LED External Assembly

By integration of LEDs in an external assembly, for instance, in a PCB (Printed Circuit Board), more failure sources like malfunctions of electrical joints due to bad solder contacts must be considered. Especially for high power LEDs, thermal contact and heat dissipation are very critical effects impacting degradation. The assembly should ensure and guarantee stable thermal contact during complete life. Since humidity in LEDs, especially during the soldering process, may lead to the so-called “Popcorn-Effect”, moisture-proof storage should be ensured. In some applications, the LEDs are covered by a protective lacquer or an external joint compound. Mechanical or thermal stress, as well as a reaction with outgassing materials, can cause failures in the internal construction of an LED¹³.