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50 SMT007 MAGAZINE I APRIL 2025 attached to the area of interest where radia- tion needed to be measured using a Kapton tape. Radiation was measured in both types of machines: automated X-ray inspection (AXI or 3D X-ray) and manual X-ray inspec- tion (MXI or 2D X-ray). ree BGAs with different geometries of board and substrate were chosen for evalu- ation of the dosage experienced by on-pack- age DRAM. BGA #1 had a 0.58 mm thick substrate and was placed on a 10L 0.6 mm thick PCB. BGA #2 had a 1.56 mm thick sub- strate and was placed on a 16L 1.58 mm thick board. BGA #3 had a 2.27 mm thick substrate and was assembled on a 28L 3.175 mm thick board. All three BGA construction types serve as test vehicles that have the on-pack- age DRAM memory completely exposed. If there is a heat spreader (IHS), then it could provide additional shielding from the X-ray radiation and that is not in the scope of this paper. e radiation absorbed by the on- package DRAM was characterized for the three BGA construction types in a typical AXI as well as MXI scans. Figure 3: BGA #2 X-ray dosage results. Variability Chart for Dosimeter reading (rad) A 10L 0.5 mm thick PCB with BGA #1 assembled on it was used to characterize the influence of various inspection parameters on the X-ray dosage. Table 1 shows the parame- ters that were varied to characterize the effect of the radiation. All these DOEs were con- ducted in a 2D X-ray (MXI) machine so that the various parameters could be controlled more accurately. ree types of filter mate- rials, namely aluminum, copper, and zinc, were evaluated for their efficacy in shielding radiation. e inspection time, X-ray power, a c b d e