SOLAR

After the report by Isofoton regarding reliability testing of Bi-based alloys for tabbing ribbon, the world learned that Bi-based alloys could survive the lamination process and function in use. If you haven’t seen it yet, I consider this mandatory reading! Here is the info: B. Lalaguna, P.Sanchez-Friera, I.J. Bennett, L.J. Caballero, J. Alonso, “Evaluation of Bismuth-Based Solder Alloys for Low-Stress Interconnection of Industrial Crystalline Silicon PV Cells", 22^nd EU PVSEC, Milan, 2007Milan, 2007.

We all know the Bi based alloys like 57Bi/42Sn/1Ag and 58Bi/42Sn can be used in a standard module assembly process, but is there an advantage to using Bi/Sn or Bi/Sn/Ag when Sn/Pb and Sn/Pb/Ag alloys are so well known and trusted in the industry?

I’ll give you 3 benefits:

1)    1) Bi/Sn/Ag and Bi/Sn are Pb-Free

2)    2) Bi/Sn/Ag and Bi/Sn are low-temperature alloys, they allow you to lower your tabbing process temperatures

3)    3) When paired with the correct flux and metallization, these Bi alloys form a powerful bond without microcracks (due to the lower process temperature)

Below are results with SunTab^TM ribbon assembled on a Komax X series stringer and tested on a XYZTEC Condor 150-3 bond tester (provided by the respective companies).

You’ll probably notice the lack of y-axis scale – I’m not going to give away all the cool information that easily! Contact me at jhisert@indium.com to learn more.

Yes, here in the central New York (CNY) region, a lot of state-funded activity is beginning to bud, even in the middle of a New York winter. Local academics have been busy. Professor Wolf Yeigh, President of State University of New York Institute of Technology at Utica/Rome (SUNY-IT) recently commented on his team's plans for academic excellence in nanotechnology and semiconductors:

"The projected Computer Chip Commercialization Center (Quad-C) and Center for Advanced Technology (CAT) complex will be on the main campus of SUNYIT. Construction will begin this year, and we envision that the complex will be 120,000 ft² of lab and office spaces complemented by up to 30,000 ft2 of clean room for Quad-C. The academic CAT building will be around 65,000 ft2 of academic and research space. The two buildings will be connected by a rotunda collaboratorium, and the entire complex layout will be similar to what you'd see at the Center for Nanoscale Science and Engineering (CNSE) in Albany, allowing a free flow of academic and industry R&D interaction along with the standard teaching and learning spaces.

Rather than duplicating fundamental research done at CNSE, our facility will emphasize further application and integration of nanotechnology research and development, including testing and evaluation. The academic departments at SUNYIT, working in conjunction with CNSE faculty, will offer courses and programs in nanotechnology applied to semiconductors, materials, informatics, biology and engineering (electrical, computer, civil, mechanical, bio, and materials).

Our major connectivity within the NY school system will be with CNSE. We will also work with community colleges and private institutions in the regions just as CNSE works with community colleges and institutions in the Capital Region and beyond."

The not-for-profit Mohawk Valley (MV) Edge group has been actively promoting the area as suitable for development, with control over 400 acres of land leased from NY State adjacent to the SUNY-IT facility in Marcy. Despite the fact that several years ago, the MV Edge failed in its bid to have AMD (now Global Foundries) locate their fab in Marcy, the region still stands ready to host a manufacturing facility. Already appropriately zoned and wetland permit-approved, with all new infrastructure ideal for a semiconductor fab or similar high-technology facility, the area may be ideally suited - if not for a fab - certainly for BEOL / 2.5D and 3D assembly processes, as the site is an easy drive (less than 2 hours) from the Global Foundries Saratoga Springs, and the adjacent SUNY-run CNSE facility in Albany, the New York state capital.

Local semiconductor, solar and LED-focused companies like Indium Corporation, and the first tenants in the proposed Quad-C building, Valutek and nfrastructure, will derive benefits from the close proximity of the SUNYIT facilities.

Nestled in the foothills of the Adirondack mountains (which remains the largest park in the United States), it looks like a brand new chapter may be about to be written, as the small Mohawk Valley region transforms from its old electronics moniker "RF Valley" to "Nano Valley".

Cheers!  Andy

Recently I was testing the resistance of a new low temperature metallization paste* (for solar photovoltaic assembly) in the lab. The samples were initially tested with a 4-point probe, just before entering a chamber set at 85°C and 85% relative humidity. To my surprise, the resistance dropped noticeably (as seen in the chart).

I brought the results to the material’s creator in our R&D department, ready to wow him with my discovery. I exclaimed, “I just finished testing the samples we put into the 85/85 chamber and can’t believe the values I’m getting!” Without a flinch he replied: “The resistance went down, didn’t it? That’s a unique feature of this material.”

While I didn’t gain any cool points in R&D for discovering an awesome new feature of an upcoming product, I hope the trait of this material can be useful for our customers (some of whom have since noted the improved characteristics after reliability testing).

The thing I learned from this experience is how important end of life testing is for metallization paste – all too often samples are only compared based on time-zero testing. This will change the way I compare metallization pastes from now on.

~Jim

*For my followers who aren't familiar with low-temperature metallization paste,it is also referred to as "grid ink", "silver ink", and "conductive ink". Low-temperature metallization paste is a silver-filled contact material used in the assembly of photovoltaic solar cells. It gets its low-temperature label because it is processed at lower-than-traditional glass frit temperatures of ~1,000°C. In addition to its role as a contact for thin-film connections, low-temperature metallization paste is also useful as a low-temperature alternative metallization on Si-based cells.

Learn more here.

Here is a list of tricks to help you overcome the issues that can arise while hand soldering silicon-based solar cells (and other applications as well). Some of these ideas are obvious for most, but all the suggestions can help you form a better solder joint - and build a better final product:

1)    Use the correct soldering tip. I’ve made the mistake of using an inappropriate solder tip before, and so have many of my customers. It’s a frustrating problem you will only let happen to you once: everything is set up perfectly but nothing will melt, until you notice the solder tip is not the correct size or shape. This has happened to many of my customers who were initially using cone point soldering tips when they were working with 2mm wide solder coated tabbing ribbon. Simply changing the tip to a 2mm wide chisel point made all the difference, and promoted soldering readily. Why such a big difference in performance? The chisel tip allows heat to flow across the ribbon, instead of only heating a single point. More heat flow = more heat in your solder joint.

2)    Pre-tin the soldering iron. Just as an appropriately sized soldering tip will distribute heat across the soldering surface, a bit of molten alloy can help create a thermal interface to maximize heat transfer. Remember to melt a small amount of solder onto the tip of your iron before soldering, and be sure it’s the same alloy you are soldering with. (Leave the custom alloying to us ;)

3)    Consider the alloy you are soldering. All the heat your typical soldering iron can produce will not be enough to melt some of the highest temperature alloys. Be sure to have a good understanding of the alloy you have selected. In some cases with low-temperature alloys (like bismuth or indium alloys), excessive soldering temperature can de-wet the alloy and char low temperature fluxes.

4)    Use the correct flux. Fluxes are quite different, I’ve spent my entire soldering career trying to get that point across. There are fluxes for high temperatures or low temperatures, cleaning with water or not cleaning at all. There are specialty fluxes for specialty alloys and there are fluxes for different soldering surfaces. Use the correct flux. If you don’t know what the best flux for the application is - just ask; that’s what I am here for.

5)    Use a bottom side heater. Silicon is known to pull heat away – that c-Si solar cell that needs to be soldered is a heatsink! Some solder equipment vendors also provide underside heating pads to help prevent excessive heat loss.

6)    Keep your soldering iron clean. That black crud that builds up on your soldering iron tip, it’s not helping you form a good solder joint. Those oxides and charred flux residues can easily be removed by wiping the hot iron across the wet sponge (that should be at your soldering station). A clean tip will lead to better heat transfer, and it will make the fluxes you use more effective.

This is the soldering station I use, it’s a PS-900 supplied by OK International. Just about any soldering iron will work, but they won’t all work as well – or come with as good support.

I’m still learning all the tricks to hand soldering, so feel free to share any you have learned over the years!

~Jim

As unlikely as it sounds, your reaction to this picture is probably similar to my reaction to Solar Power International 2011. Allow me to explain…

Aside from the fact that both the picture and the conference took place in Dallas Texas, there was another similarity: The show seemed to lack a clear audience. Just as you might ask, “Why am I looking at this picture?”, or “Why did you take that picture?”, I could not answer my own question of “Who is the audience for SPI 2011?”.

At SPI there were vendors who were selling retail solar water heaters, there were big name module assemblers, and there were materials manufacturers like us. There was no clear group of people on which the tradeshow seemed to focus. The result was a slow stream of traffic throughout the show compared to events like InterSolar, PVSEC, and SNEC.

In the end, it was still a good chance to meet with some industry partners, and with customers I haven’t seen in a few months. It was also a great chance to work with the IPC team on the upcoming module assembly documents. That, in itself, was a good enough reason to visit Texas!

~Jim

A friend recently mentioned to me that I don’t look like I’m really happy in my pictures online, this one is for you…



I found this picture that someone took from across the way at the PVSEC (European Photovoltaic Solar Energy Conference and Exhibit) in Germany a few weeks ago. (It has been zoomed in and cropped.) I don’t always love to travel, but I must admit that this was a very good trip. Our team had a great time in Germany – and met with many of the key people we talk with throughout the year. I felt that the show this year was a little slow, although our conference room was almost always full and our leads have been rather successful so far.

So here’s what I thought about the 2011 PVSEC:

• The conference hall (as usual) was a long walk from the exhibition. Tech guys are sometimes spread thin between working at an exhibit and catching a presentation. It would be great if it was easier to juggle these activities.
• Germany IS the location for the premier solar show of the year, good job!
• There is so much to see. Four-day tradeshows are long, but this one stayed interesting with so many things going on.
• It’s good to see so many equipment vendors still showing off their products. Other shows this year have been (in my opinion) light on equipment, but the PVSEC is the place to be to get demos – especially for tabbing/stringing lines.

If you made it out to the show, feel free to leave a message - I’d be interested in knowing what you thought of the PVSEC this year!

Your PV Application Engineer,
~Jim

Last week I spent some time in the simulation lab with Eric Bastow, verifying the printing characteristics of our newest low temp metallization paste LT-918. Due to its current success with a variety of customers, we needed to take production capacity to the next level. New equipment was purchased to keep up with the demand, but there is always the chance that material may not perform the same when it is made in substantially larger batches. Our testing confirmed the printing characteristics of the material made on the new equipment surpassed that of previous batches. That’s good news for everybody.

As you can see from the picture, we used a standard printer designed for stencil printing solder paste onto electronic circuit boards. The printer was not the only similarity to solder paste printing though. An interesting characteristic of LT-918 is that it has a higher viscosity than most metallization pastes, which helps with print definition. The high viscosity of LT-918 helps it print like a solder paste, this is great for solder paste printers (like Eric and I, and many of you for that matter) from the SMT and semiconductor assembly industries.

In my opinion, LT-918 is the best metallization paste currently available for interconnecting thin-film cells. It has not only excelled in printing, it also has industry-leading resistivity scores, and has passed customer reliability testing including thermal cycling, damp heat stability, and accelerated UV tests. Much of the data that we can share will be available soon as a product brochure that we hope to have ready for you at EU-PVSEC in September.

Typical Tabbing Ribbon Solders

Only a few solder alloys have become common, industry-wide, among solar module assemblers, and those can be pared down into three categories:

• BiSn alloys (58Bi42Sn, 57Bi42Sn1Ag)
• SnPb alloys (63Sn37Pb, 62Sn36Pb2Ag)
• SnAg alloys (96Sn4Ag)

Tin-Silver Solder (SnAg)
SnAg has become the most widely used Pb-free solder alloy, particularly in tabbing ribbon designed for cell interconnection. Historically, its melting temperature (221°C) made it an obvious replacement for processes previously running SnPb solders.

In designs where step soldering is necessary (however uncommon in back end solar module assembly), SnAg can be used as the step previous to soldering with Sn63 or similar Pb-Free solder (albeit carefully since the second soldering temperature is quite near 221C). 

While SnAg eutectic solder is a desirable composition for electronic component soldering, for instance, power semiconductors, recent studies using this alloy for stringing solar modules have indicated that the other common alloys listed for this application are easier to work with and better designed to meet the needs of this solar assembly application.  SnAg does have a high melting temperature, and the preferred fluxes for module assembly are not yet optimized for this solder composition.     

Regardless, SnAg has its benefits.  When a solder that melts somewhat above the melting point of a “standard” solder alloy is needed, and it must be Pb-free, this is it!!  Check it out!

Happy Testing!!

Amanda

I recently had a discussion with Frank Zimone (VP of Business Development at Angstrom Sciences) about sputtering target utilization. He stressed the point: although "material by weight sputtered off the target" is how most folks define the ‘target utilization’, when judging the efficiency of a process, it is only the material that makes it to the product that counts. Frank said:

“What is happening now, is that we are seeing that many companies, after the rush to set up a process to create a good product and “get to market”, are now working on dialing in the process to save money by lowering production costs. This can be achieved by putting more of the target material onto thin-film cells, and wasting less by depositing less of the material elsewhere in the production tool.

“We have recently completed a study with a major photovoltaics company which evaluated enhanced magnetics from multiple competitors.  In a back-to-back comparison with identical process conditions (power density, line speed, etc.) both targets were utilized ~85%  as measured by weight loss.” (Remember folks – this is application specific.) “The main difference between the seemingly similar depositions was that one set of magnetics yielded 20% more material on the substrate.”

I asked the obvious question at this point: “How was that possible?”

Frank replied:

“One set on magnetics was able to get the 2 erosion racetracks more closely aligned, and more perpendicular to the target surface. This translated into higher dynamic deposition rate and less wasted material on the chamber shields.”

It’s a simple concept if you understand the physics of sputtering, and Frank agreed that most customers know this from an academic point but do not have the time/resources to properly test. He said, “More established customers are now looking into these particular issues.”

To learn more about moving magnetics, contact Frank Zimone at FZimone@angstromsciences.com or stop by and see him at InterSolar this week!

I'll be there, as well. Look for me in the Indium Corporation exhibit #5325.

~Jim

Today I received an interesting email that could be useful for my readers. Here goes:

“Dear Jim,

I saw your recent blog. I am in the process of prototyping a photovoltaic application. I am aware that Indium Corporation has a lead-free alternative for tabbing and bus wire. Can you comment on why the photovoltaic industry, specifically in the US, has not adopted this standard as a better non-toxic solution and what Indium Corporation has done to promote this alternative? I look forward to hearing your point of view!

Best Regards,”

That’s definitely an important question, what an ice breaker! This was my response:

“First of all, thank you for reading the blog and thank you for the thoughtful question.

What many people do not realize, is that there are actually a few different types of lead-free alternatives for cell tabbing. The 3 most common alloys for tabbing ribbon are :

• 96.5Sn/3.5Ag
• 57Bi/42Sn/1Ag
• 58Bi/42Sn

Here are the main reasons that people stick with Sn/Pb based tabbing ribbon coatings:

• Sn/Pb and Sn/Pb/Ag have been extensively proven with many different module designs  
  
• Indium (the metal) based alloys are quite expensive compared to Sn/Pb based alloys
• Sn/Ag melts at a higher temperature range, causing greater expansion of the base copper (and therefore greater coefficient of thermal expansion mismatches).
• Some people fear the melting point of Bi/Sn and Bi/Sn/Ag may be too low for their subsequent processes (such as lamination)

The key point I’d like to note is that there are companies currently using each one of these alternative, and finding them feasible in regards to cost and reliability. We promote the use of these alloys - I would personally like to see the 57Bi/42Sn/1Ag alloy take over the market. I like to see my customers making good modules and feeling good about the materials they use too!

All the best,

          ~Jim”

Later on in the day we discussed the technical aspects of using lead-free alloys and settled on Bi/Sn/Ag and GS-5454 as the go-to materials. It was great to have this conversation with someone focused on conscious material selection and eager to learn more about lead-free options.

What are your thoughts?

On behalf of our solar PV team here at Indium Corporation, I’d like to mention how excited we are to see you at Intersolar in July. I look forward to going to this event every year; what’s not to love? A beautiful city, 2 simultaneous premier tradeshows, and many of the customers, partners, and vendors I’ve been planning on meeting or just catching up with.

I hope that you do stop by and say ‘hello’. If you’ve already mapped out your stops at the show I’d like to note that we will be located in a different aisle than originally planned. According to the event organizers:

“Currently Indium is located in booth 5228, we will be relocating you to booth 5328.  Please reference the attached floorplan for your new location as well as access the online floorplans for an overview of North Hall. The new location has been updated in the print directory now in development as well as with our vendor partners for all orders submitted to date.”

Here’s the important message: come visit us at booth #5328!

Send me an email if you want to set up an appointment to chat.

~Jim

As a tech guy, I couldn’t be more excited about testing these 8 different c-Si solar cell / metallization designs!

Q1) What the heck are we looking at in this picture?

A1) It’s a CuGa (copper gallium) target being sputtered at Angstrom Sciences, Inc. test lab. Since CuGa rotary sputtering targets are becoming more popular in the CIGS deposition industry, we wanted to see how they work with AS cathodes. The result: a winning combination!

Angstrom Sciences Lab








Q2) Why haven’t Cu-Ga rotary targets been more popular for production of CIGS solar cells (a thin film technology)?

A2) The big problem has historically been segregation of the copper and gallium in traditionally cast targets. This was a hot topic for those who stopped by the booth at the Society of Vacuum Coaters TechCon and checked out our full size CuGa display target. It is only natural to question if a display piece actually works well in a production sputtering process. In order to make this product work, we had to manufacture it using our proprietary hybrid consolidation technique.

Without giving away all the juicy details, I can tell you that it was a learning experience and that there were some setup issues that led to improved applied power settings. Our customers have been pleased with the results of our CuGa targets, although the fine tuning is proprietary to them and we cannot share their learnings. Now we have a much better understanding of the maximum power we can use for this type of target. That's why it was so important to work with an equipment supplier.

One thing that is obvious from looking at the spent target is the lack of an erosion groove from magnet dwell - a nice feature of the magnetron that was used. The spent target is on display in my boss’ office. It serves as a reminder of the time we spent with the Angstrom Science guys sputtering the target, gathering data, and learning from the team.

This year’s Society of Vacuum Coaters Technical Conference was certainly as focused on vacuum deposition as it has been over the years, but we were delighted by the new emphasis placed on solar cell fabrication. As I mentioned before , one of our key topics was thermal evaporation material - although we also presented on the topics of nano-bonding sputtering targets and the availability of indium and gallium. Along with these topics, the audience was treated to themes of cell fabrication, increasing solar cell efficiency, and roll-to-roll processing.

At the show, we had a chance to discuss new ideas with many of our existing and potential customers. Improved throughput and eliminating alloy segregation were hot topics at the Indium booth. Many customers wanted to learn more about CIGS materials like indium forms for evaporation, or full-size Cu-Ga, CIG, & In rotary targets for magnetron sputtering.

2011 raised the bar for the Society of Vacuum Coaters Tech Convention, I can’t wait for the 2012 event to top it!

这两年美国的西北部有越来越多的光伏太阳能公司在这里开设工厂，有些公司是前些年在加州硅谷地区把技术研发成功了，然后再把工厂开设在美国西北部（利用这里相对廉价的总成本，和联邦政府和州政府的补贴或投资的政策和条款）

在太阳能板子的组装方面，平时客户们问得最多的就是互联条和汇流带了(tabbing ribbon; bus ribbon)。这两种产品和普通的焊接带有一点区别，它们两一般是镀锡铜带。一般的客户都会有自己对互联条和汇流带的详尽规格说明(specifications)，比如说要求铜的规格是什么，镀锡的合金、厚度、误差范围(tolerance)，成品的宽度、厚度等。其中，与普通焊接带(solder ribbons)特别不同的是，互联条和汇流带一般有以下四点规格要求：

---Camber 曲弧度:简单来说，就是一条线拉直了，曲翘的程度不能超过多少。

---Elongation 延伸率: 一般有最小的百分比要求。

---Yield Strength 屈服强度: 材料开始产生宏观塑性变形时的应力。一般互联条要求的范围值比汇流带要求的范围值会低，毕竟每一段互联条要链接相邻太阳能板子的正反两面，要比较相对容易形变一点。

---Tensile Strength 拉伸强度: 是指材料产生最大均匀塑性变形的应力. 

Indium公司还提供各种太阳能溅射靶材(Sputtering Target)，太阳能低温焊锡膏(metallization paste)。 www.indium.com/solar

Pic：Indium Corporation

PS: 卖各种焊接产品给太阳能公司的生意不容易做啊。但是有机会，有潜在客户，总比根本没客户没机会好：-）最近有一个潜在大客户的进展很不错，让我顶着大肚子都往那里跑，常常为它忙乎着：-）

最近拜访了一个正在蓬勃发展的太阳能公司。当它的工艺工程师带我参观他们刚运行起来的太阳能模块组装工厂时(Solar Cell Module Assembling plant)，向我介绍了焊接互联条(tabbing ribbon)的Z-Bend工艺。

光伏太阳能(PV, Photovoltaic )的互联条一般是镀锡铜焊带。 焊接的原理与一般SMT相似，但也不尽相同。 所用的设备就不一样。一般焊接互联带的设备统称叫做Solar Cell Tabbing String Machine (CTS).  目前太阳能公司们常用的设备有这些牌子的： Spire, Komax, Somont, Applied Materials….

Z-Bend主要是互联条在连接相邻太阳能板子的正面与反面时，设备让互联条顺着本面形成一个弯曲的角度，这样可以减缓由于互联条拉紧后对太阳能板子可能产生的压力；压力有可能损伤太阳能板子。

有些公司的设备设计，可以做Z-Bend这个工艺，但是有些设备却不行。这也看太阳能板子的组装是否需要这项工艺。

现在美国这里也有越来越多的家庭在房顶上装太阳能板来发电了。光伏太阳能产业也慢慢走近民用了。

Cheers!

Pic:

1.      Jim Hisert withIndium Corporation

2.      Google Image

PS:

1． Z-Bend看来还是一个很新的词汇。我查了Baidu, Google, Youtube, Wikipedia, 都没有相关Z-Bend的解释链接。

2． 这个太阳能工厂从去年刚开始进行wafer production到现在的solar cell module assembling, 我前后参观了五六次了，还带了许多不同的朋友们去参观。每次都觉得很开眼界。

3． Acknowledge to: Jim Hisert with Indium Corporation  

I’ve been told that sometimes a good headline will include two things that seem to disagree. Using that logic, I’d say “cell interconnection” and “standardization” make a good headline, since there is no unified standardization in the tabbing and stringing process.

My new friends (pictured at right) hope to help change that. Dirk Schade and Cynthia Blank from XYZTEC have agreed to help Indium Corporation and the IPC Solar committee work toward building a standard for tabbing ribbon-to-cell bond strength testing.

XYZTEC is known for their high precision test equipment, which was developed for the semiconductor industry. They have since modified their equipment to handle c-Si cells, and to test the interconnection as well as the mechanical strength of the cells. Check it out here. 

Is there a cell/flux/ribbon/equipment combination that you would like to understand better? Maybe we could test your application!

It was a pleasure interviewing Pat Gallagher, who developed the first automated photovoltaic solar cell tabbing and stringing machine back in 1979. (Before I was even born!) Pat has seen the tabbing industry mature, and he was kind enough to help answer some questions about the process that I’ve grown to love. 

Jim: What were the initial design goals? How have they evolved over the years with customer’s needs?

Pat: Our primary goal was to replace variable hand labor in soldering with a machine and a process. That still holds today. Back then, solar cells were very expensive, thick, brittle, and not very efficient. So the biggest issue was to avoid breaking cells. Our first advice to the cell people was to turn the crystal 45 degrees to the bus bars so that the sides of the cell wouldn't break off along the solder joints. That little trick remains in place today.


Jim: Were the first machines designed to tab and string separately, or in a combined process?

Pat: Our first design was to make strings of cells in one shot. The two-step process, fronts then backs, was a holdover from hand soldering and there was no reason to do that anymore. Surprisingly, however, we ended up accidentally inventing the mechanized tabber on the way to creating a fully automated one-step stringer.

Jim: So that’s where the stand-alone tabber came from! I would have guessed it was the other way around. Have there been any changes to the heating method?

Pat: Oddly, the first thing we tried was induction heating. It was wonderful except that it took 5,000 watts to bring a small solar cell to temperature. It seemed rather wasteful, but that was the smallest industrial RF system available. Then we tried IR light, which also worked well. That's what we used in the first automated system.

Jim: Early tabbing ribbon must have been pretty crude. Have you noted anything that has changed with the copper or solder coating used over the years?

Pat: Basically, it's the same flat conductor that we started with in the 70's. The coating chemistry has changed dramatically. Taking cues from the electronics people, we started with lightly tinned copper and that was it. Solder was introduced on the cell so the ribbon did not need a heavy solder coating as is common now.

No-Lead (Pb-free) has been challenging mostly because the process window is smaller and simply hotter. The cells can be hurt if heat exposure is too long or too fast.

If you’d like to meet Pat (the President of Solar Automation) and learn more, you can email him by clicking here or visit the Solar Automation website.

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

Since I couldn’t find a good beginners guide to c-Si metallization paste, (not even from Wikipedia) I thought I’d provide an explanation of this important module assembly material:

The silicon solar cell has a low-temperature glass-frit paste applied to the active surface. This combination of glass, Ag, and other binder materials is printed onto the solar cell and fired around 850-1000degC to form the solderable metallization on the cell. This glass-silver mixture recombines during the firing process to break through the passivation/antireflective coating layer on the cell and form a strong bond to the cell. During firing the glass and silver are suspended in a mixture with silver forming an electrically conductive path from the top to the bottom of the deposit – and ideally a silver-rich layer is formed on top. This silver is the surface that tabbing ribbon is soldered onto when interconnecting cells.

Because the structure of the glass-silver is formed in the firing process, the firing can impact the solderability of the final metallization. That is the reason it is so important to determine the bond strength and diffusion/intermetallic formation of the interface between the cell metallization and tabbing ribbon solder coating.

Now here’s my challenge to you:

If you know of another good description, post a link to the document in the comments field below!

Thanks,

          ~Jim H.