An electronic device may be provided with a display mounted in a display frame assembly that includes a plastic structure overmolded over a display frame. A housing midplate may be used to provide the electronic device with mechanical rigidity and strength, and may also be used as a sensor plane. For sensor plane applications, accurate placement and assembly of the midplate in the housing can be critical. The housing midplate may be accurately assembled to the display frame using connections formed using welded tabs, welded and screwed nuts, overmolded plastic heat stake structures, or overmolded plastic structures and adhesive. Rework and repair operations may be performed by disconnecting connections such as welds using cutting equipment, by using solvent to dissolve adhesive, by unscrewing welded nuts, or by removing heat stake structures. Following rework or repair, a fresh midplate and associated components may be attached to the display frame.