Blog - Screaming Circuits

What is Personal Manufacturing?

There's a lot of buzz floating around these days, about "Personal Manufacturing." Screaming Circuits has more than a decade of bringing personal manufacturing to engineers. We pretty much started the category in the electronics industry, so we're quite familiar - but not everyone knows what personal manufacturing is. I'll do my best to describe it, and what it can do for you.

The short answer, is that personal manufacturing is building your boards on your terms, not on the terms of some nameless, faceless factory.

The longer answer is probably more useful. 

Traditional manufacturing is all about statistics and fractions of a penny. Those factors are important; especially if you're manufacturing millions. But, when you just need a few boards, or a few hundred boards, those factors can make your job nearly impossible.

With personal manufacturing, you can decide when you want or need assembled boards on your workbench. You won't need to beg for time on a busy volume manufacturing line. In the case of Screaming Circuits, it's cloud-based manufacturing so you can order online from your desktop, when you're ready, rather than waiting for someone to pick up a telephone.

With personal manufacturing; you design it, get some prototypes, make a few mods, lather, rinse, repeat. Then, you'll get a few dozen, few hundred, or few thousand, and start selling. You'll get what your budget allows and don't need to commit to minimum volumes, or long-term business. You can polish your design faster, with less hassle, and you can get to market faster, with less hassle. Faster to market and less hassle both mean more time and money for you.

NPI (new product introduction) has never been easier than it is with personal manufacturing. Years ago, I was a product manager at a start-up. The entire NPI process was a nightmare. Our engineers couldn't get anything built without half a dozen support staff. Someone had to make the documentation usable. Someone had to hunt down sample quantities of parts. Someone had to make sure the board would fit on the volume manufacturers' assembly line. It went on and on like that, taking up months of the design cycle. We were at the mercy or people who only cared about making their part of the process easier.

Rather than producing the quality product we wanted, our new products would be shipped to customers with mod wires. I recall one board that needed 64 mod operations before it could be shipped. Yes, that was on a released, shipping product.

With personal manufacturing, as Screaming Circuits provides, you can get a few prototypes built right away. If need be, you can modify, and get a few more built at your convenience. When the mode wires are gone, you can build up a hundred and get them out to customers without delay. It's not about what works best for Screaming Circuits; it's about what works best for you.

Duane Benson
Right now a personal pan pizza delivered to my desktop would work for me.



Manufacturability Index in practice

My prior blog covered the Screaming Circuits Manufacturability Index. It's something I'll be using from time to time when discussing new components I run across. I've got a few examples to put the numbers into context.

On the low side of the index, we have:

7400 TH1: Just about anyone could hand solder the part
Examples: Thru-hole parts

The SN7400 quad NAND Gate, shown on the right, is a good example. It's big, it's thru-hole, and if someone has trouble hand soldering it, they really need a few more classes.

Closer to the other end, is a new chip I've run across. The Silego GPAK4 is a small FPGA-like mixed signal device. It's got a number of analog peripherals, a bank of programmable logic, and the ability to configure it up the way you want. Take a look at it below:

GreenPAK4 cropped

This little thing is housed in a 2 mm X 3 mm QFN package. That's pretty tiny by the standards of my giant fumble-fingers. I've given it a rating of 4.b, on the Screaming Circuits manufacturability index. The number ranking "4" means: "Needs advanced automated assembly technique", and the letter suffix "b" means: "Typical level of challenge within the number rank." In other words, right up our alley.

Unless you posses super-human abilities, and maybe lasers in your eyes, you won't be hand soldering these. You'll have them assembled by us (or someone with the same technical capabilities as us), where it will be a standard process.

If you do want to put one or more of these in your design, you will want to make (or find) a custom library footprint for your CAD software. Due to the variable length pads, a standard one-size-pad footprint might lead to solder joint reliability issues.

Duane Benson
The chips go marching one by one, hurrah, hurrah
The chips go marching one by one,
The little one stops to suck her thumb
Just to see if the solder is lead-free


Screaming Circuits Component Manufacturability Index

Screaming Circuits Manufacturability Index

Ranks the difficulty of assembling a component. Index is one to five, with one being easiest, and five being the most complex

Sub index: a, b, c

    a: Not a challenge within the number rank
    b: Typical level of challenge within the number rank 
    c: Fits in the ranking, but likely needs special process, fixtures or attention

1: Just about anyone could hand solder the part
Examples: Thru-hole parts

2: Surface mount. Should be machine placed, but big enough to hand solder
Examples: 0805 or larger surface mount passives, SOIC packages

3: Pretty much any grade of surface mount equipment can handle this component
Examples: TSSOP or larger, 0.8mm pitch BGAs

4: Needs advanced automated assembly techniques
Examples: 0.4mm pitch BGAs or QFNs, CSP (chip scale package) or WSP (wafer scale package) BGAs, 0201 size passives, Package on Package (POP)

5: More or less R&D at this point. Few companies have or will assemble this part
Examples: 0.3mm pitch micro BGA, 1,700+ ball BGAs, 01005 passives

Just about everything 4b, and below are routinely within Screaming Circuits standard (guaranteed) process. 4c, 5a, 5b, 5c, are becoming more common here. These are special process (falling outside of our guarantee), but we can usually do a good job with them. You'll need to speak with a manufacturing engineer before placing the order.

Duane Benson
a colossal negative space wedgie of great power coming right at us at warp speed
Readings are off the scale, captain

Mark Those Diodes!

MarcoPOLOLogo5Every now and then, I write about ambiguity with diode marking; like here, here, or here. It's a pretty important subject to get right, but what does it have to do with Marco Polo, you ask? Well, that depends on whether you're asking about the person or the game.

In the game, people try to find someone, without sufficient information. One person, designated "Marco" closes their eyes and periodically yells out "Marco." The other people respond with "Polo", and the Marco tries to find one of those other people with just the audible cue. For some critters, that's an easy task, but for the average human it's not always so easy - especially when the diode doesn't audibly respond to "Marco."

If you're talking about the explorer, Marco Polo; well, he set off on an adventure, got lost, and either saw a bunch of cool stuff, or made up a bunch of cool stuff (depending on whom you ask).

Again, you ask... "What does this have to do with hamburgers in a handbag, or with diodes?"

It has to do with the fact that he didn't know where he was going, and, that without clear marking, it's not always possible to know which way to point the diode.

BlackPOLOSo, we're celebrating Marco Polo month with our Screaming Circuits Marco Diodo Polo shirt.

If you place an order with Screaming Circuits during May, 2015, we'll send you an email with instructions telling you how to get a free Marco Diodo Polo shirt after your next order (provided the order is placed between May 1, 2015 and on or before June 5, 2015). If you place an order between now and then, and promptly respond to the email, you can get one for free (a shirt. Not an order).

Duane Benson
Fifty-four fourty, or fight!

Via in Pad - Why and How

There are many reasons you shouldn’t use via in pad. It’s not good practice, and those via holes act like BGA via in padlittle capillary straws and suck solder off of the pad or the BGA.

That said there are some applications that may require, or seem to require, via in pad. Here are a few examples of why you might need to use via in pad:

  • If there is not enough space on the board.
  • It can help with thermal management.
  • Trace routing may be easier with via in pad.
  • High frequency designs benefit from the shortest possible routing to bypass capacitors, which may indicate via in pad.

So if you don't have a choice, here are some methods you can try when using via in pad:

  • Filled viasHave the board fab house plug the via and then plate copper over it. This is our favorite option. It will give you all of the benefits of via in pad without causing problems in assembly. It's really our only recommended via-in-pad method.
  • Use a micro-via that only goes through one layer of the board. Although this may be an okay option, the solder can still wander down into the via, leaving voids.
  • Cap the underside of the board with solder mask. This is our least favorite option because sometimes the cap can pop open, and the void may be big enough to still pull too much of the solder off of the pad.

For more information on via in pad, check out this video.

Internet of Things Got Your Tongue?

By now, most of you have heard about the Internet of Things (IOT). If not, here's a quick summary:

The Internet of Things is the concept of having pretty much everything connected to the Internet in some way shape or form. At the simplest, it's the ability to turn a light bulb off and on with your smart phone. At a more complex point, it is all of the devices in your house, car, recreation, services, and office connected and talking.

Lights will automatically go on and off as you move through your house or office. When it's time to get up for work, your coffee will be brewed, your car will pull up to your door, your house will know when you leave and will lock down and turn off unnecessary devices - all without any intervention from you. The streets will talk. Utilities will talk. Everything will talk, coordinate, and manage.

It won't be enough for your computer to "ding" when an email arrives, or your phone to "buzz" when a text comes in. No; the IOT wants to control your life. And, it wants to nag you about all of it too.

The IOT will be good for us, because it will require a lot of super small parts, which we happen to like. In honor of that, we declared April, 2015 to be Internet of Things month, and created an "Internet of Things gone Bad" poster. The poster, by local graphic designer Kyle DeVore, is 18" x 24" and suitable for framing.

The early birds already have theirs, but we have a few more. If you're a current customer and would like one, shoot an email to We'll give them out until we run out. First come, first served.

Iot_poster_final_OL copy

Screaming Circuits introduces new Cordwood assembly service!

Tired of all those small parts? Can't figure out how to route traces to all 1,900 balls on that hot new FPGA? If 0201 passives have you running scared and the possibility of 01005 parts coming soon has you on the floor, Screaming Circuits has the answer.

Take a few steps back and use our new Screaming CordwoodTM assembly process. It'll feel good to put your hands on a honk'n 2-Watt, through-hole resistor again. No need for fancy, multi-headed SMT assembly robots with Screaming Cordwood. No need for precision anymore. Just put those parts a quarter inch apart and you'll be suckin amps just like the good old days. And if you don't think it's high-tech enough; consider that Cordwood construction has taken man to the moon and back. You can't say that about surface mount!

Indicating Polarity On Diodes

Everyone knows which way current flows through a diode. Right? Of course they do. Diodes only allow current to flow in one direction.

Well, sort of.

In the case of your garden variety rectifier, barrier diode, or LED, that's true. That line of thinking leads a lot of people to assume that you can indicate diode polarity by putting a plus sign "+" next to the anode.

Here's why you can't.

Zener and TVS diodes have a breakdown voltage. They are put in the circuit with their cathode on the positive side. In that configuration, they don't conduct unless the voltage rises above their breakdown point. Zeners and TVSs are used for regulation, transient suppression, and things of that sort.

But wait! There's more!

Regular diodes can be pointed backwards too. Anytime an inductive load is switched, like a solenoid or motor, you need a flyback diode to protect the switching logic. A MOSFET switching a solenoid on and off is a good case to look at.

N-MOSFET SolenoidWhen the MOSFET turns off, the current in the solenoid coil starts to drop. As it starts to drop, the magnetic field generated by the current flow starts to collapse. The collapsing magnetic field generates an opposite current, referred to as flyback, or back EMF.

To save your silicon switching device, you put a flyback diode across the coil, or motor, terminals, pointing backwards from normal current flow - with the cathode pointed toward +V. Doind so shorts the flyback current back into the coil, preventing damage to the MOSFET. These are typically Schottky diodes, but can be ordinary rectifier diodes.

A "+" plus sign alone, doesn't tell anyone anything. For more information on what to do, read this post. Just for fun, read this post too.

Duane Benson
Diodes. Not just for breakfast anymore

Using the Newest gen ARM, Part III

The continuing saga of the 0.4 mm pitch KL03 ARM microcontroller. If you haven't yet done so, read part I, and part II.

Today, I have a look at the good, the bad, and the ugly - or more accurately, the good, and the bad and ugly. As I expected, I was quite pleased with the job done here in house. The board is nice and clean, the parts are well centered, and the solder joints are solid. No surprise here.

Here's a top-view of one we did here in Screaming Circuits:

4mil top view 800

Next, I've got one that I did at home. It actually surprised me and came out better than I had expected. Here's a top-down view of the one I did at home with home-grade tools (No, I didn't intentionally make it look bad. The board surface is just a bit shinier than the one above.):

Home top view 800

Of course, "better" is a relative term. I didn't say good. I could call this both bad and ugly. I did manage to center the parts quite well - that took a lot of careful nudging with sharp tweezers and and an X-Acto knife blade.

All of those little round shiny spots are solder balls. That's what happens when you get too much solder on the board, get solder off the pads, or have the wrong reflow profile. They might look harmless, but if there are too many under the chip, the connections could be shorted.

The fillets on the 0201 capacitor are a little lean on solder in the one I did, and there's a solder ball on the right side, but, again, it looks better than I expected.

Next time, I'll post the X-rays and show what's under the hood.

Duane Benson
Carburetors, man.
That's what life is all about


I'm a bit behind in my blog work - well, way behind, actually. I started this series back in January with the intro post.

Here's where I am right now:

  1. I have three different sets of PC boards.
  2. One set, I took home to see if it's possible to solder a micro BGA at home. (As someone working at a car manufacturer might want to see if they could balance a crankshaft at home, for fun)
  3. Two sets, from our partner, Sunstone Circuits, are here in my desk with parts, ready to go through our machines.

After I've got all three sets built, I'll have them X-rayed to see how they look under the hood. Finally, I'll solder thru-hole headers on and fire up the chips to see if the shared escape system works.

Here's one of the boards without access to the inner pads:

KL03 SunstoneFF 4mil (2)-001

And, here's the shared escape:

KL03 SunstoneFF 4mil (3)-001

The main concern I have is that Reset is on one of the inside pins (B4). I'm not sure if I can get the chip to a state where it will operate properly without unobstructed access to reset.

The routing I've chosen is probably the only possible option for reset. Pin A4, right above, is used for the single-wire debug (SWD) clock. I'm assuming that can't be shared. B5 is Vdd, so that's out. It might be possible to go down. C4 defaults to one of the crystal pins, and D4 defaults to a disabled state.

In the route I've chosen, B3 is an ADC input, so it should start out high-impedance, and therefore not interfere. A3 defaults disabled, so it won't get in the way.

Next step: solder time!

One other thing - The images above show non-solder mask defined (NSMD) pads. Those are standard for BGAs 0.5mm pitch and higher. This part is 0.4mm pitch. Some manufacturers recommend solder mask defined pads (SMD) for 0.4mm and smaller. I'm actually testing several pad styles: SMD, NSMD and solder mask opening = copper.

KL03 footprint contenders

Duane Benson
Run it up the flag pole and see who solders