stable performance across -55°C to +260°C . |
| Long-format linear array |
3.0mm thick F4BM255 with warp ≤0.010 mm/mm ensures flatness across 521mm length . |
| Cost-effective PTFE alternative |
F4BM255 offers comparable performance to imported PTFE at competitive pricing . |
| Solderable surface |
ENIG finish provides excellent solderability for component attachment and wire bonding . |
Q1: What does F4BM255 mean?
A: F4B = Wangling's PTFE woven glass laminate series; M = ED copper foil; 255 = dielectric constant 2.55 .
Q2: What is the difference between F4BM and F4BME?
A: F4BM uses standard ED copper (general RF applications). F4BME uses reverse-treated RTF copper for ultra-low PIM (≤-159 dBc) – ideal for carrier-grade base station antennas .
Q3: Does F4BM255 require special processing like imported PTFE?
A: F4BM255 does not require sodium etch for standard ED copper. However, for PTH metallization, plasma treatment or sodium-naphthalene solution is recommended .
Q4: Why choose 2oz copper for this design?
A: 2oz (70µm) copper provides lower DC resistance and better thermal dissipation for high-power RF circuits. It also supports the high-current requirements of large antenna feed networks .
Q5: What is the maximum warp for 3.0mm F4BM255?
A: For 3.0–5.0mm thick boards, maximum warp is ≤0.010 mm/mm – ensuring flatness across the 521mm length .
Q6: What is the minimum hole size for F4BM255?
A: Minimum mechanical drill size is 0.4mm (as specified in this design). Drilling parameters require standard carbide tooling with controlled feed rates .
Q7: Is ENIG the only surface finish available?
A: No. ENIG is specified for this design. Other options include OSP, HASL, immersion silver, immersion tin – depending on your application requirements .
Q8: Can F4BM255 be used for millimeter-wave (mmWave) applications?
A: Yes. F4BM255 has been used in microwave and millimeter-wave bands (cmWave, mmWave) for antennas and feed networks. The Df of 0.0018 @ 20 GHz demonstrates suitability up to 20 GHz+ .
Q9: What is the lead time for this 521mm × 59mm board?
A: Typical prototype lead time is 7–10 working days for double-sided boards with ENIG and 2oz copper. Large-format production may require additional time for panel optimization.
Q10: Can you provide impedance control for this long-format board?
A: Yes. With stable Dk = 2.55 ± 0.05, we can design and control impedance across the entire 521mm length. Final impedance values are verified by TDR testing.
Contact Us
As a specialized PCB supplier based in China, we have extensive experience with Wangling F4BM255 PTFE laminates, heavy copper (2oz+) PCBs, and long-format microwave substrates .
We provide:
- Full material traceability (certificates from Wangling)
- Large-format PCB fabrication up to 521mm length
- Heavy copper etching (2oz+)
- ENIG and other surface finishes per your requirements
- Impedance testing (TDR) with detailed reports
- 100% electrical testing prior to shipment
- IPC Class 2 and Class 3 qualification
For technical inquiries, stack-up review, or quotation requests, please contact our sales team directly. We are ready to support your microwave antenna, RF distribution, and high-power RF projects.
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