NanoFoil

Power amplifiers and transistors come in many shapes and sizes. The performance requirements vary as well. Attaching them can be a critical aspect of your design.

Both Pb and Pb-free alloys can be manufactured as a solder preform with a flux coating.(Learn more)  Selecting the right alloy and flux coating can be crucial to meeting your void criteria.  

A high-tech SOLDERING solution might include NanoFoil®, which effects a solder joint while minimizing heat exposure to your components.

There are also thermal interface materials such as the HEAT-SPRING® which utilize the unique properties of indium to create a superior thermal connection, similar to a solder joint.

There are many different attachment methods available, contact me with your design parameters and we can find your solution.  

The SNEC 4th International Photovoltaic Power Generation Conference & Exhibit in Shanghai is known as one of the BIG solar shows of the year. Indium Corporation’s Bill Jackson (Director of Solar Products) commented that the 2010 SNEC was: "A busy, well attended show exuding with confidence about the beginning of a worldwide economic recovery and good solar-related growth for the foreseeable future".  That’s good to hear! Luckily, we had a strong team there to handle technical inquiries. Attendees from Indium Corporation included:

• Bill Jackson
• Thomas Tong
• William Aw
• Tommy Fan
• Michael Qiu
• David Hu

Even Indium Corporation President Greg Evans stopped by to visit the booth, to network, and to take the pulse of the industry.

This year, the SNEC was especially important for us. We had a chance to show off some of our new technology and sputtering target capability. The visitor interest seemed to mirror this thought with “…high interest in rotary CIG (Copper Indium Gallium) and Cu-Ga targets, also high interest in target bonding with NanoFoil®".

I also wanted to take a second to thank the people behind the scenes that help to make shows like this possible. Special thanks to Bill Wilson for helping to make sure our display targets looked their best, Gene Loparco and his team for dealing with the logistics of transporting our materials to/from the show, and Anita Brown for helping out with the details of coordinating the show.  These Indium Corporation employees help us all shine at solar trade shows!

~Jim

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

At the heart of it, NanoFoil^® is simply the aluminum and nickel chemical reaction just waiting to happen.  A lot of energy and a lot of heat strapped into thousands of alternating layers of atoms.  Each atomic layer of aluminum is waiting for just the right energy to move into the nickel layer and combine - to release up to 1250 Joules of energy per gram of material and as much as 1500ºC (2730ºF).

But, why don’t nickel and aluminum just react in real life? And more importantly, how do we make the NanoFoil react to release heat precisely where we want it? 

The former question is answered by going back to basic chemistry and a concept called activation energy.  Activation energy is defined as that energy that must be overcome in order for a chemical reaction to take place.  In regular use, when aluminum and nickel come into contact with one another they do not react, and this is a good thing. Imagine if your nickel-coated nickel reacted with your aluminum money clip in your pocket…hot!  The activation energy of the reaction is too high to promote this reaction naturally.  ‘

 There are a few ways to reduce this activation energy, the most common being via a catalyst, which is a substance that modifies the transition state which, in turn, lowers the activation energy of the reaction.   In the case of the NanoFoil, instead of a chemical modifier we have taken advantage of a physical modifier, surface area.  By layering the aluminum and nickel atoms very thinly and in a very precise method, we rely on the increase in surface area to decrease the activation energy necessary to start the reaction…in most demos we use only a 9 volt battery!   

 The second question is a frequent one fielded by Indium engineers, and worth a deeper look!

 How is the NanoFoil Activated/Ignitied?

The reason I will use the term "activation" over "ignition" is that ignition implies the beginning of a sustained burn, where the NanoFoil is a reaction that lasts for less than a millisecond, and only requires activation.

The reaction will start with 250ºC of localized heat, or a very localized form of energy.  The trick is getting a very concentrated form of energy to come into contact with the NanoFoil.  Touching the NanoFoil with the point of a resistance soldering iron that is at 250ºC is much more likely to activate the NanoFoil than throwing the NanoFoil on a hot plate that has been heated to 250ºC.  In general, there are three types of energy you can put into foil to activate it.

1. Mechanical Energy
2. Thermal Energy
3. Electrical Energy
   

Mechanical Energy – In the case of mechanical energy, dropping the NanoFoil on a concrete or hard surface could activate it IF it lands on its edge and all of the impact energy is concentrated on the corner.  Generally, the NanoFoil does not go off with contact, but friction between the NanoFoil and itself, in the form of a small shard, has produced enough energy to activate the NanoFoil.

Thermal Energy – In the case of thermal energy, as discussed above, a concentrated amount of 250C heat will activate the NanoFoil.  In the case of ohmic heating, which is what we do in demos, by shorting the leads of a battery, the current must be 100-120Amps for a 15um contact diameter, and 250-300 Amps for a 300µm contact diameter.  A hot filament or flame, such as a lighter, will also activate the NanoFoil.

Electrical Energy – In this case a spark will activate the NanoFoil, but it is about concentration of power, or power density.  With a momentary point contact from an electrical probe, 10 Amps and 5 Volts is sufficient as long as it is POINT contact.  The foil can be activated remotely through the use of a dedicated trace on a board, and this requires testing to determine the amount of energy that will travel the distance of the trace.

In my next blog post I will talk about Laser Ignition, ESD sensitivity, and some of the tools that Indium has developed to control the activation.

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.

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

Cheers!  Andy

Tommy: NanoFoil...it's kind of like aluminum foil in thickness and look, but a little stiffer and when you put energy into it, like a spark, it heats to 1500 degrees Celsius (which is hotter than lava in a volcano) for less than a millisecond!

My engineering and non-engineering friends display puzzled looks, you know the ones you get when you start explaining that your favorite sport is water polo and it has nothing to do with horses...ok the look you have right now

Engineering Friend: Umm so what can I blow up with it?

Non-Engineering Friend: So wait, if it's that fast and that hot, I bet you could make really fast grilled cheese. Have you called Healthy Choice yet?

Good Grief!

Al + Ni -> AlNi  (You didn't know there'd be chemistry involved did you?)

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.

这段时间在学习vertical markets,  学习完后，就要开始规划各种vertical markets, 做好一些计划和具体的行动规划了。其中一个特别有意思的产品NanoFoil，就有很具体的vertical market (某种程度上，也可以叫做细分市场niche market). 

Indium公司完全收购RNT公司之后，拥有NanoFoil的专利权，生产权，销售权，和使用权。这种薄薄的纳米材料，中间有无数相间的Al和Ni层。给一点初始的能量，这种材料能迅速释放出巨大的能量，并且快速冷却，连接两个金属界面（如Al界面），起到很好的机械性能和电性能。 请看如下录像。

在SMT电子表面贴装领域，或许因为微型化(Miniaturization) 和NanoFoil需要初始能量激发的原因，目前应该还不能广泛应用。但是这种高精尖的纳米材料，还是有vertical markets以及很广泛的应用前景的，特别是在太阳能Target Bonding领域。

Cheers!    

Video source: Youtube