Abnormal inspection when checking by X-Ray machine

[Do Van Hiep]

Hello Experts,

When I use a X-Ray machine to check appearance of NRF52840 . But I found out that there were some abnormal phenomen as same as a photo below:

Any body can explain what they are and is it normal or defect?

Thank you.

[Do Van Hiep]

ketiljo In case we need to verify air bubbles inside might be affected to our components. What are your recommendation?