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High-power diode lasers from Rofin-Baasel can be used for selective soft-soldering applications, such as intricate tasks on electronic components and fragile solar cells.

This is thanks to their ability to quickly modulate laser power, coupled with non-contact temperature measurement.

Using a laser for selective soldering operations allows the thermal energy required to be applied directly to the joint with no physical contact.

In addition, the ability to focus the laser energy to a concise point means that the heat input area is localised and accurate.

The narrow beam profile of the laser also enables soldering operations to be carried out in hard-to-reach areas.

Traditional soldering technologies can pose problems when applied to delicate or temperature-sensitive parts.

A soldering iron requires direct mechanical contact and this can involve the risk of contamination in the joint.

The size of the iron can make it difficult to gain access and there is little in the way of temperature control using this method.

According to the company, reflow soldering techniques are not always appropriate owing to the presence of adjacent parts or access to the specific joint area and hot air principles pose a potential heat risk to surrounding components.

Using the laser process, solder can be presented by an automated solder wire feed system or in the form of solder paste or pre-tinned contacts.

Process control in laser soldering is achieved using a pyrometer, which also serves as a quality monitor.

This non-contact method of measuring the temperature of the soldering process enables a closed-loop system to be created, balancing temperature and laser power to provide consistent and predictable results.

Diode lasers are also said to have all of the properties necessary for laser soldering and contacting on thin-film solar cells.

The solder joints, which can be achieved by using c/w diode lasers, cover several square millimetres.

This non-contact technology, together with the accurate and localised thermal input, limits the potential for thermal stress in the cell.

Si solar cells are usually interconnected to strings, which, in turn, are laminated into the modules.

This process requires subsequent handling with additional equipment for these long and fragile strings.

Using a laser and galvo-scanner combination, however, the string handling can be completely eliminated by soldering directly through the laminate layers without the need to move the optics or the cell.

The typical composition for these modules is glass, polymerised ethylene vinyl acetate (EVA), tinned ribbons, a solar cell, tinned ribbons and a transparent polyvinyl fluoride (PVF) back sheet.

The front and rear sides of the PV module are transparent to laser radiation.

As a result, soldering can be done before or after lamination.

With regard to peel force and contact resistance, the quality of the laser-soldered joints exceeds that of other contacting technologies, according to Rofin-Baasel.

The peel force is higher by a factor of three, whereas the thermal resistance is only about 14 per cent of the contact solder joint.

Rofin-Baasel UK Ltd is the UK sales and support subsidiary of Rofin Sinar Technologies Inc, which is one of the world’s largest manufacturers of industrial lasers and is quoted on the USA NASDAQ stock exchange. Rofin makes lasers and laser systems for marking, welding, cutting, drilling and perforating and offers sources and solutions across all the main industrial laser technologies CO2, solid state and fibre lasers. Our lasers are employed in most manufacturing markets to give customers unprecedented results in terms of quality and throughput. We have over 30,000 installations in industries such as medical device, electronics, automotive, jewellery, tool and mould, aerospace and solar power. Examples demonstrating the range of capabilities of Rofin lasers include: * In-line packaging material manufacturers use our lasers to create ‘easy open’ perforated lines in packaging. * High street jewellers buy our microwelding workstations to make and repair jewellery. * Surgical tool and implant manufacturers produce clean and permanent identification marks on their products with Rofin markers. * Photovoltaic customers rely on laser operations from scribing to drilling to make solar panels and wafers. Rofin-Baasel welcomes the opportunity to show customers what lasers can do for them.

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