Indium Corporation Blogs

A traditionally bonded sputtering target experiences a wide range of temperatures over its life cycle. It is bonded at over 200°C – usually almost 300°C for Sn/Ag/Cu bonding. Since this is the temperature it is bonded at, all changes in temperature will expand or contract the materials.  Next, it cools down to room temperature. It is then operated at temperatures around 100°C and repeatedly cycled over the course of its usable life.

In an alternative approach to traditional sputtering target bonding, NanoFoil^® can be used as described in Eliminating Bond Stresses of Sputtering Targets at Operating Temperatures:

“Incoming aluminum and molybdenum pieces were initially tested for flatness as a gauge for the expected deflection after bonding. In preparation for bonding, the aluminum and molybdenum pieces were coated with solder, as is standard procedure for bonding with reactive multilayer foils. The aluminum was coated with 96.5Sn/3.0Ag/0.5Cu using mechanical agitation. The molybdenum was media-blasted to roughen the surface, then coated with 96.5Sn/3.0Ag/0.5Cu solder using an ultrasonic soldering iron and an adhesion layer of activated solder. These solder layers on the two pieces of metal were then machined flat to provide coplanar surfaces for bonding.”

More information regarding the NanoBond^® Process can be found here.

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

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

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.

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

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.

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.

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.

I recently noticed something that appeared in a 3^rd party lab report that a customer shared with me. This lab report was an analysis of a NanoBond^® the customer had performed and sent out to verify. The thing that struck me was that the technician reported “This sample exhibited small fractures in the [NanoFoil^®] core material which we have seen before…” I started thinking about this, and there are very few products in the solder world other than NanoFoil that you would like to crack. In this case, cracking is a good thing!

You wouldn’t expect most soldering products to crack, but NanoFoil^® isn’t like other soldering products. As the aluminum and nickel layers react, the foil shrinks and tends to curl. Since the curling action of the foil is restricted, the foil cracks. Solder flows between the cracks and bonds to the reacted NanoFoil^® as well, creating a sort of micro-scale concrete.

Pretty interesting, huh? Here’s a link to learn more.

…And here’s a link to try it out!

A NanoBond^® acts like a traditional solder bond in many ways. After reaction, the bulk properties of NanoFoil^® are similar to that of many solders. To me, the property that is most attractive (since it is similar to that of a solder) is the thermal conductivity of reacted NanoFoil^®.

Just like tradition solder bonds, NanoBonds far surpass the thermal conductivity of conductive epoxy (by around 6x-10x), making it an exceptional material for thermal interface applications.

If you’d like to try NanoFoil^® for a thermal application, kits are available here.

I’m not the only one presenting new NanoFoil^® data at this year’s SVC (Society of Vacuum Coaters) Conference. Another member of our team will be in attendance to teach you about some of the breakthrough work he’s been doing to help you create better performing target bonds. As his abstract reads:

“There is a desire for a high 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 new NanoBond^® process using a high temperature thermally sprayed Zn/Al alloy with melting temperatures as high 380°C. We will compare this with Sn-based solders typically used in the NanoBond^®process, specifically looking at shear strengths, void analysis, and cross sectional analysis.”

Come meet the Indium Team in booth #313 at the 2013 SVC Technical Conference and Exhibit!

I invite you to come to the Emerging Technology session of the SVC (Society of Vacuum Coaters) Conference on Wednesday April 24^th – where I’ll be discussing interesting new ways to use NanoFoil^® to create sputtering target bonds with better operational performance.

Here’s a little background, if you missed some of our past presentations at the SVC in recent years: NanoFoil^® has been proven to eliminate CTE (Coefficient of Thermal Expansion) stresses imparted during the bonding of sputtering targets. Per the abstract:

“Reactive multilayer foil bonding has been used to eliminate stresses in sputtering target assembly caused by coefficient of thermal expansion mismatches between the target and the backing plate materials. Since a significant portion of the materials (except the innermost few microns) remain at room temperature throughout the reactive multilayer foil bonding process, the materials are bonded with an ambient temperature “zero stress point.” This low stress bond reduces the effects of thermal expansion, leading to less deflection of the sputtering target assembly. In most high temperature large area bonding applications, targets that deflect after bonding are mechanically stressed until they are truly planar again. This compounds the stress resulting from the bonding and flattening operation. In this paper we will explore the possibility of setting the “zero stress point” at other temperatures to further minimize stress and deflection during operation.”

If the presentation doesn’t answer all your questions regarding target bonding, no worries – the Indium Team will be there to chat with at booth #313. You will NOT be disappointed. See you there!

~Jim

NanoFoil^® can be packaged in tape & reel, bulk containers, or waffle packages. Here are the main advantages of each type of packaging:

• Tape & Reel: great choice for high-volume automated pick & place equipment

• Waffle Pack: perfect for hand placement or low-volume automated placement machines

• Bulk: most economical way to order

Packaging NanoFoil^® is actually a lot like packaging standard solder preforms. (Here is a complete list of our packaging options for preforms.)

NanoFoil^® is a great localized heat source, but it can cause some ugly looking aesthetic defects if the process is not set up correctly. Let’s take a look at how you can use high temperature tape to mask off parts during NanoBonding.

With certain NanoFoil^® thicknesses and assembly pressures, solder may be ejected from the bond area. To protect these parts from “solder spitting”, simply mask them off with high temperature tape. In the picture shown here (right), excess solder and pressure were used with a higher energy version of NanoFoil^®.

Similar parts were again prepared for bonding (left), this time with high temperature tape covering the area around the solder joint.

After a similar reaction, we see the telltale signs of excessive pressure and solder. This time, however, we can simply peel away the excess solder (right).

After bonding, the tape can be peeled off the surfaces, revealing the fresh, clean surface underneath.

This is a very flexible solution - to mask parts during reflow. In high volume, metal shims and shutters can be used to keep solder where it belongs. The best solution is to optimize the solder thickness, assembly pressure, and NanoFoil^® thickness. We can help you do that.

* This post is part of the NanoFoil^® Do-It-Yourself Tips and Tricks series

Sometimes one piece of NanoFoil^® just isn’t enough…

We often NanoBond^® sputtering targets which are large enough to require multiple sheets of NanoFoil^® to cover the width or length of a bond. You may even need to use two pieces of NanoFoil^® that were sized for a different application, or if someone made a mistake cutting foil. Oops!

Luckily, butting two pieces of NanoFoil^® up to each other is quite easy, and although visible with ultrasonic testing the small gap should not cause much of a difference structurally or performance-wise. To secure the pieces during preparation, you can use high-temperature tape (as long as it is not in the bond interface). The heat from the first piece will active the second if they are in close proximity. This chain reaction is useful for both prototyping with incorrect sized pieces or mass production with pieces that are not large enough.

* This post is part of the NanoFoil^® Do-It-Yourself Tips and Tricks series

If you have some NanoFoil^® on hand at your facility and you do not have the original packaging, all hope is not lost. We can quickly figure out what it is with a set of calipers and a quick visual inspection.

First, note the appearance of the foil. If the foil is shiny and mirror-like, it is bare NanoFoil^®. The other option is plated NanoFoil^®, which will appear silver to light gray, but with a matte finish. Plated NanoFoil^® is most commonly coated with around 10um of pure tin per side.

Second, measure the thickness of the foil with a set of calipers. Most NanoFoil^® is provided in one of three thicknesses: 40um, 60um, and 80um. Take your measurement and round down to the closest foil size. It may not be exact, and remember that plated foil generally adds 20um to the overall thickness.

If you are still unsure what you have, simply contact us and we can look up what has been ordered in the past.

* This post is part of the NanoFoil^® Do-It-Yourself Tips and Tricks series

Hand cutting is only one option for shaping NanoFoil^®, however it is quick, easy, and inexpensive.

All you need to cut NanoFoil^® with this method is a good cutting surface, metal straight edge or ruler, and a glass cutter.

Step 1: Measure and mark the section of NanoFoil^® you want to cut. You can mark NanoFoil^® with a fine-tip permanent marker. As the old saying goes: “measure twice, cut once”.

Step 2: Use the straight edge or ruler as a guide, aligning one edge to the section you just marked on the NanoFoil^®.

Step 3: Score the NanoFoil^® along the metal edge. If you need to make a second pass, do so in the same direction as your initial pass. Remember that you are scoring the NanoFoil^®, not trying to cut through it like a pizza!

Step 4: Using a bending action, break the scored section away. I like to use flat tweezers to lift the foil – for added safety in case it is activated. This is where you learn how good you are at step 3!

If all goes well, you have just cut a piece of NanoFoil^® with clean edges. If not, you will notice cracking or chips in the NanoFoil^® around the edges. If the chips are outside the bond area, it is okay to use the piece (that’s why it is good to cut your NanoFoil^® slightly oversize). After NanoBond^® and cleanup no one will ever know the NanoFoil^® didn’t look perfect just before activation. Your secret is safe with me.

* This post is part of the NanoFoil^® Do-It-Yourself Tips and Tricks series

A few years back, Indium Corporation's own Eric Bastow set up a prototype NanoFoil^® plating process to demonstrate the material and cost savings of setting up a small plating bath. One of the things that he plated in his test set up was NanoFoil^®. Not only did he demonstrate how easy it is to set up a small plating process, he also showed us a way to break free from the chains of contract plating for small jobs.

Let us know if you’d like to try plating NanoFoil^® and we can help you get up to speed in no time!

* This post is part of the NanoFoil^® Do-It-Yourself Tips and Tricks series

Using NanoFoil^® can be very easy, and there are many things you can do yourself to make prototyping or production easier, save money, and get the results you want quickly – without outsourcing services.

1. Electroplating NanoFoil^®
2. Immersion Tin Plating NanoFoil^®
3. Hand Cutting NanoFoil^®
4. Masking a  NanoBond^® Area
5. Applying Solder to Copper, Nickel, and Platinum (Flux)
6. Applying Solder to Aluminum and Aluminum Alloys (Scrubbing)
7. Applying Solder to ­­Molybdenum, Titanium, and Tungsten (Ultrasonic Soldering)
8. Determining What NanoFoil^® You Have
9. Connecting NanoFoil^®

These ideas will help you save money and feel confident about processing and using NanoFoil^® in different ways. They'll also help make you more successful and powerful in your job.

For more information about NanoBonding, check out the NanoBond^® Process Series. For a NanoFoil^® kit to get you started, click here.

All the best,

          ~Jim