I am working on a Power Supply Board. I am wondering what consideration do I need to consider when it comes to power and ground planes and what trace width do I need to use for power signals. I am thinking of 4 layer Stackup.
Following is just an idea.
L1: Power
L2: GND
L3: GND
L4: Routing of Control and Monitor Circuits.
If we go for standard 1.6 mm thick FR4 PCB than which thickness should I use between the layers.
In order to keep power ground coupling, there should be thinner dielectric between L1 (Power) and L2 (GND).
The L3 (GND) should be close to L4 (Routing).
This means there sill be a thick core between L2 (GND) and L3 (GND). What should be appropriate the thickness of the core ?
Do we have calculator for current measurement on traces ? In my case the voltage is 3.0 V and the current has to be up to 4.0 A. How much trace width should be fine ? and thickness of copper layer should be 35 um (1 oz) or it has to be more ?
I don’t think I should use 18 um (1/2 oz) for power plane.
Thanks for your reply. I just have used the tool you mentioned. I notice that copper thickness 70 um (2 oz) is even better and have lower DC drop and lower power loss at max current.
For a 4 Layer board, L2 and L3 will generally have a core in between them. and depending on the finished thickness requirement. Dielectric thickness can be adjusted or constructed to reach the required target finished thickness.
You can use our tool for Stackup construction
I have seen a table in your books in which via drill holes for various copper layer thickness is shown and also with reference to IPC compliance. I am not able to find that document but it exist somewhere.
Is there any explanation (or known history) to explain why going from 35mil/1oz copper to 70mil/2oz makes such a tiny difference? (Less than half the specified additional thickness is actually required?)
The starting or base copper on an outer layer is a piece of foil that comes in standard thicknesses as outlined on the left but finished plated thickness is something else. The important thing is to get at least .0008” of plating in the holes for Class 2 which don’t have any copper in them at all after drilling except for the layer interconnects. The standard process is to take the base thickness and add .0008” to get the final finished thickness – 1 oz copper @ .0014” thick + .0008” for the holes = .0026” on the surface. This is called a pattern plate where the holes and traces get plated at the same time. Unless something else is specified, the .0008” remains constant so thicker base foil is used to increase surface thickness. For fine line/HDI the base copper is usually kept to a minimum – down to 3um – to improve etching and the panels are plated up to the desired surface thickness. This process is referred to a semi-additive or modified semi-additive. The .0008” in the holes remains the same.
That’s a question for our sales but the copper foil is a pretty small part of the total build cost. Regarding aspect ratio, no real optimum but anything 12:1 or below if fine - lower is better.
