Last call for reviews of this dumb GPIO expander before I send it to manufacturing on Monday. At the very least the BGA fanout looks fantastic, maybe I should put it on a t-shirt (oh wait, that doesn't work here). Even reviewing the readme would be helpful: https://github.com/joelpmichael/PCAL6534EV-breakout/
I am now at the “shifting 0.09mm-wide trace positions by 0.01mm” stage of BGA fanout. I also length-matched the I2C SDA and SCL lines to 0.0004mm for shits and giggles #electronics#maker
@NormanDunbar it was surprisingly easy. Only had to touch up 4 or 5 traces to centre them between the BGA pads, and the new length tuning tools in KiCad 8 make modifying length matching serpentines dead simple
It seems to be a thing this week with both @ktemkin and @azonenberg bashing their heads against manufacturing limitations. I’m trying Andrew’s trick of squishing some of the BGA lands to try and sneak a 0.09mm trace through, because I can live with missing the two unconnected balls in the middle. I’ve submitted an “order” with JLCPCB to see if they can actually manufacture this fanout
@jpm@ktemkin If I were doing this for real I'd just go laser microvias at Multech. Anything else would possibly be fine for prototyping but I wouldn't trust in volume.
@azonenberg@ktemkin mostly curiosity, also only available in WLCSP, and maybe turn it into an actual (small) product later. It’s a PCAL6534EVJ - 34-bit (but I can’t get 2 of the lines out on one layer) I2C GPIO expander. Fastest lines are the I2C, and those only go up to 1MHz. I’ve sent a board off to JLCPCB, the worst they’ll do is say no
@jpm There is the option to go via crazy (including blind vias) and break it out on 3 layers without any traces threading between pads, but that isn't going to make it easier to manufacture.
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