The BGA collapse amount is a meter of the  ball diameter, the weight of the
component, the pads/land size and the solder / balls materials.

The space between balls, conductors, via hole and component / PCB surface
are the parameters to be checked.

Generally, the collapse numbers are in percentage of the diameter.

Best  Regards

ROKAH Reuven




                      Lum Wee Mei
                      <[log in to unmask]         To:      [log in to unmask]
                      .SG>                     cc:
                      Sent by: TechNet         Subject: [TN] BGA Query
                      <[log in to unmask]
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                      02/10/2003 05:23
                      Please respond
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                      Please respond
                      to Lum Wee Mei





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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