AD255C is a low-Dk woven-glass PTFE laminate for antenna-oriented RF structures. It offers a useful comparison point with AD250C and with the separately characterized AD255C-IM copper construction. The standard grade's design value and loss should not be silently transferred to the IM variant.
Material system
Woven-glass-reinforced PTFE
Technical properties
| Property | Reported value | Conditions / source |
|---|---|---|
| Process dielectric constant | 2.55 | Typical; 10 GHz, 23°C/50% RH; IPC-TM-650 2.5.5.5 clamped stripline; direction is not separately recorded here. Source |
| Design dielectric constant | 2.6 | Typical; 10 GHz, microstrip differential phase length method, C-24/23/50 conditioning. Source |
| Dissipation factor | 0.0013 | Typical; 10 GHz, 23°C/50% RH; IPC-TM-650 2.5.5.5; direction is not separately recorded here. Source |
| Thermal conductivity | 0.35 W/(m·K) | Typical, through thickness; ASTM D5470. The product table does not state test temperature. Source |
| Thermal coefficient of dielectric constant | -110 ppm/°C | Typical; 0°C to 100°C, IPC-TM-650 2.5.5.5 (modified temperature measurement); 10 GHz. Source |
| Water absorption | 0.03 % | Typical; E1/105 + D48/50, IPC-TM-650 2.6.2.1. Source |
Typical reported values are not a purchase specification. Process Dk, design Dk and values measured at different frequencies are not interchangeable.
Selection and design notes
- Consider it for antenna feeds where low dielectric loss and a controlled printed-circuit process are important. Evaluate the resulting radiator dimensions and line widths before deciding whether a higher-Dk alternative would fit the product better.
- For a PIM-sensitive design, compare complete foil constructions and realistic feed assemblies. The relevant difference may be the copper interface and joint quality rather than the bulk dielectric constant.
Thickness and copper options
Examples in the selector include 20, 30, 40, 60 and 125 mil; verify the current orderable construction and tolerance.
Standard ED, reverse-treated and IM-related options are distinct. Use the dedicated IM record when that cladding is required.
Fabrication considerations
- Specify panel orientation, foil and core thickness, then review drilling and plated-hole preparation with a PTFE-capable fabricator. Measure representative transmission structures using the same copper finish and connectors as the antenna assembly.
Application fit
- Base-station antennas
- Low-loss feed networks
- Printed antenna panels
Limits and substitution checks
- The AD255C-IM datasheet reports different Design Dk and Df observations from the base AD255C sheet. That is a reason to treat an IM upgrade as a characterized construction change. Neither low loss nor low PIM at laminate level guarantees array efficiency or system intermodulation after assembly.