I never bought a BGA component and I'm wondering if they arrived already with the soldering ball on it, so the component is ready for the placement and the heating. Maybe it'a a choice of the manufacturer or maybe is a standard.
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3\$\begingroup\$ Why would a supplier sell a ball-grid-array without a ball? \$\endgroup\$– Andy akaCommented Jul 26, 2018 at 8:59
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3\$\begingroup\$ If there are no balls underneath, a package is called LGA (land grid array). \$\endgroup\$– Turbo JCommented Jul 26, 2018 at 10:46
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\$\begingroup\$ How is this not directly answered in the datasheet? Surely that would show dimensions of any balls. Also, what exactly do you think the term ball grid array refers to if there are no balls. \$\endgroup\$– Olin LathropCommented Jul 26, 2018 at 10:46
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2\$\begingroup\$ Guys relax! I never seen one BGA and I thought that the balls were applied during the placement process. Maybe I was confused by some video on web that do a purely re-balling process. I thought also that the possibility of the "non-balled" component could arise from some mechanical reason. Why then the manufacturer don't place a little solder on component's pin (QFP for example) to facilitate the soldering (little enough to don't create too space between chip and the board)? These are two different cases, I know, but why not? And why the LDAs don't have already solder on it? \$\endgroup\$– thorazCommented Jul 26, 2018 at 11:02
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\$\begingroup\$ Sometimes the balls are removed and the package is reballed, for example to replace Pb-free with Pb balls (or for repairs). \$\endgroup\$– Spehro PefhanyCommented Jul 26, 2018 at 12:40
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1 Answer
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Yes they arrive with solder balls already attached. It is difficult to apply your own solder, and the process of replacing them is called re-balling. It requires a stencil to accurately apply the paste. For various reasons, reballing likely to create voids inside the ball (especially lead free).
Factory balling is preferred as this is done in a tightly controlled atmosphere with extreme cleanliness, suitable flux and precision stencils.
FYI IPC states the maximum allowable voiding is 25%, which would look like a bubble inside the ball on an X-ray.
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\$\begingroup\$ You can actually buy the balls pre-formed and not have to try to create them from paste and surface tension. \$\endgroup\$ Commented Jul 26, 2018 at 14:44
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\$\begingroup\$ I'd never heard of that until just now! \$\endgroup\$– MIL-SPECCommented Jul 26, 2018 at 14:52