Define the application that drives the choice
Start by stating the channel or RF requirement that motivates the material. A long digital interconnect, a phase-sensitive RF path, and a compact package escape ask different questions of the stackup. Isola provides material and construction data for I-Tera MT40; use those resources to select inputs relevant to the intended geometry. Keep application-specific requirements visible so that the material review does not become a comparison of unrelated headline properties.
Identify the dielectric around every critical route
For an embedded route, review both sides of the trace, including the bonding layers. For an outer-layer route, record the surface configuration and the intended reference plane. If only selected cores use I-Tera MT40, ask which material surrounds the transition into another routing layer. A channel can cross multiple dielectric environments. Build the model from those segments instead of assigning the chosen brand to the entire board by default.
Ask process questions early
Present the intended microvia spans, hole filling, copper geometry, and lamination sequence to the fabricator before final layout. Obtain a proposed construction that can be sourced and processed together. Do not infer that a process compatible with another laminate can be reused without review. If a different bonding material is suggested, ask how it changes cured thickness, adhesion requirements, and the electrical environment. Resolve the answer before freezing the impedance geometry.
Set a focused qualification and acceptance plan
Use the critical requirement to decide what evidence is needed. A loss-limited digital lane may justify a representative channel coupon; a phase-sensitive design may also need propagation characterization. Keep launch definitions, frequency range, construction, and conditioning consistent between simulation and measurement. Record the accepted material variant and foil in the release. If the production source proposes an alternative, require the comparison to address the same requirement that originally justified this material.
A construction is more than its laminate name
Dielectric · geometry + material
Core or build-up dielectric
Illustrative only. Copper thickness, dielectric construction and via spans require a reviewed stackup.
Common questions
Does choosing I-Tera MT40 eliminate the need for via optimization?
No. A favorable dielectric does not remove reflections, stubs, asymmetry, or return-path discontinuities in the channel.
Can it be mixed with another material?
A hybrid may be possible, but it requires review of the exact bonding system, electrical field distribution, process sequence, and dimensional behavior.
References & further reading
Method & assumptions · General design guidance. Validate the proposed construction and acceptance criteria for your project.