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How to Measure Creepage Clearances [message #168025] Fri, 09 December 2016 17:57 Go to next message
Bob Starr
Messages: 99
Registered: April 2008
Member
I have a client that is working to get a PCB through UL certification. I
need some way to measure the minimum clearance between any two nets. In
other words I might need to know the minimum clearance between any two
traces/polys (eg, whats the min clearance between +15V and +5V? for
example).

Is there any ULP or way to figure the minimum clearance between two
different net signals on a board? Any suggestions would be greatly
appreciated!

Best Regards,

Bob Starr
Re: How to Measure Creepage Clearances [message #168030 is a reply to message #168025] Mon, 12 December 2016 08:37 Go to previous messageGo to next message
Hans Sorgatz
Messages: 21
Registered: June 2014
Junior Member
Hi
you can try CLASS in the "Matrix-mode"
One for the +15V net and one for +5V net
than you can go higher step by step the Clearence till the Error-Message in the DRC

CLASS 2 TEST5V ; CLASS 3 TEST15V 2:0.4mm
CHA CLASS 2 click the +5V-Net
CHA CLASS 3 click the +15V-Net
DRC

best regards,
Hans Sorgatz

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Re: How to Measure Creepage Clearances [message #168032 is a reply to message #168030] Mon, 12 December 2016 14:59 Go to previous messageGo to next message
Bob Starr
Messages: 99
Registered: April 2008
Member
Hi Hans,

Thanks for the tip, I'll give this a shot. To be honest, I've never really understood how the class matrix stuff worked or what it was used for. Tracking down all the places to put the nets will the hard part. But, maybe it won't be so bad if this can give me the info they need.

Regards,

Bob

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Re: How to Measure Creepage Clearances [message #168033 is a reply to message #168025] Mon, 12 December 2016 15:25 Go to previous messageGo to next message
Tilmann Reh
Messages: 2068
Registered: October 2004
Senior Member
Bob Starr schrieb:
> I have a client that is working to get a PCB through UL
> certification. I need some way to measure the minimum clearance
> between any two nets. In other words I might need to know the minimum
> clearance between any two traces/polys (eg, whats the min clearance
> between +15V and +5V? for example).

That's not /exactly/ true. You don't need to (numerically) know the
minimum distance, you just need to make sure that you don't fall below a
specified minimum distance anywhere on the board.

However, that makes using CLASS (as already suggested) the perfect
solution. Simply enter your minimum distance requirements in the matrix,
assign the nets to the proper classes and run DRC. If DRC does not
complain, your layout is compliant.

The matrix is simple to use: you just specify the minimum distances for
signals within the same class and between their own and all other classes.

These distance requirements are also used by polygon calculation, so you
don't need to check them explicitly - provided you take care of using
different RANKs where needed.

Final word: enter slightly too large distances in the CLASS distance
matrix to provide for manufacturing tolerances in the production.

Tilmann
Re: How to Measure Creepage Clearances [message #168036 is a reply to message #168033] Mon, 12 December 2016 16:31 Go to previous messageGo to next message
Bob Starr
Messages: 99
Registered: April 2008
Member
I found the following in the manual and trying to figure this out between the DRC clearance matrix:

Clearance between net classes
If a clearance is given in the form number:clearance, it defines the minimum clearance between signals in this net class and signals in the net class with the given number. The command
CLASS 3 1:0.6mm 2:0.8mm
defines a minimum clearance of 0.6mm between signals in net classes 1 and 3, and one of 0.8mm between signals in net classes 2 and 3. Note that the numbers in number:clearance must be less than or equal to the number of the net class itself ('3' in the above example), so
CLASS 3 1:0.6mm 2:0.8mm 3:0.2mm
would also be valid, whereas
CLASS 3 1:0.6mm 2:0.8mm 3:0.2mm 4:0.5mm
would not be allowed.
A clearance value of '0' between two net classes means, there is no specific value. Then the higher value of the participating net classes will be used.

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Re: How to Measure Creepage Clearances [message #168040 is a reply to message #168036] Mon, 12 December 2016 17:14 Go to previous messageGo to next message
Tilmann Reh
Messages: 2068
Registered: October 2004
Senior Member
Bob Starr schrieb:
> I found the following in the manual and trying to figure this out
> between the DRC clearance matrix:
> .....

Why don't you simply enter CLASS and then expand the matrix with the
button in the lower right corner?

Tilmann
Re: How to Measure Creepage Clearances [message #168046 is a reply to message #168040] Tue, 13 December 2016 08:20 Go to previous messageGo to next message
eaglecandies
Messages: 186
Registered: September 2011
Location: Cincinnati
Senior Member
I asked a similar question not too long ago:

Would be nice to have as part of the measuring tool--Eagle already has the capability built in, since it can run DRC rules.

http:// www.eaglecentral.ca/index.php/m/167295/be3518208fb87eb707150ee1fad3d02e/#ms g_167295

Re: How to Measure Creep age Clearances [message #168049 is a reply to message #168040] Tue, 13 December 2016 13:25 Go to previous message
Bob Starr
Messages: 99
Registered: April 2008
Member
I was able to get the info I needed in the DRC matrix mode, now we'll see what the UL guy says.

Thanks for the help, now I finally have a basic understanding of how to use matrix mode.

Best Regards!

Bob

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