Two phone interviews and one on-site.

It was not really hard. The phone interviews were given by the office manager and the lead mechanical engineer, who also became my mentor. They focused mainly on the skills and working/project experiences listed on my resume.

Then, after one week, there was an on-site interview. The office manager, lead mechanical engineer, and a software engineer interviewed me. It took around 1-2 hours. It was not really hard. I just had to remain calm and illustrate what I had done before.

Talk about the experiences shown on the resume.

Also, ask for some skills that will be used during the internship and how well you know them.