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39 votes
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Why is there a difference between pad-to-trace and trace-to-trace clearance?

But it makes me wonder why the PCB manufacturer sees the 2 as different things. It's likely that this is due to the solder mask tolerance. With two side-by-side tracks, the solder resist ...
Andy aka's user avatar
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15 votes

Will a cut or a slot in a PCB change clearance or creepage?

You are correct: Here is a nice picture of the definitions of creepage and clearance: Note that adding a barrier will increase the clearance. Adding a barrier increases the physical length of ...
Peter Smith's user avatar
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10 votes
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Why does increasing altitude (low air pressure) results in lower resistivity/ breakdown voltage?

The behaviour is described by Paschen's Law. Electrons are accelerated in the electric field between two electrodes. If there are gas molecules in the path of the electron it will collide with them ...
jusaca's user avatar
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8 votes
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PCB trace clearance in 220V circuit

Here's what Creepage and clearance means in UL60950: - Numbers in millimetres. "Functional" is the minimal that you are aiming at so, 12 thousandths of an inch is nowhere near enough. Across a plain ...
Andy aka's user avatar
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8 votes
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What is a correct method to measure safe maximum voltage of a PCB?

It really depends on what standard you need to adhere to. This involves whatever NRTL or ETL you'll take to get the product tested (if you do so). If you are going the NRTL route, you might be able to ...
Voltage Spike's user avatar
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7 votes
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Creepage between layers on a PCB

Do I need to consider the distance towards the board outline, up/down to the other layer and to the component Yes you do but, path 2 in your diagram doesn't represent this; it appears to show the ...
Andy aka's user avatar
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7 votes

What is a correct method to measure safe maximum voltage of a PCB?

IPC standards for minimum electrical clearance provide for voltages above 500VDC (or peak AC) at 0.00305mm/V past the 0.8mm/500V range of table 6.1 of IPC-A-610. Your board's 1mm spacing with (edit:) ...
vir's user avatar
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7 votes

What are good values for standard design rules (like clearance, trace width, etc.) in PCB design?

The below image is table 6-1 from the IPC-2221 standards. These are the minimum conductor spacings as a function of the voltage between two conductors, for various scenarios: In my experience, these ...
rdtsc's user avatar
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6 votes
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Maintaining clearances in HV MOSFET footprints

I've wondered about this myself. What I ended up doing for a 230VAC mains project: I created a custom footprint for the TO-220 part, where I moved the outer two legs out to approximately a 4mm pitch (...
marcelm's user avatar
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5 votes
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Minimum spacing between PCB components

Unless you have high voltage issues crosstalk (by electric fields) between components heat dissipation issues then pack the components as tightly as you are able to insert the thru holes. You can ...
analogsystemsrf's user avatar
5 votes
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PCB clearance/creepage with dead metal

The metal would (at best) subtract from the clearance by its width. It may be worse than that as deemed by safety agencies. I suggest a through-hole zero-ohm resistor as an option.
Spehro Pefhany's user avatar
4 votes

Will a cut or a slot in a PCB change clearance or creepage?

Slots will only increase creepage. You need a barrier if you need to increase clerance. Also, remember to make the slot >2 mm wide, otherwise it does not count by most standards.
winny's user avatar
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4 votes
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How is clearance affected by altitude (air pressure)?

It would change the length of the clearance, so if the electrical design is in a rocket or a high altitude balloon (or airplane), then it's something to take into consideration. Here is a description ...
Voltage Spike's user avatar
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4 votes
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Altium Microstrip routing

Your best bet would be to create a new clearance rule (Design -> Rules -> right-click "Clearance" in the left pane, select "New Rule", open up the new rule you just created (it'll be titled "...
DerStrom8's user avatar
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4 votes
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KiCAD Component Pad Clearances

KiCad (version 5) works on a maximum required clearance model. That means that it will select the smallest clearance possible from the combination of requirements. In your case, although your pad ...
Seth's user avatar
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4 votes
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High Voltage Capacitor Lead Clearance

Most of these components is unsuitable for continuous high voltage. On top of what @Spehro said, creepage will be impossible without immersing it in transformer oil and I would not be allowed to put ...
winny's user avatar
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4 votes

Maximum allowable voltage between PCB traces

I've done a lot of research on this and unfortunately it's not as straight-forward as you would think. Everyone refers to IPC2221A because that's the defacto standard but the tests that UL performed ...
Sparky's user avatar
  • 41
4 votes

Minimum spacing between PCB components

Just so you know, that PCB example you posted has very wide spacings. How closely together you can place traces and components depends is limited by things like how the high voltage and noise. But as ...
DKNguyen's user avatar
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4 votes

What are good values for standard design rules (like clearance, trace width, etc.) in PCB design?

The IPC (formally the Institute for Interconnecting and Packaging Electronic Circuits) standards discuss minimum trace spacing and trace widths for circuit boards. They contain a lot of great ...
C. Dunn's user avatar
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4 votes
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Same net overlapping pads ok?

This is generally fine as long as you obey the manufacturer's minimum hole-to-hole spacing rule. The Design Rule Check (DRC) of your PCB software will tell you whether you've violated those rules ...
Jonathan S.'s user avatar
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4 votes

How to interpret External Clearance spec on HCPL3700M IC?

It depends on what the max voltage and the IEC\IPC specs the design needs to adhear to. The IPC-2221B is a good starting point. One problem is since this design is connected directly to AC mains it ...
Voltage Spike's user avatar
  • 83.4k
4 votes

PTH Pad too close, how to resolve?

One sneaky way to fix this is to place the annulus rings alternating between the top and bottom layers on alternate pins. You do have to take care if soldering by hand but there has not ever been a ...
Dwayne Reid's user avatar
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3 votes
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Altium individual clearance for polygonpour

You should create a pad class and add the pads you want to have a larger clearance to it. Go to Design -> Classes, right-click "Pad Classes" in the left-hand pane and select "Add Class". Name the ...
DerStrom8's user avatar
  • 21.3k
3 votes

Creepage distance over pcb

How to measure creepage distance over pcb ? Is creepage and clearance distance measure by pbc layout or soldering? This might help: - Picture from this site.
Andy aka's user avatar
  • 460k
3 votes

Electrical isolation problems when routing between pads of SMT resistors/caps

Most, not all, SMT components have insulator on the bottom, between the end caps, so the solder mask is not actually acting as a critical insulator and even if it wasn't there the trace would not ...
Spehro Pefhany's user avatar
3 votes

How is clearance affected by altitude (air pressure)?

Well, to start with, "creepage" has nothing to do with the air at all — it relates to currents flowing in surface contaminants. "Clearance" has nothing to do with the conductivity of air, but ...
Dave Tweed's user avatar
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3 votes
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minimum trace spacing error

In Pcbnew, click Tools -> DRC. This open the Design Rule Checking (DRC) tool. It checks trace spacing (clearance), as well as trace widths and via sizes. Minimum clearance between traces is set up in ...
vofa's user avatar
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3 votes
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What's the name of the Altium designer rule that warns if component "enters" another component area (PCB)?

You're looking for the "Component Clearance" rule under "Placement". You may also have to deal with the standard "Clearance" rule under "Electrical" if the pads/polygons/tracks are of different nets ...
DerStrom8's user avatar
  • 21.3k
3 votes

TO-277A Package Rated for 1000V

It can be rated for that voltage because it is not a coated FR4 circuit board. As you've said yourself as part of your question, the 2.325mm clearance as stated by the IPC2221B standard is for a '...
metacollin's user avatar
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