Hello, guys,

The problem - BGA with pitch of 1 mm and components in 0402 packages just under the BGA. 



The thickness of the PCB - 110 mils (2.7 mm), hence of through vias drilling diameter is 12 mils (aspect ratio - 1:9). To keep annular ring of 5 mils the pads diameter is 22 mils. To place components between two adjacent vias I allowed 24 mils square pads over the via holes with deep hole plugging (50% to 80% hole length). The plugging was pretty good (as seen in cross sections) and the soldering results were also not too bad, although required some touch up. This was acceptable for the production of low to medium volume. 



We are going now to manufacture in high volume. The solution is not economical any more. Hence, I am considering three options, all of them requires us to place pads for the components between the vias holes:

1.	Round 24 mils pads. 

2.	Round 20 mils pads with tear drop to enhance the area

3.	19 mils square pads



Since the design will port in no time to LF soldering, but I can't test it now due to lack of time and components - can you advise which is the best solution?



Regards

Ofer Cohen

Manager

Quality Assurance, Reliability and Production Technologies

Seabridge Ltd. - A Siemens Company