Silver Filled Vias v/s Regular Vias
Typically, there are two methods that are used to fill vias: Conductive and Non-conductive filled vias. Most have gotten away from using the conductive epoxy (silver filled vias) because it does not provide the ability to fill the holes as well as the non-conductive epoxy. When you do not get a good fill, the pad or surface has a tendency to slump or appear as a dimple. Out-gassing can also take place if you do not get a good reliable fill.
These days, most companies are switching from conductive to non-conductive filled vias. The dimple effect does not provide a flat surface ideal for BGA placement.
The thermal profile used for both the silver filled vias and regular vias are almost identical. There is very little difference in the temperature settings when you are using the same board. The peak temperature difference is typically less than1ºC.
Images of both the epoxy filled vias and regular vias.
Figure shows regular vias in “dog bone” layout form.
Figure shows regular vias with solder mask.
Figure shows epoxy filled vias (via in pad).
The main reason that companies are switching to via in pad design is due to real estate on a layout. The via in pad allows the design team more room to run circuits between the pads which the regular “dog bone” vias won’t allow.