基于改进多路径匹配追踪的芯片超声信号去噪方法

针对高频超声检测倒装焊芯片微缺陷的回波信号受噪声影响的问题，提出了一种基于改进多路径匹配追踪算法(MMP)的高频超声信号稀疏去噪方法。利用MMP算法获取全局最优的原子，针对MMP计算量过大的问题，在迭代过程中设置阈值和引入剪枝操作，筛选误差较大的路径，减少迭代路径，降低算法复杂度。为了避免字典维度上升导致的计算量过大，通过构建连续原子库对重构信号参数进行调整，最终实现芯片超声检测信号噪声的抑制。通过仿真和实验证明，提出的方法能够有效的去除倒装芯片高频超声检测信号中的噪音，与其他去噪算法相比，所提方法通过增加少量的计算，实现信号重构精度的提高，提升了B扫图的清晰度。

Denoising method of chip ultrasonic detection signals based on the improved multipath matching pursuit

To reduce the influence of noise on the high frequency ultrasonic detection of flip chip defects, a sparse denoising method of high-frequency ultrasound signals based on the multipath matching pursuit (MMP) is proposed. The MMP algorithm is used to obtain the atoms which are globally optimal. Aiming at the excessive calculation of MMP, the setting thresholds and the introducing pruning operations during iteration are introduced. To avoid the excessive calculation amount caused by the increase of the dictionary dimension, the contiguous atom dictionary is established to adjust the reconstructed signals and realize the noise suppression. Proved by simulation and experiment, the proposed method can effectively remove the noise in high-frequency ultrasonic detection signals of flip chip. Compared with MMP, the proposed method can improve the signal reconstruction accuracy and the clarity of B-scan by adding a small amount of computation.