The effects of accelerated aging on optical components : Application to vehicle camera systems

University essay from Linköpings universitet/Institutionen för fysik, kemi och biologi

Abstract: Companies providing products have many requirements, both from standards and customers, that they need to comply with in order to be able to sell their product. Veoneer AB is a leading automotive machine vision supplier, providing mono, stereo, night vision and driver monitoring systems consisting of both electronic, mechanical and optical components. These systems have to withstand certain environmental tests in order to assure the lifetime of the totalsystems. Since the life time is usually several years accelerated tests are used that correspond to a few weeks ormonths. The tests used at Veoneer are specified for electronic equipment and what Veoneer does not know today is ifthe accelerated environmental tests stated for electronic equipment are relevant for the optical component of the visionsystem. In this master thesis project two different accelerated environmental tests, dry and damp heat, have been chosen inorder to investigate the effect of temperature and relative humidity on the adhesive in the optical component connecting the sensor and lens. The optical components where characterized by measurement of focus position and mechanicalstrength. Different combinations of temperature and relative humidity where chosen in order to compare the effect of different stress levels but also for the purpose of deriving parameters needed for accelerated testing models such as theArrhenius, Eyring, Lawson and Peck model. Amongst the results from this thesis work is the focus shift measurement which follows the same trend as seen in previous research regarding the effect of temperature and relative humidity on adhesives. With an exponentialdistribution being seen in different directions for the respective stresses. Pull tests show a greater degradation withhigher stress levels, where one test case shows the greatest degradation. Calculations regarding activation energy and constants for models match previous research where one model, combining temperature and relative humidity, showssimilar values as found in literature. Calculations also show that standard accelerated life time tests overexpose adhesives due to calculations of test times with lower activation energies.

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