Removing VG DRC

Generally you should not get a fabrication or reliability issue if the vias or the via and pin are well spread out. Incase the vias or via and the pin comes too close to each other or overlaps then you could see issues in fabrication. 

Hi TCHA,

Thankyou for the reply. so you meant we can ignore the Via Gap DRC. 

Regards,
Jithindev

The BB Via gap is mainly done for manufacturing reasons. It could be the BB vias are first created on individual layers before creating the layer stackup, so to have a minimum gap between any two vias in a stack-up, this gap has been introduced.

You can however choose to add the 'BBVIA_SEPARATION' property to specify the span of layers where the MIN VIA GAP check is applied. By default, the span is infinite, which means that all the non-connected vias are checked even if these appear on the opposite sides of the design. So with a proper value set for BBvia_separation, you can choose to avoid the BB Via Gap DRC errors

The BBVIA_SEPARATION is a design-level integer property. You can also set the value from through Setup > Constraint > Modes > Design/General.

Hi TCHA,

Better if you briefly explain the manufacturing reason. since I have failed to find any.

Thank you
Jithindev

The Blind/Buried drill depths can sometimes vary causing the drill to pass beyond the drill stop layer into the adjacent dielectric layer. In such cases, a drill can get close to an adjacent layer drill start or stop layer causing a short during lamination cycles. Issues are not limited to fabrication only. It also can occur during assembly with the PCB going through multiple heat cycles. With todays modern fabrication processes these may not be a big concern but the rule is still relevant. Before sending out the board, you should consult your fabrication vendor.

As discussed earlier about the BBVIA_SEPARATION property, note, it is not realistic to set a Min Via Gap without also setting the BBVIA_SEPARATION. This is because a via drilled from Layer 1 to 2 will not be anywhere near a via drilled from Layer 12 to 11 so seeing a DRC in those cases will not be required.