Tag Archives: PCB design

Safe in the Cloud

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Data are safer in the cloud.

That’s what tech industry research firm Aberdeen concludes, based on findings from multiple benchmark studies on best practices in content security and security software.

Aberdeen says its analysis shows that users of cloud-based web security had substantially better results than users of on-premise web security implementations when it comes to security, compliance and reliability (and cost, by the way).

Over a 12-month span, cloud-based web security solutions users had 58% fewer malware incidents, 93% fewer audit deficiencies, 45% less security-related downtime, and 45% fewer incidents of data loss or data exposure than did their on-premise web security colleagues.

Extrapolated to the PCB design industry, the report suggests Altium’s move to a cloud-based server environment isn’t as fraught with security hurdles as some have posited.

BGA Pads with Vias

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Via eyeballs

No. This isn’t a closeup of an owl face.

There is still some debate on how best to create a land pattern for a 0.4mm pitch BGA. We recommend solder mask defined pads at that pitch. But that’s not really what this post is about. Although this land pattern uses non-solder mask defined pads which can encourage bridges. If you need to cross a river, encouraging bridges is good. If you’re trying to make a board work, they are not.

In the case of the two BGA pads shown, I really doubt you would have to worry about bridging. That’s because the solder ball would most likely be sucked off the BGA due to the capillary action of the via in the middle of the pad. You most likely wouldn’t get bridging. You most likely wouldn’t get any contact of any kind at all. This will not work.

Duane Benson
Hoot. Hoot.

http://blog.screamingcircuits.com/

All’s Well at West

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We really had an outstanding week at PCB West. Preshow registration rose to nearly 2,000 (!) and actual attendance was up more than 30% over last year.

Congratulations to Judy Warner and Michael Ingham, whose talk on RF/microwave design and fabrication drew more than 100 attendees, the most in the conference. Newcomer Jamin Taylor’s presentation on flex construction also drew more than 80 folks. Well done!

I also want to congratulate the winners of the PCD&F NPI Award for best new software tools of 2011. They include:

  • Design Verification Tools: DfR Solutions (Sherlock Automated Design Analysis)
  • Computer-aided Design (CAM) Tools: Downstream Technologies (CAM350)
  • Documentation Tools: Polar Instruments (Professional HDI Stackup Design & Documentation)
  • PCB Design Tools: Altium (Altium Designer 10)
  • System Modeling and Simulation Tools: Sigrity (SystemSI – Parallel Bus Analysis)

We have posted the full announcements on PCD&F’s site. Thanks to all who attended!

A New Trend in Assembly Shows?

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Years ago, three major events dotted the US electronics assembly trade show landscape. They included Nepcon East, Surface Mount International, and the mother of them all, Nepcon West.

While Nepcon West was the undisputed champ, all three shows were worth attending, and exhibitors often made new product announcements at each one.

Interestingly, and for reasons too detailed to get into here, none of those shows exist today. And for much of the 2000s, the place to roll out new products became IPC’s Apex. Other events were relegated to regional status, and traditionally were staffed as much by distributors as by OEMs.

There’s a few small signs that trend may be shifting again. While IPC Midwest, taking place this week in the Chicago suburbs remains a local show (and honestly, could they make seeing the exhibitor list any more user-unfriendly?), SMTAI is at long-last beginning to fill the niche for a seasonal alternative to Apex. To wit, we’ve received numerous press releases of late reporting new products to be introduced at SMTAI. That’s evidence suppliers see the venue as a viable place to make product launches.

Also at SMTAI, on Oct. 18, I am cochairing (with CIRCUITS ASSEMBLY columnist Sue Mucha) a panel titled “Global Strategies for Lowering EMS Costs” at SMTAI in Ft. Worth, TX. Topics include EMS in Eastern Europe; networking technical trends; improving quality, delivery and cost in high mix manufacturing; and vapor phase technology, and feature speakers from Kimball, Tailyn, Fabrinet and IBL Technologies. We conclude with a panel on building an EMS cost model.

I can’t mention these events without touting our own. Next week marks the 20th annual PCB West conference and exhibition at the Santa Clara (CA) Convention Center. Traditionally the industry’s leading conference for printed circuit board design and fabrication, we have beefed up the electronics assembly side (with a big assist from the Silicon Valley SMTA Chapter). Highlights include papers on low silver solder alloys, advanced packaging, new plasma-based PCB surface finishes, and lead-free electronics risk reduction, presented by such leading companies as Hewlett-Packard and Amkor. Check out the program at pcbwest.com.  We really hope to see you there.

And Another Footprint Thing

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 When you are creating a footprint in your favorite CAD program, or reusing someone else’s footprint, double check the zero orientation. This post discusses the IPC-7351 specified zero rotation orientation.

This picture on the left shows a library component with the improper zero rotation orientation. Your centroid file will never be correct if you start from the wrong point.

IPC-7351 states that the LED should be oriented horizontally and the cathode (pin 1) should be to the left. Obviously, vertical and cathode up is not the same thing as horizontal and cathode left. If it’s obvious, why do I feel the need to state it? I don’t know. I just do.

Duane Benson
Red is gray and Yellow white
But IPC decides which is right

http://blog.screamingcircuits.com/

How to Build a Footprint

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Well, not really how to build one in a technical sense, but some thoughts on how to better ensure that you get it right. In theory, it shouldn’t be that difficult. You download the datasheet and build the land pattern based on the information in the datasheet. That usually works, but not always.

I had a through-hole battery holder that didn’t match up with any of the land patterns in my library, so I modified one that was close. That worked mostly okay, but there was one measurement in the data sheet that was a little ambiguous. I ended up with the mounting holes being off by a millimeter or so. Not too much, but enough to make the fit difficult.

I went in and shifted the leads over by the same amount, used it again, got another PCB fabbed and discovered that I had shifted the pins the wrong way! Then it hit me. In the first application, I had the battery holder on the bottom side of the PCB but I had looked at it through the mounting holes from the top side of the PCB. D’oh! One reason why I’m not a professional designer.

The other part was a little tiny SMT trim pot. Since there are pretty close to a million different little trim pots, the likelihood of me finding an exact match in my CAD library was precisely zero. I didn’t want to Gieger VR mistake close re-invent the little zig zag resistor symbol, so I just found a part that looked the same. Well, it was almost the same. The footprint I found is for a 4 x 4mm part and the part I ordered is 3 x 3mm. That’s a tiny trim pot. Somehow, when looking at the datasheet, I got the measurements wrong. Once the part came in the mail, it was quite obviously too small.

The pad pretty much ends right at the edge of the trim pot. We won’t be able to reflow that part. No solder paste would be touching the pads on the trim pot. I’ll see if our guys on the floor can figure out how to get the thing soldered on there. If they can’t, I’ll need to look for a larger part to put in it’s place.

Fortunately, I physically looked at the part and the PCB before assembly. Unfortunately, I got the measurements wrong. If at all possible, get some sample parts before you order your PCBs. Then you can print out a 1:1 image of your PCB and lay the parts out on it. That would have saved me in both of the above cases.

Duane Benson
Is it “datasheets” or “data sheets”?

http://blog.screamingcircuits.com/

Where Design is King

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Just posted a profile of Automated Circuit Design, a Dallas-area electronics manufacturing services provider that I visited last week.

ACD started as a design bureau and VAR, and one of the interesting things I noticed was how it has stayed true to its designer roots: all its designers have their own offices (not cubicles), and seven of them are CID+.

Designer Salaries by Region, Revisited

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Some readers have asked for a more complete explanation of the data contained in Table 5 of PCD&F senior editor Chelsey Drysdale’s annual designer salary survey.

The table shows the current annual salary range by region, but due to an editing error, the salary percentages were not broken out in a meaningful way.

The graph below should help. (Right click on the graph to enlarge it.)

0.4mm Pitch BGA Redux

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I’ve written about it before, and again here.

When dealing with new technology parts, it’s really important to look up all of the manufacturer’s component information that is available. I’m going to quote from the Texas Instruments document “PCB Design Guidelines for 0.4mm Package-On-Package (PoP) Packages,” Section 10 (PDF page 8):

Industry reliability studies have revealed that NSMD-type pads are highly recommended for most 0.5mm pitch BGA applications. However, there is a problem with this approach at 0.4 mm pitch.

Real-world assembly experiments with the BeagleBoard and the OMAP35x EVM revealed a tendency for solder bridging between pads when NSMD were used. There was insufficient solder mask webbing between the pads to ward off bridging. Therefore, a SMD design was used which resulted in much better assembly yields with no solder bridging.

If you are using a 0.4 mm pitch BGA with the balls aligned in a grid (as opposed to staggered), read the design guidlines from the manufacturer before laying out the board.

In a presentation about the development of the Beagleboard, Gerald Coley, Beagleboard designer, notes that their first two runs had non soldermask defined pads, resulting in a 10% yield. After another run of PCBs where the pads on the PCB were the same size as the pads on the device and the PCB pads were soldermask defined, yields rose to 96%. And verify that your PCB house does in fact follow your instructions. Some will think they know better and will change the mask layout.

If you are still unsure or think your design will have different requirements, call an applications engineer at the component manufacturer and discuss your project and the layout.

Duane Benson
Trust but verify

http://blog.screamingcircuits.com/

Paying the Price

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Interesting discussion going on at LinkedIn, where a handful of folks are debating the going rates for PCB design in China.

It started when someone asked what the “least per hour charges” to attract a client for PCB layout outside China (emphasis mine). (The question was asked by a LinkedIn member in Pakistan.) Quickly others chimed in with the usual “you get what you pay for” refrain (when it comes to PCB design, I tend to agree).

Someone from Israel noted that they charge by the pad. Those who commented on hourly charges relayed reports (unconfirmed, by the way) of $5 (China) to $10 (Pakistan).

PCD&F conducts an annual salary survey, and certainly a $10/hour contract rate would undermine even the lowest paid designer responding to that questionnaire. But keep in mind, these are not confirmed quotes. And as the folks at PCB West last week showed in spades, there’s no comparison between a button pusher and a PCB design engineer.