Blog - Screaming Circuits


Freescale KL03 and PCB123 at 0.4mm pitch

Small component packages seem to be a recurring theme with me. It's understandable, I guess. Super tiny packages are becoming more and more common and we build a lot of product with them.

The smallest we've built is 0.3mm pitch. Those aren't common enough to be considered standard - they're still an experimental assembly - but not many chips use them yet. 0.4mm, on the other hand, is something we see on a pretty regular basis.

What's so tough about that?

The biggest challenge with these form-factors seems to be footprint design and escape routing. I can see why. There really isn't room to follow any of the standard BGA practices. You can't fit escape vias between the pads and you can't put vias in the pads, unless they are filled and plated over at the board house. Filled and plated vias are the easiest way to go, but it can make for an expensive board fab.

KL03 WLCSP20 on a US Lincoln Penny

1-DSC_0008One of my side-projects involves trying to make the smallest possible motor driver. For this project, I've chosen the Allegro A3903 driver. It's a 3mm X 3mm DFN (dual flatpack no leads) with 0.5mm pitch pads and a thermal pad in the middle. The microcontroller will be the new Freescale KL03 32-bit ARM in a 1.6mm X 2.0mm WLCSP (wafer level chip scale) package. It also comes in a 3mm X 3mm 0.5mm pitch 16 pin QFN. Without an expensive PCB, that may be my only option.

Pick your CAD package

I'm using the newest version (5.1) of Sunstone Circuit's CAD package, PCB123, but the principles here will apply to any CAD software. If you don't already have a copy, download PCB123 V5.1 here.

If you've got fast Internet, you're done now, so go ahead and install it. You'll need the manual too, which you can get here.

I need to eat now, so stay tuned for Part 2.

Duane Benson
Nerfvana - It's like Nerdvana, but with more foam darts.

VTP - Very Tiny Parts

FreescaleKL03A while back, I wrote about a new ARM Cortex M0+ chip from Freescale. It's not the first M0+, but I do believe that it's the smallest. I've been checking stock off and on and finally found the smallest package to be in stock and available to ship.

I actually bought a couple of different types. First, there's the WLCSP 20. It's got 32K FLASH, 2K SRAM and an 8K bootloader. The real kicker is that the package is only 1.6mm X 2.0 mm. I also got a few in the QFM 16 package, which is a bit more workable at 3mm X 3mm.

Finally, I bought a Freedom development board with th 4mm X 4mm QFN 24 package. The dev board is hardware compatible with Arduino shields, so that will make for some interesting possibilities.

Anyway, here at Screaming Circuits, I'm most interested in that 1.6mm X 2.0mm package to see how easy (or difficult) it is to use - see if there are any particular layout challenges. The other stuff is just for after hours play time.

Duane Benson
I'm not a number. I'm a free development board!
(Free, as in named "Free...", not free as in "don't cost nothin")

Cost Reduction in Design - More Advice for Makers

If you're looking for the absolute, cheapest possible assembly service, you'll need to look outside of North America. If you really need a decent price with good quality and good service, you can keep your gaze West of the Atlantic and East of the Pacific.

Like everything else in the modern world, design decisions can have a pretty big impact on your cost. So, lets take a look at some design decisions that can make your manufacturing more affordable.

  • Accept longer lead times

Lead times are one of the biggest factors in electronics manufacturing. Screaming Circuits can turn a kitted assembly job overnight, but it costs a lot of money to do that. Screaming Circuits also has a 20 day turn-around that is much, much more affordable. Accepting longer lead times on PCB fab will drop your cost as well.

  • Avoid leadless packages like QFNs and BGAs

We build tons of QFN and BGA boards - even down to 0.3 mm pitch micro BGAs. That's great if you need those packages. However, since all of the leads are underneath, we have to x-ray every part. That adds a bit of cost to the process. If you can, stick with TSSOPs and other parts with visible leads.

  • Use reels, or 12" or longer continuous strips

Tab routed multi panel 1024We will gladly assemble parts on strips of almost any size. But, to save costs, use full or partial reels or continuous strips of at least 12" long. It costs us less time to work with reels and continuous strips, and we pass those saving on.

  • Stick with surface mount

These days, thru-hole components tend to be hand soldered. That costs more than machine assembly, so use surface mount wherever possible. Surface mount components tend to be less expensive than thru-hole too. If you do need a few thru-hole parts, this is an opportunity to put in a little sweat equity by soldering the thru-hole yourself and save a bit of money.

  • Panelize small boards

We can work with really tiny boards individually, but sticking with a larger size makes the job easier, and, again, we'll pass those saving on. If your PC board is smaller than 16 square inches, panelize it. We put in less labor and you get a price break.

By sticking with Screaming Circuits, you get the same care and quality that we give to boards going up into space, down into the ocean, and everywhere in between. By sticking with Screaming Circuits, you get a known turn-time; not an "about ..."

By following these guidelines, you get a decent price and really good quality and service.

Duane Benson
That would be telling

Choose Your Package Wisely

As I mentioned in my prior blog, there are reasons to consider different packages than just physical size.

Sometimes it is just space available on the PC board, but there may be other considerations as well. One of the first to consider with really small size packages, is the capability of your manufacturer. Not all assembly service providers can TI ESD CSP 007 croppeddeal with super-duper small parts.

That's a paperclip next to the little ESD protection chip in the photo on the left. At Screaming Circuits, we can go down to 0201 passive parts and 0.4 mm pitch BGAs. We've even done a few 0.3mm pitch BGAs, but those are pretty rare still.

Some manufacturers stop at 0402 (or even 0603) parts. If that's the case with your manufacturer, then you'll need to eliminate sizes smaller than their limit (or find someone else to build the board).

Cost might also come into play. It probably won't be enough of a factor to worry about during prototyping, but it may be worth looking at for volume production. Sometimes the smaller form-factors add cost. Sometimes the part value you need may not even be available in the smallest packages.

TI TPS62601 front and backIf both cost and size are significant drivers, weigh the cost savings from reducing the PC board area against any additional cost with smaller packages.

Noise can factor into your package choice too - especially regarding bypass capacitors on high speed chips. You want your bypass capacitors as close to the power and ground pins as possible. The higher the speeds, the more important this is. Dropping your package size down to 0402 or 0201 can make it easier to put the caps closer to power and ground pins.

Duane Benson
You don't need to ask Alice because your parts aren't ten feet tall

QFN? QFP? QFwhat?

The QFN (quad flat pack, no leads) has become my favorite integrated circuit package. It's very compact, yet is easier to use than a micro BGA.

Micro BGAs of 0.5mm and smaller pitch become a bit more difficult and costly with more than two rows of pins. At those geometries, escape routing can involve plugged and plated vias which adds complexity and cost to the board fab. QFNs can be almost as small, but have all of the pins exposed around the edges - so, no need for escape routing.

One thing that's important to note, is that despite sharing the first two letters (Q and F), the QFP and QFN footprints are not interchangeable. We do, from time to time, see boards laid out for one along with the other form packaged part. Arduino w QFN and QFP

Take a look at this PCB layout clip from the Arduino Leonardo. It has both footprints on the board. You can see how much bigger the QFP package is.

They put down both footprints because the Atmega32U4 chip used in the Leonardo sometimes has supply issues in one package or the other. This gives them the flexibility to use either without making any changes on the board.

You might consider this as an option if you have the space for a QFP and are concerned about the available of one package variant or the other.

If you do, there are some very important things to check out:

  • Make sure the pin-outs match. Some parts will vary the pin-out a bit between packages or have extra pins on one or the other.
  • Make sure the extra space won't cause noise problems. Generally, you want bypass caps as close as possible to the supply pins. This amount of extra space probably won't be a problem when using a QFN, but in some designs, it might.
  • Make sure the board won't be in an environment where unsoldered pads will be a problem. Some harsh environments could attack the unsoldered pads. If that's the case, consider conformal coat.

Duane Benson
We're always being pushed and shoved by people trying to beat the clock
But we like it - it's what we do

Does Anybody Really Care?

The upside of a visible identity is that people see you can might possibly care and understand. The downside, is that people can find you. Today, I'm sort of treading the line between the two.

I'm testing out some Twitter ads right at the moment. As someone that has a service to present, I have to do things like that. Ideally, it won't be intrusive and will just give information, but that's not the point.

One of the steps in putting together a Twitter ad is to select categories of Twitter users that might be interested in what I do. The process of picking those categories reminded me of something that's almost always annoyed me when I have to pick my categories for anything. Namely, my categories aren't there.

This particular ad, is sending people to eBay to buy (hopefully) a coffee mug with the Sputnik 1 transmitter schematic on it. We're doing it to help out our local FREE GEEK place. (Yikes! Three links in a row) Again, that's not the point here.

I'm thinking that electrical engineers would be interested, as would space fans. Well, those categories don't really exist. The have a major category: "Business." The closest sub category in Business is "Technology." That's somewhat close, but do engineers really want to be classified as in the business world?

 "Careers"; nothing close in the sub categories. "Education"; nothing close. "Events" has "Tech Tradeshows" as  a sub-category, but as with business, it's not really where I'd look.

"Hobbies and Interests"? Nope. They have "Astrology", but no hobby electronics.

There's the category "Science", but its subs look like chapter headings in a sixth-grade science book.

Wait! There's "Technology and Computing"! That looks promising... But... No. It's pretty much software and IT.

And, that's it. I see this sort of thing all over the place. Software, IT and businessy stuff get categories, but electronics design, embedded computing, robotics... Other than in the direct EE press, these types of categories just don't seem to exist.

Duane Benson
What time it is?

PART 2, SCREAMING CIRCUITS AND THE MAKER COMMUNITY

My last post mused on the affordability of assembly at Screaming Circuits for the maker/very small business/kickstarter community. My hypothetical Arduino-compatible dual motor driver Kickstarter came out to $9.81 per board at a quantity of 250. That's probably more than a cheap off-shore assembler, but we'll get you 100% yield. They probably won't.

TI TPS62601 front and backIt's more than just cost though. Many of the budget manufacturers won't do the most complex parts. For example, I could shave about a square inch off of the board size - maybe two - by using 0402 or 0201 passive parts. That's about $.50 - $.75 less per board for the blank PC board. Most discount assembly shops won't assemble 0201 parts. Many won't assemble 0402 parts. Screaming Circuits will assemble 0201s, and your little micro BGAs too!

The part on the right is a tiny wafer scale BGA next to the edge of a U.S. dime. We can build that.

If you're just designing the board and not hand assembling, putting in 0402 or 0201 parts is no big deal. You just design it and let the robots build it. If your assembly house can't deal with those small parts, you're stuck. You've lost some freedom of choice.

Now, you would expect me to be biased, because I work here, but more than bias, it's a matter of picking the right tool for the job.

If time is your key driver and cost isn't an issue, you'd want quick-turn Full-Proto; our Short-Run production would be the wrong tool.

If cost is your key driver, you have more time, you need predictability, and need good yields, our 24 hour Full-Proto service might be overkill, but our 20 day Short-Run can do all of the hard work for you, and you'd know exactly what you're getting, and when: 250 working boards in 20 days, for a decent price.

Here's a Kickstarter project we built earlier this year.

Duane Benson
Don't use a Marten64 0-dot-19 Freembulator when you really need a Model B Mitchel Warbler brand size 32.125 green Sackcombobulator.

 

Part 1, Screaming Circuits and the Maker community

Yes, a Maker can get 250 custom-design Arduino-compatible boards built for about $10.00 each at Screaming Circuits.

How can Screaming Circuits, a full-service assembly provider, compete with a low-cost assembly house?

Upon first thought, it might seem like Screaming Circuits, would be too expensive for anything but well-funded big-business and big-education. In reality, that may not at all be the case. Like so many other things in life, there are trade-offs between time, effort, and money. The nice thing about Screaming Circuits is that, unlike the low-cost small volume manufacturers, we can cover both ends of the spectrum.

Our least expensive service is not as cheap as the lowest-cost assemblers. We don’t sell on price, but when you start to add in reality and practicality, the cost difference gets much smaller.

OpenHardware logoIf you need that maximum performance, “I need it now, now, now!” service, there’s no question that you need a premium manufacturer, like Screaming Circuits. But let’s do some compare and contrast on the other end of the spectrum. Can Screaming Circuits be a good deal for a maker?

I’ve got an open source Arduino-compatible robot motor board that I designed a while back. I’ve hand-built a few, because I enjoy soldering, but for this exercise, we’ll pretend I’m a maker with a Kickstarter and I need more built up.

I’ll need 250 for the hypothetical Kickstarter project. The 1.5” x 3.5" board uses an ATMEGA32U4 processor with the Arduino Leonardo bootloader. From a software perspective, it looks just like a Leonardo. It uses a different hardware form-factor than the standard Arduino to better fit a mobile robot.

1-DSC_0001It’s got 26 different components (26 line items in the Bill of Materials). Due to some part types being used in multiple places, that’s a total of 48 surface mount (SMT) placements. I’ll ignore the few thru-hole parts. As a Kickstarter, I would supply the board with all of the SMT parts installed and let the customer solder in the thru-hole parts. That’s pretty common practice in the hobby, maker and Open Source world.

You can quote the assembly on the Screaming Circuits website without registering, so let’s do just that. It’s got:

  • 250 desired board quantity
  • 26 unique parts (BOM line items)
  • SMT on 2 sides? Yes
  • Lead-Free? No (If you’re shipping into Europe, you’ll need lead-free)
  • Class III? No
  • ITAR? No
  • 48 SMT parts
  • 0 thru-hole
  • 0 BGA/QFN

For 20 day, Short-Run production service, this comes out to $9.81 per board - less than $10.00 each.

Soldering by hand, I can do about two an hour. Some folks are faster than me, but some are slower. At two per hour, I’d spend 12 ten-hour days hand soldering the 250 boards. Ouch!

You can most likely find a cheap overseas manufacturer that would build 250 them for less, but they may not want such a small job. You may end up with concerns about intellectual property theft, and you may not get the yields you need.

At Screaming Circuits, we treat every job as proprietary, we’re happy with a run of 250 without any commitments for more, and we promise 100% assembly yield. Finally, a job like this, that totals out to $2,452.48, gets the same process and care as does a $10,000 quick-turn complex prototype.

Food for thought.

Duane Benson
Here's a Kickstarter we built back in 2012

National Low Earth Orbit (LEO) Month

Sputnik 1Coming soon, on the heals of National High Voltage AC month, Screaming Circuits has declared October 2014 to be National National Low Earth Orbit (LEO) Month in honor of the October 4, 1957 launch of Sputnik.

This month, rather than T-shirts, we're offering a custom coffee mug sporting the schematic diagram of Sputnik 1's transmitter. The first 100 customers who place an order in September, 2014, will have the opportunity to get one of these mugs for free.

After your order is confirmed, we'll send you instructions explaining how you can get yours and what the deadlines are.

If you don't have anything to order, you can still get your mug by buying one (through ebay) for a measly $10.00. The whole price, less ebay/PayPal fees will be donated to FREE GEEKs. From the FREE GEEK website: "a Portland-based
NLEO month mockup501(c)(3) nonprofit offering free computers, technology and education powered by reuse & recycling in association with Oregon E-Cycles."

We think that's pretty cool, so the money from these mug sales will go to them.

Also, the first person to build a working copy of the transmitter will get another mug free. It could be hard, though. You might have to fabricate the tubes yourself (People do that, you know). If you can get it working and into ordit, you'll get one more for free.

Duane Benson
WARNING! This is a plot complication!
WARNING! This is a plot complication!

Remote ESD

ESD, or electrostatic discharge, is of great concern to anyone who deals with electronics. That's obvious. What's not necessarily so obvious, is that some times, you don't even need to be all that close to the circuit board or component to damage it.

This article by Douglas C. Smith illustrates why sometimes, just a wrist strap isn't enough.

That's why we don't only use wrist straps, but also have a grounded conductive floor and use ESD jackets and conductive foot straps to protect the boards and components out on our manufacturing floor.

Here's a video showing the dreaded ESD monster and us protecting your gear from him: 

Duane Benson
Greased lightning is an interesting concept
Would it reduce power line transmission losses?