Make the requirement unambiguous

Ask the customer or product team which declaration, standard, revision, and material scope the requirement refers to. The requested evidence may concern the laminate system, the finished bare board, or a larger assembly. Keep that scope in the purchasing record. Avoid using an informal green label as a release criterion. Where formal compliance is required, obtain the current supplier declaration and have the responsible compliance team confirm that it satisfies the product requirement.

Treat the variant as its own material choice

Panasonic introduced a specifically designated halogen-free MEGTRON6 material. The relevant lesson is that a family name can contain distinct variants. Preserve the full product designation in the stackup and quotation request. Do not assume that a familiar standard variant and a halogen-free variant have identical constructions, copper options, or processing requirements. Ask for the data and availability of the material that will actually be supplied.

Recheck the HDI construction

Evaluate thin dielectric availability, laser processing, resin flow, adhesion, and the planned lamination sequence. An existing board may need a different ply arrangement when its material system changes. Request a revised stackup and compare critical dielectric separations before approving the conversion. Also ask whether the same via structures and assembly exposure are covered by existing qualification evidence. Treat unsupported details as open engineering items rather than assuming the composition requirement resolves them.

Close the electrical and sourcing review together

Recalculate impedance and channel performance using the proposed construction. Record any changes to width, spacing, or timing assumptions, and check their effect on dense package escapes. Then define how substitutions will be handled if the designated material is unavailable. A substitution request should include both the required declaration and the engineering comparison. This prevents a supply problem from being solved with a composition-compliant material that has not been evaluated electrically or mechanically.

  • Record the exact variant and declaration revision.
  • Keep environmental documentation separate from test evidence.
  • Require review of both material and construction changes.
DESIGN NOTE / SCHEMATIC

A construction is more than its laminate name

Signal copper

Dielectric · geometry + material

Reference copper

Core or build-up dielectric

Signal copper

Illustrative only. Copper thickness, dielectric construction and via spans require a reviewed stackup.

Common questions

Does halogen-free mean the material is low loss?

No. Composition requirements and dielectric performance are different specifications. Use the appropriate construction data for electrical comparison.

Can a RoHS statement replace a halogen-free declaration?

Do not treat the terms as interchangeable. Ask the responsible compliance team to verify the exact documentation required for the product and jurisdiction.

References & further reading

Method & assumptions · General design guidance. Validate the proposed construction and acceptance criteria for your project.