Copper filling and resin filling serve different construction needs. A plated barrel with resin and a copper cap is not the same structure as a copper-filled laser microvia.
What to consider
Select the process by via dimensions, thermal and electrical role, pad planarity and the next connection in the stack. Do not infer current capacity or thermal performance from the word “filled.” The barrel, fill, interfaces and copper cap all need to be considered in the completed structure.
A practical review example
A mechanically drilled core hole may use nonconductive resin fill and cap plating beneath a later microvia. Review the composite structure as one interconnect rather than treating the upper microvia as an isolated feature.
Checks before release
- Name the fill material and process.
- Specify acceptable cap and surface condition.
- Review stacked structures with the factory.
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.
- Record depth and diameter using the same units and measurement convention.
- Check capture lands, target lands and registration together.
- Match the test coupon to the actual interconnect construction.
Technical references
Fabrication design guidelinesHistorical IPC microvia reliability warning (2019)References checked 2 October 2026. Manufacturer data describes its stated construction and is not an HDIPCB.org manufacturing commitment.