Hello,

It's me again, the curious cat. I have more questions on BGA :

1. IPC-7095 states that when the balls goes through reflow, it will be
reduced by 0.25mm to 0.3mm. As a newcomer to this field, I think this
value is quite reasonable and acceptable for ball diameter greater than
0.5mm. However, I cannot quite accept this value for ball diameter in
the range of 0.3 to 0.4mm? Won't we find the package almost flat to the
board after reflow?

2. Is there a lsit of standoff height values available after reflow as
part of the assembly acceptable criteria. Are we not at our assembler's
mercy, to find BGAs mounted almost flat onto the board but cannot reject
just because the X-ray does not show shorts between balls?

Hope to hear from you soon.

Regards,
Wee Mei

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