A new method of characterizing material viscoelastic property by using vector fitting

A numerical algorithm is first established to characterize viscoelastic properties of materials by using vector fitting which is used more commonly for system identification in the field of electronic and automatic control. Combining with correspondence principle, the present numerical algorithm is employed to predict the viscoelastic properties of no-flow underfill material. The predicted results are compared with the experiment data. Very good agreement between numerical algorithm and experiment results is illustrated for the materials. As the form is simple, the relaxation modulus can be easily switched from frequency domain to time domain by using inverse Laplace transformation. The present algorithm can also be used to characterize viscoelastic properties of other materials.