Solder

最近的客戶拜訪中，大家都對Indium公司的新焊錫棒(Solder Bar) Sn995十分感興趣。 Sn995是一種無鉛的焊錫材料，不含銀，主要成分是99.5%的Sn, 大約0.5%的Cu, 還有一些微量元素。Sn995的主要微量元素，是Cobalt 鈷 (Co)。

先在市面上的無鉛焊錫棒，除了SAC305， 也有很多SnCu+Ni的材料。在我們各種可靠性試驗中，都發現“Cobalt is a better grain refiner.”

²       Functional Test 整板功能性測試

²       Thermal Cycling Test 熱循環測試

²       Intermetallic Growth Test

²       Wetting Test 潤濕測試

²       Shear Test 剪切力測試 

²       Pull Test 拉力測試

²       Accelerated Aging Test 老化測試

²       Hole Fill test 填孔測試

²       Copper Loading Test

²       Dross Test

在以上的所有測試試驗中，Sn995 都呈現出相同或是更好的性能。進一步的詳細測試信息，歡迎隨時聯係我們: askus@indium.com china@indium.com

Cheers!

Picture: Jim Hevel with Indium Corporation

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!

Over the past few years, I have been forced to come to terms with my current (and ever-growing) knowledge of “things”. It is easy to become overwhelmed by the engineering veterans who have minds swollen with information following their decades of professional exposure. The key is to admit what you do not know so that you can learn from their explanation, and then chime in when your own expertise fits and appears helpful.

I am not an expert of all “things.” In fact, I am so terrible at Jeopardy that my husband has developed his own character skit of me “playing” the show (and losing miserably) from my living room couch as he listens in humor from the kitchen. I am an expert in some things though, and these are what I highlight in my thermal blog. 

This is why I am so excited to see a fellow engineer starting his own thermal blog!! Highlighting his expertise in the thermal benefits of AlSiC, Mark Occhionero describes the usefulness of this material in various applications such as hermetic packages, baseplates for power modules, and lids for microprocessors. 

AlSiC materials have great thermal conductivity and the ability to shift CTE based on the amount of SiC filler used. This allows for CTE matching of lids to dies, and packages. With CTE-matched substrates, high reliability soldering for bonding and thermal interconnections is a breeze!!

剛剛看見一篇挺有意思的文章，標題是“全球LED三大陣營比較及廠商排名”，不禁讓我想起最近確實有更多的客戶問起關於LED的封裝和散熱材料了。

除了傳統用的焊接材料(soldering material)外，最近的好些客戶都問到關於散熱方面的材料，主要是針對高功率，高亮度(High Power High Brightness HP HB)的LED應用。傳統的硅膠(thermal grease)因爲其化學特性，導熱率比較低，而且容易在界面中移動，不能使接觸面都均勻導熱。最重要的是，隨著時間的流逝，硅膠的導熱性能會越來越差，所以現在越來越多的客戶在尋求更好的解決方案。

Indium公司的散熱界面材料（Thermal Interface Materials TIM）， 都是使用導熱係數比較高的金屬/合金，加上特殊的表面處理后，能更完整均勻地接觸導熱界面。而且即使隨著時間流逝，金屬的TIM的導熱性能也能保持穩定。

Indium公司還特意推出的網上的購買，為各種學校/機構/小量使用購買者提供方便。

Cheers!

Image: Indium Corporation.

Folks,

Patty and Rob return from their honeymoon.......

Patty had just finished some emails and was ready to head off to meet Rob and some of their buddies for lunch. When she and Rob returned from China a month ago, Sam, the site GM, told both of them he was giving them an extra week of vacation for their honeymoon. Their China trip had been an unqualified success in helping the China teams achieve more productivity and higher yields. Sam had received numerous positive reports from the Chinese managers involved. There were several requests to have Patty and Rob stay a year in China to help with the many process issues that the China team has. Fat chance of that happening, Sam needed Patty and Rob here! Sam also mentioned that he knew that the trip was a little stressful coming so close to their wedding, so the extra week was ACME’s gift to the young couple for their sacrifices.

The wedding went off without a hitch. Patty was touched at how choked up her dad was in “giving her away.” The weeding reminded Rob and Patty how close they were to their parents. They both agreed that the support of their parents was crucial in any success that they had in life.

For their honeymoon they decided to tour France, Italy, and Germany. Rob was really proud that he handled the languages a little better than she did. Of all the things that they saw, they were most impressed with Pompeii. Because the city was covered in hot ash in a matter of moments, it was as if Pompeii was frozen in 70AD.  Visiting Pompeii was like stepping back into the time of the Caesars.

Truth be told, Patty was happy things were back to “normal.” It was pleasant to have their working schedule and to go home to their apartment at night. A couple nights a week, and most Saturdays and Sundays, she and Rob played golf. He had improved somewhat and she was a little annoyed that so far this year he had beaten her more than half of the time….and yes, he was rubbing it in.

As Patty approached the cafeteria she heard a friendly but heated discussion.

“No way can you evaluate an assembly company with just 10 questions,” Phil Anderson stated emphatically.

“I’m really convinced we can, I’ve thought it through a lot,” responded Rob.

“What’s the spirited debate about?" asked Patty as she sat down.

“Rob thinks you can evaluate an assembly company by asking a lead process engineer only 10 questions. Phil thinks he’s nuts,” responded Patty’s best friend Jan Curtis.

“I’ve thought about this quite a bit,” said Rob. “I’ve just finished reading Malcolm Gladwell’s ‘Blink.’”  “Gladwell claims that often the best judgments can be made quickly with just a sampling of data,” Rob went on.

“Be specific,” challenged Phil.

“OK, I actually developed 10 proposed questions to evaluate a assembler, let me list them and then defend them. Maybe you guys have better ones,” said Rob. 

Patty thought, as she heard this, that it was good news that ACME was looking to buy more assembly companies to handle their ever increasing workload……not like AJAX that was laying folks off.

Rob had come prepared, he actually had some print outs. His ten questions were:

1.      What is the composition of SAC305?

2.      What are tin whiskers?

3.      In a stencil aperture, what is the area ratio?

4.      What is an approximate peak temperature for a reflow oven in lead-free assembly?

5.      A board is inspected after wave soldering and one lead is not soldered to the board. The board is run through the wave solder machine again and has the same defect on the same lead. What is the most likely cause of the defect?

a.       The solder temperature is too low.

b.      The pad on the board is oxidized.

c.       The preheat temperature is too high.

6.       What are local fiducials on a PWB for?

7.       What does thixotropic mean in regard to solder pastes?

8.       A chip shooter places passives at a rate of 36,000 per hour. It is placing 300 passives on a PWB, how many seconds will the chipshooter take to place the passives on one board?

9.       A reflow oven belt speed is 100 cm/min. The PWB is 40 cm long. What is the minimum cycle time that the oven can support?

10.   What is tombstoning?

“You have got to be kidding,” shouted Phil, “everyone will score 100% on that test.”

Jan chimed in, “I’m not so sure. We hang around people all day who study this stuff. I’m not sure the typical process ‘engineers’ have enough time to study and learn new things…..Remember the 'water in the solder' and the 'isopropyl in solder paste' incidents?”

At this comment, Phil spit up his ice tea and started choking from laughter. One of their friends, Sally Herman, had been sent to a recently acquired company to help them with assembly process issues. One of the “process engineers” introduced himself by bragging that he was saving the company money by taking used, dried solder paste and mixing it with isopropyl alcohol so that the paste could be used again. Later in the day, the same chap shared that he thought he had a solution to the poor hole fill problem in lead-free wave soldering…….the solder was too thick, if it was mixed with water it would fill the holes better he opined.

Jan added, “As a minimum these questions act as a good screening process.”

Rob interjected, “That’s my point. I’m not saying this tells us everything, but you will agree that if a lead process engineer can’t handle these questions, it is unlikely he or she would be able to solve graping, or the head-in-pillow defect, right?"

All at the table murmured agreement.

“On second thought, maybe you have something here Rob," Phil said. “What do you propose as a passing score," he went on?

“Seventy percent,” Rob answered. 

Are Rob’s questions reasonable to evaluate an electronics assembler? What are the answers? Comment with your answers. Stay tuned to find out.

Cheers,

Dr. Ron

The image above is from: http://en.wikipedia.org/wiki/File:Blinkgla.jpg

在表面貼裝技術(SMT, Surface Mount Technology)以前，主要流行的是波峰焊(Wave Soldering).   雖然現在大部分的電子產品焊接都是SMT，但是某些不需要微型化(miniaturization)的產品，如DVD播放機，還有波峰焊的低成本優勢，都是波峰焊技術至今還存在的主要原因。 Indium公司的資深顧問Dr. Ron Lasky曾經説道，波峰焊技術在我們的下一代，下下一代，都應該還存在的。

最近又有一個客戶和我們一起探討波峰焊助焊劑(wave flux)的殘留問題。他們使用的是免洗(no clean)助焊劑。正是因爲免洗，所以各種不同的助焊劑，有不同量的殘留。 而客戶的客戶，也在對殘留的多少有一定的疑問。 其實現在在IPC的規定中，沒有具體規定免洗波峰焊殘留的多少是符合要求的。 最後我們根據客戶對焊接外觀和可靠性的綜合要求，推薦了最適合的一款產品。

Cheers!

PS: 一些年長的客戶或是合作夥伴總是開玩笑說“我在這個行業工作的時間一定比你的年齡長。想當年手工焊接或是波峰焊的時候……”

Pic: http://enc.ic.polyu.edu.hk/Zhengde/z2003/ws/images/pic2.png

Folks,

Tin Whiskers (TW) continue to generate considerable interest. People often suggest that their risk is great and yet unknowable. RPN may help to clarify the TW risk. What is RPN? It is the risk priority number from failure mode and effect analysis.  As this link tells us:

A failure modes and effects analysis (FMEA), is a procedure in product development and operations management for analysis of potential failure modes within a system for classification by the severity and likelihood of the failures. A successful FMEA activity helps a team to identify potential failure modes based on past experience with similar products or processes, enabling the team to design those failures out of the system with the minimum of effort and resource expenditure, thereby reducing development time and costs. It is widely used in manufacturing industries in various phases of the product life cycle and is now increasingly finding use in the service industry.

RPN is an important part of FMEA. It is the product of three numbers that range from 1 to 10. The first number is the severity (S) of a possible fail. A “10” would be given if the failure injured someone, “7” would be assigned if the failure caused a high degree of customer dissatisfaction, whereas a “2” would be given if the failure has only minor negative effects.

The second number is occurrence (O) of a fail. The highest rating is a “10,” which would be a failure every day (reminds me of Windows ME!) or one fail in 3 events, whereas a “7” would be a failure every month or one in 100 events. A “2” is a six sigma fail rate.

The last number is detection (D) of a potential fail. A”10” would suggest that the detection of a potential fail is either not performed or not possible. A “7” is a manual detection approach that may not be reliable, whereas a “2” is 100% effective potential failure inspection.

So obviously a product with a RPN of 10x10x10 = 1000 is a disaster, its failure is dangerous, frequent and incapable of being detected beforehand. Industry rules of thumb suggest that and RPN of 200 needs to be addressed and an RPN of 75 is usually considered acceptable.

Let’s look at a “ball park” RPN for tin whiskers (TW). We will assume the application is a critical IC in a PC.  Let’s assume that a severity rating of “S” of 8 (failure renders the unit unfit for use) is reasonable. TW are hard to inspect for future fails, so detection, “D,” could be as high as a 10. At this point we are at 8 times 10 equals 80 for both. A bad start.

Occurrence , “O” for TW failure modes is dramatically different. When trying to assess the occurrence of TW fails, one is often directed to NASA’s web page . Many reference this web site that lists a little more than a score of TW fails. What escapes me is that people don’t seem to appreciate the rarity of less than 100 fails in decades of data collection. Surely TW fails are not common. I could find no report of a failure of a RoHS compliant product anywhere on the internet. So it would be hard to rate “O” any higher than a “2.” I suspect that the reason few TW fails have apparently occurred is due to TW mitigation techniques that are widely practiced.

I would expect that “modern” process defects like the head-in-pillow or graping defects could have a much higher RPN than TW, if assembled without proper process controls and materials. However, there is little need to worry about these defects either, if you use the right solder paste and practice some assembly process precautions.

I’m really excited about a new option for those of us who are prototyping solar assemblies or evaluating new tabbing ribbon materials. I’ve been waiting for something like this – everything you need to solder solar cells together in one package. The turn around time is key too – you may recall an older post where I learned how quickly these materials shipped.

On the website where these kits are offered, the description reads:

“Tabbing ribbon kits come with everything you need to evaluate how Indium Corporation materials will work with your solar cells and assembly process. The kits can be used to:
- Evaluate which tabbing ribbon size is best for your design
- Determine which flux is best for your operation
- Experiment with new solder coating alloys
- Assemble a few solar panels”

The tabbing ribbon kits come in 3 flavors:

- Standard Sn/Pb/Ag (62Sn/36Pb/2Ag)

- Pb-Free (96Sn/4Ag)

- Low Temp Pb-Free (58Bi/42Sn)

I have a feeling the Low Temp Pb-Free kits are really going to be the most popular of the 3 that are offered though. Application temperature ranges will determine which kit to use, but all three versions of the kits are said to offer similar base copper sizes and tolerances:
“The ribbon itself is industry standard CDA 110 (99.9% Cu) core flat wire, coated with a precisely controlled layer of solder. Each ribbon is manufactured using our proprietary softening process so you can increase the yield of your stringing process.” Basically, this means that the softer tabbing ribbon will help eliminate the breakage of thinned cells during the heating/cooling cycle.

It also includes some matching bus ribbon to complete your panel build. If you’re trying to find the right flux, this kit serves dually as a flux evaluation kit as well. The kit is loaded with VOC-Free flux, rosin-based flux, and resin-based tabbing fluxes. I prefer GS-5454 as a flux for most tabbing operations, but you can see how the others stack up as well.

Let me know how you like the kit after you try it out!

~Jim

(jhisert@indium.com)

最近有越來越多的客戶問到金錫焊接材料。這些客戶中，多數是做航空航天製造的，醫療器械/零件組裝製造的，或是軍用製造的；它們都對成品的可靠性要求十分高(High Reliability).

金錫電子焊接材料(AuSn Soldering Materials)，通常使用共晶合金80%金20%錫，熔點溫度是280⁰C.  這種合金有很強的焊接強度，抗腐蝕，而且熱傳導效能很好(high thermal conductivity).   如果客戶的板子是厚金鍍層，或是要和貴金屬焊接在一起的，又或有分溫度階梯焊接需求的(step soldering)，金錫焊接材料都是很好的選擇。

 金錫焊接材料焊接材料可以做成焊綫(wire)，泊帶(ribbon)，各種形狀和尺寸的焊片(preform)，或是焊錫膏(solder paste)。Indium公司有專門介紹金錫焊接材料的blog，歡迎參閲。

Cheers!

Pic: Indium Corporation

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

Wandering through the references to indium metal on the internet, I sometimes see it referred to as, "that 'rare' metal."  But is it really so rare?  I recently talked to my colleague, Claire Miko, Director, Metals and Chemicals for Indium Corporation and asked if the reports of the rarity of the metal (like the death of Mark Twain) were greatly exaggerated.

Question:  The element indium is widely used today in many electronic (glass coating, low temperature solder, hermetic sealing and thermal interface material) and solar applications (CIG solar panels), but very little is known about it.  Can you tell us where indium metal comes from?

Claire:  Indium is a by-product of several base metals such as zinc, lead, copper, tin and other poly metallic ores. It is very abundant on the crust of the earth (much more than silver for example and the annual silver production is at least 40 times bigger than the annual indium production). Geographically indium is abundant in South America, Canada, Australia, China and the CIS, i.e. the reserves are widely spread.

 
Question:     Does indium have to be refined after it is mined?

Claire:    Indium is present in the base metal ores at ppm levels. It first needs to be separated from the base ore and concentrated. This is done at the base metal smelter (for example during the refining of zinc, lead, copper, tin etc). It is then further refined and purified at indium refineries.

Question:  Indium Tin Oxide (ITO) is the one of largest indium-containing products today.  How much of the indium mined goes to making ITO?

Claire:   About 50% of the indium refined is used for making ITO. A larger percentage is needed to start the ITO target productions but the sputtering process used (when putting the ITO layer onto the glass) is inefficient and generates a large quantity of indium which is reclaimed and is then recycled and put back into circulation.

Question:     Is there enough indium available to meet the current and future needs of the marketplace?

Claire:   The indium production has always expanded to meet growing demand. Indium production grew from 70MT (metric tonnes/year to over 500MT/year over the last 20 years. At the moment only one-third of the indium mined yearly is being refined in indium metal, another third accumulates in residues that are more expensive to treat but they remain available for future processing, and the last third is currently lost because it does not reach a base metal smelter which has the equipment to separate it from the base metal ore. Investments at these smelters would enable the extraction and refining of these quantities if the need arose.

Question:    Are there recycling programs in place to recover unused ITO from the targets used to deposit it onto the glass surfaces where it is used?  What is the rate of recovery?

Claire:   There is ample capacity to treat spent ITO targets (as per point 3) and the recovery process is now mature and very efficient. The cycle time of this process has also now become very short enabling a very quick return of the refined indium for new consumption.

Question:    Are there any viable alternatives to ITO?

Claire:   A far as we know ITO remains the best material for LCD and other flat panel displays applications. It offers the best performances in terms of optical transparency, electrical resistivity, uniformity of both transparency and resistivity, chemical and mechanical stability, resistance to corrosion, and, finally, uniformity of etching.

The cost of the ITO on 42” TV represents less than $2 and less than 1% of the display cost. It is a small cost to pay to ensure that the quality of the display is maintained. Alternative materials have shown significant process problems with resistivity, uniformity and chemical and mechanical stability.

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

• It stays pliable at cryogenic (-150C) temperatures.  This means that indium seals that are exposed to these cold temperatures will not crack or fail like other metals will.
• Indium is great for bonding non-metallics such as glass, quartz and certain ceramics.
• Since metals expand at different rates, this mismatch can cause a bond to break during heating and cooling.  Indium compensates for these differences.
• Indium cold welds to itself so you can apply an indium coating to two surfaces like glass, quartz or certain ceramics that cannot be soldered and cold weld them together.

前段時間有一個客戶，詢問了我們如何解決解決錫膏粘刮刀問題。 產品是Indium公司有鉛產品的黃牌Indium 92J.

詳細了解了客戶的使用過程后，我們給出了以下4個建議：

1．   提高印刷速度print speed.  錫膏的flux設計中，有一種叫做Rheological Additives的材料。正是這種材料，能使錫膏在儲存的時候，金屬粉和flux能夠均勻融合在一起，不會出現分層現象。而在印刷時，印刷的剪切力使viscosity 下降，能很好的下錫。但是，如果印刷速度太慢，Rheological Additives不能使錫膏很好的滾動起來，就會出現錫膏粘刮刀問題。 所以，印刷速度因該在合理的範圍内。

2．    関掉EAU Environmental Air Control.  很多新買的印刷設備，使用時都會忘記關上EAU，就是“空調”。 太冷了容易使錫膏viscosity 增加，造成錫膏粘刮刀。

3．    檢查金屬成分比Metal Load.  每一款產品，都由最適合自己的金屬成分比。金屬成分比稍微偏高了，也會造成錫膏粘刮刀。  隨著無鉛化和微型化，無鉛的4號粉金屬成分會相對低一點。

4．     檢查錫膏在網板上面的放置。 一般來説，在網板上面不能放置太多的錫膏，使錫膏粘到刮刀的holder上面了。這樣當然會粘住刮刀，不利于印刷。

如果有任何技術問題，歡迎隨時訪問Indium的online support網站：http://knowledge.indium.com/  或者隨時發郵件給我們：askus@indium.com ,  china@indium.com

Cheers !

Pic : Indium Corporation

Solderspheres or solder spheres, or even solder balls: whatever you call them, Indium Corporation has been making them for years and has rightly acquired the reputation for doing whatever it takes to meet our customers' unique needs.

Unique Alloys:

Hard to find alloys (like multipart alloys; low-melting alloys and even gold/tin (80Au/20Sn)) are our bread and butter. As "Indium Corporation" it should be no surprise that we lead the world in our ability to supply low-melting indium-alloy solder spheres, as well as other forms of these alloys, such as engineered solders or solder pastes.

Unique Quantities:

We don't want you to buy more than you absolutely need. If you just want 100 spheres, we can easily do that: if you want more - we can do that, too. But remember that, because each customer's need is unique, our prices may be higher than our competitors, especially for more standard alloys. Some customers also have unique inventory-control needs, so we work with many customers to ship on-demand by retaining a buffer stock of spheres here at Indium.

Unique Sizes:

Our current dimensional capabilities as of this writing are from 80microns to 0.062inches, or even bigger. Generally, the bigger the sphere - the less spherical it is (within the limits of surface tension and viscosity), and we can't control the laws of physics, so instances where a very large amount of solder is needed, a preform may have better dimensional control. Also, notice that we won't ask that you order in a specific unit of diameter measurement, like the mil or the micron or the millimeter: we're a global company - just tell us what you need.

Unique Packaging:

Often needed for more delicate alloy spheres, we can offer specialty overpacking that eliminates oxides from the atmosphere around the solder spheres, essentially stopping oxidation in its tracks. It's the same technique we use to package our soft solder die-attach (SSDA) wire: a technique that showed that the very reactive wire was still "as new" 3 years later. We also offer spheres in tape & reel packaging (see image) for 24mil, 35mil and 62mil diameter spheres.

Unique Tolerances:

Just as a case in point, a MEMS customer of ours had a need for a low-melting indium-alloy solder sphere with a tolerance of +/-5microns (+/-0.005mm) for a sphere with a 350micron diameter. That demands a tolerance of just over 1% - pretty demanding, but we did it.

Our standard tolerance is +/-1mil (1 thousandth of an inch, or 25.4microns), but as you can see, we have the capability to go to much tighter tolerances using three proprietary manufacturing techniques.

Other Needs:

We are also seeing people asking for doped-alloy spheres; low-alpha emission solder spheres and other things that we could never have dreamed of...

So please just let us know what you need. We'd be happy to help out, and if we can not do what you ask - we'll let you know why.

Cheers!  Andy

I mentioned in a previous a blog posting that the primary driver for halogen-free electronics is ostensibly environmental, but that the confusion about “which halogens and which molecules and what level?” has seemingly decoupled the laudable desire for an improved environment from the reality and made it more of a marketing tool. All this notwithstanding, there remain some instances where the performance of the final product itself can be directly impacted by the presence of halogens, usually as ionic halides. This is the reason why Indium Corporation recently developed what appears, at first glance, to be an odd combination: a high-Pb (high-lead) alloy halogen-free die-attach solder paste, Indium9.72-HF.

The halogen-related failure mode for die-attach solder pastes is the corrosion of wirebond pads on the topside of Power Semiconductor die which are soldered to the leadframe with halogen-containing solder paste. Many manufacturers producing high volumes of identical power devices may also use die-attach (sometimes called “soft solder die attach”, SSDA) wire to attach the die to the leadframes in a fluxless process, but many manufacturers prefer the inherent flexibility of a solder paste-based process for medium mix / medium volume applications.

Long term blog readers will recall that I did a posting on solderspatter (a.k.a. soldersplatter or soldersplash), and that it can be caused by bubbles of solvent vapor or moisture outgassing from solder paste deposits during reflow. In bursting, the tiny flux droplets or solder particles from the surface of the bubble can be propelled quite a distance (several feet). While solder on wirebond pads is clearly a failure from a reliability viewpoint, certain wirebond pad metallizations may also be subject to corrosion from flux. A poorly maintained reflow oven may also drip flux condensate (usually in the exit – cooling – zone), and this too can be a cause of organic materials on wirebond pads.

As long as the bondwire is gold, and wirebond pads are covered in a uniform layer of gold, there is no problem (as long as the flux residue is washed off) since gold is unreactive, even in corrosive environments. Aluminum (Al) or aluminum/silicon (Al/Si) bondpads, however, are potentially reactive. Halogenated materials, such as fluxes and overmolding compounds may react with them to either reduce the wirebond pull strength and/or increase the wirebond junction resistance, leading to localized heating and subsequent thermal-related joint failure. Even covalently-bonded (C-X, where X is a halogen) materials may dissociate at high temperatures: which is how the banned brominated flame retardants work, of course.

The biggest danger of halogenated flux corroding wirebond pads is when:

1/ Completed assemblies (between the reflow process and the cleaning process) are left for a long time before cleaning; particularly if they are exposed to high humidity (high %RH) before cleaning.

2/ The cleaning process is inadequate: either due to poor selection of the cleaning solution, or poor bath maintenance, or inadequate “scrubbing” energy being imparted to the surface to be cleaned, or simply if inadequate time is allowed for cleaning.

Note that even optimizing 1/ and 2/ may still lead to bondpad corrosion.

The Indium9.72-HF paste is available in both type 3 and 4 powder, in the standard high-Pb alloys, Indalloy 151 (92.5Pb/5Sn/2.5Ag) and Indalloy 163 (95.5/2Sn/2.5Ag), and for larger die that need a higher reliability joint, we also offer the Indalloy 164 (92.5Pb/5In/2.5Ag). A Product Datasheet is available for download, of course.

Cheers! Andy

最後和大家分享空洞的審核標準以及監測空洞的方法。

根據IPC-A-610D, Class 1, 2, & 3 產品Acceptable的標準是： 25% or less voiding of the ball X-Ray image area.  請注意，這裡是指“X-Ray Image Area”, 是一個影像圖面積的佔有百分比，不是真實體積佔有的百分比。

在影像圖片中，很有可能有些空洞的影像被別的更大的空洞完全遮蓋住了，或是重疊了，所以沒有計算上。況且，正如上篇“空洞對可靠性的影響”所說的，空洞的大小很有可能沒有空洞所在的位置重要。 但是這個是目前業界最普遍的使用方法。

關於各種空洞的監測方法，Raiyo和大家詳細分析了這五种：

1.      2D Transmission X-Ray. 目前業界最流行的方法，但是正如Raiyo總結的，這種方法不能準確測出voids所在的位置，大小，數量等。

2.      3D CT X-Ray. 測試voids的黃金工具。但是慢，對大產量的生産，可能會成爲降低生産效率的瓶頸。

3.      X-Ray Laminography. 最快的測試方法。但是準確性有待提高，一般作爲大產量pass/fail的衡量工具。

4.      Cross-Section. 對焊點有破壞性，慢，通常在實驗室使用。

5.      Ball Shear. 常作爲檢測BGA package land to surface interface的voids工具。

至此，完結！  Cheers! 

Picture, table, and Reference: Raiyo’s SMTA Voids in Solder Joints Presentation