Experimental Study on the Reliability of PBGA Electronic Packaging under Shock Loading

Plastic Ball Grid Array (PBGA) one of the most important electronic packaging methods, is widely used in aeronautical industry field. According to the JEDEC standard, shock tests of PBGA assemblies are conducted under different loading conditions. Several important parameters, such as the fatigue life of PBGA assemblies, the relationship between solder joint positions and fatigue life, the relationship between strain energy density and fatigue life, are analyzed based on experiment results. The failure modes of PBGA assemblies are studied by optical microscope (OM). The results show that during the shock tests, the strains of the solder joints near the center of the specimen are larger than other positions, and these solder joints are prone to form micro cracks. With the increase of the shock times, these micro cracks extend rapidly which will eventually cause the failure of the PBGA electronic packaging.

Automatic Segmentation Method for Segmenting PBGA Package and PWB Regions During Warpage Measurement of Unpainted PWB Assembly

Among the various warpage measurement techniques, digital fringe projection (DFP) technique is recent trend because of its noncontact, full-field, and high-resolution measurement capabilities for measuring the warpage of chip packages, printed wiring boards (PWBs), and PWB assemblies (PWBAs). When using the DFP technique, reflective painting is generally sprayed on a sample surface to ensure uniform surface reflectance and to obtain better image contrast for the measurement process. However, because painted samples may no longer be reused, and the spray-painting process is not suitable inline, warpage measurement of unpainted chip packages, PWBs, and PWBAs using the DFP technique is required. One of the important tasks for measuring the warpage of unpainted PWBAs is segmentation of the chip package and PWB regions in unpainted PWBA images so that separate warpage of the chip packages and the PWBs can be determined. This paper presents a novel automatic segmentation method, region-growing method (RGM), which segments plastic-ball grid array (PBGA) packages and PWB regions in unpainted PWBA images. The experimental results show that the RGM successfully segments the PBGA package and PWB regions in unpainted PWBA images. The results also show that the RGM can be used in a DFP system to measures the warpage of PBGA packages and PWBs in unpainted PWBAs.

Automatic Segmentation Method for Segmenting PBGA Package and PWB Regions during Warpage Measurement of Unpainted PWB Assembly

Among the various warpage measurement techniques, the digital fringe projection (DFP) technique is recent trend because of its noncontact, full-field, and high-resolution measurement capabilities for measuring the warpage of chip packages, printed wiring boards (PWBs), and PWB assemblies (PWBAs). When using the DFP technique, reflective painting is generally sprayed on a sample surface to ensure uniform surface reflectance and to obtain better image contrast for the measurement process. However, because painted samples may no longer be re-used, and the spray-painting process is not suitable inline, warpage measurement of unpainted chip packages, PWBs, and PWBAs using the DFP technique is required. One of the important tasks for measuring unpainted PWBAs is segmentation of the chip package and PWB regions in unpainted PWBA images so that separate warpage of the chip package(s) and the PWB can be determined. In this paper, an automatic image segmentation method that is used to segment plastic ball grid array (PBGA) package and PWB regions in unpainted PWBA images is presented. Because the patterns such as the copper patterns and traces, and inscriptions on a PWBA can cause measurement errors, the patterns and inscriptions are automatically masked out during the segmentation. The method is experimentally tested by segmenting the PBGA package and PWB regions in three different PWBA samples and measuring the warpage of the PBGA packages and the PWB in an unpainted PWBA.

Analyses of PBGA Packaging under Strong Vibration

Experimental and numerical analyses on the solder joint reliability of plastic ball grid array under harsh random vibration were presented. The chips were assembled on the daisy chained circuit boards for the test samples preparation, and a half of the samples were processed for underfill to investigate the underfill effects on the solder failures. Two consequential steps of the random vibrations, named as acceptance and qualification levels, were applied. Overall controlled RMS of the power spectrum densities of the steps were 22.7 Grms and 32.1 Grms, respectively. It was found that the samples did not show any solder failure during the tests, demonstrating the robustness of the packaging structure for potential avionics and space applications. Finite element analyses were performed to calculate the sample vibration behaviors and the solder stresses, and the results were compared with the test data.