PCB Stackup Design Process Thought Process Explained!

[@sean3994]

This was really interesting, I've moved into a PCB layout role and now have been avidly following the videos coming out of Altuim academy. The intricacy of layer stack up is so important to get right early on in the design process and this extends out to the designers choice of via spans on high density boards. I haven't had to go down the HDI route yet but it's only a matter of time. May of the videos dealing with BGA break out gloss over the process of dropping a via down a number of layers and don't go into the layer thickness to hole diameter complexity and even allude the the use of sintering processes rather than HDI microvias. I love to see a video on the sintering process in terms of its maturity and reliability, as sintering seems to be the 'holly grail' in my office.

[@mathewtomy3823]

Why 2nd layer can be the reference?

[@sean3994]

The second layer could have been the reference but this would mean a thin trace to achieve 50 ohm characteristic impedance. Skipping a layer provides greater distance from the trace to the reference plane and this allows a thicker (lower loss) signal trace.

[@mathewtomy3823]

@@sean3994 Oh okay understood

[@mathewtomy3823]

@@sean3994 Oh okay understood