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Land pattern for LSM9DS1?

Question asked by Bill Burgess on Jun 3, 2017
Latest reply on Jun 12, 2017 by Bill Burgess

In TN0018 "Surface mounting guidelines for MEMS sensors in an LGA package", on Page 5 it offers different guidance on land pad dimensions depending on whether the "LGA pin spacing" is (a) greater than 0.2 mm or (b) equal to or less than 0.2 mm.  If (a), it says oversize the land pads by 0.1 mm in both length and width; if (b), the land pads are not oversized.


QUESTION 1:  Does the phrase "LGA pin spacing" mean open space between pins or pin pitch?  I don't think I've seen a part with 0.2 mm pitch, to say nothing of less than that; the smallest microBGA parts I've seen have a pitch more than 0.2 mm.  Anyway, the LMS9DS1 has a pitch of 0.43 mm, but its open space between pins is exactly 0.2 mm.  Do we go by pitch, and oversize the land pads by 0.1 mm in both length and width?  Or do we go by open space between pins, and not oversize the land pads?  Or...?


QUESTION 2:  In this thread -- Recommended Land Pattern for LIS2HH12TR -- Miroslav B refers to TN0018, and goes on to suggest oversizing the land-pad length by 0.1 mm but the land-pad width by only 0.05 mm.  This contradicts the oversizing suggestion on Page 5 of TN0018.  If the answer to QUESTION 1 is "yes, we should oversize the land pads for the LSM9DS1", then should we follow TN0018 guidance and oversize the land pads by 0.1 mm in both dimensions?  Or should we follow Miroslav B's recommendation for the LIS2HH12, and oversize only the length of the land pads by 0.1 mm, oversizing their width by only 0.05 mm?