SOLAR

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.

You’re reading this because you want to know more about LTTF-6363 low temperature metallization paste right? Perfect.

I wanted to get your attention, because I want to talk to you about using this material. We have released a tech paper and (more recently) presented a poster at EU-PVSEC in Valencia earlier this year. With all the buzz about the “Novel Flexible Silver Paste”, I’ve had a chance to print, cure, and solder to LTTF-6363. I’ve had a chance to get my hands (well, gloves…) dirty like a good applications engineer should.

As you may already know from studying the other documents surrounding this material, it was designed for thin-film solar cell interconnection, as a solderable polymer met paste. It went a long way towards teaching us what properties we still need to work on. The material is currently not a product we actively promote, because we know there are properties that need to be improved to give you a wide process window for high volume manufacturing.

Soldering to an epoxy-based material has many intricacies, as I’ve learned. Maximum temperature, Ag dissolution, and a short pot life make processing challenging – honestly, it’s not good for everyone. Of course there’s no way I could have tested the material in every application, but I’m starting to get a good feel for the type of applications that it could work in. 

If you want to evaluate if this material will work for your application, please save yourself some time searching for the answer and just call me: (315) 853-4900 x7592. I can help make your decision easier. 

~Jim Hisert

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

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

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

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

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

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

“Hi, this is Jim Hisert. I just read an interesting article and I wanted to share it with you. In the 2010, October edition of PV magazine, the cover story on page 70 was pretty interesting, so here it is…

It’s called Rotatable Rotatables, and it discusses rotatable targets. The really nice thing about the article is: it goes through the physics of sputtering and gives you the background of what magnetron sputtering is all about. Then it talks about different kinds of targets. It talks about the difference between rotatable targets and planar targets, the different compositions of targets. And then it also goes into talking about the supply of indium and gallium, different target materials, as well as the difference between thermal vapor deposition and sputtering – the advantages and the disadvantages. It even wraps up with refining and recycling of the material and talks about the process overall.

So I advise that you check this out. It’s in the latest (October) edition of PV magazine. Thank you.”  ~Jim

Keywords: Solar, sputtering targets, copper indium gallium, CIG, indium, thin film technology

Last week in L.A. I met up with Hoa Nguyen (VP of R&D, OKInternational) at Solar Power International. The full post and video are available here.

Are you scaling up to a rotary sputtering system from your current planar target line?

That’s a big jump! New equipment, new materials, new process challenges. I hope we can help you make this an easier transition. One of the issues you may be concerned with is the segregation of gallium in the new targets. Fortunately we produce our rotary targets using a hybrid consolidation process. Although I cannot share the processing details of this method, I can say that it sets Indium Corporation’s targets apart from what few competitors are out there right now. We offer Copper Indium Gallium sputtering targets as well as Copper Gallium sputtering targets. If you’re interested and would like to learn more just follow this email link: solar@indium.com

Sure, you could buy some dirt-cheap tabbing ribbon off ebay.

If you want some very awesome solder-coated ribbon and you won’t be laminating your panels over 100°C – I have a much better option for you.

The Indium Corporation makes ultra-low temp tabbing ribbon (melts ~100°C). The advantage? You can use a standard soldering iron and solder solar cells much more quickly because the solder melts more rapidly.

Note: I advise using GS-5454 flux – it may be the only flux that promotes wetting onto the cell as quickly as you’ll be soldering!

Click here to get a hold of this stuff!

The picture above is some of my private stock that I use for testing at work. The picture below is how we package spools – way better than the no-name ball of crinkled ribbon you sometimes get from stock vendors online.

Happy tabbing!

~Jim

最近小忙，少讀書了，也少和大家分享了；不過工作之餘，翻看了一下《A Seat at The Table》一書，覺得裏面有些道理也蠻有啓發的。比如説此書中一直圍繞這個主題來展開了論述“Today, the only thing your customer cares about is value.”

就這個觀點，再對照一下Indium公司的兩個主要系列產品：

²       電路板組裝焊接材料(Solder Materials):  這裡也要分產品而論。對於技術含量較高，工藝使用要求較多的焊錫膏(Solder Paste)材料，重視成品可靠性的客戶們會更多的關注產品帶來的“價值”。 如果只圖便宜的材料，但是用起來“錯漏百出”的，最後還是事倍功半：返工，復修，廢棄率高（特別是浪費貴的不能翻修的板子），產出率低，總體成本也自然高了。 對技術含量較低，工藝已經“模式化”的產品，像錫棒(Solder Bar)，錫綫(Solder Wire),  性价比會更關鍵……在目前日益高漲的金屬原材料市場中，Indium公司考慮到客戶們的成本壓力，也推出了性能可以和SAC305錫棒媲美的有成本優勢的Sn995錫棒。

²       半導體封裝材料(Semiconductor Materials):  整個半導體行業應該算是一個高成本，高投資，高回報（運營得好的話）的三高行業。半導體封裝材料也像是其中的經絡血脈吧，連接各個部分，讓整體最後順暢無阻的工作。半導體各個部分的材料都不便宜，設備更是不菲；對材料性能的表現要求和驗證都很嚴格，畢竟都投資那麽多，不能“功虧一簣”嘛。所以客戶們一般會十分重視產品的價值。 Indium 公司目前提供的半導體材料有：Wafer Flux, Wafer Paste, Micro Spheres, Flip-Chip Flux, Substrate Paste, Ball Attach Flux, Die-Attach Paste/Wire, PoP Fluxes, etc. 

Indium公司還為大家提供散熱界面材料(Thermal Interface Materials)，工程焊料(Engineering Solders)，薄膜光付太陽能板製造材料&太陽能板組裝焊接材料(PV Solar Materials)，和銦金屬及其化合物等。 這些材料使用在比較領先的應用中，新興行業，或是細分市場中，客戶們都十分重視產品和服務能給自己帶來的價值。

Cheers!  

Pic: Indium Corporation

PS: 前些日子看了中央4台的《第三屆漢語橋在華留學生漢語比賽》，感慨不已！除了感嘆這些留學生們對“那麽難”的漢語的精湛掌握，對中國文化和歷史的了解，甚至對中國的熱愛；更感慨的是，這些活動也説明了祖國的強大！現在越來越多的留學生們來中國學習，想進一步了解中國，和中國人民交流；中國話也在慢慢傳播到全世界！以前中國學子們苦讀英語，考TOFEL, 雅思，GRE什麽的；現在金髮碧眼的學生們也在場上比拼誰更了解我們的“四書五經”了，哈哈！

The word ‘cadmium’ (Cd) has a negative connotation to anyone who deals with solder alloys or health and safety regulations. If you are using toxic cadmium sulfide as a buffer layer for CIGS PV cells, I urge you to explore indium sulfide (In₂S₃) as a replacement. Alternative energy should focus on being environmentally conscious, starting with the bill of materials for the solar cell.

I had a call with a few engineers today who wanted me to answer a question, “Which solder paste do I pick for my application.” Sure there were a few application-specific details that I feel were too specific to discuss with a general audience, but I think I can answer the question for any of you that are out there wondering the same question while reading this.

It’s an easy answer really; start with SR-8 unless:

1)     You are using laser reflow equipment.

2)     You have noticed solder spatter issues related to your design.

3)     Your company or end customers require you to use only halogen-free materials

4)     The residue must be clear and almost non-existent (ultra-low residue levels)

If you said “yes” to any of the above, you’ll want to try SR-7 (as long as you have nitrogen reflow capability). If you said yes to answer 3 (halogen-free) but you do not have nitrogen reflow capability, try SR-089.  

Jim’s note: This post was written in August 2010 – but it will be available to anyone searching for the info for quite some time. For updated information on newer solder pastes, send an email to Solar@Indium.com. Thanks! ~Jim

Some people collect stamps, or coins, or baseball cards – my father collects hardware. Almost every time I go to my parent’s house I notice a few jars or boxes of bolts, nuts, screws, washers, and clamps. They are bought in bulk and sorted by size. I used to think it was ridiculous to do this, but my Dad actually uses enough of the hardware to save money, and I have never needed to run to the store during a project to get a special size piece of hardware. An old bolt may not look as pretty as a new bolt, but in applications that are simply for utility, an old bolt works just as well.

Solar panels that do not live up to visual specifications also share a utility, much like old bolts. They are certainly cheaper - and for a solar farm, small imperfections may not matter to the customer.

So now it’s my time to collect something. I’m not looking to collect old hardware or utility grade solar panels, I’m searching for the different criteria that module assemblers use to determine if modules are fit for residential or commercial use. This information can be used to help set the (IPC) standards for the industry. If you have information that could help, please send it to jhisert@indium.com. Thanks! 

As many of you know, I’m focused on applications for the solar industry and the semiconductor industry. In fact, many of the readers of this blog have spent a good amount of time working in both fields as well. Dr. Ernest Levine is just like us, except he makes these topics way more interesting to learn about than I have figured out how to do yet…

Whether you’re learning about semiconductors or solar cells for the first time, you’re planning on learning more, or maybe you just want a refresher course – check out one of these courses in October. The IC Fabrication Class is offered Oct. 12-13 and the Photovoltaic Class is offered Oct. 26-27.

Back in 2008 I attended the IC Fab class and interviewed Ernest to learn more: http://blogs.indium.com/blog/jim-hisert/0/0/ic-fab-course.