2072 - What is the optimum PCB solder mask opening and pad diameter for a Lattice package?
Solution:
This question is best answered by reviewing table 3.2 in FPGA-TN-02024.
In the table, the Solder Mask Defined (SMD) and Non Solder Mask Defined (NSMD) PCB processing values are given. For the question of which type to use (SMD vs. NSMD), that is best answered by your PCB fabrication vendor.
From Lattice's perspective, where possible, we recommend customers design their PCB using the same SMD or NSMD type and dimensions as the package (types and values are given in table 3-1) in order to result in solder joints which are evenly matched on top and bottom. However, we understand that this is not always possible due to customer preference so that is why we provide optimum dimensions for both SMD and NSMD.