Blog - Screaming Circuits


Surface Mount, But Not Really

Sometimes parts labeled as surface mount aren't quite ready for prime time. I've written about this subject before (read here), and I'm going to write about it again - whether you like it or not. This time, however, I'm not talking about components that aren't up to thermal par. Today, it's about components that can take the heat, but aren't set up to be machine assembled.

Surface mount machines need a flat surface to pick on. They use small vacuum nozzles that need to seat on that flat spot. Chips, of course, are flat on top, as are most other components. Connectors, however, are often not flat on top. That doesn't leave any place for the "pick and place" machine to pick.

Single row header with pick and place padGenerally, manufacturers will place a small tab of Kapton® tape or a small snap-in plastic pad on top of the connector, giving the machine a surface to work with. You can see that in the photo on the left. Once the board has been fully assembled, the tape or plastic pad is simply removed.

Every now and then, we'll see connectors come in without that flat pick and place surface (like on the right). That means the machine can't place it, so it will have to be placed by hand. 1.25mm-Wafer-SMT-Connector

When buying your surface mount connectors, if you have a choice between a part with the tape and one without, you're better off picking the one with the tape. No offence intended to all of you humans, but machine assembly is generally preferred over human assembly.

Duane Benson
Only three more days until Mitten Tree Day!

How Do You Know?

This isn't a Thanksgiving blog. It is Thanksgiving day, and if it were a Thanksgiving blog, I would have to be working today, but we're shut down for the holiday, so I'm not working. I just woke up pondering what it would be like to do business with us (or anyone like us) and decided that I wanted to hear myself speak (metaphorically) for a bit. A word of warning though; I'm in a long-winded rambling mood today.

Take an example; the Beagleboard. I use that because it's a complex board that's open source, so I can freely talk about it. It was originally put together by Gerald Coley and Jason Kridner. I don't know how Beagleboard face onlong they spent designing it, but according to a UBM study, a typical product design cycle is about a year.

So, what we're really talking about is a year of a couple of engineer's lives. It can be a lot of cash money too. When ordered in large quantities, the Beagleboard and it's progeny are inexpensive enough to be sold for quite a decent price. However, when purchased in small quantities - say five - it can cost several thousand dollars.

When the Beagleboard was new, we built a few just to kind of show off. We took the open source files and ordered all of the parts. We tried to get some PCBs fabbed, but in that quantity, they would have cost us $1,200. Instead, I posted a request on the Beagleboard.org forum and found someone with some bare Beagleboard fabs.

I got those boards and the parts and ran them through our system. Had a customer quoted the build, it would have cost somewhere (if my memory serves correctly) around $800 per board for assembly. That would be $10,000 for a set of prototypes. That may seem like a lot for a board that retails for $150.00, but that's the difference between ordering hundreds of thousands and ordering five.

That cost comparison isn't the point. If you're in this business you know that getting small quantities of complex stuff in short notice is expensive in direct dollars, but more than worth it in time and effort saved. The point is that, while we build a lot of sub-$1,000 orders, we are frequently given orders that are valued at $10,000 or more. Sometimes CONSIDERABLY more. We've seen projects where parts alone are tens of thousands of dollars. I've seen a single FPGA cost several thousand dollars alone. Yikes!

You've spent a year of hard labor on a design. You hit "Save" for the last time. If you're like me, you want nothing more than to get a working board into your hands. The gap between that save and a fully built board is painful for me. But the prospect of shelling out $20,000 to some unknown company for the purpose of turning that year of my life into a physical product is positively terrifying.

Well, if you don't already do business with us, we are that "some unknown company." That makes me wonder how this all happens. I design boards myself - not the big ones, but I do design a fair number of them. Right now, I have four boards I'm actively working on and about that many that I've shelved for a few months. I understand a bit of the fear of handing a design off. Of course, I have an unfair advantage. I can just send some boards through our shop and get them done just about any time.

It's easy for me to trust us. I got a job here and I know that I take the stewardship of that big check and year of your life very seriously. I treat it like it were my own. I also know that I don't work for companies that don't share that philosophy. I've tried, out of necessity, twice in my career, working for companies that didn't treat customers they way I would and I ended up pushing my agenda so hard that I got fired. It wasn't pretty.

I've established that I (as in me) trust us. How do you get to the point that you can give us (or anyone else) the same trust? The Beagleboard guys didn't know us enough to do so. We built some of their boards on our own. Plenty of people do know us well or are somehow willing to make that leap. We quite literally* have built things that have gone up into space, down into the ocean and everywhere in between. It's pretty fun to look through our customer list and see so many names of companies doing really cool stuff.

All of the marketing mumbo-jumbo I spit out is designed to somehow convince you to let us take care of your design. But those are just words. Words are meaningless without the deeds. It's what all of the other people in my company do that really counts. I spill out glurge. They do their best to treat your project with the same respect and care that you do. I'm thankful for that, because if they didn't do that, I wouldn't want to work here. If they didn't do that, my job would be meaningless and stupid. Hey - this did turn out to be a Thanksgiving post!

Happy Thanksgiving!

Duane Benson
* The word "literally" is terribly misused these days, but I'm actually using it by the correct definition. Well, okay, the "everything in between" isn't quite literal, but "space" and "under water" are. And it's comprehensive a representative sample that I'm in the spirit of "literal."

Boo

Nosferatu-le-vampire-05-gGooood evening (said with my best vampire accent)

Turn out the lights. Hide your Mosfets. Keep your phase-locked loops locked. Calm your Verilog.

Your simulation is useless against the terrors of the infinite state machine. Your impedance is no longer matched and your bypass caps have stopped bypassing. Your RF signals will not stop reflecting.

Beware

Beware

But, do not fear the evil lectroids

  

More Fun File Facts: ODB++

In my last post, I wrote about the up and coming IPC-2581 PCB manufacturing file format. While IPC-2581 may be looked at by PCB fabricators and assemblers as a holy grail of sorts, it's not yet widely adopted by CAD software. But, that doesn't mean that Gerbers are the only option.

ODB++ was developed by Valor in the waning years of the last century as an improved method for getting manufacturing data into their CAM systems. Valor and, hence, ODB++ was purchased by Mentor Graphics in 2010. ODB++ is still widely available, however there's concern in some circles that it's not truly open. That concern is where IPC-2581 came from. In fact, IPC-2581 is somewhat derivative of ODB++.

I can see how a CAD software developer might fear the use of something owned by a rival. However, my understanding is that Mentor does it's best to treat it like an open standard and has made it available more or less as though it is open.

The history isn't really important. What is important is that ODB++ is a more complete format than the Gerber and is widely supported. Pretty much everything good that I said about IPC-2581 in my prior post also applies to ODB++.

The bottom line is that, regardless of whether Screaming Circuits is your fab (through our partner Sunstone) and assembly (through our factory right here) provider, ODB++ is a good thing. It makes the job easier and more accurate than does use of Gerber files. Both "easier" and "more accurate" help keep costs down and keep ambiguities to a minimum. As you know, ambiguity is the bitter enemy of both accuracy and quality.

Unfortunately, for all of you Eagle users, Eagle does not yet support ODB++. If anyone out there is really good with Eagle ULP scripting, you might want to create a on ODB++ and/or IPC-2581 creation ULP.

Duane Benson
I was ionized, but I'm better now. 

Fun Facts About Manufacturing Files

Circuit boards live and die by their manufacturing files. Without complete and accurate information, the board fab house can't fab the boards, the assembly house can't assemble your boards and nobody can buy the parts.

Our old standard, the Gerber file, has been around since about the time King Arthur pulled the inductor out of the solder pot. It's old. We all use it because it's familiar, but it's day is done. It's time to pass the torch.

IPC-2581 is the new standard in manufacturing files. It hasn't been fully adopted, but it's showing up in more and more CAD packages. The IPC-2581 format is much more advanced and has the complete data set in one file. While we still work with Gerbers every day, we can also accept IPC-2581 manufacturing files.

I've been called the champion of bad analogies, but I'll try one out anyway.

Imagine, if you will, a map of the city. All of the streets are there. All of the houses are there. What's missing are all of the street names. No street names, no numbers and no landmarks of any sort are labeled.

Given that information, find John Smith, at 1620 SW 14th Avenue. There is a house at 1620 SW 14th Avenue. There are a dozen or so houses at 1620 something. You just don't know where 14th is, or which direction 14th runs, or where the street numbering starts.

You can physically walk each and every street until you find John's name on his mailbox, but it's not an easy nor error-safe process. And, hopefully, the town only has one John Smith. That's a Gerber file.

IPC-2581, on the other hand, is an electronic map, with everything clearly labeled, and a GPS guiding you. Which would give you more confidence?

Duane Benson
IPC-2581 is like shatter-proof glasses for Henry Bemis

The Dangers of ESD

Question:

EsdWhat do a conductive floor, foot grounding straps, conductive work smocks, wrist ground straps, foot grounding testers, ESD training, bench-top grounding monitors, anti-static bags, anti-static boxes, grounded carts, anti-static attitudes, conductive desk mats and grounded tools have in common?

Answer:

They are some of the things that Screaming Circuits uses to protect components and circuit boards from the dangers of electrostatic discharge.

Ideally, those are things that everyone handling electronic components and circuit boards would use. This is the real world, though, so there are likely companies that don't use such tools or follow good ESD control procedures. Some companies might even charge extra for what is essentially a basic right. Bad news.

Just the act of getting up from a chair can cause an in body potential of 10 kV. The human threshold for feeling a shock is around 25 kV. Silicon chips can sometimes be damaged at significantly less than that. One of the worst things about ESD damage is that sometimes the failure mode doesn't show up until the device is out in the field.

One of our many missions here at Screaming Circuits is to keep the dreaded ESD monster away from your boards. Your PCBs and your trust are very important to us.

 

Duane Benson
"Zero potential" is bad when when coming from
your parents talking about career prospects.
But it's good when evading ESD.

PCB Assembly Parts Kit

Watch and see what's important when putting together your parts kit

 

Duane Benson
Who's on first?
I don't know.
PCB Assembly 

 

 

Pads on Ground Plane

Pour-no thermalGenerally, small pads for passive parts are connected  with a single PCB trace of equal size to each pad. That's the right way to do it.

However, sometimes, circumstances dictate a little different approach. The illustration on the upper right here shows something of a worst-case. This is for a snubber (resistor, capacitor pair) between two power planes.

A couple of things will likely happen. The power plane will act as a heat sink, preventing the solder paste on one side from melting, resulting in a poor connection. Or, the unequal melting could lead to surface tension pulling the part up, causing tombstoning.

Pour-with thermalMost designers are aware of that, but sometimes, thermals will be deliberately turned off to allow for better current capacity to and from the large power Mosfets (not shown). If that's the case, make sure that you can turn the thermals (see image on lower right) on or off by the part, rather than just by the plane.

Duane Benson
The rain falls mostly on the ground plane due to static attraction

Geek Week on Youtube

In case you haven't heard, it's Geek Week on Youtube. In honor of that, here are the top ten most incredible pieces of trivia from ancient Geek Mythology. You can scroll down and read them here, or have the questions read to you, by me, over on our Youtube channel. 

 

First question:

F: Everyone has heard the trite phrase: “There are 10 types of people; those who understand binary and those who don’t.” Who’s missing?

E: All your _____ are belong to us. Fill in the blank.

D: Who, in the late ‘70s correctly predicted that by the turn of the century, it would be possible to use our computers to find the answer to any question?

C: And, what name did he give his computer?

 B: Bell is reputed to have said: “Watson, come here. I need you.” What was Charlie Klien’s equivalent statement in 1969?

A: Who caused the “Y2K” problem? And, no, that’s not it. You’re already wrong.

9: Who did business under the name “Traf-O-Data”, starting in 1971?

8: One particular semi-nautically named person wrote the first word processor for the Apple II while in prison. Who was that?

7: And, what was that word processor? Bonus points if you’ve actually used it.

6: Who, in 1995, while on his deathbed, claimed to be DB Cooper? Bonus points if you know why I might know this.

5: How many tubes did a standard superhetrodyne radio have?

4: Name them.

3: When did the first man go into space? Be advised that you’re probably wrong.

2: When someone refers to “scout water”, what are they referring to?

1:  How many instructions did the first CPU have?

Now, drum roll please… ,

0: What is the least known, yet probably the most significant law that enabled the personal computer revolution to happen?

And... This is a contest. The first five people, in North America, to get the correct answers will receive a T-Shirt from us - or the five closest to complete and correct. You have until next Monday (8-12-13), when we post the answers. If you choose to submit answers, send them to dbenson @ screamingcircuits . com with the subject line "Trivia answers"

Duane Benson
According the The Buggles, video killed the radio star
If so, then why do we still have radio telescopes? 

Designing The Future: The Automobile

Here's a small glimpse into the future of the automobile. Granted,these guys had to take the dash off and hard wire in, but imagine this with a not-secure-enough wireless access.

 

Duane Benson
And... some of us here are helping to make this happen...