The numbers behind RT/duroid 5870 and 5880 in one place: dielectric constant, loss tangent, moisture absorption and what they mean in practice.
RT/duroid 5880 and 5870 are PTFE glass fibre reinforced composites. The micro-glass fibres are randomly oriented through the material rather than woven in layers, which provides strength in every direction and keeps the electrical behaviour isotropic — useful for both the circuit itself and the production process. For a wider view of this family, our RT/duroid 5880 parameter reference covers the surrounding grades.
These laminates sit at the low end of the dielectric constant range among comparable materials, and their dissipation factor is the headline number. Measured at 10 GHz under IPC-TM 2.5.5.5, RT/duroid 5880 comes in at 2.20 ± 0.02 for Dk and 0.0009 for Df. That combination is what makes the material suitable for high-frequency and broadband designs where dispersion and loss have to be minimised, and it supports operation up to Ku-band and beyond.
Moisture absorption of just 0.02% matters as much as the electrical figures. Water in a laminate raises loss and shifts Dk, so a material that barely absorbs moisture holds its performance in humid conditions and after repeated thermal cycling. The electrical characteristics also change very little with frequency, which is what lets one material serve a wide band instead of a narrow slice of it.
| Property | Value | Condition |
|---|---|---|
| Dielectric constant (Dk) | 2.20 ± 0.02 | 10 GHz, IPC-TM 2.5.5.5 |
| Dissipation factor (Df) | 0.0009 | 10 GHz, IPC-TM 2.5.5.5 |
| Moisture absorption | 0.02% | — |
| Useful frequency range | up to Ku-band and higher | — |
| Copper cladding | 8–70 µm electrodeposited | — |
| Lead-free assembly | Compatible | — |
RT/duroid 5880 cuts and shapes easily, which is not a trivial point: it adapts to the cavity and cut-out geometries that high-frequency designs ask for. The laminate also resists the acidic and alkaline reagents used in processing and survives the high- and low-temperature steps of a normal build.
Electrodeposited copper cladding is available from 8 to 70 µm, giving designers room to trade copper weight against impedance and current capacity. In practice most of the difficulty with this family sits on the PTFE side of the process rather than the material side, so it is worth reading the known production challenges with Rogers 5880 before a first build. If you are weighing it against glass-cloth PTFE alternatives, our notes on PTFE glass fibre cloth copper clad laminate cover that comparison.
The two grades share the same reinforced-PTFE platform and the same basic profile: the lowest dissipation factor available in reinforced PTFE materials, low moisture absorption, isotropic electrical behaviour, and characteristics that barely move with frequency. That is why they appear together in the same application lists, from microstrip and stripline work through to millimeter-wave hardware and military radar.
Treat 5880 as the reference point when loss is the binding constraint, and 5870 as the same family with a different balance of properties. For the wider picture, our material overview of the RT/duroid 5880 platform and the ultra-low-loss case for 5880 in millimeter-wave designs both pick up where the datasheet figures stop.
Frequently Asked Questions
2.20 ± 0.02 at 10 GHz under IPC-TM 2.5.5.5, one of the lowest values available among reinforced PTFE laminates.
0.0009 at 10 GHz under the same standard — the lowest dissipation factor available in reinforced PTFE materials.
Yes. It is specified as compatible with lead-free processes and withstands the higher reflow temperatures they involve.
Water in a laminate raises loss and shifts the dielectric constant. A material that barely absorbs moisture keeps its electrical behaviour in humid conditions and after thermal cycling.
Electrodeposited copper cladding from 8 to 70 µm, which lets you trade copper weight against impedance and current capacity.
Tell us the grade, copper weight and stack-up and we will confirm availability and lead time.
Get a Fast Quote Fast Reply on WhatsApp