Separate board build-up from package substrates
Ajinomoto describes ABF as an insulating film used in semiconductor build-up substrates that supports laser processing and copper formation. That example shows why dielectric chemistry and circuit-forming process are connected. It does not mean a PCB fabricator can substitute a package-substrate film into an ordinary HDI stackup. Establish the intended manufacturing technology and supply chain first, then discuss materials that are actually supported for that board construction.
Describe the opening and the target
Give the fabricator the layer pair, dielectric thickness, entry geometry, landing-pad dimensions, and surrounding copper features. Ask which dimensions refer to the laser opening and which refer to the finished plated feature. A design can appear feasible in plan view while leaving an unfavorable three-dimensional geometry. Use a microvia aspect-ratio estimate as a screening aid, then have the proposed stackup and hole profile reviewed against the production process.
Include what happens after the laser
The design review should cover debris removal, target-pad condition, metallization continuity, and filling requirements. A visually open hole is only an intermediate process state. Ask what inspection or qualification evidence represents the intended material and via span. If a new dielectric is proposed, determine whether established cleaning and plating conditions still apply. Record the outcome as a process-qualified construction rather than merely adding laser drillable to the material description.
Choose geometry before pursuing minimum size
For a dense package escape, compare a slightly larger pad or a thinner build-up layer with the smallest nominal opening under consideration. The alternative may resolve a process constraint without adding another lamination cycle. Conversely, a smaller opening may not help if its landing pads still block the routing corridor. Review the full escape pattern and return paths alongside the material choice. The useful result is a repeatable connection that enables routing, not an isolated minimum feature.
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
Can every low-loss material use the same laser settings?
No. Material composition and construction influence processing. The fabricator must establish suitable conditions for the chosen dielectric and copper arrangement.
Does a successful laser opening prove reliability?
No. Cleaning, metallization, filling where required, interfaces, and thermal exposure must also be represented in the evidence.
References & further reading
Method & assumptions · General design guidance. Validate the proposed construction and acceptance criteria for your project.