What is it?

What is this and what does it have to do with PCBs?

As you ponder that question, if you care to ponder that question, keep in mind that I have at my disposal, not just the work of my company, Screaming Circuits, but I have the entire Internets to draw from and the Internets have photos from all of the history of electronics. So, this photo might actually not relate directly to via-in-pad or small component tombstoning.

There will be no prize for the correct answers, but you will likely get at least 3.2 picoseconds of fame if you post your answer as a comment here. And while a picosecond may not seem like much, if you could save picoseconds in a leyden jar, and then do the same over and over again, you could eventually end up with a usable duration.

Duane Benson
To have enough time
to do the things you want to do
you just need a fast enough internal clock speed

Friday The 13th

I'm always writing about stuff that goes wrong (and, hopefully doing a decent job of describing how to avoid such problems). But here it is, Friday the 13th - the traditional bad day of bad days. Break a mirror and watch a black cat cross your path while walking under a ladder.

Or not.

Here's a QFP part we soldered on. The land-pattern was right. The size and spacing was good. The pad size was good. The fillets all look good. The solder-mask registration is good. No problems. It's an IPC, class II job and everything meets IPC class II. Cool.

No vias in these BGA pads. No open vias without mask near the pads. Decent registration on the soldermask. Nice, planar surface on the pads. Even the vias between the pads are plated over and masked off.

The via caps do look kind of funky, being bigger then the BGA land pads, but that's okay. It's just a nice decent silver finish PCB. And, no tarnish or surface contamination to be seen anywhere.

Duane Benson
Hmmm. Interesting.

Microcontroller In The Middle

I've written about Open Source hardware before, such as the beagleboard and Arduino. Those are both great options for folks needing to get moving on embedded microcontroller development. The Arduino is pretty low-end and the Beagleboard is pretty high-end. I think I've run across a good step right in the middle.

A while back at the ESC show, we spoke with a gentleman from ARM about a project that would include an online IDE, and now, here it is. It's not exactly the same as open source, but it solves many of the same problems that open source solves. Mainly, it's a quick and easy way to get up and running with an ARM processor. Well, it looks easy, anyway. I haven't tried it yet. I think I'll see if I can get one and give it a shot.

By the way, we did not build this board. We have built some Beagleboards, but not this particular product. It certainly wouldn't be a problem for us, but that's not why I'm writing about it. It just looks like a great half-way point between something like the Atmel-based Arduino (or the PIC microcontrollers that I use) and the Beaglboard which uses the super-speedy ARM Cortex-A8.

If I can run one down and find the time to fiddle with it, I'll let you know what I think of it in actual use.

Duane Benson
Stay tuned. Bulletins as event warrant.
Maybe...

Speaking of Art in the Process

I really like this picture. It's nothing particularly special. Just a BGA-type attachment point of load (POL) power module in the middle of a big PCB, but the contrasting colors, the angle, the range of focus, the component positioning...  It just looks cool to me.

I know the function is supposed to be the most important thing, but I've always felt that there is a lot of art in PCB design. It's been said that an airplane that looks good will fly good and I think there's something in that phrase for electronics too.

No. I'm not advocating putting the visual appeal ahead of clock rise times, trace impedance and current capacity. It is first and foremost, an electronic device with an important function to deliver. But, I think a visually attractive, while still superbly functional, product makes a statement about the designer's overall attention to detail.

Duane Benson
Or, it might just be making a statement about how tight the development schedule is...

And, Another Thing...

I got a couple of pretty thorough comments on my copper pour post over in the Circuits Assembly blog where it's also posted.

David le Comte wrote:

"...On two layer boards (with 5V CMOS logic in particular) it is very difficult to pass CISP-22 EMC tests without a well grounded flood plane.

In the 1980s it became a requirement for more and more categories of electronic equipment to be tested for EMC compliance.

From first hand experience, I have seen how just adding a flood plane to two-layer boards can reduce EMC by 20dB. (We had to revise existing boards to pass EMC tests during the late 80s and 90s)..." (See his entire comment on the Circuits Assembly blog link above)

That brings up a very good point. EMI. In the prototype/experimental world and the hobby world, there are so many cases where EMI isn't too much of an issue. We don't always think about it. If your project is going into a consumer or business consumer product, no questions, though, EMI is a big consideration. As David indicates, a grounded pour or plane can go a long ways toward keeping stray interference down.

I wonder if an Arduino could pass any EMI standards. Has anyone run it through a lab? Maybe with some good shielding. I bet the "Knight Rider" teeth I made for my pumpkin this Halloween (with a point to point wired PIC16F819) just radiates all over the place.

Duane Benson
Pore, pour, pitiful me

Pour Or Not - Just What Is My Opinion?

I posed a question about using copper pours (AKA flood) a not long ago. The premise was a simple microcontroller board with a 20MHz clock and no special requirements.

I had a couple of different comments on the post with some very good insight. Myself, I generally don't use copper pours. My only reason is that I think it usually looks better without. Although, I do like the look of the cross-hatch pour on the Arduino. A well done flood can be pretty cool, but still my inclination is to only use it if it's needed. If it's a shop doing the PCB, the metal will be recovered and recycled, so the conservationist in me is pleased.

If it's a home etched deal, then a pour is probably a better idea because it will reduce the amount of etchant needed. Although you do need to be careful to keep plenty of space between things to prevent solder bridges. Solder bridging isn't such a big deal on a PCB with a good solder mask, but it certainly is on a board with no mask or thin mask.

If there is a good reason, I will. Like a high-current motor driver - I use the pour to keep the current capacity up and the kelvons mellow. Heat sinking is a good reason for a pour. Hi speed stuff usually benefits from a flooded plane of some sort too and in four-layer boards, using the inner planes for power and or ground is nice and convenient. But you all know that. I'm just rambling now.

Duane Benson
Does high speed stuff on a flooded plane require a speed boat?
Will too much heat sink it?

To Pour, Or Not To Pour. That Is The Question

I know there are plenty of times when a copper-pour ground or power plane is a good idea, sometimes even a requirement. But, is it always so? Take a simple embedded microcontroller board. It has a 20MHz clock speed. Nothing too dramatic. No big power drains anywhere. Just milliamps going here and there.

Does it still help? What about the "greenness" of it? If more of the copper is etched off, more metal will be recovered from the fab company's chemical vats. Or does the additional etch time and and acid required for clearing the board of copper outweigh the benefits of the additional recovered copper?

Looking at all of the boards we get through our assembly lines here, I can't really tell a general industry preference. It's hard to detect an internal plane visually and surface pours don't seem to be any more popular then the lack of them. So, I don't know what the world says.

Any thoughts on this? Anyone? Anyone?

Duane Benson
Bueller...
Bueller...
Bueller...

More Thoughts on Education

This is a follow-up post to one I wrote yesterday about education and new chip technologies. Well, the whole post wasn't about that. But part of it was.

On the flight home, after I wrote the post, I sat next to a rather brilliant Georgia Tech EE and chatted a bit about this issue with him. He's a lot more recent from school than I am and has spent a lot more time on campuses then I have in general.

His observation was very different from what I've heard. He talked about huge grants from private industry and government, research centers set up by private industry at universities and all of the micro-technology research and development that goes on at these places. So maybe the outlook isn't grim at all - at least in many schools.

My guess is that there's a bit of a "have" and "have-not" scenario going on here. If young folk can get to the good schools, the money and the technology is there. If not, then it's a case, like I mentioned, of being prepared for a job that doesn't exist anymore. So, maybe we should be proud of parts of our educational system and yet still looking for places to help with the "have-not" schools.

When I started school to learn how to program, we were still using - yes, it's true - punch cards. We'd write up our COBAL, RPG II and FORTRAN programs in punch cards and feed the deck of cards into an ancient boat-anchor of a card reader to be sent across the state to run at a University computer (An Amdahl 370). In short, we were being prepared for jobs twenty years in the past. It was like time-travel. We did eventually get a little Prime mini computer and a bunch of Apple IIs, but the card reader stayed on as well so I certainly understand this issue.

Duane Benson
Herman Hollerith says "what?"

Beagleboard and Package on Package Assembly

So, what's the big deal about the Beagleboard and us building it? If you aren't familiar with it, check out www.beagleboard.org for all the details.

In short, it's an open source hardware design development board / embedded system utilizing the Ti OMAP processor and a Micron memory chip in a POP (package on package) form factor. The POP is the significant point here. Well, that plus some 0.4mm pitch BGAs.

  
We assembled this one. The image below left is AbiWord running on the board pictured here.

The Ti processor is a 0.4mm pitch BGA and the Micron chip that goes on top of it is a 0.5mm pitch BGA. The power management / audio chip on the Beagleboard is also a 0.4mm pitch BGA. That's some pretty tough stuff and not a lot of folks can build it. Not only can we build it, but we can build it in small prototype quantities - as few as one at a time. We're proud of our capabilities and dedication to both quality and on-time delivery. (So, yes, there is a bit of self-horn blowing here.)

If you're primarily a software person and just want a working beagleboard, the least expensive route is to go to Digi-Key or Special Computing and buy one preassembled. But, if you want a derivative design, or just any old design using a POP part, you'll need someone that can build it properly. We've been assembling small volume prototypes of difficult designs for over six years now and we love doing the tough stuff. From 0201 passives, flex boards, rigid-flex and now POP. We also do easy stuff.

The beauty of the open source design is that Ti, through the Beagleboard organization, has made the Gerber files, the schematics and the CAD files available open source. That can give you a significant head-start in getting your custom design up and running. And, then, once you're done and need someone to put all of those parts on the boards and chips, connect up with us. We can assemble it for you. This is considered a special process, so you'll need to get confirmation from us on what turn-times we can support for your specific board before placing the order.

Duane Benson
Quaffing root beer with Bill Mauldin

Happy - zap - Birthday - zap - Nikola - zap - Tesla

I don't normally celebrate the birthdays of people that I haven't personally met, unless, of course, I get a day off work because of them, but I was over on the RF Cafe website this morning and they noted today as being Mr. Tesla's birthday back in 1865. On the other hand, the "never in err" Wikipedia lists Tesla's birthday as July 10. Hmmm. In any case, we should all know that without Tesla, electrons would only go in one direction, and that would be boring.

RF Cafe also notes (Ok, I'm paraphrasing to the (n-2)^th degree) that if you transpose the last two digits in the year of Tesla's birth, you get the deathday of Count Amedeo Avogadro. Without Mr Avogadro, millions of chemistry students would have been denied the pleasure of relieving boredom during long lectures by attempting to calculate the depth that a mole of moles would cover the earth. (Quick - who has the answer to that calculation?)

Duane Benson
Approximately 2.62 feet???