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40 SMT007 MAGAZINE I JULY 2025 X-ray Imaging X-ray inspection is a vital non-destructive tech- nique for evaluating internal solder joint structures, especially beneath BGAs, enabling detection of hidden defects like shorts, opens, and head-in-pil- low issues that are not visible through standard visual inspection (Figure 3). To maximize effective- ness, it's important to capture images from multiple angles, use appropriate magnification, and regu- larly calibrate the system to ensure accurate imag- ing. Additionally, thorough training for technicians in image analysis is essential for accurately iden- tifying defects such as voids or solder bridging. Proper calibration and skilled interpretation signif- icantly enhance defect detection, ensuring higher quality, reliability, and improved overall assurance in electronic assemblies. Dye and Pry Testing Dye and pry testing is a valuable, though destruc- tive, method for assessing solder joint quality, par- ticularly in BGA rework. The process involves applying dye to solder joints to reveal cracks, voids, or insufficient coverage, followed by care- fully prying the BGA package away from the PCB to visually inspect the interface for defects. While highly effective for failure analysis and critical qual- ity checks, it permanently damages the component and PCB. Proper procedure, including even dye application and controlled force, along with skilled interpretation by trained technicians, is essential for accurate results. This method helps identify hid- den defects that could impact long-term reliability, supporting higher quality assurance in electronic assemblies. Summary Since the late 1990s, BGA packages have become the preferred choice for electronic device pack- aging, offering significant space savings and high- density integration vital for modern applications. Despite their advantages, reworking BGAs presents numerous challenges, including precise tempera- ture control, handling of underfilled or large pack- ages, warpage, and the complexities of stacked or package-on-package (PoP) configurations. Effective rework involves a range of techniques, from hot air, infrared, vapor phase, to laser reflow, each suited to specific scenarios and requiring advanced equip- ment and skilled technicians. Critical processes such as BGA reballing, inspection (visual, X-ray, dye and pry), and trou- bleshooting are essential for ensuring reliable, defect-free connections. Addressing inherent risks, such as adjacent device damage, warpage, and solder joint defects, demands meticulous process planning, proper tools, and rigorous qual- ity checks. Ultimately, a combination of innova- tive techniques, continuous operator training, and thorough inspection standards ensures high-qual- ity, reliable BGA rework, supporting the ongoing miniaturization and complexity of modern elec- tronic systems. SMT007 Nash Bell is president of BEST, Inc., and an I-Connect007 columnist. To read Nash's columns, click here.