Indium Corporation Blogs

Why do we care so much about target bonding? This is important because a sputtering target that truly performs will allow greater process flexibility, and higher throughput. An introduction from Eliminating Bond Stresses of Sputtering Targets at Operating Temperatures:

“…It was observed that bonding with reactive multi-layer foil as a localized heat source allows use of higher temperature solders for joining target and backing plates for sputtering. This permits the use of higher power densities and higher operational temperatures, since the bond is generally the first part of the target assembly to fail at higher temperatures.

After learning that a condition of low stress can be set at ambient temperatures, it is a logical next step to explore setting a low stress point at other temperatures. If the theory is true, that a zero stress point could be set at operational temperature, then a sputtering target would be able to operate with no stress imparted by thermal expansion. This would allow higher sputtering power densities, which would result in an increase of throughput.”

Whenever two materials with different coefficient of thermal expansion values are bonded together, they will expand and contract as the temperature changes.

Assuming these two materials are bonded rigidly, there are two things that can happen as the temperature changes: 1) the bond will break apart or 2) the assembly will bend to accommodate the stresses. Either of these outcomes can be disastrous for a sputtering target. The important thing to realize is that this is a function of temperature change. Limit the temperature change and you will reduce the effects of CTE (Coefficient of Thermal Expansion) mismatch.

The answer to this is found in the conclusion of Eliminating Bond Stresses of Sputtering Targets at Operating Temperatures:

“Reactive multilayer foils can be used to form a low stress bond at room temperatures. This is especially important for sputtering target assembly. The same bonding process can also be performed at elevated temperatures for a zero stress point at or near operational temperatures. With a firmly bonded bi-metallic assembly, curvature over a large temperature range cannot be ignored, but the effects of this can be mitigated through selectively setting a zero stress point at a strategic temperature.”

Fluxes are an interesting element of working with many solder applications. With so many specialized fluxes there is usually a perfectly-tailored flux for removing oxides from any solderable surface. Even though we love fluxes at Indium Corporation – not all of our customers share that same affection.

It is understandable; some applications cannot tolerate flux contamination. If a customer chooses to say goodbye to flux we still have a few tricks to form a solder bond without that formulation of organic acids and solvents with which we are so familiar. One of those tricks is to use NanoFoil^® to bond the two parts. For a comprehensive background of the process, click here.

In an earlier post I mentioned one of the presentations we gave at the 2013 SVC TechCon. The other presentation that our team delivered at the show (presented by Jacques Mateau) regarded another very interesting topic. The paper, High Temperature, Pb-Free, Metallic Sputtering Target Bonding Using Reactive Multilayer Foil, deals with creating high temperature NanoBonds®:

“Metallic bonds provide excellent thermal and electrical conductivity, but are limited by the relatively low melting point of the solder material used, 157°C for indium or 217°C for tin-based alloys. This limits the power input, which in turn limits sputtering rates and final film properties. There is a desire for a higher temperature (>300°C) metallic bonding process that can produce flat, stress-free target assemblies, enabling targets to run at higher temperatures for longer periods of time. We will demonstrate a metallic bonding process using reactive multilayer foils and a high temperature alloy with melting temperatures as high 380°C. We will compare this with traditional Sn-based solders typically used, specifically comparing shear strengths, void analysis, and cross sectional analysis.”

The image shown here is a bond formed with a 98Zn/2Al alloy and 60μm thick NanoFoil^®. You can follow the link above to read to paper, and email me if you have any questions or are interested in this process for bonding your sputtering targets.

~Jim

A visitor at our booth during the 2013 SVC (Society of Vacuum Coaters) conference suggested this video. In the video, a piece of indium is rubbed against a piece of gallium. The result is the formation of a room temperature alloy (75.5%Ga/24.5%In, mp: 15.7°C).

One of the fun parts of my job is talking with the people I meet at tradeshows. You never know what you might be asked or what you might learn.

For anyone who couldn’t make it to the 2013 SVC, just email me at jhisert@indium.com and I can make sure you receive a copy of “Eliminating the Bond Stress of Sputtering Targets at Operating Temperatures”. This paper discusses alternative processes for bonding targets - alternative processes that demonstrate the unique capabilities of NanoFoil^® and open your mind to currently undiscovered methods.

Interested? Let me know!

An unfortunate misconception about nanotechnology is that it needs to be cutting-edge technology. This is most likely a manufactured perception, created by all the people out there trying to sell nanotechnology as the “next big thing”. While there are huge advancements in various industries being made due to nanotechnology, the use of these materials overall is nothing new. Keep in mind that, by the broadest definition, nanotechnology simply deals with materials with features <100µm in measurement.

NanoFoil^® is classified as a nanotechnology due to the thickness of each aluminum and nickel layer, however NanoFoil^® is a very simple material. It is interesting, useful …maybe even amazing. But regardless, it is simply Ni and Al foil. To make a point of how simple this is, let’s look at a common item I’m sure you have seen before: a metallized potato chip bag. The metal layer on these bags range from 40-50 µm thick, which is approximately the thickness of each bi-layer of NanoFoil^®. While this product would be considered nanotechnology, it doesn’t excite the average consumer. (This consumer was also NOT excited about how many chips were in this package when I opened it…)

Perhaps an easy way to sort out the high-tech nanotechnology applications is to distinguish anything that makes use of quantum physics effects of the nano scale materials? Or maybe we should categorize them based on how difficult they are to produce? In the end, nanotechnology does not always equal high-tech. I argue: why does it need to?

~Jim

In a somewhat recent post, I mentioned that my favorite NanoFoil^® application note was “NanoBond^® of Ceramic and Metal Sputtering Targets”. That document has some really useful data points for you. In addition, I’d like to mention another very interesting document: “NanoBond^® Thermal Interface”.

The really interesting part of this application note is that it is more of a case study of a particular thermal interface, which demonstrates the NanoBond^® procedure as well as the results. If you’re interested in how this compares to thermal greases and other TIM technologies, you’ll like the test data that is included.

Check out the full application note here.

~Jim

As an application engineer working with various NanoFoil^® applications, I have learned which common items are very handy to have with me whenever I am working with NanoFoil^®. Leather gloves, tweezers, a glass cutter, metal strait edge / ruler, 9V battery, hydraulic or spring loaded press, high-temp tape, foam, and aluminum blocks are all used often. With the exception of the press, this equipment is all quite portable and inexpensive. There are good reasons for each item on the list:

• Leather gloves: Protect your hands when you must handle reactive foil.
• Eye protection: This should be fairly self-explanatory. Your eyes are important – keep them safe!
• Nitrile gloves: Used to keep finger oils away from bonding surfaces.
• Flat tweezers: Better than gloves for handling preforms and positioning parts.
• Glass cutter: Easily cut pieces of foil to size/shape.
• Metal straight edge / ruler: Used to guide the glass cutter for a straight cut.
• 9V battery: Can be used as a backup for activation of foil.
• Hydraulic or spring loaded press: Applies pressure during assembly and compensates for minute but important settling of the assembly.
• High-temp tape: Used to shield surfaces from excess solder or to position foil or parts.
• Foam and aluminum blocks: Distribute pressure evenly during assembly.

These items are all used on a daily basis here at the Indium Corporation, where we are the supplier and also one of the largest users of NanoFoil^® in the world.

One of our most demanding customers is ... the Indium Corporation! While we supply the world with NanoFoil^®, we also use a large amount for target bonding services. That’s right, we are one of our most demanding customers, using large amounts of reactive foil to turn slabs of materials into precision bonded sputtering targets for the semiconductor, solar, and other coating industries.

As a materials supplier, this bonding service is unique for us – but it has many advantages. One huge advantage is that is gives us hands-on experience with many unique bonding applications. Another benefit is that this allows us to observe NanoFoil^® from a customer’s point of view - for maximum quality control and performance feedback.

I know I’ve probably made it sound like we use all the foil for ourselves, but I assure you we have enough for your NanoBond^® process too. In fact, we already have a kit on the shelves waiting for you!

The attachment of concentrated photovoltaic (CPV) cells is the perfect application for NanoFoil^®. Due to the isolated heating during bonding, less stresses are imparted due to coefficient of thermal expansion. Unlike conductive adhesives or epoxies, NanoBonds® are full metal interfaces which offer higher conductivity values. These 2 points together reveal how NanoBonding incorporates the main advantages of other bonding technologies. This sounds great, doesn’t it? Well, here’s the catch:

Most people have experience gluing parts together, and many handy engineers have learned how to solder wires, pipes, or other common items in the past. In contrast, very few people have ever dealt with a bonding process like NanoBonding. The principal of NanoBonding is simple, but it does require a small amount of research. Luckily, you’re in the right place. From here you can browse the many posts regarding the NanoFoil^® material and the NanoBond^® process. After learning the basics, simply click on one of the contact buttons on this page or follow this link for tech service. Our technical support team can help you become confident with the technology quickly.

When dealing with bonding, we often mention CTE (Coefficient of Thermal Expansion). This is a very important topic when designing a soldered interface, whether you are choosing materials that will expand and contract at the same rate or bonding alloys or processes that will handle the stress of deformation caused by these changes. This topic has been explored by hundreds of people, but I like this video because the presenter is both thorough and fun:

We’ve heard your requests and are now offering Sn-plated NanoFoil^® activation kits. (Check out the product page here.)

These kits are perfect for bonding gold or silver metallized parts. The kit includes Sn-plated NanoFoil^®, 1” x 1” ENIG substrates to practice bonding, a handy 9-volt battery, and a few tools to make the activation portable and easy. 

Jim

A professor told me (on many occasions), “work smart, not hard”. Although he had good intentions, he was not a great mentor – as even his peers have since confided in me. This teacher had seen me try to tackle engineering problems with brute force instead of finding an easier way to accomplish the same goal. While I do agree with the first half of the motto, I cannot, and will not, be content with the second.

Let’s say you do, indeed, work smarter than your equally-talented competition, and you can accomplish the same task as they do in half the time and with half the overall effort. Would it not be logical that you may be able to expend the same energy and time as your competitor, and, by working carefully, complete twice the work? I would argue that it is better for a person to “work smart, AND hard”.

I was not brought up to take the easy way out, which, I admit, has made some tasks unnecessarily more difficult. But, I am fortunate. For it is easier for most people to work on the ‘smart’ part than to learn a good work ethic. If you want to succeed in anything you do in life, start by working hard at whatever you do. Next, love what you are doing so that you will naturally desire to be the best. When you love what you do, you will be drawn to learn every facet of it and it will be much easier to find the smart way to accomplish your goals.

Recognition and reward will follow if you focus on working smart, AND hard.

Best Wishes,

          ~Jim

NanoFoil^® requires a threshold of energy to activate. What happens if that energy value is not met?: Interdiffusion and inhibition of the NanoBond^® reaction.

This can happen if NanoFoil^® activation is attempted and failed. I have seen this happen in a few instances when I used a dying 9 volt battery which had been strained from many tradeshow NanoFoil^® demonstrations. I noticed that, with a new battery, the reaction was more easily started on a section of the foil on which activation had not yet been attempted. There is a threshold of energy needed to activate a reactive foil, slowly heating the foil will only allow the Ni and Al layers to diffuse - and raise the required activation energy.

In the picture shown here, notice the distinction between the light and dark layers. Each stack of one aluminum layer and one nickel layer is refered to as a 'bi-layer'. The bi-layer thickness and integrity are both important for the foil to activate at the proper temperature and release the proper amount of heat.

To learn more about using NanoFoil^®, please check out the NanoBond^® Process Series.

Many surface finishes are solderable with the right flux. Many of our electronic devices use solder to bond copper, silver, gold, and other metals, but did you know that you can solder wooden surfaces too? Soldering to wood is easy with the correct flux.

There are many great uses for wood bonding:

• Grounding static sensitive antique furniture
• Harnessing “green energy” from trees
• Electrical resistance testing of hardwoods and softwoods

Happy April Fool’s Day!

~Jim

In a previous post, one of our experts clarified that Nanotechnology is about more than just a physical size-range, it’s about the unique properties of these materials due to quantum physics effects. Further, I’d say it would be almost stereotypical to think that every material with features measured in nanometers would actual display these bizarre effects. Sometimes, short of unique changes to the physics of materials, Nano-Scale materials are still important due to other (size related) properties.

As he mentioned “…It depends on the material system, the exciton Bohr radius of that material and the size of the crystal.  With that said, nanoparticles in the 50-100 nm range, for many material systems, would not contain quantum physics effects, but, can be printed easier by inkjet (less likely to clog the nozzle – although agglomeration could occur), have a greater surface area (which can be both positive and negative), can give better dispersions, and have unique thermal conductivity properties, and lower annealing temperatures.”

These unique material properties change the way we think about our currently available materials. No longer can we simply say the thermal conductivity of ‘element X’ is ‘Y W/mK’, because it may be quite different when it is produced as a nano-scale material. The same holds true for many other properties that we all know for traditional materials. The world has a lot to re-learn.

Here at Indium Corporation we use punch presses to die cut NanoFoil^® for our NanoFoil^® research kits. We use this equipment to singulate the most common parts that we need to cut for our customers. This process results in parts with edge precision much better than hand-cut foils, approaching that of laser cut parts.

The really interesting thing about punching NanoFoil^® parts is that it’s so simple, quick, and the results are quite good. Equipment can be as modest as a hand operated set of dies to a full-on automated set up. The choice is yours.

A while back I wrote a series of posts regarding corrosion. Since I have been at the Corrosion 2013 tradeshow this week, I’ve decided to resurrect the aged posts regarding:

1) A brief definition

2) Corrosion effects on electronics

3) Sources and prevention

4) References for more information

5 years later my interest has expanded to another area of corrosion. You can expect product based in-depth posts on the subject in the near future.

All the best,

          ~Jim

Let’s start with a bit of fiction to get us on the same page…

Mike is working with NanoFoil^®, getting ready to bond a small, round, planar sputtering target. He has prepared his backing plate and target material and is ready to assemble the stack after cutting a piece of NanoFoil^® to fit. He carries the foil from storage to the cutting area on the metal backing sheet on which it was supplied. After marking the foil, he uses a glass cutter to trim off the excess, and brushes the scraps off the table into a metal bucket with the other scrap he cut for the last job. Suddenly he notices a red-orange glow and feels the warmth of the reacting NanoFoil^® near his leg. Mike didn’t get burned this time, but he realized he should not let scrap NanoFoil^® build up. The last piece of foil he threw into the pile had activated by landing on a corner and caused a chain reaction in the metal bucket.

It is natural to have a tendency to treat the scrap as, somehow, less reactive. But, NanoFoil^® scrap pieces are every bit as reactive as the useful pieces from which they are cut. If you are cutting your own NanoFoil^®, make sure you use equal care with both your main pieces and your scrap.

Here are a few tips on how to handle NanoFoil^® scrap:

1. Designate a metal container for NanoFoil^® scrap only
2. Do not allow the scrap to accumulate in the container
3. Be careful not to drop foil into the container

Always follow the NanoFoil^® safety guidelines (like wearing leather gloves while handling) and stay safe!

Feel free to contact our technical support department for best practice suggestions as well.