X-ray micro-CT and DVC based analysis of strains in metallization of flexible electronics

Flexible substrates have been widely used for the fabrication of flexible or wearable electronics. The large deformation of flexible material in wearable electronics can reduce the reliability or cause premature failure of the electronics interconnects. Rapid adoption of flexible electronics for high reliability applications requires the development of methods for in-situ non-destructive measurement of deformation and strains under operational loads. The DVC based methods allow for the computation of the deformations in reference to an initial configuration. A common difficulty with the use of x-ray based measurements for the soft materials is the near transparency under exposure to x-ray sources resulting in poor geometry definition in the finished rendering. The low grayscale values traditionally limit the measurement capabilities or the extension of the x-ray based grayscale methods to soft materials. In order to overcome those difficulties, a technique that could measure the deformation of flexible material in addition to the rigid materials has been developed in this paper. The methodology has been used to compute the deformation of flexible materials for X-ray CT scans. In first part of the study, the ability of the method to allow for reconstruction of low-density material and its detectability has been demonstrated. In the second part of the study, the deformation has been computed and verified in the tests, in which the strain gauges have been mounted on the flexible material. Measurements show good correlated of DVC measurements with the strain gage and theoretical values.