30
votes
Accepted
What exactly is prepreg and core in a PCB?
The important difference is this.
Core is a layer of FR4 with copper either side, that's made in a core factory. The layer of FR4 is formed between two smooth foils of copper, to a specified ...
- 171k
25
votes
Why has the auto-router put my PCB traces on two different layers?
It appears that your autorouter is using one layer for north-south traces (red) and another for east-west traces (blue).
Figure 1. This side of the board is almost all north-south routing. The east-...
- 178k
24
votes
Accepted
Purpose of multiple layer PCB without possibility of blind/buried vias?
I think you misunderstood the through-hole via.
Regardless of the number of layers, a through-hole via can have an electrical connection to all of the inner layers thanks to its full (not partial) ...
- 38.1k
16
votes
Accepted
Why has the auto-router put my PCB traces on two different layers?
Here's some advice - never use an auto-router until you have had several years experience in designing circuit boards. If I were to tell you what to do based on my own experience (many years) my ...
- 466k
15
votes
Accepted
Mechanical construction of PCB. What is between the layers?
You've got several parts to your question.
Those parts are represented by the red, blue, and green arrows I've added to the drawing:
The blue part references what's between the layers where there's ...
- 73k
13
votes
Accepted
Can I lay traces on internal layers of 4 layer PCB?
Tip. Keep ground as an inviolate layer, and use the 3 other layers for signals and power.
Treat power as a signal. While there are theoretical benefits to having a power plane, it is rarely worth it....
- 171k
13
votes
Accepted
Power line crossing data lines via the ground plane
it's less about the fact that these are power traces, it's problematic because now the return current for these data lines can't travel directly below them, but needs to take a shared detour around ...
- 98.2k
12
votes
Accepted
Are Gerber files of inner layers interchangeable?
The Gerber files do not specify the order of layers. As long as you don't use blind or buried vias, the layers can be stacked in any order.
The file names for the individual Gerber files may vary ...
- 60.2k
12
votes
Accepted
(Not) Impossible to separate AGND from DGND
For what it's worth, at my last two jobs I've had the pleasure of working with a super-talented electrical engineer (different person at each company), and in both cases the engineer's preferred ...
- 2,593
12
votes
4-layer PCB - Using bottom layer as power plane
It's fine. I use signal/gnd/-15/+15 stack up for opamps. It's amazing how much signal you can route on top layer when those pesky criss crossing dual supplies are out of the way.
Note the +5 plane on ...
- 80.3k
11
votes
The best stack-up possible with a four-layer PCB?
As the others said, it depends on your application. Another stackup I've found useful is
Signals (low speed)
Power
Signals (impedance controlled)
GND
This keeps the two signal groups well isolated ...
- 12.7k
11
votes
The best stack-up possible with a four-layer PCB?
Sig-GND-PWR-Sig will work just fine in many applications. However, I would not recommend it as a default choice.
What I personally use as default stack-up is this one:
Sig + Routed and/or Poured ...
- 3,446
11
votes
Accepted
Are core and prepreg dielectrics interchangeable?
Generally Core is more reproducible than Prepreg, for both thickness and dielctric constant. It is made in a factory making core to a specific thickness.
When prepreg is assembled into the final ...
- 171k
11
votes
Accepted
PCB base copper weight vs plating thickness
Base copper weight or thickness is the amount of copper that is on the PCB before they do anything to it.
Plating is what they do to the board to finish it, which also fills in the vias and holes ...
- 18.4k
11
votes
Accepted
How to calculate the size of ground plane we need to use in a PCB (printed circuit board) design
There are two aspects of a ground plane: its performance, and its appearance. The first is important. The second is not. Unfortunately, many people starting out concentrate on the second, to the ...
- 171k
11
votes
Accepted
PCB stencil layer for cutout
Solder paste layer is literally the layer intended to produce a stencil. That's its only purpose.
Typically the solder mask layer (which is used to produce the solder mask) is a bit different size ...
10
votes
Accepted
What are the advantages and disadvantages of Manhattan-Style routing?
The primary advantage of a Manhattan route is that it can always be completed. You just need to have enough board area to accommodate all of the traces — but otherwise, you'll never find ...
- 176k
10
votes
Accepted
Which is better for signal integrity in a two layer PCB? Two ground planes or one power and one ground plane?
If a 2 layer PCB is your only option: make the second layer ground and route your signals and power on the first. A proper ground/return plane is key for every signal and avoid sharing of the return ...
- 746
10
votes
Putting caps, resistors, etc on back side of board
It's pretty common to do that around BGA parts to get the bypass caps close to the pads.
I would be inclined to limit "back side" parts to a limited variety of mostly small passive parts ...
9
votes
Accepted
Routing and placement of decoupling capacitor when using power plane
As others have mentioned it's important to place the decoupling capacitors as close to the IC pins as possible to minimize the trace inductance between the capacitor and the IC supply pins. Otherwise ...
- 21.5k
9
votes
Are Gerber files of inner layers interchangeable?
If you want to swap the layers directly in KiCAD, the option you need is Edit -> Swap layers.
After swapping the layer contents, you can update the layer names in Design rules -> Layer setup.
- 9,021
9
votes
What exactly is prepreg and core in a PCB?
A core is a thick, more rigid layer of glass fiber while a prepreg is a thin layer of glass fiber/copper laminated onto a core. In the past, there only ever was one thick core, so the distinction made ...
- 14.4k
9
votes
Mechanical construction of PCB. What is between the layers?
The copper sections should all be connected -- the lines in the original diagram are not meaningful in terms of the resulting structure. Here's an updated diagram with fewer lines:
- 5,984
9
votes
Accepted
4-layer PCB - Using bottom layer as power plane
I was then wondering if I could use the bottom copper to define
multiple power planes around where they are used and created. They
could also act as thermal dissipater.
I don't see why not. This is ...
- 466k
9
votes
6-layer stackup
None of your proposals is the most conventional and cost effective because they use blind and/or buried vias. Blind and buried vias cost extra. Don't use them unless you actually need them.
https://...
- 57k
9
votes
Power line crossing data lines via the ground plane
If you need to do this in two layers, you can reduce the impact of the gap by routing a ground line on the top layer.
Ideally you will route it from the source of the signals to the destination (...
- 9,021
8
votes
Accepted
Is routing signal traces under components a good idea
The answer as always is: it depends.
In general, if the PCB design rules allow it (i.e. you are not violating minimum spacing, etc.), you should be OK. There are a few other reasons to avoid doing so,...
- 733
8
votes
Accepted
What are the rules to make different drill pairs for VIAs in PCB layers?
Generally, is there any suggestion for multilayer PCB drill pairs that is practically possible to fabricate and has the minimum limits for traveling between layers and also has the minimum impact on ...
- 132k
8
votes
Are Gerber files of inner layers interchangeable?
To make sure that you didn't make mistake, install an external Gerber file viewer (not connected to or produced by KiCAD). Then, after renaming, view the project in this viewer and imagine what others ...
- 2,370
Only top scored, non community-wiki answers of a minimum length are eligible