When it comes to manufacturing solar panels and components, engineers need solutions that offer performance and reliability over the long term. These solutions are even more attractive when they maximize productivity and minimize the total cost of ownership for the manufacturers. 3M has supplied a broad class of materials to the solar industry for more than a decade, and continues to develop new products that can help deliver the attributes that solar manufacturers desire.
Adhesives and tapes are one of the many core areas of expertise for 3M. The company offers a complete portfolio of products in this area to the solar industry. 3M’s family of adhesives span structural adhesives, such as epoxies, acrylics and urethanes, as well as non-structural adhesives, which include contacts, aerosols, hot melts and sealants. These adhesives are used in many custom applications in solar panel manufacturing and installation. Attachment of flexible panels to roof substrates, junction box potting, and bonding various structural elements in parabolic troughs for Concentrating Solar Power (CSP) installations are some examples of these applications. 3M works with customers to develop new applications based on their specific needs. 3M can supply adhesives in a wide variety of packaging, from user friendly manual cartridges to large quantity drums and totes.
While adhesives and sealants are used in the manufacture and installation of solar panels, tapes are also very popular. That’s because tape requires no cure time. Parts can be moved almost immediately to the next work center when tapes are used, enabling high productivity in manufacturing. There is also little need for clean-up of the excess adhesive (which is typical when using liquid solutions).
Solutions for Crystalline Silicon PV
3M invented the world’s first practical pressure-sensitive adhesive tape more than 80 years ago and over the decades continually refined and improved products to meet changing needs. 3M tapes can be found everyday in many consumer, industrial, electrical and electronics and medical applications. 3M introduced high-performance Acrylic Foam Tapes in the 1980’s. These tapes are composed of sophisticated acrylic-based foamed adhesives, and have found their way into many mission-critical outdoor applications including those in construction and transportation industries. This technology and experience-base is well suited for the solar market. 3M™ Solar Acrylic Foam Tapes (SAFT) are currently used by many manufacturers for frame and junction-box bonding applications.
Frame bonding can require frequent roll changeover. SAFT is available in level-wound rolls (the tape is spooled like the line on a fishing reel, allowing for hundreds of meters of tape to be packaged in a relatively small format). For junction box attachment, SAFT can be die-cut into custom shapes, allowing engineers maximum flexibility in their designs. Since, there is no squeeze-out of the excess liquid around the edges making the end result cosmetically superior. Another practical benefit of SAFT is the closed-cell foam construction, which seals against dust, dirt and rain.
The Advantage of Acrylic Chemistry
To understand why SAFT is well-suited for solar applications, it is important to understand its chemical properties. Acrylic polymers are durable due to the presence of carbon-carbon single bonds on the polymer chains. Such bonds are highly resistant to heat or ultraviolet light, as well as to chemical attack. This translates into improved outdoor durability in the application.
Most foam tapes have only a thin adhesive layer on each side of a foam structure. In contrast, SAFT consists of a foamed adhesive that permeates all the way through the cross section. Thus, when SAFT is used to bond substrates that have different coefficients of thermal expansion, the entire foam core of the tape can accommodate the shear strain. Therefore, it can routinely accommodate 300% shear strain (that is, a lateral movement between the substrates of three times the thickness of the tape).
In addition to frame and junction box bonding uses for tape, there are other specialized applications for tapes in crystalline silicon panel for cell positioning, edge protection, ribbon hiding, electrical isolation between lead foil layers and cosmetic needs.
Solutions for Thin-Film PV
3M also offers a portfolio of adhesive tapes for charge collection and dielectric insulation for power management in thin film panels. Consistent with the value proposition of tape solutions, these specialty tapes enable rapid lay down which improves manufacturing productivity, and decrease the total cost of ownership. The new tape introductions are well-suited for the increasing current loads and higher voltage insulation required for the panels of tomorrow.
3M™ Charge-Collection Solar Tapes consist of tin-plated copper foil with acrylic-based, pressure sensitive adhesives. They offer stable electrical performance, and the tin-plating allows for solderability and corrosion resistance. They are compatible with typical lamination processes, and are available in many formats to suit various manufacturing processes. 3M™ Dielectric Tapes consist of a dielectric film with acrylic adhesive on one or both sides, and perform as reliable insulators when used in conjunction with buses and/or foils in thin film solar panels.
3M Solar Acrylic Foam Tapes have also proven useful for niche applications in the Concentrated Photovoltaic (CPV) segment. Since the optical path-length is critical for success in CPV applications, the uniform thickness of tape helps ensure a consistent separation between the bonded surfaces, thereby maintaining the quality of the focused beam.
Evaluating a Solution for Your Needs
When considering a bonding solution for a solar application, engineers typically consider three main factors: the material’s performance, consistent quality, and cost. The industry uses a number of standard tests (like UL and IEC) to determine a panel’s performance under various environmental conditions. When determining a tape or adhesive’s suitability for a given application, it is important for engineers to understand these tests and to examine the various solutions that could apply. 3M can perform tests using the various adhesives and tapes on the customer’s substrates. Static shear, Dynamic shear and T-peel tests are some of the standard tests that are employed to help guide the customer to identify an optimum solution.
Consistent quality is another important consideration for routine, large-scale operations. Particularly when solar panels are being manufactured in multiple locations, as is common for multinational manufacturers, product consistency becomes vital. Customers should confirm that a supplier is well-equipped to provide the same product made to identical specifications at every location of interest. Finally, cost is of obvious importance to PV manufacturers. When comparing the costs between various solutions, it is important to understand the true total cost involved, which may be more than just the cost of the tape or adhesive by itself.
Application Support and Guidance
Customer needs are different as PV products are different. Every substrate requires careful consideration on how to properly bond to it. To help customers determine the most suitable products for their individual applications─whether it be adhesives or a tapes, 3M’s global technical service group stands ready with a full-fledged team capable of performing custom testing. This strong global presence helps answer questions, providing guidance for customers all over the world, and enabling them to leverage the maximum potential of their PV products.
The race to grid parity has manufacturers all over the world examining their product designs and looking for ways to add efficiency and reduce cost. Taking a product’s total cost of ownership into account and pursuing components that help save money in the long run are important steps to helping PV technologies advance. By using reliable products that enable efficient manufacturing and longevity in the field, PV manufacturers can continue to lower costs while increasing performance.
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