The Top 10 in CIRCUITS ASSEMBLY

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For the past several years, we have taken a few moments at year-end to look back at the best-read articles of 2015.

The list includes features that were published for the first time in calendar 2015. Rankings are based on web site hits, and do not include — for obvious reasons — the number of reads in the print version of the magazine.

We’ll start today with the top 10 from CIRCUITS ASSEMBLY. Tomorrow we will list the best-read articles from PCD&F.

1. “How Clean is Clean Enough?” by Terry Munson, Paco Solis, Nick Munson, Steve Ring and Evan Briscoe

2. “01005: Size Does Matter,” by Arbel Nissan.

3. “Designing Flex Circuits For Wearable Electronics,” by Mark Finstad.

4. “Depaneling of Circuit Boards,” by Ahne Oosterhof and Thomas Nether.

5. “What You Cannot See Can Be Hand Soldered,” by Paul Wood and Bob Wettermann.

6. “A New SPI Tool for Defect Prevention,” by Chrys Shea.

7. “Zooming in on Digital Microscopes,” by Chrys Shea and Kristoffer Tømmergaard.

8. “China in Charge, by Dr. Hayao Nakahara.

9. “US or Mexico: Which Option Makes Most Sense for Your Project?” by Joe Villanueva.

10. “Cost/Benefit Tradeoffs of Capacitor Part Size vs. Manufacturing Efficiency,” by Chris Reynolds.

As you can see, a mix of technical and business-related pieces made up the top 10 this year. Interest was high in cutting-edge technology (multiple pieces on 01005s, wearable flex circuitry), but tutorial-type pieces on conventional technology held its own as well (cleaning, circuit board depaneling).

As always, we are grateful for our loyal readers and the many authors who contribute their expertise each month.

Happy Holidays!

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With 2015 almost over, UP Media Group would like to take this opportunity to thank our advertisers, exhibitors, colleagues and loyal readers for another successful year. It was a good year for us, topped by another terrific PCB West.

We wish everyone the best for the holiday season and for a buoyant 2016!

 

In SMT Assembly, Even 1 Second of Cycle Time Can Affect Profitability

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Folks,

Patty had just returned from SMTAI 2015. It was a sentimental meeting with the retirement of longtime executive administrator JoAnn Stromberg. At one of the technical sessions, Patty was especially interested in epoxy flux being used as an underfill. She couldn’t wait to discuss it with The Professor.

As she drove up to Ivy University’s campus, she was struck by the many hundreds of students walking to class. No one was overweight and no one was smoking. She reminded herself to discuss this topic in her statistics class. Surely Ivy U did not represent the typical 18-22 year-olds in this regard.

Soon, she arrived at her office. After clearing her laptop of emails, she headed to The Professor’s office.

Patty had been working to improve her French. Since French was one of the 18 languages in The Professor’s repertoire, they often spoke it to improve (for Patty) and keep sharp (for The Professor). Patty chuckled to herself that her French was now good enough to hear The Professor’s Quebecois accent. He learned French as a pre-teen, as his parents were missionaries for Wycliffe Bible Translators and worked with some remote Indian tribes in northern Quebec.

“Bonjour Professeur, comment allez-vous?” Patty dit gaiement.

“Je suis bon Patty, comment étais SMTAI?” Le professeur a répondu.

The remainder of the discussion will be translated into English for our non-Francophone readers.

“It’s too bad that you couldn’t make it this year. The retirement dinner for JoAnn was touching,” Patty began.

“It will be hard to replace her, indeed. Her commitment was extraordinary,” The Professor responded.

After discussing this topic for a few minutes, The Professor changed the subject.

“Were there any interesting papers presented at the SMTAI tech sessions?” he asked.

“That’s why I’m here,” Patty replied. “There was a paper on epoxy flux as an underfill material. It was a great talk comparing epoxy fluxes to standard underfills. The speaker mentioned how using epoxy flux allows the operator to avoid using a separate dispensing process and curing oven that standard underfills require. His point was that the epoxy underfill approach would save a lot of money, as long as the epoxy process only added one second or less to the cycle time. This one second was the time it took to dip the flip chip or BGA into the flux.”

Patty immediately saw the troubled look on The Professor’s face.

“Professor, I sense you are thinking the same thing that I was,” Patty said.

“Yes, one second is a long time,” The Professor replied. “One second is 5% of a 20-second cycle time, so your production is reduced by 5%. Not a trivial amount.”

“My sense is that this one second would be a greater cost than paying for the dispenser and curing oven in a standard underfill process that keeps the cycle time at 20 seconds,” Patty said.

The Professor nodded his head in agreement and then went to his laptop. In just 3 or 4 minutes, he had calculated four different scenarios using ProfitPro software.

“Well, in most cases, the cost of that 1 second/cycle lost by the epoxy flux process costs the operator somewhere between a few hundreds of thousands of dollars to more than one million dollars per line per year,” The Professor explained. “This estimate even considers the fact that the standard process already needs a dispenser and curing oven.”

“You know what I always say.” The Professor started.

“It never pays to reduce productivity,” Patty chimed in, always the faithful student.

“Take a look at this one example. A large ESM manufactures a product with a 3-shift, 5-day/week operation on a state-of-the-art SMT line. The default, as shown in the figure, is the financial result for one year of production, using a typical underfill, assuming $200K for a dispenser and curing oven and a 28 second cycle time.

“The second run shows the financial results using an epoxy flux that requires a one second longer cycle time (29 seconds), but saves capital cost in that the line does not need a dispenser or reflow oven.”

“Wow, the company loses over $100,000 per year with the epoxy flux!” Patty exclaimed.

“Precisely,” The Professor responded.

“But, this doesn’t mean that people shouldn’t use epoxy flux as an underfill,” Patty stated.

“Right, they just need to avoid losing the one second.” The Professor agreed. “Where do you think the one second can be found?”

“Probably in line balancing,” Patty responded. “About the closest you can balance a line is within a second or two. It could be as simple as having the epoxy-fluxed part placed by the fastest placement machine.”

“And if there are many components that use epoxy flux?” The Professor asked.

“It would likely pay to get another placement machine,” Patty answered quickly.

“As always, there is never one right or wrong way to address a problem like this,” The Professor pointed out. “But, we should always perform the calculations to determine which approach makes the most sense.”

“Yes, and always remember that it never pays to reduce productivity,” Patty joked.

They both smiled as Patty left The Professor’s office.

Cheers,

Dr. Ron

The Common Parts Library

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The two most common causes of delay in small volume manufacturing here at Screaming Circuits (and presumably, others like us) are component availability, and footprint mismatches.

We don’t substitute parts without your approval for a number of reasons. I’ve written about those reasons a few times before. (Here, here, and here.)

Incorrect footprints can lead to a host of headaches as well. (Read more here, here, and here.)

Until recently, I haven’t seen a lot of progress toward solving these problems for the hordes of engineers that don’t have big support departments at their disposal. In fact, with the proliferation of newer, and small, component packages, and evolution of the supply chain, it’s really gotten worse.

However, there are a couple of Knights in Shining Armor riding in to try and solve both problems. The Common Parts Library (CPL), created by Octopart, aims to create a list of components with the highest probability of being available and staying available (there are no guarantees where component supply is concerned).

The other exciting entrant is SnapEDA. SnapEDA has a massive, and growing, library of component footprints. I’ve used their footprints with good success for high pin-count devices, and other parts with complex packages. It can save a lot of time and give better confidence that all of the pins go to the right functions.

Duane Benson
Map makers put fake roads in as copyright traps
These folks don’t do that. Nice.

http://blog.screamingcircuits.com/

Made in the USA

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This is a pet peeve, so forgive me in advance.

Manufacturing in the US is by no means dead.

We don’t have nearly the number of unskilled or semi-skilled manufacturing jobs as once before, thanks in part to hands-free automation and a higher level of engineering knowledge / skilled labor needed for the non-automated work. Overall employment in the sector dropped about 12% between 2003 and 2013, and more than 20% from 1993 to 2013.

We are no longer the global leader in either manufactured goods — a title lost in 2010 — or valued added manufacturing — which we ceded in 2013 — although the data are skewed of late in China’s favor because of currency valuation changes.

And here’s no question manufacturing as a percent of GDP has certainly slipped in the US (and not to our advantage, but that’s a different discussion).

But even given that, in terms of how much the US produces, we still produce north of $2 trillion worth of manufactured goods every year.

That’s a really big number.

Now, how to get some of that back in the US printed circuit industry?

Automakers ‘Dashing’ for 3d Party Platforms

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The fight for the dashboard is heating up as reports surfaced this week that two major automakers will ditch their current embedded software systems in favor of alternatives from Google and Apple.

Ford, which has dabbled with Apple’s CarPlay for two years even while using Microsoft Windows Embedded for its infotainment systems, drop Microsoft and migrate to an Apple-compatible platform, reports indicate.

Likewise, Hyundai is going all in on CarPlay and a competing system from Google called Android Auto.

There’s big money at stake. Automakers generate substantial profits on infotainment and related on-board gear: Ford bundles Sync with Sirius radio and other options in a package, priced at $1,250, which is purportedly nearly $1,000 higher than the OEM’s costs.

While the tools not only control today’s dashboard displays, they could be even more significant down the road as self-driving cars start to populate the roads, freeing vehicle occupants to do tasks once considered unthinkable in moving cars, such as shopping online.

So while the prospect of moving toward more interactive onboard systems holds promise and profits for the automakers themselves, major OEMs like Apple and Google stand to benefit from a captive audience inside the vehicle.

In the future, “keep your eyes on the road” may be replaced with “keep your eyes on the dash.”

Failure Rate Calculation

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Folks,

Let’s see how Patty, Rob, and Pete are doing helping Mike Madigan establish his Zero Defects program.

“So let me see if I got this straight: if I want to establish that the defect rate is 1 per million or less, I need to have 3 million in the field with no fails?” Mike asked.

“That’s correct,” Rob responded. “Patty and I developed an Excel spreadsheet that will calculate the number of samples needed, with no fails, to verify a given defect rate. I sent a copy to your email account. Open it.”

“Select the sheet titled,  ‘Calculate Number of Samples.’ Now enter ‘95’ in the blue cell after ‘Percent Confidence Desired’ and 1E-6 in the blue cell after ‘Failure Rate to Verify.’ The number of samples needed to verify this defect rate is in the gray cell. Note that it is a little short of 3 million.”

From a different perspective,” Patty added, “if you have a certain number of samples in the field and want to verify the defect rate they can support, if none fail, the sheet ‘Calculate Failure Rate’ will make that calculation.”

“Let me see if I can use it,” Mike replied.

Mike entered 95% and a desired defect rate of 1E-6.

“Wow! It works!” Mike exclaimed, “It says I need a little less than 3 million samples.”

“So how many samples do you need to demonstrate 0 defects?” Pete teased.

Mike thought for a while and then responded, “Three times infinity! Yikes!”

“I think three times infinity is infinity,” Pete teased again.

Patty glared at Pete.

The group ended by discussing the nobility of a zero defects plan, but the futility of demonstrating it by field sampling.

After they hung up, Patty looked a little agitated.

“Sometimes you two act like 12-year-olds,” she scolded.

Both Rob and Pete had a “Who? Me?” look.

“Why do you say that?” Rob asked sheepishly.

“Both of you laughed when Mike proposed a sample size of 20 to demonstrate zero defects, and then Pete teased about 3 times infinity equals infinity,” Patty responded. “Mike deserves to be treated with respect. We shouldn’t laugh at people when they don’t know or understand something that we do. Especially now that we are all at Ivy U, we are here to help people learn.”

“But he was so annoying when we worked at ACME,” Pete shot back.

“That doesn’t matter. And besides, for whatever reason, we all agree he is much nicer now.”

Both Pete and Rob murmured in agreement.

“Ma’am, we will be better in the future,” Rob and Pete teased in unison.

“Hey, Patty. Remember your concern that almost 50% of Ivy U students did not know who wrote A Christmas Carol?” Rob asked.

“Sure,” Patty responded.

“I asked Pete and he said ‘J. K. Rowling,’” Rob said.

“Well at least I got the right country,” Pete replied.

Patty couldn’t help herself; she burst out laughing with the other two.

Cheers,

Dr. Ron

  1. If you would like a copy of the Excel Spreadsheet that performs the defect rate calculations discussed in this post, send me an email at [email protected].

 

 

Raspberry Pi — What’s It All Mean?

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What would you do with a computer that costs $5?

First, let me explain a bit. The Raspberry Pi, if you don’t know, is a small, inexpensive single board computer designed by the non-profit Raspberry Pi foundation in England. Its mission is to make computer-related education less expensive and more accessible to the masses. As a next step in that mission, it just introduced the Raspberry Pi Zero, with an MSRP of $5. So, you can buy a Big Mac, or a Pi Zero. You could buy some peanut butter, jelly and a loaf of bread, eat that for the next five lunches, and buy five Pi Zeros.

Now some folks have complained that it’s not very useful on its own. It needs a wall bug power supply, a micro SD card, a few cables, and a USB hub to connect a keyboard and mouse to.

That’s true, if you want to use it as a full PC workstation, which you can. It runs the “Raspian” distribution of Linux. But, I don’t think that’s where the greatest potential for this thing lies. No, I wouldn’t use this as a workstation. It’s biggest potential, in my opinion, is as an inexpensive embedded controller.

It has I2C, SPI, and RS232 pins available, as well as plenty of GPIO. Attach a small daughter card with accelerometer, gyro, magnetometer, and GPS, and you’ve got a nice drone auto pilot. Attach a few sensors and a cell phone module, and you’ve got a remote data logger. What would you do with one of these?

Duane Benson
Little Jack Horner couldn’t get a plum out of this pi.

http://blog.screamingcircuits.com/

Talking About the AirAsia Crash Report

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A great discussion of the final report of last year’s AirAsia crash is taking place on the IPC TechNet listserv this week. Investigators say solder fatigue on the plane’s rudder control warning system precipitated the disaster.

To register, send an email using the following format:

     TO: [email protected]

     SUBJECT:

     MESSAGE: subscribe TechNet Your Name

Or click here for more details.

The Rule of 3/N for Estimating Field Failure Rates

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Folks,

It looks like Patty is a bit troubled….

When she was younger, Patty was always annoyed by cranky old people, and now she was worrying that she might become one. The trigger making her cranky was what students know and don’t know. It all started when a colleague showed her the “Texas Tech Politically Challenged Video.” 

“How could so many students not know who won the American Civil War, who the Vice President is, or who the United States won its freedom from?” she thought.

Some of her colleagues felt the video was staged, but the producers came up with a response video that strongly suggested that it was not. What was even more unsettling was the fact that all the students knew who Snooki was and who Brad Pitt’s wife was.

Some of Patty’s statistics students got wind of this video and decided to make a similar video at Ivy University. The results were mostly comforting: 49 out of 50 students knew who won the Civil War, and the one student who didn’t was from India. They also did well with some other questions, 85% knowing that Joseph Stalin was the leader of the Soviet Union in World War II, and a high number knew that Joe Biden was the VP.

But Patty was most troubled that almost 50% did not know who wrote A Christmas Carol. She had discussed the topic with Rob and was further annoyed that he didn’t seem as troubled as she was. Rob pointed out that some international students might not have had English literature in their studies, and being a story about Christmas, it could be a cultural thing. Patty was unconvinced by his arguments. It still seemed troubling to her.

Charles Dickens in 1867, 24 years after he authored “A Christmas Carol”

As she was mulling over these thoughts, the phone rang. It was Mike Madigan, CEO of her former employer, ACME.

“Hey, Patty, it’s Mike,” Madigan said cheerfully. “I need your help with a statistic problem. It might be good if Rob and Pete were involved, so could we do a teleconference?”

Patty scheduled the teleconference for later in the day. When the time came, Pete and Rob were in Patty’s office and she called Madigan. After exchanging pleasantries, Madigan got to the point.

“We have a demanding customer from the military,” Mike started. “They have a Zero Defects program and want to know how we can guarantee it after field exposure.”

“To clarify, you mean guarantee zero defects for units in the field?” Pete asked.

“Yeah,” Mike replied.

“The way I figure it, if we have 20 units in the field and none fail, we can say with 95% confidence that we have zero defects, because one unit is 5% of 20, and if none fail, that means we can be 100%-5% or 95% confident,” Mike said.

Patty instinctively reached for the mute button, as Rob and Pete went into hysterics. She glared at both of them.

“Hello, hello, are you there?” Mike asked as he heard no response.

Finally, with Patty continuing to glare, Pete and Rob had stopped laughing. So she unmuted the phone.

“Sorry Mike, the failure rate in the situation you described is that you can be 95% confident that is it less than or equal to 15%” Patty replied.

The other end of the conference call was quiet for a while and finally Mike answered,

“Yikes! OK, can you explain?”

“Patty and I have developed the math to explain how to calculate confidence limits on field failure rates,” Rob responded. “For 95% confidence we have developed what we call The Rule of 3/N.”

“How does it work?” Mike asked.

“If you have N samples in the field, and none have failed, you can say with 95% confidence that your failure rate is 3/N or less. As an example, let’s say you have 300 units in the field and none fail. You can then say with 95% confidence that the failure rate is less than or equal to 3/300 = 1/100 = 0.01 = 1%.”

“If we have 300 units with no fails, we can only have confidence in a 1% failure rate?” Mike groaned.

“One percent or less, with 95% confidence,” Patty chimed in.

Is demonstrating a 0% failure rate possible?  Will Patty and the team find a way to help Mike? Stay tuned for more details.

Cheers,

Dr. Ron