Category Archives: Dr. Ron

Materials expert Dr. Ron Lasky is a professor of engineering and senior lecturer at Dartmouth, and senior technologist at Indium Corp. He has a Ph.D. in materials science from Cornell University, and is a prolific author and lecturer, having published more than 40 papers. He received the SMTA Founders Award in 2003.

Thoughts for the New Year

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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 the US 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 six billion a day. If you lined up all the seven 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. Keyboard 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 for 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 US Navy’s Manhattan Project.

4. 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

Revelations at ACI

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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 the recent workshops at ACI.

Indium colleague Ed Briggs and I gave a three-hour presentation on “Lead-Free Assembly for High Yields and Reliability.” I think Ed’s analyses of “graping” and the “head-in-pillow” defect are 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 five years or so, but not for military/aerospace electronics where lifetimes can be up to 40 years and under harsh service conditions. These vast product lifetime and consequences of failure differences are depicted in Fred’s chart (see the pdf link). 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 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 $100 million program in 2013.

For those that missed this free workshop, another is planned in about six months.

Cheers,

Dr. Ron

Reducing Conversion Costs

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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 or BGA warping during reflow, and, occasionally, 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 Mr. Madigan, I’ll do my best,” Patty responded.

“I already have an assignment for you,” Madigan continued. “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 three weeks,” Madigan finished.

“I’ll get right on it, Mr. Madigan, and will have an update in three 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 was why the folks at NEMI didn’t emphasize these types of cost performance metrics in newer roadmaps.

Best Wishes,

Dr. Ron

Rob Heads to Guadalajara

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As Rob sat on the airplane, he was excited to go to GDL (Guadalajara, Mexico) to help solve the voiding problem. He knew Patty would be a little peeved that he asked for Pete to come along, but she was gracious, recognizing that Rob would benefit from a success in this effort.

As the plane circled for a landing, Rob was preparing for the somewhat comical trip through customs. He always thought the red light/green light method of determining if they were going to search your bags was unusual. Oh well, go with the flow.

The ride from the airport was about 40 km to the factory through Guadalajara’s bustling traffic. After arriving at the plant Rob was relieved to see that Miguel Mendoza was there to meet him. Rob had worked with Miguel in the past and respected him as a process engineer. Miguel told them that a kickoff meeting was scheduled with the site GM, a fellow from the US named Grant Wilson.

As the meeting started, Rob introduced himself to Wilson in Spanish.

“Wow,” Wilson chuckled, “when asked if I am bilingual, trilingual or American, I have to say I am American. But, I am taking Spanish lessons.”

Rob looked at Miguel and saw him roll his eyes. But Rob thought it was at least a nice gesture that Wilson was taking Spanish lessons.

“Perhaps someone could share what actions have been taken and what the status is,” Rob suggested.

“Miguel, could you give Rob an overview of where we are?” Wilson asked.

Miguel began, “The warranty send-back rate is 5% on Droid phones. Almost all of these failures have been traced to high-powered QFNs that have significant voiding under the thermal pad. The voiding percentage is about 50-70%. About a week ago we obtained Derrick Herron, Dr. Yan Liu and Dr. Ning-Cheng Lee’s recent paper, Voiding Control at QFN Assembly, at SMTAI 2011.  We changed our stencil design, as suggested in the paper, to allow for venting of the solder paste volatiles, and voiding went down to 30 to 50%.”

“What level of voiding would be acceptable?” Rob asked.

“We’re not sure,” Miguel answered.

“So it seems we have two issues, one is to determine if 30 to 50% voiding is OK, and the other is to see if we can reduce it further,” Grant Wilson reasonably commented.

“My sense is that we need to be in the less than 30% range,” Rob added. “This may require that we use solder preforms. Voiding is caused by outgassing, but also by insufficient solder,” Rob finished.

“OK, you two go and solve the problem and get back to me. You have 3 days,” Wilson commanded.

Rob, Pete, and Miguel headed off to get started on their assignment. Rob was really glad Pete was there.  He was an expert in setting up and optimizing the component placement machines that were at this site.  Fortunately, Rob had also brought some solder preforms with him, expecting they would be required. A call to the QFN vendor confirmed that less than 30% voiding should be the target. Rob looked at the data and x-ray images of the work that Miguel and his team did to reduce the voiding by improving the venting of the flux volatiles. He was impressed, but he didn’t think it would be enough.

(Dialogue translated from Spanish)

“Miguel, I’m almost certain that we will need to use solder preforms on the two most critical QFNs,” Rob began. “There are two major reasons for voiding: The first is flux volatiles forming voids; the second is solder starvation. Most people don’t realize that solder paste is only 50% by volume metal. In cases like this, where we really need low voiding, often the only path to success is to use solder preforms to add solder metal,” he finished.

Rob then showed Miguel Seth Homer’s SMTAI 2011 paper, Minimizing Voiding in QFN Packages Using Solder Preforms. This paper describes the process steps needed to achieve a successful QFN solder preform process. Rob and Miguel spent the better part of a day setting up one assembly line to assemble with the solder preforms using this paper as a guide. They assembled 100 phones, and the voiding level was 10.5%.

Early the next morning, they met with Grant Wilson.

“By the smiles on both of your faces, I gather you were successful?” Wilson asked.
Rob went on to explain how they determined that solder preforms were needed. He explained the process and waited for questions.

“What do solder preforms cost?” Grant asked.

“They are about $0.02 (US) in quantity, but understand that your warranty cost per $200 phone is at least $10 right now (0.05 x 200),” Rob answered.

“Did you have to slow the process done?” Wilson asked. “I have been a fan of the work that you and Patty Coleman have done with The Professor, you have convinced me of the importance of throughput,” he finished.

“The Professor has pointed out that almost never is a line completely balanced. Your flexible placers were waiting four seconds for the chipshooters. We put the preforms on the flexible placer and tuned up both machines by optimizing the feeder placement. The cycle time is now 1.25 seconds faster for the 3 phone per PCB,” Rob answered.

“I’m curious, what was the greatest challenge?” Grant asked.

“Rob pointed out that the correct placement of the preform on the solder paste deposit for the heatsink part of the QFN is critical. We needed to assure that the preform was pushed into the paste far enough to leave a ring of paste around the preform to assure good mating with the QFN. We couldn’t have done this without Pete, he really knows the placement machines,” Miguel answered.

Miguel then showed Wilson an image from Seth Homer’s paper that displays this situation.
“Guys, thanks for the great work. I have to admit that I didn’t really know anything about solder preforms before today. In certain cases, it is obvious that they can be lifesavers!” Grant summed up the situation.

“To celebrate your success, I’m treating for dinner tonight at the Santo Coyote. Let’s meet there at 7 PM,” Wilson suggested.

“Thanks,” Rob, Pete, and Miguel said in unison.

Santo Coyote was Rob’s favorite restaurant in Guadalajara, but it was Patty’s too. Rob was a little sad she couldn’t join them.

Epilogue: Three months later it was confirmed that warranty send back rate was approaching zero. Miguel was promoted to senior engineer for his part in the solution to this costly problem.

Best Wishes,

Dr. Ron

Toward a Pb-Free Consensus

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Folks,

Some time ago, I mentioned that I was working on a consensus of the status of Pb-free/RoHS-compliant assembly. My hope is to find data and facts that will support the consensus. I am making progress, but at this time I would like to share the subtopics in the consensus. Look them over and see what you think:

1.       Was/is lead-free electronics/RoHS needed to protect the environment?

2.      Is Pb-free solder easier and safer to recycle than Pb-containing solder?

3.      How has the increased use of tin and silver affected their supply and price?

4.      How much did it cost to implement Pb-free/RoHS-compliant electronics?

a.      What is the cost adder to a typical Pb-free product?

5.      What are the process challenges of Pb-free assembly? Are these challenges being addressed? If so, how?

6.        What is the reliability of Pb-free vs, leaded electronics for commercial applications (e.g., 0°C to 100°C thermal cycle, drop shock, etc.)?

7.        What is the reliability of Pb-free vs leaded electronics for harsh environment/military applications (e.g., -55°C to 125°C thermal cycle, other Mil stress tests)?

8.      What is the threat of tin whiskers, tin pest and other similar Pb-free related reliability phenomena?

9.      What is the status and need for halogen-free assembly?

Help me by suggesting topics that I have left out.

Best wishes,

Dr. Ron

Pb-Free Reliability Under Harsh and Commerical Environments

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Folks,

In gathering information on the status of lead-free soldering, some helpful friends pointed out two great sources of information: NASA and the US Navy.

NASA sponsored an impressive lead-free reliability investigation: “Lead-Free Solder Testing for High Reliability Project 1.” This project is finished and the reports are online. A follow-on project, NASA DOD Lead-Free Electronics Project 2, is underway.

The Navy sponsored a project with ACI and the summary is here. I am currently studying these documents to help develop the consensus. Some preliminary info follows:

Regarding -20°C to +80°C thermal cycling, NASA concluded:

Under the conditions of this test, Sn3.9Ag0.6Cu (SAC) and Sn3.4Ag1.0Cu3.3Bi (SACB) were always more reliable than eutectic SnPb regardless of component type (CLCC, TSOP, BGA or TQFP).

It has been shown that conditions that highly stress the solder joints by maximizing the CTE difference between the PWB and the component will favor SnPb over SAC6. Conversely, conditions that minimize the stress put on the solder joints (e.g., compliant components such as BGA’s and/or a thermal cycle with a small delta T) will favor SAC over SnPb. The current test falls into the latter category and we can say with some confidence that the lead-free alloys tested will outperform eutectic SnPb under field conditions that are even less stressful than the -20 to +80°C thermal cycle test conditions.

For -55°C to +125°C thermal cycling, the conclusions were more cautious, likely because the data were mixed:

The feasibility of using Pbfree solder alloys in place of SnPb solder alloys for new product designs was demonstrated under thermal cycle test conditions. Additional investigation and characterization of Pbfree solder alloys will be required as a segment of a Pbfree solder alloy implementation plan. The application/introduction of Pb-free soldering processes for legacy product designs is not recommended without extensive materials characterization and product design review.

These results seem to be consistent with what others report: namely, lead-free assembly produces good thermal cycle results for commercial-type thermal cycling, but the results are mixed for harsh environment thermal cycling.

More to follow.

Cheers,
Dr. Ron

Tin Bells Going Off

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You may remember that more than a year ago there was much speculation that tin whiskers may be behind the Toyota unintended acceleration problem. At the time I spoke out because there was no data to support the speculation. Now there are data, as Mike Pecht and his CALCE Team at the University of Maryland have found numerous tin whiskers in the Toyota brake assemblies of concern.

Although the tin whiskers were not implicated in any failure, their presence is cause for alarm, and action should be taken to address this issue. Tin whiskers should not be found in mission critical devices. Pecht’s team has an algorithm that calculates the risk from tin whiskers that are discovered. The risk is 140 per 1 million — not high, but with a million or so Toyotas on the road, clearly this is cause for alarm.

As you may know, I live in Woodstock, Vermont.  Many friends have asked how we are doing after hurricane Irene. Personally, my wife and I escaped with no damage to our house and only a bit of inconvenience (no water for 5 days). The town of Woodstock suffered considerable damage, but was, on the whole, fortunate. Some of the neighboring towns had all roads in and out washed away. Route 4 between Woodstock and Rutland has numerous sections destroyed. The flooding was declared by the governor to be the worst disaster in Vermont history. The photo is from the Valley News. It shows a wooden pedestrian bridge built to carry supplies into Bethel, VT by foot. There is no passable road, even for ATVs.

Best,

Dr. Ron

 

Is a Pb-Free Consensus Achievable?

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Folks,

Recently I posted a note about a flurry of Technet posts in which I was misquoted regarding the status of lead-free electronics assembly.  Harvey Miller then weighed in.  I responded. And this in turn raised more comments.

All of this caused me to wonder, is it possible to achieve a consensus on the state of Pb-free assembly? I think it might be and am going to try. The main thing that I think is important in this quest is that any points for the consensus, or lack thereof, be supported by data and analysis, not emotion.

If you have a point to add, that is backed by data and analysis, please share it with me.  One of the things I hope to accomplish is to develop a list of references, that can be referred to to support the consensus.

Stay tuned for more info on this effort.

Cheers,

Dr. Ron

Electricity Use in Pb-Free

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Folks,

An obvious disadvantage of lead-free electronics soldering assembly is that the oven must be hotter and therefore will use more electricity (versus SnPb37 soldering). But is the extra amount of electricity significant?

KIC’s Brian O’Leary claims that a typical SMT oven uses $7,000 worth of electricity a year at $0.072/Kilowatt hour (Kwh) or about 100,000 Kwh. That number strikes me as about right, as a household uses about 5-20,000 Kwh per year.

In the late 1990s there were 35,000 SMT lines in the world. At a 3% growth rate that would be about 50,000 lines now. So worldwide SMT reflow oven use would be about 5E9 KWhr (50,000 ovens x 100,000 Kwh/per year) worldwide.

With most heat loss be due to convection, the increase in energy use will be approximately proportional to the difference between the oven temperature and the room temperature (25°C). An oven processing tin-lead solder would run at about 210°C versus lead-free’s 250°C. So the added energy for a lead-free oven would be about (250-25)/(210-25), or about 22% more. So if all assembly lines in the world are SMT the added energy use would be about 0.22x 5E9 Kwh = 1E9 Kwh. The cost of this extra electricity would be about $100 million at $0.10/ Kwh. The electronics industry generates about $1.5 trillion in sales. So this added cost would be about 0.0067% of sales. Since world electrical use is about 150,000 E9 Kwhr per year, this increase is about 1/150,000 of all of the electrical use or 0.00067%.

So although more electricity is used, the increase is not significant to the value of the electronics sold or the total world use of electricity.

Best Wishes,

Dr. Ron

On Misstatements and Pb-Free

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Folks,

Here is an interesting turn of events related to the reliability of lead-free (Pb-free) soldering reliability.

I was reminded recently by something Carl Sagan said, or, actually, did not say: Billions and Billions Although this term is strongly associated with him, he never said it. Sagan believed that this term was connected to him because Johnny Carson mimicked him and used the term.

Although not even close to being in Sagan’s league, I find that I am now equally unfairly associated with the term “lead-free solder is a grand success.”

This came about in an interview by Rob Speigel, which he summarized in a blog post. In reading the post, you will see that  “lead-free solder is a grand success,” is Rob’s term, not mine. Well, Rob’s post resulted in a string of postings on IPC’s Technet. One person opined:

Irresponsible statements like “lead-free solder is a grand success” should NOT be ignored. Those who make such statements in the face of all of the contrary evidence should be noted, and treated as motivated only by greed. Lead-free soldering certainly has been known for many “thousand$” of successes.

I have learned that it is not even worth the bother to refute such statements with those who make them. It may be a “grand success” for PhDs who contract to solder paste companies, but it certainly has not been a “grand success” to literally thousands of companies dealing with the reliability elephant sitting in the room getting larger by the day, and the associated fallout as a result.

Ouch!

Another shared:

I disagree with the stated and implied affect of RoHS, on PWBs expressed in this article. Lead free assembly reduces reliability by 50%. There can be no doubt about that. There are too many studies that confirm lead free assembly significantly degrades reliability. There are so many studies that demonstrate a reduction in reliability that Rod’s contention is almost laughable. We are now faced with increased failures of copper interconnections and dielectric material due to high assembly temperatures. There is an increase in crazing that can support CAF, significant copper dissolution, and cratering in assembly, Switching to lead free in most HDI applications is a significant challenge. Lead free assembly has a profound affect by degrading PWB’s organic component (epoxy) due the temperature required and copper interconnection and also the exaggeration of the z-axis expansion of the dielectric.

I have asked for copies of the many reliability studies referred to. No response yet.

Finally someone hit the heart of the matter:

I’m curious if “grand success” were Dr.Lasky’s words or Rob Spiegel’s editorializing.  Lasky does mention the lack of long term results, and Speigel, in the comments, enumerates a number of reliability problems. ISTM that neither truly believes those words.

Correct! Thanks.

Here was my response as posted on Technet:

Pete is correct. I never said lead-free implementation was a grand success. These were Rob’s words in his blog post.

I have said repeatedly that adequate lead-free reliability has been demonstrated for consumer products like mobile phones, PCs, portable electronics with service lives less than 5 years. This level of reliability has been demonstrated in numerous studies and more importantly with field data. Vahid Goudarzi, of Motorola, stated that field reliability of lead-free assembled mobile phones has been equal or better than leaded assembly units. His data go back to 2001 (not 2006. Motorola started early for reasons discussed below).

The reason Motorola shipped early with lead-free products is due to the fact that lead-free solder does not spread as well. Because of this poorer spreading, Motorola was able to decrease lead spacings without getting shorts, thus increasing the amount of electrical function in a smaller space. Since increased function in a smaller space is the defining attribute of portable electronics, the importance of this lead-free advantage cannot be overstated. Admittedly, lead-free’s poorer wetting is a challenge in other regards, especially hole fill in wave soldering, but the Motorola Droid X2 could not be assembled with leaded solder, there would be too many shorts. Since the packaging density of the iPhone and similar devices is on a par with the Droid X2, I suspect this statement is true for most mobile products.

I have also repeatedly stated that lead-free reliability for long term service, mission critical devices has not been demonstrated. As a result, these types of devices should not consider lead-free solder at this date.

I regularly discuss these topics in my blogs. The most recent post shows a striking photo of leaded solders spreading — which is too “good” for portable electronics.