Solder Quality

Folks,

The impetus for writing the Patty and the Professor series, in 2009,  <posts here>  <hardcopy book here> came from my observations that many assemblers were not very focused on productivity.  Productivity seemed to be an afterthought.  Since then little has changed.  This conclusion seems astounding, since all assemblers are in business to make a profit.

In light of this situation, I have developed 10 questions, valued at 10 points each, to help assemblers assess their profitability potential. If You are a printed circuit board assembler, take this quiz and see how you rate:

1. Although quality may be job 1, our company has a strong focus on productivity. At all levels everyone understands that, when the line is down, we are not making money.
2. We have a practice, understood by all, that if a line is down more than a specified amount of amount time, the line down situation is escalated through the management chain.
3. All of our operators, technicians, and engineers have been trained in procedures to assure the minimum amount of downtime.
4. We measure and graph our line uptime and other productivity metrics.  Everyone knows the approximate value of these metrics.
5. Our component placement machines are time balanced.
6. We use feeder racks and other preparation devices to prepare for the next job while the current job(s) are running.
7. A major consideration in the purchase of our assembly equipment is its effect on productivity, not the equipment’s cost alone.
8. A major consideration in the purchase of our assembly materials, such as solder paste, is its effect on productivity (e.g. poor paste response to pause would be a strong rejection criteria,) not the material’s cost alone.
9. We us productivity and cost metrics, such as non-material assembly per I/O assembled (NMAC/I/O), to track our performance.
10. We understand that sometimes an added expense, such as solder preforms, can actually reduce the total cost and increase productivity and profitability.

Ratings:

• World Class: ≥ 90
• Above Average: 75 - 89
• Average:  55 - 74
• Below Average: < 55

How did you do?  Let me know what you think. We hope to have this online soon.

Cheers,

Dr. Ron

PS:  Here is my golf score in a recent one man scramble. I was hoping to break 60 and it worked out.

I recently had a chance to catch up with a friend and colleague, Jasbir Bath. If you’ve spent time in the electronics assembly industry you have most likely met him, heard of him, or used an industry standard that he has helped create. Jasbir is a founding member of The Solar Engineering & Manufacturing Association,  SEMA. Who better to talk to about a new association than a founding member?

Jim: The Solar Engineering and Manufacturing Association (SEMA) is a relatively new association for engineers in the solar industry. Can you tell me a little about why it was created?

Jasbir: It was created about 2 years ago based on a need by the solar engineering/manufacturing base to address issues in the industry. There are many organizations in the solar industry but none are wholly dedicated to the engineering/manufacturing profession. SEMA was formed to address this need. We are working to address a number of gaps in the industry highlighted by the SEMA membership which include Education, Training, Standards, Reliability, Cost Reduction and Technology Gaps.

SEMA is a group of engineers, manufacturers and related professionals in the solar manufacturing and related disciplines who volunteer to conduct activities in the organization. The projects/programs we work on are driven by the active involvement of the membership.

Further details on SEMA and what we do can be found on the SEMA website at www.solar-ema.org

Our membership costs are low as we are not an organization looking to make a profit but to encourage participation and work to advance the solar industry as well as advancing education, training and collaboration within the solar manufacturing industries.

Jim: I heard there’s a new solar conference coming up? Can you tell me what makes this one different than all the other solar conferences we go to throughout the year?

Jasbir:  SEMA is collaborating with SMTA (Surface Mount Technology Association) to develop a conference meant for engineers and managers in the field to look at the areas of concern in the industry and develop ways to address them. We don’t see a similar conference to this which covers such a broad range of subjects which is specifically focused to address the needs of the industry. The program will consist of presentations and discussion covering the reliability testing of PV Modules covering gaps and where future work needs to be done. It will highlight various reliability programs being done in the industry with an assessment of current and evolving standards in manufacturing and reliability.

We are pleased to have a great line up of speakers and presentations. SEMA will present its reliability report assessing the reliability of PV modules at the conference. We will also have speakers from UL, IPC and NREL to discuss international solar standards together with a discussion of the work of the PV QA Task Force forum from leaders in that Task Force group. Areas covered will include temperature, humidity, voltage, mechanical and UV testing of PV modules and diode testing.

We will also have presentations on the reliability of microinverters/inverters and future trends from organizations including Sandia. PV Manufacturing Issues will be discussed by companies including Flextronics. The Global Solar Outlook will be reviewed by companies including Navigant, Custer Consulting and Prismark. Finally we will review general PV Module hazardous issues such as Electrical and Fire Concerns and well as Module Warranty/ Traceability Issues.

In addition we have industry leading training courses at the event on PV Module Manufacturing and Troubleshooting and PV Standards in addition to exhibitions.

The SEMA/SMTA Conference, Training Courses and Exhibition are from March 21^st to 23^rd at the Fairmont Hotel in San Jose. Further details on the program and sign up can be found at http://www.smta.org/solar/

Jim: One more question for you Jasbir. I know from working with you in different associations, that you are personally invested and involved in the future of module assembly. What attracted you to this field, and what keeps you interested in it?

Jasbir: I have been involved previously in the electronics manufacturing industry during the transition from tin-lead to lead-free soldering due to environmental legislation requirements. This was a challenge being involved in both from a technical and logistics perspective, but it was also fun as you saw the rewards of your efforts when the transition occurred successfully.

The solar/PV industry has challenges in addressing how to produce good quality and reliable products at lower cost, and it gives me the opportunity to try to make a positive contribution in an evolving expanding industry.

Jasbir and I look forward to seeing you in San Jose!

~Jim

Two categories of solder are available to choose from when the in-service environment for a device reaches above 125°C either in continuous operation or thermal cycling accelerated life testing. These categories are those comprised primarily of lead, and those of gold. From the electronics industry’s drive to eliminate lead, many manufacturers who have traditionally used lead solders are treading cautiously, looking now at the gold solders, primarily at Indalloy 182 (80Au20Sn).

The most common concern regarding this switch relates to the strength of AuSn, which is much higher than the lead solders. The degree that this should be of concern however, should be realized within the scope of the application.

For instance, review this case scenario:

Indalloy 159 (90Pb10Sn) was used in a device for years to adhere high temperature sensors to a calibration probe that is slowly cycled in operation from 350K (~75°C) to 500K (~225°C). The solder joins a nickel and gold plated Kovar™, or platinum or platinum coated, nickel lead to a tinned copper lead. The solder joint is not placed under tension or shocked.

Considering the high temperature solder options in this scenario, the AuSn would be mechanically preferred.

Why?

Well, tin-bearing soft solders will leach gold from gold metallizations during soldering, creating a brittle Au-Sn intermetallic layer within the solder joint. The more gold available, the more consumed, and the greater the thickness of the resultant intermetallic layer. The brittle nature of this layer, situated intimately next to the relatively soft PbSn solder layer, creates differential stresses that promote crack propagation upon thermal cycling.

AuSn was not considered previously because the engineers were familiar with its hardness and, given the cracking failure described using a softer solder, they did not anticipate improvement. It was a pleasant surprise to them to find that switching to a lead-free solder would not sacrifice the quality of their device. AuSn is a brittle alloy but, unlike the description above, no differential stresses are involved. 

Note: Eutectic gold solders have been used for many years to solder nickel plated Kovar™ lids to high reliability ceramic packages and have a good history of fatigue performance.

Folks,

I have often pointed out that SAC solder's poor wetting is both a curse and Godsend.  It is a curse when trying to fill a through-hole in wave soldering, and a Godsend when assembling close lead spacings as shown in the image (below). Indium Corporation colleague and friend, Mike Fenner (image below), pointed out that, when I say that, "SAC solder doesn't wet well", I should be saying, "it doesn't spread well". His explanation follows:

SAC is different from SN63, and I think it is helpful to explain the difference by making a subtle differentiation between wetting and spreading.

The way that solders spread and wet to a surface is a balance of competing forces. We have surface tension acting to make the molten solder shrink into a ball, and wetting forces trying to make it spread across the surface. Wetting is also the action of the solder dissolving into the surface to form an intermetallic. This intermetallic is essence of the solder joint. The balance changes with different alloys, surfaces, and processes.

Most people are very familiar with the way that tin lead solders behave - and that governs their expectations. The different balance in SAC means the solder tends to spread less for the same wetting and, therefore, can give the impression of a lower quality joint. This lack of spread is usually expressed as 'poor wetting'.

I would explain this by saying the “active ingredient” in both solder families is tin. SAC alloys have a ~50% higher concentration of tin than the Sn63 solder alloy. This gives them a higher surface tension which increases the balling (coalescing) force. At the same time, the less dilute tin, in SAC solders, dissolves into a surface faster. So the final SAC joint can have a well formed intermetallic, but not high spread. These relationships will vary with surface finish and, of course, flux chemistry and process conditions come into play, but that’s for another day. Meanwhile I hope this simplified explanation helps.

Thanks Mike!

Cheers,

Dr Ron

The solder image is courtesy of Vahid Goudarzi of Motorola.

At the time of writing, the price of silver (Ag) was approaching the USD$50/tr.oz. (Troy ounce) level, and threatening to go higher. With 1 Troy ounce being 31.1grams, this makes the cost of pure silver ingot close to USD$1.60/gram.

Image from goldsilveroz.com

Materials costs are therefore a major consideration for anyone using silver in any form. Naturally, we are now seeing a few Power Semiconductor packaging houses evaluating the possibility of moving away from silver-filled epoxies for die-attach. The alternatives they are considering include the adoption of solder paste (or solder in some other form: wire / ribbon / preforms) versus a silver-filled epoxy.

Here are some thoughts on the Power Semiconductor assembly pros and cons, based on using solder paste as an alternative to silver-filled epoxies.

Good news (+)

+   Reduced materials costs
+   Improved pot-life / shelf-life *
+   Improved high temperature thermal-cycling
+   Strong, metallurgical joint formed between leadframe (substrate) / joining material / die
+   Improved thermal conductivity
+   Faster throughput (more units per hour, UPH)**
+   Easy clean-up ***
+   Does not wick onto NiPd surface to cause poor wire bondability

 * Although it is true that solder pastes are stored under refrigerated conditions, they do not require the -40C storage that is typical of silver-filled epoxies. 

 ** The dispense of solder paste is very rapid and can be done using multi-dot dispense heads. It undergoes rapid temperature reflow, versus the slow cure needed for metal-filled epoxies, which can be up to typically 1-3 hours, depending on the volume of silver epoxy.

 *** Because the solder paste flux does not cure like a polymeric material,  tubing and other conduits for the solder paste are easily cleaned out using common solvents, or can be simply purged with flux.


  ==================

Bad news (-)

-   Capital costs #
-   Adoption time / new process learning ##
-   Needs a solderable die surface
-   Voiding increase ####

 # The main cost-drivers here are:

- Reflow: Specialty reflow equipment is required for high temperature solders, such as
Heller or BTU reflow ovens

- Cleaning: If wirebonding is required after the reflow process, standard cleaning equipment and cleaning chemistry (aqueous or solvent-based) will be needed to remove flux residues

- Gas: Forming gas (H2/N2) or simple nitrogen may be needed to assist reflow.

Note that increasingly, for clip-bonding (non-wirebonding) applications using the new ultralow residue solder paste Indium9.32, even cleaning may not be needed, as the residue has been found to be compatible with compatible with a number of molding compounds in the industry.

 ## By partnering with a company like Indium Corporation with many years of experience in die-attach soldering, the ramp-up time can be significantly reduced.

 ### A solderable surface is usually a sequence of Ti / Ni / (Ag or Au) plated layers. The thickness of the silver (Ag) or gold (Au) precious metal layer is usually limited to 100nm (0.1microns). Compare this to a standard silver-epoxy bond line thickness (BLT) of 0.5-2mils (12-50microns).

 #### Acceptable voiding of less than 5% of the total die area is fairly easily achieved with good quality substrates and die-finishes.

  ==================

In closing, I am indebted to my friend and colleague Sehar Samiappan (Indium Corporation Area Technical Manager - South East Asia) for his insights.

Contact me to discuss this further.

Cheers!   Andy

我自己是一个电子焊接材料销售人员，虽然是B2B，但是生活中当我评估B2C的销售人员时，也常常想到自己的客户们……最近我们想把花园里的一棵斜树砍了，朋友介绍了他曾经用过的4家公司。于是我逐一联系比较。

第一家：没人接电话，留言了也一直没有回复。---客户服务不及时，比较差，不考虑了。

第二家： 一个老头接了电话，我们约好了时间来看树。老头准时出现在我家门口，整齐的穿着，礼貌亲善的销售，职业的打招呼和握手。看了树，问了我的需求后，他用专业的纸条写下了情况和报价，并详细解释了我对砍树的一些问题：几个人来砍，时间多长，有多复杂等。 此外，他还适当“销售”了一下自己和自己的公司： 经验丰富，口碑好等。最后，老头留下了自己公司的保险和营业执照等信息，就礼貌职业地握手离开了。--- 这一家总体感觉不错；但是我不知道他的价位是否合理，再比比看。

第三家：没人接电话，于是留言了；第二天一个年轻人回复了并来看树了。礼貌职业的握手，但是全身十分肮脏的穿着（或许他刚给别人砍完树吧）。年轻人看了树后，报价了；价格区间和第二家老头的不相上下。但是当我问到砍树的一些细节时，他的回答和老头的回答有比较大的差别（这些差别让我感到他是故意在显得自己的报价已经是相当的实惠了）。后来我说我会考虑的，因为我还在货比三家，年轻人显得有点点急了，说他可以明天就来完工，还问我找了哪几家…..最后他还是职业礼貌地离开了；没有留下报价单或是其他信息。---总体感觉一般；虽然待客户比较职业，但是少了老头那种特别专业和比较从容、真诚做生意的感觉。价格区间既然和老头那家差不多，就应该是这个范围了。

第四家---电话约好了时间，但是一个中年人提早了1个半小时就来敲门了，说他自己在同一时间被安排2个客户，所以只能提早到我这里（但是为什么没有任何提前通知呢？万一我不在家呢？）。没有因为提前的抱歉，没有职业的招呼。他看完树后，表现出很难办的感觉，并开了一个天价。 我说再想想吧，那个中年人居然什么都没有说，头也不回地甩门就走…… --- 看来是没有最差，只有更差啊！

我录用了第二家老头的砍树公司。联想一下自己平时做电子焊接材料(Electronic Solder)销售，代表的不仅仅是个人，更是整个公司在客户面前的形象，我自己做到以下这些基本的要求了吗？

---能否完成这项工作。我联系的这四家公司是朋友曾经用过并推荐的，起码都完成过砍树工作。 如果换成是Indium的产品，那么就是我们产品的质量好坏(Product Quality)，以及产品质量的稳定性(Product Quality Consistence)。这对客户们的产率(Yield Rate)和不良率(Defect Rate) 都有很大的影响。而我作为销售，对自己公司的产品了解吗？有信心吗？这些，都会在和客户交流的过程中潜移默化地表现出来的。

---基本的销售要求 (Basic Sales Requirement): 认真准备，准时，有礼貌，打招呼，整齐的穿着等。

---销售的技巧(Sales Skills): 是否了解客户的真正需求而有针对性的销售；是否有销售的工具协助；是否会“过犹不及”或是没有给客户全面的有用的信息等。(Goal Oriented---Begin With The End!)

---客户服务和支持(Customer Service & Support): 及时准确地给客户信息回馈和支持。

---其他：价格，客户关系和客户关系的维系（特别是对于B2B的客户来说），公司的形象、口碑和声誉等等……  

时常对照反省，自勉之。

Cheers!

Pic:Google Image

Jon major recently joined the Indium Corporation as a Product Manager for Solar back-end assembly products. I greeted him with this impromptu interview.

Jim: First of all Jon, welcome. It’s great to have you as a new addition to the team!

Jon: Thank you Jim – it’s an exciting time to be at Indium Corporation and a fantastic time to be a part of the growing solar industry. I am extremely enthusiastic about my new position and am looking forward to making a positive contribution to the solar industry.

Jim: I noticed it didn’t take you long to get up to speed. Your time in Silicon Valley must have helped.

Jon: Coming from the electronics industry with a focus on product development, new product introduction, manufacturing, and external partner management, I am excited that my past experiences can contribute both to the industry and to Indium Corporation. After joining Indium only a few weeks ago, not only am I getting used to Upstate NY weather, but I have been immersing myself in solar with the goal of gaining a comprehensive understanding of:

•       Both rigid and thin-film technologies

•       Technology trends

•       Global and regional markets (EU, China, US, North America)

•       Solar supply chain (Silicon, wafers, cells, module, equipment, inverters, integrators)

•       Equipment manufacturers, contract manufacturers, and how we can collaborate with them to move the industry forward

•       Our products and pricing

•       Our current and future customers

•       Our short and long term opportunities

•       Our competition

•       Our roadmap

•       Our strengths, weaknesses, and threats

•       Our manufacturing capabilities and our QA process

•       Our sales channels, value proposition, key differentiators

•       All Indium processes

Jim: I know you've got solar products on your mind. Let our readers know a little bit more about your role here at Indium?

Jon: As a Solar Backend Product Manager I will focus (officially) on the business development and growth of Indium’s Solar Back End product offerings.  Now that sounds great but what does it actually mean? I could cut and paste my official job description but I prefer to explain it in my own words. As I think about the first part of that statement, “business development and growth…”, I see my role as:

–      Know the market, the customers, the product, and the competition

–      Develop relationships with the Indium team, reps, partners, equipment manufacturers, and, of course, customers

–      Write valuable data sheets, publications, and sales literature

–      Listen to our customers' needs and provide solutions

–      Manage schedules and orders with minimal surprises

–      Build cross-functional collaboration (sales, distribution, marketing, engineering, R&D, QA, production, management)

–      Never let down partners or customers

–      Support all functions of the organization, both internal and external

–      Deliver above & beyond commitments

–      Make great bets – on technology, customers, and opportunities

–      Understand the product life-cycle

–      Ship high quality, consistent product

The second part of that statement “..of Indium’s Solar Back End product offerings” is fairly straightforward. Of course this means I will focus on Indium’s current back end products (tabbing ribbon, bus ribbon, metallization paste (or as I prefer to call it – “grid ink”), flux and flux cored wire). With a product development background, this also means I have an opportunity to work with customers, partners, and R&D to develop and bring new products to market that will advance the module assembly industry – very exciting for me personally.

Ultimately, I think of my role as both building awareness of Indium’s products and superior technical support available to our customers as well as helping to shape our growing industry.

Jim: Okay Jon, you’ve had a while to settle in and get familiar with our Solar Team’s past and present – what are you planning for the future of module assembly?

Jon: Regarding the future of module assembly it’s a bit early to know for sure but I am excited about our low-temperature bismuth-containing alloys. These low temperature, lead-free, bismuth-containing alloys reduce the soldering process temperatures, thus reducing thermal stresses. I’m also working with the Indium production team to further reduce our tabbing and bus ribbon yield strength. A lower yield strength will reduce mechanical stress on cells during the assembly process. This is crucial to minimizing the possibility of microcracks and cell breakage during the solar module assembly process.

In closing, having lived in California for the last 10 years, I am not 100% familiar with our Upstate New York climate, and especially not all the snow shoveling. I see in my future a solar powered driveway heater!

Jon can be reached at jmajor@indium.com

Although most scientists today feel that alchemy has been widely discredited, and I have been taught to agree, the idea of it is whimsical and exhilarating.  Of course, I don’t have a hope of changing the makeup of bismuth or transforming it into another metal, but in a modern way, it’s very interesting how bismuth can be used to change the properties of other metals significantly - through alloying. In my last post on bismuth, I outlined its physical properties, some of which I find rather unusual. The main reason I originally researched bismuth was because of its viability for use as a low temperature Pb-free alloy.

BACKGROUND:
I'm not an alchemist like Newton, I can't transmute bismuth to gold like Seaborg, but I can use bismuth and metallurgy to transform an alloy.

I just read a fascinating article about Sir Isaac Newton titled, “Moonlighting as a Conjurer of Chemicals”. Newton is widely regarded as one of the most important people in the history of science, and he was very devoted to his work. The revelation in this article about the depth of his interest in alchemy left me somewhat awestruck. In my previous reading about Newton, I remember perhaps a mention of his interest in alchemy, but I guess I figured it was because science and alchemy, at that time, were fairly closely related. As scholars are starting to translate more of his diaries, they are discovering that his passion was alchemy and he saw it as the path to complete control over the natural world.  

I suppose if it was still socially acceptable to be an alchemist that is what I would have wanted to be; it just never seemed to be a viable option. What I have chosen to do now kind of makes sense considering chemistry/metallurgy is about as close as you can get nowadays. 

Reading this article reminded me of some interesting information I had come across while researching bismuth a couple months ago; namely that, although bismuth wasn’t one of the seven central metals in alchemy, it has an "alchemical" symbol (#52 in the image to the left) and was frequently used, although it’s not known for what purpose. I also came across this bit of information:

“In 1980, a scientist named Glenn T. Seaborg was able to transmute a minute quantity of bismuth into gold at the Lawrence Berkeley Laboratory, via nuclear collisions.” 

Seaborg is a fascinating scientist in his own right and discussion about him could fill quite a number of blog posts. Is it possible that alchemists underestimated bismuth and should have focused more on turning it into gold?

BACK TO MODERN TECHNOLOGY:
The eutectic alloy of 58Bi/42Sn has been used since the Pb-free transition as a low temperature (138°C liquidus) option for soldering products used at ambient temperatures - such as consumer electronics.  Note the low melting temperature of this alloy, despite the individual melting temperatures of bismuth and tin, 271°C and 232°C, respectively. Although bismuth is typically known to be quite brittle, this alloy has been shown to perform similarly to the SnPb eutectic solder (in response to a comment on my last post, for further data-based information, please feel free to contact me directly). In cases where more ductility is desirable, 1% silver can be added, further improving thermal shock and fatigue resistance. Perhaps the similarity in performance makes sense because of bismuth’s proximity (right next to) lead on the periodic table, although they differ in several other qualities such as toxicity.

The more I learn about bismuth, the more interested I become. Now if only I could find some in-depth alchemical information about it from Sir Isaac Newton.

I was reading a blog post (click here to read it) authored by the owner of Taylor Guitars, and I started relating it to how I feel about solder. For those of you that don’t know, Taylor guitars are beautifully crafted instruments, not the kind of “dime-a-dozen” toys that you find at garage sales or music sections of department stores – they are the real-deal. Last year I happened upon a tour

of the Taylor Guitar facility in El Cajon, CA after a trade show and I was blown away by how much care goes into each of the guitars that are produced there. Taylor’s core customers realize how special the product is, and they will settle for nothing less.

So, how the heck does this relate to solder? As a tech guy I get calls from people who want Indium Corporation material - they don’t know which product they need yet, but they want to use our products if at all possible. It might be because they feel good about the quality, packaging, technical support, supporting documentation, or just because they feel like they have a connection with us. To me, that’s awesome! I admit - I am the same way with some things I purchase. Feel free to give us a call, even if it’s just to chat!

The following is an example of how a simple procedure like cleaning a soldering iron tip can make a world of difference in the quality of a solder joint. Eric Bastow responded to a customer after doing some testing in the lab – and confirming that a clean iron tip contributes to a clean solder joint:

“As I mentioned in our conversation, I did not think that a flux coated preform would fare any worse than a cored wire in a hand soldering application where charring is concerned. Rosin is rosin is rosin, regardless of whether it is within a cored wire or coating a solder preform. I did a quick experiment to see what would happen.

Using a Weller WS80 soldering station, set to an abusively high temperature of 850F/455C, I soldered some .250” square x .005” thick Sn63 preforms (folded-up as small as I could do by hand), flux coated with 1% NC9, to a nickel metallized FR4 test coupon. The contact time of the iron to the solder was ~5 seconds. The results look pretty good. The charred flux that you do see is flux that burnt to the iron and was transferred to the solder from the previous preform. I would anticipate this sort of appearance with a flux cored wire, as well, used under these conditions. I believe that with frequent cleaning of the tip, the amount of unsightly flux residue with be minimal, especially if a more appropriate iron temperature were used.” -Eric

The bottom image is what happens when you don't clean a soldering iron tip.

Soldering Basics

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.

Folks,

After a bit of a break, the adventures of Patty, Rob, and The Professor continue:

The plane droned on as it made its slow march from Detroit to Tokyo.   Patty looked down at Rob as he slumbered peacefully. She caught a glimpse of The Professor,  he looked at both of them from across the aisle with a satisfied smile. The proud mentor looking at his mentees. 

This was the first time in a while when Patty didn’t feel totally stressed. She had resisted going to China only three weeks before her wedding, but senior management insisted. She would arrive home only 5 days before the big day. She and Rob had their first real fight, she got angry with him because he wasn’t appreciating the pressure that she felt. However, with one long weekend with their moms, she was able to get most of the tasks done and finally felt relaxed that the wedding plans were in good shape.

She had to chuckle at Rob. He was all nervous being with The Professor by himself. The plans that they had made had Rob and The Professor focusing on productivity improvements at ACME’s new acquired plants in China. While they were working on these tasks, Patty would handle some process materials related issues. 

The rest on the trip went smoothly and after a night’s rest they were off to the first of ACME’s new factories. This one was located in Shenzhen. Our trio was ushered in to see the site GM, Peng Zhou, a native of the area. He addressed them in quite good English. When Rob and Patty answered in better Mandarin, he seemed shocked. When The Professor answered him in flawless Cantonese he and Patty and Rob were stunned. 

"要不咱们都讲中文吧，既然咱们中文都不错。" said Rob. ("Perhaps we should all speak in Mandarin, since we speak it well." For our non Mandarin speakers)

Rob and The Professor went off to audit a few assembly lines, while Peng accompanied Patty to visit an assembly line that was having a quality problem.

(Dialogue translated from Mandarin)

“I’m very impressed with how well you all speak Mandarin,” said Peng. “Where did you learn it?” he continued.

“Thank you,” replied Patty. "Both Rob and I studied Mandarin in college and we did an internship in China,” she went on.

“ Very impressive,” Peng commented. “But I have to tell you, I’ve never heard any American speak Cantonese at all, let alone as well as The Professor does. It’s like he was born here,” he went on.

“He never ceases to amaze me,” Patty responded.

Patty and Peng finally arrived at the assembly line. Patty was introduced to the line engineer, Elvis Chang. She chuckled inside, this was the third Asian person her age she had met that had chosen “Elvis” as an English nickname. Elvis was relieved that Patty spoke Mandarin. They went to a stereo microscope and looked at some of the assembled PCBs that had quality issues. Patty was quick to pick out the problem:  graping. She looked at the stencil and the pad sizes on the PCB. She performed a few calculations and appeared satisfied that she had the answer. Patty suggested that, if Elvis would like, she could give a brief presentation on what she thought the problem was.

“Patty, that’s a great idea, but it might be best to wait until after lunch,” Elvis suggested.

Elvis, Patty, and a few other young engineers went together for lunch. They seemed to be fascinated with Patty, especially her ability to speak Mandarin. They all spoke some English and were all studying it as they recognized that their ability to be promoted to a senior level required fluency in English. One of them pointed out that she had read that about 250 million Chinese people are studying English, while only 20,000 Americans are studying Chinese.

Patty enjoyed Chinese food and was happy to find Sea Cucumber on the menu. One of her friends said it was the only Chinese food he couldn’t eat. She tried it and liked it.

After lunch, Patty asked for a few hours to prepare her presentation. Her main points are summarized below:

1.        The aperture size for the pads that experience graping is 8 mils in diameter for the 4 mil thick stencil.

2.       The resulting area ratio (D/4t, D= diameter, t = stencil thickness) for this aperture is 0.50, less than the recommended 0.66.

3.       The very small solder paste deposit doesn’t not have enough flux to avoid oxidation of the solder particles in reflow. The resulting defect looks like a bunch of grapes so it is called graping.

4.       Likely solutions:

a.       Use a square aperture. An 8 mil square aperture provides 27.3% more volume, and it has better transfer efficiency. (Transfer efficiency is the volume of the solder paste deposit divided by the volume of the aperture times 100.) The result would be > 30% more solder paste. The more solder paste, the less likely to experience graping

b.      The solder paste they were using was not best of breed re: graping resistance. She recommended another one, which she knew performed well in all respects - and minimized graping. This solder paste’s flux was robust and designed to minimize defects like graping.

Her presentation was received very well. Fortunately some of this excellent solder paste she recommended was being used for another job in the plant. So with approval from Peng, the team switched to this paste.

After the meeting, Patty thought about how much one of the technical engineers from one of her favorite solder paste suppliers had helped her to understand graping and how to minimize it. His name is Ed Briggs and she had just attended SMTA Toronto where Ed gave a paper on graping. Much of the information in her presentation came from Ed’s paper. She had also learned from one of his blog posts on graping.

Epilogue: Three weeks later, the graping had disappeared from Elvis’s assembly line. They didn’t even need to adopt a stencil with square apertures, the solder paste change, itself, was enough.

Cheers,

Dr. Ron

Folks,

 Bob Landman’s comments to my tin whisker posts appear below. Friendly dialogue such as this helps us to all learn more and is appreciated. Thank you Bob, keep me honest!

However, Bob’s comments do not change my position, which is:

1.     Tin whiskers exist and can cause failures

2.     However, there is yet no data that suggest that there are numerous tin whisker failures, or that a significant reliability risk exists due to tin whiskers in RoHS-compliant products.  NASA's TW website notes only 26 fails.

3.     Although not completely understood, tin whiskers can be created in the lab, and mitigation (not elimination) and reliability test techniques exist and have been demonstrated.

4.    With well over $1 trillion in RoHS-compliant electronics manufactured since the early 2000s, there have been no significant reliability issues as compared to tin-lead solder.

5.     Long term lead-free reliability (> 5yrs) has not been demonstrated. Hence, mission critical products should not use lead-free electronics at this time.

6.     Tin-lead solder does not assure defect-free electronics with perfect reliability.

As I type this post, I am surrounded by more than 20 RoHS-compliant products, some dating from 2005. Outside my office, at Dartmouth’s Thayer School of Engineering, is our computer center. The thousands of RoHS-compliant products that the computer center buys each year (they get me my laptop, etc)  are almost all RoHS-compliant. No unusual reliability issues have been noted.

Bob mentions that CALCE reports that 31% of laptops fail in 3 years. This number actually seems low to me. Upon reading the paper, one finds that over 10% of the 31% is due to accidents. 
A study of 100,000 hard drives at Google suggests that hard drive fails are in the 5% range per year, which may account for much of the 20% of fails in 3 years. But what solid conclusion can be made from these data? Nothing, unless failure analysis is performed.

The sky is not falling. Lead-free has process-ability and reliability challenges, such as graping, head-in-pillow, voiding, etc. With data-driven process optimization at all steps in the manufacturing of the ICs, components and assemblies, good lead-free yield and reliability can be achieved.

Lead-free is here to stay. It is up to us to perform the experiments and develop the techniques to assure that RoHS compliant products have acceptable reliability.

Bob's comments follow:

My source for the dead vehicles that arrive at car dealers having whisker problems, comes from my former professor of physics, Dr. Henning Leidecker at NASA Goddard Space Flight Center in Greenbelt MD.   Dr. Leidecker said that in the last four years his office has been contacted by seven major suppliers of automotive electronics inquiring about failures in their products caused by tin whiskers. He said his office has contacted Toyota offering to help analyze its acceleration problem, but hasn't heard back. For full context, read the rest of the article [http://wtop.com/?nid=108&sid=1898265].

Ron Lasky confirms that parts plated in pure tin will grow tin whiskers "with a certain amount of aging". According to NASA, whiskers can grow in hours, days, weeks, months or years. It depends on at least six factors; the quality of the tin plating, the residual stress in the coating, was the coating annealed or not, grain uniformity, temperature, humidity, and unknown other factors we don’t yet understand which is what makes it so difficult to stop whiskers from growing and is why there are so many papers published on the subject (as you can clearly see at John Barnes website) yet we still do not understand why or how they grow.

So yes, is entirely within the realm of possibility that "new" products have failed due to tin whiskers or perhaps dendritic growth.

NASA cannot tell us who the manufacturers are who reported these events due to confidentiality agreements.  Dr. Leidecker says they get these calls from other industries as well and most request a non-disclosure agreement.  NASA feels it’s better to get some information rather than none, don't you agree?

Last  week at CALCE at UMd. it was reported that 31% of all laptops fail within 3 years. This is the link to the report http://www.squaretrade.com/pages/laptop-reliability-1109/  No information is given as to what has failed. Is it due to whiskers?  We do not know.

What we do know is that the laws of physics have not been repealed.  Tin will most certainly grow whiskers so using leadfree solder and tin plated components has to result in tin whiskers growing.

NASA continues to log failures.  NASA Goddard is now studying the Toyota incidents for NHTSA.  Again, a non-disclosure statement has been signed so they cannot comment on the study at this time.

Dr. David Gilbert of Southern Indiana University has demonstrated that a low resistance or shorted input between the wires from the pedal electronics to the electronics control module will cause Toyotas to open their throttles full.  Perhaps the problem is due to leadfree manufacturing (which Toyota admits it began in 2002-3)?  Perhaps it is software?  We don't yet know but we can be reasonably certain that not all the accidents are caused by the owners of the vehicles.  You can see pictures of the Toyota parts at my website [www.hlinstruments.com//RoHS_articles/Toyota/]   The pedal has a pc board layout that I would have been comfortable with.  In particular, the SOIC part that converts the signals from the Hall effect sensors (that sense pedal position) into 1-5Vdc signals sent to the electronic control module is very close to the edge of the board.  The board has serrated edges which indicates it was snapped out of a large panel of these boards after the parts were soldered to it.  It's possible a trace or lead has fractured or one of the capacitors or resistors.  We know that leadfree solder is more brittle than tin-lead. Perhaps a few boards are marginal and over time a lead opens or becomes intermittent?

The EU was warned that tin whiskers and brittle joints would result if lead was banned from electronic assemblies but went ahead and banned lead from tin-lead solder and platings on parts. They acknowledged the possibility of reduced reliability under intense pressure from hi reliability industries and did exempt some products (military, aerospace, etc...).  What difference did it make since the majority of component manufacturers refused to continue to offer tin-lead plated leads?  That is why NASA replates it's components with tin-lead at Corfin Industries and uses only tin-lead solder.


Bob Landman

http://www.hlinstruments.com//RoHS_articles/Toyota/Toyota%20Dr%20Gilbert%20Preliminary_Report022110.pdf

Andy Mackie: What role does gold play in protecting surfaces in SMT and semiconductor assembly processes?

Lenora Toscano: Gold does not form an oxide; it protects the nickel from oxidation or passivation. A clean nickel surface has very high solderability for most solder types, but its oxide is very difficult to remove with standard flux types. Also, gold dissolves almost instantaneously into most solders during assembly, thus promoting superior wettability.

Andy Mackie: What standards exist on the thickness of gold for different electronics and semiconductor assembly applications?

Lenora Toscano: The main application of ENIG (electroless nickel/immersion gold) coating is in chip-on-board (COB) technology, the typical thickness of the immersion gold layer on the HDI substrate being 3-5 micro-inches.

Edge connectors typically require the use of hard gold. Acid gold deposits are used for compliance with MIL-STD-275, which states that gold shall be in accordance with MIL-G-45204, Type II, Class 1. The thickness shall be 50-100 micro-inches, typical thickness is 30-50 micro-inches on 150micro-inches nickel.

On the other hand, for solderable surfaces, typical thickness is 5-15 micro-inches on 150micro-inches nickel.

For wire bonding, in general, gold plating of a minimum of 30 micro-inches on 200 micro-inches nickel works well. Soft gold is generally preferred. Soft gold processes are also used for boards designed for semiconductor chip (die) attachment. These qualities comply with Type I and III of MIL-G-45204.

Andy Mackie:  What are the differences between gold layers deposited by immersion gold and electroplated gold processes?

Lenora Toscano: There are five main differences:

1. The coating thickness is different. Immersion gold is a displacement reaction, gold displaces the nickel on the surface, and is self-limiting as the nickel surface is coated with the immersion gold. Common baths cannot produce thicknesses of much more than 10 micro-inches, while with electroplated gold the thickness depends on current and time. The higher current or longer the plating time the thicker the gold coating.
2. The structure of the gold deposit layers is different. Electroplated gold is denser that the naturally porous immersion deposit.
3. The hardness is usually different. Electroplated gold often has other metals introduced into the plating that make the deposit harder.
4. Porosity is different. Immersion deposits have more porosity that electroplated deposits; it is the nature of the plating system.
5. Deposition composition (purity) varies with additives in the bath. Immersion gold baths contain gold as the only plated metal, while electroplating systems may introduce small amounts of other metals.

Andy Mackie: How thick does gold have to be to fully protect the underlying surface, and what are the trade-offs as customers attempt to reduce their gold costs?

Lenora Toscano: Per IPC-4552 ENIG specification, 1.97 micro-inches is the recommended minimum at +/-4 sigma from the mean, with 3 – 5 micro-inches being typical.

The immersion gold deposit is porous by definition. It does offer very good protection to the underlying nickel, but over time the porosity of the deposit results in the passivation of the nickel surface and the wetting forces will be reduced. Of course, this process should take years to occur, but if the gold coating is too thin (below the minimum requirement), it will occur sooner and affect the solderability. 

Andy Mackie: What advantage does gold have over silver or other metals?

Lenora Toscano: Again, gold has good tarnish resistance and solderability after storage because it does not form an oxide or hydroxides, so it is unaffected by temperature and storage conditions that might reduce the shelf-life of the other finishes. It meets requirements for lead-free (Pb-free) assembly while offering a coplanar surface that is both solderable and aluminum-wire and gold-wire bondable.

Gold has good electrical conductivity, and produces a contact surface with low electrical resistance. Electroplated gold is also an excellent etch resist.

Electroplated silver is not widely used in the printed circuit industry. Under certain conditions or electrical potential and humidity, silver will migrate along the surface of the deposit and through the body of insulation to produce low-resistance leakage paths. Alkaline cyanide baths for silver electroplating are highly toxic.

Immersion silver is susceptible to problems if not correctly stored and even packaged. Packaging materials that contain sulfur or allow exposure to air will result in tarnishing of the surface (sulfide, sulfate, and chloride formation). High levels of surface contamination can detrimentally affect solderability.

Folks,

While at SMTAI a few weeks ago, I ran into Patty. She agreed to sit down for an interview. Here it is.

Dr. Ron (DR): Patty, it’s great to see you here at SMTAI. Congratulations on your promotion and many accomplishments over the past year.

Patty: Thanks. BTW, I really enjoyed your talk, “SMT: The Next Twenty-Five Years.” Was there really a song, when the transistor radio came out, called “Transistor Sister?”

DR: Absolutely! “Transistor Sister,” was a part of my youth. It was sung by Freddy Cannon in 1961.

Patty, a number of folks wrote in saying that they liked my blog postings about you, but they felt that the stories couldn’t possibly be true in a modern electronic assembly company.  Can you enlighten us?

Patty: Yes, I saw those comments. All of the blog postings have been real case studies, if anything they are understated. The Professor claims that ten to fifteen years ago, when profit margins were higher and OEMs did much of their own assembly, assembly optimization was viewed as a science and assembly was orchestrated more like a ballet. Process discipline existed. As assembly left the OEMs and profit margins decreased, there was little money for assembly process optimization analysis. Electronic assembly entered the era of “hockey” management. Much of assembly became disorganized and subject to “the tyranny of the urgent.”

DR: So I gather your point would be that right when we need process science the most, we aren’t investing in it?

Patty: Process science would be nice, but I’m convinced if management just had a sense of urgency about line uptime and productivity it would make a world of difference.

DR: “Hockey Management,” “Tyranny of the Urgent?”

Patty: “Hockey Management” is a term developed by Phil Crosby in his book, “Quality is Free.” He tells us that electronic assembly should be orchestrated like a ballet. Everything is planned ahead, we know where the stencil is for the next job, the parts are on the feeder racks or at least the reels are ready, etc. This is “Ballet Management” (everything organized.) An example of “Hockey Management, “ would be a case where the team has lined up the next job, all set up is complete……management calls and tells the team to run another job…..6 hours is lost. In an assembly line, that is a loss of at least $15-75K of product. Profit lost…never to be found again.

DR: “Tyranny of the Urgent?”

Patty: You are so busy doing what is urgent (i.e. switching the job that lost 6 production hours) that you never do what is important (i.e. setting up a system that minimizes such job switching.) BTW, as you can imagine, I learned all of this stuff from The Professor.

DR: He’s an interesting guy. I know him a little, I’ve seen him a few times when I visited Ivy University. Give us your perspective.

Patty: In addition to being super smart, he is very kind. But, I have to admit that traveling with him is a little stressful.

DR: How so?

Patty: Well, in addition to being smart, he is strongly convinced that it is important to be able to perform calculations in your head. He claims that if Fred (Of the "Saving a House, Losing a Mansion" story, DR), could do this and practiced it, he would have known instinctively that the solder paste that “Saved a House” was “Losing a Mansion.” His first thought would have been to estimate what the minutes of downtime, caused by the cheaper paste, cost.

DR: I’m still not sure I understand why traveling with The Professor stressful?

Patty: Oh, yeah I forgot. He wants to make sure I am an “ace” at doing math in my head. He is always giving me problems to calculate when we travel…..it can be a little stressful when he is disappointed when I don’t know something or can’t perform the calculation.

DR:  Can you give us an example?

Patty: On our last trip he asked me to calculate the amount of times the proven oil reserves of Saudi Arabia would fill Cayuga Lake. He gave me the proven oil reserves of Saudi Arabia as about 300 billion barrels and the dimensions of Cayuga Lake as approximately 50 miles long, 2 miles wide and 200 feet deep. You should have seen the look in his eyes when I told him that I didn’t know that there were 40 gallons in a barrel and one cubic foot of water weighs 62.4 pounds. Knowing this and the fact that a gallon of water is 8 pounds, you can calculate that a cubic foot is about 8 gals, hence a barrel is about 5 cubic feet. He thinks that everyone knows things like this that, of course, they don’t really know.  How many square feet per acre, how many acres in a square mile yada, yada, yada? But he means well.

DR: Well we should probably go back to the conference. Can you close by giving us a summary of the key things to do to improve productivity?

Patty: Sure, in order of importance:

1.       Measure line uptime

a.       Set continuous improvement goals for line uptime

b.      Have a plan to reduce downtime, especially for changeovers and line assists

2.       Use the best performing materials (solder paste, underfill, flux, prefroms, etc.) and supplies (stencils, squeegees, etc)

a.       Remember the lessons in “Saving a House, Losing a Mansion), the best performing materials and supplies are always the cheapest.

3.       Have a “Line Down Management Escalation Plan”

a.       Senior management should be alerted if the line is down for an unplanned reason for more than 30 minutes.

4.       Assure that your lines are time balanced.

There are a few more points we can discuss at another time, but these are likely the most important. Oh, and all of Saudi Arabia’s proven oil reserves would fill Cayuga Lake 2 to 3 times!

I polled some of our field sales force to find out what common questions customers ask them.  You (the reader) probably have similar questions.  We’re always available to ask, but it’s nice to see the Q/A that others have been through.

According to Jeff Anweiler, the North-East US had these questions:
 

Q1) Do you have local service and stock?

A1) In most cases we can make it convenient for the customer to do business with us whether it be through distribution, rep managed stock or another plan. 

Q2) How will you make sure I don’t run out of material?

A2) Once we establish a system we don’t let the customer down. 

Q3) What’s the price?  (and can you do better!)

A3) You get what you pay for [expediting, higher solder quality, tighter tolerances, field support].  That’s where the customer needs to determine if the value we provide (quality and tech) is worth a bit more. 

Here are some questions that our South-East US customers had:

Q4) How long will the solder paste last on my stencil?

A4) Solder paste is designed to be used for at least one 8 hour shift (some are specified for at least 12 hours).  Of course, there are customers out there who go well beyond that, but only after evaluating their process.

Q5) We use a ramp to spike profile and I don’t want to change that. Can your paste operate with my profile?

A5) Assuming the alloy is the same in the new paste, yes – although it may be optimized further if you can adjust the profile. 

If you have questions you'd like answered on the Indium Corporation blog, send them to jhisert@indium.com and mention this post. 

          These pictures were sent to me by my friend Drew Jones, after he was done skydiving last week (he is the one wearing black).  Drew always has a way of joking around and providing social commentary at the same time.  The joke is obvious, he is using his Blackberry while he falls to the earth.  I’ve gotta say – you don’t see that everyday.  Supposedly, he responds to his technical work matters even in the most extreme conditions.

         
          If you read into this, he is saying much more than that though – with no words at all.  Our society has become more than ‘connected’, we have become tethered to our little electronic windows into cyberspace.

          Here’s what that has to do with solder:  Our electronics are becoming extensions of our bodies.  Although this might seem silly, I bet there are some people out there who would rather give up an organ than forfeit their smartphone.  So should the assembly of these devices be held to the same solder reliability standards as the medical industry?  It is ultimately the customers who will dictate that, through the evolution of electronics – the theory of ‘natural [gizmo] selection’.  Solder quality is important, solder defects must be reduced, and customers need to be impressed with the durability, functionality, and reliability of a product to truly set a brand apart in today’s electronics marketplace.

Thanks for the pictures Drew.  I thought it was bad when you text while driving…