Can somebody please explain the above problem, i am really stuck
Stacked partial vias are not supported in PADS Layout. If you use them you may see problems in Verify Design, CAM, IPC netlists and ODB++.
Expedition does support stacked partial vias.
If the PADS does not support stacked microvia then how i can route the 0.4mm pitch, 196pin BGA package in PADS?. Any guidance?.
Since "stacked" microvias aren't supported, you must stagger them. Otherwise it's the same thing. Use the Drill Pair settings to set them up.
It helps if you make the actual drill sizes slightly different for each via if you want to do a combined drill chart. For instance I might use a hole size of 0.1012mm for the via used to connect layer pair 1-2, and a hole size of 0.1034mm for the layers 3-4 pair. The CAM operator will know that you want the same size hole (0.1mm) for both vias, so it won't be a problem. If I remember correctly, you don't need to do anything special if you can do separate drill drawings for each drill pair.
we defined a microvia via a certain diameter from L1 to L3.
Then we described in a specification for the pcb manufactuerer, that he had to produce it as 2 stacked microvias from L1 to L2 and from L2 to L3