FR408HR is an Isola laminate and prepreg system used when electrical loss and thermal performance matter. Select the actual construction, not only the family name.
What to consider
The manufacturer provides material and processing resources. Dk and Df vary with frequency and construction, so a single headline number is not a full impedance model. Confirm available cores, resin content and copper foil with the factory, then use the appropriate data in a stackup and channel analysis.
A practical review example
Compare an FR408HR candidate with the existing FR-4 construction at the actual channel length and edge rate. A lower-loss material is useful only if it improves a channel requirement that the design actually needs to meet.
Checks before release
- Use construction-specific Dk/Df data.
- Check pressed dielectric thickness and foil roughness.
- Confirm sequential-lamination suitability for the proposed via structure.
Connect this decision to fabrication
Use the material selector to organize the initial discussion. Keep proposed values separate from the approved drawing and document the effect of any change on the rest of the construction.
- Identify the exact grade, glass style, resin content and copper foil.
- Compare Dk and Df only with their frequency and test method.
- Confirm the material system is qualified for the proposed via structure.
Technical references
FR408HR material and processing resourcesReferences checked 2 October 2026. Manufacturer data describes its stated construction and is not an HDIPCB.org manufacturing commitment.