A coupon should reproduce the relevant materials, geometry and process history of the production structure being evaluated.
What to consider
Include the via combinations and interfaces that drive the risk, not only the easiest standalone microvia. Coupons consume panel space but provide controlled access for measurements. Their dimensions, net topology and test method should be agreed with the fabricator and product quality team.
A practical review example
For stacked microvias over a filled core hole, ask whether the proposed coupon contains that complete sequence. A coupon with only isolated L1–L2 microvias does not represent the same interconnect.
Checks before release
- Match the production stack and materials.
- Identify the worst-case relevant structures.
- Keep test reports linked to manufacturing lots.
Connect this decision to fabrication
Use the design checklist 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.
- Specify acceptance and thermal exposure before requesting a quotation.
- Match coupon structure and process history to production.
- Review deviations and failure evidence with the responsible engineer.
Technical references
Historical IPC microvia reliability warning (2019)Fabrication design guidelinesReferences checked 2 October 2026. Manufacturer data describes its stated construction and is not an HDIPCB.org manufacturing commitment.