Electrical Engineering Stack Exchange
Electrical Engineering Stack Exchange

Questions tagged [pcb]

PCB is the acronym to Printed Circuit Board. A PCB is a carrier for the circuit's components and their electrical connections.

Most are made from a version of fiberglass and epoxy resin called FR-4. These boards are usually green, but can be any color. PCBs are typical 63 mils (1.6 mm) thick (1 mil = 1/1000"). Other thicknesses used are 39 mils (1 mm) and 31 mils (0.8 mm). PCBs can be single layer (traces on one side), two layers (traces on both sides), or multilayer (traces (or planes) on both sides and internal layers).

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Why are there teardrops on PCB pads?

What's the use of the teardrop shapes around some PCB pads?
Federico Russo
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Why does there seem to be a missing component in many PCBs?

I've seen some PCBs were some components have been sketched, but they don't seem to be mounted on the board. See, this image (of a PlayStation 2) where the transformer has been drawn: Why is this done on some circuits?
jinawee
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PCB colors - what's available, and why?

A question so simple I've never thought about it before. Usually I get my PCBs made in standard green, but have been offered a blue for my next revision of an existing (green) board at no extra cost. What colors are available as standard, and why…
Dirk Bruere
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What are the advantages and disadvantages of thinner PCB thickness (<1.6 mm or 0.063'')?

What are the advantages and disadvantages of thinner PCB thickness (<1.6 mm)? My approach: Better capacitance interplane and better power decoupling. Better track-plane coupling. Problems with assembly process with heavy components Problems with…
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PCB 90 degree angles

Not a dup of which barely attends to the technical reasons for or against using 90 degree routes. As a hobbyist who's enrolling in an EE program in the fall, should I just get in the habit of avoiding right angles in PCB layout? Is this always a…
inbinder
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Why thermal reliefs on vias?

My EDA software (PCAD, but I guess others do this too) adds thermal reliefs on vias in a copper pour. What's the use? Vias aren't soldered. (I know why you use them on regular PTH pads)
stevenvh
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When do I use fiducials for individual components on a PCB?

Obviously the panel needs fiducials, and I also place three of them on each PCB. Some IC footprints however also show local fiducials. I've seen them for instance for certain TQFP footprints. When are they required?
stevenvh
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How can you tell how many layers a PCB has?

This is a question purely out of curiosity. I have several various PCBs, and I'm curious as to how many layers they use, which helps me decide how many layers to use in my project (for example a cheap competing product using 4 layers suggests to me…
Thomas O
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Have a look at my PCB design and tell me how I can improve

Here's the current design for Super OSD Lite, an open hardware project to bring a low cost on screen display to the masses. The price target is $71 to $90. bigger image There are components on the bottom, but most components are on the top. It's…
Thomas O
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Is it OK for traces to come off SMD pads at the corners?

I'm working on a PCB and have found it very convenient to connect adjacent passive components by running traces between them diagonally, as shown below: Is this bad for any reason?
Nate
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What are these round pads on the bottom of a PCB?

What are these round pads on the bottom of a PCB marked ScX? I don't think these are test points - this board has some (not in the picture) and they're labelled with TP and the pad size and shape are different. My best guess is that they're…
avg
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Homebrew PCB tips?

At home, I etch single and double sided PCBs but there are a few of areas I've always had trouble with. Can anyone help? Tinning The PCBs I make are useless for hot air rework or skillet reflowing. Once the copper heats up it oxidises, then I'm…
Toby Jaffey
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Why is it bad to have traces close to the edge of the board?

I keep reading that one shouldn't have traces close to the edge of the board and am curious as to whether there is an electrical reason behind this or if it's a mechanical issue (like when they cut the pcb, it might somehow rip up the traces)?
Alex
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How much more does it cost to fab a 4 layer board compared to a 2 layer board and is it worth it?

I'm wondering at the moment with my Super OSD project whether to go to a 4 layer board. At the moment, it consists of two micros and some additional circuitry such as a discrete audio amp and switch logic, and a serial EEPROM plus a temperature…
Thomas O
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What does the term "turnkey" means or refer to in the Engineering/Manufacturing environment?

I keep hearing this expression thrown around when talking about or to PCB fab houses. Can someone tell me what it means, or refer to ?
igorvanhelsing
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