How To Choose the Footprint for SMD Chip Resistor

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   How do you choose
the footprint for SMD Resistor case 0402?

Vishay have
3 recommendations for footprints.

Yageo one
recommended but it’s different from Vishay.

Vishay recommendation:

L=0.5 A=0.4
B=0.6

BASED ON
IPC-7351

L=0.4 A=0.55
B=0.6

BASED ON IEC 61188-6-2

L=0.55 A=0.35
B=0.55

Yageo

L=0.5 A=0.5 B=0.6

I am very confused by all the recommendations.
I would appreciate a suggestion or any guidance on how to choose a footprint.

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Ariel_Levy Members Profile Send Private Message Find Members Posts Add to Buddy List New User Joined: 5 hours 32 minutes ago Status: Offline Points: 2	Post Options Post Reply Quote Ariel_Levy Report Post Thanks(0) Quote Reply Topic: How To Choose the Footprint for SMD Chip Resistor Posted: 5 hours 25 minutes ago at 5:07am
	How do you choose the footprint for SMD Resistor case 0402? Vishay have 3 recommendations for footprints. Yageo one recommended but it’s different from Vishay. Vishay recommendation: L=0.5 A=0.4 B=0.6 BASED ON IPC-7351 L=0.4 A=0.55 B=0.6 BASED ON IEC 61188-6-2 L=0.55 A=0.35 B=0.55 Yageo L=0.5 A=0.5 B=0.6 I am very confused by all the recommendations. I would appreciate a suggestion or any guidance on how to choose a footprint.



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: 6032	Post Options Post Reply Quote Tom H Report Post Thanks(0) Quote Reply Posted: 2 hours 18 minutes ago at 8:14am
	IPC-7351 uses Min/Max Mode technology. the resulting footprint takes into consideration the package tolerances to calculate the pad stacks. The solder pattern should accommodate the package in the minimum, nominal and maximum material condition. The average 0402 tolerance range is +/-0.05 to +/-0.10. It seems like component manufacturers use their nominal package dimensions and add a Toe, Heel and Side. They use Nominal Mode technology and ignore the tolerances they provide in their datasheets. The average dimensions on an 0402 are L=1.00, W=0.50, T=0.25. Your pad stack pattern will depend on what dimensions and tolerances you use. However, if you run into a 0402 chip manufacturer that has tolerances greater than 0.10, I would highly question the accuracy of their machine process. Ideally, manufacturers try to produce packages that are Nominal. That's the goal. Maybe in the future package tolerances will be 0.00 and then the Nominal Mode technology will take over and the IPC-7351 mathematical model will be history.
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feynman Members Profile Send Private Message Find Members Posts Add to Buddy List Active User Joined: 06 Feb 2020 Status: Online Points: 13	Post Options Post Reply Quote feynman Report Post Thanks(0) Quote Reply Posted: 18 minutes ago at 10:14am
	Ask a/your assembler. They probably assembled millions of parts and are probably the best source for a reliable footprint.