Post #4253078
2026-07-30 20:49 UTC
If we allow 1mm clearance between the components and 1mm on the perimeter, as a floor on overall SoM size, we'd be looking at 14mm x 21mm in this scenario, although there will probably need to be some voltage regulators and SPI flashes and passives so I'm not yet sure how small I could actually pack it.
Assuming 13 x 20mm ball field, with an 0.8mm ball pitch that gives roughly 16 x 25 = 400 ball sites available for connecting to the host board which should be sufficient.
Still a lot of open questions, one of the biggest being if we can figure out how to do ball attach on my friends' PnP in a cost effective / scalable manner because tweezering hundreds of balls is not happening
Replies (1)
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@azonenberg@ioc.exchange 2026-07-30 20:53
You can buy solder spheres on tape-and-reel packaging, but they're expensive as hell. A reel of 20K 0.4mm balls on tape is $450 or 2.25 cents per ball, so for a 400 ball SoM that's $9 just for the solder balls. For comparison, a jar of 25K 0.4mm SAC305 balls loose is $26. The only way I see this being viable is if I can figure out a way to place solder spheres from some kind of 3d printed/machined tray rather than having to buy them on tape.