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.”

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

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.

Folks,

A reader writes:

Dear Dr. Ron, I need to measure the void content of an alloy.  Is there an easy way to do it?

After a little thought, it occurred to me that the densities of the voided and unvoided material will likely hold the answer.  I derived the result below.  Assuming we know the density of the unvoided material, we can measure the density of the voided material with the Wet Gold Technique, discussed in recent posts, if the voids are not connected (closed cell.)  If the voids are connected (open cell), you could machine the foam to the shape of a rectangular parallelepiped and determine the density of the foam as the mass divided by the volume.

As an example, let’s say you have a closed cell aluminum foam. We use the wet gold technique to measure its density at 1.5g/cc. The density of solid Al is 2.7g/cc.

So the volume fraction of voids is:

Sadly, this technique could not be used to find void content in solder joints, or in BTC (e.g. QFN) thermal pad connections (which are so handily mitigated by using solder preforms.)

:   :   :   :   :   :   :

Global Warming Musings:  My recent post on GW generated many comments.   I will be sharing additional reasons why I am a skeptic at the end of posts like the one above. 

It is important to state the distinction between a GW Skeptic (me) and a GW Denier.  As a Skeptic, I am not convinced that the warming trends are alarming or unusual, especially since the atmosphere has not warmed in more than a decade.  Also, I am not convinced that the main driving force for the warming trend up to the late 1990s can conclusively be attributed to human activities.  Lastly, I’m not convinced that even with Draconian measures, we could affect a change that would matter.

The Carbon Cycle

In this post, I would like to share the data relating to how much carbon dioxide is produced and put into the atmosphere.  More specifically, what percent of carbon dioxide generated each year is from human activities. Would it be 30%, 40%, 50%?  The answer is 3%.  The remaining 97% of carbon dioxide generated on the earth each year is generated by natural processes in the oceans and on the land.  See the image below.  The GW argument is that even though human activities are only 3%, this amount offsets the delicate balance that nature provides.  Working with and modeling data all of the time, I find this argument unsatisfying.  Collecting accurate data and developing an accurate model on data like this is difficult.  Making incontrovertible conclusions (it is certain GW is caused by humans) more so. Freeman Dyson, arguably one of the most accomplished physicists of this era, has a similar view:

The models solve the equations of fluid dynamics, and they do a very good job of describing the fluid motions of the atmosphere and the oceans. They do a very poor job of describing the clouds, the dust, the chemistry and the biology of fields and farms and forests. They do not begin to describe the real world we live in...

It is interesting also to note that throughout history the temperature of the earth determined the carbon dioxide content in the atmosphere, not vice versa.

Cheers,

Dr. Ron

.

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:

As I discussed in my last post, the industry has found that reducing the silver content of SAC alloys helps to improve its mechanical shock performance.  However, low-Ag alloys such as SAC105 are still inferior to its Sn/Pb predecessors in some important ways.  The graph below shows this trend.

Indium Corporation spent several years developing an alloy that bridges the gap between SAC solders and Sn/Pb solders for mechanical shock resistance.  The culmination of this research has led to the development of SACM™.  SACM™ not only outperforms SAC105 but is superior to Sn/Pb when it comes to mechanical shock.  For complete test data on SACM™ visit www.indium.com/SACM.

*This post is part of the Introducing SAM™ series.

It is no secret that automotive semiconductor customers are becoming increasingly demanding. The "under the hood / bonnet" electronics environment is arguably one of the most thermally stressful environments on the planet. Electronics close to the engine block can experience extremes ranging from frigid winter cold to tropical heat, with the added heat source of the adjacent internal combustion engine.

The moisture sensitivity level (MSL) standard from JEDEC / IPC was developed to cover the moisture-absorption and "popcorning" effects of polymeric overmolded materials, but has been expanded in usage to cover a variety of different packaging situations and failure modes. The standard does allow for a certain amount of delamination, even under the MSL1 conditions usually required by automotive semiconductor customers. However, now "zero tolerance for delam" is the most common request from automotive design engineers. In order to meet this need, both overmolding materials manufacturers and leadframe suppliers have been working on how to drive to zero delamination. Leadframe manufacturers have developed a variety of approaches to their products that enhance the adhesion between the leadframe metal itself and the overmolding compound. Usually, this takes the form of physical and chemical texturing of the copper, using a process such as brown oxide formation.

It is no surprise that this need for adhesion enhancement (AE) drives leadframe treatments that are antithetical to the need for formation of void-free, high conductivity electrical connections between the die and the leadframe - basically, it messes with the solderability of the preform or solder paste. In order to get around this issue, leadframe manufacturers have increasingly moved to the use of spot-plating of silver onto copper, with thicknesses ranging from 2-9microns. Why is the silver so thick, in comparison to silver sputtering onto the die surface? Simply because copper diffuses very quickly into the silver, so a thicker silver layer leads to a longer shelf-life for the leadframe. Note also that plating does not have as good process control as sputtering, but it is a lot cheaper and faster.

You can see (below) a schematic of solder paste printed onto one of these leadframes.

An emerging failure mode is one of incomplete wetting onto the leadframe, leading to failures at the sites where solder has failed to flow over the silver plated area completely - "delamination sites" - (below). The flat, shiny, silver finish is not a suitable surface for overmolding compounds to bond to.

So why isn't the solder wetting well? The answer becomes clear pretty quickly when you do some back-of-the-envelope calculations of the expected final silver content of the finished joint. Let's assume some bondline thicknesses (BLT) is (25,75microns) of a solder containing 2.5%Ag (such as Indalloy 151 or 163) and the plating thickness is (3-9)microns. Typical plating thicknesses of 2-9microns may be seen, based on a recent customer survey), with a mean around 3microns.

So what is the silver content of the final joint, assuming all the silver is dissolved?

The calculations, therefore, show that it is from 6 to 27% silver. The 27% level is well beyond the solubility limit of silver in these types of solder, and in fact in most solders, at the expected soldering temperatures. The mechanism of non-wetting is clear: solder can no longer wet onto silver, once it has become filled with insoluble intermetallic particles.

The message to power semiconductor component suppliers is:

• Maintain the silver thickness at a consistent, low level: set up tighter specifications on the silver spot-plating from your supplier.
• Update your incoming quality control inspection so you can be sure you are getting what you paid for in terms of thickness of silver and consistency.
• Manage leadframe inventory so you run leaner, so you do not run into leadframe lifetime issues with copper diffusing through the thin silver layer and oxidizing (solderability / voiding problems).

You do have an alternative (moving to an alternate solder type), but then you are into a lengthy requalification procedure.

As always, please contact me if you need assistance.

Cheers!  Andy

Engineered solders are solders that can make a HUGE difference with your thermal management, IGBT, die-attach, medical device, hermetic sealing, or connector assembly application. The possibilities are endless.

One of my personal favorite engineered solders is Solder Fortification® Preforms. Obtaining the correct amount of solder to ensure a strong solder joint is critical in electronics manufacturing. Solder Fortification® Preforms are the solution for many challenging manufacturing issues from miniaturization to tightly fitted components to achieving just the right amount of solder in just the right place.

Solder Fortification® Preforms are generally rectangular pieces of alloyed metal that do not contain any flux. The preform is added to a deposit of solder paste using standard pick and place equipment. Since the alloy for both the preform and the solder paste is the same, the preform will reflow at the same temperature as the solder paste, with the solder paste providing the necessary flux. The preform increases the volume of solder over what could be achieved with solder paste alone, especially for stencils with a pitch of 0.3mm or less.

Tell me where engineered solders, especially Solder Fortification® Preforms, might help you. I'll take it from there.

Seth

As the world began transitioning to Pb-Free solder in the early 2000’s, the electronics industry determined that SAC387 (95.5Sn/3.8Ag/0.7Cu) was the most appropriate alloy to replace eutectic SnPb.  While it did have a higher melting point than eutectic SnPb, SAC387 was seen as the best option relative to solderability and usability.  The industry quickly shifted to SAC305 (96.5Sn/3.0Ag/0.5Cu) because its lower Ag content resulted in a lower price.

At that time, the industry didn’t realize the performance impact of the Ag content.  We now know much more.  Ag has a significant impact on a solder alloy's reliability. When thermal cycling higher Ag content SAC alloys (3-4% Ag), the performance tends to be quite good (Ag adds creep resistance to the alloy).  However, because of the alloy's rigidity (more Ag - more rigid), it is more prone to brittle fractures during mechanical shock.  We achieved significantly improved mechanical shock resistance at the expense of sacrificed thermal cycling performance.  The diagram depicts the balance between mechanical shock resistance and thermal cycling performance.

Over the past several years, the Indium Corporation has developed an alloy that minimizes this SAC solder alloy composition compromise.  SACM™ is a low-Ag alloy that is doped with Mn.  This not only improves the mechanical shock resistance over other low-Ag alloys, it also enhances the thermal cycling performance, making it comparable to SAC305.  For more information about SACM™, check out our website at www.indium.com/SACM.

*This post is part of the Introducing SACM™ 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

Folks,

I am a global warming skeptic.  This term, however, requires some explanation.   I believe in climate change.  The climate is always changing.  However, I don’t think it is clear that the world has been getting warmer in the last decade.  I also am not convinced that humans are the main drivers of whatever  climate change has occurred.  The following explains why.

Point 1: For the Last 12 years the World Not Getting Warmer

The global warming scenario that exists today is that human emissions of carbon dioxide are the main reason that the climate is warming.  So, it is natural then to ask, is the climate really warming?  One look at USA Today’s cover story “Why You Should Sweat Climate Change” on 1 March 2013 would appear to settle the story.  Just look at  Figure 1 below.

Figure 1. Graph from USA Today Cover Story March 1,2013.

A quick scan of the graph shows 55.34°F last year and 50.56°F in 1895.  A 5 degree increase.  Wow!  A little closer analysis reveals that these temperatures are individual data points.  If you look at the years 1900 and 2010, you get 53°F for both years, essentially no change.  The thick red line is the long term trend and admittedly it increases from about 51.3°F to about 53°F in the 117 year period. 

Note the icon in the upper right corner, it shows the globe with a dramatic upward trend line.  However, this causes you to now note that this graph is for US temperatures, not world temperatures.  What was the world temperature like?  As this thought crosses your mind, you remember that 2012 brought Europe its coldest winter in recent memory. So you go on the internet and find out that 2012, for the world,  was the ninth hottest year on record.  Scary.  But then you think, “Wait a minute, that means that eight years were hotter.” So you wonder, what do the last 10 or so years look like for world temperatures.  The graph is below in Figure 2:

Figure 2. World Temperature 2001-2012. Graphed by Dr. Ron

Note that for the last twelve years, the trend is flat (actually a little down).  Where are all of the headlines sharing this important information?  So it is not clear that the world is continuing to get warmer.  

Am I the only one that finds it troubling that the media seem to universally tout the scary stories about global warming, but don’t seem to mention obvious counterpoints such as the graph above?  This information is profoundly important.

Point 2: In the Past, Nature Along has Delivered Stunning Climate Change by Itself

I am writing this post from my home Woodstock, VT. I look out my window and view two beautiful, large rocks, each about the size of a house.  These monoliths were likely left as the glaciers in the last ice age retreated, these rocks probably originated in Quebec.  Woodstock was under thousands of feet of ice during the last ice age, Canada was completely under ice.  New York State's Long Island is a glacial terminal moraine. The extent of the ice coverage is shown in Figure 3 below.  However, the forces of nature alone, raised the temperature of the earth by 12 degrees Celsius (with no help from mankind), melting the glaciers and allowing me to live in the Green Mountain State (Vermont = Ver (green) mont = mountain, in French.)  

Figure 3. The Extent of the Ice Coverage in the Last Ice Age  http://www.iceagenow.com/

The natural processes that caused the warming are many.  They include the precession of the earth on its axis, variation in the output of the sun, changes in the ocean and atmosphere, and others.  These processes  have resulted in the past temperature changes as shown in the Figure 4 below.

Figure 4. Temperature of the Earth in the Past 800,000 Years.

This figure shows as much as a 20°C (36°F!) temperature swing produced by nature alone.  The change in world temperature between 1900 and 2010 would be about as thick as the line in this figure. 

I find the proposition that the main driving force in global warming (if it is occurring)  being human produced CO₂ alone is hard to accept, when we see what mother nature has given us in the past.  It would be similar to someone taking the position that the only thing that affects stencil printing quality is the stencil.  When others point out that it might be the solder paste, or the print head, or separation speed, etc., they are shouted down as being unscientific.

Point 3: It was Warmer in the Middle Ages than Today

The United Nations commissioned a panel to study climate change in 1988.  The Intergovernmental Panel on Climate Change IPCC  was established.  In 1990, the panel came out with an assessment of past world temperatures as shown below in Figure 5.  The estimating of temperatures before the mid 1800s is difficult due to lack of records and thermometers before this time.

Figure 5. The First IPCC Assessment of World Temperatures, 800AD to the Present

There is some argument that the Medieval Warm period and Little Ice Age were local events, however they clearly existed and profoundly affected much of the Northern Hemisphere.  But more recent temperature IPCC plots lose them, as seen in Figure 6. below.   The Medieval Warm Period enable the Vikings to settle in Greenland and red wine to be grown in England. When the Little Ice Age came, the Vikings had to leave and England has not been as warm since. 

Figure 6. Third IPCC Temperature Assessment.  Note the Medieval Warm Period and Little Ice Age Disappear.  Because of the abrupt change in temperature after 1900, this graph has earned the moniker, The Hockey Stick Graph.

The controversy over the Hockey Stick graph  is interesting reading and is the source for Figures 4-6.  

In 2003, MacIntyre and McKitrick presented a detailed criticism of the IPCC 3^rd Assessment's Hockey Stick Graph in Figure 6 .  I find their criticism compelling.

I could go on and on,  but to summarize why I am a global warming skeptic:

• For the  past decade the world has not gotten warmer
• Natural forces overwhelm CO₂ as a driving force for climate change
• Sloppy science is behind the hockey stick graph

Please share your science- and fact-based comments.

Cheers,

Dr. Ron

Being the Indium Corporation, we know what indium is, where it comes from, and how to use it.  But sometimes we forget that not everyone is as immersed in indium as we are.

So what is indium?  Of course it is an element with an atomic number of 49, an atomic weight of 114.818amu, a relative density of 7.31g/cm³, and a melting point of 157°C.  I have known that for most of the 27 years I have worked at Indium Corporation, but what exactly does that mean?

Well, the atomic number is important because it is the number of protons in the nucleus - and this is what gives each element its physical characteristics.  It also places it in the periodic table (directly to the left of indium on the chart is cadmium which has an atomic number of 48 and to the right is tin, which has an atomic number of 50).  This puts indium in the group of metals known as "Other Metals", along with bismuth, tin, zinc, antimony, gallium, and germanium.  The atomic weight is a measurement of the total number of particles in the nucleus of the atom.  If you want to know more about protons, electrons, and neutrons, go to the Jefferson Lab site.

The specific gravity or relative density of an element, which, in the case of indium, is 7.31g/cm³, depicts its relative density compared to water.  If the relative density of an element is less than one, then it will float in water.  If it is greater than 1 then it will sink.  If you compare indium's relative density to that of lead, which is 11.35, you will see that, if you had a piece of each material cut to the exact same dimensions, the lead would be heavier than the indium.

Between the atomic number and the specific gravity, I use the specific gravity more often.  It is used in a formula to find the weight of a solder part, or of a length of wire or ribbon.

So where does indium come from?  Since indium is an element, it comes from the earth's crust.  It is generally refined as a by-product of zinc ore mining.  There is an ongoing debate about the availability of indium.  But a lot of work is being done to create more efficient extraction methods and reclaim, particularly of ITO targets, to assure an adequate indium supply for existing and emerging technologies for decades to come.

Okay, now for the fun part. Where is indium used?  It would probably be shorter to say where it ISN'T used!  If you are involved in any of the following areas, you have a need for indium:

• Cryogenic sealing
• Hermetic sealing
• Low temperature soldering for temperature sensitive devices
• Step soldering
• Solar panels (CIS & CIGS)
• Coatings for displays and glass (ITO & IGZO)
• Pb-free soldering
• Fuses
• CTE mismatch when bonding dissimilar materials
• Thermal management

Indium is certainly one of the more versatile metals because it works and plays well with others.  Read more about indium:

Indium Solder and Sealing

Thermal Management

Heat Spring

Low Temperature Solder

We like new challenges and applications, so if we can help you (or you think you can stump us), email me at cgowans@indium.com.

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!

Folks,

In my last post we saw how you could measure density with only a scale.  In this post, we will expand on that technique and learn how to measure metal content in gold/quartz ore.  In principle, this technique could be used for other ore, but the ores can only be two part (e.g. gold and quartz) systems.  Gold is a “natural” for this analysis as it is typically pure gold with quartz.

Gold is often found “veined” in quartz.  I was certain that this was the origin of the “Golden Fleece.”   The fleece being the white quartz with the gold on top.   However, a little research did not clarify this belief.

Anyway, let’s assume you take a few weeks off from work.  Leaving the world of solder paste, TIMS, ITO, wave solder flux and solder preforms behind, you set out for the west in search of some large gold nuggets.  Fate was with you in that, in a short time, you find a gold/quartz specimen as shown below.   The images, and the new “wet gold” weighing technique I will discuss, are from Bill and Linda Prospecting.

You are so excited you are shaking.  The only tools you brought are a scale, some string and a beaker.  To determine that gold content, you need to measure the weight of the gold in air and under water.  But you only have the scale as shown below.  What can you do?

After measuring the weight of the ore in air, fill the beaker part way with water, place it on the scale and zero the weight.  Then insert the ore on a string as shown below.  The scale will now read the weight of the volume of water that the ore displaces.  Let’s call this weight of the water displaced W_D .  The wet weight of gold (weight of gold under water) will be the weight in air minus W_D.  So we now have the weight in air and the weight in water.

The derivation of the equation that tells us how much gold is in the ore is at the end of this post.  The final equation we need is W_Au = 3.07W_W – 1.91W_Air.  For our ore sample W_Air = 25.1 pennyweight (pw). A pennyweight is 1/20^th of a troy oz.  W_D as shown in the photo above is 8.3 pw.  So W_W = W_Air – W_D = 25.1-8.3 = 16.8 pw.  So W_Au = 3.05*16.8 – 1.91*25.1 = 3.635 pw.  Subsequent analysis showed that the gold content was actually 3.9 pw and error less than 7%.  Not too bad for a simple field measurement.  At $1600/oz our ore sample contained. a little over $300 dollars of gold.

This technique could be used to measure the density of an alloy as in the last post.

Cheers,

Dr.Ron

The Derivation of the Equation

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.

Folks,

In the category of interesting requests, Ron, a gold worker, from Guyana, sent me the following note:

Dr. Ron,

My colleagues use a “wet” gold technique to measure gold alloy density.  Is this valid?  Where does the formula come from?

Sincerely,

Ron

Well, to tell the truth, I had never heard of it and was skeptical.  How can you measure density (mass/volume) by only measuring weight?  So, I investigated. The technique claims that one can measure density with only a scale, by measuring the alloy’s weight in air and in water.

I could find no derivation, so I thought about it and derived it on my own.  As far as measurements go, as stated, you only have to measure the weight in air and water.  If you don’t have a scale that can handle being immersed in water, you can use a hanging scale (think weighing a fish).  So, after weighing the alloy in air, you immerse it in water. It will weigh the amount of water it displaces less.  The derivation is below:

As an example, let’s say you have a gold alloy ingot that weighs 1,000 grams (OK, I know grams is mass, but we are all sloppy and use it as weight, too) in air.  You weigh it in water and it weighs 930 grams. From the formula below, the alloys density is:

r = 1000/(1000-930) = 14.29g/cc

Since the density of gold is 19.3g/cc, the alloy is not pure gold.  If you knew the alloying element, say copper, you could use Indium’s Solder Alloy Density Calculator to determine that the alloy was 69.8% gold, 30.2% copper.  If there are multiple alloying elements, since most of the common elements have a density of about 9 g/cc, you can even estimate the fineness of the gold.

Could this technique be used to measure the alloy density of say a handful of solder preforms. Sure, you could put them in a woven bag of non-hygroscopic material and weigh them in air and water.  Admittedly, measuring the density of solder paste, with this technique, would be a challenge.

Next posting, I will show how this technique is used to measure the quantity of gold in gold/quartz ore.

Cheers,

Dr. Ron

上周在圣地亚哥(San Diego), 业界一年一度的盛会APEX落下了帷幕。Indium公司一如既往地参加和支持APEX，并在会上发表4篇技术文章。

在展会上，我们介绍的重点仍然是Indium8.9系列的焊接产品。这些产品分有卤素和无卤素的(halogen contained or halogen free)，每种产品都有自己突出的特点，但是整个系列的产品都是针对免洗无铅(no-clean Pb-free)而设计的，可以与fine powder 兼容，能够很好的帮助客户解决枕头效应(head-in-pillow), graping 等问题。

Indium发表的技术文章可以在我们公司的网站上免费下载：http://www.indium.com/technical-documents/whitepaper/

• QFN Voding Control Via Solder Mask Patterning on Thermal Pad
• Material and Process optimization for HIP Defect Elimination
• Voiding Mechanism and Control in Mixed Solder Alloy System
• The Effects of Human-Induced Contamination on PCB Assembly Electrical Reliability

我很高兴能参加这次盛会，并见到了许多新老客户。期待明年4月份Las Vegas 的APEX.

Cheers!

PS: 隆重祝贺Indium公司的好朋友和我的好友，Intel公司的Raiyo Aspandiar 荣获Distinguished Committee Service Award (from IPC at IPC APEX EXPO in February in recognition of Raiyo’s outstanding contributions to the development of IPC-7095C, Design and Assembly Process Implementation for BGAs.) 实至名归！！…… 有的书把Steve Jobs 05年Stanford 演讲的名言”Stay hungry, stay foolish” 翻译成 “求知如渴，虚怀若谷”。 我觉得这是绝妙的翻译，也是Raiyo 的真实写照！！ 恭喜你Raiyo!!

Pic: Indium Corp

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!