Sign & Digital Graphics

The 2015 LED & EMC Report

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12 • June 2015 • L E D & E M C LED/EMC LED Technology Advances in LED Chip Technology Light emitting diodes have come a long way, baby B y J . B r y a n V i n c e n t , P h . D . LED advancements have under- gone tremendous change over the past two decades. Light emitting diodes are semiconductor diodes that emit light when connected to a direct current. The basic principles governing LEDs were originally observed by British scientist Henry Joseph Round when he noticed that when a 10V potential was applied to silicon carbide, a yellow col- ored light was emitted. However, it was not until 1961 that a GE researcher developed the first true light emitting diode that emitted light in the visible frequency range. In the early days development was slow. LED technology continued to plod along and as the price per chip began to decrease, LEDs began to find applications as indi- cators and displays in devices like hand- held calculators. It was not until 1994 when Shuji Nakamura with Nichia Corporation developed the first commercially viable blue LED that he paved the way for LED use in broader lighting applications. Most white LEDs today are basically a blue LED that has a yellow phosphor coating that converts monochromatic light to broad-spectrum white light in a similar manner as a fluorescent lamp. So How are LEDs Made? Generally speaking, diodes are made from very thin layers of semiconducting material. One layer contains an excess J. Bryan Vincent is an expert in the field of solid state lighting and electronic materials. He has dedicated the past 10 years to developing LED solutions specific to the sign industry and is a partner at Principal LED. He has a bachelor's degree in chemistry and a Ph.D. in chemistry/materials science. Semiconductor clean- room used in LED wafer production.

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