What Happens When My Customers Exceed the Maximum Ambient Operating Temperature?
The maximum ambient temperature has been determined by qualification tests. Exceeding this limit may cause a significant increase in catastrophic failures or degradation. Initially, light output degradation will increase. However, continued operation above maximum ambient temperatures may cause catastrophic failures. The farther the limit is exceeded, the faster degradation and catastrophic failures will occur. These failures are due to limitations in the packaging. For lamps the coefficient of thermal expansion changes. This change causes increased stress on the LED wire bonds. Eventually the wire bond breaks. At high ambient temperatures the optical epoxy can discolour and significantly reduce the light output. Also, light output degradation increases. Thus, catastrophic and parametric failures will increase when the maximum ambient temperature is exceeded.
