Screaming Circuits: The Evils of Parts Libraries


The Evils of Parts Libraries

Well, maybe "evil" is too strong of a word, but it sometimes seems fitting, given the amount of grief caused by parts libraries in CAD packages. Sometimes it's because the part isn't in the library. Sometimes it's because the solder paste stencil pattern would lead to poor soldering. Sometimes the part size is just wrong.

Caps_under_bga

Here's a case where the part outline didn't quite match the package. The designer wanted to get bypass caps in as close to the BGA pins as is possible - that can be very important with many components these days, especially RF and high-speed parts.

Unfortunately, the part outline in the CAD library did not match the actual outline of the part. I don't know why. Maybe this is a functionally equivalent substitution from another manufacturer. In any case, it speaks to the value of verifying things like actual part dimensions before sending the board out for fab.

Duane Benson
actual size may vary

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Comments

well...I would go with evil.
I don't know why layout packages sell on the basis of number of parts in a library; bad parts may as well be 'no parts included!'
My decrepit old version of IVEX stays around precisely because I have a ton of Corrected and designed-by-me library components and it seems no one in the market will/can afford to make a correct part for a commercial pcb design package? why not, are the mil packages' artwork copyrighted?...I am about to learn Sunstone's PCB123; but am holding my breath all the same.

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