Screaming Circuits: March 2008

Point Of Load Power Supply

POL or Point-of-load seems to be a hot topic these days. Just to be clear, I'm not talking about Internet traffic or construction - although point of load, as well as load bearing capacity are also quite important in Pth05060_on_boardthose areas as well. I'm referring to power distribution and regulation in electronics systems.

It wasn't that long ago when most things could be run off of +5 volts or +/- 12 volts. That was easy. You just have three power busses and a ground bus. You might have to double some up or take care what is next to what to make sure you have enough current carrying capacity and to reduce noise, but it was fairly easy.

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Who does the PCB Layout?

We've done some PCB layout surveys with our customers recently; how long it takes, what is the most tedious task, where do mistakes happen, etc.  One thing we've noticed is that you are tasked with the design and layout for most projects; and sometimes you choose to outsource the PCB layout.


We’ve been doing blog posts that help schematic designers with layout; starting with a five part series titled “5 Basic Steps to a Successful PCB Layout,” with posts on "BGA Layout" and "QFN CAD Libraries".

What makes you choose to outsource a layout?  What have been some of the biggest pitfalls and successes in bringing in an outside resource?  What have you learned from all this?  What are the costs you didn’t account for?

We are asking you to email your stories and experiences to us, to: info @  and are taking stories for this up to April 30, 2008.

Submitted stories will be compiled for articles in May, if you have something you’ve learned the hard way with outsourcing PCB Layout please share it with us so we can post it for others.

Thank you,


Product Development Manager

Screaming Circuits

Will The CAD Library Madness Never End?

Here's another parts library gone wrong. The electrical connectors fit fine. That's good. But the clippies are spaced too far apart for the mounting holes. Most likely, the CAD library part was made for a similar connector, but with solderable metal tabs sticking down. This part is similar but has a plastic mounting structure. Since this is a prototype, we were able to make it fit by clipping the outer half of the plastic mounting tabs, but that's not a good practice and you'd never want to do that for something that will get a lot of use past the test stage.


Duane Benson
I cried and I cried and I clipped...

RoHS Options Close By

Sometimes you feel like a nut and sometimes you don't. I hope that phrase isn't copyrighted by the Peter Paul Mounds candy company. Hmm. I'll just claim "fair use." I'm pretty sure that when I started writing this, it fit in somehow but now I can't really remember where I was going with it.

Oh yeah. Sometimes you feel like Immersion Silver and sometimes you feel like ENIG. Right? Well, if that's the case, we have some good news for you. A lot of you are loyal pcb customers of (or the old name and have to build RoHS boards. Sunstone has been offering Immersion Silver for quite some time now and they have just recently added ENIG finished pcbs.

Silver is pretty good but ENIG can have a longer shelf life and better corrosion resistance. Check it out at

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