27 votes
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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 ...
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  • 142k
24 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-...
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  • 160k
23 votes
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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) ...
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17 votes
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Breakaway PCB Design

But for a mechanical strain relief for over stress on users with kids and USB plugs getting torn out, it is excellent. The main board has a good 3 point screw hole mount to eliminate torsional ...
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16 votes
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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 ...
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  • 384k
15 votes
Accepted

Is it always possible to reduce the number of layers on a PCB by making the board larger

Ah the horror of trying to make DDR work in two layers :) The long answer is of course to learn about signal integrity and try to understand exactly what you are doing. I have seen this done before, ...
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15 votes
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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 ...
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  • 58.5k
14 votes
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Hide particular airwires/nets in eagle

Yep, and it's pretty straightforward. Just click on the Info button , select the airwire you want to hide, and click on the "Airwires hidden" checkbox. All airwires on that same net will be hidden. ...
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  • 8,344
13 votes
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50MHz SPI PCB routing, use vias or resistors?

SPI bus at 50MHz can easily run a couple of inches thru a few vias without hitch. Wavelength of 50MHz is 6 metres but realistically because fast edges are used you need to think ten times faster. Even ...
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  • 384k
13 votes
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Can differential USB traces be routed relative to Power (not Ground) planes?

The short answer is you're going to be fine, route it above VCC and make sure you have some VCC to GND decoupling caps near your chip. Plus your route is pretty short at 600mil, I've seen some people ...
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13 votes
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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....
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  • 142k
12 votes

The best stack-up possible with a four-layer PCB?

"best" depends on the application. Theres really two questions to address in your post "Conventional" (signals on outer layers, planes on inner layers) VS "inside-out" (signals on inner layers, ...
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  • 19.3k
12 votes
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How do I disable clearance check for a layer or for only some certain elements?

You can specify a design rule for that component: Design > Rule > Placement > Component Clearance, Add new rule like this: Advanced query: ...
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  • 136
12 votes
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4 layer PCBs with Fritzing

If you want to make 4 layer boards, use a real tool, not a toy. Design Spark PCB is easy to learn. KICAD is a bit more difficult. Both are free, and support unlimited layers and pins. As has already ...
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  • 13.6k
12 votes

Enabling extra routing layers in Eagle (paid version) PCB design

As Dave posted in his answer (+1), you need to enable the layers in the DRC. Here's an example: And from the EAGLE help file (which is an excellent resource by the way): Layers The Layers tab ...
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  • 11.6k
11 votes

4 layer PCBs with Fritzing

Fritzing only supports two copper layers, you can see an example at the Fritzing's View options tutorial and it only has the copper 0 and copper 1 layers available for display. As for the maximum ...
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  • 16.9k
11 votes
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Return path on a PCB

When TX switches low-to-high, the current flows like this: Power supply Vcc -> PCB Vcc plane -> U1.Vcc pin -> U1.TX pin -> U2.RX pin -> U2.Gnd pin -> "return path" -> PCB Gnd plane -> Power supply ...
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11 votes
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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 ...
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  • 142k
11 votes
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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 ...
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11 votes
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(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 ...
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  • 2,423
11 votes
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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 ...
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  • 142k
10 votes
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PCB, pads with holes but with different nets on top and bottom sides

I don't see any reason why you can't create a footprint with overlayed pads on top and bottom going to different pins. Just specify the hole as unplated. If you avoid drilling one of the holes (make ...
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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 ...
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  • 165k
9 votes
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Tips on routing multiple powers(+5/-5/+15/-15/3.3 and etc. ) for a four-layer PCB

Generally you don't need separate planes for power. If you have a good solid ground everywhere (you do want a plane for that in many cases), then the only issue for power is that the voltage drops ...
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9 votes
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PCB Tinning to increase current

While DrFriedParts provided an answer to the question you asked, I feel I ought to respond to your premise, instead. Specifically, "i do know this decreases the resistance of the tracks and increases ...
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9 votes
Accepted

PCB Stackup - Current return path

Difference between core and prepreg is that core has cooper filled on both sides of dielectric and prepreg is just full dielectric, no copper on any side of the material. Since you just sandwiched ...
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  • 121k
9 votes

Is it always possible to reduce the number of layers on a PCB by making the board larger

There are number of reasons in which you have multilayer boards, and when it comes to high speed design, DDR3 for instance, there is alot more happening than just the connections from pin to pin. At ...
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  • 11.5k
9 votes
Accepted

Four layer PCB, leaks current on edges

If there is exposed copper at the edges, then the board was designed improperly. Almost certainly whatever software you are using to design this board has a parameter that controls how close edges ...
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9 votes
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What is the "Eco1.User" layer in KiCad?

For recording "Engineering Change Order" documentation, comments, artwork changes, etc. (Similar to a list of revisions with graphic capabilities.)
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  • 5,779
9 votes
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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 ...
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