Read the value with its test condition
Rogers lists RO4350B as a reinforced hydrocarbon/ceramic laminate. Its RO4000 datasheet distinguishes a process Dk of 3.48 ± 0.05 at 10 GHz/23°C using the stated clamped-stripline method from a design Dk of 3.66. The datasheet also identifies a different process value for the 4 mil construction.
These numbers answer different characterization needs. Keep the method, frequency, direction and construction with the value used in a model. Do not silently replace a design value with a process-control value because one appears more precise.
Define more than a laminate name
Specify the exact grade, dielectric thickness and copper option, together with the layer construction. A shortened reference such as RO4350 can leave the intended product unclear. Obtain the relevant current manufacturer data and confirm the proposed construction with the fabricator.
Copper profile, trace geometry, finish and adjacent materials contribute to the finished channel. A dielectric constant does not independently determine insertion loss, launch quality or impedance tolerance. Include the actual structure in the electrical model.
Review the modeled and manufactured structures
Ask the fabricator to review the stackup and any controlled-impedance structures before layout release. Document the material-property assumptions and which geometric adjustments require approval. If a hybrid construction is used, identify every material and bonding layer.
Do not treat a manufacturer typical property as a guarantee for every finished board. Define the project acceptance evidence, such as material identity, geometry, coupons or assembled RF measurements. Distinguish these checks from qualification of the complete product.
Prepare the quotation package
Provide quantity, board outline, layer data, drill information, material construction and critical electrical or mechanical requirements. Identify approved alternatives explicitly; a proposed substitute should receive an engineering review rather than being accepted by brand similarity.
Retain the accepted stackup, data revision and manufacturing assumptions with the release. Availability and lead time are confirmed for the requested construction. This material guide does not imply that every thickness or copper option is held in stock.