Indium Corporation Blogs

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.

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.

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.

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!

The 2013 IPC APEX Expo , the premiere electronics assembly event, is right around the corner - and our technology experts are ready to share their experience and knowledge on a variety of topics.

Ning-Cheng Lee, PhD, VP of Technology will present a paper on voiding control in mixed solder alloy systems. He will also present on the hot topic of QFN voiding.     Dr. Lee is a world-renown soldering expert (EVERYBODY knows Dr. Lee!).  In addition to his work at Indium with solders (for 27 years), he is also an expert on polymers, underfills, and adhesives.

Ronald Lasky, PhD, PE, Senior Technologist will be presenting a paper on Material and Process Optimization for Head-In-Pillow Minimization.  Dr. Lasky is one of our most popular bloggers, check out his blog!  He approaches the world of electronics assembly from some interesting directions, including the exploits of Patty and the Professor.  Dr. Lasky will also talk about Applications of Solder Preforms to Improve Reliability, and A Focus on Productivity: Several Case Studies.  He has also found some time to teach two professional development courses: An Introduction of DOE, SPC and Weibull Analysis; and Manufacturing for High Yields in Assembly. Another busy man!

Senior Technical Support Engineer, Eric Bastow will be presenting on The Effects of Human Induced Contamination on PCB Assembly Electrical Reliability.  Eric has looked at the impact of oil, grease, and hand creams and how they can create reliability issues in small components.  Eric provides technical support to our customers by phone and in person. 

The APEX Expo will feature over 400 exhibitors and lots of technical sessions. It provides you the opportunity to have face-to-face discussions with many of our materials experts, so bring your soldering challenges and visit us at Booth 1127.

Can't make it to San Diego?  Call or email us and we can help you anytime!

Carol Gowans

February 2013

There have been a variety of people who were key to the development of indium metal in general, and Indium Corporation in particular, over the years.

People such as:

• Hieronymus Theodor Richter and Ferdinand Reich who discovered indium metal in 1863
• Daniel Gray, William S. Murray and J. Robert Dyer who formed the original Indium Corporation back in March of 1934 and who hold patents on processes and applications involving indium
• Frieda Nojeim who joined the company in 1966 and was elected vice president in 1971

And, in 1972, Charles E.T. White joined the Indium Corporation as a vice president (he was elected executive vice president in 1981).  I had the pleasure of knowing Mr. White before he retired.  He was indeed a character, but he also knew a LOT about indium.

In 1986 (a lifetime ago in the electronics industry) Mr. White published an article called: Indium: High Technology Metal in Advanced Materials and Processes magazine.  I ran across a copy of it the other day and, after reading it, was interested in how relevant it still is today, even though technology has marched forward.

Of course the physical characteristics of indium are still as valid today as they were then. 

• Resistance to thermal fatigue
• High thermal conductivity
• Wetting of non-metals (glass, quartz, ceramics)
• Malleability and ductility, even at cryogenic temperatures
• Electrical conductivity for a variety of screens
• Indium does not work harden

But one might expect the technology described in an article from nearly 30 years ago to have evolved or gone entirely away, resulting in the elimination of the need for the indium.  The truth is, many of applications that Mr. White mentioned still exist today:

• "Conforming gasket material for cryogenic vessels."
• "Indium is present in every wristwatch and computer screen that uses a liquid-crystal display."  Okay, so no one wears wristwatches anymore, but the screens on our phones (the new time-telling devices) have indium tin oxide coatings.
• "...used in lens blocking and in temperature-overload devices such as safety links, fuses and sprinkler plugs."
• "Many solder alloys containing indium have been developed to take advantage of indium's enhancement of thermal-fatigue resistance, reduced gold scavenging, and resistance to alkaline corrosion."
• "Glass sealing alloys containing indium ...have been developed for electronic device packaging where high temperatures cannot be used."
• "Indium's use in solder alloys is likely to increase as specialty solders become more important in electronic assembly techniques."
• "The whole area of conductive films of indium oxide and indium-tin oxide has good potential for growth.  This includes solar cells: silicon-cell efficiency can be improved with an indium or indium-tin oxide coating."
• "New applications such as solar cells made of indium-copper-diselenide/cadmium-sulphide are under active development."

And while these indium applications still exist today, R&D continues to find new opportunities for this very unique metal.  We have several Research Solder Kits that you can use to evaluate the value of indium in your process.  Just go to our e-commerce page or contact our engineers to see how indium can work for you.

Carol Gowans

We’ve heard about the solder paste “graping” defect, but the same oxidation challenge occurs in other solder forms as well, such as solder washer preforms used to attach small connectors. 

Solder graping is a defect that arose as a result of small solder paste deposits and higher (than were used in the past) reflow temperatures.  The peak reflow temperature for SnPb alloys were just over 200°C, but. with SnAgCu alloys, that peak is as high as 260°C.  New solder pastes have been developed that address this defect by utilizing flux chemistries that function as an oxidation barrier.

But what about other solder forms? 

I was recently working with a customer who was evaluating solder preforms for a connector application.  These solder washers (outside diameter of 0.025”), like the small solder paste deposits, had a large surface area with a tendency to oxidize on their heated journey to melting.  These washers were made of SnAgCu, so the peak temperature required of them was no different than it would be for Pb-Free solder paste.

I found that the same 1°C ramp that causes graping of solder paste can do so for preforms as well.  The difference though, is that the non-molten portion of solder takes the shape of its un-reflowed form, that of a small washer in this case, as opposed to the “grapes” of aggregated solder powder.  

Fortunately, the issue can be addressed in 3 ways, and I encouraged my customer in this case to process their assembly using the combination:

1. Adjust the reflow profile. Ed Briggs' recommendations work well here.  Further, use a fast ramp to peak. I tested the reflow on a hot plate set to 250°C; this improved the wetting.  Preforms are unique from solder paste in that they are solid metal, as opposed to a mixture of metal and flux.  They do not benefit from the same heating controls that solder paste requires. 
2. Reflow in nitrogen.  By purging out the environmental oxygen during the reflow process, the solder preform will not oxidize.
3. Apply a tacky RMA flux, such as Tac007.  RMA fluxes provide stronger oxidation barriers than other non-rosin flux types. 

In the second image here, it is evident the improvement these changes made in terms of the spread and coalescence of the solder preforms. Note that the addition of tacky flux left an amber-colored no-clean residue, however, this can easily be washed away using a mild solvent.

Any questions?  AskUs@indium.com!

InCuSil™ is a common term for an alloy of indium, copper, and silver which (depending on composition) has various melting points in the brazing range. We at the Indium Corporation use InCuSil™ as an outer coating on standard NanoFoil^®, to help the Ni/Al bond with the surrounding solder layers. (Seen here: a thin layer of InCuSil™ [right] partially stripped from reacted NanoFoil® [left].)

When alloyed at 61.5%Ag, 24%Cu, and 14.5%In, the resulting metal has a solidus point of 630°C and a liquidus of 705°C. It is applied to the NanoFoil^® as a final PVD (Physical Vapor Deposition) coating step, to a thickness of 1 micron (μ) per side.

Since the only function of the InCuSil™ alloy on NanoFoil^® is to promote bonding, there are some applications where it is not needed – and therefore not applied. These applications are generally for fuses and other pyrotechnic devices.

If you’d like to learn more about NanoFoil^®, send us a question!

There are a lot of parameters to consider when choosing the right solder for your application:

1) The operational temperature of the final device

2) The metallizations that you are soldering to

3) Temperature sensitivity of any components that you are soldering

4) Need for Pb-free

5) Drop test requirements

6) Reliability requirements

Each individual application will, no doubt, have additional requirements.  But, generally, one of the first considerations will be the melting temperature of the solder.

Many applications need a low-temperature solder that will reflow below 180C.  For example, LED attach, optics assembly, and MEMS mounting all have low temperature solder requirements.  There are two metals, in particular, that help fulfill this need.  One is indium and the other is bismuth.

There are five common solder alloys that are well suited for your low-temperature, Pb-free requirements.  As a matter of fact, they are so popular we have packaged them together in a kit (in the solder paste version) for you to evaluate.

Our Low Temperature Pb-Free Solder Paste Research Kit allows you to evaluate any two alloys in a side-by-side comparison to determine the optimum paste for your application. The five alloys that you can choose from in our Low Temperature Pb-Free Solder Paste Kit are:

• Indalloy 1E (52In 48Sn) Eutectic at 118C
• Indalloy 281 (58Bi 42Sn) Eutectic at 138C
• Indalloy 282 (57Bi 42Sn 1Ag)  140C/139C
• Indalloy 290 (97In 3Ag) Eutectic at 143C
• Indalloy 4 (99.99In) Melting Point of 157C

In this kit, each alloy is matched with the proper flux vehicle so you can comparatively test multiple alloys to see which is the best option for your application. 

The kit is available on line and our Application Engineers are available to help steer you in the right direction as to which two alloys to choose.

Over the years, solder alloy choices have been pretty stable.  In the last century, SN63 and SN62 could be found at any company making any kind of electronic device, and both alloys were the backbone of every company making solders.

But, when lead was identified as causing health issues, it was legislated out of everything from paint to gasoline to electronics, including solders.  In 2003, RoHS (Restriction of Hazardous Substances) was passed in Europe to restrict the use of lead (as well as mercury, cadmium, hexavalent chromium, and polybrominated diphenyl ethers: PBDE) in electronics and electronic equipment.

The electronics industry is now focused on SAC alloys (so named because they contain Sn, Ag, and Cu).  But, there is also SnAg, which was used in the lead era when a higher melting point was required.  The addition of the copper (in SAC) offers the benefit of improving wetting and potentially reducing the silver content from a non-copper alloy like 96.5Sn 3.5Ag. 

But, there are many applications where SnAg works well. Changing from it would require customer and/or government approval, and that involves a lot of extra money and time. This lead-free alloy works well in the assembly of a variety of medical devices that use non-traditional metallizations and fluxes.  The Cu addition (in a SAC alloy) probably would not improve the results enough to warrant the cost of requalifying an existing medical device through government agencies, so they stay with what works. 

So, if you are using 96.5Sn 3.5Ag (or 96Sn 4Ag), don't be afraid to stick with it.  Indium Corporation offers both of these solder alloys (and over 250 other alloys) in a variety of forms: preforms, wire, paste, and ribbon.   And, if you want to look at the SAC alloy family to see if it works better in your application, we will help you with that, too.  Just contact our Application Engineering Staff for help.

Carol

Printed circuit boards containing both surface mounted and through-hole components are common, and are often referred to as "mixed technology" boards.  In mixed technology assembly, solder paste is used to attach the components to the surfaces and wave soldering attaches the components that are inserted through holes in the board.  For low volume production, hand soldering is often utilized - for the attachment of through-hole components.  Both of these methods require additional steps after the original reflow of the solder paste.

To increase your profits (saving you time and money while improving your quality and productivity) InTEGRATED PREFORMS^® have found a place in mixed technology assembly.  InTEGRATED PREFORMS^® are interconnected solder washers, designed to fit the pin pattern of a through-hole component.  These arrayed solder washers are sized to deliver the precise solder volume required to fill the holes and to produce excellent solder fillets at each joint. 

In some cases, to add even more solder, solder paste is deposited over the holes and the InTEGRATED PREFORM^® is placed into the paste. The component is then inserted through the solder preform, the solder paste, and the hole. 

In other applications, TacFlux® (that is compatible with the solder paste's flux vehicle) is applied to the preform before it is placed on the component's pins, or is placed directly on the board, and the component is inserted as described above.  Whichever method is used, only one reflow step and only one cleaning step are required.

In traditional wave soldering, components with long pins are a special challenge because they are very difficult to attach without getting alloy on the pins during wave or hand soldering.  InTEGRATED PREFORMS^® can be applied to the top or bottom side of the board and are reflowed along with the components held down with solder paste.

InTEGRATED PREFORMS^®  are designed and built to address the unique characteristics of each specific application.  To build your InTEGRATED PREFORMS® we require the following information, so the solder volume and washer spacing are correct for your specific pin configuration:

• Hole size
• Pin size
• Board thickness
• Center to center spacing of the pins (within the row, and row to row)
• Solder Alloy
• Is the preform going to be used to add to the volume of solder from the paste?

Separate (individual) solder washers can also be used in place of connected InTEGRATED PREFORMS^®.  They can be designed to deliver the same consistent volume of solder required for each joint.   Care must be taken, however, to place only one preform on a pin, and not miss any.  This is what makes InTEGRATED PREFORMS^® desirable.  The solder washer array is designed and manufactured to fit the pin configuration so only one washer goes on a pin.  If extra solder volume is required, InTEGRATED PREFORMS^® can be easily stacked.

With today's drive to optimize profits, InTEGRATED PREFORMS^® present an excellent opportunity.  The biggest advantage of InTEGRATED PREFORMS^® is the fact that quality can be improved while costs are reduced.  If you are looking for any easy way to cut costs, increase production, improve quality, improve customer satisfaction, and, ultimately, increase your profits, talk to me about InTEGRATED PREFORMS^®.

Paul Socha psocha@indium.com

BONUS: Read our white papers regarding InTEGRATED PREFORMS^® .

One of the biggest misconceptions about NanoFoil^® is that it is a form of solder. While it may contain a solder coating if specified (usually tin), it is really a heat source. A NanoBond^® requires solder, whether it comes from a plating on the joining surfaces, additional solder preforms, or on the NanoFoil^® itself.

Surface Coating

There are many ways to deposit solderable coatings onto parts that will be NanoBonded. Sputtering, thermal evaporation, thermal spray, plating, and HASL (hot air solder leveling) are just a few of the options. Coating the parts that will later be bonded tends to make assembly a bit easier.

Solder Preforms

If the parts have a gold or silver surface finish already, a thin solder preform is a very simple way to apply solder in the assembly. Preforms are sold as custom-shaped foil for your application.

NanoFoil^® Coating

Although Sn is the most popular solder coating for NanoFoil^®, it has been custom plated for individual customer applications with indium, traditional solder alloys, and even Au/Sn.

By the way, make sure there is solder on both sides of the NanoFoil^®. I almost overlooked this very point today while I was bonding a set of industrial batteries. There was solder on the battery terminal, and I was about to use bare NanoFoil^® to bond it to a gold plated board. Luckily we had some tin plated NanoFoil^® that I used instead – to ensure there was sufficient solder on the board side of the interface.

*This post is part of the NanoBond^® Process series

When helping customers with the optimization of their soldering process, the question often comes up;

“What will my solder bond line thickness be when utilizing this material?” 

The amount of volume lost to flux content while utilizing a solder paste, in comparison to a flux-coated preform, is much greater.  Whereas a flux-coated preform only contains about 1-2% flux by weight, a stencil printing solder paste is approximately 10% flux by weight.   This may not sound like much, but when you consider the density of the powdered alloy in the solder paste (7.40 g/cm³ for SAC305) versus the density of the flux (~1 g/cm³), you end up with a material that is almost 50% flux by volume! 

Therefore, if you were to print a 0.5” x 0.25” deposit utilizing a 0.005” thick stencil (0.001in³ of printed solder paste volume), you would only end up with approximately 0.0005in³ of actual metal solder.  In short, your final bond line thickness will be half of the thickness of the solder paste printed.

For help determining your bond line thickness, or for help determining the appropriate solder material for your application, please contact AskUs@indium.com.

It won't be long until we in the northern hemisphere are complaining about the snow and the cold, but right now, it is all about the heat! 

In particular about the heat that is needed to reflow high melting point (HMP) alloys.  These are generally high-Pb alloys that see very high operational temperatures. They are used for applications such as automotive under-hood or down-hole drilling equipment .

If you try and use a flux that is not formulated to withstand higher (greater than 220C) temperatures, your flux will burn off and char and never get a chance to really do its job.

So, the key is to use a flux that is specially formulated to activate at higher temperatures, like our 807HMP used in our flux cored wire.  It is ROL1 but has only 650 PPM of halogens.

You may also want to consider an alloy with a small amount of indium in it (such as Indalloy #164 which is 92.5Pb 5.0In 2.5Ag) since indium is well known for its thermal fatigue resistance.  This alloy works very well with the 807HMP.

Choosing the right alloy and the right flux are key to keeping your cool!

Carol

Individually, indium and gallium each have some pretty interesting characteristics.

Gallium is liquid at 30°C (86°F) and, because it is less toxic than mercury and has a lower vapor pressure at higher temperatures, it is used as a mercury replacement in thermometers and other applications. 

Indium, as I have discussed in previous blogs, has many unique characteristics including high thermal and electrical conductivity, resistance to thermal fatigue and reduced scavenging of gold in soldering.

But, combine the two, add a little tin, and the resulting alloys are liquid at, and below, room temperature (8°C to 25°C) and are very effective in conducting or dissipating heat away from temperature sensitive components. They can also conduct heat and/or electricity between metallic and non-metallic surfaces.

A recent study published by researchers at the McCormick School of Engineering, working with scientists around the world, discusses the use of an indium-gallium based alloy (EGaIn) to make stretchable electronics.  The indium-gallium content overcomes the loss of conductivity that occurs when the material is stretched.  The liquid alloy allows the "electricity to flow consistently even when the material is excessively stretched".

In 2009, researchers at the North Carolina State University used InGa to form antennae that would not break.  Again it is the flexibility and the electrical conductivity of the liquid alloy that make this work.  Michael Dickey and Gianluca Lazzi who headed the research, indicated they "were surprised" that the alloy operated at about 90% efficiency, similar to the efficiency of copper.

So whether on their own or combined, indium and gallium can be the solution to a variety of electronic challenges faced today.  The Possibilities Are Endless!

Carol

Indian electronics manufacturers and solder users. This info is for you.

After many years of discussion and policy making, the Indian Government rolled out its WEEE/RoHS directive, effective 01 May 2012. This directive is known as e-waste (Management and Handling) Rules 2011 thru the vide number S.O No. 1035 (E) by The Government of India, Ministry of Environment & Forests. (for Hindi version click here).

This directive has 6 chapters covering electrical and electronics waste handling, responsibilities, recycling, etc. It also restricts the usage of certain hazardous substances in electrical and electronics equipment. This section is very similar to the European Union’s RoHS directive; but there is a two year time period to achieve this. So the India RoHS will be in force starting 01.May.2014 (this date applicable only to restriction of using hazardous substance mentioned in e-waste rule, 2011).

As with other RoHS directives, the Indian e-waste rules 2011 also come with an exemption list.

This directive compels consumers (including government departments) to strictly follow the ‘e-waste rule’ during their purchase and usage of electrical electronics equipment.

While industry has yet to discuss this rule in particular, the European Union’s WEEE/RoHS has been driving the Indian electronics industry for the last few years - and most of the manufacturers are complying with RoHS. This will have a big impact on local electronics manufacturers and governmental companies. From a lead-free solder alloy perspective, there will be big impact on knowledge transfer, training, and so on for local manufactures.

There are still many questions, like how this will be implemented, who will be responsible, how this will be rolled out to stakeholders, and more.

Indium Corporation would like to know what you think about this. We are happy to help customers and governmental agencies roll out this directive by providing technical information and other knowledge - sharing our support.

Please feel free to contact me with questions.

Liya

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