Microelectronic encapsulants show evolving properties that change prominently with environmental exposures such as isothermal aging and thermal cycling. Such aging effects are exacerbated at higher temperatures typical of thermal cycling qualification tests for harsh environment electronic packaging. In this work, the mechanical behavior of UV curable solder mask materials has been explored. A microscale tension-torsion testing machine has been used to determine the uniaxial tensile stress-strain and creep behaviors of solder masks used in PBGA substrates for various UV curing times and testing temperatures. A specimen preparation procedure has been developed to make 80 × 3 mm uniaxial tension test samples with a specified thickness of 0.30 mm. The test specimens are prepared in a unique way and no release agent is required to extract them from the Teflon coated molds. The mechanical behavior changes were recorded for the various durations of UV exposure followed by thermal curing. Results showed that an optimum UV exposure provide better mechanical properties compare to other exposure time. After UV and thermal curing, a microscale tension-torsion testing machine was used to find the complete stress-strain behavior of the material at room temperature. In addition, the viscoelastic mechanical response of solder mask has also been characterized via creep testing for a large range of applied stress levels.
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