Via (electronics)
[1] As vertical structures crossing multiple layers, they are specified differently from most of the design, which increases the chance for errors.
If either the hole or any layer is slightly out of place, the wrong electrical connections may be made; this may not be visible from the surface.
Even an initially good board may develop problems later because the via reacts to heat differently from the substrate around it.
For cheaper boards, only through holes are made and antipad (or clearance) is placed on layers which are supposed not to be contacted to vias.
This differential expansion and contraction will induce cyclic fatigue in the copper plating, eventually resulting in crack propagation and an electrical open circuit.
[5][6] To ensure via robustness, IPC sponsored a round-robin exercise that developed a time to failure calculator.
[8] A via connecting the lowest layer of metal to diffusion or poly is typically called a "contact".
( 1 ) Through hole .
( 2 ) Blind via.
( 3 ) Buried via.
The gray and green layers are nonconducting, while the thin orange layers and red vias are conductive.
