Match the via to the connection
A through via traverses the board. Blind and buried structures connect selected layers. Microvias support short, fine interconnect transitions within an HDI construction. The choice affects routing space, process complexity and the approved stack-up.
Think about the pad and barrel together
Hole size, copper plating, annular ring, registration and material expansion influence the finished interconnect. Specify finished-hole requirements clearly and have the construction reviewed as a system.
Handle via-in-pad deliberately
An open via in a solder pad can alter solder behavior. Where via-in-pad is necessary, agree filling, planarization and surface requirements with the fabricator and assembly team. Tenting is a different treatment and should not be used as a substitute for a filled structure without review.
Evaluate signal and thermal effects
Vias can create electrical discontinuities and unused stubs. They can also form part of a thermal path. A single via geometry rarely optimizes routing density, signal performance, heat flow and cost at the same time.