If the
via has less cross-sectional area than the conductor, then multiple
vias can be used to maintain the same cross-sectional area as the conductor.
Small
vias on HASL finished boards (leaded or lead-free) often look closed, but will melt through in the reflow oven.
Vias are alternative interconnect strategies that help designers optimize layer utilization.
The other reason is attributed to silkscreen; tenting the
vias will permit more room for any required silk.
Vias are actually very nonuniform, and in some cases, depending on the application, require use of a 3D field-solver to be properly characterized and simulated.
There are no universally good approximations to estimate the electrical properties of single-ended or differential
vias.
Via-hole current return path localization may be used to separate the
vias into two groups for analysis purpose.
8 mm, aligning the
vias cannot be done because there isn't enough room between the ball pads for
via patterns; in fact most of the time, there is only room to put the
vias in the pads.
