Research On Detection Of Layered Detects In PBGA Based On Laser Shear Speckle Interferometry

PBGA packaging is widely used in automobile industry,aerospace industry and other domains because of its low manufacturing cost and good electrical performance.However,PBGA packaging plastic sealing material is a polymeric material which has the property of hygroscopicity.It is very easy to produce delamination at the junction of different materials in the packaging during manufacturing and serving,which seriously affects the reliability of integrated circuits.Therefore,the detection of internal delamination defects is very important.This paper takes the delamination defect at the juncture of PBGA packaging plastic seal and substrate as the research object,detects it based on laser shear speckle interferometry,analyzes the influence of different parameters on the detection through experiment and simulation,and finally studies the off-surface displacement fields measurement based on laser shear speckle interferometry.The research contents mainly includes:1.Firstly,the principle of laser shearing speckle interferometry is deeply studied,as well as the speckle information processing technology.Aiming at the problem that the traditional sine and cosine filtering does not have self-adaptive system,this paper proposes a sine and cosine transform wavelet average threshold denoising method.Compared with other filtering methods,the proposed method not only filters the phase diagram noise,but also retains the detailed information of the phase jump,and the denoising is significantly effective.As a result,The quality of phase diagram is improved.2.In this paper,the out of plane displacement measurement is deeply studied based on laser shear speckle interferometry.When reconstructing the off-surface displacement fields by traditional integration method,the error will be transmitted along the integration path due to the influence of noise and outliers.To solve this problem,a Fourier transform bidirectional shear off-surface displacement fields arithmetic method is proposed in this paper.By comparing the reconstruction results of the two methods through simulation and off-surface displacement fields measurement experiment of aluminum plate,it is proved that the proposed method not only ensures the arithmetic efficiency,but also achieves a high degree of accuracy.3.Basing on the simulation of four step phase-shifting laser shearing speckle interferometry system,the effects of different test conditions(shear amount,loading load,defect size and defect depth)on the detection results were analyzed.The laser shearing speckle interferometry testing platform is used to test the defect samples with different parameters.It is proved that the experimental results under different test conditions are consistent with the simulation experimental results.Finally,the Fourier transform bidirectional shear method was used to reconstruct the off-surface displacement fields of different size defects under different loading conditions.