Looking at the development and production of fluxes over the last decades, they are mainly used in industrial applications, such as brazing, and electronics applications, such as soldering. In solar industry applications, experience from the electronics industry is used. Emil Otto has specialized in all industrial soldering techniques since 1901, including the solar industry. This commitment is now being expanded.

With respect to mechanical connections and electrical contacting of solar cells to solar modules, the requirements are very similar to contacting in the electronics industry. For this reason, inquiries from the solar industry have increased sharply at Emil Otto in recent months. The focus is on high-performance alternatives to established fluxes that have been in use for years and no longer meet current industry requirements, for example in terms of process efficiency, purchasing costs, reduction of defect rates and minimization of ancillary production costs, such as cleaning cycles. Emil Otto therefore developed its own range of solar fluxes years ago. But fluxes from electronics manufacturing are also used in solar cell production.

“Well-known international solar cell manufacturers now obtain their fluxes from us. These are used in the stringer soldering process, as well as in the production of classic electronics around the solar cell,” explains Markus Geßner, Marketing and Sales Manager at Emil Otto GmbH. Emil Otto now offers a whole range of fluxes that have been specially adapted for the solar industry, such as the solar flux EO-S-002. With 2.0 % solids and a very low resin content, the flux is increasingly being used in stringer production. Simply put, the activator system of the solar flux is a composition of organic acids and synthetic resins. This results in adaptation possibilities with respect to process time, soldering temperature, type of metallization, application technique or residue behavior. The EO-S-002 is much cleaner, both in soldering and in residues in the system. Soldering results are also better than with conventionally used fluxes. With EO-S-007, Emil Otto has another flux in its portfolio that is increasingly used in the solar industry. This flux also has a solid content of 2.0%, but unlike EO-S-002, it is resin-free.

Furthermore, Emil Otto is the only manufacturer worldwide to offer fluxes as concentrates, including for the solar industry. Since conventional alcohol- or partially alcohol-based fluxes are dangerous goods in the sense of transport regulations, requirements must be met that can make a product increasingly more expensive, especially due to the more costly transport. Shipping by air freight is also impossible, as in these cases the fluxes may only be packed in small containers. This restricts large quantity purchases. In order to circumvent these problems, Emil Otto has for some time been developing flux concentrates on a granulate basis, which do not represent hazardous goods. By optimizing transport, the flux concentrates can be transported over long distances in an economically attractive way, since freight forwarders charge much lower costs for non-hazardous goods. Mixing the flux on site is very simple. Each product comes with the necessary information on which liquid to add to the concentrate and in what dosage.

Another increasingly relevant trend is the use of partially water-based or purely water-based fluxes. This also has cost-related reasons, as water lowers the direct product costs compared to isopropanol and purely water-based fluxes are therefore stable in price. Especially during the Corona crisis, when prices for isopropanol rose sharply, many companies switched to the water-based alternatives, which achieved equally good soldering results. In addition, water-based fluxes reduce consumption, are non-flammable and therefore not subject to hazardous materials regulations. “For example, the flux EO-G-003 is used in the manufacture of inverters for solar modules and has passed various tests with very good results that were above the dew formation test in the automotive industry,” explains Geßner. “But alcohol-based fluxes from the highly successful GSP series are also used in the manufacture of inverters. Thus, very good soldering results can be achieved with the GSP-2533/RX, regardless of the respective application and use types,” Geßner continues. The cleanliness is very good, and it has been shown in practice that, with proper application, washing of the surfaces treated with this flux can be largely eliminated.