Solder Mask Defined Variant

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   Hi,
Is there a quick way to generate SMD footprint variants for parts?  

I'm looking at power parts where some pins have skinny traces connecting to them, and others have planes. 

I want SMD footprints to prevent uneven solder height due to spreading during reflow.

Thanks,
John

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ransonjd Members Profile Send Private Message Find Members Posts Add to Buddy List Advanced User Joined: 15 Nov 2016 Status: Offline Points: 139	Post Options Post Reply Quote ransonjd Report Post Thanks(0) Quote Reply Topic: Solder Mask Defined Variant Posted: 26 Feb 2018 at 7:56am
	Hi, Is there a quick way to generate SMD footprint variants for parts? I'm looking at power parts where some pins have skinny traces connecting to them, and others have planes. I want SMD footprints to prevent uneven solder height due to spreading during reflow. Thanks, John



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: 5716	Post Options Post Reply Quote Tom H Report Post Thanks(0) Quote Reply Posted: 26 Feb 2018 at 8:14am
	By "Variants" are you referring to Library Expert Preferences? Can you provide some real application examples?
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ransonjd Members Profile Send Private Message Find Members Posts Add to Buddy List Advanced User Joined: 15 Nov 2016 Status: Offline Points: 139	Post Options Post Reply Quote ransonjd Report Post Thanks(0) Quote Reply Posted: 26 Feb 2018 at 10:16am
	This is mostly an issue with power components, which require thick traces or pours to certain pads for electrical or thermal dissipation reasons. An example would be a dual power transistor in a leadless package where the sources and drains have to be directly connected to pours for heat dissipation, but you want skinny traces to the gates to minimize capacitance. With NSMD pads, the pour-connected pads end up with extra exposed copper. They are effectively starved for solder paste, since the paste only covers the nominal pad area.

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: 5716	Post Options Post Reply Quote Tom H Report Post Thanks(0) Quote Reply Posted: 26 Feb 2018 at 10:44am
	All of this can be done in FP Designer. FP Designer is available in both V2018.02 Library Expert Pro and Enterprise. You have complete pad stack design and placement control.
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ransonjd Members Profile Send Private Message Find Members Posts Add to Buddy List Advanced User Joined: 15 Nov 2016 Status: Offline Points: 139	Post Options Post Reply Quote ransonjd Report Post Thanks(0) Quote Reply Posted: 26 Feb 2018 at 10:53am
	Can it be done just through a preferences file? I often already have a part entered that I'm using in a new way, and I need a version with NSMD pads. It would be great if I could just pick a set of preferences and pop out a new footprint. If not, it's no big deal.

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: 5716	Post Options Post Reply Quote Tom H Report Post Thanks(0) Quote Reply Posted: 26 Feb 2018 at 10:59am
	The preference file only has settings for "Terminal Lead" styles like Gull Wing, J-Lead, Flat Lead. Preferences are mainly used for the Calculator to auto-generate patterns. However, you have 100% full editing rights to adjust the Toe, Heel and Side goal for any Terminal Lead form. You also have a preference for Thermal Tab Paste Mask Reduction. I think you need the ability to create custom pad stacks and FP Designer does that.
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