Solder Suppliers

Eric Bastow recently wrote about using our Indalloy Flux #2 for soldering to Nitinol.  He did many tests and wrote an Application Note called Soldering to Nitinol.

Fort Wayne Metals, a leading supplier of medical wire (including Nitinol) also did a test on various fluxes as they relate to break load (maximum load before the joint breaks.

The fluxes tested included:

• Indalloy Flux #2 and Flux #3
• Indalloy Flux #5RMA; #5R; #5RA
• Indalloy Flux #4R
• Flux #400 (no longer commercially available)

The #5 series and the #4R were found to not be strong enough to clean off the tenacious oxides formed on Nitinol. Therefore, they didn't enable the solder to wet the surface properly.

Flux #2 and Flux#3 gave the best results (of the fluxes tested for break load) since they removed more of the oxides and allowed for a stronger solder bond.

Want to know more about soldering to this important medical material?  You can contact Eric Bastow directly at ebastow@indium.com or email us at medical@indium.com. 

Carol Gowans

cgowans@indium.com

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

Anyone who has used wave soldering to assemble PCBs knows about that chunky layer of metal that collects on the smooth surface of the molten solder. This is solder dross; it is composed of oxidized metals and impurities that collect as the molten solder contacts the air and manufacturing environment. This happens regardless of alloy and is a normal part of the process, often consuming up to 50% of the bar solder added to the solder pot. In the past, this dross was collected as waste and disposed of, but solder dross is more than 90% valuable metal. This value should be recovered.

Nowadays, typically, this dross is collected and returned to a metals supplier for recycling. Indium Corporation now offers two programs for recycling solder dross. The first program involves simply sending back dross waste in return for a portion of the metal value as a credit. The second option involves sending back dross, which is converted to bar solder (within the original spec) and returned, with you paying only a fee for processing. When dross arrives, regardless of which program is chosen, it is electrolytically refined and the pure metals are recovered and converted back into usable bar solder. Often, this reclaimed/recycled metal has a better purity than virgin metal.

Dross is not the only form of solder that can be recycled. For instance, when changing to a different alloy in a wave soldering process, the entire solder pot will need to be emptied. The old alloy can be collected and recycled, lowering the amount of capital necessary to switch alloys. Bar solder and wire that have not been used within the shelf life can also be recycled to get back some of their value.

Contact me if you want to discuss this.

Solder powder particle size and shape impacts the functionality of solder paste in many ways: printing/dispensing/dipping; solderballing; graping; voiding; tack and so on.

For this reason, I just spent an interesting couple of months leading a cross-industry (two solder paste suppliers and two solder paste users) group to help my old friend Brian Toleno, chair of the IPC 5-24b (Solder Paste Task Group) put the finishing touches to the final version of the J-STD-005A. The concerns were with the definitions of powder size in paste: both the distribution and the “maximum allowable particle size”. We reached a nice pan-industry consensus, which should allow the J-STD-005A to see the light of day as a published document in 2012. I also saw some recent work by colleagues on the effect of particle size on surface area. I didn’t see the derivation of this work, so I want to show you how to calculate the surface area of solder powder in a paste.

Assume solder paste at a weight loading of x%. [Note that: As the solder powder size (diameter) decreases, the metal loading is usually also decreased by 0.5% or more to compensate for the boundary layer of thixotropic flux adhering to the particle surface, but let's make the first order assumption that x is independent of particle size]. So 1 gram of solder paste contains (x/100) grams of solder metal.

If the metal has a density of r (rho), then the volume of metal (v) per gram of solder paste:

               v = x / (r * 100)

Let’s assume that the metal particles are monodispersed (i.e.: all the same diameter (d)), so the number of particles per gram of paste (n) is then simply v (total volume of metal per gram) divided by the volume of one particle (v_p).

               n = v / v_p = x / (r * 100 * (4/3) * pi * (d/2)³ )

We can now also calculate the solder powder surface area (s) per gram of paste from our knowledge of n and the surface area per solder powder particle (s_p):

               s = n * s_p = n *4 * pi * (d/2)²

It is a simple matter of algebra to show that the ratio of surface area to volume is merely an inverse of the particle radius or diameter (I’ll leave that as homework for you):

A while back, I did a little Excel numerical integration to show the effect of powder type on the population distribution, and hence how powder “type” (2,3,4,5 and so on) affects the surface area, with some assumptions thrown in about the width of the distribution. The results are shown below, and are pretty much as you would expect. As you go from type 3 to type 6, you see about a 10 fold increase in the surface area.

Folks,

It was five years ago today that RoHS was launched, amid concerns that the world of electronics would collapse due to the many challenges of lead-free (Pb-free) soldering. Well, we have five years of field data with no “the sky is falling” lead-free reliability events. But, has it been just five years?

No. As I mentioned in a recent post, Motorola implemented lead-free soldering around 2001 to take advantage of lead-free solder’s poorer spreading.  Hmmmm,  so it has been ten years! Not too bad!

Well it is actually better than that. SnAg3.5 solder has been used for decades in both:

1.     Step soldering:  with a eutectic temperature of 221C, SnAg3.5 can be used as the step previous to soldering with Sn63 or similar Pb-Free solder. The principle is to solder first with the SnAg3.5 and then with a lower melting temperature solder. The second soldering step is performed at a lower temperature, therefore not disturbing the SnAg3.5 solder joint or bond. 

2.      Mid-Temp Pb-Free alloy:  when a solder that melts somewhat above the melting point of a “standard” solder alloy is needed, and it must be Pb-free, SnAg3.5 is often the choice.  The automotive industry has used SnAg3.5 in these applications for decades.

While I still agree that lead-free solders need some time and experience, especially in harsh environments, to establish acceptable reliability for mission critical applications, the experience with SnAg3.5 is adding to lead-free solder’s reliability portfolio.

This information came to light with the recent announcement by a major solder materials supplier that they would no longer supply SnAg3.5. But take heart, Indium Corporation still supplies SnAg3.5.  

Spending back-to-back weeks at two electronics assembly trade shows is a unique experience, to me.

First up was SMTAI in Orlando, FL where I helped present a paper on Solder Fortification Preforms. 

How does one "help" present a paper?  Have you ever listened to a great paper and then, at the end, seen so many people rush around the speaker that no one can get a chance to make a further connection?  My role was to be available as an additional resource for answering questions after the presentation.

The second show was IMAPS 2010 in Raleigh, NC.  This is one of the best showcases for our Engineered Solder Materials.

There are many facets to the trade show experience. 

• There is the booth, which has to have the right message and the right pictures to draw the right people in. Our message is "From One Engineer to Another". Most of our staff IS engineers. Our team is extremely knowledgeable about materials and assembly processes.  We provide the best service when we are talking with Process or Design Engineers that need our soldering or bonding expertise.   
• There are the technical presentations, as mentioned above.
• There is the networking with industry leaders.  Being able to visit a variety of complimentary suppliers and discussing topics we have in common is tremendously valuable.

Even in the face of the myriad technology devices that keep us connected 24 hours a day, there is still nothing like that face-to-face experience.  The IMAPS Global Business Council presented two speakers during the show: one from DuPont and one from Dow.  One of them (I am sorry I can't remember which one) stated the overwhelming importance of getting their Application Engineering staff into the field to work face-to-face with customers.  

So if you want to more about what we know, check out our blogs.  When you see something you like or want to know more about, call us or email us.  We are glad to work with you!

And if you want to hear another viewpoint on trade shows, check out Andy Mackie's blog.

Folks,

The adventures of Patty and Rob continue.......

Rob bolted upright in bed. He had that terrible feeling that he had overslept for an important appointment. His eyes quickly found the clock and it said 10:30! 

“Wait a minute!” he thought, “It’s Sunday.”

He looked a Patty peacefully sleeping and decided to let her sleep. They had had a tough two months. Ever since they proposed increasing uptime to greater than 60% on two “experimental lines”, they were working 90 hour weeks. They just felt they needed to constantly monitor two lines, to assure that things were going smoothly. They felt satisfaction that they achieved 68.8% uptime in a two month period, compared to the company average 30.4%, which is still very good.

The local newspaper got word of this effort and did a story on Rob and Patty’s work. The article was well written and very complimentary to both he and Patty, as well as ACME. Sam Watkins, the site general manager, was very pleased with the good PR. The accompanying photos were really nice too.

The big shocker came this past Tuesday. “Sixty Minutes” called and said they wanted to do a segment on “The US Competing with the Far East in Electronics Manufacturing.” In agreeing to be interviewed, Rob and Patty insisted that members of their ACME team be included. In addition, they felt it was only fair to include the efforts of Rita from their stencil printer and reflow oven supplier and States, their colleague from the component placement company. And they couldn’t forget Eric, from ACME’s prime solder paste supplier. These three folks helped Rob and Patty and their team to develop the plan to achieve the 60+% uptime.

An even bigger shocker came when the Sixty Minutes crew told them that Andy Grove would be in the segment because of his recent article in Business Week, How America Can Create Jobs

 Grove insisted that to participate in the piece, he wanted to visit ACME to see what Rob and Patty were doing. So the Sixty Minutes crew was visiting ACME’s plant this week as were Rita, States, Eric and now “Andy.”

“Maybe we should call him Mr. Grove,” Rob thought.

Rob had suggested that he and Patty go to Berdick’s in nearby Walpole, NH for Sunday brunch and then to play golf. Rob had to chuckle, it was mid July and he and Patty had played golf 27 times (she kept a spreadsheet), he had beaten her 14 times and she was miffed. Even during their 90 hour weeks they would take a break 3 times a week to play 9 holes.

On Monday they were meeting with site GM, Sam Watkins, to discuss what they would tell Sixty Minutes.

Rob and Patty’s Sunday was delightful. The brunch was delicious and relaxing and they both played golf well, Patty’s 68 beating Rob’s 69.

It seemed like no time at all and Rob and Patty were in Sam’s office.

“Just assure me that this Sixty Minutes thing is not some expose that will embarrass ACME or put me in jail,” he teased.

Patty took the lead and explained what they had done. They trained the operators on the importance of line uptime, they worked with Rita, States, and Eric to develop a plan to assure that there would be minimum unscheduled downtime. They had to order extra spare parts and solder paste to assure no stoppages due to parts or paste shortages. One obvious thing is that they would be using two times or more the normal amount of solder paste. The two lines in the high uptime experiment had an average of one change over per day, consistent with ACME’s business.

They also increased routine maintenance on all machines. Both this maintenance and added spares was an increased cost, but these costs were second order effects compared to the dramatic profit increases due to almost 70% uptime.

Preparation for the next three jobs for each line was meticulous, so that setup time was minimized.  Feeder racks were used extensively in minimizing setup time for changeovers. In addition tape splicing was employed to minimize any assist time for component placement. States’ help was crucial in the component placement part of their efforts, Rob pointed out.

Patty went on to describe how Rita helped them in their efforts to develop minimum assist times for the stencil printing process.  The reflow oven presented the least concerns in assist or unscheduled downtime.

The solder paste they selected was robust in that it had a very good response to pause, excellent tack, and minimal slump.  The paste also had the best track record for minimizing defects like Head-in-Pillow and Graping.  Eric also participated as an enthusiastic partner in the effort.

Patty mentioned that their colleague, Phil, had agreed to monitor uptime for two standard lines during the two month trial to compare downtime metrics to the high uptime experiment. These would be experimental “controls.”

She then showed the uptime data for the two high uptime lines and Phil’s control lines. The control lines had ACME’s respectable 30% uptime, but the high uptime lines had almost 70% uptime. Rob went on to explain all of the things the team did to minimize downtime, most of it was common sense. Sam was especially interested in one downtime category.

“What is floundering time?" Sam asked.

 “That is time when the line is not operating due to some unplanned error,” Rob answered.

“Can you give an example?” asked Sam.

“Sure, you know how we have a quite organized approach to setups?” Rob responded.

“You mean our use of white boards to write down all of the things needed for the next 3 jobs on each line?” Sam came back.

“Yes, that is one of our biggest sources of floundering time,” Rob replied. He went on, “Someone will write that they have the stencil for the next job, when they just think they know where it is. When it comes time for that job the stencil cannot be found and an hour is lost.”

“Phil also noted a case where a job was finished on a line at 11:15AM, since lunch was at 12 noon, the changeover for the new job was not started until after lunch. Forty five minutes was lost, forever,” Patty added.

Sam gulped.

“So we are losing more than 25% uptime to ‘floundering?’” Sam weakly asked.

“According to the Professor, it’s endemic in the industry,” Patty interjected. “He coined the term, ‘Floundering time’,” she went on.

Sam then mentioned how the “bean counters” at ACME we really impressed with the two high uptime lines. ACME’s CEO wants a concerted effort to transition all of ACME’s assembly lines in North America  to higher uptime performance. Manufacturing in North America would also mean no 2-4 weeks of transportation time from the Far East. Patty, Rob, and their “team” were to form a new group in ACME to do this. Patty would be the Director of the group.

As the meeting was about to close, Sam asked what surprises Patty and Rob had during this experiment.

Rob then shared, “It relates to floundering time.   We found that even among the engineers, no one appreciated the value of one hour of production time. We asked a group of operators what an hour of production was worth and the figures ranged from $50 to $500 dollars. ACME runs two shifts at 30% uptime, that’s about 1500 hrs per year. Our typical line produces $30 million per year, that’s $20,000 per production hour. When we told the operators this, floundering time dropped significantly.”

Patty added, “The other thing we saw is that a “watchdog” is needed. If someone isn’t constantly watching things, floundering and assist times will go up. Since productivity is doubled with a high uptime line, the added cost of a watchdog is insignificant.”

Epilogue: The Sixty Minutes Segment was a great success. Patty was made Director of Corporate Productivity, but was also asked to manage Pete, who would take over her old group. No one seemed to worry that Patty was Rob’s boss, except maybe Rob!

Patty, Rob, and The Professor finished their tasks in Shenzen and were flying to Shanghai for their last set of challenges in electronics assembly.  Then they would head back to the US, Rob and Patty being only a week away from their wedding day.

As usual Rob, conked out as soon as the plane lifted off. Surprisingly, The Professor also drifted off to sleep. Patty was too excited to sleep. Rob’s mother had given her and Rob their wedding presents early … an iPad  for each. They decided to bring only one laptop and one iPad. Patty was a little nervous about using the iPad for presentations but it worked quite well. She was still surprised that the iPad did not have a USB port. The Professor also gave each of them an early wedding present, a Pickett slide rule for Rob and a K&E slide rule for her. She must be the only person in the world right now that was watching a movie on an iPad and solving a math problem with a slide rule!

True to form, The Professor was passionate about how learning to use a slide rule helped improve a person's innate math ability. He showed Patty and Rob how to use them and gave them several assignments. Rob was better with his slide rule than Patty due to the amount of “one on one” time he had with The Professor. She had to admit that using the “slip stick” gave one more of a feel for calculations and it was consistent with one of The Professor’s adages: “Always know approximately what the answer to a calculation should be…..it will help you to avoid errors."

In addition to the iPad and slide rule, Patty was excited to be going to Shanghai at the time of the World Expo 2010. Our trio had scheduled some time at the expo into their busy schedule.

Their plan was for Rob and The Professor to work on some productivity issues and for Patty to take on some of the process materials related problems. The three of them again met with the site GM for ACME’s newly acquired plant in Shanghai, a Mr. Wong. Wong was relieved to find that they all spoke Mandarin, as his English was a little rough. When The Professor addressed him in excellent Shanghainese, everyone was speechless. Patty was determined to ask him about this later. No American spoke Mandarin, Cantonese, and Shanghainese!

They again agreed to stick to Mandarin. Patty headed out to the line, accompanied by a young Chinese engineer, Zhou Chang, who seemed to be taking more interest in her than expected. She tried to make her engagement ring visible, but she wasn’t sure the he knew of the significance of it. When she got to the line that was experiencing yield problems, the Engineering Manager, Fei Ding, met her. He showed her some of the fails and she quickly identified the head-in-pillow (HIP) defect as the likely culprit. After investigating some more fails, looking at stencil printing, some of the BGA components, and component placement, she asked Zhou Chang what spec was used to thermal profile the line.

“I don’t understand what you mean,” Zhou said in Mandarin.

“How do you determine what the reflow profile should be?”  Patty responded.

With more discussion, Patty determined that they had one profile for all products! Fortunately most of the products were of similar, small thermal mass.

“What solder paste do you use for this line?", Patty asked.

The embarrassed silence suggested that Zhou did not know! They grabbed a tube and Patty was relieved to see that it was one of her favor solder pastes. Since profiling was so rarely performed, Patty and Zhou had to go to another part of the complex almost a mile away to find a reflow profiling unit. After taking the profile, the likely solution appeared. The 11 zone oven was very long and the reflow profile had a long thermal  “soak” before the temperature went above liquidus. This long soak probably exhausted the flux, so that when the PWB went above liquidus, there was little flux left, resulting in oxidation and poor reflow.

All during their time together she had mentioned that her fiancé Rob was here, with her on the trip. This information seemed to do the trick.

“Zhou, why don’t you look up the solder paste spec on the web and then set up the right type reflow profile,” Patty suggested.

It was clear that Zhou was troubled. It became obvious to Patty that Zhou did not know how to profile a reflow oven. Patty set about working with Zhou to accomplish this mission. Within an hour they had re-profiled the oven and, over the next two hours, 300 PCBs were manufactured with the yield improved to 95%.

Patty asked Fei if she could give a brief presentation on the head-in-pillow defect to his team and he cheerfully agreed. Fortunately for Patty, her friend Mario Scalzo had given her his presentation that he gave at APEX 2010 on HIP (head-in-pillow). Patty always enjoyed visiting Mario in Utica, NY, as he always knew the best restaurants in town.

Her major points were:

HIP is caused by the failure of the BGA sphere to reflow with the solder paste. There are 3 major reasons for HIP:

1.       Supplier Issues

a.       Solder BGA sphere oxidation

b.      Silver segregation to the BGA sphere surface

2.       Process Issues

a.       Stencil Printing

                                                               i.      Registration accuracy

                                                             ii.      Insufficient solder paste

b.      Component Placement

                                                               i.      Off pad

                                                             ii.      Out of plane

                                                            iii.      Non optimum pressure

c.       Reflow

                                                               i.      Inappropriate reflow profile

                                                             ii.      Flux exhaustion

                                                            iii.      PWB warpage

3.       Material Issues

a.       Poor solder paste transfer efficiency

b.      Insufficient solder flux oxidation barrier

c.      Solder paste slump

d.      PWB or BGA warpage

Patty went on to say that she had investigated all of these issues with Zhou, and that the reflow profile was not optimum as the very long soak time had exhausted the flux. The other possible issues in the list did not seem to be a concern.

At the end of the day Patty, Rob, and The Professor met at the GM’s office to leave together for dinner and the Expo. Patty had to ask, “Professor, how can you possible know Mandarin, Cantonese, and Shanghainese?”

“Actually I speak Min reasonably well too,” he replied.

“How can this be?", Rob inquired.

“Mother and father were missionaries with Wycliffe Bible Translators,” The Professor answered.

“I grew about around many languages during my youth. Mother and father speak more than I do,” he finished.

Patty went on to tell about the interest that Zhou Chang seemed to have in her, and how she had to discourage him.

“The burdens of being a beautiful young woman,” Rob teased.

Patty elbowed him, but they all left the taxi laughing as they headed for a restaurant near the Expo.

Best Wishes,

Dr. Ron 

The Shanghai, slide rule, and HIP images are from: 

http://pool14.files.wordpress.com/2008/12/shanghai_skyline_g.jpg

http://www.hpmuseum.org/powerlog.jpg

http://ppsimanufacturing.files.wordpress.com/2010/03/bga100.gif

My friend and colleague, Eric Bastow, got back last month from an IPC standards meeting with some interesting news for those of us who supply and use solder paste. Here I’m talking about everything from standard SMT printing and Power Semiconductor die-attach solder paste (type 3 and 4) down to PoP and waferbumping solder pastes (type 5, 6, 7 etc). I had heard that there were some changes in the way the powder types are categorized and wanted to learn more. Here is what we discussed:

[Andy Mackie] What is the current status of solder powder “type” designations from the new IPC J-STD-006B (Oct 2009)?

[Eric Bastow] In the original J-STD-006B (Oct 2008) and its two amendments, a solder particle size distribution (PSD) table, Table 3-1, was included as part of the standard to define the different powder “types”: 3, 4, 5 and so on. However, this table has been removed from the version published exactly 1 year later (October 2009) and also, somewhat confusingly, called J-STD-006B. This latter standard refers the reader to the old J-STD-005 (Solder Paste) for powder type determination by PSD, tables 2A and 2B.

[Andy Mackie] So how are solder powder types currently (May 2010) defined by the IPC? 

[Eric Bastow] The responsibility for defining the powder size distribution for the respective types now goes by default to IPC Task Group 5-24b, which maintains the J-STD-005 and its amendments and associated documents. This standard and its amendment were created in the early 90’s, and then published in January 1995, when even type 4 paste was uncommon at best, so its relevance now in the second decade of the third millennium is rather questionable, particularly given the enormous changes in solder powder manufacturing methodology and analytical characterization that have occurred in that timeframe.

[Andy Mackie] I understand that there are even some concerns about the test methods used to define the PSD.

[Eric Bastow] Yes, very much so. It is interesting to note that the original J-STD-006B Table 3-1 recognized that “Types 5, 6 and 7 are shown as general industry accepted size ranges for development purposes. Current listed methods for measuring these particle sizes may not be accurate enough for exact size and range distribution”. That initial sentence is very revealing about the tentative nature of these “type” definitions. These same concerns were raised at the J-STD-005 meeting at APEX in April 2010, and I also raised issues about the relevance of the test methods (see below) that were in use.

Note that none of these addresses the possibility of pure solder powder being the sample.

[Andy Mackie] How did you and Indium Corporation drive the Solder Paste Task Group (5-24b) into the next phase?

[Eric Bastow] We realized that using 15year old test methods and standards for solder powder based exclusively on extraction from solder paste would raise serious concerns with our customers. As a start, Indium Corporation suggested round-robin testing amongst the various solder powder suppliers. The testing will involve the use of the in-house measurement techniques of those suppliers on representative powder samples from each of those suppliers, to see what sort of data scatter is observed. We helped the task group to recognize that defining the particle size distribution of the various types, especially the finer types, does not make much sense without first determining a reliable and repeatable method of measuring the particle size.

Once that is complete, we can begin to define what we mean by each powder type, and also if there is a need for such “hybrid” categorizations as type 4.5.

[Andy Mackie] Eric: thank you, and please keep up the good work.

===

The interesting thing is that it will not affect the way Indium Corporation supplies or manufactures solder powder and paste materials according to our customers’ needs: just how we define them.

Cheers!   Andy

In the surface mount technology (SMT) electronics and semiconductor packaging industries, Indium Corporation has a reputation for offering custom solutions.  In the world of solar cell manufacturing, I hope that same status is obvious.  I feel custom solutions are even MORE important in emerging technology fields like CIGS cell manufacturing.  Being the leading global supplier of indium (the metal), and a supplier of unique solder alloy shape/size/tolerance forms, we are well equipped to offer you evaporation sources that are tailored to your application.  Sure, we can supply round shot, teardrop shot, wire, ingot, preforms, and various other bulk forms of solder to keep your evaporation chamber filled.  Did you know we can also make custom solder castings to fit your particular crucible?  The process is easy, let us know if you are interested!

(Just click here to get started)

Folks,

After a bit of a break, the adventures of Patty, Rob, and The Professor continue:

The plane droned on as it made its slow march from Detroit to Tokyo.   Patty looked down at Rob as he slumbered peacefully. She caught a glimpse of The Professor,  he looked at both of them from across the aisle with a satisfied smile. The proud mentor looking at his mentees. 

This was the first time in a while when Patty didn’t feel totally stressed. She had resisted going to China only three weeks before her wedding, but senior management insisted. She would arrive home only 5 days before the big day. She and Rob had their first real fight, she got angry with him because he wasn’t appreciating the pressure that she felt. However, with one long weekend with their moms, she was able to get most of the tasks done and finally felt relaxed that the wedding plans were in good shape.

She had to chuckle at Rob. He was all nervous being with The Professor by himself. The plans that they had made had Rob and The Professor focusing on productivity improvements at ACME’s new acquired plants in China. While they were working on these tasks, Patty would handle some process materials related issues. 

The rest on the trip went smoothly and after a night’s rest they were off to the first of ACME’s new factories. This one was located in Shenzhen. Our trio was ushered in to see the site GM, Peng Zhou, a native of the area. He addressed them in quite good English. When Rob and Patty answered in better Mandarin, he seemed shocked. When The Professor answered him in flawless Cantonese he and Patty and Rob were stunned. 

"要不咱们都讲中文吧，既然咱们中文都不错。" said Rob. ("Perhaps we should all speak in Mandarin, since we speak it well." For our non Mandarin speakers)

Rob and The Professor went off to audit a few assembly lines, while Peng accompanied Patty to visit an assembly line that was having a quality problem.

(Dialogue translated from Mandarin)

“I’m very impressed with how well you all speak Mandarin,” said Peng. “Where did you learn it?” he continued.

“Thank you,” replied Patty. "Both Rob and I studied Mandarin in college and we did an internship in China,” she went on.

“ Very impressive,” Peng commented. “But I have to tell you, I’ve never heard any American speak Cantonese at all, let alone as well as The Professor does. It’s like he was born here,” he went on.

“He never ceases to amaze me,” Patty responded.

Patty and Peng finally arrived at the assembly line. Patty was introduced to the line engineer, Elvis Chang. She chuckled inside, this was the third Asian person her age she had met that had chosen “Elvis” as an English nickname. Elvis was relieved that Patty spoke Mandarin. They went to a stereo microscope and looked at some of the assembled PCBs that had quality issues. Patty was quick to pick out the problem:  graping. She looked at the stencil and the pad sizes on the PCB. She performed a few calculations and appeared satisfied that she had the answer. Patty suggested that, if Elvis would like, she could give a brief presentation on what she thought the problem was.

“Patty, that’s a great idea, but it might be best to wait until after lunch,” Elvis suggested.

Elvis, Patty, and a few other young engineers went together for lunch. They seemed to be fascinated with Patty, especially her ability to speak Mandarin. They all spoke some English and were all studying it as they recognized that their ability to be promoted to a senior level required fluency in English. One of them pointed out that she had read that about 250 million Chinese people are studying English, while only 20,000 Americans are studying Chinese.

Patty enjoyed Chinese food and was happy to find Sea Cucumber on the menu. One of her friends said it was the only Chinese food he couldn’t eat. She tried it and liked it.

After lunch, Patty asked for a few hours to prepare her presentation. Her main points are summarized below:

1.        The aperture size for the pads that experience graping is 8 mils in diameter for the 4 mil thick stencil.

2.       The resulting area ratio (D/4t, D= diameter, t = stencil thickness) for this aperture is 0.50, less than the recommended 0.66.

3.       The very small solder paste deposit doesn’t not have enough flux to avoid oxidation of the solder particles in reflow. The resulting defect looks like a bunch of grapes so it is called graping.

4.       Likely solutions:

a.       Use a square aperture. An 8 mil square aperture provides 27.3% more volume, and it has better transfer efficiency. (Transfer efficiency is the volume of the solder paste deposit divided by the volume of the aperture times 100.) The result would be > 30% more solder paste. The more solder paste, the less likely to experience graping

b.      The solder paste they were using was not best of breed re: graping resistance. She recommended another one, which she knew performed well in all respects - and minimized graping. This solder paste’s flux was robust and designed to minimize defects like graping.

Her presentation was received very well. Fortunately some of this excellent solder paste she recommended was being used for another job in the plant. So with approval from Peng, the team switched to this paste.

After the meeting, Patty thought about how much one of the technical engineers from one of her favorite solder paste suppliers had helped her to understand graping and how to minimize it. His name is Ed Briggs and she had just attended SMTA Toronto where Ed gave a paper on graping. Much of the information in her presentation came from Ed’s paper. She had also learned from one of his blog posts on graping.

Epilogue: Three weeks later, the graping had disappeared from Elvis’s assembly line. They didn’t even need to adopt a stencil with square apertures, the solder paste change, itself, was enough.

Cheers,

Dr. Ron

Folks,

 Bob Landman’s comments to my tin whisker posts appear below. Friendly dialogue such as this helps us to all learn more and is appreciated. Thank you Bob, keep me honest!

However, Bob’s comments do not change my position, which is:

1.     Tin whiskers exist and can cause failures

2.     However, there is yet no data that suggest that there are numerous tin whisker failures, or that a significant reliability risk exists due to tin whiskers in RoHS-compliant products.  NASA's TW website notes only 26 fails.

3.     Although not completely understood, tin whiskers can be created in the lab, and mitigation (not elimination) and reliability test techniques exist and have been demonstrated.

4.    With well over $1 trillion in RoHS-compliant electronics manufactured since the early 2000s, there have been no significant reliability issues as compared to tin-lead solder.

5.     Long term lead-free reliability (> 5yrs) has not been demonstrated. Hence, mission critical products should not use lead-free electronics at this time.

6.     Tin-lead solder does not assure defect-free electronics with perfect reliability.

As I type this post, I am surrounded by more than 20 RoHS-compliant products, some dating from 2005. Outside my office, at Dartmouth’s Thayer School of Engineering, is our computer center. The thousands of RoHS-compliant products that the computer center buys each year (they get me my laptop, etc)  are almost all RoHS-compliant. No unusual reliability issues have been noted.

Bob mentions that CALCE reports that 31% of laptops fail in 3 years. This number actually seems low to me. Upon reading the paper, one finds that over 10% of the 31% is due to accidents. 
A study of 100,000 hard drives at Google suggests that hard drive fails are in the 5% range per year, which may account for much of the 20% of fails in 3 years. But what solid conclusion can be made from these data? Nothing, unless failure analysis is performed.

The sky is not falling. Lead-free has process-ability and reliability challenges, such as graping, head-in-pillow, voiding, etc. With data-driven process optimization at all steps in the manufacturing of the ICs, components and assemblies, good lead-free yield and reliability can be achieved.

Lead-free is here to stay. It is up to us to perform the experiments and develop the techniques to assure that RoHS compliant products have acceptable reliability.

Bob's comments follow:

My source for the dead vehicles that arrive at car dealers having whisker problems, comes from my former professor of physics, Dr. Henning Leidecker at NASA Goddard Space Flight Center in Greenbelt MD.   Dr. Leidecker said that in the last four years his office has been contacted by seven major suppliers of automotive electronics inquiring about failures in their products caused by tin whiskers. He said his office has contacted Toyota offering to help analyze its acceleration problem, but hasn't heard back. For full context, read the rest of the article [http://wtop.com/?nid=108&sid=1898265].

Ron Lasky confirms that parts plated in pure tin will grow tin whiskers "with a certain amount of aging". According to NASA, whiskers can grow in hours, days, weeks, months or years. It depends on at least six factors; the quality of the tin plating, the residual stress in the coating, was the coating annealed or not, grain uniformity, temperature, humidity, and unknown other factors we don’t yet understand which is what makes it so difficult to stop whiskers from growing and is why there are so many papers published on the subject (as you can clearly see at John Barnes website) yet we still do not understand why or how they grow.

So yes, is entirely within the realm of possibility that "new" products have failed due to tin whiskers or perhaps dendritic growth.

NASA cannot tell us who the manufacturers are who reported these events due to confidentiality agreements.  Dr. Leidecker says they get these calls from other industries as well and most request a non-disclosure agreement.  NASA feels it’s better to get some information rather than none, don't you agree?

Last  week at CALCE at UMd. it was reported that 31% of all laptops fail within 3 years. This is the link to the report http://www.squaretrade.com/pages/laptop-reliability-1109/  No information is given as to what has failed. Is it due to whiskers?  We do not know.

What we do know is that the laws of physics have not been repealed.  Tin will most certainly grow whiskers so using leadfree solder and tin plated components has to result in tin whiskers growing.

NASA continues to log failures.  NASA Goddard is now studying the Toyota incidents for NHTSA.  Again, a non-disclosure statement has been signed so they cannot comment on the study at this time.

Dr. David Gilbert of Southern Indiana University has demonstrated that a low resistance or shorted input between the wires from the pedal electronics to the electronics control module will cause Toyotas to open their throttles full.  Perhaps the problem is due to leadfree manufacturing (which Toyota admits it began in 2002-3)?  Perhaps it is software?  We don't yet know but we can be reasonably certain that not all the accidents are caused by the owners of the vehicles.  You can see pictures of the Toyota parts at my website [www.hlinstruments.com//RoHS_articles/Toyota/]   The pedal has a pc board layout that I would have been comfortable with.  In particular, the SOIC part that converts the signals from the Hall effect sensors (that sense pedal position) into 1-5Vdc signals sent to the electronic control module is very close to the edge of the board.  The board has serrated edges which indicates it was snapped out of a large panel of these boards after the parts were soldered to it.  It's possible a trace or lead has fractured or one of the capacitors or resistors.  We know that leadfree solder is more brittle than tin-lead. Perhaps a few boards are marginal and over time a lead opens or becomes intermittent?

The EU was warned that tin whiskers and brittle joints would result if lead was banned from electronic assemblies but went ahead and banned lead from tin-lead solder and platings on parts. They acknowledged the possibility of reduced reliability under intense pressure from hi reliability industries and did exempt some products (military, aerospace, etc...).  What difference did it make since the majority of component manufacturers refused to continue to offer tin-lead plated leads?  That is why NASA replates it's components with tin-lead at Corfin Industries and uses only tin-lead solder.


Bob Landman

http://www.hlinstruments.com//RoHS_articles/Toyota/Toyota%20Dr%20Gilbert%20Preliminary_Report022110.pdf

Folks,

After my recent post on the fact that there was no data linking tin whiskers to the Toyota sudden acceleration issues, there continue to be more posts saying things like “Tin Whiskers Implicated in Unintended Acceleration Problems.”  Many of these posts link back to the earlier TechEye post.   The basis for all of the posts, is a paper written by EurIng Keith Armstrong .   Armstrong’s paper is titled: “Toyota ‘sticking pedals’ recall is a smokescreen, Their sudden unintended acceleration problem is caused by electronics either due to EMI, lead-free soldering or software ‘bugs.’” It does not appear that Armstrong’s paper was sponsored or refereed. 

Since it appears that this entire wave of reporting implicating tin whiskers, in this important issue, emanates from Armstrong's paper, it is helpful to quote his entire comments on Tin Whiskers:

            "9.0 Lead-free soldering:

In recent years, various countries and trade blocs (including the European Union) have banned the use of lead on electrical solder, on the basis that lead going into landfill when electrical and electronic products are disposed of is bad for the environment, and hence for people.

But many accuse them of being shortsighted – lead has been added to solder in quite large amounts for many decades because it made the other main constituent, tin, behave much better, considerably improving reliability.

Now that lead has been removed from solder, which is now mainly tin (with a little silver and copper added) all sorts of new possibilities arise for short-circuits and open-circuits, and intermittent shorts and opens, mainly on printed circuit boards (PCBs) and mainly associated with small-footprint integrated circuits (ICs), especially ball-grid arrays (BGAs).

Its really just another cause of intermittent or fixed short-or-open circuits in electronic PCBs and modules - but one that would not have been any problem until a few years ago, and so could have caught Toyota by surprise.

John R Barnes has created a monumentally huge library of references to the problems of lead-free soldering, especially tin whiskering, see www.dbicorporation.com/rohsbib.htm. Prepare to be totally overwhelmed!

Removing lead from solder has the following effects:

9.1 Tin whiskers

These will grow out of soldered joints and can contact other conductors, causing short-circuits between PCB copper traces and the pins of connectors. They are often no longer than 0.5mm (about 1/50th of an inch) but can grow to 1mm (about 1/24th of an inch) or longer, especially in damp conditions.

Even at 1/50th of an inch they can short between the pins on a modern integrated circuit (IC). And the process of removing the PCB for inspection can brush them off, so you never find them.

And if you didn't accidentally brush them off, they are so thin they are very hard to see - you need a powerful microscope. They are as fine as the finest spider-web threads, yet can carry sufficient current to short-out the electronics. You won’t see them unless you are looking for them.

Being so thin, they can wave around in the breeze and/or due to shocks, vibration and acceleration, causing intermittent short-circuits.

The iNEMI organisation has published guidelines (www.inemi.org) on how to ensure that tin whiskers don’t grow too long, but I don’t know to what extent these are followed by suppliers of electronics to the car industry in general, or Toyota in particular."

Note that, in this paper,  there is no data or any evidence re: tin whiskers discussed from investigating any of the vehicles in question. All of this paper is an opinion.   In addition, the title of Armstrong’s paper leaves no room for any other cause, it has to be electronics or software. This position is very strong indeed for having no supporting data.

More recently Bob Landman added these comments to the tin whisker discussion:

“the increased use of electronics in automobiles when mixed with RoHS can make for a deadly cocktail. We don’t know what the causative agent [in regard to the Toyota recalls] was, but I have heard recently of new autos showing up at dealers that will not start. That cause has been linked to tin whiskers.”

Bob heard this. There is no report and no data. Until Bob gives us a reference for some analysis and data, his comments are little more than hearsay.  I searched the web in vain to find information related to Bob’s quote. In addition this comment is a little surprising, tin whiskers are usually associated with a certain amount of aging, hence not usually found in new products.   

That tin whiskers exist and cause failures is irrefutable. NASA  has an excellent website related to tin whiskers and failures caused by them. However, the total number of tin whisker fails reported is less than 100. Many other types of electronic failure modes would appear to be much more common.

My purpose of writing this post is not to suggest that tin whiskers are not a concern in lead-free electronics. However, it is a fundamental principle in engineering and science to only make pronouncements on how something failed, when they can be supported with data. No data supports implicating tin whiskers in the Toyota incidents. It is also troubling how readily many people referenced the work of Armstrong without apparently reading what he said and checking his sources and lack of data.

Patty was checking her email. She noticed a note from someone who had attended last night’s SMTA meeting. Patty 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 people 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 thought that this perspective was 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 shows like APEX and SMTAI. 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 isperformed in poorer countries with chemically unsafe processes. 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 poore 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, "我可能要出差去中国探访几家ACME在那里的新工厂。我想你可能也要在焊接工艺上做一些工作。"

(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 5 weeks before their wedding.

“Easy girl,” 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 3 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 of their dads had 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.

Forming gas is a complicated topic, so I will provide some preliminary background in this section, then get into the soldering part next time.

Don't you mean "formic"?
 

Forming gas is a mixture of hydrogen (H2) and an inert gas (usually nitrogen, N2) that is used to reduce oxides on metal surfaces to water. Please don’t confuse this with formic acid (HCO2H), which I hope to touch on in another posting later this year.

Safety

The reason for the dilution of hydrogen by the inert gas is to keep the hydrogen below 5.7% (by volume), as this is the point above which the hydrogen can spontaneously combust. Gas companies such as Linde and Air Products consider forming gas at less than this level to be an inert mixture, so the fittings used for gas cylinder attach are the standard CGA580 type used for nitrogen, argon, helium and so on. Depending on the gas supplier, they may allow a maximum of either 5.0% or 4.0% hydrogen, to ensure they are within safety margins.

All this notwithstanding, 100% hydrogen furnaces are used around the world in a variety of different processes, and I have also seen soldering processes around the world where 10% and even 20% hydrogen/nitrogen forming gas is in use. I am not saying that >5% H2/N2 can not be safely used, but you have to be careful when using it.

 
Gas Supply

There are three ways of supplying gas for forming gas-based soldering processes:

1/ Mixing hydrogen and nitrogen in a special panel. Sometimes this may also incorporate a catalytic reactor that reacts ppm traces of oxygen, with hydrogen to form water: the water  is then removed by adsorption. This process makes a very "clean" forming gas that will have optimal reducing properties. Usually, the nitrogen source is from vaporised cryogenic N2, and the hydrogen is from a cylinder or "tube"-based sources.

2/ Cylinder supply. A single cylinder, or a manifolded bank of cylinders may be used to provide the gas as a mixture. Usually, this is used as-received without being cleaned up.

3/ Ammonia cracking. Basically, NH3 -> 3N2 + H2. This is feasible, but results in a fixed 3:1 ratio of N2 to H2, and is never used (to my knowledge) in soldering. It is also massively inefficient in terms of costs and power usage to make the ammonia, plus the ammonia usually has a much higher moisture content than a nitrogen plus hydrogen gas mixture.

What does it do in soldering? I’ll get into that next time: I'll be talking thermodynamics and kinetics, and there WILL be a test.

Cheers! Andy

Today I made my rounds in the office, collecting ideas for you from our tech guys  - ideas to help you speed the alloy and flux selection process.  The team gave me ideas from the start of the design process all the way up to speeding the order process, and all the steps in between.  These are solder basics, but they can help you get your process up on its feet quicker - if you put together a little information up-front:

1) Call a tech guy early, but be prepared by knowing the specifics of your material needs, like powder size, flux type, and any design requirements.

2) If you’re an engineer specializing in component attachment, get yourself involved with the component or board design team. It may mean extra meetings, but it will save many headaches in the long run after you help the team remember the meaning of “design for manufacture”.

3) Define the details of your application, equipment, and process before selecting a material. For instance, knowing the needle size that you will be utilizing in a dispense machine will speed the powder size selection for die-attach solder paste.

4) Be aware of cleaning requirements and your current in-house cleaning equipment and chemicals before choosing a flux or flux vehicle.

5) Understand the operational temperature of your assembly and the maximum processing temperatures of the components. This will make alloy selection much faster.

6) Don’t get hung up at the ordering process – know what size packaging you need. Do you have equipment that only fits a certain size syringe or cartridge?  Knowing this ahead of time will save you a second call to verify while talking with an Account Specialist.

7) For alloy compatibility and metallurgical considerations, be prepared to lets us know the composition and thickness of your surface finish. This will also save a second call, because it is required information in order for us to get you the right alloy and the perfect flux for your application.

8) For solder paste printing recommendations, know the specifications of the stencil you will be using. Aperture size, stencil thickness, and any other dimensions you can provide will help guide which flux vehicle and powder size we will recommend to you.

9) For preform selection, try using thinner preforms. For prototype situations you can stack the thinner preforms to build solder volume, and it is much quicker to order preforms in 1 thickness as opposed to many thicknesses.

10) Understand your process bottlenecks. By letting us know your material needs we can usually suggest a few materials, but perhaps one of those materials can help eliminate a problem that is slowing your process down.

11) Consider your company’s roadmap for the next 5 years. It doesn’t make sense to select a material and need to select a new one only a year later. Save yourself the time involved in a second solder evaluation and know what the future holds regarding safety/environmental concerns. Likewise, understand the roadmap of your supplier, their future materials, and how their current materials will fit your company’s future plans.

As a supplier of electronics materials, Indium Corporation is constantly faced with customer requests for “halogen-free” (HF) soldering fluxes and associated materials. This is an interesting trend, but we face several challenges here:

1/ What is “halogen-free”? We have not seen any consistent message from our customers on what they mean by a halogen-free flux. As a materials-supplier this is an absolute show-stopper.

Based on several conversations with interested parties, my understanding of the IPC status is as follows, and apologies for any misunderstandings to Tim Jensen (Indium Corp.) and Tom Newton (IPC). The IPC’s 4-33a Task Group, which was looking at a universal halogen-free material standard (J-STD-709), saw a failure of a second ballot on the standard, even when it got downgraded to a guideline. The 4-33a group faced numerous differences of opinion: on what materials should be included; what halogen levels are allowable; or even whether a single component could be considered a "homogeneous material” to be ground up and analyzed for halogens and so on. The task of defining HF will now reportedly be taken up by two separate groups from IPC and JEDEC.

Meanwhile, in March of this year, the Japanese organization JEITA quietly released their understanding (ET-7304) of what is meant by HF fluxes and solder pastes, using a 1000ppm halogen limit. This definition is clearly at odds with the IEC's definition of HF. That is, 900ppm by weight maximum of chlorine or bromine atoms, or a maximum of 1500ppm of both: the so-called “9-9-15” limit. .

2/ Which halogens? The strict definition of a Group VII element (halogen) is one of Fluorine (F), Chlorine (Cl), Bromine (Br), Iodine (I) and radioactive Astatine (At). From environmental reasons, chlorine and bromine in halogenated fire-retardant (HFR) materials that emit dioxins and similar compounds when heated should be eliminated. However, some customers are also throwing fluorine and iodine into this definition, too. This may be based on fears of electrical reliability, but from my perspective the customer is becoming defocused from the necessity of meeting environmental concerns.

3/ Does halogen = halogenated fire retardant? Not every halogen found in an electronic material is an indicator of a halogen-containing fire retardant!

Greenpeace is the main driver behind this, and I have, to date, been unable to get a response from them on how they will detect halogens on circuit boards. The fear from our customers, and our customers’ customers, is that an electronic device (iPhone / flat-screen TV or other) will be obtained by an environmental group; pulled apart; and X-ray fluorescence (XRF) used to detect halogens. The minimum sample size that can give a quantifiable result for halogen-free is reportedly 2grams: contrast this with the milligrams of material (residue) present from a no-clean flux in a cellphone, and you can see the issues in quantifying halogen levels based on flux residues. We can’t do it reliably.

4/ How can we confirm “zero” halogens? Contrast the JEITA standard with the requests from many customers for zero halogens / “no intentionally added” halogens / “elemental halogen-free” fluxes or some such. However, since many customers insist on third-party data-reporting, we are reliant on these analytical labs to reliably give us data. One of the challenges we face is when, for example, a lab reports “63ppm of chlorine”, based on a reported limit of detection (LOD) of 50ppm. Our customer is outraged: “You said it was halogen-free!”

Those of you familiar with the statistics of analytical chemistry will immediately see the two fallacies here: the first is that they have reported not the method detection limit (MDL), but the much-lower LOD. The MDL is a function of analytical equipment PLUS the errors in sample preparation and handling. The second fallacy is that you can not report 63ppm as a reliable, reproducible number, since the limit of quantitation (LOQ) – the limit at which you can actually give a figure for the concentration – is more than 3 x the MDL. The limit of analytical capability to reliably quantify the amount of halogen present is therefore around 150ppm or greater.

Instead of reporting “63ppm halogen”, a more accurate statement is: “In our single test, we found a small peak in our spectrum at the same elution time as a halide-ion. It may be a halogen, or it could be one of the millions of anionic organic species that elute at the same retention time. The quantity found is well below the method detection limit, so we have no way of knowing if it is from contamination during the sample preparation, and we certainly can not tell how much is present.”

5/ What is a ‘homogeneous material”? Some customer standards require the level of halogen in a homogeneous material to be reported. We can probably safely say that a flux is a “homogeneous material”, but is a solder paste truly homogeneous? Both JEITA and Indium Corporation can agree that the flux-content needs to be the focus of the analysis, but a solder paste supplier may, for example, take the analysis of a 90%w/w metal solder paste, and report the results as “890ppm chlorine”, knowing that the level in the (10%) flux is 8,900ppm chlorine, essentially diluted by the 90% metal content.

Conclusion:

As a global electronics materials supplier, we at Indium Corporation can see three possible solutions to all these dilemmas:

a/ Adopt the JEITA specification – even though it goes against the 9-9-15 EIC recommendation. This allows us to be on a level footing with our Japanese competitors, but appears to put us at odds with the needs of some of the semiconductor assembly and electronics assembly industries.

b/ Adopt a three-tier specification based on the IPC/IEC recommendation – the Indium Corporation approach is given here (below).



Why three levels? Because our more discriminating customers are telling us that truly halogen-free fluxes are simply not as effective as those that contain small amounts of halogen. For those who are concerned about end product reliability, a “halogen-compliant” tier allows the best of both worlds.

c/ Report the atomic chlorine and bromine levels present in the flux component, and allow the customer to choose what they want, based on this.

If you are a user of Indium Corporation materials, or even a competitor of ours - what makes most sense here? Or is there a fourth or fifth way?

Cheers! Andy

Dr Jennie Hwang

I recently had the opportunity to discuss several issues in Pb-free die-attach and other solder applications with Jennie Hwang PhD, DSc, and world-renowned consultant in solder and  electronics assembly processes. 

Cheers! Andy

You may notice that many of the solar grade fluxes and solder pastes are designated 'no-clean'.  This classification is used to describe a flux or flux vehicle that does not need to be removed (cleaned) after soldering.  In much the same way as the mosquito in "Jurassic Park" was preserved, flux activators are also encapsulated within no-clean flux as it cures during a typical heating cycle.  Unless you plan on fully removing the no-clean flux residue with a commercially available cleaner specified for that flux, it is better to leave the residue alone.  Partial cleaning of no-clean residues can uncover small amounts of flux activators – like uncovering the mosquito in the tree rosin.  The flux activators have the potential to cause corrosion or electro-migration when exposed – so make sure you get the right solvent if you do plan on cleaning these materials! 

It might sound scary, but no-clean fluxes are very common in today's electronics assembly – including military, medical, and high-reliability applications.  There is no question that electronics assemblers and material suppliers have done their due diligence in qualifying no-clean materials.  In the end you can put your mind at ease, modern no-clean materials are classified as such after standardized testing for electro-migration and surface insulation resistance.  This testing allows flux suppliers to safely provide no-clean materials that can function well in various soldering situations and eliminate the need for a post-assembly cleaning process.