Indium Corporation Blogs

There have been a variety of people who were key to the development of indium metal in general, and Indium Corporation in particular, over the years.

People such as:

• Hieronymus Theodor Richter and Ferdinand Reich who discovered indium metal in 1863
• Daniel Gray, William S. Murray and J. Robert Dyer who formed the original Indium Corporation back in March of 1934 and who hold patents on processes and applications involving indium
• Frieda Nojeim who joined the company in 1966 and was elected vice president in 1971

 

And, in 1972, Charles E.T. White joined the Indium Corporation as a vice president (he was elected executive vice president in 1981).  I had the pleasure of knowing Mr. White before he retired.  He was indeed a character, but he also knew a LOT about indium.

In 1986 (a lifetime ago in the electronics industry) Mr. White published an article called: Indium: High Technology Metal in Advanced Materials and Processes magazine.  I ran across a copy of it the other day and, after reading it, was interested in how relevant it still is today, even though technology has marched forward.

Of course the physical characteristics of indium are still as valid today as they were then. 

• Resistance to thermal fatigue
• High thermal conductivity
• Wetting of non-metals (glass, quartz, ceramics)
• Malleability and ductility, even at cryogenic temperatures
• Electrical conductivity for a variety of screens
• Indium does not work harden

 

But one might expect the technology described in an article from nearly 30 years ago to have evolved or gone entirely away, resulting in the elimination of the need for the indium.  The truth is, many of applications that Mr. White mentioned still exist today:

• "Conforming gasket material for cryogenic vessels."
• "Indium is present in every wristwatch and computer screen that uses a liquid-crystal display."  Okay, so no one wears wristwatches anymore, but the screens on our phones (the new time-telling devices) have indium tin oxide coatings.
• "...used in lens blocking and in temperature-overload devices such as safety links, fuses and sprinkler plugs."
• "Many solder alloys containing indium have been developed to take advantage of indium's enhancement of thermal-fatigue resistance, reduced gold scavenging, and resistance to alkaline corrosion."
• "Glass sealing alloys containing indium ...have been developed for electronic device packaging where high temperatures cannot be used."
• "Indium's use in solder alloys is likely to increase as specialty solders become more important in electronic assembly techniques."
• "The whole area of conductive films of indium oxide and indium-tin oxide has good potential for growth.  This includes solar cells: silicon-cell efficiency can be improved with an indium or indium-tin oxide coating."
• "New applications such as solar cells made of indium-copper-diselenide/cadmium-sulphide are under active development."

 

And while these indium applications still exist today, R&D continues to find new opportunities for this very unique metal.  We have several Research Solder Kits that you can use to evaluate the value of indium in your process.  Just go to our e-commerce page or contact our engineers to see how indium can work for you.

Carol Gowans

Since the NanoBond^® process is almost instantaneous, fluxes are not used. (They just don’t have enough time to heat up to their activation temperature and remove oxides.)

So, because this is a fluxless soldering application, surface choice and preparation become very important. We no longer have the chemical power of a flux to break down surface oxides, instead we must make sure our surfaces are ready to be joined.

The first choice to make is: will you have solder on the parts to be bonded, or will you use solder-coated NanoFoil^®?

If you decide to use bare NanoFoil^®, the parts must have a solder finish such as pure indium, SAC 305, or tin. If you choose to use a solder-coated NanoFoil^®, you can bond gold and silver metallized parts.

 

Need help figuring out what to do? Ask us: AskUs@indium.com

*This post is part of the NanoBond^® Process series

The first time I was taught how to solder (as a child), I was told: “All the surfaces need to be mechanically cleaned and chemically cleaned.” The person who told me this was referring to pipes, I was learning about plumbing. (I would have never thought we'd be using nanotechnology to create solder joints!) Although your application is probably far from a plumbing job, the basics of soldering remain the same. The best solder bonds are formed when oxides and contaminants are not present.

These two points are taken care of in traditional electronics soldering by using a flux. Flux can flush away light contaminants like dust, and reduce oxides on certain metal surfaces. But, in the NanoBond^® process, we aren’t using flux.

Luckily, NanoFoil^® can power through the soldering process as long as the proper surface finishes are used, and they are ready to be soldered to. Different surfaces are prepared in different ways. Here is a list of some common surface finishes and what preparation they require:

• Gold – Wipe with isopropyl alcohol if aged
• Silver – Wipe with isopropyl alcohol if aged
• Tin – Remove oxides with 10% HCl if aged
• Solder coating - Remove oxides with 10% HCl if aged
• Aluminum – Add solder coating
• Molybdenum – Add solder coating
• Titanium – Add solder coating
• Naval Brass – Add solder coating

And for any surface you don’t see, feel free to contact askus@indium.com so we can find a solution for you.

 

*This post is part of the NanoBond^® Process series

Indalloy Flux #2 is not the only option for soldering to Nitinol.  There is also Indalloy Flux #3.

Both fluxes are strong enough to clean the tenacious oxides off Nitinol, as well as aluminum and stainless steel.

So what are the differences?  To start with, it is the consistency of the material.  Flux #2 is a liquid flux; Flux #3 is much more viscous and is usually applied by brushing it onto the surface.  Flux #2 can also be brushed on, but it can also be sprayed or dispensed.

If you are using a higher temperature solder or have particularly tough oxides, Flux #3 is the right choice.

If your solder contains indium, you will want to choose the Flux #2 because the indium is sensitive to chloride-induced corrosion.  However, if you are using a tin-based solder, Flux #3 is an excellent alternative.

Where these two fluxes are the same is that they both require good cleaning and should not be used in electronics applications.  Both fluxes MUST be cleaned as soon as possible after reflow.  This can be done with warm (not greater than 50°C) water and mechanical scrubbing.  If the water is greater than 50°C, you risk additional reactions and possible pitting of the material.

Both of these fluxes are available online at http://buy.solder.com/Medical-Assembly-Materials/C1036_1/ .  If you have more questions, check out our medical products page or contact me and I will be glad to help!

Carol Gowans

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

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

 

image

We are often asked if it is possible to solder to stainless steel and, if so, what is the best procedure. As you may already know, stainless steel is not easy to solder but it can be done with a little preparation and using the correct flux and solder alloy.

FLUX:
To solder directly to stainless steel, Indalloy #2 Flux (activation range 100-371°C) must be used to remove the surface oxides, allowing a clean surface for the solder to wet. This flux is recommended for mechanical assembly joining only. Due to the corrosiveness, it is not recommend for electrical applications because, if the post reflow flux residue is not thoroughly removed using warm water with mechanical scrubbing, the joint will be compromised due to the potential for corrosion during its life. An alternate solution would be to nickel plate the stainless steel, so a weaker flux (RA, ROL1) can be used that is less corrosive and can be easily removed with an appropriate solvent.   

Another alternate solution is to use a forming gas consisting of nitrogen and hydrogen. This method of oxide removal is generally used when the soldering temperature can be above 350°C which is ideal for activating the hydrogen to reduce the oxides. With this method, there is no post-reflow flux residue to clean up.

SOLDER:
The solders usually recommended for stainless steel joining applications contain a considerable amount of tin; however, the actual solder choice has to fit the temperature range of the application. Generally, a low-temperature application may require Indalloy #1E (52In,48Sn) - 118°C (eutectic), while Indalloy #182 (80Au,20Sn)- 280°C (also eutectic) is a great solder choice for high temperature. If you are looking for a solder in the moderate range of temperatures, Indalloy #121 (96.5Sn, 3.5Ag); 221°C (eutectic) is an excellent choice as well as any of the SAC alloys in the same temperature range. There are also many other solders to choose from that will work equally as well. Please see our solder alloy physical properties chart or consult our Applications Engineering staff at Indium Corporation.

Folks,

I’m taking a few moments from Wassail Weekend , held annually in my village, Woodstock VT, “The prettiest small town in America”, to write a post about last week’s workshops at ACI.

Indium colleague Ed Briggs and I gave a 3 hour presentation on “Lead-Free Assembly for High Yields and Reliability.” I think Ed’s analysis of “graping” and the “head-in-pillow” defect is the best around. 

There was quite a bit of discussion on the challenges faced by solder paste flux in the new world of lead-free solder paste and miniaturized components (i.e. very small solder paste deposits.) One of the hottest topics was nitrogen and lead-free SMT assembly. There seemed to be uniform agreement that solder paste users should be able to demand that their lead-free solder paste perform well with any PWB pad finish (e.g. OSP Immersion silver, electroless nickel gold, etc.) without the use of nitrogen. Not only does using nitrogen cost money, but it will usually make tombstoning worse. However, in the opinion of most people, nitrogen is a must for wave soldering and, since it minimizes dross development, it likely pays for itself.

After Ed and I finished, Fred Dimock, of BTU, gave one of the best talks I have ever experienced on reflow soldering. He discussed thermal profiling in detail, including the importance of assuring that thermocouples are not oxidized (when oxidized they lose accuracy). He also discussed a reflow oven design that minimizes temperature overshoot during heating, and undershoot when the heater is off. Understanding these topics is critical with the tight temperature control that many lead-free assemblers face.

Fred Verdi of ACI finished the meeting with an excellent presentation on “Pb-free Electronics for Aerospace and Defense.” Fred’s talk discussed the work that went into the “Manhattan Project.” A free download of the entire project report is available.

There appears to be agreement that acceptable lead-free reliability has been established for consumer products with lifetimes of 5 years or so, but not for military/aerospace electronics where lifetimes can be up to 40 years in harsh service conditions. These vast product lifetime and consequences of failure differences are depicted in the Fred's chart (above). Commercial products are in quadrant A and military/aerospace products in quadrant D.

One of the greatest risks faced by quadrant D products is tin whiskers. Fred spent quite a bit of time discussing this interesting phenomenon. One of the challenges of this risk is that there is no way to accelerate it, so you can’t do an equivalent test to accelerated thermal cycling or drop shock. Fred mentioned that there have now been verified tin whisker fails, the Toyota accelerator mechanism being a confirmed one.

In addition to tin whiskers, lead-free reliability for quadrant D products (with a service life of up to 40 years) in thermal cycle and other areas remains a concern.  I mention that tin pest was not on the list of issues for this quadrant.

Fred and the Manhattan Project Team have identified many "gaps" that need to be addressed to determine and mitigate the risk of lead-free assembly for quadrant D products.  They plan to start this approximately $100M program in 2013.

For those that missed this free workshop, ACI host Mike Prestoy is planning another one in 6 months.

Cheers,

Dr. Ron

Here is a list of tricks to help you overcome the issues that can arise while hand soldering silicon-based solar cells (and other applications as well). Some of these ideas are obvious for most, but all the suggestions can help you form a better solder joint - and build a better final product:

 

1)    Use the correct soldering tip. I’ve made the mistake of using an inappropriate solder tip before, and so have many of my customers. It’s a frustrating problem you will only let happen to you once: everything is set up perfectly but nothing will melt, until you notice the solder tip is not the correct size or shape. This has happened to many of my customers who were initially using cone point soldering tips when they were working with 2mm wide solder coated tabbing ribbon. Simply changing the tip to a 2mm wide chisel point made all the difference, and promoted soldering readily. Why such a big difference in performance? The chisel tip allows heat to flow across the ribbon, instead of only heating a single point. More heat flow = more heat in your solder joint.

2)    Pre-tin the soldering iron. Just as an appropriately sized soldering tip will distribute heat across the soldering surface, a bit of molten alloy can help create a thermal interface to maximize heat transfer. Remember to melt a small amount of solder onto the tip of your iron before soldering, and be sure it’s the same alloy you are soldering with. (Leave the custom alloying to us ;)

3)    Consider the alloy you are soldering. All the heat your typical soldering iron can produce will not be enough to melt some of the highest temperature alloys. Be sure to have a good understanding of the alloy you have selected. In some cases with low-temperature alloys (like bismuth or indium alloys), excessive soldering temperature can de-wet the alloy and char low temperature fluxes.

4)    Use the correct flux. Fluxes are quite different, I’ve spent my entire soldering career trying to get that point across. There are fluxes for high temperatures or low temperatures, cleaning with water or not cleaning at all. There are specialty fluxes for specialty alloys and there are fluxes for different soldering surfaces. Use the correct flux. If you don’t know what the best flux for the application is - just ask; that’s what I am here for.

5)    Use a bottom side heater. Silicon is known to pull heat away – that c-Si solar cell that needs to be soldered is a heatsink! Some solder equipment vendors also provide underside heating pads to help prevent excessive heat loss.

6)    Keep your soldering iron clean. That black crud that builds up on your soldering iron tip, it’s not helping you form a good solder joint. Those oxides and charred flux residues can easily be removed by wiping the hot iron across the wet sponge (that should be at your soldering station). A clean tip will lead to better heat transfer, and it will make the fluxes you use more effective.

 

This is the soldering station I use, it’s a PS-900 supplied by OK International. Just about any soldering iron will work, but they won’t all work as well – or come with as good support.

 

I’m still learning all the tricks to hand soldering, so feel free to share any you have learned over the years!

 

~Jim

Solder wire is generally used for manual soldering operations, including rework.  But, it can also be used in automated applications such as die-attach soldering.  Solder wire can be flux-cored, or solid with a separate flux used.

Each application can have different requirements for the wire.  For example, wire used in die-attach applications needs tight dimensional tolerances to insure an exact, repeatable amount of solder is deposited each time.  Reduced oxides are also critical to eliminate any "splattering" of the molten solder during the deposition process.

Wire can also be used for non-soldering applications. For example, indium (and indium alloys) wire are often used as a sealing material (particularly in cryogenic sealing applications) - more here) and as a thermal interface / management material.

Decades ago, 0.030" (0.76mm) diameter was the standard size, but today we are able to produce diameters as small as 0.001" (0.025mm) in tin silver (Sn Ag), tin silver copper (SAC) and gold tin (Au Sn) alloys.  Considering that a human hair is about 4X that size, that is a very small diameter!  Pure indium wire is limited to 0.010" (0.254mm), but alloys containing indium can be produced smaller than that.

The wide variety of diameters available in Au Sn make this alloy ideal for the complex applications in medical, aerospace, and other high reliability applications.  However, the Sn Ag and the Sn Ag Cu are used across a variety of standard applications that require lead-free materials.  Sn Ag is particularly good in soldering to Nitinol.

At first look, wire seems like a pretty simple product.  But specifying the right alloy, diameter, tolerances, and packaging can make all the difference.  It can help you achieve a repeatable process that gives you high yields, strong solder joints, and enhanced profitability.  For further information - contact me.

Carol Gowans

Folks,

When the industry was preparing to transition to lead-free solders almost ten years ago (can it have been that long), tin-bismuth solders were serious candidates. Their low melting point, of about 138C, made these solders interesting candidates to replace tin-lead solder. However, if contaminated with lead, tin-bismuth solders can produce a eutectic phase that melts at 96C. In such situations the resulting solder joint exhibits poor performance in thermal cycle testing. Since early in the transition to lead-free solders it was expected that there would be numerous components and PWBs with lead-based surface finishes, this property made tin-bismuth solders unacceptable.

Another aspect of tin-bismuth solders is that they expand on cooling. This phenomenon can result in fillet lift in through-hole solder joints.

However, as we are now well into 2011, almost no components or PWBs have lead-containing finishes and many portable electronic devices have no through-hole components, so it may be time to reconsider tin-bismuth for some applications.

Some years ago, Hewlett Packard (HP) had performed work to show that adding 1% silver to tin-bismuth solder enabled this alloy to outperform eutectic tin-lead solder in 0 to 100C thermal cycle testing. Even at these low reflow temperatures, HP demonstrated solder joint strength with SAC BGA solder balls that was 65% that of tin-lead solder. Expanding on this work, Indium Corporation's Ed Briggs and Brook Sandy performed stencil printing and reflow experiments consistent with the requirements of current miniaturized components using this 57Bi-42Sn-1Ag solder. All of their results were promising. Ed presented a paper at SMTA Toronto,summarized the Hewlett Packard work, and reviewed the results of this new work.

So for applications consistent with 0-100C thermal cycling, 57Bi-42Sn-1Ag solder may be something to consider if the high temperature of SAC solder paste is an issue to components or PWBs in a product

Cheers,

Dr. Ron 

PS: Read my follow-on posting about bismuth.

The image is of a bismuth crystal with an iridescent oxide surface from http://en.wikipedia.org/wiki/File:Wismut_Kristall_und_1cm3_Wuerfel.jpg

ITO is one of the materials that makes the magic of flat panel displays (monitors, TVs, etc.) possible. When sputtered on in a thin layer, it acts as a transparent conductive film. However, the process of sputtering is very inefficient in its use of ITO. And, with the explosion of flat panel display sales, large amounts of ITO end up as "waste".

It is important to understand the economics of ITO. The main precursor of ITO is indium (metal). Indium is a semiprecious metal and trades on the open market like gold and silver. It is subject to price fluctuations just like the other precious metals. So, there is an economic impetus to reclaim as much of the unused ITO as possible.


As mentioned earlier, flat panel displays employ a sputtered ITO coating. The indium metal must first be converted to indium oxide and then blended with the appropriate amount of tin oxide. The result is a pale green powder.

In order for the ITO to be usable, it must first be compressed in to a sputtering target. Planar sputtering targets are the dominant form of sputtering target used for sputtering of ITO. The geometry of the ITO sputtering target is often a rectangle or disc. Compressing the powder causes it to take on a darker color.

Inherent to the sputtering process is the uneven erosion of the sputtering target. The target material erodes in a "race track" pattern. These images of a spent nickel-vanadium sputtering target show the classic "race track" erosion pattern (valley).

The remaining material is unusable in the sputtering process. In the case of an ITO sputtering target, the unused portion can represent a significant amount of indium. It makes sense to reclaim or recycle as much of the target as possible.

The target user will break up the remaining target in to chunks.

The chunk ITO is sent to a recycling/reclaim center where the chunk ITO is converted back in to indium metal. And the cycle starts all over again.

Yesterday was a pretty interesting day. I happened to stop by the lab, and I had a chance to help mix silver into what will soon be the newest low-temperature metallization paste for the solar industry! It was an experience that I will not soon forget - one that made me feel a little more in tune with the new product.

Soon I hope to be able to test this new product on indium-tin oxide coatings, and in customer-supplied thin film technology applications. If you have an application that calls for a metallization paste that cures below 200°C- let us know how we can help you!

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.

 

For more information:
www.indium.com/supply.php
http://en.wikipedia.org/wiki/indium

The Society of Vacuum Coaters 2010 technical conference took place last week, so this week I’ve been rounding up the display sputtering targets and evaporation sources to display at our next event in China. If you’re not familiar with it, the SVC (Society of Vacuum Coaters) conference focuses on deposition materials, equipment, and processes. The Indium Corporation has a specific interest in both sputtering and thermal evaporation since we provide materials for these processes. There are too many applications to list, but some specific sputtering/evaporation apps that are close to my heart are:

 

• Absorber layer (ex. Copper Indium Gallium) for thin film solar cells
• TCO layer (ex. Indium Tin Oxide) deposition – also for the solar industry
• Sputtering target bonding with NanoFoil®

 

Last week we set up a very impressive array of sputtering targets (shown in the picture), so I hope they all make it safe and sound to SNEC next week!

 

~Jim

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 caught up with Alan Rae after a recent IWLPC committee meeting, where he jokingly asked me to, “Stop asking important questions” - LOL! He was kind enough to give me a few moments of his time to share his wit and wisdom, and answer some technology questions that, yes, I thought were kind of important…

 

[Andy Mackie] You’re increasingly being seen as “Dr Nano” by the electronics industry – how did you arrive as the focus of so much of this technology?

 

[Alan Rae] At the start of my career I was in the structural ceramics business. In the days of “ceramic fever” in the 1980’s the mantra was sub-micron and monosize (monodisperse) for lower temperature processing and better properties. It worked. Then at TAM Ceramics we made “sub-micron” barium titanate and other ceramic materials but we didn’t call it nano then. When I was at Cookson Electronics in the early 2000’s we started to see nanotechnology emerging from the woodwork with people saying the same about nanomaterials for the electronics industry. Then I joined NanoDynamics in 2004 and realized the scope and potential, ranging from semiconductors to touch screens to printable electronics, to LED lighting, to solar power, to materials such as nano solders, dielectrics, conductors…the list is growing but the leitmotiv is the same – small, monosize, tightly-controlled. 

 

[Andy Mackie] OK, so Nanotechnology has been a buzzword for quite a while – is there a clear definition yet, and what current uses are there for nanotechnologies that may not be immediately obvious?

 

[Alan Rae] Well, the definition has been really tough to derive – ISO TC 229 “Nanotechnologies” came up with a definition that one dimension of a particle, needle or plate should be less than 100nm but it’s really tough to define…should all particles be less than 100 nm? 50%? Any? And should it be exactly 100nm? There are a lot of opinions. The Woodrow Wilson Institute lists over 800 consumer products containing nanomaterials on the market now – industrially the products range from semiconductors, to fillers in packaging materials and underfills, to antimicrobial and self-cleaning coatings for phones. Solar panels, especially thin film ones, depend on nanomaterials in their manufacture.

 

[Andy Mackie] What is in the pipeline for nanotech electronics and semiconductor interconnect materials? I know that nanosolders are starting to gain ground in some areas – what else is upcoming?

 

[Alan Rae] Much of the work in nano metals is being done by universities and small companies – for example my small company is working with Purdue and the Air Force to develop a novel solder technology – but commercialization will come by partnering with established companies like Indium Corporation, who have the distribution and technical support so that customers will be comfortable with a new material. Cost and reliability are king. Indium is already in the reactive nano foil business; there are existing and near-term applications for silver, silver-coated copper, alumina coated boron nitride and their combinations in adhesives, shielding materials and thermal interface materials.

 

[Andy Mackie] Several years ago, quantum dots were being promulgated for tunable band-gap detectors and quantum computers. How close are quantum dots to seeing real uses, and what else is on the horizon?

 

[Alan Rae] Quantum dots are unique and have great potential in medical imaging and as frequency shifters for LEDs. The markets haven’t developed yet because of the cost and because some of the best dots are cadmium (toxic metal) based. I’m working with a group at University of Buffalo which has a silicon quantum dot process that looks like a promising alternative. Quantum dots will have their time…but not just yet. In terms of new developments – they range from core shell and modulated structures for thermoelectric to replacing indium tin oxide with carbon nanotubes or graphene. The US National Nanotechnology Initiative tracked $1.6 billion in Government spending (check out www.nano.gov) in the last year at Universities and small businesses and NSF has set up centers of excellence at Cornell and other great universities that are really working hard to translate science into technology so we can make practical products.

=======

Alan, many thanks for your time, and for sharing your insights with us.

Cheers!  Andy

I just sat down to talk to Tommy Acchione (pronounced “akki-OWN”) Applications Engineer with Indium Corporation’s  new product line, Reactive NanoTechnologies’ (RNT) NanoFoil^®, about the technology, and its offerings into the semiconductor, power semiconductor assembly, LED and display assembly industries.

 

[ACM] First of all: welcome to Indium Corporation! Can you tell us, in just a few words, what the basis of the RNT Technology is?

 

[Tommy Acchione] NanoFoil^® technology is a thin metal sheet (“foil”) made up from alternating ultrathin layers of aluminum and nickel (Al and Ni). The reaction between these two metals is stoichiometrically very simple:

 

            Al+2Ni -> AlNi₂

 

And extremely exothermic (heat-generating). This reaction (see picture) is started by a very localized heat or other high-energy source, such as a 9V battery or even a laser beam. For a fraction of a second, the alternating thousands of sandwiched layers reach temperatures as high as 2000degC, and this isotropic heatwave radiates away from the initial hot-spot through the foil at speeds of about 5-8meters/second.

 

Just banging two lumps of Ni and Al together will never initiate a reaction this intense, as the two large pieces of metal act as very effective heat sinks, but by layering the metals together, the heat-generating reaction propagates by allowing the adjacent layers of Ni and Al to rapidly interdiffuse, so giving out more heat, causing the nearby layers of Ni and Al to interdiffuse and so on.

 

[ACM] How are these materials manufactured?

 

[Tommy Acchione] First, we pull a high vacuum, equivalent to those vacuums found in outer space, then we sequentially deposit the alternating layers by a sputtering process onto a specially-made metal block.

 

For a bonding material, a layer of a specialized brazing material is initially deposited onto the metal block, then the Al and Ni are put down, then a final capping layer of braze is deposited. The initial brazing layer both enhances subsequent bonding and also helps with easy removal from the surface of the metal block.

 

[ACM] I understand that the uses of these materials are expanding all the time. Can you give some examples that you can talk about?

 

Well, as you know we have about 30 patents on this technology and 35 outstanding patent applications, but I still have to be careful talking about newer applications, which are emerging all the time.

 

The biggest uses are in sputtering target manufacture (which is a little ironic, since that is how they are made!); Component mounting; and what we can call “reaction initiation”, or “energetics” - things requiring an instantaneous heat-source.

 

Sputtering Targets: For sputtering targets of non-refractory metals, standard indium or diffusion may be the preferred method. For most refractory metals and ceramics, solder wetting and CTE mismatches make bonding with standard processes difficult. NanoFoil^® allows for these materials to be bonded at room temperature, thus removing any CTE mismatches during bonding or subsequent cooling processes.

 

However, as targets get larger for flat panel displays (and we are seeing needs for up to 3m x .4m targets with higher generation depositing), indium starts to become too weak to take the weight of the indium-tin oxide (ITO or InTO) target itself, and only the strength of a NanoBond^® is sufficient to hold the target in place. Another key factor is that a manual bond of a large target to its backing plate starts to become simply physically unwieldy for an operator, as its size and weight increase. NanoFoil^® becomes the elegant and simple solution here.

 

Component Bonding: One major market that we are seeing is in component bonding. I can’t talk too much about this, but for high-brightness LED’s (HB-LED’s) and photovoltaic concentrators (CPVs) there is a growing demand for a high-temperature stable, thermally-conductive flux-less bonding material able to provide low junction temperatures over the lifetime of the device.

 

Energetics: Here we are talking about fuses and timed devices, with specially-shaped initiators that take advantage of the ignition properties and the reaction rate and energy produced by the NanoFoil^®.

  

[ACM] Tommy: very interesting! Many thanks for your time.

     In this report by the National Renewable Energy Laboratory (NREL), ITO (indium tin oxide) is proven to be more resistant to moisture than aluminum doped ZnO (AZO). 

     “As you know, PV modules are expected to last 25-30 years, and depend on moisture barrier plastic encapsulation to protect both the TCO and absorber layer from moisture degradation.

     Moisture absorption in the TCO layer increases the resistivity of the TCO, which directly correlates to a reduction in power output of the module.  The degradation process occurs over time and depends on temperature and humidity exposure, time in service, TCO type and thickness so there is no established moisture level that can be cited that will causes problems; the power output just linearly declines. 

     Moisture can enter the TCO by means of a lamination failure or directly through the plastic lamination over many years since no plastic is a perfect moisture barrier.

     The case for using ITO simply is that if moisture does penetrate, ITO will degrade less than AZO.”*

     Feel free to share your take on the report and what may be learned from it.  Do you think the industry will shift from AZO to ITO based on moisture sensitivity or other concerns?

*A special thanks to Jim Slattery (Indium) for sharing this report and his thoughts.