Sunday, 3 July 2016

surface mount - Size of SMD pads for components with high tolerances


I'm building an Eagle component for an LSM115J.



The connectors on this part have fairly large tolerances (1.85-2.21mm width, 0.76-1.52mm length). There is no recommended land pattern.


Should I go for the largest size (so the part will never need to be partially soldered on top of the stop mask), the smallest size (so the part has a well-defined placement) or something in the middle?



Answer



That package is an SMB. Here is Diodes Inc. suggested footprint for their SMB (almost the same):


enter image description here


The IPC footprint expert would give you a somewhat different footprint (more prone to shorting in the center IMO).


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