Carol Gowans

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

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

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

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

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

The two alloys:

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

What they have in common are:

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

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

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

Let us help!

Carol Gowans

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

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

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

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

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

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

Carol Gowans cgowans@indium.com

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

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

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

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

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

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

Carol

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

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

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

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

1) Touch screens

2) Battery chemistry

3) Electronic thermal interface materials

4) Solders

5) Cryogenic and hermetic sealing

6) Solar panels

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

Carol

cgowans@indium.com

+1-315-853-4900

Eric Bastow recently wrote about using our Indalloy Flux #2 for soldering to Nitinol.  He did many tests and wrote an Application Note called Soldering to Nitinol.

Fort Wayne Metals, a leading supplier of medical wire (including Nitinol) also did a test on various fluxes as they relate to break load (maximum load before the joint breaks.

The fluxes tested included:

• Indalloy Flux #2 and Flux #3
• Indalloy Flux #5RMA; #5R; #5RA
• Indalloy Flux #4R
• Flux #400 (no longer commercially available)

The #5 series and the #4R were found to not be strong enough to clean off the tenacious oxides formed on Nitinol. Therefore, they didn't enable the solder to wet the surface properly.

Flux #2 and Flux#3 gave the best results (of the fluxes tested for break load) since they removed more of the oxides and allowed for a stronger solder bond.

Want to know more about soldering to this important medical material?  You can contact Eric Bastow directly at ebastow@indium.com or email us at medical@indium.com. 

Carol Gowans

cgowans@indium.com

• Five Solder Families and How They Work (Eric Bastow)
• Solder Preform Basics (Paul Socha)
• A Quick Guide to Solder Preforms (Jim Slattery and Paul Socha)
• The Basics of Soldering (Chris Nash)

• It remains malleable at cryogenic temperatures
• It is soft and pliable so it fills imperfections in mating metal surfaces and creates a hermetic seal

Solder starvation

• weak solder joint strength
• open solder joints
• intermittent short circuits
• reduced first-pass yields
• increased inspection
• increased rework
• field failures
• damage to your company's brand & image
• reduced sales and profits

• The single-thickness stencil is designed for the majority of smaller components, starving the few larger components of solder volume.
• High-use interfaces, such as connectors and USB ports, require extra solder - to assure their solder joints survive the constant use in the field.
• Smaller, more tightly compacted circuit boards don't allow for deposition of enough solder paste.

• You can add solder just where you need it without overprinting solder paste or working with step stencils.
• Preforms deliver precise, repeatable volumes of solder.
• Preforms can be added during your existing SMT process with existing pick & place equipment.
• Preforms eliminate the need for rework or hand soldering at the end of the process.

The week of March 14th Indium Corporation will be exhibiting at the MD&M (Medical Design & Manufacturing) show in Orlando, Florida.  Actually it is one of many MD&M shows held throughout the country.

We have attended previous shows as visitors but this will be our first as an exhibitor.  We will be showcasing our Flux #2 and lead-free solders for soldering to Nitinol.  Eric Bastow recently wrote a blog post on using Flux #2 and either 96.5Sn 3.5Ag or 80Au 20Sn for this application.

Flux #2 cleans off the very tenacious oxides that form on the Nitinol, giving it a clean surface to solder to.  We will be providing further details and samples of the 96.5Sn 3.5Ag in wire form at the show.  You can also request a sample of the Flux #2 by giving us your contact details.  Stop by and see us at Booth 248-250.

Or you can contact Eric Bastow by email at ebastow@indium.com or me by email at cgowans@indium.com.

November 21st is the birthday of one of the men who co-discovered indium metal back in 1863.  Hieronymus Theodor Richter, along with F. Reich, made the discovery but it wasn't until 1924 to 1933 when Daniel Grey created a process to extract and refine indium that the commercial possibilities began to be explored. Their work led to the founding of The Indium Corporation in 1934.

Dr. William S. Murray, the founder of Indium Corporation, received the first patent to process indium in 1926.  The first commercial quantities of indium were discovered in Kingman, AZ in the same year.

The importance of indium metal grew through the rest of the 20th century, in conjunction with each new technology discovered.  Whether it was its malleability (even at cryogenic temperatures), its low melting point, its electrical conductivity, or its thermal properties, indium has become a standard in almost every industry for unique as well as common place applications. 

Today indium is used in a variety of applications: as a low melting solder in electronics applications, as a coating for touch screens, LCDs, and solar panels, as well as a thermal interface in many of our heat-producing electronics.

Although indium has a relatively short history, particularly from a commercial standpoint, new discoveries and applications for this unique metal continue to be made.

For more information on indium, go to www.indiumsolders.com.

Spending back-to-back weeks at two electronics assembly trade shows is a unique experience, to me.

First up was SMTAI in Orlando, FL where I helped present a paper on Solder Fortification Preforms. 

How does one "help" present a paper?  Have you ever listened to a great paper and then, at the end, seen so many people rush around the speaker that no one can get a chance to make a further connection?  My role was to be available as an additional resource for answering questions after the presentation.

The second show was IMAPS 2010 in Raleigh, NC.  This is one of the best showcases for our Engineered Solder Materials.

There are many facets to the trade show experience. 

• There is the booth, which has to have the right message and the right pictures to draw the right people in. Our message is "From One Engineer to Another". Most of our staff IS engineers. Our team is extremely knowledgeable about materials and assembly processes.  We provide the best service when we are talking with Process or Design Engineers that need our soldering or bonding expertise.   
• There are the technical presentations, as mentioned above.
• There is the networking with industry leaders.  Being able to visit a variety of complimentary suppliers and discussing topics we have in common is tremendously valuable.

Even in the face of the myriad technology devices that keep us connected 24 hours a day, there is still nothing like that face-to-face experience.  The IMAPS Global Business Council presented two speakers during the show: one from DuPont and one from Dow.  One of them (I am sorry I can't remember which one) stated the overwhelming importance of getting their Application Engineering staff into the field to work face-to-face with customers.  

So if you want to more about what we know, check out our blogs.  When you see something you like or want to know more about, call us or email us.  We are glad to work with you!

And if you want to hear another viewpoint on trade shows, check out Andy Mackie's blog.

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.

• It stays pliable at cryogenic (-150C) temperatures.  This means that indium seals that are exposed to these cold temperatures will not crack or fail like other metals will.
• Indium is great for bonding non-metallics such as glass, quartz and certain ceramics.
• Since metals expand at different rates, this mismatch can cause a bond to break during heating and cooling.  Indium compensates for these differences.
• Indium cold welds to itself so you can apply an indium coating to two surfaces like glass, quartz or certain ceramics that cannot be soldered and cold weld them together.