I was referred to the company through a staffing agency.
The process was essentially two stage:
1) Phone interview/panel interview: you'll be asked a series of questions by personnel in engineering and HR. The questions are typical questions (give me an example of a project you...). You should know very quickly (even right in the same call) if you'll be invited for an on-site interview.
2) The on-site interview is very relaxed, consisting of two panel interviews, a plant tour and some 1 on 1 time. The staff here is great, and if you're a typical hands-on geeky engineer type, you'll probably fit in well.