So, I have a board with a bunch of devices, including an Analog Devices ADXL330, which has the footprint of the LFCSP16. The board kept getting aperature errors, which i finally narrowed down to the ADXL330. The error reported is that there was an aperature that was too thin (.0028").
I checked the pads for the LFCSP16 in the spec sheet, which are thin, but not that thin — .30x.50 mm.
The pads in the package design are .01378" x .027559" — I suspect this error reported (.0028") is the pad length which is too thin? But, .027559" is 27.599 mil, so that can’t be a problem, can it?
But, clearly I’m stabbing in the dark — the aperature that is too thin is reported as .0028", and the pad is .028"…so, what the frack? The LFCSP16 is small, but none of its dimensions are onthe order of .0028"
I tried just laying out a board only with this device, and still got an error. Then I tried — just for laughs — making a new variant of the device with my own package, and still got the errors. Then, I made the pads of my own package bigger and spaced them out…still, the error.
Yeah, you know — I thought that might’ve been an issue, and I did have letters in copper on top, but I took that out and it still failed. I tracked it down to this particular part by mirroring each part, one by one, until the failure occured on the bottom of the board rather than the top.
But, now I’m not 100% sure why this particular part is having this aperature problem. I’m going to try and make my own package working from the device spec and see how that goes. I’ve verified that a trivial part with two SMD pads the same size as those for this particular device pass the DRC just fine — no aperature problems.
I’ll email you directly with a .zip of the Gerber files in question — but…the file upload never got so far as to actually place an order. I got this aperature error before I even got to the page where you select what CAD software was used.