Indium

现在在中国和亚洲的大规模SMT生产，都是 air convection reflow 空气回流炉，应该很少有vapor phase reflow 气相回流了。因为气相回流时间长，每次回流的板子量少，而且回流使用的液体成本相对较高，这些都不利于SMT的大规模量产。

可是在美国这里，却有不少客户在使用，准备使用，或是在咨询关于气相回流的信息以及我们相应的锡膏推荐。我总结了一下，客户大概分为这两种：

·      医疗器械：不单单是美国这里，许多欧洲公司也越来越多用气相回流来做医疗器械板子。主要的驱动原因是气相回流有助于减少tin whiskers。 有许多实验数据证明，气相回流可以大大减少 tin whiskers,无论是有铅还是无铅的焊接材料。医疗器械的电子产品一般使用的时间相对较长，而且关于到生命、密切的人体接触，很多产品都是3类产品；所以对“需要时间来形成的tin whisker”问题会比较关注。 如果你搜索一下“vapor reflow + tin whisker”，网上应该会有许多相应的文章的。

·      大的厚的板子： 在普通的回流炉里，大的厚的板子很容易受热不均匀，最高温点和最低温点的差值大而产生各种问题。比如说板子厚，板面和板底温度差大，而使板子表面先扩张而弯曲（板翘）。而在气相回流炉里，整个板子均匀受热，可以大大减少许多这些因为温度差或是受热不均匀产生的问题。

Indium公司的各种焊接产品，比如说 Indium8.9 系列产品，都不单单能应用在普通回流炉中，也能应在在气相回流中。

Cheers!

Image source.

I have been asked to explain why someone would want to use rotary sputtering targets instead of planar sputtering targets.

Certainly there is some expense involved with larger targets and new equipment (assuming you are currently using a planar system), but in a high volume process (such as roll-to-roll thin film deposition) the advantages lead to a lower cost of ownership:

• Compared to planar targets, rotary targets generally have more surface area per given length.

• Rotary targets have much more surface area, so the magnetron power can be spread out over a larger area in a given amount of time. This helps keep the target running cooler, decreases nodule formation, and reduces the occurrence of arcing.

1. Since rotary sputtering decreases nodule formation, targets can have longer continuous runtimes.
2. There is generally more material available to sputter on a rotary target, which increases runtimes.
3. Rotary target utilization is usually ~80%, as opposed to ~30% for planar targets – which decreases scrap and increases runtimes.

• Rotary targets are well suited for continuous sputtering processes. Continuous processing increases throughput since there is less time wasted preparing the sputtering chamber.

• Rotary targets are more cost effective for high volume processes. They provide a good platform for long runtime processes, with less chance of defects and downtime.

• Planar targets are still best suited for prototype work or elemental experimentation, especially when large amounts of material are not needed at once.

If you are interested in discussing sputtering targets, contact our team at: Solar@Indium.com

~Jim

I was recently asked to gather some data comparing Indium Corporation’s tabbing fluxes and our largest competitor’s leading tabbing fluxes. Using a new method of solder spread testing found in an upcoming issue of Global Solar Technology, two Indium Corporation tabbing fluxes were directly compared to three of the leading competitor’s fluxes.

The test consists of these simple steps:

• Apply flux to cell
• Dry flux on cell
• Apply solder preforms on cell metallization
• Reflow on a hotplate
• Measure solder length

Finally, the measurements are plugged into the equation:

S = (L_f/L_i)100-100

                   Where:         S = Increase in preform length

                                      L_f= Final solder length

L_i= Initial length of preform

In the end, the Indium Corporation tabbing fluxes (GS-3434 and GS-5454) both caused the solder to spread ~44% further on a given cell – compared to only 13%, 15%, and 16% for the competitors' fluxes.

If you’d like to learn more about the test method or the results, or want help conducting your own evaluation, send me an email at solar@indium.com.

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

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

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

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

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

The two alloys:

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

What they have in common are:

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

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

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

Let us help!

Carol Gowans

Maria Durham, Indium’s new Technical Specialist in Semiconductor and Advanced Assembly Materials, has been doing some research on indium lead (In/Pb) solder alloys. We chatted about her findings this week. 

 [Andy C. Mackie: ACM] Which indium/lead solder alloys are most common, and what are their properties?

[Maria Durham: MD] Firstly, the use of lead-(Pb-)containing solders in some soldering applications is restricted due to local environmental and RoHS compliance, but there are still many applications where they are  allowed. Many military, aerospace, and industrial equipment uses, as well as many applications related to vehicles, are exempt. The table below shows the most common indium/lead (In/Pb) alloys (pink) and their properties, sorted by liquidus temperature; the higher of the two melting points (solidus and liquidus) seen for non-eutectic alloys. In blue are three comparison materials.

Indalloy 205 is the most commonly used, probably because it has the closest liquidus temperature to the tin/lead eutectic (183°C), 63Sn/37Pb (Indalloy 106). This means it can be reflowed using a standard Sn/Pb eutectic profile. The next most common alloys that are used are Indalloy7, 204, and 206.  Besides the melting range, indium has comparable thermal and electrical conductivity to standard materials.

[ACM] What makes indium-lead (In/Pb) solders so attractive, and why have we seen a recent resurgence in their usage?

 [MD] One main attraction to using indium/lead (In/Pb) solder alloys in soldering to precious metal surfaces is that, unlike tin-containing solders, they do not leach gold. That is, gold does not dissolve in them to any appreciable extent. During discussions at Semicon West in 2011, one of our California customers reported going through 8 simulated reflows with Indalloy 205 in contact with a gold surface with no loss of joint strength and no joint embrittlement. That is pretty impressive. Note that embrittlement is often caused by gold-intermetallic formation. It has been noted that even at 250°C, 50In/50Pb dissolves Au at a rate 13 times slower than it does into 63Sn/37Pb, although this, of course, is a kinetic, not a solubility limit, study.

The higher melting Indalloy 164 (92.5Pb/5In/2.5Ag) has the lowest coefficient of thermal expansion (CTE) of all of the In/Pb solders and is able to withstand the higher temperature excursions that can be seen in step-soldering type applications (where a very high melting solder is used to form the first joint, followed by a next lowest melting alloy, and so on). This is seen in applications such as power electronics assembly, where the first step solder is often used for die-attach either as a solder paste, wire, or preform. The high melting point helps the solder withstand the operational temperatures associated with under-the-hood electronics, in applications such as engine control modules, where Indalloy 151 (92.5Pb/5Sn/2.5Ag) or Indalloy 163 (95.5Pb/2Sn/2.5Ag) are most commonly used. In/Pb solder is excellent on very rigid structures such as ceramic-to-metal or ceramic-to-ceramic. The desired solidus / liquidus temperature range can be adjusted by changing the indium:lead ratio, making it very easy to “dial in” the alloy to a specific reflow process.

Another attraction to using In/Pb solders is that they exhibit good fatigue resistance in thermal cycling from -55°C to 125°C.  In testing, the 50In50Pb solder joint fatigue life is about 100 times greater than that for 63Sn/37Pb.

 [ACM] What fluxes are used in these applications, and how are they formulated differently?

 [MD] The fluxes most compatible with the lower melting point (<200°C) indium-containing solders are NC-SMQ-80 (solder paste) or the lower-tack TacFlux® 012 (suitable for use with wire, preforms, and spheres). These are no-clean fluxes, specifically formulated for lower temperature reflow.  Under appropriate low temperature reflow these fluxes leave behind benign residues that do not need to be cleaned off (“no-clean” flux), although they are often cleaned off in most practical applications, usually to ensure reliable wirebonds absent of flux spatter.

 To learn more, please contact us.

 Cheers!  Andy

Are you plating indium metal? If so, here’s a tidbit of information you might find useful [From a customer inquiry on the Indium Corporation website]:

Question: “Can the indium be deposited in specific areas of the target piece, i.e. a target with several metallic regions, where we would like to isolate just one? Or can it be easily masked?”

Answer: “Areas of metallizations not requiring plating can easily be masked off either by the use of plater’s tape, or, more commonly, with a screenable resist, either thermal cure or UV cure.”

For more information, always feel free to contact us at AskUs@Indium.com.

Solders, as a class, are "interesting" metals.  And the properties of indium-containing solders are exceptionally interesting.  Indium’s (and indium's alloys') physical and mechanical properties are unique when compared to the metallic elements and alloys typically examined.

To put this into context, a metallurgist from a customer company called me because, after looking over our table of solder alloy properties, he claimed our data couldn’t possibly be correct!  After a detailed conversation, I understood the nature of his concern.  His background was not in solder materials, and the shear strength data for indium (890PSI) is exceeded by its tensile strength (273PSI). This "interesting" situation prompted further questioning.  These numbers are, however, accurate.

The graph on right numerically depicts the shear nature of this material.  Over a test area of approximately 0.5 square inches, a soldered interface that was sheared at a rate of 1mm/minute to fracture extended 1.6mm before yielding. This extension is indicative of the putty-like nature of pure indium.  As expected, The load at yield roughly matched the shear strength cited above for the bulk material  because the yield location in this assembly was through the bulk material, rather than along the intermetallic edge.    

More extensive information on the physical constants of indium can be found in this application note.

Finally, click here to link to more information on indium metal properties and its uses.

As a sneak peak:

• Indium has a low vapor pressure when molten, rising quickly as the boiling point approaches (2080°C)
• Indium cold welds to itself
• Molten indium will wet glass and glazed ceramics
• Although the softest metal, indium will impart hardness, when added as an alloying agent to other metals such as gold. In fact, the gold indium alloys are used in dental crowns.

上周是一年一度的行业盛会APEX, 这次的地点在风景优美的海滨城市San Diego. 

我代表公司参加了展会。这次的客户流还是很多的，许多客户都是带着特定的问题来和我们交流。同事们都热情招待了客户，提供了解决方案和介绍了产品。 我们也很高兴看到许多现有的“老客户”特意来我们的展台和我们打招呼！

在众多的技术论文和演讲中，Low Ag Alloy, Parkage-on-Package (PoP), Finer Solder Powder, QFN Voiding等是热门的话题。许多客户和同行们都十分欣赏Indium公司常常能发表如此有科技含量的技术文章。其实这些文章都能够在Indium公司的主页上免费下载：http://www.indium.com/techlibrary/whitepapers/

最好笑的是我们的一位同事听到一个竞争对手在公众场合大声讲电话，那个人说公司所有经理都几乎被老板骂了，因为老板看见Indium公司有8篇技术文章在展会上被演讲，而这个公司一篇文章都没有……

Cheers!

PS: 一个有意思的小插曲，展会的某天晚上和一个重要客户吃完饭后，我和同事在回酒店的路上碰见同行朋友，被抓去当地的钢琴酒吧（钢琴手现弹现唱，并和在场的所有人互动）。同行朋友和我开玩笑，“骗”钢琴手和在场所有人说那天是我的生日，结果我被拱上台，坐在钢琴上面，听现场所有男士起立唱了一首美国著名情歌“You’ve lost the loving feeling” ala Top Gun；第一排的男士还半跪做各种深情的动作……Hahaha，城市中劳累了一天的人们都以各种理由找些乐子，放松放松。

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

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

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

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

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

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

Carol Gowans cgowans@indium.com

Reducing the surface oxides of Nitinol is just the first step in getting a good solder joint with this versatile medical assembly material.

Next you have to choose the right solder alloy.  You will probably want to stay away from anything containing lead, cadmium, or antimony, particularly in medical applications.  And you will want something with a high tensile strength.

The best choice is Indalloy #121 (96.5Sn 3.5Ag).  It has a tensile strength of 5,620 PSI and a melting temperature of 221C and is obviously lead-free.  It wets well to the cleaned Nitinol.

If you need a higher melting temperature solder (one that can withstand autoclave temperatures for example) you should consider Indalloy #182 (80Au 20Sn) which melts at 280C, has a tensile strength of 40,000 PSI, and has long been considered a highly reliable solder.  Additionally, this alloy is available in very fine diameter solder wires to minimize waste.

Soldering temperatures should be 25C to 50C above the liquidus temperature of whichever solder you use and proper cleaning should be always be performed afterwards.

Contact us at medical@indium.com for more information about soldering for medical devices or visit our web site at www.indium.com/medical

Carol

It is common to hear people that are skeptical about CIGS technology ask questions like:

• "Aren't indium and indium tin oxide (ITO) thin film deposition processes wasteful and inefficient?"
• “Aren’t we going to run out of indium soon? Doesn't the world use more than we produce!”

What are the truths?

Here they are:

WASTEFUL: A well-run process is NOT wasteful. Why? Recycling!

At first glance, a process like indium planar target sputtering seems ridiculous – generally only 30% of the indium actually makes it onto the substrate it is destined for (and that’s in a well-tuned process). As it turns out, the material that doesn’t land on the substrate is too valuable to just scrap. This translates into recycling, a lot of recycling…

According to presentations given at Minor Metals 2012: “indium production will total 1,500-1,700 tonnes in 2012, with virgin supply accounting for around a third of total output”.  It’s incredible that recycling accounts for such a large percentage of the indium used in the world today.

INDIUM AVAILABILITY AND SUPPLY: Another important conclusion made at the conference was (as reported in Metal Bulletin):

“proven indium reserves from existing mines at 50,000 tonnes, a volume that will be sufficient to satisfy demand for the next 75 years”.

While it’s not news at Indium Corporation, it is definitely assuring news for those looking to get involved with CIGS technology.

~Jim

在平时和客户们的会议交流中，因为Indium公司的产品线比较广，不同的客户群常常有针对自己独特的应用或是技术、销售服务等各种问题。

刚刚开始正式做一线销售，我有时候在会议前会有点紧张（特别是新的客户），怕自己回答不上客户的各种问题，帮不上忙。但是后来老练了一点，即使有些问题我自己真的不懂或是即时没有答案，但是总是可以“follow up”跟进的。会后积极主动利用各种资源找出答案，及时回复客户就好了。 现在的会议中， 我更会了“审时度势”的提问，从客户口中问出对项目、生意有用的信息。

最近我们在联系一个国际大客户做一些项目。 客户要求我们的科研副总裁李宁成博士(Dr.Ning-Cheng Lee)过来和他们交流，做一个roadmap meeting. 客户还提出相关的内容请李博士来讲。在我们和李博士内部交流后，决定先向客户提问，问清楚他们的需求后，我们才好“对症下药”。 比如说，客户想了解低银合金Low Ag Alloy, 低温合金在波峰焊中的使用Low Temp Alloy for Wave Soldering，微间距印刷0.3mm fine pitch printing等等。我们知道客户已经在使用别的供应商的SAC0307的低银合金了，并且客户的NPI工厂里没用波峰焊，但是为什么客户会叫我们来介绍呢？对现在的SAC0307合金不满意？哪些性能不满意需要改进呢？波峰焊又是怎么一回事呢？等等。 所以，我们也决定向客户提问，问清楚他们为什么有这些“需求”，真正的原因是什么……

有一个销售同事更有意思，当我告诉他我有一个做激光设备的客户（他们在使用我们含铟金属的材料），有一次我被客户的几个“资深工程师”追问关于铟金属的一些不太相关的问题，我根本不知道答案……我的销售同事建议说，以后出现这种情况，当你觉得他们问的东西有点过的时候，你可以反问他们一句“Why you asked this question? Why you want to know?”  这样就可以尝试挖掘出客户问问题的真正目的了。当然，要见机而行!

Cheers!

Pic: Google Image

Somewhat related: I found this picture in a reference text at a bookstore. It reminded me of the picture that Carol Gowans shared in her latest blog post about indium availability.

The caption states: “A lapel pin from a company obviously proud of its work with indium.”

It's true, we ARE very proud of our history and our company. If you have questions about indium metal, why not talk to people who share live your interest?

Send your questions to AskUs@indium.com.

~Jim

Folks,

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

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

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

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

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

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

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

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

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

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

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

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

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

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

“What is the conclusion? Patty asked.

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

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

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

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

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

“What was that?" she asked.

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

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

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

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

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

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

She then showed her third slide and spoke to it.

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

“Can you explain your methodology?” Sam asked.

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

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

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

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

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

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

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

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

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

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

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

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

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

Cheers,

Dr. Ron

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As reported in Metals Bulletin, Malcolm Harrower of Indium Corporation recently addressed the topic of indium availability and supply as he told the delegates at the Minor Metals 2012 conference in Brussels that:

• there is no shortage in the supply of indium metal
• nearly 1,500 tonnes of indium was produced in 2010
• there are 50,000 tonnes of proven indium reserves in existing mines, a volume that will be sufficient to satisfy demand for the next 75 years,

Just 80 years ago, the potential for indium was just being discovered.  An article that I found in the archives of Science News from 1932 indicated that 10 lbs. of indium was due to be produced that year and it would give scientists a chance to do some great research on the possible uses of indium.  Twelve years later in 1944 another article was written on one of those uses which was to lubricate ball bearings to make them last longer (an application still in use today).  That article stated that the output had reached 500,000 troy ounces (34,250 lbs). 

Now 80 years after indium was first commercially produced, the yearly output has reached nearly 1,500 tonnes (3,300,000 lbs) per year, with about two-thirds of that being reclaimed and recycled material.  The versatility of indium has certainly driven that growth into all kinds of applications including:

1) Touch screens

2) Battery chemistry

3) Electronic thermal interface materials

4) Solders

5) Cryogenic and hermetic sealing

6) Solar panels

And as technology evolves, we expect to see more uses as time goes on.  Learn more by visiting our web site at www.indium.com. Or email/call me to discuss your needs.

Carol

cgowans@indium.com

+1-315-853-4900

No one likes being controlled by the cost of silver. We deal with fluctuating Ag costs here at Indium Corporation on a very large scale – so I understand the issues with using Ag-filled low temperature metallization paste for thin-film solar cell interconnection.

People always ask for alternative fillers like copper – although the chemistry of metallization paste doesn’t allow the substitution of most filler materials. Our solution is a new material: silver-plated copper particles.

Silver-plated copper particles allow us to utilize a very low amount of silver precisely where it needs to be, on the surface of the particles. By tricking our metallization paste chemistry into thinking it is still working with silver flakes, we are able to maintain the same high levels of flexibility, fine line printing, and adhesion that we have become accustom to with materials such as LT-918 metallization paste.

Due to the inherent bulk conductivity difference between copper and silver, very lowest resistances will still be achieved with solid silver flake metallization pastes. The silver-plated copper material has performed unexpectedly well in electrical performance though, winning over some customers due to a substantial difference in price.

Our new silver-plated copper particle material is currently in beta testing, and has completed over 2,000 hours of dry and damp heat testing. Our data so far has confirmed superior print performance, and customers like the fact that the material can be shipped at room temperature. If you are interested in beta testing the material, please let me know.

~Jim

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

Back in 2005 a customer left a question on our website and it was answered by one of my solder heroes. Here is the Q&A:

Question: “With regard to Indium Corporation's indium sulfamate plating bath… …can it be deposited onto platinum-gold thick film inks? Namely DuPont solderable inks on 96% alumina?”

Answer: “Thick film inks often contain low melting glass frit particles which enhance bondability to the alumina substrate. Solderable thick film inks are designed so that the glass particles do not reside on the surface, thus allowing the solder to wet. As in solder wetting, having a glass frit-free particle surface will also allow electrodeposition of any metal. Therefore if the ink is solderable it should be plateable.”

I learned from this answer so I thought it would be good to share with you. Call me or email me to discuss your questions.

~Jim

Readers have asked how to visually assess a tabbing ribbon interconnection after a bond test.

This image is a cell that has been bond tested after soldering.

The first indication that you have a good bond is the physical resistance during the bond test. Even if you are peeling the ribbon off by hand, you will still notice if the ribbon jerks as it tears away from the cell. Fluctuation of bond strength may be caused by insufficient or inconsistent tabbing parameters, incomplete fluxing, or even contamination on the tabbing ribbon. If the resistance varies rapidly across the length of the bond, there could be an issue with microcracks. Microcracking of the underlying silicon is usually caused by built-up CTE (Coefficient of Thermal Expansion) stresses from tabbing. The ideal bond will peel apart where the tabbing ribbon meets the metallization, and it will be uniform. It should look like the image seen here.

There are some things you can do before, during, and after tabbing to get a better looking, and higher reliability, tabbing bond.

Before

Consider using alternative tabbing alloys and fluxes. Using Bi-based alloys at lower temperatures will lower the stresses caused by CTE mismatch and help eliminate microcracking. Softer tabbing ribbon can help keep stresses to a minimum as well.

During

Cell tabbing/stringing machines have many adjustable parameters. You owe it to your customers to explore the effects of parameter changes so you know you are building the best modules possible. (If I have time I’ll probably come to your facility to help – all you have to do is ask.)

After

Not everyone has time to wait, but if you have the luxury to let the tabbed cells sit for a day you should notice much better test results. Stresses built up in the silicon are partially relieved after 24-48 hours, which will result in less microcracking.

Let me know if I can help you make some beautiful cell interconnections!

~Jim (jhisert@indium.com)

A customer raised an interesting question regarding the use of our indium plating baths. I thought it was interesting enough to share. The question is:

“What are – if any – the health, safety, and environmental issues with this (indium plating) process?”

The answer: Indium metal has a toxicity similar to copper and a TLV of .1 mg/m³ in air as particulate air borne particles, which is not normally encountered using a plating bath. The plating bath would be toxic if ingested. Routine hygiene/safety practices include wearing safety glasses, wearing plastic gloves when handling, and washing hands after handling the metal or plating bath solution.

From time to time our Technical Service department conducts plating experiments, and it really is pretty simple when you know what to expect. (Especially compared to some of the other electronics manufacturing process they encounter.) If you have questions or concerns about the indium plating process, make sure you contact the experts: askus@indium.com