Footprint Error Pad-Pad clearance fail

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

   Generating a footprint for a Vishay-Siliconix DG2722 Library fails to maintain the specified Pad to Pad clearance with the clearance rule set at 0.2mm. Between pads 1-10, 2-3, 5-6, 7-8  it delivers a clearance of only 0.14. To achieve the clearance, dimension S1 should have increased to 1.0mm.
Is this behaviour expected?
Have I missed something?
Bill

Author	Message Topic Search Topic Options Post Reply Create New Topic Printable Version Translate Topic
wawaus Members Profile Send Private Message Find Members Posts Add to Buddy List Active User Joined: 09 Jul 2013 Location: Melbourne Status: Offline Points: 30	Post Options Post Reply Quote wawaus Report Post Thanks(0) Quote Reply Topic: Footprint Error Pad-Pad clearance fail Posted: 22 Jan 2018 at 11:54pm
	Generating a footprint for a Vishay-Siliconix DG2722 Library fails to maintain the specified Pad to Pad clearance with the clearance rule set at 0.2mm. Between pads 1-10, 2-3, 5-6, 7-8 it delivers a clearance of only 0.14. To achieve the clearance, dimension S1 should have increased to 1.0mm. Is this behaviour expected? Have I missed something? Bill



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: 23 Jan 2018 at 7:33am
	I cannot find this part on www.pcblibraries.com/POD ; The Vishay DG2722 datasheet - https://www.vishay.com/docs/68379/dg2722.pdf ; Indicates that the footprint requires a longer Pin 1 and therefore must be created in FP Designer using the mfr. recommended pattern. The Preferences > Rules > Minimum Pad to Pad is for Standard Calculated parts only and does not have anything to do with custom FP Designer footprints that use the mfr. recommended patterns.
	Stay connected - follow us! X - LinkedIn

wawaus Members Profile Send Private Message Find Members Posts Add to Buddy List Active User Joined: 09 Jul 2013 Location: Melbourne Status: Offline Points: 30	Post Options Post Reply Quote wawaus Report Post Thanks(0) Quote Reply Posted: 23 Jan 2018 at 2:48pm
	Hi Tom, I accept your comment about the Mfr recommended pattern, but that does not change the fact the calculated footprint Did Not maintain the clearance I specified between the end of one calculated pad and the side of another adjacent calculated pad. Bill

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: 23 Jan 2018 at 2:53pm
	I don't know how you created a QFN with a longer Pin 1 in the Calculator, it does not have that feature. Send us the FPX file for this Calculator part and your Preference .dat file so we can take a look. Never seen this issue in the past 15 years.
	Stay connected - follow us! X - LinkedIn

wawaus Members Profile Send Private Message Find Members Posts Add to Buddy List Active User Joined: 09 Jul 2013 Location: Melbourne Status: Offline Points: 30	Post Options Post Reply Quote wawaus Report Post Thanks(0) Quote Reply Posted: 23 Jan 2018 at 7:50pm
	I did not create it with a longer pin 1, I created a symetrical footprint, but with a 0.2mm clearance requirement the corner pads are closer than the the clearance specified and there was no warning that the rule had been violated.

wawaus Members Profile Send Private Message Find Members Posts Add to Buddy List Active User Joined: 09 Jul 2013 Location: Melbourne Status: Offline Points: 30	Post Options Post Reply Quote wawaus Report Post Thanks(0) Quote Reply Posted: 23 Jan 2018 at 7:53pm
	I tried to add some screenshot snips but they appear not to have gone through.