Analysis of total dose exposure to integrated circuits resulting from laminographic inspection of surface-mount-package solder joints

The ionizing total dose delivered to semiconductor devices packaged in leadless chip carriers in-place on a surface-mount technology (SMT) module during exposure to X-rays from X-ray laminography inspection techniques was determined. Laminography is an X-ray imaging technique that uses slices of the region of interest for subsequent image analysis by computer software algorithms. The high-speed, automated image analysis has been reported to result in much lower ionizing dose than that of conventional radiography. The authors discuss the dosimetry, radiation-absorbed dose dosimetry-calibration techniques, total dose profiles for integrated circuits (ICs) mounted on one type of SMT modules, and module design considerations resulting in maximum exposure to ICs. Design conditions that result in high total dose deposited in ICs when exposed to X-ray laminography have been identified. The conditions occur when small packages are placed in a dense layout, on a double-sided printed wiring assembly design, with solder joints on one side in line with ICs on the other