Solder ball

 ( Packaging ) 

In integrated circuit packaging, a solder ball, also a solder bump (often referred to simply as "ball" or "bumps") is a ball of solder that provides the contact between the chip package and the printed circuit board, as well as between stacked packages in ; Definition of: solder ball, PC Magazine glossary in the latter case, they may be referred to as microbumps ( μbumps, ubumps), since they are usually significantly smaller than the former. The solder balls can be placed manually or by automated equipment, and are held in place with a tacky flux. Soldering 101 - A Basic Overview

A coined solder ball is a solder ball subject to coining, i.e., flattening to a shape resembling that of a coin, to increase contact reliability. Patent US 7622325 B2, prior art description

Ball grid array, chip-scale package, and flip chip packages generally use solder balls.

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Underfill After the solder balls are used to attach an integrated circuit chip to a printed circuit board (PCB), often the remaining air gap between them is underfilled with epoxy. "Underfill revisited: How a decades-old technique enables smaller, more durable PCBs". 2011. "Underfill".

In some cases, there may be multiple layers of solder balls—for example, one layer of solder balls attaching a flip chip to an interposer to form a BGA package, and a second layer of solder balls attaching that interposer to the PCB. Often both layers are underfilled. "BGA Underfill for COTS Ruggedization". NASA. 2019. "Underfill Applications, Materials & Methods". 2019.

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Usage in flip chip method Image:Flip chip pads.svg|Pads Image:Flip chip flipped.svg|Balls Image:Flip chip mount 1.svg|Alignment Image:Flip chip mount 2.svg|Contact Image:Flip chip mount 3.svg|Solder reflow Image:Flip chip mount underfill.svg|Adhesive underfill Image:Flip chip mount final.svg|Final result

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See also

• Head-in-pillow defect, a solder ball failure

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