42
votes
Accepted
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 ...
- 473k
10
votes
Accepted
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 ...
- 9,749
8
votes
Accepted
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 ...
- 88.8k
7
votes
Accepted
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 (...
- 2,625
7
votes
Accepted
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 ...
- 473k
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:) ...
- 23.1k
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 ...
- 16.4k
5
votes
Accepted
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 ...
- 35k
5
votes
Accepted
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.
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 ...
- 41
4
votes
Accepted
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 ...
- 16.8k
4
votes
Accepted
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 ...
- 88.8k
4
votes
Accepted
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 ...
- 4,772
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 ...
- 57.3k
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 ...
- 1,557
4
votes
Accepted
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 ...
- 20.5k
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 ...
- 88.8k
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 ...
- 24.1k
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.
- 473k
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 ...
3
votes
Accepted
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 ...
- 21.6k
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 ...
- 178k
3
votes
Accepted
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 ...
- 1,769
3
votes
Accepted
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 ...
- 21.6k
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 '...
- 29.3k
3
votes
Accepted
Why does the IPC standard allow for smaller clearance on inner layers than external layers?
A good quality shop can support track and gaps on any layer of;
3 mil (0.12mm) in std quality and
2 mil (0.08mm) on advanced ($) build.
So it is not a process limitation but a contaminant ...
- 148k
3
votes
Why does the IPC standard allow for smaller clearance on inner layers than external layers?
External layers are plated-up with additional copper after etching, whereas internal layers usually aren't. This can lead to larger manufacturing tolerances, though one could argue that it's the ...
- 6,195
3
votes
Accepted
How does trace/via clearance affect parasitic inductance if they go to the same net
The more via's you use in parallel the less inductance you have. Each via can be modeled as an inductor with a few 10's of nH. If you really want to find the inductance closely there are calculations ...
- 88.8k
3
votes
When to use slots instead of barriers in high voltage design?
One of the risks with attaching barriers to a pcb is that they aren't consistently attached ("cemented" is the UL term) to the board with variation in effectiveness both along their length, and from ...
- 5,739
3
votes
Barrier and slot within reduced area on a PCB
The clearance is probably going to be the thing that determines the distance as any bare conductors, so creepage doesn't really matter. Usually slots and barriers are used to decrease the distance ...
- 88.8k
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