Power Integrations DPA-Switch family can't use such narrow traces. 

http://www.powerint.com/products/dpa-switch-family/dpa-switch

Figure 13 page 17 - look at that layout.  You can't do that with his design rule.

http://www.powerint.com/sites/default/files/product-docs/an31.pdf

The design requires a single-sided layout to dissapate the heat.

Bob Landman
H&L Instruments, LLC

-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Tontis, Theodore
Sent: Tuesday, January 11, 2011 1:42 PM
To: [log in to unmask]
Subject: Re: [TN] Trace Widths Entering SMT

Simply request data supporting the reasoning behind the requirement.
Before doing so, collect your own data supporting your reason for breaking the rule. I find it strange that the engineer is willing to put it out there that you have to follow this rule that he cannot confirm the reason for and this is done just because we have been doing it this way for xyz years. Maybe you have been doing it wrong for the last xyz years? 
At some point there will be a design that will require breaking that rule and a compromise will need to be made. It is best to find a way to work this through or find out why this is a blanket rule, then to wait until the time comes you don't have a choice but stand your ground.

Ted T.

-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Cote, Clint (GE Intelligent Platforms, US)
Sent: Tuesday, January 11, 2011 12:21 PM
To: [log in to unmask]
Subject: Re: [TN] Trace Widths Entering SMT

Yes, standard FR4 multi-layer with soldermask. I asked the Engineer and he isn't sure because the requirement pre-dates him.  But, he is adamant that the requirement must be met.


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