Consider the following table to calculate the dimensions for SMD and NSMD pad types when designing hardware with BGA package FAB024 for optimum board-level reliability. See Figure 1.
SMD and NSMD Pad Types
|
Solder mask defined (SMD) pad type |
Non-solder mask defined (NSMD) pad type |
|
Solder mask opening = min. Solder ball size (1:1)
These values should be such that PCB metal pad (Ball land pad) > Solder ball size > Solder mask opening |
Solder mask opening = (Solder ball diameter x (0.8 ~ 1.0)) + 0.15 mm The values should be such that PCB metal pad (Ball land pad) < Solder ball size < Solder mask opening For NSMD, solder mask opening is 0.15 mm larger than solder pad to secure enough space for excess solder. |
Note: These values depend on the designer’s decision on the solder ball diameter size when processing; note that these are only recommendations. Take into account the BGA pad pitch to make sure that the solder balls are clearly apart from each other to prevent short circuits.
Figure 1
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