Abstract: The echo signal in flip-chip high-frequency ultrasonic testing is weak and highly susceptible to environmental noise and grain scattering. The B-scan image reconstruction speed for flip-chip bumps is slow, and the low resolution hinders clear identification of solder ball defects. This paper proposes a Focused Transducer Phase Shift Migration (FTPSM) algorithm based on the Local Sign Coherence Factor (LSCF) to accelerate B-scan image reconstruction, enhance spatial resolution, and improve defect detection accuracy. First, time-domain compensation is applied to the echo signals received by the focused ultrasonic transducer. Next, the cross-correlation coefficient is computed for each local region of the chip’s B-scan image; the local phase coherence factor is then derived using Phase Coherence Imaging (PCI), and used to suppress noise amplitude in the B-scan matrix. Finally, the weighted B-scan matrix is extrapolated in the frequency–wavenumber domain. A high-frequency ultrasonic simulation model of flip-chip bump defects is established using COMSOL Multiphysics 5.6, and simulation results are validated against experimental data. Results demonstrate that the proposed algorithm is compatible with synthetic aperture focusing techniques. Compared with the conventional phase coherence algorithm, the B-scan images processed by FTPSM exhibit an average signal-to-noise ratio (SNR) improvement of 10.5 dB and an average signal amplitude increase of 13.4 dB. Moreover, the lateral resolution is significantly enhanced, and noise interference is effectively suppressed.