Area of solder mask opening for MMA845x.

[yosukeohkuma]

Dear All,

A customer asks us that the area of solder mask opening of MMA845x series is a little bit larger compared with general QFN package.

If you possible, please let me know why is the below figure recommended?

Solder mask opening : PCB land pad edge + 0.113 mm larger all around.

(Document Number: AN4077)

I would appreciate if you help for this question.

Best Regards,

[yosukeohkuma]

Hi Josh

Thank you very much for your reply.

I could understand my asked point clearly.

Appreciated for your help.

Best Regards,

Yosuke

[Joshevelle · Accepted solution]

Hello Yosuke,

Thanks for using our community.

The recommended PCB land pattern is designed in compliance to IPC Standard, you will find detailed information in page 63 of the following document:

http://pcbget.ru/Files/Standarts/IPC_7351.pdf

The extra area in the solder mask helps self-alignment of the small package in reflow soldering.

Please let me know if I can help any further.

-Josh