Screaming Circuits: January 2010

Than Thara Wara Nona

I recently received an email comment about my blog writing that I think does a very good job of illustrating one of the frustrations that many design engineers face.

"Please have someone teach Duane the difference between "then" and "than". It really makes him look dumb, and I very much doubt that Duane is dumb. It's just painful see these everywhere in his blog. regards"

I've also been called out on "it's" vs. "its" before too. At least, I seem to mostly have the "to", "too" and "two" down. Now, I'm a reasonably educated person and writing is a significant part of my job, so you would think that I wouldn't fall into traps like this. Undeniably, I do. It drives me nuts. I even have a couple of websites that I refer to (when I think about it) to help with such things. Site one and site two, but obviously I still fall into the traps.

So, how does that relate to the frustrations of a design engineer? Well... read my blog. Most of my writing is about a very similar issue. Check this one about via in pad. And this one about parts libraries. Or this one about shorting potential under a QFN.

None of those problems were created by "dumb" people. Likely all of those boards were created by intelligent, highly skilled, well trained engineers - people who got picked on in school for blowing the curve, or were called "Spock" by the kids not on a college track. Yet, what does such an error get? It may get a blog post here. It may get a Twitter comment like this that I wrote about. Of course, some times silly little oversights like this have more dire or more expensive consequences.

And the moral of the story - attention to detail and continuous learning. Never stop trying to learn. Never stop double checking. I have to keep referring to my two grammar sites and other references. If you're a designer, never stop researching. Dig into those data sheets. Read up on best practices. If you're working a job over multiple sites, always make sure everyone's using the same rules.

Now over the next few days, I'm going to go back through my past posts and see how many of these "than/then" errors I can find and rework. Ugh.

Duane Benson
Never give up. Never surrender.

The Next Industrial Revolution - Is Happening In 1910

Matt, our product manager, sent me a couple of interesting links about the next Industrial Revolution. The first was an article in Wired Magazine by Chris Anderson. The second was a rebuttal in Gizmodo by Joel Johnson. Both had some interesting points. Both, as far as my thoughts go, have some truth and both have some silliness, again as far as my thoughts go.

RCA12ax7_sq_arms Regarding the idea that what is going is something new and revolutionary, well, maybe the products are new, but the process really isn't, but for a few specific details. A while back, the country was coming off of an economic down turn and a wholesale group of young folk with tools at hand built an industry in garages and barns. That was the auto industry.

All of those farm kids grew up around machinery. They all had the tools at hand and the knowledge to use them. Communications (teletype, telephone, newspapers) was changing the way information flowed around the country and world. Transportation (railroad and the autos/trucks that they were building) was in revolution and changing the accessibility of new markets.

Car companies were coming and going all over the place. Sound familiar? Then there was consolidation, conformity, near-monopoly, bloatware and then crash. Yeah, and the same thing started with electronics and computing back in the 60's, 70's and 80's. It's happening again now too. Big surprise. It happens whenever there is a convergence of the cycles of low-barrier to entry (good, cheap tools), emerging technology and bright young folks with time on their hands.

I see some of what Chris is talking about in our electronics manufacturing customers. I just have a bit of a different take on it. First, rather than seeing this all as new, I kind of feel like "here it goes again." Second, I think what he misses is the concept of scale. On certain scales, what he says is very true and very workable. However, companies that spend a few years developing their products would like to eat food and send their kids to college, so they need to earn money for that intellectual property they have developed. That being the case, they still need a place to build their things, but a place that wont steal that intellectual property and deny the company's kids their college education and food.

There's a place for the model Chris is describing. There's also a place for megalithic industry producing gajillions. And there's a place for companies like Screaming Circuits that cost more than open source but focus on making life easy for an engineer and can build prototypes or flexible low to mid volume manufacturing without the hassle of big industry or the risk of losing a livelihood to people with a very liberal interpretation of who owns what. (see #1101 in this post)

Duane Benson
Danger Will Robinson!

Screaming Circuits New Service

Screaming Circuits has added new capabilities to its website. You can now order not only speedy PCB assembly, but also order raw PCBs (made by Sunstone Circuits) at the same time.

With fab screen cap

On Tuesday January 26, 2010 (that's today, if you are reading this today), starting @ 3:30pm Pacific Standard Time, Screaming Circuits added PC board quoting and ordering to the assembly quote and order process.

Now, you can quote your assembly cost, quote the cost of boards from and order both at the same time!

Simply start your assembly quote and check the "ADD PCB FABRICATION" box under the quote questions. Our website will walk you through the process of quoting and ordering your PCBs. Sunstone will deliver them to us. We'll build everything up and ship you fully assembled boards ready for test, sale, or whatever you need to do with them.

If you have any questions please just call 1-866-784-5887 or email us:

Duane Benson
Mmmm. Crunchy.

My Top Ten Electronics Predictions for 2010

White crystal ball Yeah, yeah. Top ten predictions for the new year really need to be out in either the last week of the prior year or the first week of the new year. But I'm late. It's because my oatmeal is lumpy and I've just been trying to decide if I should have a top predictions for the new year or for the decade. Some people would say that we're still in the old decade, because, you know, 1 - 10. But I say, it's only analog jockeys that say that. Digital drivers go from 0 - 9 (or 0 - 1 or 0 - F or 0 - 7... now I'm confused again. Not many go 0 - 7 these days). For the purposes of this document, I'm claiming to be more digital than analog, so the new millenia started in 2000 and this new decade starts now. Or, does that mean that the new millenia should start in 2048? Or, rather 0x800? Crud. That's not a thousand. Okay, I don't want to wait until 4096. I might be dead by then. Fine. It's the year 3732. I have my handy 74LS90 and I'm going to count out my top ten predictions.7490 block

Starting at count 0, with Qa = L, Qb = L, Qc = L and Qd = L:

0000: By the end of the decade, 50% of all passives will be embedded passives and 20% of all PCBs will have 90% or more of their passives embedded.

0001: By the end of the decade, Quad stack POP (package on package) will be commonplace.

0010: By the end of the decade, Each individual human will have their own IP address. Several of us will have more than one. That way, we can jury rig accelerometers into our hands and feet so we can wirelessly know where each of our extremities are at all times. Cats will have them too.

0011: By the end of the decade, solder paste will be used less often than not when assembling components on to PCBs.

0100: By the end of the decade, nearly all hydraulics and pneumatics in new motor vehicles will have been replaced by electrics.

0101: By the end of the decade,the first semi-autonomous passenger vehicle will be on display on the auto-show circuit. Hobbyist built semi-autonomous cars will already be on the road.

0110: By the end of the decade, "airline pilot" will generally be a really, really, really boring job. That's a bit of a problem.

0111: By the end of the decade, most military "foot action" will consist of two soldiers in command of a squad of robots and those two soldiers will as likely be in Fort Lewis, Washington as in the combat zone.

1000: By the end of the decade, the president of the US will be promising health care reform as the highest priority.

1001: By the end of the decade, routine bioengineering will be, well, routine. Very scary.

1010: By the end of the decade, the 2019 recession will be looming large and all of the people that have forgotten about the 2009 recession and the 2001 recession and the 1985 recession and the 1975 recession... will be freaking out again.

1011: By the end of the decade, lead will be gone from 98% of new electronics. Bummer.

1100: By the end of the decade, four of the substances that replaced the substances removed from electronics due to ROHS and similar regulations will have been found to be significantly more harmful to the environment and the people recycling the materials than are the substances that they replaced.

1101: By the end of the decade, the world of intellectual property will be in even more of a mess than it is today. Virtually everything will be accessibly for easy theft and cheap replication. (this is pretty much a big "duh")

1110: By the end of the decade,building your own mutli-purpose robot will be as easy as building your own PC was in 1988. Hardware components and operating systems will be off the shelf, but standards will be pretty loosely defined, interoperability will be more theory than reality and applications will be sketchy and buggy.

1111: By the end of the decade, still no flying cars and personal jet packs, dadgummit!

Duane Benson
Sorry. I didn't have a 74LS90. I only had a 74LS93

A Little Something Extra

Most of what we do here at Screaming Circuits is PCB assembly. We build prototypes and short run production - putting parts on boards. We actually do more then that though. Our parent company, Milwaukee Electronics, has been around for about 60 years building volume production and providing custom engineering design services.

WhenMR early layout 150 we started Screaming Circuits, in 2003, we decided to just focus on the prototype assembly - putting parts on boards. That's been a pretty good deal and we're happy with it. What's been happening lately though is that we've been getting more and more requests for higher assembly volumes and for engineering design services. We put together our ShortRun production offering last year to answer the first request. For the second, we've been gradually connecting our engineers with folks that request such services.

Check out our Design Engineering Group.

Duane Benson
"I like nonsense; it wakes up the brain cells" (Dr Seuss)

mbed Development - USB Programming Forever

I'm still fiddling with my mbed. Although, I haven't put it to real use yet. I've got some ideas, but I just don't have the time these days. One of the nice things about its programming system is that if I do have to step away for a while, it's easy enough that I don't have to go through any kind of learning curve again. The plug and go USB programming and online IDE is that easy.

Contrast that to one of my little PIC based boards. I recently wanted to do something with one that I hadn't used for a while. I dug it up and pulled out my programmer. I somehow ended up with two different versions of the programmer software installed on my computer, and I had to try both. My programmer uses the FTDI USB/serial chip, so I had to try and guess which COM port to set my programmer software too.

Six permutations later, I had that figured out. I then loaded up an old known-working hex file and took my best guess at what the fuse settings needed to be and guessed wrong. Tried again and guessed wrong. Tried a dozen different combination and gave up and dug up the PDF of the data sheet. Once I found the setting and translated them to the language used in my programmer's software, I finally figured it out and got it all working.

Granted, if I were using this every day, I wouldn't have forgotten all those silly little details, but think about someone learning for the first time. Or, consider a hardware engineer that rarely uses microcontrollers. Once a year or so, some design does need a controller and some programming. I'm a big fan of PICs, but the programming system for many of them seems pretty archaic compared to a product like the mbed.

Duane Benson
I need gravy for the mashed potatoes in yesterday's post

Ambiguous PCB Markings

Which ref for which partHere's a little issue we run into now and then. Which reference designator goes with which part? Quick. I need to know. Now. Now. Now!

It's less of an issue with SMT parts because we machine place them and use your centroid file to do the programming. Still though, It's always good to have things marked clearly in case rework is needed and for visual inspection.

For thru-hole, though, it is definitely an issue because a real human being is putting the parts in and the visual markings are the programming for the human type person.

For best results, take a little extra time and make sure all of your ref designators are clearly associated with the correct part. It's also always a good idea, when possible, to have all the designators in the same position relative to their part. Consistency is a good thing here. Consistency is a good thing with mashed potatoes too. Who likes lumpy mashed potatoes?

Duane Benson
You say poe-ta-toe, I say ugly brown tuber

Oxidized PCB Finish

I've written a few times about potential and actual problems with different PCB finishes. Sometimes, the results are tragic and sometimes, just annoying. I'm not sure where this one falls on the continuum between the two extremes, or maybe even outside. I suppose it depends on who's paying the bill and how close these need to be to a final production product.

Oxidized pcb surface 

The surface on the pads had been exposed to the elements a little too long such that, even with good flux, the solder balled up instead of adhering as it was supposed to.

PCB finishes are more robust then they were even a few years ago, (although, a few years before that when we were mostly using leaded HASL, things weren't so bad) but still, your raw boards should be treated more like food then like shoes. Avoid fingerprints and other contaminants. Try to use them promptly. Store them properly. If your air quality is poor, be even more cautious in your handling and storage.

Duane Benson
Let not the sands of time get in your lunch

Inverted QFN Land Pattern

Have you ever experienced the heartbreak of inverted land pattern? It's not supposed to happen, but every now Inverted QFN land pattern 2and then, it does. Maybe something happened when creating a custom footprint. Maybe, somehow it got inverted in the CAD software and then placed on the wrong surface layer.

Maybe it was a subliminal attempt to make up for those giant open vias in the thermal pad. Who knows. But, it happened, so now what?

You could re-spin the whole board. Ugh. That's, like, wasteful and stuff. Certainly, if this is a production build, you'll have to re-spin. For some prototype applications - like if it's a high frequency or RF thingy, you may very well have to get a new set of PCBs fabbed up too.Inverted QFN land pattern

But, sometimes in the prototype world, you may be able to salvage the board run. We used to do stuff like this all the time with  thru-hole parts - need an extra chip, just dead bug hang it on up there. 

Flip the chip over and use some small gauge wire - maybe wire-wrap wire - and hand wire to the upside down chip. Gluing it down first may be helpful. Just keep in mind that since the thermal pad isn't soldered to the board, you will lose some of your thermal performance. Maybe solder a small heat sink on it or something. And don't forget to wire that pad to ground too (if it's supposed to be grounded).

Duane Benson
Just put it on the seventh surface of your tesseract and it will fit right.

LED Lighting Assembly

When I first attached a 280 ohm resistor in series with a 5mm red LED, the word on the street was that LEDs were low power, forever-lasting devices that would just about completely replace incandescent bulbs for simple binary indicators. LEDs spent a brief period as the numerical display device of choice too, until supplanted by the LCD. Regardless, the bottom line was that LEDs were really easy to work with. Just put that resistor in series - usually, you didn't even need to do the ohms law calculation - rules of thumb were good enough.

Lots of LEDs

Well, for simple binary indicators, that still holds true, but the big noise in LEDs these days has little to do with binary indicators. It's in illumination, and in illumination, all the rules are different.

800px-2007-07-24_High-power_light_emiting_diodes_(Luxeon,_Lumiled) High-brightness LED illuminations devices are some pretty seriously engineered systems. Most have current regulated power supplies. Portable applications often have buck/boost supplies allowing for constant brightness over the life of the battery. And most have serious thermal design work put into them as well. LED lighting designers not only need to worry about all those power supply issues, but also about heat sinking and exotic design techniques such as metal core PCBs and heavy copper. Though it's just an LED, the layout and assembly issues are far from trivial.

Duane Benson
Wear shades 'cause when you're cool, the sun always shines.
Or maybe someone's just trying to blind you with a bright LED flashlight because your ego got too big.

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