I got two phone interviews. The first lasted 30 min. I was asked question about my master, the courses I chose, the university I come from. Then the interview turned rapidly technical!
I was asked to explain completely how a Flyback converter works. He gave me a sheet about "TRIAC-Dimmable, Primary-Side-Control Offline LED Controller with Active PFC". It told me to read and prepare it for the second interview.
This second interview lasted 50min. He asked me many questions about that sheet. I did not understand everything and was not able to answer all the questions but the interviewer told me he would ask his boss.
Then I received an email. The told me to come to Danvers (MA). They paid for the plane, hotel...
I had several face to face interviews: 5 with different people: Mgr Engineering, Principal Special Tech Eng, Director R&D, Corporate Recruiter... Many technical questions about power converters and a project I worked on during my studies using a STM 32 microcontroller.
Two weeks later I received an email with their final decision