IPC-7351 Collapsing and Non-Collapsing BGA Balls
Printed From: PCB Libraries Forum
Category: Libraries
Forum Name: PCB Library Construction Guidelines
Forum Description:
URL: https://www.PCBLibraries.com/forum/forum_posts.asp?TID=3370
Printed Date: 09 Apr 2025 at 1:29pm
Topic: IPC-7351 Collapsing and Non-Collapsing BGA Balls
Posted By: Tom H
Subject: IPC-7351 Collapsing and Non-Collapsing BGA Balls
Date 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.  ------------- Stay connected - follow us! https://twitter.com/PCBLibraries" rel="nofollow - X - http://www.linkedin.com/company/pcb-libraries-inc-/" rel="nofollow - LinkedIn |
Replies:
Posted By: Tom H
Date 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.  ------------- Stay connected - follow us! https://twitter.com/PCBLibraries" rel="nofollow - X - http://www.linkedin.com/company/pcb-libraries-inc-/" rel="nofollow - LinkedIn |
Posted By: mking
Date Posted: 28 Mar 2025 at 11:39am
|
For the collapsing BGA ball with a diameter between the values listed what is appropriate reduction? My example is a 0.242 mm diameter. Is the recommended reduction 15%, 20%, or 19.2% (linear interpolation)?
|
Posted By: Tom H
Date Posted: 28 Mar 2025 at 1:38pm
|
If the Ball diameter is on the dividing row between percentages the new ball size will take the lower values.
Here is a sample BGA terminal option table where the 0.24 mm Ball Diameter was added.  ------------- Stay connected - follow us! https://twitter.com/PCBLibraries" rel="nofollow - X - http://www.linkedin.com/company/pcb-libraries-inc-/" rel="nofollow - LinkedIn |