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By Ed Hurley, Eric Tobin

The Worldwide Photovoltaic (PV) market is expected to grow rapidly as costs of installed PV systems approach grid parity. This is driving interest by new companies to enter the PV market and for PV system installers to vertically integrate into module manufacturing. However, with module production now dominated by large Asian manufacturers, it is becoming more difficult for new market entrants to succeed. Furthermore, general market uncertainty and significant recent fluctuations in module demand and pricing add risk, complicate capital investment decisions, and make financing more difficult to obtain. The traditional approach of establishing a comprehensive front- and back-end PV module production factory, where cells are made into finished modules, represents more risk than many worldwide companies are willing to accept in the current environment.

An integrated post-lamination assembly line is a low-risk alternative business model to the traditional full factory approach. In this approach, laminates--unfinished modules consisting of encapsulated cells--are assembled into finished and tested modules close to the point-of-sale (Figure 1). The post-lamination model has many advantages, and interest is being driven by numerous factors such as:

-Reduced financial risk based on low-cost CAPEX market entry, lower operating costs and significantly reduced floor space requirements

-Ability to leverage low-cost, reliable Asian laminate suppliers to achieve competitive cost per watt economics

-Accelerated market entry (typically 4-5 months) and ability to rely upon UL and TUV certification of laminate components from ‘design-qualified’ suppliers

-Ability for manufacturers to claim local (city and state) PV system content requirements and for manufacturers, installers and end-users to obtain associated local incentives

-Higher production yields, since most of the fallout occurs in upstream processes

-Lower shipping costs of laminates vs. full modules

-Rapid local customer service and response to maintain peak PV system performance and lowest life cycle costs

-Flexibility: Post-lamination lines can be used for production of either crystalline silicon or thin-film modules; they can also be installed for stand-alone production or as an upgrade/expansion to an existing factory

-Scalability: Allows manufacturers to expand operations once stable manufacturing and sales bases are achieved

Since the back-end process is very similar to c-Si, FAST lines can be easily adapted for thin-film modules, where they offer particular advantages. Manufacturing thin-film modules requires a great deal of capital investment and is not easily deployable in many regions of the world. Additionally, the overall capital cost for a thin-film FAST line can be lower than that for c-Si when frameless modules are used.

This article discusses post-lamination module production lines, also referred to as Final Assembly, Simulation and Test (FAST) lines, and examines the key issues that manufacturers must consider when designing, installing, and operating a post-lamination line including: the process flow and equipment involved in final assembly; testing of laminates; incoming laminate quality; module certification considerations; and investment costs and payback.

Post-Lamination (Back-End) Process Flow and Equipment

The input material to the back-end process flow is the laminate, which consists of a laminated module without the frame and junction box. Since laminates are only several millimeters thick, they are much easier to package and ship than finished modules. The most common laminates today are 60- and 72-cell c-Si modules, and they are available in a variety of mono and multi c-Si configurations and sizes, providing a large degree of product flexibility.

A typical post-lamination line consists of eight equipment stations (Figure 2):

1. Edge trimming (optional)

2. Module edge sealing or taping

3. Framing

4. Junction box installation

5. Sun simulation, electrical isolation, ground path continuity testing

6. Electroluminescence testing

7. Manual (lift/tilt) inspection

8. Automatic label printing, binning and pack out

Automated material handling, including buffer storage and automated transport between process stations, is also typically included. Additionally, complete data integration provides data tracking and database upload to a host MES system.

Modules are transported by conveyors and processed face down in all stations, which use the same standard handshake protocol to communicate with upstream and downstream automation. The equipment process stations are modular and can be arranged in different sequences. Networked controllers allow real-time product and data integration, and test data acquisition and tracking. Bar codes on the backs of modules can be used with scanners to track and assign data to individual modules by serial number.

Key Equipment Considerations

Although the basic equipment set is similar from line to line, several options exist for selecting a layout. Foremost among these are the capacity of the line and the level of automation. Selecting a throughput level closely matched to projected volumes is important for optimizing capital equipment utilization. A high-quality PV equipment supplier will work to optimize line throughput and best match user needs. A typical back-end line throughput rate is 60 MW per year, but this can be higher or lower depending on market demand.

The level of automation is also an important consideration and will affect both staffing level requirements and line throughput. Automation levels can range from passive conveyors to fully automated systems with integrated robotics. Although module manufacturers currently use minimal automation for their post-lamination processes, some level of automation is typically desired since it can result in significant labor cost savings, improved product quality, and increased throughput. Fully automated (robotic) systems represent significantly higher cost and are thus typically used only in areas with high local labor costs.

Post-lamination module production lines are flexible and can be set up in a variety of different configurations depending on user requirements. Although manufacturers might be tempted to save money by focusing primarily on the assembly equipment at the expense of the metrology measurement tools, this strategy will ultimately increase production costs. The metrology equipment is also vitally important. For instance, although Electroluminescence (EL) inspection is not an absolute requirement, it provides an important quality check for both incoming laminates and outgoing modules. EL testing can reveal defects not visible to the naked eye, and assures that the incoming laminate supply is of adequate quality. Other module tests such as high voltage isolation and ground continuity are required for selling modules in many regions. Data collection and information management are also important considerations and become critical for optimizing production in higher throughput, automated lines.

Incoming Laminate Quality and Other Material Considerations

The choice of laminate supplier is critical, and a prospective module manufacturer must consider several factors when making the selection. Quality and pricing are often considered the most important considerations. Additionally, as many of the laminate materials as possible should be certified to UL or IEC module design qualification standards. One should begin with a detailed and well defined laminate specification including size, power rating, and acceptable defect levels (quantity and sizes of bubbles, bends, cuts, chips). A well qualified PV equipment supplier can help generate a detailed laminate specification and tailor it to your production environment. Since the laminate supplier is critical to the overall process, visiting their manufacturing site is a requirement. A site visit will help determine which laminate supplier optimally combines the best manufacturing practices, including a certified quality control system, with low laminate pricing. In some cases it may make sense for your selected PV equipment supplier to visit the laminate suppliers at the same time. If possible, manufacturers should maintain two laminate suppliers to hedge against supply interruptions, quality problems, or sudden price increases.

Other important material considerations include the use of corner keys versus screw frames, and edge tapes vs. sealants. Determining the best approach is based on factors such as reliable local suppliers, operational plans, target markets, and end-user customer requirements.

Module Certification Considerations

Module certification is required for all modules, and the process to obtain UL or IEC certification can take up to 4 months and cost over US$60,000. Qualified and experienced equipment suppliers can help manufacturers navigate the certification process, build modules for certification, and even supply certified module designs to accelerate market entry. In many cases, the module certification process can be initiated and completed while the line is being built and installed.

Costs and Return on Investment (ROI) Analysis

Naturally, return on investment is of primary concern when making an investment decision for a module line. Before funding a project, detailed financial models should be created to predict costs and income. These should include all relevant inputs such as laminate costs, labor, number of shifts, building and facility costs, overhead, depreciation, cost of financing, etc. Capital costs require special consideration, and as discussed above factory equipment must be carefully selected to minimize assembly costs. The PV equipment supplier can also assist the manufacturer with an appropriate analysis and help to evaluate trade-offs such as running single vs. multiple shifts and use of different materials (i.e., edge tape vs. sealant). This allows companies to determine the best operating model for their market. Due to rapid changes in the price of materials, financial models may need to be run several times during the decision process. Be sure to work closely with your PV equipment supplier to assure that investment decisions are based on accurate and up-to-date cost analyses.

Table 1 shows a simplified pro-forma P&L for an automated 60 MW per year post-lamination line. The analysis shows that depreciation represents a relatively minor portion of the overall costs, and the initial capital investment for the line is returned in less than a year.

The installation of a post-lamination (FAST) line for module production is an ideal way for manufacturers to enter the market and assess opportunity while minimizing capital expense and risk. This business model provides a viable alternative to operating a full module production line while offering the opportunity to expand later if desired. Furthermore, post-lamination assembly lines offer a great degree of flexibility and can be readily integrated into existing front-end module production lines to reduce costs and improve final product quality. Installation of such a line requires careful selection of a PV equipment supplier who can provide not only reliable equipment but also support services that extend from the initial planning phase through project management, installation, supply chain support, line start-up and operation, module certification assistance, and on-going applications support.

Edward Hurley is Vice President of Sales for Spire Corporation (www.spirecorp.com), a global provider of solar equipment used to manufacture solar modules and solar cells. Hurley is responsible for international sales covering mainly Europe and the Far East. Hurley, who has an engineering degree, has spent over fifteen years selling, marketing and designing capital equipment to the solar and electronic marketplace.

Eric Tobin is Vice President of Product Management at Spire. His current responsibilities encompass Spire’s portfolio of solar equipment products and include market opportunity assessment, product roadmap strategies and timeline development, product positioning, and creation of product collateral and advertising material. Tobin has been with Spire for over 20 years, working primarily in the company’s Biomedical division, where he has held several positions including Process Development Engineer, Director of R&D, and Vice President of Operations.