Trim Pad Under Component Feature

Message Topic Search Topic Options Post Reply Create New Topic Printable Version Translate Topic

Hi
I see a big difference between PCB Footprint Expert 2012.21 and LP Calculator see below I understand there is a small difference but this is big. Does anyone else see this.

Author	Message Topic Search Topic Options Post Reply Create New Topic Printable Version Translate Topic
dipakdesai Members Profile Send Private Message Find Members Posts Add to Buddy List New User Joined: 08 Aug 2012 Location: Frisco, Texas Status: Offline Points: 8	Post Options Post Reply Quote dipakdesai Report Post Thanks(0) Quote Reply Topic: Trim Pad Under Component Feature Posted: 20 Sep 2012 at 7:27pm
	Hi I see a big difference between PCB Footprint Expert 2012.21 and LP Calculator see below I understand there is a small difference but this is big. Does anyone else see this.



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: 5717	Post Options Post Reply Quote Tom H Report Post Thanks(0) Quote Reply Posted: 20 Sep 2012 at 8:24pm
	Is it the Component Rotation or the JEDEC Dimensions or the program Header?

jameshead Members Profile Send Private Message Find Members Posts Add to Buddy List Expert User Joined: 20 Mar 2012 Location: Oxfordshire, UK Status: Offline Points: 576	Post Options Post Reply Quote jameshead Report Post Thanks(0) Quote Reply Posted: 21 Sep 2012 at 12:26am
	I think perhaps dipakdesai has spotted the Y dimension difference because FPX uses IPC-7351C with no pad triming on the pad.

dipakdesai Members Profile Send Private Message Find Members Posts Add to Buddy List New User Joined: 08 Aug 2012 Location: Frisco, Texas Status: Offline Points: 8	Post Options Post Reply Quote dipakdesai Report Post Thanks(0) Quote Reply Posted: 21 Sep 2012 at 8:41am
	It is the Y (L in New) dimension Thanks Dipak

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: 5717	Post Options Post Reply Quote Tom H Report Post Thanks(0) Quote Reply Posted: 29 Dec 2012 at 12:13pm
	Dipak, Download the Power Point presentation that describes the upcoming changes for IPC-7351C. It's called "PCB Optimization Starts in the CAD Library" - http://www.pcblibraries.com/forum/pcb-library-construction-guidelines_forum30.html Slide 16 explains that pad trimming is not an IPC standard and that the pad should extend under the component body. However, you can still "Trim Pads" in the Footprint Expert if you want to. i.e.: The "Trim Pad" feature is still there, the component stand-off default value is set to zero "0". If you want to turn on the "Trim Pad" featurre go to "Setup > User Preferences > Setup > Rules > Minimum Trim Stand-off Height > Value". Set the "Value" to whatever component body stand-off you need to start trimming pads from under the component.