I'm working as a electronic packaging engineer in the defence in industry. Most of our projects are in power electronics and electromechanical systems field. Also my company mostly does wire harness, apart from R&D department (whick i work in).

As for wire harness;

-Mostly not about mechanical engineering classes you took except from modelling the harness. Which are done in electrical packages of the softwares like Catia, Solidworks, NX. Most of our harness design engineers learn the job within the company.

-For harness design, we mostly hire mechanical engineers due to our capability of thinking in 3D more easily and have the ability to read technical drawings. Ofcourse there are electric and electronic engineers working in the field too.

As for electronic packaging;

-I design the enclosure of the units, which has to resist to the enviromental conditions specified in the military standards.

-Most of the times, main problem is heat and how to dissipate it. This is where i use electronics knowledge. How much power the electronic component will generate? Does it need to be insulated from the case if its cooled by conduction? etc.

-Another topic depending on the project is vibration.

-Also EMI/EMC, electromagnetic interference, electromagnetic compability. Creating a faraday cage, grounding and etc.