Abstract
One of the most commonly used LED packages on market is the mid-power LED in a lead-frame package, because of its low cost and high lumen efficiency. However, as the lead-frame package consists silver plated copper and white plastic housing, both for increased light reflection; it can gradually become yellowing or darkening when reacting with certain organic gases or chemical compounds when accelerated by high temperature and light radiation. As a result, light decay or lumen reduction can occur in LED lightings. This paper presents an overview on light decay failure modes of commonly used lead-frame LED package. Four types of failure root cause will be discussed: 1) sulfur induced silver darkening; 2) Halogen (Br, Cl) induced silver and silicone encapsulation yellowing; 3) incompatible volatile organic compounds (VOCs) resulted darkening on or around of LED chips; 4) plastic housing material yellowing.
Published Version
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