This disclosure details exemplary battery pack designs for use in electrified vehicles or other electrified components. An exemplary battery pack may include a heat exchanger plate assembly having a metallic plate and a polymeric plate that are joined together to establish a coolant circuit therebetween. The metallic plate or the polymeric plate may include a protrusion that extends through an opening of the other of the metallic plate or the polymeric plate. The protrusion may either be crimped or heat staked to a surface surrounding the opening in order to join together the metallic plate and the polymeric plate of the heat exchanger plate assembly.