Blog - Screaming Circuits


Do you need PCB Assembly Services?

Do you need PCB Assembly Services, or do you not? That is the question. Well, it's A question. Just one of many, I suppose.

TI TPS62601 front and backOne of many, but it is a question just about every electronics developer needs to answer at some point. The answer isn't always yes, nor is it always no. The answer is quite often "It depends." I work here and I don't always have a clear answer to the question. I've sent some board through our plant, and have hand built a few.

For me, it comes down to a few options:

Use Screaming Circuits PCB Assembly Services:

  • Does it need to be done right?
  • Is time a consideration?
  • Are there too may placements for me to deal with?
  • Are there more than one or two boards?
  • Are the parts too small?
  • Are there any BGA packaged chips?
  • Will it be monotonous?

Build it myself if:

  • It's a no-hurry project.
  • The parts big enough.
  • It be fun.
  • It will be a valuable learning experience.

I can enjoy building up a board myself in the same way that someone working for a car manufacturer might rebuild cars at home as a hobby. 0805 passives aren't a problem for me to hand solder. I don't mind a small number of 0603's. I'll hand solder 0402's in a pinch. I've tried a few 0201's with poor results.

Forchips, I don't have a problem with SOIC's. I'm not bad with a TSSOP. QFN parts are a challenge, but some types have enough exposed metal on the side to solder. I really can't place BGA's, but I'm experimenting to see if I can find a way to solder small ones in my toaster oven.

With the impending advent of desktop pick and place machines, there will be a few more options, but the basic question will remain the same as it is with "build vs. buy" in any industry: "Which do I have more of, time or money?"

Duane Benson
Let's get small!

Using the Newest gen ARM Microcontrollers

KL03 on stampI've written a few times about the new Freescale KL03 ARM Cortex M0+ microcontroller. This particular part comes only in very small packages, with the smallest being a 1.6mm x 2mm WLCSP (wafer level, chip scale package) 0.4mm pitch, 20 bump, BGA. That's a mouthful - albeit a very tiny mouthful. Maybe just a toothful.

On the left, here, I've got a pair of them on a US postage stamp.

For us, it's not a particularly difficult part to assembly; just a garden variety 0.4 mm pitch BGA, as far as we're concerned. We place loads of them. But, it can be a very different story for a designer. Conventional wisdom says that a PCB designer has two choices with a part like this: a very expensive PC board, or don't use the part.

Escape routing becomes very difficult (read: expensive) at 0.4 mm pitch. This part only has six connections that need to be escaped, but that can still be a problem. You can't fit vias between the pads KL03 SunstoneFF 4mil 800to escape out the back side. You can't put vias IN the pads, unless you have them filled and plated over at the board house. That's expensive in small quantities.

This blog post series is going to examine some possible ways to use these parts with more of a standard fab, such as Sunstone quickturn. I've got three different process blank PC boards, each with four different land patterns.

I've been asked about home reflow too, so as a bonus, I've done my best to duplicate hobbyist conditions for one of the board sets.

Check back next week for the first set of results, and be sure to quote your assembly job at Screaming Circuits or your PC boards at Sunstone.com.

Duane Benson
"Screaming Reflowster" not sold here

Polarized non-polarized components: Inductors


We have a number of manufacturing engineers running around here at Screaming Circuits. They're very good at what they do, as are our operators and technicians. They are not, however, electrical engineers. Our parent company has a big group of electrical engineers, but they're at a different location

What that means is, though we endeavor to be experts at building things, we often don't know what the circuits and components do in your specific application. People tend to send us their difficult projects so we've probably seen just about everything possible go through our plant. But, every now and then we see something unfamiliar. It doesn't happen very often, but it does happen.

20150114_19440220150114_194410Sometimes it's an exotic new package (like the 0.3mm pitch wafer scale BGAs now
showing up). Other times, it's something a bit older, but just not clear. Rather than put a job at risk, if we aren't sure, we'll always hunt down the designer and ask.

Okay. That was a long winded intro.

We recently ran across just such an unknown; a "polarized" inductor, without an accompanying "polarity" mark on the PC board. Not only that, but the markings on the inductor were a bit ambiguous. One half is black and the other half is green. The datasheet is in black and white, so there's more room for interpretation than we're comfortable with.

At first glance, you might wonder why polarity / direction matters in an inductor. I did. It's just wire. Right? 

Almost: it's not just wire, it's coiled wire. In most cases, the direction doesn't matter, but in cases with multiple inductors, or with super high speeds, it can matter due to the fact that the coil winding direction has an influence on the flux and the actual induction.

I won't go into all of the theory, but think of walking. In most cases, it doesn't matter whether you start with your left foot or your right. However, if you're marching in a coordinated group, you want everyone to start with the same foot.

Look at the two sets of air-core inductors above. When set like this, directionality starts to make a bit of sense. Imagine the electrons being pushed around in theses things and try to picture the resulting lines of flux.

The moral of the story: eliminate ambiguity. If the part is polarized, either mark the board, or make it the direction clear to your manufacturer in build documentation. Do this even if the polarity doesn't matter to you, 'cause we don't know that.

After photographing these, I ended up recalling this bit of knowledge. It's just so rarely needed that it had vanished in to the fog. I put a few more photos after my signature.

Duane Benson
Which way did he go?
Which way did he go?

20150114_19431320150114_194348

 

Do you Need that Part? Or, is it Just Habit?

At the moment, I'm working on an Arduino compatible clock. Like most of my Arduino compatible boards, this one uses an Atmega32U4, with USB built in. With the Atmega32U4, I sacrifice a little in program memory and SRAM, but gain a bit in reduced parts count.

A USB capable Arduino-compatible is, of course, programmed via USB, and can be powered by the USB port. Most Arduino boards also have a 5 volt regulator to be used when being powered by a wall-bug power supply. Naturally, I put the USB connector on the clock board, as well as the 5 volt regulator. With the two different supplies, I also put in circuitry to auto switch sources and protect the USB host when both supplies are connected at the same time.

NeoPowerSupplyMy first PCB revision required a few hand-mods, but not many. Still, I decided to re-spin the board and remove the two mod wires. While doing so, it suddenly occurred to me - a blinding flash of the obvious - that most cell phones and other small devices are charged with a USB-connector 5 volt wall-bug power supply. Why then, would I also need a separate power supply and on-board 5 volt regulator?

By pulling the regulator off of the board, I could eliminate a few capacitors and the supply auto-select / protection circuitry. Not only did I save in component cost, but I was able to reduce the PC board size, and thus cost, by about a third.

  1. I had the 5 volt regulator in the design because Arduinos can be powered by either USB or a non-regulated power supply.
  2. The reverse power protection is necessary to prevent damage to the USB host if the other power is also connected.
  3. The auto-power switching circuit is necessary so that a user doesn't need to flip a switch or change a jumper when changing power sources.
  4. I had two extra LEDs to indicate which supply was powering the clock.

I questioned my original assumptions, found a "because it's always done that way" and eliminated it. Assumptions are meant to be challenged.

Duane Benson
Question authority!
And then get squashed
(or, squash extra space out of your PCB)

Rossum's Universal Robots Month

I'm not sure who first used the term "drone", but "Robot" was first publicly used by Karel Čapek in his 1921 play "R.U.R.", or "Rossum's Universal Robots." January is not only the month the play premiered, but Karel Čapek was born on January 9, 1890. With that, Screaming Circuits is declaring January, 2015 to be Rossum's Universal Robots month!

RUR T-shirt mock upIn celebration of this momentous occasion, we've produced an exclusive "Rossum's Universal Robots month" T-Shirt. When the singularity comes, wearing this shirt will inform our new robot overlords of your support for their cause. Not that it will protect you or anything, but perhaps they will assimilate you with a bit more care.

Every customer who places an order before January 9, 2015, 5:00 PM, PST, will have the opportunity to get a Free "Rossum's Universal Robots month" T-Shirt, designed by local graphic artist, Kyle DeVore.

Look for instructions via email on how to get a free T-shirt after your next order (provided the order is placed between today and on or before January 9, 2015). If you place an order between now and then, and promptly respond to the email, you can get one for free.

But, what if you don't have anything to order? Well, you can still celebrate our impending doom at the hands of our own creations by buying the T-shirt from our page on teespring.com [Click here to buy on Teespring]. We don't want grease money, so we're selling them on teespring at our cost.

Robot revolutionDuane Benson

Poor Alquist ceded care of the world to Primus and Helena.
He set off on a hopeless search to find any last human survivors.
To no avail, he searched the seven continents and the seven seas.
Until at last, he saw beings, not robots, on a small island near Sumatra.
Poor Alquist, being not a newt, was never again seen on land or at sea.

Chips Making Faces

Chip face

Not too late for a Screaming Circuits electronics business card holder

In November, we started our electronic business card holder program. We ended up building more than we had planned, so it will be available for December as well - at least until we run out.

Business card holder top viewHere's how you get one: If you're an existing customer of ours, we’d like to share with the world, and with our production floor, a little about you. Us marketing folks keep a close eye on what you need, but it's more difficult for the people a little further from the phone to do so. Little videos help.

Send us a short video - somewhere around 30 seconds to 2 minutes - about who you are and what you do. No need to worry about equipment. A cell phone video is fine.  If you send it in before we run out, we'll send you a free business card holder.  We only have 40 of this limited edition available so submit your video today! 

Here's the rules:

  • Must have ordered from us to submit an entry.   
  • You can use any video recording device (cellphone or video camera)

Still not sure if you need one?  Watch this video. 

Who Are We?

People sometimes ask who we are as Americans, or who we think we are.

We are a diverse lot. We are people who couldn't hack it in the old world. We left the old world because we were chased out, kicked out or kidnapped out. We left the old world because we saw opportunity to be free or the opportunity to exploit. We left because we didn't fit in or didn't like the life open to us. Some of us were here first and weren't able to fare well against the newcomers. Some of us escaped the old world because we simply wanted better. We are a mixture of everything that we don't like about the world and of everything that we do like about the world. We are an amalgam of all that is good an all that is bad. We are proof that when you mix good and bad together, the result is more good than bad.

We are a symbol. We are a symbol to the world that you can change governments without violence. We are a symbol that individuals really do have a voice and a choice. We are a symbol that opportunity for the human spirit still exists. We are this for two reasons: people are willing to dream for it, and people are willing to die for it.

Today is a day set aside in this country, for us to thank those that have been willing to die for it. Without them, the dreamers would never have more than a dream.

Duane Benson

Images

New Electronic Screaming Circuits Business Card Holder

It isn't easy to differentiate yourself from the rest of the world.  Use this electronic business card holder to impress your peers and customers. And well, it's just plain cool.  

BizCardHolder

If you are an existing customer of ours, we’d like to share with the world a little about you.  Submit a 30 second to 2 minute video about who you are and what you do.  If you are one of the first 40 entries, you will receive a free business card holder.  We only have 40 of this limited edition available so submit your video today! 

Here's the rules:

  • Must have ordered from us to submit an entry.   
  • You can use any video recording device (cellphone or video camera)

Still not sure if you need one?  Watch this video. 

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.