IPC-7351 or Manufacturer Recommended Footprint?

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   How to choose between a footprint made with LE and the manufacturer recommended footprint when they are sightly different?

i have made a footprint for the NCP176 (XDFN6 / Case 711AT) with LE and I compare it with the manufacturer recommended footprint. 

I notice differences, the MRF does not respect the IPC-7351 design rules (pad to tab iso for example), all the pads are bigger...

How to choose the right footprint for production?

What is your opinion, in a general matter how do you choose the final footprint?

Thanks in advance for your reply.

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sdavid63 Members Profile Send Private Message Find Members Posts Add to Buddy List New User Joined: 21 Mar 2018 Status: Offline Points: 2	Post Options Post Reply Quote sdavid63 Report Post Thanks(0) Quote Reply Topic: IPC-7351 or Manufacturer Recommended Footprint? Posted: 15 Jun 2020 at 8:44am
	How to choose between a footprint made with LE and the manufacturer recommended footprint when they are sightly different? i have made a footprint for the NCP176 (XDFN6 / Case 711AT) with LE and I compare it with the manufacturer recommended footprint. I notice differences, the MRF does not respect the IPC-7351 design rules (pad to tab iso for example), all the pads are bigger... How to choose the right footprint for production? What is your opinion, in a general matter how do you choose the final footprint? Thanks in advance for your reply.



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: 5718	Post Options Post Reply Quote Tom H Report Post Thanks(0) Quote Reply Posted: 15 Jun 2020 at 8:59am
	IPC-7351 has been downgraded from a Standard to a Guideline. All of the Preference Values in Library Expert are user definable and you should discuss the rules with your assembly shop and study IPC-J-STD-001 for Solder Joint Goal acceptability. Library Expert draws the Terminal Lead where the metal hits the pad so you can visually see the Toe, Heel and Side goals. If the mfr. recommended pattern relocates the Terminal Leads off the pad, this is not acceptable. Remember that IPC-7351 is a 3-Tier Density Level guideline and maybe the mfr. recommended pattern uses the Most Density Level. I would say that any mfr. recommended pattern that is between the Least and Most density level is OK to use. The mfr. could have created a reference design and ran it through stress tests for solder joint goal reliability. It depends on the mfr. Today, all good component manufacturer's test their land patterns.
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