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Footprint Error Pad-Pad clearance fail

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wawaus View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote wawaus Quote  Post ReplyReply Direct Link To This Post 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
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Tom H View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Tom H Quote  Post ReplyReply Direct Link To This Post Posted: 23 Jan 2018 at 7:33am
I cannot find this part on www.pcblibraries.com/POD ;

The Vishay DG2722 datasheet - 

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. 

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wawaus View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote wawaus Quote  Post ReplyReply Direct Link To This Post 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
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Tom H Quote  Post ReplyReply Direct Link To This Post 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. 

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Post Options Post Options   Thanks (0) Thanks(0)   Quote wawaus Quote  Post ReplyReply Direct Link To This Post 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.



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Post Options Post Options   Thanks (0) Thanks(0)   Quote wawaus Quote  Post ReplyReply Direct Link To This Post Posted: 23 Jan 2018 at 7:53pm
I tried to add some screenshot snips but they appear not to have gone through.
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