Start with the electrical connection you need
Map the source and destination layers for each via type. A through via extends across the board, while a blind via connects an outer layer to an internal layer and a buried via connects internal layers without opening at either finished surface. The required connection should drive the structure rather than choosing a more complex process by default.
Consider routing access, component escape and the reference environment around the transition. A via may save routing space while introducing a transition that needs electrical analysis. Identify any critical high-speed nets and the board thickness so engineering can review the actual construction. Do not infer signal performance solely from the via’s name.
Distinguish layer structures from surface treatments
Terms describing the opening are not interchangeable with terms describing layer span. A through via may be open, masked or specially filled; a blind feature may also require its own filling process. State the intended result on a section drawing when terminology could be interpreted in more than one way.
Tenting refers to covering an opening with solder mask. Plugging and filling describe other forms of hole treatment whose details must be defined. A filled and copper-capped structure intended to form part of a solder land needs a different specification from a simple mask-covered via away from components. Confirm the process and acceptance expectation rather than using covered as a complete instruction.
| Term | Describes | Question to resolve |
|---|---|---|
| Through via | Connection across board depth | Finished hole, pad and plating |
| Blind via | Outer-to-inner connection | Layer span and build sequence |
| Buried via | Internal connection | Subassembly and inspection |
| Tented via | Mask over an opening | Which side and what acceptance |
| Filled / capped via | Specified hole treatment | Fill, cap and surface requirements |
Use geometry calculations for the question they answer
Pad diameter, hole diameter and board thickness can support useful geometric checks. A nominal radial annular ring follows from the difference between pad and hole diameters. A simple aspect ratio compares the relevant depth with the relevant drill size. These calculations organize the discussion; they do not establish process capability or long-term reliability.
Be explicit about whether a hole dimension is drilled or finished after plating. Positional tolerances and fabrication variation matter to the retained copper around a real hole. A calculator that assumes concentric circles cannot certify the manufactured annular ring. Provide the complete drill definition and let the accepted process and inspection requirements determine the final limits.
Review assembly interactions near solder lands
An opening inside or immediately beside a solder land can influence the available solder and the printed-paste pattern. The importance depends on the component package, land geometry and assembly process. Review thermal-pad vias and dense escape patterns with the component manufacturer’s attachment guidance rather than applying one treatment to every package.
If solder migration is a concern, compare relocating the via, changing the land arrangement or specifying an appropriate filled structure. Each option can affect routing, thermal behavior and cost. Keep the package land-pattern requirements visible throughout the decision. A mask change should not be treated as automatically equivalent to a planar copper-capped via.
Connect the via choice to the reliability requirement
The service environment, thermal cycles, assembly exposures and chosen construction all matter when defining validation. More vias or smaller holes do not create an automatic reliability improvement. Identify the loading conditions and the evidence needed for the actual application, especially when changing from a previously qualified structure.
For a design revision, record which via types have changed and why. If a new structure changes the fabrication sequence, request confirmation of the manufacturing and inspection approach. Keep material and copper assumptions aligned with the via drawing. A geometric rule inherited from another board may be irrelevant when thickness, material or operating conditions have changed.
Release a via table rather than scattered notes
List each via type, connected layers, hole and pad dimensions, treatment, and any special acceptance requirement. Use the same identifiers in the drawing and design data. Separate component holes from vias and non-plated mechanical holes so the intended processing is unambiguous.
The via geometry checker supports basic calculations without claiming current capacity or reliability. Review via-in-pad requirements and HDI construction where relevant, then return to capabilities for the broader build. Attach the via table to Request a Quote and ask for engineering review of the combined structure, material and board thickness.
Via construction checklist
Use this checklist to prepare your inquiry. These selections stay in this browser and do not submit a project.
Frequently asked questions
Is a tented via the same as a filled via?
No. Mask coverage and a specified hole-filling process create different structures. Define the required cross-section, surfaces and acceptance criteria rather than treating the terms as interchangeable.
Should I specify drill diameter or finished hole diameter?
Make the convention explicit. The fabrication package must distinguish the tool-related dimension from the finished plated opening and keep that convention consistent across drill data and drawing notes.
Does a geometry checker prove a via is reliable?
No. It calculates defined geometric relationships. Process capability, plating, material, thermal exposure and the validation plan remain necessary to assess the manufactured structure.
Are blind vias always needed for fine-pitch components?
Not automatically. Package escape requirements, available layers, routing space and permitted geometry determine the need. Review the actual footprint and layout before choosing a more complex build sequence.
Can via treatment be changed without changing the design?
It may affect assembly, routing or validation even when the netlist is unchanged. Record the proposed process change and obtain the appropriate approval before releasing revised fabrication instructions.