Defects Ultrasonic Detection in Seal Region of Flexible Package Using BEEI Method

Ultrasonic non-destructive testing method was introduced to detect flexible package seal quality.The channel defects with diameters of between 50 and 150μm in the seal area of flexible package were detected using Backscattered Echo Envelope Integral(BEEI) imaging method.The echo signal for each scan point in time-domain was Hilbert-transformed to produce its envelope,and was further integrated over the entire signal envelops to obtain the BEEI value.The BEEI value was calculated producing a two-dimensional BEEI-value matrix.The matrix was aligned into a rectilinear pattern mapped at the scan pattern grid,and then was interpolated.The final interpolated matrix was used to yield the gray scale image.The images were formed with a spot focused 22.66 MHz ultrasound transducer scanned over a 2.98 mm×1.50mm rectangular gird.Coefficient of variation(CV) values of BEEI-matrix for each sample were studied.The variations of the BEEI values in the direction vertical to the edge of the heat seal and in the direction parallel to the edge of the heat seal were compared.The results show that channel defects and inclusion defects in flexible package can be effectively detected using BEEI imaging method.The CV values are lower than 8%for channel and inclusion defect, which indicate the variation of the BEEI values in matrix is small.The mean BEEI values on the defect region are about greater between 30%and 40%than that on the background region.