Determination of LEDs degradation with entropy generation rate

Abstract

We propose a method to assess the degradation and aging of light emitting diodes (LEDs) based on irreversible entropy generation rate. We degraded several LEDs and monitored their entropy generation rate (Ṡ) in accelerated tests. We compared the thermoelectrical results with the optical light emission evolution during degradation. We find a good relationship between aging and Ṡ (t), because Ṡ is both related to device parameters and optical performance. We propose a threshold of Ṡ (t) as a reliable damage indicator of LED end-of-life that can avoid the need to perform optical measurements to assess optical aging. The method lays beyond the typical statistical laws for lifetime prediction provided by manufacturers. We tested different LED colors and electrical stresses to validate the electrical LED model and we analyzed the degradation mechanisms of the devices.

Entropy Generation Methodology for Defect Analysis of Electronic and Mechanical Components—A Review

“…The entropy generation rate can be described as the input power (P) at a certain temperature (T). Normally, the internal heat generated during the operation of electronic devices, such as resistors [11], capacitors [12], LEDs [13], is conducted into the external environment. The entropy generation of a resistor is introduced as a typical example below.…”

“…Following a similar idea to that for resistors, Cuadras et al [12] investigated the entropy characterization of overstressed capacitors for lifetime prediction and found that entropy generation was related to capacitor parameters, including capacitance, structural size, and operating voltage. Subsequently, Cuadras et al [13] carried out a similar investigation into LED lights and determined the entropy generation rate with LED degradation. A thermodynamic damage parameter S(t) was proposed to project an LED lifetime.…”

“…First, the failure of electronic devices due to electromigration coupled with thermal migration is analyzed on the basis of entropy theory [9]. The defect prediction of key interfaces, such as die-attach (DA) layers [10], resistors [11], capacitors [12], LEDs [13], and chips, is also investigated. Second, entropy generation on mechanical structures is considered in several defect cases.…”

“…The optimization of entropy generation calculation is integrated with the optimization of thermal resistance and indicates an adequate temperature distribution [26][27][28][29]. [12], resistor [11], light emitting diode (LED) [13], pyroelectric sensor [30], through silicon via [15], solder ball [9], 304 stainless steel [18], aluminum block [7], sink [25], fin [31], circuit board [22], and heat exchanger).…”

“…Characterizing the defects of electronic and mechanical components to diagnose component lifetime systematically has gradually become a hot topic in recent years. The current work aimed to review previous defect analysis studies that used entropy generation methodologies for electronic [12], resistor [11], light emitting diode (LED) [13], pyroelectric sensor [30], through silicon via [15], solder ball [9], 304 stainless steel [18], aluminum block [7], sink [25], fin [31], circuit board [22], and heat exchanger).…”