IPC-A-610 revision G page 8-93 indicates that you can have a 30% void in your solder ball. We recently had a STM32F417IGH6 device over heat. Upon X-ray, we discovered that about 80% of the solder balls had voids near 30%.
Danish,Yes, I was surprised as well to find that the device was overheating. I didn't have a thermal imager at that time so I cannot tell you the exact temperature of the device. This was not typical of how the device normally operates in the design...
