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From:
"Decker, Scott Collins" <[log in to unmask]>
Reply To:
TechNet E-Mail Forum <[log in to unmask]>, Decker, Scott Collins
Date:
Mon, 28 Jan 2019 20:49:26 +0000
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Bob,

   Yes, for the short answer. You are correct in that the internal layers "should" be as good as the outer for spacing but that's assuming the same voltage. Since I'm in Aerospace I tend to take the higher values unless I'm really pressed for space and even then, there is generally a conversation with the engineers on what is expected and best. It's been a 50/50 win rate for the most part... :-) 

Later...



Scott Decker | Senior Engineer, PCB Design Services CID+ | Electronic Systems Center

COLLINS AEROSPACE

3445 S. 5th Street, Suite 170, Phoenix, AZ 85040 U.S.A.

Tel: 602 308 5957  FAX: 602 243 2347

[log in to unmask]  www.collinsaerospace.com



CONFIDENTIALITY WARNING: This message may contain proprietary and/or privileged information of

Collins Aerospace Systems and its affiliated companies. If you are not the intended recipient please 1) do not disclose, copy,

distribute or use this message or its contents, 2) advise the sender by return e-mail, and 3) delete all copies (including all

attachments) from your computer. Your cooperation is greatly appreciated.





-----Original Message-----

From: TechNet [mailto:[log in to unmask]] On Behalf Of Robert Kondner

Sent: Monday, January 28, 2019 11:47 AM

To: [log in to unmask]

Subject: Re: [TN] [External] [TN] IPC2221 Electrical Conductor Spacing Requirements



Hi,



 For internal layers I am under the impression that higher voltage can be handled at the same distances as on external layers.



 The assumption here is internal glass and epoxy is a much better insulator than the air and solder mask on the external. 



 Yes / No? Any thoughts?

Bob K.



-----Original Message-----

From: TechNet <[log in to unmask]> On Behalf Of Decker, Scott Collins

Sent: Monday, January 28, 2019 12:34 PM

To: [log in to unmask]

Subject: Re: [TN] [External] [TN] IPC2221 Electrical Conductor Spacing Requirements



Steven,

  I would go with the maximum 31-50V option. For starts, the spacing for the 16-30 is pretty small, so unless you are working with some really high density trace spacing, use the 31-50V value. Understanding that this is for the B4 bare board external traces with a Soldermask. Even if you are on internal layers, I would use the higher value just to be safe. In my opinion, you are just looking to make it more robust and reliable in the long run. If you want cutting edge, maybe you push it, but over time, you might find yourself wishing you didn't? :-) Since you didn't mention what layers these lines were on or if you had Soldermask on the outside, but if not I would for sure go with the larger voltage spacing value. Hope that helps.

Later... 



Scott Decker | Senior Engineer, PCB Design Services CID+ | Electronic Systems Center COLLINS AEROSPACE

3445 S. 5th Street, Suite 170, Phoenix, AZ 85040 U.S.A.

Tel: 602 308 5957  FAX: 602 243 2347

[log in to unmask]  www.collinsaerospace.com



CONFIDENTIALITY WARNING: This message may contain proprietary and/or privileged information of Collins Aerospace Systems and its affiliated companies. If you are not the intended recipient please 1) do not disclose, copy, distribute or use this message or its contents, 2) advise the sender by return e-mail, and 3) delete all copies (including all

attachments) from your computer. Your cooperation is greatly appreciated.



-----Original Message-----

From: TechNet [mailto:[log in to unmask]] On Behalf Of Steven Schell

Sent: Monday, January 28, 2019 9:55 AM

To: [log in to unmask]

Subject: [External] [TN] IPC2221 Electrical Conductor Spacing Requirements



Hello  Technetters,



I am trying to interpret the electrical clearance requirements in the IPC2221A standard, under section 6.3.

Table 6-1 lists minimum spacing requirements for various voltage ranges between conductors.

The table indicates that this is for AC or DC peaks.

I am trying to interpret that last part.

Our application has a tracking power supply that provides a variable DC output voltage.  The average DC voltage is between 16 and 30V, but the peak instantaneous DC voltage exceeds 31V.  

In this case, should I be complying with the minimum spacing requirements for 16-30V, or should I be complying with the minimum spacing requirements for 31-50V.



I guess I am not clear what the intent of the voltage thresholds is.



Thank you for any help or insight.


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