I used the following Stackup - in respect to recommendations provided by my board house and the responses to this question.
This is a 6-Layer, 0.5mm thick, 1 + 4 + 1 HDI board (Copper thicknesses are not correct in the image).
As pointed towards in the comments, i had a look at some youtube videos.
Secrets of PCB Optimization - Rick Hartley - AltiumLive 2020 from 1:18:50 anwards gave me a good hint!
Good video for HDI Design Basics
As further information seems to be helpful: Here it is!
I am working on a very small board (3x7mm) with double sided load.
Packages used are 0201, BGA (0.35mm, 0.4mm and 0.5mm Grid) and 2x2 12-LGA.
This is a "medium frequency (MCU runs at 150MHz)", low power (15mA), purely digital design.
As previous attempts to route the design on 4 layers failed because of "messy results, bad GND-Layers etc. etc." I decided to give 6-Layers a shot.
From Top to Bottom: Signal-GND-Signal-Signal-GND-Signal.
There are no dedicated power planes, as I can decouple each device and there is only little power draw. I used GND planes as sensitive electronics are used (Strictly recommended by IC manufacturer to use multiple GND-Planes).
Issues I am having:
-As I have double sided load, I use plugged through-vias only very carefully and not to break-out the BGAs.
-As this product will be a small lot size, I need a cost effective PCB design.
My current routing:
Currently I plan on routing like this: Fan-Out BGAs on top/bot layer and via Blind-Vias to associated GND plane (1-2 and 15-16) - Caution: The BGAs are 4x4 Grid - therefore, I only need to fan-out 4 signals to the GND plane.
Signals that need to run from TOP to BOT components are routed by means of through vias. As these signals runs all across the board - yes I tried many component orientations and placements - I need to "unravel" these signals on the inner signal layers.
My question is:
-Which via-arrangement will be - in your experience - the most cost effective?
Yes, I talk to my board-house but I like the input from this forum very much!
I am interested in information regarding the "correct" way to define a 6-layer board.
My objectives are:
- Use the "cheapest" stackup available to fit my requirements
- Be independent of a specific board house
My requirements are:
6-layer with vias from 1-2, 15-16 (1=top, 16=bottom, you get the system)
Option to interconnect 2-15 and 3-14 in some way
What I came up with:
- My first idea is to use the following build-up:
This way, there are three cores (etched, drilled, plated) - then pressed with prepreg and drilled and plated again.
- My second idea is the following stack-up:
This way, there are two cores etched and pressed, then two prepregs pressed, etched, laser-drilled and drilled normally - then plated.
- My third idea is the following stack-up:
This way, there are two cores etched, pressed, drilled and plated - then two prepregs pressed and etched, laser drilled and plated.
My question is:
- What is the most cost-effective and conventional stackup of these three?