Thermally induced stresses resulting from coefficient of thermal expansion differentials between an LED sub-mount material and various mounting substrates

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Abstract
A study has been conducted to determine the effects of mechanical stresses induced from the coefficient of thermal expansion (CTE) differential between a light emitting diode (LED) chip, and various substrate materials to which the LEDs were mounted. The LEDs were bonded to typical packaging materials including ceramics, copper and metal matrix composites. The objective of this investigation was to determine the viability of implementing alternate substrate materials for packaging of LED power chips. In particular, thermally induced stresses resulting from the CTE differentials between the alternate substrate materials and the LED sub-mount material were analyzed and compared against the stresses resulting from the nearly ideal CTE match that is realized with traditional ceramic substrates.