newbie 4-layer question

Community PCB Design
1

Suppose I have a 4-layer circuit board, stacked up as

Signal1

Gnd

Power

Signal2

and I want a via connecting Signal1 to Signal2. Should there be a ring of copper surrounding the hole in the Gnd and Power layers? Obviously it should not connect to the gnd/power planes, but does there have to be first a ring of copper inside the ring of clearance?

Thanks very much

Henry

2

The PCB software should automatically provide clearances around the via on the inner layers. You can check with a Gerber viewer if you want to see for yourself.

Leon

3

Thanks, but I am trying to figure out what settings I should put into the Eagle design rules dialog. The names and descriptions for the various measurements don’t exactly match 1:1 with the tolerances quoted by PCB houses.

4

I don’t use Eagle. The default values for the software I use are fine for the four-layer boards I’ve designed.

Leon

5

henryhallam:
Suppose I have a 4-layer circuit board, stacked up as

Signal1

Gnd

Power

Signal2

and I want a via connecting Signal1 to Signal2. Should there be a ring of copper surrounding the hole in the Gnd and Power layers? Obviously it should not connect to the gnd/power planes, but does there have to be first a ring of copper inside the ring of clearance?

Thanks very much

Henry

Generally speaking, no. However your design rule must maintain a clearance anyway - even if there is no annular ring on the layer.

The Geek

6

henryhallam:
Suppose I have a 4-layer circuit board, stacked up as

Signal1

Gnd

Power

Signal2

and I want a via connecting Signal1 to Signal2. Should there be a ring of copper surrounding the hole in the Gnd and Power layers? Obviously it should not connect to the gnd/power planes, but does there have to be first a ring of copper inside the ring of clearance?

Thanks very much

Henry

Henry - annulars (rings of copper) are typically present on all layers that a via touches. You could get away with not having annulars on the layers that the via does not have a trace/plane connecting to it - but you still can't run traces/planes right next to the hole. In a perfect world you could, but unfortunately PCB fabs cannot drill holes at exactly the center you specified - so you have to leave some space around the holes in case they miss by a little bit.

The exact amount of space you have to leave is PCB house dependent.