Dripping Wet Is Too Much

Well, that's obvious. But what's not so obvious is that some components may look perfectly fine but act like Orville Redenbacher when in the reflow oven. Well, they won't actually act like Orlville, but rather, like his pop corn. Sort of. With popcorn, you can tell when it's popped. With a popped chip, you can't always tell right away.

Moisture sensitivity is a bigger issue with RoHS-compliant components, but can be an issue in leaded components as well. Even though the parts look like water-tight plastic, they really aren't. They do absorb 
moisture and after improper storage, moisture-sensitive chips may popcorn or crack subtly underneath. This MSD logo 75 can create hard to find or intermittent defects. It is often more of an issue with prototypes because components are quite frequently consigned in partial lots. This may result in impaired moisture sensitive packaging or storage beyond recommended shelf life.

So, the message here is that if your parts are labeled as moisture sensitive, don't open the moisture barrier packaging before sending them to Screaming Circuits. Or, if you have to open the package, please let us know. We'll bake them at the proper temperature

Duane Benson
Easy-Bake Oven: $25.99 from Hasbro
No. You can't use an Easy-Bake oven for your parts

To Lead or not to Lead. That is the question

Back at the Embedded Systems Conference in September, I had a number of folks ask me about mixing leaded and lead-free components on a PCB. It's a difficult situation for some people - especially when using old and very new BGA form-factor components.

We generally tell people to follow the BGA. Since the BGA has those little solder balls on it, it's the most sensitive to temperature as far as soldering is concerned. Reflow a leaded BGA at no-lead temperatures and the flux may all burn off and the solder may sag down too far and bridge or dry and crack. Do the reverse and reflow a no-lead BGA at leaded temps and you won't get a good intermetalic mix and the solder joint will be prone to cracking and other bad stuff.

In most cases no-lead components, other than BGAs can be used on a leaded board. Going the other way isn't always so easy though because of the additional 20 degrees C in the no-lead process. Everything's more sensitive to moisture absorption so baking parts or keeping them sealed in moisture-free packaging is more important. Some components may melt, especially chip LEDs. And metal can capacitors can pop.

In a prototype world, where you just need to see if something works, you can sometimes get away with a lot more than you can in production, but it's still not an easy question to answer. Unfortunately if you're in the situation of one of the guys that asked about it and have one leaded BGA and one no-lead BGA, you may have to get one of the BGAs re-balled or you may just need to redesign on of them out. No easy answer there.

Duane Benson
My 24 hours is almost come
When I to sulphrous and tormenting flames
Must reflow up myself

Updated Centroid Documentation

Passives orientation r2 A little housecleaning is usually a good thing. Here at Screaming Circuits, we try to be as flexible as possible and we'll do a lot of different things - standard and non-standard. But we really should, when passing on documentation, give out the standard form of data. And that's what housecleaning has done for us today.

I got a comment on an old blog post calling out an error relating to our centroid (AKA XY rotation / pick & place file), so I went back and cleaned up the blog post and linked to a PDF we have describing our centroid file requirements. It matches IPC-7351A now. And that kind of match is a good thing.

Duane Benson
Matchmaker, Matchmaker,
Plan me no plans
I'm in no rush
- actually, we're always in a rush.

IPC-A-610 Class III Assembly

The Screaming Circuits website will now offers instant online quoting and ordering of prototype and short-run production PCB assembly built and inspected to IPC-A-610 Class III standards. By default, Screaming Circuits assembles and inspects to IPC-A-610 Class II, but with the new capability, the higher reliability standard can be quoted and ordered just as easily.

Just what is IPC Class III and why should you care? IPC-A-610 covers workmanship for electronic assemblies - the boards you design and get built up. The higher the number, the more stringent the build and inspection requirements are. Class II is the general commercial standard: items produced and inspected to IPC-A-610 Class II are deemed quality for typical commercial applications. Class III are deemed to be appropriate for hi-reliability and mission critical applications.

For most prototype and small volume applications, IPC Class II workmanship and inspection will be just fine. However, for some with tighter reliability requirements, e.g. aerospace, military, medical, harsh environments, class III workmanship and inspection may be required. Class III service is available as an option on the Screaming Circuits "Full Proto" and "Short-Run" assembly services.

Duane Benson

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 Sunstone.com 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: sales@screamingcircuits.com.

Duane Benson
Mmmm. Crunchy.

A Few Hints of The Centroid File

NOTE: I've recently (8/18/2010) updated this post and the downloadable PDF to match the IPC 7351. We will properly assemble both ways, but this now matched industry standard.

Every now and then, we get questions on the centroid file (AKA Pick and place file or SMT locations file). Most CAD applications will create one for you. If you use Eagle, download our ULP and run it to create a centroid from your board.

If you want to poke around and need some hints on what's what you can download our Understanding the Centroid file r2. Here are a couple of illustrations from the guide. Fist, the point of origin needs to be centered in the part.

Chip originCopy of inline SMT connectorIt should be centered in a box that contains the outline of the pins as well as the body of the part. The chips on the left are easy. The connector, to the right, is a little more ambiguous, but as you can see, it's centered around the imaginary box containing the area.

Top-side rotation goes counter clockwise as shown on the left image and rotation on the bottom side is simply aChip rotation Chip rotation Bottommirror image left to right, with clockwise rotation.

Diodes and other passives should have their zero rotation horizontal, with pin one (if there is one) on the left. Passives orientation r2

That would place the cathode left for diodes and the positive side left for electrolytics and other polarized two lead parts.

Duane Benson
If you get dizzy spinning counter clockwise, go to Australia

A New Place To Find Screaming Circuits PCB Assembly

Screaming Circuits and Sunstone Circuits have partnered for board fab and assembly for many years and now, we've made things easier for our common customers. You can order Screaming Circuits Assembly at Sunstone while your order your board fab.

Just order your boards from Sunstone like you always have, but on the Sunstone.com quote page (for PCBexpress or Full Featured PCBs), check the box labeled: "NEW! Quote & Order Assembly" as shown in the screen capture below.

NEW quote

Check the box pointed at by the big red arrow I added in to the screen capture above. Then, you'll get a Assembly options_cbox to pop up with two choices: "Drop Ship Assembly" and "Bundle Assembly". If you select to drop ship with the button "Select Assembly", after your boards are fabbed, they will be sent directly to Screaming Circuits. With this option, you'll have to go ahead and come to our website and place your order separately before the boards get here. We've had that option for quite a while.

If you choose the new option, to bundle, by clicking "Quote Assembly" you will see a quote form and you'll be able to quote and order your assembly rightAssembly quote_c then and there. The order will be placed with us, the boards will be shipped to us and you'll get fully assembled boards from us. You will still have to send us the parts and make sure we have all the files we need though. We'll get your order ready in our system and give you a call to make sure that we have everything that you need.

You can, of course, still order your boards and your assembly separately. That's not a problem at all, but if you are getting your PCBs fabbed by Sunstone Circuits, we hope this added feature will make your job just a little bit easier.

Upcoming Maintenance = New Goodness!

On Tuesday 8/18 starting @ 3pm Pacific Daylight Savings Time, our site will be offline for a bit as we make a few upgrades.

We expect to have everything back up and running by 5pm PDT or sooner. We apologize for the inconvenience!

If you have questions or need to place an order while we are away, please don't hesitate to call 1-866-784-5887 or email us: sales@screamingcircuits.com.

What "new goodness" are we adding?

Just you wait and see... I wouldn't want to spoil the surprise!

Matt Mirande (new-ish guy)
What can't you build with a hammer?

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

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...