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Laser welding plastic tail lights

Erlangen, Germany - SL Corporation, a well-known supplier to automotive manufacturers in Korea is, for the first time, welding plastic automotive tail lights with hybrid laser welding systems from LPKF Laser & Electronics AG. The technology combines laser light with infrared radiation and is very effective and economical for welding of large plastic parts.

Conventional joint technologies such as adhering or vibration welding produce joint lines that have to be covered to hide visually unsightly joint areas. SL Corporation (www.slcorp.co.kr) carried out serveral tests with procedures for three-dimensional welding of tail light housings, and hybrid laser welding was best in terms of visual appearance and high strength of the joint lines at the highest process rate throughput.

The housing is made from polymethylmethacrylate (PMMA) colored with black, gray, and red pigments. The lens is clear or red colored polycarbonate (PC).The seam length is 1000 mm. Some modifications were made to the design of the rear lamp to obtain an equal seam quality along the complete contour. The laser hybrid welding process is about five times faster than conventional welding while it assures a high joint firmness. A tail light can be welded in 30 seconds independent of the coloring of the absorbant joint partner.

The Plastics Welding Division is a fast-growing section of LPKF (www.lpkf.com), with 2006 turnover on laser welding systems increased by 120%. The technology of laser welding plastics is being used increasingly by the automotive industry all over the world.

LPKF develops systems and process solutions for the electronics and automotive subcontracting industries. The company is a global leader in equipment for PCB prototyping and laser cutting machines for stencil production.

Laser cutting silicon for solar cell production

San Jose, CA - Work conducted here by Dr. Tony Hoult at the U.S. applications facility of SPI Lasers (www.spilasers.com) shows promising results in processing 0.2-0.8mm thick polycrystalline silicon as used in solar cell production. Using a 200W CW-M 1070nm fiber laser with a novel cutting technique, cutting speeds of up to 6m/min on 200µm silicon ribbon have been readily achieved.

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Reportedly, analysis of the cuts shows very smooth surfaces with minimal debris or spatter, 40µm kerf with no appreciable spatter.

Dr. Bill O’Neill, of the Cambridge Institute of Manufacturing in the U.K., said, “The current laser cutting process requires expensive DPSS lasers, which require higher levels of maintenance and are considerably slower. The early promise shown by the SPI Laser trials will prove of real benefit to a rapidly growing sector that aims to reduce cost, increase throughput, and improve product energy conversion efficiency.”

On the home front

Industrial Laser Solutions will be launching a new trade publication targeted at the growing European industrial laser systems market. Industrial Laser Europe is scheduled for release in April 2008 with well-known German journalist Franz J. Gruber taking the helm as Chefredakteur/Editor-in-Chief. This German-language publication will be distributed to 10,000 qualified readers. Contact David Belforte (Belforte@pennwell.com) for more information.

Industrial Laser Solutions is pleased to announce the addition of Dr. Mariana G. Forrest as a contributing editor for the automotive industry. Dr. Forrest is the founder and president of LasAp, an engineering and manufacturing consultancy dedicated to accelerating the development pace and to transferring into production of advanced manufacturing technologies. Prior to founding LasAp, Dr. Forrest was senior manager of advanced joining technologies development group in the materials engineering department at DaimlerChrysler Corp. She can be reached at mariana.forrest@las-ap.com.

Industrial Laser Solutions has completely redesigned its website-www.industrial-lasers.com-to offer the latest industrial laser materials processing news and information conveniently categorized by application: laser cutting, laser welding, laser marking & engraving, laser microprocessing, laser drilling, and laser surface treatment. Visit www.industrial-lasers.com or contact Laureen Belleville (laureenb@pennwell.com) for more information.

Laser joining solar cells

Aachen, Germany-For solar cells to produce sufficient power, sunlight must be captured simultaneously by an array of cells. These cells are connected in series using tiny strips of metal known as stringers. Each stringer must be positioned in precisely the right spot, then its solder coating is melted using a hot electrode. When the solder sets, it forms a stable bond with the metallic coating on the silicon. The amount of heat induced in the stringer and the silicon depends on the contact between the soldering electrode and the stringer. Applying too much energy causes thermal stress, which, in the worst case, could destroy the solder joint, leaving a break in the electrical circuit that makes the solar module unfit for use.

Researchers here at the Fraunhofer Institute for Laser Technology (ILT) have developed a non-contact soldering system in which the temperature is constantly monitored. If the temperature deviates beyond set limits, the system automatically adjusts it to an acceptable value. “Instead of an electrode, we use a laser beam for the soldering operation,” says ILT department head Dr. Arnold Gillner. “To melt the solder, we pass a laser beam over the solder-coated stringer. An infrared heat camera derives the temperature of the silicon and of the metal strip from real-time measurements of their emitted radiant heat. If the temperature is too high or too low, a feedback control circuit automatically adapts the laser output within milliseconds.” The system is already in use for industrial surface engineering applications. Solar applications could be on the market in a year or so.

The researchers’ next project is to develop a faster, more reliable method of connecting solar cells by means of laser welding. “Whereas soldering only involves melting the solder, in laser welding the stringer itself is melted,” explains Gillner. This means applying more heat than for soldering, but only for a very short time. “Since the laser is only in contact with the materials for a brief instant, only a small amount of energy is transferred to the materials despite the higher temperature-resulting in even fewer heat-induced defects,” he adds. What complicates the matter is the fact that the stringer has a diameter of about 200 µm, whereas the metallic coating on the silicon required to conduct electricity has a thickness of a mere 10 µm. The laser beam has to be modulated in such a way that the stringer will melt while leaving the coating on the silicon intact.

Visit www.ilt.fraunhofer.de for more information.

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