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From the CAD Library: Periphery Solder Joint Goals, Part 2
Wednesday, July 27, 2011 | Tom Hausherr, CID+, Mentor Graphics

Continuing the discussion I began last week, let’s move on to BGA packages. The BGA land is considered the first “periphery” land introduced to the electronics industry. However, the collapsing BGA ball is the only land calculation that creates a smaller land than the component lead. Non-collapsing BGA balls require a larger land size than the ball size.

Via-in-pad in a flat-lead LGA produces better solder joint results than BGA technology because there are no voids in the flat LGA component lead after reflow. Figure 1 is a BGA ball cross-section that illustrates trapped air holes using via-in-pad BGA void issues.

Figure 1. A BGA ball cross-section.

However, voids created by trapped air in blind or through-hole vias can be eliminated by plugging or filling the hole prior to the land plating process. Figure 2 illustrates various types of vias that contribute to trapped air and cause voids in BGA balls.

Figure 2. Types of vias that contribute to trapped air, causing voids.


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Related Articles:
  • From the CAD Library: Periphery Solder Joint Goals, Part 1
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