Tag Archives: lead-free soldering

RoHS, Six Years After

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Folks,

I was at IPC Apex Expo the other week.  San Diego is a great venue for the show, but I always forget how cold it can be (55°-65°F) this time of year.

While at the show, I was interviewed on lead-free reliability and its cost for consumer electronics. These are topics I think about often, so let’s discuss them a bit. First, let’s consider reliability.  RoHS was enacted on July 1, 2006, more than 6 ½ years ago. Each year more than $1 trillion worth of electronics are made, therefore, in this period of time, something over $3 trillion worth of consumer electronics have been manufactured. There have been no “the sky is falling”-type of reliability issues in this time. How can I say this? Well, my office at the Thayer School of Engineering at Dartmouth is across the hall from the IT (information Technology) Dept. They purchase all the millions of dollars worth of PCs, printers, displays etc. that Thayer uses. Several years ago (say early 2011) I stopped by when most of the department was in and cheerfully asked if the reliability of the equipment they purchase has gone down since lead-free assembly was enacted. They asked me in unison, “What’s lead-free assembly.” After I explained what lead-free assembly was, they confirmed that they have noticed no changes in reliability. Since RoHS, my family has purchase about 100+ electronic devices, a few have had reliability problems, about as many as in the past. Most were attributed to hard drive fails. Of the scores of friends and colleagues I have, no one has ever commented that they have noticed an increase in electronics fails. So, my conclusion is that consumer product reliability is not “practically” worse if my family and  these many  other folks haven’t noticed it.

I have made an informal study of reliability data of lead-free vis-a-vis tin-lead solders published in papers. A statement from Rockwell Collins’ JCAA/JGF-PP No Lead solder Project: -55C-125C Thermal Cycle Testing Final Report  sums up my overview conclusion nicely: “Test vehicles assembled with lead-free materials (notably tin-silver-copper) exhibited lower reliability under some test conditions.”  Naysayers might be quick to suggest that this statement says that lead-free is no good. However, the statement could be reworded to say: “In considerably more than half of the test conditions, test vehicles assembled with lead-free materials had higher reliability.” Counting the comparisons in the Rockwell-Collins paper shows lead-free better in 51 cases, tin-lead better in 31 cases, and one draw. However, it is disturbing that a small percentage of lead-free assembled test vehicles had much much worse reliability than tin-lead test vehicles. This later information makes me believe that lead-free is not yet ready for mission-critical, high-reliability, long-life products. These small numbers of much poorer reliability assemblies must be understood and corrected before lead-free is ready for mission-critical prime time. The much shorter lifecycle of today’s consumer electronics may also mask this concern.

What about cost? I don’t at all want to minimize the expense that many went through to go lead-free and RoHS compliant. In about 2007, one of our colleagues estimated that it cost the electronics industry $20 billion to become RoHS compliant. I think this number is low, but, from a consumer’s perspective, there has been no cost hardship. The price of a PC continued to go down during and after RoHS implementation, as shown in the figure below. While performing my non-scientific survey of co-workers, family, and friends on reliability, I also asked about cost. All agreed, electronics are cheaper than ever.

 

Challenges still exist, even in consumer electronics with the Head-in-Pillow, Graping, non wet opens, and other defects.  However, we can all purchase lead-free, RoHS compliant products at a reasonable cost and reliability.

 

Cheers,

Dr. Ron

The source for the image is :http://thomaslah.wordpress.com/2010/02/03/apple-and-intel-defying-gravity/

 

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

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.

 

The Patty Chronicles: Leaning on Suppliers

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Patty was checking her email. She noticed a note from someone who had attended last night’s SMTA meeting. She had just been elected chapter president, after giving a talk on the head-in-pillow defect.

In her talk, she also shared how important it was to work closely with your materials and equipment suppliers. To her, it was obvious that her suppliers were interested in her success. If they were competent, why shouldn’t she rely on them for technical information and help? If she didn’t think they were competent, she should get new suppliers. She was surprised at how much “push back” she got from the attendees. Several stated that they felt that suppliers where just out to make a sale and that a smart person just bought from the supplier with the cheapest price.

Patty found this perspective negative and self-destructive. She was sure that 60% of all process knowledge was learned from her suppliers, either in person or at the technical conferences. She felt the main reason to go to these shows was the technical program. And some of the best papers were presented by the better equipment and materials suppliers. One of their marketing VPs even told her, “We believe that the more technical help we give our customers, the more successful we will be.”

Well, wasn’t that a condensation of what good business should be like? He who helps his customer is the most successful, she thought.

As she was thinking these thoughts a new email popped up on her PC. It was from Hal Lindsay, a noted curmudgeon. Patty read on.

“I heard you telling some of the people at the meeting last night that lead-free assembly had some process advantages. Hogwash. Lead-free has no process advantages, and it’s not needed,” he started.

After a few more complaints, he finished, “It’s because of young tree-huggers like you that never stood up and fought lead-free that we are in this mess to begin with.”

In preparing her response, Patty’s mind went back to some conversations about this she had had with The Professor. He had made two strong points:

1. The first purpose of RoHS is to make recycling safer. So much recycling unsafe processes is performed in poor countries with unsafe practices. RoHS-compliant products will save the lives of the unfortunate people who have to perform this type of recycling to survive.

2.  Lead-free soldering is challenging because the solder does not wet as well. This situation forced us to develop assembly processes with tighter process windows. However, an initially unseen benefit is that tighter lead spacings are possible with lead-free soldering because of this poor wetting. Many portable products such as mobile phones could not be assembled with leaded solder. There would be too many shorts.

Patty was including this information in her response to grumpy Mr. Lindsay, when the phone rang. It was Rob.

He began, “?????????????ACME???????????????????????????”

(For our few readers that can’t read Mandarin: “It looks like I will be traveling to China to visit some of ACME’s new factories there. I think you will be going to work on some soldering issues too.”)

“Whoa!,” Patty exclaimed, “Why would you be going to visit ACME’s factories in China?”

Rob went on, “You know things haven’t been going well here at AJAX, we never adopted “Lean Sigma” techniques like ACME did. Today, we had a layoff and I got hit.”

“Yikes!” screamed Patty. Her mind went through many scenarios with Rob being unemployed five weeks before their wedding.

“Easy,” Rob implored. “My GM called me in and said that he was sorry to see me go, but being a friend with your GM, he got me a job at ACME. I am to be the liaison for the three factories that ACME has in China. My fleuncy in Mandarin made the difference,” he finished.

Patty and Rob were unusual for Americans in that they both spoke Spanish and Mandarin. Both had fathers who encouraged them to take Mandarin at Tech as they had both taken many years of Spanish in high school. Both did a language study abroad (LSA) term and an internship in China. As their dads said, “If you can speak English, Spanish, and Mandarin, you can speak to almost any professional in the world.” Both Patty and Rob found that their language skills gave them a ready bond when they were abroad. One German colleague even told Patty that she was the only American he knew that would not fit the European view of Americans when they ask, “Are you bilingual, trilingual or American?”

After Patty calmed down, she asked Rob why he thought she would be going.

He responded, “When your GM gave me the job offer on the phone, he alluded to a team visit to China, by me and this genius young woman that is a process expert. Apparently, they have some head-in-pillow, graping and productivity issues. I will be handling the business aspects, you the technical. He also mentioned he would like The Professor to go. I don’t think he knows we are engaged.”

Patty congratulated Rob and finished to conversation. She hoped that their being married wouldn’t create any issues in working together. She also was a little annoyed that she always seemed to be the last to know about trips that the executives were planning for her and her team. It was especially annoying that Pete seemed always know before her when they would need to go on one of their adventures. After all, she was Pete’s boss. Well, at least this time it was Rob, not Pete. There is now way Pete could know about this potential adventure.

She went back to finishing her note to cranky Hal Lindsay when she heard, “Pack your bags kiddo, it looks like China this time. Oh, and Rob is going.”

Cheers,
Dr. Ron

I saw Patty at a recent SMTA meeting.  I mentioned that many of her fans would like to see a photo of her.  Surprisingly, neither of us had a camera.  As you remember she is also a self taught artist,  I asked if she would mind sketching herself.   Here tis.

The reflow image of leaded and lead-free solder coutesy of Motorola.

All the best,

Dr. Ron