Soldering Products

Folks,

The impetus for writing the Patty and the Professor series, in 2009,  <posts here>  <hardcopy book here> came from my observations that many assemblers were not very focused on productivity.  Productivity seemed to be an afterthought.  Since then little has changed.  This conclusion seems astounding, since all assemblers are in business to make a profit.

In light of this situation, I have developed 10 questions, valued at 10 points each, to help assemblers assess their profitability potential. If You are a printed circuit board assembler, take this quiz and see how you rate:

1. Although quality may be job 1, our company has a strong focus on productivity. At all levels everyone understands that, when the line is down, we are not making money.
2. We have a practice, understood by all, that if a line is down more than a specified amount of amount time, the line down situation is escalated through the management chain.
3. All of our operators, technicians, and engineers have been trained in procedures to assure the minimum amount of downtime.
4. We measure and graph our line uptime and other productivity metrics.  Everyone knows the approximate value of these metrics.
5. Our component placement machines are time balanced.
6. We use feeder racks and other preparation devices to prepare for the next job while the current job(s) are running.
7. A major consideration in the purchase of our assembly equipment is its effect on productivity, not the equipment’s cost alone.
8. A major consideration in the purchase of our assembly materials, such as solder paste, is its effect on productivity (e.g. poor paste response to pause would be a strong rejection criteria,) not the material’s cost alone.
9. We us productivity and cost metrics, such as non-material assembly per I/O assembled (NMAC/I/O), to track our performance.
10. We understand that sometimes an added expense, such as solder preforms, can actually reduce the total cost and increase productivity and profitability.

Ratings:

• World Class: ≥ 90
• Above Average: 75 - 89
• Average:  55 - 74
• Below Average: < 55

How did you do?  Let me know what you think. We hope to have this online soon.

Cheers,

Dr. Ron

PS:  Here is my golf score in a recent one man scramble. I was hoping to break 60 and it worked out.

Folks,

Some time ago I wrote a post, “In Search of Tin Whiskers,”  Michael responds below.  He makes some good points.

Dr. Ron, I'm responding to your  blog regarding tin whiskers. I actually have a failure analysis report I did a couple of years ago in which failure of our product was due to this issue and occurred on a part that came into RoHS compliance only 3 months prior.
 

I'm not sure that your question of identifying whisker issues in product that proper steps have been taken to mitigate the problem is a constructive one. The fact is that many of the component manufacturers from overseas jumped into compliance without any thought or regard to this issue thereby flooding the industry with components such as plagued my company. We have not had this issue since we've specified an alternate finish.

These whiskers are so delicate that most problems disappear when the technician starts to work on the failed unit and the problem never re-appears so it is written off as an anomaly, loose/bad connection and not investigated any further. It was only my own curiosity as to the number of "no problem found" failures of our keypads we had suddenly encountered that caused me to dig deeper and when I looked into the connector I was amazed at the crystal city staring back at me. I couldn't believe what I was seeing after all of these years.

After seeing this problem first hand I became, and am, quite convinced that there were and are people who will be losing life, limb, and property because this forced compliance with its risk was not given proper worldwide attention.

Michael.

A popular topic Re my blog is solder density calculations. Rhonda writes……

Hi Dr. Lasky,
I am a precious metals recycler and would very much appreciate your verifying the validity of an equation that approximates the Karat Value of various alloys of gold based on S.G. which I will call density or "D," and the Karat Value is "K." The equation is seems to hold relatively true even when the exact composition of the alloy is unknown, although the percent of error obviously will increase as density decreases. I would also appreciate not only verification but also more specific information on percent of error for densities below about 14 or 15 g/cc. Here is the equation:

K = 0.0089D^3 - 0.550D^2 + 12.5299D - 77.06

Thank you so much for whatever assistance you can provide.

Rhonda

These types of equations can only work for one alloying metal with the gold.  This one is only for copper.  It is also calibrated in Rhonda’s favor as it reads the karat level about 10% low.   I was able to determine this by using the Excel Solder Density worksheet that I developed. If the alloy was gold and lead, a 50% by weight gold (12 karat) would show as 15.7 karat with this equation and Rhonda would lose her shirt.

In response to my blog post on copper as the precursor to civilization, Harvey writes about pollution from early mining operations…..

Also interesting, early copper mining and processing led to the first examples of human induced environmental damage. There are documented sites in the Alps where copper processing by prehistoric peoples has left areas treeless to this day, due to heavy metal contamination.

Harvey

Mining and smelting were very tough businesses in ancient days.  In addition to pollution, many workers died from toxic fumes.

Dr. Ron

Do you ever have a need for a "low temperature" solder (meaning an alloy that melts at less than 175C)?

You may have delicate components that cannot withstand standard reflow temperatures, or maybe you are looking to reduce costs by lowering the reflow temperature, or you may be step soldering.  Whatever your reason, there are two unique metals that are used extensively in low temperature solder alloys.

The first one I am sure you can guess: Indium.  The other one is Bismuth. While these two elements are used extensively in the over 100 alloys available in the 50C to 175C range, they couldn't be more different from each other.

Indium is a very soft, malleable metal and remains so even at cryogenic temperatures. It melts at 156C.  Bismuth, on the other hand, is very brittle, even at room temperature, and melts at 271C.  But both lend themselves very nicely to solder alloys that melt below 175C.

Let's look at the two most common alloys in these families.

The two alloys:

• 52In 48Sn (Indalloy #1E) Melts at 118C
• 58Bi 42Sn (Indalloy #281) Melts at 138C

What they have in common are:

• Both are lead-free
• Both are tin-based
• Both are eutectic (liquidus and solidus temperatures are the same, with no plastic range)
• Both can be made into a wide variety of solder forms and can be used in low temperature applications

But the indium-based alloy will give you better compensation of coefficient of thermal expansion (CTE) mismatch than the bismuth alloy.  The bismuth alloy has greater tensile strength but has a lower shear strength than the indium alloy and is generally not recommended in applications where the product has potential to be dropped (like cell phones).  The indium alloy will give you greater thermal conductivity than the bismuth, as well.  The bismuth will give you a cost advantage.

So, which alloy do you use?  Well, that depends on the metallizations you are working with and the environment in which your final product will be operating. For example, if you are soldering to two different surfaces that expand at different rates, then you will want to go with the indium alloy - to keep your solder joints from cracking.  But, there are a lot more considerations when choosing a low temperature solder, and we can help you sort through them.  Check out our Low Temperature Solder page on the web or contact us at AskUs@indium.com or contact me directly at cgowans@indium.com and we can answer your questions or put you in touch with one of our local experts to review your entire process for the best solution.

Let us help!

Carol Gowans

SMT: A Story of Solder Paste Printing Speed

近期我们有一个客户在解决一个和锡膏、芯片、工艺流程等相关的不良率问题。这是一款十分热门的电子消费类产品，在中国的两个主要加工厂量产。

我们公司十分积极帮助客户探讨最优的解决方案，除了及时送样品，我们的技术团队和销售团队还经常拜访客户，提供试样现场技术支持等。但是让我们很吃惊的一点是，客户在做各种试样测试时，锡膏的印刷速度居然是25mm/sec，这是行业里我见过的最低的印刷速度，虽然美国很多中小 加工厂都在用这个速度，因为他们的最终产品是高精尖的军用、航天、医疗器械等，数量不多，而且印刷速度不是瓶颈。

但是在中国或是很多亚洲国家生产的电子消费类产品 (consumer electronics),都是 low mix high volume 的大规模量产，每一条SMT线就像一台印刷钞票的机器，越短的 cycle time, 就能生产处越多的产品，那就更有更高的生产率（high productivity）。印刷速度有时候是瓶颈，所以在亚洲的加工厂，一般印刷速度比较快。

就拿这个客户在中国的两个加工厂来说，印刷速度在 50mm/sec到120mm/sec之间。 也就是说在这个印刷速度的条件下（虽然这只是条件之一）出现了问题……不同的印刷速度，很多时候会影响到锡膏的性能，因为印刷速度和压力能够影响到 shear force and shear speed，这些都是下锡量多少的重要决定因素。而下锡量多少，对很多锡膏性能表现的好坏都会起到决定性的作用，特别是客户现在在研究的不良率。

Musings on Metals: Copper

It could be argued that civilization began with the smelting of copper.  Although thousands of years before, humans fired clay to make figurines and containers, smelting required several non-obvious steps.  After all, the firing of clay, at some level, can be accomplished by simply dropping clay into a fire.

To smelt copper, our ancestors had to:

1. Take malachite (see photo) or another copper ore, grind it up or break it into small pieces
2. Mix the ground malachite with carbon
3. Heat the mixture in a vessel to 1,085^oC. 

Malachite Ore

Achieving this temperature with a wood fire is, to me, astounding.  Think about those days when you are grilling some burgers.  You leave the grill on after the burgers are done, to burn off the grease.  You come back 20 minutes later and the grill is at 500^oF.  You can feel the heat.  Even touching the knob to turn the gas off is intimidating, as the heat drives you back.  This temperature, 500^oF, is only 260^oC!  The ancients reaching 1,085^oC with wood and bellows is, indeed, impressive. By the way, a good rule of thumb to convert degrees C to degrees F from 100^oC to 1,500⁰C is that 2XC=F, this fast approximation is accurate to about 10% in this range.

The confluence of the three procedures is not only non-intuitive, but think how many times the smelter of old could only reach 900^oC and failed.  I have argued that if copper melted at 1,200^oC or so, civilization would have never gotten started.  This temperature is perhaps a little too high to reach with a wood fire.  The smelting of copper encouraged investigations into other metals, eventually resulting in the discovery of the processing of iron, an even less intuitive process than smelting copper.  So, I believe that the success with copper was necessary to the production of steel. 

Copper smelting became an industry that encouraged permanent settlements and stimulated trade, which encouraged writing and ciphering.  An effective copper smelter would likely keep secret some of his craft as he wanted a competitive advantage.  He could make more by smelting copper than doing anything else, so he almost certainly was an early specialist.

Considering all of this, I believe that without the discovery of copper smelting, we might still be living in huts or teepees, using stone tools, and living a nomadic existence without commerce, writing, or mathematics.  Examples to support this thesis are the state of native peoples in the Americas in the 1400s.  These native peoples had never learned to smelt metals and hence also lacked the follow-on aspects of civilization mentioned above.

Today, copper is a foundation material for electronics, given its excellent electrical conductivity, second only to silver.  Copper’s ductility likely aids in the formation of PWB traces and plated through-holes in that it resists cracking.

Additionally, copper's ability to form an electrical and mechanical bond with solder is another trait that makes it a winner as an electrically-conductive assembly material in modern electronics.

Copper has been used for more than 10 millennia, but, as with most metals, 90 to 95% of it has been mined since 1900.  About 15,000,000 metric tons (MT) are used each year, third to aluminum’s   22,000,000 MT and steel’s unequaled 1,000,000,000 MT.

In the next installment, we will discuss tin and how it forms an intermetallic with copper during soldering.  Thus making solder paste, solder wire, and solder preforms critical components of electronics assembly.

 Cheers,

Dr. Ron

Folks,

One of the nice aspects of being a Professor at Dartmouth is teaching a course like ENGS 1: The Technology of Everyday Things.  This course is designed for non-engineering students and fills a technology and applied science requirement for them.  In the course, we cover the technology of the automobile, mobile phone, GPS, DVD players, the personal computer, etc.

This year, I purchased an iPad 2 and an Amazon Kindle Fire and added them to the topics.  I had three basic goals in this effort:

1. Discuss how they work
2. Compare them
3. Answer the question, “Will they replace my personal computer?”

So this week, instead of discussing solder paste, cost of ownership, solder preforms, or productivity, let’s see what I learned.

I did this analysis with two of my graduate students and reviewed the basic conclusions with Dartmouth IT staff and students in the class.  Here is a summary:

The iPad is a terrific device for organizing and consuming content such as videos, music, photographs, and, perhaps most importantly, games.  It is extremely intuitive.  My four, five and six year old grandchildren use it for games with no coaching.   With the iCloud, content can be organized and stored very simply.

However, for creating verbal or mathematical content, it is not intuitive or simple.  As an example,  assume you have a letter or paper from a colleague on a USB memory stick that you need to edit.  Apple so controls the “experience” of the iPad that you cannot load anything from a memory stick or any other device, like your PC, onto it.  You must send an email or load the content into iCloud.  The recommended software (or apps) for word processing, spreadsheets, or presentations for the iPad will work with MS Office, but I didn’t find the apps that great.  Saving and filing documents is also not that straightforward.  When I tried to create letters, papers, spreadsheets, or presentations on my iPad 2, I found myself longing for my laptop. I’m not saying it can’t be done, I’m just saying it wasn’t easy for me.  An external keyboard (about $70) makes data entry much easier. 

The Amazon Kindle Fire is only about 25-35% of the cost of an iPad.  In my opinion, the Android software is pretty good.  For consuming content, such as movies, books, photos, etc. the Fire is very good, but not quite as good as the iPad.  I don’t do games enough to make a comment. (Sometimes I feel as though I am the only one in the world who does not play Angry Birds.) For verbal and numeric content creation, the Fire makes working with MS Office documents easier.  It is also easy to store and load documents from a PC with a USB connection.

Both devices are beating the rest of the competition with their seamless connection to their respective stores.  I think this advantage that Apple and Amazon have over other devices has been understated. I believe Amazon Prime is a strong reason to consider the Kindle Fire.  In addition to free two-day shipping for purchases, members get many free videos and have access to a free lending library.

Steve Job’s said it best when he announced the iPad.  Quoted in Walter Isaacson’s outstanding  biography of Jobs, he said something like, “We have the iMac and we have the iPhone, now we have something in between.”  I think that is a fair summary.   The portability of tablets can make them ideal for passing family photos around, or for police to have a larger than mobile phone photo of a suspect to share with colleagues and witnesses.  Tablets can be stored in a suitcase or briefcase when going through airport security, a definite advantage.  But they are not a replacement for the full functionality of a PC.

The higher resolution of the iPad 3 enables viewing x-rays and CT scans and, of course, HD video.  The 10 hour battery life frees one from needing to have a power cord during the day, so it could be beneficial in meetings.  However, I found the Penultimate app, which allows writing on the screen, not that usable.  It was harder to get neat writing than with pen and paper, and the words were too large.  See the image.  The documents formed would (again!) have to be emailed to get them from the iPad to another device.  It would make more sense, to me, to take notes on paper and scan the paper into a PDF. Modern scanners make this act a snap. Apple makes it almost a necessity.

In summary, for a user like me who creates papers, blog posts, Excel® spreadsheets and PowerPoint® presentations, a tablet is a weak substitute for a laptop.  For consuming content like videos, books, music, and photos, or for playing games, they are tough to beat.

Which of the two do I use the most?  The Kindle Fire, mostly due to the connection to the Amazon store for books and free videos from Amazon Prime.  I think this device, at a fraction of the cost of an iPad3, may be more of a threat to the iPad than many people think.

I'd like to hear your thoughts and opinions. Please comment!

Cheers,

Dr. Ron

Folks,

Let’s look in on Patty and Pete and see how they are handling Rex “The Torrent.”

Patty wanted to give Pete a little more exposure so she nodded to him to chime in.

“It is true that Pinnacle’s line cost only 70% of Optoplace’s line and it does have a lower ‘cost of ownership’ in that it costs less to own, but we lose our shirt because of its 6 hours per week less uptime,” Pete began.

Torant stormed in, “There ain’t no way that 6 hours a week can make up for 30% savings in cost of ownership. We must be talking about over $600,000 dollars difference in capital cost.”

Patty heard this comment and wondered why people that make poor arguments need to add bad grammar, too.

“Torant makes a good point Pete,” Madigan quickly interjected.

“Actually it is $660K in additional initial capital investment per line, plus about $40K a year in service for the higher profit potential line,” Pete responded with a smile.

“I told you so,” Torant said excitedly.

At this comment Pete put up a PowerPoint® slide that showed the resulting comparison:

Pete explained, “The average of 6 hours/week of increased uptime in our typical 3 shift operation results in the additional production of more than 22,000 units per line per year for the higher profit potential line.  Each line producing on average more than $340,000 more profit.”

“But that’s not as much as the additional $660K cost of the line,” Torant countered.

“The extra capital cost is included in the calculation,” Pete calmly replied.

“Well, Torant, that’s one you lost,” Mike Madigan said in a way that indicated that discussion on this point was finished.

Torant looked temporarily defeated, but he recovered quickly. “What about the solder paste? Ultima costs $0.02/gram less than the ElectroMaterials paste,” Torant challenged.

“That’s true,” said Patty. “But we have to stir it out of the jar for it to print well, and it has poor response to pause.”

Torant wouldn’t let her finish, “But that can’t make up for two cents per gram,” he snarled.

“Not true,” Patty snapped back. “Every time the line is down for a short time we have to wipe the first print because the transfer efficiency is so poor.  We lose an hour a week of production time.  In addition, when we are printing a lot, the paste shear thins and we have to replace it with fresh paste.  We actually pay more for the Ultima paste because we scrap so much.  However, the lost time is what hurts the most financially.”

“Only one hour per week!" Torant screamed. “I spend more time than that on smoke breaks. One hour per week can’t possibly make a big difference.”

Patty rolled her eyes and then displayed another slide that showed the profit comparison.

“This slide shows that by using the Ultima paste we lose over 3,700 units of production and over $140K of profit per year per line in that 1 hour hour per week.  One hour per week is 52 hours per year, let's not forget” Patty responded.

At this, Torant slammed his fist on the table, packed up his briefcase, and literally left the room in, well.... a torrent.

Patty, Pete, Madigan, and Sam just looked at each other.

“Well, maybe we won’t have to put up with him for awhile,” Pete said smiling.

“Nice work Patty and Pete", Madigan said. "Let’s develop an implementation plan phasing everything in you recommended as soon as is practical.”

Patty was always surprised when Madigan showed a little warmth by calling her and Pete by their first names.

“Sure thing, Mike,” she answered.  It was the first time she ever called him by his given name.

“Oh, and I guess it was a good thing we didn’t get around to discussing solder preforms,” Patty teased. "The ones Torant sells have too much flux and they gum up the pick & place nozzles.”

With that comment, they all chuckled and took it as a key that the meeting was over.

Cheers,

Dr. Ron

March 13th is the 78th anniversary of the founding of Indium Corporation.  Dr. William S. Murray, J. Robert Dyer JR, and Daniel Gray combined to create a company that was, in 1934, on the cutting edge of technology at the time - and that still is today.

Although some of the initial attempts to utilize indium were decidedly low-tech (plating of silverware and use in gold dental alloys), the first real breakthrough came when Mr. Dyer developed the process to indium-plate aircraft engine bearings to make them last longer.  Today our indium metal is in thermal interface materials, batteries, medical devices, aerospace devices, solar panels, flat panel displays. Of course, the full range of Indium Corporation products (including materials that contain no indium at all) can be found in a myriad of electronic devices.  We hold a wide variety of patents and have conducted endless tests and experiments including some aboard the space shuttle.

In between we have been featured in the Wall Street Journal, Business Week and many other technology journals and received awards for our technical expertise and our customer service.

Our original founders were very "hands on" in their approach to developing their company and we still follow that approach today.  Our sales and technical staff, locally located around the world, are as comfortable in a lab or on a production floor as they are presenting a technical paper.

Contact us at AskUs@indium.com to utilize our expertise and let us help you with your challenge.

Shown here is an original bottle of indium solder preforms with a hand written label.  Today we have a variety of packaging options with printed labels and bar codes to fit your product and application.

Carol Gowans cgowans@indium.com

Folks,

Patty is getting ready for her meeting on "Copy Exactly" with Mike Madigan.......

It was after 6:30 PM and Patty was just arriving home.  Since Patty was working late, Rob had agreed to make his signature dish, crispy macaroni and cheese.  Patty and Pete had just finished their project to develop a copy exactly strategy for ACME.  They would present it tomorrow to CEO Mike Madigan.  The local GM, Sam Watkins, would be there too.  Technically Mike was her boss in her Senior VP position, but since she had an office at the ACME facility in Exeter, NH, she reported to Sam - “dotted line.”  Patty had been working late for weeks on this project and was glad that the greatest portion of the work was over.

As she opened the door to her house, her twin 2 year old boys ran up to her in their excitement to see their mom and nearly knocked her over.  She tussled with them for a few minutes and then went to give Rob a hug.  He had the dinner on the table and they all quickly sat down.  Rob and Patty had a "no technology" rule at meals…..no mobile phones, iPads etc.  Meal time was family time.  After discussing the events of the day, Rob’s face lit up.

“I found out today that there is something we look at more than anything else,” Rob stated.

“OK, OK, let me guess,” Patty replied.

After a number of tries, she hadn’t gotten it.

Alright, I give up, Patty said with playful exasperation.

“Indium, or really Indium Tin Oxide (ITO), it is a transparent conductor of electricity.  We look through it when we look at our computer, tablet or mobile phone screens.  Think about it, for most of us we probably look through ITO for 8 to 10 hours a day.  It’s like we have a love affair with the stuff,” Rob explained.

Patty almost choked on some of the mac and cheese on the last comment.

“Why have you become such an expert on this stuff?” Patty asked.

“Well, you remember that ACME may go into component assembly? Sam asked me to look into indium thermal interface material (TIM)  for some of the component packages that need to dissipate a lot of heat,” Rob answered.

Patty knew a little bit about TIMs, but not about ITO.

“But why did you learn about ITO?” she asked.

“Sam is worried that Indium supplies may not be enough to satisfy TIM requirements, so he asked me to look into it,” Rob answered.

“What is the conclusion? Patty asked.

“Well, Indium is about as common in the earth’s crust as silver, but a little more difficult to extract.  This probably gives it the reputation of being rare.  Fortunately for me a recent analysis was performed that showed that the indium supply will be more than adequate for the next 75 years ,” Rob said.

Rob went on, “Indium is a very interesting material, it is one of the few materials that wets glass, so it enables metal sealing to glass.  It was only discovered in 1863 and it wasn’t until the 1930s that the first practical use for indium was discovered: aircraft bearing lubrication.  In a sense, it could be argued that it is one of the materials of the future, as we are just now learning about its potential.”

While he was talking, Rob reached into his backpack and took something out.

“Look at this, or rather listen,” Rob said.

With that, he took a thin bar of metal and bent it. A crackling sound came from the metal.  Patty was fascinated.

“What was that?" she asked.

“When a thin bar of indium is bent, it gives off a sound.  It is called “Indium Cry.”  The salesman for the TIMs we are using let me borrow it for a presentation I am giving to Sam Watkins next week,” Rob answered.

Dinner was soon finished and Patty had to get the boys to bed after playing with them for awhile.  Today was Spanish day and all of their discussions were in that language.  Another day was Mandarin Chinese day.  The boys already understood the three languages spoken at home.

A few hours later, Patty lay in bed - energized by the thought of her meeting tomorrow.

When she woke up the next day, she exercised at home, ate breakfast, and took the boys to day care.  See arrived at the office 30 minutes before the big meeting.  After checking emails, she went to the conference room where the meeting would be held, to set up her computer.  At precisely 8AM, Mike Madigan and Sam Watkins arrived.

“OK Coleman, let’s get this show on the road,” Madigan commanded.

“Since our last meeting we have analyzed assembly equipment and materials to determine which ones would be best for a copy exactly strategy,” Patty began.

She then showed her third slide and spoke to it.

“The winner for component placement equipment is Optoplace, as are their stencil printer and reflow ovens.  Exactotest makes the winning testers and ElectoMaterials the best solder paste and solder preforms,” Patty went on.

“Can you explain your methodology?” Sam asked.

“We looked at what The Professor calls ‘Profit Potential,’ simply the equipment and material that gives the most profit, assuming you are running a well tuned organization.  Fortunately, since ACME has 80 assembly lines we were able to get real process performance data on all of the major machines available, ” Patty answered.

“You answer seems a little evasive, why didn’t you use ‘Cost of Ownership?’” Madigan challenged.

“Some machines cost less to own, but they are down more for assists and when they need repair, we have to wait longer for the repair man.  From what The Professor taught us, uptime is very important. Anything that hurts uptime, like a late repairman or a machine that needs more assist time, will hurt profits.  The same is true for materials like solder paste.  If they cost less, but result in line downtime for response to pause issues or some other fault, they hurt profitability.” Patty responded.

Just then Sam’s administrative assistant, Clare Perkins opened the door.

“As you requested Mr. Madigan, your guest is joining the meeting,” Clare said.

“Well Torant, looks like Coleman said you lost,” Madigan said to the new arrival.

Upon seeing Rex Torant, Patty became a little unsettled and Pete turned his famous crimson red.  Patty and Pete called him “Rex the Torrent” as he spoke so rapidly when trying to sell them something.  Both found this manufacturer’s “rep” annoying.

“Everyone, I invited Rex to the meeting.  We met at the airport last night and started chatting.  He assured me that his Pinnacle equipment line and Ultima solder paste would be the winners today since they have the lowest cost of ownership,” Madigan explained.

Torant saw the slide announce Optoplace, Exactotest and ElectoMaterials as the winners.

“My products are just as reliable and cost 30% a year less to own,” Torant fumed at Patty.

Patty had not anticipated Torant’s attendance at the meeting but had prepared for this type of question.

“Mr. Torant is correct, however Pinnacle’s component placement machines have more downtime for machine assists and, when the equipment does malfunction, it is down for repairs on average for 28 hrs, whereas Optoplace is only down for 14 hrs.  All in all, Optoplace machines are up 6 hrs more a week in a two shift operation,” Patty calmly responded.

Will Patty’s arguments win the day?  Can a 30% more expensive machine really have more “Profit Potential?”  And what about the solder paste and materials?  Stay tuned.

Cheers,

Dr. Ron

image

I recently had a chance to catch up with a friend and colleague, Jasbir Bath. If you’ve spent time in the electronics assembly industry you have most likely met him, heard of him, or used an industry standard that he has helped create. Jasbir is a founding member of The Solar Engineering & Manufacturing Association,  SEMA. Who better to talk to about a new association than a founding member?

Jim: The Solar Engineering and Manufacturing Association (SEMA) is a relatively new association for engineers in the solar industry. Can you tell me a little about why it was created?

Jasbir: It was created about 2 years ago based on a need by the solar engineering/manufacturing base to address issues in the industry. There are many organizations in the solar industry but none are wholly dedicated to the engineering/manufacturing profession. SEMA was formed to address this need. We are working to address a number of gaps in the industry highlighted by the SEMA membership which include Education, Training, Standards, Reliability, Cost Reduction and Technology Gaps.

SEMA is a group of engineers, manufacturers and related professionals in the solar manufacturing and related disciplines who volunteer to conduct activities in the organization. The projects/programs we work on are driven by the active involvement of the membership.

Further details on SEMA and what we do can be found on the SEMA website at www.solar-ema.org

Our membership costs are low as we are not an organization looking to make a profit but to encourage participation and work to advance the solar industry as well as advancing education, training and collaboration within the solar manufacturing industries.

Jim: I heard there’s a new solar conference coming up? Can you tell me what makes this one different than all the other solar conferences we go to throughout the year?

Jasbir:  SEMA is collaborating with SMTA (Surface Mount Technology Association) to develop a conference meant for engineers and managers in the field to look at the areas of concern in the industry and develop ways to address them. We don’t see a similar conference to this which covers such a broad range of subjects which is specifically focused to address the needs of the industry. The program will consist of presentations and discussion covering the reliability testing of PV Modules covering gaps and where future work needs to be done. It will highlight various reliability programs being done in the industry with an assessment of current and evolving standards in manufacturing and reliability.

We are pleased to have a great line up of speakers and presentations. SEMA will present its reliability report assessing the reliability of PV modules at the conference. We will also have speakers from UL, IPC and NREL to discuss international solar standards together with a discussion of the work of the PV QA Task Force forum from leaders in that Task Force group. Areas covered will include temperature, humidity, voltage, mechanical and UV testing of PV modules and diode testing.

We will also have presentations on the reliability of microinverters/inverters and future trends from organizations including Sandia. PV Manufacturing Issues will be discussed by companies including Flextronics. The Global Solar Outlook will be reviewed by companies including Navigant, Custer Consulting and Prismark. Finally we will review general PV Module hazardous issues such as Electrical and Fire Concerns and well as Module Warranty/ Traceability Issues.

In addition we have industry leading training courses at the event on PV Module Manufacturing and Troubleshooting and PV Standards in addition to exhibitions.

The SEMA/SMTA Conference, Training Courses and Exhibition are from March 21^st to 23^rd at the Fairmont Hotel in San Jose. Further details on the program and sign up can be found at http://www.smta.org/solar/

Jim: One more question for you Jasbir. I know from working with you in different associations, that you are personally invested and involved in the future of module assembly. What attracted you to this field, and what keeps you interested in it?

Jasbir: I have been involved previously in the electronics manufacturing industry during the transition from tin-lead to lead-free soldering due to environmental legislation requirements. This was a challenge being involved in both from a technical and logistics perspective, but it was also fun as you saw the rewards of your efforts when the transition occurred successfully.

The solar/PV industry has challenges in addressing how to produce good quality and reliable products at lower cost, and it gives me the opportunity to try to make a positive contribution in an evolving expanding industry.

Jasbir and I look forward to seeing you in San Jose!

~Jim

Folks,

A reader writes:

My company makes an electronic product that requires a 40 year shelf life. We assemble with tin-lead solder on FR-4 PWBs. The product is to replace older technology (i.e. 1960-70s), but has some newer components such as BGAs, SOICs, and PQFPs. The product will be stored in dry nitrogen at 70F.  We take great care in manufacturing, by cleaning, inspecting, and testing the end product.

My question is, do you know of any studies that would discuss the reliability of products stored or in use for 40 years?

My sense is that our reader will be successful, but his question is profound and hard to answer with confidence. The military would like their electronics to perform for that long, but realistically much of it is replaced every ten years or so. If you look at something like the B-52 bomber, which debuted in 1952, the electronics have been upgraded regularly. So there isn’t as much 40 year electronics experience as one might think. An exception being the IBM AP-101 computer. This computer was kept in service for over 30 years, because it served its function and had survived the rigorous and expensive military qualification testing.

However, anecdotal data might support optimism for 40 year shelf life. In a class I teach at Dartmouth, The Technology of Everyday Things, I have sought out some old transistor radios from the late 1960s and early 70s to show the class how this old technology works. Anytime I have every found an old device like this, they always work, unless the batteries have leaked inside the radio.

This question raises an interesting thought. Although those of us in electronic assembly are concerned with tin-lead and lead-free solder joint life, what about the modern devices inside the components? Forty years is a long time. How will the 3D-22 nanometer copper circuit lines in a modern microprocessor hold up over this amount of time? These circuit lines lines are so fine that the 22 nanometer width is only about 70 atoms.  In addition, copper integrated circuits are still a relatively new technology. I’m sure much accelerated life testing has been done on such circuits, but would such testing confirm 40 years of shelf or service life?

I would appreciate any thoughts that readers have on these questions.

Cheers,

Dr. Ron

Folks,

Patty arrived at work an hour early to prepare for her meeting with ACME CEO Mike Madigan. Nineteen days ago, he had asked her to develop an electronics assembly metric that would correlate with profitability. This metric would, in turn, be able to help pinpoint opportunities for improvement. He gave her 3 weeks, so she was two days early. Mike was in town to meet with Sam Watkins, the local plant manager, so he ordered that they meet. 

Patty had quickly identified non-material assembly cost per I/O (NMAC/I/O) as a good metric candidate. She went to five of ACME’s plants and, after a day or two at each one, she collected all of the data she needed to prove her point. Rob helped her by writing an Excel® macro that would calculate NMAC/I/O and plot it versus profitability. The correlation coefficient was an outstanding 0.983.

While visiting the five factories, she tried to learn why those that had a poor NMAC/I/O were performing poorly. After a little checking, she and Pete discovered that the poor performing sites typically had lines that were not time balanced, had slow component placement machines, and occasionally had very slow printers or solder paste with poor response to pause. There was even one plant that was using a full wave solder process, when only 8 solder preforms would have done the job in the reflow process. None of these “problems” would show up if you were only tracking line uptime. In light of this situation, she also developed a plan to use NMAC/I/O to identify and implement opportunities for improvement.

As Patty headed toward Sam’s office, Sam’s administrative assistant invited Patty into the conference room to allow Patty to get her laptop set up. Just as she finished setting up and her Powerpoint® presentation was on the screen, Sam and Mike walked in.

“Coleman, we’re counting on you to take us to the next level,” Mike said a little gruffly, so let’s get this show going.”

Patty looked at Sam and could tell that Sam was uncomfortable with his boss’s abrupt demeanor.

“I performed quite a bit of research and concluded that non material assembly cost per I/O is the best metric,” Patty started.

“That’s great Coleman, but what the hell is non material whatever you said,” Madigan interrupted.

Patty’s cell phone vibrated, but she ignored it.

“Non material assembly cost per I/O is the total cost of running a factory less the components, hardware, and PWBs used. Some people call this the conversion cost,” Patty answered.

“If you think about it, it is almost obvious that this is the best metric,” Patty went on, “it measures all of the non material cost divided by how much we produce.”

“I get it,” said Sam, “we are producing I/Os or solder joints, we measure the total cost to make solder joints and divide by the number of solder joints. It’s that simple.”

“Precisely,” Patty responded.

“I understand now, why uptime alone wasn’t a complete metric. You can be up and running, but be doing it inefficiently,” Mike said with a rare smile on his face.

Patty’s cell phone vibrated again.

“Exactly,” Patty commented.

“OK, so we are going to measure NMAC/I/O,” Mike commanded, “How does it correlate to profit?” He finished.

“It is nearly perfect,” Patty said.

They continued their discussions and reviewed Patty’s plan to improve productivity at the sites with a high NMAC/I/O. Patty would take the lead on this effort.

As Patty got up to leave, Mike commanded, “Oh, and Coleman, find out why so few people use NMAC/I/O.”

Patty thought this was something to discuss with the Professor.

As Patty walked out of Sam’s office, Clare Perkins, Sam’s Admin stopped her.

“Ms. Coleman, your mother-in-law called, Rob has been taken to the hospital,” Clare said.

Cheers,
Dr. Ron

Folks,

I thought I would post a few short thoughts as the new year begins. Here it goes:

1.    A billion hours ago the stone-age was the future, a billion minutes ago Caesar ruled Rome, a billion seconds ago Jimmy Carter was President, a billion passives ago you took your last break (about 4 hours ago). As exciting as the latest quad core microprocessor is, the largest number of components that we assemble is passives, approaching two trillion per year. That is about 6 billion a day. If you lined up all of the 7 billion people in the world, each year you could give every man, woman and child several hundred passives from all of the passives that are produced. If two trillion passives (assume 0402s) were lined up end to end they would circle the earth 50 times!

2.    Schools in Indiana are no longer required to teach cursive writing. Key board skills are considered more important.  Yikes! I’m all for keyboard skills, but I want my grandkids to be able to write in cursive. If not, how do they write their names? Are we less than a generation away from people writing their names as an “X?”

3.    Thoughts on lead-free solder reliability in long term mission critical environments from a NASA study:

        “Test vehicles assembled with lead-free materials (notably tin-silver-copper) exhibited lower reliability under some test conditions.”

Some people would respond to this statement by saying, “I told you that lead-free solder was no good.” However, another way of stating the results would be, “Lead-free solder performed better in more tests than tin-lead solder did.” The ratio, by my count, was about 5 to 3 in favor of lead-free. However, I agree that lead-free is not ready for mission critical (>20-year) service life. The main reason being that, in some cases, when lead-free solder joints failed in these types of studies, the results were much, much worse than tin-lead solder joints. These failure modes need to be understood and addressed. In addition, tin whiskers and pad cratering are looming problems in these, mission critical, long service life quadrant D applications as discussed in the Navy's Manhattan Project (http://www.navyb2pcoe.org/pdf/LFEMP_book.pdf).

4.    SACM has arrived. SACM is a SAC105 alloy that is doped with manganese. Work performed on SACM by Liu, Lee, et al was reported in a May 2009 ECTC paper, Achieving High Reliability Low Cost Lead-Free SAC Solder Joints Via Mn Or Ce Doping. The thorough testing reported in this paper suggests that SACM has promise as a material candidate for quadrant D applications mentioned in #3. In explaining the superior performance of this material the authors state:

“The mechanism for high drop performance and high thermal cycling reliability can be attributed to a stabilized microstructure, with uniform distribution of fine IMC particles, presumably through the inclusion of Mn or Ce in the IMC.”

We have had to wait awhile for this material to become commercially available as it is a challenge to manufacture doped solders like this in large quantities.  I think this paper should be on you "must read" list.

5.   I had not planned on reading Steve Job’s biography , as I thought I knew quite a bit about him from reading recent articles in Forbes, Fortune and Business Week. But I went ahead and downloaded it to my Kindle anyway. This work by Walter Isaacson is a masterpiece. To share one tidbit from it that relates to those of us in electronic assembly: 

"In almost all cases electrical engineers first design the circuits that perform the functions of some device like a mobile phone or tablet. Mechanical Engineers are then left to fit the circuits into the “box.” (Hence MEs are often called “box stuffers” by EEs). Jobs completely changed this approach. He told the engineering team how he wanted the product to look and function first, then they had to determine how to make it work that way. I’m convinced that only through this approach are the revolutionary design concepts that Jobs and Apple came up with possible."

The book also points out his many flaws (e.g. Jobs would regularly park in handicap spots, the author reports several times that Jobs just didn’t think the rules applied to him, etc.). Another interesting thought (read it and see if you agree with me) that if Steve was not Paul Jobs' adopted son, Apple would have never happened.

Cheers,

Dr. Ron

Folks,

I’m taking a few moments from Wassail Weekend , held annually in my village, Woodstock VT, “The prettiest small town in America”, to write a post about last week’s workshops at ACI.

Indium colleague Ed Briggs and I gave a 3 hour presentation on “Lead-Free Assembly for High Yields and Reliability.” I think Ed’s analysis of “graping” and the “head-in-pillow” defect is the best around. 

There was quite a bit of discussion on the challenges faced by solder paste flux in the new world of lead-free solder paste and miniaturized components (i.e. very small solder paste deposits.) One of the hottest topics was nitrogen and lead-free SMT assembly. There seemed to be uniform agreement that solder paste users should be able to demand that their lead-free solder paste perform well with any PWB pad finish (e.g. OSP Immersion silver, electroless nickel gold, etc.) without the use of nitrogen. Not only does using nitrogen cost money, but it will usually make tombstoning worse. However, in the opinion of most people, nitrogen is a must for wave soldering and, since it minimizes dross development, it likely pays for itself.

After Ed and I finished, Fred Dimock, of BTU, gave one of the best talks I have ever experienced on reflow soldering. He discussed thermal profiling in detail, including the importance of assuring that thermocouples are not oxidized (when oxidized they lose accuracy). He also discussed a reflow oven design that minimizes temperature overshoot during heating, and undershoot when the heater is off. Understanding these topics is critical with the tight temperature control that many lead-free assemblers face.

Fred Verdi of ACI finished the meeting with an excellent presentation on “Pb-free Electronics for Aerospace and Defense.” Fred’s talk discussed the work that went into the “Manhattan Project.” A free download of the entire project report is available.

There appears to be agreement that acceptable lead-free reliability has been established for consumer products with lifetimes of 5 years or so, but not for military/aerospace electronics where lifetimes can be up to 40 years in harsh service conditions. These vast product lifetime and consequences of failure differences are depicted in the Fred's chart (above). Commercial products are in quadrant A and military/aerospace products in quadrant D.

One of the greatest risks faced by quadrant D products is tin whiskers. Fred spent quite a bit of time discussing this interesting phenomenon. One of the challenges of this risk is that there is no way to accelerate it, so you can’t do an equivalent test to accelerated thermal cycling or drop shock. Fred mentioned that there have now been verified tin whisker fails, the Toyota accelerator mechanism being a confirmed one.

In addition to tin whiskers, lead-free reliability for quadrant D products (with a service life of up to 40 years) in thermal cycle and other areas remains a concern.  I mention that tin pest was not on the list of issues for this quadrant.

Fred and the Manhattan Project Team have identified many "gaps" that need to be addressed to determine and mitigate the risk of lead-free assembly for quadrant D products.  They plan to start this approximately $100M program in 2013.

For those that missed this free workshop, ACI host Mike Prestoy is planning another one in 6 months.

Cheers,

Dr. Ron

Tombstoning

• the transition to Pb-Free (higher reflow temperatures, and related flux issues)
• miniaturization (0201s and 01005s)

• The reflow oven operator can slow down the ramp rate. A slower ramp rate allows for more uniform warming of the PCBA.
• Another technique is to employ a "soak" just below the melting temperature (solidus) of the alloy. For example, for a SAC305 profile (217°C solidus), one may implement a "soak" at 205 to 210°C for 30 to 120 seconds. This allows for the cooler parts of the PCBA to "catch up" to the warmer parts. After thermal equilibrium has been achieved, one can spike the temperature up to the appropriate peak temperature (i.e. 245°C). This technique (depicted in the reflow profile shown at the right) allows for all of the solder paste deposits to melt and wet the component terminations at roughly the same time; thereby, mitigating tombstoning.

Phone: +1.315.853.4900
E-mail: ebastow@indium.com

Folks,

Let's look in on Patty......

Patty was just finishing a report on work that she and Pete had performed with a team of her ACME colleagues  on reducing the Head-in-Pillow (HIP) defect at a plant in Minnesota. HIP can be caused by printed circuit board and/or a BGA warping during reflow, and, occasionally, by poor wetting BGA solder balls. Fortunately, this case of HIP was due to just a little warping, so replacing the solder paste with one of the new formulations that was designed to minimize HIP had done the trick. Ten thousand boards were produced with no detectable HIP defects.

As Patty wrote the last sentence in the report, she gazed out the window at the dusting of snow that had fallen. She liked living in southern New Hampshire and was thrilled with the house that she and Rob had purchased six months ago in Exeter.  She had to admit that Phillips Exeter Academy was also a draw. She hoped her 18 month old sons, Michael and Peter, would attend high school there, when the time came.

Patty was jarred from these thoughts by the ringing of her phone. She looked at the caller ID and saw that it was Mike Madigan, the CEO of all of ACME. Her stomach tied up in a knot. Sam, her boss, had alluded to the fact that senior management wanted to make her a VP. He asked if she had any requirements to accept such an offer. She said that she wanted to stay located where she was and she wanted Pete to be on her staff. Still, she was a bit nervous about such a big change.

“Patty Coleman, how may I help you?” Patty answered.

“Coleman, this is Mike Madigan. Congratulations, you are our new VP of Technology and Productivity. You will report to me, but, since you are staying in New Hampshire, I want you to report dotted line to Sam for day-to-day things. Coleman, don’t let me down. You are the youngest VP in the history of ACME by 5 years,” Madigan said.

Patty was a little put off by his gruff manner, but had been told to expect it.

“Thank you Mister Madigan, I’ll do my best,” Patty responded.

“I already have an assignment for you,” Madigan went on.

“You have done great things by improving line uptime at many of our sites, and profitability is up everywhere, but I sense we are still missing something. Do you know why?” he asked.

“Because the correlation between profitability and uptime is not as strong as one would like?” Patty asked.

“Coleman, I’m already glad I promoted you! That is exactly my concern.   Explore the situation, fix it and give me a better metric. I want all sites to use this new metric so I will know which locations to focus on. I want a status report in 3 weeks.” Madigan finished.

“I'll get right on it Mister Madigan and will have an update in 3 weeks or sooner,” Patty answered, exhilarated, but a little shaky.

“Good! Oh and Patty, call me Mike. It’s not the 1960s you know,” he chuckled as he hung up.

Patty hung the phone up feeling happy and stressed. She was glad to get the promotion, but knew she had to deliver.

Patty had thought about this productivity metric concern in the past. She knew where to start, she would call The Professor. She was surprised when he picked up on the first ring.

“Patty, it’s great to hear from you. How are Rob and the boys? We expect to see your sons here at Ivy University as students in 16 years,” The Professor chuckled.

After exchanging a few more pleasantries and sharing the news about her promotion, Patty got right to the point.  

“Professor, I need a metric that measures total productivity in electronics assembly. Uptime is a great metric, but it doesn’t correlate one-to-one to profitability,” Patty explained.

Patty expressed her surprise that no metric for total productivity was in wide use. They discussed the issue for a few more moments and then The Professor had a recommendation. “Read the NEMI (National Electronics Manufacturing Initiative) 1998 and the iNEMI 2011  Technology Roadmaps. Focus on board assembly and I think you will find your answer,” The Professor suggested.

After a few more pleasantries, The Professor had a request.

“Patty, I am getting a little award in Washington, DC. I have room for two guests at the award presentation. I was hoping you and Rob would come,” The Professor requested.

Patty said she would check their schedules, but was sure it would work out. She was honored that he thought so much of her and Rob.

As she hung up the phone, she went to ACME’s Tech Library in search of the iNEMI roadmaps. She quickly found the 1998 NEMI Technology Roadmap, but unfortunately only a summary of the 2011 iNEMI Roadmap was available. She thought she would read the 2011 Roadmap summary first. It was overwhelmingly impressive in its coverage of technology, at the wafer, chip, component, and board levels. The thoughtful inputs of over 575 participants, from over 310 organizations, were clearly evident. All of the current and emerging technologies were presented in detail.

“What a treasure of information,” Patty thought.

But she didn’t see an answer to her question.

So she went to the “Board Assembly” section of the 1998 Roadmap and in a few minutes she saw the answer: Board Assembly Conversion Cost in cents/I/O.

“What a simple concept,” she thought.

As she studied the document it became clear that about 30% of it focused on reducing conversion costs. Conversion costs were defined as all of the cost of assembly minus materials cost. To give this metric meaning, to enable comparisons between different manufacturing sites, the total amount of conversion cost for a manufacturing site was divided by the total number of input/output (I/O) terminals (i.e. component leads) assembled.

“This makes sense,” she thought. “You add up all of the non-material costs of assembly and divide by all of the leads you assemble. This metric shows how efficiently you assemble each lead.”

It then dawned on her that she had seen a metric like this before. She saw the notebook from The Professor’s workshop on Cost Estimating in her bookcase.  She grabbed it and flipped through it. There it was: non material assembly cost per I/O (NMACIO).

The great mystery to her is why the folks at NEMI didn't emphasize these types of cost performance metrics in newer roadmaps.

Here is a list of tricks to help you overcome the issues that can arise while hand soldering silicon-based solar cells (and other applications as well). Some of these ideas are obvious for most, but all the suggestions can help you form a better solder joint - and build a better final product:

1)    Use the correct soldering tip. I’ve made the mistake of using an inappropriate solder tip before, and so have many of my customers. It’s a frustrating problem you will only let happen to you once: everything is set up perfectly but nothing will melt, until you notice the solder tip is not the correct size or shape. This has happened to many of my customers who were initially using cone point soldering tips when they were working with 2mm wide solder coated tabbing ribbon. Simply changing the tip to a 2mm wide chisel point made all the difference, and promoted soldering readily. Why such a big difference in performance? The chisel tip allows heat to flow across the ribbon, instead of only heating a single point. More heat flow = more heat in your solder joint.

2)    Pre-tin the soldering iron. Just as an appropriately sized soldering tip will distribute heat across the soldering surface, a bit of molten alloy can help create a thermal interface to maximize heat transfer. Remember to melt a small amount of solder onto the tip of your iron before soldering, and be sure it’s the same alloy you are soldering with. (Leave the custom alloying to us ;)

3)    Consider the alloy you are soldering. All the heat your typical soldering iron can produce will not be enough to melt some of the highest temperature alloys. Be sure to have a good understanding of the alloy you have selected. In some cases with low-temperature alloys (like bismuth or indium alloys), excessive soldering temperature can de-wet the alloy and char low temperature fluxes.

4)    Use the correct flux. Fluxes are quite different, I’ve spent my entire soldering career trying to get that point across. There are fluxes for high temperatures or low temperatures, cleaning with water or not cleaning at all. There are specialty fluxes for specialty alloys and there are fluxes for different soldering surfaces. Use the correct flux. If you don’t know what the best flux for the application is - just ask; that’s what I am here for.

5)    Use a bottom side heater. Silicon is known to pull heat away – that c-Si solar cell that needs to be soldered is a heatsink! Some solder equipment vendors also provide underside heating pads to help prevent excessive heat loss.

6)    Keep your soldering iron clean. That black crud that builds up on your soldering iron tip, it’s not helping you form a good solder joint. Those oxides and charred flux residues can easily be removed by wiping the hot iron across the wet sponge (that should be at your soldering station). A clean tip will lead to better heat transfer, and it will make the fluxes you use more effective.

This is the soldering station I use, it’s a PS-900 supplied by OK International. Just about any soldering iron will work, but they won’t all work as well – or come with as good support.

I’m still learning all the tricks to hand soldering, so feel free to share any you have learned over the years!

~Jim

Folks,

In addition to electronics assembly productivity, solder paste and solder preform applications, and other electronics assembly concerns, many of you know that I teach statistics and have been a life-long math nerd. So, I was intrigued when good friend Rick Short, alerted me to the New Orleans Saints football team being 0-11 for coin tosses this season. One naturally asks, how unusual is this result?

Assuming a fair coin, there is a 50% chance of winning or losing on each flip. The chances of losing two times in a row is 0.5 x 0.5 = 0.25. The chances of losing 11 times in a row, in the first 11 tosses, is 0.5^11= 0.00048828125. Or about 2000 to 1 ( 1/0.00048828125 = 2048) as the article points out. Wow!, seems unusual. However, there are 32 teams, and it has only happened to one team. So what is the likelihood of this happening to one team this year? This calculation is a little more tricky. The easiest way to calculate it is to ask the question, what is the likelihood of this event not happening to any team?

The chances of not losing 11 in a row, in the first 11 tosses, for any team is 1-0.00048828125 =0.99951171875. So the chances that none of the 32 teams would lose 11 coin tosses in a row is 0.99951171875^32=0.98449268023. The chances that at least one team might lose 11 in a row is 1 minus this number or 1-0.98449268023= 0.015507319766 or about 1.55%. This number is still quite low. But what if we looked a 50 seasons?

The chances that 50 seasons would go by and no team would lose the first 11 coin tosses in a row is 0.98449268023^50 = 0.45774601688. So in 50 seasons, with a 32 team league, the chances are 45.77% no team would lose the first 11 coin tosses in a row, or 54.23% that at least one team would. Since these odds are close to 50/50, in fifty years, the Saint coin toss loss string is a 50 year event.

The article goes on to state:

               “And while the Saints are 7-3 and lead the NFC South despite coming up short every single time on what should be a 50-50 proposition, coin-toss statistics — yes, they do exist — show that the NFL team that won the pregame flip wound up winning 52.1 percent of the time through Week 10 this season, according to STATS LLC.

That’s about the same as the 52.6 percent that STATS shows for coin-toss “victories” matching up with game victories since the start of the 2008 season, when the NFL changed the rules to allow the team that wins the toss to defer its choice until the second half.”

If there is interest, I will see I can calculate the statistical significance of this apparent coin toss win 2.6% advantage. My guesstimate is that the difference is quite statistically significant.

Note: Some readers may ask why I have used so many decimal places in my answers. Experience has taught me that when you are taking numbers to very high powers (the 32^nd and then the 50^th) that rounding errors can be great.  In addition, noticed that I often said the "first 11 coin tosses." The odds would be higher to get eleven in a row out of a larger number of tosses, say 16.

Cheers,

Dr. Ron