Looking Forward

The Taiwan Printed Circuit Association (TPCA) announced at a press conference attended by nearly 100 members of the government, industry, research institutes, academia and the media that it will publish a white paper in September to address the future Taiwan PCB industry challenges – both in Taiwan as well as China. It will take on production constraints, labor shortages (including skilled and semi-skilled), and end-of-market changes.

TPCA is calling for its government to lead the country’s PCB industry to develop next-generation products and to promote (sponsor?) industry upgrades. Taiwan’s PCB makers have lost its momentum and are likely to generate a CAGR of only 1.2% in the 2010-2014 period. The targeted goal for 2014-2020 was said to be 6% to 7%. Sales of Taiwan owned production at home and abroad (including China) is forecast to be $18.3 billion this year.

Dateline July 23, 2014 5:40PM EST: It is with great sadness and deep regret that I must inform you of the passing this morning of Dieter Bergman, Global Industry Icon of the printed circuit industry, colleague, and friend of the past half century. He worked selflessly and tirelessly with great charm and wit his entire life in behalf of the industry, enabling the impossible to become the possible. The accolades that are sure to follow will be dwarfed by his actual accomplishments.

Do Not Penalize! – Motivate! Incentivize! Negotiate!  License!
Renewable energy is the way of the future. Make no mistake about it. Achieving a cost-effective path is the challenge. Slamming China and Taiwan with enormous duties on assembled solar PV panels shipped to the US is the wrong approach. We should be grateful for the support of China’s  and Taiwan’s governments to their industry that allows us to buy them cheaply. The whole industry is based on government subsidies. The net effect of this new DOC action is to increase prices to the American consumer. The  US government has thrown away hundreds of millions of dollars by investing in unproven, doomed-to-fail companies during the past few years. It should have been providing job creating tax incentives for the manufacture of such panels in America.

Let’s see if the USA will be the first to commercialize (in high volume) the very efficient multi-juncture PV solar panel technology shown at the recent SemiCon West in San Francisco.

Wake up America! It has been 5 years since we have been the world’s leading innovator!

Report: The United States not even close to being top global innovator. By Pam Tobey July 23 at 5:39 AM – Source: The Washington Post

Switzerland is a four-time champ when it comes to global innovation. The United States? Not so much lately — the country last achieved that spot in 2009. The United Kingdom jumped ahead of Sweden to claim the No. 2 spot behind Switzerland in the recently released Global Innovation Index 2014, put out jointly by the business school INSEAD, the World Intellectual Property Organization and Cornell University. The index covers many variables that contribute to innovation, including institutions, human capital and research, infrastructure, market and business sophistication, knowledge and technology and creativity. It gathers data for 81 different indicators in 143 economies to come up with rankings. In 2007, the United States was at the top of the list. In 2010, it plummeted to 11th place, partially due to the battering of the economy by the financial crisis. Among the regions in the report, Europe holds the top spot, followed by North America.

 

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The False Positive Paradox

Folks,

Let’s check in on Patty…

Patty was intensely preparing a lecture on Bayes’ Theorem. She always felt that this theorem was the most profound in probability and statistics. She remembered a real application, when her best friend took the Tine test for tuberculosis before she got married – and tested positive. The test claimed to be 99.9% accurate in identifying someone with TB. Her friend was devastated to find out that she apparently had this ancient, dreaded disease. Further investigation uncovered that the 99.9% number was more accurately stated as, “if you have the disease, this test will pick it up 99.9% of the time.” There was an important number not told: false positives. This rate was 5%. With so few people having TB, a 5% false positive rate would indicate that almost everyone that tested positive for TB, would be a false positive, hence not have TB. So it was, much to the relief of many, with her friend. This situation is an example of the false positive paradox.

While Patty was deep in thought, she was startled by the sound of her phone ringing. She looked at the area code and exchange and knew it was from her old company, ACME. She picked up the phone.

“Professor Coleman,” Patty answered. She liked the sound of that.

“Hey, Patty! It’s Reggie Pierpont!” the cheery voice declared.

Patty’s heart sank. Reggie was an OK guy, but he always got involved in things he didn’t understand and often convinced management to pursue expensive and ineffective strategies. He was that persuasive.

“Reggie, what’s up?” Patty said half-heartedly.

“Well, Madigan insisted I call you before we order some new testers. I think it is a waste of your time, but I’m following orders,” Pierpont said.

“What are the details?” Patty asked.

“We have a contract to produce one hundred thousand Druid mobile phones a week. We are confident our first pass yield is greater than 99%,” he began.

“Impressive,” Patty said with sincerity.

“I want to order some testers that identify a defective phone in a rapid functional test with 99.9% certainly. The testers are very expensive, so Madigan wants a sanity check before buying them. The other important info is that we get a huge penalty from the customer for any defected phone we ship,” Reggie continued.

“Well, with a large penalty, 99.9% is the right number. What do you do with the units the tester determines are defective?” Patty asked.

“Well, it is a good thing yields are high. The phones are so complex that we have quite a drawn out process to find the defect and fix it. Just finding a defect can cost $5 to $10 dollars in burdened labor, but, considering the value of a phone, it’s worth it. Like I said, it’s a good thing yields are high so we don’t have too many units needing this procedure,” Pierpont continued.

“What about false positives by the tester?” Patty asked.

“Shouldn’t be a problem, remember the tester is 99.9% accurate,” Pierpont answered.

Patty knew that Pierpont was missing her point, but she didn’t want to embarrass him……too much.

“Reggie, from what you told me, if a unit is defective the tester will catch it 99.9% of the time. What I am asking is, if a unit is good, how often does the tester say it is bad? This situation is usually called a ‘false positive’,” Patty responded.

“Well, it would be 100 – 99.9 or 0.1%,” Pierpont replied.

“That’s the percentage of bad units that would be called good. These units are often called ‘escapes.’ The only way to determine false positive rate is by a test, you can’t determine it from the 99.9% number,” Patty went on.

There was silence at the other end of the phone.

“What do I need to do to get the false positive number?” Reggie asked.

“You need to test about a 1,000 known good units and see how many the tester says are bad,” Patty said.

“I’ll do that with the loaner tester the tester company is letting us use and get back to you,” Pierpont replied.

Patty hung up the phone. She thought it interesting that Pierpont’s problem was so closely related to both Bayes’ Theorem and her friend’s false positive with the Tine test.

Two days went by and Patty, Rob, and Pete had just returned from lunch with the Professor. They would all meet with him quite often to discuss technical problems they were having. So, they offered to treat him to lunch.

As she walked into her office, Pete spoke up.

“Did Reggie Pierpont ever get back to you?” Pete asked.

“No, maybe I’m off the hook,” Patty chuckled.

At that instant, her phone rang. It was Pierpont.

“Hey, Reggie! What’s up?” Patty asked with more enthusiasm than she felt.

“Well, the tester says 5% of the good units are bad, I think you are going to tell me this is a problem,” Peirpont began.

“What if you run them through the tester again?” Patty asked.

“That IS running them through two or more times! If we run them through just once, it was 7%,” Reggie sighed.

“Well, let’s look at the numbers. You are making 100,000 units a week, with a 5% false positive rate that’s 5,000 units. Your yield loss is 1% or 1,000 units. So, you will have about 6,000 units the tester will declare as bad when only 1,000 really are. These numbers are off a little bit. Bayes’ Theorem would give us the precise numbers, but these are very close. Since your process to analyze fails after the tester costs at least $5 per unit, you will be losing $25K per week due to false positives,” Patty elaborated.

“Time for a new strategy,” Pierpont sighed.

Patty and Pete agreed to help Pierpont work with the tester vendors to develop a better strategy.

Epilogue

Patty and Pete helped Pierpont develop an effective test strategy working with a tester vendor. Neither Patty nor Pete had known Reggie well before… but, after this joint effort, they grew quite close. Reggie became quite engaged in the process and seemed to learn quite a bit. Patty was able to use some of the data in her classes.

A few weeks later she got a beautiful card in the mail. She opened it. It read, “Dear Patty, Thanks for all of your help. We wouldn’t have made it without you and Pete helping us with our testing strategy. Best Regards, Your faithful student, Mike Madigan.”

Patty got a little choked up.

Cheers,

Dr. Ron

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Why Soldering’s Loss was Design’s Gain

Catching up on your summer reading? Consider Dickie: Memoirs of a Mad Scientist, by Richard Nedbal.

Though not seen around the industry much anymore, Rich, many longtime readers will recall, revolutionized CAD and CAM software as founder of P-CAD, which at one point boasted the world’s largest ECAD installed base, and Advanced CAM Technologies (ACT), which developed the still popular CAM350.

Rich has spent the better part of his post-ACT days working on bettering engine injection systems. (He also was inducted into the Dieter W. Bergman PCB Design Hall of Fame last year at PCB West, which coincidentally takes place in September at the Santa Clara Convention Center.) In his spare time, he has written a startlingly funny and self-deprecating book about his childhood and early adult years.

Rich spins great yarns about growing up in Chicago, his occasionally inspiring parents, learning about electrons (which he mastered) and soldering (which he butchered), first jobs, monkey races (seriously), starting college, and joining the Air Force, where he escaped the hated “Dickie” moniker of his youth, only to be recast by an angry Air Force sergeant as “Airman Kneeball.”

A lifetime love of math and science took him to Carnegie Mellon, where an engineering manager tapped him to help with digital logic design, launching his Hall of Fame career in electronics.

Rich’s wit, intellect and most of all, never-say-die attitude are on display in spades throughout this charming tale, released this summer by Strategic Book Publishing and available via Amazon. I would have expected nothing less.

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The Post-Silicon Era

Masamitsu “Matt” Aoki has updated his detailed charts of “Build-Up Types of Printed Wiring Boards and Their Applications in Japan” (Version 14.1) and “Thin Types of Printed Wiring Boards and Their Applications in Japan” (Version 24.1). They are both now current through June 2014. Write to us at gene@weiner-intl.com if you wish a copy.

 Who will share in IBM’s vision of the future? During the next 5 years IBM will invest $3 billion in R&D for “the post-silicon era.” Which equipment and material suppliers will partner with it? Who else has such a forward looking budget? According to CIO Bernie Meyerson, the investments include programs in areas such as III-V materials expected to be used around the 5nm node, which some say could be the last generation of silicon-based chip technology. They also include a broad set of programs ranging from 3D chip packaging to computer architectures such as quantum and neural processing and post-silicon chip materials such as carbon nanotubes and graphene. “This is not about semiconductors per se but a broad statement about reinventing computing,” he said. Today’s silicon CMOS processes will hit atomic limits (a brick wall) somewhere around the 5nm node in about 2020. Many of the IBM programs are about finding new techniques that will drive hardware performance beyond that point. “The real issue is silicon goes quantum mechanical at these dimensions. It no longer works. At this time, there is no consensus on what’s next.” However, “we still have a 5-10 year horizon” to find solutions.

 Someone forgot to tell them…

…about the economic recovery. Microsoft will chop 18,000 jobs in the next year as it lays off 14% of its workforce. 2/3 of the cut will come from the phone and tablet work force in order to eliminate the post Nokia acquisition bulge. I guess CEO Satya Nadella won’t be running for US president in the near future.0

It was not too long ago when “everyone” just wanted a very small cellphone. Smartphones with screens larger than 5.5″ seem to be cutting into the tablet market, especially those with 7 to 7.9″screens which accounted for 58% of the market in 2013. Tablet shipments the first quarter of 2014 declined about 5% from the same period last year. This is the first time such a drop has been noted in tablet sales since their introduction.

Good move, Ray! Have you noticed the shortage of RF substrates? Isola announced increased production of and a 24-hr response service to provide designers with a turnkey solution for all the calculations, testing, characterization and material recommendations to fill the gap with its “low loss materials.” Target applications include 23GHz, and 76-79Hz frequencies used in advanced driver frequencies.

It is not too early …

… to start planning your participation and attendance at the early key Fall events. Have you wondered if the lost board business has all gone overseas or if something else is occurring? Have advances in packaging and system technology supplanted portions? Are segments morphing into newer technologies? Do you know what these opportunities (threats to your conventional business) are?

You will have an opportunity to view, discuss, and evaluate, these at the rebranded 2nd annual Electronic Systems Technologies Conference and Exhibition to be held at the IPC TechSummit in Raleigh, North Carolina October 28-30. Some of the topics presented and discussed at the original held in Las Vegas have already begun to move into the mainstream. Chaired once again by Intel’s Dr. Senol Pekin, this year’s event has already attracted key interconnect industry figures who will discuss trends, what matters to them, and new technologies.

It is also worth noting that Dr. Michael Osterman, director of CALCE at the University of Maryland will chair the 8th Annual Tin Whiskers Conference during TechSummit.

It’s a cut-and-paste world. One of my Korean business associates, a retired research engineer, says that Korea is a “Copy and Paste Technology” country. Korean companies buy the minimum order for state of the art equipment from Japanese companies and conduct a detailed tear down analysis. From this reverse “R&D,” they build their own equipment with minor modifications. There is no innovative idea in the new machines — the only difference is a much lower cost. The executive teams from Samsung Electronics recognize the lack of innovation from their engineering staff, and are encourage its R&D departments to generate new ideas. Unfortunately, nothing new has come from them over the last several years. One R&D director told me that he has more than 50 engineers with PhDs from universities in Japan and the US, but none of them can come up with any creative ideas. From the engineers view, one R&D manager grumbled that his department forwards many proposals to the executive managing teams, but none of them are ever accepted. The executive teams ask for accurate forecasts from potential products or ideas, but the R&D teams cannot accurately forecast the potential for a product that is not in the market. — Dominique N.

 

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Does Rising Nationalism Pose Threat to Electronics Supply Chain?

The amount of geopolitical discord around the world at present is stunning: Thailand, Vietnam, Korea and other major electronics manufacturing hubs are seeing a rise in nationalism and severe internal tension over how to address foreign pressure.

Thailand in May endured yet another military coup — its 19th since declaring independence from its monarchy in 1932. Some observers feel the military wants a permanent seat in the national parliament, a move that could hinder its democratic movement.

In Vietnam, citizens are outraged at what it feels is Chinese strong-arm tactics. Its Northern neighbor has provoked many Southeastern nations over the past few years, often by occupying seaborne territory that others had staked claims to in the past. (The Philippines have a similar complaint dating to 2012, when China evicted Philippine fishermen from their long-held fishing grounds.) Lately, Chinese oil rigs took up in Vietnamese waters, leading to riots at Fittec, Foxconn and elsewhere, where domestic workers took aim at their Chinese* employers.

Korea is losing business to Vietnam, aided in part by its own OEMs: Korea is now the largest investor there, pumping in nearly 23% of all outside investments in the first quarter this year. As Samsung relocates its cellphone manufacturing there, Vietnam is on track to produce 250 million handsets this year, versus 200 million in China and just 30 million in South Korea. As the linked article indicates, as of March 2014, Samsung Electronics subcontractors had invested an aggregate $2 billion in Vietnam. Meanwhile, while Samsung buys a reported 53% of its parts from Japan, South Koreans now view Japan as their second-leading military threat, next to North Korea, and resentment from World War II is rising once again.

Indonesia is suffering through a contested presidential election, one that involves an ex-general and the possibility of an overturned ballot result.

Japan, my friend Dr. Hayao Nakahara tells me, has essentially stopped investing in new manufacturing sites in China, with the only new developments minor capacity add-ons to existing plants. The two nations have been at odds over everything from possession of uninhabited islands in the East China Sea to a rehashing of wartime atrocities.

Southeast Asia is home to the bulk of the world’s electronics production, and holds the majority share of products built for the consumer, industrial/instrumentation, telecommunications, PC and peripherals end-markets (not to mention the vast majority of the raw materials and components supply). We’ve absorbed several of nature’s bullets of late — flooding in Thailand, the typhoon in Malaysia and of course the 2011 earthquake and subsequent tsunami in Japan. I am told that the media reports have exaggerated what’s happening on the ground in Southeast Asia, and that on a day-to-day basis little dissent is noticeable. That may be true, and to be sure, the self-inflicted disruptions have thus far been held to a minimum. Given the number of countries involved – unprecedented in recent times — and the enormity of what’s at stake, we can’t help but feel it will take some luck if the next supply-chain breakdown is only as bad than the last.

*Fittec is based in Hong Kong, Foxconn in Taiwan, but most employees and manufacturing for both companies are in China.

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Conflict Minerals, Meet US Sanctions

Here comes another layer of “conflict minerals” restrictions.

President Obama last week set the stage for expanded sanctions against the Democratic Republic of the Congo and vicinity’s militia-ravaged region. A new Executive Order specifies that sanctions are called for against “individuals and groups tied to militias involved in the illicit trade of natural resources from the region” of the Democratic Republic of the Congo or DRC. If that criteria doesn’t include conflict minerals, what does?

Penalties to companies and individuals that fail to adhere to the expanding sanctions can include:

  1. Fines of at least $250,000
  2. Fines twice the amount of the underlying transaction
  3. Criminal penalties of up to $1,000,000
  4. Imprisonment for up to 20 years

Other conduct that will trigger future US sanctions:

  1. Actions or policies that threaten the peace, security, or stability of the DRC
  2. Actions or policies that undermine democratic processes or institutions in the region (DRC)
  3. The targeting of women and children with acts of violence (including killing, maiming, torture, and rape or other sexual violence), abduction, forced displacement, or attacks on schools, hospitals, religious sites, or locations where civilians are seeking refuge, or through conduct that would constitute a serious abuse or violation of human rights or a violation of international humanitarian law
  4. The use or recruitment of children by armed groups or armed forces
  5. Obstructing the distribution of, or access to, humanitarian assistance
  6. Attacks against United Nations missions, international security presences, or other peacekeeping operations.

Earlier this month, ahead of the Executive Order, US and United Nations Security Council added a Ugandan rebel group, the Allied Democratic Forces, to the sanction lists for “targeting children in situations of armed conflict through rape, killing, abduction and forced displacement.”

As far as conflict minerals go, this is yet another reason to know thy product ingredients and to continue tracking conflict minerals for compliance.

Thanks to many sources for these updates, for this one in particular thanks to Christopher T. McClure, Crowe Horwath LLP.

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Demonstrating Zero Defects In SMT Production?

Folks, let’s see how Patty is doing at Ivy U …

Patty had to admit that she really liked being a professor at Ivy University. No, that wasn’t strong enough; she was ecstatic. The combination of the stimulating and collegial environment and the flexible schedule was terrific. She was able to play a little more golf and spend more time with Rob and the boys. 

In addition to developing a course on manufacturing processes, she was asked to teach an additional offering on statistics. Engineering enrollments had increased so much that another stats class was needed. Teaching stats gave her an opportunity to delve into topics she was interesting in learning more about, such as non-parametric analysis, cluster analysis, and numerous other statistical concepts.

She was also happy for Pete. As much as he enjoyed working with her at ACME, he, too, was thrilled to be at Ivy U. As a research associate, he spent a lot of time working with students on projects for their classes. He was surprised at how grateful the students were for his practical experience.

As Patty was thinking these pleasant thoughts in her office, suddenly Pete was at the door.

“Hey, Professor Coleman! The folks we left behind at ACME are being asked, forced really, to guarantee zero defects by examining a small sample size, say 20 samples,” Pete announced. Pete had stopped calling her “kiddo” and now teased her by calling her “Professor Coleman.”

“We both know that’s impossible. Tell me more,” Patty answered.

“Well, ACME just hired our favorite SMT engineer … after Hal Lindsay,” Pete responded.

“Oh, no! Not Reggie Peirpont,” groaned Patty.

Reggie was a well-meaning sort of chap who had some good ideas. But, his follow through was often sloppy and only touched the surface of what was needed from an engineering perspective. He was a very good salesman of his ideas and had a following in some SMT circles.

“What is he foisting on ACME?, Patty asked.

“A zero defect program,” Pete replied.

“Sounds like a worthy goal. But, let me guess, he has convinced everyone that they can demonstrate with 95% confidence they have zero defects by only sampling 20 units,” Patty said.

“Precisely,” Pete chuckled.

“I’ll contact Mike Madigan,” Patty said.

Patty had agreed to Mike’s request that she be available to consult for a year or so. And, he also made her promise to contact him if she knew they were doing something foolish.

Patty sent Mike an email with her concerns, and with some analysis. She suggested a teleconference.

Time passed quickly and, before they knew it, Patty and Pete were on a telecon with Madigan, Peirpont, and a few staff people.

Their discussion started with the good points of a zero defects program. On this topic, everyone was in agreement. Eventually, Madigan grew impatient.

“Peirpont! According to Coleman, your assessment that we only need to sample 20 units to demonstrate zero defects with 95% confidence is bull s__t.” Mike began, always getting quickly to the point.

Patty then said, “Let’s let Reggie explain his analysis.”

“Well it’s simple,” Reggie began. “All you have to do is recognize that 1 is 5% of 20, so if you sample 20 and don’t get a defect you can be 95% confident you have no defects,” he finished.

“Yikes,” Patty thought.

“Well, Coleman?” Madigan asked.

“That approach is not correct. A correct method is what I sent to Mike in an email” Patty answered.

“Before we begin the analysis, look at the photo I sent. The red bead is one bead in 2,000 white ones. Ask yourself how you could detect this one “defect” by sampling only 20 beads?” Patty said.

There was some murmuring and groaning, Patty could tell this visual really help to define the issue.

“OK, Patty. Please explain your analysis,” Mike asked.

“Let’s say that the defect level is 1 in a thousand. If I sample the first unit, the chance it is good is 0.999. What is that chance that the first two units would be good?” Patty began.

“0.999*0.999,” Pete answered.

“Correct!” Patty said.

“Let’s say I keep sampling until the likelihood that I have still found no defects is 0.05,” Patty went on.

“Let me take this one,” Madigan said.

“You now have 0.999^n = 0.05. So there is only a 0.05 chance you would not have found a defect if the defect rate is one in a thousand,” Madigan continued.

“So what could you say about the defect rate if you found no defects in n units? Patty asked.

“I got it! I got it!” Madigan shot back enthusiastically.

Patty was incredulous. Mike Madigan, CEO of multibillion dollar ACME Corp, was like a second grader excited to show the teacher he understood.

“You can say that the defect rate is 1 in a 1000 with a confidence of 1–0.05, or 95%,” Madigan said with excitement.

“Actually, you can say that the defect rate is 1 in a thousand or less,” Patty said.

“But we need to know n,” Madigan implored.

“Well, let’s solve for n with logarithms,” Patty suggested.

Groaning was heard over the telecon. No one likes logarithms!

Since their telecom was on GoToMeeting, Patty showed the solution:

n = log 0.05/log .999 = 2994.23

“Man! So we have to sample almost 3,000 units with no defects to demonstrate 1 defect per 1,000 or less?” Madigan asked with disappointment in his voice.

“Yes,” Patty responded.

She continued, “It ends up with a good rule of thumb. Since n is close to 3,000, let’s say that is the number we need to analyze. To demonstrate 1 in 10,000 defects or less, n is 30,000, one in a million or less, and n is 3 million.”

“So, n is 3 times 1 divided by the defect level you are trying to establish?” Madigan asked.

“Exactly,” Patty answered.

Patty wrote it on the PowerPoint slide:

To establish a certain defect level or less with 95% confidence, one must sample n units with no defects

n = 3 x 1/defect level

“That means to establish zero defects, we need an infinite sample,” Madigan sighed.

“Yep!” Patty replied.

“Peirpont! What do you have to say for yourself?” Madigan barked.

“Well, in the first case, Patty said 1 defect per thousand or less. It still could be zero defects,” Peirpont responded glumly.

Patty was going to respond, but Madigan beat her to it.

“But, you can’t prove it is zero. Only 1 in a thousand or less. So, to be conservative, we would say that the defect level would be 1 in a 1,000. That’s what is proved,” Madigan opined testily.

The meeting ended with Madigan expressing his thanks, an unusual thing for him. Peirpont said little else. It was clear he was probably going to get a talking to by Mike Madigan.

Patty was a little wistful after the meeting. She missed ACME and the folks there, even the occasionally cranky Mike Madigan. But every day she felt more like her home was at Ivy U.

Cheers,

Dr. Ron

Epilogue. As with all Patty and the Professor posts, this one is based on a true story. After sharing this concept with a colleague who had to get FDA approval for drug trials, she decided to ask statistician job applicants: “Do you think you could develop a sampling plan that could assure with 95% confidence that there were no defects in a population?” The last I talked to her, most job candidates had said yes.

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Alloy Density Calculator Generates Most Interest of All Blog Posts

Folks,

In the nearly 10 years that I have been blogging, I am continually surprised by the interest in a spreadsheet I created that calculates alloy densities.  I get about numerous inquiries a year on this topic.  We just renewed the link to the software, so I thought I would write a summary blog on its use and applicability.

First of all, the algorithm is intended for metals that form an alloy. Examples would be most solders and other metal systems where the metal atoms replace each other in the lattice. So, in addition to solders, copper and nickel would also work. The calculation assumes perfect mixing and that the sum of the initial volumes of the metals equals the total final volume. The correct formula for calculating densities is:

1/Da = x/D1 + y/D2 + z/D3

where

Da = density of final alloy

D1 = density of metal 1

x = mass fraction of metal 1

And the same for metals 2 and 3. 

This formula was derived in a past blog post. People are often surprised that the simple formula Da = xD1 + yD2 + zD3 is not correct.  The reason it is not correct is that density is inversely proportional to volume.  The error with this formula is discussed in another post.  The error, by using this formula, can be quite large. See the graph below for gold and copper. In some cases the error is more than 15%.

One example where the algorithm does not work would be for intermetallic compounds. The reason is that an intermetallic is a compound, not an alloy. Another example where the formula does not work is carbon in iron. The carbon atom is so small that it fits in between the iron atoms.

How accurate is the formula?  Work that I have performed with solder alloys suggests is it about 1-2% accurate. The accuracy can be affected by grain boundaries and the small amount of intermetallics that can form in some solder alloys.  An example is the small amount of  intermetallic “silver plate” (Ag3Sn) that can form in SAC alloys. I hope that many readers continue to find the density calculator useful.

Cheers,

Dr. Ron

Math musings. I read a fun book, The Joy of X. In the book, the author, Steven Strogatz, pointed out that the sum of consecutive odd numbers is always a perfect square. Try it: 1+3 = 4 = 2^2,  1+3+5 = 9 = 3^2 , 1+3+5+7 = 16 = 4^2, and so on.

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Panel Rails — What Are They?

I referred to “panel rails” in my blog about V-score panels, but I didn’t explain the “whats” and whys” of panel rails. You might find yourself asking “what are panel rails and why would I want to use them?”

Well, first of all, for our Full-Proto service, we don’t require panels or panel rails. We’ll take just about any old board that’s bigger than 0.75″ x 0.75″ and smaller than 14.5″ x 19.5″ and run it through our machines. For our short-run production service, we only require panelization for boards less than 16″ sq.

That being said, panel rails do have a purpose. They give the machines a spot to grab onto without coming close to components. They’re also a convenient place to put fiducials (more fiducial info here).

As you can see in the image below, the panels give a clear area for handling the panel.

Tab routed panel

There are two important things to note about this panel. First, look closely at the four outside corners. You can see the scoring for easy separation of the rails. This designer made sure that there isn’t any copper where the scores are. That’s the right way to do it. The V-Score blog shows a panel rail done the wrong way – with copper across the cut.

Next, this board has fiducials. Good. But, the fiducials are in a symmetrical pattern. Not so good. IPC-7351b-3-10 specifies a non-symmetrical pattern so that the board can only be processed in one orientation.

Duane Benson
Once I build a panel rail, now it’s done
Brother can you spare a diode

http://blog.screamingcircuits.com/

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How Far Should Sustainability ‘Standardization’ Go?

My longtime friend and industry colleague Pam Gordon blogged today about the role trade associations should play in driving the industry toward sustainability practices. In it, she writes

Associations will not necessarily push members to the next level of sustainability practices. But members can raise the baseline through their involvement and commitment — emphasizing that the industry’s continued profitability and continuity rests in good part on meeting customers’ increasing efficiency requirements, avoiding dependence on dwindling materials, and reducing costs through design-for-environment principles.

I agree with all that. But Gordon also mentions a colleague’s discussion of the possibility of trade groups offering certification in supply-chain sustainability, suggesting that those that do not are behind the curve. There, I’m very reluctant to concur.

I am a huge fan of standards, but I also recognize their limits. I view sustainability as an extension of innovation. And innovation is not something that can be standardized. Those companies that consistently adapt fastest to market demands are always the winners in the long run. I think the same will be true with design for recycling and reuse and other such initiatives. Companies will either pursue that course or not, but to add a layer of bureaucracy in the form of yet another pursuit of paper isn’t the way to go.

Pam writes that some associations help members raise their own sustainability goals above the level of current regulations by giving them workable frameworks, such as the codes of conduct from the Electronics Industry Citizenship Coalition. I have long felt the EICC’s code of conduct is a sham. Under Labor, for instance, the first rule is, “Participants are committed to uphold the human rights of workers, and to treat them with dignity and respect as understood by the international community.” Yet EICC members include Foxconn and Pegatron, which are routinely cited by watchdog groups for worker abuse. It may be a code, but its toothless.

Pam is tuned in to the industry and always makes her readers think. Her note that the industry lacks roadmaps for best practices in sustainability is dead on. A roadmap isn’t a certification, however, and that’s where I call on trade associations to draw the line.

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