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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.

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253 votes
9 answers
94k views

Decoupling caps, PCB layout

I guess I've been somewhat ignorant when it comes to the finer details of pcb layout. Lately I've read a couple of books that try their best to lead me on the straight and narrow. Here is a couple of ...
morten's user avatar
  • 4,693
69 votes
4 answers
163k views

How do I identify SMD components? (or how do I identify any component)

How do I identify the markings on an SMT component and match it up with a part number so I can be a good designer and actually look at a datasheet (and read the whole thing)? Or identify a part to ...
Voltage Spike's user avatar
  • 84.8k
80 votes
13 answers
126k views

How to connect USB Connector shield?

How should I route USB Connector shield on PCB? Should it be connected to GND plane right where USB is placed, or should the shield be isolated from GND, or should it be connected to ground through ...
Andrzej H's user avatar
  • 1,005
55 votes
7 answers
65k views

What is the usage of Zero Ohm & MiliOhm Resistor?

I am new to PCB design and I noticed that some schematics use 0Ω or 100mΩ resistors. What is their purpose and why do we need to use them in our PCB design? Normally if we wish to probe how much ...
Dennis's user avatar
  • 1,421
53 votes
7 answers
44k views

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

I'm designing a 4 layer PCB and I know that the standard stack-up is Signals GND VCC Signals (GND and VCC can be switched depending on the layer with more signals) The problem is, I don't really ...
mux's user avatar
  • 1,906
82 votes
11 answers
43k views

Why is there such a strong preference for 45 degree angles in PCB routing?

I've always wondered this: every single modern PCB is routed at 45 degree angle increments. Why does the industry prefer this so much? Doesn't any-angle routing offer more flexibility? One plausible ...
Roman Starkov's user avatar
54 votes
6 answers
172k views

Standard PCB trace widths?

Is there a standard for the sizes of PCB traces? That is are some 25 mil and others 10 mil or is can you choose your own? I plan to run 400mA through some thicker traces, but less than 30mA for all ...
Thomas O's user avatar
  • 31.9k
43 votes
2 answers
8k views

Why wiggle nearby tracks on a PCB?

I've been reading an article (TheMagPi eMagazine) relating to the Raspberry Pi; "An ARM GNU/Linux box for $25." In the article, page 17 at the bottom it shows an area on the Pi where a track zigzags ...
George Duckett's user avatar
57 votes
5 answers
48k views

How can PCB trace have 50 ohm impedance regardless of length and signal frequency?

Hmm, this seems to be just another question on line impedances. I understand that when we say "transmission line" effects we talk about things like cross talk, reflections and ringing (I guess that ...
quantum231's user avatar
52 votes
2 answers
51k views

Competing PCB Crystal layout recommendations

This is related to this question: How's my crystal oscillator layout? I'm trying to layout a 12MHz crystal for a micro controller. I've been reading through several recommendations specifically for ...
helloworld922's user avatar
73 votes
6 answers
43k views

What is Copper Thieving and why use it?

On many boards I've seen, there are little copper dots used for the purpose of "Copper Thieving". They're small round copper dots connected to nothing and arranged in an array. Supposedly they're for ...
Gustavo Litovsky's user avatar
48 votes
8 answers
21k views

Can we build capacitors on a PCB board?

For the magnitude of nF or µF capacitors, I hope I can build them on a PCB board. The capacitor is like a two metal layer and something between them. Is this possible? Not buying the capacitor, ...
alan's user avatar
  • 807
126 votes
10 answers
231k views

Are solder fumes bad for me?

I do a fair bit of soldering (lead-free). Is breathing in solder/flux/paste fumes actually going to harm me? Are cheap fume extractors worth buying?
Toby Jaffey's user avatar
  • 28.9k
52 votes
4 answers
82k views

How to make traces on an universal PCB?

I hope this question won't be closed as too subjective. I'd like to know best practice - how to make traces on universal PCB's with individual holes without traces (like the following image). My idea ...
Al Kepp's user avatar
  • 3,001
69 votes
4 answers
140k views

What kind of glue should I use for PCB-mounted components to avoid vibrations?

I want to protect the PCB-mounted components from vibrations. What kind of glue/substance should I use? What are the most prone to failure components due to vibrations?
m.Alin's user avatar
  • 10.8k
45 votes
3 answers
36k views

What are the advantages of having two ground pours?

I've seen many 2-layer PCBs that have a ground pour on both the top and bottom layers, I was wondering why do that ? and wouldn't it be better to use the top layer for power and signals and the bottom ...
mux's user avatar
  • 1,906
11 votes
2 answers
8k views

Does my circuit need decoupling caps? [duplicate]

I have a very simple design that I'm now working on the PCB layout for. And at the moment I'm thinking about the issue of decoupling capacitors. The board is very simple and only consists of this: <...
David Högberg's user avatar
44 votes
15 answers
11k views

What are low cost circuit and PCB design software? [closed]

Do you know of any freeware or low cost circuit / PCB design software? I know a few which I have listed below but I was wondering if there were more of its kind. Please mention the good features and ...
Edward's user avatar
  • 1,339
36 votes
4 answers
6k views

Why do characteristic impedances matter only when traces are longer than half a wavelength?

Why are characteristic impedances of traces not considered when the traces are shorter than half a wavelength? I've had the same issue with light diffraction, which happens when pinholes are smaller ...
user42875's user avatar
  • 1,344
26 votes
6 answers
48k views

PCB 90 degree angles [duplicate]

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 ...
inbinder's user avatar
  • 1,057
13 votes
2 answers
21k views

Creating a high-current bus on a PCB

I'm planning a custom power-distribution / fuse-board for in-car application, but that requires carrying high currents (50A+ @12v*) on a PCB trace. Since I'd like to keep the board cost, and physical ...
John U's user avatar
  • 7,159
6 votes
3 answers
2k views

Decoupling cap routing on a 4 layer PCB

I would like to place some decoupling caps for an IC. The IC is on the top while the caps will be on the bottom, opposite side. How should I route them: A single VIA that connects the IC pin, power ...
Manos's user avatar
  • 355
49 votes
3 answers
33k views

Why are vias placed this way on a PCB?

I used to check complex commercial PCBs specially those of graphics cards to see how professional PCB designers do their layout and learn from their techniques. When I checked the card shown below I ...
Abdella's user avatar
  • 2,612
38 votes
6 answers
6k views

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 ...
jinawee's user avatar
  • 1,086
24 votes
5 answers
17k views

Cleaning Circuits with Compressed Air

I've been arguing with a colleague whether it is a sensible solution to clean dusty PCBs with compressed air. While I think this is the best solution (nothing touches the PCB), he claimed that ...
Count Zero's user avatar
23 votes
1 answer
4k views

What is this squiggly trace for?

It's on pin 14, which is the master clock input (MCLK) of a WM8761: Low cost stereo DAC. I'm guessing it's meant to act as a small inductor? But why would you want that on a clock input?
endolith's user avatar
  • 28.8k
22 votes
3 answers
21k views

How do I create a permanent application from something prototyped with Arduino?

Part one of a three part series on transitioning from Arduino to a plain AVR microcontroller and minimum supporting components (part two, part three) I've built up a project on my Arduino Uno to ...
user avatar
19 votes
3 answers
5k views

Is case grounding compulsory in typical 32.768kHz crystal for Real Time Clock?

Pictures shown below is a typical 32.768kHz crystal, commonly use in Real Time Clock circuit (e.g: DS1307 & DS1337) Referring to an earlier question posted here, it is a good practice that ground ...
Dennis's user avatar
  • 1,421
17 votes
2 answers
20k views

The "right" 0805 footprint land pattern

My PCB design software comes with some libraries that include some common components, like chip resistors and capacitors. I have noticed, however, that the footprint land pattern for the 0805 ...
ajs410's user avatar
  • 8,551
114 votes
9 answers
39k views

Best One-Off DIY PCB Creation Technique

I have finally built up a lab to design electronics in. I have quite a few designs I would like to test. I have tried the printer toner/iron technique a few times but have found that I cannot create ...
66 votes
4 answers
244k views

What do the PCB markings mean?

On a printed circuit board, I see lots of tiny letters and numbers. Is there some kind of standard that dictates what letter indicates what type of component?
kinokijuf's user avatar
  • 906
47 votes
9 answers
57k views

Vias directly on SMD pads?

I was looking at an example board schematic provided by TI and I noticed something rather curious: vias were placed directly on SMD pads. Is this a normal/acceptable practice to follow, or is it ...
helloworld922's user avatar
38 votes
8 answers
7k views

How to prototype?

How is prototyping done in a professional EE environment? Do you do your prototypes on breadboards, on copper clad boards, Manhattan style, or do you just draw schematics, order PCBs made and ...
29 votes
7 answers
47k views

How to carry high current on PCB

I need to pass high current on some part of my circuit. I used an online PCB track width calculator to see that required track width is about 5mm and minimum clearance is 1mm, which makes it about 7mm ...
hkBattousai's user avatar
  • 14.1k
24 votes
2 answers
13k views

Via fences for noise reduction of a chip antenna?

I'm working on a 4-layer PCB that has a wifi module and a chip antenna, the antenna is placed at the corner of the PCB and the copper beneath it is removed, I see that via fences are used on the ...
mux's user avatar
  • 1,906
22 votes
8 answers
3k views

Pre-programming surface mount ICs

I'm trying to set up a PCB with an atmega168 and no programming header. I intend to use a serial bootloader (there is a ft232 on the board) to reprogram but I am wondering about the best way to ...
jeremy's user avatar
  • 5,115
14 votes
3 answers
14k views

About waterproofing a circuit board

I would like to waterproof an FR4 circuit board that has no external connectivity requirements other than permanently attached USB cable, but it does have a number of SMD LEDs that must show. Most ...
Aashima A's user avatar
  • 213
13 votes
4 answers
30k views

Implementing guard trace/ring in PCB design

I have read here and there some articles about pcb guard trace/ring. But none of them discussed how to correctly implent it. What I could find were some pictures and comparison that cant help me at ...
Dumbo's user avatar
  • 3,284
13 votes
5 answers
27k views

Cleaning PCBs... using water?

I found this video where a technician with a lot of experience seems to clean his PCBs using water, and then he just puts it in the sun so it can dry. I was just amazed to see the circuit keeps ...
GoatZero's user avatar
  • 1,547
12 votes
3 answers
8k views

multi-layer board copper pour

I have a 6-layer board where the internal 4 planes are +15,GND,VCC,-15. I was wondering if there was any advantage to doing a copper pour on the top and bottom layers? I would probably leave them ...
Ross W's user avatar
  • 447
11 votes
2 answers
4k views

Why is a broken ground plane not as effective as an unbroken one?

I did a two layer board a few weeks ago which had a dedicated ground plane. I routed 90% of the signals on the top layer and for the last 10% I had to route them through the bottom (ground) plane. I ...
Saad's user avatar
  • 5,419
9 votes
2 answers
6k views

Air gap on isolation space

The below photo belongs to a PSU. I wonder what was the reason of placing air gaps on the 8 mm isolation. Is it to improve the isolation or provide a thermal relief (although there is no component ...
Angs's user avatar
  • 3,305
9 votes
3 answers
31k views

Minimum clearance between two traces that have a potential difference of 1000VDC

I am designing a PCB and there will be high voltages. What is the recommended clearance that I should have between two traces that have a voltage difference of 1000VDC and 2000VDC? Additionally, is ...
Shicon Wen's user avatar
6 votes
2 answers
5k views

Castellation metal loop connector

Here's a module with castellated pads attached to an eval board: (source: alicdn.com) Looking closely at the wires interfacing with the castellated pads, they're clearly soldered to the eval board. ...
Tim Sheridan's user avatar
3 votes
1 answer
1k views

Basic voltage divider issue in my amateur circuit XBee

Once again I need your help in my project. I have a 4,5v powered circuit. I put a voltage divider with 2 resistors in series to reduce my initial voltage of 4.5 V to 3.4 V (to feed an XBee module). ...
Xavi Gómez Canals's user avatar
31 votes
11 answers
20k views

What is the most amazing PCB artwork you've ever seen?

Have you ever looked at a PCB and burst out laughing? Have you ever looked at a PCB and said "Wow, that is amazing"? Have you ever seen a PCB that artistically expressed criticism of society's ...
30 votes
6 answers
18k views

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 ...
Jesus Castane's user avatar
30 votes
5 answers
37k views

What is the purpose of solder mask expansion?

I see recommendations of 2-4 mils for solder mask expansion. But why is it necessary?
ajs410's user avatar
  • 8,551
30 votes
2 answers
14k views

Connectorless USB on a PCB

I would like to make a board which can be plugged directly into the USB port of a computer, instead of using a separate male "USB-A" connector. I have seen this system used for very small USB memory ...
drxzcl's user avatar
  • 3,775
28 votes
5 answers
13k views

Standard PCB Layout Book

Are there any good references on advanced PCB design/layout/routing? There seems to be a large wealth of circuit design books, books about RF PCB design, and books dealing with high-speed digital ...

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