Category Archives: Laying It Out

Off-grid thoughts from a burned-out designer turned editor.

Rain, Rain, Go Away

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It’s almost June here in the Pacific Northwest. At least, that’s what the calendar says. I’m not sure I believe it at the moment. The weather is acting more like October. It’s a bit warmer than January, but every bit as wet. That pretty much equals October. We’ll just call it Junetober.

And what does Junetober have to do with electronic assembly?

MSD logo Moisture. That’s what it has to do with electronics assembly. Most of the parts running around in the world today have some level of moisture sensitivity. Despite my lament of the rain here, you have to consider component moisture no matter what your climate may be.

Looking at IPC-M-109, you can see the there are sensitivity levels MSL-1 though MSL-6. There are actually eight levels: 2A and 5A make up the extra two. If you’ve got an MSL-1 part, you really don’t have to worry about. I wouldn’t store it in your fish bowl, but the standard says you don’t have to bake it. Up at MSL-6, you have to bake the parts before use no matter what.

When you buy moisture-sensitive components, they should come in a moisture barrier antistatic bag with an indicator card and a little baggy of moisture absorbing desiccant. The best approach with these components is to leave them in the original, unopened bag. We’ll use what we need and properly seal up the rest just the way IPC-M-109 wants us to.

If you do need to open the bag and ship parts to us without the moisture protection, we may need to bake them for a while to make sure they are properly dried out before putting them in the reflow oven.

Duane Benson
Gore-Tex is a registered trademark of W. L. Gore & Associates.
http://blog.screamingcircuits.com/

CAD This or CAD That

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I use Eagle CAD a lot. I can get away with the “Light” version, because the designs I create are small and noncommercial. I do use it sometimes to illustrate points here on my blog, but I think that still meets the qualifications of the free version. It’s a good program and the multiple license levels from the free version up to the full professional version add a lot of flexibility to have the software grow with you.

Our partner, Sunstone, builds most of our PCBs here, which is a nice segue into an alternative CAD package. There are a lot of reasons to pick one CAD package over another. I won’t go into that here because those reasons tend to be specific to the application. Most CAD packages are sold as a lump-sum purchase up front. A lot of them also have yearly license renewal fees. That works sometimes, but there are other times where up front costs are more important. The model that Sunstone uses for PCB123 is to provide the software at no charge and just add a little tiny bit of the software cost onto the PCB board purchase.

PCB123 isn’t the only package that follows this business model and is tied into a specific PCB vendor. But, as far as I can tell, PCB123 is the only package of its sort that has enough capability to be a viable replacement for more traditional pay-first CAD packages.

I recently downloaded V4.1.11 and have started to run it through my own personal “can I use this for my stuff” test. I know it’s a good package because we, here at Screaming Circuits get boards of all sorts designed with PCB123 to assemble from all manner of company. But, something can be a good package and still not fit an individuals specific requirements. Hence my personal tests.

I do find it odd, but not really an issue, that it starts you off in the layout editor instead of the schematic editor for a new design. Oh well. One click and I’m in the schematic where I can search for my parts. I use PIC chips and it’s pretty rare that I find the exact chip. I always seem to have to find something close and then modify it, which just adds more opportunities for error. I know there’s a jillion 28-SOIC,M28B_sml varieties, but once in a while it would be nice to just find the actual part.

Fortunately, today I’m looking for PIC18F2320 in an SOIC package. Fortunately, because it’s actually there! I hit the “Insert” menu and choose “Add Part”. Then I put “PIC18F23” in the search box, and there it is, but not on the computer. It was in their online labraries. (In the cloud?) It took all of about 15 seconds to automatically download the library footprint though, so first test = passed.

And the really cool thing is that once I have that part in there (for the parts found pre-made in the library), I just select the “Bill of Materials” tab down on the bottom and I can see if DigiKey has the part in stock and how much it costs.

Duane Benson
If it’s in Oregon, the “cloud” is probably a rain cloud

http://blog.screamingcircuits.com/

From the Office of the Dean

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You know how a song gets stuck in your mind and goes ‘round and ‘round, and you find yourself humming the melody or even singing the song out loud? Well lately Leon Russell has been stuck somewhere between my parietal lobe and medulla oblongata. (Dang it, now I’m stuck on “obla lon, oblagata, yeah, la, la la, la life goes on”). Anyway, the lyric “I’ve been so many places in my lifetime…” has been stuck up there because I’ve been thinking about the path I took to get here. In short, I was a draftsman, PCB designer, editor, publisher, business owner and now a university dean.

That’s right, when we launched Printed Circuit University last February, it was decided I would be Dean Pete, replacing my former job title, Grand Poobah. All of this leads to an update (long promised) on what is going on with Printed Circuit University. For those of you who visited PCU from the days of bethesignal.com, you’ve probably noticed some incremental changes in the layout and navigation of the site, as well as new member content. In addition, we’ve planned a new redesign of the site that you’ll see in the near future. The current layout helped us get PCU launched, and now the goal of the redesign is to make it even easier to locate specific content, and hopefully, more pleasing to the eye.

We’ve also been working with some industry experts – in keeping with the university theme, we’ll call them professors – on new curricula that will come online through this summer and fall. Some of the curricula we have in the works include DFM, HDI, RF and Microwave, Flex/rigid flex and a few others that are still in various stages of planning.

In the meantime, this might be a good time to go over a few basics of the site. With your free membership – it only requires a short registration – you are able to view more than 500 papers, lectures and videos on various topics. Using the search function (search is your friend) will help you drill down to some pretty specific topics, or you can review content by using either the dropdown menus in the nav bar or in the three areas at the bottom of the home page. As a member, you can also review the tuition-based content as a member, but you will be required to subscribe (either by course or as an “all-you-can-eat” annual subscriber) to take the tuition-based courses.

It is a good idea to check the site often, because we are constantly adding content. For instance, just this week we’ve added four new tuition-free presentations on considerations for high-speed design, thermal management for LED applications, wrap plating for blind and buried vias and counterfeit components. All of these are under the tuition-free dropdown. High-speed is under tuition-free>SI>articles, and the rest are under tuition-free>other.
And, of course, I should probably give a shout out to our current sponsors: Mentor Graphics and EMA. We appreciate their support and urge you to visit their offerings by clicking on the appropriate banners and tiles.

Last but not least, this site was born with the goal that it will be THE go-to place for designers, engineers and everyone else who are involved in or have questions about printed circuits. We will be depending on feedback from you regarding the current content and content you want to see on printedcircuituniversity.com. That includes member content, as well as tuition-based content. nd by the way, if you think you have what it takes to be a PCU professor, drop me a note and let’s talk about it.

Until then, stay in touch,

Dean Pete

Top 10 Ways to Use the Summer to Your Advantage

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Now, we’re talking in an engineering context here. There certainly are plenty of ways to use the summer to your advantage if you like to water ski or go backpacking, but this is a specific list. Here are my top-ten suggested ways to use the summer to your advantage as an electronics designer:

#Europa – Work longer. You can spend an extra few hours with you friend the Oscilloscope fighting the demons of clock jitter. With the longer days in the summer, you can do so and still get home just before sunset, as everyone else in the family is ending their relaxing evening and getting ready for bed.

#Luna – Be Green. All of those extra photons bouncing around during the summer will help to keep your solar panels producing at high-output. If only you had thirty years of continuous summer, you could pay for them before they wear out. If you live in Oregon, you’d probably need sixty years because even our summers can be pretty cloudy and rainy.

#Io – Debug thermal problems. Especially if you don’t have working air conditioning. Late afternoon, the ambient in your lab will have raised up to at least 90. With the stifling lack of air movement, now is the time to turn on the high powered design that seemed to work just fine when you first prototyped it over the winter, but burps at seeming random intervals when used in the field, down in West Texas.

#Callisto – Increase your workspace. It’s hot. It’s clear. And, the open road beckons you. Get out your bicycle and pedal the 20 miles from home into the office. You’ll be adding to #Luna, and if you don’t take a shower when you arrive at the office, you’ll be given plenty of extra lab workbench area.

#Mercury – Help marketing out with some product specs. Say you’ve developed a short-range wireless device. You know how well it works in a real world application. You’ve been testing it in the lab for several months now. You know how much things like walls and microwave ovens will reduce the practical range. But, it rained all winter and spring so you couldn’t go outside and get the absolutely-will-never-happen-in-the-real-world range specs that will go on the brochure and be used to entice and mislead potential customers.

#Titan – Blow some stuff up. Not in the Mythbusters sense, but taking a cue from #Io, you can forget to plug in the cooling fan on your deck of MOSFETs in that new H-bridge you’ve been working on. Crank the PWM up to about 95% and they seem to be handling things okay – at least from the outside view. Then, with the confidence built from that exercise, put a heavy load on the motor and set the PWM at 20%. It’s not gun shots. It’s not popcorn. It’s exploding MOSFETs!

#Ganymede – Waste some time. This works best if you have a window view. You’ve got a lot to do. You’re overworked, underpaid and not given the help you need to get your job done on time. Rather than stressing out of all of that, arrange your cube so that no one walking by can see you monitor, but you have a clear view out the window. Then sit back in your chair, stare past your monitor, out the window and daydream about golf and barbecuing. People will think you’re pondering solutions to design problems.

#Mars – Get more glory. All of your co-workers have been ahead of you throughout the winter. They’ve finished their projects and get to take vacation while you slave away back at the office. While they’re out, fake problems in their designs and then fake the solutions. They’ll all get reprimanded when they return and you’ll be the star of the department. At least you will until the next design review when your boss wants to know why your design is only half finished despite how busy you’ve been all summer.

#Venus – Slip out an actual working product. This is the complement to #Mars for people who are actually good at their jobs. Normally, you’d be under artificially created pressure to release the project before it’s quite ready. There’s some press tour or show or something else that everyone wants it done before. You mess with the company vacation calendar so that the people who want to show it off are never in the office at the same time. That way you’ll be able to ge that extra couple of weeks you need and should have been given to make sure the thing works right the first time and every time.

#Earth – And, drum roll please, the anti-climactic #Earth way you can use summer to your advantage: Clear your head. It’s been a long, rough year, with downsizing, parts on allocation, competitive pressures and a host of other factors that have put you on the fast track to breakdown. Schedule yourself some vacation time. Leave all that junk behind and take your mountain bike to Moab or something. Just don’t take a sharp left when you’re on the “Killer B” trail.

Duane Benson
Don’t look! Heisenberg may have been right.

Getting ‘Mixed Signals’ from Your PCB supplier?

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A few weeks back, I was having a chat with a national PCB broker who has a unique and broad perspective of the printed circuit board and electronics industry. We were waxing nostalgic about the “old days” and philosophizing about the days to come.

When she asked about our company, Transline Technology, I told her that we manufacture a wide variety of boards, but that our strength and focus lay in RF and microwave products, which account for about 60% of our business. I was bragging about our work and our customer base when she abruptly interrupted, “You know, Judy, not all board suppliers who say they can make RF boards really can.”

I was caught off guard and asked her to elaborate. She recounted several horror stories whereby she had placed RF/MW PCB orders for her customers and the suppliers failed, in one form or another, leaving her embarrassed and in search of a more qualified supplier.

This puzzled me. Although I have been in this industry for over 17 years, only this past year has involved RF/MW PCBs. Transline is a relatively small shop, and we are very successful with RF, so I assumed most others were as well. I wondered why, in some cases, much larger, far more well-recognized suppliers were failing? I tucked this question away for later consideration.

A week or so later, I was talking to the owner of a RF/MW design firm, a new prospect, who tends to take on very complex RF boards. It was like déjà vu. I was bragging … then interrupted … and the tales of woe poured out like an overdue confession on Sunday morning. This time I dug deeper. By the end of the conversation I had a new friend and customer.

Same week … different RF engineer … same story. Déjà vu, squared.

By the end, of these exchanges I was left with this conclusion: Not all PCB suppliers that say they can build RF/MW PCBs can!

So what makes RF/MW boards uniquely challenging to build? Why do some otherwise excellent board suppliers, have trouble with RF/MW PCBs?

I sat down with the owners of Transline, Larry Padmani and Chris Savalia, and asked them to share some of the inherent challenges in manufacturing RF/MW PCBs. They looked at me with cocked heads and compassionate smiles, as if a wee toddler just stumbled into their offices and asked them where babies come from. Clearly, these were loaded questions.

Their patient answers came and I soon experienced the proverbial sensation of “drinking from a fire hose.” It soon became clear that the answers were many and complex. I soon understood that there existed a chasm between most RF/MW engineers and their board suppliers that sorely need to be filled. It was then, I decided, I wanted to somehow help fill this gap … for a couple of reasons. Altruistically, I wanted to spare RF/MW engineers from needless suffering, before they found a well qualified PCB supplier. More selfishly, I knew if I could adequately inform the RF/MW community, they could more easily discern between a qualified and non-qualified supplier — and I knew it would become clear which camp we fall into.

So, I decided I would write an article for one of the trade magazines.(I may not be able to do complex RF calculations … but I can write!) I began by putting out questions to the RF/Microwave professionals via LinkedIn, asking what they would specifically like to know about RF/MW PCB manufacturing. There came a small flood of questions that continue to flow. I felt suddenly naïve and ill-equipped for the job!

Then two small miracles happened. I met a colleague who spent most of his career working for Rogers and Taconic on a nationwide scale. He offered his help in educating me on material properties and helping understand both the engineering issues and manufacturing challenges. His help, along with patient tutelage of owners of Transline, promise to bring me up to speed.

The second miracle was meeting Pat Hindle from Microwave Journal, who was commenting amidst the mix of my brewing discussions on LinkedIn. He pointed me to helpful resources and, he astutely observed, that this topic may be too broad for one article. In the weeks ahead I will take on the challenge of addressing the broad range of questions and issues surrounding RF/MW PCBs one-by-one. I know I will learn much, and hope to teach a little and help bridge the gap between RF/MW engineers and board manufacturers.

Keep the questions coming, both here and on the LinkedIn RF and Microwave community. I will do my best to address each one!

— Judy

http://www.translinetech.com/

Ed.: Judy Warner is director of sales and marketing for Transline Technology, Inc., in Anaheim, CA. She has been in the printed circuit board industry for nearly two decades. Her career began with Details, Inc. (later to become DDi). She was a top-producing sales professional for 10 years for Electroetch Circuits (later to become Tyco, then TTM). She also spent several years as an independent sales representative, including time as the owner of her own rep firm, Outsource Solutions.

Blackout at ESC

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There’s always excitement at ESC. Almost always, anyway. I think in 2009, it was mostly just spooky quiet. If I remember correctly, the theme for that year was: “But I’m not dead yet …”

Our booth, 823, is across from LeCroy this year. They do cool test equipment. I visited them a few years back to get humiliated by Guitar Hero on the Wii. I didn’t play Guitar Hero this year, but I did get to watch the line for their beer cart and the longer line to get the little robots from Atmel, also near us.

Being mostly stuck in my booth, I haven’t been able to get out and about much to see what else is here, but  Blackout fortunately, some of the excitement came to me. At approximately 4:36, the hall went dark in black out. As you can see from the photo, it was completely out except for the occasional dim glow of a laptop here and there. Me and my booth crew considered doing some looting, but we couldn’t agree on who would pick up a chair and throw it through a window or a monitor.

Half a minute later, we had some emergency lighting and about ten minutes after that, the main lights started coming back on with the convention center’s generators. The power stayed out for the final 45 minutes of the show. As frequently happens, stories of unknown legitimacy started flowing around. The best was that the power was our from Gilroy to just South of San Francisco. Record heat was given as a reason in one case. I’m not sure that 80 degrees should qualify as record heat, but who knows.

Back at the hotel, the elevators were running slowing on generator power. I chose to take the stairs. After a brief stop in our rooms, we were going to go out and hunt down a wild beast to cook on the open fires in the street, but the power came back on and we couldn’t find any open fires.

Duane Benson
Tomorrow we we eat ham and jam and Spam a lot.

http://blog.screamingcircuits.com/

Grounded in Reality?

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LED scroller 006 thin trimmed

Looking back, I think I could have done a few things different.

For example, I don’t really need a separate power-on LED. I could either just not populate it, or rev the schematic a little to make it a software controlled indicator rather than hard linked to the power switch. That change would allow me to put the device to sleep. The PIC18F25K20 draws somewhere around a tenth of a microamp while in sleep mode. That being the case, I might just discard the power switch all together. Otherwise, it’s cool.

I cuold have given each LED its own via to the ground plane, too. That’s supposed to reduce noise a bit. Although, this will probably never be clocked high enough to make much difference, nor used in an environment where it matters.

Duane Benson
Only half of 10 the types of people will understand

http://blog.screamingcircuits.com/

Done and Done

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LED scroller 005 trimmed And … (drum roll, please) … it works.

I put in a couple of batteries, programmed the MCU and turned it on. It works.

I’m always surprised when something I design works on the first try. This being such a simple design, I probably shouldn’t be surprised, though. I should at least give myself a little more credit.

The unpopulated lands on the board in the photo are supposed to be unpopulated. I left a few things out because they aren’t needed for what I’m doing with this piece now and leaving them off keeps the cost down.

So, what did I learn from the process?

  • If you have a lot of different parts laying around, it’s pretty easy to grab the wrong one.
  • I ran into some variability in the “zero rotation” position in the CAD library land patterns.
  • The whole process is pretty easy, but start to finish, there are quiet a few steps.
  • It’s a nerve-racking wait after sending off a box of parts.
  • Good communications between designer and assembler are very important.
  • Clear documentation from the designer is very important.
  • This was a WHOLE LOT easier than hand soldering all the SMT parts (I’ve done that before).

That’s a good set of educational results. Next time, I think it will be easier.

Note the large diode polarity indicators on either side of the long row of LEDs and by LED D25. D1, the Schottky on the upper right has the same polarity indicator, but it’s in between the pads, under the part. In case you’re interested, I have a 3V supply. The LEDs drop 1.8V and I’ve got a 150 ohm resistor for each. That gives me a theoretical 8 mA per port for a total maximum of 176 mA with all 22 lit up. That’s within spec in the -40C to 85C temperature range but too much when above 85C. I’m not sticking this in an engine compartment or anything, so no worries there.

Duane Benson
0x45 0x53 0x43 0x20 0x62 0x6F 0x6F 0x74
0x68 0x20 0x38 0x32 0x33 0x20 0x20 0x20

http://blog.screamingcircuits.com/

My Mistake — Naturally

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I received my PCBs for this project from Sunstone yesterday at about 10:10. I quickly dropped them into my box of parts and delivered it to the receiving pile-of-boxes in our shipping.receiving department. At 11:40 a.m. yesterday, I received an email from our auditing department informing me of a BoM mismatch.

BOM mismatch Yes. I had made a mistake in my bill of materials. The board has a bunch of yellow LEDs and one red LED. I had mistakenly only packed up yellows. Our audit department caught my mistake and sent me a quick email. If I hadn’t have responded yesterday, I would have received another email at midnight. I could have just told the Downsized_0421110938a manufacturing folks to put a yellow LED in that spot, but the yellows are for a display and the red is a power-on indicator so I got my red LEDs and delivered them to receiving.

This morning I got my assembled boards all nicely wrapped in anti-static bags along with all my leftover parts in their original packaging. Next step, get some batteries and power them up.

Duane Benson
Thor, Dog of Thunder, is not allowed

http://blog.screamingcircuits.com/

Short Cuts Don’t Always Make Long Delays

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The saga continues. I have my parts kit. The PCBs should be here from Sunstone tomorrow. When I placed the order on our website, I estimated that I’d have the parts and PCBs today. I knew it would be tomorrow, but I wanted to see how our communications goes when something is late. Obviously, an assembler can’t start building until the parts have arrived, so the Industry standard is to start the turn-time once everything is in the shop.

If a box is late and the sender doesn’t know it, unintended delays can be added into the process. Knowing this, we recently did a lot of work to improve our communications, on such issues as late parts, to help reduce delays. Sure enough, I dropped on over to the website and right on the top of the home page is a note that I have an issue (late parts) with my job. Tonight at midnight, I should receive an email telling me the same thing too.

On the subject of the PCBs, I sent Gerbers to Sunstone. That works just fine, but I’m always a bit nervous about the accuracy of my layer mapping. They double check, so I’ve never had problems, but I still get nervous.

If I’d waited a few days, like until today, I could have taken a short cut by just sending in my CAD board file — they just started accepting native CAD files. You can still use Gerbers, but if you use Altium, Eagle, OrCAD, National Instruments’ Circuit Design Suite, Ivex Winboard or PCB123, you can just send in the board file and save some time and hassle.

When I get the boards tomorrow, I’ll pack everything up and deliver it to the receiving folks. Then I’ll see how the rest of the build process goes from the other side of the fence, and I’ll see how we deal with extra parts. I did that on purpose also. With a couple of parts, I’m delivering several hundred more than I need. With a few other, just the requisite 5% over. It will be interesting to see just how I get the extras back.

Yes. I know. I work here, so I shouldn’t have any doubt about how all of this stuff works. I do know how it goes, but it’s always a good thing to, every now and then, check and see how well practice matches up with theory.

Duane Benson
Grip, Fang, Wolf! Guard the mushrooms!

http://blog.screamingcircuits.com/