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A review of three types of nondestructive equipment: 2-D x-ray, endoscopic and 3-D x-ray.
While BGAs offer certain advantages over gull-wing parts, the equipment used to verify and maintain solder joint integrity in BGAs adds a step to the inspection process and increases costs. Among the three types of nondestructive BGA inspection equipment - 2-D x-ray, endoscopie and 3-D x-ray - each has its own particular capabilities.
2-D x-ray transmission systems generally show many obvious defects such as bridging, voids or missing balls. In many cases, the systems have difficulty detecting other common defects such as opens and insufficient or cold soldering. These types of defects require a high-powered system (100 to 165 kv) with oblique view at highest magnification (OVHM) capability and an experienced technician. Standard 2-D x-ray offers image resolution of 8 to 10 µm, while many advanced systems can achieve a resolution of less than 1 µm.
As an alternate method to x-ray, endoscopic inspection technology (a form of optical inspection) can be used to locate defects such as opens, insufficient or unreflowed solder, lifted pads and debris. It, too, has limitations when inspecting center balls of a BGA component. While these systems are capable of seeing 10 to 15 rows in, it is difficult to make observations on the entire ball, as viewing is limited to the outer edge of...