Screaming Circuits: June 2009


Holiday Schedule

Fireworks We'll be shut down for the Independence Day holiday this Friday, the 3rd, Saturday, the 4th and Sunday, the 5th. These days won't be counted toward turn-times.

Enjoy the holiday!

Loose Parts

I think every good engineer has a little box or two full of loose parts. You know, you take a few from a cut strip, fiddle with them, and then just never bother to put them back. It's not always easy to put them back in the strip anyway. It's not such a big deal for passives and inexpensive parts. When you need something assembled, you just buy another strip of ten (or however many you need) for $0.29.

We sometimes can assemble from loose parts, but it's never a good idea. They can be dirty, damaged or of mixed value. It takes us extra labor time too and we'll probably have to charge for that. Since we're using robots to assemble, we'll have to put all of those loose parts into an empty strip. Ugh. Components manufacturers don't want you to store your parts loose either. They know that having the things rattle around can cause damage or contamination.

Bent pins But when it comes to the bigger, more expensive parts like BGAs or QFPs and things, it can be more of an issue. Still, though, your ultimate goal is a sold, reliable piece of hardware. If the QFP ended up with some pins bent (as in this picture) or the BGA had some balls drop off, you've probably lost your goal no matter what. So keep those expensive parts in their original packaging.

When you look at the total system cost, a new part or two probably doesn't seem so expensive anyway. A Freescale MCIMX31LVKN5B processor in a 457 ball BGA is only $26.00 from Digi-key. Getting a new one of those is pretty cheap compared to the risk of spending a week trying to diagnose a problem caused by a BGA ball that cracked because of poor storage.

There are some processors, FPGAs and other specialized components that can cost hundreds or even thousands of dollars each. Those parts are probably worth repair if pins are bent or balls are knocked loose, but the best bet is to keep them in their original, not extra crispy, packaging.

Duane Benson
We don't have 11 herbs and spices in our solder paste

Non Solder Mask Defined pads on BGAs

OSP NSMD bga pads The industry generally recommends NSMD (non solder mask defined) pads on BGAs and so do we. There are some exceptions though. When you get into really small ball pitch, you probably need solder mask defined pads to help prevent bridging. See this post here.

This photo does a good job of showing NSMD pads up close and personal. The registration could be a bit better, but this isn't too bad. There's a nice small gap around the pad with no mask up on the copper.

You'll also notice that there's a good bit of solder mask between the pad and the escape via. That's also good practice. And, of course, no vias in these pads.

You can put vias in the pads, but if you do, you really want them filled and plated over. Never, never, never put an open via in a BGA pad. There are plenty of options at the board house for filling and plating these days.

Duane Benson
I hope NSMD doesn't mean "Never Send Money to Duane"

Top-ten ways to get a jump on the nearing economic recovery

I have no evidence in reality if the economy is starting to get better or still has more sinking to go, but I do hear some predictions that we're seeing the light at the end of the tunnel. Of course, to be a bit trite, it could always be an oncoming train. But heck, why not be an optimist and assume the worst is over. If it's any indication, we're sailing along fine here now.

So, let's talk about what we should do in anticipation of and in preparation for things getting better:

#10. First, it's mood change time. All summer long, we complain that it's too hot and all winter long, we complain that it's too cold. The world's been complaining that business is too slow for a while so all you folks should get a jump on things and start complaining now that you've got so much business that you don't know what to do with it.

#9. With that mood change comes consumption change too. To keep up with all of that rediscovered demand, we need more caffeine. Sleep is for wimps. Just triple up on the lattes and start running around like a maniac gerbil.

#8. All three of you that took my advice (see #7) can now do Octal math without a calculator and without first converting to decimal or hex or anything. Now is the time when you discover that no one does anything with Octal anymore. Oops. Sorry.

#7. If you've been looking for work, by now you're pretty danged discouraged. Stop it. Pretend like you're starting over. Toss out the old resume and start over from scratch. It'll give you a chance to remind yourself about all the good things you've done and you'll see any holes you might still have that can be plugged with some night classes or on-line study. But, no. You can't list your six months of flipping burgers as "entropic bovine-protein thermal engineering."

#6. Read some more. Go read every bit of tech news that you can find. Figure out what's changed in the last year and what you need to be talking about (if you're looking for a job) and what you need to be designing with (if you still have one). It'll remind you of how fast technology moves and how easy it was for you to get out of date.

#5. Take a break. Have a soda. Watch a video. Snack on some chips and salsa. Kick back and chill for a bit. Enjoy the reasonable workload because you'll be back to the 60 hour work weeks before you know it.

#4. Get out your Deming, Tom Peters and Geoffrey Moore books and start reading up because as soon as you no longer have time for it, you can bet that all those quality, time management and other efficiency classes will get stuffed into your calendar. And you can spend some "quality time" rhetorically asking yourself "why didn't the company do that stuff when we all had the time for it?"

#3. If you've been out of work, lay rusty nails and broken glass all over the floor at your house. That way you'll get used to wearing shoes again, which are generally required in job interviews.

#2. Juggle hot soldering irons. I'm guessing you're a little out of practice so all of those burn marks us solderers have are now healed up. Tossing hot soldering irons around (and catching them) will give you a nice distribution of fresh little burn marks that will make it look like you've been busy all of this time instead of just drinking soda and watching movies like you have been doing.

Drum roll please... And the number one thing we should do to get a jump on the impending economic recovery...

#1. Go back to sleep. Either you're going to be trashed-busy soon enough and won't have time for good sleep anymore or we've got another year of this recession crud so it just doesn't matter.

Duane Benson
Boil that dust spec. Boil that dust spec
Boil it, boil it, boil it!

Ohm the Eskimo

...or, one of the best website names ever.

I ran across www.mightyOhm.com while checking out my web traffic source statistics. First, I love the name. Second and more important, the site and blog has some cool content centered around DIY electronics and a good set of other electronics blogs worth checking out.

Back in my day - in the dark ages (or golden age, depending on your perspective) of DIY electronics, everybody was building stuff. Our building blocks were discreet logic chips, op-amps and eight bit microprocessors and that was about it. I was an RCA 1802 guy myself. That was an odd duck processor, but it was good enough to go to Jupiter, so that's good enough for me.

If we needed to write code, we just used an assembler provided by the manufacturer or hand assembled and entered the machine code through a hexadecimal keypad. The barriers to entry were very low.

In the '80s, every thing became much more complex. The tools got expensive and DIY was set back quite a bit. In the '90s, it was all about the Internet and software DIY was king. But now, thanks in large part to companies like Microchip and Atmel, DIY is back with a vengeance. And it's both hardware and software these days. It's both analog and digital.

So here's a question: Why should a PCB assembly company encourage DIY electronics? Well, for one, it's very cool. I build junk too (I'm a Microchip PIC guy). Second, it encourage the spread of geekdom into mainstream society, and that's a very good thing. This is the technology century and the more people that get it, the better we'll all be. Finally, the commercial side of me says: engineer by day, hacker/bender by night.

Along with the MightyOhm, here are a couple of other DIY sites I spend some time on:

These aren't the only DIY web sites, but it's a good, fun set of them. Gobs of useful information.

Duane Benson
When Ohm the Eskimo gets here
Everybody's gonna jump for joy

Internet Explorer 8 Compatibility

[UPDATE: We have fixed this problem in the screamingcircuits.com website. You'll notice that the little broken page button goes away on some parts of the Screaming Circuits site now. You shouldn't have any more problems. I'm going to go ahead and leave this post up because the same fix should work with other sites that have problems with ie8.]

ie8 Compatibility mode:

Version 8 of Internet Explorer has caused some problems with our website. It can make the quote and order system invisible. That's no good. Fortunately, Microsoft put in an easy to find and easy to use compatibility mode into ie8.

You'll find a little button that looks like a broken piece of paper up on the top bar, just to the right of the URL bar. See the red arrow on the image here.

Ie8 compatibility button 1 

Just click on the button and everything will come back to normal. When compatibility mode is on, the little icon will be a subtle shade of grey. To turn the mode off, just click the button again. Easy.

Ie8 compatibility button 2 

We're working on the website to fix this. Hopefully it will be taken care of soon, but until then, that little compatibility mode button is our friend.

Duane Benson
It just goes to show you, It's always something...

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