Questions tagged [pcb-design]

About designing the boards which carry the components of an electronic circuit. For questions about getting them built instead use PCB-fabrication. If your question is specific to a certain CAD tool, say which tool and version you are using.

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6
votes
1answer
5k views

Analog & Power Ground Planes Doubts

Working on a new board, I have to face some requirements to ensure the performance of the whole system once is manufactured. PCB is a 4-layer one, and it has both analog and digital components. But ...
31
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2answers
12k views

Purpose of “wave shaped” PCB traces

On some PCB designs, specific traces are routed in curious ways. This probably has to do with high frequency design considerations and general signal behavior that I am not familiar with. Let's take ...
38
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2answers
6k 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 ...
38
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2answers
33k 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 ...
58
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6answers
31k 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 ...
44
votes
7answers
53k 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 ...
40
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4answers
26k 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 Singals (GND and VCC can be switched depending on the layer with more signals) The problem is, I don't really ...
33
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4answers
12k views

Reason of multiple GND and VCC on an IC

What is the reason that most of ICs (e.g. MCU) has multiple (A/D)GND and (A)VCC pins? If it is to increase performance of an IC, how does it help to performance? or is it easier for the IC designer ...
43
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8answers
15k 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, ...
11
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5answers
7k views

What parts would one typically use for automated PCB testing?

I have a circuit board in production, primarily through-hole, to the tune of ~400 units per year. Each one is manually inspected and tested. The board has ten distinct voltage rails, four voltage ...
14
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4answers
25k views

How should I connect AGND and DGND

I have been reading about grounding in a mixed signal systems. Do I get it correct that it is best to group analog and digital elements and then have a single ground plane, as long as the digital ...
11
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5answers
7k views

How's my crystal oscillator layout?

The HC-49 xtal is an 8 MHz crystal, and the radial crystal is an RTC 32.768 kHz crystal. C11, C12 are 22pF, and C13, C14 are 18pF. The traces go directly into a micro (a PIC24F.) I tried to follow ...
38
votes
2answers
25k 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 ...
29
votes
5answers
8k views

Should I really divide the ground plane into analog and digital parts?

I am about to design my first PCB as part of my graduation project. Of course, as the first step, I try to learn as much as possible. A part of the research I found this 3 part article, that suggests ...
43
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3answers
27k 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 ...
29
votes
2answers
16k views

Why route air gaps for voltage isolation on PCBs?

Learning about PCB design for power supplies, I frequently see boards with routed gaps to separate low and high voltage sections of the layout. Why go to the trouble of routing an air gap when ...
11
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2answers
9k views

How do I lay out PCB traces for a given “differential impedance”

This is an attempt to craft a good general question and answer for a topic that's been asked before, but only in specific situations. Could you describe what I need to know, prior to laying out a PCB ...
29
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3answers
9k views

Should I worry about the risk of tombstoning?

A colleague has (apparently unsuccessfully :-)) tried to convince me of the risk of tombstoning in the following situation: He claims pad 1 for R55 and R59 will lose heat faster during ...
2
votes
4answers
69k views

How to build a motherboard [closed]

I am building my own laptop, and found out that the motherboard for a laptop has to be designed based on the case. So, I am designing my own motherboard. The thing is, I have no idea how a ...
13
votes
4answers
9k views

Best edge connector for my pcb?

I am making a PCB where the goal is to keep BOM as low as possible and also the cost to the lowers. It has proven to be quite a difficult task but I am at a final stage now. My PCB needs to be ...
17
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3answers
4k 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 ...
8
votes
2answers
14k views

Why Characteristic Impedance must be 50 ohms?

Where does this number come from? For single ended it must be 50 ohm and for differential pairs 100 ohm. Why? For PCB with controlled-impedance these are that common numbers. Outside of the PCB you ...
111
votes
8answers
36k 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 ...
27
votes
5answers
66k views

What pad hole (drill) size is appropriate for a given through-hole lead diameter?

I am making some new through-hole parts in Eagle for components that are not already in the various libraries. I've realized that the drill size needs to be a little larger than the lead diameter, but ...
13
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5answers
15k 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 ...
26
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5answers
11k 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 ...
36
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8answers
6k 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 ...
9
votes
1answer
13k views

Clearance rules for outer/inner layers?

I found some information about general creepage and clearance distances here but it doesn't mention what is OK for inner layers, which are insulated and not subject to contamination the way outer ...
23
votes
3answers
20k views

Should I isolate grounds of an isolated DC/DC converter?

If I use an isolated DC/DC converter, when designing the PCB, should I isolate the ground of the input and the ground of the output as shown below? I've never isolated grounds (except for AGND and ...
7
votes
3answers
12k views

Missing components in Eagle Library

I am missing libraries of certain ICs for use in Eagle. Can someone guide me to a source where I can find these IC libraries? I am asking this question to find out if there is any central repository ...
16
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2answers
3k views

Mixed signal PCB layout for PSoC

I am developing a PCB for an analogue sensing application. It uses the internal ADC on a PSoC3. As usual, the application is very space constrained (11mm x 21mm), so I have had to make some ...
19
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4answers
3k views

Removal of unused pads?

I was reviewing a design earlier, and I noticed something interesting. The designer had removed unused pads on the chip. I have never seen this done before. Is this something that is good practice? ...
2
votes
2answers
71 views

4 layer board back bypass capacitor power plane connection guideline reason

I'm reading Power Bus Decoupling Guidelines for Printed Circuit Boards with Widely Spaced Power Distribution Planes. And they have these recommended connection configurations for bypass capacitors ...
1
vote
1answer
2k views

Why do some PCBs have zig-zag tracks? [duplicate]

I've seen many boads with weird zig-zag shaped tracks just like the one below. Why are they designed like that?
9
votes
2answers
10k views

Eliminating Thermal Isolation Pads in Eagle

When creating a ground plane in Eagle, Eagle automatically creates a thermal isolation for the pad. My first question is, does this isolation limit the current compared to a pad that is "completely"...
5
votes
2answers
2k views

How to do Jumperless Jumpers?

Is there a way to do "jumpers" without actually using a jumper connector on a PCB? Ideally just using holes or pads. For example, one idea for doing it is to use pads on the edge of a PCB then using ...
3
votes
1answer
1k views

How do I design correctly ground plane separation for Texas Instruments TPS63060 IC?

I'm concluding my two-layer PCB design and my last obstacle is ground planes. Specifically, the problem is the TPS63060 IC that requires Power Ground separation from Control Ground (pin 7). That is a ...
1
vote
1answer
341 views

How to create a mixed signal pcb

I want to create a board that has both high speed digital components (specifically the SAM3X8E - from arduino DUE) and an analog audio circuit. The analog parts were originally a shield to the ...
1
vote
2answers
1k views

Why do circuit boards use strange paths? [duplicate]

First, let me say that I'm no electrical engineer, I'm just a curious student. Here's a photo of a Raspberry Pi A+. I (as one completely ignorant of PCB design) would expect the electrical paths to ...
56
votes
4answers
153k 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?
49
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3answers
13k views

How to go from a development board to a production board?

Ok, I am a software guy and new to electronics. My product needs a small computer and currently I have developed everything on development boards like raspberry pi and such. As the development board ...
33
votes
10answers
24k views

Looking for a good freeware/open source PCB design software equivalent to Altium [closed]

I am familiar with Altium PCB design software in my workplace. But thats an expensive suite to maintain. Is there any decent enough free software which I can use at home for my pet projects? I have ...
20
votes
2answers
10k views

Termination resistors: are they needed?

For a project I'm designing, I'm using an IS42s32800 (TSOP) SDRAM with an LPC1788 (QFP) microcontroller. On the PCB I have 4 layers with a ground plane right below the top signal layer and a VDD plane ...
27
votes
4answers
6k views

At what frequencies does PCB design get tricky?

I have designed many mixed-signal PCB's where the highest-frequency component is the microcontroller's crystal oscillator itself. I understand the standard best practices: short traces, ground planes,...
22
votes
4answers
19k views

When to use ground plane cutouts?

I've been reading more about proper grounding techniques and using ground planes. From what I've read, ground planes provide a large capacitance with adjacent layers, faster heat dissipation, and ...
27
votes
7answers
29k 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 ...
14
votes
3answers
7k views

High Voltage PCB Design

I want to design a 4 layer PCB with the following voltage levels. GND, 5V, 3.3V and 80V. In the circuit there are some MOSFETs which are driven by 3.3V and MOSFET switch 80V (required current is very ...
11
votes
4answers
24k 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 ...
20
votes
2answers
15k views

Castellated/Edge-plated PCBs: Comments on Mechanical/Electrical contact reliability

(This is a follow-up to this related question). I'm interested in some feedback from people's design results/experiences with Castellated PCBs as a method of attaching one PCB to another. By ...
15
votes
5answers
11k views

Ideas for attaching / connecting / stacking one PCB onto another with no gap

What methods might be feasible for attaching/stacking one PCB immediately on top of another PCB, with the following conditions: Zero spacing/gap between the two PCBs Electrical contacts are needed, ...