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If I took that to my assembly guy he'd :eek:
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I always ask the assembly company what they can handle first :)
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No, that's why I kept saying they mirrored the BGA pads on the bottom of the board.
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Actually, you said two things; you said mirrored and you said on the ends of the vias.
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Sheesh, you academics (my dad was/is one so I know what you're like).
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I live in the middle of nowhere, so have noone to talk to ... sniff sniff ... seriously though, I have noone to talk to about this type of PCB design, so I wanted to clearly understand what you were doing.
Just call me pedantic :)
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I'm not sure if we're using 'tenting' to mean the same thing.
To me (and most on the Altium forums I think) 'tenting' means the via is covered in solder resist, but if your vias were tented you wouldn't be able to solder your caps on them.
Do you mean they've been filled (I think they use epoxy) so the solder that's down for the caps won't wick down the via?
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Ah, I think you are right ... sorry 'bout that.
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It would be interesting to see how having the cap directly connected to the via affects it's impedance, as seen from the BGA pad, compared to having the short stub as in my example.
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I'm sure no stub is better :)
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Is this the sort of thing you could get students to do as project work?
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Alas, I really am in the middle of nowhere. No students in sight ... (none that I'd give a soldering iron to anyway)
http://en.wikipedia.org/wiki/combined_array_for_research_in_millimeter-wave_astronomy --- Quote Start ---
Another experiment would be incrementally removing decoupling caps from a working board and make noise measurements on the supplies.
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I haven't tried removing caps. I'd be afraid that I might reflow a BGA ball. The boards are 18 layers thick, with a lot of copper.
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Just shows there's no 'correct' way of doing things.
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It is nice to discuss the possible solutions though.
Thanks for sharing your knowledge.
Cheers,
Dave
Honored Contributor
