Dual Flat No-Lead (DFN) -- Rounded Rectangle

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   Not sure if this is really a bug or not.  
In User Setup Preferences under "Dual Flat No-Lead (DFN)" for the "Default Pad Shape" only Rectangle is available.  
There is no Rounded Rectangle option.  
Not sure if this is due to IPC specs or if this is a slight bug?

Thanks, Mike

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mike_aes Members Profile Send Private Message Find Members Posts Add to Buddy List Active User Joined: 29 Sep 2014 Status: Offline Points: 27	Post Options Post Reply Quote mike_aes Report Post Thanks(0) Quote Reply Topic: Dual Flat No-Lead (DFN) -- Rounded Rectangle Posted: 17 Oct 2014 at 8:30am
	Not sure if this is really a bug or not. In User Setup Preferences under "Dual Flat No-Lead (DFN)" for the "Default Pad Shape" only Rectangle is available. There is no Rounded Rectangle option. Not sure if this is due to IPC specs or if this is a slight bug? Thanks, Mike



Tom H Members Profile Send Private Message Find Members Posts Add to Buddy List Admin Group Joined: 05 Jan 2012 Location: San Diego, CA Status: Offline Points: 5719	Post Options Post Reply Quote Tom H Report Post Thanks(0) Quote Reply Posted: 17 Oct 2014 at 10:26am
	The DFN and LGA are "Bottom Only" terminals. The solder joint goal for DFN's is 0 (zero) and the only pad periphery is the lead and manufacturing tolerances. It's a very small periphery (annular) solder joint and rounded corners do not work well. The solder joint goal for micro-miniature DFN pad size is equal to the lead size and subtracts -0.04 mm to compensate for the lead and manufacturing tolerances. We can't have exposed component leads without a pad under them. However, the QFN (where the lead goes all the way to the component body edge and up the side 0.20 mm) should have a Rounded Rectangle pad shape. So we're adding that option in V2015.01 as a new feature.
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