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IPC-7351 Collapsing and Non-Collapsing BGA Balls

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Tom H View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Tom H Quote  Post ReplyReply Direct Link To This Post Topic: IPC-7351 Collapsing and Non-Collapsing BGA Balls
    Posted: 07 Apr 2024 at 1:31pm
IPC has a rule for BGA pad size tolerances. They take a Nominal Ball and reduce or increase the pad size by a percentage, then add a pad size tolerance (variation). IPC-7351 recommends using the Maximum Material Condition of the Variation. 

All BGA balls collapse. Non-collapsing BGA balls are created by the PCB librarian by solder mask defined pads or making the pad size larger than the Ball. 

Collapsing Ball.




Non-Collapsing Ball defined by Solder Mask.




IPC-7351 BGA tables for pad size reduction for collapsing balls and pad size increase for non-collapsing balls. The pad size increase is normally used for fine pitch BGA's that require via-in-pad technology for fanout. 

There are 3 Density Levels A, B and C that indicate the percentage amount for pad size calculation.



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Tom H View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Tom H Quote  Post ReplyReply Direct Link To This Post Posted: 07 Apr 2024 at 1:39pm
The Solder Mask Defined BGA pad helps secure the pad to the prepreg. This helps during drop tests. 



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