2. For QFN solderability inspection and testing, electrical tests along with optical sensors or X-rays are used to detect solder issues; poor X-ray imaging can make identifying problems challenging, sometimes requiring destructive experiments like inspecting BGA solder. 3. To address voids in QFN solder joints, solutions include conducting solderability tests, revising circuit board wiring designs, introducing thermal resistance pads, adjusting reflow soldering parameters, and redesigning ground pads to prevent excessive solder paste application and floating parts.