Development Of Inline Rapid Thermal Transient Test System For Crack Detection Of AlInGaP On Germanium Carrier
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Date
2018-02
Authors
Annaniah, Luruthudass
Journal Title
Journal ISSN
Volume Title
Publisher
Universiti Sains Malaysia
Abstract
LEDs are the ultimate light source in the lighting technology and growing at double digit percentage for the past few decades. Despite of many virtues in LEDs, there are many challenges it have. One of it is die crack. In this work, the focus is on die-crack on die substrate of an AlInGaP LED at die attach (DA) process. Here the impact on electro-optical and thermal properties were investigated and a detection method was invented. The cracks were artificially created at Ge substrate using industrial grade DA equipment at bond force range from 40gF to 210gF. Die-crack length were measured using high magnification scope. A few dice were analysed using Scanning Electron Microscope (SEM) for their crack formation. Some of the cracked dice were packaged and undergone stress test (Temperature Cycle and Power Temperature Cycles) to analyse its impact on electro-optical performance. Thermal resistance (Rth) of the cracked LED die were measured using 3Tster. The die-cracked LEDs were further characterized using oscilloscope to check their thermal transient behaviour. The investigation results shows crack length and crack severity increases as the bond force increases. The electro-optical results after stress test shows no significant changes before and after stress test for all the die-crack LED cells. Cross-section of the substrate shows that the crack remains at surface level and did not reach the active layer, hence no impact on electro-optical properties. However, observed fatigue-failure at substrate surface level, in which large chunk of Ge separated from the main body. But, the investigation on different die sizes shows that smaller die has severe crack formation compared to the bigger die. Further analysis
on such die-crack LEDs for thermal behaviours shows that its LED Rth increases relatively to the crack severity.
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Keywords
Inline rapid thermal transient test system , crack detection of alingap on germanium carrier