IPC-7351 Collapsing and Non-Collapsing BGA Balls

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   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 Members Profile Send Private Message Find Members Posts Add to Buddy List Admin Group Joined: 05 Jan 2012 Location: San Diego, CA Status: Offline Points: 5718	Post Options Post Reply Quote Tom H Report Post Thanks(0) Quote Reply 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 Members Profile Send Private Message Find Members Posts Add to Buddy List Admin Group Joined: 05 Jan 2012 Location: San Diego, CA Status: Offline Points: 5718	Post Options Post Reply Quote Tom H Report Post Thanks(0) Quote Reply 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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