PCB effect

Mar 11, 2020 3 Replies
J

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When I paved over the power pins of this part with solid copper, parts of the pins became solder-mask-defined pads. That's fine here, where all 4 pins are common. It could be tricky in other situations.



Layout software and PCB fab houses both take liberties with solder masks. That can get serious for BGAs.



I kind of miss my old flip phone and kinda hate this fancy Samsung thing, but it sure has a great camera. This was shot looking into my Mantis, which is hard to do with a conventional big-lens camera.



John Larkin Highland Technology, Inc picosecond timing precision measurement jlarkin att highlandtechnology dott com http://www.highlandtechnology.com
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W

R23 has a small pad and a big pad. :-)

Thanks, - Win
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J

Same effect, a mostly unintentional solder-mask-defined pad, caused by the part pad being buried in a bigger piece of copper, in this case the 50 ohm output trace. That's fine here. It's only 1 GHz or so.

This PCB is really the test case for our new enclosures, the ones that replace the horrible Hammond boxes. It's (maybe) a 1 GHz optical-electrical converter and if it works we may as well try to sell it. It's the Tektronix feed-beside idea, separate AC and DC gain paths combined late in the process.

It took forever to get the boards, coronavirus side effect.

John Larkin Highland Technology, Inc picosecond timing precision measurement jlarkin att highlandtechnology dott com http://www.highlandtechnology.com
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R

R23 is polarized - 2/5 of the electrons go one way, and the other 3/5 go the other way. The bigger pad decreases electron crowding...

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