Blog - Screaming Circuits


Those Danged LEDs again.

I fell into one of my own favorite traps last week: the dreaded LED footprint mess.

I designed a board based on the Microchip PIC32 - it's a ChipKIT Arduino-compatible board - that has a number of RGB LEDs. on it. I used Part number LTST-C19HE1WT, from Lite-On. Their datasheet is easy to find, and they put the footprint information right up front, just the way we like it.

LTST-C19HE1WT RGB LED
Almost all is well, but I somehow missed taking my own advice, and I didn't double check the footprint.The footprint I used is more or less 180 degrees off from this one. The common Anode is still on pin 4, but the numbering is different. It's got pin one in the same place, then pin two is in the lower left. Pin 3 is on the same place, and pin 4 is on the upper right. That's the conventional pin numbering order.

Fortunately, the fix won't require any mod wires. If I rotate the LEDs 180 degrees, the anode will be in the right spot. All I'll need to do is adjust my software for the correct R, G, and B pin locations.

Duane Benson
I'm dizzy with rotation

PCB West - September 16, 2015

Come join us!

If you're going to be in Santa Clara, California, on September 16th, drop in to the Convention Center. Screaming Circuits will be there, along with our PCB fabrication partner, Sunstone Circuits. We'll be in booth 510, and they'll be in 508.

While you're there, ask us or Sunstone about a special offer you can get by using both of our services.

But wait! There's more! I'll be speaking on best practices at 4:00, on the 16th. Look for session 38: PCB Design: Best Practices for More Reliable Manufacturing. in the conference program guide.

Here's a handy show floor map:

PCBWest 2015 floor map

Duane Benson
Do you know the way to San Jose?
Then, turn left and go Northeast
'cause we'll be in Santa Clara


Disruption and The Internet of Things

Every few years something new rears its head and changes everything. The old rules break, convention gets unconventional, storied institutions get shaken to the core. We call this, "Disruption."

Automobiles disrupted the horse and buggy industry. Airplanes disrupted the passenger ship industry. Computers disrupted the typewriter industry. In 2003, Screaming Circuits brought disruption to the electronics manufacturing industry by bringing it online, with performance and flexibility previously unheard of.

The latest disruptive current is the Internet of Things (IOT). It means everything will be connected. Everything will be intelligent, and everything will be complex inside.

I recently spoke on "The Peggy Smedely Show", a part of the Connected World Network, about disruption, the IOT, and how Screaming Circuits is, again, driving disruption, this time by helping enable the IOT. 

Give yourself a little over twelve minutes and hear what I had to say.

Duane Benson
A QFN says "What?"

 

Running Out of Time - You'd Rather be up on the Mountain

How many times can the project manager come in and ask how the PC board design is doing? Why can’t management understand that it’s difficult to say how long it will take to do something that’s never been done before? This is totally new ground. It’s innovation in its purest form. And you, the designer are driving it home.

If only you could squeeze a few more days into the week. If only you could have the confidence that the boards will be built right – this is complex stuff, with wafer scale 0.4mm pitch micro BGAs, QFNs all over the place, and 0201 resistors and capacitors sprinkled around like salt and pepper.

 - You can squeeze more time in. You can be assured that the complex parts will go on right. You can keep the boss happy. Screaming Circuits quick-turn assembly service can build your job remarkably fast. Mount_Hood_reflected_in_Mirror_Lake,_OregonShort deadlines and difficult boards are our bread and butter.

It’s 6:00 pm on Friday. Hit “save” on your CAD file for the last time, and hop on over to ScreamingCircuits.com. A quick quote, order, and files upload, and you’re off to join your college buddy on the climb up My Hood you’ve been talking about for a month.

Don't delay, the mountain awaits your boot prints.

Duane Benson
Because it's there...

What's In Your Way?

If you're attempting to cross the median of a busy four-lane highway, it's entirely possible that there's a Jersey Barrier in your way. In that particular setting, having something sturdy blocking your way is probably a good thing. On the other hand, I would bet that, for the majority of you reading this, there are some barriers around you that you'd much prefer not to run into.

Jersey barrier dimensionsBarriers can bring on stress, uncertainty, risk, and a general sense of despair. Despair can lead to hopelessness. Hopelessness can lead to you being rolled up in a fetal position under your desk, tangled up in the nest of cables that every good engineer has under their desk. As everyone knows, if you're under your desk tangled in cords and whimpering when your boss walks in the room, you're probably not going to get a Christmas bonus.

That's where smart outsourcing can help. We talk about PCB Assembly as being our thing, but conceptually, it's more of a case of us trying to remove some of your barriers. We'd prefer that you get your Christmas bonus rather than getting carted off on a gurney, too afraid to open your eyes for fear of the glare of your abandoned co-workers.

Here's what we suggest:

  • Spend a little extra time on design review to increase your confidence (ever find an overlapping trace the day after sending the design out?) 
  • Double check that your BOM and or parts kit is current (If you chose the parts a few weeks ago, some may have gone out of stock)
  • Drink some water (dehydration can interfere with a clear, logical thought process)

If the extra day or two doing so causes a problem, just order a faster turn-time.

Duane Benson
129 °F in June of 2013?!
Well, what did you expect from a place called "Furnace Creek"?

No need to waste parts

We love parts on reels. Who doesn't? But reels aren't always practical - and it's not just about cost. Cost is, of course, important, but there may be other factors to consider.

Say, for example, you need 20 2.2K Ohm, 5% 0805 resistors. You could buy a small strip of 25 from Digikey for $0.32. That gives the 20 you need, plus a few spares just in case.

Alternately, you could buy a digi-reel ( a custom quantity reel). On the reel, you'll probably want more parts to keep the strip long enough for the feeder. Let's go with 250 parts for $1.39. Digikey charges $7.00 extra to create a custom reel, so that's a total of $8.39. Still peanuts.

For a third choice, you could just buy a full reel of 5,000 for $10.64. Still peanuts. If you're gong to need the same part for a lot of designs, this might make sense. But, there's more than just cost to consider. You need to store and ship it. Shipping two dozen reels gets pretty expense. Storing and inventorying several dozen reels can become a hassle too.

Cut strips on plateThe beauty of Digikey, Mouser, and other places that sell cut strips is that they essentially become your parts warehouse. You pay the $0.32 cents and never have to worry about whether the part is in your inventory, how many are in your inventory, digging it out of wherever you stuffed the reel when you last needed it...

If you do buy and store the whole reel, you don't need to ship the entire reel to us. Just cut a strip with the number you need, plus about 10% for that "just in case" (50% extra for tiny 0201 parts).

Of course, if you need a few thousand of the parts, go ahead and send us the reel. It would make sense then.

Duane Benson
Reel, reel your part
Solder it, solder it, solder it, solder it
Cost is but a factor

Packing Parts for Personal Manufacturing

Manufacturing, especially small volume one-time-only builds (like a prototype) is hard. It's not wise for most people to actively seek out chaos, but that's what we do, and we do it wisely. That's what we've been doing since 2003. 

We do it because it's hard and because it's necessary.

A big part of quality manufacturing involves risk reduction. Prototyping and quick-turns inherently add in a lot of risk. While we've designed our processes and systems around turning that risk into a quality product, there are a few things that you, the customer, can do to help reduce risk even further.

One of the best things you can do to reduce risk is to prepare a well organized kit, as shown in this video.

 

You can send us your parts in short, cut strips, like you get from Digikey or Mouser, long continuous strips, full or partial reels, tubes or trays. We machine place from all of those types of packages. What's important is clear labeling and organization.

Individual, or mixed/loose components are not good, though. Pins get bent, leads get contaminated, values get mixed... Leave them in the strip, even if it's short. If you've got multiple short strips of the same part, we can still machine place. Don't tape them together. We can deal with them as is.

Duane Benson
Peter Piper Picked a Peck of Pickeled Manufacturing

Proper PC board storage - The top three hazards

It's late. Do you know where your PC boards are? Let me rephrase that: Can unused PC boards be stored for future use?

Yes, they can - if stored properly. Keep them wrapped up, or sealed in a bag. Anti-static isn't necessary in this case, but it won't hurt. Keep them in a cool, dark place. Keep them clean. Do your best to avoid dropping them on the floor and stepping on them.

The board in this photo was left out on a desk for a while, and then shoved into a desk drawer. The environment took its toll on the immersion sliver finish, making it very much unusable.

Old Beagleboard

What can go wrong:

#1: Fingerprints: The oils on your finger can etch your fingerprints into ENIG or immersion silver PC board surfaces. If you plan on committing a crime, go ahead and do this so we can catch you. If you aren't going to start a life of crime, be careful to not get your fingerprints on the board surface. Handle on the edges, or at least, don't touch any exposed metal.

#2: Moisture: Moisture is good for your skin, but not for your PC boards. Over time, PCBs can absorb moisture, especially in a humid location, or the ocean. If thrown into a reflow oven, they then might laminate. Do your best to store boards in a dry environment. If stored for a long time, you may want to pre-bake them prior to use.

#3: Atmosphere: Sometimes dirty air can contribute to tarnish or corrosion on the exposed land pads. Dust can settle onto the boards as well. Tarnish and dust can usually be cleaned off, but corrosion can't. Wrap up your boards for long-term storage.

Treat your boards well and you can likely use them at a later date. Don't treat them well and you may need to replace them, wasting a bunch of money. Often, the damage isn't as clear as in the above photo, but could still lead to poor solderability.

Duane Benson
Don't surf on your silver

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.

Vertical_markets
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